JP2013103866A - Method for producing crystallized glass, crystallized glass, and top plate for cooking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing crystallized glass capable of adjusting a color tone easily by changing a crystallization condition, and hardly spoiling transmission characteristics of a visible ray or an infrared ray even when used for a long time, and to provide crystallized glass, and a top plate using the same.SOLUTION: This method for producing crystallized glass includes: a mixing step for mixing raw material powder so as to obtain a composition containing, in terms of mass%, 55-73% SiO, 17-25% AlO, 2-5% LiO, 2.6-5.5% TiO, 0-0.9% SnO, 0.01-0.4% VO, and not containing substantially AsOand SbO; a precursor preparing step for preparing precursor glass by melting the raw material powder; and a crystal nucleus formation step for subjecting the precursor glass to heat treatment in a temperature zone of 660-700°C for 10 minutes to 10 hours.

Description

  The present invention relates to a crystallized glass having high heat resistance and a method for producing the same, and more specifically, a crystal used for a top plate of a cooker having an IH (electromagnetic induction heating device), a halogen heater or the like as a heat source. The present invention relates to a vitrified glass and a method for producing the same.

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, a low expansion transparent crystallized glass having a main crystal of β-quartz solid solution (Li ₂ O—Al ₂ O ₃ —nSiO ₂ (n ≧ 2)) is known, and the top plate It is used as.

  Low-expansion crystallized glass is formed into various shapes by a mixing process in which various glass raw materials are mixed at a predetermined ratio, a melting process in which glass raw materials are melted at a high temperature of 1600 to 1900 ° C. to obtain a homogenized fluid, and various methods It is manufactured through a forming step, an annealing step for removing strain, and a crystallization step for precipitating fine crystals. The crystallization process includes a nucleation process for precipitating microcrystals serving as crystal nuclei and a crystal growth process for growing 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.

_However, coloration of the glass due to colorants such as V 2 _{O 5} is believed to be strengthened by interaction with _As 2 _{O 3} and _Sb 2 _{O 3} which is 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. When simply exclude _As 2 _{O 3} and _Sb 2 _{O 3} from a conventional glass composition, coloring efficiency by colorant tends to be lowered. Although it is possible to improve the visible light shielding effect by increasing the amount of the colorant, according to the method, the raw material cost increases due to the increase in the amount of the colorant added, or the infrared transmittance decreases. There's a problem.

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

Since the glass described in Patent Document 1 and Patent Document 2 contains As ₂ O ₃ or Sb ₂ O ₃ as a raw material, it is possible to easily adjust the color tone by changing the crystallization conditions. However, there is a problem that the color tone tends to change when used as a top plate of a cooking device for a long time. Being able to maintain a high infrared transmittance even after long-term use is important from the viewpoint of energy saving as well as cooking performance. In addition, the visible light transmittance of the heated portion may decrease due to long-term use, and there is also a problem that even if the cooking performance is not directly affected, only the heated portion is discolored and the appearance is impaired.

On the other hand, when SnO ₂ is added without adding As ₂ O ₃ or Sb ₂ O ₃ as in Patent Document 3, a nucleation temperature of 720 to 780 ° C., which is a general crystallization condition, or 800 to 950 ° C. Even if the holding temperature and holding time are adjusted at the crystal growth temperature, there is a problem that the color tone of the crystallized glass hardly changes and the color tone is difficult to adjust.

  Therefore, the present invention is a crystallized glass whose color tone can be easily adjusted by changing the crystallization conditions, and in which visible light and infrared transmission characteristics are hardly impaired even when used for a long time, and a method for producing the same, In addition, it is a technical problem to provide a top plate using the same.

  As a result of intensive studies, the present inventor has found that the color tone of the crystallized glass can be easily controlled by changing the heat treatment time in a specific temperature range when forming crystal nuclei. Furthermore, the deterioration of the visible light and infrared transmission performance due to long-term use is caused by crystallization re-advancing due to heating during use, changing the composition of the matrix glass phase, and white turbidity due to crystal transition. I found out. And based on these knowledge, it came to propose this invention.

That is, the present invention is primarily in _{mass%, SiO 2 55~73%, Al} 2 O 3 17~25%, Li 2 O 2~5%, TiO 2 2.6~5.5%, SnO ₂ 0 to _0.9%, containing _V 2 O 5 0.01 to 0.4% formulating raw material powder so as to be substantially free composition of _as 2 _{O 3} and _Sb 2 _{O 3} formulation Characterized in that it includes a step, a precursor preparation step in which a raw material powder is melted to prepare a precursor glass, and a crystal nucleus formation step in which the precursor glass is heat-treated in a temperature range of 660 to 700 ° C. for 10 minutes to 10 hours. This is a method for producing crystallized glass.

  According to the present invention, a crystallized glass can be obtained in which the color tone of the crystallized glass can be easily adjusted, and the visible light and infrared transmission characteristics are hardly impaired even when used for a long time. Details will be described below.

  First, the reason why the color tone of crystallized glass can be easily adjusted according to the present invention will be described.

The coloring mechanism of the crystallized glass obtained by the production method of the present invention is as follows. In general, V ions are present mainly in the 3-5 valence state in the glass, but the coloration of the crystallized glass is presumed to be caused by tetravalent V ions present in the matrix glass phase. . Then, it is considered that when the tetravalent V ions are combined with TiO ₂ present in the matrix glass phase, the degree of coloring is further increased (the visible light transmittance is reduced).

Here, it is considered that the more TiO ₂ precipitates as crystal nuclei, the lower the TiO ₂ concentration in the matrix glass phase. Therefore, the color tone of the crystallized glass can be controlled by controlling the amount of precipitation of TiO ₂ as crystal nuclei. In the present invention, when the precursor glass having the above composition is crystallized, the precipitation amount of TiO ₂ as a crystal nucleus can be easily controlled by appropriately changing the heat treatment time in the temperature range of 660 to 700 ° C. It is. That is, according to the present invention, the color tone of the crystallized glass can be easily adjusted by changing the crystallization conditions.

In addition, although the valence of V ion mentioned above changes with presence of Sn (especially redox action of Sn ion), in the present invention, by appropriately limiting the contents of V ₂ O ₅ and SnO ₂ By adjusting the amount of tetravalent V ions, it is possible to maximize the coloring effect of V ₂ O ₅ .

  Next, the reason why it is possible to obtain a crystallized glass that does not easily deteriorate visible light and infrared transmission characteristics even when used for a long time according to the present invention will be described.

In the conventional top plate for a cooker, when used for a long period of time, crystallization may further progress due to heating during use. As crystallization proceeds, the matrix glass composition changes and the concentrations of tetravalent V ions and TiO ₂ in the matrix glass phase increase relatively. As a result, tetravalent V ions and TiO ₂ are easily bonded, and the transmittance in the visible region and the infrared region may be reduced.

On the other hand, in the present invention, when the precursor glass having the above composition is crystallized, a large amount of TiO ₂ can be precipitated as crystal nuclei by performing a heat treatment in a temperature range of 660 to 700 ° C. for 10 minutes to 10 hours. it can. As the number of crystal nuclei per unit volume increases, the distance between crystal nuclei decreases and the room for growth of individual crystals decreases. Therefore, when a large number of crystal nuclei are precipitated as described above, the crystal grain size can be reduced when the crystal is grown, and crystallization can be sufficiently advanced in a short time. Accordingly, the crystallized glass produced by the production method of the present invention is almost completely crystallized, and hardly undergoes crystallization even when subjected to heating for a long time. That is, in the crystallized glass of the present invention, even when heated for a long time, the bonding state between V ions and TiO ₂ in the matrix glass phase hardly changes. Therefore, according to the production method of the present invention, it is possible to obtain a crystallized glass having high durability compared to the conventional products, with the transmission characteristics in the visible region and the infrared region being hardly impaired.

A crystallized glass containing a general β-quartz solid solution as a main crystal is obtained by heating a β-quartz solid solution to a β-spodumene solid solution (Li ₂ O—Al ₂ O ₃ —nSiO ₂ (n ≧ 4)) by heating over a long period of time. ) Has a property of causing crystal transition and white turbidity. 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 such crystal transition.

In that respect, since the crystallized glass obtained by the production method of the present invention does not substantially contain As ₂ O ₃ and Sb ₂ O ₃ , it is difficult to undergo crystal transition, and the transmittance in the visible region and infrared region due to long-term use. Is hard to change.

Moreover, since the crystallized glass obtained by the production method of the present invention does not substantially contain As ₂ O ₃ or Sb ₂ O ₃ which is considered to have a large environmental load, the environmental load at the time of disposal can be reduced. 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 0.01% or less.

  Secondly, the method for producing crystallized glass according to the present invention further includes a crystal growth step of heat-treating the precursor glass in which crystal nuclei are formed at a temperature range of 800 to 930 ° C. for at least 10 minutes. .

  According to this configuration, crystallization is further facilitated, and the temporal change in transmission characteristics in the visible region and the infrared region can be further reduced.

Third, the method for producing crystallized glass of the present invention is characterized in that the SnO ₂ content is 0.01 to 0.7%.

According to this configuration, by appropriately regulating the content of SnO _2, while obtaining a high color developability can be prevented devitrification.

  4thly, this invention relates to the crystallized glass produced by the said any manufacturing method.

  Fifth, the crystallized glass of the present invention is characterized in that the absorbance change rate at a wavelength of 700 nm after heat treatment at 900 ° C. for 50 hours is 20% or less.

Sixth, the crystallized glass of the present invention, in _{mass%, SiO 2 55~73%, Al} 2 O 3 17~25%, Li 2 O 2~5%, TiO 2 2.6~5.5% , SnO ₂ 0-0.9%, V ₂ O ₅ 0.01-0.4%, substantially free of As ₂ O ₃ and Sb ₂ O ₃ , The absorbance change rate at a wavelength of 700 nm after the heat treatment is 20% or less.

  Seventh, the present invention relates to a top plate for a cooking appliance using any one of the above crystallized glasses.

In the production method of the present invention, first, by mass%, SiO ₂ 55 to 73%, Al ₂ O ₃ 17 to 25%, Li ₂ O 2 to 5%, TiO ₂ 2.6 to 5.5%, SnO ₂ 0 The raw material powder is prepared so as to have a composition containing 0.01 to 1%, V ₂ O ₅ 0.01 to 0.4%, and substantially not including As ₂ O ₃ and Sb ₂ O ₃ . The reason for limiting the composition in this way 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.

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. 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 2.6 to 5.5%, preferably 2.6 to 5%, more preferably 2.8 to 4.8%, and still more preferably 3 to 4.5%. When the content of TiO ₂ is reduced, it is difficult to change the color tone because it is difficult to precipitate as crystal nuclei even if heat treatment is performed at 660 ° C. to 700 ° C. in the crystallization step. Further, when the content of TiO ₂ is reduced, the amount remaining in the matrix glass phase without being used as crystal nuclei is reduced, so that it is difficult to combine with tetravalent V ions, and the coloring efficiency tends to be lowered. Further, when crystallization proceeds by heating for a long period of time, 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, so that the degree of coloring is inappropriate. (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. SnO ₂ content is 0-0.9%, 0.03-0.7%, 0.03-0.6%, 0.03-0.3%, 0.03-0.25%, especially It is preferable that it is 0.05 to 0.23%. 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. Further, even with the same composition, the color tone tends to change easily due to slight differences in melting conditions and crystallization conditions.

V ₂ O ₅ is a coloring component. The content of V ₂ O ₅ is preferably 0.01 to 0.4%, 0.02 to 0.2%, and particularly preferably 0.03 to 0.15%. 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.

Note that As ₂ O ₃ and Sb ₂ O ₃ are not substantially contained for the reasons described above.

  In addition to the above, various components can be added as long as the required properties are not impaired.

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 2.0%, preferably 0 to 1.5%, 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.

The total amount of TiO ₂ and ZrO ₂ is 3.8 to 6.5%, preferably 4.2 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.

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.

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 0.8% or less, preferably 0.5% or less, more preferably 0.3% 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. Further, 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 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 they are components that are considered to have a large environmental load, and are components that promote crystal transition, so it is important that they are not substantially contained. It is.

  When a colored transition metal element (for example, Cr, Mn, Fe, Co, Ni, Cu, Mo, Cd, etc.) not described above is contained, infrared rays are absorbed or the ability to reduce Sn ions is lost (the colored transition metal). The element reacts with Sn ions, and as a result, the reaction between V ions and Sn ions may be hindered).

  The raw material powder prepared as described above is melted to obtain a crystalline precursor glass. Although a melting temperature is not specifically limited, In order to fully advance vitrification, it is preferable that it is 1600-1900 degreeC, for example. In addition, as a shaping | molding method of a molten glass, various shaping | molding methods, such as a blow method, a press method, a rollout method, and a float method, are applicable. The formed precursor glass is subjected to annealing as necessary.

Next, heat treatment is performed on the precursor glass in a temperature range of 660 to 700 ° C. for at least 10 minutes to 10 hours, more preferably 15 minutes to 7 hours, and even more preferably 20 minutes to 4 hours. Crystal nuclei can be precipitated in the heat treatment step. When the heat treatment temperature is out of the range of 660 to 700 ° C., it is difficult to form a sufficient number of crystal nuclei. The temperature range of 660 to 700 ° C. is the range in which TiO ₂ is most likely to precipitate as crystal nuclei, and crystal nuclei can be sufficiently formed. However, if the heat treatment time is shorter than 10 minutes, the color tone of the glass immediately after crystallization tends to become dark. On the other hand, even if the heat treatment time is longer than 10 hours, the amount of crystal nuclei formed is hardly increased, which is disadvantageous in terms of productivity and energy. In addition, the color tone of glass can be adjusted by adjusting the length of the heat processing time in the said 660-700 degreeC temperature range within the range of 10 minutes-10 hours. More specifically, the longer the heat treatment time, the more crystal nuclei can be formed and the color tone can be adjusted to a deeper color tone.

  Next, the precursor glass is further subjected to the following heat treatment to grow crystals to obtain a desired crystallized glass. Here, the heat treatment is preferably performed at 800 to 930 ° C., preferably 850 to 920 ° C., more preferably 870 to 910 ° C. for at least 10 minutes to 2 hours in order to sufficiently promote crystallization. When the heat treatment time is shorter than 10 minutes, the color immediately after crystallization is light and tends to cause white turbidity. On the other hand, even if the heat treatment time is longer than 2 hours, the amount of crystal nuclei formed is hardly increased, which is disadvantageous in terms of productivity and energy.

  The crystallized glass obtained by the production method of the present invention has a transmittance of 35% or less, more preferably 30% or less at a wavelength of 700 nm at a thickness of 3 mm. According to such a characteristic, it becomes possible to fully shield the internal structure of a cooking appliance. On the other hand, when displaying temperature, thermal power, etc. using LED etc., it is desirable that the transmittance at a wavelength of 700 nm is 15% or more, and further 18% or more at a thickness of 3 mm. According to such characteristics, when used for the top plate of a cooker, it is possible to sufficiently recognize the display by the LED or the like through the crystallized glass.

  The crystallized glass of the present invention preferably has a transmittance of 85% or more, more preferably 86% or more at a wavelength of 1150 nm at a thickness of 3 mm. According to such characteristics, heat rays (infrared rays) can be transmitted efficiently.

  In addition, even if it uses for a long time for uses, such as a top plate for cookers, it is preferable that a high infrared transmittance is not impaired, and further, the visible light transmittance is not easily changed. Specifically, the crystallized glass of the present invention is 3 mm thick, and the change in transmittance at a wavelength of 1150 nm after heat treatment at 900 ° C. for 50 hours as an accelerated test is 5% or less, 3% or less, particularly 2% or less. Preferably there is. In the acceleration test, the change in transmittance at a wavelength of 700 nm is preferably 5% or less, 3% or less, particularly 2% or less.

  The crystallized glass of the present invention preferably has an absorbance change rate at a wavelength of 700 nm of 20% or less, particularly 10% or less after heat treatment at 900 ° C. for 50 hours. The absorbance change rate is calculated by the following formula.

Absorbance = −log ₁₀ (transmittance (%) / 100)
Absorbance change rate = (absorbance after heat treatment−absorbance before heat treatment) / absorbance before heat treatment × 100 (%)
The thermal expansion coefficient in the temperature range of 30 to 750 ° C. of the crystallized glass of the present invention is preferably −10 × 10 ⁻⁷ to 30 × 10 ⁻⁷ / ° C., more preferably −10 × 10 ^{−7 to} 20 ×. 10 ⁻⁷ / ° C. 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.

  The crystallized glass obtained by the production method of the present invention may be subjected to post-processing such as cutting, polishing, bending, reheating press, etc., and the surface may be painted or filmed.

  The crystallized glass thus produced can be used as a top plate for IH cookers equipped with IH heaters, halogen heater cookers equipped with halogen heaters, gas cookers equipped with gas burners, and the like.

  EXAMPLES Next, although this invention is demonstrated in detail using an Example, this invention is not limited to these Examples. Table 1 shows the composition of the sample glass used in this example. Sample No. shown in Tables 2-7. 1 to 14 are Examples, Sample Nos. Reference numerals 11 to 25 denote comparative examples.

First, glass raw materials were prepared so as to have compositions A, B, C, D, E, and F shown in Table 1, and five types of batches were produced. In addition, all of the compositions A, B, C, D, and E are compositions within the scope of the present invention described above. On the other hand, the composition F contains As ₂ O ₃ and is outside the scope of the present invention.

  Each batch was then melted using a platinum crucible at 1600 ° C. for 20 hours and further at 1700 ° C. for 4 hours. Thereafter, two spacers having a thickness of 5 mm were placed on the carbon plate, molten glass was poured out between the spacers, and the plate was formed into a plate having a uniform thickness with a roller. Next, the obtained plate-like sample is put into an electric furnace maintained at 700 ° C., held for 30 minutes, then the power is turned off, and the glass is gradually cooled (annealed) to room temperature in the furnace over 10 hours. Was made.

  Subsequently, the precursor glass after cooling was crystallized by heat-treating it in the following step in an electric furnace to obtain crystallized glass. The heat treatment conditions were changed for each sample as shown in Tables 2-7.

Step 1: The precursor glass is charged into the electric furnace. Step 2: The temperature is increased from room temperature to the temperature of Step 3 at the speed in the table. Step 3: The temperature and time conditions in the table are maintained (crystal nucleation step).
Step 4: Increase the temperature at the speed in the table to the temperature of Step 5 Step 5: Hold at the temperature and time conditions in the table (crystal growth step)
Step 6: Decrease the temperature to normal temperature at the speed shown in the table Step 7: Take out from the electric furnace Each sample obtained as described above was evaluated for transmittance and Y value in the visible and infrared regions.

  The transmittances of 700 nm and 1150 nm were measured using a spectrophotometer (V-760 manufactured by JASCO Corporation) after mirror-polishing both surfaces of each sample glass to process them to a thickness of 3 mm. The measurement conditions were a measurement range of 1500 to 380 nm and a scan speed of 200 nm / min.

  The Y value is a value indicating the brightness of the color when the color is expressed in the xyY color system, and is also called brightness. In this example, the Y value was calculated according to JIS Z 8701 based on the transmittance in the visible light region (wavelength 380 to 780 nm).

  Furthermore, assuming the case where each of the above-mentioned sample glasses was used for a long time, heat treatment (acceleration test) was performed at 900 ° C. for 50 hours, and the transmittance in the visible and infrared regions after the heat treatment was evaluated. More specifically, each sample glass was put in a heat treatment furnace set at 900 ° C., and taken out after 50 hours, and transmittance was measured.

  Hereinafter, evaluation results of absorbance, transmittance, and Y value measured and calculated as described above will be described.

  Sample No. using composition A In 1-5, the color tone (Y value and 700 nm transmittance) changes according to the passage time in the temperature range of 660 to 700 ° C. That is, it is shown that when performing the heat treatment for crystallization, the color tone can be adjusted by changing the holding time within a range of 10 minutes to 10 hours in a temperature range of 660 to 700 ° C. On the other hand, sample Nos. 15 and 16 both have a passing time in the temperature range of 660 to 700 ° C. of about 2 minutes. Therefore, the color tone could hardly be changed even if the holding time in the temperature range (crystal nucleation step) around 780 ° C. was changed thereafter.

  In addition, No. 6-8 and no. Nos. 17 to 18 are obtained by crystallizing glass of composition B, sample Nos. Samples Nos. 9 to 10 and Sample 19 were obtained by crystallizing glass of composition C, Sample No. Samples 11 to 12 and Samples 20 to 21 were obtained by crystallizing the glass of Sample D, Sample No. Samples 13 to 14 and Samples 22 to 23 are obtained by crystallizing Sample E. Regarding these samples, the color tone of the sample that passed through the temperature range of 660 to 700 ° C. over 10 minutes to 10 hours could be adjusted according to the passage time. On the other hand, the sample that passed through the temperature range of 660 to 700 ° C. in less than 10 minutes could hardly change the color tone.

  Sample No. containing no As in the composition was used. As for 1 to 23, the color tone (Y value and absorbance at a wavelength of 700 nm) and infrared transmittance (wavelength of 1150 nm) were maintained substantially the same as before the test even after the acceleration test. That is, it was shown to have high durability. On the other hand, the sample No. In 24-26, the Y value, absorbance, and infrared transmittance values fluctuated before and after the acceleration test, and the color tone and visible and infrared transmission characteristics could not be maintained.

  As described above, the sample No. prepared based on the composition and manufacturing method within the scope of the present invention. As for 1 to 14, it was shown that the color tone can be easily adjusted by changing the crystallization condition, and also has high durability.

  The crystallized glass of the present invention is suitable as a top plate for cooking appliances such as gas, IH and halogen heaters. 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. Moreover, the manufacturing method of the crystallized glass of this invention is useful as a method of manufacturing the crystallized glass of the said use easily.

Claims (7)

By _{mass%, SiO 2 55~73%, Al} 2 O 3 17~25%, Li 2 O 2~5%, TiO 2 2.6~5.5%, SnO 2 0~0.9%, V 2 A blending step of blending raw material powder so as to have a composition containing 0.01 to 0.4% of O ₅ and substantially not including As ₂ O ₃ and Sb ₂ O ₃ ;
A precursor glass production step of melting the raw material powder to produce a precursor glass;
And a crystal nucleus forming step of heat-treating the precursor glass in a temperature range of 660 to 700 ° C. for 10 minutes to 10 hours.   2. The crystal growth step according to claim 1, further comprising a crystal growth step of heat-treating the precursor glass having crystal nuclei formed in a temperature range of 800 to 930 ° C. for 10 minutes to 2 hours after the crystal nucleation step. A method for producing crystallized glass. The method for producing crystallized glass according to claim 1 or 2, wherein the content of SnO ₂ is 0.01 to 0.7%.   A crystallized glass produced by the production method according to claim 1.   The crystallized glass according to claim 4, wherein the absorbance change rate at a wavelength of 700 nm after heat treatment at 900 ° C for 50 hours is 20% or less. By _{mass%, SiO 2 55~73%, Al} 2 O 3 17~25%, Li 2 O 2~5%, TiO 2 2.6~5.5%, SnO 2 0~0.9%, V 2 Having a composition containing 0.01 to 0.4% of O ₅ and substantially free of As ₂ O ₃ and Sb ₂ O ₃ ;
A crystallized glass characterized in that the absorbance change rate at a wavelength of 700 nm after heat treatment at 900 ° C. for 50 hours is 20% or less.   A top plate for a cooking appliance using the crystallized glass according to any one of claims 4 to 6.