Enamel product and method of manufacturing an enamel product

Abstract

To provide an enamel product excellent in withstand voltage characteristics of a glass layer.SOLUTION: Provided is an enamel product in which a plurality of glass layers are laminated on a metal product, wherein a conductive glass layer composed of a conductive glass composition containing a conductivity imparting material is provided on the outermost layer of the plurality of glass layers, and an antistatic glass layer having a higher dielectric breakdown voltage (kV / mm) than the conductive glass layer is provided between the conductive glass layer and the metal product.SELECTED DRAWING: Figure 1a

Description

[Technical Field]

[0001] The present invention relates to an enamel product and a method for its manufacture. [Background technology]

[0002] Traditionally, enamel products have been widely used in building materials such as bathtubs and wall panels, and cooking equipment such as pots. In addition to these general-purpose enamel products (hereinafter also referred to as "general-purpose enamel products"), enamel products known as glass-lined products are widely used in the manufacturing processes of pharmaceuticals, chemical products, processed foods, and the like. Glass-lined products and general-purpose enamel products are given functionality such as corrosion resistance on the surface by coating metal products with glass. Among enamel products, glass-lined products are required to meet the quality specified in the former JIS R 4201, and meticulous inspections are carried out to check corrosion resistance and other aspects when these glass-lined products are manufactured.

[0003] In glass-lined products, static electricity can accumulate on the surface of the glass layer and penetrate the glass layer, causing discharge, which can impair the performance of the glass layer. Therefore, glass-lined products are provided with a conductive glass layer made of a conductive glass composition containing a conductivity-imparting material such as precious metal fibers, as a measure to prevent the accumulation of static electricity (see Patent Document 1 below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-270296 Summary of the Invention [Problem to be solved by the invention]

[0005] The need to prevent degradation of the glass layer's performance due to static electricity discharge is also a requirement for general-purpose enamel products other than glass-lined products, and is a requirement for enamel products in general. Previous efforts to prevent degradation of the glass layer's performance due to static electricity have focused on transmitting static electricity in the planar direction and dissipating it from the edge of the glass layer, but no sufficient consideration has been given to improving the voltage resistance characteristics of the glass layer. Therefore, an object of the present invention is to provide an enamel product in which the glass layer has excellent voltage resistance characteristics. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides: An enamel product in which multiple glass layers are laminated to a metal product, a conductive glass layer made of a conductive glass composition containing a conductivity imparting material is provided on the outermost layer of the plurality of glass layers; The enamel product has an anti-static glass layer between the conductive glass layer and the metal product, the anti-static glass layer having a higher breakdown voltage (kV / mm) than the conductive glass layer.

[0007] In order to solve the above problems, the present invention provides: 1. A method for manufacturing an enamel product comprising a metal product and a plurality of glass layers laminated to the metal product, the method comprising: carrying out a firing step of firing the plurality of glass layers onto the metal product; In the firing step, forming a conductive glass layer by adding a conductivity imparting material to at least one of the plurality of glass layers to be fired onto the metal product; and adding a breakdown voltage improving material to at least one of the plurality of glass layers to form an anti-electrical glass layer having a breakdown voltage (kV / mm) higher than that of the conductive glass layer. The present invention provides a method for manufacturing an enamel product, in which the conductive glass layer is provided as the outermost layer of the plurality of glass layers, and the anti-static glass layer is provided between the conductive glass layer and the metal product. [Effects of the Invention]

[0008] According to the present invention, by providing a conductive glass layer made of a conductive glass composition containing a conductivity imparting agent as the outermost layer, when static electricity occurs, the charge can be widely diffused, thereby suppressing the occurrence of electric field concentration. Furthermore, according to the present invention, by providing an anti-static glass layer with excellent voltage resistance inside the conductive glass layer, it is possible to prevent discharges penetrating in the thickness direction and prevent damage to the glass layer caused by localized discharge of static electricity. [Brief explanation of the drawings]

[0009] [Figure 1a] FIG. 1a is a schematic cross-sectional view showing the stacking state of glass layers in an enamel product in one embodiment. [Figure 1b] FIG. 1b is a schematic cross-sectional view of an enamel product in which the state of the edge of the glass layer is different from that of FIG. 1a. [Figure 2a] FIG. 2a is a schematic cross-sectional view of an enamel product having a different lamination state of glass layers from the enamel product shown in FIG. 1a and the like. [Figure 2b] FIG. 2b is a schematic cross-sectional view of an enamel product having a different lamination state of glass layers from that of the enamel product shown in FIG. 1a and the like. [Figure 3] FIG. 3 is a schematic cross-sectional view of an enamel product having a different lamination state of glass layers from the enamel product shown in FIG. 1a and the like. [Figure 4] FIG. 4 is a schematic cross-sectional view of an enamel product having a different lamination state of glass layers from the enamel product shown in FIG. 1a and the like. [Figure 5] FIG. 5 is a schematic cross-sectional view of an enamel product having a different lamination state of glass layers from the enamel product shown in FIG. 1a and the like. [Figure 6] FIG. 6 is a schematic cross-sectional view of an enamel product having a different laminated state of glass layers from the enamel product shown in FIG. 1a and the like. [Figure 7] FIG. 7 is a schematic cross-sectional view of an enamel product having a different lamination state of glass layers from the enamel product shown in FIG. 1a and the like. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described below with reference to the drawings. As shown in Figure 1a, an enamel product 100 of this embodiment comprises a metal product 10 as a base and a coated glass 20 covering the metal product 10. The enamel product 100 illustrated in Figure 1a has a planar direction P that runs along the surface 10a of the metal product 10 and a thickness direction T of the coated glass 20 that is perpendicular to the planar direction P (the normal direction to the surface 10a of the metal product 10), and the coated glass 20 is composed of multiple glass layers stacked in the thickness direction T.

[0011] In the enamel product 100 of this embodiment, the entire surface of the metal product 10 is not covered with the coated glass 20, and the surface 10a of the metal product 10 includes a covered area 10a1 that is covered with the coated glass 20 and an uncoated area 10a2 that is not covered with the coated glass 20. That is, the surface 10a of the metal product 10 is provided with an uncoated area 10a2 that extends from the edge 20e of the coated glass 20 in a direction away from the coated glass 20. The enamel product 100 of this embodiment has an earth path EL electrically connected to the metal product 10 so that when static electricity accumulates on the coated glass 20, the accumulated charge can be dissipated by a ground fault through the metal product 10. The earth path EL and the metal product 10 can be electrically connected, for example, at the uncoated area 10a2.

[0012] The multiple glass layers in the enamelware product 100 illustrated in Figure 1a include a base glass layer 21 that is baked onto the metal product 10 and laminated directly to the metal product 10, and two top glass layers laminated on the base glass layer 21. That is, the multiple glass layers in the enamelware product 100 illustrated in Figure 1a are arranged in the order of base glass layer / top glass layer / top glass layer, in the direction away from the surface 10a of the metal product 10, with an intermediate glass layer between the topmost glass layer and the innermost glass layer (base glass layer 21). In this enamelware product 100, the topmost glass layer is a conductive glass layer 23 made of a conductive glass composition containing a conductivity-imparting material, and the intermediate layer disposed between the base glass layer 21, which is laminated directly to the metal product 10, and the conductive glass layer 23 is an electric-resistant glass layer 22 with a higher breakdown voltage (kV / mm) than the conductive glass layer 23.

[0013] In the enamel product 100 illustrated in FIG. 1a, the area in which the undercoat glass layer 21 is provided is wider than the anti-electrical glass layer 22 and the conductive glass layer 23, and the undercoat glass layer 21 extends slightly outside the edge of the anti-electrical glass layer 22 in the planar direction P, so that the edge of the undercoat glass layer 21 becomes the edge 20e of the coated glass 20.

[0014] For example, as shown in FIG. 1b, the enamel product 100 may be configured such that the conductive glass layer 23 extends outward from the antistatic glass layer 22 at the edge of the coated glass 20, so that the edge of the conductive glass layer 23 directly overlaps the edge of the undercoat glass layer 21. In the enamel product 100 of this embodiment, in which the undercoat glass layer 21 extends outward from the conductive glass layer 23, spark discharge to the metal product 10 can be prevented when static electricity accumulates in the conductive glass layer 23. The undercoat glass layer 21 may extend outward from the conductive glass layer 23 by 1 mm or more, or by 2 mm or more. Alternatively, the conductive glass layer 23 may extend outward from the undercoat glass layer 21, so that the edge of the conductive glass layer 23 is directly baked onto the metal product 10. This configuration allows for rapid dissipation of electrical charge when static electricity occurs in the coated glass 20.

[0015] The glass composition constituting the undercoat glass layer 21 (hereinafter also referred to as "undercoat glass composition") may be, for example, a silicate glass composition containing 50 mol % or more of SiO2, or a borosilicate glass composition further containing B2O3. The undercoat glass composition may be composed of only a glass component, or may contain a glass component and an additive component that is not completely dissolved in the glass component.

[0016] The glass components of the subbing glass composition (hereinafter referred to as "subbing glass components") include, for example, 58 mol% to 70 mol% SiO2, 3 mol% to 8 mol% Al2O3, 13 mol% to 17 mol% B2O3, 12 mol% to 18 mol% Na2O, 2 mol% to 7 mol% K2O, and 1 mol% to 7 mol% CaF2 as essential components, and may further include, as optional components, 0 mol% to 3 mol% CaO, 0 mol% to 0.5 mol% CoO, 0 mol% to 0.7 mol% MnO2, and 0 mol% to 0.8 mol% NiO. The subbing glass composition may also include, as additive components, one or more selected from the group consisting of TiO2, Al2O3, La2O3, B2O3, and ZnO.

[0017] The glass composition (hereinafter also referred to as "glass composition for top coating") that constitutes the top glass layer (constituting the anti-static glass layer 22 and the conductive glass layer 23) may be, like the glass composition for undercoating, a silicate glass composition containing 50 mol % or more of SiO2, or a borosilicate glass composition that further contains B2O3. The glass composition for undercoating may be composed only of a glass component, or may contain a glass component and an additive component that is not completely dissolved in the glass component.

[0018] The glass components in the glass composition for top drawing (hereinafter referred to as "top drawing glass components") may include, for example, 50 mol% to 75 mol% of SiO2, 2 mol% to 15 mol% of ZrO2, 10 mol% to 25 mol% of R2O (where "R" represents Na, Li, K, or Cs), and 2 mol% to 12 mol% of R'O (where R' represents Mg, Ca, Sr, or Ba). The glass composition for top drawing may include, as an additive component, one or more selected from the group consisting of TiO2, Al2O3, La2O3, B2O3, and ZnO. More specifically, when the glass composition for top drawing contains only one selected from the group consisting of TiO2, Al2O3, La2O3, B2O3, and ZnO, the content can be 0.1 mol% to 4 mol%. When two or more types are contained, the content of each can be 0.1 mol% to 4 mol%, with the total content being 5 mol% or less. When the glass composition for size drawing contains only one selected from the group consisting of TiO2, Al2O3, La2O3, B2O3, and ZnO, the ... and ZnO.

[0019] The conductive glass composition constituting the conductive glass layer 23 may contain a conductivity-imparting agent as an additive component. Examples of conductive substances contained in the conductivity-imparting agent include metals. Metal oxides whose crystalline structure has been disrupted by doping with a dopant (impurity) can also be used as conductive substances. Examples of such conductive substances include noble metals, impurity-doped titanium oxide, and tin oxide. More specifically, examples of conductive substances include indium compounds such as indium oxide and tin oxide-containing indium oxide; antimony compounds such as antimony oxide and antimony oxide-containing tin oxide; noble metals such as silver, gold, and platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum); and noble metal compounds such as ruthenium dioxide and iridium dioxide.

[0020] The conductivity enhancer may be a single particle composed only of these conductive materials, or a composite particle in which a conductive material is coated on a base particle (e.g., ceramic particle) composed of a material other than a conductive material. The shape of the conductivity enhancer may be spherical, fibrous, plate-like, or irregular.

[0021] The preferred content of the conductivity imparting agent in the conductive glass composition varies depending on the type of conductive substance, but the conductivity imparting agent can be contained in the conductive glass composition so as to impart a predetermined conductivity (e.g., surface resistivity) to the conductive glass layer 23. When a glass composition having all the same components, including the content ratio, as the conductive glass composition except for not containing the conductivity imparting agent is used as the base glass composition, the conductivity imparting agent can be contained so as to reduce the surface resistivity of the conductive glass layer 23 to one-tenth or less of that of a glass layer formed from the base glass composition, and may be contained so as to reduce the surface resistivity to one-hundredth or less.

[0022] When a glass layer is formed using a surface coating glass composition that does not contain a conductivity imparting agent, the surface resistivity of the glass layer is usually 1×10 under standard conditions (e.g., 22±1°C, 60±5% RH). 13The surface resistivity of the conductive glass layer 23 in the standard state is, for example, 1×10 11 The surface resistivity of the conductive glass layer 23 in the standard state is adjusted to 1×10 10 The surface resistivity of the conductive glass layer 23 in the standard state may be, for example, 1×10 6 The surface resistivity of the conductive glass layer 23 in the standard state is 1×10 7 It may be Ω / sq or more, and may be 1×10 8 It may be Ω / sq or more, and may be 1×10 9 The surface resistivity of the conductive glass layer 23 can be measured, for example, by the method specified in JIS C 2139:2008 "Solid electrical insulating materials -- Measurement method of volume resistivity and surface resistivity."

[0023] The presence or absence of a conductivity-imparting agent does not significantly affect the voltage resistance characteristics of the size-drawn glass composition. That is, the breakdown voltage (kV / mm) does not change significantly between a glass layer made of the base glass composition and a conductive glass layer 23 made of a conductive glass composition obtained by adding a conductivity-imparting agent to the base glass composition. Therefore, to increase the breakdown voltage (kV / mm) of the electrical-resistant glass layer 22 compared to the conductive glass layer 23, it may be insufficient for the glass composition constituting the electrical-resistant glass layer 22 to simply not contain a conductivity-imparting agent. The electrical-resistant glass layer 22 is preferably made of an electrical-resistant glass composition containing a glass component and an additive component, with some or all of the additive component being a breakdown voltage improving agent.

[0024] The addition of the breakdown voltage improving material can provide the electric-resistant glass layer 22 with a superior breakdown voltage (kV / mm) compared to the conductive glass layer 23 or a glass layer formed from a base glass composition of the conductive glass composition. When the base glass composition of the electric-resistant glass composition is a glass composition that is the same as the electric-resistant glass composition in terms of all other components, including their contents, except that it does not contain the breakdown voltage improving material, the breakdown voltage improving material is used to provide the electric-resistant glass layer 22 with a superior breakdown voltage (kV / mm) compared to a glass layer formed from the base glass composition.

[0025] The breakdown voltage improving agent is preferably a non-conductive substance that exhibits a higher breakdown voltage (kV / mm) by itself than the glass layer composed of the base glass composition to which it is added. The breakdown voltage improving agent is a substance that can improve the breakdown voltage (kV / mm) when added to the glass layer. It can be added without decomposing in the glass, thereby increasing the breakdown voltage of the glass layer to which it is added. Examples of breakdown voltage improving agents include mica and tin oxide. Examples of mica include muscovite, phlogopite, and biotite, with muscovite being preferred. The non-conductivity of the breakdown voltage improving agent can be confirmed by measuring the volume resistivity in accordance with JIS C 2139:2008, "Solid Electrical Insulating Materials - Measurement Methods for Volume Resistivity and Surface Resistivity." For example, a cylindrical main electrode with a diameter of 50 mm, a disk-shaped counter electrode with a diameter of 83 mm, and a resin pipe with a length of about 10 mm and an inner diameter (diameter 50 mm) corresponding to the main electrode are used, the resin pipe is placed at the center of the horizontally supported counter electrode, and dry powder of a material for improving dielectric breakdown voltage is poured into the resin pipe in an amount such that the deposited thickness is about 1 mm. The dry powder is smoothed as flat as possible, and the main electrode is placed on top of it. When the volume resistivity is measured in this state, pressure is applied from above so that a load of about 100 N is applied to the dry powder, including the weight of the main electrode, and the measured value is 1×10 10 If the measured value is Ωcm or more, it can be determined that the dielectric breakdown voltage improving material is non-conductive.

[0026] The electric-resistant glass layer 22 may be formed to exhibit a breakdown voltage (kV / mm) that is 0.1 kV / mm or more higher than that of a glass layer made of the base glass composition of the electric-resistant glass layer 22 or the conductive glass layer 23. The improvement in breakdown voltage (kV / mm) of the electric-resistant glass layer 22 compared to a glass layer made of these base glass compositions may be 0.2 kV / mm or more, 0.3 kV / mm or more, 0.5 kV / mm or more, or 0.7 kV / mm or more. The improvement in breakdown voltage (kV / mm) is typically 4 kV / mm or less.

[0027] The content of the breakdown voltage improving material in the electrical glass composition to achieve the above-mentioned effects is, for example, 1% by mass or more. The content of the breakdown voltage improving material may be 2% by mass or more, or 3% by mass or more. More preferably, it may be 5% by mass or more, or even 10% by mass or more. The breakdown voltage improving material preferably exhibits the above-mentioned effects when added to the electrical glass composition to a content of 30% by mass. The content of the breakdown voltage improving material to achieve the above-mentioned effects may be 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less.

[0028] The conductive glass layer 23 has a resistance of, for example, 1×10 11 The antistatic glass layer 22 is prepared so as to have a surface resistivity of 1×10 Ω / sq or less under standard conditions. 12 It is prepared to be Ω / sq or more.

[0029] The enamel product 100 has an electrically-resistant glass layer 22 that is less conductive than the conductive glass layer 23 and has a higher breakdown voltage (kV / mm) than a glass layer made of a glass composition (base glass composition) obtained by removing the conductivity-imparting agent from the conductive glass composition, thereby enabling the coated glass 20 to exhibit excellent voltage resistance characteristics.

[0030] The electric-resistant glass layer 22 preferably exhibits a breakdown voltage (kV / mm) of 18.5 kV / mm or more, and more preferably exhibits a breakdown voltage (kV / mm) of 19.0 kV / mm or more.

[0031] The breakdown voltage (kV / mm) of the glass layer can be determined, for example, by measuring the breakdown voltage (kV) using a dielectric strength tester manufactured by Toko Kizai Co., Ltd. (Tokyo Transformer Co., Ltd.) and converting the measured value to a value per unit thickness (per mm) of the glass layer. The breakdown voltage (kV / mm) can be determined, for example, by subjecting a test specimen having a glass layer to the method specified in JIS C 2110-1:2016 (IEC 60243-1:2013) "Solid Electrical Insulating Materials - Test Methods for Dielectric Breakdown Strength - Part 1: Testing by Applying Power Frequency AC Voltage." The breakdown voltage can be determined by determining the voltage (kV) at breakdown of the glass layer according to the standard and dividing the voltage (kV) by the thickness (mm) of the glass layer on the test specimen. The test can be performed using electrodes shaped as specified in "5.2.1.3 Ball-Plate Electrodes" in the standard, using a 20 mm diameter spherical (brass) upper electrode and an iron plate lower electrode. The test specimen is a 100 mm square metal plate with a glass layer of approximately 1 mm thick formed from the glass composition. Conditioning for at least 24 hours at 22±1°C and 60±5% RH is required before testing. The test can be performed by immersing the test specimen and the electrodes in oil (e.g., silicone oil, an insulating oil conforming to JIS C 2320) at 22°C. The voltage rise rate can be selected so that dielectric breakdown of the test material generally occurs within 10 to 20 seconds, based on "10.1 Short-Term (Rapid Voltage Rise) Test" in the standard. The standard recommends a voltage rise rate of 100 V / s, 200 V / s, 500 V / s, 1000 V / s, or 2000 V / s. For the glass layer of enamelware, the voltage rise rate is usually either 1000 V / s or 2000 V / s. The breakdown voltage (kV / mm) can be determined as an arithmetic mean value when the above test is performed on a plurality of test pieces (for example, three or more pieces).

[0032] In an enamel product 100, static electricity is usually generated on the surface of the coated glass 20. In the enamel product 100 of this embodiment, the conductive glass layer 23, which is the outermost layer of the multiple glass layers that make up the coated glass 20, forms the surface of the coated glass 20, and therefore, if static electricity occurs, the charge can be widely diffused. In the enamel product 100 of this embodiment, the presence of the anti-static glass layer 22 suppresses discharge in the thickness direction T, so there is less need to quickly move static electricity in the planar direction P, and the thickness of the conductive glass layer 23 can be made thinner, allowing for a reduction in the amount of precious metals and other materials used.

[0033] The thickness (t1) of the conductive glass layer 23 is, for example, 0.1 mm or more. The thickness (t1) of the conductive glass layer 23 may be 0.2 mm or more. The thickness (t1) of the conductive glass layer 23 is, for example, 0.5 mm or less. The thickness (t1) of the conductive glass layer 23 may be 0.4 mm or less.

[0034] The thickness (t2) of the electric-resistant glass layer 22 is, for example, 0.2 mm or more. The thickness (t2) of the electric-resistant glass layer 22 may be 0.3 mm or more. The thickness (t2) of the electric-resistant glass layer 22 is, for example, 1.0 mm or less. The thickness (t2) of the electric-resistant glass layer 22 may be 0.6 mm or less. The thickness (t2) of the electric-resistant glass layer 22 may be 0.5 mm or less. The ratio (t2 / t1) of the thickness (t2) of the electric-resistant glass layer 22 to the thickness (t1) of the conductive glass layer 23 may be, for example, 0.4 times or more and 10 times or less, or 1.2 times or more and 3.0 times or less.

[0035] In this way, among the multiple top-coated glass layers laminated on the undercoated glass layer 21, providing a top-coated glass layer that is thicker than the conductive glass layer 23 is advantageous in increasing the dielectric breakdown voltage (kV / mm) of the entire coated glass 20, and also ensures sufficient corrosion resistance even if pinholes occur in the surface layer.

[0036] To achieve the above-described effects, for example, as shown in FIG. 2a, three or more overlaid glass layers may be provided, with a third overlaid glass layer, i.e., an intermediate glass layer 24, interposed between the outermost conductive glass layer 23 and the anti-electrical glass layer 22. Alternatively, as shown in FIG. 2b, the third overlaid glass layer 25 may be interposed between the anti-electrical glass layer 22 and the underlaid glass layer 21, rather than between the conductive glass layer 23 and the anti-electrical glass layer 22. The third overlaid glass layer (24, 25) such as the intermediate glass layer 24 is preferably a glass layer having a lower conductivity than the conductive glass layer 23 and preferably has a thickness equal to or greater than that of the conductive glass layer 23. The third overlaid glass layer (24, 25) such as the intermediate glass layer 24 may be composed of a glass composition that does not contain, for example, a conductivity-imparting agent or a breakdown voltage-improving agent, and may be a glass layer composed of the base glass composition of the anti-electrical glass layer 22 or the conductive glass layer 23. For example, the third top glass layer (24, 25), such as the intermediate glass layer 24, has a surface resistivity of 1×10 12 The glass layer may have a breakdown voltage (kV / mm) of Ω / sq or more and less than 18.5 kV / mm. The number of overlaid glass layers may be four or more. The glass composition (base glass composition) obtained by removing the conductivity-imparting agent from the conductive glass composition and the glass composition (base glass composition) obtained by removing the breakdown voltage-improving agent from the anti-electrical glass layer may have the same composition or different compositions. Because the electrical properties of the conductive glass layer 23 and the anti-electrical glass layer 22 are significantly different, providing a third overlaid glass layer (intermediate glass layer 24) between the conductive glass layer 23 and the anti-electrical glass layer 22, which has lower conductivity than the conductive glass layer 23 and lower breakdown voltage than the anti-electrical glass layer 22, can prevent a sudden change in the electrical properties in the thickness direction T of the coated glass 20 and can be advantageous for mitigating the electric field when static electricity is generated. Furthermore, compared to when only the undercoat glass layer 21 is provided between the anti-static glass layer 22 and the metal product 10, providing the third glass layer 25 between the anti-static glass layer 22 and the undercoat glass layer 21 can prevent the electrical properties of the coated glass 20 from changing suddenly in the thickness direction T, which can be effective in mitigating the electric field when static electricity is generated.

[0037] Instead of the intermediate glass layer 24 in Fig. 2a, a second electric-resistant glass layer 22b containing a breakdown voltage improving material may be provided as shown in Fig. 3. As shown in Figs. 1a and 1b, the glass layer in contact with the conductive glass layer 23 from the metal product 10 side may be used as the electric-resistant glass layer 22, or as shown in Fig. 3, a first electric-resistant glass layer 22a and a second electric-resistant glass layer 22b may be provided and the second electric-resistant glass layer 22b may be abutted against the conductive glass layer 23, so that the conductive glass layer 23 and the electric-resistant glass layer 22 are adjacent to each other in the thickness direction T, thereby enabling the coated glass 20 to exhibit excellent voltage resistance characteristics.

[0038] When a first and second electric-resistant glass layer 22a and 22b are provided, the subbing glass layer 21 in the embodiment shown in Figs. 1a and 1b may be replaced with a second electric-resistant glass layer 22b as shown in Fig. 4. The enamelware 100 shown in Fig. 4 comprises a second electric-resistant glass layer 22b baked directly onto the metal product 10 between the conductive glass layer 23 provided on the outermost surface and the metal product 10, a first electric-resistant glass layer 22a in contact with the second electric-resistant glass layer 22b from the side opposite the metal product 10, and an intermediate glass layer 24 interposed between the first electric-resistant glass layer 22a and the conductive glass layer 23. The intermediate glass layer 24 may be formed, for example, from the base glass composition of the conductive glass layer 23 and the electric-resistant glass layers 22a and 22b. The intermediate glass layer 24 may also have a surface resistivity of, for example, 1 × 10 12 The glass layer may have a breakdown voltage (kV / mm) of at least Ω / sq and less than 18.5 kV / mm.

[0039] When multiple electric-resistant glass layers including the first and second electric-resistant glass layers 22a and 22b are provided, the types and amounts of breakdown voltage improving materials may be different. For example, one of the first and second electric-resistant glass layers 22a and 22b may have a higher muscovite content (mass %) than the other, or one of the first and second electric-resistant glass layers 22a and 22b may have a higher tin oxide content (mass %) than the other. Alternatively, one of the first and second electric-resistant glass layers 22a and 22b may have a higher muscovite content (mass %) than the tin oxide content (mass %), and the other may have a higher tin oxide content (mass %) than the muscovite content (mass %). Here, "the muscovite content (% by mass) is made higher than the tin oxide content (% by mass)" does not only mean "containing both muscovite and tin oxide, with a correlation between their contents," but also "containing only muscovite and no tin oxide." The same applies to "making the tin oxide content (% by mass) higher than the muscovite content (% by mass)."

[0040] As shown in Fig. 4, when the undercoat glass layer is a second electric-resistant glass layer 22b and a first electric-resistant glass layer 22a is provided on top of that, the intermediate glass layer 24 can be eliminated, and the coated glass 20 can have a laminated structure as shown in Fig. 5. The enamelware product 100 shown in Fig. 5 is similar to the enamelware product 100 shown in Fig. 4 in that it has a second electric-resistant glass layer 22b baked directly onto the metal product 10 between the outermost conductive glass layer 23 and the metal product 10, and a first electric-resistant glass layer 22a in contact with the second electric-resistant glass layer 22b from the side opposite the metal product 10, but differs from the enamelware product 100 shown in Fig. 4 in that the first electric-resistant glass layer 22a and the conductive glass layer 23 are in direct contact with each other. Like the enamel product 100 shown in Figures 1a, 1b, and 3, the enamel product 100 shown in Figure 5 can also exhibit excellent voltage resistance characteristics because the anti-static glass layer and the conductive glass layer 23 are in direct contact with each other.

[0041] When the undercoat glass layer is an anti-static glass layer 22, the anti-static glass layer 22 may be disposed only in the area in contact with the metal product 10, with an intermediate glass layer 24 provided between the anti-static glass layer 22 and the conductive glass layer 23, as shown in Fig. 6, or a two-layer covering glass 20 may be provided, with the anti-static glass layer 22 in contact with the metal product 10 and the conductive glass layer 23 overlapping the anti-static glass layer 22, as shown in Fig. 7. These embodiments have the advantage that the structure of the covering glass 20 can be made relatively simple. The intermediate glass layer 24 in the embodiment shown in Fig. 6 may also have a surface resistivity of, for example, 1 x 10 12 The glass layer may have a breakdown voltage (kV / mm) of at least Ω / sq and less than 18.5 kV / mm.

[0042] Although the effect of the breakdown voltage improving material on improving voltage resistance has not been fully confirmed, it is believed that mica, being a silicate mineral, has excellent affinity with glass, making it less likely to generate partial discharges at the interface with the glass even when high voltages are applied to the coated glass 20. Furthermore, its plate-like structure is believed to suppress the formation of discharge paths, such as dark currents and electron avalanches, along the thickness of the glass layer. Tin oxide is also believed to have the effect of mitigating the electric field. Therefore, the breakdown voltage-improving effect of a tin oxide-containing anti-electrical glass layer can be more pronounced by being disposed in contact with either or both of the conductive glass layer 23, which has excellent conductivity, and the metal product 10. On the other hand, the breakdown voltage-improving effect of a mica-containing anti-electrical glass layer is believed to be improved whether it is disposed between the conductive glass layer 23 and the metal product 10.

[0043] In addition to the above-described embodiments, various other embodiments may be employed for the enamel product 100. For example, the enamel product 100 may have multiple conductive glass layers including a conductive glass layer 23 provided as the outermost glass layer, or may have multiple intermediate glass layers that do not contain a conductivity-imparting material or a breakdown voltage improving material.

[0044] The above-described enamel product 100 and other types of enamel products can be manufactured by carrying out a pre-processing step in which a base metal product 10 is prepared and a glaze that will be used to form each glass layer is prepared, followed by a glazing step in which the metal product 10 is coated with glaze, and a firing step in which the metal product 10 after the glazing step is heated to melt the glaze and bake it onto the metal product 10 to form a glass layer.

[0045] In the pre-processing step, a slurry may be prepared by dispersing glass particles composed of glass components and particles of each additive in a dispersion medium, and the glazing step may be carried out using the slurry. Furthermore, in the pre-processing step, a roughening treatment may be carried out to appropriately roughen the surface 10a of the metal product 10 in order to improve adhesion between the glass layer and the metal product 10.

[0046] In the pre-processing step of this embodiment, a slurry for the conductive glass layer containing a conductivity-imparting agent and a slurry for the electrical-resistant glass layer containing a breakdown voltage improving agent are separately prepared. The glazing step can be carried out by pouring or spraying the prepared slurry onto the metal product 10. The glazing and firing steps may be repeated for each glass layer, or multiple glass layers may be glazed and then fired together.

[0047] In this embodiment, an example in which a conductivity imparting material or a material for improving dielectric breakdown voltage is added has been described, but in addition, a material having a different function may be added. Such a material may include a material for improving abrasion resistance or impact resistance, such as glass fiber or ceramic fiber.

[0048] This specification provides the above examples of enamel products and their manufacturing methods, but enamel products and their manufacturing methods are in no way limited to the above examples, and this specification also includes the following disclosures.

[0049] (1) An enamel product in which multiple glass layers are laminated to a metal product, a conductive glass layer made of a conductive glass composition containing a conductivity imparting material is provided on the outermost layer of the plurality of glass layers; An enamel product in which an anti-electrical glass layer having a higher breakdown voltage (kV / mm) than the conductive glass layer is provided between the conductive glass layer and the metal product.

[0050] (2) The enamel product according to (1), wherein the anti-static glass layer has lower electrical conductivity than the conductive glass layer and higher breakdown voltage (kV / mm) than a glass layer made of a glass composition obtained by removing the conductivity-imparting agent from the conductive glass composition.

[0051] (3) The enamel product according to (1) or (2), wherein the anti-static glass layer has lower conductivity than the conductive glass layer and a breakdown voltage of 18.5 kV / mm or more.

[0052] (4) The enamel product according to any one of (1) to (3), wherein the anti-static glass layer is thicker than the conductive glass layer.

[0053] (5) The plurality of glass layers includes a base glass layer in contact with the metal product and a plurality of top glass layers laminated on the base glass layer, The enamel product according to any one of (1) to (4), wherein the plurality of coated glass layers includes a coated glass layer that is thicker than the conductive glass layer.

[0054] (6) The enamel product according to any one of (1) to (5), wherein the anti-electrical glass layer contains a breakdown voltage improving material that improves breakdown voltage when added to a glass composition obtained by removing the conductivity imparting material from the conductive glass composition.

[0055] (7) The enamel product of (6), wherein the dielectric breakdown voltage improving material contains at least one of muscovite and tin oxide.

[0056] (8) The plurality of glass layers includes a base glass layer in contact with the metal product and a plurality of top glass layers laminated on the base glass layer, The enamel product according to any one of (1) to (7), wherein the plurality of coated glass layers includes the anti-static glass layer.

[0057] (9) The enamel product according to any one of (1) to (8), wherein the anti-static glass layer is in contact with the conductive glass layer.

[0058] (10) The enamel product according to any one of (1) to (9), wherein the glass layer directly laminated on the metal product is the anti-electricity glass layer.

[0059] (11) The enamel product according to any one of (1) to (10), wherein an intermediate glass layer is interposed between the conductive glass layer and the anti-static glass layer.

[0060] (12) 1. A method for manufacturing an enamel product comprising a metal product and a plurality of glass layers laminated to the metal product, the method comprising: carrying out a firing step of firing the plurality of glass layers onto the metal product; In the firing step, forming a conductive glass layer by adding a conductivity imparting material to at least one of the plurality of glass layers to be fired onto the metal product; and adding a breakdown voltage improving material to at least one of the plurality of glass layers to form an anti-electrical glass layer having a breakdown voltage (kV / mm) higher than that of the conductive glass layer. A method for manufacturing an enamel product, in which the conductive glass layer is provided as the outermost layer of the plurality of glass layers, and the anti-static glass layer is provided between the conductive glass layer and the metal product. [Example]

[0061] The present invention will now be described in more detail with reference to experimental examples. 1. No additives (measurement of breakdown voltage with base glass composition) A glaze containing glass powder used in general silicate glass-based glazed glass was applied to one side of a 100 mm square metal plate, and the glazed metal plate was fired to produce a test specimen with a glass layer formed on one side. The test pieces were prepared so that the thickness of the glass layer after firing would be approximately 1 mm. Three test pieces were prepared and conditioned in an environment of 22±1°C and 60±5% RH for 24 hours or more before being used in the dielectric breakdown test. After measuring the thickness of the glass layer of the test piece, the voltage value (kV) at which dielectric breakdown occurs was measured using a dielectric strength tester manufactured by Tokyo Transformer Co., Ltd. The test was carried out in silicone oil (insulating oil conforming to JIS C 2320) at a temperature of 22°C. The electrodes used were "ball-plane electrodes" (upper electrode: φ20 mm brass spherical electrode, lower electrode: iron plate). The test was conducted in accordance with "10.1 Short-time (rapid voltage increase) test" in JIS C 2110-1:2016 "Solid electrical insulating materials - Test methods for dielectric breakdown strength - Part 1: Tests using power frequency AC voltage application," and the voltage increase rate was 1000 V / s. The breakdown voltage per thickness of the glass layer (kV / mm) was calculated from the test results, and the results of the three test pieces were averaged.

[0062] The surface resistivity of the prepared sample was measured and found to be 1×10 13 Furthermore, when antimony-containing tin oxide was added to the glass composition used at this time and a sample was prepared in the same manner as above, the surface resistivity of the sample was confirmed to be 2 to 3 × 10 9 It was confirmed that the resistance was Ω / sq.

[0063] 2. Verification of the effect of additives on improving breakdown voltage The dielectric breakdown test was carried out in the same manner as in the case of no additive, except that the test piece was prepared so that the additive was contained in the glass layer at a ratio of 10 mass %. As additives, inorganic particles such as spherical alumina, machinable ceramics, magnesia, and zirconia were used in addition to materials for improving the dielectric breakdown voltage, such as tin oxide and muscovite. In addition, the surface resistivity of the sample using tin oxide and the sample using muscovite was measured and found to be 1×10 13 It was confirmed that it was Ω / sq or more. The results are shown in Table 1.

[0064] [Table 1]

[0065] It can be seen from the above results that the present invention, which provides an anti-electricity glass layer with excellent breakdown voltage as described above, provides an enamel product with excellent voltage resistance characteristics. [Explanation of symbols]

[0066] 10: metal product, 10a: surface, 10a1: coated area, 10a2: uncoated area, 20: coated glass, 20e: edge, 21: undercoat glass layer, 22: anti-electrical-proof glass layer, 22a: first anti-electrical-proof glass layer, 22b: second anti-electrical-proof glass layer, 23: conductive glass layer, 100: enamel product.

Claims

1. An enamel product in which multiple glass layers are laminated to a metal product, a conductive glass layer made of a conductive glass composition containing a conductivity imparting material is provided on the outermost layer of the plurality of glass layers; An enamel product in which an anti-electrical glass layer having a higher breakdown voltage (kV / mm) than the conductive glass layer is provided between the conductive glass layer and the metal product.

2. 2. The enamel product according to claim 1, wherein the anti-static glass layer has lower electrical conductivity than the conductive glass layer and a higher breakdown voltage (kV / mm) than a glass layer made of a glass composition obtained by removing the conductivity-imparting agent from the conductive glass composition.

3. 2. The enamel product according to claim 1, wherein the anti-static glass layer has a lower electrical conductivity than the conductive glass layer and a breakdown voltage of 18.5 kV / mm or more.

4. 4. The enamel product according to claim 1, wherein the anti-static glass layer is thicker than the conductive glass layer.

5. The plurality of glass layers includes a base glass layer in contact with the metal product and a plurality of top glass layers laminated on the base glass layer, 4. The enamel product according to claim 1, wherein the plurality of glass layers includes a glass layer that is thicker than the conductive glass layer.

6. 4. The enamel product according to claim 1, wherein the electrical-resistant glass layer contains a breakdown voltage improving material that improves breakdown voltage when added to a glass composition obtained by removing the conductivity-imparting material from the conductive glass composition.

7. 7. The enamel product according to claim 6, wherein said breakdown voltage improving material contains at least one of muscovite and tin oxide.

8. The plurality of glass layers includes a base glass layer in contact with the metal product and a plurality of top glass layers laminated on the base glass layer, 4. The enamel product according to claim 1, wherein the plurality of glass layers includes the anti-static glass layer.

9. 9. The enamel product of claim 8, wherein the anti-static glass layer is in contact with the conductive glass layer.

10. 4. The enamel product according to claim 1, wherein the glass layer directly laminated on the metal product is the electrical resistant glass layer.

11. 4. The enamel product according to claim 1, wherein an intermediate glass layer is interposed between the conductive glass layer and the anti-static glass layer.

12. 1. A method for manufacturing an enamel product comprising a metal product and a plurality of glass layers laminated to the metal product, the method comprising: carrying out a firing step of firing the plurality of glass layers onto the metal product; In the firing step, forming a conductive glass layer by adding a conductivity imparting material to at least one of the plurality of glass layers to be fired onto the metal product; and adding a breakdown voltage improving material to at least one of the plurality of glass layers to form an anti-electrical glass layer having a breakdown voltage (kV / mm) higher than that of the conductive glass layer. A method for manufacturing an enamel product, in which the conductive glass layer is provided as the outermost layer of the plurality of glass layers, and the anti-static glass layer is provided between the conductive glass layer and the metal product.

Images