Patent Description:
The present disclosure relates to the field of additive manufacturing, and more specifically, relates to composite release films, and devices and methods using the composite release film in the field of additive manufacturing.

With the development of computer and mechanical science and technology, various additive manufacturing techniques or three-dimensional (3D) printing techniques have developed rapidly. Generally speaking, the technical principle of the additive manufacturing techniques or the 3D printing technology techniques may include layering a 3D model of an object constructed by software (e.g., computer-aided design (CAD)), obtaining contour information or image information of each layer of the 3D model, and manufacturing the 3D object by printing layer by layer using bindable materials (e.g., powder metal, resin, etc.). As one of the additive manufacturing techniques, a photocuring 3D printing technique mainly uses liquid resin as raw materials, and completes a printing process by using a characteristic that the printing raw material (e.g., the liquid resin) is cured under irradiation of light with a specific wavelength and intensity. The photocuring 3D printing usually includes following operations. Firstly, the 3D model is layered in one direction to obtain the contour information or the image information of each layer of the 3D model, and then a light pattern of each layer is irradiated on the printing raw material. After the printing raw material is irradiated by light, a curing reaction occurs to form a cured layer. After the light pattern of the layer is cured, a next layer is cured. The operations are repeated, and finally, a complete printed part (i.e., the 3D model) is formed.

The photocuring 3D printing technique may include two types. A first type of the photocuring 3D printing technique is referred to as a top-down printing. In the top-down printing, a curing light source is located above a resin tank storing the printing raw material (e.g., the liquid resin). After each layer is cured, a printing and build platform is moved down a certain distance. In the top-down printing, the photocuring occurs on a surface of the liquid resin, so a printing height is defined by a depth of the resin tank. Generally speaking, an amount of the liquid resin to be placed in the resin tank is far more than an amount of really cured resin, which may cause a certain waste of the raw material. In addition, the top-down printing usually needs to be equipped with a liquid level control system (e.g., a coating scraper) to help the liquid resin flow until the liquid resin covers a completed cured layer. The cost of the printing device is high and operations of the printing device are complex. A second type of the photocuring 3D printing technique is a bottom-up printing. In the bottom-up printing, the curing light source is placed under the resin tank, and the photocuring occurs at a bottom portion of the resin tank. After each layer is cured, the printing and build platform is moved up a certain distance to drive a printed part to move up. If a viscosity of the liquid resin is not very large, the gravity may drive the liquid resin to flow back, thereby filling a space caused by the upward movement of the printed part so as to cure a next layer. The bottom-up printing needs no liquid level control system, and the cost of the printing device is relatively low. However, the bottom-up printing also has defects. For example, each time the build platform moves up after curing, the cured layer and the photocuring surface at the bottom portion of the resin tank need to be separated, which may cause damage to a fine structure of the cured layer. In addition, the separation process also seriously restricts a printing speed. In the prior art, a release film made of an elastic polymer material and placed on the bottom portion of the resin tank is usually used to facilitate rapid and non-destructive release. For example, an elastic separation layer technique is disclosed in <CIT>.

In addition, some improved bottom-up printing techniques may be disclosed. For example, a continuous liquid interface production (CLIP), generated by carbon company in the United States, uses a transparent and breathable Teflon film as a bottom material of the resin tank for light and oxygen to pass through. Due to inhibition effect of oxygen, the oxygen entering the resin tank inhibits the photocuring of the liquid resin nearest to the bottom portion of the resin tank. Therefore, a thin liquid film (referred to as "dead zone") may be formed at the bottom portion of the resin tank. The cured layer cured above the dead zone is no longer separated from the resin tank, but separated from a liquid film in the dead zone, thereby increasing the printing speed to realize continuous printing. The CLIP also has some defects. For example, the dead zone is very sensitive to temperature, and small temperature fluctuations may cause printing failure. In addition, an oxygen content in the dead zone also needs to be accurately controlled, which complicates operations of the printing device and increases the cost.

Therefore, the photocuring 3D printing needs better alternative devices and printing techniques, especially for a solution of cured layer separation in the bottom-up printing.

<CIT> discloses a method and apparatus for making a three-dimensional object from a solidifiable material such as a photopolymer. In accordance with the method, positions relative to a build axis are subdivided into first and second exposure data subsets, and the first and second exposure data subsets are solidified in alternating sequences to reduce the surface area of solidified material in contact with a solidification substrate. <CIT> discloses a 3D printer material tray that can accommodate light cured resin. Specifically, an elastic film is sequentially combined in multiple layers on a surface of a release film to form a light transmitting film. <CIT> discloses a container for use in an additive fabrication device configured to fabricate parts by curing a liquid photopolymer to form layers of cured photopolymer. The container may comprise a laminated multi-material layer having an elastic first layer that aids in separation of cured photopolymer from the container in addition to a barrier layer on an upper surface that protects the first layer from exposure to substances in the liquid photopolymer that may not be compatible with the material of the first layer.

Those skilled in the art may understand the technical features and technical advantages of elements, devices, and methods disclosed in the present disclosure from the following detailed descriptions. It should be noted that the elements, devices, and methods have various forms of embodiments, but the following descriptions may include specific embodiments. Those skilled in the art should understand that the embodiments of the present disclosure are illustrative and do not limit the present disclosure to the specific embodiments described herein.

These embodiments are non-limiting exemplary embodiments, and wherein:.

In order to more clearly illustrate the purpose, the technical solutions, and the advantages of the embodiments of the present disclosure, the following will briefly introduce the accompanying drawings needed in the description of the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and do not limit the present disclosure. On the contrary, the present disclosure covers any substitution, modification, equivalent method, and scheme defined by the claims on the essence and scope of the present disclosure. Further, in order to give the public a better understanding of the present disclosure, some specific details are described in the following detailed description of the present disclosure. For those skilled in the art, the present disclosure may be fully understood without the description of these details.

Space-related terms, such as "below," "under," "lower," "above," "upper," etc., may be used herein for ease of description to describe a relationship between an element or component as shown in the drawings and one or more other elements or components. It should be understood that the space-related terms are intended to include different orientations of devices in use or operation in addition to the orientations depicted in the drawings. For example, if the devices in the drawings are reversed, the elements described as "below" or "lower" other elements or components may be oriented "above" other elements or components. Thus, the exemplary term "below" may include both upper and lower orientations. The device may be oriented in other ways (rotated <NUM> degrees or other orientations), and the space-related descriptors used in the present disclosure may be accordingly explained. Similarly, unless otherwise expressly indicated, the terms "up," "down," "vertical," "horizontal," etc., are used herein merely for explanation.

As described in BACKGROUND, in the traditional bottom-up printing, the separation process between the current cured layer modeled at the bottom portion of the resin tank of the liquid resin and the photocuring surface may cause damage to the fine structure of the cured layer. In addition, the separation process may also restrict the printing speed. In the prior art, a release film made of an elastic polymer material and placed on the bottom portion of the resin tank is usually used to facilitate the rapid release. For example, an elastic release film is disclosed in <CIT>. The elastic release film needs to select a suitable material to ensure that the elastic release film does not stick to the bottom portion of the resin tank. During the release process, an adhesion force between the cured layer and the release film needs to be greater than an adhesion force between the release film and the bottom portion of the resin tank, so as to ensure that the release film may be elastically deformed by an increase of the adhesion force between the cured layer and the release film at a beginning of the release process, and a portion of the release film may leave the bottom surface of the resin tank. At this time, the elasticity of the elastic release film may provide an elastic recovery force. When the elastic recovery force is greater than the adhesion force between the cured layer and the release film, the release film may peel off from the cured layer and restore an initial shape of the release film. The use of the elastic release film may avoid a previous process that the cured layer needs to be peeled directly from the bottom portion of the resin tank, and greatly improve the printing speed and continuity. The elastic release film disclosed in the <CIT> may adopt an elastic material, such as latex, silicone rubber, etc..

The material of the elastic release film used in the prior art is prone to "aging. " That is, after printing for a period of time, since a local position is repeatedly pulled up and then peeled off, a portion of the elastic recovery force provided by the elastic release film is attenuated, and a release effect becomes worse. In addition, when some printing resin materials used for photocuring printing include molecules with small molecular weight, the molecules may enter a 3D network structure of the elastic release film, and a "swell" occurs. The swelling phenomenon may also affect the mechanical properties of the elastic release film and reduce the release effect. A composite release film disclosed in the present disclosure may solve the above problems in terms of the structure and the material selection, and also provide some additional advantages.

<FIG> is a schematic diagram illustrating an exemplary device for photocuring 3D printing according to some embodiments of the present disclosure. According to the invention, the device <NUM> for photocuring 3D printing includes a resin tank <NUM> for storing a photocurable resin <NUM>, and a composite release film <NUM> placed on a bottom portion of the resin tank <NUM>. The bottom portion of the resin tank <NUM> is transparent. The composite release film <NUM> may include an upper plastic layer <NUM> and a lower elastic layer <NUM>. An upper surface <NUM> of the plastic layer <NUM> is in contact with the photocurable resin <NUM>, and a lower surface <NUM> of the plastic layer <NUM> fits with an upper surface <NUM> of the elastic layer <NUM>. The device <NUM> for photocuring 3D printing also includes a build platform <NUM> for driving a movement of a 3D printed part <NUM>. The build platform <NUM> and the upper surface <NUM> of the plastic layer <NUM> defines a printing region. The device <NUM> for photocuring 3D printing also includes a light source <NUM> for supplying energy <NUM> to the printing region to cure the irradiated photocurable resin. In a typical process of preparing a 3D object using the device <NUM> for photocuring 3D printing according to the invention, a control system (not shown in <FIG>) of the device <NUM> for photocuring 3D printing irradiates a pattern of a current cured layer onto the printing region using the light source <NUM>. The energy <NUM> radiated by the light source <NUM> cures the photocurable resin <NUM> in the printing region to form the current cured layer, and the current cured layer is attached to the build platform <NUM>. If the cured layer is not a first cured layer, the cured layer is attached to a last cured layer. After the photocuring process is completed, the build platform <NUM> drives all cured layers to move up a certain distance, thereby driving the current cured layer to separate from the upper surface <NUM> (i.e., a photocuring surface, also referred to as a cured layer release surface) of the plastic layer <NUM>, and then the photocurable resin <NUM> flows to fill a space generated after the current cured layer is released. That is, a next cured layer is printed. The operations is repeated until the entire 3D printed part <NUM> is printed.

A definition of the "plastic layer" used in the present disclosure may be used to distinguish the "elastic layer" by name, and neither refer to materials with high compressive tensile strength or capable of producing large plastic deformation, nor intend to distinguish different characteristics of stress-strain curves of the materials of the two layers in the composite release film. In some embodiments, an elastic modulus of a material of the plastic layer of the composite release film disclosed in the present disclosure may be greater than an elastic modulus of a material of the elastic layer of the composite release film. In some embodiments, the elastic modulus of the material of the plastic layer of the composite release film disclosed in the present disclosure may be within a range of <NUM> Mpa to <NUM> Mpa. The elastic modulus of the material of the elastic layer of the composite release film disclosed in the present disclosure may be less than the elastic modulus of the material of the plastic layer of the composite release film. In some embodiments, the elastic modulus of the material of the elastic layer of the composite release film disclosed in the present disclosure may be within a range of <NUM> Mpa to <NUM> Mpa.

The composite release film disclosed in the present disclosure may adopt a composite structure. According to the invention,the upper surface of the plastic layer is used as the photocuring surface. The material of the upper surface of the plastic layer may not be dissolved with the photocurable resin. In some embodiments, the material of the plastic layer of the composite release film and the photocurable resin may not be wetted with each other. Therefore, when the photocurable resin is cured on the upper surface of the plastic layer to form the cured layer, an adhesion force between the cured layer and the plastic layer may be small, which facilitates a separation of the cured layer and the photocuring surface. The definition of "not wetted" disclosed in the present disclosure may be that a contact angle between the photocurable resin and the upper surface of the plastic layer is not less than <NUM> degrees. In some embodiments, the contact angle between the photocurable resin and the upper surface of the plastic layer is not less than <NUM> degrees. In some embodiments, the contact angle between the photocurable resin and the upper surface of the plastic layer is not less than <NUM> degrees. In some embodiments, the contact angle between the photocurable resin and the upper surface of the plastic layer is not less than <NUM> degrees.

A resistance to swelling of the material of the plastic layer may be better than a resistance to swelling of the material of the elastic layer, so as to avoid small molecules included in the photocurable liquid resin from entering the material of the release film and swelling. In the composite structure, the elastic layer may be configured to provide the elastic recovery force in the release process. The elastic modulus of the material of the plastic layer may be larger than the elastic modulus of the material of the elastic layer. Since the plastic layer and the elastic layer need to go through the process of lifting and peeling together during the releasing process, an interface stress between the two layers may be small. The interface stress may include a compressive stress, a tensile stress, an extrusion stress, a shear stress, or the like, or any combination thereof. If a difference between the elastic modulus of the material of the plastic layer and the elastic modulus of the material of the elastic layer is too large, the interface stress of the materials of the two layers may accordingly increase. Therefore, the elastic modulus of the material of the plastic layer should not exceed the elastic modulus of the material of the elastic layer too much. In some embodiments, a ratio of the difference between the elastic modulus of the material of the plastic layer and the elastic modulus of the material of the elastic layer to the elastic modulus of the material of the elastic layer may not be larger than <NUM>%. That is, the elastic modulus of the material of the plastic layer may not be larger than <NUM> times of the elastic modulus of the material of the elastic layer. In some embodiments, the ratio of the difference between the elastic modulus of the material of the plastic layer and the elastic modulus of the material of the elastic layer to the elastic modulus of the material of the elastic layer may not be larger than <NUM>%. In some embodiments, the ratio of the difference between the elastic modulus of the material of the plastic layer and the elastic modulus of the material of the elastic layer to the elastic modulus of the material of the elastic layer may not be larger than <NUM>%. In some embodiments, the ratio of the difference between the elastic modulus of the material of the plastic layer and the elastic modulus of the material of the elastic layer to the elastic modulus of the material of the elastic layer may not be larger than <NUM>%. In some embodiments, the ratio of the difference between the elastic modulus of the material of the plastic layer and the elastic modulus of the material of the elastic layer to the elastic modulus of the material of the elastic layer may not be larger than <NUM>%. In some embodiments, the ratio of the difference between the elastic modulus of the material of the plastic layer and the elastic modulus of the material of the elastic layer to the elastic modulus of the material of the elastic layer may not be larger than <NUM>%.

In some embodiments, exemplary materials of the plastic layer of the composite release film disclosed in the present disclosure may include polytetrafluoroethylene (PTFE), polyethylene (PE), polyvinylidene fluoride (PVDF), fluorinated ethylene propylene (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinyl fluoride (PVF), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), thermoplastic polyurethane (TPU), polyamide (PA) (or nylon), polyimide (PI), polypropylene (PP), polyvinyl chloride (PVC), polymethylmethacrylate (PMMA), polystyrene (PS), polybutene (PB), polyoxymethylene (POM), polycarbonate (PC), polysulfone (PSU), polyphenylene oxide (PPO), polyvinyl alcohol (PVA), polyacrylonitrile-styrene (AS), polyacrylonitrile-butadiene-styrene (ABS), fluoroethylene resin (FR), or the like, or any combination thereof (e.g., a polymer including optional two or more of the polymers, a blend polymer, or a block polymer, or an interpenetrating network polymer formed by polymerization of their monomers).

In some embodiments, the elastic layer <NUM> of the composite release film <NUM> disclosed in the present disclosure may be shown in an enlarged portion of <FIG>. According to the invention, the elastic layer <NUM> includes a reinforcing scaffold <NUM> and an elastic medium <NUM> of the elastic layer <NUM> filled in the reinforcing scaffold <NUM>. The elastic layer <NUM> may be configured to provide the elastic recovery force during the release process. The reinforcing scaffold <NUM> in the elastic layer <NUM> may be configured to improve a mechanical strength of the elastic layer <NUM>, so that the usage time of the elastic layer <NUM> may be improved. The elastic medium <NUM> of the elastic layer <NUM> may be configured to provide the elastic recovery force during the release process. In some embodiments, an elastic modulus of a material of the reinforcing scaffold <NUM> in the elastic layer <NUM> may be larger than an elastic modulus of a material of the elastic medium <NUM> of the elastic layer <NUM>. In some embodiments, a ratio of a difference between the elastic modulus of the material of the reinforcing scaffold <NUM> of the elastic layer <NUM> and the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> to the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> may not be larger than <NUM>%. That is, the elastic modulus of the material of the reinforcing scaffold <NUM> of the elastic layer <NUM> may not be larger than <NUM> times of the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM>. In some embodiments, the ratio of the difference between the elastic modulus of the material of the reinforcing scaffold <NUM> of the elastic layer <NUM> and the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> to the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> may not be larger than <NUM>%. In some embodiments, the ratio of the difference between the elastic modulus of the material of the reinforcing scaffold <NUM> of the elastic layer <NUM> and the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> to the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> may not be larger than <NUM>%. In some embodiments, the ratio of the difference between the elastic modulus of the material of the reinforcing scaffold <NUM> of the elastic layer <NUM> and the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> to the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> may not be larger than <NUM>%. In some embodiments, the ratio of the difference between the elastic modulus of the material of the reinforcing scaffold <NUM> of the elastic layer <NUM> and the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> to the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> may not be larger than <NUM>%. In some embodiments, the ratio of the difference between the elastic modulus of the material of the reinforcing scaffold <NUM> of the elastic layer <NUM> and the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> to the elastic modulus of the material of the elastic medium <NUM> of the elastic layer <NUM> may not be larger than <NUM>%. In some embodiments, in order to further reduce the interface stress between the plastic layer and the elastic layer, the material of the reinforcing scaffold in the elastic layer may be the same as the material of the plastic layer. In some embodiments where the elastic layer of the composite release film includes the elastic medium of the elastic layer and the reinforcing scaffold, when suitable materials of the elastic layer and the plastic layer are selected by comparing the elastic moduli, the elastic modulus of the material of the plastic layer and the elastic modulus of the material of the elastic medium of the elastic layer may be compared. That is, the comparison may be performed by taking the elastic modulus of the material of the elastic medium of the elastic layer as the elastic modulus of the material of the elastic layer.

In some embodiments, the reinforcing scaffold in the elastic layer of the composite release film disclosed in the present disclosure may be composed of polymer fiber materials and may have a plurality of structures. In some embodiments, the reinforcing scaffold in the elastic layer may be a spiderweb-like microporous structure, wherein the micropores may be formed by interconnected polymer microfibers. In some embodiments, the reinforcing scaffold in the elastic layer may be composed of short polymer fiber materials arranged in an orderly manner, wherein short polymer fibers may be parallel to each other so as not connected. In some embodiments, the reinforcing scaffold in the elastic layer may be composed of the short polymer fiber materials arranged disorderly. In some embodiments, a diameter of the polymer fiber materials of the reinforcing scaffold in the elastic layer of the composite release film disclosed in the present disclosure may be within a range of <NUM> nanometers to <NUM> microns, <NUM> nanometers to <NUM> microns, or <NUM> nanometers to <NUM> microns. In some embodiments, the reinforcing scaffold in the elastic layer of the composite release film disclosed in the present disclosure may be a porous PTFE film. A surface morphology of the porous PTFE film may be a spiderweb-like microporous structure, and pores may be formed between PTFE microfibers. The microporous structure may be formed by entanglement and connection of the plurality of microfibers. A diameter of the pores may be within a range of <NUM> nanometers to <NUM> microns. In some embodiments, a longitudinal cross-section of the PTFE film may be a network structure. A 3D structure of the micropores may include complex changes, such as a network connection, a hole inlay, a hole bending, etc. For example, a channel may be composed of the plurality of micropores. Alternatively, a micropore may be connected with a plurality of channels. Exemplary materials of the reinforcing scaffold in the elastic layer may include PE, PVDF, FEP, PFA, PCTFE, ETFE, PVF, PET, PBT, TPU, PA, PI, PP, PVC, PMMA, PS, PB, POM, PC, PSU, PPO, PVA, AS, ABS, FR, or the like, or any combination thereof (e.g., a polymer including optional two or more of the polymers, a blend polymer, or a block polymer, or an interpenetrating network polymer formed by polymerization of their monomers). In some embodiments, the material of the reinforcing scaffold in the elastic layer of the composite release film disclosed in the present disclosure may be the same as the material of the plastic layer of the composite release film.

In some embodiments, the material of the elastic medium of the elastic layer of the composite release film disclosed in the present disclosure may be any suitable elastomer. Exemplary materials of the elastic medium of the elastic layer may include polyester elastomers, propylene-based elastomers, styrene elastomers, olefin elastomers, diene elastomers, vinyl chloride elastomers, lipid elastomers, amide elastomers, siloxane polymers, epoxy polymers, silicone elastomers, organic fluorine elastomers, or the like, or any combination thereof. In some embodiments, the material of the elastic medium of the elastic layer may include silicone, rubber, silicone rubber, thermoplastic vulcanizate (TPV), nitrile butadiene rubber (NBR), butyl rubber, thermoplastic polyurethane (TPU), thermoplastic polyester elastomer (TPEE), polyamide thermoplastic elastomer (TPAE), T-NR-trans-polyisoprene rubber (TPI), trans-<NUM>,<NUM>-polybutadiene (TPB), organic fluorine thermoplastic elastomer (TPF), thermoplastic phenolic resin (NOVALC resin), thermoplastic chloride polyethylene (TCPE), methyl chlorosilane, ethyl chlorosilane, benzene chlorosilane, thermoplastic polyvinyl chloride elastomer (PVC), polydimethylsiloxane (PDMS), polyethylene, polystyrene, polybutadiene, polyurethane, polyisoprene, polyolefin elastomer (POE), ethylene-propylene-diene monomer (EPDM), styrene ethylene butylene styrene rubber (SEBS), styrene-butadiene-styrene rubber (SBS), polyether block amide (PEBA), ethylene-vinylacetate copolymer (EVA, EVM), linear low density polyethylene (LLDPE), polyacrylate rubber, fluorosilicone rubber, fluoroelastomer, or the like, or any combination thereof (e.g., a polymer including optional two or more of the polymers, a blend polymer, or a block polymer, or an interpenetrating network polymer formed by polymerization of their monomers).

In some embodiments, a preparation of the elastic layer of the composite release film including the reinforcing scaffold and the elastic medium of the elastic layer disclosed in the present disclosure may include the following operations. <NUM>) Reactive precursor components of the materials of the elastic medium of the elastic layer may be measured, respectively, and the reactive precursor components of the materials of the elastic medium of the elastic layer may be mixed in ration. <NUM>) The material of the reinforcing scaffold may be impregnated in a mixture of the reactive precursor components of the material of the elastic medium of the elastic layer before the material of the elastic medium of the elastic layer is cured. The material of the reinforcing scaffold may be in a form of a fiber structure or a porous polymer film. <NUM>) Appropriate reaction conditions may be selected to make the reactive precursor components of the material of the elastic medium of the elastic layer polymerize in the reinforcing scaffold and cure to the elastic medium of the elastic layer, so as to complete the preparation of the elastic layer of the composite release film. In some embodiments, the mixture of the reactive precursor components of the elastic medium of the elastic layer may be liquid. A technique that is used to impregnate the reinforcing scaffold of the elastic layer in the mixture, and make the reactive precursor components of the material of the elastic medium of the elastic layer polymerize in the reinforcing scaffold and cure to the elastic medium of the elastic layer to form the composite release film disclosed in the present disclosure may include hand layup, spraying, winding, resin transfer molding, vacuum infusion, pultrusion, reaction injection pultrusion, extrusion, weaving pultrusion, lamination, molding, sheet molding compound pressing, lump molding compound pressing, injection, reaction injection, prepreg molding, autoclave molding, pipe rolling, centrifugal rotary molding, blow molding, slush molding, or the like, or any combination thereof, selected from a composite material molding process.

As shown in <FIG>, in some embodiments of the composite release film disclosed in the present disclosure and according to the invention, the reinforcing scaffold <NUM> of the elastic layer <NUM> extends beyond a lower surface <NUM> of the elastic layer <NUM> to form a plurality of protrusions <NUM>. For a clear example, a structure of the plurality of protrusions <NUM> at the lower surface <NUM> of the elastic layer <NUM> in <FIG> may be enlarged rather than shown in ration. The plurality of protrusions <NUM> are located between the lower surface <NUM> of the elastic layer <NUM> and a bottom surface of the resin tank <NUM>, thereby reducing a contact area between the lower surface <NUM> of the elastic layer <NUM> and the bottom surface of the resin tank <NUM>. Only the plurality of protrusions <NUM> may be in contact with the bottom surface of the resin tank <NUM>. Reducing the contact area between the lower surface of the elastic layer and the bottom surface of the resin tank may reduce the adhesion force between the elastic layer and the bottom portion of the resin tank, so as to help a deformation process in which the elastic layer and the plastic layer are lifted together by the cured layer during the release process, and reduce a deformation time. The elastic layer deformed by the lifting may provide the elastic recovery force required for the subsequent cured layer to be peeled from the plastic layer. The plurality of protrusions may also help the elastic layer to be lifted by eliminating a cavity with negative pressure and hence, pulling down the elastic layer that may be formed between the lower surface of the elastic layer and the bottom surface of the resin tank, thereby further helping deformation of the elastic layer.

A resolution of the object obtained by the photocuring 3D printing may be limited by a resolution of the used light source. In some embodiments, even if a photocuring printed part is printed using a transparent resin material, a large amount of pixels may be displayed on a surface of the photocuring printed part, which may affect the transparency of the printed part. The plurality of protrusions may introduce a gas-solid interface between the lower surface of the elastic layer and the bottom surface of the resin tank, so that a portion of incident light passing through the optically transparent bottom surface of the resin tank may be refracted. The refraction may cause blurring of a boundary of each curing pixel of the cured layer at a macroscopic level, thereby improving the transparency of the printed part.

In some embodiments, a preparation of the plurality of protrusions of the reinforcing scaffold on the bottom surface of the elastic layer may include the following operations. <NUM>) The reactive precursor components of the materials of the elastic medium of the elastic layer may be measured, respectively, and the reactive precursor components of the materials of the elastic medium of the elastic layer may be mixed in ration. <NUM>) The liquid mixture of the reactive precursor components of the material of the elastic medium of the elastic layer may be coated on a substrate material before the material of the elastic medium of the elastic layer is cured. In some embodiments, the substrate material may include glass or other suitable materials. <NUM>) The material of the reinforcing scaffold may be coated on the mixture of the reactive precursor components of the material of the elastic medium of the elastic layer. The liquid mixture of the reactive precursor components of the material of the elastic medium of the elastic layer may penetrate into pores of the reinforcing scaffold through capillary action. The material of the reinforcing scaffold with a suitable ration may be selected, and simultaneously, an upper surface of the reinforcing scaffold may not be covered by the cured material of the elastic medium of the elastic layer through the action of gravity, thereby ensuring that a surface of the cured elastic layer away from the substrate material includes the plurality of protrusions of the material of the reinforcing scaffold. <NUM>) Appropriate reaction conditions may be selected to polymerize the reactive precursor components of the material of the elastic medium of the elastic layer, and the elastic medium of the elastic layer may be cured. <NUM>) The cured elastic layer may be peeled off from the substrate material, so as to complete the preparation of the elastic layer of the composite release film.

In some embodiments, a thickness of the plastic layer of the composite release film disclosed in the present disclosure may be selected within a range of <NUM> microns to <NUM> microns. In some embodiments, the thickness of the plastic layer of the composite release film may be selected within a range of <NUM> microns to <NUM> microns. In some embodiments, the thickness of the plastic layer of the composite release film may be selected within a range of <NUM> microns to <NUM> microns. In some embodiments, a thickness of the elastic layer of the composite release film disclosed in the present disclosure may be selected within a range of <NUM> microns to <NUM> millimeters. In some embodiments, the thickness of the elastic layer of the composite release film may be selected within a range of <NUM> microns to <NUM> millimeters. In some embodiments, the thickness of the elastic layer of the composite release film may be selected within a range of <NUM> microns to <NUM> millimeters. In some embodiments, a height of one protrusion of the reinforcing scaffold in the bottom surface of the elastic layer of the composite release film disclosed in the present disclosure may be selected within a range of <NUM> nanometers to <NUM> microns. In some embodiments, the height of the protrusion of the reinforcing scaffold in the bottom surface of the elastic layer may be selected within a range of <NUM> nanometers to <NUM> microns. In some embodiments, the height of the protrusion of the reinforcing scaffold in the bottom surface may be selected within a range of <NUM> nanometers to <NUM> microns.

The plastic layer and the elastic layer (including the elastic medium of the elastic layer and the reinforcing scaffold) of the composite release film disclosed in the present disclosure may be optically transparent. Unless otherwise specified, the "optically transparent" in the present disclosure may refer to that energy used to irradiate the photocurable resin in the printing region to cause a curing reaction may have a transmittance of <NUM>% to <NUM>%. In some embodiments, an "optically transparent" material or element may have a transmittance of at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, or at least <NUM>% to the photocuring energy for irradiating the printing region. The "optically transparent" material or element may allow transmission of a light within a wide range of wavelengths. The wavelengths may include wavelengths corresponding to X-ray radiation, ultraviolet (UV) light radiation, visible light radiation, infrared (IR) radiation, microwave radiation, or the like, or any combination thereof.

In some embodiments, a preparation of the composite release film disclosed in the present disclosure may include the following operations. <NUM>) The elastic layer may be prepared according to the preparation disclosed in the present disclosure. The elastic layer may include the elastic medium of the elastic layer and the reinforcing scaffold. One surface of the elastic layer may include the plurality of protrusions which is the exposed part of the reinforcing scaffold. <NUM>) A film stretching device may be used to fix the surface of the elastic layer with the plurality of protrusions on the substrate material, such as, glass. <NUM>) The plastic layer may be paved on the surface of the elastic layer without the plurality of protrusions composed of the plurality of reinforcing scaffolds, and the plastic layer may be flattened with a roller and/or other devices to ensure that an interface between the plastic layer and the elastic layer has no bubbles and folds. In some embodiments, in operation <NUM>, the elastic layer with the plurality of protrusions may be fixed directly on the substrate material that can be directly used as the bottom portion of the resin tank. In some embodiments, after performing the operation <NUM>, the prepared composite release film stretched over the substrate material on the bottom surface of the resin tank may be directly used for the photocuring 3D printing device. Exemplary substrate materials that can be directly used as the bottom portion of the resin tank for storing the photocurable resin may include glass, low iron glass, sapphire glass, quartz, sodium-calcium (BK7) acrylic acid, fused silica, fused silica, germanium, borosilicate, silicon nitride, or the like, or any combination thereof. In some embodiments, after performing the operation <NUM>, the prepared composite release film may be peeled off from the substrate material used in the operation <NUM>, and then may be placed on the bottom portion of the resin tank of the device for photocuring 3D printing for use.

The composite release film disclosed in the present disclosure may be used in an additive manufacturing of free radical photocuring and cationic photocuring. Exemplary free radical photocurable resin materials may include acrylic acid, methacrylic acid, N-vinyl pyrrolidone, acrylamide, styrene, olefins, halogenated olefins, cycloolefins, maleic anhydride, alkynes, carbon monoxide, functionalized oligomers (e.g., oligomers functionalized with acrylate or methacrylate groups, such as epoxides, urethanes, polyethers, or polyesters), functionalized polyethylene glycol (PEG), or the like, or any combination thereof. Exemplary cationic photocurable resin materials may include epoxy groups, vinyl ether groups, or the like, or any combination thereof. In some embodiments, the resin materials may include styrene compounds, vinyl ethers, N-vinyl carbazole, lactones, lactams, cyclic ethers (e.g., epoxides), cyclic acetals, cyclosiloxanes, or the like, or any combination thereof. For a digital light processing (DLP)/laser cladding deposition (LCD) photocuring 3D printing system, vinyl ethers, acrylates, and methacrylates (including oligomers having the groups) may be preferred.

Another aspect of some embodiments of the present disclosure may disclose a device for preparing a 3D object based on a photocuring 3D printing technique by using the composite release film disclosed in some embodiments of the present disclosure. The device according to the invention includes following components:.

Another aspect of some embodiments of the present disclosure may disclose a method for preparing a 3D object using the device for the photocuring 3D printing disclosed in the present disclosure. The method according to the invention includes following operations:.

In the operation c), when the build platform <NUM> drives the current cured layer to move up, the plastic layer <NUM> may be locally deformed firstly as the current cured layer is moved up due to the adhesion force between the upper surface <NUM> of the plastic layer <NUM> and the current cured layer. The upper surface <NUM> of the elastic layer may undergo a same deformation due to the adhesion force and the surface tension between the upper surface <NUM> and the lower surface <NUM> of the plastic layer <NUM>. When the elastic deformation occurs to a certain extent, the resilience force of the material of the elastic layer <NUM> may exceed the adhesion force between the upper surface <NUM> of the plastic layer <NUM> and the current cured layer, resulting in the peeling of the upper surface <NUM> of the plastic layer <NUM> from the current cured layer. The elastic recovery force of the elastic layer <NUM> may drive the plastic layer <NUM> and the elastic layer <NUM> to return to an initial state of the composite release film <NUM>. The surrounding liquid resin <NUM> may quickly return to a space generated after the upper surface <NUM> of the plastic layer is peeled from the current cured layer, and the printing of a next cured layer may be continued. The thickness of the elastic layer <NUM> of the composite release film <NUM> disclosed in the present disclosure may be larger than the thickness of the plastic layer <NUM>, so as to provide the elastic recovery force for the release process, and ensure that the elastic deformation in the release process may quickly return to the initial state of the composite release film <NUM>. At the same time, the reinforcing scaffold <NUM> in the elastic layer <NUM> may provide an internal support, enhance a mechanical strength of the elastic layer <NUM>, and improve a service life of the elastic layer <NUM>. The plurality of protrusions <NUM> of the reinforcing scaffold <NUM> of the elastic layer <NUM> on the lower surface <NUM> of the elastic layer <NUM> may reduce the contact area between the lower surface <NUM> of the elastic layer <NUM> and the bottom portion of the resin tank <NUM>, which may help the elastic layer <NUM> to undergo the rapid elastic deformation, and then quickly provide the elastic recovery force to complete the release. At the same time, the help of the plurality of protrusions <NUM> for the lifting deformation of the elastic layer <NUM> may eliminate the cavity with negative pressure and hence, pull down the elastic layer between the lower surface <NUM> of the elastic layer <NUM> and the bottom surface of the resin tank <NUM>, thereby further promoting the deformation of the elastic layer <NUM>. The plastic layer <NUM> of the composite release film <NUM> may provide a resistance to swelling to prevent small molecules in the printing raw material (e.g., the liquid resin) from entering the composite release film <NUM>.

PDMS (Dow Corning, PDMS, Sylgard <NUM>) was mixed in a mass ratio of <NUM>:<NUM> (bulk: a curing agent) and stirred. After removing bubbles, <NUM> microns of PDMS was scraped and coated on a glass substrate using a scraper, and then a reinforcing scaffold layer (e.g., a porous PTFE film (Shenzhen Gorestec Technology Co. , GT-<NUM>)) with <NUM> microns was spread onto a surface of the scraped PDMS. The liquid PDMS was permeated into pores of the porous PTFE film due to the capillary action. After the filling, the whole system was placed into an oven for thermal curing at <NUM> for <NUM> minutes to complete the preparation of the elastic layer. Due to the action of gravity and a predetermined material ration, the PDMS could not cover up all the reinforcing scaffold. Therefore, a portion of the reinforcing scaffold was exposed from an upper surface of the PDMS to form a plurality of microstructure protrusions. <FIG> is an electron microscope diagram illustrating an exemplary elastic layer of a composite release film according to some embodiments of the present disclosure. Filamentous structures were PTFE fibers, and pores between PTFE fibers were filled with PDMS elastomers.

The elastic layer prepared in Embodiment <NUM> was peeled off from the glass substrate. One side of the elastic layer with exposed protrusions of the reinforcing scaffold was paved on optical glass, and the elastic layer and the optical glass were fixed together to a lower clamping piece of a cassette of the film stretching device. A plastic layer (DuPont, FEP casting film) was paved flat on an upper surface of the elastic layer (i.e., a surface without the protrusions of the reinforcing scaffold). The plastic layer was rolled flat using a roller to ensure that no bubbles, wrinkles, and other structures were between the plastic layer and the elastic layer. An upper clamping piece and the lower clamping piece of the cassette were fixed together, and excess materials of the plastic layer and the elastic layer around the upper clamping piece and the lower clamping piece were cut off to obtain an optical glass cassette with a stretched composite release film. The cassette was directly installed on the corresponding resin tank to form the bottom surface of the resin tank which was optically transparent and covered with the composite release film.

Claim 1:
A composite release film, configured to separate a current cured layer from a photocuring surface during a photocuring three-dimensional (3D) printing process, the composite release film being configured to be placed on a bottom portion of a resin tank (<NUM>), wherein the composite release film includes a plastic layer (<NUM>) and an elastic layer (<NUM>), an upper surface of the plastic layer (<NUM>) being the photocuring surface, a lower surface of the plastic layer (<NUM>) fitting with an upper surface of the elastic layer (<NUM>),
characterized in that, the elastic layer (<NUM>) includes an elastic medium (<NUM>) of the elastic layer (<NUM>) and a reinforcing scaffold (<NUM>), the elastic medium (<NUM>) of the elastic layer (<NUM>) being filled in pores of the reinforcing scaffold (<NUM>), the reinforcing scaffold (<NUM>) in the elastic layer (<NUM>) includes a plurality of protrusions (<NUM>) on a lower surface of the elastic layer (<NUM>), and the plurality of protrusions (<NUM>) are configured to be located between the lower surface of the elastic layer (<NUM>) and a bottom surface of the resin tank (<NUM>).