Cooker top plate and method for manufacturing cooker top plate

Abstract

The invention provides a top plate for a cooker, which can improve damage resistance and adhesion of an inorganic layer. The top plate (1) for a cooker comprises: a glass substrate (2) having a cooking surface (2a) on which a cooking appliance is placed and a back surface (2b) on the opposite side from the cooking surface (2a); and an inorganic layer (3) disposed on the rear surface (2b) side of the glass substrate (2). The inorganic layer (3) contains glass, a coloring pigment, and an extender pigment having an average particle diameter of less than 0.5 [mu] m.

Description

Technical Field

[0001] The present invention relates to a top plate for a cooker and a method for manufacturing the top plate for a cooker. Background Art

[0002] Cookers having a cooker top plate and a light source such as an LED (Light Emitting Diode) are widely used. The cooker top plate used in combination with the light source generally has a transmissive portion that allows light from the light source to pass through and a non-transmissive portion that shields the light from the light source. The user of the cooker can confirm light signals (various information) such as the on / off state of the power supply and the heating state based on the light from the light source that passes through the transmissive portion.

[0003] For example, the following Patent Document 1 discloses a cooker top plate, which includes: a glass substrate having a cooking surface for placing a cooking utensil and a back surface opposite to the cooking surface, and a transmissive portion for transmitting light from a light source and a non-transmissive portion for shielding light from the light source. In the cooker top plate, the transmissive portion has a first colored layer provided on the glass substrate, the non-transmissive portion has a light shielding layer provided on the glass substrate, and the color difference ΔE between the transmissive portion and the non-transmissive portion in the L*a*b* color space measured from the cooking surface side of the glass substrate is 2 or less. Patent Document 1 also describes a method in which the first colored layer is a layer composed of glass and a color pigment.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-186905 Summary of the invention

[0007] Technical problem to be solved by the invention

[0008] As described in Patent Document 1, in a cooker top plate, a layer (inorganic layer) containing glass and a coloring pigment is sometimes disposed on the back side of a glass substrate. The light transmittance of the inorganic layer can be adjusted by adjusting the content of the coloring pigment, for example.

[0009] However, in the existing inorganic layer containing glass and coloring pigments, the damage resistance and adhesion of the inorganic layer cannot be fully improved. When the damage resistance and adhesion of the inorganic layer are low, for example, when the inorganic layer of the cooker top plate contacts the surrounding parts during the process of assembling the cooker, the inorganic layer may be scratched or the inorganic layer may be peeled off from the glass substrate.

[0010] The present invention aims to provide a cooker top plate capable of improving the scratch resistance and adhesion of an inorganic layer. The present invention also aims to provide a method for manufacturing a cooker top plate capable of improving the scratch resistance and adhesion of an inorganic layer in the obtained cooker top plate.

[0011] Technical solutions for solving technical problems

[0012] Hereinafter, each aspect of a cooker top plate and a method for manufacturing the cooker top plate that solves the above-mentioned technical problems will be described.

[0013] The top plate for a cooker involved in mode 1 of the present invention is characterized in that it includes: a glass substrate having a cooking surface for placing cooking utensils and a back surface opposite to the cooking surface; and an inorganic layer arranged on the back surface side of the above-mentioned glass substrate, the above-mentioned inorganic layer containing glass, a coloring pigment and a body pigment with an average particle size of less than 0.5μm.

[0014] In the cooker top plate according to aspect 2, preferably, in aspect 1, the cooker top plate includes a transmission portion that transmits light from a light source, and the transmission portion includes the inorganic layer.

[0015] In the top plate for a cooker according to aspect 3, preferably in aspect 1 or aspect 2, the extender pigment contains barium sulfate.

[0016] In the cooker top plate according to aspect 4, preferably in any one of aspects 1 to 3, the content of the extender pigment is 10% by mass or more and 55% by mass or less in 100% by mass of the inorganic layer.

[0017] In the cooker top plate according to aspect 5, in any one of aspects 1 to 4, it is preferred that the average particle size of the coloring pigment is 0.4 μm or more and 3 μm or less.

[0018] In the cooker top plate according to aspect 6, preferably, in any one of aspects 1 to 5, there is provided a non-transmitting portion for shielding light from the light source, wherein the non-transmitting portion includes a light shielding layer provided on the inorganic layer.

[0019] The top plate for a cooker involved in mode 7 of the present invention is characterized in that it includes: a glass substrate having a cooking surface for placing cooking utensils and a back side opposite to the cooking surface; and an inorganic layer arranged on the back side of the above-mentioned glass substrate, and the above-mentioned inorganic layer contains glass, a coloring pigment and barium sulfate.

[0020] The manufacturing method of the cooker top plate involved in mode 8 of the present invention is characterized in that the above-mentioned cooker top plate includes: a glass substrate having a cooking surface for placing cooking utensils and a back side opposite to the cooking surface; and an inorganic layer arranged on the above-mentioned back side of the above-mentioned glass substrate, and the above-mentioned manufacturing method includes: a step of applying an inorganic layer forming paste on the above-mentioned back side of the above-mentioned glass substrate; and a step of firing the above-mentioned glass substrate coated with the above-mentioned inorganic layer forming paste, and the above-mentioned inorganic layer forming paste contains glass material, coloring pigment and body pigment with an average particle size of less than 0.5μm.

[0021] In the method for producing a top plate for a cooker according to aspect 9, preferably in aspect 8, the extender pigment contains barium sulfate.

[0022] Effects of the Invention

[0023] According to the present invention, there is provided a cooker top plate capable of improving the scratch resistance and adhesion of an inorganic layer. According to the present invention, there is also provided a method for manufacturing a cooker top plate capable of improving the scratch resistance and adhesion of an inorganic layer in the obtained cooker top plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic cross-sectional view showing a top plate for a cooker according to the first embodiment of the present invention.

[0025] Figure 2 It is a schematic cross-sectional view showing a top plate for a cooker according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0026] Hereinafter, preferred embodiments will be described. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each of the drawings, components having substantially the same function are sometimes referred to by the same reference numerals.

[0027] In addition, in this specification, a "cooker top plate" may be abbreviated as a "top plate".

[0028] [First embodiment]

[0029] Figure 1 It is a schematic cross-sectional view showing a top plate for a cooker according to the first embodiment of the present invention.

[0030] Figure 1The top plate 1 for a cooker 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 a surface on the side where a cooking utensil such as a pot or a frying pan is placed. The back surface 2b is a surface facing a light source or a heating device on the inner side of the cooker. Therefore, the cooking surface 2a and the back surface 2b are in a front-back relationship.

[0031] The inorganic layer 3 is disposed on the back surface 2b side of the glass substrate 2. The back surface 2b of the glass substrate 2 is in contact with the inorganic layer 3. The inorganic layer 3 contains glass, a coloring pigment, and an extender pigment having an average particle size of less than 0.5 μm.

[0032] A light shielding layer 4 is disposed on the back surface 2b side of the glass substrate 2. The back surface 2b of the glass substrate 2 is in contact with the light shielding layer 4. Figure 2 Unlike the top plate 1A of the top plate 1, the back surface 2b of the glass substrate 2 is in contact with the light shielding layer 4. In the top plate 1, the light shielding layer 4 may not be arranged on the surface of the inorganic layer 3 on the side opposite to the glass substrate 2. In the top plate 1, the light shielding layer 4 may be arranged at the end of the surface of the inorganic layer 3 on the side opposite to the glass substrate 2. In the case where the light shielding layer 4 is arranged at the end of the surface of the inorganic layer 3 on the side opposite to the glass substrate 2, the light shielding layer 4 may be arranged at a position of 0 mm to 2 mm inward from the end of the inorganic layer 3, or may be arranged at a position of 0 mm to 5 mm.

[0033] A light source 20 is provided below the top plate 1. As the light source 20, a light source composed of an LED or a liquid crystal component can be cited.

[0034] The top plate 1 has a transparent portion D1 that allows light from the light source 20 to pass through, and a non-transparent portion D2 that blocks light from the light source 20. In the top plate 1, the inorganic layer 3 is a layer that can transmit light from the light source 20, and the light-shielding layer 4 is a layer for shielding light from the light source 20. The transparent portion D1 of the top plate 1 has the inorganic layer 3, more specifically, it does not have a light-shielding layer but has the inorganic layer 3 and the glass substrate 2. The non-transparent portion D2 of the top plate 1 has the light-shielding layer 4, more specifically, it has the light-shielding layer 4 and the glass substrate 2. Of course, in the case where the light-shielding layer 4 is arranged at the end of the surface of the inorganic layer 3 on the side opposite to the glass substrate 2 side, the portion having the light-shielding layer 4, the inorganic layer 3 and the glass substrate 2 is also the non-transparent portion D2. The transparent portion D1 corresponds to the portion of the top plate 1 where the light-shielding layer 4 is not arranged. The non-transparent portion D2 corresponds to the portion of the top plate 1 where the light-shielding layer 4 is arranged.

[0035] The light from the light source 20 is emitted to the outside (above the top plate 1) in the transparent portion D1, and is shielded in the non-transparent portion D2. When the top plate 1 is viewed from above, the transparent portion D1 is an area that uses the light from the light source 20 to display information. As the above-mentioned information, there can be listed information showing that the power is on, or information showing that heating is in progress, etc., which shows the state of the cooker. In the top plate 1, for example, by changing the top view shape of the transparent portion D1, it is possible to emit light corresponding to the top view shape of the transparent portion D1 to the outside, and text, numbers, symbols, etc. can be displayed. In addition, by transmitting patterned light through the transparent portion D1, text, numbers, symbols, etc. can also be displayed. Alternatively, by transmitting light from a liquid crystal component through the transparent portion D1, text, numbers, symbols, etc. can also be displayed.

[0036] In the top plate 1, the inorganic layer 3 contains glass, coloring pigments and a body pigment having an average particle size of less than 0.5 μm, thereby improving the scratch resistance and adhesion of the inorganic layer 3. In the top plate 1, the adhesion between the glass substrate 2 and the inorganic layer 3 and the scratch resistance of the inorganic layer 3 can be improved.

[0037] When the inorganic layer 3 contains glass, a coloring pigment, and barium sulfate, it is also possible to improve the scratch resistance and adhesion of the inorganic layer 3. In this case, the average particle size of the barium sulfate in the inorganic layer 3 is preferably less than 0.5 μm.

[0038] Hereinafter, the members constituting the top plate 1 and the details of each layer will be described.

[0039] (Glass Substrate)

[0040] The glass substrate 2 is preferably a glass substrate that transmits at least a portion of light within a wavelength of 450nm to 700nm (for example, a wavelength of 580nm). The glass substrate 2 is preferably a transparent glass substrate. The glass substrate 2 may also be colored and transparent, but from the perspective of further improving the aesthetics of the top plate 1, it is preferably colorless and transparent. In this specification, the "transparency" of the glass substrate means that the transmittance of at least a portion of light within a wavelength of 450nm to 700nm (for example, a wavelength of 580nm) in the visible wavelength domain is 70% or more.

[0041] Heating and cooling are repeated on the top plate 1. Therefore, the glass substrate 2 preferably has high thermal shock resistance and low thermal expansion coefficient. Specifically, the softening temperature of the glass substrate 2 is preferably 700°C or higher, more preferably 750°C or higher. In addition, the average linear thermal expansion coefficient of the glass substrate 2 within 30°C to 750°C is preferably within a range of -10×10 -7 / ℃~+60×10 -7 / ℃, more preferably -10×10 -7 / ℃~+50×10 -7 / ℃, more preferably -10×10-7 / ℃~+40×10 -7 / ℃ range. For example, the glass substrate 2 is preferably composed of low expansion crystallized glass. As a specific example of low expansion crystallized glass, for example, "N-0" produced by Nippon Electric Glass Co., Ltd., which is a LAS-based crystallized glass, can be cited. In addition, as the glass substrate 2, a borosilicate glass substrate or a quartz glass substrate can also be used.

[0042] The thickness of the glass substrate 2 is not particularly limited. The thickness of the glass substrate 2 can be appropriately set according to light transmittance, etc. The thickness of the glass substrate 2 can be set to about 2 mm to 6 mm, for example.

[0043] (Inorganic layer)

[0044] The inorganic layer 3 is arranged on the back side 2b of the glass substrate 2. The inorganic layer 3 is in contact with the back side 2b of the glass substrate 2. In addition, in the present invention, other layers may be arranged between the inorganic layer 3 and the glass substrate 2. The inorganic layer 3 is a layer that can transmit light from the light source 20. The inorganic layer 3 contains glass, a coloring pigment, and a body pigment having an average particle size of less than 0.5 μm. By adjusting the type or content of the coloring pigment in the inorganic layer 3, the light transmittance of the inorganic layer 3 can be adjusted.

[0045] <Glass>

[0046] The inorganic layer 3 contains glass. As the glass, conventionally known glasses can be used. The glass may be used alone or in combination of two or more.

[0047] Examples of the glass include borosilicate 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.

[0048] The content of the above-mentioned glass in the inorganic layer 3 (the content of the above-mentioned glass in 100 mass % of the inorganic layer) is preferably 10 mass % or more, more preferably 20 mass % or more, preferably 60 mass % or less, more preferably 40 mass % or less. When the content of the above-mentioned glass is less than the above-mentioned lower limit, the heat resistance of the top plate 1 is likely to decrease, and the damage resistance and adhesion of the inorganic layer 3 are likely to decrease. On the other hand, when the content of the above-mentioned glass exceeds the above-mentioned upper limit, the mechanical strength of the top plate 1 is likely to decrease.

[0049] <Coloring Pigments>

[0050] The inorganic layer 3 contains a coloring pigment. By using the coloring pigment, the light transmittance of the inorganic layer 3 can be adjusted. The coloring pigment may be used alone or in combination of two or more.

[0051] The coloring pigment is not particularly limited as long as it is a colored pigment. Examples of the coloring pigment 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 of Ti-Sb-Cr and Ti-Ni series; red inorganic pigment powders of Co-Si series; brown inorganic pigment powders containing Fe; black inorganic pigment powders containing Cu; inorganic pigment powders having a pearly color, etc.

[0052] 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 powders. Examples of Co-Al-Ti inorganic pigment powders include CoAl2O4-TiO2-Li2O powders.

[0053] Examples of green inorganic pigment powders containing Co 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 powders. Examples of Co-Ni-Ti-Zn inorganic pigment powders include (Co,Ni,Zn)2TiO4 powders.

[0054] Examples of the Fe-containing brown inorganic pigment powder include Fe—Zn-based inorganic pigment powders, and examples of the Fe—Zn-based inorganic pigment powder include (Zn, Fe)Fe2O4 powders.

[0055] Examples of Cu-containing black inorganic pigment powders include Cu-Cr-based inorganic pigment powders and Cu-Fe-based inorganic pigment powders. Examples of Cu-Cr-based inorganic pigment powders include Cu(Cr,Mn)2O4 powders and Cu-Cr-Mn powders. Examples of Cu-Fe-based inorganic pigment powders include Cu-Fe-Mn powders.

[0056] As the above-mentioned coloring pigment, pearl-tone pigment can also be used. As the pearl-tone pigment, for example, a pigment whose surface is coated with a metal oxide as a body pigment can be used. Specifically, a pigment obtained by coating the surface with titanium oxide, tin oxide, zirconium oxide, iron oxide, etc. as metal oxides using mica, talc, kaolin, sericite, silicon oxide, calcium carbonate, barium sulfate, etc. as a body pigment can be used. Among them, it is preferred to use a pearl-tone pigment obtained by coating the surface with titanium oxide using natural mica as a base material. Thereby, the design of the top plate 1 can be further improved. In addition, these pearl-tone pigments can be used alone or in combination.

[0057] The average particle size of the coloring pigment is preferably 0.4 μm or more, more preferably 0.5 μm or more, and further preferably 0.6 μm or more, preferably 16 μm or less, more preferably 3 μm or less, and further preferably 2.8 μm or less. When the average particle size of the coloring pigment is above the lower limit and below the upper limit, the aggregation of the coloring pigment can be suppressed, the color unevenness of the inorganic layer 3 can be effectively suppressed, and the coloring pigment of the inorganic layer 3 is not easy to protrude from the surface of the inorganic layer 3 to the outside. As a result, when the top plate 1 is used to assemble a cooking utensil or when it is used as a cooking utensil after assembly, it can be suppressed that the surface of the inorganic layer 3 is caught by peripheral parts or fingers, etc., causing the inorganic layer 3 to peel off.

[0058] The average particle size of the coloring pigment is a median particle size derived from a volume distribution measured by a laser diffraction scattering method.

[0059] The content of the coloring pigment in the inorganic layer 3 (the content of the coloring pigment in 100% by mass of the inorganic layer) is preferably 10% by mass or more, more preferably 25% by mass or more, preferably 65% ​​by mass or less, more preferably 55% by mass or less. When the content of the coloring pigment is above the lower limit and below the upper limit, the light-transmitting portion D1 of the top plate 1 easily obtains the desired light transmittance.

[0060] When the coloring pigment includes the pearlescent pigment, the content of the pearlescent pigment in the inorganic layer 3 (the content of the pearlescent pigment in 100% by mass of the inorganic layer) is preferably 20% by mass or less, more preferably 15% by mass or less, preferably 10% by mass or less, and more preferably 7% by mass or less. When the content of the pearlescent pigment exceeds the upper limit, it is difficult to improve the damage resistance and adhesion of the top plate 1.

[0061] <Extended pigment>

[0062] The inorganic layer 3 contains a body pigment. The body pigment is a body pigment having an average particle size of less than 0.5 μm. The body pigment is different from the glass and the coloring pigment. By using the body pigment, the damage resistance and adhesion of the inorganic layer 3 to the glass substrate 2 can be improved. The body pigment can be used alone or in combination of two or more.

[0063] By using the above-mentioned body pigment, the reason why the damage resistance and adhesion of the inorganic layer 3 are improved is still uncertain, but it can be considered as follows. Generally speaking, body pigments with a melting point higher than glass frit will not melt at the firing temperature of the glass frit, so there is a tendency to hinder the flow of molten glass frit during firing. The smaller the average particle size of the body pigment, the smaller the tendency. Therefore, when using a body pigment with an average particle size less than 0.5 μm, compared with the case of using a body pigment with an average particle size of more than 0.5 μm, the molten glass frit is easily mixed with the body pigment, and the contact area of ​​the molten glass frit and the body pigment increases, so that the adhesion of glass to the body pigment in the inorganic layer 3 is easily improved. As a result, it can be considered that the hardness of the inorganic layer 3 increases and the damage resistance improves. The reason why the adhesion of the inorganic layer 3 is improved can be considered as follows. When using a body pigment with an average particle size less than 0.5 μm, as mentioned above, the fluidity of the molten glass frit is improved, the molten glass frit is easily uniformly spread throughout the entire inorganic layer 3, and the body pigment present near the interface with the glass substrate 2 is also well covered by the molten glass frit. In addition, the surface area of ​​the body pigment with an average particle size less than 0.5 μm is greater than the surface area of ​​the body pigment with an average particle size of more than 0.5 μm. As a result, it can be considered that the contact area between the molten glass frit present near the interface with the glass substrate 2 and the back side 2b of the glass substrate 2 increases, and the inorganic layer 3 is more firmly bonded to the glass substrate 2. In addition, by improving the adhesion as mentioned above, the damage resistance is also improved accordingly.

[0064] Examples of the extender pigment include talc, mica, calcium carbonate, glass beads, zirconium oxide, and barium sulfate.

[0065] The body pigment is preferably a colorless and transparent pigment, more preferably contains barium sulfate, and further preferably barium sulfate. Barium sulfate is a colorless and transparent pigment, and thus can further improve the light transmittance of the inorganic layer 3. The barium sulfate may be surface-treated barium sulfate or untreated barium sulfate. As the surface-treated barium sulfate, for example, barium sulfate treated with SiO2-Al2O3 can be cited.

[0066] From the viewpoint of exerting the effect of the present invention, the average particle size of the above-mentioned body pigment is less than 0.5μm. In addition, in the case of further improving the damage resistance and adhesion of the inorganic layer 3, the average particle size of the above-mentioned body pigment is preferably 0.001μm or more, more preferably 0.005μm or more, preferably 0.3μm or less, more preferably 0.1μm or less, further more preferably less than 0.1μm, further more preferably 0.06μm or less, further more preferably 0.04μm or less. On the other hand, in the process of mixing the components when making the coating (paste for forming the inorganic layer), in the case of suppressing the sedimentation or separation of the body pigment and improving the productivity, the average particle size of the above-mentioned body pigment is preferably 0.05μm or more, more preferably 0.1μm or more, preferably 0.4μm or less, more preferably 0.35μm or less.

[0067] The average particle size of the extender pigment is a median particle size derived from a volume distribution measured by a laser diffraction scattering method.

[0068] When the average particle size of the body pigment is less than 0.1 μm, the content of the body pigment in the inorganic layer 3 (the content of the body pigment in 100% by mass of the inorganic layer) is preferably 10% by mass or more, more preferably 15% by mass or more, further preferably 30% by mass or more, preferably 55% by mass or less, and more preferably 45% by mass or less. When the average particle size of the body pigment is 0.1 μm or more, the content of the body pigment in the inorganic layer 3 (the content of the body pigment in 100% by mass of the inorganic layer) is preferably 2% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, preferably 55% by mass or less, more preferably 35% by mass or less, and further preferably 25% by mass or less. When the content of the body pigment is above the lower limit and below the upper limit, the damage resistance and adhesion of the inorganic layer 3 can be further improved, and the light transmittance of the inorganic layer 3 can be further improved.

[0069] In the inorganic layer 3, the mass ratio of the content of the above-mentioned body pigment to the content of the above-mentioned coloring pigment (the content of the body pigment / the content of the coloring pigment) is preferably 0.1 or more, more preferably 0.15 or more, further preferably 0.3 or more, preferably 2 or less, more preferably 1.5 or less, further preferably 1 or less. When the above-mentioned mass ratio (the content of the body pigment / the content of the coloring pigment) is above the above-mentioned lower limit and below the above-mentioned upper limit, the light transmittance of the inorganic layer 3 can be further improved, and the scratch resistance and adhesion of the inorganic layer 3 can be further improved.

[0070] <Other details of the inorganic layer>

[0071] The total content of the above-mentioned glass, the above-mentioned coloring pigment and the above-mentioned physical pigment in the inorganic layer 3 (the total content of the above-mentioned glass, the above-mentioned coloring pigment and the above-mentioned physical pigment in 100 mass% of the inorganic layer) is preferably 35 mass% or more, more preferably 50 mass% or more, further preferably 99 mass% or more, particularly preferably 99.5 mass% or more, and most preferably 100 mass%.

[0072] As long as the effect of the present invention is not hindered, the inorganic layer 3 may also contain other components different from the three components of the glass, the coloring pigment and the body pigment (body pigment with an average particle size of less than 0.5 μm). As the other components, heat-resistant resins such as silicone resins, body pigments with an average particle size of more than 0.5 μm, etc. can be listed. Among them, the content of the other components in the inorganic layer 3 is as small as possible.

[0073] The thickness of the inorganic layer 3 is preferably 1 μm or more, more preferably 1.5 μm or more, further preferably 2 μm or more, preferably 10 μm or less, more preferably 5 μm or less, further preferably 3 μm or less, and particularly preferably 2.6 μm or less. When the thickness of the inorganic layer 3 is above the above lower limit, the coloring pigments and body pigments in the inorganic layer 3 are not easy to protrude from the surface of the inorganic layer 3 to the outside. As a result, when the top plate 1 is used to assemble a cooking utensil or when it is used as a cooking utensil after assembly, it is possible to prevent the surface of the inorganic layer 3 from being scratched by peripheral parts or fingers, etc., causing the inorganic layer 3 to peel off, thereby improving the adhesion of the inorganic layer 3. When the thickness of the inorganic layer 3 is below the above upper limit, the light transmittance of the inorganic layer 3 can be further improved, and the desired light transmittance can be easily obtained. In addition, the amount of material used to form the inorganic layer 3 can be further reduced, and the manufacturing cost of the top plate 1 can be suppressed. Among them, the thickness of the inorganic layer 3 can be measured using a scanning electron microscope (SEM).

[0074] (Light-shielding layer)

[0075] The light-shielding layer 4 is arranged on the back side 2b of the glass substrate 2. The light-shielding layer 4 is in contact with the back side 2b of the glass substrate 2. In addition, in the present invention, other layers may be arranged between the light-shielding layer 4 and the glass substrate 2. The light-shielding layer 4 is a layer for shielding light from the light source 20. In addition, the light-shielding layer 4 can also improve the concealment of the internal structure of the cooker. Furthermore, by appropriately adjusting the color tone of the light-shielding layer 4, the design of the top plate 1 can also be improved. As the light-shielding layer 4, the structure of the currently known light-shielding layer used in the top plate can be adopted.

[0076] The light shielding layer 4 usually contains a coloring pigment. The light shielding layer 4 may be a layer containing a heat-resistant resin and a coloring pigment or a layer containing glass and a coloring pigment. From the viewpoint of improving the mechanical strength of the top plate 1, a layer containing a heat-resistant resin and a coloring pigment is preferred.

[0077] <Coloring Pigments>

[0078] As the coloring pigment that can be used in the light-shielding layer 4, the coloring pigments described in the above-mentioned inorganic layer can be cited. The type of the coloring pigment can be appropriately changed according to the desired color tone of the light-shielding layer, etc. The coloring pigment can be used alone or in combination of two or more.

[0079] The content of the color pigment in the light-shielding layer 4 (the content of the color pigment in 100% by mass of the light-shielding layer) is preferably 10% by mass or more, more preferably 20% by mass or more, preferably 70% by mass or less, more preferably 60% by mass or less. When the content of the color pigment is above the lower limit, the light-shielding property of the light-shielding layer 4 can be further improved. The concealment of the internal structure of the cooker can also be further improved. When the content of the color pigment is below the upper limit, the decrease in the adhesion of the light-shielding layer 4 caused by the difference in the thermal expansion coefficient with the glass substrate 2 can be effectively suppressed.

[0080] <Heat-resistant resin>

[0081] Silicone resins and polyimide resins are exemplified as the heat-resistant resin that can be used in the light-shielding layer 4. The heat-resistant resin may be used alone or in combination of two or more.

[0082] From the viewpoint of further improving heat resistance, the heat-resistant resin is preferably a silicone resin. The light-shielding layer 4 is preferably a layer containing a silicone resin and a coloring pigment. From the viewpoint of further improving heat resistance, the silicone resin is preferably a silicone resin having a methyl group or a phenyl group as a functional group. In this case, the silicon atom may be directly bonded to a methyl group, the silicon atom may be directly bonded to a phenyl group, or the same silicon atom may be directly bonded to a methyl group and a phenyl group.

[0083] The content of the heat-resistant resin in the light-shielding layer 4 (the content of the heat-resistant resin in 100% by mass of the light-shielding layer) is preferably 20% by mass or more, more preferably 30% by mass or more, preferably 70% by mass or less, more preferably 60% by mass or less. When the content of the heat-resistant resin is above the lower limit, the heat resistance, solvent resistance and impact resistance of the light-shielding layer 4 can be further improved. When the content of the heat-resistant resin is below the upper limit, the mechanical strength of the top plate 1 can be further improved.

[0084] <Glass>

[0085] Examples of the glass that can be used in the light shielding layer 4 include the glasses described in the above-mentioned inorganic layer. The glass may be used alone or in combination of two or more.

[0086] The content of the above-mentioned glass in the light-shielding layer 4 (the content of the above-mentioned glass in 100% by mass of the light-shielding layer) is preferably 20% by mass or more, more preferably 30% by mass or more, preferably 70% by mass or less, more preferably 60% by mass or less. When the content of the above-mentioned glass is above the above-mentioned lower limit, the strength and heat resistance of the light-shielding layer 4 can be further improved. When the content of the above-mentioned glass is above the above-mentioned lower limit and below the above-mentioned upper limit, the adhesion of the light-shielding layer 4 can be further improved. In addition, even if the top plate 1 is used for a long time, the discoloration of the light-shielding layer 4 can be effectively suppressed.

[0087] <Extended pigment>

[0088] The light-shielding layer 4 preferably contains a body pigment. The body pigment is different from the glass and the coloring pigment. The light-shielding layer 4 may be a layer containing a heat-resistant resin, a coloring pigment and a body pigment, or a layer containing glass, a coloring pigment and a body pigment. From the viewpoint of improving the mechanical strength of the top plate 1, the light-shielding layer 4 is preferably a layer containing a heat-resistant resin, a coloring pigment and a body pigment. The body pigment may be used alone or in combination of two or more.

[0089] Examples of the extender pigment that can be used in the light shielding layer 4 include talc, mica, potassium carbonate, glass beads, barium sulfate, potassium titanate, calcium silicate, and titanium oxide.

[0090] From the viewpoint of further improving the damage resistance of the light-shielding layer 4, the above-mentioned physical pigment contained in the light-shielding layer 4 preferably includes a pigment having a needle-like shape (needle-like pigment), more preferably includes at least one of potassium titanate having a needle-like shape, calcium silicate having a needle-like shape and titanium oxide having a needle-like shape, and further preferably includes potassium titanate having a needle-like shape.

[0091] In the present specification, whether or not a pigment has a needle-like shape can be confirmed by observation using a scanning electron microscope, a transmission electron microscope, or the like.

[0092] From the perspective of further improving the damage resistance of the light-shielding layer 4, the above-mentioned physical pigment contained in the light-shielding layer 4 preferably includes a pigment having a scaly shape (scaly pigment), more preferably includes at least one of talc having a scaly shape and mica having a scaly shape, and further preferably includes mica having a scaly shape.

[0093] In the present specification, whether or not a pigment has a scaly shape can be confirmed by observation using a scanning electron microscope, a transmission electron microscope, or the like.

[0094] From the viewpoint of further improving the scratch resistance of the light-shielding layer 4 , the extender pigment contained in the light-shielding layer 4 more preferably includes a needle-shaped pigment and a flaky pigment.

[0095] The reason why the damage resistance of the light shielding layer 4 is further improved by including the needle-shaped pigment and the flaky pigment in the above-mentioned body pigment in the light shielding layer 4 is as follows. The flaky pigment and the needle-shaped pigment each function as a skeleton in the light shielding layer 4. In particular, when the flaky pigment and the needle-shaped pigment are entangled with each other, or the needle-shaped pigments are entangled with each other, the hardness of the light shielding layer 4 can be further improved, and damage caused by external impact can be suppressed.

[0096] When the light-shielding layer 4 contains an extender pigment, the content of the extender pigment in the light-shielding layer 4 (the content of the extender pigment in 100% by mass of the light-shielding layer) is preferably 3% by mass or more, more preferably 10% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less. When the content of the extender pigment is greater than the lower limit and less than the upper limit, the scratch resistance of the light-shielding layer 4 can be further improved.

[0097] When the light-shielding layer 4 contains a needle-shaped pigment, the content of the needle-shaped pigment in the light-shielding layer 4 (the content of the needle-shaped pigment in 100% by mass of the light-shielding layer) is preferably 1% by mass or more, more preferably 10% by mass or more, preferably 50% by mass or less, more preferably 30% by mass or less. When the content of the needle-shaped pigment is above the lower limit and below the upper limit, the scratch resistance of the light-shielding layer 4 can be more effectively improved.

[0098] When the light-shielding layer 4 contains a flaky pigment, the content of the flaky pigment in the light-shielding layer 4 (the content of the flaky pigment in 100% by mass of the light-shielding layer) is preferably 1% by mass or more, more preferably 10% by mass or more, and preferably 50% by mass or less, more preferably 30% by mass or less. When the content of the flaky pigment is greater than the lower limit and less than the upper limit, the scratch resistance of the light-shielding layer 4 can be more effectively improved.

[0099] In the light-shielding layer 4, the mass ratio of the content of the above-mentioned flaky pigment to the content of the above-mentioned needle-shaped pigment (the content of the flaky pigment / the content of the needle-shaped pigment) is preferably 10 or less, and more preferably 3 or less. When the above-mentioned mass ratio (the content of the flaky pigment / the content of the needle-shaped pigment) is below the above-mentioned upper limit, the surface peeling of the light-shielding layer 4 can be prevented, and the damage resistance of the light-shielding layer 4 can be more effectively improved.

[0100] <Other details of the light shielding layer>

[0101] The light shielding layer 4 may contain other components different from the four components of glass, heat-resistant resin, coloring pigment, and extender pigment unless the effects of the present invention are impaired.

[0102] The thickness of the light-shielding layer 4 is preferably 5 μm or more, more preferably 10 μm or more, preferably 30 μm or less, more preferably 20 μm or less. When the thickness of the light-shielding layer 4 is above the above lower limit, the light-shielding property of the light-shielding layer 4 can be further improved. The concealment of the internal structure of the cooker can also be further improved. In addition, the coloring pigments and body pigments in the light-shielding layer 4 are not easy to protrude from the surface of the light-shielding layer 4 to the outside. As a result, when the top plate 1 is used to assemble a cooking utensil or when it is used as a cooking utensil after assembly, it is possible to prevent the surface of the light-shielding layer 4 from being scratched by peripheral parts or fingers, causing the light-shielding layer 4 to peel off. When the thickness of the light-shielding layer 4 is below the above upper limit, the decrease in the adhesion of the light-shielding layer 4 caused by the difference in thermal expansion coefficient can be effectively suppressed. Among them, the thickness of the light-shielding layer 4 can be measured using a scanning electron microscope (SEM).

[0103] (Other details of the top plate)

[0104] The light transmittance of the transmissive portion D1 at a wavelength of 580 nm is preferably 1% or more, more preferably 3% or more, further preferably 5% or more, particularly preferably 8% or more, preferably 50% or less, more preferably 40% or less, further preferably 15% or less, particularly preferably 10% or less. When the light transmittance is above the lower limit, the visibility of the information displayed by the transmissive portion D1 when the light source 20 is turned on can be further improved. When the light transmittance is below the upper limit, the concealment of the internal structure of the cooker can be improved in a state where light is not irradiated from the light source 20 (for example, in a power-off state).

[0105] The light transmittance of the non-transmitting portion D2 at a wavelength of 580 nm is preferably 15% or less, more preferably 5% or less, and further preferably 1% or less. When the light transmittance is below the upper limit, the light shielding property can be further improved. The concealment of the internal structure of the cooker can also be further improved.

[0106] The absolute value of the difference between the light transmittance of the transmissive portion D1 at a wavelength of 580 nm and the light transmittance of the non-transmissive portion D2 at a wavelength of 580 nm is preferably 3% or more, more preferably 5% or more, and preferably 50% or less, more preferably 40% or less.

[0107] (Manufacturing method)

[0108] The method for manufacturing the top plate 1 includes, for example, a step of applying an inorganic layer forming paste to the back surface 2b of the glass substrate 2 and a step of firing the glass substrate 2 coated with the inorganic layer forming paste. The method for manufacturing the top plate 1 preferably includes a step of applying a light shielding layer forming paste to the back surface 2b of the glass substrate 2 and preferably includes a step of firing the glass substrate 2 coated with the light shielding layer forming paste.

[0109] Formation method of inorganic layer:

[0110] The inorganic layer forming paste is a material of the inorganic layer 3 and contains glass frit, coloring pigment, and extender pigment having an average particle size of less than 0.5 μm. The inorganic layer forming paste preferably contains a component that volatilizes by heating, such as a resin binder and a solvent.

[0111] The inorganic layer forming paste is applied to a predetermined area on the back side 2b of the glass substrate 2. Preferably, the inorganic layer forming paste is applied continuously and evenly. As a method for applying the inorganic layer forming paste, for example, a screen printing method can be used. In addition, in this case, masking can be performed by providing a mask on the screen printing plate for printing.

[0112] The coating speed and viscosity of the inorganic layer forming paste can be appropriately set according to the contents of the coloring pigment and the extender pigment in the inorganic layer forming paste.

[0113] The method for manufacturing the top plate 1 may or may not include a step of drying the paste for forming the inorganic layer. The drying temperature of the step of drying the paste for forming the inorganic layer may be, for example, 50° C. to 100° C., and the drying time may be, for example, 30 seconds to 100 hours.

[0114] Next, the glass substrate 2 coated with the inorganic layer forming paste is fired. By firing, the glass frit is melted, and an inorganic layer 3 containing glass can be obtained. Since the inorganic layer forming paste contains a body pigment, the fluidity of the molten glass frit is not easily hindered in the process of firing the glass substrate 2 coated with the inorganic layer forming paste, and the molten glass frit easily spreads near the surface of the glass substrate 2 side. Therefore, the molten glass frit can be effectively present near the surface of the glass substrate 2 side of the inorganic layer 3. As a result, the adhesion of the inorganic layer 3 can be improved. The firing temperature is not particularly limited, but is preferably 700°C or more, and more preferably 800°C or more. In addition, the firing temperature is preferably 900°C or less, and more preferably 850°C or less. The firing time can be, for example, 10 minutes or more and 3 hours or less.

[0115] Method for forming the light shielding layer:

[0116] The light-shielding layer forming paste is the material of the light-shielding layer 4. The light-shielding layer forming paste may contain glass frit and coloring pigments, or may contain heat-resistant resin components and coloring pigments. The light-shielding layer forming paste preferably contains components that volatilize by heating, such as solvents. The light-shielding layer forming paste may also contain extender pigments.

[0117] The light-shielding layer forming paste is applied to a predetermined area on the back side 2b of the glass substrate 2. Preferably, the light-shielding layer forming paste is applied continuously and evenly. As a method for applying the light-shielding layer forming paste, for example, a screen printing method can be used. In addition, in this case, masking can be performed by providing a mask on the screen printing plate for printing.

[0118] The coating speed and viscosity of the light-shielding layer forming paste can be appropriately set according to the contents of the coloring pigment and the extender pigment in the light-shielding layer forming paste.

[0119] The method for manufacturing the top plate 1 preferably includes a step of drying the light shielding layer forming paste. The drying temperature of the step of drying the light shielding layer forming paste may be, for example, 50° C. to 100° C., and the drying time may be, for example, 30 seconds to 100 hours.

[0120] The method for manufacturing the top plate 1 may include a step of firing the glass substrate 2 coated with the light-shielding layer forming paste. When the light-shielding layer forming paste contains glass frit and a coloring pigment, the method for manufacturing the top plate 1 preferably includes a step of firing the glass substrate 2 coated with the light-shielding layer forming paste. The firing temperature is not particularly limited, but is preferably 100° C. or higher, and more preferably 150° C. or higher. Furthermore, the firing temperature is preferably 500° C. or lower, and more preferably 450° C. or lower. The firing time may be, for example, 1 minute or longer and 3 hours or shorter.

[0121] In the method for manufacturing the top plate 1, the light-shielding layer 4 may be formed after the inorganic layer 3 is formed, or the inorganic layer 3 may be formed after the light-shielding layer 4 is formed. In the method for manufacturing the top plate 1, the light-shielding layer forming paste may be applied after the inorganic layer forming paste is applied, or the inorganic layer forming paste may be applied after the light-shielding layer forming paste is applied. The drying of the inorganic layer forming paste and the drying of the light-shielding layer forming paste may be performed separately or simultaneously. The firing of the glass substrate 2 coated with the above-mentioned inorganic layer forming paste and the firing of the glass substrate 2 coated with the above-mentioned light-shielding layer forming paste may be performed separately or simultaneously.

[0122] [Second embodiment]

[0123] Figure 2 It is a schematic cross-sectional view showing a top plate for a cooker according to a second embodiment of the present invention.

[0124] Figure 2The top plate 1A for a cooker 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 a surface on the side where a cooking utensil such as a pot or a frying pan is placed. The back surface 2b is a surface facing a light source or a heating device on the inner side of the cooker. Therefore, the cooking surface 2a and the back surface 2b are in a front-back relationship.

[0125] The inorganic layer 3A is disposed on the back surface 2b side of the glass substrate 2. The back surface 2b of the glass substrate 2 is in contact with the inorganic layer 3A. The inorganic layer 3A contains glass, a coloring pigment, and an extender pigment having an average particle size of less than 0.5 μm.

[0126] A light shielding layer 4A is disposed on the back surface 2b of the glass substrate 2. The light shielding layer 4A is disposed on the surface of the inorganic layer 3A opposite to the glass substrate 2. The inorganic layer 3A is in contact with the light shielding layer 4A. The back surface 2b of the glass substrate 2 is not in contact with the light shielding layer 4A.

[0127] The light shielding layer 4A usually contains a coloring pigment. The light shielding layer 4A may be a layer containing a heat-resistant resin and a coloring pigment, or may be a layer containing glass and a coloring pigment. The light shielding layer 4A may further contain an extender pigment.

[0128] A light source 20 is provided below the top plate 1A.

[0129] The top plate 1A has a transmissive portion D1 that transmits light from the light source 20 and a non-transmissive portion D2 that shields light from the light source 20. In the top plate 1A, the inorganic layer 3A is a layer that can transmit light from the light source 20, and the light shielding layer 4A is a layer for shielding light from the light source 20. The transmissive portion D1 of the top plate 1A has the inorganic layer 3A, more specifically, the inorganic layer 3A and the glass substrate 2. The non-transmissive portion D2 of the top plate 1A has the light shielding layer 4A, more specifically, the light shielding layer 4A, the inorganic layer 3A, and the glass substrate 2. The transmissive portion D1 corresponds to a portion of the top plate 1A where the light shielding layer 4A is not provided. The non-transmissive portion D2 corresponds to a portion of the top plate 1A where the light shielding layer 4A is provided.

[0130] In the top plate 1A, the inorganic layer 3A contains glass, coloring pigments and extender pigments, so the scratch resistance and adhesion of the inorganic layer 3A can be improved. In the top plate 1A, the adhesion between the glass substrate 2 and the inorganic layer 3A and the scratch resistance of the inorganic layer 3A can be improved.

[0131] When the inorganic layer 3A contains glass, a coloring pigment, and barium sulfate, the scratch resistance and adhesion of the inorganic layer 3A can also be improved. In this case, the average particle size of the barium sulfate in the inorganic layer 3A is preferably less than 0.5 μm.

[0132] The details of the glass substrate 2 are as described in the first embodiment, so the description is omitted. In addition, the preferred modes of the inorganic layer 3A and the preferred configuration of the glass, coloring pigment and body pigment in the inorganic layer 3A are the same as the preferred modes of the inorganic layer 3 described in the first embodiment. In addition, the preferred modes of the light-shielding layer 4A and the preferred configuration of the heat-resistant resin, glass, coloring pigment and body pigment in the light-shielding layer 4A are the same as the preferred modes of the light-shielding layer 4 described in the first embodiment. Furthermore, the preferred modes of the light transmittance of the transparent portion D1 of the top plate 1A at a wavelength of 580 nm and the light transmittance of the non-transparent portion D2 of the top plate 1A at a wavelength of 580 nm are the same as the preferred modes of the above-mentioned light transmittance of the transparent portion D1 and the non-transparent portion D2 of the top plate 1 described in the first embodiment.

[0133] In the top plate 1A, the total thickness of the inorganic layer 3A and the light shielding layer 4A is preferably 5 μm or more, more preferably 6 μm or more, and preferably 30 μm or less, more preferably 20 μm or less. The total thickness of the inorganic layer 3A and the light shielding layer 4A can be measured using a scanning electron microscope (SEM).

[0134] Regarding the method for manufacturing the top plate 1A, the same method as that of the first embodiment can be employed except that the light shielding layer 4A is formed after the inorganic layer 3A is formed.

[0135] As shown in the above-mentioned embodiments, in the top plate involved in the present invention, the inorganic layer contains glass, coloring pigment and body pigment. The above-mentioned inorganic layer is arranged on the back side of the glass substrate. In the present invention, the above-mentioned inorganic layer can be in contact with the back side of the glass substrate, and other layers can also be arranged between the above-mentioned inorganic layer and the glass substrate. But preferably, the above-mentioned inorganic layer is in contact with the back side of the glass substrate.

[0136] As shown in the above-mentioned embodiments, the top plate involved in the present invention preferably has a light shielding layer. The light shielding layer and the inorganic layer can be arranged side by side in a direction orthogonal to the thickness direction of the top plate as shown in the first embodiment. The light shielding layer and the inorganic layer can also be arranged side by side in the thickness direction of the top plate as shown in the second embodiment.

[0137] The top plate involved in the present invention may have a layer different from both the above-mentioned inorganic layer and the above-mentioned light-shielding layer. For example, the top plate involved in the present invention may have a transparent resin layer containing a heat-resistant resin (such as a silicone resin and a polyimide resin, etc.). The above-mentioned transparent resin layer may be arranged on the surface of the above-mentioned inorganic layer on the side opposite to the glass substrate side, or on the surface of the above-mentioned light-shielding layer on the side opposite to the glass substrate side, or on the surface of the above-mentioned inorganic layer on the side opposite to the glass substrate side and on the surface of the above-mentioned light-shielding layer on the side opposite to the glass substrate side. The transparent portion of the top plate involved in the present invention may have the above-mentioned transparent resin layer. The non-transparent portion of the top plate involved in the present invention may have the above-mentioned transparent resin layer. Preferably, the transparent portion of the top plate involved in the present invention has the above-mentioned transparent resin layer. The above-mentioned transparent resin layer is usually a layer that does not contain a coloring pigment. The above-mentioned transparent resin layer is preferably a layer containing only the above-mentioned heat-resistant resin.

[0138] Hereinafter, the present invention will be described in more detail based on examples. However, the following examples are only illustrative and the present invention is not limited to the following examples.

[0139] The following glass substrates were prepared.

[0140] Transparent crystallized glass plate ("N-0" produced by Nippon Electric Glass Co., Ltd., average linear thermal expansion coefficient at 30℃~750℃: 0.5×10 -7 / ℃, thickness: 4mm)

[0141] Prepare the following inorganic layer materials.

[0142] Glass Frit:

[0143] Glass frit ("Glass frit NPF" produced by Nippon Electric Glass Co., Ltd.)

[0144] Coloring Pigments:

[0145] Black pigment (average particle size: 0.8 μm)

[0146] Pearlescent pigment (a pigment made by coating natural mica with a titanium oxide layer, average particle size: 1μm to 15μm)

[0147] Extender Pigment:

[0148] Barium sulfate A ("BF40" manufactured by Sakai Chemical Industry Co., Ltd., average particle size: 0.01 μm)

[0149] Barium sulfate B ("BF20" manufactured by Sakai Chemical Industry Co., Ltd., average particle size: 0.03 μm)

[0150] Barium sulfate C ("BF34" produced by Sakai Chemical Industry Co., Ltd., average particle size: 0.3 μm, barium sulfate treated with SiO2-Al2O3 (surface treatment))

[0151] Resin adhesive

[0152] Prepare the following materials for the light shielding layer.

[0153] Silicone resin:

[0154] Methylphenyl silicone resin ("TSR-145" produced by Momentive)

[0155] Coloring Pigments:

[0156] Black pigment (average particle size: 0.8 μm)

[0157] Extender Pigment:

[0158] Needle-shaped pigment: Potassium titanate ("Tismo D" manufactured by Otsuka Chemical Co., Ltd.)

[0159] Flake Pigment: Mica

[0160] Solvent:

[0161] Xylene

[0162] (Example 1)

[0163] Preparation of paste for forming inorganic layer:

[0164] Glass frit, black pigment, barium sulfate A, and resin binder were mixed at a mass ratio (glass frit: black pigment: barium sulfate A: resin binder) of 12:12:16:60 to prepare an inorganic layer forming paste.

[0165] Preparation of light shielding layer forming paste:

[0166] A silicone resin, a black pigment, an extender pigment (needle-shaped pigment, flaky pigment), and a solvent were mixed at a mass ratio (silicone resin: black pigment: needle-shaped pigment: flaky pigment: solvent) of 50:20:5:15:10 to prepare a light-shielding layer-forming paste.

[0167] Production of top plate for cooking device:

[0168] The inorganic layer forming paste is screen-printed in the area corresponding to the transparent part on the back of the transparent crystallized glass plate to make it 2.5μm thick. Then, after heating and drying at 80°C for 1 minute, it is fired at 800°C for 30 minutes to form an inorganic layer. Then, the shading layer forming paste is screen-printed in the area corresponding to the non-transparent part on the back of the transparent crystallized glass plate to make it 15μm thick. Then, it is fired at 300°C for 10 minutes to form a shading layer. Among them, the resin adhesive is completely volatilized by heating and drying. In addition, in Table 1, the content of each component in the inorganic layer and the shading layer is recorded.

[0169] (Examples 2 to 13 and Comparative Examples 1 and 2)

[0170] A cooker top plate was produced in the same manner as in Example 1 except that the types and contents of the coloring pigment and the extender pigment in the inorganic layer-forming paste were changed and the composition and thickness of the inorganic layer were changed as shown in Tables 1 and 2.

[0171] [evaluate]

[0172] (1) Damage resistance and adhesion of the inorganic layer

[0173] The obtained cooker top plate is placed on the platform in a way that the cooking surface side is grounded. Disposable chopsticks (Yanagi Products company production, plant forest Yuanlu chopsticks) are fixed on a pencil hardness tester, and are set in a way that the front end of the disposable chopsticks contacts the top plate surface. Make the pencil hardness tester go back and forth 10 times at a speed of 5cm / second with a distance of 30mm. Afterwards, the part of the cooking surface side of the top plate that the disposable chopsticks go back and forth is irradiated with a white light source, and the boundary between the part and other parts of the disposable chopsticks that go back and forth is observed from the back side of the top plate by visual observation. The damage resistance and tightness of the inorganic layer are judged according to the following evaluation criteria.

[0174] <Evaluation Criteria>

[0175] ○○: Can’t see the boundary;

[0176] ○: The boundary can be slightly seen, and the part of the disposable chopsticks that goes back and forth is dark gray;

[0177] △: The boundary can be clearly seen, but the part where the disposable chopsticks go back and forth is gray;

[0178] ×: The boundary is clearly visible, and the part where the disposable chopsticks go back and forth is almost white.

[0179] (2) Light transmittance

[0180] The light transmittance of the obtained cooker top plate at a wavelength of 580 nm at the transmission portion and the light transmittance of the non-transmission portion at a wavelength of 580 nm were measured using a spectrophotometer ("V-770" manufactured by JASCO Corporation).

[0181] (3) Mechanical strength of the top plate

[0182] The steel ball drop test was conducted using a method in accordance with the UL858 standard. Specifically, a steel ball with a mass of 535 g and a diameter of 50.8 mm was dropped from a height of 100 mm from the cooking surface of the cooker top plate to the center of the cooking surface side of the obtained cooker top plate. The height of the steel ball drop was increased by 100 mm each time, and the height at which the cooker top plate first cracked was taken as the damage height, and the value of the damage height minus 100 mm was recorded. The above test was conducted 5 times, and the average value was used as the evaluation index of mechanical strength, which is shown in Tables 1 and 2.

[0183] The details and results are shown in Tables 1 and 2 below.

[0184] [Table 1]

[0185]

[0186] [Table 2]

[0187]

[0188] According to Tables 1 and 2, since Examples 1 to 13 contain a body pigment with an average particle size of less than 0.5 μm, the scratch resistance and adhesion of the inorganic layer are better than those of the comparative examples. In addition, the mechanical strength of Examples 1 to 13 is sufficient as a top plate. On the other hand, the scratch resistance and adhesion of the inorganic layer of Comparative Examples 1 and 2 are low.

[0189] Explanation of symbols

[0190] 1. 1A: top plate for cooker; 2: glass substrate; 2a: cooking surface; 2b: back surface; 3. 3A: inorganic layer; 4. 4A: light shielding layer; 20: light source; D1: transmissive part; D2: non-transmissive part.

Claims

1. A top plate for a cooking device, characterized in that: include: A glass substrate having a cooking surface on which a cooking utensil is placed and a back surface opposite to the cooking surface; and an inorganic layer disposed on the back side of the glass substrate, The inorganic layer contains glass, a coloring pigment and an extender pigment having an average particle size of less than 0.5 μm.

2. The top plate for a cooker according to claim 1, wherein: The cooker top plate has a transmission portion that transmits light from a light source. The transmission portion includes the inorganic layer.

3. The top plate for a cooker according to claim 2, wherein: The extender pigment comprises barium sulfate.

4. The top plate for a cooker according to claim 2 or 3, characterized in that: The content of the extender pigment in 100 mass % of the inorganic layer is 10 mass % or more and 55 mass % or less.

5. The top plate for a cooker according to claim 2 or 3, characterized in that: The coloring pigment has an average particle size of 0.4 μm or more and 3 μm or less.

6. The top plate for a cooker according to claim 2 or 3, characterized in that: The cooker top plate has a non-transmitting portion that shields light from a light source. The non-transmitting portion includes a light shielding layer provided on the inorganic layer.

7. A top plate for a cooking device, characterized in that: include: A glass substrate having a cooking surface on which a cooking utensil is placed and a back surface opposite to the cooking surface; and an inorganic layer disposed on the back side of the glass substrate, The inorganic layer contains glass, a coloring pigment and barium sulfate.

8. A method for manufacturing a top plate for a cooker, characterized in that: The top plate for the cooker comprises: a glass substrate having a cooking surface on which a cooking utensil is placed and a back surface opposite to the cooking surface; and an inorganic layer disposed on the back side of the glass substrate, The manufacturing method comprises: a step of applying a paste for forming an inorganic layer on the back side of the glass substrate; and a step of firing the glass substrate coated with the inorganic layer forming paste, The inorganic layer forming paste contains glass frit, a coloring pigment, and an extender pigment having an average particle size of less than 0.5 μm.

9. The method for manufacturing a top plate for a cooker according to claim 8, wherein: The extender pigment comprises barium sulfate.

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