Method for three-dimensional object volume printing through polychromatic light polymerization of light-cured resin

Abstract

The invention relates to a method and equipment for three-dimensional object volume printing through polychromatic light polymerization of light-cured resin. The method includes an irradiation process based on a plurality of printing parameters: curing the resin with light of a first wavelength and illumination light of a second wavelength different from the first wavelength, forming a three-dimensional object in at least one direction by polychromatic light polymerization, where the light of the two wavelengths intersect in a forming area. At least one printing parameter (such as energy intensity, irradiation sequence, focus parameter and the like) is dynamically adjusted in the irradiation process, and the curing behavior of the light-cured resin is optimized, so that the structural isotropy of a three-dimensional object is improved, shrinkage and deformation are reduced, and the geometric accuracy and the structural fidelity are improved. The apparatus comprises an irradiation device and a controller for controlling spatial and temporal variations of printing parameters.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for volumetric printing of a three-dimensional object by multi-color photopolymerization, in particular bi-color photopolymerization, of a photocurable resin, wherein the method comprises an irradiation process for irradiating the photocurable resin based on a plurality of printing parameters: irradiating the photocurable resin with light of a first wavelength and light of a second wavelength (the second wavelength being different from the first wavelength), forming the three-dimensional object in at least one direction by multi-color photopolymerization, in particular bi-color photopolymerization, wherein the light of the first wavelength and the light of the second wavelength intersect within a build area. BACKGROUND

[0002] Various methods for volumetric printing of a three-dimensional object by multi-color photopolymerization, in particular bi-color photopolymerization, of a photocurable resin are known in the art. The specific implementations of these methods include the “Xolography” principle as described in WO 2020 / 245456 Al, for example.

[0003] While the various volumetric printing methods are generally capable of printing a three-dimensional object in a short time, in particular compared to conventional additive printing techniques which require a rather time-consuming layer-by-layer building of a three-dimensional object, the volumetric printing methods face the challenge of printing a three-dimensional object with anisotropic structure. The anisotropic structure of the printed three-dimensional object can lead to undesired shrinkage and undesired distortion of the printed three-dimensional object. These effects impair the geometric accuracy and the structural fidelity of the three-dimensional object, respectively.

[0004] Therefore, there is a need to improve the respective volumetric printing methods in order to enhance the quality of the three-dimensional object, in particular by achieving a higher structural isotropy of the three-dimensional object to reduce undesired shrinkage and undesired distortion, while improving the geometric accuracy and the structural fidelity.

[0005] In view of this, it is an object of the present invention to provide an improved method for volumetric printing of a three-dimensional object by multi-color photopolymerization of a photocurable resin. SUMMARY

[0006] A first aspect of the present invention relates to a method of volumetrically printing at least one three-dimensional object by multi-color photopolymerization, in particular dual-color photopolymerization, of a photocurable resin. The method comprises an irradiation process of irradiating the photocurable resin with light of a first wavelength and light of a second wavelength different from the first wavelength based on a plurality of printing parameters, thereby forming the three-dimensional object in at least one direction by multi-color photopolymerization, in particular dual-color photopolymerization. Accordingly, the method comprises an irradiation process of irradiating the photocurable resin with light of a first wavelength and light of a second wavelength different from the first wavelength to form the at least one three-dimensional object in at least one direction by multi-color photopolymerization, in particular dual-color photopolymerization, wherein the irradiating the photocurable resin with light of the first wavelength and light of the second wavelength is performed based on one or more printing parameters. The at least one direction can be or comprise a build direction of the respective three-dimensional object to be printed, i.e. a direction in which the respective three-dimensional object is printed. The method is generally capable of volumetrically printing one or more three-dimensional objects in at least one direction or at least one build direction. The build direction can also be regarded or denoted as a printing direction.

[0007] The light of the first wavelength can comprise a wavelength in the range of, for example, 350 nm - 500 nm, in particular 375 nm - 450 nm, more in particular 385 nm - 440 nm, more in particular 395 nm - 420 nm, more in particular 400 nm - 410 nm. The light of the first wavelength can comprise a spectrum of wavelengths, in particular at least partially covering the respective range of wavelengths as mentioned above. As a specific example, the first wavelength can be about 375 nm. In general, the first wavelength is chosen taking into account at least the photochemical properties, in particular the photochromic properties, of the at least one photoinitiator molecule in the photocurable resin.

[0008] The light of the second wavelength can comprise a wavelength in the range of, for example, 400 nm - 1000 nm, in particular 425 nm - 750 nm, more in particular 450 nm - 675 nm, more in particular 500 nm - 650 nm. The light of the second wavelength can comprise a spectrum of wavelengths, in particular at least partially covering the respective range of wavelengths as mentioned above. For example, the second wavelength can be about 475 nm. Preferably, the light of the second wavelength can comprise a range of wavelengths which does not comprise the range of wavelengths of the light of the first wavelength. In general, the second wavelength is chosen taking into account at least the photochemical properties, in particular the photochromic properties, of the at least one photoinitiator molecule in the photocurable resin.

[0009] The light-curing resin is irradiated with light of the first wavelength and light of the second wavelength such that the light of the first wavelength and the light of the second wavelength intersect in the build region. In this way, the light of the first wavelength can be irradiated into the light-curing resin at a different angle relative to the light of the second wavelength. For example, the light of the first wavelength can be irradiated into the light-curing resin at an angle of about 90° relative to the light of the second wavelength. The build region is typically a region in which the light-curing resin undergoes photopolymerization, thereby causing photocuring and / or solidification of the light-curing resin, which in turn forms at least one cross-section of the three-dimensional object to be printed.

[0010] The respective printing parameters can typically be or comprise irradiation process parameters that influence the spatial and / or temporal irradiation of the light-curing resin with the light of the first wavelength and the light of the second wavelength. The respective printing parameters can additionally or alternatively be or comprise the number of irradiation steps in which one or more volume elements (e.g. voxels) of the light-curing resin are irradiated with the light of the first wavelength and / or the light of the second wavelength. The respective printing parameters can thus be or comprise control parameters of a volumetric printing device used to carry out the method, which control parameters relate to the spatial and / or temporal irradiation of the light-curing resin with the light of the first wavelength and the light of the second wavelength, thereby forming the three-dimensional object in at least one direction by multicolor photopolymerization, in particular by dual-color photopolymerization. The respective printing parameters can be or comprise control parameters of an irradiation device in the volumetric printing device, which irradiation device is configured to irradiate the light-curing resin with the light of the first wavelength and the light of the second wavelength, thereby forming the three-dimensional object in at least one direction by multicolor photopolymerization. The respective printing parameters can also be or comprise control parameters of a drive device in the volumetric printing device, which drive device is configured to move, for example in at least one direction, the light-curing resin or a container that contains the light-curing resin.

[0011] The method comprises varying at least one printing parameter spatially and / or temporally during the irradiation process, in particular at least one printing parameter affecting the curing or the curing behavior of the photocurable resin. Accordingly, the irradiation process of the method comprises a coordinated and precise spatial and / or temporal control of the irradiation process, which comprises a coordinated and precise variation of at least one printing parameter, in particular at least one printing parameter affecting the curing behavior of the photocurable resin, during the irradiation process. The respective spatial and / or temporal variation of the at least one printing parameter can also comprise a focal point variation of the light of the first wavelength and / or a size variation of one or more images or one or more image elements, such as pixels, of the light of the second wavelength. The respective spatial and / or temporal variation of the at least one printing parameter can also relate to the number of irradiation steps in which one or more volume elements, such as voxels, of the photocurable resin are irradiated with the light of the first wavelength and / or the light of the second wavelength. Accordingly, the respective spatial and / or temporal variation of the at least one printing parameter can also comprise a variation of the number of irradiation steps in which one or more volume elements, such as voxels, of the photocurable resin are irradiated with the light of the first wavelength and / or the light of the second wavelength. The respective spatial and / or temporal variation of the at least one printing parameter can also relate to a direction of movement and / or a rate of movement of the photocurable resin, in particular a direction of movement and / or a rate of movement of the photocurable resin relative to the light sheet formed by the light of the first wavelength. Accordingly, the respective spatial and / or temporal variation of the at least one printing parameter can also comprise a variation of a direction of movement and / or a rate of movement of the photocurable resin, in particular a variation of a direction of movement and / or a rate of movement of the photocurable resin relative to the light sheet formed by the light of the first wavelength.

[0012] Accordingly, based on the spatial and / or temporal variation of the at least one printing parameter, the irradiation process can comprise printing at least one first portion of the three-dimensional object to be printed (first object portion) using at least one printing parameter which is different from the printing parameter employed with respect to at least one other portion of the three-dimensional object to be printed (other object portion). The respective first object portion can comprise one or more first volume elements, such as voxels, of the photocurable resin which are located at one or more first positions within the photocurable resin. The respective other object portion can comprise one or more further volume elements, such as voxels, of the photocurable resin which are located at one or more further positions within the photocurable resin. The respective further volume element can be a volume element which is located behind the respective first volume element in the build direction.

[0013] Generally, the spatial and / or temporal variation of the at least one printing parameter enables irradiating each volume element of the photocurable resin with an individual printing parameter, in particular a printing parameter affecting the energy, the energy density, the energy intensity, etc. received by the respective volume element during the irradiation process.

[0014] Spatial and / or temporal changes to at least one printing parameter can include or enable irradiation of each volume element of the photocurable resin by an individual light intensity of a second wavelength. For example, the intensity of each pixel in one or more projected images of the second wavelength light can have a numerical intensity value from 0 to 1, where 0 represents a black pixel with no intensity, 1 represents the pixel with the highest intensity, typically represented as a white pixel, and values ​​between 0 and 1 represent gray pixels with intensities lower than white pixels but higher than black pixels. It is worth noting that terms such as "white," "gray," and "black" can refer to light intensity. Therefore, spatial and / or temporal changes to at least one printing parameter can include or enable grayscale adjustment (which will be further elaborated below).

[0015] The printing parameters for each volume element of the UV-curable resin can be selected based on its position within the UV-curable resin and its position within the 3D object to be printed. For example, the printing parameters for a volume element of one or more UV-curable resins adjacent to or close to uncured or uncured UV-curable resins can differ from those for volume elements adjacent to or close to cured or uncured UV-curable resins. In this way, spatial and / or temporal variations in at least one printing parameter can specifically account for the so-called proximity effect, which causes volume elements close to another cured volume element to exhibit specific curing behaviors, such as curing more easily or faster, which differ from the curing behavior of volume elements not close to another cured or photopolymerized volume element. It is worth noting that in traditional volumetric printing methods, the proximity effect often leads to undesirable structural anisotropy in the 3D object, as well as associated undesirable shrinkage and deformation.

[0016] Therefore, the method described herein can print three-dimensional objects with higher structural isotropy and lower undesirable shrinkage and deformation by spatially and / or temporally altering at least one printing parameter during irradiation, resulting in three-dimensional objects exhibiting higher geometric accuracy and structural fidelity, respectively.

[0017] The following will describe exemplary implementations and related examples of this method. It is worth noting that one, more, or all of the exemplary implementations and examples can be used in any combination.

[0018] According to an exemplary embodiment, a photocurable resin may be disposed in a container defining a container volume. This container volume may contain a working volume in which a three-dimensional object can be printed. One or more walls of the container may be made of a material that allows light of a first wavelength and a second wavelength to irradiate the photocurable resin within the container. The corresponding material may be, for example, a transparent material. The corresponding transparent material may be glass or a polymer, such as polycarbonate, polymethyl methacrylate, or a cyclic olefin copolymer.

[0019] According to another exemplary embodiment, irradiating a photocurable resin with light of a first wavelength causes one or more photoinitiator molecules in the photocurable resin to change from an initial state to an intermediate state. Compared with the initial state, the optical properties of the photoinitiator molecules in the intermediate state change, so that one or more photoinitiator molecules in the intermediate state can absorb light of a second wavelength, and thus cause one or more photoinitiator molecules to change from the intermediate state to an active state by absorbing light of the second wavelength, thereby locally triggering the polymerization of the photocurable resin to form at least one three-dimensional object.

[0020] For example, a photocurable resin can be a photocurable monomer resin or a photocurable oligomer resin, such as acrylates, methacrylates, thiols + alkenes, epoxides, oxetanes, oxetanes, or vinyl ethers. Multicolor photopolymerization can include multiphoton photopolymerization of photocurable resins, particularly two-photon photopolymerization. Photopolymerization of photocurable resins is typically achieved by irradiating the photocurable resin with light of a first wavelength, particularly by simultaneously irradiating it with light of a second wavelength different from the first wavelength. This causes molecules of one or more photoinitiators in the photocurable resin to transition from an initial state (in which the molecules of one or more photoinitiators (substantially) do not absorb the second wavelength) to an intermediate state in which their optical properties change compared to the initial state, for example, due to absorption of the first wavelength of light. This causes the molecules of one or more photoinitiators in the intermediate state to absorb the second wavelength of light, and subsequently, the molecules of one or more photoinitiators transition from the intermediate state to the active state, thereby locally triggering the polymerization of the photocurable resin to form at least one three-dimensional object.

[0021] For example, the reverse reaction of one or more photoinitiator molecules from an intermediate state to an initial state can be thermally induced. Therefore, at the printing temperature of the photocurable resin, the intermediate state can be returned to the initial state by heating. Preferably, the intermediate state can be thermally returned to the initial state at the corresponding printing temperature by a reaction or reaction sequence described by one or more rate constants, wherein the maximum value of the rate constant is greater than k = 0.01 s. -1 Preferably, at least one rate constant of the thermal reverse reaction is greater than 0.02 s⁻¹. -1 More preferably higher than 0.05s -1Even more preferably, higher than 0.1s -1 More preferably higher than 1.0s -1 The optimal value is higher than 5.0s. -1 Therefore, the rate constant can be 0.05 s. -1 to 1.0s -1 Within the range of the above values, or within any other range formed by the above values. A higher rate constant can improve the resolution of the printed 3D object.

[0022] Alternatively, the intermediate state may not substantially revert to its initial state by heating at the corresponding printing temperature of the photocurable resin. Preferably, the intermediate state can thermally revert to its initial state at the printing temperature in a reaction or reaction sequence having one or more rate constants, wherein at least one rate constant is less than k = 100 s. -1 Preferably, at least one rate constant of the thermal reverse reaction is less than 1 s. -1 More preferably less than 0.1s -1 Even better, less than 0.01s -1 More preferably less than 0.001s -1 The optimal value is below 0.0001s. -1 Therefore, the rate constant can be 0.1 s. -1 to 0.0001s -1 Within the range of, or within any other range formed by the above values.

[0023] Alternatively, the intermediate state can be substantially not reverted to its initial state by heating at the printing temperature of the photocurable resin. Preferably, the intermediate state can be thermally reverted to its initial state at the printing temperature in a reaction or reaction sequence having one or more rate constants, wherein the highest rate constant is below k = 100 s. -1 Particularly preferably, the highest rate constant of the thermal reverse reaction is less than 1 s⁻¹. -1 More preferably less than 0.1s -1 Even better, less than 0.01s -1 More preferably less than 0.001s -1 The optimal value is below 0.0001s. -1 Therefore, the rate constant can be 0.1 s. -1 to 0.0001s -1 Within the range of, or within any other range formed by the above values.

[0024] For photoinitiators suitable for the corresponding photocurable resins, please refer to the following documents: US5230986A, WO2020245456A1, WO2023034398A1, WO2023034404A1, WO2023034402A1, WO2023220461A1, and WO2023220463A1, the contents of which are incorporated herein by reference.

[0025] According to another exemplary embodiment, the light of the first wavelength can form a light sheet comprising multiple beams passing through a photocurable resin. Each beam can comprise two or more (substantially) parallel beams. For example, the beams can form a light plane. This light plane can be or comprise a light plane in which multiple beams (e.g., substantially) parallel beams extend adjacent to each other, such that there is no intermediate gap between directly adjacent beams. Notably, at least partially directly adjacent beams can also partially overlap. Optionally, the light plane can be or comprise a light plane in which multiple beams extend adjacent to each other, such that there is an intermediate gap between directly adjacent beams. Each beam can be generated by a directional light-emitting device (e.g., a laser device), which can form part of the irradiation apparatus of a volumetric printing device for implementing the method.

[0026] Each light plate or beam may have a principal extension direction, which can generally be understood as the direction of extension of the corresponding individual light plate or beam between opposing walls or wall portions of the container defining the working volume. Specifically, the principal extension direction of each corresponding light plate or beam can be understood as the principal propagation direction of the light from the light plate or beam between opposing walls or wall portions of the container defining the working volume. Therefore, the principal extension direction of the corresponding light plate or beam may correspond to the direction along a line that halves the divergence or divergence angle of the light plate or beam within the working volume.

[0027] The height direction or height extension of each light plate or beam can generally be understood as the direction with the greatest spatial extension that is orthogonal to the main extension direction. Specifically, the height direction or height extension can be a direction or extension parallel to the container wall or wall portion that defines the working volume, through which the light plate or beam enters the working volume.

[0028] According to another exemplary embodiment, the light of the second wavelength may comprise an image projection corresponding to the cross-sectional geometry of the three-dimensional object to be printed, or may comprise a plurality of points or lines corresponding to the cross-sectional geometry of the three-dimensional object to be printed. The individual points or lines may form a pattern, such as a shadow pattern. The corresponding projection may be generated by a light projection device (e.g., a digital light projection device), which may constitute part of the irradiation device of the volumetric printing apparatus for implementing the method. The individual points or lines may be generated by a directional light emitting device (e.g., a laser device), which may constitute part of the irradiation device of the volumetric printing apparatus for implementing the method.

[0029] According to another exemplary embodiment, at least one molding region moves at a nominal rate of motion along at least one direction, particularly relative to a corresponding container containing photocurable resin (as described above). This at least one direction may include the molding direction of the three-dimensional object to be printed. The movement of the at least one molding region may, for example, be relative to at least one functional component of a volumetric printing apparatus used to implement the method. The functional component of the volumetric printing apparatus may be, for example, the corresponding container or an irradiation device. Thus, during irradiation, at least one molding region may actively move at a nominal rate of motion along at least one direction (particularly the molding direction) through at least a portion of the container volume while the container remains stationary. Alternatively, during irradiation, the container may actively move along at least one direction (particularly the molding direction) while at least one molding region remains stationary. Alternatively, both at least one molding region and the container may actively move, wherein at least one molding region and the container may move in the same direction or in opposite directions. Furthermore, the nominal rate of motion and / or direction of motion of at least one molding region and / or the container along at least one direction (particularly relative to the container) can serve as examples of printing parameters, since the nominal rate of motion, particularly spatial and / or temporal variations of the nominal rate of motion, also affects the curing behavior of the photocurable resin. Alternatively or concurrently, one or more irradiation devices in the dual-color irradiation apparatus of the device may be actively moved along at least one direction (particularly the forming direction), while simultaneously at least one of the containers or at least one forming area is actively moved. Moving one or more irradiation devices in the dual-color irradiation apparatus of the device can serve as a means of focusing light of a second wavelength. Therefore, embodiments are also envisioned in which each of the one or more irradiation devices in the dual-color irradiation apparatus of the device, at least one forming area, and each of the containers is actively moved before, during, or after at least one irradiation process. All such movements can be controlled by the device's controller.

[0030] According to another exemplary embodiment, altering at least one printing parameter, particularly a printing parameter affecting the curing (behavior) of the photocurable resin, spatially and / or temporally can include irradiating the photocurable resin with light of a first wavelength first, and then irradiating it with light of a second wavelength. Therefore, altering at least one printing parameter can include irradiating the photocurable resin with light of a first wavelength first, and then irradiating it with light of a second wavelength. In this way, one or more volume elements of the three-dimensional object to be printed can be irradiated with light of the first wavelength before being irradiated with light of the second wavelength. The one or more volume elements of the photocurable resin can each comprise a first volume element of the three-dimensional object to be printed. In other words, the irradiation process can include irradiating one or more volume elements (solely) with light of the first wavelength spatially and / or temporally, and then irradiating subsequent volume elements with light of the first wavelength (and typically also with light of the second wavelength). Irradiating the volume elements of the photocurable resin with light of the first wavelength only can pre-activate these volume elements, thereby achieving a better curing effect when these volume elements are subsequently irradiated with light of the first wavelength and the second wavelength, thus improving the structural properties of the three-dimensional object to be printed.

[0031] For example, spatially irradiating a photosensitive resin with light of a first wavelength followed by irradiation with light of a second wavelength can include the following process: irradiating the photocurable resin with light of the first wavelength starting from a first position p1, and irradiating the photocurable resin with light of the second wavelength starting from a second position p2, wherein the second position p2 is located behind the first position p1 in the molding direction. The second position is typically the location within the volume of the photocurable resin where the corresponding three-dimensional object to be printed is formed, and therefore is the location inside the corresponding three-dimensional object to be printed. Specifically, the second position can be the location within the volume of the photocurable resin where the corresponding three-dimensional object to be printed is formed, and therefore is the location of the surface of the corresponding three-dimensional object to be printed. Therefore, the three-dimensional object to be printed can include a portion located behind the second position relative to the molding direction, or the three-dimensional object can be formed behind the second position relative to the molding direction. Therefore, the second position can include a first volume element of the three-dimensional object to be printed relative to the molding direction, such as a first voxel. The first position can also be a location within the volume of the photocurable resin where the three-dimensional object to be printed is formed, and therefore is also the location inside the three-dimensional object to be printed. Specifically, the first position is the position within the volume of the photocurable resin before the three-dimensional object to be printed is formed, and therefore is the position outside the three-dimensional object to be printed.

[0032] An example of irradiating photosensitive resin with light of a first wavelength first, followed by irradiation with light of a second wavelength, can include the following process: irradiating the photocurable resin with light of the first wavelength begins at a first time t1, and irradiating the photocurable resin with light of the second wavelength begins at a second time t2, where t2 > t1. The second time typically corresponds to the moment when the volume of photocurable resin constituting the three-dimensional object to be printed is irradiated. Specifically, the second time can correspond to the moment when the volume of photocurable resin constituting the outer boundary or edge (i.e., the surface position constituting the three-dimensional object) is irradiated. Therefore, the three-dimensional object to be printed may include portions printed after the second time, or the printing of the three-dimensional object may be completed after the second time. Thus, the second time can include the moment when the first volume element (e.g., the first voxel) of the three-dimensional object to be printed is printed relative to the forming direction. The first time can also correspond to the moment when the volume of photocurable resin constituting the three-dimensional object to be printed is irradiated. However, the first time can also correspond to the moment when the volume of photocurable resin not constituting the three-dimensional object to be printed is irradiated.

[0033] According to another exemplary embodiment, changing at least one printing parameter, particularly a printing parameter affecting the curing (behavior) of a photocurable resin, spatially and / or temporally can include irradiating the photocurable resin with light of a first wavelength after irradiating it with light of a second wavelength. Therefore, changing at least one printing parameter can include irradiating the photocurable resin with light of a first wavelength spatially and / or temporally after irradiating it with light of a second wavelength. In this way, one or more volume elements of the three-dimensional object to be printed can be irradiated with light of a first wavelength after being irradiated with light of a second wavelength. The one or more volume elements of the photocurable resin can particularly include the final volume elements of the three-dimensional object to be printed. In other words, the irradiation process can include irradiating one or more volume elements spatially and / or temporally (only) with light of a first wavelength after previous volume elements have been irradiated with light of a second wavelength (and typically also with light of a first wavelength). Irradiating the volume elements of the photocurable resin with only light of a first wavelength can result in post-activation of these volume elements, thereby causing these volume elements to further promote their curing after being irradiated with light of both the first and second wavelengths, thereby improving the structural properties of the corresponding three-dimensional object to be printed.

[0034] An example of irradiating a photocurable resin with light of a second wavelength followed by irradiating it with light of a first wavelength can include: irradiating the photocurable resin with light of the second wavelength ending at a third position p3, and irradiating it with light of the first wavelength ending at a fourth position p4, wherein the fourth position p4 is located after the third position p3 in the molding direction. The third position is typically the location within the volume of the photocurable resin where the corresponding 3D object to be printed is formed, and therefore is a location inside the corresponding 3D object to be printed. Specifically, the third position can be the location within the volume of the photocurable resin where the outer boundary or edge of the corresponding 3D object to be printed is formed, and therefore is a location on the surface of the corresponding 3D object to be printed. Therefore, the 3D object to be printed can include a portion located in front of the third position relative to the molding direction, or the molding of the 3D object relative to the molding direction is completed in front of the third position. Therefore, the third position can include the last volume element of the 3D object to be printed relative to the molding direction, such as the last voxel. The fourth position can also be located within the volume of the photocurable resin that forms the corresponding 3D object to be printed, and therefore is also located inside the corresponding 3D object to be printed. Specifically, the fourth position is located within the volume of the photocurable resin in which the corresponding three-dimensional object to be printed has not yet been formed, and is therefore located outside the corresponding three-dimensional object to be printed.

[0035] Another example of irradiating the photocurable resin with light of a second wavelength followed by irradiating it with light of a first wavelength could include: irradiating the photocurable resin with light of a second wavelength ending at a third time t3, and irradiating it with light of a first wavelength ending at a fourth time t4, where t4 > t3. The third time typically corresponds to the moment when the volume of photocurable resin constituting the three-dimensional object to be printed is irradiated. Specifically, the third time can correspond to the moment when the volume of photocurable resin constituting the outer boundary or edge (i.e., the surface position constituting the three-dimensional object) is irradiated. Therefore, the three-dimensional object to be printed may include portions printed before the third time, or the printing of the three-dimensional object may be completed before the third time. Thus, the third time can correspond to the moment when the last volume element (e.g., the last voxel) of the three-dimensional object to be printed is printed relative to the forming direction. The fourth time can also correspond to the moment when the volume of photocurable resin constituting the three-dimensional object to be irradiated. However, the fourth time can also correspond to the moment when the volume of photocurable resin not constituting the three-dimensional object to be irradiated is irradiated.

[0036] Therefore, altering at least one printing parameter, particularly those affecting the curing behavior of the photocurable resin, in space and / or time can include irradiating the photocurable resin with light of a first wavelength in a volume separate from the volume of the three-dimensional object to be printed, particularly in an adjacent volume, and more particularly in a directly adjacent volume, especially where the volume is located before and / or after the volume of the three-dimensional object to be printed in space and / or time relative to at least one forming direction of the three-dimensional object. In this way, pre-activation or post-activation of the photocurable resin can be achieved, thereby positively influencing the structural properties of the three-dimensional object to be printed.

[0037] Therefore, spatially and / or temporally, irradiating the photocurable resin with light of the first wavelength before or after irradiating it with light of the second wavelength typically includes irradiating volume elements in the photocurable resin that do not constitute the three-dimensional object to be printed (only) with light of the first wavelength. These volume elements may be located before or in front of the volume elements that constitute part of the three-dimensional object to be printed, preferably before or in front of the first volume element of the three-dimensional object to be printed relative to the molding direction; or after or behind the volume elements that constitute part of the three-dimensional object to be printed, preferably after or behind the last volume element of the three-dimensional object to be printed relative to the molding direction.

[0038] However, it is also conceivable that the volume elements of the photocurable resin that do not form part of the three-dimensional object to be printed can be irradiated (only) with light of a second wavelength, so that the above description can also be applied to light of a second wavelength.

[0039] According to another exemplary embodiment, changing at least one printing parameter in space and / or time, particularly printing parameters affecting the curing behavior of the photocurable resin, can include: irradiating the photocurable resin with light of a first wavelength and / or a second wavelength, and changing the energy, particularly the energy intensity, of the first wavelength and / or the second wavelength light in space and / or time along at least one direction. Changing the energy, particularly the energy intensity, of the first wavelength and / or the second wavelength light in space and / or time along at least one direction can also have a positive impact on the structural properties of the three-dimensional object to be printed, for example, because it allows control over the amount of energy received by each volume element of the three-dimensional object to achieve the desired curing effect. This overcomes or at least reduces problems caused by different curing degrees of different volume elements of the three-dimensional object to be printed, which often also lead to undesirable structural anisotropy in the three-dimensional object. Similarly, the proximity effect (as described above) can also be overcome or at least reduced, because one or more volume elements adjacent to other cured or photopolymerized volume elements can be irradiated with different energies relative to volume elements not near other cured or photopolymerized volume elements.

[0040] Specifically, changing the energy or energy intensity spatially and / or temporally can include changing the energy level of the first wavelength of light from a first energy level to at least a second energy level, which is higher or lower than the first energy level. Therefore, during irradiation, the energy or energy intensity of the first wavelength of light can dynamically or gradually increase or decrease spatially and / or temporally, particularly relative to a nominal value, which can be (but is not limited to) the minimum or maximum energy or energy intensity.

[0041] Additionally or alternatively, changing the energy or energy intensity of the second wavelength of light spatially and / or temporally may include: varying the energy level of the second wavelength of light from a first energy level to at least a second energy level, which is higher or lower than the first energy level. Therefore, during irradiation, the energy or energy intensity of the second wavelength of light may dynamically or gradually increase or decrease spatially and / or temporally, particularly relative to a nominal value, which may be (but is not limited to) a minimum or maximum energy level or energy intensity level.

[0042] For example, changing the energy (particularly the energy intensity) of a second wavelength of light spatially and / or temporally along at least one direction can include changing the energy or energy density of one or more image elements (e.g., pixels) of various images corresponding to the cross-sectional geometry of the three-dimensional object to be printed, respectively, spatially and / or temporally. In other words, the corresponding projections of one or more images can contain image elements with different energies or energy densities. Changing the energy or energy density of individual image elements can include changing the energy level or energy density level between a minimum energy level or a minimum energy density level and a maximum energy level or a maximum energy density level. Similarly, changing the energy or energy density of individual lines or points can include changing the energy level or energy density level between a minimum energy level or a minimum energy density level and a maximum energy level or a maximum energy density level. Changing the energy or energy density of image elements or points or lines can be achieved by controlling the irradiation device used to generate the projections of images or points or lines respectively.

[0043] Another example is that changing the energy (particularly the energy intensity) of a second wavelength of light spatially and / or temporally along at least one direction can include: for one or more image elements (e.g., pixels) of various images corresponding to the cross-sectional geometry of the three-dimensional object to be printed, and / or for one or more image elements (e.g., pixels) of various images not corresponding to the cross-sectional geometry of the three-dimensional object to be printed, changing the energy or energy intensity spatially and / or temporally so as not to affect the curing of the photocurable resin. Therefore, changing the energy (particularly the energy intensity) of a second wavelength of light spatially and / or temporally can include: setting the energy or energy intensity spatially and / or temporally to a level that will not cause the photocurable resin to cure, or setting it to a level that causes insufficient curing of the photocurable resin. However, it is also conceivable that changing the energy (particularly the energy intensity) of a second wavelength of light spatially and / or temporally can include: setting the energy or energy intensity spatially and / or temporally to a level that causes over-curing of the photocurable resin. Specifically, altering the energy (particularly the energy intensity) of the second wavelength light spatially and / or temporally along at least one direction can include irradiating a first volume element of the three-dimensional object to be printed with a higher intensity of the second wavelength light than other volume elements of the three-dimensional object to be printed, relative to the forming direction. In this way, a method for compensating for proximity effects is provided.

[0044] According to another exemplary embodiment, a photocurable resin can be irradiated with light of a first wavelength at a first energy level in an initial volume of a three-dimensional object to be printed. This first energy level can be a relatively higher energy level compared to a nominal energy level or a second energy level. The initial volume, with a spatial extension in at least one direction, represents at most 10%, particularly at most 9%, more particularly at most 8%, more particularly at most 7%, more particularly at most 6%, more particularly at most 5%, more particularly at most 4%, more particularly at most 3%, more particularly at most 2%, more particularly at most 1%, more particularly At most 0.9%, more particularly at most 0.8%, more particularly at most 0.7%, more particularly at most 0.6%, more particularly at most 0.5%, more particularly at most 0.4%, more particularly at most 0.3%, more particularly at most 0.2%, more particularly at most 0.1%, more particularly at most 0.09%, more particularly at most 0.08%, more particularly at most 0.07%, more particularly at most 0.06%, more particularly at most 0.05%, more particularly at most 0.04%, more particularly at most 0.03%, more particularly at most 0.02%, more particularly at most 0.01%. Irradiating the photocurable resin in the initial volume of the three-dimensional object to be printed with light of a first wavelength at a higher energy level in at least one direction can, in particular, compensate for or at least reduce the proximity effect, thereby obtaining a three-dimensional object with lower structural anisotropy and improved structural properties.

[0045] Alternatively or alternatively, the photocurable resin can be irradiated with light of a first wavelength at a first energy level for a certain initial time. This first energy level can be a relatively higher energy level compared to a nominal energy level or a second energy level. The initial time is: at most 10 seconds, particularly at most 9 seconds, more particularly at most 8 seconds, more particularly at most 7 seconds, more particularly at most 6 seconds, more particularly at most 5 seconds, more particularly at most 4 seconds, more particularly at most 3 seconds, more particularly at most 2 seconds, more particularly at most 1 second, more particularly at most 0.9 seconds, more particularly at most 0.8 seconds, more particularly at most 0.7 seconds, more particularly at most 0.6 seconds, and more particularly at most 1 second. At most 0.5 seconds, more particularly at most 0.4 seconds, more particularly at most 0.3 seconds, more particularly at most 0.2 seconds, more particularly at most 0.1 seconds, more particularly at most 0.09 seconds, more particularly at most 0.08 seconds, more particularly at most 0.07 seconds, more particularly at most 0.06 seconds, more particularly at most 0.05 seconds, more particularly at most 0.04 seconds, more particularly at most 0.03 seconds, more particularly at most 0.02 seconds, more particularly at most 0.01 seconds; this initial time corresponds to the total duration of the irradiation process, particularly the total duration of the irradiation process for printing three-dimensional objects by multicolor photopolymerization curing of photocurable resin. Each time interval can correspond to at least the first frame of the image projection of the second wavelength of light irradiating the photocurable resin during the irradiation process, particularly at most the first 100 frames, more particularly at most the first 90 frames, more particularly at most the first 80 frames, more particularly at most the first 70 frames, more particularly at most the first 60 frames, more particularly at most the first 50 frames, more particularly at most the first 40 frames, more particularly at most the first 30 frames, more particularly at most the first 20 frames, and more particularly at most the first 10 frames.

[0046] According to another exemplary embodiment, changing at least one printing parameter, particularly a printing parameter affecting the curing behavior of the photocurable resin, in space and / or time can include changing focal parameters, such as the size and / or position of the focal point of a first wavelength of light, and / or changing image parameters, such as the size and / or position of an image projected with second wavelength light or at least one image element (e.g., a pixel) of the projected image. Therefore, focal parameters, such as the size and / or position of the focal point of the first wavelength of light, focal length, depth of focus, and depth of field, can serve as printing parameters that can be changed during irradiation, thereby affecting the curing result within the forming area and the feature resolution of the three-dimensional object to be printed, respectively, in space and / or time. The first wavelength of light can include multiple beams, particularly multiple (substantially) parallel beams, which pass through the photocurable resin, for example, in the form of light sheets. Changing one or more focal parameters of the first wavelength of light can be achieved by one or more optical elements (e.g., (movable) lenses) assigned to an irradiation apparatus for generating the first wavelength of light and corresponding beams passing through the photocurable resin. The corresponding optical elements can form part of a focal adjustment device of the irradiation apparatus, which can be configured to adjust one or more focal parameters of the first wavelength of light. Additionally or alternatively, image parameters, such as the projected image of the second wavelength of light or the size and / or position of at least one image element (which may include an image projection corresponding to the cross-sectional geometry of the three-dimensional object to be printed), can be printing parameters that are variable during irradiation. These image parameters, for example, can affect the curing effect within the forming area and the feature resolution of the three-dimensional object to be printed in space and / or time. Changing one or more image parameters of the second wavelength of light can be achieved by assigning one or more optical elements (e.g., (movable) lenses, pixel generators, etc.) to the irradiation apparatus used to generate the second wavelength of light and the respective images corresponding to the cross-sectional geometry of the three-dimensional object to be printed. The respective optical elements can form part of an image adjustment device of the irradiation apparatus, which can be configured to adjust one or more image parameters of the second wavelength of light. The corresponding image adjustment device can be a hardware and / or software implementation component of a light projection device (e.g., a digital light projection device).

[0047] According to another exemplary embodiment, changing the energy of the second wavelength of light spatially and / or temporally can include altering the energy or energy distribution of at least a portion (e.g., at least one pixel) of at least one projected image corresponding to the cross-sectional geometry of the three-dimensional object to be printed, or altering the energy or energy distribution of at least one point or line of at least one beam corresponding to the cross-sectional geometry of the three-dimensional object to be printed. Specifically, the energy of the second wavelength of light can be varied along at least one direction, such that an upstream portion of the three-dimensional object to be printed and a downstream portion of the three-dimensional object to be printed are exposed to different energy levels of the second wavelength of light relative to the forming direction. As described above, altering the energy of the second wavelength of light spatially and / or temporally can reduce the structural anisotropy of the three-dimensional object and improve its structural properties.

[0048] As an example, changing the energy or energy intensity of light of a second wavelength in space and / or time can include: changing the energy or energy intensity of at least a portion (particularly at least one image element, such as at least one pixel) of at least one image in a sequence comprising at least three energy levels E1, E2, and E3 (or energy intensity levels, E1, E2, and E3 respectively), wherein the energy level or energy intensity level changes from E1 to E2, and E2 > E1; the energy level or energy intensity level changes from E2 to E3, and E2 > E3, particularly E3 > E1, or for example, E1 = 0. Specifically, the first energy level E1 can be assigned to one or more volume elements of the photocurable resin, in which a small amount of photopolymerization is undesirable or only desired; these volume elements of the photocurable resin can include volume elements that do not constitute part of the three-dimensional object to be printed. Therefore, the first energy level can also be (substantially) zero (E1 = 0). Specifically, the second energy level E2 can be assigned to one or more volume elements of the photocurable resin that constitute part of the three-dimensional object to be printed. Specifically, the second energy level E2 can be allocated to one or more volume elements of the photocurable resin that constitute at least a first volume element of the three-dimensional object to be printed, or to one or more volume elements of the photocurable resin that constitute a first volume element of the three-dimensional object to be printed, the first volume element being relative to the molding direction. In particular, the third energy level E3 can be allocated to one or more volume elements of the photocurable resin that constitute other volume elements of the three-dimensional object to be printed, these other volume elements being located behind the first volume element of the three-dimensional object to be printed relative to the molding direction. Furthermore, a fourth energy level E4 can be implemented and allocated to one or more volume elements of the photocurable resin that do not constitute a part of the three-dimensional object to be printed. Specifically, the fourth energy level E4 can be allocated to volume elements of the photocurable resin located after the last volume element of the photocurable resin constituting the three-dimensional object to be printed. Therefore, the fourth energy level E4 can also be (essentially) zero (E4 = 0).

[0049] According to another exemplary embodiment, varying at least one printing parameter, particularly those affecting the curing behavior of the photocurable resin, in space and / or time can include irradiating the photocurable resin with light of a first wavelength and / or a second wavelength during irradiation when at least one molding region does not move relative to the container or corresponding container, or when at least one molding region moves at a varying rate of motion lower than the nominal rate of motion. The corresponding varying rate of motion can also be zero. Therefore, the rate of motion of at least one molding region, particularly relative to the container or corresponding container, is also a printing parameter that can vary in space and / or time, for example, for achieving the printing of three-dimensional objects with higher structural isotropy.

[0050] For example, during irradiation, when at least one molding area does not move relative to the container or corresponding container, or when at least one molding area moves at a rate lower than the nominal rate of movement, irradiating the photocurable resin with light of a first wavelength and / or a second wavelength may include: when the photocurable resin moves relatively slowly or even not at all relative to the container, irradiating the photocurable resin with light of the first wavelength such that corresponding volume elements of the photocurable resin are irradiated by light of the first wavelength for a relatively long period of time. During this period, for example, the second wavelength of light may form a constant or static image. Alternatively, during this period, for example, no second wavelength of light is irradiated into the photocurable resin and the working volume.

[0051] According to another exemplary embodiment, changing at least one printing parameter in space and / or time, particularly printing parameters affecting the curing behavior of the photocurable resin, may further include irradiating the photocurable resin with light of a first wavelength and / or a second wavelength while at least one molding region moves along two different directions. Therefore, the direction of movement of at least one molding region (particularly relative to the direction of movement of the container or corresponding container) is also a printing parameter that can be changed in space and / or time, for example, for printing three-dimensional objects with higher structural isotropy.

[0052] For example, at least one forming area can move along a first movement path in a first movement direction when irradiated by light of a first wavelength and / or a second wavelength, particularly when irradiated only by light of the first wavelength; and at least one forming area can move along a second movement path in a second movement direction (particularly in the opposite direction to the first direction) when irradiated by light of the first wavelength and / or a second wavelength, particularly when irradiated simultaneously by light of the first wavelength and a second wavelength. Specifically, the first movement direction can be a movement direction toward or away from the irradiation device (particularly a digital light projection device) used to implement the device for generating light of the second wavelength, while the second movement direction can be a movement direction toward or away from the irradiation device (particularly a digital light projection device), and vice versa.

[0053] Another example is that the first motion path can differ from the second motion path, particularly in length. Specifically, the first motion path can be shorter than the second motion path. Therefore, when at least one molding area moves along the first motion path, the irradiation time of the photocurable resin by light of a first wavelength applied to the photocurable resin can be shorter than the irradiation time when at least one molding area moves along the second motion path.

[0054] According to another exemplary embodiment, changing at least one printing parameter, particularly those affecting the curing behavior of the photocurable resin, in space and / or time can include (this is particularly applicable to embodiments of methods requiring the printing of multiple independent three-dimensional objects, especially those simultaneously printing multiple independent three-dimensional objects): for example, by setting the starting position and / or starting time and / or ending position and / or ending time corresponding to the second wavelength of light used for printing the first three-dimensional object to irradiate the photocurable resin, which can be different from the starting position and / or starting time corresponding to the second wavelength of light used for printing another three-dimensional object to irradiate the photocurable resin. In particular, this exemplary embodiment enables the photocurable resin to continue being irradiated with the second wavelength of light even after the printing of at least one three-dimensional object has been completed, which will result in higher structural fidelity for the first completed three-dimensional object. It is worth noting that this embodiment is particularly applicable to situations where multiple three-dimensional objects to be printed are arranged laterally. Thus, the respective forming directions of these three-dimensional objects are parallel to each other.

[0055] According to another exemplary embodiment, at least one printing parameter, particularly a printing parameter affecting the curing behavior of the photocurable resin, can be spatially and / or temporally modified by printing at least one auxiliary object. Specifically, printing at least one auxiliary object can be initiated spatially and / or temporally before printing the actual three-dimensional object (i.e., the actual three-dimensional object to be manufactured). More specifically, printing at least one auxiliary object can be completed before printing the actual three-dimensional object. In either case, at least one auxiliary object can be printed in a first volume of a container, while the actual three-dimensional object to be printed is printed in a second volume of the container, wherein the second volume is located behind and / or after the first volume in space and / or time. Thus, printing at least one auxiliary object can include: first, moving a light sheet of a first wavelength along at least one direction (particularly relative to the corresponding container containing the photocurable resin (as described above)) through the first volume to generate at least one auxiliary object by multicolor photopolymerization (as described above); then, moving the light sheet of the first wavelength through the second volume. When the first wavelength light passes through the second volume, the intensity of the second wavelength light can be zero or at least (significantly) reduced, such that the photocurable resin in the second volume is (substantially) irradiated only by the first wavelength light.

[0056] A real 3D object can be printed based on one or more target attributes, which are typically defined according to the intended application or use of the 3D object. For example, a real 3D object may have a target shape or optical properties, which can be defined based on the intended application or use of the 3D object as an optical element. At least one auxiliary object may differ from one or more target attributes in at least one attribute. Referring to the example above, therefore, at least one auxiliary object may deviate from the intended shape or have lower optical properties than the real 3D object to be printed. Therefore, the quality requirements for at least one auxiliary object may be lower than the quality requirements for the real 3D object to be printed.

[0057] At least one auxiliary object may have a longitudinal shape having a spatial extension direction extending along the direction of movement of the light sheet through the container. For example, at least one auxiliary object may be or include a rod-shaped shape having a spatial extension direction extending along the direction of movement of the light sheet through the container. In either case, the volume of at least one auxiliary object may be smaller than the volume of the actual 3D object to be printed. For example, the volume of at least one auxiliary object may be at least one of the following proportions of the volume of the actual 3D object to be printed: 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 6, 1 / 7, 1 / 8, 1 / 9, 1 / 10, etc.

[0058] At least one auxiliary object may be or include a sacrificial object, which can be discarded after printing. Specifically, at least one auxiliary object may be attached to at least one 3D object to be printed. Therefore, one or more connection portions may exist, such as one or more connection points, one or more connection lines, or one or more connection regions, through which at least one auxiliary object is physically connected to the actual 3D object. Each connection portion may include predetermined separation or disconnection structures that allow at least one auxiliary object to be removed from the actual 3D object after printing, for example, by disconnection. Alternatively, at least one auxiliary object may also be arranged adjacent to, or spatially offset from, at least one 3D object to be printed, such that there are no connection portions for physically connecting at least one auxiliary object to the actual 3D object. The distance between at least one auxiliary object and the actual 3D object to be printed can be very small, preferably <10 mm, more preferably <5 mm, even more preferably less than 1 mm, still more preferably <500 μm, and most preferably <100 μm.

[0059] At least one auxiliary object may have at least one function. For example, at least one auxiliary object may have a support function that supports a three-dimensional object attached thereto, such as facilitating the removal of a three-dimensional object from a container.

[0060] According to another exemplary embodiment, changing at least one printing parameter in space and / or time, particularly printing parameters affecting the curing behavior of the photocurable resin, can include non-uniformly changing the temperature and / or density of the photocurable resin within the container. Thus, the temperature and / or density of the photocurable resin at position L1 can be higher than that at position L2; particularly at the same time, especially at the initial moment of printing the three-dimensional object, the temperature and / or density of the photocurable resin at position L1 can be higher than that at position L2. This can be achieved by first printing at least one auxiliary object (particularly the sacrificial object as described above) and then printing the actual three-dimensional object. The at least one auxiliary object can have a shape and / or size adapted to the actual three-dimensional object to be printed. In particular, the at least one auxiliary object can have a plate-like shape, such as a rectangular plate, a polygonal plate, or a circular plate. The position and / or orientation of the plate within the container can be such that the normal on its main extending plane is (substantially) parallel to at least one direction in which at least one molding area moves relative to the container containing the photocurable resin (as described above). This allows any heat generated during the printing of at least one auxiliary object (e.g., heat generated due to the polymerization of photocurable resin) to cause temperature changes, particularly temperature rises and / or temperature gradients, within the volume of at least one three-dimensional object to be printed.

[0061] In particular, the surface of at least one auxiliary object may have a shape opposite to that of the surface of the actual 3D object to be printed (especially the surface of the 3D object to be printed or the opposite surface). For example, when the actual 3D object to be printed has a concave surface, at least one auxiliary object may have a convex surface.

[0062] Surprisingly, it has been found that printing at least one auxiliary object before printing the actual 3D object can improve the structural realism of the actual 3D object. While not subject to any theoretical constraints, the explanation for this phenomenon is that during the polymerization of the photocurable resin to form at least one auxiliary object, the temperature of the photocurable resin within the volume used to form the actual 3D object rises due to the heat of polymerization, causing the photocurable resin near the already printed portion of the object within that volume to expand. Therefore, the subsequently printed portion of the actual 3D object will be formed within the expanded resin (the expansion is caused by the temperature increase). By printing at least one auxiliary object before printing the actual 3D object, the expansion of the resin within the volume used to print the actual 3D object allows the initial portion of the 3D object to be formed within the expanded resin, which helps the photocurable resin shrink more evenly after cooling and reaching equilibrium.

[0063] According to another exemplary embodiment, the irradiation process may include: in a first irradiation step, irradiating a photocurable resin with light of a first wavelength and light of a second wavelength to form a prepolymerized three-dimensional preform; and in at least one subsequent irradiation step, irradiating the prepolymerized three-dimensional preform with light of the first wavelength and light of the second wavelength to form a three-dimensional object, particularly after completing the first irradiation step and / or after completing at least one subsequent irradiation step, and more particularly, after completing the first subsequent irradiation step among a plurality of subsequent irradiation steps, irradiating the prepolymerized three-dimensional preform with light of the first wavelength and light of the second wavelength to form a three-dimensional object. Therefore, the number of individual irradiation steps can also be printing parameters that can be varied spatially and / or temporally. It is noteworthy that this embodiment may include forming a prepolymerized three-dimensional preform in the first irradiation step, which may already have a shape and / or size corresponding (basically) to the three-dimensional object to be printed. However, the degree of curing of the photocurable resin of the three-dimensional preform may differ from that of the actual three-dimensional object to be printed. In other words, the degree of curing of the photocurable resin of the three-dimensional preform may be low; for example, the degree of curing of the three-dimensional preform may render it inoperable. However, printing actual 3D objects using appropriate intermediate preforms can improve the structural properties of the actual 3D objects.

[0064] For example, in the first irradiation step, a photocurable resin can be irradiated with light of a first wavelength and light of a second wavelength to form a prepolymerized three-dimensional preform; in the second irradiation step, the prepolymerized three-dimensional preform is irradiated with light of the first wavelength and light of the second wavelength, thereby further polymerizing the prepolymerized three-dimensional preform; wherein, the second irradiation step can be repeated multiple times. It is worth noting that in the first irradiation step, the forming region can move along a first movement path in a first movement direction; in at least one second irradiation step, the forming region can move along a second movement path in a second movement direction (particularly in the opposite direction to the first movement direction).

[0065] Typically, a photocurable resin is irradiated with light of a first wavelength in a first irradiation step to form a prepolymerized photocurable resin; and, in at least one subsequent irradiation step, the prepolymerized photocurable resin is irradiated with light of a first wavelength and light of a second wavelength to form a three-dimensional object, particularly after the completion of the first irradiation step and / or after the completion of at least one subsequent irradiation step, and more particularly, after the completion of the first subsequent irradiation step in a plurality of subsequent irradiation steps, the prepolymerized photocurable resin is irradiated with light of a first wavelength and light of a second wavelength to form a three-dimensional object.

[0066] Specifically, in the first irradiation step, the photocurable resin can be irradiated with light of a first wavelength and light of a second wavelength to form a prepolymerized photocurable resin; and in at least one subsequent irradiation step, the prepolymerized photocurable resin is irradiated with light of the first wavelength and light of the second wavelength to form a three-dimensional object, particularly after completing the first irradiation step and / or at least one subsequent irradiation step, and more particularly after completing the first subsequent irradiation step among a plurality of subsequent irradiation steps, the prepolymerized photocurable resin is irradiated with light of the first wavelength and light of the second wavelength to form a three-dimensional object. Specifically, the intensity of the first wavelength and / or the second wavelength of light in the first irradiation step may be lower than the intensity required to initiate the curing or solidification of the photocurable resin, or lower than the intensity of the first wavelength and / or the second wavelength of light required to form a three-dimensional object. Specifically, in the first irradiation step, the intensity distribution of the second wavelength of light is non-uniform. More particularly, in the first irradiation step, the second wavelength of light may have a lower intensity in the outer region near the container wall defining the working space, and a higher intensity in the inner region of the working volume (e.g., the center of the working volume). For example, the second wavelength of light may be projected as an image with higher intensity in each of the inner regions. For example, the corresponding image can be a grayscale or whitescale image. Furthermore, printing actual 3D objects by forming an intermediate pre-polymerized photocurable resin can improve the structural properties of the actual 3D objects.

[0067] According to another exemplary embodiment, changing at least one printing parameter, particularly those affecting the curing behavior of the photocurable resin, spatially and / or temporally can include making the intensity distribution of the second wavelength light non-uniform, particularly in a direction orthogonal to the molding direction. Specifically, the pixels of the projection or projected image of the second wavelength light may have lower intensity in the outer region near the container wall defining the working volume, and higher intensity in the inner region of the working volume (e.g., the center of the container defining the working volume). As described above, the second wavelength light can be projected as an image, wherein the image has pixels with higher intensity in the corresponding inner image region (particularly including the image center), and pixels with lower intensity in the corresponding outer region (particularly including the outer edge of the image surrounding the corresponding inner image region). As described above, the respective images may be, for example, grayscale or whitescale images.

[0068] Specifically, the non-uniform intensity distribution of the second wavelength light can be set according to the intensity distribution of the first wavelength light. For example, the first wavelength light can enter the working volume from one side (incident side) in the form of a light sheet, such that the side of the light sheet entering the working volume has a higher intensity, while the side of the light sheet leaving the working volume (exit side) has a lower intensity. In this case, the pixels of the projection or projected image of the second wavelength light have a higher intensity in the forming region near the exit side of the light sheet, while the pixels of the second wavelength light have a lower intensity in the forming region near the incident side of the light sheet. Another example is that the first wavelength light can enter the working volume from different sides of the container (especially opposite sides of the container) in the form of a light sheet, which will result in a lower intensity of the first wavelength light near the middle of the working volume, while a higher intensity of the first wavelength light near the edge of the working volume, especially at the locations where the light sheet enters and leaves the working volume. In such an example, it is advantageous that the pixels of the projection or projected image of the second wavelength light have a higher intensity in the central region of the forming region between the exit and incident sides of the light sheet, while the pixels of the second wavelength light have a lower intensity in the forming regions near the incident and exit sides of the light sheet. In other words, in the molding region, where the intensity of the first wavelength light is low, the pixel intensity of the second wavelength light can be higher, thereby achieving a more uniform curing or polymerization degree of the photocurable resin. In particular, the intensity variation of the second wavelength light can follow at least one gradient distribution from white pixels to gray pixels or black pixels from the outer region to the inner region of the working volume, and vice versa.

[0069] Specifically, the pixels of the projection or projected image of the second wavelength of light can have different intensities along the height direction of the light sheet of the first wavelength of light. Specifically, along the height direction of the light sheet, the pixels of the projection or projected image of the second wavelength of light can have lower intensity in the forming region near the center of the light sheet, and higher intensity in the forming regions at the top and bottom of the projected image. Therefore, the non-uniformity of the light intensity of the first wavelength of light along the height direction of the light sheet can be compensated by overlapping the pixels with higher intensity in the projection or projected image of the second wavelength of light with the regions with lower intensity in the light sheet (especially along the height direction) in the forming region (and vice versa).

[0070] Surprisingly, without any theoretical constraints, it has been observed that light sheets may exhibit a non-uniform intensity distribution along their height direction, leading to uneven curing of the photocurable resin. Specifically, the light intensity along the height direction of each light sheet may be related to the sheet's formation. For example, the light intensity of a light sheet may follow, for example, a Gaussian, Cauchy, or parabolic distribution, resulting in higher intensity at the center of the light sheet relative to its outer edges (e.g., the edges), or vice versa. This non-uniform intensity distribution of light sheets with higher central intensity may lead to a higher degree of polymerization of the photocurable resin at the center of the light sheet (e.g., relative to its height direction). This non-uniform intensity distribution can be compensated for by setting pixels of a second wavelength of light with different intensities along the height direction of the light sheet, specifically making its intensity distribution opposite to that of the light sheet along the height direction. In other words, in the forming region, where the intensity of the first wavelength of light is low, the intensity of the second wavelength light pixels can be increased, thereby achieving a more uniform degree of curing or polymerization of the photocurable resin. In particular, the intensity variation of the second wavelength of light can follow at least one pixel gradient from white to gray or black from the outer region to the inner region of the working volume, and vice versa.

[0071] The intensity variation of the second wavelength of light can be achieved by processing (particularly software-based processing) one or more images of the second wavelength of light. The corresponding processing may include applying or implementing at least one filter to the image of the second wavelength of light such that the intensity distribution of the second wavelength of light is non-uniform between the outer and inner regions of the image. Additionally or alternatively, optical filtering elements may be considered. The corresponding optical filtering elements may be or include so-called neutral density filters, such as those available from Thorlabs (see, for example, https: / / www.thorlabs.com / thorproduct.cfm?partnumber=NDL-25C-2).

[0072] The corresponding non-uniform intensity distribution of the second wavelength of light may include an intensity distribution profile, which includes one or more portions (which may include pixels) with higher intensity in the inner image region and one or more portions (which may include pixels) with lower intensity in the outer image region.

[0073] As an example, the corresponding intensity distribution profile may include: one or more first portions or first pixels disposed at a first edge of the image (e.g., a first side edge) having a first intensity; one or more second portions or second pixels disposed at the center of the image having a second intensity higher than the first intensity; and one or more third portions or third pixels disposed at a second edge of the image (e.g., a second side edge), particularly the second edge opposite to the first edge, having a third intensity lower than the second intensity. It is worth noting that the third intensity may be close to or equal to the first intensity.

[0074] As an example, the corresponding intensity distribution profile may include: one or more first portions or first pixels disposed at a first edge of the image (i.e., the top or bottom edge relative to the height direction of the light sheet), having a first intensity; one or more second portions or second pixels disposed at the center of the image, having a second intensity higher than the first intensity; and one or more third portions or third pixels disposed at a second edge of the image (i.e., the bottom or top edge), particularly the second edge opposite to the first edge, having a third intensity lower than the second intensity. It is worth noting that the third intensity may be close to or equal to the first intensity.

[0075] The corresponding intensity distribution profile can be based on or include a predefined intensity distribution. For example, the predefined intensity distribution can be or includes a linear or nonlinear distribution. The predefined distribution can be represented by a mathematical function. Therefore, the predefined distribution can be or includes Gaussian, Cauchy, exponential (based on exponential functions), multinomial (based on multinomial functions), parabolic, and hyperbolic (based on hyperbolic functions) distributions.

[0076] The choice of a specific intensity distribution profile can be based on simulation, modeling, or experimental results, for example, describing the intensity distribution of a light sheet passing through the working volume.

[0077] Optionally or additionally, in addition to varying the intensity of the second wavelength of light in each image of the second wavelength light, the intensity of the second wavelength light can also be varied in the forming direction, such that the first image of the second wavelength light can contain or have a first intensity distribution, while at least one subsequent image of the second wavelength light projected after the first image can contain or have a second intensity distribution. In this way, one or more pixels of the second image can have a different light intensity relative to one or more pixels of the previous first image, wherein each pixel has the same position in the respective image. In this manner, proximity effects that may lead to over-curing and undesirable deformation in at least some areas of the 3D object to be printed can also be reduced. Furthermore, experiments have surprisingly shown that when the intensity of the second wavelength light is varied in the forming direction, the outer edges of the 3D object can be printed with higher fidelity.

[0078] According to another exemplary embodiment, changing at least one printing parameter, particularly those affecting the curing behavior of the photocurable resin, in space and / or time can include making the intensity distribution of the second wavelength light non-uniform, particularly in a direction orthogonal to the forming direction. Specifically, pixels of the projection or projected image of the second wavelength light have lower intensity when surrounded by high-intensity pixels and higher intensity when surrounded by low-intensity pixels. Specifically, the intensity of a single pixel depends on the number and intensity of surrounding pixels (particularly adjacent pixels), and the intensity value of each surrounding pixel (particularly each adjacent pixel). In particular, the intensity of a pixel depends on the sum of the intensities of its surrounding pixels, and more particularly, the intensity of a pixel depends on a product factor of the intensity of each surrounding pixel and the distance from the pixel to each surrounding pixel. More particularly, the intensity of a pixel depends on whether the object needs curing at the corresponding location; for example, pixels in locations where curing is not required may undergo different intensity processing than pixels in locations where curing is required. For example, pixels surrounded by higher-intensity pixels may have lower intensity, while pixels in locations requiring curing may have higher intensity if surrounded by low-intensity or no-intensity pixels. Without any theoretical constraints, adjusting the intensity of a single pixel to match the intensity of its neighboring pixels can reduce unnecessary over-hardening caused by the proximity effect. For example, a pixel's intensity can also depend on the pixel intensity of the preceding or following image in the image sequence used during printing. The same process regarding pixel intensity variation described above can be applied to surrounding pixels in the preceding and following images; for example, the intensity of a single pixel can depend on the relationship between pixel intensity and distance between at least two images. Here, the image thickness corresponds to the slice thickness obtained during image creation.

[0079] According to another exemplary embodiment, the photocurable resin may contain chemical components or formulations with a strong grayscale response. Therefore, the photocurable resin will cure less or not at all under low-intensity second-wavelength light. Low intensity can refer to, for example, intensity below a specific threshold of the material. Using such a photocurable resin whose reactivity can be affected, for example, by adding inhibitors or less reactive photoinitiators or co-initiators, can improve the aforementioned grayscale-related effects. Using such a photocurable resin is a unique method that is not typically employed by those skilled in the art, as the usual practice is to use photocurable resins that already exhibit high reactivity at low intensities of second-wavelength light.

[0080] Alternatively, the corresponding photocurable resin can contain components with relatively low heat of polymerization. This reduces the thermal expansion of the photocurable resin during curing, which also positively impacts the structural fidelity of the three-dimensional object. As an exemplary example, the apparatus described in WO2021089090A1 can be used to print a flat plate with dimensions of 16mm × 8mm × 2mm (height x width x length) using a conventional photocurable resin containing 0.05 w% of a two-color photoinitiator (e.g., compound 2 described in WO2020245456A1), 64.95 w% of Genomer 4247 (polyurethane dimethacrylate manufactured by Rahn), 30 w% of SR833S (manufactured by Sartomer Arkema), and 5 w% of N-methyldiethanolamine. Post-processing of the three-dimensional object printed from such a material yields a curved panel with a specific radius of curvature. When the composition of the photocurable resin is changed to include 0.05 wt% (w / w) of a two-color photoinitiator (e.g., compound 2 in WO2020245456A1), 64.95 wt% (w / w) of Genomer 4247, 30 wt% (w / w) of SR834 (manufactured by Sartomer Arkema), and 5 wt% (w / w) of N-methyldiethanolamine, the radius of curvature of the post-treated sheet increases significantly, and the deformation caused by using SR834 is smaller compared to using SR833S. Therefore, the photocurable resin containing SR834 has a lower heat of polymerization, which can be measured, for example, by differential scanning calorimetry. Although SR833S and SR834 have the same backbone, SR833 is a methacrylate, while SR833S is an acrylate. Therefore, using a methacrylate, which typically has a lower heat of polymerization than acrylates, is beneficial for improving the structural fidelity of the resulting three-dimensional object. Therefore, this example demonstrates that shape fidelity can be improved by using a component with a lower heat of polymerization to reduce the heat of polymerization.

[0081] According to another exemplary embodiment, the forming time of the three-dimensional object can be set to a maximum of 1 minute for each millimeter of extension in at least one direction. Therefore, the method can be implemented at a high printing speed, which is another exemplary printing parameter affecting the curing behavior of the photocurable resin.

[0082] According to another exemplary embodiment, the method may include printing at least one three-dimensional object having at least one hollow internal volume, such as a closed hollow internal volume, containing uncured photocurable resin. Therefore, the three-dimensional object printed according to this method can contain at least one hollow internal volume, such as a closed hollow internal volume, containing uncured photocurable resin. Surprisingly, compared to printing a solid three-dimensional object (of the same shape and size), when the object contains at least one hollow internal volume, the deformation of the object can be reduced because the amount of photocurable resin that needs to be cured to form the green state of the three-dimensional object can be reduced. For example, the uncured photocurable resin contained in the hollow internal volume can be cured in a post-processing step. The at least one hollow internal volume may contain a mesh structure, such as a spiral structure or any other filling structure, which can stabilize the formed three-dimensional object and its blank. Therefore, the formed three-dimensional object and its blank can be processed separately, for example, sent to a post-processing station.

[0083] It is worth noting that this exemplary embodiment may relate to an independent aspect of the invention and is therefore not necessarily related to any other aspect or embodiment of the invention. Therefore, this disclosure also relates to a method for volumetrically printing a three-dimensional object by multicolor photopolymerization of a photocurable resin, the method comprising an irradiation process of irradiating a photocurable resin with light of a first wavelength and light of a second wavelength different from the first wavelength, based on a plurality of printing parameters, thereby forming a three-dimensional object in at least one direction by multicolor photopolymerization, wherein the first wavelength and the second wavelength intersect in a forming region, wherein the three-dimensional object includes at least one hollow internal volume, such as a closed hollow internal volume, the hollow internal volume containing uncured photocurable resin.

[0084] Another exemplary embodiment of the invention, or even another independent aspect, may include: varying at least one printing parameter spatially and / or temporally such that each volume element of the photocurable resin can be irradiated with light of a second wavelength. For example, a first pixel in a projected image of light of a second wavelength can be irradiated with a first specific wavelength (e.g., green light), and a second pixel in the projected image or another projected image can be irradiated with a second specific wavelength (e.g., red light), wherein the two specific wavelengths may have (substantially) the same physical intensity. For example, a specific first wavelength and a specific second wavelength representing the second wavelength can be selected based on the absorption spectra of the photocurable resin and the photoinitiator (particularly an intermediate state of the photoinitiator). In particular, a second wavelength with a large overlap area with the absorption spectrum of the intermediate state of the photoinitiator can achieve a higher degree of curing compared to a second wavelength with little or no overlap with the absorption spectrum of the intermediate state of the photoinitiator.

[0085] Generally, the terms "white" or "high intensity" refer to a second wavelength at which the intermediate state of the photoinitiator in the photocurable resin has a high extinction coefficient, particularly a maximum absorption value, thus absorbing more light of the second wavelength. The terms "black" or "low intensity" refer to a second wavelength at which the intermediate state of the photoinitiator has a low extinction coefficient, particularly an extinction coefficient of 0, thus absorbing less or no light of the second wavelength. "Gray" refers to a second wavelength at which the extinction coefficient of the intermediate state of the photoinitiator in the photocurable resin is between that of "white" and "black," or "gray" can refer to a second wavelength that includes a mixture of "white" and "black." Therefore, intensity variations in the process can be achieved by alternating the second wavelength, even though the physical light intensity may be essentially the same. Thus, "intensity distribution" can refer to pixels having essentially the same physical light intensity but emitting light of different colors.

[0086] Specifically, the non-uniform intensity distribution of the second wavelength light can be set according to the distribution of the intermediate-state photoinitiator in the photocurable resin, as described above, which is generated by irradiating the photocurable resin with the first wavelength light. More specifically, the intermediate-state photoinitiator of the photocurable resin can emit fluorescence under irradiation with the first wavelength light, which can be recorded by a camera, particularly a camera that captures an image of the working volume from a position perpendicular to the light sheet. The brightness of each pixel in the obtained fluorescence image can correspond to the concentration of the intermediate-state photoinitiator molecules. For example, the fluorescence image can be converted into a grayscale image, and then the black and white values ​​of all pixels can be inverted. The resulting image exhibits an improved intensity distribution, which can be used to adjust the intensity of the projected image of the second wavelength light during the printing process. The grayscale value of each pixel in the final image can be used to calculate the grayscale value of each pixel in the projected image during the printing process. In particular, the grayscale value of the final image can be multiplied by a factor that is constant for all pixels of at least one image.

[0087] The intensity variation of the second wavelength of light can be achieved by processing one or more images of the second wavelength of light (particularly software-based processing). The corresponding processing may include applying or implementing at least one grayscale distribution map according to the described embodiment to a corresponding image of the second wavelength of light, thereby causing a non-uniform intensity distribution of the second wavelength of light. The corresponding processing may include combining two or more different grayscale distribution maps.

[0088] This method can be implemented by at least one optical modulation device assigned to an irradiation apparatus, wherein the at least one optical modulation device is configured to: modulate the spatial extension direction of two or more beams of a plurality of beams of a first wavelength in at least one optical plane, such that the two or more beams extend non-parallel to each other, and / or generate at least two beams of a first wavelength with different polarizations or polarization states at at least one point within the working volume, and / or generate at least two beams of different wavelengths (particularly within a specific wavelength range) at at least one point within the working volume. Therefore, at least one optical modulation device can be configured to: generate at least two beams of a first wavelength with different polarizations or polarization states at at least one point within the working volume, and / or generate at least two beams of different wavelengths (particularly within a specific wavelength range) at at least one point within the working volume. This can be a separate configuration of the at least one optical modulation device, particularly independent of a configuration in which the at least one optical modulation device is configured to modulate the spatial extension direction of two or more beams of a plurality of beams in at least one optical plane such that the two or more beams extend in a non-parallel arrangement relative to each other.

[0089] The principle of angular diversity can include generating or using light beams of a first wavelength that extend at an angle to each other such that they intersect at at least one point (e.g., an intersection). Specifically, angular diversity can include generating or using light beams of a first wavelength that extend at different angles to each other such that they intersect at at least two points, and more particularly, generating multiple distributed intersections across the entire sheet. In particular, the principle of angular diversity can be implemented at an angle (especially orthogonally) to the forming direction of the object to be printed, especially to avoid or reduce resolution loss in the forming direction.

[0090] Specifically, at least one optical modulation device may be configured to intentionally alter the spatial extension direction and / or orientation of at least two beams, causing the at least two beams to extend in a non-parallel manner relative to each other, resulting in the intersection of the two or more beams at one or more intersection points within at least one optical sheet, thereby affecting (particularly at least partially reducing) the optical coherence of the beams within at least one optical plane. Altering the spatial extension direction and / or orientation of the at least two beams, causing them to extend in a non-parallel manner within at least one optical plane, also results in at least one optical plane containing beams with angular spatial extension directions, which have angular extension directions as they pass through, travel through, or propagate through the working volume. In particular, the at least two beams may pass through, travel through, or propagate through the working volume at an angle to each other other than 0°. The intersection of the at least two beams at one or more intersection points within at least one optical plane may also include the at least two beams overlapping at one or more intersection points.

[0091] When applying one or more of the above principles (such as the principle of angular diversity) to a light sheet of the first wavelength, obtaining the ideal grayscale for each image may require a significant amount of computation. Therefore, when applying the principle of angular diversity to a light sheet, it is preferable to use a simple gradient method, a grayscale filter obtained by measuring the intermediate state distribution through fluorescence imaging, or to determine grayscale values ​​that are independent of the first wavelength of light.

[0092] The specific intensity distribution curves of each projected image of the second wavelength of light can be selected based on simulation, modeling, or experimental results. These results describe the intensity distribution of the light sheet extending across the working volume, or the absorption behavior or characteristics of each volume element or voxel in the working volume. For example, these absorption behaviors or characteristics can be influenced by switching a two-color photoinitiator from an initial state to an intermediate state, and / or by initiating and forming absorption byproducts that lead to photobleaching of the intermediate state. Therefore, photophysical processes (e.g., absorption, (light) switching) and physical parameters (e.g., light intensity, light sheet thickness) can be incorporated into the modeling.

[0093] Furthermore, the experimental results can serve as data for printed objects (especially structural data) and applied process parameters (especially those containing grayscale information), which can be used to train one or more algorithms or software incorporating such algorithms. The corresponding algorithms can respectively implement the principles of artificial intelligence and machine learning to find improved process parameters, particularly those containing grayscale information.

[0094] Another aspect of the invention relates to an apparatus for volumetric printing of three-dimensional objects via multicolor photopolymerization of a photocurable resin. The apparatus includes an irradiation device for performing an irradiation process according to a plurality of printing parameters: irradiating the photocurable resin with light of a first wavelength and light of a second wavelength different from the first wavelength to form a three-dimensional object in at least one direction via multicolor photopolymerization, wherein the first wavelength and the second wavelength intersect in the forming region. The apparatus includes a hardware and / or software-implemented controller configured to spatially and / or temporally change at least one printing parameter during the irradiation process, particularly printing parameters affecting the curing (behavior) of the photocurable resin. Therefore, the apparatus is configured to implement the method of the first aspect of the invention, and all descriptions relating to the method of the first aspect of the invention also apply to the apparatus of the other aspect of the invention, and vice versa.

[0095] Therefore, the device is typically configured to form at least one three-dimensional object by volumetric printing using multicolor photopolymerization (especially two-color polymerization) based on photocurable resin. The corresponding three-dimensional object can be a technical component or a part of a technical component. For example, the technical component can be an optical component or a part of an optical component. For example, the corresponding optical component can be a diffractive element, a transmission element, or a lens element. Therefore, the term "three-dimensional object" specifically refers to a technical component that can generally be used directly (except for possible post-processing steps).

[0096] The device may be or may contain a volumetric 3D printing apparatus, particularly a Xolography apparatus, i.e., an apparatus configured to perform the basic principles of Xolography. The basic principles of Xolography are described in detail in WO2020 / 245456A1, the contents of which are incorporated herein by reference.

[0097] The device typically includes a container for holding a photocurable resin. This container can be movably supported in at least one direction. This at least one direction can be, or may include, the forming direction of the three-dimensional object to be printed.

[0098] The device may also include a dual-color irradiation unit for irradiating a photocurable resin within or in a container. The dual-color irradiation unit is configured to irradiate the photocurable resin with light of a first wavelength, and particularly simultaneously with light of a second wavelength different from the first wavelength. The dual-color irradiation unit may include: at least one first irradiation unit comprising at least one first light source for generating light of the first wavelength; and at least one second irradiation unit comprising at least one second light source for generating light of the second wavelength. The dual-color irradiation unit may be configured to generate a light sheet using light of the first wavelength, wherein the light sheet extends in the plane of the light sheet. Furthermore, the dual-color irradiation unit may be configured to generate a light projection of the second wavelength, wherein the light projection intersects the light sheet at a certain angle, particularly at an angle of approximately 90°. The light projection of the second wavelength can be generated by simultaneously or sequentially emitting multiple beams of second wavelength. Therefore, the light projection of the second wavelength of light can include at least one of the following: an image of the second wavelength of light, which may contain image elements (e.g., pixels) of different intensities, resulting in a non-uniform or uniform intensity distribution of the image; or, a sequential depiction (shading) of different locations (e.g., points or lines) to form an image composed of the second wavelength of light, which may contain image elements (e.g., pixels) of different intensities, resulting in a non-uniform or uniform intensity distribution of the image.

[0099] Therefore, at least one first irradiation device may include at least one light source configured to irradiate light of a first wavelength onto a photocurable resin to produce at least one first light projection, thereby forming a light sheet. The corresponding light sheet may include multiple beams extending along the same plane. At least one first irradiation device may be constituted, for example, a laser or a light-emitting diode, or may include a laser or a light-emitting diode. At least one first irradiation device may also include at least one optical element, which may include, for example, at least one of the following: a Powell lens, a cylindrical lens, a diffractive optical element, a beam spreading element, a collimating optical element, etc. Additionally or optionally, at least one first irradiation device may include a light deflection unit, such as a (movable or rotatable) mirror, a galvanometer scanner, or a multifaceted scanner, for deflecting light onto the photocurable resin. At least one first irradiation device may be configured to change the focal point or at least one focal parameter of at least one corresponding first light projection within the working volume, particularly at least one of the following: focal position, focal length, depth of focus, or depth of field. Specifically, at least one first irradiation device may be configured to change the focal point or at least one focal parameter according to the size of the molding area. At least one first irradiation device may include one or more controllers configured to change the focal point or at least one focal parameter of at least one corresponding first light projection within the working volume, particularly at least one of the following: focal position, focal length, depth of focus, or depth of field. Additionally or alternatively, at least one first irradiation device may include one or more optical elements, such as lenses, particularly adaptable or adjustable lenses, configured to change the focal point or at least one focal parameter of at least one corresponding first light projection within the working volume, particularly at least one of the following: focal position, focal length, depth of focus, or depth of field. The light emitted or irradiated by at least one first irradiation device may include wavelengths within the following ranges: 350 nm–500 nm, particularly 375 nm–450 nm, more particularly 385 nm–440 nm, more particularly 395 nm–420 nm, and more particularly 400 nm–410 nm. The light of the first wavelength may encompass a certain wavelength range of the spectrum, particularly at least partially covering the wavelengths of the corresponding ranges described above. For example, the first wavelength may be approximately 375 nm. Generally, when selecting the first wavelength, the photochemical properties of the photoinitiator molecules in the photocurable resin, especially the photochromic properties, should be considered.

[0100] Therefore, at least one second irradiation device may include at least one second light source, which is an image of light of a second wavelength continuously emitted onto the photocurable resin, wherein each image may correspond to a specific cross-section of the three-dimensional object to be printed, or to multiple points or lines corresponding to the cross-sectional geometry of the three-dimensional object to be printed. The second irradiation device may be constructed as or include an image projection device (particularly a digital light projection device) or a directional light emitting device. At least one second irradiation device may also include one or more light projection optics. At least one second irradiation device may be configured to change the size of at least one image of the projected image, or to change the size of at least one image element (e.g., a pixel) of at least one image of the projected image. At least one second irradiation device may include one or more controllers configured to change the size of at least one image of the projected image, or to change the size of at least one image element (e.g., a pixel) of at least one image of the projected image. Additionally or alternatively, at least one second irradiation device may include one or more optical elements, such as lenses, configured to change the size of at least one image of the projected image, or to change the size of at least one image element (e.g., a pixel) of at least one image of the projected image. The light emitted or irradiated by at least one second irradiation device may include wavelengths within the following range: 400 nm–1000 nm, particularly 425–750 nm, even more particularly 450–675 nm, and even more particularly 500 nm–650 nm. The second wavelength of light may encompass a certain wavelength range of the spectrum, particularly at least partially covering the wavelengths within the aforementioned corresponding ranges. Typically, the selection of the second wavelength takes into account at least the photochemical properties of the photoinitiator molecules in the photocurable resin, particularly their photochromic properties.

[0101] As described above, a two-color irradiation apparatus can be configured to generate an image projection using light of a second wavelength, wherein the image projection intersects the light sheet at a certain angle, particularly an angle of approximately 90°. Therefore, a two-color irradiation apparatus can typically be configured to irradiate the first wavelength of light at a first angle (particularly an angle from 0° to 180°) and the second wavelength of light at a second angle (specifically an angle from 0° to 180°), both angles being relative to the main extension plane of at least one forming region. These angles are particularly between 15° and 165°, more particularly between 30° and 150°, even more particularly between 90° and 150°, or between 30° and 90°. Specifically, the second wavelength of light can be irradiated at a 90° angle relative to the first wavelength of light. Attached Figure Description

[0102] The invention can be more fully understood by referring to the following description of the accompanying drawings, in conjunction with the many advantages and features set forth below, wherein:

[0103] Figure 1 A schematic diagram of at least a portion of an apparatus for printing three-dimensional objects according to an exemplary embodiment is shown;

[0104] Figures 2 to 6 Schematic diagrams are shown showing how one or more printing parameters vary spatially and / or temporally according to exemplary embodiments;

[0105] Figure 7a to Figure 7b and Figures 8a to 8c Schematic diagrams of methods according to other exemplary embodiments are shown respectively; and

[0106] Figures 9a to 9d and Figures 10a to 10b Schematic diagrams of methods according to other exemplary embodiments are shown respectively. Detailed Implementation

[0107] Figure 1 A schematic top view shows at least a portion of a device 10 for printing at least one three-dimensional object according to an exemplary embodiment.

[0108] The device 10 is configured to volumetrically print at least one three-dimensional object by two-color photopolymerization of a photocurable resin 20, and the device 10 includes an irradiation device 30 for performing an irradiation process based on multiple printing parameters: irradiating the photocurable resin 20 with light L1 of a first wavelength and light L2 of a second wavelength different from the first wavelength, thereby achieving two-color photopolymerization in at least one direction ( Figure 1 (As shown by the middle arrow P1) to form a three-dimensional object, the at least one direction can be the forming direction of the three-dimensional object to be printed or include the forming direction of the three-dimensional object to be printed. From Figure 1 As can be seen, the first wavelength light L1 and the second wavelength light L2 intersect within the forming region FZ.

[0109] The first wavelength of light L1 can form a light sheet containing multiple beams passing through the photocurable resin 20. For example, the individual beams can form a light plane. This light plane can be or include a light plane in which one or more beams (particularly (substantially) parallel beams) are arranged adjacent to each other without intermediate gaps. Notably, at least partially directly adjacent beams can partially overlap. Alternatively, the light plane can be or include a light plane in which one or more beams are arranged adjacent to each other with intermediate gaps. The individual beams can be generated by a directional light-emitting device (e.g., a laser device), which can form part of the irradiation apparatus in a volumetric printing device for carrying out the method of the present invention.

[0110] The second wavelength of light L2 may contain an image projection corresponding to the cross-sectional geometry of the three-dimensional object to be printed, or may contain multiple points or lines corresponding to the cross-sectional geometry of the three-dimensional object to be printed. The points or lines may form a pattern, such as a fill pattern. The corresponding projection may be generated by an optical projection device (e.g., a digital optical projection device), which may constitute part of the irradiation apparatus of a volumetric printing apparatus for implementing the method of the present invention. The points or lines may be generated by a directional light-emitting device (e.g., a laser device), which may constitute part of the irradiation apparatus of a volumetric printing apparatus for implementing the method of the present invention. Both the optical projection device and the directional light-emitting device can serve as examples of the second irradiation apparatus 32, which will be further described below.

[0111] The device 10 includes a hardware and / or software implemented controller 40 configured to spatially and / or temporally change at least one printing parameter during irradiation, particularly printing parameters affecting the curing (behavior) of the photocurable resin 20. Therefore, the device 10 is configured to implement a method, exemplary embodiments of which will be combined with... Figures 2 to 6 To provide a more detailed explanation.

[0112] The apparatus 10 may be or include a volumetric 3D printing apparatus, particularly a Xolography apparatus, i.e., an apparatus configured to perform the fundamental principles of Xolography. The fundamental principles of Xolography are described in detail in WO2020 / 245456A1, the contents of which are incorporated herein by reference.

[0113] The apparatus 10 includes a container 50 for containing a photocurable resin 20. The container 50 defines a container volume 51, which may contain a working volume for printing three-dimensional objects therein. One or more walls of the container 50 may be made of a material that allows light of a first wavelength L1 and a second wavelength L2 to irradiate the photocurable resin inside the container. The corresponding material may be, for example, a transparent material. The corresponding transparent material may be glass or a polymer, such as polycarbonate, polymethyl methacrylate, or a cyclic olefin copolymer.

[0114] Container 50 can be in at least one direction ( Figure 1 The movement (in the direction indicated by the double arrow P2) is, for example, carried out by a related drive device 60 (e.g., an electric motor) in at least one direction. From Figure 1 As can be seen, the at least one direction can be or include the forming direction of the corresponding three-dimensional object to be printed. It is worth noting that the drive device 60 can also be connected to the first irradiation device 31 of the irradiation device 30 of the device 10 to move the first irradiation device 31 in a similar manner along at least one direction.

[0115] The apparatus 10 also includes a dual-color irradiation device 30, configured to irradiate the photocurable resin within the container 50 with light of a first wavelength L1 and light of a second wavelength L2. Specifically, the dual-color irradiation device 30 is configured to simultaneously irradiate the photocurable resin 20 with light of the first wavelength L1 and light of the second wavelength L2. The dual-color irradiation device 30 may be configured to generate a light sheet using light of the first wavelength L1, wherein the light sheet extends in the plane of the light sheet. Furthermore, the dual-color irradiation device 30 may be configured to generate, for example, a light projection using light of the second wavelength L2, wherein the light projection intersects the light sheet at a certain angle, specifically, the angle is approximately 90°.

[0116] from Figure 1 As can be seen from the above, the dual-color irradiation device 30 may include a first irradiation device 31, which includes at least one first light source for generating and emitting light L1 of a first wavelength; and a second irradiation device 32, which includes at least one second light source for generating and emitting light L2 of a second wavelength.

[0117] The first irradiation device 31 may include at least one light source configured to irradiate the photocurable resin 20 with light L1 of a first wavelength to generate a light sheet. The first irradiation device 31 may be, for example, constituted by a laser or a light-emitting diode, or may include a laser or a light-emitting diode. The first irradiation device 31 may also include at least one optical element, for example, which may include at least one of the following: a Powell lens, a cylindrical lens, a diffractive optical element, a beam spreading element, a collimating optical element, etc. Additionally or optionally, the first irradiation device 31 may include a light deflection unit, such as a (movable, particularly rotatable) mirror, a galvanometer scanner, or a multi-faceted scanner, for deflecting light onto the photocurable resin 20. The first irradiation device 31 may be configured to change the focal point or focal parameter of at least one corresponding first light projection within the working volume, particularly at least one of the following: focal position, focal length, depth of focus, or depth of field. In particular, the first irradiation device 31 may be configured to change the focal point or at least one focal parameter according to the size of the molding area. The first irradiation device 31 may include one or more controllers configured to change the focal point or focal parameter of at least one corresponding first light projection within the working volume, particularly at least one of the following: focal position, focal length, depth of focus, or depth of field. Additionally or optionally, the first irradiation device 31 may include one or more optical elements, such as lenses, particularly adaptable or adjustable lenses, configured to change the focal point or focal parameter of at least one corresponding first light projection within the working volume, particularly at least one of the following: focal position, focal length, depth of focus, or depth of field. The wavelength range of the light L1 emitted or irradiated by the first irradiation device 31 may be: 350nm-500nm, particularly 375nm-450nm, more particularly 385nm-440nm, more particularly 395nm-420nm, more particularly 400nm-410nm. The light L1 of the first wavelength may encompass a certain wavelength range of the spectrum, particularly at least partially covering the wavelengths of the aforementioned corresponding ranges. For example, the first wavelength may be approximately 375nm. Typically, when selecting the first wavelength, the photochemical properties of the photoinitiator molecules in the photocurable resin 20, especially the photochromic properties, should be considered.

[0118] The second irradiation device 32 may include at least one second light source configured to continuously emit images of light L2 of a second wavelength onto the photocurable resin 20, wherein each image may correspond to a specific cross-section of the three-dimensional object to be printed, or to multiple points or lines corresponding to the cross-sectional geometry of the three-dimensional object to be printed. The second irradiation device 32 may be constructed as or include an image projection device (particularly a digital light projection device) or a directional light emitting device. The second irradiation device 32 may also include one or more light projection optics. Therefore, the second irradiation device 32 can generate image elements, such as voxels, with specific focal points and / or sizes. The second irradiation device 32 may be configured to change the size of at least one image in the projected images, or to change the size of at least one image element (e.g., a pixel) of at least one image in the projected images. The second irradiation device 32 may include one or more controllers configured to change the size of at least one image or at least one image element (e.g., a pixel) of the projected images. Additionally or optionally, the second irradiation device 32 may include one or more optical elements (e.g., lenses) configured to change the size of at least one image or at least one image element (e.g., a pixel) of the projected images. The wavelength range of the light L2 emitted or irradiated by the second irradiation device 32 can be: 400nm-1000nm, particularly 425nm-750nm, even more particularly 450nm-675nm, and even more particularly 500nm-650nm. The second wavelength of light L2 can encompass a certain wavelength range of the spectrum, particularly at least partially covering the wavelengths within the aforementioned corresponding ranges. Typically, the selection of the second wavelength takes into account at least the photochemical properties of the photoinitiator molecules in the photocurable resin 20, particularly its photochromic properties.

[0119] As described above, the dual-color irradiation device 30 is typically configured to irradiate a first wavelength of light L1 at a first angle (particularly an angle from 0° to 180°) and a second wavelength of light L2 at a second angle (particularly an angle from 0° to 180°) relative to the direction of extension of the first wavelength of light L1. Specifically, the corresponding angle can range from 15° to 165°, more particularly from 30° to 150°, even more particularly from 90° to 150°, or from 30° to 90°. In particular, the second wavelength of light L2 can intersect the first wavelength of light L1 at a 90° angle (e.g., ...). Figure 1 (As shown).

[0120] Equipment 10 is configured to implement a method for volumetric printing of three-dimensional objects via multicolor photopolymerization (particularly two-color photopolymerization) of a photocurable resin, an example of which will be provided below. Figures 2 to 6 Further explanation.

[0121] The method generally includes an irradiation process based on multiple printing parameters, in which a photocurable resin is irradiated with light of a first wavelength L1 and light of a second wavelength L2 (different from the first wavelength) to form a three-dimensional object in at least one direction through multicolor photopolymerization (especially bicolor photopolymerization). Therefore, the method includes an irradiation process in which a photocurable resin is irradiated with light of a first wavelength L1 and light of a second wavelength L2 (different from the first wavelength) to form a three-dimensional object in at least one direction through multicolor photopolymerization (especially bicolor photopolymerization). The irradiation of the photocurable resin with light of the first wavelength L1 and light of the second wavelength L2 is based on one or more printing parameters. The at least one direction may be or includes the forming direction of the corresponding three-dimensional object to be printed.

[0122] As described above, the first wavelength of light L1 can encompass wavelengths within the following wavelength ranges: for example, 350nm-500nm, particularly 375nm-450nm, even more particularly 385nm-440nm, even more particularly 395nm-420nm, and even more particularly 400nm-410nm. The first wavelength of light L1 can encompass a certain wavelength range of the spectrum, particularly wavelengths that at least partially cover the aforementioned corresponding ranges. As a specific example, the first wavelength can be approximately 375nm.

[0123] As described above, the second wavelength light L2 can encompass wavelengths within the following wavelength range: 400nm-1000nm, particularly 425nm-750nm, more particularly 450nm-675nm, and even more particularly 500nm-650nm. The second wavelength light L2 can encompass a spectrum of a certain wavelength range, particularly at least partially covering the wavelengths within the aforementioned corresponding ranges. For example, the second wavelength can be approximately 475nm.

[0124] As described above, light of a first wavelength L1 and light of a second wavelength L2 irradiate the photocurable resin 20, and the first wavelength L1 and the second wavelength L2 intersect within the molding region FZ. The first wavelength L1 can irradiate the photocurable resin 20 at different angles relative to the second wavelength L2. For example, the first wavelength L1 can irradiate the photocurable resin at an angle of approximately 90° relative to the second wavelength L2. The molding region FT is the region where photopolymerization occurs in the photocurable resin 20, causing the photocurable resin 20 to photocur and form at least one cross-section of the three-dimensional object to be printed.

[0125] Each printing parameter can typically be or includes irradiation process parameters that affect the spatial and / or temporal irradiation of the photocurable resin 20 by light of a first wavelength L1 and light of a second wavelength L2. Each printing parameter can also be or include an irradiation step in which one or more volume elements (e.g., voxels) of the photocurable resin 20 are irradiated by light of the first wavelength L1 and / or light of the second wavelength L2. Therefore, each printing parameter can be or includesFigure 1 The control parameters of the device 10 relate to the spatial and / or temporal irradiation of the photocurable resin 20 with light of a first wavelength L1 and light of a second wavelength L2 to form a three-dimensional object in at least one direction through multicolor photopolymerization (particularly two-color photopolymerization). The individual printing parameters may be or include... Figure 1 The control parameters of the irradiation device 30 of the equipment 10. Each printing parameter may also be or include... Figure 1 The control parameters of the drive unit 60 of the device 10.

[0126] The method includes spatially and / or temporally altering at least one printing parameter during irradiation, particularly at least one printing parameter affecting the curing or curing behavior of the photocurable resin 20. Therefore, the irradiation process of this method includes coordinated and precise spatial and / or temporal control of the irradiation process, which includes coordinated and precise alteration of at least one printing parameter during irradiation, particularly at least one printing parameter affecting the curing behavior of the photocurable resin 20. The corresponding spatial and / or temporal variation of the at least one printing parameter may also be related to the number of irradiation steps in which one or more volume elements (e.g., voxels) of the photocurable resin 20 are irradiated by light of a first wavelength L1 and / or light of a second wavelength L2. Therefore, the corresponding spatial and / or temporal change of the at least one printing parameter may also involve a change in the number of irradiation steps in which one or more volume elements (e.g., voxels) of the photocurable resin 20 are irradiated by light of the first wavelength L1 and / or light of the second wavelength L2. Therefore, the corresponding spatial and / or temporal change of the at least one printing parameter may also include a change in the focal point of the first wavelength light L1 and / or a change in the size of one or more images or one or more image elements (e.g., pixels) of the second wavelength light L2. A corresponding spatial and / or temporal change in at least one printing parameter may also involve the direction and / or speed of movement of the photocurable resin 20, particularly relative to the direction and / or speed of movement of the photosheet formed by the light L1 of the first wavelength. Therefore, a corresponding spatial and / or temporal change in at least one printing parameter may also include a change in the direction and / or speed of movement of the photocurable resin 20, particularly relative to the direction and / or speed of movement of the photosheet formed by the light L1 of the first wavelength.

[0127] Therefore, based on spatial and / or temporal variations of at least one printing parameter, the irradiation process may include: printing at least one first portion (first object portion) of the three-dimensional object or volume element to be printed using at least one printing parameter different from at least one other portion (other object portion) of the three-dimensional object or volume element to be printed. The corresponding first object portion may contain one or more first volume elements (e.g., voxels) of the photocurable resin 20, the one or more first volume elements located at one or more first positions within the photocurable resin 20. The corresponding other object portion may contain one or more other volume elements (e.g., voxels) of the photocurable resin 20, the one or more other volume elements located at one or more other positions within the photocurable resin 20. The corresponding other volume elements may be in the forming direction (e.g., ... Figure 1 The volume element located behind the corresponding first volume element (as indicated by the middle arrow P1). Other corresponding volume elements can also be volume elements located near the 3D object to be printed, for example, volume elements that do not constitute part of the 3D object to be printed. In particular, other corresponding volume elements can also be located in front of or behind the 3D object to be printed relative to the forming direction, and thus these other volume elements can be volume elements that do not constitute part of the 3D object to be printed.

[0128] In general, spatial and / or temporal changes in at least one printing parameter enable each volume element of the photocurable resin 20 to be irradiated with individual printing parameters, particularly printing parameters such as energy, energy density, and energy intensity that affect each volume element during irradiation.

[0129] The printing parameters for each volume element in the photocurable resin 20 can be selected based on the position of the volume element in the photocurable resin and the 3D object to be printed. For example, for one or more volume elements adjacent to or close to uncured or uncured photocurable resin 20, irradiation can be performed using different printing parameters than for one or more volume elements adjacent to or close to cured or uncured photocurable resin 20. In this way, spatial and / or temporal variations of at least one printing parameter can be specifically applied to address the so-called "proximity effect," which causes volume elements adjacent to another cured volume element to exhibit specific curing behaviors, such as curing more easily or faster, which differ from the curing behavior of volume elements not adjacent to another cured or photopolymerized volume element. It is worth noting that in conventional volumetric printing methods, the proximity effect often leads to unintended structural anisotropy in the 3D object, resulting in associated undesirable shrinkage and deformation.

[0130] Therefore, this method can achieve the printing of three-dimensional objects with higher structural isotropy and lower unwanted shrinkage and deformation based on the spatial and / or temporal changes of at least one printing parameter during irradiation, resulting in three-dimensional objects that exhibit higher geometric accuracy and structural fidelity.

[0131] Irradiating the photocurable resin 20 with light of the first wavelength L1 causes one or more photoinitiator molecules of the photocurable resin 20 to change from an initial state to an intermediate state. Compared with the initial state, the optical properties of the intermediate state have changed, so that one or more photoinitiator molecules in the intermediate state can absorb light of the second wavelength L2, thereby causing one or more photoinitiator molecules to change from the intermediate state to an active state by absorbing light of the second wavelength L2, thereby locally triggering the polymerization of the photocurable resin 20 to form at least one three-dimensional object.

[0132] The photocurable resin 20 can be a photocurable monomer resin or a photocurable oligomer resin, which may include, for example, acrylates, methacrylates, thiols-olefins, epoxides, oxetanes, oxetanes, or vinyl ethers. Multicolor photopolymerization can include multiphoton photopolymerization of the photocurable resin 20, particularly two-photon photopolymerization. Therefore, the photopolymerization of the photocurable resin 20 is achieved by irradiating the photocurable resin 20 with light of a first wavelength L1, and particularly simultaneously with light of a second wavelength L2. This causes molecules of one or more photoinitiators in the photocurable resin 20 to transition from an initial state (in which the molecules of one or more photoinitiators (substantially) do not absorb light of the second wavelength L2) to an intermediate state with altered optical properties compared to the initial state, for example, by absorbing light of the first wavelength L1. Subsequently, the molecules of one or more photoinitiators in the intermediate state absorb light of the second wavelength L2, causing the molecules of one or more photoinitiators to transition from the intermediate state to the active state, thereby locally triggering the polymerization of the photocurable resin 20 to form at least one three-dimensional object.

[0133] Suitable photoinitiators for the corresponding photocurable resin 20 are known, for example, from US5230986A, WO2020245456A1, WO2023034398A1, WO2023034402A1, WO2023220461A1, and WO2023220463A1, the contents of which are incorporated herein by reference.

[0134] As described above, at least one molding region FZ can move at a nominal rate of motion along at least one direction, particularly relative to a corresponding container 50 containing the photocurable resin 20. This at least one direction can include the molding direction of the three-dimensional object to be printed. The movement of the at least one molding region FZ can be, for example, relative to at least one functional component of the device 10 for carrying out the method. The corresponding functional component of the device 10 can be, for example, the container 50 or the irradiation apparatus 30. Thus, during irradiation, at least one molding region FZ can actively move at a nominal rate of motion along at least one direction (particularly the molding direction), thereby passing through at least a portion of the container volume 51 while the container 50 remains stationary. Alternatively, during irradiation, at least a portion of the container volume 51 can actively move along at least one direction (particularly the molding direction) while at least one molding region FZ remains stationary. Furthermore, at least one molding region FZ and at least a portion of the container 50 can actively move simultaneously, wherein at least one molding region FZ and at least a portion of the container 50 can move simultaneously in the same direction or in opposite directions. Furthermore, the nominal motion rate of at least one molding area FZ and / or container 50 moving along at least one direction (particularly relative to container 50) can also serve as an example of printing parameters, since the nominal motion rate, particularly spatial and / or temporal variations of the nominal motion rate, also affects the curing behavior of the photocurable resin. Additionally or alternatively, the second irradiation device 32 of the dual-color irradiation device 30 can also be actively moved along at least one direction (particularly the molding direction), while at least one of the container 50 or molding area FZ is also actively moved. Moving the second irradiation device 32 of the dual-color irradiation device 30 can serve as a means of focus correction for the second wavelength light L2 within at least one molding area. Therefore, the following implementation is also contemplated: before, during, or after at least one irradiation process, the first irradiation device 31 of the dual-color irradiation device 30 or at least one molding area FZ, the second irradiation device 32 of the dual-color irradiation device 30, and the container 50 are actively moved, respectively. The corresponding movements can be controlled by the controller 40.

[0135] Figure 2 This is a schematic diagram, where the vertical axis represents the energy level of the first wavelength light L1 (solid line) and the energy level of the second wavelength light L2 (dashed line), and the horizontal axis represents the position x or time t within the container volume 51 or the photocurable resin 20, respectively.

[0136] Specifically, Figure 2It is shown that altering at least one printing parameter (particularly printing parameters affecting the curing (behavior) of the photocurable resin 20) spatially and / or temporally can include irradiating the photocurable resin 20 first with light of a first wavelength L1, and then irradiating the photocurable resin 20 with light of a second wavelength L2. Therefore, altering at least one printing parameter can include irradiating the photocurable resin 20 spatially and / or temporally first with light of the first wavelength L1, and then with light of the second wavelength L2. In this way, one or more volume elements of the three-dimensional object to be printed can be irradiated with light of the first wavelength L1 before being irradiated with light of the second wavelength L2. One or more volume elements of the photocurable resin 20 can specifically include the first volume element of the three-dimensional object to be printed. In other words, the irradiation process can include irradiating one or more volume elements spatially and / or temporally with light of the first wavelength L1 only before irradiating subsequent volume elements with light of the second wavelength L2 (and typically also with light of the first wavelength L1). By irradiating the volume elements of the photocurable resin 20 with only the first wavelength light L1, these volume elements can be pre-activated. This allows for improved curing effects when adjacent volume elements are subsequently irradiated with the first wavelength light L1 and the second wavelength light L2, thereby improving the structural properties of the corresponding three-dimensional object to be printed.

[0137] from Figure 2 An example (spatially) can be derived of first irradiating the photocurable resin 20 with light of a first wavelength L1, and then irradiating the photocurable resin 20 with light of a second wavelength L2. This includes: irradiating the photocurable resin 20 with light of the first wavelength L1 starting from a first position p1, and irradiating the photocurable resin 20 with light of the second wavelength L2 starting from a second position p2, wherein the second position p2 is located behind the first position p1 along the molding direction. The second position p2 is typically located within the volume of the photocurable resin 20 that constitutes the three-dimensional object to be printed, i.e., within the three-dimensional object to be printed. In particular, the second position p2 can be the location within the volume of the photocurable resin 20 where the outer boundary or edge of the corresponding three-dimensional object to be printed is formed, i.e., the location of the surface of the corresponding three-dimensional object to be printed. Therefore, the three-dimensional object to be printed can include a portion located behind the second position p2 relative to the molding direction, or in other words, the three-dimensional object is formed behind the second position p2 relative to the molding direction. Therefore, the second position p2 can contain a first volume element of the three-dimensional object to be printed relative to the molding direction, such as a first voxel. The first position p1 can also be the position within the volume of the photocurable resin 20 where the corresponding three-dimensional object to be printed is formed, that is, the position inside the corresponding three-dimensional object to be printed. However, the first position p1 can also be a position within the volume of the photocurable resin 20 where the corresponding three-dimensional object to be printed is not formed, that is, a position outside the corresponding three-dimensional object to be printed.

[0138] from Figure 2Another example (in terms of time) can be derived where the photocurable resin is first irradiated with light of a first wavelength L1 and then with light of a second wavelength. This includes: the first wavelength light L1 irradiates the photocurable resin 20 at a first time t1, and the second wavelength light L2 irradiates the photocurable resin 20 at a second time t2, where t2 > t1. The second time t2 typically corresponds to the time when the volume of the photocurable resin 20 constituting the three-dimensional object to be printed is irradiated. In particular, the second time t2 may correspond to the moment when the volume of the photocurable resin 20 constituting the outer boundary or edge of the three-dimensional object to be printed is irradiated, i.e., the moment when the volume of the photocurable resin 20 constituting the surface position of the three-dimensional object to be printed is irradiated. Therefore, the three-dimensional object to be printed may include the portion to be printed after the second time t2, or the printing of the three-dimensional object may be completed after the second time t2. Therefore, the second time t2 may include the moment when the first volume element (e.g., the first voxel) of the three-dimensional object to be printed is printed relative to the forming direction. The first time t1 may also correspond to the moment when the volume of the photocurable resin 20 constituting the three-dimensional object to be printed is irradiated. However, the first time t1 can also correspond to the moment when the volume of the photocurable resin 20, which does not constitute the three-dimensional object to be printed, is irradiated.

[0139] Figure 3 Here is another schematic diagram, where the vertical axis represents the energy level of the first wavelength light L1 (solid line) and the energy level of the second wavelength light L2 (dashed line), and the horizontal axis represents the position x or time t within the container volume 51 or the photocurable resin 20, respectively.

[0140] Figure 3Specifically, altering at least one printing parameter (particularly those affecting the curing (behavior) of the photocurable resin 20) spatially and / or temporally can include irradiating the photocurable resin 20 with light of a first wavelength L1 after irradiating it with light of a second wavelength L2. Therefore, a change in at least one printing parameter can include irradiating the photocurable resin 20 spatially and / or temporally first with light of a second wavelength L2 and then with light of a first wavelength L1. In this way, one or more volume elements of the three-dimensional object to be printed can be irradiated with light of a first wavelength L1 after adjacent volume elements have been irradiated with light of a second wavelength L2. The corresponding one or more volume elements of the photocurable resin can specifically include the last volume element of the three-dimensional object to be printed. In other words, the irradiation process can include irradiating one or more volume elements (only) spatially and / or temporally with light of a first wavelength L1 after previous volume elements have been irradiated with light of a second wavelength L2 (and typically also with light of a first wavelength L1). Irradiating the volume elements of the photocurable resin 20 with only light of the first wavelength L1 can lead to the post-activation of these volume elements and their adjacent volume elements, thereby causing these volume elements to be further cured after being irradiated with light of the first wavelength L1 and light of the second wavelength L2 respectively, thereby improving the structural properties of the corresponding three-dimensional object to be printed.

[0141] from Figure 3 An example (spatially) of first irradiating the photocurable resin 20 with light of a second wavelength L2 and then irradiating it with light of a first wavelength L1 can be derived. This can include: the irradiation of the photocurable resin 20 by the second wavelength L2 ending at a third position p3, and the irradiation of the photocurable resin 20 by the first wavelength L1 ending at a fourth position p4, wherein the fourth position p4 is located after the third position p3 in the forming direction. The third position p3 is typically located inside or at the outer boundary or edge of the volume of the photocurable resin 20 constituting the three-dimensional object to be printed, i.e., inside the three-dimensional object to be printed. In particular, the third position p3 can be located inside or at the outer boundary or edge of the volume of the photocurable resin constituting the three-dimensional object to be printed, i.e., at the surface of the three-dimensional object to be printed. Therefore, the three-dimensional object to be printed can include a portion located in front of the third position p3 relative to the forming direction, or in other words, the three-dimensional object is formed in front of the third position p3 relative to the forming direction. Therefore, the third position p3 can contain the last volume element of the three-dimensional object to be printed relative to the forming direction, such as the last voxel. The fourth position p4 can also be located within the volume of the photocurable resin 20 where the corresponding three-dimensional object to be printed is formed, i.e., inside the corresponding three-dimensional object to be printed. However, the fourth position p4 can also be located within the volume of the photocurable resin 20 where the corresponding three-dimensional object to be printed is not formed, i.e., outside the corresponding three-dimensional object to be printed.

[0142] from Figure 3Another example (in terms of time) can be derived from irradiating the photocurable resin with light of the second wavelength L2 and then with light of the first wavelength L1. This includes: the irradiation of the photocurable resin 20 by the second wavelength L2 ends at a third time t3, and the irradiation of the photocurable resin 20 by the first wavelength L1 ends at a fourth time t4, where t4 > t3. The third time t3 typically corresponds to the moment when the volume of the photocurable resin 20 constituting the three-dimensional object to be printed is irradiated. In particular, the third time t3 can correspond to the moment when the volume of the photocurable resin 20 constituting the outer boundary or edge of the three-dimensional object to be printed is irradiated, that is, the moment when the volume of the photocurable resin 20 constituting the surface position of the three-dimensional object to be printed is irradiated. Therefore, the three-dimensional object to be printed may include portions to be printed before the third time t3, or in other words, the printing of the three-dimensional object is completed before the third time t3. Therefore, the third time t3 can include the moment when the last volume element (e.g., the last voxel) of the three-dimensional object to be printed is completed relative to the forming direction. The fourth time t4 can also correspond to the moment when the volume of the photocurable resin 20 constituting the three-dimensional object to be printed is irradiated. Furthermore, the fourth time t4 can also correspond to the moment when the volume of the photocurable resin 20 that does not constitute the three-dimensional object to be printed is irradiated.

[0143] therefore, Figure 2 and Figure 3 Exemplary embodiments (which may also be implemented in combination) demonstrate the spatial and / or temporal alteration of at least one printing parameter (particularly printing parameters affecting the curing behavior of the photocurable resin 20), wherein the photocurable resin 20 is irradiated with light L1 of a first wavelength in a volume separate from the volume of the three-dimensional object to be printed (particularly adjacent volumes, more particularly directly adjacent volumes), particularly irradiated only with light L1 of the first wavelength, particularly wherein this volume is located spatially and / or temporally before and / or after the volume of the three-dimensional object to be printed relative to at least one forming direction of the three-dimensional object to be printed. In this way, pre-activation or post-activation of the photocurable resin can be achieved, thereby effectively improving the structural properties of the three-dimensional object to be printed.

[0144] Therefore, relative to the irradiation of the first wavelength light L2, irradiating the photocurable resin 20 with the first wavelength light L1 first or later in space and / or time typically includes: volume elements in the photocurable resin 20 that do not constitute part of the three-dimensional object to be printed can be irradiated (only) with the first wavelength light L1. These volume elements may be located before or in front of the volume elements that constitute part of the three-dimensional object to be printed, or after or behind the volume elements that constitute part of the three-dimensional object to be printed, relative to the molding direction of the three-dimensional object to be printed.

[0145] Similarly, it can be imagined that the volume elements of the photocurable resin 20, which do not constitute part of the three-dimensional object to be printed, can be irradiated (only) with light of the second wavelength L2, so that the above description can also be applied to light of the second wavelength L2.

[0146] Figure 4 and Figure 5 This is another schematic diagram, where the vertical axis represents the energy level of the first wavelength light L1 (solid line) and the energy level of the second wavelength light L2 (dashed line), and the horizontal axis represents the position x or time t within the container volume 51 or the photocurable resin 20, respectively.

[0147] Figure 4 Specifically, this illustrates altering at least one printing parameter, particularly those affecting the curing behavior of the photocurable resin 20, in space and / or time. This can include irradiating the photocurable resin 20 with light of a first wavelength L1 and / or a second wavelength L2 along at least one forming direction, and altering the energy, particularly the energy intensity, of the first wavelength L1 and / or the second wavelength L2 in space and / or time. Altering the energy, particularly the energy intensity, of the first wavelength L1 and / or the second wavelength L2 in space and / or time along at least one forming direction can positively influence the structural properties of the three-dimensional object to be printed. For example, it allows control over the specific energy received by each volume element of the three-dimensional object, thereby achieving the desired curing effect for the corresponding volume elements. This overcomes or at least reduces problems caused by differences in the curing degree of different volume elements of the three-dimensional object, which typically lead to undesirable structural anisotropy in the three-dimensional object. Similarly, the inhomogeneity caused by the proximity effect (as described above) can be overcome or at least reduced because one or more volume elements adjacent to other volume elements that have been cured or photopolymerized can be subjected to differentiated energy irradiation relative to one or more volume elements that are not adjacent to other volume elements that have been cured or photopolymerized.

[0148] Figure 4 Specifically, it illustrates the spatial and / or temporal variation of energy or energy intensity, wherein the energy level of light L1 of a first wavelength can vary from a first energy level E1 to at least a second energy level E2, which is lower than the first energy level E1. Therefore, the energy or energy intensity of light L1 of the first wavelength can dynamically or gradually increase or decrease spatially and / or temporally during irradiation, particularly relative to a nominal value, which can be (but is not limited to) a minimum or maximum energy or energy intensity. Thus, the energy level of light L1 of the first wavelength can reach a peak at the beginning of the irradiation process, such as... Figure 4 As shown.

[0149] Figure 5Specifically, the energy or energy intensity of a second wavelength of light L2 is varied spatially and / or temporally, wherein the energy of the second wavelength of light L2 can vary from a first energy level to at least one second energy level, which can be higher or lower than the first energy level. Therefore, during irradiation, the energy or energy intensity of the second wavelength of light L2 can be dynamically or gradually increased or decreased spatially and / or temporally, particularly relative to a nominal value, which can be (but is not limited to) a minimum or maximum energy or energy intensity.

[0150] As another example, changing the energy (particularly the energy intensity) of light L2 of a second wavelength in space and / or time along at least one direction can include changing the energy or energy density of one or more image elements (e.g., pixels) of various images corresponding to the cross-sectional geometry of the three-dimensional object to be printed, respectively, in space and / or time. In other words, the corresponding projections of one or more images can each contain image elements with different energies or energy densities. Changing the energy or energy density of individual image elements can include changing the energy level or energy density level between a minimum energy level or minimum energy density level and a maximum energy level or maximum energy density level, respectively. Similarly, changing the energy or energy density of individual lines or points can include changing the energy level or energy density level between a minimum energy level or minimum energy density level and a maximum energy level or maximum energy density level, respectively. Changing the corresponding energy or energy density of a corresponding image element or point or line can be achieved by controlling the corresponding irradiation device used to generate the corresponding projection of the image or point or line.

[0151] As another example, changing the energy (particularly the energy intensity) of the second wavelength light L2 in space and / or time along at least one direction can include: changing one or more image elements (e.g., pixels) of various images corresponding to the cross-sectional geometry of the three-dimensional object to be printed and / or one or more image elements (e.g., pixels) of various images not corresponding to the cross-sectional geometry of the three-dimensional object to be printed, such that the energy or energy intensity does not affect the curing of the photocurable resin 20. Therefore, changing the energy (particularly the energy intensity) of the second wavelength light L2 in space and / or time can include: setting the energy or energy intensity in space and / or time to a level that does not cause the photocurable resin 20 to cure, or setting it to a level that causes the photocurable resin 20 to under-cur. However, it is also conceivable that changing the energy (particularly the energy) of the second wavelength light L2 in space and / or time can include: setting the energy or energy intensity in space and / or time to a level that causes the photocurable resin 20 to over-cur.

[0152] from Figure 4It is evident that the photocurable resin 20 can be irradiated with light L1 of a first wavelength at a first energy level within the initial volume of the three-dimensional object to be printed. This first energy level can be a relatively higher energy level compared to a nominal energy level or a second energy level. The initial volume occupies a spatial extent in at least one direction that extends the spatial extent of the three-dimensional object to be printed by: at most 10%, particularly at most 9%, more particularly at most 8%, more particularly at most 7%, more particularly at most 6%, more particularly at most 5%, more particularly at most 4%, more particularly at most 3%, more particularly at most 2%, and more particularly at most 1%. More particularly at most 0.9%, more particularly at most 0.8%, more particularly at most 0.7%, more particularly at most 0.6%, more particularly at most 0.5%, more particularly at most 0.4%, more particularly at most 0.3%, more particularly at most 0.2%, more particularly at most 0.1%, more particularly at most 0.09%, more particularly at most 0.08%, more particularly at most 0.07%, more particularly at most 0.06%, more particularly at most 0.05%, more particularly at most 0.04%, more particularly at most 0.03%, more particularly at most 0.02%, more particularly at most 0.01%. In at least one direction, irradiating the photocurable resin 20 in the initial volume of the three-dimensional object to be printed with light of a first wavelength at a higher energy level can, in particular, compensate for or at least reduce inhomogeneities caused, for example, by proximity effects, thereby obtaining a three-dimensional object with less structural anisotropy and improved structural properties.

[0153] from Figure 4It is evident that the photocurable resin 20 can be irradiated with light L1 of a first wavelength at a first energy level within an initial time. This first energy level can be a relatively higher energy level compared to a nominal energy level or a second energy level. The initial time is at most 10 seconds, particularly at most 9 seconds, more particularly at most 8 seconds, more particularly at most 7 seconds, more particularly at most 6 seconds, more particularly at most 5 seconds, more particularly at most 4 seconds, more particularly at most 3 seconds, more particularly at most 2 seconds, more particularly at most 1 second, more particularly at most 0.9 seconds, more particularly at most 0.8 seconds, more particularly at most 0.7 seconds, more particularly at most 0.6 seconds, and more particularly at most 1 second. At most 0.5 seconds, more particularly at most 0.4 seconds, more particularly at most 0.3 seconds, more particularly at most 0.2 seconds, more particularly at most 0.1 seconds, more particularly at most 0.09 seconds, more particularly at most 0.08 seconds, more particularly at most 0.07 seconds, more particularly at most 0.06 seconds, more particularly at most 0.05 seconds, more particularly at most 0.04 seconds, more particularly at most 0.03 seconds, more particularly at most 0.02 seconds, more particularly at most 0.01 seconds; wherein the initial time refers to the time period during the entire irradiation process, particularly the time period during the irradiation process of curing the photosensitive resin 20 to print a three-dimensional object by multicolor photopolymerization. Each time period can correspond to a time period of the irradiation process during which the image projection of the second wavelength light L2 is irradiated into the photosensitive resin 20. The image projection of the irradiated second wavelength light L2 includes at least a first frame, particularly at most the first 100 frames, more particularly at most the first 90 frames, more particularly at most the first 80 frames, more particularly at most the first 70 frames, more particularly at most the first 60 frames, more particularly at most the first 50 frames, more particularly at most the first 40 frames, more particularly at most the first 30 frames, more particularly at most the first 20 frames, and more particularly at most the first 10 frames.

[0154] Optionally or additionally, changing at least one printing parameter in space and / or time, particularly printing parameters affecting the curing behavior of the photocurable resin 20, may include changing the focal parameters of the first wavelength light L1, such as the size and / or position of the focal spot, and / or changing the image parameters of the image projected by the second wavelength light L2, such as the size and / or position of at least one image element (e.g., a pixel). Therefore, the focal parameters of the first wavelength light L1 (which may include multiple beams passing through the photocurable resin, such as beams in the shape of a sheet), such as the size and / or position of the focal spot, can be printing parameters that vary during irradiation, which can affect the curing result in the forming region FZ and the resolution of the features of the three-dimensional object to be printed, respectively, in space and / or time. Changing one or more focal parameters of the first wavelength light L1 can be achieved by one or more optical elements (e.g., movable lenses) assigned to the irradiation apparatus 30 for generating the first wavelength light L1 and the corresponding beams (particularly beams forming a sheet, such as beams passing through the photocurable resin 20). Corresponding optical elements may form part of a focusing device of the irradiation apparatus, which may be configured to adjust one or more focus parameters of the first wavelength light L1. Additionally or alternatively, image parameters, such as size and / or position, of the projected image of the second wavelength light L2 or at least one image element (which may include an image projection corresponding to the cross-sectional geometry of the three-dimensional object to be printed) may be printing parameters that can be varied during irradiation, thereby affecting, for example, the curing effect in the forming region FZ and the resolution of the features of the three-dimensional object to be printed in space and / or time. Changing one or more image parameters of the image of the second wavelength light L2 may be achieved by one or more optical elements (e.g., (movable) lenses, pixel generators, etc.) assigned to the irradiation apparatus 30 for generating the second wavelength light L2 and generating various images corresponding to the cross-sectional geometry of the three-dimensional object to be printed. The respective optical elements may form part of an image adjustment device of the irradiation apparatus 30, which may be configured to adjust one or more image parameters of the second wavelength light L2. The respective image adjustment devices may be hardware and / or software implementation components of a light projection device (e.g., a digital light projection device).

[0155] Figure 4 and Figure 5It is also generally shown that changing the energy of the second wavelength light L2 in space and / or time can include changing the energy or energy distribution of at least a portion (e.g., at least one pixel) of at least one projected image corresponding to the cross-sectional geometry of the three-dimensional object to be printed, or changing the energy or energy distribution of at least one point or line of at least one beam corresponding to the cross-sectional geometry of the three-dimensional object to be printed. Specifically, the energy of the second wavelength light L2 can be varied along at least one direction, such that upstream and downstream portions of the three-dimensional object are exposed to different energy levels of the second wavelength light L2 relative to the forming direction. As described above, changing the energy of the second wavelength light L2 in space and / or time can reduce the structural anisotropy of the three-dimensional object and improve its structural properties.

[0156] For example, changing the energy or energy intensity of the second wavelength light L2 spatially and / or temporally can include changing the energy or energy intensity of at least a portion of at least one image (particularly at least one image element, such as at least one pixel), the order of change including changes of at least three energy levels E1, E2, and E3 or energy intensity levels E1, E2, and E3, wherein the energy level or energy intensity level changes from E1 to E2, and E2 > E1; and the energy level or energy intensity level changes from E2 to E3, and E2 > E3, particularly, E3 > E1. Specifically, the first energy level E1 can be assigned to one or more volume elements of the photocurable resin 20, in which the photocurable resin 20 requires little or no photopolymerization; these volume elements of the photocurable resin 20 can include volume elements that do not constitute part of the three-dimensional object to be printed. Therefore, the first energy level can also be zero (E1 = 0). Specifically, the second energy level E2 can be assigned to one or more volume elements of the photocurable resin 20 that constitute part of the three-dimensional object to be printed. Specifically, the second energy level E2 can be allocated to one or more volume elements in the photocurable resin 20 that constitute at least a first volume element of the three-dimensional object to be printed relative to the molding direction. In particular, the second energy level E2 can be allocated to one or more volume elements in the photocurable resin 20 that constitute a part of the three-dimensional object to be printed. In particular, the third energy level E3 can be allocated to one or more volume elements in the photocurable resin 20 that constitute a part of other volume elements of the three-dimensional object to be printed, these other volume elements being located behind the first volume element of the three-dimensional object to be printed relative to the molding direction. Furthermore, a fourth energy level E4 can be implemented and allocated to one or more volume elements in the photocurable resin 20 that do not constitute a part of the three-dimensional object to be printed. Specifically, the fourth energy level E4 can be allocated to volume elements of the photocurable resin located after the last volume element of the photocurable resin that constitutes a part of the three-dimensional object to be printed. Therefore, the fourth energy level can also be zero (E4 = 0).

[0157] According to another exemplary embodiment, changing at least one printing parameter in space and / or time, particularly printing parameters affecting the curing behavior of the photocurable resin 20, may include irradiating the photocurable resin 20 with light of a first wavelength L1 and / or light of a second wavelength L2 during irradiation when at least one molding region FZ does not move relative to the container 50 or the corresponding container 50, or when at least one molding region FZ moves at a variable rate of motion lower than the nominal rate of motion. The corresponding variable rate of motion may also be zero. Therefore, the rate of motion of at least one molding region FZ, particularly the rate of motion relative to the container 50 or the corresponding container 50, is also a printing parameter that can be changed in space and / or time, for example, a printing parameter used to achieve printing of a three-dimensional object with higher structural isotropy.

[0158] For example, during irradiation, when at least one molding region FZ does not move relative to the corresponding container 50, or when at least one molding region FZ moves at a rate lower than the nominal rate of motion, irradiating the photocurable resin 20 with light of a first wavelength L1 and / or light of a second wavelength L2 may include: when the photocurable resin 20 moves relatively slowly or even not at all relative to the container 50, irradiating the photocurable resin 20 with light of the first wavelength L1 such that the individual volume elements of the photocurable resin 20 are irradiated by light of the first wavelength L1 for a relatively long period of time. During this period, for example, the second wavelength light L2 may contain a constant image or a static image. Alternatively, during this period, for example, no second wavelength light L2 is irradiated into the photocurable resin 20 and the working volume.

[0159] According to another exemplary embodiment, changing at least one printing parameter in space and / or time, particularly printing parameters affecting the curing behavior of the photocurable resin 20, may further include irradiating the photocurable resin with light of a first wavelength L1 and / or light of a second wavelength L2 while at least one molding region FZ moves in two different directions. Therefore, the direction of movement of the at least one molding region FZ (particularly relative to the container 50 or the corresponding container 50) is also a printing parameter that can be changed in space and / or time, for example, a printing parameter for printing three-dimensional objects with higher structural isotropy.

[0160] For example, at least one forming region FZ may be irradiated with light of a first wavelength L1 and / or light of a second wavelength L2 while moving along a first movement path in a first movement direction, especially irradiated with light of the first wavelength L1 only; at least one forming region FZ may be irradiated with light of the first wavelength L1 and / or light of the second wavelength L2 while moving along a second movement path in a second movement direction (especially in the opposite direction to the first direction), especially irradiated with light of the first wavelength L1 and light of the second wavelength L2 simultaneously. In particular, the first movement direction may be the direction of movement away from the irradiation device 30 (especially the digital light projection device) of the apparatus 10 for implementing the method of generating light of the second wavelength L2, while the second movement direction may be opposite to the first movement direction, and vice versa.

[0161] Another example is that the first motion path can differ from the second motion path, particularly in length. Specifically, the first motion path can be shorter than the second motion path. Therefore, when at least one molding region FZ moves along the first motion path, the irradiation time of the photocurable resin 20 by light of a first wavelength applied to it can be shorter than the irradiation time of the photocurable resin 20 when at least one molding region FZ moves along the second motion path.

[0162] Figure 6 Here is another diagram, where the vertical axis represents the energy level of light of the first wavelength L1 (solid line) and the energy level of light of the second wavelength L2 (dashed line), and the horizontal axis represents time t.

[0163] Figure 6Specifically, the irradiation process may include: in a first irradiation step S1, irradiating a photocurable resin 20 with light of a first wavelength L1 and light of a second wavelength L2 to form a prepolymerized three-dimensional preform; and in a second irradiation step S2, irradiating the prepolymerized three-dimensional preform with light of the first wavelength L1 and light of the second wavelength L2 to form a three-dimensional object. In particular, the second irradiation step S2 is performed after completing the first irradiation step and / or after completing at least one subsequent irradiation step, and more particularly, after completing a first further irradiation step among multiple subsequent irradiation steps. Therefore, the number of individual irradiation steps can also be printing parameters that can vary spatially and / or temporally. It is worth noting that this embodiment may include forming a prepolymerized three-dimensional preform in the first irradiation step S1, which may already have a shape and / or size corresponding (basically) to the three-dimensional object to be printed. However, the degree of curing of the photocurable resin in the three-dimensional preform may differ from that of the actual three-dimensional object to be printed. In other words, the degree of curing of the photocurable resin in the three-dimensional preform may be low; for example, the degree of curing of the three-dimensional preform may render it inoperable. However, printing actual 3D objects using appropriate intermediate preforms can improve the structural properties of the actual 3D objects.

[0164] It is worth noting that the corresponding energy levels of the first wavelength light L1 and / or the second wavelength light L2 applied in the first irradiation step S1 and the second irradiation step S2 can be different (e.g., Figure 6 (As shown in the example), but can also be (basically) the same.

[0165] from Figure 6 It can also be seen that in the first irradiation step S1, the photocurable resin 20 can be irradiated with light of a first wavelength L1 and light of a second wavelength L2 to form a prepolymerized three-dimensional preform; in the second irradiation step S2, the prepolymerized three-dimensional preform is irradiated with light of the first wavelength L1 and light of the second wavelength L2 to further polymerize the prepolymerized three-dimensional preform; wherein, the second irradiation step S2 can be repeated multiple times. It is worth noting that in the first irradiation step S1, the molding region FZ can move along a corresponding first motion path in the first motion direction; in at least one second irradiation step S2, the molding region FZ can move along a corresponding second motion path in the second motion direction (especially in the direction opposite to the first motion direction).

[0166] Typically, the photocurable resin 20 is irradiated with light of a first wavelength L1 in a first irradiation step to form a prepolymerized photocurable resin; in a second irradiation step, the prepolymerized photocurable resin is irradiated with light of the first wavelength L1 and light of the second wavelength L2 to form a three-dimensional object. Specifically, the second irradiation step S2 is performed after completing the first irradiation step and / or at least one subsequent irradiation step, and more particularly, after completing the first subsequent irradiation step among multiple subsequent irradiation steps. Furthermore, by using the corresponding prepolymerized photocurable resin as an intermediate before printing the actual three-dimensional object, the structural properties of the actual three-dimensional object can be improved.

[0167] According to another exemplary embodiment, changing at least one printing parameter (particularly printing parameters affecting the curing behavior of the photocurable resin) spatially and / or temporally can include (particularly applicable to embodiments of methods requiring the printing of multiple independent three-dimensional objects, particularly simultaneous printing of multiple independent three-dimensional objects): setting a start position and / or start time and / or end position and / or end time for irradiating the photocurable resin with light of a second wavelength for printing a first three-dimensional object, which differs from the start position and / or start time for irradiating the photocurable resin with light of a second wavelength when printing another three-dimensional object. In particular, this exemplary embodiment allows the photocurable resin to continue being irradiated with light of a second wavelength, for example, through so-called "dark images," even after the printing of at least one three-dimensional object has been completed, resulting in higher structural fidelity for the initially completed three-dimensional objects. It is worth noting that this exemplary embodiment is particularly applicable to situations where multiple three-dimensional objects to be printed are arranged laterally. Therefore, their respective forming directions are parallel to each other.

[0168] Figure 7a schematically illustrates the principle of the method according to the prior art in top view form. Figure 7b A schematic diagram of a method according to another exemplary embodiment is shown in top view form. Figures 7a to 7b Figure 7b The term "digital object" used here refers to a representation of a digital file (such as an STL-formatted build file) used in the volume printing process.

[0169] Figures 8a to 8c The top view shows a schematic diagram of a method according to another exemplary embodiment. Figures 8a to 8c The text elements in this document are for reference only and are not restrictive. Figures 8a to 8c In the diagram, the light plate is represented by a dashed line and the label "L1", while the light projection of the second wavelength is represented by a large arrow and the label "L2".

[0170] Figure 7b as well as Figure 8a – Figure 8cSeveral exemplary embodiments are shown in particular, in which at least one printing parameter, especially printing parameters affecting the curing behavior of the photocurable resin, is changed spatially and / or temporally by printing an auxiliary object AO. Specifically, the printing of the auxiliary object AO can be performed on an actual three-dimensional object O (e.g., see...). Figure 8a –8c, i.e., the actual 3D object O to be manufactured, begins spatially and / or temporally before printing. More specifically, the printing of the auxiliary object AO can be completed before the actual 3D object O begins printing. In either case, the corresponding auxiliary object AO can be printed in the first volume of container 50, and the actual 3D object O to be printed can be printed in the second volume of container 50, wherein the second volume is in the printing direction (see Figures 7a to 7c). Figure 7b and Figures 8a to 8c (As indicated by the arrow in the diagram) is located spatially and / or temporally behind the first volume. Therefore, printing the auxiliary object AO can include: first moving a light sheet of a first wavelength along the printing direction (particularly relative to the container 50 containing the photocurable resin (as described above)) through the first volume to generate the auxiliary object AO by multicolor photopolymerization (as described above), and then moving the light sheet of the first wavelength through the second volume. However, when the light sheet passes through the second volume, the intensity of the second wavelength light can be zero or at least (significantly) reduced, such that the photocurable resin in the second volume is (essentially) only affected by the first wavelength light.

[0171] The actual 3D object O can be printed according to one or more target attributes, which are typically defined based on the intended application or use of the 3D object O. For example, the actual 3D object O may have target shape or optical properties, defined based on the intended application or use of the 3D object as an optical element (e.g., a lens). An auxiliary object AO may differ from one or more of the aforementioned target attributes in at least one attribute. Referring to the examples above, the auxiliary object AO may deviate from the intended shape or have lower optical properties than the actual 3D object O to be printed. Therefore, the quality requirements for at least one auxiliary object AO may be lower than the quality requirements for the actual 3D object O to be printed.

[0172] from Figure 8a and Figure 8b As can be seen, at least one auxiliary object OA can be longitudinally shaped, with its spatial extension direction along the printing direction, i.e., along the direction of movement of the light sheet through the container 50. For example... Figure 8a and Figure 8bAs shown, the auxiliary object AO, or at least one auxiliary object AO, may be or comprises a rod-shaped shape, the spatial extension direction of which is along the printing direction, i.e., the spatial extension direction is along the direction of movement of the light sheet through the container 50. In either case, the volume of the auxiliary object AO can be smaller than the volume of the actual three-dimensional object O to be printed. For example, the volume of the auxiliary object AO can be at least one of 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 6, 1 / 7, 1 / 8, 1 / 9, 1 / 10, etc., of the volume of the actual three-dimensional object O to be printed.

[0173] An auxiliary object AO may have at least one function. For example, an auxiliary object AO may have a support function to support a three-dimensional object O attached to it, such as facilitating the removal of a three-dimensional object from a container (see [link]). Figure 8c ).

[0174] The auxiliary object (AO) may be or contain a sacrifice object that can be discarded after printing. Specifically, the auxiliary object (AO) may be attached to at least one 3D object to be printed (e.g., see...). Figure 8c Therefore, there can be one or more connection portions CP, such as one or more connection points, one or more connection lines, or one or more connection regions, through which the auxiliary object AO is physically connected to the actual 3D object O. The corresponding connection portion CP can contain predetermined separation or disconnection structures, which can remove the corresponding auxiliary object AO from the actual 3D object O after printing, for example, by disconnecting the connection. Alternatively, the auxiliary object AO can also be arranged adjacent to the 3D object O to be printed, i.e., spatially offset relative to the 3D object O (e.g., ...). Figure 8a , Figure 8b As shown), this arrangement ensures that there is no physical connection between the auxiliary object AO and the actual 3D object O. The distance between the auxiliary object AO and the actual 3D object O to be printed can be very small, preferably less than 10 mm, more preferably less than 5 mm, more preferably less than 1 mm, even more preferably less than 500 μm, and most preferably less than 100 μm.

[0175] Figure 7b The illustrated embodiment demonstrates an approach in which altering at least one printing parameter (particularly those affecting the curing behavior of the photocurable resin) spatially and / or temporally can include causing non-uniform variations in the temperature and / or density of the photocurable resin within container 50. Consequently, the temperature and / or density of the photocurable resin at position L1 may be higher than at position L2, particularly at the same time, especially at the initial moment of printing the three-dimensional object O. This can be achieved by first printing at least one auxiliary object (see...). Figure 7bThis is achieved by first printing the auxiliary object AO, specifically the sacrificial object as described above, and then printing the actual 3D object O. The shape and / or size of the auxiliary object AO can be adapted to the actual 3D object to be printed. In particular, at least one auxiliary object AO can have a plate-like shape, such as a rectangular, polygonal, or circular plate. The position and / or orientation of this plate within the container 50 can be set so that the normal (substantially) on its main extension plane is parallel to the printing direction, and thus parallel to the direction in which at least one molding area moves relative to the container 50 containing the photocurable resin (as described above). This allows any heat energy generated during the printing of the auxiliary object AO (e.g., heat generated by the polymerization of the photocurable resin) to cause temperature changes, particularly temperature increases and / or the formation of temperature gradients, within the volume of at least one 3D object O to be printed.

[0176] Figure 7b Furthermore, it is shown that the surface of the auxiliary object AO can have a shape corresponding to or the reverse shape of the surface of the actual 3D object to be printed (especially the opposite surface of the 3D object to be printed). For example, when the surface of the actual 3D object O to be printed is concave, the surface of the auxiliary object AO can be convex.

[0177] Surprisingly, it has been found that printing the auxiliary object AO first, and then printing the actual 3D object O, can improve the structural fidelity of the actual 3D object O (from Figure 7a and...). Figure 7b (As can be seen from the comparison). Although not limited to any specific theory, this effect can be explained as follows: During the polymerization of photocurable resin to form the auxiliary object AO, the temperature of the photocurable resin within the volume of the actual 3D object O to be formed rises due to the heat of polymerization, causing the photocurable resin near the already printed portion of the object to expand. Therefore, the subsequently printed portion of the actual 3D object O will be formed in the expanded resin (the expansion is caused by the temperature rise). By printing the auxiliary object AO before the actual 3D object O, the resin within the printing volume of the actual 3D object O expands, allowing the first part of the 3D object O to be formed in the expanded resin, thus enabling the photocurable resin to shrink more uniformly after cooling and reaching equilibrium.

[0178] Figures 9a to 9d and Figures 10a to 10b Schematic diagrams of methods according to other exemplary embodiments are shown respectively. Figures 9a to 9d and Figures 10a to 10b This document demonstrates various exemplary principles that illustrate how grayscale processing can be combined with the principles described herein for changing at least one printing parameter spatially and / or temporally.

[0179] Figures 9a to 9c This section explains in detail how to achieve different intensity distributions within a second-wavelength projection image through grayscale processing—specifically by adjusting the intensity of one or more pixels in the second-wavelength projection image.Figure 9a This shows the situation before the pixel intensity was changed (adjusted); Figure 9b This shows the result after changing (adjusting) the pixel intensity; Figure 9c This illustrates a scenario where no pixel adjustment is performed after applying grayscale processing (e.g., by applying a grayscale filter with higher brightness (intensity) to the center of the projected image); Figure 9d This illustrates a scenario where no pixel adjustment is performed after applying grayscale processing (e.g., by applying brighter (higher intensity) grayscale filters at the top and bottom of the projected image).

[0180] from Figures 9a to 9d and Figures 10a to 10b It can be further seen that spatial and / or temporal variations in at least one printing parameter can enable each volume element of the photocurable resin to be irradiated by a separate second wavelength. For example, a first pixel of a projected image of a second wavelength of light can be irradiated with a first specific wavelength (e.g., green light), and a second pixel of the same projected image or another projected image can be irradiated with a second specific wavelength (e.g., red light), where the two specific wavelengths can have (substantially) the same physical intensity. For example, a specific first wavelength and a specific second wavelength belonging to the second wavelength can be selected based on the absorption spectra of the photocurable resin and the photoinitiator (especially the intermediate state of the photoinitiator). In particular, a second wavelength with a large overlap area with the absorption spectrum of the intermediate state of the photoinitiator can achieve a higher degree of curing compared to a second wavelength with little or no overlap with the absorption spectrum of the intermediate state.

[0181] Generally, "white" or "high intensity" refers to a second wavelength at which the intermediate state of the photoinitiator in the photocurable resin has a high extinction coefficient, particularly a maximum absorption value, thus absorbing more light of the second wavelength. "Black" or "low intensity" refers to a second wavelength at which the intermediate state of the photoinitiator has a low extinction coefficient, particularly an extinction coefficient of 0, thus absorbing less or no light of the second wavelength. "Gray" refers to a second wavelength at which the extinction coefficient of the intermediate state of the photoinitiator in the photocurable resin is between that of "white" and "black," or "gray" can refer to a second wavelength that includes a mixture of "white" and "black." Therefore, although the physical light intensity may be essentially the same, intensity variations relative to the process can be achieved by alternating the second wavelength. Thus, intensity distribution can refer to pixels having different colors of light, but all pixels having essentially the same physical light intensity.

[0182] Specifically, the non-uniform intensity distribution of the second wavelength light can be set according to the distribution of the photoinitiator in the intermediate-state photocurable resin, as described above, where the distribution of the photoinitiator in the intermediate-state photocurable resin is generated by irradiating the photocurable resin with the first wavelength light. More specifically, the photoinitiator in the intermediate-state photocurable resin can emit fluorescence under irradiation with the first wavelength light, which can be recorded by a camera, particularly a camera that captures an image of the working volume from a position perpendicular to the light sheet. The brightness of each pixel in the obtained fluorescence image can correspond to the concentration of the intermediate-state photoinitiator molecules. For example, the fluorescence image can be converted into a grayscale image, and then the black and white values ​​of all pixels can be inverted. The resulting image exhibits an improved intensity distribution, which can be used to adjust the intensity of the projected image of the second wavelength light during the printing process. The grayscale value of each pixel in the final image can be used to calculate the grayscale value of the corresponding pixel in the projected image during the printing process. In particular, the grayscale value of the final image can be multiplied by a factor that is constant for all pixels of at least one image.

[0183] The intensity variation of the second wavelength of light can be achieved by processing one or more images of the second wavelength of light (particularly software-based processing). The corresponding processing may include applying or implementing at least one grayscale processing configuration according to the described embodiment to a corresponding image of the second wavelength of light, resulting in a non-uniform intensity distribution of the second wavelength of light. The corresponding processing may include combining two or more different grayscale processing configurations.

[0184] This method can be implemented by at least one optical modulation device assigned to an irradiation apparatus, wherein the at least one optical modulation device is configured to: modulate the spatial extension direction of two or more beams of a plurality of beams of a first wavelength in at least one optical plane such that the two or more beams are non-parallel to each other, and / or generate at least two beams of the first wavelength with different polarizations or polarization states at at least one point within the working volume, and / or generate at least two beams of different wavelengths (particularly within a specific wavelength range) at at least one point within the working volume. Therefore, at least one optical modulation device can be configured to generate at least two beams of the first wavelength with different polarizations or polarization states at at least one point within the working volume, and / or generate at least two beams of different wavelengths (particularly within a specific wavelength range) at at least one point within the working volume. This can be an independent configuration of the at least one optical modulation device, particularly independent of a configuration in which the at least one optical modulation device is configured to modulate the spatial extension direction of two or more beams of a plurality of beams in at least one optical plane such that the two or more beams extend in a non-parallel arrangement relative to each other.

[0185] The principle of angular diversity can include generating or using light beams of a first wavelength that extend at an angle to each other, such that they intersect at at least one point (e.g., at least one intersection point). Specifically, angular diversity can include generating or using light beams of a first wavelength that extend at different angles to each other, such that they intersect at at least two intersection points, and more specifically, generating and distributing multiple intersection points across the entire sheet. In particular, the principle of angular diversity can be implemented at an angle (especially orthogonal) to the forming direction of the object to be printed, especially to avoid or reduce resolution loss in the forming direction.

[0186] Specifically, at least one optical modulation device may be configured to intentionally alter the spatial extension direction and / or orientation of at least two beams, causing the at least two beams to extend in a non-parallel manner, resulting in the intersection of the two or more beams at one or more intersection points within at least one optical sheet, thereby affecting (particularly at least partially reducing) the optical coherence of the beams within at least one optical plane. Altering the spatial extension direction and / or orientation of the at least two beams, causing them to extend in a non-parallel manner within at least one optical plane, also results in at least one optical plane containing beams with angular spatial extension directions, which have angular extension directions as they pass through, travel, or propagate through the working volume. In particular, the at least two beams may pass through, travel, or propagate through the working volume at an angle to each other that is not 0°. The intersection of the at least two beams at one or more intersection points within at least one optical plane may also include the at least two beams overlapping at one or more intersection points.

[0187] When applying one or more of the above principles (such as the principle of angular diversity) to a light sheet of the first wavelength, determining the ideal grayscale adjustment for a single image may require a significant amount of computation. Therefore, when applying the principle of angular diversity to a light sheet, it is preferable to use a simple gradient method, a grayscale filter obtained by measuring the intermediate state distribution through fluorescence imaging, or to determine a grayscale value independent of the first wavelength of light.

[0188] The specific intensity distribution curves of each projected image of the second wavelength of light can be selected based on simulation, modeling, or experimental results. These results describe the intensity distribution of the light sheet extending across the working volume, or the absorption behavior or characteristics of each volume element or voxel in the working volume. For example, these absorption behaviors or characteristics can be influenced by switching a two-color photoinitiator from an initial state to an intermediate state, and / or by initiating and forming absorption byproducts that lead to photobleaching of the intermediate state. Therefore, photophysical processes (e.g., absorption, (light) switching) and physical parameters (e.g., light intensity, light sheet thickness) can be incorporated into the modeling.

[0189] Furthermore, the experimental results can serve as data for printed objects (especially structural data) and applied process parameters (especially those containing grayscale information), which can be used to train one or more algorithms or software incorporating such algorithms. The corresponding algorithms can respectively implement the principles of artificial intelligence and machine learning to find improved process parameters, particularly those containing grayscale information.

[0190] Figures 10a to 10b This shows an example pixel array containing a sample arrangement of 7x7 pixels. Figures 10a to 10b Specifically, this demonstrates the following principle: If a pixel that should be "off" (black) is surrounded by many white pixels, the pixel naturally remains off; if a pixel that should be "off" is surrounded by a few white pixels, the pixel becomes brighter because the brightness of these white pixels is insufficient to trigger solidification. Here, the proximity effect is fully utilized. If a pixel that should be "on" (white) is surrounded by many white pixels, the pixel becomes darker; if a pixel that should be "on" is surrounded by many black pixels, the pixel becomes brighter.

[0191] In any embodiment, the molding time for the three-dimensional object can be up to 1 minute for every 1 millimeter the three-dimensional object extends in at least one direction. Therefore, this method can be implemented at a high printing speed, which is another exemplary printing parameter affecting the curing behavior of the photocurable resin 20.

[0192] One, more, or all aspects associated with at least one embodiment may be used in combination with one, more, or all aspects associated with at least one other embodiment.

Claims

1. A method for volumetric printing of a three-dimensional object by multicolor photopolymerization of a photocurable resin, the method comprising an irradiation process based on multiple printing parameters: irradiating the photocurable resin with light of a first wavelength and light of a second wavelength different from the first wavelength to form a three-dimensional object in at least one direction by multicolor photopolymerization, wherein the first wavelength and the second wavelength intersect in the forming region, wherein the method comprises changing at least one printing parameter spatially and / or temporally during the irradiation process, particularly printing parameters affecting the curing behavior of the photocurable resin.

2. The method according to claim 1, wherein, Changing at least one printing parameter in space and / or time, particularly printing parameters affecting the curing behavior of the photocurable resin, includes: irradiating the photocurable resin with a first wavelength of light before irradiating it with a second wavelength of light, wherein irradiating the photocurable resin with the first wavelength of light begins particularly from position p1, and irradiating the photocurable resin with the second wavelength of light begins particularly from position p2, wherein position p2 is located behind position p1 in the molding direction; and / or irradiating the photocurable resin with the first wavelength of light begins particularly from time t1, and irradiating the photocurable resin with the second wavelength of light begins particularly from time t2, wherein t2>t1.

3. The method according to claim 1, wherein, Changing at least one printing parameter in space and / or time, particularly printing parameters affecting the curing behavior of the photocurable resin, includes: irradiating the photocurable resin with light of a first wavelength after irradiating it with light of a second wavelength, wherein irradiating the photocurable resin with light of a second wavelength ends particularly at position p3, and irradiating the photocurable resin with light of a first wavelength ends particularly at position p4, wherein position p4 is located after position p3 in the molding direction; and / or irradiating the photocurable resin with light of a second wavelength ends particularly at time t3, and irradiating the photocurable resin with light of a first wavelength ends at time t4, wherein t4 > t3.

4. The method according to claim 2 or 3, wherein, Changing at least one printing parameter in space and / or time, particularly printing parameters affecting the curing behavior of the photocurable resin, includes: irradiating the photocurable resin with light of a first wavelength in a volume separated from the volume of the three-dimensional object to be printed, particularly in a volume adjacent to the volume of the three-dimensional object to be printed, and more particularly in a volume directly adjacent to the volume of the three-dimensional object to be printed, particularly wherein, relative to at least one direction of the three-dimensional object, the volume is located in front of and / or behind the volume of the three-dimensional object to be printed.

5. The method according to claim 1, wherein, Changing at least one printing parameter in space and / or time, particularly printing parameters that affect the curing behavior of a photocurable resin, includes: irradiating the photocurable resin with light of a first wavelength and / or a second wavelength, and changing the energy or energy intensity of the first wavelength and / or the second wavelength of light in space and / or time along at least one direction.

6. The method according to claim 5, wherein, Changing the energy of light of a first wavelength in space and / or time includes changing the energy of light of the first wavelength from a first energy level to at least a second energy level, the second energy level being less than the first energy level; And / or changing the energy of the light of the first wavelength in space and / or time includes changing the energy of the light of the first wavelength from a first energy level to at least a second energy level, the second energy level being higher than the first energy level, wherein, particularly in the initial volume of the three-dimensional object to be printed, the photocurable resin is irradiated with the light of the first wavelength at the first energy level, the initial volume having a spatial extension in at least one direction accounting for at most 5%, particularly at most 3%, more particularly at most 1% of the three-dimensional object to be printed, and / or wherein the initial time of irradiation of the photocurable resin with the light of the first wavelength at the first energy level is at most 10 seconds, particularly at most 5 seconds, more particularly at most 1 second, even more particularly at most 0.1 seconds, and most particularly at most 0.01 seconds.

7. The method according to claim 5 or 6, wherein, Changing the energy of light of a second wavelength in space and / or time includes changing the energy or energy distribution of at least a portion, such as at least one pixel, of an image corresponding to the cross-sectional geometry of the three-dimensional object to be printed, or changing the energy or energy distribution of at least one point or line of at least one beam corresponding to the cross-sectional geometry of the three-dimensional object to be printed. Changing the energy of the second wavelength in space and / or time specifically includes changing the energy of at least a portion, particularly at least one pixel, of the image in a sequence comprising at least three energy levels E1, E2, and E3, wherein the energy level changes from E1 to E2, and E2 > E1, and the energy level changes from E2 to E3, and E2 > E3, and particularly E3 > E1.

8. The method according to claim 7, wherein, Changing at least one printing parameter in space and / or time, particularly printing parameters that affect the curing behavior of the photocurable resin, includes changing the focus parameter of the first wavelength of light and / or changing the image or at least one image element, such as the image parameter of at least one pixel, projected by the second wavelength of light.

9. The method according to claim 1, wherein, Changing at least one printing parameter in space and / or time, particularly printing parameters that affect the curing behavior of the photocurable resin, includes: irradiating the photocurable resin with light of a first wavelength and / or a second wavelength during irradiation, while at least one molding area does not move relative to the container during irradiation, or at least one molding area moves at a rate of motion lower than the nominal rate of motion.

10. The method according to claim 1, wherein, The irradiation process includes: in a first irradiation step, irradiating the photocurable resin with light of a first wavelength and light of a second wavelength to form a prepolymerized three-dimensional preform; and in a subsequent irradiation step, irradiating the prepolymerized three-dimensional preform with light of the first wavelength and light of the second wavelength, thereby causing the formation of a three-dimensional object, particularly after completing the first irradiation step and / or after completing at least one subsequent irradiation step, and more particularly after completing the first subsequent irradiation step among a plurality of subsequent irradiation steps, irradiating the prepolymerized three-dimensional preform with light of the first wavelength and light of the second wavelength to form the three-dimensional object; wherein, in particular, in the first irradiation step, irradiating the photocurable resin with light of the first wavelength and light of the second wavelength to form the prepolymerized three-dimensional preform, and in the second irradiation step, irradiating the prepolymerized three-dimensional preform with light of the first wavelength and light of the second wavelength to cause further polymerization of the prepolymerized three-dimensional preform; wherein the second irradiation step can be repeated multiple times.

11. The method according to claim 10, wherein, In the first irradiation step, the photocurable resin is irradiated with light of a first wavelength to produce a prepolymerized photocurable resin, and wherein, in a subsequent irradiation step, the prepolymerized photocurable resin is irradiated with light of a first wavelength and light of a second wavelength to form a three-dimensional object, particularly after the completion of the first irradiation step and / or after the completion of at least one subsequent irradiation step, and more particularly after the completion of the first subsequent irradiation step among a plurality of subsequent irradiation steps, the prepolymerized photocurable resin is irradiated with light of a first wavelength and light of a second wavelength to form the three-dimensional object.

12. The method according to claim 1, wherein, Changing at least one printing parameter in space and / or time, particularly printing parameters that affect the curing behavior of the photocurable resin, including moving at least one molding area in two different directions during the irradiation of the photocurable resin.

13. The method according to claim 12, wherein, While at least one molding area is irradiated by light of a first wavelength and / or a second wavelength, particularly when at least one molding area is irradiated only by light of the first wavelength, the at least one molding area is moved along a first movement path in a first movement direction; and wherein, while at least one molding area is irradiated by light of the first wavelength and / or a second wavelength, particularly when at least one molding area is irradiated by light of both the first and second wavelengths, the molding area is moved along a second movement path in a second movement direction, wherein, in particular, the first movement path differs from the second movement path, particularly in length, and in particular, the first movement path is shorter than the second movement path.

14. The method of claim 1, wherein the forming time of the three-dimensional object is at most 1 minute, which is the time required for the three-dimensional object to extend 1 millimeter in at least one direction.

15. The method according to claim 1, wherein, Irradiating the photocurable resin with light of a first wavelength causes one or more photoinitiator molecules in the photocurable resin to change from an initial state to an intermediate state. Compared with the initial state, the optical properties of the intermediate state change, such that one or more photoinitiator molecules in the intermediate state can absorb light of a second wavelength. As a result, the one or more photoinitiator molecules change from the intermediate state to an active state by absorbing the second wavelength of light, thereby locally triggering the polymerization of the photocurable resin to form at least one three-dimensional object.

16. An apparatus for volumetric printing of a three-dimensional object via multicolor photopolymerization of a photocurable resin, the apparatus comprising an irradiation device for performing an irradiation process based on a plurality of printing parameters, the irradiation process comprising irradiating the photocurable resin with light of a first wavelength and light of a second wavelength different from the first wavelength to form a three-dimensional object in at least one direction via multicolor photopolymerization, wherein, The first wavelength of light and the second wavelength of light intersect in the forming region, wherein the device includes a controller configured to change at least one printing parameter spatially and / or temporally during irradiation, particularly printing parameters that affect the curing behavior of the photocurable resin.

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