Enamel paste, method for forming enamel coating, enamel-coated substrate, and use thereof

Abstract

The present invention relates to an enamel paste, a method for forming an enamel coating using said enamel paste, an enamel-coated substrate obtainable or obtained by said method, and the use of said enamel-coated substrate as a decorative and / or functional article in the fields of automotive, marine, aerospace, consumer electronics, laboratory ware and tableware, pharmaceutical packaging, architecture, and information technology.

Description

[Technical Field]

[0001] The present invention relates to an enamel paste, a method for forming an enamel coating using said enamel paste, an enameled substrate obtainable or obtained by said method, and the use of said enameled substrate as a decorative article. [Background technology]

[0002] (Introduction) Decorating an article with enamel requires a coefficient of thermal expansion (CTE) match, usually equal to or less than that of the substrate. If the difference in thermal expansion between the substrate and the enamel of the article is too great, stresses will build up due to the difference in thermal expansion of the substrate and the enamel. If the CTE of the enamel is too large compared to the substrate, microcracks may form, which can adversely affect the mechanical properties and thermal shock resistance of the decorated article.

[0003] This is particularly true for low CTE substrate materials such as glasses, glass-ceramics and ceramics, e.g., glasses from the borosilicate, boroaluminosilicate or aluminosilicate glass families, glass-ceramics such as lithium aluminosilicate (LAS) glass-ceramics, or ceramics such as sapphire, cordierite, mullite or technical porcelain. These materials typically have a CTE of 2-6×10. -6 K -1 The present invention has a technical CTE in the range of, for example, 6×10 -6 K -1 This addresses the issue of substrate materials having a low thermal expansion less than, or at least a lower coefficient of thermal expansion than, conventional window glass. Summary of the Invention

[0004] The present invention relates to an enamel paste according to a first aspect, a first material selected from glass, ceramic, or glass-ceramic particles; a second material selected from glass, ceramic, or glass-ceramic particles; an organic carrier medium; Including, the first material has a first coefficient of thermal expansion (CTE1), a first grain size D90, and a first transition temperature (T1); the second material has a second coefficient of thermal expansion (CTE2), a second grain size D90, and a second transition temperature (T2); CTE1 <CTE2、および T1>T2, The particle size D90 of said first material relates to an enamel paste that is >2 times (more than 2 times) the particle size D90 of said second material.

[0005] A second aspect of the present invention is i) depositing an enamel paste composition according to any of the preceding claims on a substrate having a third coefficient of thermal expansion (CTE3); ii) firing the enamel paste to form an enamel coating on the substrate, the enamel coating having a non-uniform microstructure in which particles of the first material are embedded in a matrix of the second material; After deposition and firing, the enamel has a composite coefficient of thermal expansion (CTE-COMP): The present invention relates to a method for forming an enamel coating in which CTE-COMP≦CTE3.

[0006] A third aspect of the present invention is It relates to an enamel coated substrate obtainable or obtained by the method according to the second aspect.

[0007] A fourth aspect of the present invention relates to the use of an enamel coated substrate according to the third aspect as a decorative and / or functional article in the fields of automotive, marine, aerospace, consumer electronics, laboratory and tableware, pharmaceutical packaging, architecture, and information technology. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Detailed Description of the Invention) According to the present invention, there is provided a thermal expansion device comprising a first material selected from glass particles, ceramic particles, or glass-ceramic particles, a second material selected from glass particles, ceramic particles, or glass-ceramic particles, and an organic carrier medium, wherein the first material has a first coefficient of thermal expansion (CTE1), a first particle size D90, and a first transition temperature (T1), and the second material has a second coefficient of thermal expansion (CTE2), a second particle size D90, and a second transition temperature (T2), and the CTE1<CTE2、およびT1> An enamel paste is provided, wherein the particle size D90 of the first material is more than twice the particle size D90 of the second material.

[0009] In the present specification, the term thermal expansion (CTE) typically refers to the increase in dimensions of a material with increasing temperature. Materials typically have a positive coefficient of thermal expansion, although (as shown in the examples below) it is possible for a first material to have a very low CTE, resulting in a negative CTE. Such negative thermal expansion is a unique physicochemical process in which heating causes a material to contract, as opposed to expanding as most other materials do.

[0010] The first material typically has a low CTE, selected to be lower than the CTE of the substrate to be coated. Thus, the first material functions as a CTE-modifying phase, enabling the achievement of an enamel with a very low overall CTE that matches the CTE of the low-CTE substrate. Meanwhile, the second material in the matrix phase has a lower transition temperature, ensuring adhesion to the substrate and internal cohesion between the components within the enamel. Therefore, the low-CTE enamel of the present invention is highly suitable for application to low-CTE substrates. The use of this enamel opens up the opportunity to reduce glass embrittlement and realize highly impact-resistant automotive glazing, thereby improving passenger and traffic safety. Furthermore, it is possible to realize lightweight glazing products made of borosilicate glass, such as automotive glazing products including windshields, over-side windows, rear windows, quarter glass, sunroof glass, backlight glass, and door glass, which contributes to reducing fuel consumption during driving.

[0011] When the enamel paste of the present invention is deposited (or applied) and fired, the frit of the second material sinters around the particles of the first material. A feature of the enamel of the present invention is that upon firing, the materials do not fuse into a homogeneous region within the enamel coating, but rather form a continuous, heterogeneous frit microstructure comprising two intertwining, percolating three-dimensional (3D) networks of functional particles of the first material ("bricks") and particles of the second material ("mortar"). Thus, the microstructure of the fired enamel is reminiscent of a "bricks-and-mortar structure," with the first material forming the "bricks" and the second material sintering to form the matrix or "mortar."

[0012] The first material and the second material have different transition temperatures, the transition temperature of the first material being higher than the transition temperature of the second material. The term "transition temperature" herein refers to the temperature at which an abrupt change in physical properties occurs, such as a phase change or a change in crystalline structure. The term "glass transition temperature" applies to glasses and glass-ceramics, specifically the residual glass phase in glass-ceramics. It is the temperature at which an amorphous material transitions from a solid state to a supercooled molten state (or vice versa, depending on whether heating or cooling occurs). This transition also changes the macroscopic behavior of the material, from solid-like to liquid-like behavior, including, but not limited to, a change from elastic behavior to viscous flow. Because the transition occurs gradually, the glass transition temperature is representative of a temperature range. Experimentally, it is determined using a differential scanning calorimeter at a standardized heating rate of 10 K / min. The commonly used symbol is Tg. Because ceramic materials generally do not exhibit a glass transition temperature, the term "liquidus temperature" is sometimes used to identify a transition temperature similar to the glass transition temperature for these materials.

[0013] The first and second materials can be selected from glass particles, ceramic particles, or glass-ceramic particles, with the first (brick) material having a higher transition temperature and a lower CTE than the second (mortar) material. The type and amount of the first material can be selected to adjust the thermal expansion of the enamel to match (or match) the thermal expansion of the substrate. In one embodiment, the first material is formed from glass particles. In another embodiment, the first material is formed from glass-ceramic particles. In another embodiment, the first material is formed from ceramic particles. Ceramics are crystalline, while glasses are amorphous. Glass-ceramics are a combination of a crystalline phase and an amorphous glass phase. They contain at least one functional crystalline phase and a residual glass phase.

[0014] Although ceramics usually exhibit high transition temperatures, many useful glass species in the present invention may exhibit lower transition temperatures. In this regard, when the first material is a ceramic, the second material is a glass ceramic or glass material, preferably a glass frit. Along these lines, when the first material is a glass ceramic, the second material may suitably be a glass material. Also, both the first material and the second material may be glass or glass ceramic, but have different CTEs and transition temperatures according to the above requirements.

[0015] The present invention has a thermal expansion coefficient of 6×10 -6 K -1 The present invention addresses the problem of substrate materials having a low thermal expansion coefficient of less than 6 ppm / K, or at least a thermal expansion coefficient lower than that of conventional window glass. In the present specification, the CTE refers to the CTE in the temperature range of 25 to 300°C.

[0016] The CTE of the final enamel depends on the type and amount of the components and their respective properties. The overall CTE of the enamel before firing, α, is v * can be calculated in advance according to the following formula, where ξ i is the volume fraction of the i phase, and α i is the CTE of the pure i phase.

[0017]

number

[0018] The CTE of the enamel can be designed based on the CTE of the substrate (referred to as CTE3 in this specification). In this regard, the overall CTE of the enamel after firing (referred to as CTE-COMP of the enamel in this specification) must match (or be consistent with) or be lower than the CTE of the substrate. That is, CTE-COMP ≤ CTE3. It should be understood here that generally (depending on other CTE modifying additives contained in the enamel), the CTE of the first material is lower than the CTE of the substrate (that is, CTE1 < CTE3). On the other hand, in the present invention, it is possible to use a second material having a CTE significantly higher than the CTE of the substrate (that is, CTE2 > CTE3), thereby expanding the range of material selection suitable for the low-CTE enamel of the present invention. In other words, according to the present invention, it is not limited to the use of low-CTE materials, and high-CTE materials and low-CTE materials having desirable advantageous characteristics in the desired applications can be included in the enamel. Based on the above, an appropriate CTE3 is < 6 × 10 -6 K -1 (6 × 10 -6 K -1 less than), and typically 2 - 6 × 10 -6 K -1 , or can be at least a value lower than that of conventional window glass. An appropriate CTE2 of the second material may be 2 - 6 × 10 -6 K -1 or more, but on the other hand, the CTE1 of the first material is considerably lower than this, and in the temperature range of 25 - 300 °C, for example, - 3 - 2 × 10 -6 K -1 , preferably - 2 - 1.5 × 10 -6 K -1 , more preferably - 1.5 - - 1.0 × 10 -6 K -1 . Within these ranges, CTE1 is, in the temperature range of 25 - 300 °C, for example, 0 - 2 × 10 -6 K -1 , preferably 0 - 1.5 × 10 -6 K -1 , more preferably 0.05 - 1.0 × 10-6 K -1 is.

[0019] In a preferred embodiment, CTE<8×10 -6 K -1 In a particularly preferred embodiment, CTE1 is −3 to 4.5×10 -6 K -1 It is entirely possible that CTE1 is a negative CTE.

[0020] In a preferred embodiment, CTE2<10×10 -6 K -1 In a particularly preferred embodiment, -6 K -1 In this specification, the values ​​of CTE1, CTE2, and CTE3 refer to the CTE value of the enamel before firing. CTE1, CTE2, CTE3, or the properties of each component may change after heat treatment (firing).

[0021] Regarding the selection of the first and second materials, it should be noted that if the first material is ceramic, the transition temperature of the first material must typically be higher than the transition temperature of the second material and higher than the firing temperature. In this regard, the preferred transition temperature T1 of the first ceramic material may be >800°C, or >900°C, or >1000°C. On the other hand, if the first material is glass, the transition temperature may be lower than or equal to the firing temperature. Even in such cases, the viscosity at these temperatures is typically so high that the particle shape remains almost unchanged after firing. From this perspective, the brick phase in the enamel exhibits little or no fusion between particles of the same type (i.e., minimal "brick-to-brick contact"). At the firing temperature, the material in the brick phase has a higher viscosity than the mortar phase, and the brick phase material remains solid and does not exhibit significant viscous flow.

[0022] Most ceramic materials meet these requirements. Therefore, ceramic materials may be highly suitable as the first material in the context of the present invention. The present invention also contemplates the use of infiltrated ceramics or liquid phase sintered materials, so there is no particular limitation on the solidus temperature of the first material.

[0023] In the context of the present invention, the brick particles themselves are usually isotropic, but their structure may have anisotropic constituent phases. In this regard, the material of the brick particles itself may also be anisotropic.

[0024] The first material may comprise one type of particle or multiple types of particles, e.g., they may differ in composition. Suitable first materials for forming bricks may be selected from the group consisting of oxide materials, aluminosilicates, fused silica, LAS-based (glass) ceramics including β-eucryptite glass ceramics and β-spodumene solid solution ceramics, ceramic components of the pseudo-brookite type, cordierite, perovskite-type materials, magnesium pyrophosphate, low CTE glass frits, or mixtures of these or other materials meeting the requirements of the first material set forth above.

[0025] The first material is preferably an oxide material (as opposed to nitrides, carbides, borides, and other non-oxide materials). Oxide materials ensure compatibility and bond-forming with the mortar phase, which is important for the internal cohesion of the enamel, while non-oxide brick materials may behave differently and potentially lead to defects. Oxide materials can include zinc sulfide frit. Those skilled in the art will appreciate that the term "oxide material" refers to a comprehensive group of materials, and that the presence of multivalent ions as part of the composition does not necessarily indicate a preference or prevalence of these ions in their oxidized state. For example, zinc sulfide silicate frit is an oxide material, but its internal redox state is dominated by reduced multivalent ions, such as sulfides, rather than sulfates. As another example, an iron-containing oxide glass may be dominated by FeO rather than Fe2O3. Therefore, suitable oxide materials within the scope of the present invention include all materials within that group, regardless of their individual redox state, provided they have a sufficiently low CTE to effectively serve their purpose as a CTE modifier for enamel. In the compositions described herein, the amount of each component is given in weight percent. These weight percents are relative to the total weight of the composition or material. The weight percent of an oxide is the proportion, in oxide terms, of the starting material used to prepare the material, such as the glass frit composition described above. As will be understood by those skilled in the art, starting materials other than oxides of specific elements may be used in preparing materials, such as frits, within the scope of the present invention. When non-oxide materials are used to provide the oxide of a specific element in a composition, the appropriate amount of starting material may be used to provide the equivalent molar amount of the element as if the oxide of that element were provided in the stated weight percent. This approach to defining such compositions is common in the art. As will be readily understood by those skilled in the art, volatile components, such as oxygen, may be lost during the manufacturing process of a material, and therefore the resulting material may not exactly match the weight percent of the starting material expressed herein in oxide terms.Analysis of the calcined material by methods known to those skilled in the art, such as, for example, inductively coupled plasma optical emission spectroscopy (ICP-ES), can be used to calculate the starting components of the initial composition.

[0026] Suitable first materials can include bismuth- and boron-free frits. Such materials typically have a low CTE. Suitable first materials can also include glass frits, glass ceramics, or ceramics with a high silica and / or alumina content, which have been found to be useful in achieving low CTE values. In this regard, suitable first materials may contain >30 wt% (greater than 30 wt%) SiO2, preferably >40 wt% (greater than 40 wt%) SiO2, or >50 wt% (greater than 50 wt%) SiO2, preferably >60 wt% (greater than 60 wt%) SiO2, or even higher wt% SiO2, such as fused silica.

[0027] An exemplary LAS-based first material may have a composition consisting of mullite, and β-spodumene and petalite (including solid solutions). An exemplary oxide composition of an LAS-based ceramic used as the first material may contain 4.5-7 wt% LiO, 20-32 wt% AlO, and 63-75 wt% SiO, with a molar ratio of (LiO:AlO:SiO) between 1:1.1:6.9 and 1:1.8:5.7, resulting in a CTE of 0-2×10 in the temperature range of 25-300°C. -6 K -1 , preferably 0 to 1.5 × 10 -6 K -1 , and more preferably 0.05 to 1.0 × 10 -6 K -1 The material obtained is:

[0028] Another exemplary LAS-based first material may be a glass-ceramic used as the first material, which may have 4.0 to 6 wt. % LiO, 13 to 19 wt. % AlO, and 25 to 42 wt. % SiO, in other words, a molar ratio of (LiO:AlO:SiO) of (1:0.9:3.5) to (1:1.2:4.5), resulting in a CTE of -3 (negative CTE) to 2 × 10 before firing in a temperature range of 25 to 300 °C. -6 K -1 , preferably -2.0 to 1.5 × 10 -6 K -1 , and more preferably −1.5 to 1.0×10 -6 K -1 The material obtained is:

[0029] The primary role of the second material is to provide the internal cohesive strength of the enamel and adhesion to the substrate, as well as to act as a matrix for embedding functional additives such as pigments, seed materials, etc.

[0030] The first material may contain one type of particle, or multiple types of particles, which may, for example, differ in composition.

[0031] The second material should be selected to obtain a high-density enamel after firing. Sintering can occur during firing, which densifies the enamel. However, normal processing times and temperatures do not allow for 100% densification during the firing process. Therefore, amorphous materials / frits are preferably used as the second material, as these materials exhibit viscous flow and contribute to densifying the enamel without creating residual porosity. Therefore, a suitable second material (mortar material) may be glass frit, which exhibits moderate viscous flow during the firing cycle, allowing the enamel to achieve maximum density and minimize porosity as much as possible. Furthermore, crystallization should not occur too easily, which could hinder flow and result in undesirable voids. Therefore, the second material is preferably in the form of crushed glass frit. It should also be noted that these frits generally have lower transition temperatures than the ceramics or glass-ceramics preferred as the first material, making them particularly useful as the second material in the present invention.

[0032] In a preferred embodiment, the glass frit of the second material may be a glass frit belonging to bismuth silicate-based, aluminoborosilicate-based, LAS-based, and bismuth borate-based glasses, or the second material may contain such a glass frit.

[0033] A suitable glass frit of the second material may contain 25-50 wt% Bi2O3 and 20-40 wt% SiO2, preferably 30-45 wt% Bi2O3 and 23-32 wt% SiO2. Such glass frit may further contain 2-20 wt%, e.g., 3-20 wt% B2O3, 2-20 wt% Al2O3, 2-12 wt% ZnO, >0-11 wt% (greater than 0-11 wt%) alkali oxides (e.g., >0-8 wt% (greater than 0-8 wt%) Li2O and 0-3 wt% Na2O), or other components to bring the total to 100 wt%. A preferred glass frit of the second material may contain 30-45 wt% Bi2O3, 23-32 wt% SiO2, 6-16 wt% B2O3, 4-18 wt% Al2O3, 4-12 wt% (e.g., 4-10 wt%) ZnO, >0-8 wt% (greater than 0-8 wt%) alkali oxides (e.g., including 0.5-6 wt% Li2O and 0-2 wt% Na2O), and may contain any other components to bring the total to 100 wt%.

[0034] The CTE of the enamel can be further tuned by balancing the components based on the individual CTE and volume fraction of each component, using specific particle sizes to create a brick-and-mortar structure characterized by a first material phase being brick and a second material phase being mortar, where the first material has a particle size D90 >2x (more than) the particle size D90 of the second material.

[0035] The first and second materials can be selected depending on the target firing temperature in the end use application, and the first and / or second materials may be selected to impart color to the fired coating or not (in the latter case, they are non-pigment materials).

[0036] During firing, the second material softens and sinters to form a matrix, binding the particles of the first material and bonding the enamel coating to the underlying substrate, resulting in a non-homogeneous brick-and-mortar microstructure. In addition to selecting materials based on transition temperature parameters, the first material may be processed to have a larger grain size than the second material to achieve a brick-and-mortar structure after firing. The specific grain size of the frit may vary depending on the desired microstructure. To achieve such a microstructure, the first material may have a first grain size D90 and the second material may have a second grain size D90, with the first grain size D90 being more than twice the second grain size D90. In a preferred embodiment, the first material has a grain size D90 that is greater than or equal to 5 times the grain size D90 of the second material. Alternatively, or in addition, grain size may be expressed in terms of the D50 grain size. In that case, the first material preferably has a particle size D50 that is >4 times (more than 4 times) the particle size D50 of the second material.

[0037] For example, the first material may have a particle size that meets one or more of the following characteristics: a D90 of at least 6 microns, 7 microns, 8 microns, 8.5 microns, or 8.8 microns; not more than 20 microns, 15 microns, 13 microns, 12.5 microns, or 11.8 microns; or within a range defined by any combination of the above lower and upper limits; 3.8 microns or 3.6 microns; or within a range defined by any combination of the above lower and upper limits; a maximum particle size not more than 40 microns, 35 microns, 30 microns, or 26 microns.

[0038] Additionally, the second material may have a particle size that meets one or more of the following characteristics: a D90 of at least 0.5 microns, 0.8 microns, 1.0 microns, or 1.2 microns; or less than 20 microns, 17.5 microns, 15 microns, 13 microns, 10 microns, 7.5 microns, 6.5 microns, 6.35 microns, 5.9 microns, 4.4 microns, 4.25 microns, 4 microns, 3.5 microns, 3 microns, 2.2 microns, 1.9 microns, or 1.8 microns; or within the range defined by any combination of the above lower and upper limits; a D50 of at least 0.1 microns, 0.2 microns, 0.3 microns, 0.4 microns, or 0.5 microns; or not more than 1.4 microns, 1.3 microns, 1.2 microns, or 1.0 microns; or within the range defined by any combination of the above lower and upper limits; or a maximum particle size not more than 10 microns, 9 microns, 8 microns, 7 microns, or 6 microns. A highly suitable exemplary particle size D50 is 1.4 to 1.7 microns.

[0039] For example, the first material may have a particle size D90 of 8.5 to 12.5 microns, preferably 8.8 to 11.8 microns; a particle size D50 of 1.5 to 5.5 microns, e.g., 5.2 microns, or 1.8 to 3.8 microns, preferably 1.9 to 3.6 microns; and a maximum particle size typically less than 26 microns. The second material may have a particle size D90 of 1.2 to 4 microns, e.g., 1.2 to 3.5 microns, or 1.2 to 2.2 microns, or 1.2 to 1.9 microns, e.g., 3.3 microns; a particle size D50 of 0.5 to 1.2 microns, preferably 0.5 to 1.0 microns; and a maximum particle size typically less than 6 microns.

[0040] It should be understood that the above-mentioned example particle sizes D50 and D90 and their ranges may be selected in any combination, as long as the requirement that the particle size D90 of the first material is >2 times (more than 2 times) the particle size D90 of the second material is met.

[0041] The material may be milled to the desired particle size by a suitable process, including, for example, jet milling, dry or wet ball or bead milling, or a combination thereof. The medium used in the wet milling process may include water, alcohol, glycol, and may also be mixed with an appropriate addition of a dispersant. The wet-milled powder may then be subjected to a suitable drying process, such as flame spray drying or tray drying, or incorporated as a slurry into the final product (paste or ink) formulation. Particle size distribution may be measured by laser diffraction to obtain the volume-equivalent spherical diameter.

[0042] In some examples, the first material may form a larger volume fraction and / or weight fraction of enamel than the second material, or vice versa, which may be desirable when the functional parameters of the first material are desired to dominate the functional properties of the fired composite enamel.

[0043] In view of the above, it will be appreciated that the type and amount of the first and second glass frits can be tailored to the particular combination of functional performance characteristics desired.

[0044] In addition to the glass frit component, the composition may also contain other additives, such as seed additives, as known in the art for adjusting the properties of glass / ceramic materials. Seed materials are used as nucleating agents to promote crystallization as needed. Typical seeds are bismuth silicate- or zinc silicate-based. The weight ratio of the materials may actually be limited by the amount of functional additives, such as seed materials and pigments, that need to be embedded in the mortar or matrix phase containing the second material. In the context of the present invention, this functions as a matrix that embeds the functional additives. The amount of each functional additive depends on the customer's requirements and the process parameters, and may vary depending on the firing and bending processes. Such variations also affect the weight ratios of the frit and other components of the enamel paste.

[0045] The enamel paste may further contain pigment particles, resulting in a substantially ink-like form. Such pigments may include mixed metal oxide pigments or carbon black pigments. If such pigments are used, their content may not exceed about 55% by weight, preferably 10-30% by weight of the particle mixture, depending on the desired range of color, gloss, and opacity of the enamel.

[0046] Suitable pigments may include complex metal oxide pigments such as, for example, corundum-hematite, olivine, plydalite, pyrochlore, rutile, and spinel. Other categories, such as baddeleyite, borates, garnets, periclase, phenacite, phosphates, sphenes, and zircons, may also be suitable in certain applications.

[0047] Representative complex metal oxide pigments that can be used to produce black in the automotive industry include transition metal oxides having a spinel structure, such as spinel structure oxides of copper, chromium, iron, cobalt, nickel, manganese, etc. Although these black spinel pigments are preferred for use in the automotive industry, other metal oxide pigments for producing a variety of other colors can also be used in the present invention.

[0048] Examples of commercially available pigments suitable for use in the present invention include copper manganese chromite pigments, copper chromite pigments, CuCr2O4, (Co,Fe)(Fe,Cr)2O4, (NiMnCrFe), and the like.

[0049] A mixture of two or more pigments may be used in the particle mixture of the present invention.

[0050] Preferably, the particle size D90 of the pigment particles is equal to or smaller than the particle size D90 of the glass frit particles, and more preferably, the particle size D90 of the pigment particles is smaller than the particle size D90 of the glass frit particles.

[0051] Using the pigments identified above, an exemplary coated substrate can have an enamel coating with less than 0.01% transmittance in the UV-VIS-NIR spectrum.

[0052] The organic carrier medium containing the first and second materials, as well as any pigments and other additives, may preferably contain a dispersant, a solvent, and a binder. Thus, an enamel paste or ink can be obtained by dispersing inorganic particle components in the organic carrier medium, which contains the dispersant, the solvent, and the binder and is burned off during the firing process.

[0053] The enamels of the present invention are well suited for coating low CTE substrate materials, for example, 6×10 slabs, including, but not limited to, standard glass substrates. -6 K -1The coating can also be used to coat substrates having a high CTE of 6×10 or higher. In this respect, the substrate may be an inorganic, non-metallic substrate selected from the group consisting of glass, preferably oxide glass, ceramics, and glass-ceramics. Suitable examples include, but are not limited to, substrates selected from the group consisting of soda-lime glass, borosilicate glass, aluminosilicate glass, lithium-alumina-silicon (LAS) glass-ceramics, fused silica substrates, and technical porcelain. Typical technical CTEs for such substrates are 6×10 or higher. -6 K -1 is less than.

[0054] To form an enamel coating, the enamel paste composition is deposited (or applied) on a substrate. Deposition can be performed by any suitable method known to those skilled in the art, including, but not limited to, a deposition technique (or application technique) selected from the group consisting of screen printing, digital printing, inkjet printing, curtain coating, spin coating, and slip casting. The particle sizes of the materials used in the enamel of the present invention can be adjusted to suit a particular deposition technique, as long as the particle size ratio of the first material and the second material satisfies the specifications of the present invention.

[0055] After deposition, the enamel may be dried and then fired, or may be fired without drying (wet fired).

[0056] The firing process softens the substrate, which can then be bent into its final shape. Exemplary firing conditions suitable for the enamels defined above include firing at a temperature of 600°C to 700°C for 3 to 15 minutes, e.g., the firing temperature is at least 600°C, 620°C, 635°C or 650°C and does not exceed 680°C, 690°C or 700°C, and the firing time is at least 3 minutes and does not exceed 15 minutes, preferably less than 10 minutes, and more preferably less than 6 minutes.

[0057] After firing, the fired enamel substrate composite may be reshaped to obtain the desired coated article, for example, by sag bending or press bending.

[0058] The enamel-coated substrates of the present invention are particularly useful as decorative articles in the fields of automobiles, marine, aerospace, household appliances, laboratory and tableware, architecture, and information technology. By way of example, the enamel-coated substrates are well suited for automotive glazing, such as windshields, cover side windows, rear windows, quarter windows, sunroof glass, backlight glass, and door glass. [Example]

[0059] The present invention will be further described with reference to the following examples, which are intended to be illustrative and not limiting. In the examples and comparative examples, the materials specified in Tables 1, 2, and 3 were used. The exemplary pastes were applied as pastes by screen printing to deposit wet layers of 20-18 microns in thickness. These examples provide 100% inorganic compositions.

[0060] [Table 1]

[0061] [Table 2]

[0062] [Table 3]

[0063] The transition temperatures, CTEs and particle sizes D90 of these materials are shown below in Table 4. In this table, CTEs are calculated CTE values ​​before firing.

[0064] [Table 4]

[0065] Exemplary enamel pastes were prepared as shown in Table 5 below. In this regard, Comparative Example 1 is a commercially available composition with a transition temperature of 454°C, a CTE of 78x10 -7 K -1 The first frit (frit 1) had a particle size D90 of 13 microns, a transition temperature of 430°C, and a CTE of 85×10 -7 K -1 , a second frit (frit 2) with a particle size D90 of 10.5 microns and a CTE of 110 × 10 -7 K -1 and copper chromite pigment having a particle size D90 of 1.8 microns.

[0066] [Table 5]

[0067] To measure the CTE match between the enamel and the substrate, the so-called ring-on-ring (ROR) strength test procedure, test method: EN1288-5, was performed. ROR is a mechanical bending stress measurement using a ring-on-ring geometry, and the ROR value indicates the maximum stress that leads to failure of the enamel. A high ROR value indicates a good CTE match between the enamel and the substrate on which it is fired.

[0068] For each test condition, at least 15 specimens (100 mm x 100 mm annealed float glass square plates (size ±2 mm), nominal thickness 3.8 mm) were fired at the designated furnace temperature. A Zwick (universal mechanical testing machine) equipped with a load cell with load control function achieving stress rates of 2 MPa / s and ±0.4 MPa / s with an accuracy of better than ±2% in the range of 100 N to 5000 N was used. Additionally, a R30 ring-on-ring tool with a 30-50 IRHD silicone rubber ring (ring size, tool surface finish) conforming to EN 1288-5 was used. Structure, color, and opacity were also analyzed.

[0069] (Examples 1 to 3 and 8 to 10 vs. Comparative Example) Table 6 shows the results of several example enamels and comparative examples fired onto borosilicate glass.

[0070] [Table 6]

[0071] The calculated CTE before firing of Comparative Example 1 was 89 × 10 -7 K -1 The calculated CTE before firing of Comparative Example 2 was 49.3 × 10 -7 K -1 The calculated CTE of Example 1 before firing was 45 × 10 -7 K -1 The calculated CTE of Example 2 before firing was 40 × 10 -7 K -1 The calculated CTE of Example 3 before firing was 70 × 10 -7 K -1 It was.

[0072] It should be noted that during firing, the mortar phase of Examples 1-3 and 8-10 partially crystallizes, effectively lowering the CTE, resulting in a significantly lower fired enamel CTE after firing. The comparative examples do not exhibit this CTE reduction due to the absence of such mortar phase, and therefore Examples 1-3 have a lower enamel CTE after firing. This is further evidenced by the fact that, as shown in Table 6, higher ROR values ​​can be achieved for Examples 1-3 and 8-10 according to the present invention compared to the comparative examples.

[0073] (Examples 4 and 5) To evaluate the effect of varying the particle size of the first material (brick material), tests were conducted on borosilicate glass using two commercially available low CTE glass fillers with particle sizes D90 of ~6 μm (approximately 6 μm) and ~18 μm (approximately 18 μm) (Examples 4 and 5, respectively). The results are shown in Table 7.

[0074] [Table 7]

[0075] Table 7 shows that the ROR value can be controlled by adjusting the particle size of the first (brick) material.

[0076] (Examples 6 and 7) To evaluate the effect of the presence or absence of pigment, tests were conducted on borosilicate glass using two different enamel pastes, one containing copper manganese chromite pigment (Example 6) and one without pigment (Example 7). The results are shown in Table 6.

[0077] [Table 8]

[0078] Table 6 shows that the overall CTE of the enamel, and therefore the ROR, varies with the amount of pigment.

[0079] (Example 1 tested on a different substrate) To test the influence of the substrate, the enamel paste of Example 1 was used to bond two different types of commercially available borosilicate glass (CTE 38×10 -7 K -1 borosilicate glass 1 and CTE 38 x 10 -7 K -1 borosilicate glass2) and CTE of 80 × 10 -7 K -1 Tests were performed on commercial soda lime glass without pigment. The results are shown in Table 9.

[0080] [Table 9]

[0081] Table 9 shows that the bending strength varies depending on the glass substrate used.

Claims

1. a first material selected from glass, ceramic, or glass-ceramic particles; a second material selected from glass, ceramic, or glass-ceramic particles; an organic carrier medium; Including, the first material has a first coefficient of thermal expansion (CTE1), a first particle size D90, and a first transition temperature (T1); the second material has a second coefficient of thermal expansion (CTE2), a second particle size D90, and a second transition temperature (T2); CTE1<CTE2, and T1>T2, An enamel paste, wherein the particle size D90 of the first material is more than twice the particle size D90 of the second material.

2. CTE1 < 8 × 10 －６ K －１ and 2. The enamel paste of claim 1, wherein the value of CTE1 relates to the CTE value before firing.

3. CTE1 is -3 to 4.5 x 10 －６ K －１ and 3. The enamel paste of claim 2, wherein the value of CTE1 relates to the CTE value before firing.

4. CTE1 is a negative CTE, 4. Enamel paste according to claim 2 or 3, wherein the value of CTE1 relates to the CTE value before firing.

5. CTE2 < 10 × 10 －６ K －１ and An enamel paste according to any one of claims 1 to 4, wherein the CTE2 value relates to the CTE value before firing.

6. CTE2 is 6 to 9 x 10 －６ K －１ and 6. The enamel paste of claim 5, wherein the CTE2 value relates to the CTE value before firing.

7. the first material is a ceramic material; 7. The enamel paste according to claim 1, wherein T1 > 800°C, or T1 > 900°C, or T1 > 1000°C.

8. The first material is more than 30% by weight of SiO ２ and preferably more than 40 wt. % SiO ２ , for example more than 50 wt. % SiO ２ or more than 60 wt. % SiO ２ The enamel paste according to any one of claims 1 to 7, comprising:

9. 9. The enamel paste of claim 1, wherein the first material is selected from the group consisting of oxide materials, aluminosilicates, fused silica, β-eucryptite-based glass-ceramics, LAS-based glass-ceramics including β-spodumene solid solution ceramics, pseudobrookite-type ceramic components, cordierite, perovskite-type materials, magnesium pyrophosphate, low CTE glass frits, or mixtures thereof.

10. The first material contains 4.0 to 6 wt. % Li ２ O, 13 to 19 wt. % Al ２ O ３ , 25 to 42 wt. % SiO ２ a glass ceramic comprising: CTE1 before firing is -3 to 2 × 10 －６ K －１ , preferably −2.0 to 1.5×10 －６ K －１ , and more preferably −1.5 to 1.0×10 in the temperature range of 25 to 300° C. －６ K －１ The enamel paste according to any one of claims 1 to 9,

11. An enamel paste according to any one of claims 1 to 10, wherein the second material is a crushed glass frit.

12. The glass frit is a glass frit belonging to the bismuth silicate, aluminoborosilicate, LAS, and bismuth borate glass families; or 12. The enamel paste of claim 11, wherein the second material comprises such a material.

13. The second material is 25 to 50 wt% Bi ２ O ３ , and 20 to 40% by weight of SiO ２ The enamel paste according to any one of claims 1 to 12, wherein the glass frit comprises

14. The second material further comprises: 2 to 20% by weight of B ２ O ３ , 2 to 20% by weight of Al ２ O ３ , 2 to 12 wt. % ZnO, and >0-11% by weight of alkali oxides 14. The enamel paste of claim 13, comprising:

15. The second material is 30 to 45 wt% Bi ２ O ３ , 23 to 32 wt. % SiO ２ , 6 to 16% by weight of B ２ O ３ , 4 to 18 wt. % Al ２ O ３ , 4 to 12 wt. % ZnO, >0-8% by weight of alkali oxides 15. The enamel paste of claim 14, comprising:

16. An enamel paste according to any one of claims 1 to 15, further comprising a pigment. 。

17. 17. An enamel paste according to claim 16, wherein the pigment content is 12 to 55% by weight of the enamel paste, for example 12 to 30% by weight.

18. An enamel paste according to any one of claims 1 to 17, further comprising a nucleating agent.

19. An enamel paste according to any one of the preceding claims, wherein the organic carrier medium comprises dispersant, solvent and binder components.

20. i) depositing an enamel paste composition according to any one of claims 1 to 19 onto a substrate having a third coefficient of thermal expansion (CTE3); ii) firing the enamel paste to form an enamel coating on the substrate, the enamel coating having a non-uniform microstructure in which particles of the first material are embedded in a matrix of the second material; After deposition and firing, the enamel has a complex coefficient of thermal expansion (CTE-COMP): A method for forming an enamel coating, wherein CTE-COMP≦CTE3.

21. 21. The method of claim 20, wherein CTE1<CTE3.

22. 22. The method of claim 20 or 21, wherein the depositing step is carried out by a deposition technique selected from the group consisting of screen printing, digital printing, inkjet printing, curtain coating, spin coating, slip casting.

23. 23. The method according to any one of claims 20 to 22, wherein the firing step is carried out at a temperature of 600°C to 700°C for 3 minutes to 15 minutes.

24. CTE3 < 6 × 10 －６ K －１ , typically 2 to 6 × 10 －６ K －１ The method according to any one of claims 20 to 23, wherein

25. The method according to any one of claims 20 to 24, wherein the substrate is an inorganic, non-metallic substrate selected from the group consisting of glasses, preferably oxide glasses, ceramics, and glass-ceramics.

26. 26. The method of claim 25, wherein the substrate is selected from the group consisting of soda-lime glass, borosilicate glass, aluminosilicate glass, lithium-alumina-silicon (LAS) glass-ceramics, fused silica substrates, and technical porcelain.

27. A method according to any one of claims 20 to 26, wherein the shape of the fired enamel substrate composite is changed, for example by sag bending or press bending.

28. An enamel coated substrate obtainable or obtained by the method according to any one of claims 20 to 27.

29. 29. The enameled substrate of claim 28, wherein the enamel coating has a transmittance of less than 0.01% in the UV-VIS-NIR spectrum.

30. 30. Use of an enamel coated substrate according to any of claims 28 or 29 as a decorative and / or functional article in the fields of automotive, marine, aerospace, household appliances, laboratory and tableware, pharmaceutical packaging, architecture, and information technology.

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