JP4315075B2 - Top plate for cooker and method for manufacturing the same - Google Patents

Description

  The present invention relates to a top plate for a cooker made of crystallized glass and a method for producing the same.

  Conventional cookers for home and business use not only gas cookers that use gas stoves, but also infrared cookers and electromagnetic heating (IH) cookers that use radiant heaters and halogen heaters. I came.

  In particular, a top plate used in an electromagnetic heating cooker is required to have high thermal efficiency, safety, and thermal shock, and therefore, a crystallized glass substrate having a low electromagnetic induction heating amount and a low thermal expansion coefficient has been used. .

  By the way, the original role of the top plate for a cooker is to prevent water, seasoning, food, etc. from splashing against the heating device, but recently, in addition to this role, the heating device, wiring, etc. It is also demanded to improve the aesthetics by hiding the internal structure of the cooker.

  When a crystallized glass substrate is used as the material for the top plate for the cooker, there are mainly two methods for hiding the internal structure of the cooker.

  The first method is to make the low expansion crystallized glass substrate itself opaque or translucent. For example, the following Patent Document 1 describes a low-expansion crystallized glass colored in a dark color with a colorant, and the following Patent Document 2 has visible light transmission characteristics ranging from transparent to opaque. Low expansion crystallized glass is described.

  The second method is to form a decorative film on the surface of a transparent low expansion crystallized glass substrate using a printing method, and to conceal the internal structure of the cooker with this decorative film. For example, Patent Document 3 below describes a cooker top plate in which a raster-colored decorative film made of a noble metal and a base metal is provided on the back surface (the surface opposite to the cooking surface).

  However, since the low-expansion crystallized glass described in Patent Document 1 has a dark color tone, there is a problem that it is difficult to check the light of the indicator that displays the amount of applied electric power. That is, in the case of the top plate of an electromagnetic heating cooker, the indicator is often provided on the back side of the top plate, but the light of the red indicator is barely visible from the cooking surface side, and the indicator emits a color other than red. Even in this case, since the top plate does not transmit light other than red (for example, blue or yellow) at all, light of such a color cannot be displayed on the cooking surface side. Therefore, when the indicator emits a color other than red, in order to display the light of that color on the cooking surface side, it is necessary to make a hole in a predetermined portion of the top plate. There is a problem that it is easy to occur.

  Also, as one of the factors that enhance the commercial value of the top plate for cooking utensils, appearance design is being emphasized. Previously, dark colors were the mainstream, but recently, colors with bright gloss are being favored. . However, the crystallized glass of Patent Document 1 has a dark color and cannot sufficiently meet the recent consumer preferences.

  Further, the low expansion crystallized glass described in Patent Document 2 contains 2 to 5% by weight of ZnO in order to precipitate zinc spinel in the glass. Sometimes glass tends to devitrify. For this reason, particularly when trying to obtain a translucent color tone, there is a manufacturing problem that the color tone tends to change slightly and cannot be produced stably.

  Furthermore, since the color tone and gloss of the decorative film are directly reflected in the appearance of the top plate for a cooker, the top plate of the cooker of Patent Document 3 is not conspicuous with the entire kitchen, and is not preferable in terms of aesthetics. Sometimes. In addition to being too glossy, there is a safety problem that the person who cooks is dazzling and it is difficult to cook, discomfort due to flickering, and eye strain.

Under such circumstances, Patent Document 4 proposes a cooker top plate having a new appearance and optical characteristics.
Japanese Patent Publication No. 3-9056 JP-A-5-213629 Japanese Patent Publication No. 7-17409 Special table 2001-501168

The top plate for a cooker described in Patent Document 4 is made of Li ₂ O—Al ₂ O ₃ —SiO ₂ -based low expansion crystallized glass and exhibits a cloudiness of 50% or more. A milky white crystallized glass containing a β-spodumene solid solution having a diameter of 80 nm or less is disclosed.

  However, such a crystallized glass with a small crystal grain size is less likely to scatter visible light, and thus tends to have high transparency. Therefore, even if a milky white appearance is obtained, the color tone is very thin and the effect of concealing the internal structure of the cooker is poor.

  The object of the present invention is to have a bright luster, not to be too conspicuous, and to conceal the internal structure of the cooker, easily check the light of various indicators, and has an anti-glare effect It is providing the top plate for cookers, and its manufacturing method.

The top plate for a cooker of the present invention is, by mass percentage, SiO ₂ 55 to 70%, Al ₂ O ₃ 15 to 30%, Li ₂ O 2.5 to 6%, ZnO less than 2%, BaO 0 to 5%, Contains TiO ₂ 1-6%, ZrO ₂ 0-4%, P ₂ O ₅ 0-5%, MgO 0-3%, Na ₂ O 0-4%, K ₂ O 0-4%, main crystals A top plate for a cooker formed from a Li ₂ O—Al ₂ O ₃ —SiO ₂ low expansion crystallized glass containing a β-spodumene solid solution as a phase, wherein the β-spodumene solid solution has an average particle size of 100 ˜1000 nm , and the coefficient of variation of particle size is 10% or less .

The method of manufacturing a top plate for a cooking appliance of the present invention, by mass _{percentage, SiO 2 55~70%, Al 2} O 3 15~30%, Li 2 O 2.5~6%, ZnO less than 2%, BaO 0 _{~5%, TiO 2 1~6%,} ZrO 2 0~4%, P 2 O 5 0~5%, 0~3% MgO, Na 2 O 0~4%, K 2 O 0~4% of the composition The glass substrate is prepared by heat-treating the glass substrate at a temperature range of 700 to 900 ° C. for 30 to 180 minutes and then heat-treating at a temperature range of 900 to 1100 ° C. for 10 to 180 minutes. It is characterized by depositing a solid solution.

The top plate for a cooker of the present invention is formed from a Li ₂ O—Al ₂ O ₃ —SiO ₂ based low expansion crystallized glass containing a β-spodumene solid solution as a main crystal phase, and the average particle diameter of the β-spodumene solid solution Is 100 to 1000 nm, it is possible to obtain an elegant opal-like appearance with a bright and soft hue.

  Moreover, since the light incident on the crystallized glass is moderately scattered in the visible range, it has an excellent antiglare effect. That is, the crystallized glass containing the β-spodumene solid solution as described above has an advantage that an opal-like appearance is easily exhibited and an appropriate scattering effect is easily obtained in the visible range. In the present invention, the opal tone means an appearance or a color tone having a unique visible light scattering characteristically shown in the opal. Such appearance and color tone can be obtained by scattering the particles that are the scatterers in the short wavelength region of the visible light so that the transmitted light of the object is yellowish and the scattered light is bluish.

  In the present invention, the β-spodumene solid solution that is the main crystal phase has an average particle size of 100 to 1000 nm. That is, when the average particle size of the β-spodumene solid solution is less than 100 nm, the visible light scattering effect is reduced, the transparency is increased, and an opal-like appearance is hardly exhibited. On the other hand, if the average particle size exceeds 1000 nm, the cloudiness becomes too strong and the transparency is lost. A preferable range of the average particle diameter of the β-spodumene solid solution is 150 to 900 nm, and a more preferable range is 200 to 800 nm.

  The β-spodumene solid solution is desired to have a uniform crystal grain size, and the coefficient of variation (CV value) of the grain size represented by the following formula is preferably 10% or less.

CV = (σ / D) × 100 [%]
In the above formula, σ means standard deviation, and D means average particle diameter.

  That is, since the wavelength of light scattered in the crystallized glass is determined by the crystal grain size, if the coefficient of variation exceeds 10%, the crystal grain size becomes non-uniform and it becomes difficult to obtain an opal-like appearance. In addition, there is a possibility that the strength of the crystallized glass may be lowered due to the non-uniform region of the crystal grain size as the starting point of the fracture.

The crystallized glass of the present invention has a lightness value L ^{* of} L ^* a ^* b ^* display system based on JIS Z8729 of 30 to 87, preferably 30 to 80, more preferably 40 to 60, with a thickness of 4 mm. When it is within the range, an opal-like appearance with particularly excellent aesthetics can be obtained, which is preferable.

  Furthermore, the crystallized glass in the present invention preferably has an average transmittance at a thickness of 4 mm of 0.1 to 60% at a wavelength of 400 to 800 nm. That is, when the average transmittance at a thickness of 4 mm is less than 0.1%, the amount of light transmitted through the top plate is excessively reduced, the translucency is poor, and it is difficult to obtain an opal-like appearance. Also, it is difficult to confirm the light from the indicator provided on the back side of the top plate. On the other hand, if it exceeds 60%, the light scattering property becomes weak and the color tone becomes very thin, so that it is difficult to conceal the internal structure of the cooking device. When the average transmittance at a thickness of 4 mm is 0.1 to 60% in the visible range of 400 to 800 nm, even if a glossy decorative film is formed on the back surface of the top plate, the reflected light from the decorative film However, since it is appropriately scattered inside the top plate, there is an advantage that a sharp glossy color is relaxed and a high-grade appearance having a soft gloss is obtained. The average transmittance is more preferably 1 to 60%, and further preferably 2 to 50%. In particular, when it is desired to transmit light of a blue or yellow indicator, it is desirable to set the average transmittance to 30% or more.

  Moreover, the crystallized glass in the present invention easily transmits heat rays, and the average transmittance at a thickness of 4 mm is 50% or more in the infrared region having a wavelength of 1 to 2 μm so that the food can be efficiently heated. It is preferable that A more preferable range is 60% or more, a further preferable range is 70% or more, and a most preferable range is 80% or more.

Moreover, since the crystallized glass used for the top plate for cooking appliances is repeatedly heated and cooled, it is required to have a low coefficient of thermal expansion and excellent thermal shock resistance. If the average linear thermal expansion coefficient at 30 to 750 ° C. is in the range of −10 to + 30 × 10 ⁻⁷ / ° C., even if a difference occurs in the temperature distribution inside the top plate during heating, cracking may occur due to the expansion difference. It is preferable because it is not. Furthermore, if the average linear thermal expansion coefficient in 30-750 degreeC is -10- + 20 * 10 < ^-7 > / degreeC, since very outstanding thermal shock resistance is obtained, it is more preferable.

The crystallized glass of the present invention, by mass _{percentage, SiO 2 55~70%, Al 2} O 3 15~30%, Li 2 O 2.5~6%, ZnO less than 2%, BaO 0 to 5%, It preferably contains TiO ₂ 1-6%, ZrO ₂ 0-4%, P ₂ O ₅ 0-5%, MgO 0-3%, Na ₂ O 0-4%, K ₂ O 0-4%. .

  The reason for limiting the composition range of the crystallized glass as described above is as follows.

SiO ₂ is a glass network former and a component constituting a crystal. However, if its content is less than 55%, the glass tends to be devitrified and the chemical durability is also lowered. On the other hand, if it exceeds 70%, the solubility of the glass becomes worse. The preferable content of SiO ₂ is 60 to 69%.

Al ₂ O _{3 is} also a component constituting the crystal, but if it is less than 15%, the meltability of the glass is deteriorated. On the other hand, if it exceeds 30%, the glass tends to devitrify and the chemical durability is lowered. The preferable content of Al ₂ O ₃ is 15 to 25%.

Li ₂ O is also a component constituting the crystal, but if it is less than 2.5%, it becomes difficult to deposit a desired crystal. On the other hand, when it exceeds 6%, the chemical durability of the glass is deteriorated. The preferable content of Li ₂ O is 3 to 5%.

  ZnO is a component that facilitates the precipitation of crystals, but its content must be strictly regulated. That is, when the amount of ZnO increases, the glass tends to devitrify, and different crystals tend to precipitate during slow cooling or crystallization of the glass. Therefore, the ZnO content should be regulated to less than 2%, preferably less than 1.5%, more preferably less than 1%.

  BaO is a component that improves the meltability of the glass and prevents the generation of devitrified substances. However, if it exceeds 5%, it is difficult to obtain a desired amount of crystals, and the thermal expansion coefficient becomes high, resulting in thermal degradation. Characteristics are degraded. The preferable content of BaO is 0 to 4%.

TiO ₂ is a component that acts as a nucleating agent. If it is less than 1%, crystallization does not occur stably and the crystal becomes coarse, resulting in a decrease in chemical durability. On the other hand, if it exceeds 6%, the color tone becomes brown and the transparency is impaired. The preferable content of TiO ₂ is 1 to 5%.

ZrO _{2 is} also a component that acts as a nucleating agent, but if it exceeds 4%, devitrified substances are likely to be generated in the glass. The preferable content of ZrO ₂ is 0 to 3%.

TiO ₂ and ZrO ₂ are preferably in the range of ₂ to 6.9% in total. That is, if the total amount of TiO ₂ and ZrO ₂ is less than 2%, sufficient nucleation does not occur, the crystal becomes coarse, and the chemical durability decreases. On the other hand, if the content is more than 6.9%, the solubility of the glass deteriorates and the color tone becomes brown and the transparency is impaired.

P ₂ O ₅ is a component having an effect of remarkably improving the poor solubility of ZrO ₂ , but if it exceeds 5%, the glass tends to phase-separate and it becomes difficult to obtain a uniform glass. The preferable content of P ₂ O ₅ is 0 to 3%.

  MgO is a component that facilitates precipitation of crystals, but if it exceeds 3%, the thermal expansion coefficient becomes too large. A preferable content of MgO is 0 to 2%.

Na ₂ O and K ₂ O are components that improve the solubility of the glass. However, when the content is more than 4%, the chemical durability is remarkably deteriorated. Further, if the total amount of these components is more than 7%, the crystallinity is deteriorated and the thermal expansion coefficient becomes too high, which is not preferable.

In addition, in the present invention, in addition to the above components, components such as As ₂ O ₃ , Sb ₂ O ₃ , CaO, PbO and the like can be incorporated up to 2% each, so that the solubility, workability, uniformity, etc. of the glass can be improved. Can be improved. However, As ₂ O ₃ is an environmentally hazardous substance and should be avoided as much as possible. Furthermore, in order to improve the stabilization of the glass, one or more of F ₂ , Cl ₂ , SO ₃ and Fe ₂ O ₃ can be contained in a total amount of 0.5%.

  The crystallized glass in the present invention can be produced by heat-treating a glass molded body having the above composition under desired conditions. For example, β-spodumene solid solution tends to have a larger average particle size as the heat treatment temperature for crystallization is increased. More specifically, glass is heat treated at a temperature range of 900 to 1100 ° C. for 10 minutes or more. By doing so, a desired crystal can be deposited. In order to perform crystallization more stably, first, heat treatment is performed at a temperature range of 700 to 900 ° C. for 30 to 180 minutes to perform nucleation, and then heat treatment is performed at a temperature range of 900 to 1100 ° C. for 10 to 180 minutes. It is preferable to deposit uniformly.

  Further, as described above, when a glossy decorative film is formed on the back surface of the top plate made of a transparent crystallized glass substrate, it tends to become dazzling. However, the crystallized glass in the present invention exhibits an opal-like appearance, so that FIG. As shown in FIG. 3, even if a glossy decorative film 11 (for example, a TiN film) is formed on the back surface 10a of the top plate 10 for a cooker, the reflected light is scattered within the interior, and as a result, a high-grade luxury with soft gloss. A pleasing appearance can be obtained. That is, the top plate of the present invention has an anti-glare effect that moderately suppresses regular reflection light, and therefore the gloss of the decorative film formed on the back surface is not limited. Therefore, the design variation is greatly expanded, and a product having a higher appearance design than that of the prior art can be easily obtained.

  As the decorative film used in the present invention, one kind of metal nitride selected from the group consisting of Ti, Nb, W and Mo, Si, Ti, Al, Nb, W, Mo, Sn, Cr, Pt and One kind of metal selected from the group consisting of Au, one kind of alloy selected from the group consisting of stainless steel, hastelloy, inconel and nichrome, one kind of alloy selected from the group consisting of stainless steel, hastelloy, inconel and nichrome A film containing a nitride of is suitable. In particular, a light-shielding film made of TiN has a stepless change in appearance from silver, gold, red-black, and black in ascending order of nitrogen by changing the nitrogen content in the film, so that a desired color tone can be easily obtained. preferable.

  In addition to the light shielding film, an antioxidant film can be formed. The antioxidant film is selected from the group consisting of one or more metal nitrides selected from the group consisting of Si, Ti, Al, Nb, W, Mo, Ta and Sn, or the group consisting of Si, Al and Ti. A film containing one kind of metal oxide is suitable, and can be formed on the light shielding film or between the glass substrate and the light shielding film. By forming the antioxidant film, the light shielding film is less likely to be oxidized, and the deterioration of the light shielding film due to heat can be suppressed.

  Hereinafter, the top plate for a cooking device of the present invention will be described based on examples.

First, by weight percentage, SiO ₂ 65.9%, Al ₂ O ₃ 22.0%, MgO 0.1%, Li ₂ O 4.0%, Na ₂ O 0.5%, K ₂ O 0.5% , P ₂ O ₅ 1.5%, ZrO ₂ 2.5%, TiO ₂ 2.0%, As ₂ O ₃ 1.0%. After melting at 16 ° C. for 16 hours, it was poured out on a carbon table and formed into a sheet of glass having a thickness of 5 mm by roller molding. Next, this plate glass was furnace-cooled at 700 ° C.

The plate-like glass thus obtained was heated to 780 ° C. at a rate of 300 ° C./hour, held at that temperature for 120 minutes for nucleation, and then at the temperature shown in Table 1 at a rate of 80 ° C./hour ( The temperature was raised to (secondary treatment temperature) and held at each temperature for 120 minutes for crystal growth to produce crystallized glass. In addition, the main crystal phase, average crystal grain size, particle size variation coefficient, brightness value L ^* , visible light average transmittance, infrared light average transmittance, thermal expansion coefficient, appearance and antiglare property of each crystallized glass were investigated. The results are shown in Tables 1 and 2. In addition, (beta) -S described in the main crystal phase in a table | surface shows (beta) -spodumene solid solution, (beta) -Q shows (beta) -quartz solid solution.

As is clear from the table, in the crystallized glasses of Examples 1 to 4, the main crystal phase is β-spodumene solid solution, the average crystal grain size is 300 to 800 nm, the grain size variation coefficient is 8% or less, and the lightness value L ^* Is 40 to 70, visible light average transmittance is 8 to 50%, infrared light average transmittance is 55 to 85%, and thermal expansion coefficient is +5 to + 11 × 10 ⁻⁷ / ° C. The antiglare property was good.

On the other hand, in Comparative Example 1, the main crystal phase is β-quartz solid solution, the average crystal grain size is 70 nm, the grain size variation coefficient is 12%, the brightness value L ^* is 5, and the visible light average transmittance is 86%. The appearance was transparent and the antiglare property was poor.

In Comparative Example 2, the main crystal phase was β-spodumene solid solution, but the average crystal grain size was 1500 nm, the grain size variation coefficient was 11%, the brightness value L ^* was 90, the visible light average transmittance was 0%, Since the infrared light transmittance was 30% and the appearance was white and opaque, the antiglare property could not be evaluated.

  The main crystal phases in Tables 1 and 2 were confirmed by X-ray diffraction by the powder method. The average crystal grain size was determined by observing a part of the crystallized glass with an electron microscope. The particle size variation coefficient (CV) was calculated from the following equation by obtaining the average crystal grain size (D) and standard deviation (σ) with an electron microscope.

CV (particle size variation coefficient) = (σ / D) × 100 [%]
The lightness value L ^* was measured using a side color difference meter (JP7200F / C, manufactured by JUKI Corporation). Visible light average transmittance and infrared light average transmittance are obtained by polishing each sample glass to a thickness of 4 mm, and then using a spectrophotometer equipped with an integrating sphere at a wavelength of 400 to 800 nm and a wavelength of 1 to 2 μm. The average transmittance at is measured. The coefficient of thermal expansion measured the average coefficient of linear thermal expansion in 30-750 degreeC using the differential detection type relative dilatometer. Appearance was judged by visual observation. When the sample glass was placed on a black background, pale scattered light was observed and transmitted light was observed as yellow. Anti-glare properties are obtained when a TiN film having a film thickness of 0.5 μm is formed on one side of each sample glass by a sputtering method and the reflected light when the surface on which the film is not formed is illuminated with a 40 W lamp is directly viewed. When it did not feel dazzling, it was set as “good”, and when it was dazzled, it was set as “bad”.

  As described above, the top plate for a cooker of the present invention has a bright luster, is not excessively conspicuous, can easily check the light of indicators other than red, and has an excellent anti-glare effect. Have. Therefore, it is suitable as an infrared heating cooker or an electromagnetic heating (IH) cooker, and can also be used for a gas cooker.

  Moreover, according to the manufacturing method of this invention, it is possible to manufacture said top plate for cookers easily.

It is a fragmentary sectional view which shows the top plate for cookers of this invention.

Explanation of symbols

10 Top plate 10a for cooking device Back surface 11 Decorative film

Claims (10)

By mass _{percentage, SiO 2 55~70%, Al 2} O 3 15~30%, Li 2 O 2.5~6%, ZnO less than _{2%, BaO 0~5%, TiO} 2 1~6%, ZrO 2 _{0~4%, P 2 O 5 0~5} %, 0~3% MgO, Na 2 O 0~4%, containing K 2 O 0~4%, Li containing β- spodumene solid solution as the predominant crystalline phase ₂ O—Al ₂ O ₃ —SiO ₂ -based top plate for a cooker formed of low expansion crystallized glass, wherein the β-spodumene solid solution has an average particle size of 100 to 1000 nm and is represented by the following formula: A top plate for a cooking appliance, wherein the coefficient of variation (CV) of the particle size is 10% or less .
CV = (σ / D) × 100 [%] (where σ is a standard deviation, D is an average particle size) The top plate for a cooking appliance according to claim 1, wherein the appearance is opal-like. The β-spodumene solid solution has a mean particle size of 150 to 900 nm, and the top plate for a cooking device according to claim 1 or 2. Crystallized glass, the thickness of 4 mm, according to any one of claims 1 to 3 based on the JIS Z8729 ^{L * a} * ^b * display system lightness value ^{L *} which is characterized in that in the range of 30 to 87 Top plate for cooking utensils. The top plate for a cooker according to any one of claims 1 to 4 , wherein the crystallized glass has an average transmittance of 0.1 to 60% at a wavelength of 400 to 800 nm at a thickness of 4 mm. Crystallized glass, the average transmittance at a thickness 4mm is, top plate for a cooking appliance according to any one of claims 1 to 5, characterized in that 50% or more at a wavelength of 1 to 2 [mu] m. The crystallized glass has a ZnO content of less than 2% by mass, and the top plate for a cooking device according to any one of claims 1 to 6 . Crystallized glass has an average linear thermal expansion coefficient at 30-750 ° C. is, top plate for a cooking appliance according to any one of claims 1 to 7, characterized in that a ^{-10~ + 30 × 10 -7 / ℃} . The top plate for a cooking device according to any one of claims 1 to 8 , wherein a decorative film is formed on a surface opposite to the cooking surface. By mass _{percentage, SiO 2 55~70%, Al 2} O 3 15~30%, Li 2 O 2.5~6%, ZnO less than _{2%, BaO 0~5%, TiO} 2 1~6%, ZrO 2 _{0~4%, P 2 O 5 0~5} %, 0~3% MgO, Na 2 O 0~4%, a glass substrate was prepared containing K 2 O 0~4%, the glass substrate 700 A top plate for a cooking appliance characterized by depositing a β-spodumene solid solution therein by heat-treating in a temperature range of 900 ° C for 30 to 180 minutes and then heat-treating in a temperature range of 900 to 1100 ° C for 10 to 180 minutes. Production method.