Metal complexes and formulations for preparing metal oxide optical layers

Abstract

The present invention relates to a metal complex, a formulation comprising the metal complex, and a method for preparing a metal oxide optical layer using the formulation and the metal complex. The resulting metal oxide optical layer is particularly suitable for use in optical devices, such as in augmented reality (AR) and / or virtual reality (VR) devices.

Description

Technical Field

[0001] The present invention relates to a metal complex, a formulation and a method for preparing a metal oxide optical layer. The metal complex, the formulation and the method according to the present invention are particularly suitable for preparing a metal oxide optical layer for optical applications or optical devices, such as diffraction gratings for augmented reality (AR) and / or virtual reality (VR) devices. The metal oxide optical layer shows (a) favorable optical properties, such as a high refractive index (RI) of >1.7, preferably >2.0 and low absorption (optical loss) at a wavelength of ≤520 nm; (b) favorable mechanical properties, such as low shrinkage; (c) favorable coating properties, such as a dense layer and a flat surface structure; and / or (d) favorable filling properties, such as uniform filling of topographical features on a patterned substrate.

[0002] Embodiments of the present invention allow for the preparation of metal oxide optical layers on the surface of both patterned and non-patterned substrates. The metal oxide optical layers contain metal oxides embedded in a solidified matrix. The layers can form various structures, such as layers covering the surface of a non-patterned substrate and / or fillers covering topographical features such as gaps on the surface of a patterned substrate, thereby providing high refractive index optical structures. In particular, embodiments of the present invention allow for the preparation of advanced optical gap fillers with low overburden, thereby enabling easy and cost-effective mass production of complex optical devices by avoiding typical problems that occur when depositing layers or gap filling with physical vapor deposition (PVD) or chemical vapor deposition (CVD) techniques, such as incomplete or excessive gap filling due to unfavorable deposition and layer growth characteristics, such as reduced or increased deposition or growth rates at corners and edges.

[0003] Embodiments of the present invention are particularly suitable for preparing metal oxide optical layers with high refractive index for use in optical devices, such as diffraction gratings used in AR and / or VR devices.

[0004] Finally, the present invention provides an optical device, preferably an AR and / or VR device, comprising a metal oxide optical layer obtainable by the method according to the present invention. Background of the Invention

[0006] Cutting-edge optical devices often include optical gratings made of composite materials, with a substrate as a carrier and a complex interlaced pattern on the substrate, the pattern consisting of different layers or stacks of multiple layers. Typically, producing these complex interlaced patterns requires a structuring process, which becomes increasingly challenging as the size of the structure to be produced decreases.

[0007] Besides being used in a wide range of applications, such as in spectrometers or optical storage systems (CD, DVD, etc.), diffraction gratings are also core components of so-called XR devices, mainly glasses. In this case, R stands for the term "reality" and X stands for different properties, such as virtual, augmented, mixed, etc. Diffraction gratings therefore form part of the core of the so-called optical engine in XR devices, in particular in augmented reality glasses and mixed reality glasses. Virtual reality glasses, when constructed as head-mounted displays, usually consist of conventional liquid crystal (LC) organic light-emitting diode (OLED) displays embedded in the device and therefore do not necessarily require diffraction gratings. In contrast, augmented reality glasses and mixed reality glasses are designed to enable consumers to get a visual impression of their environment, in the best case as if they were not wearing any glasses at all. However, they can also provide and serve digital information and also project it into the individual's field of vision. The additional digital information is collected by identifying and analyzing the environment that the individual is examining or currently viewing. In order to transmit and project the supporting digital information into the eyes of the individual, the augmented reality glasses or mixed reality glasses are equipped with an information supply unit, which is coupled to an optical waveguide system, through which the optically encoded supporting information is transmitted directly to the lenses of the glasses. Here, the information passes through a diffraction grating, which couples the incident light into the lens and splits it by diffraction according to its angular information and its spectral band. After the light is coupled in, the lens acts as a waveguide, enabling the light to be transmitted to and enter the pupil of the individual. The position of the light coupling in is independent of any preferred position and therefore independent of the influence of technical requirements. The direction of the light traversal inside the lens is determined by the diffraction grating that diffracts or splits the light. At specific positions of the lens, a second and a third diffraction grating are used to change the direction of the light traversal, thus forcing the light to be projected into the pupil of the user. The light traversal in the glasses is achieved by total internal reflection (TIR) ​​of the light, thus bouncing several times between the interfaces of the glasses until it reaches another diffraction grating, thereby changing the internal TIR direction of the light (see Figure 2 ). The second and third gratings are geometrically arranged in different directions relative to the first grating and the coupling-in grating, for example by a certain angular distortion of the longitudinal axis, thereby allowing the propagation direction of the totally internally reflected light to be changed. It goes without saying that the lens itself or the material from which it is made should be non-absorbent. Otherwise, the supporting information never reaches the user's pupil or only reaches the user's pupil in the case of a strong depletion of the light intensity. This process is effective regardless of whether a reflection grating or a transmission grating is used. Usually, lenses are equipped with both types of gratings in order to guide the light correctly. It should also be mentioned that there are differences in the optical properties of reflection gratings and transmission gratings, which, however, are no longer of interest in the context of the present invention. The basic structure of the gratings is very similar, which is more important at this point.

[0008] However, there are different designs and structures, such as surface relief (SR) or volume phase holographic (VPH) gratings to realize waveguides. Both types are very similar in appearance. In the simplest case, the grating is fixed in some way to the surface of the waveguide material (here, the lens). The grating itself consists of an array of fine structures, mainly grooves of a first material type material 01 with a refractive index RI01, but not limited to this. The geometry of the grooves can be varied, from rectangular to V-grooves, U-grooves, etc. The width, including structures of different widths, the geometric form of the grooves, their spacing and their depth, including different depths, are specifically designed to influence the diffraction pattern of the incident light to be diffracted.

[0009] In the case of SR gratings (SRGs), a groove or structure of a first material type (Material 01) having a refractive index (RI 01) is filled with a second material type (Material 02) having a refractive index (RI 02) that is incrementally different from RI 01 (see Figure 1 and Figure 3 ). For the sake of completeness, it should be mentioned that material 01 or material 02 can be composed of a stack of structured layers, each layer containing a different material composition with a different refractive index, stacked on top of each other, thereby forming material 01 or material 02 with an effective refractive index or a gradient refractive index RI 01 or RI 02, respectively. Incidentally, the (effective or gradient) refractive index RI 01 and RI 02 depend on the refractive index of the waveguide or lens constituting the glasses. If a glass lens with a high refractive index is used (n03>1.46), the (effective or gradient) refractive index of material 01 and material 02 is considered to be higher than the lens itself, so that RI values ​​of 2.0 can be reached and exceeded. High performance gratings, especially SR-type gratings, can be manufactured using microfabrication, such as standard lithography and deposition techniques known from integrated circuit manufacturing.

[0010] These standard techniques typically include physical vapor deposition (PVD) or chemical vapor deposition (CVD) processes that often result in incomplete gap filling due to unfavorable deposition and / or layer growth deposition characteristics, including increased deposition and / or growth rates at corners and edges. This incomplete gap filling results in the formation of voids within the structures to be filled by the PVD and CVD materials. In addition to the formation of voids, the surface of the substrate is covered with a PVD and / or CVD layer having a thickness that is nearly the same as the maximum depth of the deepest structure to be filled by the deposited gap fill material (see Figure 4 and Figure 5). However, in some applications it may be desirable to expose the surface of the substrate so that it can be used for further processing. Therefore, it is desirable to remove the unwanted overlying layer from PVD or CVD, for example by chemical mechanical planarization (CMP), but without damaging the underlying original substrate surface. Although CMP has long been used in the process of manufacturing integrated circuits, CMP is a time-consuming and expensive process and can be seen as a potential economic disadvantage for mass production of leading-edge optical devices, especially diffraction gratings. Therefore, there is a need for an advanced and cost-effective solution for manufacturing optical gratings, where gap filling does not require CMP (see Figure 6 ).

[0011] The present invention solves various shortcomings of the technology for preparing optical gratings for cutting-edge optical devices as described above. The focus here is on improving optical properties, improving mechanical properties, improving coating properties and improving filling properties.

[0012] Purpose of the Invention

[0013] An object of the present invention is to provide a metal complex, a formulation and a method for preparing a metal oxide optical layer, wherein the layer is particularly suitable for optical applications and can be used in optical devices, such as diffraction gratings for AR and / or VR devices. The resulting metal oxide optical layer shows (a) favorable optical properties, such as a high refractive index (RI) of >1.7, preferably >2.0 and low absorption (optical loss) at a wavelength of ≤520 nm; (b) favorable mechanical properties, such as low shrinkage; (c) favorable coating properties, such as a dense layer and a flat surface structure; and (d) favorable filling properties, such as uniform filling of topographical features on a patterned substrate.

[0014] Furthermore, it is an object of the present invention to provide a metal complex, a formulation and a method for easily and cost-effectively preparing metal oxide optical layers.

[0015] Another object of the present invention is to be able to prepare metal oxide optical layers on the surface of both patterned substrates and non-patterned substrates. The metal oxide layer can form various structures, such as a layer covering the surface of the non-patterned substrate and / or a filler covering topographical features such as gaps on the surface of the patterned substrate, thereby providing a high refractive index optical structure.

[0016] It is therefore an object of the present invention to provide a metal complex, formulation and method for preparing optical metal oxide layers which allow for advanced optical gap fillers with low coverage, thus enabling easy and cost-effective mass production of complex optical devices.

[0017] Another object of the present invention is to provide a metal complex, a formulation and a method for producing an optical metal oxide layer which avoids typical problems occurring during layer deposition or gap filling by PVD or CVD techniques, such as incomplete or excessive gap filling due to unfavorable deposition and layer growth characteristics, such as a decrease or increase in deposition or growth rate at corners and edges.

[0018] It is an object of the present invention that the metal complex and the formulation are particularly suitable for producing metal oxide optical layers with high refractive index and at the same time low absorption (optical losses) for optical devices, such as diffraction gratings for AR and / or VR devices.

[0019] Finally, an object of the present invention is to provide an optical device, preferably an AR and / or VR device, comprising a metal oxide optical layer obtainable by the method according to the invention and thereby exhibiting the above-mentioned beneficial effects. Summary of the invention

[0020] The inventors of the present invention surprisingly found that the above object is achieved by the following embodiments:

[0021] A metal complex, comprising:

[0022] one or more, preferably two or more metals M, selected from V, Nb and Ta, preferably Nb; and

[0023] One or more ligands L, wherein L is an organic ligand comprising an ester group, preferably a carboxylate group and a carboxylic acid group, said organic ligand being optionally deprotonated.

[0024] A preparation comprising:

[0025] (i) a metal complex according to the invention as a metal oxide precursor;

[0026] (ii) epoxy resin mixture; and

[0027] (iii) Photoinitiator.

[0028] A method for preparing a metal oxide optical layer, the method comprising the following steps (a) to (c):

[0029] (a) providing a formulation according to the present invention;

[0030] (b) applying the formulation to a surface of a substrate; and

[0031] (c) converting the formulation into a metal oxide optical layer on the surface of the substrate.

[0032] Finally, an optical device is provided, comprising a metal oxide optical layer, which is obtainable by or is obtained by the method according to the present invention, wherein the optical device is preferably an augmented reality (AR) and / or virtual reality (VR) device.

[0033] Preferred embodiments of the invention are described below and in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 : Schematic cross-sectional view of an SR grating having material 01 and material 02, wherein the difference between the refractive index IR01 of material 01 and the refractive index IR02 of material 02 is increasing.

[0035] Figure 2 : Schematic cross-sectional view of an SR grating capable of diffracting light (transmission case), including propagation of the diffracted light within a waveguide (e.g., a lens) by total internal reflection.

[0036] Figure 3 : Schematic cross-sectional view of an SR grating provided with a gap (groove) to be filled with a high refractive index material (material 02), wherein the difference between the refractive index of material 02 and the refractive index of material 01 on both sides of the gap (groove) is increasing.

[0037] Figure 4 : Schematic diagram of the PVD or CVD mediated gap filling process and removal of unwanted capping layers.

[0038] Figure 5 : Schematic diagram of the PVD or CVD mediated gap filling process creating and leaving voids within the gap and deposited layer.

[0039] Figure 6 : Schematic diagram of a gap filling process using a formulation containing the metal complex of the present invention or a formulation converted into a metal oxide.

[0040] Figure 7 : SEM cross-sectional view of substrate showing surface feature filling after spin-coating 5 / 5% (w / w) Nb citraconic acid / epoxy mixture A as described in Example 1, prebaked at 100°C for 1 min, then UV cured with 365 nm light for 20 min and baked at 350°C for 10 min.

[0041] Figure 8 : SEM cross-sectional view of substrate showing surface feature filling of spin-coated Nb citraconic acid 5% (w / w) PGME solution annealed at 300°C for 10 minutes as described in Example 1.

[0042] Fig. 9: SEM cross-sectional views of substrates showing the surface feature filling properties of Nb citraconic acid / epoxy mixture A at various mixing ratios and baking temperatures as described in Example 2. DETAILED DESCRIPTION

[0043] definition

[0044] The term "metal complex" as used herein refers to a coordination complex consisting of one or more central metal atoms or ions forming one or more coordination centers and a surrounding array of binding molecules or ions as ligands, the ligands containing one or more electron pairs that can be shared with the metal. In a metal complex, the metal atom or ion usually acts as a Lewis acid, while the ligand usually acts as a Lewis base. Metal complexes can be neutral, positively charged, or negatively charged. Charged metal complexes can also be referred to as complex ions.

[0045] The term "metal-organic complex" as used herein refers to a class of metal complexes containing a metal and an organic ligand that has solubility or volatility in an organic solvent. Compounds with these properties have a variety of applications in metal organic vapor deposition (MOCVD) or sol-gel processing materials science. The unique term "metal-organic complex" refers to metal-containing compounds that lack direct metal-carbon bonds but contain organic ligands. Metal alkoxides, metal carboxylates, metal β-diketonates, metal dialkylamides, and metal phosphine complexes are representative members of this class.

[0046] As used herein, the term "ligand" refers to an ion or neutral molecule (having one or more functional groups) that combines with a central metal atom or ion to form a metal complex. Bonding to a metal generally involves formally donating one or more ligand electron pairs, usually through a Lewis base. The nature of the metal-ligand bonding can range from covalent bonding to ionic bonding. In addition, the metal-ligand bond order can range from one to three. Ligands are generally considered to be Lewis bases, but there are few known cases involving Lewis acid ligands. Depending on how many electrons are provided for the bond between the ligand and the central atom, the ligand is classified as L or X (or a combination thereof). L ligands donate two electrons from a lone electron pair, thereby forming a coordinate covalent bond. X ligands donate one electron and the central atom donates another electron, thereby producing a regular covalent bond.

[0047] The term "alkyl" or "alkyl group" as used herein relates to a linear, branched, cyclic or bridged cyclic alkyl group which forms part of the structure of a chemical compound and is bonded via a carbon atom. The alkyl group may contain one or more heteroatoms selected from N, O, S and P. The alkyl group may be unsubstituted or substituted, preferably with one or more substituents selected from: -C(O)R v 、-C(O)ORv 、-NR v R w 、-OR v , -R x , -CN, -F and -Cl, where R v = H, C3-C10 aryl or C1-C10 alkyl, R w = H, C3-C10 aryl or C1-C10 alkyl, and R x = C3-C10 aryl or C1-C10 alkyl, preferably R v = H, methyl, ethyl, propyl or phenyl, R w = H, methyl, ethyl, propyl or phenyl, and R x = phenyl. The alkyl group may contain one or more functional groups, preferably selected from: carbon-carbon double bonds, carbon-carbon triple bonds, amides, carbamates, carbonates, carboxylic acids, esters, ethers, secondary or tertiary amines and ketones. The alkyl group connecting two adjacent structural units in a chemical compound is called an "alkylene group".

[0048] The term "aryl" or "aryl group" as used herein relates to a monocyclic or polycyclic aromatic group that forms part of the structure of a chemical compound. A polycyclic aromatic group comprises two or more linked aromatic ring systems fixed in one plane. An aryl group may be (i) a hydrocarbon aryl group, or (ii) a heteroatom-containing aryl group, also referred to as a heteroaryl group. A hydrocarbon aryl group contains an aromatic ring structure consisting of carbon atoms, whereas a heteroaryl group contains an aromatic ring structure that additionally contains one or more heteroatoms selected from N, O, S and P. An aryl group may be unsubstituted or substituted, preferably with one or more substituents selected from: -C(O)R v 、-C(O)OR v 、-NR v R w 、-OR v , -R x , -CN, -F and -Cl, where R v =H, C3-C10 aryl or C1-C10 alkyl, R w = H, C3-C10 aryl or C1-C10 alkyl, and R x = C3-C10 aryl or C1-C10 alkyl, preferably R v = H, methyl, ethyl, propyl or phenyl, R w = H, methyl, ethyl, propyl or phenyl, and R x = methyl, ethyl, propyl or phenyl.

[0049] The term "fluorene epoxy resin" as used herein relates to a compound having both fluorene and epoxy groups.

[0050] The term "acrylate epoxy resin" as used herein relates to compounds having both acrylate and epoxy groups, thereby providing crosslinking functionality. Acrylate epoxy resins are so-called dual-reactive compounds, which contain a first reactive group (acrylate group) and a second reactive group (epoxy group).

[0051] The term "optical device" as used herein refers to a device containing one or more optical components for forming a light beam, including but not limited to gratings, lenses, prisms, mirrors, optical windows, filters, polarization optics, UV and IR optics, and optical coatings. In the context of the present invention, preferred optical devices are augmented reality (AR) glasses and / or virtual reality (VR) glasses.

[0052] Preferred Embodiments

[0053] Metal complexes

[0054] The present invention relates to a metal complex comprising: one or more, preferably two or more metals M, wherein the metal M is selected from V, Nb and Ta, preferably Nb; and one or more ligands L, wherein L is an organic ligand comprising an ester group, preferably a carboxylate group and a carboxylic acid group, wherein the organic ligand is optionally deprotonated.

[0055] Ester groups are derived from acids (organic or inorganic) in which at least one -OH (hydroxyl) group is replaced by an -O-alkyl (alkoxy) group.

[0056] Preferred is a metal complex comprising: one or more metals M selected from V, Nb and Ta; and one or more ligands L, wherein L is an organic ligand comprising an ester group, preferably a carboxylate group and a carboxylic acid group, wherein the ligand L is optionally deprotonated.

[0057] More preferred is a metal complex comprising: one or more metals M selected from V, Nb and Ta; and one or more ligands L, wherein L is an organic ligand comprising a carboxylate group and a carboxylic acid group, and the ligand L is optionally deprotonated.

[0058] Most preferred is a metal complex comprising: Nb; and one or more ligands L, wherein L is an organic ligand comprising a carboxylate group and a carboxylic acid group, said ligand L being optionally deprotonated.

[0059] Preferably, L is an organic ligand further comprising a carbon-carbon double bond.

[0060] Preferably, L is coordinated to the one or more metals M via the carboxylic acid group.

[0061] Preferably, the metal complexes according to the invention are polynuclear.

[0062] In a preferred embodiment of the present invention, L is a compound represented by formula (1), which is optionally deprotonated at the carboxylic acid group:

[0063] Formula (1),

[0064] in:

[0065] The curve represents a divalent hydrocarbon group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 3 to 5 carbon atoms and one or more carbon-carbon double bonds, preferably one or two carbon-carbon double bonds, more preferably one carbon-carbon double bond; and

[0066] R is an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, or an aryl group having 5 to 20 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms, more preferably 5 or 6 aromatic ring atoms, and the alkyl group or aryl group may be substituted or unsubstituted.

[0067] Preferably, L is a compound represented by formula (1), which is optionally deprotonated at the carboxylic acid group, wherein:

[0068] The curved line represents a divalent hydrocarbon group having 2 to 10 carbon atoms and one or two carbon-carbon double bonds; and

[0069] R is an alkyl group having 1 to 10 carbon atoms or an aryl group having 5 to 10 aromatic ring atoms, which may be substituted or unsubstituted.

[0070] More preferably, L is a compound represented by formula (1), which is optionally deprotonated at the carboxylic acid group, wherein:

[0071] The curved line represents a divalent hydrocarbon group having 3 to 5 carbon atoms and one or more carbon-carbon double bonds; and

[0072] R is an alkyl group having 1 to 5 carbon atoms or an aryl group having 5 or 6 aromatic ring atoms, which may be substituted or unsubstituted.

[0073] In formula (1), it is preferred that the substituted alkyl group contains one or more substituents selected from: -C(O)R v 、-C(O)OR v 、-NR v Rw 、-OR v , -R x , -CN, -F and -Cl, where R v = H, C3-C10 aryl or C1-C10 alkyl, R w =H, C3-C10 aryl or C1-C10 alkyl, and R x = C3-C10 aryl or C1-C10 alkyl, preferably R v = H, methyl, ethyl, propyl or phenyl, R w = H, methyl, ethyl, propyl or phenyl, and R x = Phenyl.

[0074] In formula (1), it is preferred that the alkyl group containing one or more functional groups contains one or more functional groups selected from the group consisting of carbon-carbon double bonds, carbon-carbon triple bonds, amides, carbamates, carbonates, carboxylic acids, esters, ethers, secondary or tertiary amines and ketones.

[0075] In formula (1), it is preferred that the substituted aryl group contains one or more substituents selected from: -C(O)R v 、-C(O)OR v 、-NR v R w 、-OR v , -R x , -CN, -F and -Cl, where R v = H, C3-C10 aryl or C1-C10 alkyl, R w =H, C3-C10 aryl or C1-C10 alkyl, and R x = C3-C10 aryl or C1-C10 alkyl, preferably R v = H, methyl, ethyl, propyl or phenyl, R w = H, methyl, ethyl, propyl or phenyl, and R x = methyl, ethyl, propyl or phenyl.

[0076] In a more preferred embodiment of the present invention, L is a compound represented by formula (2), which is optionally deprotonated at the carboxylic acid group:

[0077] Formula (2),

[0078] in:

[0079] R is an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, or an aryl group having 5 to 20 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms, more preferably 5 or 6 aromatic ring atoms, which alkyl group or aryl group may be substituted or unsubstituted; and

[0080] R 1 is H, an alkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, or an aryl group having 5 to 10 aromatic ring atoms, preferably 5 or 6 aromatic ring atoms, which alkyl group or aryl group may be substituted or unsubstituted.

[0081] Preferably, L is a compound represented by formula (2), which is optionally deprotonated at the carboxylic acid group, wherein:

[0082] R is an alkyl group having 1 to 10 carbon atoms or an aryl group having 5 to 10 aromatic ring atoms, which may be substituted or unsubstituted;

[0083] R 1 is H, an alkyl group having 1 to 5 carbon atoms or an aryl group having 5 or 6 aromatic ring atoms, which may be substituted or unsubstituted.

[0084] More preferably, L is a compound represented by formula (2), which is optionally deprotonated at the carboxylic acid group, wherein:

[0085] R is an alkyl group having 1 to 5 carbon atoms or an aryl group having 5 or 6 aromatic ring atoms, which may be substituted or unsubstituted; and

[0086] R 1 is H, an alkyl group having 1 to 5 carbon atoms or an aryl group having 5 or 6 aromatic ring atoms, which may be substituted or unsubstituted.

[0087] Particularly preferably, L is a compound represented by formula (2), which is optionally deprotonated at the carboxylic acid group, wherein:

[0088] R is methyl, ethyl or propyl; and

[0089] R 1 is H, methyl or phenyl.

[0090] Most preferably, L is a compound represented by formula (2), which is optionally deprotonated at the carboxylic acid group, wherein:

[0091] R is ethyl; and

[0092] R1 It's methyl.

[0093] In formula (2), it is preferred that the substituted alkyl group contains one or more substituents selected from: -C(O)R v 、-C(O)OR v 、-NR v R w 、-OR v , -R x , -CN, -F and -Cl, where R v = H, C3-C10 aryl or C1-C10 alkyl, R w =H, C3-C10 aryl or C1-C10 alkyl, and R x = C3-C10 aryl or C1-C10 alkyl, preferably R v = H, methyl, ethyl, propyl or phenyl, R w = H, methyl, ethyl, propyl or phenyl, and R x =phenyl.

[0094] In formula (2), it is preferred that the alkyl group containing one or more functional groups contains one or more functional groups selected from the group consisting of carbon-carbon double bonds, carbon-carbon triple bonds, amides, carbamates, carbonates, carboxylic acids, esters, ethers, secondary or tertiary amines and ketones.

[0095] In formula (2), it is preferred that the substituted aryl group contains one or more substituents selected from: -C(O)R v 、-C(O)OR v 、-NR v R w 、-OR v , -R x , -CN, -F and -Cl, where R v = H, C3-C10 aryl or C1-C10 alkyl, R w =H, C3-C10 aryl or C1-C10 alkyl, and R x = C3-C10 aryl or C1-C10 alkyl, preferably R v = H, methyl, ethyl, propyl or phenyl, R w = H, methyl, ethyl, propyl or phenyl, and R x =methyl, ethyl, propyl or phenyl.

[0096] It is preferred that the metal M in the metal complex of the present invention is in an oxidation state selected from the group consisting of +I, +II, +III, +IV and +V, preferably +II, +III, +IV and +V, more preferably +V.

[0097] In a preferred embodiment of the present invention, the metal complex is represented by the following formula (3):

[0098] Formula (3),

[0099] in:

[0100] M is independently at each occurrence a metal selected from V, Nb and Ta, preferably Nb;

[0101] L is, independently of one another, an organic ligand comprising an ester group, preferably a carboxylate group and a carboxylic acid group, the organic ligand being optionally deprotonated;

[0102] A is a bridging ligand selected from the group consisting of: µ-L - 、µ-OH - 、µ-OR - 、µ-F - 、µ-Cl - , µ-Br - or µ-I - , wherein R is an alkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, more preferably methyl, ethyl, propyl, butyl or pentyl; and L - is the deprotonated L;

[0103] B is the bridging ligand µ-O 2- ;

[0104] m is an integer from 1 to 10, preferably from 1 to 5, more preferably 1 or 2, most preferably 1;

[0105] n is an integer from 5 to 50, preferably from 5 to 25, more preferably from 5 to 10, most preferably 5;

[0106] a is an integer from 0 to 20, preferably from 0 to 10, more preferably from 0 to 4, most preferably 0; and

[0107] b is an integer from 0 to 10, preferably from 0 to 5, more preferably from 0 to 2, most preferably 0;

[0108] The condition is to satisfy the following formula:

[0109] , wherein S is the value of the oxidation state of M, preferably selected from 1, 2, 3, 4 and 5, more preferably selected from 2, 3, 4 and 5, most preferably 5.

[0110] Preferably, the metal complex is represented by formula (3), wherein:

[0111] M is independently at each occurrence a metal selected from V, Nb and Ta, preferably Nb;

[0112] L is, independently of one another at each occurrence, an organic ligand comprising a carboxylate group and a carboxylic acid group, said organic ligand being optionally deprotonated;

[0113] A is a bridging ligand selected from the group consisting of: µ-L - 、µ-OH - 、µ-OR - 、µ-F - 、µ-Cl - , µ-Br - or µ-I - , wherein R is an alkyl group having 1 to 5 carbon atoms; and L - is the deprotonated L;

[0114] B is the bridging ligand µ-O 2- ;

[0115] m is an integer from 1 to 5;

[0116] n is an integer from 5 to 25;

[0117] a is an integer from 0 to 10; and

[0118] b is an integer from 0 to 5;

[0119] The condition is to satisfy the following formula:

[0120] , wherein S is a value of the oxidation state of M selected from 1, 2, 3, 4 and 5.

[0121] More preferably, the metal complex is represented by formula (3), wherein:

[0122] M is Nb;

[0123] L is, independently of one another at each occurrence, an organic ligand comprising a carboxylate group and a carboxylic acid group, said organic ligand being optionally deprotonated;

[0124] A is a bridging ligand selected from the group consisting of: µ-L - 、µ-OH - 、µ-OR - 、µ-F - 、µ-Cl - , µ-Br - or µ-I - , wherein R is methyl, ethyl, propyl, butyl or pentyl; and L - is the deprotonated L;

[0125] B is the bridging ligand µ-O 2- ;

[0126] m is 1 or 2;

[0127] n is an integer from 5 to 10;

[0128] a is an integer from 0 to 4; and

[0129] b is an integer from 0 to 2;

[0130] The condition is to satisfy the following formula:

[0131] , wherein S is a value of the oxidation state of M selected from 1, 2, 3, 4 and 5.

[0132] Most preferably, the metal complex is represented by formula (3a):

[0133] Formula (3a),

[0134] in:

[0135] M is Nb;

[0136] L is, independently of each other at each occurrence, an organic ligand comprising a carboxylate group and a carboxylic acid group, said organic ligand being optionally deprotonated; and

[0137] n is 5.

[0138] preparation

[0139] The present invention also relates to a preparation, wherein the preparation comprises:

[0140] (i) a metal complex according to the invention as a metal oxide precursor;

[0141] (ii) epoxy resin mixture; and

[0142] (iii) Photoinitiator.

[0143] Preferred metal complexes that can be used in the preparations according to the invention are described above.

[0144] In a preferred embodiment of the present invention, the weight ratio of the (i) metal complex in the preparation is in the range of 0.1% to 50% (w / w), preferably 0.5% to 30% (w / w), more preferably 1% to 10% (w / w), and most preferably 5% (w / w), relative to the total mass of the preparation.

[0145] In a preferred embodiment of the present invention, the weight ratio of (ii) the epoxy resin mixture in the preparation is in the range of 0.1% to 50% (w / w), preferably 0.5% to 30% (w / w), more preferably 1% to 10% (w / w), and most preferably 5% (w / w), relative to the total mass of the preparation.

[0146] In a particularly preferred embodiment of the present invention, the weight ratio of (i) the metal complex and (ii) the epoxy resin mixture in the formulation is the same and is selected from the range of 1% to 10% (w / w), more preferably they are 5% (w / w) each.

[0147] In a preferred embodiment of the present invention, the weight ratio (w / w) of (ii) the epoxy resin mixture to (i) the metal complex in the formulation is in the range of 1:1 to 1:2, preferably in the range of 1:1.3 to 1:1.8, and more preferably in the range of 1:1.6 to 1:1.7.

[0148] In a preferred embodiment of the present invention, the (ii) epoxy resin mixture comprises:

[0149] (ii-1) one or more fluorene epoxy resins; and

[0150] (ii-2) One or more acrylate epoxy resins.

[0151] In a more preferred embodiment of the present invention, the (ii) epoxy resin mixture comprises:

[0152] (ii-1) two or more fluorene epoxy resins; and

[0153] (ii-2) One or more acrylate epoxy resins.

[0154] In a particularly preferred embodiment of the present invention, the (ii) epoxy resin mixture comprises:

[0155] (ii-1) two fluorene epoxy resins; and

[0156] (ii-2) An acrylate epoxy resin.

[0157] In a most preferred embodiment of the present invention, (ii) the epoxy resin mixture consists of:

[0158] (ii-1) two fluorene epoxy resins; and

[0159] (ii-2) An acrylate epoxy resin.

[0160] Preferably, the (ii-1) fluorene epoxy resin is represented by the following formula (4):

[0161] Formula (4),

[0162] in:

[0163] R is halogen, preferably F or Cl, an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, or an aryl group having 5 to 20 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms, more preferably 5 or 6 aromatic ring atoms;

[0164] m is an integer from 0 to 4, preferably 0 or 1, more preferably 0;

[0165] n is an integer from 0 to 4, preferably 0 or 1, more preferably 0;

[0166] p is an integer from 0 to 10, preferably from 1 to 6, more preferably from 1 to 3, most preferably 1; and

[0167] q is an integer of 0 to 10, preferably 1 to 6, more preferably 1 to 3, and most preferably 1.

[0168] More preferably, the (ii-1) fluorene epoxy resin is represented by formula (4), wherein:

[0169] R is F, Cl, an alkyl group having 1 to 10 carbon atoms or an aryl group having 5 to 10 aromatic ring atoms;

[0170] m is 0 or 1;

[0171] n is 0 or 1;

[0172] p is an integer from 1 to 6; and

[0173] q is an integer from 1 to 6.

[0174] Particularly preferably, the (ii-1) fluorene epoxy resin is represented by formula (4), wherein:

[0175] R is an alkyl group having 1 to 5 carbon atoms or an aryl group having 5 or 6 aromatic ring atoms;

[0176] m is 0 or 1;

[0177] n is 0 or 1;

[0178] p is an integer from 1 to 3; and

[0179] q is an integer from 1 to 3.

[0180] Most preferably, the (ii-1) fluorene epoxy resin is represented by formula (4), wherein:

[0181] m is 0;

[0182] n is 0;

[0183] p is 1; and

[0184] q is 1.

[0185] Preferred (ii-1) fluorene epoxy resins are "OGSOL" (registered trademark) PG 100, EG 200, CG 500, CG500H, EG 280 and CG 400 (trade names, manufactured by Osaka Gas Chemicals Co., Ltd.).

[0186] Preferably, the (ii-2) acrylate epoxy resin is represented by the following formula (5):

[0187] Formula (5),

[0188] in:

[0189] R a is H or an alkyl group having 1 to 5 carbon atoms, preferably H or CH3;

[0190] R b is a divalent organic group, preferably selected from an aromatic group, an aliphatic group or a mixed aromatic and aliphatic group, which preferably has 6 to 20 carbon atoms, more preferably -C6H4-C(CH3)2-C6H4-, most preferably -p-C6H4-C(CH3)2-p-C6H4-;

[0191] S a is an alkylene group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms, which alkylene group may be substituted with F or OH; and

[0192] S b is an alkylene group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms, which may be substituted by F or OH.

[0193] More preferably, the (ii-2) acrylate epoxy resin is represented by formula (5), wherein:

[0194] R a is H or an alkyl group having 1 to 5 carbon atoms, preferably H or CH3;

[0195] R b is a divalent organic group selected from an aromatic group, an aliphatic group or a mixed aromatic and aliphatic group, which preferably has 6 to 20 carbon atoms;

[0196] S a is an alkylene group having 1 to 6 carbon atoms, which may be substituted with F or OH; and

[0197] S b is an alkylene group having 1 to 6 carbon atoms, which may be substituted by F or OH.

[0198] Particularly preferably, the (ii-2) acrylate epoxy resin is represented by formula (5), wherein:

[0199] R a is H or CH3;

[0200] R b is a mixed aromatic and aliphatic group having 6 to 20 carbon atoms;

[0201] S a is an alkylene group having 1 to 3 carbon atoms, which may be substituted with OH; and

[0202] S b is an alkylene group having 1 to 3 carbon atoms, which may be substituted with OH.

[0203] Most preferably, the (ii-2) acrylate epoxy resin is represented by formula (5), wherein:

[0204] R a It is H;

[0205] R b is -C6H4-C(CH3)2-C6H4-, preferably -p-C6H4-C(CH3)2-p-C6H4-;

[0206] S a is -CH2-CH(OH)-CH2-; and

[0207] S b It is -CH2-.

[0208] The preferred (ii-2) acrylate epoxy resin is CN153.

[0209] Preferably, (iii) the photoinitiator is a photoacid generator (PAG) which catalyzes the radiation-induced polymerization of the epoxy resin mixture. Preferred photoacid generators (PAGs) are diazonium salts, iodonium salts or sulfonium salts, preferably sulfonium salts, more preferably triarylsulfonium salts.

[0210] Preferred photoacid generators (PAGs) are selected from: 4-nitrobenzenediazonium tetrafluoroborate,

[0211] Bis(4-tert-butylphenyl)iodonium hexafluorophosphate,

[0212] Bis(4-fluorophenyl)iodonium trifluoromethanesulfonate,

[0213] Diphenyliodonium hexafluorophosphate,

[0214] Diphenyliodonium hexafluoroarsenate

[0215] Diphenyliodonium triflate,

[0216] 4-Isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate,

[0217] (4-Nitrophenyl)(phenyl)iodonium trifluoromethanesulfonate,

[0218] [3-(Trifluoromethyl)phenyl](2,4,6-trimethylphenyl)iodonium trifluoromethanesulfonate,

[0219] [4-(Trifluoromethyl)phenyl](2,4,6-trimethylphenyl)iodonium trifluoromethanesulfonate,

[0220] (2-Methylphenyl)(2,4,6-trimethylphenyl)iodonium trifluoromethanesulfonate,

[0221] (3-Methylphenyl)(2,4,6-trimethylphenyl)iodonium trifluoromethanesulfonate,

[0222] (4-Methylphenyl)(2,4,6-trimethylphenyl)iodonium trifluoromethanesulfonate,

[0223] Cyclopropyldiphenylsulfonium tetrafluoroborate,

[0224] Cyclopropyldiphenylsulfonium tetrakis(pentafluorophenyl)borate,

[0225] Dimethylphenacylsulfonium tetrafluoroborate,

[0226] Dimethylphenacylsulfonium tetrakis(pentafluorophenyl)borate,

[0227] Triphenylsulfonium tetrafluoroborate,

[0228] Triphenylsulfonium bromide,

[0229] Triphenylsulfonium tetrakis(pentafluorophenyl)borate,

[0230] Tri-p-tolylsulfonium hexafluorophosphate,

[0231] Tri-p-tolylsulfonium trifluoromethanesulfonate, and

[0232] Tri-p-tolylsulfonium tetrakis(pentafluorophenyl)borate.

[0233] A particularly preferred (iii) photoacid generator is CPI-310B, triphenylsulfonium tetrakis(pentafluorophenyl)borate, wherein one or more of the three phenyl groups are optionally substituted the same or differently, preferably with linear, branched or cyclic alkyl and / or aryl groups.

[0234] In a preferred embodiment of the present invention, the formulation further comprises (iv) one or more solvents.

[0235] The solvent is selected to improve the suitability, wettability, deposition characteristics, filling characteristics and / or stability of the formulation. Any solvent can be used in the formulation according to the present invention as long as it dissolves or disperses the components of the formulation. Preferred solvents are selected from water, organic solvents and mixtures thereof. Preferred organic solvents are alcohols, esters, ketones, lactones, diketones, carboxylic acids, amides and mixtures thereof. Particularly preferred organic solvents are ethanol, propanol, 1-butanol, 2-butanol, diacetone alcohol, 1-methoxy-2-propyl acetate (PGMEA), 1-methoxy-2-propanol (PGME), butyl acetate, amyl acetate, cyclohexyl acetate, 3-methoxybutyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, cyclopentanone, ethyl 3-ethoxy propionate, methyl 3-ethoxy propionate, methyl 3-methoxy propionate, methyl acetoacetate, ethyl acetoacetate, methyl pivalate, ethyl pivalate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether propionate, propylene glycol monoethyl ether propionate. Acid esters, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, 3-methyl-3-methoxybutanol, N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, γ-valerolactone, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, methyl lactate, ethyl lactate, propyl lactate, tetramethylene sulfone, propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, ethylene glycol dimethyl ether or diethylene glycol dimethyl ether, N-ethylpyrrolidone, 2-pyrrolidone, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, terpineol, 3-phenoxytoluene, 4-phenoxytoluene and anisole. These solvents can be used alone or in a mixture of two or more.

[0236] In a preferred embodiment of the invention, the formulation comprises one or more other metal complexes which can be used as precursors for other metal oxides. In this case, a mixed metal oxide optical layer comprising a metal oxide obtained from the metal complex according to the invention and other metal oxides obtained from the other metal complexes can be formed.

[0237] Preferred other metal complexes comprise one or more trivalent or tetravalent metals, preferably selected from the group consisting of Sc, Y, La, Ti, Zr, Hf and Sn, more preferably one or more tetravalent metals, selected from the group consisting of Ti, Zr, Hf and Sn.

[0238] In a preferred embodiment of the present invention, the preparation comprises one, two, three, four or more other metal complexes in addition to the metal complex, wherein preferably each of the other metal complexes contains a ligand selected from inorganic ligands or organic ligands. Preferred inorganic ligands are optionally deprotonated halogens, phosphoric acid, sulfonic acid, nitric acid and water. Preferred organic ligands are alcohols, carboxylic acids, cyanates, isocyanates, 1,3-diketones, β-keto acids, β-ketoesters, organic phosphonic acids, organic sulfonic acids, oximes, hydroxamic acids, dihydroxybenzenes, hydroxybenzoic acids, dihydroxybenzoic acids, gallic acid, dihydroxynaphthalene, anthracene diols, hydroxyanthrone, anthracene triols, anthracene, halogenated hydrocarbons, aromatic hydrocarbons, heteroaromatic hydrocarbons, esters, catechols, coumarins and derivatives thereof, which are optionally deprotonated.

[0239] The presence of these other metal complexes allows for the tailoring of specific properties of metal oxide optical layers prepared therefrom, such as material hardness, shrinkage, refractive index, transparency, absorbance, and haze suppression.

[0240] Preferably, the weight ratio (w / w) between the metal complex according to the present invention and one or more other metal complexes in the formulation is in the range of 1:100 to 100:1, preferably 1:10 to 10:1, more preferably 1:5 to 5:1.

[0241] It is preferred that the total weight ratio of the metal complex according to the present invention and other metal complexes contained in the preparation is in the range of 0.1% to 50% (w / w), preferably 0.5% to 30% (w / w), more preferably 1% to 10% (w / w), most preferably 5% (w / w), relative to the total mass of the preparation.

[0242] In a preferred embodiment of the present invention, the formulation is an ink formulation suitable for inkjet printing. Typical requirements for ink formulations are a surface tension in the range of 20 mN / m to 30 mN / m and a viscosity in the range of 5 mPa·s to 10 mPa·s.

[0243] Method for preparing metal oxide optical layers

[0244] The present invention also relates to a method for preparing a metal oxide optical layer, wherein the method comprises the following steps:

[0245] (a) providing a formulation according to the present invention;

[0246] (b) applying the formulation to a surface of a substrate; and

[0247] (c) converting the formulation into a metal oxide optical layer on the surface of the substrate.

[0248] Preferably, the formulation provided in step (a) is a solution or dispersion comprising one or more solvents.Preferred solvents for the formulation provided in step (a) are the same as those described above for the formulation according to the present invention.

[0249] In a preferred embodiment of the present invention, the formulation provided in step (a) is an ink formulation suitable for inkjet printing. Typical requirements for ink formulations are surface tension in the range of 20 mN / m to 30 mN / m and viscosity in the range of 5 mPa·s to 10 mPa·s.

[0250] Preferably, the formulation is applied to the surface of the substrate in step (b) by a deposition method. Preferred deposition methods are drop casting, coating or printing. More preferred coating methods are spin coating, spray coating, slot coating or slot die coating. More preferred printing methods are flexographic printing, gravure printing, inkjet printing, EHD printing, offset printing or screen printing. Spray coating and inkjet printing are most preferred.

[0251] Depending on the specific problem to be solved, the formulation needs to be deposited by a coating process as a homogeneous and dense thin layer covering the entire surface of the substrate, or the formulation needs to be deposited locally in a structured manner, thus requiring a printing process. Both coating and printing processes require that the formulation be formulated in an appropriate manner to comply with the physicochemical requirements of the respective coating and printing process, as well as with the specific requirements of the surface of the substrate to be coated or printed.

[0252] In a preferred embodiment of the method for preparing a metal oxide optical layer according to the present invention, the surface of the substrate is pretreated by a surface cleaning process. The preferred surface cleaning process is a silicon wafer cleaning process, as described in the following documents: W. Kern, The Evolution of Silicon Wafer Cleaning Technology, J. Electrochem. Soc., Vol. 137, 6, 1990, 1887-1892, and New Process Technologies for Microelectronics, RCA Review 1970, 31, 2, 185-454. These silicon wafer cleaning processes include wet cleaning processes involving cleaning solvents (e.g., isopropyl alcohol (IPA)); wet etching processes involving hydrogen peroxide solutions (e.g., piranha solutions, SC1 and SC2), choline solutions or HF solutions; dry etching processes involving chemical vapor etching, UV / ozone treatment or glow discharge technology (e.g., O2 plasma etching); and mechanical processes involving brush scrubbing, fluid jet or ultrasonic technology (ultrasonic treatment). The surface of the substrate may also be pre-treated by silanization or atomic layer deposition (ALD) process. The pre-treatment of the surface of the substrate is used to adjust the hydrophobicity / hydrophilicity of the surface. This can improve the adhesion and filling properties of the metal oxide optical layer on the surface of the substrate.

[0253] In a more preferred embodiment, a wet cleaning process involving a cleaning solvent such as isopropyl alcohol (IPA) is combined with one or more of the following processes: a wet etching process involving a hydrogen peroxide solution (e.g., piranha solution, SC1, and SC2), a choline solution, or an HF solution; a dry etching process involving chemical vapor etching, UV / ozone treatment, or glow discharge technology (e.g., O2 plasma etching); and a mechanical process involving brush scrubbing, fluid jet, or ultrasonic technology (ultrasonic treatment).

[0254] In a most preferred embodiment, a wet cleaning process involving a cleaning solvent such as isopropyl alcohol (IPA) is combined with a mechanical process involving brush scrubbing, fluid jet or ultrasonic technology (ultrasonication) and a wet etching process involving a hydrogen peroxide solution (such as piranha solution, SC1 and SC2), a choline solution or a HF solution.

[0255] In a preferred embodiment of the present invention, step (b) of the method for preparing a metal oxide optical layer is performed once.

[0256] In a preferred embodiment of the present invention, step (b) of the method for preparing a metal oxide optical layer is performed continuously for multiple times, preferably 2 to 20 times, more preferably 2 to 10 times, most preferably 2, 3, 4 or 5 times.

[0257] In a preferred embodiment of the process according to the invention for producing a metal oxide optical layer, the preparation is converted into a metal oxide optical layer on the surface of the substrate in step I by subjecting it to irradiation, preferably in combination with a heat treatment.

[0258] Preferred exposure to radiation includes exposure to infrared (IR) light, visible (Vis) light and / or ultraviolet (UV) light. The wavelength of IR light is >800 nm. The wavelength of Vis light is 400 to 800 nm. The wavelength of UV light is <400 nm and may include extreme ultraviolet light (EUV). Exposure to radiation is not limited to any specific irradiation method or time. Depending on the type of substrate and formulation, a person skilled in the art will be able to determine the appropriate irradiation method and time.

[0259] Preferred heat treatments include exposure to high temperatures up to 400° C., preferably up to 350° C., preferably up to 300° C., more preferably up to 250° C., particularly preferably up to 200° C., and most preferably up to 150° C. The heat treatment is not limited to any specific heat treatment method or time. Depending on the type of substrate and formulation, a person skilled in the art will be able to determine a suitable heat treatment method and time.

[0260] In a more preferred embodiment of the method for preparing a metal oxide optical layer according to the present invention, in step I, the preparation is converted into a metal oxide optical layer on the surface of the substrate by: (c-1) pre-baking (soft baking) at a temperature of 40°C to 150°C, preferably 50°C to 120°C, more preferably 60°C to 100°C; (c-2) subjecting to irradiation, preferably UV irradiation; and (c-3) baking (hard baking, sintering or annealing) at a temperature of 100°C to 400°C, preferably 150°C to 350°C, more preferably 200°C to 250°C.

[0261] The purpose of pre-baking (soft baking) is to remove volatile and low-boiling components, such as volatile and low-boiling solvents or additives, from the drop casting, coating or printing film. Pre-baking is preferably carried out for a period of 1 to 10 minutes. After pre-baking, a layer of the substrate-adherent film of the preparation is obtained. The film may also contain residual solvents or additives.

[0262] In an alternative more preferred embodiment of the method for preparing a metal oxide optical layer according to the present invention, the (c-1) pre-bake can be omitted, so that in step I the preparation is directly converted into a metal oxide optical layer on the surface of the substrate by: (c-2) subjecting to irradiation, preferably UV irradiation; and (c-3) baking (hard baking, sintering or annealing) at a temperature of 100°C to 400°C, preferably 150°C to 350°C, more preferably 200°C to 250°C.

[0263] The purpose of the irradiation (curing) is to crosslink the epoxy resin mixture contained in the formulation, thereby producing a polymer matrix. The polymer matrix acts as a skeleton, thereby preventing the formation of voids due to evaporation of the ligands of the metal complex and subsequent material shrinkage. Preferably, the irradiation comprises exposure to UV light, preferably to UV light with a wavelength of 365 nm, for 1 to 60 minutes, preferably 5 to 30 minutes, more preferably 10 to 20 minutes.

[0264] The purpose of baking (hard baking, sintering or annealing) is to convert the preparation on the surface of the substrate into a metal oxide layer. In addition, by the baking treatment, the final properties of the metal oxide layer can be adjusted. Baking is preferably carried out for a period of 1 to 60 minutes, preferably 1 to 30 minutes, more preferably 5 to 20 minutes, most preferably 10 minutes, to achieve a refractive index (RI)> 2.0.

[0265] Prebaking, subjecting to irradiation, and baking may be performed in ambient atmosphere or in an atmosphere with increased oxygen content to decompose unwanted organic components which may result in a lower activation energy when forming the metal oxide layer.

[0266] In a preferred embodiment of the method for preparing a metal oxide optical layer according to the present invention, the substrate is a patterned substrate comprising topographical features on its surface, and the metal oxide optical layer forms a coating covering the surface of the substrate and filling the topographical features. Therefore, the topographical features are filled and leveled by the metal oxide optical layer.

[0267] Preferred topographical features include, for example, gaps, grooves, trenches and through holes. The topographical features may be uniformly or unevenly distributed on the surface of the substrate. Preferably, they are arranged on the substrate surface as an array or grating. It is preferred that the topographical features have different lengths, widths, diameters and different aspect ratios. It is preferred that the aspect ratio of the topographical features is 1:20 to 20:1, more preferably 1:10 to 10:1. The aspect ratio is defined as the ratio of the width of the structure to its height (or depth). From a size point of view, the depth of the topographical features is preferably in the range of 10 nm to 10 μm, more preferably 50 nm to 5 μm, and most preferably 100 nm to 1 μm.

[0268] It is also preferred that the topographic features are inclined at an angle, such as 10° to 80°, preferably 20° to 60°, more preferably 30° to 50°, and most preferably about 40°. These inclined topographic features are also referred to as tilted or blazed topographic features.

[0269] It may also be desirable to partially fill the topography with the metal oxide optical layer, either completely or to an extent that does not cover adjacent surfaces of the substrate that do not have the topography to be filled.

[0270] Therefore, it is preferred that the method for preparing a metal oxide optical layer according to the present invention further comprises the following step (d):

[0271] (d) removing a portion of the metal oxide optical layer covering the top of the topographical feature, thereby providing a filled topographical feature, wherein the coverage of the metal oxide optical layer on top of the topographical feature is reduced, preferably reduced to a coverage of 0 to 100 nm, more preferably 0 to 50 nm, and most preferably 0 to 20 nm.

[0272] Step (d) occurs after steps (a) to (c) of the method according to the invention. Preferably, the removal of the portion of the top of the covered morphology of the metal oxide optical layer in step (d) is performed by using a surface cleaning process as described above. Preferred surface cleaning processes are silicon wafer cleaning processes, as described in the following documents: W. Kern, The Evolution of Silicon Wafer Cleaning Technology, J. Electrochem. Soc., Vol. 137, 6, 1990, 1887-1892, and New Process Technologies for Microelectronics, RCA Review 1970, 31, 2, 185-454. These silicon wafer cleaning processes include wet etching processes involving hydrogen peroxide solutions (e.g., piranha solutions, SC1 and SC2), choline solutions or HF solutions; dry etching processes involving chemical vapor etching, UV / ozone treatment or glow discharge technology (e.g., O2 plasma etching); and mechanical processes involving brush scrubbing, fluid jet or ultrasonic technology.

[0273] The substrate is preferably a substrate for an optical device. Preferred substrates are made of inorganic or organic substrates, preferably inorganic substrates. Preferred inorganic substrates contain materials selected from the following: ceramics, glass, fused silica, sapphire, silicon, silicon nitride, quartz and transparent polymers or resins. There are no particular restrictions on the geometric shape of the substrate, but preferably a sheet or wafer.

[0274] In step (b) of the method for producing a metal oxide optical layer, the preparation is applied to the surface of a substrate, wherein the surface may be the surface of a base material of the substrate or the surface of a layer of a material different from the base material of the substrate, wherein such a layer has been formed before applying the preparation.

[0275] In this way, sequences of different layers (layer stacks) can be formed on top of each other. These layer stacks can also be structured, wherein the structures typically have nanoscale dimensions at least with regard to diameter, width and / or aspect ratio.

[0276] Optics

[0277] Finally, the present invention relates to an optical device comprising a metal oxide optical layer, the device being obtainable by the method for preparing a metal oxide optical layer according to the present invention or being obtainable by the method for preparing a metal oxide optical layer according to the present invention. Preferably, the optical device is an augmented reality (AR) and / or virtual reality (VR) device.

[0278] The present invention is further illustrated by the following examples below, which should in no way be considered limiting. It will be appreciated by those skilled in the art that various modifications, additions and variations may be made to the present invention without departing from the spirit and scope of the invention as defined in the claims.

[0279] Example

[0280] Analysis and measurement methods

[0281] The layer thickness, refractive index (n) and absorption index (k) of the metal oxide layers were determined by ellipsometry. The measurements were performed using an ellipsometer M2000 from JA Woolam and three different angles of incidence (65°, 70° and 75°). The measured data were analyzed using the software CompleteEase from JA Woolam, assuming completely transparent or almost completely transparent properties at wavelengths above 600 nm and applying a B-spline fit to obtain the refractive index (n) and the absorption index (k). The optical constants were averaged from three to four measured samples, each of which provided a different layer thickness after soft baking or hard baking or after a combined soft baking and subsequent hard baking.

[0282] The spectra of any sheet and substrate coated or not coated with the metal oxide layer described in the present invention were recorded under the UMA setting using Agilent's UV / Vis / NIR spectrophotometer Cary 7000. The measurements were made using dual beam mode, a scan speed of 600 nm / min, a spectral bandwidth of 4 nm, non-polarized light, and a spectral window of 350 nm to 700 nm. The transmission measurement was performed at an incident angle of 6° relative to the normal to the sample surface. The detector was aligned 180° to the incident light. The reflection measurement was performed at an incident angle of 6° relative to the normal to the sample surface, and the angle between the detector and the incident light reached 12°. The absorbance of the sample was calculated using Formula 1, where A represents the absorbance of the coated sample, R represents the reflection, and T represents the transmittance of the sample.

[0283] Formula 1

[0284] Thermogravimetric analysis was performed on a TA Instruments TGA Q 50. In the usual measurement mode, the sample was heated to 950° C. in air atmosphere with a heating rate of 20 K / min.

[0285] The elemental analysis results are received as a service from the analytical service provider, where the measurements were performed according to DIN 51732:2014-07.

[0286] NMR measurements were performed using a 500 MHz spectrometer from Bruker Biospin GmbH ( 1 H-NMR).

[0287] SEM images were recorded using a Mira 3 LMU from Tescan or a Sigma 300VP from Carl Zeiss or a Supra 35 also from Carl Zeiss.

[0288] The coating of substrates (usually wafers) was performed using a spin coater from Suess (LabSpin 150i). The spin coating process using a flat substrate was as follows: 0.5 ml of coating was deposited on a static quartz wafer, followed by a 30 s spin interval at a given spin speed, where the acceleration to reach the final spin speed was set to 500 rpm / s. 2. Different layers and coating thicknesses are achieved using different spinning speeds or different coating formulations with different concentrations of metal oxide precursors or different mixtures of metal oxide precursors. After spin coating, the coated substrate is either pre-baked at 100°C for 2 minutes to remove solvent residues and subsequently baked at high temperature, or the layers deposited on the wafer are baked directly at high temperature for a specific time. Typically, but not limited to, the coated layers are baked at 150°C, 200°C, 250°C and 300°C, typically for 5 to 10 minutes. Prebaking as well as layer baking are performed using a high-temperature hot plate from Harry Gestigkeit that allows temperatures of up to 600°C to be reached. The above conditions and parameters apply to all the following experimental examples, unless other conditions are explicitly mentioned in other sections.

[0289] Typically, quartz and / or silicon wafers, both 2 inches in diameter, are used for all coating experiments (such as spectroscopy and ellipsometry measurements) that require a flat and unstructured support for metal oxides.

[0290] The structured substrate, usually a silicon wafer, is used as a square mold with a side length of 1.5 cm to 2 cm. The wafer molds are cut and diced from a mother wafer, which is usually 8 inches in diameter. x The structure is generated and arranged in the stacked layers of the structure. The dimensions of the structure (e.g., the cross-sectional width and length of the groove) refer to the structure of Sematech mask 854. Typically, but not limited to, a cross-sectional cut perpendicular to the groove array with a width of 40 nm to 50 nm is used as the groove structure of primary interest to study its filling behavior by a metal oxide precursor applied by wet chemistry and / or a metal oxide received when the metal oxide precursor is thermally converted. In addition to the above, cross-sections of groove arrays with widths of 100 nm and 150 nm are also used to study the groove filling of metal oxides.

[0291] Unless otherwise stated, the structured wafer molds were coated by spin coating. For this purpose, the coating formulation, typically in a volume between 0.15 ml and 0.5 ml per mold (0.5" to 2" in diameter), was pipetted and cast onto the wafer surface. The formulation was allowed to spread and settle on the surface for one minute, followed by a step of distributing and spreading the formulation over the entire surface of the wafer mold at 500 rpm for 30 seconds, followed by a final stripping step at 2,000 rpm for another 60 seconds. The acceleration of the rotation speed was set to 500 rpm / s 2 The soft bake and hard bake conditions for the structured wafer mold are chosen to be similar or identical to those mentioned for the flat substrate.

[0292] Unless otherwise stated elsewhere, all chemicals used in the syntheses were purchased from Sigma Aldrich and used without further purification.

[0293] Preparation of Nb citraconic acid

[0294] A 3-necked glass flask (100 ml) was continuously flushed with N2 and 17.6116 g of citraconic anhydride and 8.160 g of 1-methoxy-2-propanol acetate (PGME) (first solution) were added to the flask. The mixture was stirred for 15 minutes under a constant N2 flow. At the same time, a mixture of 28.770 g of 1-methoxy-2-propyl acetate (PGMEA) and 10 g of niobium ethoxide (second solution) was prepared under an inert atmosphere and added to the first solution flask using a dropping funnel over a period of 1 hour. After the addition of the second solution to the first solution was complete, the reaction mixture was heated to 50°C with continuous stirring over a period of 4 hours. The mixture was then allowed to cool and filled into appropriate inertized brown glass bottles. A small volume of material was drawn off, the solvent was removed, and the remaining residue was dried until the final pressure in the sample vial reached 0.01 mbar. The remaining crude product was subjected to 1 H-NMR analysis: 6.78 ppm (s, 1 H), 5.81 ppm (m, 0.56 H), 4.16 ppm (q, 0.56 H), 4.10 ppm (q, 0.82 H), 3.29 ppm (m, 3.04 H), 2.12 ppm (s, 3.36 H), 1.98 ppm (m, 2.06 H), 1.18 ppm (m, 5.64 H).

[0295] Example 1

[0296] Preparation 1:

[0297] Epoxy resin mixture A (see Table 1 below) and 10% (w / w) citraconic acid Nb prepared above were mixed in PGME at a weight ratio of 1:1 to obtain a final concentration of epoxy resin mixture A and citraconic acid Nb of 5% (w / w) each, i.e. 5 / 5% (w / w) citraconic acid Nb / epoxy resin mixture A.

[0298] Epoxy resin mixture A:

[0299]

[0300] Table 1: Epoxy resin mixture A.

[0301] Deposition:

[0302] 100 μL of Formulation 1 was deposited on a substrate (18×18 mm) with surface features by depositing a 100 μL droplet followed by spin coating at 2,000 rpm for 25 seconds. The coated substrate was then pre-baked at 100°C for 1 minute. The substrate was then irradiated with a 365UV lamp for 20 minutes and then baked at 300°C for 10 minutes.

[0303] The formulation deposited by the above process fills the surface features.

[0304] Figure 7 Shown is the surface feature filling after spin coating of 5 / 5% (w / w) Nb citraconic acid / epoxy mixture A, prebaked at 100°C for 1 minute, then UV cured with 365 nm light for 20 minutes and baked at 350°C for 10 minutes.

[0305] Figure 8 Shown is the surface feature filling of a spin-coated Nb citraconic acid 5% (w / w) PGME solution annealed at 300°C for 10 minutes.

[0306] The optical properties (measured by ellipsometry) of the formed films prepared using UV curing followed by baking at different temperatures are shown in Table 2 below.

[0307]

[0308] Table 2: Optical properties (ellipsometry measurements) of formed films prepared using UV curing followed by baking at different temperatures.

[0309] Example 2

[0310] preparation:

[0311] Different weight ratios of Nb citraconic acid (1:1 in PGME) and epoxy resin mixture A (see Table 1 above) were prepared, spin-coated, irradiated with a 365 UV lamp for 20 minutes, and then baked at 150°C, 200°C, or 250°C for 10 minutes. The coated films were then tested for gap fill (on structured substrates), RI, and absorption (on quartz substrates).

[0312] Fig. 9 The surface feature filling properties of Nb citraconic acid + epoxy resin mixture A at different mixing ratios and baking temperatures are shown. As shown, the Nb citraconic acid concentration was kept constant at 5% (w / w), while the epoxy resin mixture A content was varied from 1% (w / w) to 5% (w / w).

[0313] In the case of 3% (w / w) : 5% (w / w) epoxy resin mixture A: Nb citraconic acid ratio and higher epoxy resin mixture A content, uniform gap filling was achieved after baking at 200°C and 250°C.

[0314] As can be seen from Table 3, for those experiments and material weight ratios (3:5 to 5:5) that achieve good filling, the refractive index n of the films can be adjusted between 1.659 and 1.758 by applying different temperatures between 150°C and 250°C.

[0315] The absorption index k at a wavelength of 460 nm is shown in Table 4. For the sample baked at 150°C, low absorption was achieved.

[0316]

[0317] Table 3: Refractive index n at 520 nm of 5% (w / w) Nb citraconic acid films with different contents of epoxy resin mixture A (as indicated) after baking at 150 °C to 250 °C.

[0318]

[0319] Table 4: Absorption index k at 460 nm of 5% (w / w) citraconic acid Nb films with different contents of epoxy resin mixture A (as indicated) after baking at 150 °C to 250 °C.

[0320] Example 3

[0321] The following solutions (5% (w / w) each): Ti isopropoxide, Ti butoxide, Nb ethanol, and Nb citraconic acid) were each spin-coated on a silicon wafer and baked at 350°C for 10 minutes. In addition, a new formulation based on a mixture of Ti isopropoxide / epoxy mixture A (5 / 5% (w / w)), Ti butoxide / epoxy mixture A (5 / 5% (w / w)), Nb ethanol / epoxy mixture A (5 / 5% (w / w)), and Nb citraconic acid / epoxy mixture A (5 / 5% (w / w)) was coated on a silicon wafer under the same conditions as above. The refractive index and absorption index of the coated films were measured.

[0322] Measuring refractive index n and absorption index k

[0323] Table 5 shows that refractive indices n greater than 2.00 can be achieved with various metal-organometallic oxide precursors. However, with the exception of Nb citraconic acid, the absorption index k of all of these materials increases significantly with the addition of epoxy resin mixture A. Only for Nb citraconic acid, k decreases when mixed with epoxy resin mixture A.

[0324]

[0325] Table 5: Refractive index (n) and absorption index (k) of various metal oxide precursors with and without epoxy resin mixture A added in a ratio of 5 / 5% (w / w) after baking at 350°C for 10 minutes.

[0326] Since k is proportional to the optical loss of the film, only the formulation containing Nb citraconic acid achieves the preferred and surprising effect when used in optical coatings, namely reducing absorption (optical loss) when mixed with an epoxy matrix, thereby improving filling properties.

[0327] Reference numerals list

[0328] 1Material 02 with RI 02

[0329] 2Material 01 with RI 01

[0330] 3. Substrate (e.g. glass)

[0331] 4 Diffraction of incident light indicated by broad arrows

[0332] 5Total Internal Reflection (TIR) ​​of Light

[0333] 6 Waveguide

[0334] 7 Structured layer stack with gaps (grooves)

[0335] 8 Substrate (e.g. glass or silicon)

[0336] 9 Covering layer of material (such as high refractive index material or high etching resistance material)

[0337] 10 Provide gap filling materials (such as high refractive index materials or high etching resistance materials)

[0338] 11 Gap

[0339] 12 Formulation (e.g. ink) of high refractive index materials (e.g. metal oxide precursors)

[0340] 13 Provides gap-filled high-refractive-index materials (e.g., metal oxides) with optional concave geometry

[0341] 14 Covering layer (optional)

[0342] 15 Energy

Claims

1. A metal complex, comprising: one or more, preferably two or more metals M, selected from V, Nb and Ta, preferably Nb; and One or more ligands L, wherein L is an organic ligand comprising an ester group and a carboxylic acid group, said organic ligand being optionally deprotonated.

2. The metal complex according to claim 1, wherein L is an organic ligand further comprising a carbon-carbon double bond.

3. The metal complex according to claim 1 or 2, wherein L is coordinated to the one or more metals M via the carboxylic acid group.

4. The metal complex according to one or more of claims 1 to 3, wherein L is a compound represented by formula (1), which is optionally deprotonated at the carboxylic acid group: Formula (1), in: The curved line represents a divalent hydrocarbon group having 2 to 20 carbon atoms and one or more carbon-carbon double bonds; and R is an alkyl group having 1 to 20 carbon atoms or an aryl group having 5 to 20 aromatic ring atoms, which may be substituted or unsubstituted.

5. The metal complex according to one or more of claims 1 to 4, wherein L is a compound represented by formula (2), which is optionally deprotonated at the carboxylic acid group: Formula (2), in: R is an alkyl group having 1 to 20 carbon atoms or an aryl group having 5 to 20 aromatic ring atoms, which may be substituted or unsubstituted; and R 1 is H, an alkyl group having 1 to 10 carbon atoms or an aryl group having 5 to 10 aromatic ring atoms, which may be substituted or unsubstituted.

6. The metal complex according to one or more of claims 1 to 5, wherein the metal complex is represented by the following formula (3): Formula (3), in: M is independently at each occurrence a metal selected from V, Nb and Ta, preferably Nb; L is, independently of each other, an organic ligand comprising an ester group and a carboxylic acid group, said organic ligand being optionally deprotonated; A is a bridging ligand selected from the group consisting of: µ-L - 、µ-OH - 、µ-OR - 、µ-F - 、µ-Cl - , µ-Br - or µ-I - , wherein R is an alkyl group having 1 to 10 carbon atoms; and L - is the deprotonated L; B is the bridging ligand μ-O 2- ; m is an integer from 1 to 10; n is an integer from 5 to 50; a is an integer from 0 to 20; and b is an integer from 0 to 10; The condition is to satisfy the following formula: , wherein S is the value of the oxidation state of M, preferably selected from 1, 2, 3, 4 and 5, more preferably selected from 2, 3, 4 and 5, most preferably 5.

7. A preparation comprising: (i) a metal complex according to one or more of claims 1 to 6 as a metal oxide precursor; (ii) epoxy resin mixture; and (iii) Photoinitiator. 8 . The preparation according to claim 7 , wherein the weight ratio of the (i) metal complex in the preparation is in the range of 0.1% to 50% (w / w) relative to the total mass of the preparation.

9. The formulation according to claim 7 or 8, wherein (ii) the epoxy resin mixture comprises: (ii-1) one or more fluorene epoxy resins; and (ii-2) One or more acrylate epoxy resins.

10. The preparation according to claim 9, wherein (ii-1) the fluorene epoxy resin is represented by the following formula (4): Formula (4), in: R is halogen, an alkyl group having 1 to 20 carbon atoms or an aryl group having 5 to 20 aromatic ring atoms; m is an integer from 0 to 4; n is an integer from 0 to 4; p is an integer from 0 to 10; and q is an integer from 0 to 10.

11. The formulation according to claim 9, wherein (ii-2) the acrylate epoxy resin is represented by the following formula (5): Formula (5), in: R a is H or an alkyl group having 1 to 5 carbon atoms; R b It is a divalent organic group; S a is an alkylene group having 1 to 10 carbon atoms, which may be substituted with F or OH; and S b is an alkylene group having 1 to 10 carbon atoms, which may be substituted by F or OH.

12. The preparation according to one or more of claims 7 to 11, further comprising: (iv) one or more solvents.

13. A method for preparing a metal oxide optical layer, the method comprising the following steps: (a) providing a preparation according to one or more of claims 7 to 12; (b) applying the formulation to the surface of a substrate; as well as (c) converting the formulation into a metal oxide optical layer on the surface of the substrate.

14. The method according to claim 13, wherein in step (b), the formulation is applied to the surface of the substrate by a deposition method.

15. A method according to claim 13 or 14, wherein in step (c) the formulation is converted into a metal oxide optical layer on the surface of the substrate by subjecting it to irradiation.

16. The method according to one or more of claims 13 to 15, wherein in step (c), the formulation is converted into a metal oxide optical layer on the surface of the substrate by: (c-1) prebaking at a temperature of 40°C to 150°C; (c-2) subjecting to irradiation; and (c-3) baking at a temperature of 100°C to 400°C.

17. The method according to one or more of claims 13 to 16, wherein the substrate is a patterned substrate comprising topographical features on its surface.

18. An optical device comprising a metal oxide optical layer obtainable by a method according to one or more of claims 13 to 17, wherein the optical device is preferably an augmented reality (AR) and / or virtual reality (VR) device.

Images