JP2010018512A - Crystallized glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide crystallized glass having an improved thermally-softened processability while maintaining thermal shock resistance. <P>SOLUTION: The crystallized glass contains Li<SB>2</SB>O-Al<SB>2</SB>O<SB>3</SB>-SiO<SB>2</SB>-based crystal in an amount of 20-70 wt.%. In the crystallized glass, the difference between the average coefficients of linear thermal expansion of matrix glass and the Li<SB>2</SB>O-Al<SB>2</SB>O<SB>3</SB>-SiO<SB>2</SB>-based crystal is ≥35×10<SP>-7</SP>/K in a temperature range of 30-380°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention can be used as a glass top plate for a cooker, in particular a decorative material such as a glass top plate of a gas stove or a top plate of a kitchen facility, and further a component of a heating appliance, and has excellent heat such as bending by heating. The present invention relates to crystallized glass having softening workability.

  In recent years, as materials used in kitchen equipment and heating appliances, materials with excellent thermal durability, chemical durability, mechanical strength, etc., as well as excellent design properties have been demanded, and various types of crystallized glass have been developed. ,Proposed. Examples of kitchen equipment include glass top plates for cooking appliances, in particular, decorative materials such as glass top plates of gas stoves and top plates of kitchen equipment. Moreover, as a member used for a heater, the wall material of a fireplace (stove), the top plate for cookers on a fireplace (stove) (top plate used for the cooker using the heat of a fireplace), etc. are mentioned. The cooking device top plate may be used in combination with a crystallized glass plate and a metal plate.

  For example, in Patent Document 1, an inorganic pigment is attached to the interface of a crystalline glass body where crystals are precipitated while softening and deforming when heat-treated at a temperature higher than the softening temperature, and the crystals are fused and integrated by heat treatment. In addition, a crystallized glass article is disclosed in which a colored layer appears at each glass body interface.

  Further, Patent Document 2 discloses that glass bodies of different colors of the same material are scattered on the surface of a plate-like crystalline glass on which crystals are precipitated while softening and deforming when heat-treated at a temperature higher than the softening temperature. An integrated patterned crystallized glass article is disclosed.

  Further, Patent Document 3 discloses a decorative low expansion crystallized glass plate in which a decorative coating of borosilicate glass frit containing an inorganic color pigment is formed on the surface of black low expansion crystallized glass.

JP-A-1-157432 Japanese Patent Laid-Open No. 2-92840 Japanese Patent Laid-Open No. 9-183631

The crystallized glass articles disclosed in Patent Documents 1 and 2 have a relatively low crystallinity of 30 and 15% by mass, respectively. Therefore, the matrix glass can be softened by being reheated at a temperature higher than the softening temperature, and can be bent into a desired shape. However, since these crystallized glass articles contain β-wollastonite (CaSiO ₃ ) and garnite (ZnAl ₂ O ₄ ), which have a large average linear thermal expansion coefficient, respectively, a line of 60 × 10 ⁻⁷ / K or more. The coefficient of thermal expansion is shown. Therefore, since the crystallized glass articles in Patent Documents 1 and 2 have a high coefficient of linear thermal expansion, they are not durable against heating when used for a top plate of a gas stove, a top plate of a kitchen facility, a component of a heating appliance, or the like. Sufficient and may cause problems such as damage.

  Although the crystallized glass article described in Patent Document 3 has no problem in thermal durability, it is difficult to be softened by reheating because the degree of crystallinity is too high, and a desired shape can be bent. Can not. Therefore, after softening by heating at the stage of crystalline glass before crystallization, heat treatment for crystallization is performed, and it is difficult to avoid shape variation and dimensional variation before and after crystallization. In addition, since the crystallinity of the crystalline glass itself is too high, the crystal is excessively precipitated by the heat treatment. For example, it is possible to obtain a crystallized glass article with high design by fusing and integrating the crystalline glass bodies. Can not.

  Therefore, the present invention provides a crystallized glass that has thermal durability, mechanical strength, and chemical durability, can be softened by heating, and can produce a crystallized glass article with excellent design. The purpose is to provide.

  As a result of intensive studies, the present inventors have adjusted the content (crystallinity) of a specific crystal that greatly contributes to the decrease in the coefficient of linear thermal expansion, and the average coefficient of linear thermal expansion of the crystal and the remaining matrix glass. The present inventors have found that the above problem can be solved by using crystallized glass whose difference is larger than a predetermined value, and proposes the present invention.

That is, first, the crystallized glass of the present invention is a crystallized glass containing 20 to 70% by mass of Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystals, the difference in the average linear thermal expansion coefficient at 30 to 380 ° C. of _{li 2 O-Al 2 O 3} -SiO 2 based crystal is characterized in that it is 35 × ^{10 -7} / K or more.

It is known that Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystals have anisotropic thermal expansion characteristics, that is, the linear thermal expansion coefficient varies depending on the crystal axis. Therefore, in the crystallized glass containing Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal, in the cooling process of the crystallization treatment, the negative expansion axis side of the Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal and Shear stress is generated at the interface with the matrix glass having positive expansion. Along with that, voids are generated at the interface between the Li ₂ O—Al ₂ O ₃ —SiO ₂ crystal and the matrix glass. The void reduces the positive expansion contribution of the matrix glass and the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal in the crystallized glass, and the negative expansion axis of the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal. The contribution of is emphasized. This effect is more effective when the difference in average linear thermal expansion coefficient between the matrix glass and the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal is larger (or the average linear thermal expansion coefficient of the matrix glass and Li ₂ O—Al ₂ O _The greater the difference in the coefficient of thermal expansion of the negative expansion axis of the ₃ -SiO ₂ crystal, the more significant it is.

  In general, the linear thermal expansion coefficient of crystallized glass is additively determined by the average linear thermal expansion coefficient and volume fraction of each of crystal and matrix glass, but according to the present invention, it is predicted from the additive law. It is possible to obtain crystallized glass having a linear thermal expansion coefficient lower than the linear thermal expansion coefficient.

In addition, the crystallized glass of the present invention has a feature that the specific heat is high because the voids as described above exist at the interface between the Li ₂ O—Al ₂ O ₃ —SiO ₂ crystal and the matrix glass. Therefore, when the crystallized glass of the present invention is used as, for example, a structural member of a heating appliance, a high heat retention effect can be obtained.

Moreover, the crystallized glass of the present invention has a crystallized amount of precipitated crystals of Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal of 20 to 70% by mass, and has thermal durability and mechanical properties. Strength and chemical durability are not impaired, and softening processing by reheating is possible. In addition, the crystalline glass body before crystallization can be fused and integrated by heat treatment and crystals can be precipitated. Therefore, the crystallized glass of the present invention has a desired shape and is excellent in design, such as a cooking appliance top plate, particularly a gas stove top plate, a kitchen utensil top plate, a table top, etc. It is suitable as a member and other various interior / exterior materials.

Secondly, the crystallized glass of the present invention has a linear thermal expansion coefficient at 30 to 380 ° C. of 30 × 10 ⁻⁷ / K or less. Here, the linear thermal expansion coefficient in 30-380 degreeC points out the value measured using the dilatometer.

Third, the crystallized glass of the present invention is characterized in that the average particle size of the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal is 1 μm or more.

  Fourth, the crystallized glass of the present invention is characterized in that the yield temperature is 950 ° C. or lower. Here, the yield temperature is a value measured using a dilatometer.

Fifth, the crystallized glass of the present invention, in _{mass%, SiO 2 55~72%, Al} 2 O 3 14~30%, Li 2 O 1.5~5%, K 2 O 1~10%, TiO ₂ 0-5%, ZrO ₂ 0-4%, TiO ₂ + ZrO ₂ 0-7%, ZnO 0-10%, MgO 0-3%, CaO 0-2.5%, BaO 0-5%, B _It contains ₂ O ₃ 0-7%, Na ₂ O 0-2%, and P ₂ O ₅ 0-0.8%.

The crystallized glass containing the above composition contains Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystals such as β-quartz solid solution and β-spodumene solid solution as the main crystal, so it has low expansion and high thermal durability. It has the feature of having. In addition, it is possible to obtain a crystallized glass in which an amount of matrix glass necessary for softening deformation due to reheating remains. Furthermore, since the crystalline glass that is the precursor of the crystallized glass of the present invention has appropriate crystallinity, it is possible to precipitate crystals while fusing and integrating the crystalline glass bodies by heat treatment.

  Sixth, the crystallized glass of the present invention is characterized in that it is used for a cooking appliance top plate, a kitchen equipment decoration material, or a component of a heating appliance.

In the crystallized glass of the present invention, the content of Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal is 20 to 70% by mass, preferably 30 to 60% by mass. When the content of the Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal is less than 20% by mass, the thermal expansion coefficient of the crystallized glass tends to increase, making it difficult to obtain the target thermal durability. Become. On the other hand, if the crystal content exceeds 70% by mass, softening due to reheating hardly occurs, and softening such as bending tends to be difficult. In addition, the crystallinity of the crystallized glass that is the precursor becomes too high, and crystals are excessively precipitated by the heat treatment. For example, a crystallized glass article having high design properties by fusing and integrating the crystalline glass bodies You will not be able to get. Furthermore, the firing temperature of the crystalline glass tends to be a high temperature, for example, 1300 ° C. or more, and the problem that it becomes unsuitable for production using a normal firing furnace tends to occur.

In the crystallized glass of the present invention, the difference in average linear thermal expansion coefficient at 30 to 380 ° C. between the matrix glass and the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal is 35 × 10 ⁻⁷ / K or more, Preferably it is 40 * 10 < ^-7 > / K or more, More preferably, it is 50 * 10 < ^-7 > / K or more. When the difference in average linear thermal expansion coefficient is less than 35 × 10 ⁻⁷ / K, the stress generated at the interface between the matrix glass and the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal particles is too small, and there is a void at the interface. Is difficult to form. As a result, the linear thermal expansion coefficient of crystallized glass is unlikely to decrease. Moreover, specific heat becomes small, and when it is used, for example as a structural member of a heater, a sufficient heat retaining effect cannot be obtained. The upper limit is not particularly limited, but if the difference in average linear thermal expansion coefficient between the matrix glass and the Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal is too large, damage due to heat tends to occur. Since cracks are likely to occur at the interface between the crystal particles and the matrix glass, and the mechanical strength of the crystallized glass tends to decrease, it is preferably 70 × 10 ⁻⁷ / K or less in practice.

The linear thermal expansion coefficient of the crystallized glass of the present invention is preferably 30 × 10 ⁻⁷ / K or less, more preferably 20 × 10 ⁻⁷ / K or less. For example, in the gas range glass top, the highest temperature of the burner port becomes 200 ° C. or more due to the influence of the gas flame. On the other hand, since the outer periphery of the glass top plate away from the burner port remains at a low temperature, there is a possibility that tensile stress is generated at the location and the glass top plate is damaged. If the linear thermal expansion coefficient of the crystallized glass is greater than 30 × 10 ⁻⁷ / K, the generated stress on the outer periphery of the glass top plate becomes about 30 MPa or more, and the probability of breakage increases. Therefore, by setting the linear thermal expansion coefficient of the crystallized glass to 30 × 10 ⁻⁷ / K or less, the stress generated on the outer periphery of the glass top plate becomes less than the fracture allowable stress of the crystallized glass and is not easily damaged by heat. Become. Similarly, when the crystallized glass of the present invention is used as a structural member of a heating appliance, temperature distribution is generated and stress is generated. Therefore, breakage is prevented by setting the above range of linear thermal expansion coefficient. Can do. Although there is no particular limitation on the lower limit, if too low, since the content of _{Li 2 O-Al 2 O 3} -SiO 2 based crystallized in the crystallization glass becomes excessive softening due to reheating is hardly caused, As a result, softening processing such as bending tends to be difficult. From such a viewpoint, the linear thermal expansion coefficient of the crystallized glass is practically preferably −10 × 10 ⁻⁷ / K or more.

In the crystallized glass of the present invention, the average particle size of Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal particles is preferably 1 μm or more, more preferably 5 μm or more. When the average particle size of Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal particles is less than 1 μm, the influence of stress generated at the interface between the crystal particles and the matrix glass is reduced, and voids are formed at the interface between the crystal particles and the matrix glass. Is difficult to form. Therefore, there is a tendency that the linear thermal expansion coefficient of the crystallized glass is difficult to decrease or the specific heat is reduced. The upper limit is not particularly limited, but if the average particle size of the Li ₂ O—Al ₂ O ₃ —SiO ₂ crystal particles is too large, cracks are likely to occur at the interface between the crystal particles and the matrix glass, and the crystal Since the mechanical strength of the vitrified glass tends to be lowered, it is practically preferably 300 μm or less.

In the crystallized glass of the present invention, the average linear thermal expansion coefficient of the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal at 30 to 380 ° C. is preferably −80 × 10 ⁻⁷ to 15 × 10 ⁻⁷ / K. More preferably, it is −50 to 5 × 10 ⁻⁷ / K. Here, the average linear thermal expansion coefficient of the Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal is calculated by the method described in the examples. When the average linear thermal expansion coefficient of the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal is less than −80 × 10 ⁻⁷ / K, the stress generated at the interface between the crystal particles and the matrix glass becomes too large, Cracks are likely to occur at the interface, and as a result, the mechanical strength of the crystallized glass tends to decrease. On the other hand, when the average linear thermal expansion coefficient of the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal exceeds 15 × 10 ⁻⁷ / K, the stress generated at the interface between the crystal particles and the matrix glass is too small. As a result, the linear thermal expansion coefficient of the crystallized glass is hardly lowered or the specific heat is reduced.

  The yield temperature of the crystallized glass of the present invention is preferably 950 ° C. or lower, more preferably 900 ° C. or lower. When the yield temperature of the crystallized glass exceeds 950 ° C., softening due to reheating becomes difficult to occur, so that the accuracy of softening processing such as bending processing tends to be lowered.

  The glass transition temperature of the crystallized glass of the present invention is preferably 600 to 800 ° C. When the glass transition temperature of the crystallized glass is less than 600 ° C., the viscosity of the matrix glass becomes too low, and the difference in thermal expansion characteristics from the crystal phase becomes large. As a result, breakage due to heat tends to occur. On the other hand, when the glass transition temperature of the crystallized glass exceeds 800 ° C., softening due to reheating hardly occurs, so that the accuracy of softening processing such as bending processing tends to be lowered.

Crystallized glass of the present invention, in _{mass%, SiO 2 55~72%, Al} 2 O 3 14~30%, Li 2 O 1.5~5%, K 2 O 1~10%, TiO 2 0~ 5%, ZrO ₂ 0-4%, TiO ₂ + ZrO ₂ 0-7%, ZnO 0-10%, MgO 0-3%, CaO 0-2.5%, BaO 0-5%, B ₂ O ₃ 0 _{~7%, Na 2 O 0~2%} , preferably contains the composition of P 2 O 5 0~0.8%.

  The reason for limiting the content of each component in this way is as follows.

SiO ₂ is a main constituent of crystallized glass and a crystal constituent. Its content is 55-72%, preferably 60-70%. When the content of SiO ₂ is less than 55%, precipitation of Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystals becomes unstable. On the other hand, when the content of SiO ₂ is more than 72%, the melting property of the glass is lowered and it becomes difficult to form the glass, and the softening temperature of the crystallized glass is increased, and the softening process by reheating becomes difficult. Tend. Furthermore, the linear thermal expansion coefficient of the matrix glass decreases, the difference from the average linear thermal expansion coefficient of the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal becomes small, and the stress generated at the interface between the two is too small. It becomes difficult to form voids. As a result, it becomes difficult for the linear thermal expansion coefficient of the crystallized glass to decrease, and the specific heat becomes small.

Al ₂ O ₃ is a crystal component, and its content is 14 to 30%, preferably 16 to 25%. If the Al ₂ O ₃ content is less than 14%, the Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal is coarsened, and the mechanical strength of the crystallized glass tends to decrease. On the other hand, when the Al ₂ O ₃ content is more than 30%, not only the meltability of the glass is lowered, but also the liquidus temperature becomes too high and devitrification is likely to occur during glass forming.

Li ₂ O is a crystal component, and its content is 1.5 to 5%, preferably 1.8 to 3.5%. When the content of Li ₂ O is less than 1.5%, uniform Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystals are difficult to obtain, and the crystallized glass tends to be unstable. On the other hand, when the content of Li ₂ O exceeds 5%, the degree of crystallinity becomes too high and it becomes difficult to soften by reheating the crystallized glass, and it becomes difficult to perform softening processing such as bending, or crystalline glass. It becomes impossible to obtain a crystallized glass article with high design by fusing and integrating the small bodies.

K ₂ O is a component that controls the degree of crystallinity, thereby adjusting the softening temperature of the crystallized glass and affecting the softening workability by reheating. Its content is 1 to 10%, preferably 2 to 7%. If the content of K ₂ O is less than 1%, the crystallinity of the crystallized glass becomes too high, the softening processability by reheating deteriorates, or the crystalline glass body is fused and integrated. It becomes impossible to obtain a crystallized glass article having high properties. On the other hand, when the content of K ₂ O exceeds 10%, precipitation of Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystals is suppressed, and thus it becomes difficult to obtain a low expansion crystallized glass.

TiO ₂ and ZrO ₂ are generally known as components that become nuclei during Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal precipitation, but are not essential components in the present invention. However, when either or both of TiO ₂ and ZrO ₂ are added to the crystallized glass of the present invention, a rutile crystal (TiO ₂ ) and a zirconia crystal (Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal) ZrO ₂ ) or zirconium titanate crystals (ZrTiO ₄ ) are precipitated. Since these crystals have a higher refractive index than Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystals and matrix glass, they can be crystallized glass with high whiteness. The content of TiO ₂ is 5% or less. Further, the content of ZrO ₂ is 4% or less, preferably 2.5% or less. Moreover, it is preferable that the total amount of both is 7% or less. If the total amount of both exceeds 7% or exceeds the upper limit of the above range by itself, the crystallization rate becomes too fast and devitrification tends to occur. The lower limit is not particularly limited, in order to obtain the above effect, it is preferable to contain at least one of the TiO ₂ and ZrO ₂ or 1%. On the other hand, when TiO ₂ and ZrO ₂ are not contained, the above-described high refractive index crystal does not precipitate, so that a crystallized glass having translucency can be obtained.

When ZnO is added to the crystallized glass of the present invention, garnite crystals (ZnAl ₂ O ₄ ) are precipitated together with Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystals. Since garnite crystals have a higher refractive index than Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystals and matrix glass, crystallized glass with high whiteness can be obtained. Further, by providing a layer made of a colorant (for example, a metal oxide powder or an inorganic pigment powder) that can be dissolved in a garnite crystal on the glass surface, a crystallized glass with clear coloring can be obtained. The content of ZnO is 10% or less, preferably 6% or less. If the ZnO content exceeds 10%, the amount of garnite crystals precipitated becomes too large, and the main crystal, Li ₂ O—Al ₂ O ₃ —SiO ₂ crystal, becomes difficult to precipitate, resulting in crystallization. The later thermal expansion coefficient tends to increase. In order to precipitate garnite crystals and obtain a coloring effect, the content of ZnO is preferably 1% or more, more preferably 2% or more. On the other hand, when ZnO is not added, a garnite crystal does not precipitate, so that a crystallized glass having translucency can be obtained.

MgO, CaO, BaO, B ₂ O ₃ and Na ₂ O are all effective components for lowering the softening temperature of the crystallized glass. However, if the above range is exceeded, it becomes difficult to deposit desired crystals. In addition, in order to acquire the said effect, it is preferable to contain 1% or more of at least 1 sort (s) among these components.

P ₂ O ₅ has the effect of reducing the crystal grain size, but when it exceeds 0.8%, devitrification becomes strong. The lower limit is not particularly limited, in order to obtain the above effect, it is preferable to contain P ₂ O ₅ 0.1% or more.

In addition, SnO ₂ can be added as a clarifier in an amount of 0 to 1%, preferably 0.1 to 0.5%. Further, As ₂ O ₃ and Sb ₂ O ₃ can be added as other clarifiers in a range where the total amount of the clarifier does not exceed 5%.

  Furthermore, a crystallized glass based on a colored crystalline glass can be obtained by adding a coloring component to the composition. The content of the coloring component is 5% or less, preferably 1% or less in the crystalline glass composition. When content of a coloring component exceeds 5%, there exists a possibility that the degree of coloring of the crystallized glass obtained may become too strong, and a texture may be impaired. In addition, since the content of other components in the glass composition is relatively reduced, there are problems such as adversely affecting each physical property of the crystallized glass, for example, increasing the linear thermal expansion coefficient due to a decrease in crystallinity. Tend. The lower limit is not particularly limited, but is preferably 0.01% or more in order to obtain a sufficient coloring effect.

  As the coloring component, transition metal oxides such as cobalt oxide, nickel oxide, iron oxide, and vanadium oxide, or rare earth oxides such as praseodymium oxide, neodymium oxide, and cerium oxide are used. These may be used alone or in combination of two or more.

  The crystallized glass of the present invention can be produced, for example, by forming into a plate shape, a rod shape, or a tube shape, or by fusing and integrating a crystalline glass body that is a precursor of crystallized glass by heat treatment. Is possible.

(Examples 1-3)
(A) Preparation of crystallized glass sample The raw materials prepared so as to have the glass compositions shown in Table 1 were uniformly mixed, and then melted at 1600 to 1650 ° C for 12 hours using a platinum crucible. The molten glass was poured onto a carbon plate, formed into a 5 mm thick plate, and then slowly cooled by lowering the temperature from 700 ° C. to room temperature at a rate of 100 ° C./h in an electric furnace to obtain a plate glass. .

  Next, the plate glass was put into an electric furnace, heated from room temperature to 750 ° C. at a rate of 100 ° C./h, held for 1 hour, and further shown in Table 1 at a rate of 100 ° C./h. After raising the temperature to a predetermined firing temperature, the temperature was maintained for 1 hour. Then, the crystallized glass sample was produced by cooling to room temperature at a rate of 100 ° C./h in an electric furnace.

(B) Characteristics of each crystallized glass sample Table 1 shows the characteristics of the crystallized glass sample obtained. Each characteristic was evaluated as follows.

  The average linear thermal expansion coefficient, glass transition temperature, and yield temperature at 30 to 380 ° C. of each crystallized glass sample were measured using a dilatometer (TD5010 manufactured by Bruker AXS).

  The analysis of the precipitated crystal in each crystallized glass sample was performed using an X-ray diffractometer (RINT2100 manufactured by Rigaku).

  The crystal precipitation state in each crystallized glass sample was observed using a scanning electron microscope (S-4300SE, manufactured by Hitachi High-Technologies Corporation). In order to clarify the contrast between the crystal particles and the matrix glass, the fracture surface of the crystallized glass sample was etched with hydrofluoric acid (2% by mass-25 ° C.) for 4 minutes. The composition of the crystal phase and matrix glass (excluding Li) was analyzed using an energy dispersive X-ray analyzer (EMAX Energy EX-250 manufactured by Horiba, Ltd.) attached to the scanning electron microscope. The average particle size of the precipitated crystals is determined by measuring the particle size of the crystals in an electron microscope image of a randomly selected observation region using an image processing system (WinRoof Ver. 5 manufactured by Mitani Corp.) and calculating the average value. Were determined. The volume crystallinity (vol%) was determined by converting the area ratio of the crystal phase obtained from the image analysis result into a volume ratio.

(C) Difference in average linear thermal expansion coefficient between matrix glass and crystal The difference between both was calculated from the average linear thermal expansion coefficient of each of the matrix glass and the crystal calculated by the following procedure.

(Average linear thermal expansion coefficient of crystal phase)
First, the SiO ₂ amount x (mol%) in the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal was determined by the following procedure. It has been reported that a proportional relationship is established between the amount of SiO ₂ in β-quartz solid solution and β-spodumene solid solution crystals and a specific interplanar spacing in the crystal lattice (The Chemical Society of Japan (1974), 505. -510, and Japan Analyst Vol. 22 (1973), pages 745-751). From this, the SiO ₂ amount x (mol%) in the β-quartz solid solution and β-spodumene solid solution crystals can be expressed by the following formulas, respectively.

β-quartz solid solution: x = (0.1004-d (406)) / 6.752E-5
β-spodumene solid solution: x = (0.1286-d (217)) / 1.009E-4
Here, d (406) and d (217) are the interplanar spacing (nm) between the (406) plane and the (217) plane in the crystal lattice of β-quartz solid solution (hexagonal crystal) and β-spodumene solid solution (tetragonal crystal), respectively. ).

Further, x is by using the following relationship can be converted to crystal composition molar ratio n when expressed as _{Li 2 O · Al 2 O 3} · nSiO 2.

n = 2x / (100-x)
Using the interplanar spacing of the Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal determined by the X-ray diffraction method, the molar ratio n of SiO ₂ amount x (mol%) and SiO ₂ in each crystal phase from the above formula. It was determined.

Subsequently, the average linear thermal expansion coefficient of the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal was determined by the following procedure. It has been reported that the thermal expansion coefficient of Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal is correlated with the molar ratio n of SiO _{2 in} the crystal (Glastechn. Ber. 40 (1967)). 385, and J. Amer. Ceram. Soc. 51 (1968), 651). Accordingly, the relationship between the average linear thermal expansion coefficient of the β-quartz solid solution and the β-spodumene solid solution crystal and the molar ratio n of SiO ₂ is expressed by the following equations, respectively.

β-quartz solid solution:
When n <3 (Average linear thermal expansion coefficient) = (84.131n-218.18) × 10 ⁻⁷
In the case of 3 ≦ n ≦ 10 (Average linear thermal expansion coefficient) = − 11.5 × 10 ⁻⁷
When 10 <n <14 (Average linear thermal expansion coefficient) = (40.115 n−403.28) × 10 ⁻⁷
β-spodumene solid solution:
When 4 ≦ n ≦ 7 (Average linear thermal expansion coefficient) = (− 0.0581 n ³ +1.3829 n ² −12.284n + 37.632) × 10 ⁻⁷
The average linear thermal expansion coefficient of the crystal phase was determined from the above formula using the molar ratio n of SiO ₂ in the Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystal determined by the X-ray diffraction method.

(Average linear thermal expansion coefficient of matrix glass)
First, in order to determine the composition of the matrix glass, the mass crystallinity was calculated from the volume crystallinity of the crystallized glass and the density of the crystal phase and the matrix glass. Here, as the density of the crystal phase, the density of crystals having a similar molar ratio n reported in the powder X-ray diffraction data file (ICDD) was used. Further, as the density of the matrix glass, the density of the crystalline glass that is a precursor of the crystallized glass was used.

Subsequently, each component content (mol%) of the remaining matrix glass was determined by subtracting each component content (mol%) of the crystal phase from each component content (mol%) of the crystalline glass. Here, from the results of energy dispersive X-ray analysis, TiO ₂ and ZrO ₂ in the composition are distributed in equimolar amounts to the crystal phase and the matrix glass, and other components other than Li ₂ O, Al ₂ O ₃ , and SiO _2. Were all distributed in matrix glass. In the partition calculation, the contents of Li ₂ O and Al ₂ O ₃ were determined so that the mass% of the crystal phase coincided with the mass crystallinity described above.

  Subsequently, the average linear thermal expansion coefficient of the matrix glass was determined by the following procedure. It is known that an additivity rule is established between the linear thermal expansion coefficient and the composition of glass, and additivity factors of each glass component have also been reported (GLASS SCIENCE AND TECHNOLOGY 9, Mathematical Approach to Glass, chapter 15-16).

Using the composition of the matrix glass determined by the above procedure, the average linear thermal expansion coefficient of the matrix glass was determined according to the procedure described in the literature (Appen or Gan Fu-Si method). It was confirmed that the linear thermal expansion coefficient of the crystalline glass calculated by this method coincided with the actual measurement value with an accuracy within ± 1.5 × 10 ⁻⁷ / K.

  The difference between the crystal phase and the average linear thermal expansion coefficient of the matrix glass determined by the above procedure was determined.

(D) Theoretical value of average linear thermal expansion coefficient of crystallized glass The average value of linear thermal expansion coefficient of crystallized glass is based on the addition rule using the average linear thermal expansion coefficient and volume crystallinity of crystal and matrix glass. It was calculated by the following formula.

(Theoretical value of average linear thermal expansion coefficient) = ((Volume crystallinity) × (Average linear thermal expansion coefficient of crystal) + (100− (Volume crystallinity)) × (Average linear thermal expansion coefficient of matrix glass)) / 100
(Comparative Example 1)
A glass raw material was prepared so as to have the composition shown in Table 1, and after melting at 1600 ° C. in a melting furnace, it was formed into a plate shape having a thickness of 4 mm to produce a plate glass. Subsequently, after crystallizing the obtained plate glass on the baking conditions shown in Table 1, it stood to cool to room temperature and obtained the crystallized glass sample. About the obtained glass sample, the physical-property evaluation was performed similarly to Example 1. FIG. The results are shown in Table 1.

As apparent from Table 1, in the crystallized glass samples of Examples 1 to 3, β-spodumene solid solution was precipitated as 50% by mass as the main crystal. Moreover, since the difference of the average linear thermal expansion coefficient in 30-380 degreeC of matrix glass and a crystal | crystallization is larger than ^35x10 < ^-7 > / K in any sample, the obtained crystallized glass sample is 30x10. A low coefficient of linear expansion of ⁻⁷ / K or less was shown. These linear thermal expansion coefficients were lower than the linear thermal expansion coefficients calculated additively using the average linear thermal expansion coefficient and volume fraction of the crystal and matrix glass, respectively. The yield temperature was 900 ° C. or lower in any sample, and bending by heating was possible.

On the other hand, the crystallized glass sample of Comparative Example 1 has a linear thermal expansion coefficient of −1.0 × 10 ⁻⁷ / K, so that the thermal durability is good, but the crystallinity is greater than 70% by mass. Therefore, the yield temperature was not detected, and bending by heating was impossible.

  The crystallized glass of the present invention is a crystallized glass used as a cooking appliance top plate, particularly a gas stove top plate, a kitchen appliance top plate, a table top or other kitchen equipment decoration material, a component of a heating appliance, or other various interior and exterior materials. It is suitable as a glass article.

Claims (6)

A crystallized glass containing 20 to 70% by mass of Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal, wherein the matrix glass in the crystallized glass and the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal A crystallized glass characterized in that a difference in average linear thermal expansion coefficient at 30 to 380 ° C. is 35 × 10 ⁻⁷ / K or more. The crystallized glass according to claim 1, wherein the linear thermal expansion coefficient at 30 to 380 ° C. is 30 × 10 ⁻⁷ / K or less. _3. The crystallized glass according to claim 1, wherein the Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystal has an average particle size of 1 μm or more.   The crystallized glass according to any one of claims 1 to 3, wherein a yield temperature is 950 ° C or lower. By _{mass%, SiO 2 55~72%, Al} 2 O 3 14~30%, Li 2 O 1.5~5%, K 2 O 1~10%, TiO 2 0~5%, ZrO 2 0~4 %, TiO ₂ + ZrO ₂ 0-7%, ZnO 0-10%, MgO 0-3%, CaO 0-2.5%, BaO 0-5%, B ₂ O ₃ 0-7%, Na ₂ O 0 The crystallized glass according to claim 1, comprising a composition of ˜2% and P ₂ O ₅ 0-0.8%.   The crystallized glass according to any one of claims 1 to 5, wherein the crystallized glass is used as a constituent member of a cooking appliance top plate, a kitchen equipment decoration material or a heating appliance.