WO2020047076A1

WO2020047076A1 - Glass-stabilized foldable oled

Info

Publication number: WO2020047076A1
Application number: PCT/US2019/048545
Authority: WO
Inventors: William Riis Hamburgen
Original assignee: Google Llc
Priority date: 2018-08-28
Filing date: 2019-08-28
Publication date: 2020-03-05

Abstract

A computing device includes at least one processor, memory storing instructions executable by the processor, and a foldable display. The foldable display includes: a back stiffening layer, a transparent frontplate layer, a transparent cover window layer, a transparent, flexible protective film layer disposable on the cover window layer, where the film layer includes a polymer material, and an OLED display layer disposed between the back stiffening layer and the frontplate layer. The OLED display layer is characterized by a Young's modulus lower than the Young's modulus of the frontplate layer and lower than the Young's modulus of the back stiffening layer. A neutral plane of the foldable display is located within the OLED display layer, and the foldable display can be folded around a bend having a radius of less than 5 mm with the cover window layer being on the outside of the bend.

Description

GLASS-STABILIZED

FOLDABLE OLED

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a Continuation of, and claims priority to, U.S. Patent Application No. 62/723,782 filed on August 28, 2018, entitled“FOLDABLE DISPLAY NEUTRAL AXIS MANAGEMENT WITH THIN, HIGH MODULUS LAYERS”, the disclosure of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

[0002] This description relates to rendering of foldable displays and, in particular, to glass-stabilized foldable OLED displays.

BACKGROUND

[0003] Modern computing devices often attempt to achieve a balance between portability and functionality. A tension can exist between having a display that provides for a rich display of information on a single surface, which suggests a relatively large form factor of the device to accommodate a relatively large display, and a device that is small enough to be easily carried and accessed by a user, which suggests a relatively small form factor of the device.

[0002] A potential solution to address this dilemma is to use a foldable flexible display in the computing device, so that in the display’s folded configuration, the computing device has a relatively small form factor, and in the display’s unfolded configuration, the computing device can have a relatively large display. To keep the form factor of the computing device small and slim, it is desirable to have relatively thin displays. However, folding a relatively thin display can result in small radius bends at the fold in the display, which may be detrimental to sensitive components of the display, for example, thin film transistors (TFTs), organic light-emitting diodes (OLEDs), thin-film encapsulation (TFE) and the like. In addition, thin displays can be relatively fragile and in need of protection against breakage from impacts to the front surface of the device.

[0003] It can be difficult to create foldable top-emitting plastic OLED displays that have a small folding radius in both directions (i.e., having two surfaces of the display that fold both towards each other and away from each other) and that can survive many fold- unfold cycles. For example, creating sturdy, durable Z-fold displays (i.e., displays with both inward and outward folds) is greatly complicated by the fragility of the thin-film layers in the display stack.

[0004] One approach to building the display stack for a functional display is to use optically clear adhesive (OCA) to join different functional layers of the stack. For example, a display stack may include from the following layers:

1. Backplate layer

2. Adhesive layer

3. Display layer (including polyimide substrate with barrier, TFT, OLED, and

encapsulation layers)

4. OCA layer

5. Touch sensitive layer (typically a multi-layer film stack)

6. OCA layer

7. Polarization layer (including a circular polarizer)

8. OCA layer

9. Cover Window (CW) layer (user-facing cover window film)

[0005] In some implementations, the polarization layer and the touch sensitive layer may be reversed, combined or eliminated. A common development direction involves building touch functionality directly on top of the display layer. This reduces the thickness of the stack of the most fragile layers and also simplifies electrical connection to the touch layer. In such implementations, the stack may include the following layers:

1. Backplate layer

2. Adhesive layer

3. Display-Touch layer

4. OCA layer

5. Polarization layer (including a circular polarizer)

6. OCA layer

7. CW layer (user-facing cover window film)

[0006] In another implementation, the cover window layer and the polarization layer can be combined, so that the stack includes the following layers:

1. Backplate layer

2. Adhesive layer

3. Display-Touch layer

4. OCA layer

5. POL-CW layer [0007] The Display-Touch layer often is manufactured in a very expensive, highly- automated OLED factory using a highly optimized recipe that cannot easily be altered to meet customer customer-specific requirements. The backplate and polarization / cover window layers may be customer-specific and are typically added in a less expensive factory setting after the display exits the OLED line. However, these customer-specific backplate layer and polarization / cover window layers may cause the neutral plane of the device to shift away from the display -touch layer, which may be detrimental to the in-system folding cycle life of the entire display.

SUMMARY

[0008] In one general aspect, a computing device includes at least one processor, memory storing instructions executable by the processor, and a foldable display. The foldable display includes: a back stiffening layer, a transparent frontplate layer, a transparent cover window layer, a transparent, flexible protective film layer disposable on the cover window layer, where the film layer includes a polymer material, and an OLED display layer disposed between the back stiffening layer and the transparent frontplate layer, the OLED display layer being characterized by a Young’s modulus that is lower than the Young’s modulus of the transparent frontplate layer and that is lower than the Young’s modulus of the back stiffening layer. A neutral plane of the foldable display is located within the OLED display layer, and the foldable display is configured to be folded around a bend having a radius of less than 5 mm with the cover window layer being on the outside of the bend.

[0009] Implementations can include one or more of the following features, alone or in any combination with each other. For example, the polymer material can be selected from the group consisting of thermoplastic polyurethane and polyethylene terephthalate.

[0010] The frontplate layer can include glass. The glass of the frontplate layer can be treated with patterned ion-implantation to induce relative weaknesses in the glass along a pattern due to the patterned ion-implantation.

[0011] The transparent, flexible protective film layer, when disposed on the cover window layer, can be attached to the cover window layer by static electric forces. An optically clear adhesive layer can be between the transparent, flexible protective film layer and the cover window layer to bond the transparent, flexible protective film layer to the cover window layer.

[0012] The computing device can include a sensor configured to determine when the protective film layer is disposed on the cover window layer. The sensor can include a camera disposed below the foldable display. The camera can be configured to detect a predetermined infrared optical indication in the protective film layer when the film layer is disposed on the cover window layer.

[0013] The computing device can include a touch layer disposed between the back stiffening layer and the transparent frontplate layer, where the sensor includes a capacitive sensor configured to sense a predetermined capacitive pattern in the protective film layer to determine when the protective film layer is disposed on the cover window layer. The touch layer can include the capacitive sensor.

[0014] The instructions can include instructions that, when executed by the processor, cause the processor to receive a signal from the sensor indicating that the protective film layer is not disposed on the cover window layer. The instructions can include instructions that, when executed by the processor, cause the processor, in response to receiving the signal, to place the computing device into a limited execution mode in which less that than the full functionality of the computing device is provided to a user of the computing device. The computing device can be placed into the limited executing mode when the foldable display is in a first physical configuration, while not being placed into the limited executing mode when the foldable display is in a second physical configuration. The first physical configuration can include a configuration in which a bend radius of the foldable display is less than a threshold bend radius, and the second physical configuration can include a configuration in which a bend radius of the foldable display is greater than the threshold bend radius.

[0015] When the computing device is in the limited execution mode, the computing device can be prevented from executing a plurality of predetermined applications.

[0016] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. l is a perspective view of a computing device that includes a foldable display with a single inward fold and the foldable display in a partially folded configuration.

[0018] FIG. 2 is a perspective view of the computing device with a single inward fold, with the display in a folded configuration.

[0019] FIG. 3 is a schematic diagram of a flexible display device having a plurality of bendable sections that are bendable in different directions. .

[0020] FIG. 4 is a schematic diagram of a flexible display device having a stack of a number of different layers.

[0021] FIG. 5 is a schematic diagram of a foldable display having a bendable section that is bent around a minimum radius, Rmin.

[0022] FIG. 6 is a graph showing an example stiffness curve for a foldable display in which the limit radius is reached when the foldable display is folded.

[0023] FIG. 7 is a schematic diagram of a foldable display having a bendable section that is bent around a minimum radius, Rmin.

[0024] FIG. 8 is an example flowchart of a process of providing computing device functionality to a user of a computing device that includes a foldable display.

DETAILED DESCRIPTION

[0025] As described herein, to control the location of the neutral plane in the final display device, after fabrication of the display-touch layer, a thin back stiffening layer and a thin transparent frontplate layer, both having high modulus, can be laminated with thin bondlines or deposited on either side of the display-touch layer. By sandwiching the delicate display-touch layers between two stiff outer layers, the location of the neutral plane can be stabilized, and subsequent layers that are added on either side can have less influence on the neutral axis location, thus improving in-system reliability. In implementations, the back stiffening layer can be combined with the backplate layer to create a surface-stiffened backplate layer.

[0026] FIG. 1 is a perspective view of a computing device 100 that includes a foldable display 102 with a single inward fold and the foldable display 102 in a partially folded configuration. The device 100 has the foldable display 102 mounted so that it folds with the viewable face inward. It is also possible to mount the foldable display 102 on the opposite side of device 100 so that the display folds with a viewable face outward (not shown). FIG. 2 is a perspective view of the computing device 100, with the display 102 in a folded configuration. The foldable display 102 may be, for example, a TFT (Thin-Film- Transistor) OLED (Organic Light Emitting Diode) display, or other appropriate display technology. The foldable display 102 may comprise appropriate circuitry for driving the display to present graphical and other information to a user.

[0027] As shown in FIG. 1 and FIG. 2, the foldable display 102 can include a first flat, rigid, or-semi-rigid, section 112, a second flat, rigid, or semi-rigid, section 114, and a third bendable section 116. In some implementations, the foldable display 102 can include more than two flat rigid sections 112, 114 and more than one bendable section 116. In some implementations, the foldable display 102 can include zero, or only one, flat rigid section 112, 114. For example, when a foldable display 102 includes zero flat rigid sections, the display 102 can be continuously bendable, and can be rolled up, as in a scroll. The foldable display 102 shown in FIG. 1 and FIG. 2 has a bendable section 116 that allows the foldable display to bend about an axis. In other implementations, the foldable display 102 can include bendable sections that allow the display to bend about more than one axis.

[0028] The bendable section 116 of the foldable display 102 allows the display 102 to bend in an arc that has a radius, and the bendable section can be made to become rigid when the radius of the bendable section reaches a specified minimum radius. This minimum radius may be selected to prevent the display from bending in a radius so small that fragile components of the display would be broken. In some implementations, the minimum radius is greater than or equal to 2.5 millimeters. In some implementations, the minimum radius is greater than or equal to 3.0 millimeters. In some implementations, the minimum radius is greater than or equal to 5 millimeters. Thus, the bendable section can be flexible when bent in a radius greater than the minimum radius and then become rigid when the bend radius is equal to or smaller than the minimum radius.

[0029] FIG. 3 is a schematic diagram of a flexible display device 300 having a plurality of bendable sections 304, 306 that are bendable in different directions. The flexible display device 300 can have a display surface 302a, 302b, 302c that can take on a“Z” shape when the device is folded in its folded, compact configuration, with a portion of the display surface 302a, 302b folded inward with the surfaces 302a, 302b facing each other, and a portion of the display 302c folded outward. To assume the“Z” shaped configuration, the display device 300 can be have a first bendable section 304 that is bendable in a clockwise direction, as shown in FIG. 3, and a second bendable section 306 that is bendable in a counter-clockwise direction, as shown in FIG. 3.

[0030] FIG. 4 is a schematic diagram of a foldable display 400 having a stack of a number of different layers. As will be described in further detail below, the exemplary stack of layers shown in FIG.4, from front to back, can include: an optional protective film later 401, a cover window layer 402, an optional optically clear adhesive (OCA) layer 404, a transparent frontplate layer 406, an optional optically clear adhesive layer 408, a flexible organic light-emitting diode (OLED) layer 410, an optional adhesive layer 412, a back stiffening layer 414, an optional adhesive layer 416, and an optional backplate layer 418.

The foldable display 400 could be used as the foldable display 102 of FIG.1. For example, in some implementations, the OLED layer 410 can be sandwiched between the back stiffening layer 414 and the transparent frontplate layer 406. The OLED layer 410 can include, at least, OLED functionality to generate the visual information displayed by the foldable display 400. In some implementations, the OLED layer 410 can also include touch-sensitive elements to detect a user’s touch at particular locations on the foldable display 400 and to generate electrical signals in response to the detected touch, and in some implementations, a layer (not shown in FIG. 4) separate from the OLED layer 410 can include the touch-sensitive elements. Furthermore, in some implementations, the OLED layer 410 can include other functional elements of the foldable display 400, such as, for example, TFTs, an encapsulation layer, and anti-reflection optical elements to reduce glare from the display, but in some implementations these functional elements can be included in separate layers from the OLED layer 410. In some implementations, the OLED layer 410 can be coupled to the frontplate layer 406 by the OCA layer 408. The OCA layer 404 can be applied to a front surface of the frontplate layer 406 to couple the frontplate layer 406 to the cover window layer 402 that serves to protect the device on the front side. In some implementations, a polarization layer can be included in the cover window layer 402, or can be included in the OLED layer 410. The polarization layer can provide anti-reflection properties to the cover window layer 402. In some

implementations, a polarization layer may not be included in either the OLED layer 410 or the cover window layer 410, but can be added to the stack of the foldable display 400 as a separate layer between the OLED layer 410 and the frontplate layer 406 or between the frontplate layer 406 and the cover window layer 402. In general, different adjacent discrete layers of the foldable display 400 can be joined by an adhesive material between the adjacent materials. Adhesive material used in the optical path between the OLED emitters of the OLED layer 410 and user’s eye are optically clear.

[0031] In some implementations, the OLED layer 410 can be coupled to the back stiffening layer 414 by the adhesive layer 412. In some implementations, the OLED layer 410 can be directly deposited on the back stiffening layer 414. In some implementations, the back stiffening layer 414 can be coupled to the backplate layer 418, for example, by the adhesive layer 416, or can be directly bonded to the backplate layer 418. One or both of the adhesive layers 412 and 416 may be OCA layers. Alternatively, one or both of the adhesive layers 412 and 416 may be optically opaque. In some implementations, the back stiffening layer 414 can be combined with the backplate layer 418 to form an integrated surface- stiffened backplate layer. As explained in more detail below, the mechanical properties of the back stiffening layer 414 and the frontplate layer 406 can be controlled to manage the location of the neutral axis of a finished product that incorporates the foldable display 400. For example, in some implementations, materials used for the frontplate layer 406 and the backplate stiffening layer 414 can include glass to provide adequate stiffness to manage the location of the neutral axis within the stack and to allow light to pass through the front place layer 406.

[0032] The foldable display 400 can include the outer transparent protective film layer 401 that is located between any layers that include glass materials (e.g., back stiffening layer 414, OLED layer 410, frontplate layer 406, and cover window layer 402) and the outermost surface of the device. As shown in FIG. 4, the outer transparent protective film layer 401 can include the outermost surface of the device. The transparent protective film layer 401 can include material that is transparent and flexible but that is not as brittle as glass. For example, the transparent protective film layer 401 can include polymer material (such as, for example, thermoplastic polyurethane (“TPU”), polyethylene terephthalate (“PET”), etc.).

[0033] In some implementations, the transparent protective film layer 401 might not be added to the foldable display 400 when the foldable display 400 is manufactured or before it is sold to an end user. For example, the protective film layer 401, in some implementations, can be added to the foldable display 400 by the user of the device. In some implementations, the transparent protective film layer 401 can be attracted to, and attached to, the other layers of the foldable display 400 by static electric forces between the protective film layer 401 and other portions of the foldable display 400. In some implementations, the transparent protective film 401 can be attached to the other layers of the foldable display 400 by an adhesive layer. In some implementations, the transparent protective film layer 401 can be removable and replaceable by an end user of the device.

[0034] Because the thickness of each layer of the stack is important to the overall thickness of the foldable display 400, it is desirable to have a relatively thin thickness for the layers. For example, in some non-limiting examples, the thickness of the flexible OLED layer 410 can be on the order of approximately 50 pm; the thickness of frontplate layer 406 and the back stiffening layer 414 can be on the order of approximately 50 pm; the thickness of the adhesive layers 404, 408, 412, 416 can be on the order of approximately 25 pm; the thickness of the cover window layer 402 can be on the order of approximately lOOpm; and the thickness of the backplate layer can be on the order of approximately 25 pm. Thus, an overall thickness of the foldable display 400 can be on the order of a millimeter and the device can have layers with individual thicknesses that are fractions of a millimeter. In some implementations, the overall thickness of the display foldable display 400 can be less than one millimeter.

[0035] The components of the stack of the foldable display 400 have different as- fabricated properties, including stresses and strains that exist in the components when the layer is fabricated. Additional stresses and strains can be induced in the layers of the stack when the display is bent into a configuration that is different from the configuration in which the layer was fabricated. For example, if the layer was flat when it was fabricated, then additional strain can be induced by stretching or bending the layer, and if the layer was fabricated in a curved configuration, then additional strain can be induced by flattening the layer. If the bend-induced strain exceeds a threshold value characteristic of a component of the stack, the component can be damaged by the strain due to cracking, buckling,

delamination, etc. This characteristic damage threshold strain may be different depending on temperature, humidity, required cycle life, and other use and environmental factors. Brittle inorganic layers of the stack can typically withstand less strain than organic layers before they are damaged by the strain, and inorganic layers may be particularly susceptible to tensile strain. Nevertheless, organic materials in the stack also can be damaged by excessive strain that is induced by bending.

[0036] FIG. 5 is a schematic diagram of a foldable display 500 having an OLED layer 502 with a bendable section 501 (the curved portion shown in FIG. 5) that is bent around a minimum radius, Rmin. The OLED layer 502 includes components that generate images on the display (emitted from the side of the display that faces toward the inside of the bend). As will be described in further detail below, the foldable display 500 can include, from back to front: an optional bend limit layer 520, a high-modulus back stiffening layer 504, the OLED layer 502, a high-modulus frontplate layer 512, a cover window-polarization layer 514, and an optional outer transparent protective film layer 511. The frontplate layer can be coupled to the OLED layer 502 and to the cover window-polarization layer 514 with OCA. The back stiffening layer 504 can be coupled to the OLED layer with an adhesive, which does not need to be an OCA. The modulus of the layers 502, 504, 512 can be parameterized by the Young’s modulus of each layer. The (Young’s) modulus of the back stiffening layer 504 and the frontplane layer 5 12 can be greater than the (Young’s) modulus of the OLED layer 502. The display 500 can also include the bend limit layer 520 that limits the radius at which the OLED layer 502 can bend to greater than or equal to the minimum radius, Rmin.

[0037] When the OLED layer 502 is fabricated in a flat configuration, then bending the OLED layer 502 in the absence of the bend limit layer 520 may cause the bendable section 501 of the OLED layer 502 to assume a radius less than the minimum radius, Rmin, which may induce excessive strain within the OLED layer 502. The OLED layer 502 can be characterized by a plane 506 at which no strain is induced when the OLED layer 502 is bent. This plane is referred to herein as the“neutral plane” 506. When the OLED layer 502 is bent and the neutral plane is in the middle of the OLED layer 502, compressive strain may be induced along the inner radius of the bend, Rinner, and tensile strain will be induced along the outer radius of the bend, Router.

[0038] If the stack of materials and material thicknesses within the device 500 is symmetric about a midplane of the OLED layer 502, then the neutral plane 506 corresponds to the midplane of the layer 502. However, different material properties (e.g., thickness, Young’s modulus, etc.) of different layers within the device 500 can cause the neutral plane 506 to be displaced above or below the midplane of the OLED layer 502. For example, having a thick, high-modulus layer on only one side of the OLED layer 502 will move the neutral plane toward the high-modulus layer. The location of the neutral plane within the device 500, along with the maximum tolerable strain values of the materials within the layers of the device 500, determines the minimum bend radius that can be tolerated without causing damage to components within the device 500, especially fragile components in the OLED layer 502.

[0039] The bend limit layer 520 can be attached to the OLED layer 502 by means of the back stiffening layer 504 to provide support for the OLED layer 502. The bend limit layer 520 can prevent the bendable section 501 of the OLED layer 502 from being bent around a radius that is smaller than its minimum tolerable bend radius. In some implementations, the functionality of the bend limit layer 520 can be combined in a single layer with the functionality of the back stiffening layer 504. The bend limit layer 520 can be reinforced with materials (e.g., reinforced with high-strength fibers) to provide strength and support for the device. Materials in the bend limit layer can have a coefficient of thermal expansion (CTE) that is close to the CTE of the OLED layer 502, so that the fragile components are not unduly stressed by thermal cycling of the device 500. For example, while many fiber materials have CTE’s that are close to zero or even negative, some ceramic fibers can have CTE’s on the order of 8 ppm per Kelvin. ETse of such fiber materials can improve thermal expansion matching to a wide range of structures, including OLED display layers. In some implementations, the CTE of the fibers can be within about 50% of the CTE of the OLED display layer 502. In some implementations, the CTE of the fibers can be within about 25% of the CTE of the OLED display layer 502. In some implementations, the CTE of the fibers can be within about 10% of the CTE of the OLED display layer 502.

[0040] The bend limit layer 520 can be relatively flexible when it is bent such that the radius of the inner portion of the OLED layer 502 is greater than Rmin and then can become stiff and inflexible when the radius of the bend approaches, or matches, Rmin. Stiffness can be parameterized by the change in bend radius per unit of applied force that causes the foldable display 500 to bend. For example, in FIG. 6, when the display is folded in half around a 180 degree bend, twice the radius of the bend is shown by the parameter, x, when a force, F , is applied to bend the foldable display. The stiffness of the foldable display 500 then can be parameterized by the derivative, k = dF/dx. The strength of the foldable display can be characterized as the maximum force, I that the foldable display 500 can withstand before failure of the display occurs.

[0041] When the foldable display 500 is laid flat in its folded configuration, it can be maintained in its folded configuration by the force of gravity on the upper folded portion of the display, such that zero additional force is needed to be applied to the upper folded portion to maintain the foldable display in its flat folded configuration, or, in other implementations, additional force can be applied by external means such as latches, magnets, etc. to maintain the display in its folded configuration. In this configuration the radius of the bend of an OLED layer 502 can be defined as the limit radius, Riimit, i.e., the radius at which the back stiffening layer 504 limits the further bending of the foldable display unless additional external force is applied. To bend the foldable display further from this configuration requires additional external force to overcome the stiffness of the bend limit layer 520. Thus, an example stiffness curve for a foldable display in which the limit radius is reached with the foldable display is folded 180 degrees, showing stiffness as a function of x is shown in FIG.

6

[0042] It can be advantageous to have a foldable display with a stiffness curve that exhibits a relatively sharp increase in stiffness once the limit radius is reached, such that the foldable display can be easily folded into its folded configuration in which Riimit is close to Rmin, and then the foldable display will become quite stiff, such that it remains in this configuration despite forces pressing it toward a radius smaller than Rumit.

[0043] The bend limit layer 520 is shown on the outside of the bend in FIG. 5, with the OLED-display layer 502 being disposed in the stack toward the inside of the bend.

However, the bend limit layer 520 also can be on the inside of the bend 501, for example, as shown in FIG. 7, in which case OLED layer 502 is on the outside of the bend and the content displayed by the display is on the outside of the bend 501. Thus, in the embodiment shown in FIG. 7, the foldable display 500 includes, from back to front: the optional bend limit layer 520, the high-modulus back stiffening layer 504, the OLED layer 502, the high-modulus frontplate layer 512, the cover window-polarization layer 514, and the optional outer transparent protective film layer 511.

[0044] The mechanical properties of the back stiffening layer 504, and the frontplate layer 512 can be controlled, so as to maintain the neutral plane 506 at, or close to the mid plane of the fragile OLED layer 502, so that the OLED layer 502 can tolerate relatively small bend radii. Because other layers of the stack (e.g., the bend limit layer 520, the CW- polarization layer 514, etc.) can affect the location of the neutral plane 506 within the device 500, the mechanical properties (e.g., the thicknesses, densities, material composition, etc.) of the back stiffening layer 504 and the frontplate layer 512 must be selected in relation to those of other layers in the stack to maintain the neutral plane at or near the midplane of the OLED layer 506. In some implementations, the mechanical properties of the back stiffening layer 504, and the frontplate layer 512 can be controlled, so as to maintain the neutral plane 506 within the OLED layer. In some implementations, the mechanical properties of the back stiffening layer 504, and the frontplate layer 512 can be controlled, so as to maintain the neutral plane 506 within the middle 50% of the OLED layer. In some implementations, the mechanical properties of the back stiffening layer 504, and the frontplate layer 512 can be controlled, so as to maintain the neutral plane 506 within the middle 20% of the OLED layer.

[0045] Referring again to FIG. 4, in some implementations, the back stiffening layer 414, or the surface-stiffened backplate layer that includes the properties of the back stiffening layer 414, can be transparent, and can include glass material. For example, if a camera or optical sensor is located behind the display, the back stiffening layer 414 can be transparent to allow light to pass from the front of the display, through the back stiffening layer 414, to the camera or sensor. In some implementations, the back stiffening layer 414 or the surface- stiffened backplate layer that includes the properties of the back stiffening layer 414 can be opaque since light from the OLED layer 410 does not need to be transmitted through it.

Therefore, the back stiffening layer 414 can be made using a large variety of materials and processes. However, the frontplate layer 406 must be transparent, because light from the OLED layer 410 must be transmitted through it. Ordinary plastic films are ill-suited as materials for the frontplate layer 406, because their modulus is relatively low, and transparent oxide thin films can be too fragile. However, the frontplate layer 406 can be made from high- modulus, transparent materials, including glass and glass composites, such as, for example, glass-fiber and polymer materials. Other high-modulus, transparent materials also can be used, such as, for example, a thin glass layer (e.g., about 30 pm - 50 pm thick), which may include high quality soda-lime or which may include ion-exchange strengthened alumino silicate.

[0046] Because the frontplate layer 406 can be covered and protected by the CW- polarization layer 402, delicate materials of the transparent frontplate layer 406 that rely on being clean and defect-free to achieve the desired mechanical properties of the frontplate layer 406 can be protected during system assembly and end use. To additionally reduce surface damage and breakage during frontplate layer lamination, the glass can be supplied in roll format with a thin, adhesion-enhancing and protective polymer layer already applied on each side.

[0047] Referring again to FIG. 5 and FIG. 7, in some implementations (particularly when the CW layer 514 and the frontplate layer 512 are on the outside of the bend 501, as shown in FIG. 7), glass used in one or more of the layers 502, 512, 514 can be fabricated to avoid the glass forming sharp shards when the glass is broken. For example, in one implementation, the glass used in one or more of the layers 502, 512, 514 can be treated with patterned ion-implantation (e.g., a grid pattern), so that when the glass breaks it is more likely to break along, or between, the pattern, thus avoiding sharp shards of glass.

[0048] In some implementations (particularly when the OLED layer 502, the CW layer 514 and the frontplate layer 512 are on the outside of the bend 501, as shown in FIG. 7), the display 500 can include the outer transparent protective film layer 511 made of transparent, flexible material that provides protection for other fragile parts of the display 500. The protective film layer 511 can include polymer materials (such as, for example, thermoplastic polyurethane (“TPU”), polyethylene terephthalate (“PET”), etc.). The transparent protective film layer 511, because of its material properties that make it less brittle than glass, can protect a user of device containing the display 500 in case of breakage of brittle sublayers of the display 500. For example, in the case of breakage of a glass layer of the display 500, the transparent protective film layer 511 can protect a user of the display 500 from delaminated shards that project outward away from the display 500, particularly along an outside surface of a bent or curved portion of the display 500, by restraining the shards from poking through the film.

[0049] In some implementations, the transparent protective film layer 511 might not be added to the display 500 when the display 500 is manufactured or before the display is sold in a finished product to an end user. For example, the protective film layer 511, in some implementations, can be added to the display 500 by the user of a device that includes the display 500. In some implementations, the transparent protective film layer 511 can be attracted and attached to the other layers of the display 500 by static electric forces between the protective film layer 511 and other portions of the display 500. In some implementations, the transparent protective film 511 can be attached to the other layers of the display 500 by an adhesive layer. In some implementations, the transparent protective film layer 511 can be removable and replaceable by an end user of a device that includes the display 500.

[0050] In some implementations, to enhance the safety of a device that includes the display 500 and to protect users of a computing device that includes the display 500, the computing device containing the display 500 can provide different functionality to a user when a protective film layer 511 is coupled to the display than when a protective film layer 511 is missing from the display 500. For example, when a protective film layer 511 is coupled to the display 500, the full functionality of the computing device that includes the display 500 can be provided to the user. However, when the protective film layer 511 is missing from the display 500, a limited functionality of the device containing the display 500 can be provided to the user. For example, in some implementations, when the protective film layer 511 is missing from the display 500, a warning message (for example,“WARNING - protective film not installed, device susceptible to breakage. Use at your own risk”) may be provided by the display 500 to the user, which the user must clear (e.g., by touching an icon on the display 500 to confirm that the user wants to use the device even without the presence of the protective film), before the user is able to access the full functionality of a device including the display 500. For example, in some implementations, when the protective film layer 511 is missing from the display 500, the computing device may continue to provide limited functionality in the form of providing notification services to a user (e.g., notifications of incoming text messages, emails, alarms, etc.) but may be prevented from executing a plurality of applications (e.g., game applications, email and text message composition applications, etc.).

[0051] In some implementations, when the protective film layer 511 is missing from the display 500, the full functionality of the device containing the display 500 can be provided to the user only when the display is in a particular configuration. For example, the full functionality of the device may be provided to the user when the display is in a flat, unbent configuration, or when a minimum bend radius of the foldable display exceeds a threshold bend radius, and the full functionality of the device may not be provided to the user when the display is in a configuration that includes a bend that has a radius below the threshold radius.

[0052] In some implementations, when the protective film layer 511 is missing from the display 500, the response of a touch layer of the display in a particular portion (or portions) of the display can be disabled to discourage the user from touching that portion (or portions) of the display. For example, to discourage a user from interacting with the portion of the touch layer that lies under a foldable portion of the display (e.g., because the foldable portion may be relatively more susceptible to breakage than an unbendable portion), a response to touch inputs to the foldable portion of the display can be disabled when the protective film layer 511 is missing from the display.

[0053] The presence of a protective film layer 511 can be determined in a number of different ways. For example, protective film layers 511 approved for use with a display 500 can include an indication of their approved status that can be sensed when the protective film layer is in position on the surface of the display. For example, the protective film layer 511 can include an optical indication (e.g., a barcode, a QR barcode) that may be detectable in visible or invisible (e.g., infrared) wavelengths. The optical indication can be detected by an optical sensor (e.g., a camera) in the device that contains the display 500. For example, the optical indication in the protective film layer may be placed over a dedicated, inexpensive sensor in the device when the protective film layer is properly installed on the display, or may be placed over a built-in front-facing camera of the device when the protective film layer 511 is properly installed on the display 500, or may be detectable when the display is held in front of a mirror and a front facing camera of the device is used to detect a reflected image the optical indication in the mirror. In other implementations, the presence of a properly installed approved protective film layer 511 can be detected capacitively. For example, each protective film layer 511 may include a unique pattern that is sensed by the touch layer of the device that includes the display 500. After installation of the protective film layer 511, the user may enter a unique serial number for the protective film layer into the device, and the entered serial number, along with the detected capacitive pattern, can be transmitted to a server for comparison. If a valid comparison is received, the server can send an authentication code to the device, which can be used to unlock the full functionality of the device containing the display. Other techniques can be used to detect and authenticate approved protective film layer 511. For example, the protective film layer 511 may include an RFID chip that sends a unique signal to the device containing the display 500 to indicate that the protective film layer 511 is present on the surface of the display 500.

[0054] FIG. 8 is an example flowchart of a process 800 of providing computing device functionality to a user of a computing device that includes a foldable display. In the process 800, device functionality is provided to a user of a computing device that includes a foldable display (802). A determination is made whether the foldable display includes a protective cover film (804). If the protective cover film is present, then the full device functionality is provided to the user (806). If the protective cover film is not present, then a determination can be made as to whether the foldable display is in an approved configuration (e.g., when a minimum bend radius of the foldable display exceeds a threshold bend radius) (808). If the condition of being in the approved configuration is met, then the full functionality of the device can be provided to the user (806). If the protective cover film is not present, and if the condition of being in the approved configuration is not met or if the condition is not applied, then the full functionality of the device may not be provided to the user and only a limited functionality of the device may be provided to the user (810). For example, when limited functionality of the device is provided to the user (810), a warning message may be provided to the user (812), or execution of a plurality of applications by the computing device can be prevented (814), or a response to a user’s touch on the display in a portion of the display can be prevented (816).

[0055] The devices and apparatuses described herein can be included as part of a computing device, that includes, for example, a processor for executing instructions and a memory for storing the executable instructions. Specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. Example embodiments, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein.

[0056] Implementations of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Implementations may be implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., in a machine-readable storage device or in a propagated signal, for execution by, or to control the operation of, data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. A computer program, such as the computer program(s) described above, can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

[0057] Method steps may be performed by one or more programmable processors executing a computer program to perform functions by operating on input data and generating output. Method steps also may be performed by, and an apparatus may be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit).

[0058] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer also may include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, solid state drives, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in special purpose logic circuitry.

[0059] To provide for interaction with a user, implementations may be implemented on a computer having a display device, e.g., a cathode ray tube (CRT) or liquid crystal display (LCD) or light emitting diode (LED) monitor, for displaying information to the user and a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback or notification, e.g., email or text message; and input from the user can be received in any form, including acoustic, speech, or tactile input, email or text message.

[0060] While certain features of the described implementations have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the implementations.

Claims

WHAT IS CLAIMED IS:

1. A computing device comprising:

at least one processor;

memory storing instructions executable by the processor;

and

a foldable display, the foldable display including:

a back stiffening layer;

a transparent frontplate layer;

a transparent cover window layer;

a transparent, flexible protective film layer disposable on the cover window layer, wherein the protective film layer includes a polymer material; and

an OLED display layer disposed between the back stiffening layer and the transparent frontplate layer, the OLED display layer characterized by a Young’s modulus that is lower than a Young’s modulus of the transparent frontplate layer and that is lower than a Young’s modulus of the back stiffening layer,

wherein a neutral plane of the foldable display is located within the OLED display layer,

wherein the foldable display is configured to be folded around a bend having a radius of less than 5 mm with the cover window layer being on an outside of the bend.

2. The computing device of claim 1, wherein the polymer material is selected from the group consisting of thermoplastic polyurethane and polyethylene terephthalate.

3. The computing device of claim 1 or claim 2, wherein the frontplate layer includes glass.

4. The computing device of claim 3, wherein the glass of the frontplate layer is treated with patterned ion-implantation to induce relative weaknesses in the glass along a pattern due to the patterned ion-implantation.

5. The computing device of any of claims 1-4, wherein the protective film layer, when disposed on the cover window layer, is attached to the cover window layer by static electric forces.

6. The computing device of any of claims 1-4, further comprising an optically clear adhesive layer between the protective film layer and the cover window layer that bonds the protective film layer to the cover window layer.

7. The computing device of any preceding claim, further comprising a sensor configured to determine when the protective film layer is disposed on the cover window layer.

8. The computing device of claim 7, wherein the sensor includes a camera disposed below the foldable display.

9. The computing device of claim 7 or claim 8, wherein the camera is configured to detect a predetermined infrared optical indication in the protective film layer when the protective film layer is disposed on the cover window layer.

10. The computing device of claim 7, further comprising:

a touch layer disposed between the back stiffening layer and the transparent frontplate layer,

wherein the sensor includes a capacitive sensor configured to sense a predetermined capacitive pattern in the protective film layer to determine when the protective film layer is disposed on the cover window layer.

11. The computing device of claim 10, wherein the touch layer includes the capacitive sensor.

12. The computing device of any of claims 7-11, wherein the instructions include instructions that, when executed by the processor, cause the processor to receive a signal from the sensor indicating that the protective film layer is not disposed on the cover window layer.

13. The computing device of claim 12, wherein the instructions include instructions that, when executed by the processor, cause the processor, in response to receiving the signal, to place the computing device into a limited execution mode in which less that than the full functionality of the computing device is provided to a user of the computing device.

14. The computing device of claim 13, wherein the instructions include instructions that, when executed by the processor, cause the processor to place the computing device into the limited execution mode when the foldable display is in a first physical configuration and not to place the computing device into the limited execution mode when the foldable display is in a second physical configuration.

15. The computing device of claim 14, wherein the first physical configuration includes a configuration in which a bend radius of the foldable display is less than a threshold bend radius, and wherein the second physical configuration includes a configuration in which a bend radius of the foldable display is greater than the threshold bend radius.

16. The computing device of any of claims 13-15, wherein, when the computing device is in the limited execution mode, the computing device is prevented from

executing a plurality of predetermined applications.

17. A method of providing functionality to a user of a computing device that

includes a foldable display, the method comprising:

determining if protective cover window film is present on the foldable display;

and

when the protective cover window film is present on the foldable display, providing a full functionality of the device to the user, and when the protective cover window film is not present on the foldable display, providing a limited functionality of the device to the user.

18. The method of claim 17, wherein providing the limited functionality to the user includes preventing execution of a plurality of applications by the user.

19. The method of claim 17 or 18, wherein providing the limited functionality to the user includes disabling a touch sensor response in a portion of the foldable

display.

20. The method of claim 17 or 18 or 19, wherein providing the limited functionality to the user includes displaying a warning message to the user.