METHOD FOR DIGITALLY PRODUCING AN OPTICAL ELEMENT WITH INTEGRATED FUNCTIONALITIES AND OPTICAL ELEMENT PRODUCED IN THIS WAY

Description

[0001] The present invention relates to a method for the digital production of an optical element with integrated functionalities, in which a three-dimensional structure is produced from a printing material containing an inorganic-organic hybrid polymer by means of 3D printing, and a region-specific modification on the surface and / or in the volume of the structure is carried out to create at least one region with an additional functionality. The invention also relates to an optical element comprising a three-dimensional structure produced from an inorganic-organic hybrid polymer by means of 3D printing, wherein the structure has at least one region with an additional functionality on the surface and / or in the volume.

[0002] Optical systems are currently composed of various optical elements, such as lenses, mirrors, apertures, etc., to achieve a defined function. In the classic case of imaging glass optics, this requires the assembly of entire assemblies, each of which must be precisely joined and is both heavy and bulky.

[0003] In state-of-the-art camera lenses, various optical components, particularly ground and polished spherical lenses and apertures, are combined into a complete assembly. In this case, a complex system of lenses is required not only to produce the image but also to correct optical aberrations (e.g., chromatic aberrations and spherical aberrations). Each individual component must be subjected to a complex anti-reflective coating, which, in addition to increasing the complexity of the optics and the resulting system costs, also reduces light throughput. Just like refractive surfaces, aperture stops (so-called baffles) are necessary within the optical system to prevent ghosting and unwanted light reflections.

[0004] The numerous components of an optical system must be precisely aligned with each other using optomechanical components, which not only results in high weight and volume, but also in high costs for components, assembly, and adjustment. The complexity of optical systems is driven in particular by the use of spherical surfaces, which can be manufactured cost-effectively by grinding and polishing. This allows excellent imaging properties to be achieved with considerable effort.

[0005] A significant reduction in the complexity of optical systems can be achieved through the use of freeform surfaces. These are manufactured, for example, using machining processes such as diamond turning or precision pressing. However, the cost advantage resulting from the smaller number of components is offset by complex post-processing steps for the freeforms and expensive tooling. More economical – and therefore relevant for many consumer optics – is the use of polymers processed into lenses using embossing processes or precision injection molding. 3D printing of polymer optics using inkjet or SLA (stereolithography) technology represents an elegant solution in this regard, as freeforms can be generated inherently. This is known from EP 2,943,331 B1, which predominantly uses organic resins (possibly with monomers).with a silicone component to improve long-term stability at short wavelengths) to create refractive surfaces for lighting applications and ophthalmology. Various variants of additive manufacturing of refractive (and partly reflective) optical components are known in the state of the art (see attached literature list), but these exhibit the typical problems of 3D-printed polymer optics: . Occurrence of layer boundaries in the volume of the printed body in the form of refractive index inhomogeneities that reduce transmission through the body. Digitization artifacts, i.e., stair-step formation on printed surfaces due to the decomposition of the body into layers with defined spacing. Limited accuracy of the realized surface and increased roughness, both compared to conventionally manufactured optics. Durability and reliability limitations due to the use of polymers.

[0006] With the aim of creating a functioning optical system through digital manufacturing and not just a single component (such as a lens), the integration of apertures made of absorbing materials or even other functional elements such as mirrors is also missing.

[0007] Apertures or absorbing structures are typically integrated into the overall optical system as optomechanical components. Subsequent, possibly additive / digital integration of aperture structures is not provided for in conventional optics manufacturing according to the current state of the art. However, the 3D volume structuring of optical glasses or polymer blocks is described, which is triggered by laser processes in the volume of the component. This involves the formation of microcracks or a targeted local blackening—possibly promoted by material modifications. However, these modifications are typically not used in the field of optical systems, and especially not in 3D-printed optical elements.

[0008] 3D shaping of optics using digital processes is possible in a few ways according to the current state of the art: 1. Selective laser etching:Typically, quartz glass is exposed to femtosecond laser pulses, thus increasing the etching rate in the focal region compared to HF or KOH. After the point-by-point exposure of a 3D structure, the etching step follows, after which the desired 3D structure remains as a negative of the exposed area (subtractive process). However, the precision and roughness of the process are insufficient for manufacturing optical components. 2. 3D printing: 3D printing of composites consisting of particles (e.g., with silica) and organic matrix materials, followed by sintering (i.e., thermal decomposition of the matrix material). This allows for the additive manufacturing of glass-like components. Similar to etching processes, the quality of the components is not sufficient for optical applications, particularly due to shrinkage during the sintering process. 3. Laser structuring and polishing: Ablation, fine ablation, polishing using CO 2 laser radiation 4. Abrasive laser treatment:Laser treatment by ablation for transmittive optics is also described for acrylates (DE 10-2017002986 A1)

[0009] S. Suresh Nair et al. ("Additive Manufacturing of Functional (Photoluminescent) Optical Components", 119th DGAO Conference, July 20, 2018) disclose a method for fabricating an optical element containing an inorganic-organic hybrid polymer and quantum dots.

[0010] Based on this, it was the object of the present invention to provide a method for the digital production of an optical element with integrated functionalities, which overcomes the disadvantages of the prior art and enables an optical element with high complexity and improved optical properties.

[0011] This object is achieved by the method having the features of claim 1 and the optical element having the features of claim 11. The further dependent claims show advantageous developments.

[0012] According to the invention, a method for digitally producing an optical element with integrated functionalities is provided, in which a) a three-dimensional structure is produced from a printing material containing an inorganic-organic hybrid polymer by means of 3D printing and b) at least one region with an additional functionality is produced in the three-dimensional structure by means of a region-by-region modification on the surface and / or in the volume of the structure, characterized in that the additional functionality is selected from the group consisting of light-refracting elements.

[0013] The challenges known in the prior art are solved according to the present invention through a targeted selection of additive and digital processes in combination with suitable materials. First, an optical element is created as a three-dimensional structure using 3D printing, e.g., inkjet printing, stereolithography, or digital light processing (DLP) technology, in order to reduce the number of refractive surfaces within the framework of a freeform approach. This essentially allows the generation of light field distributions that are not possible with conventional optics and significantly simplifies the complexity and thus the subsequent assembly and adjustment of the optical system.

[0014] According to the invention, the additional functionality is selected from light-refracting elements. If at least one further region with an additional functionality is created in the three-dimensional structure by a region-specific modification on the surface and / or in the volume of the structure, the additional functionality of the further region is selected from the group consisting of light-absorbing elements, light-reflecting elements, light-scattering elements, and electrical functionalities.

[0015] Unlike the prior art, a light-curing, i.e., photochemically crosslinkable, inorganic-organic hybrid polymer (ORMOCER) is used as the printing material instead of a purely organic polymer. This polymer contains an inorganic component, which results in better optical properties and increased stability against temperature influences and other aging phenomena, particularly yellowing. Furthermore, the material class of inorganic-organic hybrid polymers can be adapted with regard to the printing parameters and the properties of the component, so that the properties of the printed optics can generally be significantly improved compared to the prior art. This applies, for example, to the reduction of layer boundaries through an adjustment of the photochemistry, a smoother surface due to self-smoothing effects inherent in the material, and increased transmission in the visible spectral range.

[0016] It is preferred that the inorganic-organic hybrid polymer is prepared by hydrolysis and polycondensation of one or more alkoxy- or hydroxysilanes of the general formula I: R x Si(OR') 4-x (I) with R = organic group; selected from C1-C8, in particular methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, phenyl, and optionally functionalized, in particular with vinyl, allyl, glycidyloxypropyl, [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane, (meth-)acryloxypropyl, styryl, thiolenes, norbornene, R' = H, C1-Cx-alkyl, in particular methyl or ethyl,

[0017] The silicon can be at least partially replaced by zirconium and / or titanium.

[0018] The inorganic-organic hybrid polymers used are produced by hydrolysis and subsequent condensation of alkoxysilanes as precursors. This creates an inorganic backbone of Si-O units to which organic functional groups are covalently bonded. In the case of 3D-printable inorganic-organic hybrid polymers, these include UV-crosslinkable groups, particularly acrylates and methacrylates. Such hybrid polymers are typically photoresists, which are typically applied in thin layers of several micrometers and (micro)structured. The layered construction in the 3D printing process allows these materials to be processed into solid bodies.

[0019] A preferred embodiment provides that the printing material Particles with a high refractive index, preferably zirconium oxide or titanium oxide, or nanoparticles to increase laser absorption, scattering particles, particles to adjust thermal conductivity, dispersion, thermal expansion, particles as labels or combinations thereof; contains.

[0020] Nanoparticles, i.e. particles with a maximum particle diameter of up to 1000 nm, are preferably used as functional particles.

[0021] 3D printing is preferably carried out using inkjet printing, stereolithography or digital light processing technology (DLP).

[0022] When creating the three-dimensional structure using inkjet printing, the following process steps are preferably carried out: (1) Ejecting a plurality of droplets of the printing material containing the inorganic-organic hybrid polymer towards a substrate, wherein the droplets are deposited next to one another to form a layer, (2) Photochemically curing the plurality of droplets in the layer by means of irradiation, preferably UV radiation or blue LED illumination.

[0023] Steps (1) and (2) are repeated until the desired three-dimensional structure is created.

[0024] Alternatively, the layer-by-layer production of the outer contour of the 3D body by ejecting a large number of droplets with layer-by-layer photochemical curing of the outer contour is also part of the invention. In this case, the volume of the structure is subsequently flooded with the inorganic-organic hybrid polymer and exposed again.

[0025] The inorganic-organic hybrid polymers used are selected, on the one hand, to ensure that the component properties mentioned above can be realized and, on the other hand, in coordination with the respective printing process. In general, not every inorganic-organic hybrid polymer can be processed into a base body using 3D printing. For inkjet printing, for example, its viscosity must be adapted through the synthesis process (selection of precursors) or the addition of reactive diluents, so that it is preferably between 10 and 50 mPas at room temperature. A suitable reactive diluent, i.e. a molecule that co-crosslinks during the printing process, can be, for example, DDDMA (dodecanediol dimethacrylate) or ethyl methacrylate (EMA). In addition, the inorganic-organic hybrid polymer must be photochemically curable and suitable for processing in thick layers (corresponding to the layer spacing in the printing process).

[0026] Surprisingly, by manufacturing the component layer by layer with hybrid polymers of certain types, macroscopic bodies can be constructed in which, with other manufacturing processes, crack formation and embrittlement can occur due to the internal material stress.

[0027] A further embodiment of the invention provides that the following process steps are carried out when producing the three-dimensional structure by means of stereolithography: (1) Providing the printing material on a support structure in a bath (2) Layer-by-layer exposure of the printing material with a rasterized focused (UV) light source through the bottom of the bath while curing a layer, (3) Moving the support structure with the formed layer of the printing material so that a following layer of the printing material is exposed on the formed layer, wherein steps (2) to (3) are repeated until the desired three-dimensional structure is constructed.

[0028] A further embodiment of the invention provides that the following process steps are carried out when generating the three-dimensional structure using digital light processing technology (DLP): (1) Providing the printing material on a support structure in a bath (2) Layer-by-layer exposure of the printing material with a light source with a spatial light modulator through the bottom of the bath while curing a layer, (3) Moving the support structure with the formed layer of the printing material so that a following layer of the printing material is exposed on the formed layer, wherein steps (2) to (3) are repeated until the desired three-dimensional structure is constructed.

[0029] It is preferred that the region-by-region modification in the volume be carried out by emitting and focusing laser radiation with ultrashort laser pulses of <10 ps onto the region to be modified, whereby the ultrashort laser pulses carry out the region-by-region modification on the surface and / or in the volume of the structure. The laser pulses preferably have a pulse repetition rate of 1 to 500 kHz and / or a pulse energy of 10 to 3000 nJ. The laser wavelength is preferably in the range of 300 to 2200 nm. The laser beam diameter at the focus is preferably in the range of <30 µm.

[0030] The ultrashort laser pulses can preferentially carbonize the organic components of the inorganic-organic hybrid polymer, causing the area to be modified to become blackened and / or electrically conductive.

[0031] In addition to the already improved properties of the printed optical components, the selection of suitable inorganic-organic hybrid polymers as the printing material enables the integration of additional functionalities, allowing the creation of an optical system through digital processes. One specific functionality is the creation of absorbing structures within the volume of the printed body through the interaction of the printing material with laser radiation. For this purpose, a laser is focused into the body through an optical system. The interaction within the volume occurs through nonlinear absorption processes of ultrashort laser pulses, which in turn cause microscopic material modification of the printing material.The geometrical form of this modification can be manipulated through the focusing optics and the laser parameters used, whereby the modification triggered by a single pulse depends on the distance of the focus in the material to the sample surface. A combination of several modifications triggered by single pulses at a constant processing depth below the sample surface consequently allows for a macroscopic material modification of the printing material. This can also be carried out at different processing depths below the sample surface, which, however, requires depth-adapted laser process control with regard to a homogeneous macroscopic material modification. In terms of the absorbing structures to avoid ghost images and unwanted reflections, the laser-induced material modifications can specifically be carbonization, i.e.This could be a decomposition of organic ORMOCER® components, which appears in the volume as a broadband absorbing (= dark) structure. By adjusting the process parameters and / or initiating the modifications multiple times – either at the same location or in closely adjacent regions – the total absorption / transmission through the macroscopically treated area can be precisely adjusted.

[0032] The addition of nanoparticles to modify the absorption behavior in the bulk material and thus better control the laser-induced interaction for blackening digitally defined areas is also conceivable. This materials technology approach also allows for the adjustment of the refractive index of the printing material.

[0033] Triggering laser-induced carbonization also has the advantage that the modified areas are electrically conductive. This enables not only the integration of light-absorbing structures but also the subsequent integration of electrical conductors, for example, for contacting integrated electro-optical components, heating elements, or sensors.

[0034] The region-wise modification of the three-dimensional structure preferably involves the following step: producing an achromatic element by means of an inkjet printing process, in that during the inkjet printing process the first printing material is at least temporarily replaced by another printing material which has a refractive index different from the first printing material.

[0035] If at least one further area with additional functionality is created, the modification of the three-dimensional structure preferably involves at least one of the following steps: Production of light-absorbing and / or reflecting and / or scattering elements on the surface and / or in the volume of the structure by means of laser radiation. Anti-reflective coating of the surface of the structure by means of plasma etching. Production of a reflective element by means of an inkjet printing process and subsequent thermal post-treatment and / or photonic post-treatment, e.g. flash lamp illumination or laser post-treatment, wherein the printing process is preferably carried out using metallic (nano)particles, particularly preferably silver (nano)particles.

[0036] According to the invention, an optical element is also provided which contains a three-dimensional structure produced by 3D printing from an inorganic-organic hybrid polymer, wherein the structure has at least one region with an additional functionality on the surface and / or in the volume, characterized in that the additional functionality is selected from the group consisting of light-refracting elements.

[0037] According to the invention, the additional functionality is selected from light-refracting elements. If the structure has at least one further region with an additional functionality on the surface and / or in the volume, the additional functionality of the further region is selected from the group consisting of light-absorbing elements, light-reflecting elements, light-scattering elements, and electrical functionalities.

[0038] It is preferred that the additional functionality of the three-dimensional structure is an achromatic element on the surface and / or in the volume of the structure.

[0039] If the structure has at least one further region with an additional functionality on the surface and / or in the volume, it is preferred that the additional functionality of the three-dimensional structure is selected from a reflective surface of the structure, in particular formed from metallic (nano)particles, preferably silver (nano)particles; an anti-reflection coating on the surface of the optical element by plasma etching; a light-scattering element on the surface and / or in the volume of the structure; a light-absorbing element, in particular an aperture stop, on the surface and / or in the volume of the structure; and combinations thereof.

[0040] The basic approach of producing an optical system from inorganic-organic hybrid polymers using 3D printing in combination with other digital processes allows for the integration of even more complex functionalities. If the printing material is compatible with other functional materials and processes—and this can be achieved through chemistry—additional functionalities can be implemented either during the printing process between individual print layers or after the printed body has been completed.

[0041] Overall, the advantages of this approach derive, on the one hand, from the specific benefits of 3D-printed optics. On the other hand, further significant advantages result from the integration of functions resulting from the choice of printing material and process control (3D printing, laser process). These advantages include: Less weight and volume Lower costs Significantly improved material properties compared to pure polymer-based printing materials (temperature stability, yellowing, ...) Improved reliability Complete design freedom regarding the refractive surface(s) and the integrated absorber structures / baffles No ghost images and / or unwanted reflections Significantly increased functional density and further functions that were previously very difficult or even impossible to integrate into optical systems (e.g. mirrors, absorber structures) Improved optical properties: Reduced (refraction / scattering at) layer boundaries, low surface roughness, AR layers without additional layer deposition Design down to batch size 1 without tool adaptation

[0042] The subject matter of the invention will be explained in more detail with reference to the following figures and the example, without wishing to restrict it to the specific embodiments shown here.

[0043] Of the following designs, the Figure 3 does not represent an embodiment according to the invention, but is helpful to understand certain aspects of the invention. Fig.1 shows a photograph of an optical element according to the invention Fig. 2 shows a transmission spectrum of an optical element according to the invention in comparison to quartz glass and PMMA. Fig. 3 shows a photographic image of optical elements with integrated functional areas (absorbing structures).

[0044] In Fig. 1 is a photograph of an optical element according to the invention made of an inorganic-organic hybrid polymer (ORMOCER). The image shows that the optical element exhibits high transparency and no yellowing of the material is detectable. Furthermore, the upper surface is freeform.

[0045] In Fig. 2 A transmission spectrum of optical elements according to the invention is shown. The measurement was carried out on a 3D-printed plane-parallel plate with a thickness of 3 mm (material 1: commercially available ORMOCER; material 2: modified ORMOCER with DDDMA). The spectrum shows the transmission of a PMMA plate with a thickness of 1 mm (material 3) and 5 mm (material 4) as a reference, and the transmission of quartz glass as a reference for a purely inorganic material. The data demonstrate that the 3D-printed bodies have a similarly high transmission in the wavelength range from 400 to 1100 nm as the conventionally processed materials. This demonstrates the high optical quality with regard to transmission (avoidance of scattering / refracting layer boundaries) when using a suitable ORMOCER in the 3D printing process (here: inkjet).

[0046] In Fig. 3is a photograph of optical elements with integrated functional areas. The left optical element incorporates vertical absorber structures, while the right optical element incorporates horizontal absorber structures, visible as gray areas. Example

[0047] 3-(trimethoxysilyl)propyl methacrylate, diphenyldimethoxysilane, and methoxytrimethylsilane are reacted in a molar ratio of 1:1:1.75 in an acidic hydrolysis / condensation reaction using HCl. After workup, the resulting resin is adjusted to a viscosity of 40 mPas with dodecanediol dimethacrylate and treated with a suitable photoinitiator.

[0048] This material formulation is then printed into a 3-dimensional substrate using an inkjet process. This occurs layer by layer with a layer thickness of 10 µm. After the actual printing process, each printed layer is exposed to UV LEDs (wavelength: 405 nm) for 2 s, i.e., cured. The print head with the hybrid polymer is then removed from the substrate by the layer distance. The 3-dimensional structure is created by repeated printing (according to the current layer based on the computer model of the substrate), exposure, and removal of the substrate. This typically exhibits a transparency of > 90% in the visible spectral range for a total thickness of 1 mm.

[0049] For the laser-induced creation of modifications in the volume of the structure, the structure is then introduced into a laser writing system. There, an ultrashort pulse laser (wavelength 1030 nm) with a focus diameter of 1.6 µm, a pulse duration between 0.35 and 1.5 ps, and a pulse repetition rate between 1 and 500 kHz is focused into the volume with a numerical aperture of 0.4. According to the digital data representing the volume modification to be created, the laser focus is then guided along various trajectories (in the XY direction or in the YZ or XZ direction) through the 3D-printed body with a pulse energy between 10 and 3000 nJ. In terms of absorbing structures to avoid ghost images and unwanted reflections, the laser-induced material modifications can specifically be carbonization, i.e.This could be a decomposition of organic hybrid polymer components, which appears in the volume as a broadband absorbing (= dark) structure. Lighter modifications of the material below the carbonization threshold are used to introduce light-refracting or light-scattering structures.

[0050] In one embodiment according to the invention, the molded body produced in this way contains additional functions. For example, a further 3D printing process using a different hybrid polymer with a different Abbe number is possible on this molded body. Production generally takes place under comparable experimental conditions with regard to irradiation wavelength, duration, and layer spacing. The combination of two materials with different Abbe numbers is well known in optics and enables the production of color-corrected optics.

[0051] Furthermore, the printing process with the hybrid polymer can be interrupted to print an ink with silver nanoparticles in one or more layers. To form a reflective layer, the printed nanoparticles must be sintered, which is typically done in an oven at a temperature of 200 °C for 30 minutes.

[0052] Alternatively, sintering can be performed using laser radiation: The printed layer is exposed to laser radiation, which is absorbed by the particles and converted into heat. This leads to sintering of the particles. Continuously emitting or pulsed laser systems with pulse lengths > 1 ns at laser wavelengths between 200 and 3,500 nm and 9,000 and 11,000 nm are used. Either the substrate is moved under the stationary laser beam, the printed surface is processed entirely without moving the substrate or laser beam, and / or the laser beam is moved over the stationary substrate. A combination is possible, e.g., a moving substrate and a moving laser beam.In the specific example, laser sintering is carried out using a fiber laser (emission wavelength 1070 nm, continuous wave, power 32.7 W), whereby a focused laser beam (focal length of the focusing optics 254 mm, spot diameter in focus 860 µm) scans the layer of nanoparticles in a meandering pattern (scanning speed 4000 mm / s with track pitch 50 µm).

[0053] Plasma etching can be used to reduce the reflections on the refractive surfaces of the printed optical element. An Ar / O2 plasma is applied to the element's surface for 500 s, creating porous structures with a pore size between 10 and 150 nm and a depth of 50-200 nm. These so-called "moth eyes" lead to a broadband reduction of surface reflections by 4%.

Claims

1. A method for digitally generating an optical element with integrated functionalities, in which a) a three-dimensional structure is generated from a printing material, which comprises an inorganic-organic hybrid polymer, via 3D printing, b) in the three-dimensional structure, at least one region having an additional functionality is generated by modifying a region on the surface and / or in the volume of the structure, characterised in that the additional functionality is selected from the group consisting of light-refracting elements.

2. A method according to claim 1, characterised in that, in the three-dimensional structure, at least one further region with an additional functionality is produced by a modification in regions of the surface and / or in the volume of the structure, wherein the additional functionality of the further region is selected from the group consisting of light-absorbing elements, light-reflecting elements, light-scattering elements, and electrical functionalities.

3. A method according to any of the preceding claims, characterised in that the inorganic-organic hybrid polymer is produced by hydrolysis and polycondensation reactions of at least one alkoxy- or hydroxysilane of the general formula I:         RxSi(OR')4-x     (I) where R = organic group; selected from C1 - C8, in particular methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, phenyl, and optionally functionalised, in particular with vinyl, allyl, glycidyloxypropyl, [2-(3,4-epoxycyclohexyl)ethyl] trimethoxysilane, (meth)acrylox-ypropyl, styryl, thiolenes, norbornylenes, R' = H, C1-C8-alkyl, in particular methyl or ethyl, wherein Si can be at least partially replaced by zirconium and / or titanium.

4. A method according to any one of the preceding claims, characterised in that the printing material comprises • particles having a high refractive index, preferably zirconium oxide or titanium oxide, or nanoparticles for increasing laser absorption, • scattering particles, • particles to adjust the thermal conductivity, the dispersion, the thermal expansion, • particles as a label or • combinations thereof.

5. A method according to any of the preceding claims, characterised in that the 3D printing is carried out via an inkjet printing process, stereolithography or digital light processing technology (DLP).

6. A method according to the preceding claim, characterised in that, when generating the three-dimensional structure via an inkjet printing process, the following method steps are carried out: (1) ejecting a plurality of droplets of the printing material, which comprises the inorganic-organic hybrid polymer, towards a substrate, the droplets being deposited next to one another to form a layer. (2) Photochemical curing of the plurality of droplets in the layer via irradiation, preferably UV radiation or blue LED lighting, wherein steps (1) and (2) are repeated until the desired three-dimensional structure is formed, the viscosity of the printing material preferably being adjusted with a reactive thinner, in particular dodecanediol dimethacrylate or ethyl methacrylate, to be in the range from 10 to 50 mPas.

7. A method according to claim 5, characterised in that, when generating the three-dimensional structure via stereolithography, the following method steps are carried out: (1) providing the printing material on a support structure in a bath (2) illuminating, layer by layer, the printing material with a rastered, focused (UV) light source through the bottom of the bath while curing a layer, (3) moving the carrier structure with the formed layer of the printing material so that a subsequent layer of the printing material is illuminated on the formed layer, steps (2) to (3) being repeated until the desired three-dimensional structure is formed.

8. A method according to claim 5, characterised in that, when generating the three-dimensional structure via digital light processing technology (DLP), the following method steps are carried out: (1) providing the printing material on a support structure in a bath (2) illuminating, layer by layer, the printing material with a light source with a room light modulator through the bottom of the bath while curing a layer, (3) moving the carrier structure with the formed layer of the printing material so that a subsequent layer of the printing material is illuminated on the formed layer, steps (2) to (3) being repeated until the desired three-dimensional structure is formed.

9. A method according to one of the preceding claims, characterised in that the regional modification in the volume is carried out by radiating and focusing laser radiation with ultrashort laser pulses having a pulse duration of <10 ps onto the region to be modified, wherein the regional modification on the surface and / or in the volume of the structure is effected by the ultra-short laser pulses, the ultrashort laser pulses particularly causing the organic components of the inorganic-organic hybrid polymer to carbonate, which blackens the area to be modified and / or makes it electrically conductive, wherein the laser pulses preferably have a pulse repetition rate of 1 to 500 kHz and / or a pulse energy of 10 to 3000 nJ and / or the laser wavelength is in the range of 300 to 2200 nm and / or the laser beam diameter at the focus is in the range of < 30 µm.

10. A method according to any one of the preceding claims, characterised in that the regional modification is carried out by the following step: Generating an achromatic element via an inkjet printing process, in that during the inkjet printing process, the first printing material is at least temporarily replaced by a further printing material that has a refractive index differing from that of the first printing material.

11. An optical element comprising a three-dimensional structure produced from an inorganic-organic hybrid polymer via 3D printing, at least one region having an additional functionality being arranged on the surface and / or in the volume of the structure, characterised in that the additional functionality is selected from the group consisting of light-refracting elements.

12. An optical element according to claim 11, characterised in that an additional functionality is arranged in at least one further region on the surface and / or in the volume of the structure, the additional functionality of the further region being selected from the group consisting of light-absorbing structures, light-reflecting structures, light-scattering structures and electrical functionalities.

13. An optical element according to any one of claims 11 or 12, characterised in that the optical element can be produced by 3D printing, in particular by an inkjet printing process, stereolithography, digital light processing technology (DLP).

14. An optical element according to any one of claims 11 to 13, characterised in that the inorganic-organic hybrid polymer is produced by hydrolysis and poly-condensation reactions of at least one alkoxy- or hydroxysilane of the general formula I:         RxSi(OR')4-x     (I) where R = organic group; selected from C1-C8, in particular methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, phenyl, and optionally functionalised, in particular with vinyl, allyl, glycidyloxypropyl, [2-(3,4-epoxycyclohexyl)ethyl] trimethoxysilane, (meth)acryloxy-propyl, styryl, thiolenes, norbornylenes, R' = H, C1-C8-alkyl, in particular methyl or ethyl, wherein Si can be at least partially replaced by zirconium and / or titanium.

15. An optical element according to any one of claims 11 to 14, characterised in that the light-refracting elements are producible by a modification, in particular a carbonisation, of the organic components of the inorganic-organic hybrid polymer via ultrashort laser pulses.