JP5645101B2 - Cooker top plate - Google Patents

Description

The present invention, the IH (electromagnetic heating device) relates halogen heater or the like on the top plates of the cooker to the heat source.

The top plate used in cooking devices that use IH, halogen heaters, etc. as the heat source is not easily damaged (high mechanical strength and thermal shock resistance), has a beautiful appearance, and is resistant to corrosion (high chemical durability) ) And high transmittance of infrared rays, which are heat rays. As a material satisfying such characteristics, there is a low-expansion transparent crystallized glass whose main crystal is a β-quartz solid solution (Li ₂ O—Al ₂ O ₃ —nSiO ₂ (n ≧ 2)). It is used.

  Low-expansion transparent crystallized glass is prepared by mixing various glass raw materials at a predetermined ratio, melting process to melt glass raw materials at a high temperature of 1600-1900 ° C. to obtain a homogenized fluid, and various shapes by various methods. It is manufactured through a molding process for molding, an annealing process for removing strain, and a crystallization process for precipitating fine crystals.

Since the low-expansion transparent crystallized glass produced in this way is generally transparent to visible light, when it is used as it is as a top plate, the internal structure of the cooker arranged below the top plate can be directly seen. It is inferior in appearance. Therefore, the crystallized glass itself is colored with a colorant such as V ₂ O ₅ (for example, see Patent Document 1), or a light shielding film is formed on the surface of the crystallized glass (for example, see Patent Document 2). Used in a state where the visible light is sufficiently shielded.

By the way, it is thought that coloring of glass by a coloring agent such as V ₂ O ₅ is caused (intensified) by interaction with As ₂ O ₃ or Sb ₂ O ₃ used as a fining agent. However, As ₂ O ₃ and Sb ₂ O ₃ have a large environmental load, and their use is being restricted in recent years. If As ₂ O ₃ or Sb ₂ O ₃ is simply excluded from the conventional glass composition, the coloring efficiency by the colorant tends to be lowered. Although it is possible to improve the visible light shielding effect by increasing the amount of the colorant, there is a problem that the infrared transmittance is lowered according to this method.

On the other hand, it has been proposed to add, for example, SnO ₂ or the like instead of As ₂ O ₃ or Sb ₂ O ₃ as a component that enhances the coloring efficiency of the colorant (see, for example, Patent Document 3). According to this method, it is possible to obtain a top plate that has a low environmental load and is excellent in infrared transparency and visible light shielding properties.

Japanese Patent Publication No. 3-9056 JP 2003-68435 A JP-T-2004-523446

  The crystallized glass described in Patent Document 3 has excellent infrared transmittance at the start of use, but has a problem that the infrared transmittance decreases as it is used for a long time. The ability to maintain high infrared transmittance even after long-term use is important from the viewpoint of energy saving as well as cooking performance.

Therefore, the present invention provides a top plate for a cooker using crystallized glass that has sufficient visible light shielding performance, has high infrared transmittance, and does not easily lose its characteristics even when used for a long time. Is a technical issue.

As a result of intensive studies, the present inventors limited the contents of V ₂ O ₅ and Ti ₂ O in the crystallized glass and the mixing ratio of V ₂ O ₅ and SnO ₂ to a specific range, The present inventors have found that the above problems can be solved and propose the present invention.

That is, the present invention is, in terms of _{mass%, SiO 2 55~73%, Al} 2 O 3 17~25%, Li 2 O 2~5%, TiO 2 4~5.5%, SnO 2 0.05~0 .2%, V ₂ O ₅ 0.02 to 0.1%, V ₂ O ₅ / (SnO ₂ + V ₂ O ₅ ) is contained in a composition of 0.2 to 0.4, and As ₂ O ₃ and a top plate for a cooking appliance with a substantially free and a Iyui crystallized glass Sb ₂ O _3.

As described above, V ₂ O ₅ has a function as a colorant, and also has an effect of reducing infrared transmittance. In the present invention, the content of V ₂ O ₅ is suppressed as low as 0.02 to 0.1% and the mixing ratio of SnO ₂ and V ₂ O ₅ is V ₂ O ₅ / (SnO ₂ + V ₂ O ₅ ). Is adjusted to be 0.2 to 0.4, and the content of TiO ₂ is adjusted to be relatively high as 4 to 5.5%. It has become possible to increase the coloring efficiency of V ₂ O ₅ so that the internal structure of the cooking device can be shielded. The mechanism for obtaining such an effect can be roughly explained as follows.

In the glass, V ions are mainly present in a 3-5 pentavalent state, but it is presumed that the crystallized glass is colored due to tetravalent V ions present in the matrix glass phase. Furthermore, it is known that when the tetravalent V ions are combined with TiO ₂ present in the matrix glass phase, the degree of coloring is further increased (visible light transmittance is reduced). Thus, the coloring of crystallized glass is greatly influenced by the amount of tetravalent V ions and TiO ₂ in the matrix glass phase.

On the other hand, it has been found that the valence of V ions changes due to the presence of Sn (particularly, the redox action of Sn ions). That is, it is considered that the mixing ratio of V ₂ O ₅ and SnO ₂ affects the degree of coloring. In the present invention, by limiting the mixing ratio of V ₂ O ₅ and SnO ₂ to the above range, the amount of tetravalent V ions increases, and the coloring effect of V ₂ O ₅ can be maximized. To do.

Incidentally, if the sintering crystallized glass according to the present invention was used for a long as tone management dexterity top plate, by heating at the time of use, the crystallization further progresses. As crystallization proceeds, the matrix glass composition changes, and in the matrix glass phase, the concentrations of tetravalent V ions and TiO ₂ that do not contribute to the crystal composition are relatively increased. As a result, the binding state between tetravalent V ions and TiO ₂ changes, and the transmittance in the visible region and the infrared region changes. In forming crystallized glass according to the present invention, since the TiO ₂ is present in excess relative to the tetravalent V ions, even for a change in the matrix glass composition according to long-term use, the tetravalent V ions and TiO ₂ The coupling state is not easily changed, and the visible light transmittance is hardly changed.

Although forming crystallized glass according to the present invention is a crystallized glass containing beta-quartz solid solution as the predominant crystal, the heating by long-term use, beta-quartz solid solution beta-spodumene solid solution (Li _{2 O-Al} 2 Crystal transition occurs to O ₃ —nSiO ₂ (n ≧ 4), and it has the property of causing cloudiness. When white turbidity occurs in the crystallized glass, the appearance changes and the infrared transmittance decreases due to scattering. As ₂ O ₃ and Sb ₂ O ₃ are components having a large effect of promoting crystal transition, and V ₂ O ₅ is also known to have an effect of promoting crystal transition. Forming crystallized glass according to the present invention, together with free of _As 2 _{O 3} and _Sb 2 _{O 3 substantially,} since the limit V 2 _O content of ₅ is also reduced as less likely to crystal transition, long It has a feature that the transmittance change in the visible region and the infrared region due to use is small.

Further, As ₂ O ₃ and Sb ₂ O ₃ are considered to have a large environmental load, and their use is being restricted in recent years. Forming crystallized glass according to the present invention, these components for substantially free, it is possible to reduce the environmental impact upon disposal. In the present invention, “substantially does not contain” refers to a level in which these components are not intentionally added as raw materials but mixed as impurities contained in various glass raw materials. Specifically, the content is It means 0.1% or less.

Forming crystallized glass according to the present invention preferably Na ₂ O content of 0.5% or less.

Forming crystallized glass according to the present invention preferably further contains ZrO ₂ 0 to 2.3%.

Forming crystallized glass according to the present invention, it is preferable the total amount of TiO ₂ and ZrO ₂ is from 4 to 6.5%.

Forming crystallized glass according to the present invention, the transmittance at 3mm thick is preferably 35% or less at a wavelength of 700 nm, and less than 85% at a wavelength of 1150 nm. In the present invention, the transmittance of the crystallized glass is measured using a sample whose surface is mirror-polished.

A top plate for a cooker according to the present invention is characterized by using the crystallized glass described above .

  The reason why the composition of the glass is limited as described above in the present invention will be described below.

SiO ₂ is a component that forms a glass skeleton and constitutes a β-quartz solid solution. The content of SiO ₂ is 55 to 73%, preferably 60 to 71%, more preferably 63 to 70%. When the content of SiO ₂ decreases, the thermal expansion coefficient tends to increase, and it becomes difficult to obtain crystallized glass having excellent thermal shock resistance. In addition, chemical durability tends to decrease. On the other hand, when the content of SiO ₂ is increased, the meltability of the glass is lowered, or the viscosity of the glass melt is increased, so that it is difficult to form the glass.

Al ₂ O ₃ forms a glass skeleton and is a component constituting a β-quartz solid solution. The content of Al ₂ O ₃ is 17 to 25%, preferably 17.5 to 24%, more preferably 18 to 22%. When the content of Al ₂ O ₃ decreases, the thermal expansion coefficient tends to increase, and it becomes difficult to obtain crystallized glass excellent in thermal shock resistance. In addition, chemical durability tends to decrease. On the other hand, when the content of Al ₂ O ₃ increases, the meltability of the glass decreases and the viscosity of the glass melt increases, which tends to make it difficult to form the glass. Further, the glass tends to be devitrified due to the precipitation of mullite crystals, and cracks are likely to be generated in the glass from the devitrified portion, so that molding becomes difficult.

Li ₂ O is a component that constitutes a β-quartz solid solution, has a great influence on crystallinity, and lowers the viscosity of the glass to improve the meltability and moldability. The content of Li ₂ O is 2 to 5%, preferably 2.3 to 4.7%, more preferably 2.5 to 4.5%. When the content of Li ₂ O is reduced, the glass tends to be devitrified by mullite crystals, and cracks are likely to be generated in the glass from the devitrified portion, so that molding becomes difficult. Moreover, when crystallizing glass, it becomes difficult to precipitate β-quartz solid solution crystals, and it becomes difficult to obtain crystallized glass excellent in thermal shock resistance. Furthermore, the meltability of the glass tends to decrease or the viscosity of the glass melt tends to increase, making it difficult to mold the glass. On the other hand, when the content of Li ₂ O increases, the crystallinity becomes too strong and coarse crystals are likely to precipitate in the crystallization process. As a result, it becomes cloudy and a transparent crystallized glass cannot be obtained or is easily damaged. It becomes difficult to form.

TiO ₂ is a component constituting a crystal nucleus for precipitating a crystal in the crystallization step, and has an action of enhancing the coloration of tetravalent V ions. The content of TiO ₂ is 4 to 5.5%, preferably 4.1 to 5.3%, more preferably 4.2 to 5.1%. When the content of TiO ₂ decreases, the amount remaining in the matrix glass phase without being used as crystal nuclei decreases, so that it is difficult to combine with tetravalent V ions, and the color development efficiency tends to be low. In addition, when crystallization proceeds with long-term use, as described above, the concentration of tetravalent V ions and TiO ₂ in the glass matrix increases, and the bonding state of the two changes. (Especially, the color becomes darker). Furthermore, since a sufficient number of crystal nuclei are not formed, the grain size of crystals grown from the individual crystal nuclei becomes large (coarse crystals), and it becomes difficult to obtain a crystallized glass that is cloudy and transparent. On the other hand, when the content of TiO ₂ increases, the glass tends to be devitrified from the melting step to the molding step, and it becomes easy to break, so that molding becomes difficult.

SnO ₂ is a component that enhances color development by increasing tetravalent V ions, which are coloring components. The content of SnO ₂ is 0.05 to less than 0.2%, preferably 0.06 to 0.18%, more preferably 0.07 to 0.15%. When the content of SnO ₂ is reduced, tetravalent V ions are not efficiently generated, so that the coloring effect is hardly increased. When the content of SnO ₂ is increased, the glass tends to be devitrified when it is melted and molded, so that the molding becomes difficult. Moreover, when the content of SnO ₂ increases, the color tone tends to easily change due to slight differences in melting conditions and crystallization conditions even if the composition is the same.

V ₂ O ₅ is a coloring component. The content of V ₂ O ₅ is 0.02 to 0.1%, preferably 0.02 to 0.05%. When the content of V ₂ O ₅ is reduced, the coloring becomes thin and the visible light cannot be sufficiently shielded. On the other hand, when the content of V ₂ O ₅ increases, the infrared transmittance tends to decrease. Further, the crystal transition from the β-quartz solid solution to the β-spodumene solid solution is likely to cause white turbidity.

The mixing ratio of V ₂ O ₅ and SnO ₂ is such that V ₂ O ₅ / (SnO ₂ + V ₂ O ₅ ) is 0.2 to 0.4, preferably 0.25 to 0.35 in terms of mass ratio. Even if the mixing ratio of V ₂ O ₅ and SnO ₂ is larger or smaller than the above range, the amount of tetravalent V ions is reduced, so that it is difficult to obtain a high coloring effect.

Further, the sintered crystallized glass according to the present invention, in addition to the above, it is possible to add various components within a range not to impair the required properties.

MgO is a component that dissolves in β-quartz solid solution crystals instead of Li ₂ O. The content of MgO is 0 to 1.5%, preferably 0 to 1.4%, more preferably 0.1 to 1.2%. When the content of MgO is increased, the crystallinity becomes too strong and tends to devitrify, and as a result, the glass is easily broken and molding becomes difficult.

  ZnO is a component that dissolves in the β-quartz solid solution crystal in the same manner as MgO. The content of ZnO is 0 to 1.5%, preferably 0 to 1.4%, more preferably 0.1 to 1.2%. When the content of ZnO increases, the crystallinity tends to be too strong. For this reason, if the glass is molded while being slowly cooled, the glass tends to devitrify and break, and thus, for example, it is not suitable for molding by the float process.

ZrO ₂ is a component constituting a crystal nucleus for precipitating crystals in the crystallization step, like TiO ₂ . The content of ZrO ₂ is 0 to 2.3%, preferably 0 to 2.1%, more preferably 0.1 to 1.8%. When the content of ZrO ₂ increases, the glass tends to be devitrified in the melting and forming process of the glass, making it difficult to form the glass.

P ₂ O ₅ is a component that promotes phase separation of glass. Since crystal nuclei are likely to be generated at the place where the glass is phase-separated, P ₂ O ₅ serves to assist the formation of crystal nuclei. The content of P ₂ O ₅ is 0 to 2%, preferably 0.1 to 1%. When the content of P ₂ O ₅ increases, phase separation occurs in the melting step, so that it becomes difficult to obtain a glass having a desired composition and tends to be opaque.

The total amount of TiO ₂ and ZrO ₂ is 4 to 6.5%, preferably 4.5 to 6%. When the total amount of these components increases, the glass tends to be devitrified in the melting and forming process, and it becomes difficult to form the glass. On the other hand, when the total amount of these components is too small, crystal nuclei are not sufficiently formed, and the crystal is likely to be coarsened. As a result, it becomes difficult to obtain a crystallized glass that is cloudy and transparent.

Na ₂ O is a component that lowers the viscosity of the glass and improves glass meltability and moldability. The content of Na ₂ O is 0.5% or less, preferably 0.3% or less, more preferably 0.2% or less. When the content of Na ₂ O is too large, crystal transition from β-quartz solid solution to β-spodumene solid solution is promoted, and thus white turbidity due to crystal coarsening is likely to occur. In addition, the thermal expansion coefficient tends to be high, and it becomes difficult to obtain crystallized glass excellent in thermal shock resistance.

In order to reduce the viscosity of the glass and improve the meltability and moldability, it is possible to add up to 5% in total of K ₂ O, CaO, SrO and BaO. CaO, SrO, and BaO are components that cause devitrification when the glass is melted. Therefore, the total amount of these components is preferably 2% or less. Moreover, since CaO has the effect | action which accelerates | stimulates the crystal transition from (beta) -quartz solid solution to (beta) -spodumene solid solution, it is better to refrain from using it as much as possible.

As a clarifier, SO ₂ and Cl may be added alone or in combination as necessary. The total amount of these components is desirably 0.5% or less. As ₂ O ₃ and Sb ₂ O ₃ are also clarifying components, but are components that are considered to have a large environmental load, and it is important that they are not substantially contained.

  Colored transition metal elements not described above (for example, Cr, Mn, Fe, Co, Ni, Cu, Mo, Cd, etc.) absorb infrared rays or lose the ability to reduce Sn ions. Since it may react with Sn ions and, as a result, the reaction between V ions and Sn ions may be hindered), it is preferably not contained as much as possible.

Forming crystallized glass according to the present invention, 3 mm 35% transmittance at a wavelength of 700nm is in the thickness or less, more preferably 30% or less, thereby it is possible to sufficiently shield the internal structure of the cooker and Become. On the other hand, when displaying temperature, thermal power, etc. using LED etc., it is preferable that the transmittance | permeability in wavelength 700nm is 15% or more, 18% or more, and also 20% or more in 3 mm thickness. Thereby, when it uses for the top plate of cookers, such as IH, it becomes possible to fully recognize the display by LED etc. through crystallized glass.

As another index, the crystallized glass according to the present invention preferably has a change rate of absorbance of 10% or less at a wavelength of 700 nm after heat treatment at 900 ° C. for 50 hours. The rate of change in absorbance is calculated as follows.

Absorbance = log ₁₀ (transmittance (%) / 100)
Absorbance change rate = (absorbance after heat treatment−absorbance before heat treatment) / absorbance before heat treatment × 100 (%)

Further, forming crystallized glass according to the present invention, the transmittance at a wavelength of 1150nm is 85% in 3mm thick, more preferably for heat ray (infrared) can be efficiently transmitted when is 86% or more.

In addition, it is preferable that the above-mentioned crystallized glass does not impair high infrared transmittance even if it is used for a long time such as a top plate for a cooker, and further the visible light transmittance is not easily changed. Specifically, binding crystallized glass according to the present invention, the amount of change in transmittance is 5% or less at a wavelength of 1150nm after heat treatment for 50 hours at 900 ° C. as an accelerated test, 3%, 2%, 1. It is preferably 5% or less, particularly preferably 1% or less. In the accelerated test, the change in transmittance at a wavelength of 700 nm is preferably 5% or less, 3% or less, 2% or less, 1.5% or less, particularly preferably 1% or less.

Thermal expansion coefficient in a temperature range of thirty to seven hundred fifty ° C. for forming crystallized glass according to the present invention is preferably -10 to 30 × ^{10 -7} / ° C., more preferably -10 to 20 × ^{10 -7} / ° C. is there. When the thermal expansion coefficient is in this range, the glass has excellent thermal shock resistance. In the present invention, the thermal expansion coefficient is a value measured with a dilatometer.

Forming crystallized glass according to the present invention can be produced as follows.

First, various glass raw materials are prepared so as to have the above composition. If necessary, MgO and ZnO solid solution in the crystal by replacing a part of Li 2 _O, components for improving the melting property and formability of the glass, may be added to fining agent.

  Next, the prepared glass raw material is melted at a temperature of 1600 to 1900 ° C. and then molded to obtain crystalline glass. As a molding method, various molding methods such as a blow method, a press method, a roll-out method, and a float method can be applied.

  After annealing the crystalline glass, heat treatment is performed at 700 to 800 ° C. for 10 minutes to 10 hours to form crystal nuclei, followed by heat treatment at 800 to 900 ° C. for 10 minutes to 10 hours to grow β-quartz solid solution crystals. To obtain crystallized glass.

Further resulting crystallized glass, cutting, polishing, bending, reheat machining after such press, that is subjected to painting or film with such necessary processing to the surface to obtain a top plate for a cooking appliance of the present invention it can.

  Hereinafter, the present invention will be described based on examples.

Tables 1 to 3 show Examples (Sample Nos. 1 to 7 and 12) and Comparative Examples (Samples Nos. 8 to 11, 13, and 14) of crystallized glass according to the present invention.

  Glass raw materials were prepared so as to have the compositions shown in Tables 1 to 3, and melted at 1600 ° C. for 20 hours and further at 1700 ° C. for 4 hours using a platinum crucible. Two spacers having a thickness of 5 mm were placed on the carbon plate, and molten glass was poured out between the spacers, and leveled with a roller to form a plate shape.

  The obtained plate-like sample was put into an electric furnace maintained at 700 ° C., held for 30 minutes, then turned off, and cooled to room temperature in the furnace over 10 hours.

  Next, the cooled sample was crystallized with an electric furnace to obtain crystallized glass. The profile was such that nucleation was 770 ° C. for 3 hours and crystal growth was 880 ° C. for 1 hour.

  Each crystallized glass was evaluated for transmittance and devitrification in the visible and infrared regions.

  The transmittance was measured for 700 nm and 1150 nm using a spectrophotometer (V-760 manufactured by JASCO Corporation) by processing each crystallized glass into a 3 mm-thick sample whose surfaces were mirror-polished. The measurement conditions were a measurement range of 1500 to 380 nm and a scan speed of 200 nm / min. Moreover, the transmittance | permeability was similarly measured about the sample which performed the heat processing (acceleration test) for 50 hours at 900 degreeC.

  The devitrification was evaluated for 24 hours by holding each sample on a platinum foil in an electric furnace set at 1350 ° C., and evaluating whether devitrification occurred. If no devitrification was confirmed, “◯” was indicated. If devitrification was confirmed, “x” was indicated.

  As is apparent from Tables 1 to 3, sample No. 1 to 7 and 12 can sufficiently shield light in the visible region and have high infrared transmittance, and it is understood that the transmittance change in the visible and infrared regions is small even in an acceleration test assuming long-term use. .

  On the other hand, sample No. No. 8 had a large change width of transmittance in the visible and infrared regions after the acceleration test. Sample No. 9 and 11 were not sufficiently low in transmittance in the visible region after crystallization. Sample No. In No. 9, devitrification was confirmed. No. No. 10 was not sufficiently high in transmittance in the infrared region after crystallization, and devitrification was confirmed. Sample No. In 13 and 14, the change in transmittance (absorbance) before and after the heat treatment was large.

Forming crystallized glass according to the present invention is suitable gas, the IH, as top plate for a cooking appliance such as a halogen heater. It can also be used for observation windows for high-temperature furnace observation, fireproof windows, etc., in which low-expansion crystallized glass having a β-quartz solid solution as a main crystal is conventionally used.

Claims (5)

By _{mass%, SiO 2 55~73%, Al} 2 O 3 17~25%, Li 2 O 2~5%, TiO 2 4~5.5%, SnO 2 less than 0.05 to 0.2%, V ₂ O ₅ 0.02 to 0.1%, V ₂ O ₅ / (SnO ₂ + V ₂ O ₅ ) contains a composition of 0.2 to 0.4, As ₂ O ₃ and Sb ₂ O ₃ top plate for a cooking appliance, characterized by comprising using a substantially free and a Iyui crystallized glass. The top plate for a cooker according to claim 1, wherein the content of Na ₂ O in the crystallized glass is 0.5% or less. The crystallized glass further contains 0 to 2.3% of ZrO _{2. The} top plate for a cooker according to claim 1 or 2, characterized in that: The top plate for a cooker according to claim 3, wherein the total amount of TiO ₂ and ZrO _{2 in} the crystallized glass is 4 to 6.5%. 5. The top plate for a cooker according to claim 1, wherein the transmittance of the crystallized glass at a thickness of 3 mm is 35% or less at a wavelength of 700 nm and 85% or more at a wavelength of 1150 nm.