THERMOFORMED DEVICE HAVING OLED DISPLAY AND METHODS OF MANUFACTURING SAME - Patent application

Abstract

A curved human interface device is formed by thermoforming a stack including a front substrate formed of a transparent first thermoplastic material, an OLED display configured to display images through the front substrate, and a thermomechanical buffer layer formed of a transparent second thermoplastic material disposed between the front substrate and the OLED display. Heat is applied to the stack to raise the temperature of the front substrate and buffer layer to respective processing temperatures at which the first and second thermoplastic materials become flexible. The stack is thermoformed while the thermoplastic materials are flexible to form the curved human interface device. The second thermoplastic material (12m) has a lower stiffness than the first thermoplastic material at the respective processing temperatures (T1, T2).

Description

[Technical Field]

[0001] The present disclosure relates to curved OLED devices and methods of making such devices. [Background technology]

[0002] A (human) interface device, such as a touch panel, may comprise various components, such as a display device and optional sensors for human interaction with the device. While it is relatively common to fabricate display screens on flat substrates, adding curvature can be challenging. Curved (3D) substrates can be fabricated using methods such as thermoforming. Thermoforming typically involves deforming a material (stack) at elevated temperatures. For example, the substrate can be deformed to conform to the shape of a mold. Electronic circuits can be included in the stack to produce curved devices with functionality dependent on the electronic components within the circuit. For example, if an OLED display could be included in a thermoformed stack, various new applications could be enabled in the fabrication of curved (human) interfaces. However, embedding certain functions, such as OLEDs, into thermoformed / in-mold electronics has remained challenging until now due to, for example, the high temperatures and distortions associated with such processes. For example, lowering the temperature can be difficult due to material processing requirements, such as curing constraints. For example, distortion can be reduced by using smaller curvatures or smaller OLEDs, but this limits applications. A further problem that can arise, particularly with the single foil approach to in-mold electronics, is the occurrence of visual defects on the user side (front substrate) of the device. Such defects can arise, for example, due to local deformations from circuit lines, especially in larger devices such as SMD chips and OLEDs, and the adhesives required to hold those SMD components in place during formation. Summary of the Invention [Problem to be solved by the invention]

[0003] There is a need for easy manufacturing of curved human interface devices, particularly to allow for the inclusion of OLED displays during the thermoforming process. [Means for solving the problem]

[0004] An aspect of the present disclosure relates to a method for manufacturing a curved device by thermoforming a stack comprising an OLED display. A front substrate is formed of a transparent first thermoplastic material, and a thermomechanical buffer layer is formed of a transparent second thermoplastic material. The buffer layer is disposed between the front substrate and the OLED display. The stack is thermoformed into a three-dimensional (non-planar) shape to form the curved device. During or prior to thermoforming, heat is applied to the stack to raise the temperature of the front substrate and buffer layer to a processing temperature. The materials of the front substrate and buffer layer are selected so that the second thermoplastic material has a lower stiffness (stress / strain) than the first thermoplastic material at the processing temperature.

[0005] The inventors surprisingly found that inserting such a buffer layer can allow an OLED display to be included in the stack during the thermoforming process, where the OLED maintains basic functionality while causing catastrophic damage to the OLED (without the buffer layer). Without being bound by theory, the reduced damage can be partially explained by the buffer layer's lower stiffness, which allows the buffer layer to deform more than the front substrate, thereby reducing mechanical stress on the OLED, which might otherwise be transferred directly to the front substrate and, for example, cause cracks in its moisture barrier layer. Even with the reduced mechanical stress, however, it is expected that the OLED may be damaged by thermal stress. However, the inventors have actually found that the OLED can remain relatively cool while heat is applied to the stack. Even if the applied heat is carefully controlled, at least the front substrate and the buffer layer need to be heated to become flexible while in close proximity to or even in contact with the OLED. Yet, the OLED does not need to be heated to the same temperature. This can be explained, at least in part, by the additional heat capacity of the buffer layer. As will be appreciated, the heat capacity of a material undergoing a phase transition can be relatively high if the heat is used to change the state of the material rather than to increase its temperature. This is particularly true when the thermoplastic material forming the buffer layer has a lower stiffness than the front substrate at the respective processing temperatures. For example, the processing temperature at which the buffer layer undergoes a phase transition can be lower than the processing temperature of the front substrate. Thus, due to a synergistic combination of properties, the buffer layer can help reduce both thermal and mechanical stresses on the OLED during the thermoforming process.

[0006] These and other features, aspects, and advantages of the devices, systems, and methods of the present disclosure will become better understood from the following description, appended claims, and accompanying drawings. [Brief explanation of the drawings]

[0007] [Figure 1A] FIG. 1A shows a planar (flat) stack including an OLED display and a front substrate with a thermomechanical buffer layer between them. [Figure 1B] FIG. 1B shows a curved human interface device formed by thermoforming the stack. [Figure 2A] FIG. 2A shows the heating and thermoforming of the stack using a mold shape. [Figure 2B] FIG. 2B shows the heating and thermoforming of the stack using a mold shape. [Figure 2C] FIG. 2C shows the application of a backing layer to the stack by injection molding using an alternative mold configuration. [Figure 3A] FIG. 3A shows a cross-sectional view of another stack layout. [Figure 3B] FIG. 3B shows the corresponding front face of a curved human interface device that may result from thermoforming the stack. [Figure 4A] FIG. 4A shows a photograph of a curved human interface device with an OLED display fabricated according to the present method. [Figure 4B] FIG. 4B shows a photograph of a curved human interface device with an OLED display fabricated according to the present method. [Figure 5A] FIG. 5A shows a photograph of another such device with an integrated OLED. [Figure 5B] FIG. 5B shows a photograph of another such device with an integrated OLED. [Figure 5C] FIG. 5C shows a photograph of another such device with an integrated OLED. [Figure 6A] FIG. 6A shows a comparison of a stack thermoformed with an OLED and a stack thermoformed without an OLED, respectively. [Figure 6B]FIG. 6B shows a comparison of stacks thermoformed with and without OLEDs, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0008] The terms used to describe particular embodiments are not intended to be limitations of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. The word "and / or" includes any and all combinations of one or more of the associated listed items. It will be understood that the words "comprising" and / or "comprising" specify the presence of the stated feature but do not exclude the presence or addition of one or more other features. Furthermore, when a particular step of a method is referenced as following another step, it will be understood that it may follow immediately after said other step, unless otherwise specified, or that one or more intermediate steps may be performed prior to performing the particular step. Similarly, when a connection between structures or components is described, it will be understood that this connection may be established directly or through intermediate structures or components, unless otherwise specified.

[0009] The present invention will now be described more fully with reference to the accompanying drawings, in which embodiments of the invention are shown. In the drawings, absolute and relative sizes of systems, components, layers, and regions may be exaggerated for clarity. Embodiments may be described with reference to schematic and / or cross-sectional illustrations of sometimes idealized embodiments and intermediate structures of the invention. In the description and drawings, like numbers refer to like elements throughout. Relationship terms and their derivatives should be construed to refer to the orientation shown in the drawings being described or discussed at the time. These relationship terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation, unless otherwise stated.

[0010] FIG. 1A shows a planar (flat) stack 10 including an OLED display 13 and a front substrate 11 with a thermomechanical buffer layer 12 therebetween; FIG. 1B shows a curved human interface device 100 formed by thermoforming the stack 10; FIGS. 2A and 2B show heating and thermoforming of the stack; and FIG. 2C shows the application of an optional backing layer 18.

[0011] Some aspects of the present disclosure relate to the fabrication of curved devices 100. For example, (out-of-plane) curvature can be introduced by applying a deformation process to a planar stack 10. Preferably, the deformation process includes thermoforming. For example, the deformation process includes applying a predetermined macroscopic shape to the stack for thermoforming. Thermoforming is generally understood as a manufacturing process in which a thermoplastic (thermosoftening plastic) material is heated to a pliable forming temperature. Typically, above its glass transition temperature (Tg) and below its melting point, the physical properties of a thermoplastic plastic change dramatically without an associated phase change. The heated substrate can be formed into a specific shape, for example, using a mold, and trimmed to create a usable product. Typically, the stack is heated to a temperature high enough to allow the stack to be stretched into or onto a mold 21, as shown in FIG. 2A, and then cooled to the finished shape.

[0012] A particularly preferred version of thermoforming is also known as high-pressure molding. Another version of thermoforming is known as vacuum forming, which may require higher temperatures. For example, a machine can be used to heat the stack and stretch it over a mold using high pressure and / or vacuum. This method is typically used for sample and prototype parts. In other or additional applications, a manufacturing machine is utilized to heat and shape the substrate in a continuous, high-speed process, and optionally trim formed parts from the stack. Alternatively, or in addition to thermoforming, other deformation processes, such as injection molding, blow molding, rotational molding, and other forms of plastic processing at elevated temperatures, can also be used to apply the present teachings. Thus, when a thermoforming process or temperature is referenced herein, it may also be applicable to other similar processes. In some embodiments, a backing layer 18 is applied to the backside of the stack by injection molding, using, for example, a mold 22, as shown in FIG. 2C. For example, a thermosetting material is melted and injected between the mold 22 and the stack.

[0013] 1A, the stack 10 comprises a front substrate 11. For example, the front substrate comprises or consists essentially of a first thermoplastic material 11m, which is preferably transparent or at least translucent (to visible light). In a preferred embodiment, the stack comprises an OLED display 13 configured to display images through the front substrate 11. Most preferably, a thermomechanical buffer layer 12 is disposed between the front substrate 11 and the OLED display 13. For example, the buffer layer 12 comprises or consists essentially of a second thermoplastic material 12m, which is preferably transparent or at least translucent.

[0014] In one embodiment, heat H is applied to the stack 10, as shown in Figure 2A, for example. This may increase the temperature of at least the front substrate 11 and buffer layer 12. Preferably, the heat is applied so that the front substrate and buffer layer reach respective processing temperatures T1, T2. At the respective processing temperatures, the first thermoplastic material 11 and second thermoplastic material 12m may become pliable (at least substantially more pliable than at room temperature 20°C).

[0015] In one embodiment, as shown in Figure 2B, the stack 10 is thermoformed, preferably while the thermoplastic materials 11m, 12m are flexible, to form the curved human interface device 100. Although the figure shows the heat H being applied before thermoforming, the heat can alternatively or additionally be applied during thermoforming.

[0016] As described herein, the second thermoplastic material 12m preferably has a lower stiffness than the first thermoplastic material 11m at the respective processing temperatures T1, T2. In other words, the second thermoplastic material 12m is more flexible or pliable, i.e., more easily deformed, than the first thermoplastic material 11m, at least during the thermoforming process. For example, the second thermoplastic material 12m can have a lower elastic and / or plastic modulus than the first thermoplastic material 11m (e.g., at least 10 percent, preferably at least 20 percent, or even at least 50 percent lower) at the same or nearly the same processing temperatures T1, T2.

[0017] According to some aspects, the methods described herein can be used to fabricate a curved human interface device 100, such as that shown in FIG. 1B. In one embodiment, the device includes a stack 10 having a front substrate 11 formed from a transparent first thermoplastic material 11m, an OLED display 13 configured to display images through the front substrate 11, and a thermomechanical buffer layer 12 formed from a transparent second thermoplastic material 12m disposed between the front substrate 11 and the OLED display 13. Preferably, the curved human interface device 100 is formed by the thermoformed stack. For example, the front substrate 11 and buffer layer 12 are simultaneously thermoformable at processing temperatures T1 and T2 at which the first and second thermoplastic materials 11m and 12m become flexible. Most preferably, the second thermoplastic material 12m has a lower stiffness than the first thermoplastic material 11m at the processing temperatures T1 and T2.

[0018] In some embodiments, the temperature T2 of each of the buffer layers 12 can remain lower than the temperature T1 of the front substrate 11 during thermoforming. For example, the second thermoplastic material 12m has a lower glass transition temperature and / or melting temperature than the first thermoplastic material 11m, e.g., at least 5 or 10 degrees lower, preferably more. Thus, when applying heat, the energy can be used to first induce a substantial phase change in the buffer layer 12 at a relatively low temperature T2, while the front substrate 11 can reach a higher temperature T1 before a substantial phase change occurs.

[0019] In some embodiments, the second thermoplastic material 12m may be softened or even (partially) melted, while the first thermoplastic material 11m is softened less, or at least not melted, so that the flow of the second thermoplastic material 12m can substantially buffer mechanical stresses between the front substrate 11 and the OLED display 13 during stack deformation, while melting or other phase transitions can also account for a significant portion of the thermal energy.

[0020] In some embodiments, the OLED display 13 has a lower temperature T3 during thermoforming than the front substrate 11, and most preferably, also lower than the buffer layer 12. Alternatively or additionally, the substrate temperature in the covered portions of the device (by the second thermoplastic material and / or OLED) can be lower than the uncovered sections. In one embodiment, the stack has a lower temperature T3 in the area of the OLED display 13 than in the surrounding areas (not overlying the OLED) during thermoforming. For example, the temperature may be lower due to the effect of the buffer layer 12 and / or the inherent properties of the OLED display. In some embodiments, the OLED itself can have a relatively high heat capacity, e.g., higher than the front substrate 11 and / or buffer layer 12. In other or further embodiments, the stack 10 is provided with a heat sink and / or heat shield 17 attached to the OLED display 13, at least during the application of heat H. For example, a heat sink can be attached to the OLED to draw heat away from the OLED, keeping it relatively cool. For example, a heat shield can be placed over the OLED display 13 to shield the OLED from heat, whether radiated or otherwise applied. It will be appreciated that, for example, using a material such as a metal with a relatively high heat capacity and reflectivity, the functions of the heat sink and heat shield can be combined into a single structure that is attached over the OLED.

[0021] In some embodiments, the heat H is applied by radiation, preferably in the infrared wavelength range. For example, the stack 10 is heated by one or more IR lamps. In a preferred embodiment, the heat H is applied by radiation from (at least) one side of the front substrate 11 (i.e., the top side in FIG. 2A ). For example, the radiation can be applied exclusively to the front side, causing this side to heat first, while the opposite side (where the OLED is located) can remain relatively cooler. In other or further embodiments, as shown, the heat H is applied by radiation from both sides of the stack. For example, heating of the OLED can be reduced by using a heat shield to block or reflect the radiation. This can also be achieved by using a mask to irradiate the stack at a location other than the OLED. In some embodiments, heat is applied by radiation from one side of the OLED display 13, where a heat shield 17 or mask is positioned to block or reflect the radiation so that it does not reach the OLED display 13. Although radiation is preferred, other ways of applying heat to one or both sides of the stack can be envisaged, for example by contact or convection from one or both sides, which can also be done selectively, for example to avoid direct heating of the OLEDs.

[0022] In some embodiments, the respective processing temperatures T1, T2 (each) during thermoforming, preferably high-pressure forming, of the front substrate 11 and buffer layer 12 are between 100 and 200°C, preferably less than 160°C, most preferably less than 140°C, or even less than 130°C, for example, 130-160 degrees Celsius (130-160°C). During thermoforming, the temperature of the OLED is preferably lower than the temperature of the front substrate 11 and / or buffer layer 12, for example, at least 10, 20, or even 30 degrees Celsius lower. Preferably, the temperature of the OLED is below 110°C, most preferably below 105°C or lower, and is kept at least below a temperature at which the OLED is critically damaged (loses basic functionality).

[0023] In a preferred embodiment, the first thermoplastic material 11m has a glass transition temperature below 160°C, preferably below 150°C, and most preferably below 140°C, e.g., in the range of 100-130°C. In some embodiments, the second thermoplastic material 12m has a glass transition temperature lower than that of the first thermoplastic material 11m, e.g., at least 5 or 10 degrees lower. Various combinations of thermoplastic materials can be used to form the front substrate 11 and / or buffer layer 12. In one embodiment, the front substrate 11 is made of polycarbonate (PC), which has a glass transition temperature of approximately 150°C (423K), and thus gradually softens around this point, becoming deformable above approximately 155°C (428K). For example, when deforming PC, the ideal processing temperature is 155-160°C. In another embodiment, the front substrate 11 is made of poly(methyl methacrylate) (PMMA). Typically, the glass transition temperature of PMMA ranges from 85 to 165°C (depending on composition). Preferably, PMMA is used with a processing temperature around 130°C (and a Tg below). Other materials, such as ABS (acrylonitrile-butadiene-styrene), PETG (a thermoformable version of polyethylene terephthalate), PVC (polyvinyl chloride), etc., can also be used for the front substrate 11. Of course, exemplary temperatures may be different for other materials, but are preferably not excessively high.

[0024] In some embodiments, the second thermoplastic material 12m comprises a thermoplastic elastomer. Thermoplastic elastomers (TPEs), sometimes called thermoplastic rubbers, are a type of copolymer or physical mixture of polymers (usually plastic and rubber) that possess both thermoplastic and elastomeric properties. For example, the second thermoplastic material 12m substantially softens when heated to temperatures significantly higher than room temperature, e.g., in the range of 80-140°C. In a preferred embodiment, the second thermoplastic material 12m comprises thermoplastic polyurethane (TPU) or polyvinyl butyral (PVB). Thus, for example, a combination of PMMA and TPU can be thermoformed at a processing temperature of around 130°C, while a combination of PC and TPU can be thermoformed at a processing temperature of around 160°C.

[0025] In some embodiments, as shown in FIG. 1A , the stack 10 includes an electrical circuit 14 having circuit lines 141. Preferably, the circuit lines are printed on the thermomechanical buffer layer 12. For example, the circuit lines 141 are printed using a conductive ink, e.g., containing silver (Ag). The circuit lines are preferably printed on the buffer layer 12 after lamination to the front substrate 11 but before thermoforming. Other components are also preferably applied between the lamination and thermoforming steps, although these steps could, in principle, also be applied to the buffer layer 12 before lamination. Typically, the circuit lines 141 are electrically connected to electronic components disposed on the buffer layer 12, including the OLED display 13. In addition to reducing damage to delicate components, such as the OLED, the buffer layer has been found to be useful in reducing visible defects that can occur as a result of thermoforming. For example, defects may be visible on the front substrate when the stack includes relatively large and / or rigid components, such as OLEDs or other devices, e.g., SMDs, chips, etc. Alternatively, or in addition to printing circuit components on the buffer layer 12, it may be envisaged to print them directly on the front substrate 11, although this may lead to visible artifacts depending on the size and composition of the printed components, e.g., in relation to the thickness of the front substrate 11. If required, they may instead be located at the edge of the device.

[0026] In some embodiments, the stack 10 includes a sensor 15 disposed between the front substrate 11 and the buffer layer 12. For example, the stack can be thermoformed into a curved touch screen device or touch button. Preferably, the sensor 15 is configured as a proximity sensor, e.g., a capacitive sensor device capable of detecting a user interaction, e.g., a touch on the front substrate 11. Most preferably, the proximity sensor 15 is substantially transparent to allow the OLED display 13 to be viewed through the sensor. In some embodiments, components between the front substrate 11 and buffer layer 12, such as the sensor 15 shown in FIG. 1A, are electrically connected using via connections 14v through the buffer layer 12.

[0027] Although it is preferable to place the proximity sensor 15 as close as possible to the front substrate 11, e.g., to better detect touch events, in principle the proximity sensor 15 can also be placed elsewhere, for example between the buffer layer 12 and the OLED display 13 or behind the OLED display 13, and / or be integrated as part of the OLED display 13. Alternatively, or in addition to a proximity sensor, other types of sensors can be envisaged, such as light sensors or motion / movement sensors. For example, it can also be envisaged to detect movement of the whole device or parts thereof, for example pressing a (round) button having an OLED display formed by the present method.

[0028] In some embodiments, the stack 10 includes a graphical pattern 16 formed by one or more layers of opaque material 16m. Preferably, the graphical pattern 16 includes at least one window 16w for light L emitted from an image displayed on the OLED display 13 or light emitted or received from other components on the substrate, such as LEDs or light sensors (not shown here). For example, the opaque material 16m can be used to hide circuitry and other components disposed on the buffer layer 12 or between the buffer layer 12 and the graphical pattern 16. In some embodiments, the front substrate and / or buffer layer 12 are configured to function as a light guide structure, with the graphical pattern, which may be white on the side facing the buffer layer, for example, to reflect more light along the light guide. The figures of the present disclosure show the graphic pattern 16 between the front substrate 11 and the buffer layer 12, which is preferred, but it can also be envisioned that the graphic pattern or another pattern is applied onto the front substrate 11 (e.g., including a scratch-resistant layer) or between the buffer layer 12 and the circuitry, for example, applying the graphic pattern 16 onto the buffer layer 12 before or after applying the circuitry.

[0029] In some embodiments, the front substrate 11 has a thickness of 1 or 2 millimeters, preferably less, for example, 250 to 700 μm. As will be appreciated, the present method may allow for a relatively thin front substrate 11 because visible artifacts from components behind the substrate can be mitigated by the buffer layer 12 therebetween. Advantageously, it has been found that the buffer layer 12 can be effective already at a relatively small thickness, for example, at least 5 or 10 micrometers, or more. In one embodiment, the buffer layer 12 is applied as a sheet, for example, by lamination to the front substrate 11 and / or OLED display 13. In another or further embodiment, the buffer layer 12 is printed, for example, onto the front substrate 11 and / or OLED display 13. The inventors have found that, in particular, relatively thin buffer layers can be most reliably applied by printing, for example, at a thickness of less than 20 micrometers, less than 10 micrometers, down to 5 micrometers, or even less. The effectiveness of the buffer layer generally increases with thickness, and therefore, preferably, the buffer layer 12 has a thickness of 20 to 1000 μm, more preferably 50 to 500 μm, or 100 to 250 μm. As will be appreciated, even with the buffer layer, the total thickness of the front substrate 11 and buffer layer 12 can be smaller than a conventional front substrate 11 without the buffer layer 12; for example, the total thickness is less than 2 millimeters, less than 1 millimeter, or even less than 0.5 millimeters. The thinner the total thickness, the closer the OLED display 13 can appear to the front of the device. The OLED is preferably as thin as possible. The surface area of the OLED can be, for example, one square centimeter or more, e.g., up to several tens of cm. 2 It can vary up to.

[0030] 3A shows a cross-sectional view of another stack layout, and FIG. 3B shows the corresponding front view of a curved human interface device 100 that may result from thermoforming the stack 10. In some embodiments, the stack 10 includes optoelectronic components, such as an OLED display 13a and / or LEDs 13b. While the present teachings are particularly useful for the unexpected ability to integrate OLED displays in the thermoforming process, it will be appreciated that the teachings may also be beneficial for integrating other types of devices (display or not). Alternatively, or in addition to OLED displays, other types of displays, such as electronic ink (E-ink) devices / paper, may also be integrated into the stack.

[0031] In some embodiments, the stack 10 includes sensor components, such as capacitive sensors 15a and / or other types of sensors 15b, such as optical sensors, proximity sensors, time-of-flight sensors, motion sensors, etc. For some components, it may be preferable to print them. Other components can be arranged in other ways. In some embodiments, the stack 10 includes a circuit board 19 (e.g., PCB), surface-mounted components, integrated chips, FSRs, etc. These and other components, including the OLED, can be connected to an electrical circuit, including circuit lines 14l on the buffer layer 12, on the front substrate 11 (e.g., printed), and / or via connections 14v through the buffer layer 12 and / or additional layers, such as an optional backing layer 18.

[0032] In some embodiments, the stack includes a light guide structure. For example, a light shielding wall 12w can be positioned to guide light from LEDs 13b to the patterned light outlets, such as to form indicator lights as shown. In some embodiments, the backing layer 18 includes a reflective, e.g., white, material that can help guide light to the respective patterns 16p and / or windows 16w. For example, this can be achieved by vacuum forming or injection molding.

[0033] Typically, the components or devices integrated into the stack are relatively rigid, at least compared to the front substrate 11 and / or buffer layer 12. The manner in which the components are attached can also contribute to local rigidity. For example, components can be attached to the circuit lines using an isotropic conductive adhesive (ICA). This method can therefore reduce thermal and mechanical stresses on the OLED and / or other components.

[0034] 4A and 4B show photographs of a curved human interface device with an OLED display fabricated according to the present method. As shown, different images can be displayed on the device, forming, for example, dynamic indicator lights and / or buttons.

[0035] Figures 5A-5C illustrate integrity testing of another such device with an integrated OLED. Photographs of the functioning device are shown therein 11, 18, and 139 days after fabrication, demonstrating the reliability of products fabricated according to this method. In one embodiment, a curved human interface device as described herein is fabricated by applying a 0.7 mm thick TPU buffer layer to a 2 mm thick PMMA front substrate. An OLED display was applied directly to the TPU buffer layer. This stack was laminated at 90 degrees and later thermoformed at 130°C. The stack was formed using a positive half-cylinder mold as shown, in this case applying the TPU only locally rather than over the entire area (the former is preferred).

[0036] FIG. 6A shows a stack thermoformed without an OLED, and FIG. 6B shows the same stack, but thermoformed with an OLED display 13, which is peeled from the stack after thermoforming, leaving behind a mark 13i. As previously shown, e.g., with reference to FIGS. 2A-2C, the OLED display 13 is preferably an integral part of the stack during the thermoforming process. Therefore, the buffer layer and / or front substrate can be at least partially melted and / or deformed by the heating and / or thermoforming process while the OLED display 13 is attached. This can leave a mark 13i, e.g., a (at least superficial) depression, in the buffer layer according to the shape of the OLED display 13. For example, this can be seen as a relatively glossy mark 13i in FIG. 6B that is not present in FIG. 6A (the rectangular dark area in FIG. 6A is not a mark, but corresponds to a window 16w through the underlying opaque layer). In some embodiments, the imprint can be used to distinguish the curved human interface devices described herein from devices in which the OLED display 13 is not part of the stack during thermoforming but is applied later in a separate step. For example, devices formed according to the methods described herein can be recognized by the shape or roughness of the buffer layer and / or front substrate. For example, the shape of the buffer layer comprises imprints 13i of the OLED display 13, such as recessed shapes or contours, as a result of the OLED being present during thermoforming. For example, the imprints 13i may have a different roughness (e.g., be smoother) than the surrounding surface. For example, the OLED display 13 may be integrally connected to the buffer layer without an additional (adhesive) layer therebetween.

[0037] While features are described herein as part of the same or separate embodiments for clarity and conciseness, it will be recognized that the scope of the present invention may include embodiments having all or some combination of the described features. For example, while embodiments have been described with respect to embedding an OLED display device into a thermoformed stack, alternative approaches to achieve similar functions and results may be envisioned by those skilled in the art with the benefit of this disclosure. For example, components and layers may be combined or separated into one or more alternatives. Various elements of the embodiments discussed and illustrated provide certain advantages, such as preventing damage and reducing visual artifacts. Of course, it should be understood that any one of the above-described embodiments or methods may be combined with one or more other embodiments or methods to provide further improvements in design and finding and matching advantages. It will be recognized that the present disclosure provides particular advantages for the manufacture of curved human interface devices and may generally be applicable to any application where heat- and / or distortion-sensitive components are involved in a thermoforming process. For example, the present methods and systems may be applied with other surface-mount devices in addition to, or as an alternative to, OLED display devices.

[0038] It is to be understood that in interpreting the appended claims, the word "comprising" does not exclude the presence of elements or operations other than those listed in a given claim, the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements, any reference signs in the claims do not limit the scope, several "means" may be represented by the same or different items or implemented structures or functions, and any disclosed devices or parts thereof may be combined with one another or separated into further parts unless expressly stated otherwise. The present invention may be configured as follows. [Section 1] A method of manufacturing a curved human interface device (100), comprising: Providing a stack (10), wherein the stack comprises: a front substrate (11) formed of a transparent first thermoplastic material (11m); an OLED display (13) configured to display an image through the front substrate (11); and a thermomechanical buffer layer (12) formed of a transparent second thermoplastic material (12m) disposed between the front substrate (11) and the OLED display (13); the providing comprising: applying heat (H) to the stack (10) to raise the temperatures of the front substrate (11) and buffer layer (12) to their respective processing temperatures (T1, T2) at which the first and second thermoplastic materials (11m, 12m) become flexible; and thermoforming the stack (10) while the thermoplastic material (11m, 12m) is flexible to form the curved human interface device (100); Including, wherein the second thermoplastic material (12m) has a lower rigidity than the first thermoplastic material (11m) at the respective processing temperatures (T1, T2); The method. [Section 2] Item 1. The method of item 1, wherein the stack (10) comprises a printed sensor (15) disposed between the front substrate (11) and the buffer layer (12). [Section 3] 3. The method of claim 1 or 2, wherein the stack (10) comprises an electrical circuit (14) having circuit lines (141) printed on the thermomechanical buffer layer (12), wherein the circuit lines (141) are electrically connected to electronic components disposed on the buffer layer (12), including the OLED display (13). [Section 4] 4. The method of any one of items 1 to 3, wherein the stack (10) comprises a graphical pattern (16) formed by one or more layers of opaque material (16m), wherein the graphical pattern (21) comprises at least one window (16w) for transmitting light (L) from an image displayed on the OLED display (13) through the front substrate (11), and wherein the opaque material (16m) is arranged to block other components and / or circuit parts on the buffer layer (12) from being seen through the front substrate (11). [Section 5] 5. The method according to any one of paragraphs 1 to 4, wherein the stack (10) is provided with a heat sink and / or heat shield (17) attached to the OLED display (13) at least during the application of heat (H). [Section 6] 6. The method according to any one of items 1 to 5, wherein the heat (H) is applied by radiation from one side of the front substrate (11). [Section 7] 7. The method of any one of paragraphs 1 to 6, wherein heat is applied by radiation from one side of the OLED display (13), where a heat shield (17) or mask is positioned to block or reflect radiation from reaching the OLED display (13). [Section 8] Item 8. The method of any one of items 1 to 7, wherein the OLED display (13) has a lower temperature (T3) than the front substrate (11) and / or buffer layer (12) during the thermoforming. [Section 9] Item 9. The method according to any one of items 1 to 8, wherein the individual processing temperatures (T1, T2) are 100 to 160 degrees Celsius, and the temperature of the OLED display (13) is kept below 110 degrees Celsius. [Section 10] A curved human interface device (100), comprising: a front substrate (11) made of a transparent first thermoplastic material (11m); an OLED display (13) configured to display an image through the front substrate (11); a thermomechanical buffer layer (12) formed of a transparent second thermoplastic material (12m) disposed between the front substrate (11) and the OLED display (13); A thermoformed stack (10) comprising: wherein the front substrate (11) and the buffer layer (12) are simultaneously thermoformable at processing temperatures (T1, T2) at which the first and second thermoplastic materials (11m, 12m) become flexible; The second thermoplastic material (12m) has a lower rigidity than the first thermoplastic material (11m) at the processing temperatures (T1, T2), The shape of the buffer layer (12) comprises an imprint formed by the presence of the shape of the OLED display (13) during thermoforming. The curved human interface device (100). [Section 11] Item 11. The method or device according to any one of items 1 to 10, wherein the second thermoplastic material (12m) has a lower glass transition temperature and / or melting temperature than the first thermoplastic material (11m). [Section 12] Item 12. The method or device according to any one of items 1 to 11, wherein the first thermoplastic material (11m) has a glass transition temperature in the range of 100 to 130°C. [Section 13] Item 13. The method or device according to any one of items 1 to 12, wherein the second thermoplastic material (12m) comprises a thermoplastic elastomer. [Section 14] Item 14. The method or device according to any one of items 1 to 13, wherein the front substrate (11) has a thickness of 250 to 700 μm, and the buffer layer (12) has a thickness of 100 to 250 μm. [Section 15] Item 15. The method or device according to any one of items 1 to 14, wherein the front substrate (11) comprises PMMA and the buffer layer (12) comprises TPU.

Claims

1. A method for manufacturing a curved human interface device (100), comprising: Providing a stack (10), wherein the stack comprises: a front substrate (11) made of a transparent first thermoplastic material (11m); an OLED display (13) configured to display an image through the front substrate (11); and a thermomechanical buffer layer (12) formed of a transparent second thermoplastic material (12m) disposed between the front substrate (11) and the OLED display (13); the providing comprising: applying heat (H) to the stack (10) to raise the temperatures of the front substrate (11) and buffer layer (12) to their respective processing temperatures (T1, T2) at which the first and second thermoplastic materials (11m, 12m) become flexible; and thermoforming the stack (10) while the thermoplastic material (11m, 12m) is flexible to form the curved human interface device (100); Including, wherein the second thermoplastic material (12m) has a lower rigidity than the first thermoplastic material (11m) at the respective processing temperatures (T1, T2); The method.

2. 2. The method of claim 1, wherein the stack (10) comprises a printed sensor (15) disposed between the front substrate (11) and the buffer layer (12).

3. 3. The method of claim 1, wherein the stack (10) comprises an electrical circuit (14) having circuit lines (141) printed on the thermomechanical buffer layer (12), wherein the circuit lines (141) are electrically connected to electronic components disposed on the buffer layer (12), including the OLED display (13).

4. 4. The method according to claim 1, wherein the stack (10) comprises a graphical pattern (16) formed by one or more layers of opaque material (16m), and wherein the graphical pattern (16) comprises at least one window (16w) for transmitting light (L) from an image displayed on the OLED display (13) through the front substrate (11).

5. 5. The method according to any one of claims 1 to 4, wherein the stack (10) is provided with a heat sink and / or heat shield (17) attached to the OLED display (13), at least during the application of heat (H).

6. A method according to any one of claims 1 to 5, wherein the heat (H) is applied by radiation from one side of the front substrate (11).

7. 7. The method of any one of claims 1 to 6, wherein heat is applied by a radiation source from one side of the OLED display (13), and wherein a heat shield (17) or mask is placed between the radiation source and the OLED display (13) to prevent or reflect radiation of the radiation source from reaching the OLED display (13).

8. The method according to any one of claims 1 to 7, wherein the OLED display (13) has a lower temperature (T3) during the thermoforming than the front substrate (11) and / or buffer layer (12).

9. 8. The method according to any one of claims 1 to 7, wherein the individual processing temperatures (T1, T2) are between 100 and 160 degrees Celsius, and wherein the temperature of the OLED display (13) is kept below 110 degrees Celsius.

10. A curved human interface device (100), comprising: a front substrate (11) made of a transparent first thermoplastic material (11m); an OLED display (13) configured to display an image through the front substrate (11); a thermomechanical buffer layer (12) formed of a transparent second thermoplastic material (12m) disposed between the front substrate (11) and the OLED display (13); The thermoformed stack (10) comprises: wherein the front substrate (11) and the buffer layer (12) are simultaneously thermoformable at processing temperatures (T1, T2) at which the first and second thermoplastic materials (11m, 12m) become flexible; The second thermoplastic material (12m) has a lower stiffness than the first thermoplastic material (11m) at the processing temperatures (T1, T2); The shape of the buffer layer (12) comprises an imprint formed by the shape of the OLED display (13) present during thermoforming. The curved human interface device (100).

11. 11. The curved human interface device of claim 10, wherein the second thermoplastic material (12m) has a lower glass transition temperature or melting temperature than the first thermoplastic material (11m).

12. The curved human interface device according to claim 10 or 11, wherein the first thermoplastic material (11m) has a glass transition temperature in the range of 100 to 130°C.

13. The curved human interface device according to any one of claims 10 to 12, wherein the second thermoplastic material (12m) comprises a thermoplastic elastomer.

14. The curved human interface device according to any one of claims 10 to 13, wherein the front substrate (11) has a thickness of 250 to 700 μm, and the buffer layer (12) has a thickness of 100 to 250 μm.

15. The curved human interface device according to any one of claims 10 to 14, wherein the front substrate (11) comprises PMMA and the buffer layer (12) comprises TPU.

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