Cooker top plate and method for manufacturing cooker top plate

Abstract

The invention provides a top plate for a cooker and a method for manufacturing the top plate for the cooker, wherein the top plate for the cooker achieves appearance with high matte texture and has high stain resistance and high scratch resistance. The top plate for a cooker comprises: a glass substrate having a cooking surface on which a cooking appliance is placed and a back surface on the opposite side from the cooking surface; and a coating layer disposed on the cooking surface side of the glass substrate, the coating layer including an inorganic layer, and the root mean square roughness Rq of the surface of the coating layer being 0.1 [mu] m to 1 [mu] m.

Description

Technical Field

[0001] This invention relates to a top plate for a cooking appliance and a method for manufacturing a top plate for a cooking appliance. Background Technology

[0002] A cooker top plate is provided on the upper part of an electromagnetic cooker, a radiant cooker, and a gas cooker. Typically, the cooker top plate comprises a transparent or opaque glass substrate, which has a cooking surface for supporting the cooker and a back surface opposite to the cooking surface. Furthermore, a coating is sometimes provided on the cooking surface of the glass substrate to improve the design flexibility of the cooker top plate.

[0003] In recent years, with increasing emphasis on design, there has been a demand for cooktops with a matte finish on the cooking surface. For example, Patent Document 1 describes a cooktop that achieves a matte finish by stacking a high-reflectivity film (with a higher reflectivity than the glass substrate) on the cooking surface of a glass substrate made of low-expansion crystallized glass, and further stacking a patterned glass decorative layer on the high-reflectivity film. Patent Document 2 describes a cooktop that achieves a matte finish by stacking a reflective film (with a lower reflectivity than the glass substrate) on the cooking surface of a cooktop.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2008-190846 Patent Document 2: Japanese Patent Application Publication No. 2008-290917 Summary of the Invention

[0005] The problem that the invention aims to solve However, in Patent Document 1, because the exposed patterned glass decorative layer contains glass and white pigment, the white pigment hinders the flow of glass during firing, resulting in a tendency for the arithmetic mean roughness Ra of the patterned glass decorative layer to increase. Consequently, when rubbed against cooking utensils such as pots, the bottom of the pot is scratched, causing the coating to peel off, easily adhering as stains to the patterned glass decorative layer, or the patterned glass decorative layer is easily scratched. Furthermore, although Patent Document 2 describes that the patterned glass decorative layer can be composed solely of a glass composition or can contain inorganic pigments in addition to a glass composition for coloring, regardless of whether it is composed solely of a glass composition or contains inorganic pigments, when rubbed against cooking utensils such as pots, the bottom of the pot is scratched, causing the coating to peel off, easily adhering as stains to the patterned glass decorative layer, or the patterned glass decorative layer is easily scratched.

[0006] Therefore, it is difficult to improve stain resistance and scratch resistance while achieving a matte finish. In this invention, "stain resistance" refers to the ability to withstand the phenomenon where the coating of a cooking utensil peels off and adheres to the top plate of the cooking utensil when the utensil comes into contact with it; "scratch resistance" refers to the ability to withstand scratches caused by scraping the surface of the top plate of the cooking utensil when the utensil comes into contact with it.

[0007] In view of the above, the object of the present invention is to provide a cookware top plate that achieves a high matte finish and has high stain resistance and scratch resistance, as well as a method for manufacturing the cookware top plate.

[0008] Technical solutions for solving the problem After conducting in-depth research, the inventors of this invention discovered that by controlling the surface shape of the coating layer provided on the cooking surface of a glass substrate, it is possible to provide a cookware top plate that achieves a high matte finish appearance and has high stain resistance and high scratch resistance, as well as a method for manufacturing the cookware top plate.

[0009] The top plate for a cooker according to Embodiment 1 of the present invention is characterized in that it comprises: a glass substrate having a cooking surface for supporting a cooker and a back surface opposite to the cooking surface; and a coating layer disposed on the cooking surface side of the glass substrate, the coating layer comprising an inorganic layer, and the root mean square roughness Rq of the surface of the coating layer being 0.1 μm to 1 μm.

[0010] In the cooker top plate of embodiment 2 of the present invention, preferably based on embodiment 1, the inorganic layer contains inorganic beads.

[0011] In the cooker top plate of embodiment 3 of the present invention, preferably based on embodiment 1 or 2, the arithmetic mean roughness Ra of the surface of the coating layer is 0.22 μm to 0.9 μm.

[0012] In the cooker top plate of embodiment 4 of the present invention, preferably based on embodiment 2 or 3, the inorganic beads contain at least one inorganic bead selected from glass beads, alumina beads, silica beads, zirconium beads, quartz beads, feldspar beads, zeolite beads, corundum beads, and zircon beads.

[0013] In the cooker top plate of embodiment 5 of the present invention, preferably in any of embodiments 2 to 4, the inorganic beads do not protrude from the surface of the coating layer.

[0014] In the cooker top plate of embodiment 6 of the present invention, preferably in any of embodiments 2 to 5, the inorganic layer comprises a glass matrix, and the difference between the softening point of the inorganic beads and the glass matrix is ​​300°C or less.

[0015] In the cooker top plate of embodiment 7 of the present invention, preferably in any of embodiments 1 to 6, the inorganic layer comprises a glass matrix with a refractive index different from that of the inorganic beads.

[0016] In the cooker top plate of embodiment 8 of the present invention, preferably in any of embodiments 1 to 7, the inorganic layer does not contain coloring pigments.

[0017] In the cooker top plate of embodiment 9 of the present invention, preferably in any of embodiments 1 to 8, an anti-fouling layer and / or a protective layer are further provided on the inorganic layer in the coating layer.

[0018] In the cooker top plate of embodiment 10 of the present invention, preferably in any of embodiments 1 to 9, the 20° gloss value of the surface of the coating layer is 38 or less.

[0019] In the cooker top plate of embodiment 11 of the present invention, preferably in any of embodiments 1 to 10, the 60° gloss value of the surface of the coating layer is 70 or less.

[0020] The top plate for a cooker according to embodiment 12 of the present invention is characterized in that it includes: a glass substrate having a cooking surface for supporting a cooker and a back surface opposite to the cooking surface, wherein the root mean square roughness Rq of the surface of the cooking surface is 0.25 μm to 0.95 μm.

[0021] The method for manufacturing a cooker top plate according to Embodiment 13 of the present invention is used to manufacture a cooker top plate configured according to any one of Embodiments 1 to 11. The method is characterized by comprising: coating an inorganic layer forming paste containing inorganic beads onto the surface of a glass substrate, and firing it to form a coating layer containing an inorganic layer on the surface of the glass substrate, wherein the root mean square roughness Rq of the surface of the coating layer is 0.1 μm to 1 μm.

[0022] Invention Effects The present invention provides a cookware top plate that achieves a high matte finish and has high stain resistance and scratch resistance, as well as a method for manufacturing the cookware top plate. Attached Figure Description

[0023] Figure 1 This is a cross-sectional schematic diagram showing the top plate of a cooker according to an embodiment of the present invention.

[0024] Figure 2 The image is a cross-sectional image of the cooker top plate obtained in Embodiment 2 of the present invention, taken using a scanning electron microscope (SEM) (magnification: 5000x).

[0025] Figure 3The image is a cross-sectional image of the cooker top plate obtained in Example 10 of the present invention, taken using a scanning electron microscope (SEM) (magnification: 5000x). Detailed Implementation

[0026] The preferred embodiments are described below. However, these embodiments are merely illustrative, and the present invention is not limited to them. Furthermore, in the accompanying drawings, components that have substantially the same function are sometimes labeled with the same symbol.

[0027] Additionally, in this instruction manual, "top plate for cooking appliance" is sometimes referred to simply as "top plate".

[0028] Figure 1 The cooker top plate 1 shown has a glass substrate 2. The glass substrate 2 has a cooking surface 2a and a back surface 2b. The cooking surface 2a and the back surface 2b are opposite surfaces to each other. The cooking surface 2a is the surface on the side that supports the cookware such as a pot or frying pan. The back surface 2b is the inner side of the cooker, facing the light source or heating element. Therefore, the cooking surface 2a and the back surface 2b are in an inside-out relationship. A coating layer 3 is disposed on the cooking surface 2a of the glass substrate 2. The coating layer 3 includes an inorganic layer 4. That is, the cooking surface 2a of the glass substrate 2 is in contact with the coating layer 3, and the cooking surface 2a of the glass substrate 2 is in contact with the inorganic layer 4.

[0029] The following describes the components that make up the top plate 1 and the details of each layer.

[0030] The glass substrate 2 is not particularly limited. For example, the glass substrate 2 can be a white glass substrate or a transparent glass substrate. In addition, in this specification, "transparent" means that the transmittance of the glass substrate in the visible light wavelength region of 450nm to 700nm is 70% or more.

[0031] The top plate 1 is repeatedly heated and cooled. Therefore, the glass substrate 2 preferably has high thermal shock resistance and a low coefficient of thermal expansion. Specifically, the softening temperature of the glass substrate 2 is preferably 700°C or higher, more preferably 750°C or higher. Furthermore, the average linear coefficient of thermal expansion of the glass substrate 2 within the range of 30°C to 750°C is preferably -10 × 10⁻⁶. －7 / ℃~+60×10 －7 More preferably, within the range of / ℃, it is within -10×10 －7 / ℃~+50×10 －7 Within the range of / ℃, it is further preferred to be within -10×10 －7 / ℃~+40×10 －7The glass substrate 2 is preferably made of glass with a high glass transition temperature and low expansion, or crystallized glass. Specific examples of low-expansion crystallized glass include Nippon Electric Glass Co., Ltd.'s "N-11" and "N-0," which are LAS (Li2O-Al2O3-SiO2) based crystallized glasses. Alternatively, borosilicate glass substrates or the like can also be used as the glass substrate 2.

[0032] The thickness of the glass substrate 2 is not particularly limited. The thickness of the glass substrate 2 can be appropriately set according to the output temperature and structure of the heating cooker. For example, the thickness of the glass substrate 2 can be set to about 2mm to 6mm.

[0033] The arithmetic mean roughness Ra of the cooking surface 2a of the glass substrate 2 before the coating layer 3 is formed is preferably 1.5 μm or less, more preferably 1.0 μm or less, even more preferably 0.8 μm or less, and particularly preferably 0.5 μm or less. If the roughness exceeds the above upper limit, the root mean square roughness Rq and arithmetic mean roughness Ra of the surface of the coating layer 3 tend to increase after the coating layer 3 is formed. Therefore, cooking utensils are easily scratched by the uneven surface of the coating layer 3, causing the metal or coating on the bottom of the cooking utensil to be scraped off, easily adhering as stains to the coating layer 3, or the raised portions of the surface of the coating layer 3 to be scratched, easily causing scratches on the coating layer 3, which is undesirable. Furthermore, the lower limit value is not particularly limited.

[0034] The coating layer 3 is disposed on the cooking surface 2a of the glass substrate 2. The coating layer 3 includes an inorganic layer 4. That is, the coating layer 3 is a single-layer structure including one inorganic layer 4. In addition, within the range that the matte texture appearance, stain resistance and scratch resistance, which are the objectives of this invention, are not compromised, the coating layer 3 may also have layers other than the inorganic layer 4 on top of the inorganic layer 4, and may be a two-layer structure or a structure of three or more layers. In this case, the proportions of the constituent components of each layer may be different or the same. Details of the coating layer 3 having a structure of two or more layers will be described later. In addition, in the following description, "the surface of the coating layer 3" refers to "the surface of the inorganic layer 4" when the coating layer 3 is composed only of the inorganic layer 4, and refers to "the outermost surface of the layers other than the inorganic layer 4" when layers other than the inorganic layer 4 are also formed on the inorganic layer 4.

[0035] The root mean square roughness Rq of the surface of the coating layer 3 is 0.1 μm to 1 μm. More preferably, the root mean square roughness Rq of the surface of the coating layer 3 is 0.26 μm or more, further preferably 0.32 μm or more, particularly preferably 0.38 μm or more, and is 1 μm or less, more preferably 0.75 μm or less, further preferably 0.6 μm or less, and particularly preferably 0.5 μm or less. When the root mean square roughness Rq is below the upper limit and above the lower limit, the contact area between the cooking utensil and the coating layer 3 during friction can be appropriately controlled. Therefore, the frictional force generated between the cooking utensil and the coating layer 3 is easily reduced, stain resistance and scratch resistance are easily improved, and the matte texture is easily improved. When the root mean square roughness Rq of the surface of the coating layer 3 is less than the lower limit mentioned above, the contact area between the cooking utensil and the coating layer 3 becomes too large, the friction between the cooking utensil and the coating layer 3 increases, the stain resistance and scratch resistance decrease, and it is difficult to improve the matte texture.

[0036] The arithmetic mean roughness Ra of the surface of the coating layer 3 is preferably 0.9 μm or less, more preferably 0.5 μm or less, even more preferably 0.4 μm or less, and particularly preferably 0.35 μm or less. The lower limit of the arithmetic mean roughness Ra is preferably 0.22 μm or more, more preferably 0.25 μm or more, and even more preferably 0.29 μm or more. When it is greater than the above upper limit, when cooking utensils such as pots rub against the coating layer 3, the cooking utensils are easily scratched by the uneven surface of the coating layer 3, causing the metal, coating, etc. on the bottom surface of the cooking utensils to be scratched and adhered to the coating layer 3 as stains, or the raised parts on the surface of the coating layer 3 to be scratched, resulting in scratches on the coating layer 3, which is not suitable. When the arithmetic mean roughness Ra of the surface of the coating layer 3 is less than the lower limit mentioned above, when the cooking utensils rub against the coating layer 3, the contact area between the cooking utensils and the coating layer 3 becomes too large, the friction force generated between the cooking utensils and the coating layer 3 becomes high, the stain resistance and scratch resistance decrease, and it is difficult to improve the matte texture, so it is not suitable.

[0037] In addition, the arithmetic mean roughness Ra and the root mean square roughness Rq can be measured using Mitutoyo SJ-210, according to the method of JISB0601:2001, and under the following set conditions.

[0038] Measurement speed: 0.5 mm / s Cutoff values ​​λc: 0.7 mm, λs: 2.5 mm Number of intervals: 5 Gaussian filter The transmittance of the glass substrate 2 (top plate 1) with the coating layer 3 at a wavelength of 580 nm is preferably 75% or more, more preferably 80% or more, and even more preferably 81% or more. Furthermore, when the transmittance of the glass substrate is high (e.g., approximately 86% at a wavelength of 580 nm), the aforementioned transmittance value varies depending on the composition of the coating layer 3. When the transmittance of the glass substrate 2 with the coating layer 3 is above the aforementioned lower limit, color difference is less likely to occur between portions where the coating layer 3 is formed and portions where it is not formed, thus achieving a high-matte finish appearance and improving the overall design of the top plate 1. The upper limit of the transmittance of the glass substrate 2 with the coating layer 3 is not particularly limited, for example, it is 90% or less. Furthermore, the aforementioned transmittance is obtained based on the intensity (I0) of the incident light when light from a light source disposed on the coating layer 3 side is incident and the intensity (I) of the emitted light emitted from the glass substrate 2 side (back surface 2b side).

[0039] The thickness of the inorganic layer 4 is preferably 0.1–20 μm, more preferably 1–10 μm, even more preferably 2–5 μm, and particularly preferably 3–4 μm. When the thickness is below the upper limit and above the lower limit, the surface shape of the coating layer 3 can be easily adjusted to the desired degree by using glass beads, thus easily improving the matte texture while improving stain resistance and scratch resistance.

[0040] The Mohs hardness of the surface of the coating layer 3 is preferably 4 to 7, more preferably 5 to 6. When the Mohs hardness of the surface of the coating layer 3 is above the upper limit mentioned above, the metal, coating, etc. on the bottom surface of the cooking utensil are easily scratched by the surface of the coating layer 3, that is, the stain resistance is easily reduced. On the other hand, when it is below the lower limit mentioned above, the surface of the coating layer 3 is easily scratched by the cooking utensil, that is, the scratch resistance is easily reduced. In addition, the Mohs hardness of the surface of the coating layer 3 can be measured using a known Mohs hardness tester, such as the NARIKA Mohs hardness tester (MH-10R).

[0041] The following describes the components contained in inorganic layer 4.

[0042] The inorganic layer 4 contains a glass matrix as its matrix component. This glass matrix is, for example, composed of glass frit. Examples of glass compositions that can be used as the glass matrix (glass frit) include borosilicate glass, aluminoborosilicate glass, silicate glass containing at least one of an alkali metal component and an alkaline earth metal component, and phosphate glass containing zinc and aluminum. As the glass frit, for example, "Frit NPF," "Frit NPF10," or "Fine-grained Frit NPF" manufactured by Nippon Electric Glass Co., Ltd. may be used. One type of glass frit may be used, or two or more may be used in combination.

[0043] The glass matrix content of the inorganic layer 4 is preferably 55% by mass or more, more preferably higher than 55% by mass, more preferably 65% ​​by mass or more, further preferably 70% by mass or more, and preferably 99% by mass or less, more preferably 90% by mass or less, and further preferably 85% by mass or less. When it is above the lower limit and below the upper limit, it is easy to control the arithmetic mean roughness Ra and root mean square roughness Rq of the surface of the coated layer 3 within an appropriate range, thus easily improving stain resistance and scratch resistance, and easily improving the matte texture.

[0044] The inorganic layer 4 contains inorganic beads. That is, the coating layer 3 contains inorganic beads. Thus, the approximately spherical inorganic beads are scattered throughout the inorganic layer 4, making it easy to scatter light incident on the inorganic layer 4. Furthermore, the surface shape of the coating layer 3 can be easily adjusted to the desired degree. As a result, the 20° and 60° gloss values ​​of the surface of the coating layer 3 are easily reduced, thus achieving a high-matte finish appearance and easily improving stain resistance and scratch resistance. The inorganic beads preferably contain at least one selected from glass beads, alumina beads, silica beads, zirconium beads, quartz beads, feldspar beads, zeolite beads, corundum beads, and zircon beads, with glass beads being particularly preferred. This achieves a high-matte finish appearance and easily improves stain resistance and scratch resistance. Additionally, quartz beads, feldspar beads, zeolite beads, corundum beads, and zircon beads can be obtained by crushing natural or synthetic minerals such as quartz, feldspar, zeolite, corundum, and zircon used as raw materials.

[0045] Examples of glass compositions for the aforementioned glass beads include borosilicate glass, aluminoborosilicate glass, silicate glass containing at least one of alkali metal and alkaline earth metal components, and phosphate glass containing zinc and aluminum.

[0046] In addition, scanning electron microscopy and other methods can be used to confirm that inorganic layer 4 contains inorganic beads.

[0047] Preferably, the inorganic beads do not protrude from the surface of the coating layer 3. If the inorganic beads protrude from the surface of the coating layer 3, the coating on the bottom of the pot is easily peeled off, or the inorganic beads are easily scratched, thus failing to achieve the required stain resistance and scratch resistance. Furthermore, in this invention, "not protruding" means that the glass matrix and the inorganic beads are substantially in the same plane on the surface of the coating layer 3. However, a very small number of unintentionally and unavoidably protruding inorganic beads may exist; in this case, the area percentage of the surface area of ​​the coating layer 3 where the inorganic beads protrude from the surface of the coating layer 3 is less than 5%, less than 3%, or less than 1%. Whether the inorganic beads protrude can be confirmed by scanning electron microscopy.

[0048] The inorganic layer 4 preferably contains a glass matrix composed of glass beads and glass frit, and preferably the glass beads have a different softening point than the glass matrix. Furthermore, the softening point of the glass beads is preferably greater than that of the glass matrix. With this arrangement, at the firing temperature of the inorganic layer 4, the inorganic beads easily soften locally near the surface of the coated layer 3. As a result, the inorganic beads are less likely to protrude from the surface of the coated layer 3, and the surface shape of the coated layer 3 is more easily controlled to the desired degree. Therefore, stain resistance and scratch resistance are easily improved.

[0049] The difference in softening point between the inorganic beads and the glass matrix is ​​preferably 500°C or less, more preferably 200°C or less, and particularly preferably 100°C or less. With this arrangement, the inorganic beads readily soften locally near the surface of the coating layer 3 at the firing temperature of the inorganic layer 4. As a result, the inorganic beads are less likely to protrude from the surface of the coating layer 3, and the surface shape of the coating layer 3 can be easily controlled to the desired degree. Therefore, stain resistance and scratch resistance are easily improved. In view of the above, for example, the inorganic beads are preferably made of aluminoborosilicate glass, and the matrix glass is preferably made of borosilicate glass with a softening point lower than that of the glass constituting the inorganic beads.

[0050] The preferred relationship between the softening point of the inorganic beads and the firing temperature of the inorganic layer 4 is that the softening point of the inorganic beads is greater than the firing temperature of the inorganic layer 4. The difference between the softening point of the inorganic beads and the firing temperature of the inorganic layer 4 is preferably below 200°C, more preferably below 150°C, and even more preferably below 100°C. With this setting, at the firing temperature of the inorganic layer 4, the inorganic beads are less likely to protrude from the surface of the coating layer 3, and the surface shape of the coating layer 3 can be easily controlled to the desired degree. Therefore, it is easier to improve stain resistance and scratch resistance.

[0051] The softening point of the aforementioned inorganic beads is preferably below 1500°C, more preferably below 1000°C, further preferably below 950°C, and particularly preferably below 900°C. With this setting, at the firing temperature of the inorganic layer 4, the inorganic beads are less likely to protrude from the surface of the coating layer 3, and the surface shape of the coating layer 3 can be easily controlled to the desired degree. Therefore, it is easy to improve stain resistance and scratch resistance.

[0052] Furthermore, it is preferable that the refractive index of the inorganic beads is different from that of the glass matrix. As a result, light incident on the coating layer 3 is easily scattered, making it easy to achieve a high matte finish appearance.

[0053] The average particle size of the inorganic beads is preferably 1 μm to 9 μm, more preferably 2 to 8 μm, even more preferably 2.5 μm to 7 μm, and particularly preferably 3 to 6.5 μm. When the average particle size of the inorganic beads is below the upper limit and above the lower limit, it is easy to adjust the surface shape of the coating layer 3 to the desired degree, easily improve the matte texture, and improve stain resistance and scratch resistance.

[0054] The inorganic bead content of the inorganic layer 4 is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 11% by mass or more, particularly preferably 15% by mass or more, and preferably less than 45% by mass, more preferably less than 40% by mass, further preferably less than 35% by mass, and particularly preferably less than 30% by mass. When the content is above the lower limit and below the upper limit, it is easy to control the arithmetic mean roughness Ra and root mean square roughness Rq of the surface of the coated layer 3 within an appropriate range, thus easily improving stain resistance and scratch resistance, and easily improving the matte texture.

[0055] The glass bead content of the inorganic layer 4 is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 11% by mass or more, particularly preferably 15% by mass or more, and preferably 60% by mass or less, more preferably less than 45% by mass, more preferably less than 40% by mass, further preferably less than 35% by mass, and particularly preferably less than 30% by mass. When the content is above the lower limit and below the upper limit, it is easy to control the arithmetic mean roughness Ra and root mean square roughness Rq of the surface of the coated layer 3 within an appropriate range, thus easily improving stain resistance and scratch resistance, and easily improving the matte texture.

[0056] The mass ratio of inorganic beads to glass matrix content in inorganic layer 4 (content of inorganic beads / content of glass matrix) is preferably 0.01 or more, more preferably 0.05 or more, further preferably 0.1 or more, particularly preferably 0.2 or more, and preferably less than 0.81, more preferably less than 0.7, further preferably less than 0.6, and particularly preferably less than 0.4. When the content is above the lower limit and below the upper limit, it is easy to control the arithmetic mean roughness Ra and root mean square roughness Rq of the surface of the coating layer 3 within an appropriate range, thus easily improving stain resistance and scratch resistance, and easily improving the matte texture.

[0057] The mass ratio of glass bead content to glass matrix content in the inorganic layer 4 (glass bead content / glass matrix content) is preferably 0.01 or more, more preferably 0.05 or more, further preferably 0.1 or more, particularly preferably 0.2 or more, and preferably less than 0.81, more preferably less than 0.7, further preferably less than 0.6, and particularly preferably less than 0.4. When the value is above the lower limit and below the upper limit, it is easy to control the arithmetic mean roughness Ra and root mean square roughness Rq of the surface of the coating layer 3 within an appropriate range, thus easily improving stain resistance and scratch resistance, and easily improving the matte texture.

[0058] Furthermore, although beads containing organic groups can be added to the inorganic layer 4 in addition to inorganic beads, beads containing organic groups tend to protrude from the surface of the coating layer 3 at the firing temperature of the glass charge, and are therefore not preferred. Examples of beads containing organic groups include phenyl polysiloxane, methyl polysiloxane, methylphenyl polysiloxane, and organofunctionalized polysiloxane.

[0059] Preferably, the inorganic layer 4 does not contain coloring pigments. Preferably, the inorganic layer 4 does not contain extender pigments. Therefore, the inorganic layer 4 does not contain components that do not soften at the glass firing temperature and strongly impede glass flow, making it easier to control the surface shape of the coated layer 3 to the desired degree, and easily improving stain resistance and scratch resistance. Furthermore, since color difference is less likely to occur between the areas where the inorganic layer 4 is formed and the areas where it is not formed, a high matte finish appearance can be achieved, improving the overall design of the top plate 1. Additionally, within the range where the matte finish appearance and stain resistance and scratch resistance, which are the objectives of this invention, are not compromised, the inorganic layer 4 may contain either coloring pigments or extender pigments. In this case, the content of coloring pigments and extender pigments in the inorganic layer 4 is preferably 5% by mass or less, more preferably 1% by mass or less.

[0060] There are no particular limitations on the aforementioned coloring pigments as long as they are colored inorganic substances. Examples of such coloring pigments include: white pigment powders such as TiO2 powder, ZrO2 powder, and ZrSiO4 powder; blue inorganic pigment powders containing Co; green inorganic pigment powders containing Co; yellow inorganic pigment powders based on Ti-Sb-Cr and Ti-Ni systems; red inorganic pigment powders based on Co-Si systems; brown inorganic pigment powders containing Fe; and black inorganic pigment powders containing Cu. Only one of these coloring pigments may be used, or two or more may be used in combination.

[0061] Examples of co-containing blue inorganic pigment powders include Co-Al and Co-Al-Ti inorganic pigment powders. Examples of Co-Al inorganic pigment powders include CoAl₂O₄ powder. Examples of Co-Al-Ti inorganic pigment powders include CoAl₂O₄-TiO₂-Li₂O powder.

[0062] Examples of Co-containing green inorganic pigment powders include Co-Al-Cr and Co-Ni-Ti-Zn inorganic pigment powders. Examples of Co-Al-Cr inorganic pigment powders include Co(Al, Cr)₂O₄ powder. Examples of Co-Ni-Ti-Zn inorganic pigment powders include (Co, Ni, Zn)₂TiO₄ powder.

[0063] Examples of Fe-containing brown inorganic pigment powders include Fe-Zn based inorganic pigment powders. Examples of Fe-Zn based inorganic pigment powders include (Zn,Fe)Fe₂O₄ powder.

[0064] Examples of Cu-containing black inorganic pigment powders include Cu-Cr and Cu-Fe series inorganic pigment powders. Examples of Cu-Cr series inorganic pigment powders include Cu(Cr,Mn)₂O₄ powder and Cu-Cr-Mn powder. Examples of Cu-Fe series inorganic pigment powders include Cu-Fe-Mn powder.

[0065] Other examples of coloring pigments include pearlescent pigments.

[0066] The aforementioned extender pigments are inorganic pigment powders that differ from coloring pigments and inorganic beads. There are no particular limitations on the type of extender pigment used; for example, flake-like, needle-like, or spherical inorganic pigment powders can be used. Examples of such extender pigments include potassium carbonate, potassium titanate, kaolin, talc, and mica. Only one of the aforementioned extender pigments may be used, or two or more may be used in combination.

[0067] Within the scope of achieving the effects of the present invention, the coating layer 3 may also be two or more layers.

[0068] From the perspective of maximizing the effects of the present invention and improving the stain resistance of the top plate 1, it is preferable to further provide an anti-fouling layer on the inorganic layer 4 in the coating layer 3. Furthermore, in this specification, stain resistance refers to the ease with which stains such as burnt stains can be removed.

[0069] As an antifouling layer, antifouling layers containing silicon and zirconium, silicon and titanium, silicon and aluminum, silicon oxide, zirconium oxide, titanium oxide, aluminum oxide, or mixtures of silicon oxide and zirconium oxide, silicon oxide and titanium oxide, silicone resin, modified silicone resin, or fluororesin are preferred. Furthermore, from the perspective of further enhancing the effects of the present invention, an antifouling layer containing silicon oxide is particularly preferred.

[0070] Furthermore, for surfaces with high arithmetic mean roughness Ra and root mean square roughness Rq, forming a protective layer on such a surface using a layer made of the same material as the aforementioned antifouling layer can control the arithmetic mean roughness Ra and root mean square roughness Rq to the desired level, thereby achieving the effects of the present invention. In the case of forming a protective layer, it is particularly preferable to use a protective layer containing silicon oxide. Moreover, for the coating layer 3, the arithmetic mean roughness Ra and root mean square roughness Rq can also be controlled to the desired level by further forming an inorganic layer on the inorganic layer 4. In this case, it is preferable that the inorganic layer on the outermost surface does not contain inorganic beads. Furthermore, the arithmetic mean roughness Ra and root mean square roughness Rq can also be controlled to the desired level by polishing the surface of the coating layer 3. Examples of polishing methods for the surface of the coating layer 3 include physical polishing and chemical polishing. Examples of physical polishing methods include methods such as using abrasive slurry and polishing with a polishing machine for a certain period of time followed by cleaning, and methods such as using abrasive paste and polishing with a cloth or sponge for a certain period of time followed by cleaning. Examples of chemical polishing methods include methods such as applying an aqueous solution containing hydrogen fluoride to the surface of the inorganic layer 4 and leaving it for a certain period of time followed by cleaning, immersing the entire top plate 1 in an aqueous solution containing hydrogen fluoride and leaving it for a certain period of time followed by removal and cleaning, and spraying vapor of an aqueous solution containing hydrogen fluoride onto the surface of the inorganic layer 4 and leaving it for a certain period of time followed by cleaning.

[0071] From the perspective of improving the design of the top plate 1, a decorative layer or the like can be further set on the inorganic layer of the covering layer 3. From the perspective of reducing the time required for manufacturing processes, no layer needs to be set.

[0072] The 20° gloss value of the surface of the coating layer 3 of the top plate 1 is preferably 38 or less, more preferably 30 or less, even more preferably 23 or less, and particularly preferably 15 or less. When the value is below the upper limit mentioned above, a high-matte texture appearance can be obtained. The lower limit is not particularly limited, for example, it is 1 or more. Furthermore, from the perspective of achieving an improved matte texture and a high-end appearance, it is preferably 2 or more, more preferably 5 or more.

[0073] The 60° gloss value of the surface of the coating layer 3 of the top plate 1 is preferably 70 or less, more preferably 65 or less, even more preferably 60 or less, and particularly preferably 55 or less. When the value is below the upper limit mentioned above, a high-matte texture appearance can be obtained. The lower limit is not particularly limited, for example, it is 20 or more. Furthermore, from the perspective of achieving a more matte texture and a more premium appearance, a value of 30 or more is preferred, more preferably 40 or more.

[0074] The top plate 1 for a cooking appliance can be manufactured, for example, by the following manufacturing method.

[0075] First, a paste for forming the inorganic layer 4 containing glass beads and glass frit is prepared. Next, the paste for forming the inorganic layer 4 is applied to the surface of the glass substrate 2, which is called the cooking surface 2a, and then dried and fired.

[0076] As a method for applying the paste for forming the inorganic layer 4, known coating methods such as screen printing, inkjet printing, and spraying can be used. The drying temperature of the paste for forming the inorganic layer 4 can be set to, for example, 50°C or higher and 150°C or lower. The drying time of the paste for forming the inorganic layer 4 can be set to, for example, 5 seconds or higher and 50 hours or lower. The firing temperature of the paste for forming the inorganic layer 4 can be set to, for example, 600°C or higher and 950°C or lower. The firing time of the paste for forming the inorganic layer 4 can be set to, for example, 10 minutes or higher and 2 hours or lower. When the firing temperature and firing time of the inorganic layer 4 are below the upper limit and above the lower limit, it is easier to adjust the surface shape of the coated layer 3 to the desired degree, thus easily improving the matte texture and enhancing stain resistance and scratch resistance. Furthermore, when other layers (such as antifouling layers, protective layers, etc.) are formed on the inorganic layer 4 in the coating layer 3, the coating paste for forming the layers can be applied using known coating methods such as screen printing, inkjet printing, or spraying. The firing temperature of the coating paste for forming the antifouling layer and the protective layer can be set, for example, to a temperature of 400°C or higher and 800°C or lower, and the firing time can be set, for example, to a temperature of 5 seconds or higher and 50 hours or lower. When the firing temperature and firing time of the antifouling layer and the protective layer are below the upper limit and above the lower limit mentioned above, it is easy to adjust the surface shape of the coating layer 3 to the desired degree, thus easily improving the matte texture and enhancing stain resistance and scratch resistance.

[0077] As described above, it is possible to manufacture the top plate 1 for a cooking appliance.

[0078] In the first embodiment described above, for Figure 1 The above-described cooker top plate, as shown, includes a glass substrate and a coating layer disposed on the cooking surface of the glass substrate. However, in the cooker top plate of the present invention, a concealing layer may also be disposed on the back side of the glass substrate.

[0079] Furthermore, in the aforementioned cooker top plate on which a coating layer is disposed on the cooking surface of the glass substrate, the coating layer can be disposed on the entire surface of the cooking surface of the glass substrate or on a portion thereof. Moreover, the coating layer can be a single-layer structure or a multi-layer structure as a whole, or a portion thereof can be a single-layer structure or a multi-layer structure.

[0080] Furthermore, even without a coating layer on the cooking surface of the glass substrate, the effects of this invention can still be achieved by strictly controlling the root mean square roughness Rq and arithmetic mean roughness Ra of the cooking surface. In this case, the root mean square roughness Rq of the cooking surface is, for example, 0.25 to 0.95 μm. Additionally, the arithmetic mean roughness Ra of the cooking surface is 0.3 to 0.8 μm. As a method for controlling the surface condition of the cooking surface, the surface polishing method for the coating layer described above can be applied.

[0081] Example The present invention will now be described in more detail with reference to embodiments. However, these embodiments are merely illustrative and are not intended to limit the invention in any way.

[0082] Prepare the following glass substrates.

[0083] Transparent crystallized glass plate (manufactured by Nippon Electric Glass Co., Ltd., "N-0", average linear thermal expansion coefficient from 30℃ to 750℃: 0.5×10⁻⁶) －7 / ℃, thickness: 4mm) White crystallized glass plate (Nippon Electric Glass Co., Ltd. "N-11", average linear thermal expansion coefficient from 30℃ to 750℃: 13×10⁻⁶) －7 / ℃, thickness: 4mm) Prepare the following coating materials.

[0084] <Glass matrix> glass material Frit NPF (average particle size 3.5μm, softening point 660℃, borosilicate glass) manufactured by Nippon Electric Glass Co., Ltd. Frit NPF10 (average particle size 1μm, softening point 660℃, borosilicate glass) manufactured by Nippon Electric Glass Co., Ltd. "Fine-grain Frit NPF" manufactured by Nippon Electric Glass Co., Ltd. (average particle size 1.5μm, softening point 660℃, borosilicate glass) <Inorganic Beads> glass beads Uniqlo Co., Ltd. manufactures "UBS-0010E" (average particle size 6.1μm, softening point 850℃, aluminoborosilicate glass). Uniqlo Co., Ltd. manufactures "UBS-K0005E" (average particle size 3.3μm, softening point 850℃, aluminoborosilicate glass). Alumina beads "DAW-01" manufactured by Denka Co., Ltd. (average particle size 1.9μm, softening point (melting point) ≥1000℃) Silica beads "FB-3SDC" manufactured by Denka Co., Ltd. (average particle size 3.1μm, softening point (melting point) 1650℃) <Resin Adhesives> (Example 1) Glass frit (Frit NPF, manufactured by Nippon Electric Glass Co., Ltd.), glass beads (UBS-0010E, manufactured by Uniqlo Co., Ltd.), and resin binder were mixed in a mass ratio of 9:1:7.7 to prepare an inorganic layer forming paste. Next, the inorganic layer forming paste was screen-printed onto the cooking surface of a transparent crystallized glass plate (Nippon Electric Glass Co., Ltd., "N-0") to achieve a thickness of 3.5 μm after firing. Then, it was heated and dried at 80°C for 1 minute, and then fired at 800°C for 30 minutes to form an inorganic layer (coating layer). The resin binder completely evaporated during the heating and drying process. The content of each component in the dried and fired inorganic layer is shown in Table 1. Furthermore, a scanning electron microscope image of the cross-section of the obtained cookware top plate is shown. Figures 2-3 .

[0085] (Examples 2-7, 9-10 and Comparative Examples 1-2) Except for changing the proportions of each component in the inorganic layer to those shown in Table 1 below, the process was carried out in the same manner as in Example 1 to obtain a top plate for a cooking appliance.

[0086] (Example 8) The inorganic layer forming paste used in Example 3 was screen-printed onto the cooking surface of a white crystallized glass plate (Nippon Electric Glass Co., Ltd. "N-11") to achieve a thickness of 3.5 μm after firing. Next, it was heated and dried at 80°C for 1 minute, and then fired at 800°C for 30 minutes to form an inorganic layer. The resin binder completely evaporated during the heating and drying process. Then, an antifouling layer forming paste with a silicon oxide to zirconium oxide mass ratio of 1:9 was screen-printed onto the inorganic layer, and then fired at 600°C for 20 minutes to form an antifouling layer. The thickness of the antifouling layer after firing was 0.03–0.15 μm.

[0087] (Example 11) Except for changing the paste used to form the antifouling layer to 100% by mass of silicon oxide, the same procedure as in Example 8 was performed to obtain a top plate for a cooker.

[0088] (Example 12) Except for changing the paste used to form the antifouling layer to 100% by mass of silicone resin, the same procedure as in Example 8 was performed to obtain a top plate for a cooker.

[0089] (Examples 13-14) The paste used for forming the inorganic layer was the same as that used in Comparative Example 2. The paste used for forming the protective layer was changed to 100% by mass of silicon oxide. Otherwise, the process was the same as in Example 8 to obtain a cooker top plate. In addition, the film thickness of the protective layer after firing in Example 13 was 4 to 6 μm, and the film thickness of the protective layer after firing in Example 14 was 0.05 to 0.15 μm.

[0090] (Example 15) The inorganic layer forming paste used in Example 10 was screen-printed onto the cooking surface of a white crystallized glass plate (Nippon Electric Glass Co., Ltd., "N-11") to achieve a thickness of 4.9 μm after firing. Next, it was heated and dried at 80°C for 1 minute, and then fired at 800°C for 30 minutes to form an inorganic layer. The resin binder completely evaporated during the heating and drying process. Then, a paste made of glass frit (Nippon Electric Glass Co., Ltd., "Frit NPF") and resin binder was further screen-printed onto the aforementioned inorganic layer. Next, it was heated and dried at 80°C for 1 minute, and then fired at 800°C for 30 minutes to form another inorganic layer on top of the first inorganic layer. At this point, the combined thickness of the first and second inorganic layers after firing was 7.7 μm. When the total mass of the first and second inorganic layers was set to 100%, the glass comprised 94% by mass, and the silica beads comprised 6% by mass.

[0091] The cooktop plates of Examples 1-15 and Comparative Examples 1-2 were evaluated as follows (1)-(3) and (5). In addition, the cooktop plates of Examples 8 and 11-12 were evaluated as follows (4).

[0092] [evaluate] (1) The 20° gloss value and 60° gloss value of the surface of the coating layer The 20° and 60° gloss values ​​of the coating surface of the obtained cookware top plate were evaluated using HORIBA IG-331 according to JIS K5600-5-4 (1999).

[0093] (2) Light transmittance of the top plate (coating) of the cooking appliance The transmittance of the obtained cookware top plate at a wavelength of 580 nm was measured from the back side of the glass substrate using a spectrophotometer (V-770 manufactured by Japan Spectrophotometer Co., Ltd.).

[0094] (3) The stain resistance and scratch resistance of the coated surface First, clay and sand were added to a stainless steel pot with a bottom diameter of 200±10mm, adjusting the total weight to 2.0kg. Next, with the bottom of the stainless steel pot in contact with the coating, the pot was moved back and forth at a speed of approximately 1m / s over a distance of 50mm, repeated 100 times. Then, the coating was visually observed, and the degree of staining caused by scraping the bottom of the pot (stain resistance) and the degree of scratching caused by friction with the bottom of the pot (scratch resistance) were evaluated according to the following indicators. Alternatively, the stainless steel pot was replaced with an enamel pot, and clay and sand were added to the enamel pot, adjusting the total weight to 2.5kg, and the same operation and evaluation were performed.

[0095] Stain resistance ○: No visible pot stains are attached.

[0096] △: There are slightly visible pot stains attached.

[0097] ×: There are pot stains attached, which greatly reduce the design.

[0098] Scratch resistance ○: No visually identifiable scratches were produced.

[0099] △: Scratches that are slightly visible to the naked eye.

[0100] ×: This produces scratches that significantly reduce the design quality.

[0101] (4) The antifouling properties of the antifouling layer The following antifouling test 1 was conducted on Example 8, and the following antifouling test 2 was conducted on Examples 11-12.

[0102] (4-1) Antifouling test 1 First, apply 1g of commercially available barbecue sauce to the anti-fouling layer (cooking side) of the prepared cookware top plate and spread it thinly. Next, heat the top plate in an electric oven at 250°C for 30 minutes, then remove it and allow it to cool naturally at room temperature, allowing the barbecue sauce to char and adhere to the anti-fouling layer. Next, immerse the top plate in water at 20°C for 10 minutes, then remove it and wipe off the moisture with a cloth. Finally, place the top plate on a work surface covered with a non-slip mat, and with the tip of disposable chopsticks held at a 45-degree angle and a load of 750g applied, rub the charred residue back and forth horizontally 10 times. Evaluate the removal of the charred residue according to the following criteria.

[0103] ○: The charred residue can be removed.

[0104] ×: The charred residue cannot be removed.

[0105] (4-2) Antifouling test 2 Following the same steps as in the anti-fouling test 1 above, a top plate with burnt barbecue sauce adhering to its anti-fouling layer surface was prepared and immersed in water at 20°C for 10 minutes. After removal, the surface was wiped dry with a cloth. Next, the top plate was fixed on the worktable of the abrasion tester, and plastic wrap coated with glass cooktop cleaner (NIPRO AD-KZ063) was pressed onto the surface of the top plate. Under a load of 200kg applied from above, the burnt residue was wiped back and forth horizontally 50 times. The removal of the burnt residue was evaluated according to the following indicators.

[0106] ○: The charred residue can be removed.

[0107] ×: The charred residue cannot be removed.

[0108] (5) The protruding state of inorganic beads Scanning electron microscopy was used to confirm whether inorganic beads protrude from the surface of the coating layer of the obtained cookware top plate.

[0109] ○: Not highlighted.

[0110] ×: There is a protrusion.

[0111] [Table 1] [Table 2] As clearly shown in Tables 1 and 2, the top plates of Examples 1 to 15, where the coating layer includes an inorganic layer and the root mean square roughness Rq of the coating layer surface is 0.1 μm to 1 μm, have a high matte texture and high stain resistance and scratch resistance. Furthermore, compared to Comparative Examples 1 and 2, where the root mean square roughness Rq of the coating layer surface is not 0.1 μm to 1 μm, the top plates of Examples 1 to 15 have an excellent matte texture and high stain resistance and scratch resistance. In Examples 8, 11, and 12, where an antifouling layer is also formed on the inorganic layer, the arithmetic mean roughness Ra and the root mean square roughness Rq can be controlled to the desired levels, resulting in excellent matte texture, stain resistance, scratch resistance, and improved stain resistance. Furthermore, in Examples 13 and 14, where a protective layer is formed on an inorganic layer with large arithmetic mean roughness Ra and root mean square roughness Rq, the arithmetic mean roughness Ra and root mean square roughness Rq can also be controlled to the desired level, thereby improving the matte texture, stain resistance, and scratch resistance. In Example 15, where an inorganic layer composed of glass frit is also formed on an inorganic layer composed of glass frit and inorganic beads, the arithmetic mean roughness Ra and root mean square roughness Rq can also be controlled to the desired level, thereby improving the matte texture, stain resistance, and scratch resistance.

[0112] Depend on Figure 2It is clearly understood that in the top plate of Example 2, the glass beads (inorganic beads) do not protrude from the surface of the coating layer, but exist in the coating layer in a generally spherical shape. Furthermore, due to... Figure 3 It can be confirmed that in the top plate of Example 10, silica beads (inorganic beads) protrude from the surface of the coating.

[0113] Symbol Explanation 1: Top plate for cooking appliance; 2: Glass substrate; 2a: Cooking surface; 2b: Back side; 3: Coating layer; 4: Inorganic layer; 5: Inorganic beads.

Claims

1. A top plate for a cooking appliance, characterized in that, include: A glass substrate having a cooking surface for supporting a cooking utensil and a back surface opposite to the cooking surface; and A coating layer disposed on the cooking surface side of the glass substrate. The coating layer comprises an inorganic layer. The root mean square roughness Rq of the surface of the coating layer is 0.1 μm to 1 μm.

2. The top plate for a cooker as described in claim 1, characterized in that: The inorganic layer contains inorganic beads.

3. The top plate for a cooker as described in claim 2, characterized in that: The arithmetic mean roughness Ra of the surface of the coating layer is 0.22 μm to 0.9 μm.

4. The top plate for a cooker as described in claim 2 or 3, characterized in that: The inorganic beads contain at least one inorganic bead selected from glass beads, alumina beads, silica beads, zirconium beads, quartz beads, feldspar beads, zeolite beads, corundum beads, and zircon beads.

5. The top plate for a cooker as described in claim 2 or 3, characterized in that: The inorganic beads do not protrude from the surface of the coating layer.

6. The top plate for a cooker as described in claim 2 or 3, characterized in that: The inorganic layer comprises a glass matrix. The difference in softening point between the inorganic beads and the glass matrix is ​​below 300°C.

7. The top plate for a cooker as described in claim 2 or 3, characterized in that: The inorganic layer comprises a glass matrix with a refractive index different from that of the inorganic beads.

8. The top plate for a cooker as described in claim 2 or 3, characterized in that: The inorganic layer does not contain coloring pigments.

9. The top plate for a cooker as described in claim 2 or 3, characterized in that: In the coating layer, an antifouling layer and / or a protective layer are also provided on the inorganic layer.

10. The top plate for a cooker as described in claim 1 or 2, characterized in that: The surface of the coating layer has a 20° gloss value of 38 or less.

11. The top plate for a cooker as described in claim 1 or 2, characterized in that: The surface of the coating layer has a 60° gloss value of 70 or less.

12. A top plate for a cooking appliance, characterized in that, include: A glass substrate having a cooking surface for supporting cooking utensils and a back surface opposite to the cooking surface. The root mean square roughness Rq of the cooking surface is 0.25 μm to 0.95 μm.

13. A method for manufacturing a cooker top plate, for manufacturing the cooker top plate according to claim 1 or 2, characterized in that the method comprises: The process of coating an inorganic layer forming paste containing inorganic beads onto the surface of a glass substrate and then firing it to form a coating layer containing an inorganic layer on the surface of the glass substrate. The root mean square roughness Rq of the surface of the coating layer is 0.1 μm to 1 μm.

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