Methods to Fabricate Flexible OLED Lighting Devices

A method of fabricating an organic light emitting device (OLED) on a substrate includes providing a mold having surface features, forming a substrate over the mold, fabricating an OLED over the substrate while the substrate is in the mold, and removing the mold from the substrate having the OLED fabricated thereon.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

The claimed invention was made by, on behalf of, and/or in connection with one or more of the following parties to a joint university corporation research agreement: Regents of the University of Michigan, Princeton University, The University of Southern California, and the Universal Display Corporation. The agreement was in effect on or before the effective filing date of the claimed invention, and the claimed invention was made as a result of activities undertaken within the scope of the agreement.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods for fabricating flexible OILED lighting devices.

BRIEF SUMMARY OF THE INVENTION

Some embodiments of the present invention provide a method of fabricating an organic light emitting device (OLED) on a substrate including steps of providing a mold having surface features, forming a substrate over the mold, fabricating an OLED over the substrate while the substrate is in the mold, and removing the mold from the substrate having the OLED fabricated thereon.

In some embodiments, the mold is removed from the substrate by separating the mold from the substrate. In some embodiments, the mold is removed from the substrate by dissolving the mold.

In some embodiments, the mold is rigid. In other embodiments, the mold is flexible. In some embodiments, the mold has a flexural rigidity of at least 0.7 Nm.

In some embodiments, the surface features of the mold have a peak-to-trough height of at least 200 nm.

In some embodiments, the surface features of the mold have a peak-to-trough height of at least 1 micron.

In some embodiments, the surface features of the mold have a peak-to-trough height of at most 100 microns.

In some embodiments, the method further includes applying a release coating over the mold prior to forming the substrate.

In some embodiments, the substrate is formed directly over the mold without any intervening layers.

In some embodiments, the substrate is formed by applying a coating over the mold. In some embodiments, the coating is formed by applying a liquid to the mold, and subsequently curing the liquid prior to fabricating the OLED.

In some embodiments, the method further includes applying a barrier layer over the substrate before fabricating the OLED.

In some embodiments, the method further includes depositing a barrier layer over the OLED before removing the mold from the substrate.

In some embodiments, after removing the mold from the substrate, the substrate having the OLED fabricated thereon is flexible.

In some embodiments, after removing the mold from the substrate, the substrate having the OLED fabricated thereon has a flexural rigidity sufficiently low that the substrate can be wrapped around a 12-inch diameter roll without breaking.

In some embodiments, a material and thickness of the coating result in a substrate that is flexible if not supported by the mold.

In some embodiments, there is a mismatch in the coefficients of thermal expansion of the mold and the substrate.

In some embodiments, the mold includes holes that provide access through the mold to the substrate.

In some embodiments, a refractive index of the substrate is greater than 1.6. In some embodiments, the refractive index of the substrate is greater than 1.7.

Some embodiments of the present invention provide a structure including a mold having surface features; a substrate formed over the mold, the substrate formed of a transparent material and having a thickness such that the substrate, in the absence of the mold, is flexible; and an organic light emitting device fabricated over the substrate.

Some embodiments of the present invention provide a device having an organic light emitting device (OLED) disposed on a substrate having surface features. The device is prepared by the process including the steps of providing a mold having surface features, forming a substrate over the mold; fabricating an OLED over the substrate while the substrate is in the mold; and removing the mold from the substrate having the OLED fabricated thereon.

Some embodiments of the invention provide an apparatus including a belt, a mechanism to move the belt, and a flexible mold disposed on the belt, the flexible mold having surface features. The following are disposed in order along a path of the belt a dispenser attached to a source of substrate material, an energy source adapted to treat the substrate material, a plurality of dispensers attached to sources of for organic light emitting device materials, and a mechanism adapted to remove the substrate material and organic light emitting device materials from the belt.

In some embodiments, the substrate is transparent.

In some embodiments, the surface features of the mold result in the substrate having formed thereon surface features selected from spherical lenses, aspherical lenses, groves, prisms, and irregular features that have larger dimensions at the base.

In some embodiments, the device is a lighting device.

DETAILED DESCRIPTION OF THE INVENTION

Methods for Fabricating Flexible OLEDs

Building flexible OLED lighting devices on flexible substrates provide both benefits and challenges. It is easier to obtain a high refractive index from transparent plastic materials than from conventional glass substrates. This enables a better outcoupling efficiency for OLEDs on plastic. However, a flexible plastic film is very difficult to handle. Keeping it flat during fabrication process can be a challenge. Another challenge with plastic substrates is that they tend to have rough surfaces and random spikes on the surface. These defects can easily cause shorting in the OLED devices grown on them. However, the methods described herein overcome both these challenges.

FIG. 3is a high level flowchart of an exemplary method for fabricating an OLED on a substrate including a step300of providing a mold, a step310of forming a substrate, a step320of fabricating an OLED, and a step330of removing the mold from the substrate and OLED. The process shown inFIG. 3is merely exemplary and can include additional steps or fewer steps.

Step300includes providing a mold. The mold can have at least two functions: i) to act as a support during the following process steps; and ii) to generate the desired surface features on the flexible substrate to be formed on the mold in the next step. Thus, the mold can be designed to provide the desired surface features. The surface features are preferably designed to efficiently extract light from the OLED device.

The surface features on the mold are designed to produce features on the substrate that will be formed in the next step. The surface features to be made can be spherical lenses, aspherical lenses, groves, prisms, irregular features that have larger dimensions at the base, or any other topographical features that enhance light extraction. This is especially beneficial to OLED lighting devices. In some embodiments, the lens features can be radially symmetric about an axis normal to the flat surface of the mold. A spherical lens can be a hemispherical shape with H/R=1 where H and R are the peak to trough height and radius (in the plane) of the lens. Aspheric lens shape can be defined by a polynomial such as quadratic, cubic, parabolic. The aspheric lens can be shaped such that lens height H over radius R, H/R>1, H/R>2.

In some embodiments, the peak to trough height H of the surface features should be at least comparable to the thickness of the OLED device (˜100 nm). In other embodiments, H should be at least comparable to or greater than the wavelength of the light in the substrate (wavelength in vacuum divided by refractive index of the substrate material) generated in the OLED device deposited thereafter. For example, when the index of the substrate is 2.0, H should be at least comparable to 200 nm or greater. Thus in some embodiments H, can be 400 nm or greater. These minimum dimensions are preferred because, at smaller dimensions, the optics and outcoupling may be less desirable. It can also be preferred to have larger minimum dimensions to help the fabrication of the surface features on the mold. In such embodiments, the preferred H can be at least 1 μm, at least 5 μm, at least 10 μm, at least 50 μm or at least 100 μm. These minimum values for H are preferred because, as the minimum becomes larger, it becomes easier to fabricate the mold features. But, minimums different from those disclosed in this paragraph may be used depending on whether it is acceptable to trade-off optical considerations and ease of manufacturing for other considerations.

In some embodiments, the peak to trough height H of the surface features should be at most 300 μm, and preferably at most 100 μm. At larger values for H, undesirable effects may occur. For example, bubbles may form if a single thick coat is used. While these effects may be mitigated by using multiple coating steps, or through material and process parameter selection, such mitigation involves its own trade-offs. Also, if overall thickness becomes too large, flexibility may decrease, which may be undesirable for some uses.

In some embodiments, the surface features can cover an area or form an area array. Preferably, a center-to-center lateral distance between adjacent surface features is not more than ten times the value of H.

The surface features can be arranged regularly or randomly. The size can be uniform or different. It is preferred that the surface features are packed closed together with a fill factor of at least 80%, at least 90%, or at least 95%. Here Fill Factor is defined as the ratio of the surface area occupied by surface features (projection of the surface features on the base surface) over the base surface area.

In some embodiments, the mold can be rigid. This means that the mold is rigid enough to be able to withstand, without significant flexing or distortion, the normal handling associated with semiconductor or standard glass based flat panel display fabrication—i.e., the mold can easily be picked up and moved around without breaking or significantly bending. This allows the process to overcome the challenge of keeping the substrate formed on the mold flat during fabrication of the OLED. The rigidity of the mold can be determined by calculating its flexural rigidity D. This is defined as the force couple required to bend a rigid structure to a unit curvature. For a uniform substrate, flexural rigidity can be described mathematically as:

where D is flexural rigidity (in Nm), E is Young's modulus (in Nm−2), is Poisson's ratio and t is the thickness of the substrate (in m). This equation is described in J. A. Rogers, G. R. Bogart, J. Mater. Res., 16 (1), 217, 2001. The more flexible the substrate, the lower the flexural rigidity. The flexural rigidity of any substrate can be theoretically calculated if Young's modulus, Poisson's ratio and the thickness of the substrate are known.

It may be difficult to calculate flexural rigidity for thin films from material properties or from data provided in a textbook. This is especially true for composite films or multilayer films. However, once a measurement is made for a particular structure, flexural rigidity can be readily altered in a reasonably predictable way by one of skill in the art by adjusting parameters such as substrate thickness. Here we focus on the cantilever method for determining flexural rigidity. The apparatus required is a fixed angle flexometer. A rectangular strip of material is supported on a horizontal platform in a direction perpendicular to the edge of the platform. The strip is extended in the direction of its length so that an increasing part overhangs and bends down under its own weight. When the tip of the strip of material has reached a plane passing through the edge of the platform and inclined at an angle of θ=41.5° below the horizontal, the overhanging length L is equal to twice the bending length C of the specimen (C=0.5 L at θ=41.50).

Bending length (in m) is denoted by C, where C is the cube root of the ratio of flexural rigidity to the weight per unit area of the material: D=WC3, where W is weight per unit area (in Nm−2), which for a uniform strip is given by W=ρtg, such that:

Where ρ is density (in Kgm−3), g is gravitation acceleration (9.81 ms−2) and t is the thickness of the substrate (in m).

Here we use both equations 1 and 2 to determine the best mold substrate material/thickness combination to be used for making flexible electronics devices. Some examples are shown in Table 1 below. E, μ, and ρ are material properties and are determined once the material is selected.

It is common practice in the flat panel display industry to use 0.7 mm or 0.5 mm glass for display fabrication. This means a flexural rigidity of >0.7 Nm is good enough for the process. Accordingly, in some embodiments, the mold has a flexural rigidity of at least 0.7 Nm. When glass is used as the mold, the same thickness of glass can be applied. When a different mold material is used, the thickness of the material can be calculated to make sure a similar level of flexural rigidity is achieved. As can be seen in Table 1 above, stainless steel foil with a thickness of 0.33 mm has similar flexural rigidity as 0.5 mm borosilicate glass sheet. Another way to decide on the thickness of mold material is to use similar bending length. Stainless steel and glass at similar thickness give similar bending length.

In some embodiments, the mold has a flexural rigidity greater than the flexural rigidity of an assembly of the substrate and an OLED, including when the OLED includes a hard coat.

In some embodiments, the mold can include a base layer and a patterned layer having the surface features. In some embodiments, the base layer has a flexural rigidity greater than the flexural rigidity of the patterned layer.

The material for the mold can depend upon the type of material used to form the substrate and the release process. The mold can be fabricated from a material with mechanical and optical properties suitable for the process. The type of mold used can depend upon the types of surface features required and the methods available to make the surface features. If a laser is used for release the substrate, then a transparent mold material such as glass is needed.

In some embodiments, the mold can be made directly using processes such as machining or 3D printing.

In other embodiments, the mold can be formed from a master with the same shape as the desired features. A master can be made using a wide variety of materials, including semiconductor wafers and photoresists traditionally used in microfabrication. Where a master is used, the mold itself can be made by any of a variety of methods that transfer features from the master to the mold. For example, a liquid can be applied over the master, cured to solidify, and removed. Other methods, including those described herein for forming the substrate from the mold, can be used.

The features required for a mold can be machined directly onto commercially available aluminum, hardened steel, or stainless steel pieces using micromachining techniques. These can include conventional CNC machining, laser cutting, and micro-electrical discharge machining (μ-EDM). Metal molds can also be electroformed from a master immersed in a plating bath. These molds tend to be made from elemental metals such as Ni. Metal molds can also be used to emboss features into plastic sheets that have been softened by exposure to heat or solvent. When Si or glass are used to make a mold, surface features can be defined by standard semiconductor processing techniques.

Step310can include forming a substrate over the mold. As used herein, the term “over” means as measured in a direction moving away from the mold in the direction of the side of the mold with surface features, i.e., further away from the mold. The term over is intended to allow for one or more intermediate layers between the mold and the substrate. For example, where a first layer is described as “disposed over” or “formed over” a second layer, the first layer is disposed further away from mold. There may be other layers between the first and second layer, unless it is specified that the first layer is “in contact with” the second layer. For example, a cathode can be described as “disposed over” an anode, even though there are various organic layers between the cathode and anode.

In some embodiments, step310includes applying a liquid coating onto the mold and curing the coating to form the substrate over or on top of the mold. In some embodiments, the substrate can be transparent. In other embodiments, step310includes applying a solid coating onto the mold, heating the solid to form a melt wherein the melt conforms to the shape of the mold, and cooling the melt to form a solid substrate that conforms to the mold. In some embodiments, the material and thickness of the coating result in a substrate that is flexible if not supported by the mold. For example, Polyester substrate can be formed by melting the raw material (e.g. purified terephthalic acid (PTA)) and then cooled to form films. In this invention, solution deposition is preferred because of low heat and better surface quality. The thickness of the film is preferred to be larger than the height of the surface feature H. It can range from 5 μm to a few hundred μm.

In some embodiments, the substrate is formed directly over the mold without any intervening layers such that the substrate directly contacts the mold. In other embodiments, there can be one or more intervening layers between the mold and the substrate, such as, for example, a release layer.

In some embodiments, the refractive index of the substrate material can have a difference of less than 0.1 or 0.2 from the refractive index of the organic emissive materials. A high refractive index (>1.6) is preferred for better light extraction efficiency. The most preferred refractive index is a value higher than the refractive index of the light generating layer (>1.7).

Step320can include forming an OLED over the substrate while the substrate is attached to the mold. The process for forming an OLED will be discussed in more detail below with reference toFIG. 4. In some embodiments, prior to forming the OLED, a barrier layer is applied over the substrate. In some embodiments, prior to forming the OLED, bus lines can be fabricated over the substrate.

Step330can include removing the mold from the substrate having the OLED fabricated thereon. The substrate and OLED can be removed from the mold in a number of different ways as described in more detail below with reference toFIGS. 6-8.

FIG. 4illustrates an exemplary OLED fabrication process321that can be used in step320. Process321can include a step322of applying an anode, a step323of applying organic material, a step324of applying a cathode, a step325of applying a barrier layer, and a step326of applying a hard coat. Fabrication process321is merely exemplary and can include additional steps or fewer steps. For example, it can also include steps for forming layers present in OLED device100or200, but not specified in fabrication process321. The order of steps can also be rearranged. For example, if an inverted OLED, such as that described in reference toFIG. 2, is desired, then steps322and324can be reordered.

Step322can include applying an anode over the substrate. Any suitable method can be used including, but not limited to, sputtering, photolithography, and other wet or dry processes.

Step323can include applying organic material over the anode. The organic material can include one or more layers of suitable material including, but not limited to, HIL (hole injection transport), HTL (hole transport layer), EML (emissive layer), HBL (hole blocking layer), EIL (electron injection transport), ETL (electron transport layer), and EBL (electron blocking layer). The organic material can be applied using any suitable method including, but not limited to thermal evaporation, ink-jet printing, organic vapor phase deposition (OVPD), deposition by organic vapor jet printing (OVJP), and spin coating and other solution based processes.

Step324can include applying a cathode over the organic material. Any suitable method can be used including, but not limited to, sputtering, photolithography, and other wet or dry processes.

Step325can include applying a barrier layer over the OLED to encapsulate the OLED. In some embodiments, the barrier layer is a thin film so that the OLED is flexible. The barrier layer can include inorganic, organic, and hybrid materials. The application process can include, but is not limited to, sputtering, plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), and other thin film deposition processes.

Step326can include applying a hard coat layer over the barrier layer to provide extra protection to the OLED. In addition to providing a mechanical protection layer, the hard coat layer can facilitate removing the mold from the substrate and OLED device.

FIG. 5is an exemplary flowchart of a method for fabricating a flexible OLED on a substrate which can include one or more of the steps previously described in reference toFIGS. 3 and 4. The method can include a step500of providing a mold, a step510of forming a substrate, a step520of applying electrodes and organic matter, a step530of applying a barrier layer, a step540of applying a first hard coat, a step550of removing the mold from the substrate and OLED, and a step560of applying a second hard coat. The method ofFIG. 5is merely exemplary and can include additional or fewer steps. The order of steps can also be rearranged. A more detailed discussion of each of the steps follows, along with a discussion of accompanyingFIGS. 6A-6G, which illustrates views of transient structures formed after each step of the method outlined inFIG. 5.

Step500can include providing a mold and can correspond to step300discussed above in reference toFIG. 3. In some embodiments, as shown for example inFIG. 6A, a mold600can include one or more surface features, for example concave structures602. As used herein, the term “concave” means a surface that curves inward. For example, the outside surface of a sphere is convex, an inside surface of a sphere is concave. When concave structures602are shaped to form microspheres on the substrate, mold600resembles an empty egg carton.

Step510can include forming a substrate over the mold and can correspond to step310as discussed above in reference toFIG. 3. In some embodiments, as shown for example inFIG. 6B, substrate610can be thicker than the depth of concave structures602so that the top surface of substrate610is smooth and continuous. This can overcome the challenge of the substrate have a rough surface with random spikes. If the top surface of substrate610is not smooth enough, a planarization layer (not shown) can be applied on top. To help prevent any moisture or other detrimental gas/chemicals from migrating into the OLED, a barrier layer (not shown) can be deposited on top of the substrate. This barrier layer can also protect the underlying substrate layer when chemicals are used in the following steps (e.g., in a photolithography process).

Step520can include applying the electrodes and organic matter and can correspond to steps322,323, and324discussed above in reference toFIG. 3. In some embodiments, as shown for example inFIG. 6C, an OLED620can be formed comprising two electrodes622and626with organic material624sandwiched between electrodes622and626. One or more OLEDs620can be formed on substrate610. In some embodiments, OLED620can be a bottom emission OLED such that electrode622is an anode and electrode626is a cathode. In some embodiments, anode622is transparent and can be applied over substrate610according to any of the methods discussed above with respect to step322. In some embodiments, anode layer622can be patterned and/or can include extra buslines to help distribute current. In such instances, anode layer622can include insulating material for patterning and/or extra conductive materials for the extra buslines. These can be formed using standard photolithography processes or other wet or dry processes. After anode layer622is formed, one or more organic layers624can be formed over anode layer622in accordance with the processes discussed above with respect to step323. Next, cathode layer626can be formed over organic layers624in accordance with the processes discussed above with respect to step324. In some embodiments, additional layers can be deposited over cathode626. For example, a buffer layer (not shown) can be deposited over cathode626.

Step530can include applying a barrier layer and can correspond to step325as discussed above in reference toFIG. 3. In some embodiments, as shown for example inFIG. 6D, a barrier layer630is deposited over OLED device620and can include oxide, nitride, ceramic, or hybrid materials. In some embodiments, barrier layer630is sufficiently thin in thickness so that the OLED device is flexible.

Step540can include applying a hard coat and can correspond to step326as discussed above in reference toFIG. 3. In some embodiments, as shown for example inFIG. 6E, a hard coat640can be attached to barrier layer630via a glue layer642. In some embodiments, hard coat640has barrier properties to prevent exposure to harmful species in the environment including moisture, vapor and/or gases. Materials for hard coat640can include, but are not limited to, glass, metal foil, or a barrier coated plastic film.

In some embodiments, after step520,530, or540, as shown for example inFIGS. 6C-6E, respectively, a transient structure exists including a mold600having surface features, a substrate610formed over the mold and an OLED620fabricated over the substrate. As discussed above, substrate610can be transparent and can have a thickness such that the substrate is flexible in the absence of the mold. Such a transient structure exists during manufacturing and in some embodiments can be shipped or stored in this state before the remaining steps of the process, such as removal of the mold, are performed.

Step550can include removing the mold from the substrate and OLED and can correspond to step330discussed above in reference toFIG. 3. In some embodiments, as shown for example inFIG. 6F, an assembly650of OLED620and substrate610can be removed from mold600. The release step can be performed using a variety of different means.

In some embodiments, removal involves an application of force to separate mold600from assembly650. As long as the adhesion between substrate610and mold600is the weakest among all interfaces, the substrate will be detached from the mold.

In some embodiments, mold600is dissolved, thereby removing the mold from assembly650. For example, a mold can be made by forming topographical features using photoresist on a flat piece of glass. Photoresist is a standard material used for patterning purposes in photolithography processes, and can be easily removed afterwards. For example, a typical positive resist S1813, provided by Shipley, may be dissolved in acetone before hard baking. Even after hard baking, such as 150 C baking, S1813 may still be removed by photoresist remover1165, provided by Shipley, at an elevated temperature.

In some embodiments, a thermal approach can be taken to perform the removal. For example, assembly650and mold600can be heated or cooled. As a result of the mismatch of thermal expansion of mold and substrate material, the substrate can be separated from the mold. The coefficient of thermal expansion (CTE) values of some of the materials used for the mold and substrate are shown in Table 2. Typical plastic materials have very large CTE values. When paired with a mold made out of low CTE materials (e.g., Si, glass, stainless, or steel), the plastic materials can be easily released from the mold by cooling down the whole component (the plastic shrinks substantially more than the mold and as a result separates itself from the mold). For example, assume a 100 μm thick substrate coating is applied on top of the mold at room temperature. The CTE mis-match is about 50×10−6/K (plastic on glass/Si mold). When the whole component is cooled down 20 degrees Kelvin, the dimension change between the substrate and mold is 100×50×10−6×20=0.1 μm, which is a significant change and can cause the separation of the substrate from the mold.

A light source can also be used to trigger the release of the substrate. Ultraviolet, infrared or visible light sources can be used to locally heat up the interface between the substrate and the mold. The light source can include a laser. To facilitate this process, a release coating (not shown) which absorbs the photo energy, can be deposited over mold600before forming substrate610between steps500and510. Oxide material such as SiO2, Al2O3 and transparent conductive oxide material ITO can be used to convert light to heat. The thickness can range from a few nm to 100 nm.

In some embodiments, a poor adhesion between substrate610and mold600can be achieved by treating the mold surface such that it has a low surface energy, for example through the application of a release coating to mold600between steps500and510. The low surface energy release coating can include, but is not limited to fluorinated polymers (e.g., Teflon), siloxanes, or silicones. In some embodiments, when the mold is Si (e.g., oxidized Si) or glass, the low surface energy release coating can be fluorinated silane.

In some embodiments, a liquid or gas can be used to remove the mold from the assembly of the OLED device and substrate. As shown for example inFIGS. 7A-7C, mold600′ can have a plurality of holes604extending through the entire thickness of mold600′. These holes604can provide access to the substrate610from the backside of the mold. During removing step550, a liquid or gaseous substance, for example a chemical or water (either in the liquid or gas forms), can travel through holes604and change the interface adhesion between substrate610and mold600′ to facilitate removal of mold600′ from assembly650. In other embodiments, mechanical force can be applied through holes604. This mechanical force can be applied, for example, by using, a solid substance (e.g., pins), a liquid substance (e.g., a hydraulic liquid) or gaseous substance. One example of using gas can include sending a high pressure gas through holes604to push substrate610off mold600′.

In some embodiments, the dimension of the holes are sized to ensure they are not too large in order to avoid decreasing the effective lens surface and to minimize the substrate from leaking through the holes when the substrate is formed. In some embodiments the holes take less than 10% of the base area of each individual lens. For example, for a hemispherical lens with a radius of 5 μm, the hole radius should be less than 1.6 μm. It can be preferred to have a very small hole such that the coating will not fill into the through hole due to the surface tension of the coated material. For standard photolithography process, a sub-micron size (e.g., 0.5 μm) is possible with an ultraviolet light source. The surface of the mold can be treated to facilitate this process.

In some embodiments, once the mold is removed, the substrate having the OLED fabricated thereon is flexible. For example, in some embodiments, the substrate having the OLED fabricated thereon can have a flexural rigidity sufficiently low that the substrate can be wrapped around a 12-inch diameter roll without breaking.

In some embodiments, as shown for example inFIG. 6F, once the mold is removed, the substrate includes surface features complementary to the surface features of the mold from which it was removed. For example, a spherical indentation in the mold will lead to a complementary spherical bulge on the substrate of similar radius. As used herein, “complementary” allows for minor differences caused, for example, by the presence of a release layer having some thickness and irregularity between the substrate and the mold. In some embodiments, at least some of the surface features on the substrate are convex.

Turning back toFIG. 5, step560can include applying a second hard coat after step550to the outcoupling side of the device to provide extra mechanical protection and barrier protection. In some embodiments, as shown for example inFIG. 6G, a hard coat660can be applied to substrate610. A thin piece of glass or a barrier coated plastic can be used for hard coat660. In some embodiments, hard coat660can have an anti-reflective coating on both sides. Hard coats640and660can be attached together by a glue layer662. In some embodiments, glue layer662is flexible and has barrier properties. A desiccant material can be included inside the assembly between hard coats640and660to provide extra protection from moisture and oxygen.

In some embodiments, steps500through550can occur on a conveyor belt apparatus as shown for example, inFIG. 8. Stations 1 through 6 correspond with steps500through550, respectively, and with the structures shown inFIGS. 6A-6F, respectively. In such embodiments, a flexible mold600is needed. In some embodiments, mold600can be attached to a conveyor belt800and as the mold moves with the conveyor belt, different materials will be deposited on the mold. In other embodiments, the conveyor belt800can be the mold600. At the end of the process, the mold will bend around the roller and when the substrate-mold interface is the weakest interface, the assembly of the substrate and the OLED will peel off from the mold. In such embodiments, the mold is preferred to be more flexible than the assembly of the substrate and the OLED. This is because the hard coat makes the assembly more rigid than the mold. In such embodiments, the mold can be made out of thinner materials so it can bend around the rollers of the conveyor belt. In such embodiments, the corresponding apparatus can include belt800; a mechanism to move the belt, which can be any conventional belt driving means; and a flexible mold disposed on the belt, wherein the flexible mold has surface features. The apparatus can also include the following in sequential order along a path of the belt: a dispenser attached to a source of substrate material; an energy source adapted to treat the substrate material; a plurality of dispensers attached to sources for applying the materials making up the components of the OLED; and a mechanism adapted to remove the assembly of the substrate material and OLED from the mold disposed on the belt. In some embodiments, as discussed above, the mechanism adapted to remove the assembly can hold the OLED device as the substrate peels from the mold when the belt bends around the rollers.