Transparent composite material, transparent article, and method for producing composite material and transparent article

Abstract

A bendable transparent cover sheet (1) element having an optically uniform appearance is provided by introducing an optically invisible or at least nearly invisible transparent composite material (9), the transparent composite material (9) comprising a polymer matrix (13) with dispersed inorganic particles (15, 17), where the polymer matrix (13) comprises at least one elastomer, and where the composite material (9) comprises lt; 20% by volume of inorganic particles (15, 17) wherein the Abbe value of the composite material (9) is d, comp is gt; 35, and wherein for the difference between the refractive index nd, glass of the glass (4) as the first material and the refractive index nd, comp of the composite material (9) as the second material, the condition nd, glass ()-nd, comp () > lt; 0.02 is effective at each wavelength () in the wavelength range of 400 nm to 800 nm.

Description

Technical Field

[0001] In general, the present invention relates to a transparent elastic filler material, its use in flexible transparent articles, and a method for producing said transparent composite material. Specifically, the present invention relates to a transparent flexible article formed by incorporating a transparent flexible composite material into a portion of an inorganic brittle material, wherein said transparent flexible composite material is optically invisible or at least nearly invisible. Background Technology

[0002] For display applications, flexible glass is of interest. One possibility for making glass flexible is to reduce its thickness. However, this also reduces its impact resistance. This reduced strength can be compensated for by a sandwich design that combines two or more thin glass layers and polymer elements. However, sandwich structures may have other drawbacks, such as a tendency to delaminate or reduced light transmission due to the increased number of interfaces with refractive index steps.

[0003] EP 3 936 485 A1 or US 2022002185 A1 describes relatively thick glass elements with a thickness of 1 mm or more, which can be bent by structuring the glass along a bend line. The structuring of the glass results in a reduction in glass thickness along the bend line, thereby enabling the glass to bend. Apart from the bend line, the glass exhibits a greater thickness. Therefore, the glass can be bent while maintaining its impact resistance. However, due to the varying glass thickness, the structured area along the bend line is clearly visible, thus reducing the usable display area.

[0004] By filling the flexible structure of the inorganic brittle material with an elastic filler material that has matching optical properties, the optically homogeneous appearance of the flexible structure (which includes structured regions in the inorganic material) can be reduced, thereby producing an optically homogeneous appearance of the flexible structure.

[0005] WO 2021 / 07643 A1 discloses a foldable display made of glass, wherein the display includes a polymer-based portion. The polymer-based portion comprises a polymer with high light transmittance and low haze. To reduce the visibility of the polymer-based portion, the refractive index n of the polymer is... d Adjusting the refractive index to that of the glass. However, the visibility of polymer-based portions can depend on the viewing angle and the wavelength of the light. Summary of the Invention

[0006] Purpose of the invention Therefore, one object of the present invention is to provide a highly flexible transparent material as an elastic filler for inorganic brittle materials (such as glass), wherein the optical properties are matched to those of the inorganic brittle material across the entire visible light spectrum. Another object of the present invention is to provide a transparent, bendable article with a uniform optical appearance. Yet another object of the present invention is to provide a method for producing such a filler material.

[0007] illustrate The above-mentioned objectives of the invention are achieved through the technical subject matter of the independent claims. Preferred embodiments and variations are the technical subject matter of the dependent claims.

[0008] By filling the flexible structure of the inorganic brittle material with an elastic filler material, it is possible to reduce the optically uniform appearance of the flexible structure (which includes structured regions in the inorganic material). The elastic filler material has matching optical properties across the entire visible wavelength range, i.e., between 400 nm and 800 nm, thereby producing an optically uniform appearance of the flexible structure.

[0009] Therefore, one aspect of the present invention relates to a transparent, elastic filler material whose optical properties match those of an inorganic brittle material across the entire visible light spectrum. It is therefore necessary that the optical dispersion of the filler material matches that of the inorganic brittle material. To achieve this, the inorganic brittle material and the elastic filler material should have matching refractive indices and matching Abbe values. A typical inorganic brittle material is glass. Generally, glass exhibits Abbe values ​​between 20 (flint glass) and 60 (crown glass). In most cases, the Abbe value increases with the refractive index of the glass.

[0010] Transparent, elastic polymers with Abbe values ​​within a given range are described in the prior art. However, these polymers exhibit typical diffraction indices that are much lower than those of typical inorganic brittle materials, such as glass used in flexible structures (e.g., cover glass).

[0011] To overcome this problem, the present invention relates to a transparent composite material comprising a transparent polymer matrix having dispersed inorganic particles. The polymer matrix includes at least one elastomer. The transparent polymer matrix has a refractive index n. d，poly And Abe's value d，poly Compared to other polymers, the refractive index n of the polymer is... d，poly It is already relatively high, and preferably greater than 1.45. According to one embodiment, the refractive index n... d，polyThe value is in the range between 1.47 and 1.51. Furthermore, the polymer matrix exhibits a relatively high Abbe value; preferably, the Abbe value is... d，poly The refractive index is >35, preferably >40. The dispersed inorganic particles exhibit a refractive index n d，part And Abe's value d，part Preferably, the refractive index n of the inorganic particles is... d，part The refractive index n is higher than that of the polymer matrix. d，poly According to one embodiment, the refractive index n of the composite material d，comp Between the refractive indices of polymer matrices and inorganic particles: n d, poly < n d, comp < n d, part .

[0012] By having a relatively high Abbe value d，poly The polymer matrix with high refractive index n d，part By combining inorganic particles, composite materials with high refractive index and high Abbe value can be obtained.

[0013] Abbe value of composite materials d，comp It is > 35, and the refractive index n d，comp The Abbe value is in the range of 1.4 to 1.7, preferably in the range of 1.45 to 1.7. In one embodiment, the Abbe value of the composite material is... d，comp Yes > 50.

[0014] According to one embodiment, the Abbe value of the composite material d，comp Within the range of 35 to 100. Preferably, the Abbe value is... d，comp It is >50 and / or <100. By changing the amount and composition of the dispersed inorganic particles, and by changing the chemical composition of the polymer matrix, the optical properties of the composite material can be tuned to match a wide range of different glass or inorganic brittle materials in general.

[0015] The content of inorganic particles in the composite material is < 20% by volume. This content can adjust the refractive index n of the composite material. comp And Abe's value d，comp This achieves uniform dispersion of inorganic particles in the polymer matrix.

[0016] The elastic polymer matrix ensures that the composite material has sufficient flexibility, allowing for, for example, bending of the polymer matrix. Therefore, the composite material is flexible and, according to DIN ISO 527, its Young's modulus is < 5 MPa, preferably < 3 MPa, more preferably < 1 MPa. The flexibility of the composite material can be tuned by the composition and degree of polymerization and / or degree of crosslinking of the polymer matrix. Polymers having monomer units (which exhibit large-volume substituents, such as norborneol substituents) can be advantageous. Furthermore, the polymer matrix exhibits a degree of crosslinking, which allows for sufficient covalent bonding between individual polymer chains without limiting the flexibility of the polymer matrix under stress. Thus, according to one embodiment, the polymer matrix contains between 50% and 100% crosslinking groups or crosslinking compounds.

[0017] A low Young's modulus enables the composite material to be used in flexible devices and achieve a small bending radius. According to one embodiment, the Young's modulus of the composite material is between 0.5 and 5 MPa, preferably between 0.5 and 3 MPa, and more preferably between 0.5 and 2 MPa. In one embodiment, the composite material exhibits a relatively high Young's modulus of at least 1 MPa or even at least 2 MPa. This Young's modulus is relatively high compared to the Young's modulus of the corresponding polymer matrix without particles. Here, the particles not only provide optical functionality through increased refractive index but also further enhance the mechanical properties of the composite material. A Young's modulus of at least 1 MPa, preferably at least 2 MPa, ensures that the composite material is stiff enough to be used as a filler material to fill large cavities in devices made of inorganic brittle materials without reducing the mechanical stability of the device.

[0018] Furthermore, compared to a pure polymer matrix, the inorganic particles enhance the mechanical durability of the composite material. Therefore, the composite material possesses sufficient mechanical durability for use as a filler material, for example, in cover glass. According to one embodiment, the Shore hardness of the composite material is < 70, more preferably < 50, and most preferably < 30. In this specification, Shore hardness refers to Shore hardness A measured according to DIN EN ISO 868.

[0019] According to one embodiment, the Shore hardness is in the range of 10 to 70, preferably between 10 and 60. Preferably, the composite material exhibits a Shore hardness of at least 20, more preferably at least 25, and simultaneously exhibits a Young's modulus of < 5 MPa or even < 3 MPa. This is noteworthy because high Shore hardness generally corresponds to high Young's modulus. Meanwhile, the composite material is flexible, and its elongation at break, measured according to DIN EN ISO 527, can be greater than 100%, preferably greater than 200%, more preferably greater than 300%.

[0020] In the composite material according to the invention, the embedded inorganic particles enhance mechanical stability, thereby increasing Shore hardness, while the composite material exhibits sufficient flexibility. Higher Shore hardness can be achieved by increasing the amount of inorganic particles in the composite material.

[0021] Preferably, the composite material comprises >15% by volume, more preferably >10% by volume, inorganic particles. According to one embodiment, the particle content in the composite material is in the range of 1-20% by volume, preferably 1-15% by volume, more preferably 1-10% by volume, and / or the amount of polymer is in the range of 50-99% by volume, preferably 80-99% by volume. The content of inorganic particles is sufficiently large to allow for a sufficient influence on the refractive index and / or Abbe value of the composite material. Simultaneously, limiting the inorganic particle content to no more than 20% by volume and the small particle size of the inorganic particles allow for uniform dispersion of the inorganic particles within the polymer matrix. This ensures that the transparency of the polymer matrix is ​​not reduced or only minimally reduced by the inorganic particles.

[0022] Furthermore, since the inorganic particles are uniformly dispersed within the polymer matrix, the composite material can be considered a single material. This allows for calculations based on the Bruggemann effective medium model to obtain a composite material with a predetermined refractive index n. d，comp The required amount of inorganic particles in the composite material: ,in And m≥1.

[0023] The volume fraction of the polymer in the composite material is f polymer The volume fraction of the particles is f i The refractive index of the polymer is n polymer The refractive index of the particles is n part According to one embodiment, the refractive index n of the composite material 400nm-800nm, comp It is in the range of 1.4 to 1.7, preferably 1.45 to 1.7.

[0024] The relationship between refractive index and wavelength, i.e., the dispersion of light in a medium, can be determined using the Selmeyer equation. , Where n is the refractive index, λ is the wavelength, and B i and C i These are Selmayer coefficients determined experimentally. These coefficients are typically referenced in terms of λ, measured in micrometers. λ is the wavelength in vacuum, not the wavelength λ / n within the material itself.

[0025] In a preferred embodiment, the refractive index n of the inorganic particles d，part> 1.6, more preferably > 1.7, most preferably > 1.8. The inorganic particles are preferably oxides or nitrides, and are more preferably selected from ZrO2, TiO2, carbon (diamond structure), Al2O3 (α and γ phases), ITO (indium tin oxide) and / or SiN.

[0026] According to one embodiment, the composite material may comprise a mixture of different inorganic particles. By applying the mixture of different inorganic particles to a polymer matrix, the Abbe value of the composite material can be precisely adjusted. According to an improvement, the composite material comprises at least a first type of inorganic particles and a second type of inorganic particles, which differ in terms of composition, refractive index, and / or Abbe value. In a preferred embodiment, the refractive index n of the first type of inorganic particles is... d，part1 The Abbe value is > 1.6, more preferably > 1.7, most preferably > 1.8, and / or the Abbe value of the second type of inorganic particles. d，part2 The value is >60, preferably >70, and more preferably >80. According to one embodiment, the first inorganic particle exhibits an Abbe value >60. d，part1 The value is < 40. Preferably, the first inorganic particle is TiO2 and / or ZrO2 particles, and the second inorganic particle is diamond particles and / or α-Al2O3 particles.

[0027] The inorganic particles have a sufficiently small particle size to suppress scattering effects. Preferably, the inorganic particles are nanoparticles. According to one embodiment, the diameter d of the inorganic particles is... 99 The inorganic particles are < 50 nm, preferably < 30 nm, and most preferably < 15 nm. According to one embodiment, the inorganic particles are nanoparticles, and / or may be monodisperse.

[0028] Furthermore, the composite material is transparent in the visible light range. Preferably, at a thickness of 100 μm, the light transmittance of the composite material, as measured according to ISO 15368, is > 50%, > 80%, or even > 85%, and / or the haze value of the composite material, as measured according to ASTM D 1003, is < 5% or < 1%.

[0029] According to one embodiment, the inorganic particles include organic functional groups on their surface. Preferably, the surface of the inorganic particles includes large-volume organic residues to stabilize the particles in the dispersion by preventing aggregation. Furthermore, the organic residues on the surface of the inorganic particles may include polymerizable groups, particularly polymerizable groups that can copolymerize with polymerizable groups of the polymer matrix. Therefore, it can achieve covalent bonding between the inorganic particles and the polymer matrix, resulting in enhanced mechanical stability of the composite material. According to one embodiment, the inorganic particles include organic residues having acrylic functional groups on their surface.

[0030] The composite material includes a polymer matrix comprising at least one elastomer. The polymer matrix can also be represented as an elastomer matrix. According to one embodiment, the polymer matrix comprises an elastomer having acrylate monomer units. The acrylate is radiation-curable and generally exhibits high transparency and a relatively high refractive index. The elasticity of the polyacrylate can also be affected by the substitution of the monomer units. Furthermore, the refractive index of the polymer matrix can be affected by specific substituents of the monomer units. Particularly advantageous are acrylate monomer units comprising: aryl-substituted acrylates, preferably substituted phenyl acrylates and / or acrylates having cyclic alkyl substituents, preferably norbornel-substituted and / or tetrahydrofurfuryl-substituted acrylates.

[0031] Other suitable monomer units for enhancing the refractive index are, for example, monomer units comprising carbazole, fluorine, phenyl or preferably substituted phenyl groups (e.g., o-phenylphenol), diphenylmethane, and / or diphenylamine substituents. The polymer matrix may also include other monomer units having high refractive index groups, either as an alternative to or in addition to the aforementioned monomer units. The polymer matrix may comprise different monomer units, such as blends and / or copolymers of different polymers. This allows for fine-tuning of desired mechanical and optical properties such as Young's modulus, refractive index, and Abbe value.

[0032] The refractive index n exhibited by the elastomer matrix d，poly It is > 1.4, preferably n d，poly The Abbe value is >1.5, which is high for polymers and within or near the refractive index range of glass. Preferably, the Abbe value of the elastomer is... d, poly Yes > 50, more preferably > 60.

[0033] According to one embodiment, the elastomer includes at least one monomer unit with the following structure: Wherein R1: alkoxy, preferably ethoxy; alkyl, preferably methyl or ethyl; thioalkyl; R2: H, alkyl, aryl, preferably phenol, phenyl.

[0034] Preferably, the elastomer comprises at least one monomer having a plurality of monomer units, preferably having two acrylate groups. Due to the plurality of acrylate groups, the monomer unit serves as a crosslinking unit. Crosslinking the polymer matrix enhances mechanical stability. Preferably, the elastomer comprises at least one monomer unit based on bisphenol A-ethoxylated acrylate.

[0035] The elastomer can be a homopolymer or a copolymer. The polymer matrix can be a copolymer comprising at least two different monomer units, and / or the polymer matrix can include at least one monomer unit having at least two polymerizable groups.

[0036] Furthermore, the composite material may include blends of at least two different elastomers. The properties of the composite material, such as refractive index and Abbe value, can be further tuned by using blends of different polymers or copolymers.

[0037] Composite materials can be provided through a production method that includes the following steps a) to d): In step a), a polymerizable formulation is provided, comprising a monomer, an oligomer, or a prepolymer. The oligomer comprises at least three monomer units, wherein the prepolymer may comprise up to 100, preferably up to 50, monomer units. Preferably, the monomer, oligomer, and / or prepolymer comprises monomer units having at least one acrylate functional group, which can be used in polymerization and / or curing reactions.

[0038] In step b), inorganic particles are provided and dispersed in a polymerizable formulation as provided in step a) to obtain a dispersion of uniformly distributed inorganic particles.

[0039] In step c), the dispersion may be filled into the cavity.

[0040] In step d), the formulation comprising dispersed inorganic particles is cured via a polymerization reaction of polymerizable groups.

[0041] Polymerization can be initiated by radiation, particularly UV radiation. Alternatively, polymerization can be thermally initiated. Step d) is preferably carried out under anaerobic conditions, more preferably under a nitrogen atmosphere. Alternatively or additionally, step b) is carried out under anaerobic conditions. Therefore, the dispersion is free of dissolved oxygen. The term "free of dissolved oxygen" defines an oxygen content of < 2000 ppm.

[0042] Because the polymerization reaction occurs under anaerobic conditions, the inhibition of oxygen free radicals and / or the reduction of free radical chain transfer result in a uniform degree of polymerization throughout the entire volume of the polymer matrix. Therefore, the obtained composite material exhibits no gradient in degree of polymerization, or at least only a very small gradient. Since the degree of polymerization affects the refractive index of the polymer matrix, a uniform degree of polymerization is necessary to obtain a polymer matrix with a uniform refractive index throughout the entire volume of the composite material. Furthermore, high degrees of polymerization can be achieved through polymerization under anaerobic conditions. Consequently, the obtained composite material contains almost no unreacted monomers, oligomers, or prepolymers, resulting in low surface viscosity.

[0043] Another aspect of the present invention is a transparent article comprising: an inorganic brittle material as a first material; and a composite material having a second material. Preferably, the first material is glass or glass-ceramic. In the transparent article, the first material and the second material form at least one interface. The first material is preferably a material having a refractive index n. d，glass Abbe value d，glass The glass or glass-ceramic. More preferably, the refractive index n of the glass or glass-ceramic. d，glass It is > 1.50 and / or Abbe value d，glass Yes > 40.

[0044] According to one embodiment, the transparent article has two opposing sides and a circumferential edge. With opposing sides and a lower edge, the device is typically flat or plate-like. The transparent article is preferably a cover element, such as a cover element for a display. According to one embodiment, the thickness d of the transparent article is <2000 μm, more preferably <1000 μm, or most preferably <500 μm, wherein the thickness d is defined as the distance between the side surfaces of the transparent article.

[0045] The second type of material is the one mentioned above that has a refractive index n. comp (λ) composite material. To obtain an optically uniform portion, scattering at the interface between the first and second materials, i.e., between the composite material and the inorganic brittle material, must be avoided. Therefore, to obtain a uniform optical appearance in the second portion, the optical properties of the second material, i.e., the composite material, must match the optical properties of the first material.

[0046] According to one embodiment, at wavelengths λ of 400 nm and / or 800 nm, preferably at each wavelength λ within a wavelength range between 400 nm and 800 nm, the refractive index nn of the first material is... glass(λ) and the refractive index n of the transparent composite material (9) as the second material comp The difference ∆ between (λ) n absolute value ∆n(λ) = |n glass ( ) – n comp ( )| The value is < 0.02, preferably < 0.01, more preferably < 0.008, and most preferably < 0.004. By interpolating the measurements at three wavelengths, the refractive index of the composite material for each wavelength can be calculated.

[0047] Preferably, the inorganic particles in the composite material, as the second material, have an Abbe value lower than that of the polymer matrix of the composite material and lower than that of the first material. d, glass d, part d, poly d, part Alternatively or additionally, the first material may have an Abbe value. d，glass Furthermore, composite materials can possess an Abbe value. d，comp The absolute value of the difference between Abbe values | d, glass - d, comp ǀ Preferably < 40, more preferably < 30, and most preferably < 25.

[0048] In composite materials used as a second material, the polymer matrix has a refractive index n. poly (λ), which is preferably less than the refractive index n of the glass, which is the first material. glass (λ). To match the refractive index of the glass material and the composite material, the composite material contains inorganic particles, which preferably have a higher refractive index than the first material.

[0049] Due to the optical properties of the second material, the refractive index n comp (λ) and Abbe value d，compThe optical properties of the first material can be adjusted to provide a transparent article that exhibits only small deviations in refractive index and Abbe value between the first and second materials (i.e., composite materials). Therefore, in the second part, the difference between the first and second materials of the transparent element is invisible or almost invisible.

[0050] The excellent mechanical properties of composite materials allow for the use of transparent products in cover elements, such as flexible displays or display covers.

[0051] In an improvement of the invention, the transparent article has at least two parts, preferably at least one first part and at least one second part. The first part comprises a first material and is cohesive to the second part. The second part comprises a first material and a second material, wherein the first material and the second material form at least one interface. Preferably, in the second part, the first material includes at least one opening on its surface. The opening may form a channel through the element, i.e., extending from one surface of the cover element to the opposite surface. According to one embodiment, the opening forms a blind hole. The opening is filled with a second material, wherein adhesion occurs between the first material and the second material.

[0052] According to an improvement of the invention, the cover element has at least two first portions and one second portion. The first portions are adjacent to the second portions, whereby the second portions are arranged between the first portions. Thus, the cover element can form a hinge.

[0053] In one embodiment, the first material in the second portion includes an opening arrangement terminating at two opposing sides, forming a channel through the element extending from one side surface of the cover element to the opposing side surface. Alternatively, in addition to the openings forming the channel through the cover element, at least some of the openings may not penetrate the first material in the second portion, thereby creating stud holes. In this case, the first material located below and adjacent to the stud hole has a thickness d1, where d1 <d。

[0054] The opening or hole comprises a closed composite material. The first material in the second part of the transparent article has a thickness d1, and the composite material has a thickness d2. Preferably, the total thickness of the composite material and the first material in the second part is equal to the thickness d of the first material in the first part. d = d1 + d2.

[0055] Thus, the second part has greater flexibility than the first part. According to one embodiment, the openings are preferably arranged in rows side-by-side. Adjacent openings within a row are separated by a first web, and openings in adjacent rows are separated by a second web. Furthermore, the first webs of adjacent rows are arranged offset from each other. In other words, the first webs are staggered row by row. In a preferred embodiment, the rows of openings are straight, or each includes at least one straight portion. Therefore, in this embodiment, the rows are narrow rows of side-by-side openings. In this way, the second part can form a hinge for the first part.

[0056] Typically, when a thin glass sheet is bent, the convex side experiences tensile stress. However, by introducing openings filled with a flexible composite material, the straight connection along the bending line is interrupted, and the bending moment is primarily transmitted through the webs. The first and second webs form a structure designed to resemble a joint in a brick structure. When the element bends, this staggered arrangement of the first web within the second web generates torsional stress. However, torsion exerts much lower tensile stress on the material compared to bending. Therefore, by at least partially absorbing the bending stress through the torsion of the webs, the total tensile stress can be reduced. In this way, the element can be bent easily without breaking.

[0057] To further enhance the mechanical stability of transparent products, the first material can be chemically strengthened glass. Chemical strengthening involves ion exchange in the surface layer. Here, by introducing larger cations into the glass, a compressive stress zone is established within the glass. However, ion exchange in the glass alters the chemical composition of the glass region or layer, thereby changing the refractive index n of the glass at the surface layer. glass，surface (λ). Therefore, chemically tempered glass can exhibit different refractive indices depending on the layer depth. The glass has a bulk portion, which has a uniform glass composition n. glass, bulk On the surface, glass has a refractive index n glass，surface (λ). Typically, when sodium ions are replaced by potassium ions, the refractive index in the glass surface layer increases, thereby leading to… n glass, bulk ( ) < n glass, surface ( ).

[0058] In order to provide a transparent article having an invisible interface between the composite material as the second material and the chemically tempered glass as the first material, the refractive index n of the composite material is... comp It must match the refractive index and Abbe value on the surface of the chemically tempered glass, and is less of a match with the refractive index of the bulk glass: ǀnglass, bulk ( ) – n comp ( )ǀ > ǀ n glass, surface ( ) – n comp ( )ǀ.

[0059] Therefore, a composite material is selected whose optical properties (i.e., refractive index and Abbe value) match those of the chemically tempered glass surface. Preferably, the difference between the two refractive indices is within the wavelength range of 400 nm to 800 nm. glass, surface ( ) – n comp ( The )ǀ is < 0.02, preferably < 0.01, < 0.008, < 0.004.

[0060] To reduce the two refractive indices n glass，surface (λ) and n comp The difference between (λ) and the present invention discloses a coating, preferably a coating having a barrier layer, which is applied at least to the interface region between the glass and the composite material.

[0061] Furthermore, at the interface between the glass and the composite material, the surface structure of the glass, as the first material, influences the optical appearance. According to one embodiment, the glass surface of the second portion includes microstructures, preferably aspherical mussel-shaped microstructures. The mussel-shaped microstructure can be the result of glass structuring or etching processes. However, when the cover element is illuminated at low scattering angles up to 10°, the aspherical mussel-shaped pattern can cause iridescent diffraction. This is particularly relevant when the cover element is illuminated from the back (e.g., in a display).

[0062] Transparent cover elements can be produced by a method that includes at least the following steps 1) to 4): 1) A structured thin glass is provided, wherein the glass comprises: at least one first portion having a thickness of d; and at least one second portion having at least one opening; 2) Provide a formulation for use in composite materials, 3) Apply the formulation from step 2) to the glass such that the opening of the thin glass in the second portion of the glass is filled with the formulation for the composite material. 4) The formulation is cured under anaerobic conditions to obtain the composite material in the opening of the second part.

[0063] Below, for reference Figures 1 to 6 The invention will be further described below. Attached Figure Description

[0064] Figure 1 The dependence of the refractive index of chemically tempered glass on glass depth is shown. Figure 2 This demonstrates the dependence of the refractive index on wavelength. Figure 3 The dependence of refractive index in one implementation method is shown. Figure 4 A cross-sectional schematic diagram of one embodiment is shown. Figure 5 A top view of cover element 1, made of a brittle material, is shown. Figure 6 A schematic diagram of composite material 9 according to one embodiment is shown. Detailed Implementation

[0065] Figure 1 The dependence of the refractive index of chemically tempered glass on glass depth is shown. The glass is chemically tempered glass with a thickness of 100 μm. The refractive index *n* is the average refractive index. The curve is shown as a parabola. For glass depths in the range of approximately 40–60 μm, i.e., in the middle of the glass, the curve reaches a stable period with the lowest refractive index. The refractive index is higher in the region near the surface and decreases with increasing glass depth. Here, the continuous decrease in refractive index is related to the change in glass composition caused by ion exchange. The refractive index at depths of 40–60 μm corresponds to the refractive index or *n* of the corresponding untempered glass. glass，bulk (λ). Figure 1 The effect of chemical hardening on the refractive index is clearly shown. Here, the refractive index within the glass can vary by more than 0.012. To obtain a uniform optical appearance for the cover element, the refractive index n on the glass surface is... glass，surface (λ) is the target value for the refractive index of the composite material. Here, the refractive index n of the glass surface is... glass，surface (λ) and refractive index n comp A difference of less than 0.02 or even less than 0.01 between (λ) is particularly advantageous to prevent scattering at the interface between the glass and the composite material.

[0066] Figure 2 The dependence of refractive index on wavelength is illustrated in an exemplary embodiment. Here, curve a) describes the refractive index of untempered glass, and therefore also corresponds to the refractive index n in the middle of tempered glass. glass，bulk (λ). Curve b) describes the refractive index curve n of the glass used in a) on the chemically tempered surface.glass，surface (λ). The shaded area c) corresponds to the particularly favorable maximum deviation of the refractive index between the glass and the composite material. If the deviation of the refractive index is larger, the optical uniformity of the element in this embodiment example cannot be guaranteed. From Figure 2 As can be clearly seen from this example implementation, the refractive index n of the glass... glass，bulk (λ) and n glass，surface The difference between (λ) is large enough that it leaves a shaded area c). Therefore, if the refractive index of the composite material is adjusted to the refractive index n on the tempered glass surface... glass，surface (λ) instead of the refractive index n of the main glass glass，bulk (λ) is advantageous.

[0067] exist Figure 3 The image shows the wavelength dependence of the refractive index in the first embodiment. (Compared to...) Figure 2 Similarly, curve a) refers to the refractive index of the untempered glass, b) refers to the refractive index on the surface of the tempered glass, and curve c) relates to the refractive index of the composite material. In this embodiment, the glass is an ultrathin borosilicate glass. The composite material comprises a polymer matrix containing acrylate monomer units. The inorganic particles comprise ZrO2 and exhibit acrylate functional groups on their surface. The formulation used for the composite material comprises 22.25 wt% isobornyl acrylate and 66.75 wt% tetrahydrofurfuryl acrylate to construct the polymer matrix. Both acrylate derivatives exhibit high Abbe values, and the resulting polymer matrix (which comprises a copolymer of the two derivatives) has good elasticity. Furthermore, the formulation comprises 1 wt% diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide to initiate the polymerization reaction. The inorganic particles are introduced into the formulation in the form of a dispersion of ZrO2 particles in ethanol (the content of inorganic particles is 50 wt%). The amount of the dispersion in the formulation is 10 wt%. The composite material of the first embodiment exhibits high elasticity and a Young's modulus of < 5 MPa. Simultaneously, the Abbe value of the composite material is... d，comp It is > 35, refractive index n d，comp It is in the range of 1.49 to 1.53.

[0068] Figure 4 A schematic cross-sectional view of a cover element 1 according to another embodiment is shown. The cover element 1 is formed as a thin glass 4 having side surfaces 3 and 5, and here, it has a first portion 101 and a second portion 102. The first portion 101 comprises a first material, while the second portion 102 comprises the first material and a composite material 9 as a second material. In the illustrated embodiment, the first material is glass 4, which is preferably easily structurable to introduce an opening 7 in the second portion 102.

[0069] According to a first embodiment of this composition, the glass 4 of the cover element 1 comprises the following components by weight percent:

[0070] According to the second embodiment, the glass composition of the cover element 1 includes the following components by weight percent:

[0071] According to the third embodiment, the glass composition of the cover element 1 is substantially free of alkali metal oxides. The glass comprises the following components by weight percent:

[0072] Preferably, in the composition of glass 4, the total content of MgO, CaO and BaO is in the range of 8 to 18% by weight.

[0073] In the fourth embodiment, the glass composition comprises the following components by weight percent:

[0074] In addition, glass 4 may contain 0 to 1% by weight of P2O5, SrO, BaO; and 0 to 1% by weight of a clarifying agent, preferably SnO2, CeO2 or As2O3.

[0075] In the fifth embodiment, the glass composition includes the following components by weight percent:

[0076] In addition, glass 4 may contain 0 to 1% by weight of P2O5, SrO, BaO, Fe2O3, HfO2; and 0 to 1% by weight of clarifying agent, preferably SnO2, CeO2 or As2O3.

[0077] In the second part 102, the cover element 1 has two openings 7. Here, opening 70 extends across the entire thickness of the glass 4, penetrating both side surfaces 3, 5. Opening 71 is a blind hole or stud hole. Here, opening 71 extends only over a portion of the glass thickness, so that the opening does not penetrate the opposing side surface 5. Both openings 70 and 71 are filled with composite material 9. Preferably, the surface of composite material 9 is close to the side surface 3 of the glass 4.

[0078] Preferably, the glass is chemically toughened to enhance its mechanical strength. Chemical toughening involves ion exchange within the glass 4, which is a brittle material. Ions in the glass undergo larger ion exchange in regions adjacent to the surface of the glass 4, resulting in larger ions exerting compressive stress on the glass 4. Typically, alkali metal ions are exchanged to influence the toughening. Therefore, the glasses listed above are suitable for chemical toughening, provided they contain a sufficient amount of alkali metal ions.

[0079] According to one embodiment, the glass 4 forming the sidewalls of the openings 70, 71 is coated with a coating, preferably a barrier coating. Figure 3 (Not shown in the image). Here, the coating preferably acts as a barrier layer and prevents or reduces ion exchange during the chemical tempering of glass 4. This hinders the binding of foreign ions into the sidewalls of openings 70, 71, and thus hinders the reduction of refractive index n. glass，surface The increase of (λ) makes it easier for the refractive index of composite material 9 to adapt to the refractive index n. glass，surface (λ). Furthermore, the refractive index n at the center of the glass is reduced. glass，bulk The difference between (λ) and the refractive index on the glass surface in openings 70 and 71.

[0080] The following method, including steps 1) to 4), can be used to produce Figure 4 The cover element 1 shown is shown.

[0081] In step 1), a structured thin glass 4 is provided, comprising at least one first portion 101 and a second portion 102. The structured thin glass 4 preferably has a thickness d < 200 μm. Preferably, the thin glass 4 is structured by a fila-etch process and / or by chemical tempering. In the second portion 102, the glass 4 provides at least one opening 7, preferably multiple openings 7. The openings 7 can be formed as stud holes 71, or they can serve as channels 70 penetrating the glass from one surface to another.

[0082] In step 2), a formulation is provided comprising monomers, oligomers and / or prepolymers, and inorganic particles 15, 17. The proportion of inorganic particles 15, 17 is < 20% by volume. The monomers, oligomers and / or prepolymers contain at least one polymeric group, preferably an acrylic group. It has been found particularly advantageous to use monomers, oligomers and / or prepolymers having at least one phenylacrylic acid monomer unit. According to an advantageous embodiment, the formulation comprises a photoinitiator. The amount of oxygen in the formulation is preferably < 0.2% by weight.

[0083] In step 3), the opening 7 in the second region is filled with the formulation provided in step 2). Preferably, the opening 7 is filled at least to the extent that the surface of the formulation in the opening is flush with the glass surface. After filling the opening 7 of the glass with the formulation, a polymerization reaction of polymerizable functional groups is initiated in step 4), causing the formulation to solidify. Initiation can be achieved by heat, or preferably by irradiation with electromagnetic radiation, particularly preferably by irradiation with UV light. Preferably, the polymerization reaction is carried out under anaerobic conditions or at least in an atmosphere with low oxygen content. Due to the low oxygen content in the atmosphere and / or the formulation, chain termination reactions and free radical transfer caused by oxygen free radicals are significantly reduced. Therefore, a composite material 9 is obtained in the opening 7, which comprises a matrix constructed of an elastomer with inorganic particles dispersed in the matrix. The polymerization in the opening 7 also ensures good adhesion of the composite material 9 to the glass wall. Thus, the composite material 9 and the glass are bonded in the region of the opening 7.

[0084] Figure 5 A top view of one of the side surfaces 3, 5 of a cover element 1 made of a brittle material is shown. Preferably, the cover element 1 is made of glass 4. The cover element 1 includes a second portion 102 and two first portions 101, which are located in... Figure 5 The second portion 102 is located between the first portions 101. The first portion 101 preferably has a closed, flat surface and therefore no openings. In contrast, the glass 4 in the second portion 102 includes an opening 7, which forms a channel or through-hole from one side surface 3 to the opposite side surface 5. The opening 7 is filled with a flexible, transparent composite material 9, wherein the refractive index of the composite material 9 and the surface of the glass 4 in the second portion are matched. Preferably, the refractive index n of the surface of the glass 4 is matched for the entire wavelength range between 400 and 800 nm. glass，surface (λ) and the refractive index n of composite material 9 comp The difference between (λ) is < 0.02, preferably < 0.01, more preferably < 0.008: ǀn glass , surface ( ) – n comp ( )ǀ < 0.02, preferably < 0.01, more preferably < 0.008.

[0085] Without restrictions Figure 5In the specific example depicted, the openings 7 are typically arranged in an array of adjacent parallel rows. The rows of openings 7 are preferably arranged in parallel. In this way, the distance between openings 7 in adjacent rows remains constant. Due to the mesh structure of the openings 7, the second portion 102 has high flexibility, allowing the cover element 1 to be easily bent at the intermediate first portion 101. Generally, without limiting the exemplary embodiments depicted, the arrangement and shape of the openings 7 filled with composite material 9 are designed such that the flexibility of the second portion 102 having a bending axis along the longitudinal direction of the opening 7 is higher than the flexibility of the second portion 102 having a bending axis perpendicular to the longitudinal direction of the opening 7. Figure 5 A preferred bending axis 110 along the longitudinal direction of opening 7 is shown. Since the bending axis 110 extends along the boundary line between the first and second portions, the second portion 102 provides a hinge 11 to fold the two first portions 101.

[0086] According to one embodiment, the cover element 1 can be bent along the bending axis 11 in the bendable portion with a bending radius of <10 mm, preferably <5 mm, without breaking.

[0087] Figure 6 A schematic diagram of a further developed composite material 9 is shown. In this further development, different inorganic particles 15 and 17 are dispersed in a polymer matrix 13. The inorganic particles 15 and 17 have different compositions, and therefore their optical properties, refractive index and Abbe value, are also different. By using two different particles 15 and 17, the refractive index and dispersion of the composite material 9 can be better adapted to the corresponding properties of the glass used.

[0088] Figure Labels

Claims

1. A transparent composite material (9) comprising a polymer matrix (13) having dispersed inorganic particles (15, 17), wherein the polymer matrix (13) comprises at least one elastomer, and wherein the content of the dispersed inorganic particles (15, 17) in the composite material (9) is < 20% by volume, and wherein the Abbe value of the composite material (9) is... d，comp It is >35, refractive index n d，comp It is in the range of 1.4 to 1.7, and the Young's modulus is < 5 MPa.

2. The transparent composite material (9) according to the preceding claims, wherein the Young's modulus of the composite material (9) is <3 MPa, preferably <1 MPa.

3. The transparent composite material (9) according to any one of the preceding claims, wherein the refractive index n of the composite material (9) is... d，comp The Abbe value is in the range of 1.45 to 1.7, preferably in the range of 1.48 to 1.7, and / or the Abbe value of the composite material (9). d，comp It is >50 and / or <100.

4. The transparent composite material (9) according to any one of the preceding claims, wherein the polymer matrix (13) comprises at least one of the following characteristics: - The polymer matrix (13) comprises an elastomer having acrylate monomer units, preferably including aryl-substituted acrylates, preferably substituted phenyl acrylates and / or acrylates having cyclic alkyl substituents, preferably norbornyl-substituted and / or tetrahydrofurfuryl-substituted acrylates. - The polymer matrix (13) is a copolymer comprising at least two different monomer units, and / or the polymer matrix comprises at least one monomer unit having at least two polymerizable groups.

5. The transparent composite material (9) according to any one of the preceding claims, wherein the amount of the inorganic particles (15, 17) is < 15% by volume, preferably < 10% by volume and / or in the range of 1 to 15% by volume, preferably 1 to 10% by volume.

6. The transparent composite material (9) according to any one of the preceding claims, wherein the inorganic particles (15, 17) are selected from TiO2, ZrO2, Al2O3, ITO, SiN and / or mixtures thereof.

7. The transparent composite material (9) according to any one of the preceding claims, wherein the diameter d of the inorganic particles is... 99 It is < 50 nm, preferably < 30 nm, and most preferably < 15 nm, and / or exhibits a minimum size of at least 2 nm.

8. The transparent composite material (9) according to any one of the preceding claims, wherein the composite material (9) comprises a first type of inorganic particles (15) and a second type of inorganic particles (17), wherein the refractive index n of the first type of inorganic particles (15) is... d，part1 The Abbe value is > 1.6, preferably > 1.7, more preferably > 1.8, and / or the Abbe value of the second type of inorganic particles (17). d，part2 It is >50, preferably >70, more preferably >80.

9. The transparent composite material (9) according to any one of the preceding claims, wherein the composite material (9) has a refractive index n eff And the volume fraction f of the polymer matrix in the composite material polymer and the volume fraction f of the at least one or more inorganic particles i Choose according to the following equation: ,in and m ≥ 1 .

10. A transparent article (1), comprising: The first part, which has the first material; The second part includes the first material and the second material; The first material is transparent glass (4) or glass ceramic, and the second material is a transparent composite material (9) according to any one of the preceding claims, wherein the first material and the second material form at least one interface, and the first part is connected to the second part.

11. The transparent article (1) according to claim 10, wherein for each wavelength in the wavelength range from 400 nm to 800 nm The refractive index n of the first material glass ( The refractive index n of the transparent composite material (9) as the second material and the refractive index n comp ( The absolute value of the difference between ) |n glass ( )– n comp ( )| It is < 0.02, preferably < 0.01, more preferably < 0.008, and most preferably < 0.

004.

12. The transparent article (1) according to claim 10 or 11. -The absolute value of the difference in refractive index between the first material (4) and the composite material (9) at a wavelength of 400 nm. 400nm,glass - n 400nm, comp The ν is < 0.02, preferably < 0.01, more preferably < 0.008, and most preferably < 0.

004. - and / or the absolute value of the difference in refractive index between the first material (4) and the composite material (9) at a wavelength of 800 nm. 800nm,glass - n 800nm, comp The ν is < 0.02, preferably < 0.01, more preferably < 0.008, and most preferably < 0.

004. - and / or the Abbe value of the first material (4) d，glass and the Abbe value of the composite material (9) d，comp The absolute value of the difference | d, glass - d, comp | is < 40, preferably < 30, more preferably < 25.

13. The transparent article (1) according to any one of claims 10 to 12, wherein the transparent article (1) is a cover element for a display of a mobile device, the cover element comprising: At least one first part (101) is composed of the first material; And at least one second part (102), which includes the first material and the second material; The cover element has two main surfaces (3, 5), and the thickness d of the first portion (101), i.e. the distance between the side surfaces (3, 5), is < 2000 µm, preferably < 1000 µm, more preferably < 500 µm.

14. The transparent article of claim 13, wherein at least a portion of the first material in the second part (102) is chemically tempered glass. It has a main body portion, the main body portion having a refractive index of n d, glass, bulk The uniform composition, and having a refractive index of n d, glass, surface The surface portion, Where n d, glass, bulk <n d , glass, surface , And preferably, in the second part (102), for the entire wavelength range between 400 nm and 800 nm, the absolute difference |n glass, surface ( ) – n comp ( The value of | is < 0.02, preferably < 0.01, more preferably < 0.008, and most preferably < 0.

004. and / or one of them |n d, glass, bulk – n d, comp | > |n d, glass, surface – n d, comp |。 15. The transparent article (1) according to claim 12 or 13, wherein at least one second portion (102), preferably a plurality of second portions (102), of the cover element (1) is a flexible portion, and wherein preferably the cover element (1) can be bent in the flexible portion with a bending radius of < 10 mm, preferably < 5 mm, without breaking.

16. A method for producing a transparent composite material (9) according to any one of claims 1 to 9, wherein the method comprises at least the steps a) to c): a) Provide monomers, oligomers, and / or prepolymers, wherein the monomers, oligomers, and / or prepolymers comprise at least one polymerizable group, preferably an acrylic group. b) Providing inorganic particles (15, 17) and dispersing said inorganic particles (15, 17) in said monomer, oligomer and / or prepolymer, c) Fill the cavity with the dispersion obtained in step b). d) Polymerize the monomers, oligomers and / or prepolymers to generate a polymer matrix.

17. A method for producing a transparent article (1) according to claims 10 to 15, comprising at least the steps 1) to 4): 1) A structured thin glass (4) is provided, wherein the glass (4) comprises at least one first portion (101) of thickness d and at least one second portion (102) having at least one opening (7). 2) Provide the formulation according to steps a) to b) of claim 16, 3) Apply the formulation of step 2) to the glass (4) such that the opening (7) of the thin glass (4) formed in the second portion (102) of the glass (4) is filled with the formulation, and 4) The formulation is cured under anaerobic conditions to obtain a composite material (9) comprising a polymer matrix (13) and inorganic particles (15, 17).

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