Cooking container and manufacturing method of cooking container

Abstract

To provide a cooking container which shows safety and durability by modifying a part of a hard coating film which is formed on an inner surface and does not use fluorine and can be achieved at a low cost in the cooking container which accommodates a material to be cooked in the inside and cooks by heating by electrical heating means.SOLUTION: In a cooking container 10 which accommodates a material to be cooked in the inside and cooks by heating by electrical heating means 14, a hard coating film 13 made of an inorganic sintered body is formed on an inner surface. The hard coating film includes a non-transparent first layer 13a and a second layer 13b which is formed by laminating on the first layer and has light transmissivity. A prescribed part of the first layer is modified in a hue which is different from a hue in other part, and a surface of the second layer of the modified part is formed into a rough surface.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a cooking container in which food is stored and cooked by electrical heating, and to a cooking container having a hard coating film formed on its inner surface, and a method for manufacturing a cooking container having a hard coating film formed thereon. [Background technology]

[0002] An example of a cooking device that has become increasingly popular in recent years is an electric kettle with a main body that can be detachably mounted on a power base. An electric kettle is a relatively small capacity device of about 0.15 liters to 1.2 liters that meets the needs of users who want to boil a small amount of hot water quickly when they want to use it. When water is poured into the water storage section, which is a cooking container in the main body, and the electric kettle is placed on the power base, electricity is applied to the heater in the main body through the power base, and the water can be boiled in a short time of about 1 to 3 minutes. Most electric kettles do not have a heat retention function like an electric pot, and when the water boils, the user can lift only the main body from the power base and tilt the main body to pour the hot water into a coffee cup or the like from the spout by tilting the main body as if pouring hot water from a conventional kettle.

[0003] In various cooking appliances that cook food by electric heating, such as electric kettles and rice cookers, a coating film is formed on the inner surface of the metal container body of the cooking container that holds the food inside to prevent the food from sticking. Fluorine coating, which is relatively easy to form and prevents food from sticking, was the mainstream coating film for such cooking containers, but in recent years, concerns have arisen about the safety and environmental impact of fluorine compounds, and hard films such as ceramics have come to be used in place of the fluororesin coating that was previously used.

[0004] A hard coating such as ceramic is more durable than a fluororesin coating that peels off when rubbed hard, and can protect the inner surface of the container for a long period of time. However, due to the high non-adhesiveness of the ceramic coating, there was a problem that it was difficult to form a water volume mark on the inner surface of the container using conventional methods for forming the mark, such as printing and engraving.

[0005] To solve this problem, a method has been proposed in which two ceramic coating films of different colors are laminated, and holes in a memory pattern are formed in the surface film by laser processing, allowing the color of the film underneath to be seen through the holes, thereby displaying a memory showing the amount of water (see Patent Document 1).As another method, a method has been proposed in which groove-like portions are formed by scraping the surface of the ceramic coating film by laser processing, and a water amount memory is formed by injecting paint or ink into the groove-like portions (see Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-160871 A [Patent Document 2] JP 2012-5627 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the memory formation method described in Patent Document 1, the top coating layer formed on the surface of the two-layer ceramic coating is removed, which causes the coating thickness in the memory area to become thinner, making it difficult to ensure durability, and also creates a step at the boundary between the memory area and the other areas, which causes the top coating film to easily peel off. In addition, in the technology described in Patent Document 2, it is necessary to fill the grooves formed in the ceramic coating with ink or the like to improve visibility, which increases the number of processes, raising production costs, and further raising issues such as increased environmental impact depending on the ink material.

[0008] The present invention is devised to solve such problems of the prior art, and aims to provide a cooking container that contains food to be cooked inside and cooks it using an electric heating means, and that has safety, durability, and can be produced at low cost by modifying a portion of the fluorine-free hard coating film formed on the inner surface. [Means for solving the problem]

[0009] In order to solve the above problems, the heat-cooking container of the present invention is a heat-cooking container that holds food to be cooked inside and is heated by an electric heating means to cook the food, and is characterized in that a hard coating film made of a sintered inorganic body is formed on the inner surface, the hard coating film having an opaque first layer and a translucent second layer formed and laminated on the first layer, and a specific portion of the first layer is modified to a color different from other portions, and the surface of the second layer in the modified portion is roughened.

[0010] In addition, the manufacturing method of a heat-cooking container of the present invention is a manufacturing method of a heat-cooking container that contains food to be cooked inside and is heated by an electrical heating means to cook the food, and is characterized by including a coating film formation step of forming a hard coating film made of a sintered inorganic material on the inner surface of the heat-cooking container, and a laser processing step of irradiating a UV laser onto the surface of the formed hard coating film to roughen the surface. Effect of the Invention

[0011] The cooking container of the present invention has a hard coating film made of an inorganic sintered body formed on its inner surface, the hard coating film having a non-transparent first layer and a translucent second layer formed on the first layer, a predetermined portion of the first layer is modified to a color different from that of the other portions, and the surface of the second layer in the modified portion is roughened. Therefore, the modified portion of the first layer can form a mark indicating the amount of food contained therein, and the memory can be protected by the second layer covering the modified portion.

[0012] The method for producing a cooking vessel of the present invention includes a coating film forming step of forming a hard coating film made of a sintered inorganic material on the inner surface of the cooking vessel, and a laser processing step of irradiating a UV laser onto the surface of the formed hard coating film to roughen the surface. This provides an environmentally friendly coating film that is difficult to peel off, and allows the formation of a memory indicating capacity and modification of the coating film surface to be performed by a UV laser that does not cause significant damage to the coating film. [Brief description of the drawings]

[0013] [Figure 1] 1 is a perspective view showing the appearance of an electric kettle having a heating and cooking container according to an embodiment of the present invention as a water storage section. [Diagram 2] 1 is a cross-sectional view showing the configuration of an electric kettle having a heating and cooking container according to an embodiment of the present invention as a water storage section. [Diagram 3] FIG. 4 is a partially enlarged cross-sectional view showing the configuration near the bottom of the water storage section. [Figure 4] 1 is an image diagram showing the irradiation state of a UV laser when forming a water volume mark on the inner surface of the water storage part of the electric kettle of this embodiment. FIG. [Diagram 5] 1 is an image diagram for explaining a change in the beam spot due to the relationship between the focus position of the UV laser and the irradiation surface. FIG. [Figure 6] FIG. 13 is a diagram showing water volume markings formed on the side of a water storage section by laser processing using a UV laser. [Figure 7]FIG. 13 shows the change in the uneven shape of the bottom surface of the water storage section due to laser processing using a UV laser. [Figure 8] This figure shows the wettability of the bottom surface of a water storage section where the coating surface has been roughened by a UV laser. [Figure 9] FIG. 13 is a diagram illustrating the effect of a bottom surface roughened by a UV laser during heating. [Figure 10] FIG. 1 is a diagram illustrating the difference in damage to a ceramic coating caused by roughening using a UV laser and by roughening using mechanical polishing. [Figure 11] 11A and 11B are diagrams illustrating an example of forming a roughened area on the bottom surface of a water storage section. [Figure 12] 1 is a cross-sectional view showing the configuration of a rice cooker having a heating cooking container according to an embodiment of the present invention as an inner pot. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The cooking container of the present invention is a cooking container that holds food to be cooked inside and is heated by an electrical heating means to cook the food, and has a hard coating film made of a sintered inorganic body formed on its inner surface, and the hard coating film has an opaque first layer and a translucent second layer formed and laminated on the first layer, and a specific portion of the first layer is modified to a color different from other portions, and the surface of the second layer in the modified portion is roughened.

[0015] By providing the cooking container of the present invention with the above-mentioned configuration, the modified portion of the first layer allows predetermined letters or patterns to be written on the hard coating, and the second layer can protect these letters or patterns.

[0016] In the above-mentioned cooking vessel, at least one of ceramics and glass can be suitably used as the inorganic material.

[0017] It is also preferable that the first layer is made of a material that changes color by photolysis, which makes it possible to form desired characters or patterns without causing significant damage to the hard coating film.

[0018] Furthermore, the modified portion may be formed on a side surface of the cooking vessel, and the modified portion may form a scale representing the capacity of the contents.

[0019] Furthermore, by forming the modified portion on the bottom surface of the cooking vessel, the modified portion of the roughened second layer can be made hydrophilic.

[0020] In this case, it is preferable that the modified portion is a portion of the bottom surface facing the position where the electric heating means is arranged and / or a portion facing the position where a temperature sensor that detects the temperature of the cooking container is arranged.

[0021] The heating and cooking vessel may also be a water storage section of an electric kettle, or the heating and cooking vessel may be an inner pot of a rice cooker.

[0022] The method for manufacturing a cooking container of the present invention is a method for manufacturing a cooking container that contains food to be cooked inside and is heated by an electrical heating means to cook the food, and includes a coating film formation step of forming a hard coating film made of a sintered inorganic material on the inner surface of the cooking container, and a laser processing step of irradiating a UV laser onto the surface of the formed hard coating film to roughen the surface.

[0023] In this way, the method for manufacturing a cooking container of the present invention can make the roughened portion hydrophilic without causing significant damage to the hard coating.

[0024] In addition, in the coating film forming step, it is preferable to form an opaque first layer and a light-transmitting second layer laminated on the first layer, whereby the opaque first layer can be modified while leaving the transparent second layer, and characters or patterns can be formed.

[0025] The laser processing step can modify the first layer on the side surface of the cooking vessel to form a marking indicating the capacity of the food contained in the cooking vessel.

[0026] Furthermore, it is preferable that the laser processing step is performed to roughen at least one of the bottom surface of the cooking vessel, the portion facing the position of the electric heating means and the portion facing the position of the temperature sensor that detects the temperature of the cooking vessel, so that the roughened portion becomes hydrophilic and it is possible to effectively prevent the generation of large bubbles when the temperature is increased.

[0027] (Embodiment) Hereinafter, the cooking vessel according to the present invention will be described by taking as an example a vessel used as a water reservoir for an electric kettle.

[0028] The electric kettle described in this embodiment has a water storage section provided inside the main body, and the inner surface of the metal inner container is coated with a hard coating of inorganic sintered ceramic. The ceramic coating formed on the side of the water storage section has a water volume scale that indicates the water storage volume, which is the capacity of the contents. The ceramic coating formed on the bottom surface of the water storage section is roughened by laser processing using a UV laser. The electric kettle described in this embodiment has a lid that closes the opening of the main body, and a movable blocking member that is linked to a hot water supply switch that controls the opening and closing of the hot water supply path when hot water is poured from the spout, and further has a configuration that prevents hot water from spilling from the steam path when the kettle is tipped over.

[0029] FIG. 1 is a perspective view showing the appearance of an electric kettle having a heating and cooking container according to this embodiment as a water storage section.

[0030] This electric kettle comprises a main body 1, a handle 2 fixed to the outer shell of the main body 1, and a lid 3 that closes the opening at the top of the main body 1 in an openable and closable manner, and the main body 1 is removably placed on a power stand 4.

[0031] The electric kettle shown in Figure 1 has a main body 1 and a spout 5 formed at the upper end of the side radially opposite to the handle 2, for pouring liquid stored in a water storage section 10 (see Figures 2 and 3) within the main body 1, such as water or boiled water, into a coffee cup or the like.

[0032] 1, the electric kettle is structured such that the lid 3 is inserted from above the main body 1 to close the opening of the main body 1, and the lid 3 is provided with an attachment / detachment lever 6 for releasing the spring mechanism that fastens the lid 3 to the main body 1, and a hot water supply switch 7 for opening a hot water supply passage from inside the main body 1 to the spout 5 when pouring hot water stored inside the main body 1. Note that the electric kettle described in this embodiment is structured such that the spout 5 for pouring out the liquid in the water storage portion 10 also serves as a steam outlet for the steam path for releasing steam, and therefore does not have a steam outlet that is often located on the handle 2 side of the top surface of the lid 3. Also, a protruding portion 8 that partially covers the top surface of the spout 5 is formed at the end of the lid 3 on the spout 5 side.

[0033] The handle 2 is provided with a power switch 9 that starts the flow of electricity to a heater, which is an electric heating means that can heat and boil liquid such as water stored inside the main body 1. This power switch 9 has a function of automatically stopping the flow of electricity to the heater to prevent boiling on empty when it detects that the hot water inside the main body 1 has boiled.

[0034] Fig. 2 is a cross-sectional view of the electric kettle shown in Fig. 1, seen from the side of a straight line connecting the spout and the handle, and Fig. 3 is a partially enlarged cross-sectional view showing an enlarged portion of the vicinity of the bottom surface of the water storage portion.

[0035] As shown in FIG. 2, the main body 1 of the electric kettle is configured by disposing a water storage section 10, which is a cooking container according to this embodiment, inside a resin exterior case 11. In the water storage section 10, a ceramic coating 13 is formed as a coating film made of a ceramic sintered body on the inner surface of an inner container 12 made of a metal such as stainless steel, i.e., on the surface of the part that contains water. As shown in FIG. 3, in the water storage section 10, which is a cooking container according to this embodiment, the ceramic coating 13 formed on the inner surface of the inner container 12 is formed as a laminated film of a first layer 13a formed on the inner surface of the inner container 12 and a second layer 13b formed by laminating on the inner surface of the first layer 13a. As shown in FIG. 3, in the following, the part of the first layer 13a formed on the side surface of the water storage section 10 is referred to as 13a1, the part formed on the bottom surface is referred to as 13a2, and the part of the second layer 13b formed on the side surface of the water storage section 10 is referred to as 13b1, and the part formed on the bottom surface is referred to as 13b2.

[0036] As shown in Fig. 3, an annular sheathed heater 14, which is an electric heating means, is disposed below the water storage section 10 in contact with the bottom surface of the water storage section 10, and the water stored in the water storage section 10 can be heated by the sheathed heater 14 to boil water. Although not shown in the figures, in the electric kettle described in this embodiment, the sheathed heater 14 is formed as a substantially annular member having an outer diameter slightly smaller than the outer diameter of the water storage section 10. The portion of the sheathed heater 14 on the handle 2 side is not annular but is open, and wiring connecting the sheathed heater to a power supply circuit (not shown) is connected to this open end.

[0037] Furthermore, a temperature sensor 15 for detecting the temperature of the water storage section 10 is disposed inside the portion of the bottom surface of the water storage section 10 where the sheathed heater 14 is disposed. Based on the temperature of the bottom surface of the water storage section detected by the temperature sensor 15, a control circuit (not shown) controls the supply of electricity to the sheathed heater 14 to efficiently boil the water in the water storage section 10, and also takes safety measures to stop the supply of electricity to the sheathed heater 14 to prevent the water storage section 10 from boiling dry if it is suspected that there is not enough water in the water storage section 10, for example, if the temperature detected by the temperature sensor 15 rises suddenly.

[0038] The power supply stand 4 on which the main body 1 of the electric kettle is placed has a fixed surface 22 shaped to correspond to the lower surface 21 of the bottom of the main body 1. When the lower surface 21 of the main body 1 is placed on this fixed surface 22, a power plug 23 of the main body 1 fits into a power socket 24 of the power supply stand 4. By placing the main body 1 on the power supply stand 4, power supplied to the power supply stand 4 via a power cable (not shown) that is plugged into a commercial power source can be supplied to the sheath heater 14 arranged at the bottom of the main body 1.

[0039] In this way, the electric kettle shown in this embodiment heats the water stored in the water storage section 10 to boil hot water while the main body section 1 is placed on the fixed surface 22 of the power base 4, and after the water has been boiled, the main body section 1 can be removed from the power base 4 and carried by the handle 2. Then, by holding the handle 2 and tilting the main body section 1, the boiled hot water in the water storage section 10 inside the main body section 1 can be poured into a coffee cup or the like, and the main body section 1 can also be placed alone in a desired position such as on a table.

[0040] The electric kettle illustrated in this embodiment has a locking mechanism in which the lid body 3 seals the top surface of the main body, and furthermore, a water stop function in the event of tipping over is disposed within the lid body 3 to prevent hot water from spilling even if the kettle is accidentally tipped over; however, a detailed explanation of the internal mechanism of the lid body 3, including this water stop mechanism in the event of tipping over, will be omitted.

[0041] It should be noted that the overall configuration of the electric kettle described in this embodiment is conventionally known, and is merely one example of a specific configuration of an electric kettle.

[0042] <Coating film on the inner surface of cooking containers> (Ceramic coating) The ceramic coating 13, which is a coating made of a sintered inorganic material and formed on the inner surface of the water storage portion 10, which is a cooking vessel, will be described below.

[0043] As shown in Fig. 3, in the water storage section 10 which is a cooking container according to this embodiment, a ceramic coating 13 is applied to the inner surface of a stainless steel inner container 12. This ceramic coating 13 is composed of two layers: a first layer 13a formed on the surface of the inner container 12 and a second layer 13b laminated on this first layer 13a.

[0044] The ceramic coating 13 can be formed by, for example, using a colloidal sol in which a solution of a metal organic compound (metal alkoxide) or an inorganic compound is dispersed in water or the like to first coat the first layer 13a on the inner surface of the kettle inner container, which is the part to be coated, by spraying or the like, and then applying the colloidal sol onto the first layer 13a by spraying or the like to form the second layer 13b, and then heating and baking the first layer 13a and the second layer 13b to sinter the oxide solid and form a film, which is a so-called wet on wet method. The baking conditions can be 200 to 300°C for about 15 to 20 minutes, and when the film is formed, it becomes a sintered body (oxide) of an inorganic substance such as SiO2.

[0045] In addition, the water storage section 10 of the electric kettle in this embodiment uses a pigment TiO2 as the first layer 13a of the ceramic coating 13. The pigment TiO2 is opaque and changes to Ti3O5 when irradiated with a UV laser beam, which will be described later, and whose color changes from light gray to black.

[0046] For the first ceramic coating layer 13a1, for example, white pigment TiO2 in the main component SiO2 can be used to change the color from white before the UV laser irradiation to black after the irradiation. Also, for example, black pigment Cr2O3 or carbon black can be used to change the color from black before the UV laser irradiation to brown after the irradiation.

[0047] The second layer 13b of the ceramic coating 13 is made of SiO2 as a material having translucency. The translucency of the second layer 13b means that the color of the first layer 13a, which is the lower layer, is visible when the ceramic coating 13 is fired. In the water storage section 10, which is a cooking container according to this embodiment, a water volume mark indicating the amount of water contained in the water storage section 10 is formed by changing the color of the first layer 13a by irradiating the ceramic coating 13 with a UV laser. The second layer 13b only needs to have enough translucency for the user to recognize the water volume mark formed as a change in color of the first layer 13a, and it is not limited to being colorless and transparent, and colored ones can also be used.

[0048] The second layer of ceramic coating 13b may be, for example, SiO2 with silver mica dispersed therein, or a SiO2 film colored with a pigment to a desired color without losing translucency. Also, by coating glass as the second layer 13b, the water storage section 10 can be made highly transparent, making it easier to see the patterns such as the water level markings formed on the first layer 13a.

[0049] The thickness of the ceramic coating 13 is preferably about 30 μm in total from the viewpoint of preventing peeling. As described later, in the water storage section 10 described in this embodiment, the second layer 13b is left as a surface protection film when the water volume memory is formed by UV laser irradiation. For this reason, it is preferable that the thickness of the second layer 13b is about 10 to 15 μm, and the thickness of the first layer 13a is about 15 to 20 μm.

[0050] The above-mentioned ceramic coating is a representative example of a coating film made of an inorganic sintered body formed on the inner surface of a cooking vessel, and various known methods can be used as the coating method, such as porcelain enamel coating, chemical vapor deposition, physical vapor deposition, sputtering, and thermal spraying methods such as oxygen-acetylene flame and plasma jet processing, in addition to the above-mentioned sol-gel method. In addition, the inorganic material formed as the coating film of the sintered body described in this specification includes a wide range of inorganic materials, such as ceramics (so-called old ceramics) made from natural raw materials such as clay, feldspar, and quartz, new ceramics (or modern ceramics) made from artificial minerals, industrial ceramics such as alumina (Al2O3), silicon carbide (SiC), and titanium nitride (SiC), and various glasses such as acrylic glass, borosilicate glass, and quartz glass. In addition, two or more of these various ceramics and various glasses can be formed as a multilayer film. For example, strength can be improved by making the lower layer a ceramic coating film, and anti-fouling properties and design can be improved by making the upper layer a glass coating film. Since the hydrophilicity or water repellency of glass can be adjusted depending on the components used, it is possible to select and form an appropriate coating film depending on the product.

[0051] (Laser processing) The water storage section 10 of the electric kettle described in this embodiment has a ceramic coating 13 formed on its inner surface, which has been laser processed using a UV laser. A water volume scale indicating the amount of liquid contained in the water storage section 10 has been formed on the side of the water storage section 10 by laser processing using a UV laser. In addition, the bottom surface of the water storage section 10 has been roughened by laser processing using a UV laser, thereby improving the hydrophilicity of the bottom surface of the water storage section 10.

[0052] The UV laser irradiated to the ceramic coating 13 formed on the inner surface of the water storage section 10 described in this embodiment has a wavelength of 355 nm, which is one-third of the fundamental wavelength laser (1064 nm), and is called a third harmonic generation (THG) laser. The UV laser is generated by passing the fundamental wavelength laser through a nonlinear crystal to convert it into a 532 nm (green wavelength) green laser, and then passing it through another nonlinear crystal to convert it to a wavelength of 355 nm.

[0053] UV lasers have a higher absorption rate in materials than fundamental wavelength lasers and green lasers, and the irradiated light is efficiently absorbed by the irradiated surface. Therefore, when marking with a UV laser, there is no need to increase the power more than necessary, and efficient laser processing can be performed. In addition, because of its high absorption efficiency, no unnecessary thermal damage is caused even when it is irradiated on materials with high reflectivity such as metals. Another advantage is that the energy of the photon is small, making it possible to perform decomposition processing by directly breaking the molecular bonds of the irradiated object.

[0054] By using a UV laser with these characteristics to perform laser processing on the ceramic coating 13 formed on the inner surface of the water storage section 10, it is possible to form a water volume memory on the sides and roughen the bottom surface without causing significant thermal damage to the ceramic coating 13.

[0055] (Formation of water volume memory) FIG. 4 is an image diagram for explaining the state of irradiation of a laser beam when forming a water volume mark on the inner surface of the water storage part of the electric kettle described in this embodiment.

[0056] As described above, in the side portion of the water storage section 10 of the electric kettle described in this embodiment, a first layer of ceramic coating 13a1 made of TiO2 and SiO2 is formed on the inner surface of the metal inner container 12, and a second layer of ceramic coating 13b1 made of SiO2 is further laminated on this first layer of ceramic coating 13a1.

[0057] The two ceramic coating layers 13a1 and 13b1 are irradiated with UV laser light 30 to modify the first layer 13a1 on the lower side and change its color. In the water storage section 10 of the electric kettle according to this embodiment, a laser marking device is used as a means for irradiating UV laser light, so that the modified portion 31 of the first layer 13a1 can be controlled, and color change in a desired pattern is possible, so that the required number of marks can be formed in accurate positions. Note that the second layer 13b1 in the portion irradiated with the UV laser light 30 is modified and scraped off to form a depression 32, but by adjusting the output of the UV laser light 30, a part of the second layer 13b1 on the surface remains on the surface of the first layer 13a1, as shown in FIG. 4.

[0058] It is believed that even in the modified portion 31 of the first layer 13a1, a slight depression is formed on its surface due to irradiation with UV laser light, but since the second layer 13b1 remains as described above, it is believed that this will not have a significant effect on the ceramic coating 13 as a whole.

[0059] In this manner, in the water storage section 10 described in this embodiment, the denatured portion 31 of the first layer 13a1 formed as the water volume memory is covered by the second layer 13b1 and is not exposed, so that it can be prevented from being strongly rubbed or coming into contact with detergent, etc., when washing the water storage section 10, for example. This prevents the water volume memory from peeling off or becoming lighter in color, and allows the formation of a highly durable water volume memory. In addition, since the water volume memory is formed by utilizing the color change caused by the denaturation of the ceramic coating 13a itself formed as the first layer, there is no problem of environmental burden or safety for the human body, compared to the conventional technology in which a water volume memory is formed by scraping off a part of the coating film and filling the recess with ink.

[0060] As described above, in the water storage section 10 according to this embodiment, it is necessary to irradiate the ceramic coating 13 with UV laser light to modify the first layer 13a1 to form a sufficiently visible memory pattern, and to leave the second layer 13b in the portion irradiated with the UV laser light 30. As a method for realizing the irradiation intensity of the UV laser light 30 that can perform such preferable laser processing, in addition to a method of adjusting the intensity of the UV laser light 30 itself in the laser marking device used, a method of intentionally shifting the focus position of the UV laser light 30 from the position of the surface of the ceramic coating 13 irradiated with the UV laser light 30 to create a defocused state can be used.

[0061] FIG. 5 is an image diagram for explaining the change in the beam spot on the processing surface due to the relationship between the processing surface of the ceramic coating irradiated with the UV laser light and the position of the focus point of the UV laser light.

[0062] Figure 5(a) shows a state in which the focal point of the UV laser light is far from the processing surface, Figure 5(b) shows a so-called just-focus state in which the processing surface coincides with the focal point of the UV laser light, and Figure 5(c) shows a state in which the processing surface is farther away than the focal point of the UV laser light.

[0063] In addition, the inventor confirmed that the degree of change in the spot diameter of the UV laser light 30 with respect to the distances X1 and X2 was almost the same in the case where the position of the focus point 33 was far from the processing surface shown in Fig. 5(a) and the case where the position of the focus point 33 was close to the processing surface shown in Fig. 5(c). Therefore, in forming a water volume memory pattern in the water storage section 10 of the electric kettle described in this embodiment, the processing surface is placed closer to the position of the focus point of the UV laser light 30 in the state shown in Fig. 5(a) for the reason of reducing damage to the coating film caused by the proximity of the laser to the processing surface of the work (curved surface, positional deviation, etc.), the amount of change in the spot diameter when the distance X1 between the processing surface and the focus point 33 changes by 0.1 mm is defined as 1, and the defocus amount X1 is changed to examine the irradiation energy of the irradiated UV laser light 30.

[0064] More specifically, the defocus amount X1 was changed (for example, multiple values ​​were selected such as -20, -30, -40, ... -100) at a predetermined laser power value (for example, multiple values ​​were selected such as 20, 30, 40, etc.) using a laser marking device, and the side surface of the inner container 10 was actually irradiated with UV laser light 30, and the amount of color change caused by the degree of denaturation of the first layer 13a1 was visually confirmed.

[0065] In addition, whether the second layer 13b1 performs its protective function as an overcoat layer for the first layer 13a1 due to the denaturation caused by the irradiated UV laser light 30 was confirmed by a peel test in which tape (for example, Cellotape (registered trademark) manufactured by Nichiban Co., Ltd., 18 mm wide) was attached to the part of the side of the water storage section 10 where the color of the first layer 13a1 had changed after UV laser light was irradiated, and then the tape was peeled off by hand.

[0066] Through the inventor's investigations, it has been confirmed that by adjusting the value of the irradiation intensity of the UV laser light and the value of the above-mentioned defocus amount X1, it is possible to find conditions under which a change in color of the first layer 13a1 is sufficiently visible, and a certain thickness of the second layer 13b1 remains even when irradiated with the UV laser light 30, so that peeling of the ceramic coating film 13 does not occur in a peel test.

[0067] When forming a water volume memory using a laser marking device, the pulse frequency at which the UV laser light is irradiated and the scan speed, which is the moving speed of the irradiation position of the UV laser light, can be adjusted.

[0068] When the pulse frequency of the UV laser light irradiation is increased, the pulse width of the irradiated laser light tends to be increased and the energy peak tends to be lower. In this case, the irradiation time of the laser beam on the irradiated surface becomes longer, and the irradiated surface is greatly affected by heat. In the irradiation of the ceramic coat shown in this embodiment with the UV laser light, if the thermal effect on the coating is large, the damage to the second layer on the surface becomes large, and peeling becomes more likely to occur. Therefore, it was found that it is preferable to set the pulse frequency low when forming a water volume memory on the side of the water storage section.

[0069] In examining the irradiation pitch of UV laser light, it was found that decreasing the irradiation pitch caused greater modification of the first layer, resulting in greater color change and improved visibility of the memory, but it also caused greater damage to the second layer, making it more susceptible to peeling off and reducing the durability of the coating.

[0070] Considering the above characteristics, it was confirmed that the suitable conditions for forming the water volume mark on the side of the water storage part 10 of the electric kettle according to this embodiment are a UV laser light with a wavelength of 355 nm, a laser power of 50%, a scan speed of 750 mm / s, a pulse frequency of 50 kHz, a spot variable amount (X1) of -60 mm (the spot diameter becomes blurred from 50 μmφ to 137 μmφ by defocusing), a line interval of filling of 15 μm, and a printing count of 1. It goes without saying that the irradiation conditions of this UV laser light should be set appropriately by considering whether the water volume mark has sufficient visibility by modifying the first layer 13a1 and the thickness of the coating film of the second layer 13b1, and whether the damage caused to the second layer 13b1 can be secured to a thickness that is sufficient to provide durability as an overcoat film.

[0071] FIG. 6 is a diagram showing the water volume markings formed on the side surface of the water storage section under the above-mentioned preferable conditions.

[0072] The laser marking device using UV laser light was a laser marker MD-U1020 (product name) manufactured by Keyence Corporation. In addition, since the inner diameter of the water storage section was 170 mm and the position of the mark 200 located at the lowest side of the water storage section was 106 mm from the top end of the water storage section, it was not possible to form all the water volume marks at once within the scanning range of the irradiation beam on the horizontal surface of the laser marking device. For this reason, the marks were formed in two parts: the water volume marks located below the side with mark 600 as the boundary, and the water volume marks located above mark 600.

[0073] (Roughening of the container bottom surface) In the water storage section of the electric kettle described in this embodiment, in addition to forming the water volume mark on the side as described above, the bottom surface is also irradiated with UV laser light for surface treatment, and the bottom surface is roughened to improve hydrophilicity. The details are described below.

[0074] Fig. 7 is an image showing the change in the uneven shape of the bottom surface of the water storage section of the electric kettle according to this embodiment caused by irradiation with UV laser light. Fig. 7(a) shows an image of a curve showing the surface state before irradiation with UV laser light, and Fig. 7(b) shows an image of a curve showing the surface state after irradiation with UV laser light.

[0075] The UV laser light was irradiated onto the bottom surface of the water storage section 10 using the laser marker MD-U1020 (product name) manufactured by Keyence Corporation mentioned above under the following conditions: laser power 80%, scan speed 4000 mm / s, pulse frequency 100 kHz, fill line spacing 0.040 mm, and number of printings (number of repeated beam irradiations) 4, and the processing time was 265.4 sec.

[0076] As shown in Fig. 7(a), the surface of the ceramic coating 13 before irradiation with UV laser light was a relatively rough and uneven surface with an arithmetic mean roughness Ra of 0.82 (μm), whereas after irradiation with UV laser light, as shown in Fig. 7(b), fine irregularities with a surface roughness Ra of 1.65 (μm) were formed along the uneven shape shown in Fig. 7(a) before processing. Furthermore, the film thickness of the coating before and after irradiation with UV laser light was 21.5 μm before irradiation and 20.1 μm after irradiation, and it can be seen that the change in film thickness due to irradiation with UV laser light was small and the damage to the coating was not significant.

[0077] The surface roughness of the coating film was measured using a Taylor Hobson surface roughness measuring instrument, Surtronic DuO (trade name).

[0078] In this way, by irradiating the ceramic coating 13 formed on the bottom surface of the water storage section 10 with UV laser light, the coating surface becomes rough with fine irregularities formed thereon, and the surface of the ceramic coating on the bottom surface can be changed from the inherent water-repellent surface of the ceramic coating to a hydrophilic surface.

[0079] FIG. 8 is a diagram showing the state of water remaining on the bottom surface after water is poured into the water storage section irradiated with UV laser light.

[0080] As shown in Figure 8, on the bottom surface irradiated with UV laser light, a water film remained even though the surface tension of water is greater than that of alcohol, confirming that the surface has high hydrophilicity.

[0081] Next, the difference in roughening of the bottom surface of the water storage section 10 by irradiation with UV laser light between the case where UV laser light was used and the case where a hybrid laser was used was examined.

[0082] The laser marker device for irradiating the hybrid laser light used for comparison is a hybrid laser MD-X2520 (product name) manufactured by Keyence Corporation, which uses YVO4 as a light source and has a standard wavelength of 1.064 nm. The conditions for irradiating the hybrid laser light were laser power 40%, scan speed 8000 mm / s, pulse frequency 100 kHz, fill line spacing 0.080 mm, and printing once, and the processing time was 17.3 sec.

[0083] Under these conditions, the surface roughness Sa of the ceramic coating on the bottom surface after irradiation with hybrid laser light was 1.0 μm, which was not significantly different from the surface roughness Sa of 0.8 μm after irradiation with UV laser light. However, the depth of the formed irregularities was 9.9 μm, which was larger than the depth of 3.5 μm obtained when roughening was performed with UV laser light.

[0084] Figure 9 shows the results of a temperature rise test in the water storage area depending on the laser light used to roughen the bottom surface. Figure 9(a) shows the data when a UV laser was used for roughening, and Figure 9(b) shows the data when a hybrid laser was used for roughening.

[0085] For the temperature rise test, the bottom of a water storage section, which had a ceramic coating on its inner surface adjusted to a thickness of 25 μm on the bottom, was irradiated with UV laser light and hybrid laser light under the conditions described above to roughen the entire bottom surface, and then the electric kettle was turned on with 1000 ml of water at room temperature (approximately 23°C) poured into it and the water was boiled, and measurements were taken.

[0086] As shown in Figure 9(a), in the water storage section 10 whose bottom surface has been roughened by UV laser light, the heater pipe surface temperature of the sheathed heater, indicated by reference numeral 51 in the figure, can be maintained at a predetermined temperature of 190°C even after it has risen to the specified temperature, and the temperature of the water inside the water storage section 10 can be maintained constant after it has risen to 100°C about 4 minutes after heating has started. This shows that the roughening of the ceramic coating 13 on the bottom of the water storage section 10 makes the bottom hydrophilic, making it difficult for large air bubbles to form on the bottom, and therefore the temperature of the water inside the water storage section 10 can be accurately measured by the temperature sensor that detects the temperature of the outer surface part of the bottom of the water storage section 10, and the on / off control of the sheathed heater is performed correctly.

[0087] On the other hand, when the ceramic coating 13 on the bottom surface of the water storage section 10 is roughened by the hybrid laser light as shown in Fig. 9(b), the graph 53 showing the surface temperature of the sheathed heater shows that it rose rapidly after 4 minutes had passed, reached about 350°C, and then stopped operating. At this time, the water temperature in the water storage section, shown by the reference numeral 54, reached about 100°C after 4 minutes had passed, almost the same as when the surface was roughened by the UV laser light as shown in Fig. 9(a).

[0088] In the water storage section shown in Figure 9(b), where the bottom surface of the water storage section 10 was roughened by hybrid laser light, the output of the laser light was strong, and if the unevenness that appeared with the UV laser was to be formed on the coating film, the damage to the coating film was large and it was necessary to limit the printing conditions. As a result, it is believed that there was no significant change in the wettability of the bottom surface and the surface of the ceramic coating 13 remained in a hydrophobic surface state. For this reason, the air bubbles generated by the rise in water temperature did not leave the bottom surface and grew large, forming an insulating layer of air. As a result, the heat supplied from the sheath heater was not transmitted to the water, and the temperature of the bottom surface including the coating film surface rose, and it is believed that the temperature regulator malfunctioned and so-called dry boiling occurred even though the water temperature did not reach 100°C.

[0089] In this way, even when laser light was irradiated onto the ceramic coating 13 on the bottom surface of the water storage section 10, it is believed that surface treatment using hybrid laser light was not sufficient to improve the wettability of the bottom surface by roughening it, and the bottom surface remained in a hydrophobic state due to the ceramic coating.

[0090] Next, the difference in effect between the hydrophilization effect of the bottom surface of the water storage section 10 by UV laser light and the hydrophilization effect by the conventional polishing process was examined.

[0091] FIG. 10 is a diagram illustrating the difference in damage to a ceramic coating caused by surface roughening using a UV laser and surface roughening using mechanical polishing.

[0092] In FIG. 10, the circle indicated as 61 indicates the pinhole value in a thermal cycle test when the bottom surface was roughened by UV laser light as described in this embodiment, and the cross indicated as 62 indicates the pinhole value in a thermal cycle test on a water storage section whose bottom surface was roughened by polishing treatment as a comparative example.

[0093] The water storage section 10 that was roughened by UV laser light was the same as that used in the temperature rise test. On the other hand, the water storage section 10 as a comparative example was a ceramic-coated inner container adjusted so that the average thickness of the coating on the bottom surface was 25 μm, and a disk-shaped nonwoven surface treatment material Scotch-Brite (registered trademark) 8447P (product name, manufactured by 3M) was pressed against the processed part with a toggle clamp at a load of 1.3 to 1.5 kgf, and a polishing treatment was performed for 3 minutes by rotating and vibrating 400 to 450 times per minute.

[0094] The pinhole value shown in Fig. 10 was obtained by boiling cold water adjusted to 5°C for a water storage part whose bottom surface was roughened by UV laser light and a water storage part whose bottom surface was polished by Scotch-Brite (registered trademark), discarding the boiling water after boiling, adding cold water at 5°C, cooling the water storage part, and repeating the boiling again, and measuring the current value flowing when a voltage of 2.0 V was applied between the coating film surface and the container after a specified number of times. As a result of the thermal cycle test, cracks were generated in the ceramic coating film to form pinholes, and the current value flowing increases as the number of pinholes increases, so the durability of the ceramic coating film roughened by irradiation of UV laser light and the ceramic coating film roughened by mechanical polishing can be measured.

[0095] As shown in Figure 10, for the ceramic coating film roughened by irradiation with UV laser light, the current value does not change after about 100 thermal cycle tests, indicating that the degree to which cracks occur in the coating film due to temperature changes is small. On the other hand, for the ceramic coating film roughened by mechanical polishing, the current value tends to continue to increase as the number of thermal cycle tests increases, and after 300 cycles or more, the current value is 10 mA or more, which is significantly higher than the current value of 4 mA for the ceramic coating film roughened by UV laser light.

[0096] From this, it was confirmed that the hydrophilicity can be ensured without causing significant damage to the coating film by irradiating the coating film surface with UV laser light. Therefore, in the water storage section 10 of the electric kettle shown in this embodiment, the bottom surface on which the hydrophobic ceramic coating 13 is formed can be modified to be hydrophilic by irradiating the bottom surface with UV laser light to roughen it, and the inconvenience of so-called premature breakage due to the fact that large bubbles are generated on the bottom surface when the temperature is raised and the temperature sensor cannot detect the water temperature accurately can be avoided.

[0097] In the above-mentioned study to confirm the effect of roughening the bottom surface by UV laser light, the entire bottom surface of the container was roughened by irradiating it with UV laser light, but in the water storage section 10 of the electric kettle according to this embodiment, it is not necessary to make the entire bottom surface hydrophilic. In particular, by using a laser marking device that can irradiate UV laser light to a predetermined position represented by the XY coordinates of the plane to be irradiated as the UV laser light irradiation means, it is possible to selectively irradiate UV laser light to a portion of the bottom surface of the water storage section 10 that is preferably hydrophilic.

[0098] Fig. 11 is an image diagram for explaining the positions on the bottom surface of the electric kettle according to this embodiment that are roughened by UV laser light. Fig. 11(a) is a plan view showing the portion of the bottom surface that is irradiated with UV laser light, and Fig. 11(b) is a cross-sectional view showing the relationship between the portion that is irradiated with UV laser light and the positions of each member formed on the bottom surface of the water storage section.

[0099] As shown in FIG. 11(a), in the water storage section 10 of the electric kettle of this embodiment, a ring-shaped portion 71 near the outer periphery of the bottom surface and portions 72 protruding inward from two opposing points of this ring-shaped portion 71 are roughened by UV laser light.

[0100] As shown in FIG. 11(b), ring-shaped portion 71 on the bottom surface of water storage portion 10 is a portion where sheathed heater 14, which is a heat source, is disposed on the outside of the bottom surface of water storage portion 10. Furthermore, two portions 72 protruding inward are portions where temperature sensor 15, which measures the temperature on the outside of the bottom surface of water storage portion 10, is disposed. In this way, by roughening portion 71 facing the position where electric heating means, which is a heat source, is disposed, and portion 72 facing the portion where the temperature sensor, which detects the temperature of the water storage portion, is disposed, by using UV laser light, it is possible to effectively prevent the generation of large air bubbles on the bottom surface of the water storage portion, and it becomes possible to boil water while accurately measuring the water temperature with the temperature sensor.

[0101] In FIG. 11, as shown in FIG. 11(b), a step is created in the coating film between the portion facing the heat source and the portion facing the temperature control unit by varying the strength of the processing. However, it is possible to process the coating film so that there is no step between the portion facing the heat source and the portion facing the temperature control unit by keeping the processing conditions the same.

[0102] In addition, in FIG. 11, a case where a sheathed heater is used as the electric heating means is described, but even if the electric heating means is not a sheathed heater, it is preferable to roughen the position facing the arrangement position of the heating means. For example, if the electric heating means is a print heater in which a flat heating part is arranged on a substrate, it is preferable to roughen the portion facing the print heater, although the area is larger than the portion facing the sheathed heater shown in FIG. 11(a). In addition, in the above example, an example was shown in which both the portion facing the arrangement position of the heater, which is the heating means, and the portion facing the arrangement position of the temperature sensor are roughened, but even if either the portion facing the heating means or the portion facing the temperature sensor is roughened, it is possible to accurately grasp the temperature of the bottom part of the water storage section 10 and adjust the temperature inside the water storage section to boil water.

[0103] As described above, the cooking vessel as the water storage section of the electric kettle described in this embodiment has a coating film made of a sintered inorganic material formed on the inner surface of the metal inner vessel, and therefore does not cause safety concerns due to the use of fluorine, as compared with the conventional surface treatment using fluororesin. In addition, by irradiating the formed coating film with UV laser light to modify the surface, it is possible to draw a predetermined pattern such as a water volume mark by making the color of the part irradiated with the UV laser light different from that of the other parts, and the coating film surface irradiated with the UV laser light is roughened, so that the coating film surface can be made hydrophilic.

[0104] As a result, a water volume memory having excellent durability can be formed at low cost, and the surface of the hard coating film can be converted from hydrophobic to hydrophilic, effectively avoiding undesirable situations such as premature breakage due to an inability to accurately measure the temperature of the water inside.

[0105] In the above embodiment, a laminate of two hard coating layers, a first layer and a second layer, is formed on the inner surface of the water storage of the electric kettle, and a water volume mark is formed on the side and the bottom surface is roughened. However, as for the water storage as a cooking container according to this embodiment, it is also possible to form a pattern by modifying the first layer in addition to the side, or to roughen a part of the surface of the side as necessary.

[0106] In addition, when it is not necessary to form a pattern such as a water volume memory by irradiating the hard coating with UV laser light, it is possible to use a hard coating as a single layer and only perform laser processing to roughen the surface with UV laser light.

[0107] Next, as another specific example of the cooking container disclosed in the present application, an example in which the container is used as an inner pot of a rice cooker will be described.

[0108] FIG. 12 is a cross-sectional view showing the overall structure of a rice cooker employing an inner pot as a heating and cooking vessel according to this embodiment.

[0109] As shown in Fig. 12, the rice cooker with the inner pot 120 as the cooking container according to this embodiment has a main body 100 and a lid 110 arranged above the main body to cover the inner pot 120 housed inside the main body. The lid 110 can be unlocked by the user pressing a lock button 111 arranged on the front side (user side, lower side in Fig. 12) of the top of the lid 110, and the hinge mechanism 112 arranged on the rear side (upper side in Fig. 12) rotates to open the space above the inner pot 120. Note that various currently known mechanisms can be appropriately adopted as the internal structure of the rice cooker other than the inner pot, so detailed explanations will be omitted here.

[0110] In the rice cooker shown in Fig. 12, a coating film made of a sintered inorganic material is formed on the inner surface of the inner pot 120. As with the water storage section of the electric kettle described above, the configuration of which is shown in Figs. 1 to 3, the laser processing using UV laser light for the coating film 121a formed on the bottom surface of the inner pot 120 and the coating film 121b formed on the side surface can be appropriately selected as a roughening method for the shape and position of the display pattern to be formed and for the necessary places.

[0111] In the case of the inner pot of the rice cooker shown in FIG. 12, the coating film 121a on the inner surface of the bottom of the inner pot has a thickness of 30 to 40 μm, and the coating film 121b on the side surface has a thickness of 20 to 30 μm.

[0112] As shown in FIG. 12, in the rice cooker, in addition to the bottom heater 131 arranged to face the bottom of the inner pot, a second heater 132 arranged to face the part near the bottom of the side and a third heater 133 arranged near the upper opening of the side are arranged so that multiple heaters are arranged to surround the entire inner pot, and rice is cooked by controlling the amount of heat supplied from these heaters 131, 132, and 133 according to the cooking contents. The coating film formed inside the inner pot can also be controlled so that the coating film is formed under more preferable conditions on the inner surface of the inner pot by changing the surface condition of part or all of the inner pot according to the opposite parts of the heaters. Note that as the heater for the rice cooker, there are cases where different types of heaters are used in one rice cooker, such as an induction heating type IH heater as the main heating means for heating rice and an electric heating type heater for keeping rice warm after cooking is completed. For this reason, it is more preferable to select a coating film with a more appropriate surface shape according to the characteristics of each heating means as the coating film formed on the inner surface of the inner pot.

[0113] Also in the rice cooker, a temperature sensor 134 is arranged, biased by a spring or the like, so as to abut against the center of the bottom of the inner pot, as shown in Fig. 12. As in the case of the electric kettle described above, the surface roughness of the coating film 121a in the central part of the bottom surface of the inner pot, which faces the temperature sensor 134, can be made smaller than that of other parts of the bottom surface by laser processing, for example, so that the temperature of the inner pot of the rice cooker can be more accurately detected by the temperature sensor 134.

[0114] As described above, the cooking container disclosed in the present application has a coating film formed on its inner surface, which is made of a sintered inorganic material having a laminated structure consisting of an opaque first layer and a translucent second layer, and a specific portion of the first layer is modified to a color different from the other portions, and the surface of the second layer in the modified portion is roughened.

[0115] By having a coating film made of such a laminated structure inorganic sintered body, a predetermined pattern can be formed by the modified portion of the first layer, and the surface of the coating film can be modified to be hydrophilic by roughening the surface of the second layer. As a result, a surface treatment film is formed that is free of safety issues compared to a surface treatment film formed by fluororesin processing, and is strong against external forces such as rubbing applied during use, and it is possible to prevent food from adhering to the inner surface of the container during cooking, which can cause stains.

[0116] In addition, the manufacturing method of a cooking container disclosed in the present application includes a step of forming an inorganic hard coating on the inner surface of the container, and a laser processing step of irradiating the hard coating with a UV laser to roughen its surface.

[0117] As a result, the surface properties can be modified to be hydrophilic without causing more damage than necessary to the hard coating film formed on the inner surface of the cooking container, and a cooking container can be realized with a hard coating film having excellent durability.This can prevent problems such as noise and bumping caused by large bubbles being generated on the coating surface during boiling, and can also avoid the problem of false detection by the temperature sensor caused by the formation of bubbles.

[0118] Furthermore, the cooking container disclosed in the present application can be widely used in cooking containers that accommodate food to be heated by electric heating means, such as the water storage section of an electric kettle and the inner pot of a rice cooker described in the above embodiments, as well as various thermoses such as handy pots, cooking plates such as hot plates, bread cases in bread makers, containers for rotary cookers, and servers for coffee makers. [Industrial Applicability]

[0119] The cooking container of the present invention is useful as a cooking container having a surface treatment film that is highly safe and durable. [Explanation of symbols]

[0120] 10 Water storage section (heating and cooking container) 12 Inner container 13 Ceramic coating (paint film) 13a First layer of ceramic coating (paint film) 13b Second layer ceramic coating (paint film) 14 Heater (electrical heating means) 15 Temperature Sensor

Claims

1. A cooking container that contains food to be cooked inside and is heated by an electric heating means to cook the food, A hard coating made of sintered inorganic material is formed on the inner surface. The hard coating film has a non-transparent first layer and a light-transmitting second layer laminated on the first layer, A cooking container comprising: a predetermined portion of the first layer that is modified to a color different from that of the other portions; and a surface of the second layer in the modified portion that is roughened.

2. 2. The cooking vessel according to claim 1, wherein the inorganic material is at least one of ceramics and glass.

3. 2. The cooking vessel according to claim 1, wherein the first layer is formed of a material that changes color through photolysis.

4. The cooking vessel according to claim 1 , wherein the modified portion is formed on a side surface of the cooking vessel, and a scale representing the capacity of the contents is formed by the modified portion.

5. The cooking vessel according to claim 1 , wherein the modified portion is formed on a bottom surface of the cooking vessel.

6. The cooking container according to claim 5, wherein the modified portion is a portion of the bottom surface facing a position where the electric heating means is arranged and / or a portion facing a position where a temperature sensor that detects the temperature of the cooking container is arranged.

7. The cooking vessel according to any one of claims 1 to 6, wherein the cooking vessel is a water reservoir of an electric kettle.

8. The cooking vessel according to any one of claims 1 to 6, wherein the cooking vessel is an inner pot of a rice cooker.

9. A method for manufacturing a cooking container for storing food inside and cooking the food by heating the food with an electric heating means, comprising: A coating film forming step of forming a hard coating film made of an inorganic sintered body on the inner surface of the cooking container; and a laser processing step of irradiating a surface of the formed hard coating with a UV laser to roughen the surface.

10. The method for manufacturing a cooking container according to claim 9, wherein in the coating film forming step, a non-transparent first layer and a light-transmitting second layer formed and laminated on the first layer are formed.

11. The method for manufacturing a cooking container according to claim 10, wherein the laser processing step modifies the first layer on the side surface of the cooking container to form a mark indicating the capacity of the food contained in the cooking container.

12. The method for manufacturing a cooking container as described in claim 9, wherein the laser processing step roughens at least one of a portion of the bottom surface of the cooking container facing the position of the electric heating means and a portion facing the position of a temperature sensor that detects the temperature of the cooking container.

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