Coated product and method of manufacturing same

Abstract

The present invention provides a coated product that has high stain resistance and washing durability, and also has excellent coating adhesion, while maintaining the design of the base material, which is mainly made of ceramic or porcelain, such as tableware or cookware. The coated product 1 comprises a base material 2, which is mainly made of ceramic, porcelain, or glass, a glaze layer 3 on the surface of the base material 2, and a light-transmitting resin coating 4 that coats the glaze layer 3 on the surface of the base material 2, and the base material 2 is mainly tableware or cookware, and the thermal expansion coefficient of the base material 2 at 25°C to 800°C is 1.0 to 100.0 × 10 -6 / K, and the light-transmitting resin coating 4 is a heat-curable coating.

Description

[Technical Field]

[0001] The present invention relates to a coated product in which a resin coating is provided on a base material (mainly tableware and cooking utensils) mainly made of earthenware, porcelain or glass, and a method for manufacturing the coated product. [Background technology]

[0002] Pottery, such as earthenware and porcelain (collectively known as ceramics), has long been widely used as tableware and cookware. These products excel in heat resistance, chemical stability, aesthetic appeal (design), and environmental friendliness, and remain in high demand as everyday items even today. By applying a glaze to the surface of ceramic products, a glassy glaze layer is formed, which suppresses water absorption, prevents coloring and odor penetration, and also achieves a beautiful surface appearance, luster, and color expression.

[0003] Furthermore, it may be difficult to ensure sufficient stain resistance, oil resistance, waterproofing, or washing durability with glaze alone, and the glaze layer may deteriorate, particularly when used in modern household dishwashers or with strong detergents. Furthermore, because glaze is glassy, ​​it is prone to fine scratches and cracks, and dirt can accumulate there, reducing cleanability and posing hygiene problems.

[0004] Given this background, techniques for applying a resin coating on top of the glaze are also being considered. For example, a coating of acrylic resin, polyurethane resin, silicone resin, fluororesin, or the like has been applied to the surface of the glaze layer to impart stain-resistant properties (fouling resistance) and improve washing durability. In this case, it is required that the coating agent be easy to apply, be able to form a film with the required physical properties at room temperature (room temperature curing type or UV curing type), and that the film does not deteriorate over time. For example, Patent Document 1 proposes a method of forming a film using a specified emulsion composition for coating ceramic molded bodies, which is applied, left at room temperature for approximately 0.5 to 48 hours, and then dried to form a film. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-211989 Summary of the Invention [Problem to be solved by the invention]

[0006] Here, the design value of ceramic, porcelain, and glass tableware is centered on the texture, color, and pattern of the surface glaze and base material, so even when a coating is applied, it is strongly required that the visibility of the base is not impaired. In particular, when used as tableware or cookware, maintaining transparency is practically essential to visually protect the product's original beauty (patterns and glaze texture). For this reason, the application of a coating that is not transparent is undesirable, even if it has excellent functionality such as adhesion and durability.

[0007] Furthermore, room-temperature-curing and ultraviolet-curing resins do not adhere well to the ceramic surface, which is the base material, and there is a risk of peeling during use. In particular, the glaze layer has a glassy, ​​extremely smooth surface, making it difficult to achieve sufficient adhesion. When forming a resin coating on a glaze layer, it is generally difficult to achieve sufficient adhesion without performing a surface preparation such as plasma treatment or sandblasting. Such surface preparation not only complicates the process but also risks damaging the design of the base material surface.

[0008] Furthermore, when applying a heat-curing resin to the coating, it is expected that the base material may crack during the heating process in ordinary ceramics, which do not have a high degree of heat resistance. For this reason, no ceramic tableware or ceramic cookware with a heat-curing coating that requires firing at temperatures above 100°C has been found on the market.

[0009] The present invention has been made in view of the above background, and aims to provide a coated product that has high stain resistance and washing durability, and also has excellent coating adhesion, while maintaining the design of the base material, which is mainly made of earthenware or porcelain, such as tableware or cooking utensils, etc. Another aim is to provide a method for producing this coated product. [Means for solving the problem]

[0010] The coated product of the present invention is a coated product comprising a base material mainly made of earthenware, porcelain, or glass, and a light-transmitting resin coating that coats the base material, wherein the base material has a thermal expansion coefficient of 1.0 to 100.0 × 10 at 25°C to 800°C. -6 / K, and the light-transmitting resin coating is a thermosetting coating. In particular, the base material is characterized in that it is tableware or cooking utensils.

[0011] In this specification, the expression "coefficient of thermal expansion" is used to mean "1.0 to 100.0 × 10 -6 / K" is 1.0 x 10 -6 / K or more 100.0×10 -6 / K or less. The same applies to other ranges of the thermal expansion coefficient.

[0012] The base material is the above-mentioned pottery or porcelain, has a glaze layer on its surface, and the light-transmitting resin coating is a coating provided on the unprimed outer surface of the glaze layer.

[0013] The resin coating is characterized in that it is a solvent-based silicone resin coating using an organic solvent.

[0014] The method for producing a coated product of the present invention is a method for producing a coated product comprising a base material mainly made of earthenware, porcelain, or glass, and a light-transmitting resin coating that coats the base material, wherein the base material has a thermal expansion coefficient of 1.0 to 100.0 × 10 at 25°C to 800°C. -6The method is characterized in that it comprises a coating step of applying a coating liquid constituting the light-transmitting resin coating to the surface of the base material, and a heat-curing step of curing the applied coating liquid by heating. In particular, the base material is characterized in that it is tableware or cooking utensil.

[0015] The base material is the above-mentioned pottery or porcelain, has a glaze layer on its surface, and the coating step is carried out without performing a surface treatment on the outer surface of the glaze layer.

[0016] The heat curing step is characterized in that the heating is performed under baking conditions where the atmospheric temperature exceeds 100°C. [Effects of the Invention]

[0017] The coated product of the present invention has a predetermined light-transmitting resin coating on the surface of a ceramic, porcelain, or glass base material (mainly tableware and cookware), and therefore can retain the texture and pattern of the glaze layer or decorative layer of the base material while improving stain resistance, washing durability, etc. In particular, because the light-transmitting resin coating is a heat-cured coating, it has superior adhesion compared to coatings that are cured at room temperature, and as a result, the above-mentioned excellent properties can be maintained for a long period of time.

[0018] Furthermore, since the base material is earthenware or porcelain, has a glaze layer on its surface, and the light-transmitting resin coating is provided on the unprimed outer surface of the glaze layer, it is possible to suppress deterioration in the design of the product, such as a decrease in light transmittance due to the primer treatment, and manufacturing costs can also be reduced.

[0019] Furthermore, since the resin coating is a solvent-based silicone resin coating using an organic solvent, it has excellent applicability to the base material and the glaze layer on the surface of the base material, and even if a glaze layer is present, the resin coating can be formed with good adhesion without applying a primer treatment to the outer surface of the glaze layer.

[0020] The method for producing a coated product of the present invention includes a coating step of applying a coating liquid that forms a light-transmitting resin film to the surface of a ceramic, porcelain, or glass base material (mainly tableware and cookware), and a heat-curing step of heat-curing the applied coating liquid, making it possible to produce a coated product that retains the texture and pattern of the glaze layer or decorative layer of the base material while improving stain resistance, washing durability, etc. In particular, because the coating liquid applied in the heat-curing step is heat-cured, a coating with excellent adhesion can be formed compared to when the coating liquid is cured at room temperature.

[0021] Furthermore, the heat curing step involves heating under baking conditions where the atmospheric temperature exceeds 100°C, so the light-transmitting resin coating can be sufficiently cured and adhered to the base material. Furthermore, even when a solvent-based silicone resin using an organic solvent is used, the solvent can be quickly removed without remaining. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a diagram showing an example of a coated product of the present invention. [Figure 2] 1 is a process flow diagram illustrating a method for manufacturing a coated product of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The coated product of the present invention will be described with reference to Fig. 1. Fig. 1(a) is a perspective view of an example of the coated product of the present invention, and Fig. 1(b) is an enlarged vertical cross-sectional view of a portion of the product. Note that the figure is a schematic view and does not correspond to the actual dimensional ratio. As shown in FIG. 1(a), the coated product 1 is a ceramic dish. As shown in FIG. 1(b), the coated product 1 has a structure in which a base material 2 is coated with a light-transmitting resin coating 4. In this embodiment, the base material 2 has a glaze layer 3 on its surface, and the light-transmitting resin coating 4 is formed so as to cover the outer surface of the glaze layer 3. Here, the light-transmitting resin coating 4 only needs to cover a portion of the base material 2, and may be in a form in which it covers only the food-placing surface of a dish that is prone to soiling. Furthermore, "coating a base material" also includes, in the case of a ceramic or porcelain base material having a glaze layer on its surface, coating the outer surface of the glaze layer on the entire base material, including the glaze layer.

[0024] The coated product of the present invention is a product that combines excellent visual characteristics, such as maintaining the design of the base material, with functionality such as stain resistance and washing durability, by directly forming a light-transmitting thermosetting resin coating on a base material that is primarily an inorganic material such as pottery or porcelain. Depending on the properties of the coating, the product may also have excellent functionality such as water repellency, heat resistance, non-stickiness, abrasion resistance, and chemical resistance.

[0025] Examples of the base material include ceramics, porcelain, and glass. These are all non-metallic inorganic materials formed by high-temperature firing, and are highly hard and have excellent water resistance and heat resistance. This base material can usually be used as a product by itself, and existing products can also be used as the base material. The coated product of the present invention becomes a high-performance product that is imparted with the above-mentioned effects by coating such a base material product. Note that when a resin coating is applied to a ceramic base material such as ceramics or porcelain, the coated product can be called a "ceramic-coated product."

[0026] Examples of base material products include tableware and cooking utensils such as cups, bottles, rice bowls, chopstick rests, plates, heat-resistant plates, rice bowls, rice containers, teacups, mugs, sake bottles, sake cups, pots, earthenware pots, mortars, gratin dishes, induction cooker compatible containers, induction cooker plates, and oven plates; flower vases such as water basins, flower pots, and single-flower vases; aquariums such as aquaculture tanks and ornamental aquariums; plumbing components; building materials such as roofing tiles and tiles; and medical equipment.

[0027] Pottery and porcelain are both fired products made from clay, i.e., they belong to the ceramics category. Pottery is primarily made from a highly plastic clay, known as potter's clay, to which feldspar and silica are added to adjust the base material. This potter's clay contains impurities such as iron, which appear as a simple reddish or yellowish color after firing. On the other hand, porcelain is primarily made from a high-purity white clay called kaolin, which is blended with feldspar and silica. Kaolin has few impurities, so after firing it appears pure white or bluish-white, and thin products can even be translucent. These differences in raw materials directly affect the texture and surface feel of the pottery, determining the individuality of each product.

[0028] Also, earthenware is fired at a temperature range of roughly 900 to 1200°C, and can be fired at a relatively low temperature. In contrast, porcelain must be fired at a high temperature of 1200 to 1400°C, and this high temperature causes the feldspar in the base to vitrify, forming a dense structure overall. This makes the porcelain non-absorbent, fired tightly, and hard. In comparison, the thermal expansion coefficient of porcelain (white porcelain, etc.) is generally 4.1 to 6.0 x 10 -6 / K, and ceramics are 6.0 to 8.0 × 10 -6 / K. Furthermore, for heat-resistant ceramics (pottery or porcelain), the lower limit is about 1.0 × 10 -6 / K, and 5.0 × 10 -6 / K or less, 4.0×10 -6 / K or less, 3.0×10 -6 / K or less. The temperature range for measuring the thermal expansion coefficient is 25°C to 800°C.

[0029] Glass is an amorphous material whose main component is silicon dioxide. Soda lime glass is an example of the glass commonly used for tableware and cups. The thermal expansion coefficient of soda lime glass is 8.5 to 9.0 × 10 -6 / K (the measurement temperature range is 25°C to 300°C). Examples of glass used in heat-resistant glass products include borosilicate glass. The thermal expansion coefficient of borosilicate glass is 3.0 to 3.5 × 10 -6 / K (the measurement temperature range is 25°C to 300°C).

[0030] The coated part of the present invention has a base material with a thermal expansion coefficient of 1.0 to 100.0 × 10 at 25°C to 800°C. -6 / K, and a relatively wide range of thermal expansion coefficients of base materials can be used. The applicable range of thermal expansion coefficients is 3.0×10 -6 / K exceeds 100.0 x 10 -6 / K or less, 4.0×10 -6 / K exceeds 100.0 x 10 -6 / K or less, 5.0×10 -6 / K exceeds 100.0 x 10 -6 / K or less, 7.0×10 -6 / K exceeds 100.0 x 10 -6 The upper limit of the thermal expansion coefficient that can be called heat-resistant ceramics is 4.0 × 10 -6 / K or less may be used, so in the sense that it is applied to base materials that do not fall under the category of heat-resistant ceramics, within the above range group, 4.0 × 10 -6 / K exceeds 100.0 x 10 -6 / K or less. In each of the above ranges, the upper limit of the thermal expansion coefficient is 50.0×10 -6 / K or less, 30.0×10 -6 / K or less, 20.0×10 -6 / K or less, 15.0×10 -6The thermal expansion coefficient in the present invention is a value measured by using a thermomechanical analyzer and heating from room temperature (25°C) to 800°C at a temperature increase rate of 7°C / min.

[0031] Heat-curable resins used as light-transmitting resin coatings are not normally used when the baking conditions (heat-curing temperature) exceed 100°C, for example, and the base material has a high thermal expansion coefficient, due to the possibility (fear) of the base material cracking when the coating is baked. However, it is actually possible to form a coating without cracking the base material, and this invention has found this point and is characterized by the deliberate use of heat-curable resins even when a base material with a high thermal expansion coefficient is used. In other words, the coated product of the present invention has a thermal expansion coefficient of 4.0 x 10 -6 This is particularly noticeable when combined with a base material that has a large thermal expansion coefficient exceeding 1 / K.

[0032] Furthermore, when the base material is pottery or porcelain (ceramics), it is preferable to have a glaze layer on the surface. This layer is important in determining the aesthetics and functionality of ceramics. Glaze is a glassy coating applied to the surface of ceramics, which is formed by integrating with the base during firing. Glazes primarily consist of glass-forming substances, primarily silica, plus clay, lithium carbonate, feldspars, wood ash, dolomite, lime, barium, strontium, sodium silicate, bittern, cadmium, fluxes such as lead oxide and zinc oxide, and colorants such as iron oxide, copper oxide, and cobalt oxide. These components melt during firing, coating the base surface and vitrify upon cooling, forming a transparent or translucent, glossy layer. The gloss, color, texture, and texture of the surface vary significantly depending on the type and composition of the glaze, the application method, and the firing temperature, enabling a wide variety of design expressions.

[0033] Glazing methods include immersion (dipping), spraying, pouring, and brush painting. The range of expression is also expanded by combining decorative techniques, such as underglaze painting (applying a design under the glaze) and overglaze painting (applying decoration on top of the glaze). Furthermore, the transparency and gloss of glazes can be adjusted, and there are transparent glazes, opalescent glazes, and matte glazes. For example, transparent glazes used on porcelain allow the underglaze design to show through, and their transparency and gloss can be subtly altered by the firing temperature and component ratio. Glazes used on pottery also allow for a wide range of unique expressions, such as intentionally creating crazing or intentionally creating unevenness on the glaze surface to create unique landscapes. Maintaining the design of the base material with such a glaze layer is a key challenge when applying a protective layer such as a resin coating.

[0034] When the base material has a glaze layer, the light-transmitting resin coating is preferably applied to the unprimed outer surface of the glaze layer. By avoiding surface treatments that increase surface roughness or that provide an intermediate layer, the design of the product can be prevented from being impaired, and the manufacturing process can be simplified and manufacturing costs can be reduced. The surface of the glaze layer is glassy and smooth, with few adhesive active groups (such as OH groups) and low chemical reactivity. Therefore, when using room-temperature-curing or ultraviolet-curing resins as the resin coating, adhesion may be insufficient unless a surface treatment such as a primer treatment or roughening treatment is performed. In the present invention, adhesion can be ensured by using a heat-curing resin as the light-transmitting resin coating, and adhesion can be further improved by using a specific resin described below, ensuring adhesion even to the unprimed outer surface of the glaze layer.

[0035] The thermal expansion coefficient of the glaze layer is determined to be consistent (equal to) that of the base material, taking into consideration the balance with the base material, in order to prevent the occurrence of crazing, peeling, cracks, etc. during the cooling process after firing. The thickness of the glaze layer is approximately 1 μm to 1000 μm.

[0036] The light-transmitting resin coating that constitutes the coated product of the present invention will now be described in detail. This light-transmitting resin coating is a heat-curing type. Heat-curing refers to a type in which the main resin undergoes a chemical crosslinking reaction through a heating process, forming a three-dimensional network structure that significantly improves stain resistance, cleaning durability, heat resistance, mechanical properties, and other properties. Furthermore, heating improves the resin's permeability and molecular mobility, promoting an anchoring effect and physicochemical bonding with the interface. As mentioned above, this ensures adhesion to glaze layers and other layers without the need for surface treatments such as primer treatment or roughening.

[0037] The light transmittance of a light-transmitting resin coating is sufficient if it is visible when inspected visually. Light transmittance can also be confirmed by (1) using a microspectrophotometer (micro UV-Vis) to directly irradiate the surface of the coated product and measure reflection and transmission, or (2) placing a strong light source on the back of the product and photographing the surface from the opposite side. For example, if the base material is pottery or porcelain, it is difficult to measure the total light transmittance itself because it is an opaque base material, but it is sufficient if transmitted light and a transmitted image can be confirmed by transmission observation with a light source placed behind it.

[0038] As described above, the light-transmitting resin coating must have light transmittance regardless of its level. Therefore, the specific transmittance (total light transmittance: measured in accordance with JIS K 7361-1) in the visible light wavelength range of 380 nm to 780 nm is not particularly limited. However, the higher the transmittance, the better the transparency, and therefore the higher the transmittance is, in order to ensure the design of an underlying glaze layer, etc. For base materials for which the total light transmittance can be measured, for example, a value of 50% or more is preferred, more preferably 70% or more, and even more preferably 80% or more. The total light transmittance is specifically measured as follows: According to JIS K 7361-1, the total light transmittance of a test piece (cut from a product or molded) of the base material alone (e.g., glass base material) is measured using a haze meter or the like. Next, a test piece is prepared in which a light-transmitting resin coating is formed (cured) on the surface of the same base material test piece, and the total light transmittance is measured in the same manner. From the obtained measured values, a value excluding the influence of the base material is calculated, and this value is taken as the total light transmittance of the light-transmitting resin coating.

[0039] The light-transmitting resin coating is not particularly limited as long as it is transparent and heat-curable, and examples thereof include acrylic resin, urethane resin, epoxy resin, polyester resin, silicone resin, etc. These resins may be used alone or in combination by laminating two or more types. Among these resins, it is preferable to use silicone resin.

[0040] Silicone resins are organopolysiloxanes with a three-dimensional structure. They have the average composition formula: RaSiO (4-a) / 2(where R is an organic group, and a is a number from 1.0 to 1.8) includes various silicone resins represented by the formula: (where R is an organic group, and a is a number from 1.0 to 1.8). Examples of the organic group R include alkyl groups such as methyl, ethyl, and propyl; aryl groups such as phenyl; alkenyl groups such as vinyl and allyl; and groups in which some of the carbon atoms of these hydrocarbon groups have been substituted with halogen atoms, cyano groups, or the like. Such silicone resins may also be modified silicone resins modified with epoxy, melamine, polyester, or the like. Specific main components include polydimethylsiloxane, polymethylphenylsiloxane, and vinyl-terminated polydimethylsiloxane, which have Si-O-Si bonds in their main chains and can form a three-dimensional network structure by a crosslinking reaction caused by heating.

[0041] The heat curing is preferably carried out under baking conditions where the atmospheric temperature exceeds 100° C., more preferably in the range of 120° C. to 700° C. The heat curing step will be described in detail later in relation to the manufacturing method.

[0042] The Si-O-Si main chain in silicone resin has an amorphous structure, preventing crystallization and reducing light scattering. The organic groups (methyl and phenyl groups) are also lightweight and exhibit minimal optical interference. Furthermore, the low intermolecular density minimizes light scattering. This results in high light transmittance (transparency) even after film formation. Furthermore, light-transmitting resin coatings made from silicone resins have excellent heat resistance due to the high thermal stability of the Si-O skeleton, and their low surface energy provides excellent water repellency, oil repellency, non-stickiness, and chemical resistance. Furthermore, because they retain their relative flexibility even after film formation, they also contribute to stress relief at the interface with the base material and prevent peeling. As a result, the texture and pattern of the glaze and decorative layers of the base material are preserved while improving stain resistance and cleaning durability over a long period of time.

[0043] The optically transparent resin coating may contain silicone oil in all or part of its composition, such as straight silicone oils such as dimethylsilicone oil, methylphenylsilicone oil, and methylhydrogensilicone oil, and modified silicone oils in which various organic groups have been introduced into some of the methyl groups.

[0044] In the present invention, it is preferable to use a solvent-based silicone resin. A solvent-based resin is a liquid composition in which the main component resin is dissolved or dispersed in an appropriate solvent. In the case of a heat-curing type, an organic solvent is mainly used as the solvent. Examples of organic solvents include xylene, toluene, isopropanol, and butyl acetate. This solvent-based silicone resin forms a hydrophobic coating liquid when applied, which allows for good application to the glaze layer of a ceramic substrate or the surface of a glass substrate, both of which are hydrophobic, and results in excellent adhesion of the resin coating.

[0045] Crosslinking agents and catalysts that can be used with silicone resins include alkoxysilanes such as tetraethoxysilane, organotitanium compounds, tin acetate, and platinum catalysts. Other additives that can be used include water-repellent improvers such as fluorinated alkylsilanes, silver- or zinc-based antibacterial agents, and light stabilizers (ultraviolet absorbers). Furthermore, to further improve durability, ceramics (alumina or silica) may be added within the range that ensures light transmittance.

[0046] When using organic solvent-based silicone resins, if the base material is tableware or cookware, attention must be paid to the safety of residual solvents, and a composition and conditions must be selected that ensure complete removal of the solvent during heat curing (and subsequent drying). Furthermore, under the "Positive List System" based on the Food Sanitation Act, chemical substances used in food utensils and containers / packaging are limited to those listed in Ministry of Health, Labor and Welfare Notification No. 196. Materials such as polydimethylsiloxane and polymethylphenylsiloxane that make up silicone resins, as well as solvent components that are completely removed during heat curing (assuming they do not remain in the final product), are materials with a proven track record of use as food contact materials, and appropriate selection and evaluation can ensure compatibility.

[0047] The method for producing the coated product of the present invention will now be described. The method for producing a coated product of the present invention is a method for producing a coated product comprising a base material mainly made of earthenware, porcelain, or glass and a light-transmitting resin coating that coats the base material. That is, it is a method for producing the above-described coated product. The details of the base material and the light-transmitting resin coating are as described above.

[0048] The method for producing a coated product of the present invention will be described with reference to Figure 2. Figure 2 is a process flow diagram showing the method for producing a coated product of the present invention. As shown in Figure 2, the method for producing a coated product of the present invention is characterized by having an application step (S1) of applying a coating liquid that forms a light-transmitting resin coating to the surface of a base material, and a heat-curing step (S2) of heat-curing the applied coating liquid. In addition, a base material preparation step (S0) is included before the application step (S1). After the heat-curing step, a light-transmitting resin coating is formed on the surface of the base material, and a coated product is obtained.

[0049] (S0) Base material preparation process A base material (such as ceramic tableware) is selected, and surface dirt and, if necessary, grease and moisture are removed. For example, this can be done by washing with a neutral detergent, washing with an air blower, or by natural or hot air drying (degreasing and cleaning). Note that degreasing and cleaning are not essential. Furthermore, the surface of the base material (or the surface of the glaze layer, if any) is not subjected to surface preparation, such as polishing, roughening, or chemical treatment (e.g., plasma treatment, sandblasting, or primer treatment), which is typically performed to ensure adhesion. The "surface preparation" in this invention does not include the above-mentioned degreasing and cleaning processes. Therefore, the unprimed outer surface of the base material's glaze layer is not subjected to the above-mentioned surface preparation, but may have been subjected to a degreasing or cleaning process.

[0050] (S1) Coating process The coating liquid for forming the light-transmitting resin film can be a known coating liquid depending on the type of resin used. When a silicone resin is used as the light-transmitting resin film, the coating liquid is a composition in which the silicone resin is dissolved in an appropriate solvent (such as isopropanol). If necessary, a catalyst, a crosslinking agent, a water repellent, a light stabilizer, etc. are added. The coating is carried out by a spray method (air pressure type, HVLP type), a dipping method (immersion), a brush coating, a spin coating method, etc. The coating thickness is determined depending on the desired coating thickness after curing.

[0051] If necessary, immediately after application, the coating may be pre-dried at a temperature lower than that in the heat curing step (less than 100°C) to volatilize and remove some of the solvent. By performing pre-drying appropriately, air bubbles and uneven film thickness can be suppressed in the subsequent curing step.

[0052] (S2) Heat curing process The base material is maintained for a predetermined time (e.g., 5 to 60 minutes) under baking conditions where the ambient temperature exceeds 100°C. The ambient temperature can be set appropriately depending on the type of resin and the heating device conditions, and can be set, for example, in a range of more than 100°C but not exceeding 700°C, a range of 120°C to 700°C, or a range of 150°C to 500°C. Furthermore, if the product temperature can be measured directly, the above temperature range can be set as the temperature reached by the product. The progress of the curing reaction can be confirmed by the disappearance of Si-OH and the increase in the Si-O-Si stretching band in the IR spectrum. Optimal conditions are set depending on the type of resin used.

[0053] In the present invention, it is important that the base material does not crack when the resin coating is heat-cured. Therefore, it is preferable that the heating conditions be such that sufficient heat is transferred to the resin coating while heat is not transferred to the base material. The heating method can be (1) a convection method or (2) a radiation method.

[0054] (1) The convection method uses hot air from a heat source such as gas, electric heating wire, or induction heating to preferentially heat the resin coating. (2) The radiation method uses light radiation to bake (heat harden) the resin coating on the surface. This method makes it difficult for heat to be transferred to the base material itself, allowing for heating only on the surface. In either method (1) or (2), continuous degassing and ventilation are required when forming a solvent-based resin coating using an organic solvent.

[0055] Alternatively, the heat curing step can be carried out using general-purpose equipment such as a known oven furnace, conveyor furnace, hot air circulation furnace, etc. Indirect heating using air convection within a kiln or furnace is effective for preventing cracking of the base material while sufficiently heat-curing the resin coating.

[0056] As described above, the method for producing a coated product of the present invention can prevent a decrease in the design quality of the product and reduce production costs by eliminating the need for a surface treatment. In addition, the use of a heat-curable resin as the light-transmitting resin coating can ensure adhesion, and in particular, the use of a solvent-type silicone resin using an organic solvent can ensure adhesion even to the outer surface of the glaze layer that has not been subjected to a surface treatment. [Industrial Applicability]

[0057] The coated products of the present invention can be applied in a variety of fields, including: (1) household and commercial tableware (plates, bowls, cups, etc.), (2) household and commercial cooking utensils (gratin dishes, oven plates, etc.), (3) microwave-safe containers, (4) heat-resistant glass lighting covers and decorative panels, (5) medical equipment, and (6) anti-fouling treatments for wet areas (washbasins, tiles, etc.). Furthermore, by dispersing functional particles in the coating, it is possible to add advanced functions. [Explanation of symbols]

[0058] 1. Coated products 2 Base material 3 Glaze layer 4 Light-transparent resin coating

Claims

1. A coated product comprising a base material mainly made of pottery, porcelain, or glass, and a light-transmitting resin coating that coats the base material, The base material has a thermal expansion coefficient of 1.0 to 100.0 × 10 at 25°C to 800°C. -6 / K, and the light-transmitting resin coating is a thermosetting coating, the base material is the pottery or porcelain and has a glaze layer on its surface; A coated product, characterized in that the light-transmitting resin coating is a coating provided on the unprimed outer surface of the glaze layer.

2. 2. The coated product according to claim 1, wherein the substrate is tableware or cookware.

3. 3. The coated product according to claim 1, wherein the resin coating is a solvent-based silicone resin coating using an organic solvent.

4. The thermal expansion coefficient of the base material at 25°C to 800°C is 4.0 x 10 -6 / K exceeds 100.0 x 10 -6 3. The coated product according to claim 1, wherein the viscosity is 1 / K or less.

5. A method for manufacturing a coated product comprising a base material mainly made of earthenware, porcelain, or glass, and a light-transmitting resin coating that coats the base material, The base material has a thermal expansion coefficient of 1.0 to 100.0 × 10 at 25°C to 800°C. -6 / K, a coating step of coating a coating liquid constituting the light-transmitting resin coating film on a surface of the base material, and a heat-curing step of heat-curing the applied coating liquid, the base material is the pottery or porcelain and has a glaze layer on its surface; A method for producing a coated product, characterized in that the coating step is carried out without performing a surface treatment on the outer surface of the glaze layer.

6. 6. The method for manufacturing a coated product according to claim 5, wherein the base material is tableware or cooking utensils.

7. 7. The method for producing a coated product according to claim 5, wherein the heat-hardening step is a step of heating under baking conditions in which the atmospheric temperature exceeds 100°C.

8. The thermal expansion coefficient of the base material at 25°C to 800°C is 4.0 x 10 -6 / K exceeds 100.0 x 10 -6 7. The method for producing a coated product according to claim 5, wherein the viscosity is 1000 kJ / K or less.

Images