JP2011216457A - Top plate for electromagnetic heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a top plate for an electromagnetic heating cooker which is excellent on heat resistance, wherein a heat resistant resin layer is formed on a glass base plate.SOLUTION: The top plate 1 for an electromagnetic heating cooker includes the glass base plate 2, and the heat-resistant resin layer 4 formed on the glass base plate 2. The heat-resistant resin layer 4 contains inorganic pigment powder and a silicone resin. The content of the inorganic pigment powder on the heat-resistant resin layer 4 is within a range of 35-75 mass%. In the silicone resin, a functional group directly combined with silicone atoms is at least one of a methyl group and a phenyl group. A molar ratio((phenyl group)/(phenyl group)) Ph/Si of the phenyl group to the silicone atom is 0.1 or below.

Description

  The present invention relates to a top plate for an electromagnetic heating cooker.

  As a heating device of an electric cooker, an infrared heating device such as a radiant heater, a halogen heater known as a high output type, or an electromagnetic heating device such as an induction heater (IH) is used.

  Conventionally, as a top plate of a cooker equipped with an infrared heating device, a dark-colored crystallized glass plate that blocks visible light and transmits infrared light has been widely used. By using a dark-crystallized glass plate as the top plate, the members placed on the back side of the top plate can be concealed to enhance aesthetics, and the anti-glare of the infrared heating device that emits strong visible light It is because it can plan.

  In addition, since the cooker provided with the infrared heating apparatus can visually recognize the red-heated heater part through the dark crystallized glass plate, there is no need to provide a mechanism for displaying that heating is in progress.

  On the other hand, unlike an infrared heating device, a cooking device equipped with an electromagnetic heating device (hereinafter referred to as “IH cooking device”) does not generate visible light even during heat generation. For this reason, the IH cooker needs to be provided with a mechanism for indicating that heating is in progress. Conventionally, for example, a light-emitting diode is used as the display mechanism.

  However, the light from the light emitting diode is weaker than the light from the infrared heating device. For this reason, for example, when the above-described dark crystallized glass plate is used as the top plate of the IH cooker, there arises a problem that the visibility of the light-emitting diode disposed on the back side of the top plate is deteriorated.

  In view of such a problem, for example, the following Patent Document 1 proposes to use a low expansion crystallized glass having a light shielding layer formed on the surface as a top plate. Further, Patent Document 1 describes that by making the light shielding layer porous, it is possible to suppress the occurrence of cracks in the light shielding layer due to the difference in thermal expansion coefficient between the light shielding layer and the low expansion crystallized glass. ing.

  However, when a porous light-shielding layer is employed, there is a problem that adhesion marks of a temperature sensor (thermocouple) attached to the electromagnetic heating portion on the back surface of the top plate are conspicuous and are not preferable in appearance.

  In order to solve this problem, in Patent Document 2 below, as a top plate for an IH cooker, a porous light-shielding film is formed on the surface of a low expansion crystallized glass plate, and at least an electromagnetic heating portion of the light-shielding film. A top plate having a heat-resistant resin layer formed thereon has been proposed.

  Further, as described above, the low-expansion crystallized glass plate and the light-shielding film usually have different thermal expansion coefficients, so that the light-shielding film tends to crack, so that a sufficiently thick light-shielding film cannot be formed. In some cases, it may not be possible to obtain sufficient concealability with only the coating. In such a case, a heat resistant resin layer for supplementing the light shielding property may be formed on the light shielding film.

Japanese Patent Laid-Open No. 10-273342 JP 2003-338360 A

  By the way, in an IH cooker, a cooker such as a pan is directly heated by an electromagnetic heating device. For this reason, the top plate is not directly heated by the electromagnetic heating device. Moreover, since the cooking device is heated in a state where an object to be heated that normally contains moisture is placed, the temperature of the cooking device does not become so high. Therefore, the temperature of the top plate does not rise so high during normal times.

  However, when the cooking device is heated in a state where there is no food to be cooked inside, the cooking device becomes high temperature, and accordingly, the temperature of the top plate becomes high temperature of 400 ° C. or more. There is also. Then, the heat resistant resin layer may be thermally deteriorated and discolored. When the heat resistant resin layer changes color, the color change of the heat resistant resin layer is visually recognized from the use surface side, and there is a problem that the appearance is deteriorated.

  The present invention has been made to solve the above-mentioned problems of the prior art, and is a top plate for an electromagnetic heating cooker in which a heat-resistant resin layer is formed on a glass substrate, and is heat resistant. An object is to provide an excellent top plate for an electromagnetic heating cooker.

  The top plate for an electromagnetic heating cooker according to the present invention includes a glass substrate and a heat resistant resin layer. The heat resistant resin layer is formed on the glass substrate. The heat resistant resin layer includes an inorganic pigment powder and a silicone resin. Content of the inorganic pigment powder in a heat resistant resin layer exists in the range of 35 mass%-75 mass%. The silicone resin is a silicone resin in which a functional group directly bonded to a silicon atom is at least one of a methyl group and a phenyl group. In the present invention, in the silicone resin, the molar ratio of phenyl group to silicon atom ((phenyl group) / (silicon atom)) Ph / Si is 0.1 or less. For this reason, for example, even when the top plate is at a high temperature of 400 ° C. or higher, the heat-resistant resin layer is not easily discolored. Therefore, a top plate for an electromagnetic heating cooker having high heat resistance can be realized.

  In this invention, it is preferable that content of the inorganic pigment powder in a heat resistant resin layer exists in the range of 40 mass%-75 mass%.

  In the present invention, the “glass substrate” includes a crystallized glass substrate.

In the present invention, “the functional group directly bonded to the silicon atom is at least one of a methyl group and a phenyl group”
(1) When the functional group directly bonded to the silicon atom is a methyl group (2) When the functional group directly bonded to the silicon atom is a phenyl group (3) The functional group directly bonded to the silicon atom is a methyl group and a phenyl group Either the group or the group. In the case of (1) above, of the silicon atom bonds, the bonds not connected to the methyl group are bonded to oxygen or hydrogen. In the case of (2) above, of the silicon atom bonds, the bonds not connected to the phenyl group are bonded to oxygen or hydrogen. In the case of (3) above, of the silicon atom bonds, the bond not connected to the phenyl group is bonded to a methyl group, oxygen or hydrogen.

  In the present invention, Ph / Si is preferably 0 in the silicone resin. That is, the silicone resin is preferably a silicone resin that does not contain a phenyl group. In this case, discoloration of the heat resistant resin layer at a high temperature can be more effectively suppressed.

  In this invention, it is preferable that content of the inorganic pigment powder in a heat resistant resin layer exists in the range of 55 mass%-75 mass%. In this case, discoloration of the heat resistant resin layer at a high temperature can be more effectively suppressed.

  In the present invention, the top plate for the electromagnetic heating cooker preferably further includes an inorganic light shielding layer formed between the glass substrate and the heat resistant resin layer. When the top plate for an electromagnetic heating cooker having such a configuration is used, the members disposed inside the electromagnetic heating cooker can be more effectively concealed, and the aesthetics of the electromagnetic heating cooker can be further enhanced.

  The “inorganic light shielding layer” is a layer that absorbs or reflects at least part of incident light. In the present invention, the “inorganic light shielding layer” is not limited to one that absorbs or reflects all incident light.

  In this invention, it is preferable that the top plate for electromagnetic heating cookers is provided with the further heat resistant resin layer currently formed on the heat resistant resin layer. In that case, the further heat-resistant resin layer contains an inorganic pigment powder and a silicone resin, and the silicone resin contained in the further heat-resistant resin layer has a functional group directly bonded to a silicon atom at least one of a methyl group and a phenyl group. And it is preferable that Ph / Si is a silicone resin higher than the silicone resin contained in the heat resistant resin layer. In this case, the further heat resistant resin layer has a higher elastic modulus than the heat resistant resin layer. Therefore, the durability of the heat resistant resin layer can be improved by providing a further heat resistant resin layer.

  From the viewpoint of further improving the durability of the heat resistant resin layer, in the silicone resin contained in the further heat resistant resin layer, the molar ratio of methyl group to silicon atom ((methyl group) / (silicon atom)) Me / Si is 0.00. It is preferably 1 or less, and more preferably Me / Si is 0.

  ADVANTAGE OF THE INVENTION According to this invention, it is a top plate for electromagnetic heating cookers by which the inorganic light shielding layer and the heat resistant resin layer are formed on the glass substrate, Comprising: It provides the top plate for electromagnetic heating cookers excellent in heat resistance. it can.

It is a schematic sectional drawing of the top plate for electromagnetic heating cookers which concerns on 1st Embodiment which implemented this invention. It is a schematic sectional drawing of the top plate for electromagnetic heating cookers which concerns on 2nd Embodiment.

(First embodiment)
FIG. 1 is a schematic cross-sectional view of a top plate for an electromagnetic heating cooker according to an embodiment of the present invention.

  Hereinafter, a preferred embodiment in which the present invention is implemented is exemplified by a top plate 1 for an electromagnetic heating cooker (hereinafter, “the top plate 1 for an electromagnetic heating cooker” is simply referred to as “top plate 1”) shown in FIG. I will explain. However, the top plate 1 is merely an example. The top plate for an electromagnetic heating cooker according to the present invention is not limited to the top plate 1 at all.

  As shown in FIG. 1, the top plate 1 includes a glass substrate 2. The glass substrate 2 transmits at least part of light having a wavelength of 450 nm to 700 nm. The glass substrate 2 may be colored and transparent, but is preferably colorless and transparent from the viewpoint of enhancing the aesthetics of the top plate 1. In addition, being colorless and transparent means that the light transmittance in the visible wavelength region at a wavelength of 450 nm to 700 nm is 75% or more.

The top plate 1 is repeatedly heated and cooled. For this reason, it is preferable that the glass substrate 2 has high heat resistance and a low thermal expansion coefficient. Specifically, the softening temperature of the glass substrate 2 is preferably 700 ° C. or higher, and more preferably 750 ° C. or higher. The average linear thermal expansion coefficient at 30 ° C. to 750 ° C. of glass substrate 2 is preferably in the range of ^{-10 × 10 -7 / ℃ ~ +} 30 × 10 -7 / ℃, -10 × 10 -7 It is more preferable to be within the range of / ° C to + 20 × 10 ⁻⁷ / ° C. For this reason, the glass substrate 2 preferably has a high glass transition temperature and is made of low expansion glass or low expansion crystallized glass. As a specific example of the low-expansion crystallized glass, for example, Neoceram N-0 manufactured by Nippon Electric Glass Co., Ltd. can be mentioned.

  In this embodiment, the inorganic light shielding layer 3 is formed on the back surface 2a on the opposite side of the cooking surface 2b of the glass substrate 2. A heat resistant resin layer 4 is formed on the inorganic light shielding layer 3. In the present embodiment, the heat resistant resin layer 4 is formed on the entire back surface 2 a of the glass substrate 2.

The inorganic light shielding layer 3 is not particularly limited as long as it is made of an inorganic material and has a low visible light transmittance. The inorganic light shielding layer 3 can be formed of a metal film such as titanium, for example. Moreover, the inorganic light shielding layer 3 can also be formed by the layer containing an inorganic pigment and glass. In this case, for example, a Cu—Cr—Mn black inorganic pigment can be used as the inorganic pigment. Moreover, as glass, for example, B ₂ O ₃ —SiO ₂ glass powder can be used.

  In addition, the inorganic light shielding layer 3 may be a porous film or a solid film having substantially no voids.

  The thickness of the inorganic light shielding layer 3 is not particularly limited. The thickness of the inorganic light shielding layer 3 can be appropriately set according to, for example, the light transmittance of the inorganic light shielding layer 3, the mechanical strength of the inorganic light shielding layer 3, the thermal expansion coefficient, and the like. The inorganic light shielding layer 3 usually has a different thermal expansion coefficient from that of the glass substrate 2. For this reason, the inorganic light shielding layer 3 may be damaged by repeated heating and cooling. From the viewpoint of suppressing this damage, the inorganic light shielding layer 3 is preferably thin. The thickness of the inorganic light shielding layer 3 is preferably in the range of 1 μm to 15 μm, and more preferably in the range of 3 μm to 10 μm.

  The formation method of the inorganic light shielding layer 3 is not particularly limited. The inorganic light shielding layer 3 can be formed by the following method, for example.

  First, a solvent is added to a mixed powder of inorganic pigment powder and glass powder to form a paste. The paste is applied onto the glass substrate 2 using a screen printing method or the like, and dried. Then, the inorganic light shielding layer 3 can be formed by baking. The firing temperature and firing time can be appropriately set according to the composition of the glass powder used. The firing temperature can be, for example, about 200 ° C. to 400 ° C. The firing time can be, for example, about 10 minutes to 1 hour.

  Moreover, when the inorganic light shielding layer 3 consists of a metal film, it can form by sputtering method, CVD method, etc.

  The heat resistant resin layer 4 contains an inorganic pigment powder and a silicone resin. In the heat resistant resin layer 4, the inorganic pigment powder is dispersed in the silicone resin. In the present embodiment, the content of the inorganic pigment powder in the heat resistant resin layer 4 is in the range of 35% by mass to 75% by mass.

The inorganic pigment powder contained in the heat resistant resin layer 4 is not particularly limited as long as it is a colored inorganic substance. The inorganic pigment powder is, for example, white pigment powder such as TiO ₂ powder, ZrO ₂ powder, ZrSiO ₄ powder, blue or green inorganic pigment powder containing Co, green inorganic pigment powder containing Co, Ti—Sb—Cr. Series, Ti-Ni yellow inorganic pigment powder, Co-Si red inorganic pigment powder, brown inorganic pigment powder containing Fe, black inorganic pigment powder containing Cu, and the like.

Specific examples of the blue inorganic pigment powder containing Co include, for example, Co—Al-based and Co—Al—Ti-based inorganic pigment powders. Specific examples of the Co—Al based inorganic pigment powder include CoAl ₂ O ₄ powder. Specific examples of the Co—Al—Ti inorganic pigment powder include CoAl ₂ O ₄ : TiO ₂ : Li ₂ O powder.

Specific examples of the green inorganic pigment powder containing Co include, for example, Co-Al-Cr-based and Co-Ni-Ti-Zn-based inorganic pigment powders. Specific examples of the Co—Al—Cr inorganic pigment powder include Co (Al, Cr) ₂ O ₄ powder. Specific examples of the Co—Ni—Ti—Zn inorganic pigment powder include (Co, Ni, Zn) ₂ TiO ₄ powder and the like.

Specific examples of the brown inorganic pigment powder containing Fe include, for example, Fe-Zn inorganic pigment powder. Specific examples of the Fe—Zn inorganic pigment powder include (Zn, Fe) Fe ₂ O ₄ powder.

Specific examples of the black inorganic pigment powder containing Cu include, for example, a Cu—Cr based inorganic pigment powder. Specific examples of the Cu-Cr-based inorganic pigment powder include Cu (Cr, Mn) ₂ O ₄ powder.

  These inorganic pigment powders can be used alone or in combination.

  The silicone resin contained in the heat resistant resin layer 4 is a silicone resin in which the functional group directly bonded to the silicon atom is at least one of a methyl group and a phenyl group. In the silicone resin, the molar ratio of phenyl group to silicon atom ((phenyl group) / (silicon atom)) Ph / Si is 0.1 or less.

  The thickness of the heat resistant resin layer 4 is not particularly limited. The thickness of the heat resistant resin layer 4 can be appropriately set according to the light transmittance of the heat resistant resin layer 4 and the like. The thickness of the heat resistant resin layer 4 can be, for example, about 1 μm to 15 μm.

  The method for forming the heat resistant resin layer 4 is not particularly limited. The heat-resistant resin layer 4 is formed by, for example, applying a silicone resin in which inorganic pigment powder is dispersed on the inorganic light-shielding layer 3 by using a screen printing method, for example, at a temperature of about 50 ° C. to 100 ° C. for 10 minutes to It can be formed by drying for about 1 hour. Further, depending on the composition of the heat-resistant resin layer 4, it may be preferable to perform baking after drying.

  The application speed and viscosity of the silicone resin in which the inorganic pigment powder is dispersed need to be set as appropriate according to the amount of the inorganic pigment powder contained in the heat resistant resin layer 4. For example, when the content of the inorganic pigment powder in the heat resistant resin layer 4 is large, it is preferable to lower the viscosity of the silicone resin and slow down the application speed of the silicone resin.

  As described above, in the present embodiment, the heat resistant resin layer 4 includes the inorganic pigment powder and the silicone resin. Content of the inorganic pigment powder in the heat resistant resin layer 4 is in the range of 35 mass% to 75 mass%. The silicone resin contained in the heat resistant resin layer 4 is a silicone resin in which the functional group directly bonded to the silicon atom is at least one of a methyl group and a phenyl group. In the silicone resin, Ph / Si is 0.1 or less. For this reason, as can be seen in the following embodiments, for example, even when the top plate 1 is at a high temperature of 400 ° C. or higher, the heat-resistant resin layer 4 is not easily discolored. Therefore, the top plate 1 having high heat resistance can be realized.

  Although it is not certain that discoloration of the heat-resistant resin layer 4 can be suppressed by using the heat-resistant resin layer 4 according to the present invention, it is considered to be due to the following reason. That is, when the heat-resistant resin layer is exposed to a high temperature, some of the substituents that are directly substituted with silicon atoms may burn off. When the burned-out substituent is a large substituent such as a phenyl group, it is considered that voids are generated in the heat-resistant resin layer due to the burning of the substituent, and as a result, the heat-resistant resin layer is discolored.

  On the other hand, when the burned-out substituent is a methyl group, voids are unlikely to occur in the heat-resistant resin layer even when the substituent is burned off. Therefore, according to the present invention, the content of the inorganic pigment powder in the heat resistant resin layer 4 is set in the range of 35% by mass to 75% by mass, the content of the silicone resin is reduced, and the Ph / Si in the silicone resin is 0.1 or less. Thus, it is considered that the discoloration of the heat resistant resin layer at a high temperature can be effectively suppressed by reducing the phenyl groups contained in the heat resistant resin layer.

  Therefore, from the viewpoint of more effectively suppressing discoloration of the heat-resistant resin layer at high temperature, Ph / Si in the silicone resin is preferably 0.05 or less, preferably 0.03 or less, Is preferably less than 0.01, and preferably 0.

  Moreover, it is preferable that content of the inorganic pigment powder in the heat resistant resin layer 4 exists in the range of 55 mass%-75 mass%. In addition, when there is too much content of the inorganic pigment powder in the heat resistant resin layer 4, the adhesiveness with respect to the inorganic light shielding layer 3 of the heat resistant resin layer 4 will fall, and the heat resistant resin layer 4 will become easy to peel.

  Moreover, since the heat resistant resin layer 4 has fluidity until it is dried, when the heat resistant resin layer 4 is provided as in this embodiment, the back surface of the top plate 1 is flattened. For this reason, the top plate 1 more excellent in aesthetics can be realized.

  In the present embodiment, the inorganic light shielding layer 3 is provided together with the heat resistant resin layer 4. For this reason, when it sees from the cooking surface 2b side, the member arrange | positioned inside the electromagnetic heating cooking appliance can be concealed more effectively, and the aesthetics of an electromagnetic heating cooking appliance can be improved further.

  In the above embodiment, the case where the inorganic light shielding layer 3 is provided between the glass substrate 2 and the heat resistant resin layer 4 has been described. However, the present invention is not limited to this configuration. For example, an inorganic light shielding layer may be provided directly on the glass substrate.

  Moreover, in the said embodiment, the case where the heat resistant resin layer 4 was formed on the whole back surface 2a of the glass substrate 2 was demonstrated. However, the present invention is not limited to this configuration. The heat resistant resin layer 4 may be formed on a part of the back surface 2a of the glass substrate 2, for example. For example, the heat resistant resin layer 4 may be provided only on the electromagnetic heating portion of the top plate 1. Further, for example, when the inorganic light-shielding layer 3 is formed of a porous film, at least a part below the adhesive part of a temperature sensor (thermocouple) attached to the electromagnetic heating part on the back surface of the top plate 1 has a heat resistant resin. Layer 4 may be provided. In that case, adhesion marks of the temperature sensor can be made inconspicuous, and the appearance of the top plate 1 can be improved.

  In the said embodiment, the example in which the film | membrane is not formed on the cooking surface 2b of the glass substrate 2 was demonstrated. However, the present invention is not limited to this configuration. For example, a decorative coating may be formed on the cooking surface 2b as necessary for improving design properties, displaying the heater position, and the like.

  Further, a further film may be formed on the back surface 2 a side of the glass substrate 2. For example, a protective layer or the like of the heat resistant resin layer 4 may be formed on the heat resistant resin layer 4, or an adhesion layer or the like may be formed between the heat resistant resin layer 4 and the inorganic light shielding layer 3. Good.

  Hereinafter, other examples of preferred embodiments of the present invention will be described. However, in the following description, members having substantially the same functions as those of the above-described embodiment are referred to by common reference numerals, and description thereof is omitted.

(Second Embodiment)
FIG. 2 is a schematic cross-sectional view of a top plate for an electromagnetic heating cooker according to the second embodiment.

  As shown in FIG. 2, the top plate 11 for an electromagnetic heating cooker of the present embodiment is the electromagnetic heating of the first embodiment in that a further heat resistant resin layer 5 is formed on the heat resistant resin layer 4. Different from the top plate 1 for a cooker.

  Similar to the heat resistant resin layer 4, the heat resistant resin layer 5 includes an inorganic pigment powder and a silicone resin in which a functional group directly bonded to a silicon atom is at least one of a methyl group and a phenyl group. The Ph / Si of the silicone resin contained in the heat resistant resin layer 5 is higher than the Ph / Si of the silicone resin contained in the heat resistant resin layer 4. For this reason, the heat resistant resin layer 5 has a higher elastic modulus than the heat resistant resin layer 4. Therefore, by providing the further heat resistant resin layer 5, the heat resistant resin layer 4 is reinforced and the durability of the heat resistant resin layer 4 can be improved.

  From the viewpoint of further improving the durability of the heat resistant resin layer 4, in the silicone resin included in the further heat resistant resin layer 5, the molar ratio of methyl groups to silicon atoms ((methyl groups) / (silicon atoms)) Me / Si is It is preferably 0.1 or less, and more preferably Me / Si is 0.

  In addition, although the thickness of the heat resistant resin layer 5 is not specifically limited, For example, it can be set as about 1 micrometer-15 micrometers. If the thickness of the heat resistant resin layer 5 is too thin, the reinforcing effect of the heat resistant resin layer 4 may be too small. On the other hand, if the thickness of the heat resistant resin layer 5 is too thin, the strength of the heat resistant resin layer 5 itself may be too low.

  Specific examples of the inorganic pigment powder contained in the heat resistant resin layer 5 may be the same as those given as specific examples of the inorganic pigment powder contained in the heat resistant resin layer 4 described above.

  Specific examples of the method for forming the heat resistant resin layer 5 include those listed as specific examples of the method for forming the heat resistant resin layer 4.

Example 1
Hereinafter, the present invention will be described in more detail based on examples. However, the following examples are merely illustrative. The present invention is not limited to the following examples.

First, an inorganic pigment powder Cu-Cr-Mn type _black, B ₂ O 3 -SiO ₂ based glass powder _(SiO 2: 63 _{wt%, B 2} O 3: 19 wt%) of 3: 7 weight ratio of Then, a paste was prepared by adding a resin and an organic solvent. Next, this paste was applied to a transparent crystallized glass plate N-0 (average linear thermal expansion coefficient at 30 ° C. to 750 ° C .: −4 × 10 ⁻⁷ / ° C.) made by Nippon Electric Glass Co., Ltd., with a film thickness of 4 μm. It was screen printed so that Subsequently, the applied paste was dried at 150 ° C. for 5 minutes and then baked at 850 ° C. for 30 minutes to form an inorganic light shielding layer.

  Next, the inorganic pigment powder and the silicone resin are mixed so that the mass ratio is 4.5: 5.5 (that is, the content of the inorganic pigment powder in the heat-resistant resin layer is 45% by mass), and the organic solvent is added. The paste was prepared by adding. This paste is screen-printed on the entire inorganic light-shielding layer so as to have a thickness of 4 μm, dried at 150 ° C. for 5 minutes, and then baked at 300 ° C. for 30 minutes to form a heat-resistant resin layer. To complete the top plate. As the silicone resin, a silicone resin in which Ph / Si is 0 and the substituent directly bonded to the silicon atom is a methyl group was used. As the inorganic pigment, black 42-701A (manufactured by Nippon Fellow Co., Ltd.) was used.

  The produced top plate was incorporated in an electromagnetic heating device, and the pan was aired to hold the top plate at 500 ° C. for 10 minutes (air-cooking test). Then, the discoloration of the heat resistant resin layer was visually observed from the cooking surface side of the top plate. In Example 1, discoloration of the heat resistant resin layer could not be confirmed.

(Example 2)
The mass ratio of the inorganic pigment powder and the silicone resin in the paste used for forming the heat resistant resin layer was 6.7: 3.3 (that is, the content of the inorganic pigment powder in the heat resistant resin layer was 67 mass%). Except for the above, a top plate was produced in the same manner as in the above example, and the same emptying test was performed. As a result, also in Example 2, as in Example 1, no discoloration of the heat-resistant resin layer could be confirmed.

(Example 3)
In Example 3, a further heat resistant resin layer was formed on the heat resistant resin layer of the top plate produced in the same manner as in Example 2. Specifically, the inorganic pigment powder and the silicone resin are mixed at a mass ratio of 50:50 (that is, the content of the inorganic pigment powder in the heat-resistant resin layer is 50% by mass), and an organic solvent is added. A paste was prepared. This paste is screen-printed on the entire heat-resistant resin layer so as to have a thickness of 8 μm, dried at 150 ° C. for 5 minutes, and then baked at 300 ° C. for 30 minutes. Formed. As the silicone resin, a silicone resin having Me / Si of 0 and a substituent directly bonded to a silicon atom being a phenyl group was used. As the inorganic pigment, black 42-701A (manufactured by Nippon Fellow Co., Ltd.) was used.

  The top plate produced in Example 3 was also subjected to the same emptying test as in Examples 1 and 2 above. As a result, also in this Example 3, discoloration of the heat-resistant resin layer could not be confirmed as in Examples 1 and 2.

(Comparative example)
A top plate was produced in the same manner as in Example 1 except that a silicone resin having Ph / Si of 0.3 was used as the silicone resin, and the same emptying test was performed. As a result, in this comparative example, discoloration of the heat resistant resin layer was confirmed.

  From the above results, according to the present invention, the content of the inorganic pigment powder in the heat-resistant resin layer 4 is in the range of 35% by mass to 75% by mass, and the Ph / Si in the silicone resin is 0.1 or less. It can be seen that the top plate for an electromagnetic heating cooker having high heat resistance can be realized with less resistance to discoloration of the heat resistant resin layer even at high temperatures.

DESCRIPTION OF SYMBOLS 1, 11 ... Top plate 2 for electromagnetic heating cookers ... Glass substrate 3 ... Inorganic light shielding layer 4 ... Heat-resistant resin layer 5 ... Further heat-resistant resin layer

Claims (8)

A glass substrate;
A top plate for an electromagnetic heating cooker comprising a heat resistant resin layer formed on the glass substrate,
The heat resistant resin layer includes an inorganic pigment powder and a silicone resin,
The content of the inorganic pigment powder in the heat-resistant resin layer is in the range of 35% by mass to 75% by mass,
The silicone resin is a silicone resin in which a functional group directly bonded to a silicon atom is at least one of a methyl group and a phenyl group,
The top plate for an electromagnetic heating cooker, wherein in the silicone resin, a molar ratio of a phenyl group to a silicon atom ((phenyl group) / (silicon atom)) Ph / Si is 0.1 or less.   The top plate for an electromagnetic heating cooker according to claim 1, wherein the Ph / Si is 0 in the silicone resin.   The top plate for an electromagnetic heating cooker according to claim 1 or 2, wherein the content of the inorganic pigment powder in the heat-resistant resin layer is in a range of 55 mass% to 75 mass%.   The top plate for an electromagnetic heating cooker according to any one of claims 1 to 3, further comprising an inorganic light-shielding layer formed between the glass substrate and the heat-resistant resin layer. A further heat-resistant resin layer formed on the heat-resistant resin layer;
The further heat-resistant resin layer includes an inorganic pigment powder and a silicone resin,
The silicone resin contained in the further heat-resistant resin layer has a functional group directly bonded to a silicon atom at least one of a methyl group and a phenyl group, and Ph / Si is more than the silicone resin contained in the heat-resistant resin layer. It is a high silicone resin, The top plate for electromagnetic heating cookers as described in any one of Claims 1-4.   6. The electromagnetic heating cooking according to claim 5, wherein in the silicone resin contained in the further heat-resistant resin layer, a molar ratio of methyl group to silicon atom ((methyl group) / (silicon atom)) Me / Si is 0.1 or less. Top plate for dexterity.   The top plate for an electromagnetic heating cooker according to claim 6, wherein Me / Si is 0 in the silicone resin contained in the further heat-resistant resin layer.   The top plate for an electromagnetic heating cooker according to any one of claims 5 to 7, wherein the further heat resistant resin layer has a higher elastic modulus than the heat resistant resin layer.

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