JP2010075494A - Cooking pan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooking pan using copper, which prevents the oxidization of copper and improves the durability. <P>SOLUTION: A diamond-like carbon lamina layer 15 of thickness within a range which the metal color of a copper 12 that constitutes the outer surface of the cooking pan is not totally lost is installed on the surface of the copper to restrain the oxidization of copper against the heat for cooking. A beautiful copper color retains for a long period, and the durability of a coating 14 processed on the outer surface of the diamond-like carbon lamina layer 15 is improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cooking pan used for general household and business use.

  Currently, cooking pans that are widely available to the general public are often made of aluminum or stainless steel alone or a combination of these metals, but because of their good thermal conductivity, cooking pans based on copper are also popular. Is used. When copper is used as the base material, tin plating is usually applied to the inner surface under the Food Sanitation Law, and the outer surface may only be coated with an antioxidant. In many cases, acrylic resin, silicone resin, epoxy resin or ceramic transparent coating having high heat resistance is treated.

  In addition, some cooking pans that can be used in electromagnetic induction heating cookers have copper plating on the outer surface of magnetic metal such as ferritic stainless steel for the purpose of improving the appearance quality and electromagnetic induction heating efficiency. Some have been coated with a clear coat to prevent copper oxidation due to heat during cooking (for example, see Patent Document 1).

Typically, the inner surface is covered with a fluororesin coating, and the lower layer is made of aluminum with good thermal conductivity, and the outer surface, that is, the outermost surface of the pan is made of ferritic stainless steel, iron, permalloy, etc. An electromagnetic induction heating type rice cooker pan or the like in which a magnetic metal layer is provided and copper plating is processed on the magnetic metal layer.
JP 2001-145558 A

  However, in the configuration in which the conventional copper is used as a base material or a copper layer is used on the base metal by a technique such as copper plating on the base metal, the appearance of the copper is discolored by oxidation due to heat during cooking. In addition, even if the resin coating treatment such as clear coat is applied to the copper surface, the oxidation of copper cannot be completely prevented due to the occurrence of scratches during use. An oxide film may grow between the resin coating and the resin coating may eventually peel off in combination with thermal degradation of the resin coating.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a highly durable cooking pan that suppresses oxidation of copper constituting the pan.

  In order to solve the above-mentioned problems, the present invention uses copper or a combination of copper and another kind of metal as a base material for a cooking pan, and is provided with a thin film layer of diamond-like carbon (DLC) on the surface of copper.

  As described above, the cooking pan of the present invention is provided with a thin film layer of diamond-like carbon on the surface of copper constituting the outer surface. With this configuration, the beautiful color tone and luster of copper itself are not impaired. As a result of suppressing the oxidation of copper, there is an effect of preventing discoloration of copper, and the coating applied to the metal thin film layer also brings about an effect of improving the heat resistance and durability.

According to the first aspect of the present invention, the diamond-like carbon thin film layer is formed on the surface of copper constituting the outer surface of the cooking pan, so that copper is hardly oxidized in actual use, and deterioration due to copper oxidation is suppressed. can do.

  Diamond-like carbon is a carbon film having an intermediate characteristic between diamond and graphite, and a plasma CVD method or a PVD method is generally used as its production method, and by applying a dense carbon film coating on the copper surface uniformly, Gas permeation with respect to oxygen and the like is reduced and oxidative deterioration of the copper surface is suppressed.

  Other common features of diamond-like carbon are hardness, lubricity, wear resistance, chemical stability, etc., and it can be applied to the outer surface of a cooking pan that is exposed to high temperature, moisture, seasonings, or wear. Is preferred.

  It should be noted that there is no problem even if the copper is not only pure copper but also an alloy such as brass or red copper.

  In addition, this structure can be used for electromagnetic induction when the base material is made of a magnetic metal such as ferritic stainless steel or a combination of a magnetic metal and a thermally conductive metal such as aluminum and a copper thin film is provided on the outer surface. In addition, highly efficient heat generation can be obtained.

  The copper layer on the outer surface of the base metal is obtained by copper plating treatment or vapor deposition, and can form a relatively uniform copper thin film layer of copper, thereby obtaining stable heat generation particularly during electromagnetic induction heating. In addition, if the copper plating to which the brightener is added is processed, it becomes a cooking pan with excellent surface gloss.

  In addition, even if copper is copper alloy type plating such as brass, there is no problem.

  In general, when performing electromagnetic induction heating, it is common to use a metal material having a high skin electric resistance value for the heating portion of a cooking pan for electromagnetic induction heating. For example, in the case of a typical ferritic stainless steel, 430 stainless steel, when a high frequency current of 25 kHz is passed through an induction coil, the skin electric resistance value is 23.3 * 10-4 Ω, and in iron, 9.4 * 10-4 Ω is high. It can be said that it is suitable for heating. On the other hand, copper is as low as 0.39 * 10-4 and is usually a material that is not suitable for electromagnetic induction heating. Therefore, normally, when a magnetic field is applied to a nonmagnetic metal, a repulsive magnetic field is generated in the nonmagnetic metal, a repulsive current flows, the magnetic field cannot pass through the nonmagnetic metal, and a heat generation effect due to electromagnetic induction heating cannot be expected.

  However, as these nonmagnetic metal layers are also made thinner, the skin resistance eventually increases, and electromagnetic induction heating becomes possible. That is, if the copper, which is a nonmagnetic metal layer, is also sufficiently thin, the skin resistance becomes high, so that a repulsive magnetic field is hardly generated, and the magnetic field easily passes through the nonmagnetic metal. The eddy current is also generated in the magnetic metal by the magnetic field that passes, and both the copper and the magnetic metal layer such as stainless steel generate heat. The present invention utilizes this phenomenon, and by combining copper and a magnetic metal layer, even if copper that is a nonmagnetic metal is on the outer surface of the pan, it is more efficient than a simple magnetic metal layer single layer. It generates heat and cooks rice.

  This is because the total calorific value of magnetic metal and copper is verified, and after examining in detail the thickness of copper that can produce a higher calorific value than when magnetic metal alone is heated, copper of the optimal thickness is plated. It can be arranged on the outer surface of the magnetic metal layer almost uniformly by the above method, etc., and heat generation more efficient than before can be obtained.In other words, the copper thickness is verified in detail, and heat generation higher than that of magnetic metal alone is generated. It has the effect of obtaining.

In the cooking pan that has obtained high heat in this way, especially the oxidation of copper in the part that generates heat by electromagnetic induction is intense, so it is possible to suppress the oxidation of copper by overlaying a thin layer of diamond-like carbon on the copper layer, Furthermore, the durability of the resin coating layer to be coated thereon can be improved.

  According to the second aspect of the present invention, the diamond-like carbon thin film layer formed on the copper surface constituting the outer surface of the cooking pan has a thickness that does not conceal the color and luster of copper. Is approximately 5 to 30 nm. If the thickness is less than 5 nm, the color tone of copper is almost completely preserved, but the antioxidant effect cannot be expected so much. On the other hand, when the thickness exceeds 30 nm, the oxidation prevention effect of copper is high, but copper is concealed and becomes a black color peculiar to the diamond-like carbon layer that is overlaid, and the copper-colored color peculiar to copper is lost and the appearance is impaired, and electromagnetic induction heating is performed. Cooking pots can adversely affect heating performance and electrical properties.

  The thin film layer of diamond-like carbon may be processed almost uniformly on the entire outer surface of the cooking pan, but it may be processed only on the portion where the heating is strong during cooking. It is also possible to process it thinly.

  It should be noted that there is no problem even if the copper is not only pure copper but also an alloy such as brass or red copper.

  According to invention of Claim 3, It is a cooking pan of Claims 1-2 characterized by coating a resin coating on the outer surface of the thin film layer of the diamond-like carbon provided in the outer surface of copper, In particular, if the resin coating is a clear coating, which is a transparent resin coating, the color tone unique to copper can be maintained, copper oxidation can be suppressed, and the resin coating has a high gas barrier property. If a material having a high ability to block oxygen is used, the antioxidation effect of copper is further improved and the durability of the resin coating is also improved.

(Embodiment 1)
Hereinafter, an embodiment of the cooking pot of the present invention will be described with reference to FIG. 1 taking a pot used in an electromagnetic induction heating rice cooker as an example.

  FIG. 1 shows a 1.8 L rice cooker that heats and cooks a pot 9 by electromagnetic induction heating, and includes an electromagnetic induction heating coil 1, a ferrite 2, a pot bottom temperature detection sensor 3, a heating control board 4, and a board cooling fan. 5. The operation unit 6, the heating plate 7, the steam cap 8, and the pan 9 that is detachably attached to the main body are the main components, and after adding appropriate amounts of rice and water in the pan, the rice cooking and heat retaining steps are executed. However, this step is executed by program control by a microcomputer.

  The pan 9 is obtained by press-molding 1 mm thick aluminum 10, 0.8 mm thick ferritic stainless steel 11 and a clad material, and the inner surface is treated with a highly non-adhesive fluororesin coating 13 on the aluminum. ing. The outer surface of the ferritic stainless steel 11, which is a magnetic metal, is treated with a bright copper sulfate plating with a thickness of 5 μm. The copper plating layer 12 forms a heat generating layer for electromagnetic induction heating together with the ferritic stainless steel.

  In addition, in the present embodiment, in consideration of electromagnetic induction heating, ferritic stainless steel is used as the metal layer material of the pan, but the material is not limited to this, and any material capable of electromagnetic induction is used. Any material can be applied, and a magnetic metal is not necessarily required as long as it does not cause electromagnetic induction.

  In this embodiment, a high-frequency current of 25 kHz flows through the electromagnetic induction heating coil during rice cooking. At this time, the magnetic field lines generated from the induction coil enter the copper and ferrite stainless steel layers that are induction heating portions of the pan. The eddy current is generated at this time, and the pan generates heat. The rice cooking process is performed by this heat, and the rice is cooked.

  In this embodiment, a high-frequency current of 25 kHz is used. However, it is arbitrary to change this frequency depending on the situation, and it is also possible to change the thickness of copper accordingly.

  In addition, as a result of studying the copper thickness at which the heat generation amount of the copper of the electromagnetic induction heat generating portion becomes higher than that when using magnetic metal alone, the maximum value of the heat generation amount is around 5 μm in this embodiment. In order to find out that the copper has a thickness of 5 μm, copper was processed on the outer surface of the pan.

  A thin film layer 15 of diamond-like carbon is formed on the outer surface of the copper plating layer 12 by an ion plating method which is a kind of PVD. This is achieved by introducing hydrocarbon gas into a vacuum chamber in a direct current arc discharge plasma. Hydrocarbon ions are generated, and these hydrocarbon ions collide with the copper surface having a negative voltage to solidify and form a film. In the pan of this embodiment, the entire pan is a diamond-like layer with a substantially uniform thickness. The thickness of the carbon thin film layer was found to be 2 nm, 5 nm, 30 nm, and 44 nm, respectively, by precise thickness measurement using a fluorescent X-ray of the pan.

  In addition, in the thickness of the diamond-like carbon of this area | region, it did not bring about any bad influence on the electromagnetic induction heating from the rice cooker main body, and it confirmed that the rice cooking process was implemented correctly.

  Next, an epoxy resin-based clear coating 14 was applied to the surface of the diamond-like carbon layer 15 and baked at 180 ° C. for 15 minutes to a thickness of about 20 μm after baking.

  Here, as a comparative example, a pan in which the same epoxy resin mixed clear coating was applied directly to the copper surface on the outer surface of the pan without performing the diamond-like carbon step in the above-described process of making the rice cooker pan. Table 1 shows the results of a comparison of the appearance and heat durability.

  First, each rice cooker pan No. 1 made of diamond-like carbon with a thickness of 2 nm, 5 nm, 30 nm, and 44 nm formed on the copper plating layer and capable of electromagnetic induction heating was prepared in this embodiment. Comparative Examples No. 1 to 4 having an appearance color of 1 to 4 without a diamond-like carbon layer. Compared with 5, the copper-like color is almost preserved at diamond-like carbon thicknesses of 2 nm and 5 nm, and the copper color becomes lighter and darker as the thickness becomes 30 nm. However, these regions still exhibit a sufficient copper color. However, at 44 nm, the copper color remains to a slight extent, and the diamond-like carbon is almost black. Therefore, a thickness of approximately 30 nm or less is desirable in order to maintain the copper color appearance.

  Next, assuming that the cooking pan was exposed to strong heating conditions, a clear coat heat resistance test was carried out. This was done after holding the cooking pan at 200 ° C. for a predetermined time, A cross-cut test based on JIS test method standards was conducted on the surface.

  The test is held at 200 ° C. for a predetermined time, and then cooled to room temperature. Then, 11 incisions are made in the test surface at intervals of 1 mm vertically and horizontally to make 100 squares, and then Cellotape (registered trademark) is adhered to the grid. , Peeled in the 90 ° direction.

  In (Table 1), since the remaining ratio 100/100 of the clear coat is evaluated as ○, 90/100 or more as Δ, and less than 90/100 as × when the cellophane (registered trademark) is peeled off, of course, the heating holding time is Those having a high survival rate over a long period of time have excellent heat resistance.

  Compared to the comparative example having no diamond-like carbon layer, the embodiment having the diamond-like carbon layer has higher heat resistance and durability, and the tendency is more prominent as the diamond-like carbon layer is thicker. Can be determined from the results in Table 1. This is because the thicker the diamond-like carbon layer is, the less likely copper is oxidized, and the formation of brittle copper oxide is suppressed in the lower layer of the clear coat.

  Since diamond-like carbon has a relatively smooth surface, the surface of the magnetic metal layer that is the base material of the pan is subjected to a blasting process in advance so that the surface roughness Ra value is about 0.5 to 2.0 μm. If this is the case, the diamond-like carbon thin film layer also has an appropriate surface roughness, so the adhesion of the clear coat is improved.

(Embodiment 2)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 shows a cooking pan generally used for cooking by heating. The base material is copper 16 having a thickness of 1.5 mm, and the inner surface is subjected to tin plating 17. Moreover, the metal thin film layer 18 is processed on the outer surface of the copper 16 as a base material, and this is a diamond-like carbon thin film layer as in the first embodiment. By changing conditions such as the processing time, A diamond-like carbon layer having a thickness of 12 nm, 24 nm, and 30 nm is processed, and the color tone and gloss of copper can be sufficiently detected at any thickness.

  Here, in the preparation process of the cooking pot of the second embodiment, a cooking pot in which benzotriazole, which is a copper antioxidant, was applied to the outer surface of the pot without performing diamond-like carbon treatment was used as Comparative Example 2, and the above-described implementation (Table 2) shows the results of the embodiment 2 and the heat discoloration test.

  (Table 2) shows the change in surface oxidation color when the cooking pots of Embodiment 2 and Comparative Example 2 are put in a furnace at 130 ° C. by the color difference ΔE, and the color change due to oxidation increases as the ΔE value increases. Is large.

  As shown in (Table 2), in Comparative Example 2 in which only the antioxidant was treated on the copper surface, the oxidation of copper progressed rapidly, and the hue changed greatly according to the thickness of the oxide film. While no effect is seen at 130 ° C., it can be seen that in Embodiment 2, the change in color difference is slow and the color tone and glossiness unique to copper can be maintained for a long time.

  As described above, the cooking pan according to the present invention is provided with a diamond-like carbon thin film layer on the surface of copper constituting the outer surface. It can be applied to piping and building materials.

Sectional drawing of the rice cooker with which the pan of the 1st Embodiment of this invention is provided, and a pan The cooking pot which is the 2nd Embodiment of this invention, and its sectional drawing

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electromagnetic heating induction coil 2 Ferrite 3 Bottom-bottom temperature detection sensor 4 Heating control board 5 Substrate cooling fan 6 Operation part 7 Heating plate 8 Steam cap 9 Pan 10 Aluminum 11 Ferritic stainless steel 12 Copper 13 Fluoro resin coating 14 Clear coating 15 Diamond like Carbon 16 Copper 17 Tin plating 18 Diamond-like carbon 19 Handle

Claims (3)

A copper thin film is provided on the outer surface of the base material, which is copper or copper alloy, or a combination material of copper or copper alloy and other kinds of metals, or a magnetic metal or a combination material of magnetic metal and thermally conductive metal. A cooking pan, characterized in that a diamond-like carbon thin film layer is provided on the outer surface of the substrate. The cooking pot according to claim 1, wherein the thin film layer of diamond-like carbon has a thickness of 5 to 30 nm of copper. The cooking pot according to claim 1 or 2, wherein a transparent resin coating is applied to the outer surface of the diamond-like carbon thin film layer.

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