Method for producing a refractive index-graded structure

Abstract

The invention relates to a method for producing a refractive index-matched photocrosslinkable ceramic slip. The method has the steps of providing a photocrosslinkable organic matrix (110); and adding ceramic particles to the photocrosslinkable organic matrix (120); wherein the average diameter of the ceramic particles is ≤ 1 / 10 of a wavelength which is suitable for the light-induced crosslinking of the ceramic slip; the filling degree of ceramic particles is set between 0 and 90 wt.% such that a desired refractive index is achieved; and the diameter is measured by means of dynamic light scattering (DLS). The invention further relates to a method for producing a refractive-index-matched structure, to a method for producing a refractive-index-graded structure, to the use of a photocrosslinkable ceramic slip for producing a refractive-index-matched structure and / or a refractive-index-graded structure, and to a refractive-index-matched photocrosslinkable ceramic slip.

Description

METHOD FOR PRODUCING A CALCULATION INDEX-GRADED STRUCTURE TECHNICAL FIELD

[0001] The present disclosure relates to a method for producing a refractive index-matched photocrosslinkable ceramic slurry, a method for producing a refractive index-matched structure, a method for producing a refractive index-graded structure, the use of a photocrosslinkable ceramic slurry for producing a refractive index-matched structure and / or refractive index-graded structure, and a refractive index-matched photocrosslinkable ceramic slurry. TECHNICAL BACKGROUND

[0002] Refractive index-matched structures can be used for light manipulation, for example, in light transmission. Refractive index matching can enable the lossless transmission of light from a first medium, such as air, to a second medium, such as glass, with little to no reflection at the refractive index transitions.

[0003] For example, a refractive index-matched layer in the form of an anti-reflective coating can reduce reflections on a substrate surface coated with the anti-reflective coating.

[0004] Adjusting the refractive index of an optically transparent material is only possible within certain limits. For example, the refractive index of porous SiO2 can be varied within a range of approximately n=1.5 (e.g., dense quartz glass) and approximately n=1.2 for porous SiO2.

[0005] There are hardly any physical mechanisms and solutions in the state of the art to adjust and / or grade the refractive index of materials in their volume, e.g. locally.

[0006] Adjusting the refractive index in transparent materials is difficult, and porous systems, such as nanoporous SiO2, are typically used. These systems cannot usually be represented as three-dimensional structures, and in particular, grading of the structure is not possible. Porous SiO2 systems can be used as anti-reflective coatings, but due to their porosity, they are not particularly stable and / or sensitive to contamination.

[0007] US 2024 / 0017542 A1 describes "Dual Photoinitiated Nanocomposite-Ink Printing" and in particular the production of a "gradient refractive index dielectric element", using inks with two different wavelength-selective photopolymerization absorption bands, so that a spectrally discrete exposure leads to different degrees of polymerization of the inks.

[0008] DE 10 2017 101 823 A1 describes a structured composite made of matrix material and nanoparticles. WO 2005 075 348 A1 relates to dental composites based on X-ray-opaque flame spray synthesis mixed oxides. WO 2022 035 994 A1 relates to "3D printed silica with nanoscale resolution."

[0009] It is an object of the present invention to provide refractive index-adapted structures as well as refractive index-graded structures. BRIEF DESCRIPTION OF THE INVENTION

[0010] The invention is defined in the appended claims. Further embodiments, refinements, and advantages will become apparent from the dependent claims and the following description.

[0011] According to a general aspect of the present disclosure, a method for producing a refractive index-graded structure is provided. The method comprises providing a photocrosslinkable ceramic slurry containing a photocrosslinkable organic matrix and ceramic particles, wherein the average diameter of the ceramic particles is < 1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slurry, wherein the diameter is measured by means of dynamic light scattering; locally exposing the photocrosslinkable ceramic slurry such that the photocrosslinkable ceramic slurry has at least partially locally crosslinked; and exposing the photocrosslinkable ceramic slurry in such a way that the structure is completely crosslinked

[0012] The refractive index-graded structure of the slurry is created by two exposures, initially locally and then globally. This leads to crosslinking of the photocrosslinkable organic matrix contained in the slurry.

[0013] The initially localized illumination and thus local cross-linking results in a spatial or areal change in the density of the ceramic particles, whereby the locally partially cross-linked slurry, and after global cross-linking, the structure, exhibits a spatial or areal variation in the refractive index. This variation can be adjusted by the extent of the local illumination, in particular by the spatial or areal extent of the local illumination and the extent to which the local illumination leads to cross-linking. Cross-linking can occur locally only partially or locally completely.

[0014] Through local exposure, the photocrosslinkable organic matrix is ​​initially at least partially crosslinked locally, causing the photocrosslinkable organic matrix to shrink in the locally exposed areas. This shrinkage leads to local densification of the ceramic particles. At the same time, local crosslinking stabilizes the entire slurry, which can also limit the flow of the as yet uncrosslinked slurry. As a result, after local exposure, the slurry can have areas with different densities, relative to the ceramic particles. The subsequent global exposure crosslinks all areas of the slurry, i.e. both the previously locally exposed areas, provided they were not yet fully crosslinked, and also the areas of the slurry that were not crosslinked during local exposure.

[0015] According to one embodiment, the local exposure can be performed such that a first region of the slurry is exposed, while a second region of the slurry is not. In the subsequent global exposure, both the first and the second regions are exposed, typically together and with the same exposure (illuminance x exposure time), i.e., the same across the entire area or spatial area.

[0016] According to one embodiment, the local exposure can also be carried out in such a way that a first area is exposed to a greater intensity than a second area of ​​the slurry. During subsequent global exposure, both the first and second regions are exposed together. With local exposure, however, a third region of the slurry cannot be exposed. The third region is then globally exposed together with the first and second regions, typically with the same exposure, i.e., with the same surface or spatially uniform exposure. The different exposure of the first and second regions allows the slurry to shrink differently locally, allowing for finer spatial or surface adjustments of the density of the ceramic particles and, consequently, the refractive index of the finished structure.

[0017] Preferably, the local exposure is carried out using a volumetric exposure method, for example, x-ray diffraction and two-photon polymerization. For this purpose, the local exposure can be carried out using one or more masks. Different areas of the photocrosslinkable ceramic slurry can be exposed simultaneously. The exposure is not limited to the surface, but also takes place in a controlled manner within the volume of the photocrosslinkable ceramic slurry, in contrast to the method described in US 2024 / 0 017 542 A1.

[0018] Local and global exposure can be performed with light of the same wavelength.

[0019] According to one aspect of the present disclosure, providing the photocrosslinkable ceramic slurry comprises providing the photocrosslinkable organic matrix; and adding the ceramic particles to the photocrosslinkable organic matrix to form the photocrosslinkable ceramic slurry.

[0020] According to one aspect of the present disclosure, the photocrosslinkable ceramic slurry is applied to a support. Subsequently, the photocrosslinkable ceramic slurry applied to the support is first exposed locally, followed by the global exposure of the photocrosslinkable ceramic slurry applied to the support.

[0021] According to one aspect of the present disclosure, the photocrosslinkable ceramic slip is applied as a layer, for example, to the carrier. The application as a layer can be carried out, for example, by pouring or uniform spraying.

[0022] According to one aspect of the present disclosure, the photocrosslinkable ceramic slurry applied as a layer is locally exposed and then globally exposed as a layer. Local exposure thus occurs only after a layer has been completely formed, since this allows for the production of optically high-quality refractive index-graded structures.

[0023] According to one aspect of the present disclosure, a method for producing a refractive index-matched photocrosslinkable ceramic slurry is provided, comprising providing a photocrosslinkable organic matrix; and adding ceramic particles to the photocrosslinkable organic matrix. The average diameter of the ceramic particles is <1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slurry, and a filling level of ceramic particles is adjusted between 0 and 90 wt.% to achieve a desired refractive index. The diameter is measured using dynamic light scattering (DLS).

[0024] The process enables the production of a refractive index-matched photocrosslinkable slurry, which can be crosslinked, for example, using light, to obtain a refractive index-matched structure. The amount of added ceramic particles determines the refractive index of the slurry.

[0025] According to another aspect of the present disclosure, a method for fabricating a refractive index-matched structure is provided, comprising providing a refractive index-matched photocrosslinkable ceramic slurry; and forming the refractive index-matched photocrosslinkable ceramic slurry into the refractive index-matched structure.

[0026] According to a further aspect of the present disclosure, a method for producing a refractive index-graded structure is provided, comprising providing a photocrosslinkable organic matrix; and adding ceramic particles to the photocrosslinkable organic matrix to form a photocrosslinkable ceramic slurry. The average diameter of the ceramic particles is <1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slurry. The diameter of the ceramic particles is measured by means of dynamic light scattering (DLS). The method further comprises local exposure such that the photocrosslinkable ceramic slurry locally crosslinks; and Exposing the photocrosslinkable ceramic slip to light so that the structure is completely crosslinked.

[0027] According to a further aspect of the present disclosure, a refractive index-matched photocrosslinkable ceramic slurry is provided. The slurry comprises a photocrosslinkable organic matrix and ceramic particles with an average diameter of the ceramic particles <1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slurry. The diameter of the ceramic particles is measured using dynamic light scattering (DLS). The filling level of ceramic particles in the photocrosslinkable organic matrix is ​​adjusted between 0 and 90 wt.% to achieve a desired refractive index.

[0028] The details of one or more aspects of the disclosure are set forth in the accompanying figures and the following description. Other features, objects, and advantages of the principles described in this disclosure will be apparent from the description and drawings, as well as from the claims. BRIEF DESCRIPTION OF THE CHARACTERS

[0029] The invention is explained in more detail below using embodiments, without these being intended to limit the scope of protection defined by the claims.

[0030] The accompanying drawings illustrate embodiments and, together with the description, serve to explain the principles of the invention. The elements of the drawings are relative to one another and are not necessarily to scale. Like reference numerals designate similar parts.

[0031] Figure 1 schematically shows a method for fabricating a refractive index-matched structure according to embodiments of the present disclosure.

[0032] Figure 2 schematically shows a method for producing a refractive index graded structure according to embodiments of the present disclosure

[0033] Figure 3 shows a refractive index graded structure fabricated using embodiments of the present disclosure.

[0034] Figure 4 shows a three-dimensional representation of a refractive index graded structure shown in Figure 3. DETAILED DESCRIPTION

[0035] The principles described in this disclosure relate to refractive index-matched structures and refractive index-graded structures, as well as means and methods for their manufacture.

[0036] By mixing two non-light-absorbing materials with different refractive indices, all refractive indices can in principle be adjusted according to a mixture series. However, this is only possible if the materials are mixed in such a way that they appear homogeneous at the molecular or particulate level on an order of magnitude of approximately 1 / 10 of the relevant wavelength of light. For molecular mixtures, e.g., liquids, this condition is typically met. For particulate mixtures, e.g., particles mixed with a liquid, this is only met if the particles are smaller than 1 / 10 of the relevant transmitted wavelength. Furthermore, agglomeration and / or other forms of clustering of the particles in the liquid matrix must be prevented.

[0037] According to the invention, refractive index-graded structures can be adjusted by two-stage exposure. For example, two-dimensionally graded refractive indices can be introduced onto a ceramic slip applied as a thin layer by means of two-dimensional exposure. During the crosslinking process, the organic matrix in the slip typically shrinks and can thus increase the density of ceramic nanoparticles. This can lead to an increase in the refractive index. This may be due to the fact that an increased density of optically transparent particles with a higher refractive index than the organic matrix also leads to an increase in the refractive index of the composite material composed of ceramic nanoparticles and organic matrix. In a subsequent process step, the structure is essentially completely exposed to light, so that the organic matrix is ​​essentially completely crosslinked.The two-stage exposure therefore involves partial networking in a local area first, followed by global networking in the second subsequent step. Global networking can usually no longer achieve the same shrinkage as local networking, because the previously locally networked structure impedes the shrinkage during global networking, at least around the locally networked structure.

[0038] Three-dimensionally graded refractive indices can also be represented in this way by photopolymerization induced in the volume of the slurry. For local volumetric polymerization, for example, xolography, 2-photon polymerization and / or holography can be used, as can other methods of planar or point local exposure. Optical elements such as lenses and / or light guides can be written into the volume of a component in this way. For this purpose, the slurry can contain one or more photoinitiators optimized for the respective wavelength of the respective local exposure process, which are different from the one used for global crosslinking. For example, for xolography and 2-photon polymerization, a special photoinitiator can be used for local volumetric polymerization that is different from the one used for global crosslinking.

[0039] Furthermore, the use of a photocrosslinkable ceramic slip makes shaping extremely simple and the composite material can, in addition to free-standing structures, also function as a filler in spaces between optical components as a refractive index-matched transition and / or as a refractive index-graded transition.

[0040] This disclosure describes a method for producing a refractive index-matched photocrosslinkable ceramic slip. The term "refractive index-matched" can refer, for example, to a targeted adjustment of the refractive index of a slip, for example, between n=1.1 and n=1.6. The refractive index is a wavelength-dependent quantity; the information in this disclosure refers approximately to the visible range of light.

[0041] The method comprises providing a photocrosslinkable organic matrix. The matrix can preferably be a photocrosslinkable resin, which can comprise a crosslinkable monomer and / or a polymer crosslinkable therewith or with itself, a photoinitiator and, if necessary, additives for controlling the rheological properties of the slurry and the reactivity of the monomer and polymer during their crosslinking triggered by the photoinitiator. The crosslinkable monomer and the crosslinkable polymer can each have reactive groups. Crosslinking can involve a reaction of the reactive groups with each other. Thus, the photocrosslinkable resin can comprise photocrosslinkable monomers or polymers having one or more terminal double bonds, such as acrylated polyethylene glycol (PEG-DA), 1,6- Hexanediol diacrylate (HDDA), urethane dimethacrylate (UDMA), 2-hydroxyethyl methacrylate (HEMA), 4-acryloylmorpholine (ACMO), etc. Solvents, dispersants, plasticizers, inhibitors, and / or sintering reagents may also be added.

[0042] The process further comprises adding ceramic particles to the photocrosslinkable organic matrix. A higher proportion of ceramic particles by volume and / or weight typically results in a higher refractive index if the refractive index of the ceramic used is higher than that of the organic matrix.

[0043] As a rule, the ceramic particles of the photocrosslinkable slip are spherical or nearly spherical and not fractured in nature, since such small particles are not produced by grinding, but by chemical reaction, e.g., in a hydrothermal synthesis. The particle size (also referred to as diameter) of suitable particles of a suitable slip is typically less than or equal to 1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slip, e.g., the smallest. Furthermore, the particle size (also referred to as diameter) of suitable particles of a suitable slip can typically be less than or equal to 1 / 10 of a wavelength of the intended optical function of the slip and / or later of the structure formed from the slip.

[0044] In this description, particle size is a value measured using dynamic light scattering (DLS). For example, Malvern Panalytical Ltd offers instruments for DLS measurement (e.g., Zetasizer®).

[0045] The average diameter of the ceramic particles is <1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slurry, in particular a smallest suitable wavelength, and / or preferably the wavelength of a planned optical function of the slurry and / or in particular later of the structure formed from it. The average diameter can refer to d50, in particular d90. In some embodiments, substantially all of the ceramic particles can have a diameter of <1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slurry, in particular a smallest suitable wavelength, and / or preferably the wavelength of a planned optical function of the slurry and / or in particular later of the structure formed from it.

[0046] According to one embodiment, a material for the ceramic particles is selected from materials for high-performance ceramics, such as silicon nitride - Si3N4, zirconium oxide - ZrO2, aluminum oxide - Al2O3, spinels - MgAI2O4, silicon carbide - SiC, titanium oxide - TiO2, etc. The chemical formulas given correspond to an idealized chemical composition of the designated materials.

[0047] Typically, the ceramic slip does not contain any non-ceramic particles. If additional particles are added to the slip, the total particle diameter can be < 1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slip, in particular a smallest suitable wavelength, and / or the wavelength of a planned optical function of the slip and subsequently of the structure formed from it. A filling level of ceramic particles is set between 0 and 90 wt.%, preferably between 0 and 40 wt.%, so that a desired refractive index is achieved.

[0048] This disclosure further provides a method for fabricating a refractive index-matched structure. The method includes providing a refractive index-matched photocrosslinkable ceramic slurry according to the present disclosure and forming the refractive index-matched photocrosslinkable ceramic slurry into the refractive index-matched structure.

[0049] According to some embodiments, the method for producing a refractive index-matched structure may further comprise light-induced crosslinking of the organic matrix at the appropriate wavelength to form a ceramic green body.

[0050] According to some embodiments, the wavelength suitable for light-induced crosslinking of the ceramic slurry can be in a wavelength range from 100 nm to 850 nm, preferably in the range 350-550 nm, more preferably in the range 350-405 nm. When using a two-stage photocrosslinking process, the wavelength suitable for light-induced crosslinking of the ceramic slurry can be in a combination of these wavelength ranges. For this purpose, the slurry can contain one or more photoinitiators optimized for the respective wavelength of the respective process for local exposure, which can differ from the photoinitiator used for global crosslinking.

[0051] In embodiments, the light-induced crosslinking of the refractive index-matched structure may comprise a local exposure such that the photocrosslinkable ceramic slurry crosslinks locally.

[0052] Additionally, the light-induced crosslinking of the refractive index-matched structure may further comprise exposure to light such that the photocrosslinkable ceramic slurry is fully crosslinked. Such embodiments can produce a refractive index-matched and refractive index-graded structure.

[0053] According to a further aspect of this disclosure, a method for producing a refractive index-graded structure is provided. The term "refractive index-graded" can refer, for example, to at least two different refractive indices within a structure, in particular one manufactured integrally. For example, the structure comprises a first section with a first refractive index and a second section with a second refractive index, wherein the second refractive index differs from the first refractive index by at least 5%, in particular by at least 10%, preferably by at least 15%.

[0054] The method for producing a refractive index-graded structure comprises providing a photocrosslinkable organic matrix. Ceramic particles are added to the photocrosslinkable organic matrix to form a photocrosslinkable ceramic slurry.

[0055] The average diameter of the (ceramic) particles is < 1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slip, in particular the smallest suitable wavelength, and / or preferably the wavelength of a planned optical function of the slip and / or in particular later of the structure formed from it.

[0056] The method further comprises a first local exposure such that the photocrosslinkable ceramic slurry crosslinks locally in a first region. The method further comprises a second, subsequent exposure of the photocrosslinkable ceramic slurry such that the structure crosslinks in a second region encompassing the first region. The first exposure and the second exposure can be carried out at the same wavelength, duration, and / or intensity. The first region is typically smaller than the second region.

[0057] According to some embodiments, the local exposure can be performed two-dimensionally and / or three-dimensionally. The ceramic slurry can, for example, be spread into a film. In some embodiments, the slurry can be formed into a three-dimensional structure by injection molding or by filling a mold.

[0058] Local exposure can be achieved via x-ray diffraction, two-photon polymerization, and / or holography. Other methods for localized, area-wide or point-based exposure can also be used for local exposure. For example, 99.9% of the ceramic particles in the slurry can have a diameter of < 1 / 10 of the suitable wavelength, and 99.0% of the ceramic particles in the slurry can have a diameter of < 1 / 20 of the suitable wavelength. This enables longer optical path lengths for crosslinking.

[0059] In some embodiments, a filling level of ceramic particles in the photocrosslinkable organic matrix can be adjusted between 0 and 90 wt.%, in particular between 0 and 40 wt.%, such that a desired refractive index is achieved.

[0060] According to a further aspect, a refractive index-adapted photocrosslinkable ceramic slip is disclosed. The slip comprises a photocrosslinkable organic matrix and ceramic particles with an average diameter of the ceramic particles of <1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slip, in particular the smallest suitable wavelength, and / or in particular the wavelength of the intended optical function of the slip and / or in particular later of the structure formed from it.

[0061] A filling level of ceramic particles in the photocrosslinkable organic matrix is ​​adjusted between 0 and 90 wt.%, in particular between 0 and 40 wt.%, so that a desired refractive index is achieved.

[0062] In particular, reference is made below to embodiments of the disclosure, some examples of which are illustrated in the figures. Each example is intended to illustrate the disclosure, not to limit it. For example, features illustrated or described as part of embodiments may be used with other embodiments to yield further embodiments.

[0063] Fig. 1 schematically shows a method 100 for manufacturing a refractive index-matched structure according to embodiments of the present disclosure.

[0064] The method 100 comprises providing a photocrosslinkable organic matrix 110. Ceramic particles are added 120 to the photocrosslinkable organic matrix. The average diameter of the ceramic particles is <1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slurry. For example, the slurry can be configured to crosslink at a wavelength of approximately 400 nm. The average diameter d50, better d90, better of essentially all particles is then <40 nm.

[0065] The filling level of ceramic particles is adjusted between 0 and 90 wt.% so that a desired refractive index is achieved.

[0066] The method 100 further includes forming the refractive index-matched photocrosslinkable ceramic slurry into the refractive index-matched structure 130.

[0067] In embodiments, the method 100 may further comprise light-induced crosslinking of the organic matrix at the appropriate wavelength to form a ceramic green body 140.

[0068] The light-induced crosslinking can take place in such a way that the ceramic green body has a predetermined two-dimensional contour or a predetermined three-dimensional contour. For this purpose, for example, electromagnetic radiation, which brings about the photocrosslinking of the ceramic slurry, or at least the crosslinking of its organic matrix, can be directed onto a volume and / or a surface in such a way that the structure obtained by crosslinking has a desired two-dimensional geometry or three-dimensional geometry. The electromagnetic radiation can comprise two or more different wavelengths, such as approximately 400 nm and approximately 700 nm wavelength. The ceramic structure can thus be defined during crosslinking. This can take place, for example, by means of targeted beam guidance, for example with continuously or raster-guided laser light, or with the aid of photomasks and floodlight and / or laser light.For example, xolography can be used.

[0069] The resulting geometry of the ceramic structure can, for example, have a complex geometry. For example, the structure can have corners, straight, convex, and / or concave curved sections, such as edges (outer edges) and recesses, overhangs, and / or similar features. Likewise, it can have regularly or irregularly shaped openings, holes, and / or recesses distributed throughout its length.

[0070] The light-induced crosslinking of the refractive index-adapted structure may comprise a local exposure such that the photocrosslinkable ceramic slurry crosslinks locally in a first region.

[0071] Furthermore, the light-induced crosslinking of the refractive index-matched structure may comprise exposure such that the photocrosslinkable ceramic slurry crosslinks in a second region containing the first region.

[0072] Fig. 2 schematically shows a method 200 for manufacturing a refractive index graded structure according to embodiments of the present disclosure.

[0073] The method 200 comprises providing a photocrosslinkable organic matrix 110 and adding ceramic particles to the photocrosslinkable organic matrix so that a photocrosslinkable ceramic slip is formed 120. The average diameter d50, better d90, better essentially all of the ceramic particles is < 1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slip.

[0074] The filling level of ceramic particles can be adjusted so that a desired refractive index is achieved.

[0075] The method further comprises local exposure such that the photocrosslinkable ceramic slip is locally crosslinked 230. The local exposure 230 is carried out, for example, three-dimensionally via 2-photon polymerization.

[0076] The method further comprises exposing the photocrosslinkable ceramic slip such that the entire slip volume with embedded structure is completely crosslinked 240.

[0077] Figure 3 shows a refractive index graded structure produced using embodiments of the present disclosure, with its three-dimensional shape, here that of a cylinder, shown in Figure 4. The image was taken using a light microscope in reflected light mode.

[0078] For this purpose, a photocrosslinkable ceramic slurry with a photocrosslinkable organic matrix and ceramic particles was prepared. The particles have an average diameter of < 1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slurry.

[0079] The slurry was locally exposed to light such that the photocrosslinkable ceramic slurry was partially crosslinked locally. The local exposure was performed such that a cylinder with a base diameter of 15 μm was crosslinked within the slurry. The slurry was applied to a support for this purpose.

[0080] Local exposure can be achieved, for example, with a mask. The mask shields areas that should not be meshed.

[0081] Local exposure can also be achieved using xolography and / or 2-photon polymerization and / or holography. For this purpose, the slurry applied to the substrate can be locally exposed three-dimensionally.

[0082] The slip was then fully exposed to light so that the structure was completely cross-linked.

[0083] Fig. 3 shows that a refractive index transition within the material can be achieved using the method described above. The 5 x 6 rings shown in Fig. 3 indicate the refractive index transition to the base surfaces of the 5 x 6 cylinders within the slurry. The refractive index transition becomes visible in incident light mode. These are not separately inserted structures, but rather targeted changes in the ceramic slurry induced by the method according to the embodiments of the present disclosure.

[0084] Embodiments of the present disclosure will also become apparent from the following examples: Example 1: A method for producing a refractive index-adapted photocrosslinkable ceramic slurry, comprising: providing a photocrosslinkable organic matrix; and adding ceramic particles to the photocrosslinkable organic matrix; wherein the average diameter of the ceramic particles is <1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slurry; wherein a filling level of ceramic particles is adjusted between 0 and 90 wt.% such that a desired refractive index is achieved; and wherein the diameter of the particles is measured by means of dynamic light scattering (DLS). Example 2: A method for producing a refractive index-matched structure, comprising: providing a refractive index-matched photocrosslinkable ceramic slurry; and shaping the refractive index-matched photocrosslinkable ceramic slurry into the refractive index-matched structure. Example 3: A method for producing a refractive index-matched structure according to Example 2, further comprising light-induced crosslinking of the organic matrix at the appropriate wavelength to form a ceramic green body. Example 4: A method for producing a refractive index-matched structure according to Example 3, wherein the light-induced crosslinking of the refractive index-matched structure comprises a local exposure such that the photocrosslinkable ceramic slurry crosslinks locally. Example 5: A method for producing a refractive index-matched structure according to Example 4, wherein the light-induced crosslinking of the refractive index-matched structure further comprises exposure to light such that the photocrosslinkable ceramic slurry is completely crosslinked. Example 6: A method for producing a refractive index graded structure, comprising: providing a photocrosslinkable organic matrix; and adding ceramic particles to the photocrosslinkable organic matrix so that a photocrosslinkable ceramic slurry is formed; wherein the average diameter of the ceramic particles is < 1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slurry; locally exposing the ceramic slurry to light such that the photocrosslinkable ceramic slurry is locally crosslinked; and exposing the photocrosslinkable ceramic Slip such that the structure is completely cross-linked; the diameter is measured using dynamic light scattering (DLS). Example 7: Method for producing a refractive index graded structure according to Example 6, wherein the local exposure is carried out two-dimensionally and / or three-dimensionally, in particular wherein the local exposure is carried out via xolography, 2-photon polymerization and / or holography.

[0085] In the above description, a method for producing a refractive index-matched photocrosslinkable ceramic slurry, a method for producing a refractive index-matched structure, a method for producing a refractive index-graded structure, the use of a photocrosslinkable ceramic slurry for producing a refractive index-matched structure and / or a refractive index-graded structure, and a refractive index-matched photocrosslinkable ceramic slurry were presented with reference to specific examples. It should be noted that various aspects and embodiments disclosed herein may be combined in combinations other than the specific combinations illustrated in the figures.It is contemplated that various modifications may be made to the above embodiments without departing from the scope of the disclosure and the following claims.

Claims

Claims 1. Method (200) for producing a refractive index graded structure, comprising Providing a photocrosslinkable ceramic slip containing a photocrosslinkable organic matrix (110) and ceramic particles, wherein the average diameter of the ceramic particles is < 1 / 10 of a wavelength suitable for light-induced crosslinking of the ceramic slip; local exposure such that the photocrosslinkable ceramic slip is at least partially locally crosslinked (230); and Exposing the photocrosslinkable ceramic slurry to light such that the structure is completely crosslinked (240); wherein the diameter is measured by means of dynamic light scattering (DLS).

2. Method (200) for producing a refractive index graded structure according to claim 1, wherein the local exposure is carried out two-dimensionally and / or three-dimensionally, in particular wherein the local exposure is carried out via xolography, 2-photon polymerization and / or holography.

3. A method (200) for producing a refractive index graded structure according to claim 2, wherein the local exposure is carried out three-dimensionally and wherein the slurry comprises a first photoinitiator optimized for the local exposure, and wherein the slurry comprises a second photoinitiator optimized for the complete crosslinking of the structure, wherein the first photoinitiator differs from the second photoinitiator.

4. A method (200) for producing a refractive index graded structure according to any one of the preceding claims, wherein providing the photocrosslinkable ceramic slurry comprises: Providing the photocrosslinkable organic matrix (110); and Adding the ceramic particles to the photocrosslinkable organic matrix to form the photocrosslinkable ceramic slurry (120).

5. A method (200) for producing a refractive index graded structure according to any one of the preceding claims, wherein the photocrosslinkable ceramic slip is applied to a support and subsequently first the local exposure of the photocrosslinkable ceramic slip applied to the support and then a global exposure of the photocrosslinkable ceramic slip applied to the support takes place.

6. A method (200) for producing a refractive index graded structure according to claim 5, wherein during local exposure of the photocrosslinkable ceramic slurry, at least a first region of the photocrosslinkable ceramic slurry applied to the carrier is exposed without exposing at least a second region of the photocrosslinkable ceramic slurry applied to the carrier, and wherein during global exposure, both the first region and the second region are exposed.

7. A method (200) for producing a refractive index graded structure according to claim 5, wherein during local exposure of the photocrosslinkable ceramic slip, at least a first region and a second region of the photocrosslinkable ceramic slip applied to the carrier are exposed, wherein during local exposure the first region is exposed more intensely than the second region, and wherein during global exposure both the first and the second region are exposed.

8. A method (200) for producing a refractive index graded structure according to claim 7, wherein during local exposure at least a third region of the photocrosslinkable ceramic slip applied to the carrier is not exposed, and the third region is only exposed during global exposure together with the first region and the second region.

9. A method (200) for producing a refractive index graded structure according to any one of the preceding claims, wherein the refractive index graded structure has at least two regions with different refractive indices and wherein the region with the larger refractive index has been exposed both locally and globally, wherein the region with the smaller refractive index has been exposed only globally.

10. A method (200) for producing a refractive index graded structure according to any one of the preceding claims, wherein the photocrosslinkable ceramic slip is applied as a layer and then the local exposure is carried out followed by global exposure.

Images