formulation

Abstract

The present invention relates to a formulation for preparing an optical layer containing a metal oxide. The formulation may exhibit at least one of properties as an advanced material or as a high-performance material. The formulation may be used in the nanotechnology process to make semiconductor device / display device application, for example semiconductor chip, or a liquid crystal, quantum dot, OLED display fabricated on a substrate controlled by semiconductors.

Description

[0001] Formulation

[0002] Field of the invention

[0003] The present invention relates to a formulation for preparing an optical layer containing a metal oxide, method for preparing a formulation, use of a formulation, method for preparing a composite, a composite, an optical device and a display device.

[0004] Background Art

[0005] Leading edge optical devices typically include optical gratings made from composite materials having a substrate as a support and complex and interlaced patterns thereon, the patterns being made up of different layers or stacks of layers. Usually, the creation of such complex and interlaced patterns demands for structuring processes, which become increasingly challenging with decreasing size of structural dimensions to be prepared.

[0006] In addition to a wide range of possible uses in various fields of application, such as in spectrometers or in optical storage systems (CD, DVD, etc.), diffractive gratings are the core components of so-called XR devices, mostly glasses. In this context, R stands for the term reality and X denotes different attributes such as, for example, virtual, augmented, mixed and so forth. Hence, diffractive gratings form part of the core of the so-called optical engine in XR devices, specifically in augmented reality and mixed reality glasses. Virtual reality glasses, when built as a head mounted display, are often composed of a conventional liquid crystal (LC) organic light emitting diode (OLED) display being embedded in the device directly in front of the users’ eyes, and thus do not necessarily require diffractive gratings. In contrast, augmented and mixed reality glasses are designed that way to enable consumers to obtain visual impressions of their environment, at its best as if they would not wear any glasses at all.

[0007] However, they also make it possible to provide and serve digital information and to also project it into the field of vision of individuals. Additional digital information is gathered from recognizing and analyzing the environment, the individual inspects or is currently looking at. In order to convey and project supporting digital information into the eyes of an individual, the augmented or mixed reality glasses are equipped with an information supply unit, which is coupled to an optical waveguide system that transports the optically coded supporting information through it directly to the lens of the glasses. Here, the information passes a diffractive grating which couples the incident light into the lens and splits it according to its angular information and its spectral bands by diffraction. After incoupling of the light, the lens serves as waveguide enabling transport of the light to and into the pupil of an individual. The location of light incoupling is independent of any preferred position and thus of the implication of technical needs. The direction of traversal of light within the lenses is determined by the diffractive grating diffracting or splitting the light. At certain positions in the lens, a second and a third diffractive grating serves for changing the direction of light traversal and thereby enforcing the light to be projected into pupil of the user. The light traversal in the glasses is accomplished by total internal reflection (TIR) of the light, thus bouncing several times between the glass interfaces until reaching another diffractive grating, which changes the internal TIR direction of the light (see Figure 2). The second and third grating are geometrically aligned in different directions with respect to the first and incoupling grating, e. g. by a certain angular distortion of the longitudinal axis, thus allowing to change the direction of propagation of totally internally reflected light. Needless to say, the lens itself or the material of which lenses are made of shall not be absorbing. Otherwise, the supportive information never reaches the pupil of the user or only with strongly depleted light intensity. The process works regardless of the use of reflection or transmission gratings. Usually, the lenses are equipped with both types of gratings to properly guide the light. It should also be mentioned that there are differences in the optical performance of reflection and transmission gratings, which, however, are of no further interest in the context of the current invention. The basic structure of the gratings is very similar, which is more important at this point.

[0008] Nevertheless, there are different designs and structures such as surface relief (SR) or volume phase holographic (VPH) gratings to achievewaveguiding. Both types are very similar in appearance. In the simplest case, the gratings are somehow mounted onto the surface of a waveguiding material, here the lens. The grating itself is composed of an array of fine structures, mostly trenches of a first material type Material 01 with a refractive index Rl 01 , however, not limited thereto. The geometrical shape of the trenches may be manifold, from rectangular, over V-shaped trenches, U-shaped and there like. The width, including structures with different widths, the geometrical form of the trenches, their pitch as well as their depth, including different depths, are specially designed to influence the diffraction pattern of the incident light to be diffracted.

[0009] In case of VPH gratings, the trenches or structures of a first material type (Material 01 ) having a refractive index (Rl 01 ) are filled by a second material type (Material 02) having a refractive index (Rl 02), wherein Rl 02 is incrementally different from Rl 01 (see Figures 1 and 3). For the sake of completeness, it should be mentioned that Material 01 or Material 02 may be composed of a stack of structured layers, each containing a different material composition with different refractive index, stacked on top of each other, thereby forming Material 01 or Material 02 having an effective or graded refractive index Rl 01 or Rl 02, respectively. Incidentally, the (effective or graded) refractive indices Rl 01 and Rl 02 depend on the refractive index of the waveguide or the lens from which the glasses are made of. If a glass lens with high refractive index (n03 > 1 .46) is used, the (effective or graded) refractive indices of Material 01 and Material 02 are considered to be higher than that of the lens itself, whereby a Rl value of 2.0 can be reached and exceeded. Surface relief (SR) gratings may look similar and may also include a second type of material as a filler for the trenches, but the trenches can also be just air. High performance gratings, especially those of VPH-type, may be manufactured using standard lithography and deposition techniques known from micro-fabrication such as, for example, the manufacturing of integrated circuits.

[0010] Such standard techniques typically include physical vapor deposition (PVD) or chemical vapor deposition (CVD) processes and often suffer from incomplete gap filling due to unfavourable deposition and / or layer growth deposition properties including increased deposition and / or growth rates at comers and edges. Such 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 by a PVD and / or CVD layer that is almost as thick as the maximum depth of the deepest structure to be filled by the deposited gap filling material (see Figures 4 and 5). In some applications, however, it may be necessary to expose the surface of the substrate so that it is available for further processing. Consequently, undesired overburden layers from PVD or CVD need to be removed, for example by chemical mechanical planarization (CMP) without harming the original substrate surface underneath. Although CMP is very well established in the process of manufacturing integrated circuits, CMP is a time consuming and costly process and can be seen as a potential economic drawback for mass production of leading-edge optical devices, particularly the mass production of diffractive gratings. It would therefore be desirable to have a solution for an advanced and cost-efficient manufacturing of optical gratings where gap filling does not require CMP (see Figure 6).

[0011] For that reason, more cost-effective production technology allowing for lower cost of ownership is required. Summary of the invention

[0012] The inventors newly have found that there are still one or more of considerable problems for which improvement is desired, as listed below: providing a printable formulation for preparing an optical layer / composite containing a material which provide sufficiently high refractive index after curing; providing a formulation for preparing an optical layer which enables to prepare an optical layer having improved density and / or crack-less or crack-free property, providing a formulation which enables to fill up of nanoscaled cavities, trenches or gaps after curing; providing a formulation for preparing an optical layer containing a precursor material of a high refractive index material, which enables good dispersion in the formulation; simpler and / or more cost efficient method for preparing an optical layer / composite with using the formulation; realizing a more stable formulation, zero or reduced decomposition of co-solvent in the formulation, zero or reduced viscosity change of the formulation, providing a suitable formulation for ink jetting and / or realizing continuous inkjet printing.

[0013] The inventors aimed to solve one or more of the above-mentioned problems.

[0014] Then, the present inventors have surprisingly found that one or more of the above-described technical problems can be solved by the features as defined in the claims.

[0015] Namely, it is found a novel formulation for preparing an optical layer containing a metal oxide, preferably for preparing a composite, more preferably for preparing a layered composite, comprising at least, essentially consisting of or consisting of;

[0016] - a metal alkoxide, preferably said metal alkoxide contains a group 4 and / or group 5 element of the periodic table; and an acid selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids.

[0017] In another aspect, the present invention further relates to method for preparing a formulation of the present invention, containing at least, essentially consisting of, or consisting of, the following steps;

[0018] (X) mixing a metal alkoxide, preferably said metal alkoxide contains a group 4 and / or group 5 element of the periodic table; and an acid selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids.

[0019] Optionally, a solvent selected from water, preferably acidic water having hydrogen ion index (pH) below 7 and 1 or more, preferably 1 ^pH<7, an organic solvent or a mixture of said water and one more organic solvent, is also mixed in step (X).

[0020] In another aspect, the present invention also relates to use of the formulation of the present invention for preparing an optical layer containing a metal oxide, preferably for preparing a composite, more preferably for preparing a layered composite.

[0021] In another aspect, the present invention further relates to a method for preparing a composite containing a metal oxide, preferably said metal oxide is selected from metal dioxide, metal mono oxide, or a combination of these; comprising at least, essentially consisting of or consisting of, the following steps (a) and (b):

[0022] (a) providing the formulation of the present invention onto a surface of a substrate, preferably by wet deposition process, more preferably by spincoating or an area selective printing, preferably said area selective printing is an ink-jetting, even more preferably by ink-jetting; and (b) applying a thermal treatment to the formulation provided on the surface of the substrate to convert at least a part of the metal alkoxide of the formulation to a metal oxide.

[0023] Preferably said composite being a layered composite, more preferably said layered composite is an optical layer.

[0024] In another aspect, the present invention further relates to a composite, preferably being a layered composite, preferably said layered composite is an optical layer, derived from the formulation of the present invention.

[0025] In another aspect, the present invention further relates to a composite, preferably being a layered composite, preferably said layered composite is an optical layer, obtained by the method of the present invention.

[0026] In another aspect, the present invention further relates to an optical device comprising at least the composite of the present invention, and a substrate comprising a patterned surface or an uneven surface. Preferably a gap or trench of said patterned surface or an uneven surface of the substrate is at least partly filled with said composite.

[0027] Preferably said substrate is a patterned substrate comprising topographical features on the surface thereof. Preferably said composite fills at least a part of a gap of said topographical features, more preferably said composite fills a trench of the patterned substrate.

[0028] In another aspect, the present invention further relates to a display device comprising at least one functional medium configured to direct and modulate a light or configured to emit light; and the composite of the present invention.

[0029] Technical effects of the invention

[0030] The present invention provides one or more of following effects; providing a printable formulation for preparing an optical layer / composite containing a material which provide sufficiently high refractive index after curing; providing a formulation for preparing an optical layer which enables to prepare an optical layer having improved density and / or crack-less or crack-free property, providing a formulation which enables to fill up of nanoscaled cavities, trenches or gaps after curing; providing a formulation for preparing an optical layer containing a precursor material of a high refractive index material, which enables good dispersion in the formulation; simpler and / or more cost efficient method for preparing an optical layer / composite with using the formulation; realizing a more stable formulation, zero or reduced decomposition of co-solvent in the formulation, zero or reduced viscosity change of the formulation, providing a suitable formulation for ink jetting and / or realizing continuous inkjet printing.

[0031] Preferred embodiments of the present invention are described hereinafter and in the dependent claims.

[0032] Brief description of the figures

[0033] Fig. 1 : Schematic cross-sectional view of a VPH grating with a Material 01 and a Material 02, wherein the refractive index IR 01 of Material 01 is incrementally different to the refractive index IR 02 of Material 02.

[0034] Fig. 2 : Schematic cross-sectional view of a VPH grating enabling light diffraction (transmissive case) including propagation of diffracted light within waveguide (e.g. lens) by total internal reflection.

[0035] Fig. 3 : Schematic cross-sectional view of a VPH grating providing gaps (trenches) to be filled with a high refractive index material (Material 02), wherein the refractive index of Material 02 is incrementally different form the refractive index of Material 01 flanking the gaps (trenches).

[0036] Fig. 4: Schematic representation of PVD- or CVD-mediated gap filling process and removal of undesired overburden. Fig. 5 : Schematic representation of PVD- or CVD-mediated gap filling process creating and leaving voids within gaps and deposited layers.

[0037] Fig. 6 : Schematic representation of gap filling process using formulations containing inventive metal complex or formulations thereof being converted to metal oxides.

[0038] List of reference signs

[0039] 1. Material 02 with Rl 02

[0040] 2. Material 01 with Rl 01

[0041] 3. Substrate (e.g. glass)

[0042] 4. Diffraction of incident light represented by broad arrow

[0043] 5. Total internal reflection of light (TIR)

[0044] 6. Waveguide

[0045] 7. Structured layer stack with gaps (trenches)

[0046] 8. Substrate (e.g. glass or silicon)

[0047] 9. Overburden of material (e.g. high refractive index material or high etch resistant material)

[0048] 10. Material (e.g. high refractive index material or high etch resistant material) providing gap fill

[0049] 11 . Voids

[0050] 12. Formulation (e.g. ink) of high refractive index material (e.g. metal oxide precursor)

[0051] 13. High refractive index material (e.g. metal oxide) providing gap fill with optional concave geometry

[0052] 14. Overburden layer (optional)

[0053] 15. Energy

[0054] Definition of the terms

[0055] In the context of the present invention, the term “formulation medium” or the plural term “formulation media” as used herein, denote one or more compounds serving as a solvent, suspending agent, carrier and / or matrix for the metal alkoxide and any other component included in the formulation. Formulation media are generally inert compounds that do not react with said metal alkoxide and said other components. Formulation media may be liquid compounds, solid compounds or mixtures thereof. Typically, formulation media are organic compounds.

[0056] The term “surfactant” as used herein, refers to an additive that reduces the surface tension of a given formulation.

[0057] The term “wetting and dispersion agent” as used herein, refers to an additive increases the spreading and penetrating properties of a given formulation. In this way, the tendency of the molecules to adhere to each other is reduced.

[0058] The term “adhesion promoter” as used herein, refers to an additive that increases the adhesion of a given formulation.

[0059] The term “polymer matrix” as used herein, refers to an additive that acts as a macromolecular matrix for one or more components of a given formulation.

[0060] The term “optical device” as used herein, relates 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, polarizing optics, UV and IR optics, and optical coatings. Preferred optical devices in the context of the present invention are augmented reality (AR) glasses and / or virtual reality (VR) glasses.

[0061] The term “display device” as used herein, is a kind of an optical device configured to output / present information in visual or tactile form. Examples are Liquid crystal display (LCD), Light emitting diode display (LED display), organic light emitting display (OLED), micro-LED display, quantum dot display (QLED), AR display, VR display, MR display, plasma (PDP) display, electroluminescent (ELD) display.

[0062] Detailed description of the invention

[0063] The present invention relates to a formulation for preparing an optical layer containing a metal oxide, preferably for preparing a composite, more preferably for preparing a layered composite, comprising at least, essentially consisting of or consisting of; a metal alkoxide, preferably said metal alkoxide contains a group 4 and / or group 5 element of the periodic table; and an acid selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids.

[0064] - Metal alkoxides

[0065] According to the present invention, the formulation contains a metal alkoxide. Preferably, said metal alkoxide contains a group 4 and / or group 5 element of the periodic table.

[0066] As said metal alkoxide, publicly available metal alkoxides containing a group 4 and / or group 5 element of the periodic table, can be used.

[0067] In a preferred embodiment of the present invention, said metal oxide precursor (preferably metal alkoxide) is represented by following chemical formula (IV) or formula (V):

[0068] Mb1O4(Rb1Rb2Rb3Rb4) -(IV)

[0069] Mb20s(Rb1Rb2Rb3Rb4Rb5) -(V)

[0070] Wherein Mb1is a tetravalent metal of a group 4 element of the periodic table, preferably it is Ti, Zr or Hf;

[0071] Mb2is a pentavalent metal of a group 5 element of the periodic table, preferably it is Nb or Ta; Rb1, Rb2, Rb3, Rb4and Rb5are each independently selected from H, D, a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3-25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups and / or one or more adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, , preferably one or more non-adjacent CH2 groups of the above- mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, ; and where one or more H atoms may be replaced by D, ; where each of groups may be substituted by one or more groups Ra;

[0072] Rais at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents Rahere may optionally form a mono- or polycyclic, aliphatic ring system with one another.

[0073] According to the present invention, the total amount of the metal oxide precursor in the formulation is in the range from 0.1 to 40wt.% based on the total amount of the formulation, preferably it is in the range from 1 to 35wt%, more preferably from 2 to 30wt%, even more preferably from 3 to 28wt%.

[0074] -Acid

[0075] According to the present invention, the formulation contains an acid selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids. It is believed that the acid can function as a reaction mediator.

[0076] In a preferred embodiment of the invention, said sulfonic acid is represented by following chemical formula (I).

[0077] Ra1SO3H - (I) wherein

[0078] Ra1is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups Rax;

[0079] Raxis at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents Raxhere may optionally form a mono- or polycyclic, aliphatic ring system with one another; said amine hydrochloride is represented by following chemical formula (II) HCI - Ra2- (II) wherein

[0080] Ra2is selected from the group consisting of N2H4, ammonia, hydroxylamine, imidazole and 1 ,4-diazabicyclo[2.2.2]octane; and / or said carboxylic acid is represented by following chemical formula (III) Ra3- COOH wherein

[0081] Ra3is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups Rax;

[0082] Raxis at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents Raxhere may optionally form a mono- or polycyclic, aliphatic ring system with one another.

[0083] In some preferred embodiments, the acid is an amine hydrochloride represented by following chemical formula (II) HCI - Ra2- (II) wherein

[0084] Ra2is selected from the group consisting of N2H4, ammonia, hydroxylamine, imidazole and 1 ,4-diazabicyclo[2.2.2]octane. As such amine hydrochloride, hydrazinium monohydrochloride can be used preferably.

[0085] In some preferred embodiments, said acid is a sulfonic acid represented by following chemical formula (I).

[0086] Ra1SO3H - (I) wherein

[0087] Ra1is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups Rax;

[0088] Raxis at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents Raxhere may optionally form a mono- or polycyclic, aliphatic ring system with one another.

[0089] As such sulfonic acid, methane sulfonic acid (MSA), para-toluene sulfonic acid (p-TSA), benzene sulfonic acid (BSA) can be used preferably. It is believed that these sulfonic acids are particularly suitable for this invention to realize improved gap filling property and it works well even with small amount like described below ranges.

[0090] In a preferred embodiment of the present invention, the stoichiometric mole ratio of the acid and the metal alkoxide is in the range from 0.1 :100 to 120:100, preferably from 0.5:100 to 100:100 (the stoichiometric mole amount of the acid: total amount of the metal alkoxide), more preferably the relative mole amount of the acid based on the total amount of the metal alkoxide is in the range from 1 : 100 to 50: 100, furthermore preferably 2: 100 to 10:100 (the relative mole amount of the acid: total amount of the metal alkoxide).

[0091] It is believed that when the stoichiometric mole ratio of the acid and the metal oxide precursor is in the above-mentioned range, it improves film stability, improves gap filing property and / or provides improved refractive index value.

[0092] Namely, the stoichiometric mole ratio of the acid and the metal alkoxide 100:100 (acid: metal alkoxide) or less is recommended from the viewpoint of better film stability and / or improved refractive index value of the obtained film. It is preferably 50:100 or less, more preferably 10:100 or less.

[0093] From the viewpoint of improved gap filling property, the stoichiometric mole ratio of the acid and the metal alkoxide 0.1 :100 (acid: metal alkoxide) or more is recommended. It is preferably 0.5:100 or more, more preferably 1 :100 or more.

[0094] -Solvent

[0095] According to the present invention, the formulation of the present invention contains a solvent selected from acidic water having hydrogen ion index (pH) below 7 and 1 or more, preferably 1 ^pH<7, or an organic solvent or a mixture of water and one more of organic solvents. Preferably the formulation contains water and one or more organic solvents. More preferably, the formulation contains water and one or more organic solvents selected from one or more members of the group consisting of ethylene glycol monoalkyl ethers, preferably it is ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether and / or ethylene glycol monobutyl ether; diethylene glycol dialkyl ethers, preferably it is diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether and / or diethylene glycol dibutyl ether; propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and / or propylene glycol monopropyl ether; 1 ,3-dimethoxy-2-propanol, ethylene glycol alkyl ether acetates, preferably it is methyl cellosolve acetate and / or ethyl cellosolve acetate; propylene glycol alkyl ether acetates, preferably it is propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate and / or propylene glycol monopropyl ether acetate; ketones, preferably it is methyl ethyl ketone, acetone, methyl amyl ketone, methyl isobutyl ketone and / or cyclohexanone; alcohols, preferably it is ethanol, propanol, butanol, hexanol, cyclo hexanol, ethylene glycol, propylene glycol, triethylene glycol and / or glycerin; esters, preferably it is ethyl 3-ethoxypropionate, methyl 3-methoxypropionate and / or ethyl lactate; and cyclic esters, preferably it is gamma-butyro-lactone; preferably said solvent is ethylene glycol monoalkyl ethers, diethylene glycol dialkyl ethers, propylene glycol, ethylene glycol, propylene glycol monoalkyl ethers, ethylene glycol alkyl ether acetates, propylene glycol alkyl ether acetate, more preferably said solvent is selected from propylene glycol alkyl ether acetates, ethylene glycol monoalkyl ethers, propylene glycol and propylene glycol monoalkyl ethers, 1 ,3-dimethoxy-2-propanol.

[0096] It is believed that the printing, especially ink jetting of structures is considered as a highly cost-efficient production step. Thus, suitable solvents of the formulation for printing the structures or filling up of cavities and structures, is described here.

[0097] After printing, deposition and fill up of structures, at least a part of the material as the metal oxide precursor need to become converted into the respective metal oxides by any known means know to the persons skilled in the art (thermally, photochemically, etc.). -Method for preparing a formulation

[0098] In another aspect, the present invention also relates to a method for preparing a formulation of the present invention, containing at least, essentially consisting of, or consisting of the following steps;

[0099] (X) mixing a metal alkoxide, preferably said metal alkoxide contains a group 4 and / or group 5 element of the periodic table; and an acid selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids.

[0100] Preferably, a solvent selected from water, preferably acidic water having hydrogen ion index (pH) below 7 and 1 or more, preferably 1 ^pH<7, an organic solvent or a mixture of said water and one more organic solvents, is also mixed in step (X). More preferably, an organic solvent or a mixture of organic solvents is mixed in step (X).

[0101] In a preferred embodiment of the present invention, said method comprises at least, essentially consisting of or consisting of, the following steps:

[0102] (XI ) dissolving a metal alkoxide in solvent 1 , preferably said solvent 1 is dry or water-free solvent to form a metal alkoxide solution;

[0103] (X2) optionally dissolving an acid in solvent 2, preferably said solvent 2 is dry or water-free solvent, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids to form an acid solution;

[0104] (X3) optionally adding said acid solution obtained in step (X2) to the metal alkoxide solution obtained in step (X1 );

[0105] (X4) mixing water and solvent 3 to form an aqueous solvent; and

[0106] (X5) adding said aqueous solvent to the alkoxide solution obtained in step (X1 ) or the metal alkoxide solution obtained in step (X3);

[0107] (X6) optionally dissolving an acid and water in solvent 4, preferably said solvent 4 is dry or water-free solvent, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids to form an acid solution to form an aqueous acid solution;

[0108] (X7) optionally adding said aqueous acid solution (X6) to the metal alkoxide solution (X1 ), wherein said solvents 1 to 4 are independent from each other, selected from one or more members of the group consisting of propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and / or propylene glycol monopropyl ether; glycerol 1 ,3-dialkyl ethers, 1 ,3-dimethoxy-2-propanol more preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3- dialkyl ethers, glycerol 1 ,3-dialkyl ethers or a mixture of any of them, wherein said solvents 1 to 4 (solvent 1 , solvent 2, solvent 3 and solvent 4) are independent from each other, selected from one or more members of the group consisting of propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and / or propylene glycol monopropyl ether; glycerol 1 ,3-dialkyl ethers, , 1 ,3-dimethoxy-2-propanol, more preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers , glycerol 1 ,3- dialkyl ethers or a mixture of any of them.

[0109] Preferably, said metal alkoxide is a metal alkoxide containing a group 4 and / or group 5 element of the periodic table as detailly described in the section of “metal alkoxide”.

[0110] Preferably, said acid selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids is an acid as described in the section of “Acid” above.

[0111] -Use

[0112] In another aspect, the present invention also relates to use of the formulation of the present invention for preparing an optical layer containing a metal oxide, preferably for preparing a composite, more preferably for preparing a layered composite.

[0113] -Method for preparing a composite containing a metal oxide

[0114] In another aspect, the present invention also relates to a method for preparing a composite containing a metal oxide, preferably said metal oxide is selected from metal dioxide, metal mono oxide, or a combination of these; comprising at least the following steps (a) and (b):

[0115] (a) providing the formulation of any one of claims 1 to 7 onto a surface of a substrate, preferably by wet deposition process, more preferably by spincoating or ink-jetting, even more preferably by ink-jetting; and

[0116] (b) applying a thermal treatment to the formulation provided on the surface of the substrate to convert at least a part of the metal alkoxide of the formulation to a metal oxide.

[0117] Preferably said composite being a layered composite, more preferably said layered composite is an optical layer.

[0118] -Step (a)

[0119] According to the present invention, said formulation may preferably be provided onto a surface of a substrate by wet deposition process. Said wet deposition process is drop casting, coating, or printing. A more preferred coating method is spin coating, spray coating, slit coating, or slot-die coating. A more preferred printing method is flexo printing, gravure printing, inkjet printing, EHD printing, offset printing, or screen printing. Furthermore preferred printing method is spray coating and inkjet printing and the most preferred one is inkjet printing.

[0120] Thus, in a preferred embodiment, the formulation is applied onto a surface of a substrate by spin-coating or ink-jetting in step (a). From a viewpoint of cost effective, ink-jetting can preferably be used. In a preferred embodiment of the present invention, the formulation provided in step (a) of the method is an ink formulation being suitable for inkjet printing. Typical requirements for ink formulations are surface tensions in the range from 20 mN / m to 30 mN / m and viscosities in the range from 5 mPa s to 30 mPa s.

[0121] Depending on the specific problem to be solved, the formulation needs to be deposited either as a homogeneous, dense and thin layer covering the entire surface of the substrate by a coating method or the formulation needs to be deposited locally in a structured manner, thus requiring a printing method. Both, coating and printing methods require formulations to be formulated in an adequate manner to comply with the physico-chemical needs of the respective coating and printing method as well as to comply with certain needs regarding the surface of the substrate to be coated or printed.

[0122] In a preferred embodiment of the method of the present invention, the surface of the substrate is pre-treated by a surface cleaning process. Preferred surface cleaning processes are silicon wafer cleaning processes such as described in W. Kern, The Evolution of Silicon Wafer Cleaning Technology, J. Electrochem. Soc., Vol. 137, 6, 1990, 1887-1892 and in New Process Technologies for Microelectronics, RCA Review 1970, 31 , 2, 185-454. Such silicon wafer cleaning processes include wet cleaning process involving cleaning solvents (e.g. isopropanol (IPA)); wet etching processes involving hydrogen peroxide solutions (e.g. piranha solution, SC1 , and SC2), choline solutions, or HF solutions; dry etching processes involving chemical vapor etching, UV / ozone treatments or glow discharge techniques (e.g. O2 plasma etching); and mechanical processes involving brush scrubbing, fluid jet or ultrasonic techniques (sonification). The surface of the substrate can also be pre-treated by silanization or an atomic layer deposition (ALD) process. The pre-treatment of the surface of the substrate serves to modify the hydrophobicity / hydrophi licity of the surface. This can improve the adhesion and filling characteristics of the optical metal oxide layer on the surface of the substrate.

[0123] In a more preferred embodiment, a wet cleaning process involving cleaning solvents (e.g. isopropanol (IPA)) is combined with one or more of a wet etching process involving hydrogen peroxide solutions (e.g. piranha solution, SC1 , and SC2), choline solutions, or HF solutions; dry etching process involving chemical vapor etching, UV / ozone treatments or glow discharge techniques (e.g. O2 plasma etching); and mechanical process involving brush scrubbing, fluid jet or ultrasonic techniques (sonification).

[0124] In a most preferred embodiment, a wet cleaning process involving cleaning solvents (e.g. isopropanol (IPA)) is combined with a mechanical process involving brush scrubbing, fluid jet or ultrasonic techniques (sonification) and with a wet etching process involving hydrogen peroxide solutions (e.g. piranha solution, SC1 , and SC2) or HF solutions;

[0125] Thus, in a preferable embodiment, in step (a), the formulation is applied to a surface of a substrate by spin-coating or ink-jetting.

[0126] In a preferable embodiment, the formulation is at least partly converted on the surface of the substrate to a composite, wherein said composite contains a metal oxide, preferably selected from metal dioxide and / or metal mono oxide; and a metal salt precursor.

[0127] In a preferable embodiment, the substrate is a patterned substrate comprising topographical features on the surface thereof.

[0128] -Step (b)

[0129] It is believed that metal alkoxide in the formulation is at least partly converted in step (b) on the surface of the substrate to a metal oxide to form a composite by exposure to thermal treatment. Said composite is preferably a layered composite. And said solvent is usually removed in step (b).

[0130] Preferred thermal treatment includes exposure to elevated temperature from 50 to 300 °C, preferably it is from 80 to 250°C, more preferably from 100 to 200°C.

[0131] Thermal treatment is not limited to any specific thermal treatment methods or times. Depending on the type of substrate and formulation, a person skilled in the art can determine suitable thermal treatment methods.

[0132] In some embodiments of the method for preparing an optical metal oxide layer according to the present invention, the formulation is converted in step (c) on the surface of the substrate to an optical metal oxide layer by prebaking (soft baking) at a temperature from 40 to 150 °C, preferably from 50 to 120 °C, more preferably from 60 to 100 °C; and then baking (hard baking, sintering or annealing) at a temperature from 100 to 600 °C, preferably from 125 to 450 °C, more preferably from 150 to 250 °C.

[0133] Pre-baking (soft baking) serves the purpose to remove volatile and low boiling components such as e.g. volatile and low boiling formulation media or additives from the drop casted, coated or printed films. Pre-baking is preferably carried out for a period of 1 to 10 minutes. After pre-baking, layers of substrate adhering films of metal oxide precursor or metal oxide precursor mixtures are obtained. The films may still comprise residual formulation media or additives.

[0134] In an alternative preferred embodiment of the method for preparing an optical metal oxide layer according to the present invention, pre-baking is omitted so that the formulation is converted in step (c) on the surface of the substrate to an optical metal oxide layer directly by baking (hard baking, sintering or annealing) at a temperature from 100 to 600 °C, preferably from 125 to 450 °C, more preferably from 150 to 250 °C.

[0135] Baking (hard baking, sintering or annealing) serves the purpose to convert the material as the metal oxide precursor or metal oxide precursor mixture layers on the substrate into a metal oxide layer. Moreover, the final properties of the metal oxide layer may be adjusted by the baking treatment. Baking is preferably carried out for a period of 1 to 300 minutes, preferably 1 to 60 minutes to achieve a refractive index (Rl) of > 1 .7, preferably > 1.8, more preferably > 1.9, even more preferably > 1.9, most preferably > 2.0.

[0136] Pre-baking and baking may be carried out under ambient atmosphere or atmospheres with increased oxygen content in order to decompose unwanted organic components, which can lead to a lower activation energy when the composite is formed.

[0137] In a preferred embodiment of the method of present invention, the substrate is a patterned substrate comprising topographical features on the surface thereof, and the layered composite, preferably it is an optical layer, forms a coating layer covering the surface of the substrate and filling said topographical features. As a result, the topographical features are filled and levelled by said composition.

[0138] Preferred topographical features include, for example, gaps, grooves, trenches and vias. Topographical features may be distributed uniformly or non-uniform ly over the surface of the substrate. Preferably, they are arranged as an array or grating on the surface of the substrate. It is preferred that the topographical features have different lengths, widths, diameters as well as different aspect ratios. It is preferred that said topographical features have an aspect ratio of 1 :20 to 20:1 , more preferably 1 :10 to 10:1 . The aspect ratio is defined as width of structure to its height (or depth). From the viewpoint of dimension, the depth of the topographical features is preferably in the range from 10 nm to 10 pm, more preferably 50 nm to 5 pm, and most preferably 100 nm to 1 pm.

[0139] It is also preferred that the topographical features are inclined at a certain angle, such as an angle from 10 to 80°, preferably from 20 to 60°, more preferably from 30 to 50°, most preferably about 40°. Such inclined topographical features are also referred to as slanted or blazed topographical features.

[0140] It may also be necessary to fill topographical features locally with optical metal oxide layer, either completely or to a certain level, but not to cover adjacent surfaces of the substrate, where no topographical features to be filled are available.

[0141] The substrate is preferably a substrate of an optical device. Preferred substrates are made of inorganic or organic base materials, preferably inorganic base materials. Preferred inorganic base materials contain materials selected from the list consisting of ceramics, glass, fused silica, sapphire, silicon, silicon nitride, quartz, and transparent polymers or resins. The geometry of the substrate is not specifically limited, however, preferred are sheets or wafers.

[0142] In step (a) of the method, the formulation is applied onto a surface of a substrate, wherein said surface may be either a surface of a base material of the substrate or a surface of a layer of a material being different from the base material of the substrate, wherein such layer has been formed prior to applying said formulation.

[0143] In this way, sequences of different layers (layer stacks) can be formed on top of one another. Such layer stacks may also be structured, wherein such structures typically have dimensions in the nanometer scale, at least with respect to diameter, width and / or aspect ratio.

[0144] Thus, in a preferable embodiment, in step (b), the formulation is at least partly converted on the surface of the substrate to a composite, preferably it being a layered composite, by baking it at a temperature from 100 to 600 °C, preferably it is from 125 to 450°C, more preferably from 150 to 250°C.

[0145] - Composite

[0146] In another aspect, the present invention relates to a composite, preferably being a layered composite, preferably said layered composite is an optical layer, obtained or obtainable by the method of the present invention.

[0147] In a preferred embodiment of the present invention, the composite comprises at least a metal oxide derived from the formulation and the metal alkoxide of the formulation as a non-converted part of the formulation used in step (a) of the method.

[0148] Thus, preferably said metal of the metal oxide is Ti or Zr. More preferably said metal oxide is selected from the group consisting of Titanium oxide, Zirconium oxide or a combination of these.

[0149] - Optical device

[0150] The present invention relates to an optical device comprising the composite of the present invention, which is preferably obtainable or obtained by the method of the present invention as described above. It is preferred that the optical device is a waveguide for display device selected from an augmented reality (AR) device, virtual reality (VR) device and / or Mixed Reality (MR) device. Preferably said composite fills gap of said topographical features, more preferably said composite fills trench of the patterned substrate. The present invention further relates to an optical device comprising the composite of the present invention, which is prepared by using the formulation according to the present invention as described above. It is preferred that the optical device is a waveguide for an augmented reality (AR) and / or virtual reality (VR) device. Preferably said composite fills gap of said topographical features, more preferably said composite fills trench of the patterned substrate.

[0151] - Display device

[0152] Finally, the present invention relates to display device comprising at least one functional medium configured to modulate a light or configured to emit light; and the composite, or an optical device of the present invention.

[0153] Examples of said display device is selected from a Liquid crystal display (LCD), Light emitting diode display (LED display), organic light emitting display (OLED), micro-LED display, quantum dot display (QLED), Augmented Reality (AR) hardware, Virtual Reality (VR) hardware, Mixed Reality (MR) hardware, plasma (PDP) display and an electroluminescent (ELD) display. Said AR, VR and MR hardware are also called as AR, VR and MR display. Preferably said display device is AR hardware, VR hardware or MR hardware.

[0154] The present invention is further illustrated by the examples following hereinafter which shall in no way be construed as limiting. The skilled person will acknowledge that various modifications, additions and alternations may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims.

[0155] Examples

[0156] Reference example 1 : Ti butoxide (Ti(Obu)4) containing formulation Ti(Obu)4 is added to PGME (1 -methoxy-2-propanol) under argon atmosphere in two neck Schlenk flask connected to inert gas / vacuum line. The solution is stirred at room temperature and a solution of H2O in dry PGME is added dropwise at room temperature, affording a clear solution that is stirred for another 60 mins. While the solvent and amounts of starting materials are varied, mass concentration of metal alkoxide starting material is not changed. Finally Formulation 0 is obtained.

[0157] The mixing ratio is mentioned in below table 1 .

[0158] Table 1

[0159] (Total: 100wt%)

[0160] Working example 1 : Ti butoxide (Ti(Obu)4) and MSA containing formulation

[0161] Ti(Obu)4 is added to PGME (1-methoxy-2-propanol) under argon atmosphere in two neck Schlenk flask connected to inert gas / vacuum line. The solution is stirred at room temperature. Then a solution of H2O and methane sulfonic acid (MSA) in dry PGME is added dropwise at room temperature, affording a clear solution that is stirred for another 60 mins. While the solvent and amounts of starting materials are varied, mass concentration of metal alkoxide starting material is not changed. Finally Formulation 0 is obtained. Finally, formulation 1 is obtained.

[0162] The mixing ratio is indicated in below table 2.

[0163] Working examples 2-16: preparation of formulations

[0164] Formulations 2 to 16 are prepared in the same manner as described in working example 1 except for that the ingredients (raw materials) described in table 2 are used instead of the ingredients (raw materials) used in working example 1 . Table 2: ton

[0165] Reference example 2A: preparation of Sample 0 (50nm, 150 °C) Formulation 0 from reference example 1 is spin coated onto an O2 plasma pretreated SisN4 / Si substrate having 50nm width trenches to form a spin coated layer. Then the coated layer is baked at 150°C for 5m in. Finally Sample 0 (50nm, 150 °C) is obtained. The obtained sample is observed by TEM analysis.

[0166] Reference example 2B: preparation of Sample 0 (150nm, 150 °C)

[0167] Sample 0 (150nm, 150 °C) is obtained in the same manner as described in reference example 2A except for that an O2 plasma pretreated SisN4 / S i substrate having 150nm width trenches is used instead of the SisN4 / Si substrate having 50nm width trenches. The obtained sample 0 (150nm, 150 °C) is observed by TEM analysis.

[0168] Working example 17: preparation of Sample 1 (50nm, 100°C) and Sample 1 (150nm, 100°C)

[0169] Formulation 1 from working example 1 (W.E.1 ) is spin coated onto an O2 plasma pretreated SisN4 / Si substrate having 50nm width trenches on the surface. Then the coated layer is baked at 100°C for 5min. Formulation 1 is also spin coated onto an O2 plasma pretreated SisN4 / Si substrate having 150nm width trenches on the surface and it is baked at 100°C for 5m in. Finally, Sample 1 (50nm, 100°C) and Sample 1 (150nm, 100°C) are obtained. The obtained samples are observed by TEM analysis.

[0170] Working example 18: preparation of Sample 1 (50nm, 200°C) and Sample

[0171] 1 (150nm, 200°C)

[0172] Sample 1 (50nm, 200°C) and Sample 1 (150nm, 200°C) are obtained in the same manner as described in Working example 17 except for that baking 200°C for 5m in is applied to the coated layer. The obtained samples are observed by TEM analysis.

[0173] Working example 19: preparation of Sample 2 (50nm, 100°C) and Sample

[0174] 2 (150nm, 100°C)

[0175] Sample 2 (50nm, 100°C) and Sample 2 (150nm, 100°C) are prepared in the same manner as described in working example 17 except for that the Formulation 2 is used instead of Formulation 1. The obtained samples are observed by TEM analysis.

[0176] Working example 20: preparation of Sample 2 (50nm, 200°C) and Sample 2 (150nm, 200°C)

[0177] Sample 2 (50nm, 200°C) and Sample 2 (150nm, 200°C) are prepared in the same manner as described in working example 17 except for that the Formulation 2 is used instead of Formulation 1 and the baking temperature 200°C for 5min is applied instead of 100°C for 5min. The obtained samples are observed by TEM analysis.

[0178] Working examples 21-23: preparation of Samples 3-5 (150nm, 100°C) Samples 3-5 (150nm, 100°C) are prepared in the same manner as described in working example 17 except for that the Formulations 3-5 are used instead of Formulation 1.

[0179] Working examples 24-26: preparation of Samples 3-5 (150nm, 200°C) Samples 3-5 (150nm, 200°C) are prepared in the same manner as described in working example 17 except for that the Formulations 3-5 are used instead of Formulation 1 and the baking temperature at 200°C for 5min is applied instead of 100°C for 5min.

[0180] Working examples 27-37: preparation of Samples 6 -16 (50nm, 100°C) and Samples 6-16 (100nm, 100°C)

[0181] Samples 6 -16 (50nm, 100°C) and Samples 6-16 (100nm, 100°C) are prepared in the same manner as described in working example 17 except for that the Formulations 6-16 are used instead of Formulation 1 . The obtained samples are observed by TEM analysis.

[0182] Working examples 38-48: preparation of Samples 6 -16 (50nm, 200°C) and Samples 6-16 (100nm, 200°C)

[0183] Samples 6 -16 (50nm, 200°C) and Samples 6-16 (100nm, 200°C) are prepared in the same manner as described in working example 17 except for that the Formulations 6-16 are used instead of Formulation 1 and baking temperature 200°C for 5min is applied instead of 100°C for 5min. The obtained samples are observed by TEM analysis.

[0184] The following tables show the results of the TEM analysis.

[0185] “Not Filled” means that trenches are not coated or only very partly coated. Namely, the middle - bottom side inside walls of trenches are not coated.

[0186] “Partly Filled” means at least whole or part of middle - bottom side inside walls of trenches are coated but still big void(s) or many voids in the trenches in a vertical direction.

[0187] “Well Filled” means all voids of the trenches are around 80-100% filled and there is no big void(s) can be observed in the filled trenches.

[0188] “Filled” is in between “Partly Filled” and “Well Filled”.

Claims

Claims1 . Formulation for preparing an optical layer containing a metal oxide, preferably for preparing a composite, more preferably for preparing a layered composite, comprising at least; a metal alkoxide, preferably said metal alkoxide contains a group 4 and / or group 5 element of the periodic table; and an acid selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids.

2. Formulation of claim 1 , said sulfonic acid is represented by following chemical formula (I).Ra1SO3H - (I) whereinRa1is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2;where each of groups may be substituted by one or more groups Rax;Raxis at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents Raxhere may optionally form a mono- or polycyclic, aliphatic ring system with one another; said amine hydrochloride is represented by following chemical formula (II) HCI - Ra2- (II) whereinRa2is selected from the group consisting of N2H4, ammonia, hydroxylamine, imidazole and 1 ,4-diazabicyclo[2.2.2]octane; and / or said carboxylic acid is represented by following chemical formula (III) Ra3- COOH whereinRa3is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3-25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups Rax;Raxis at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents Raxhere may optionally form a mono- or polycyclic, aliphatic ring system with one another3. Formulation of claim 1 or 2, wherein the stoichiometric mole ratio of the acid and the metal alkoxide is in the range from 0.1 : 100 to 120: 100,preferably from 0.5:100 to 100:100, more preferably the relative mole amount of the acid based on the total amount of the metal alkoxide is in the range from 1 : 100 to 50: 100, furthermore preferably 2: 100 to 10: 100.

4. Formulation of any one of preceding claims, wherein said metal alkoxide is represented by following chemical formula (IV) or formula (V):Mb1O4(Rb1Rb2Rb3Rb4) -(IV)Mb20s(Rb1Rb2Rb3Rb4Rb5) -(V) wherein Mb1is a tetravalent metal of a group 4 element of the periodic table, preferably it is Ti, Zr or Hf;Mb2is a pentavalent metal of a group 5 element of the periodic table, preferably it is Nb or Ta;Rb1, Rb2, Rb3, Rb4and Rb5are each independently selected from H, D, a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3-25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, where each of groups may be substituted by one or more groups Ra;Rais at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents Rahere may optionally form a mono- or polycyclic, aliphatic ring system with one another.

5. Formulation of any one of preceding claims, contains a solvent selected from acidic water having hydrogen ion index (pH) below 7 and 1 or more, preferably 1 ^pH<7, or an organic solvent or a mixture of water and one more of organic solvents. Preferably the formulation contains water and one or more organic solvents. More preferably, the formulation contains water and one or more organic solvents selected from one or more members of the group consisting of ethylene glycol monoalkyl ethers, preferably it is ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether and / or ethylene glycol monobutyl ether; diethylene glycol dialkyl ethers, preferably it is diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether and / or diethylene glycol dibutyl ether; propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and / or propylene glycol monopropyl ether; 1,3- dimethoxy-2-propanol, ethylene glycol alkyl ether acetates, preferably it is methyl cellosolve acetate and / or ethyl cellosolve acetate; propylene glycolalkyl ether acetates, preferably it is propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate and / or propylene glycol monopropyl ether acetate; ketones, preferably it is methyl ethyl ketone, acetone, methyl amyl ketone, methyl isobutyl ketone and / or cyclohexanone; alcohols, preferably it is ethanol, propanol, butanol, hexanol, cyclo hexanol, ethylene glycol, propylene glycol, triethylene glycol and / or glycerin; esters, preferably it is ethyl 3-ethoxypropionate, methyl 3- methoxypropionate and / or ethyl lactate; and cyclic esters, preferably it is gamma-butyro-lactone; preferably said solvent is ethylene glycol monoalkyl ethers, diethylene glycol dialkyl ethers, propylene glycol, ethylene glycol, propylene glycol monoalkyl ethers, ethylene glycol alkyl ether acetates, propylene glycol alkyl ether acetate, more preferably said solvent is selected from propylene glycol alkyl ether acetates, ethylene glycol monoalkyl ethers, propylene glycol and propylene glycol monoalkyl ethers, 1 ,3-dimethoxy-2-propanol.

6. Formulation of any one of preceding claims, wherein said acid is a sulfonic acid represented by following chemical formula (I).Ra1SO3H - (I) whereinRa1is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbonatoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups Rax;Raxis at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents Raxhere may optionally form a mono- or polycyclic, aliphatic ring system with one another.

7. Formulation of any one of preceding claims, wherein the acid is an amine hydrochloride represented by following chemical formula (II) HCI - Ra2- (II) whereinRa2is selected from the group consisting of N2H4, ammonia, hydroxylamine, imidazole and 1 ,4-diazabicyclo[2.2.2]octane;8. Method for preparing a formulation of any one of the preceding claims, containing at least the following step;(X) mixing a metal alkoxide, preferably said metal alkoxide contains a group 4 and / or group 5 element of the periodic table; and an acid selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids.Optionally, a solvent selected from water, preferably acidic water having hydrogen ion index (pH) below 7 and 1 or more, preferably 1 ^pH<7, an organic solvent or a mixture of said water and one more organic solvent, is also mixed in step (X).

9. Method for preparing a composite containing a metal oxide, preferably said metal oxide is selected from metal dioxide, metal mono oxide, or a combination of these; comprising the following steps (a) and (b):(a) providing the formulation of any one of claims 1 to 7 onto a surface of a substrate, preferably by wet deposition process, more preferably by spincoating or ink-jetting, even more preferably by ink-jetting; and(b) applying a thermal treatment to the formulation provided on the surface of the substrate to convert at least a part of the metal alkoxide of the formulation to a metal oxide.Preferably said composite being a layered composite, more preferably said layered composite is an optical layer.

10. Method according to claim 9, wherein in step (b), the formulation is at least partly converted on the surface of the substrate to a composite, preferably it is being of a layered composite, by baking it at a temperature from 100 to 600 °C, preferably it is from 125 to 450°C, more preferably from 150 to 250°C.11 . Method of claim 9 or 10, wherein the formulation is at least partly converted on the surface of the substrate to a composite, wherein saidcomposite contains a metal oxide, preferably selected from metal dioxide and / or metal mono oxide; and a metal alkoxide.

12. Method according to any one of claims 9 to 11 , wherein the substrate is a patterned substrate comprising topographical features on the surface thereof.

13. A composite, preferably being a layered composite, preferably said layered composite is an optical layer, derived from the formulation of any one of claims 1 to 7.

14. An optical device comprising the composite of claim 13, and a substrate comprising a patterned surface or an uneven surface. Preferably a gap or trench of said patterned surface or an uneven surface of the substrate is at least partly filled with said composite.Preferably said substrate is a patterned substrate comprising topographical features on the surface thereof. Preferably said composite fills at least a part of a gap of said topographical features, more preferably said composite fills a trench of the patterned substrate.

15. A display device comprising at least one functional medium configured to direct and modulate a light or configured to emit light; and the composite of claim 13, or an optical device of claim 14.

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