JP2012056786A - Method for producing crystallized glass and crystallized glass article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide crystallized glass which is excellent in uniformity of physical properties within a material and in reproducibility of physical properties between different production lots, and a method for easily and inexpensively producing such crystallized glass in a high yield.SOLUTION: The method for producing crystallized glass includes at least a step preceding crystallization of thermally treating raw glass in a temperature range of At(°C) to (At+120)°C, wherein At(°C) is the deformation point of the raw glass; and a crystallization step of thermally treating, after the step preceding crystallization, the resulting glass at a temperature higher than that in the step preceding crystallization.

Description

  The present invention relates to a method for producing crystallized glass, and relates to a technique for producing crystallized glass whose characteristics and quality are very stable.

  Crystallized glass is also called glass ceramics, and refers to a crystal in which crystals are precipitated by heat-treating amorphous glass. Crystallized glass can exhibit physical properties that are not found in the original glass due to the precipitated crystals. Various materials such as zero-expansion members, hard disk substrate materials, and optical filter substrate materials for WDM (wavelength division multiplexing) optical communication systems. It is used for

Among them, when used as an optical / mechanical precision member, the quality stability is very important. That is, it is important to have uniform physical properties in any part of the crystallized glass member or in different production lots.
In order to obtain uniform physical properties, the crystallized glass needs to have high homogeneity. In the case of crystallized glass, it is crystals precipitated in the glass phase that greatly contribute to the physical properties thereof. Therefore, in order to increase the homogeneity of the crystallized glass, in particular, the crystal size should be uniform and uniform. It is preferable to disperse the crystals.

However, in the past, it was very difficult to produce crystallized glass with high homogeneity at a high yield. The reason for this is that, in order to improve the homogeneity of the crystallized glass, it is considered necessary to make the composition of the material and the production conditions for precipitating the crystals the same with high accuracy. It is very difficult to set the same factor for each part or production lot of the original glass body with high accuracy, and some of these factors are used in industrial production assuming mass production at low cost. This is because fluctuations that are not intended by the manufacturer are inevitable.
In particular, when the size of the product shape is larger, the bulk body as a whole depends on the homogeneity of the composition of the bulk body of the original glass, the amount of heat during heat treatment for crystal precipitation, the difference in heat conduction to each part of the glass bulk body, etc. As a result, it was very difficult to obtain uniform physical properties with high yield.

Patent Document 1 discloses a composition of crystallized glass for an optical filter substrate material for a WDM (wavelength division multiplexing) optical communication system. Even if this crystallized glass is manufactured by a conventional manufacturing method, It was very difficult to obtain uniform physical properties with a high yield.
JP 2001-48584 A

  The present invention relates to a crystallized glass excellent in uniformity of physical properties inside a material and reproducibility of physical properties between different production lots, and a method for manufacturing such crystallized glass easily and at low cost with a high yield. It is an issue to provide.

  As a result of intensive studies in view of the above problems, the present inventor has found that the non-uniformity of the crystallized state of the crystallized glass is not caused by the manufacturing conditions for precipitating the crystal, but causes the crystal to precipitate. I discovered that there was an essential cause before the process. It is the non-uniformity of the thermal history experienced by the original glass before the heat treatment for precipitating crystals.

Factors that cause the non-uniform thermal history of the original glass before the heat treatment for precipitating crystals include, for example, the thermal history received during strip forming of the original glass and the thermal history during annealing.
As described in Japanese Patent Application Laid-Open No. 50-51516, the original glass for producing crystallized glass is a plate-like shape called a strip while continuously flowing the molten glass into a forming mold by a continuous melting method. Or manufacture may be performed by pulling out while shape | molding continuously in a rod-shaped shape.
At this time, the temperature drop rate of the molten glass is different between the center portion and the end portion of the mold, and the temperature drop rate is faster at the end portion. In addition, for the purpose of filling the glass to the end of the mold, only the end may be heated with a burner or the like, and even in this case, the thermal history may be different between the center and the end.
The original glass after strip forming is subjected to a simple annealing treatment. This processing is performed by forming a strip placed on a conveyor after molding through a tunnel furnace. In such a tunnel furnace, a precise heat treatment is performed so that the heat conduction of each part of the glass is uniform. Is impossible.

In this way, when the heat history that the original glass is subjected to before the heat treatment for precipitating the crystal is non-uniform, the non-uniformity of the crystallization state becomes noticeable when the conventional heat treatment for precipitating the crystal is performed. The inventor has found that it appears.
However, it is very difficult to make the thermal history received by the original glass before heat treatment for precipitating crystals from the cost of manufacturing equipment and other viewpoints.
Therefore, the present inventor has found a production method for obtaining a homogeneous crystallized glass even if the heat history before the heat treatment for precipitating the crystals is a heat history that makes the crystallization state non-uniform. The present invention has been completed, and its specific configuration is as follows.

(Configuration 1)
A method for producing crystallized glass, wherein when the yield point of the original glass is At (° C.), the pre-crystallization step of heat-treating the original glass in a temperature range of At (° C.) to (At + 120) ° C., and crystallization A method for producing crystallized glass comprising at least a crystallization step of performing a heat treatment at a temperature higher than that of the pre-crystallization step after the pre-step.
(Configuration 2)
The manufacturing method of the crystallized glass of the structure 1 which has the nucleus formation process heat-processed at temperature lower than the pre-crystallization process before the pre-crystallization process.
(Configuration 3)
The method for producing crystallized glass according to Configuration 1 or 2, wherein the heat treatment time in the pre-crystallization step is 1 h to 20 h, and the heat treatment time in the crystallization step is 1 h to 20 h.
(Configuration 4)
The manufacturing method of the crystallized glass in any one of the structures 1 to 3 whose heat processing time of the said nucleation process is 1h-20h.
(Configuration 5)
The crystallized glass according to any one of the constitutions 1 to 4, wherein the first crystal phase is precipitated in the pre-crystallization step and the first crystal phase is transformed into the second crystal phase in the crystallization step. Manufacturing method.
(Configuration 6)
The crystallized glass contains lithium disilicate and at least one selected from α-quartz, α-quartz solid solution, α-cristobalite, and α-cristobalite solid solution as a crystal phase. 6. The method for producing a crystallized glass according to any one of 5 above.
(Configuration 7)
6. The method for producing crystallized glass according to Structure 5, wherein the first crystal phase contains lithium monosilicate.
(Configuration 8)
The composition of the raw glass is a mass percentage based on oxide,
SiO ₂ 60~80%,
Li ₂ O 5-15%,
K ₂ O 0-5%,
MgO + ZnO + SrO + BaO 1-10%,
P ₂ O ₅ 0.5~5%,
ZrO ₂ 0-7%,
Al ₂ O ₃ 1-15%,
The manufacturing method of the crystallized glass of the structures 1-7 containing each component of these.
(Configuration 9)
The composition of the raw glass is a mass percentage based on oxide,
CeO ₂ 0-2%,
SnO ₂ 0-2%,
Sb ₂ O ₃ 0-2%,
The manufacturing method of the crystallized glass in any one of the structures 1-8 containing each component of these.
(Configuration 10)
The crystal grain size distribution of the main crystal phase is within a range of 0.05 μm, and in the plane having the maximum area, the distribution width of the average linear expansion coefficient of the plane is 0 × 10 ⁻⁷ ° C. ^{−1 to} 3 × 10 ⁻⁷ ° C. A crystallized glass article that is ^-1 .
(Configuration 11)
The crystallized glass article according to Configuration 10, comprising lithium disilicate as a crystal phase and at least one selected from α-quartz, α-quartz solid solution, α-cristobalite, and α-cristobalite solid solution.
(Configuration 12)
Oxide-based mass percentage
SiO ₂ 60~80%,
Li ₂ O 5-15%,
K ₂ O 0-5%,
MgO + ZnO + SrO + BaO 1-10%,
P ₂ O ₅ 0.5~3%,
Al ₂ O ₃ 1-15%,
The crystallized glass article according to the constitution 10 or 11 containing each of the components.

  The present invention provides a crystallized glass excellent in uniformity of physical properties inside a material and reproducibility of physical properties between different production lots, and such crystallized glass with high yield, easily and at low cost. A method of manufacturing can be provided.

The crystallized glass article of the present invention obtained by the production method of the present invention has a crystal grain size distribution value of the main crystal phase within a range of 0.05 μm or less.
“Crystal grain size distribution” refers to a value measured by the following procedure. That is, the longest distance when an image of an arbitrary part at a magnification of 100,000 to 500,000 is obtained by a TEM (transmission electron microscope) and the crystal appearing in the obtained image is sandwiched between two parallel straight lines. Is the grain size of the crystal. This is measured for 100 randomly selected crystals, and the absolute value of the difference between the 95th and 5th percentile crystal grain size values is taken as the value of the crystal grain size distribution.

Further, in the crystallized glass article of the present invention obtained by the production method of the present invention, the distribution width of the average linear expansion coefficient of the surface is 0 × 10 ⁻⁷ ° C. ^{−1 to} 3 × 10 10 on the surface having the maximum area. ^-7 ° C ^-1 . The “distribution width of the average linear expansion coefficient of the surface” refers to the difference between the maximum value and the minimum value of the expansion coefficients measured at intervals of 1 cm in one direction on the surface. Here, since the expansion coefficient is determined by the amount of precipitated crystals in the case of crystallized glass, in accordance with JOGIS (Japan Optical Glass Industry Association Standard) 16-2003 “Measurement Method of Average Linear Expansion Coefficient of Optical Glass Near Room Temperature” By measuring the expansion coefficient measured using a single-press type dilatometer (temperature range -30 ° C to 70 ° C) and correlating this with the integrated intensity value of the crystal peak by an X-ray diffractometer (XRD), XRD The value of was converted and used as an expansion coefficient.

The crystallized glass article of the present invention obtained by the production method of the present invention has a distribution width of an average linear expansion coefficient in the direction orthogonal to the plane having the maximum area of 0 × 10 ⁻⁷ ° C. ^{−1 to} 3 × 10. ^-7 ° C ^-1 . "The distribution width of the average linear expansion coefficient in the direction orthogonal to the surface having the largest area" means the average linear expansion coefficient in the direction orthogonal to the surface having the largest area in any surface orthogonal to the surface having the largest area. This is the distribution width, which is the difference between the maximum value and the minimum value of the specimens that are ground in the direction and sample pieces are produced at 1 mm intervals, and the value of XRD is similarly converted into the expansion coefficient.

It is the heating schedule of crystallized glass manufacture in the past. Is a diagram illustrating a result of nucleation temperature test, for each heat treatment temperature, the exothermic peak temperature TP and the exothermic peak temperature of the samples not subjected to heat treatment T _P respective differences of the reciprocal of ⁰ (1 / T P _-1 / T _P ⁰⁾ is a plot of. 6 is an in-plane CTE distribution graph in Example 1, Comparative Example 1, and Comparative Example 2. It is an average linear expansion coefficient (CTE) distribution graph of the thickness direction in Example 2 and Comparative Example 2.

Generally, glass is in a thermodynamically unstable state as compared with crystals, and there is a possibility that changes to crystals occur. However, in an oxide glass, crystallization usually does not occur because migration of atoms hardly occurs at a temperature much lower than the glass transition temperature Tg.
Crystallization occurs in the Tg region or in a thermodynamically supercooled liquid state at temperatures above that. Crystallization of glass (crystals are deposited in the glass phase of the original glass) requires the generation of crystal nuclei and subsequent growth of the nuclei (crystal growth). If no crystal growth occurs, it cannot be said that crystallization has occurred.

Since the temperature at which nucleation occurs is generally lower than the temperature at which crystal growth occurs, crystallization has traditionally been considered separately in the above two processes and should be held at two temperatures to accommodate this. Heat treatment.
That is, according to the heating schedule shown in Figure 1 in the conventional performs pretreated in the vicinity of T _I where nucleation rate becomes maximum, after generating a sufficiently large number of crystal nuclei, the crystal growth rate is maximized it is common to drive growth in T _U vicinity.

Where T _I may be obtained by using a DTA (differential thermal analysis).
That is, an exothermic peak accompanying crystal precipitation or nucleation appears in the DTA curve of the original glass. Therefore, first, samples having nuclei generated by heat treatment at various temperatures from Tg to Tx (crystallization start temperature) for a predetermined time (for example, 2 hours) are prepared. When DTA is performed with the heating rate kept constant for these samples, the temperature TP of the exothermic peak due to crystallization is lower in the sample having a larger number of nuclei generated by heat treatment. The difference in the respective reciprocals of the exothermic peak temperature TP0 in this exothermic peak temperature T _P and no heat treatment is performed samples, when plotted against each heat treatment temperature _{(1 / T P -1 / T} P 0), FIG. 2 A curve as shown in FIG. Temperature giving a peak of the curve is approximately equal to T _I.
Further, T _U it can be determined by DTA exothermic peak, crystal deposition amount to obtain a final required characteristics are determined in the obtained temperature.

  On the other hand, in the present invention, three steps are defined for the heat treatment for precipitating crystals from the original glass. These three steps are defined as “nucleation step”, “pre-crystallization step”, and “crystallization step” in the order of steps, and are characterized in that each step is maintained in a specific temperature range and the original glass is heat-treated. To do. The crystallization process has a higher heat treatment temperature than the pre-crystallization process, and the nucleation process has a lower heat treatment temperature than the pre-crystallization process. The nucleation step is not essential and may be omitted.

  The steps before the step of precipitating crystals are as follows. First, in accordance with a normal method, raw materials are prepared and melted to obtain molten glass, and the molten glass is cooled to form an original glass. If necessary, this is annealed to remove the distortion of the glass.

  The raw glass thus manufactured is subjected to heat treatment for crystal precipitation. Usually, the original glass is cooled to room temperature. This raw glass is put into a heat treatment furnace and heat treatment is started. First, a nucleation process is performed. In this step, the temperature of the heat treatment furnace is increased at a predetermined rate until the temperature reaches a predetermined temperature, and this temperature range is maintained for a certain period of time after reaching the predetermined temperature range. This generates a large number of nuclei in the original glass. Compared with the case where the pre-crystallization step described later is performed by this step, it is possible to increase the rate of temperature rise from room temperature when the nucleation step is performed. The predetermined temperature range in the nucleation step is a range lower than the heat treatment temperature range in the pre-crystallization step described later. More specifically, the predetermined temperature range in the nucleation step is preferably in the range of 500 ° C. to 560 ° C., and more preferably in the range of 520 ° C. to 540 ° C. The holding time is preferably in the range of 1h to 20h, and more preferably in the range of 2h to 10h. Moreover, the temperature rising rate is preferably in the range of 30 ° C./h to 300 ° C./h, more preferably in the range of 80 ° C./h to 200 ° C./h. As described above, the nucleation step may be omitted, and after the raw glass is placed in a heat treatment furnace, the temperature may be raised to a heat treatment temperature range in a pre-crystallization step described later.

Next, a pre-crystallization process is performed. The crystallization step is a step of precipitating the first crystal phase from the generated nuclei. After finishing the nucleation step or until the temperature reaches a predetermined temperature from the start of the heat treatment, the temperature of the heat treatment furnace is increased, and this temperature range is maintained for a certain period of time after reaching the predetermined temperature range. The predetermined temperature range in the pre-crystallization step is in the range of At ° C. to [At + 120] ° C. when the deformation point of the original glass is At ° C.
By maintaining the original glass in the temperature range from At ° C. to [At + 120] ° C. and heat-treating it in this way, the uniformity of the crystallization state is increased even for the original glass that has received a non-uniform thermal history. Is possible. That is, the particle diameter of the crystals to be precipitated can be made uniform within a certain range, and the crystals can be uniformly dispersed within the certain range to precipitate the crystals.
This is presumably because the first crystal phase can be stably and uniformly precipitated by heat treatment in the above temperature range regardless of the state of the nuclei in the glass.
In order to obtain this effect, a more preferable range of the predetermined temperature range in the pre-crystallization step is [At + 10] ° C. or more and [At + 100] ° C. or less, and most preferably [At + 20] ° C. or more and [At + 80] or less. The holding time is preferably in the range of 1h to 20h, and more preferably in the range of 2h to 10h. Further, the rate of temperature rise is preferably in the range of 10 ° C / h to 100 ° C / h, and more preferably in the range of 20 ° C / h to 80 ° C / h.
In the present invention, it is important to perform the heat treatment in the above temperature range before the heat treatment for crystal growth, and the name of the heat treatment step called “pre-crystallization step” is for convenience. The use of such designations is irrelevant to the technical scope of the present invention.

  Moreover, At of original glass can be measured with the following method. A glass processed into a rod-like shape is used, and the temperature at which the glass stretches during heating is stopped by a one-push type dilatometer and the deformation starts due to a measurement load on the glass is defined as At (bending point).

After the pre-crystallization process, a crystallization process is performed. After finishing the pre-crystallization step, the temperature of the heat treatment furnace is increased at a predetermined speed until the temperature reaches a predetermined temperature, and this temperature range is maintained for a certain period of time after reaching the predetermined temperature range. As a result, the first crystal phase precipitated in the pre-crystallization step is grown, or the first crystal phase is transformed into the second crystal phase, so that the crystallized glass is finally obtained as desired. It shall have a crystal phase. By performing the pre-crystallization step, the final crystallization state after the crystallization step becomes highly uniform, and the variation in the crystallization state for each production lot becomes small.
The predetermined temperature range in the crystallization step is a range higher than the heat treatment temperature range in the pre-crystallization step. More specifically, the predetermined temperature range in the crystallization step is preferably in the range of 680 ° C. to 800 ° C., and more preferably in the range of 700 ° C. to 780 ° C. The holding time is preferably in the range of 1h to 20h, and more preferably in the range of 2h to 10h. Further, the rate of temperature rise is preferably in the range of 10 ° C / h to 100 ° C / h, and more preferably in the range of 20 ° C / h to 80 ° C / h.

The method for producing crystallized glass of the present invention finally includes at least one selected from the group consisting of lithium disilicate and α-quartz, α-quartz solid solution, α-cristobalite, α-cristobalite solid solution. This is particularly effective when producing crystallized glass.
Among them, when used for an optical filter substrate material for a WDM optical communication system, if the crystal phase contains lithium disilicate, mechanical characteristics, thermal expansion coefficient, light transmittance, etc. are likely to be desired, preferable.

In addition, when the crystal phase is finally included, it is preferable to deposit lithium monosilicate as the first crystal phase to be precipitated in the pre-crystallization step.
That is, lithium monosilicate is precipitated as the first crystal phase in the pre-crystallization step, and selected from lithium disilicate and α-quartz, α-quartz solid solution, α-cristobalite, α-cristobalite solid solution in the crystallization step. By performing phase transformation to at least one selected from the above, in particular by phase transformation to lithium disilicate, the final crystallization state becomes highly uniform.

  In order to obtain crystallized glass containing the above crystal phase, the composition range of the original glass is preferably set as follows. In addition, content of each component is shown by the mass% of an oxide basis. Here, “oxide standard” means that glass or crystallized glass is assumed on the assumption that oxides, nitrates, and the like used as raw materials for constituent components of glass or crystallized glass are all decomposed and changed into oxides when melted. In this method, the composition of each component contained therein is represented, and the amount of each component contained in the glass or crystallized glass is represented, with the total mass of the generated oxides being 100 mass%.

The SiO ₂ component is a very important component that forms lithium disilicate, α-quartz, α-quartz solid solution, α-cristobalite, α-cristobalite solid solution precipitated as the main crystal phase by heat treatment of the raw glass. If the amount is less than 60%, the precipitated crystals of the obtained glass ceramic are unstable and the structure tends to be coarsened. If it exceeds 80%, it becomes difficult to melt and form the original glass. Therefore, the content is preferably 60% to 80%, and more preferably 65% to 78%.

The Li ₂ O component is a very important component that generates lithium disilicate that precipitates as the main crystal phase by heat treatment of the raw glass. However, if its amount is less than 5%, it becomes difficult to precipitate the crystal, It becomes difficult to melt the original glass. On the other hand, if it exceeds 15%, the resulting crystals are unstable and the structure tends to be coarsened, and the chemical durability deteriorates. Therefore, the content is preferably 5% to 15%, more preferably 7% to 11%.

The K ₂ O component is a component that improves the meltability of the glass and at the same time prevents coarsening of the precipitated crystals, and can be optionally contained. However, if it is contained excessively, coarsening of the precipitated crystals, crystal phase change and chemical durability are deteriorated, so the amount is preferably 5% or less. More preferably, it is 0.5% to 3%.

  The MgO, ZnO, SrO, and BaO components improve the meltability of the glass and at the same time prevent the coarsening of the precipitated crystals and adjust the light transmittance by adjusting the refractive index of the glass phase that is the matrix. However, if the total amount of each component is less than 1%, these effects cannot be obtained, and if it exceeds 10%, the resulting crystals are unstable and the structure tends to become coarse. Therefore, the total content of these components is preferably 1% to 10%, more preferably 1% to 7%.

In the present invention, the P ₂ O ₅ component is indispensable as a nucleating agent for precipitated crystals, but 0.5% or more is preferable for obtaining the effect. Moreover, 5% or less is preferable in order to prevent devitrification of the original glass and maintain mass production stability. More preferably, it is 1% to 3%.

The ZrO ₂ component, like the P ₂ O ₅ component, functions as a nucleating agent for precipitated crystals, and has a remarkable effect on refining the precipitated crystals, improving the mechanical strength of the material, and improving chemical durability. It has been found that it can be optionally contained. In order to obtain these effects, ZrO ₂ is more preferably 2% or more. However, if it is added excessively, melting of the original glass becomes difficult and at the same time unmelted ZrSiO ₄ or the like is generated, so 7% or less is preferable.

The Al ₂ O ₃ component is a component that improves the chemical durability and mechanical strength of the glass ceramic, particularly the bending strength, and in order to obtain this effect, its amount needs to be 1% or more, More preferably, it is 4% or more. On the other hand, if the Al ₂ O ₃ component is excessive, meltability and devitrification resistance deteriorate, and β-spodumene and β-cristobalite are precipitated as a precipitated crystal phase. Therefore, the Al ₂ O ₃ component is preferably 15% or less, and more preferably 8% or less.

CeO ₂ , SnO ₂ , and Sb ₂ O ₃ and components can be added as fining agents during glass melting, but these components are sufficient to be 2% or less, more preferably 1% or less. However, the Sb ₂ O ₃ component can be substantially not included in consideration of the influence on the human body and the environment.

Similarly, As ₂ O ₃ and PbO are environmentally undesirable components and should be avoided as much as possible.

Hereinafter, the article according to the present invention will be described with reference to specific examples.
SiO ₂ 75%, Li ₂ O 10%, K ₂ O 1%, MgO 1%, ZnO 0.5%, P ₂ O ₅ 2%, ZrO ₂ 3%, Al ₂ O ₃ 7%, Sb ₂ O ₃ A composition glass composed of 0.5% was melted and flowed out onto a mold (molding die), and a plate-like glass was produced by continuous molding.
The mold was water-cooled to prevent seizure at the time of glass outflow, a roller was placed on the top to roll the glass into a plate shape, and the glass was molded so that the glass thickness was 20 mm.
At this time, the glass lot. In A, the edge of the sheet glass was not heated by a burner during molding, and the glass lot. In B, the edge part of the sheet glass was heated with the burner at the time of shaping | molding.
The glass after molding was subjected to rough annealing and cooling, and then a flat original glass of about 20 cm × 20 cm × 20 mm was obtained and subjected to heat treatment for crystal precipitation. The heat treatment conditions were carried out according to the following schedule for each example and comparative example. Each example and comparative example are described in the order of the heating rate, the holding temperature, and the holding time.
Moreover, it was 570 degreeC when At of glass was measured.

[Example 1]
Nucleation process: 100 ° C./h, 540 ° C., 5 hr
Pre-crystallization process: 30 ° C./h, 620 ° C. 2 hr
Crystallization step: 30 ° C./h, 760 ° C. 2 hr
Raw glass: Glass lot. A

[Example 2]
Nucleation step: None Pre-crystallization step: 80 ° C./h, 620 ° C. 5 hr
Crystallization step: 30 ° C./h, 760 ° C. 2 hr
Raw glass: Glass lot. A

[Example 3]
Nucleation process: 100 ° C./h, 540 ° C., 5 hr
Pre-crystallization process: 30 ° C./h, 620 ° C. 2 hr
Crystallization step: 30 ° C./h, 760 ° C. 2 hr
Raw glass: Glass lot. B

[Example 4]
Nucleation step: None Pre-crystallization step: 80 ° C./h, 620 ° C. 5 hr,
Crystallization step: 30 ° C./h, 760 ° C. 2 hr
Raw glass: Glass lot. B

[Comparative Example 1]
Nucleation step: 100 ° C./h, 540 ° C. 5 hr,
Crystallization step: 30 ° C./h, 770 ° C. 2 hr
Raw glass: Glass lot. A

[Comparative Example 2]
Nucleation process: 100 ° C./h, 540 ° C., 5 hr
Crystallization step: 30 ° C./h, 770 ° C. 2 hr
Raw glass: Glass lot. B

The comparative example is the nucleation temperature determined by the nucleation temperature determination means by DTA described above.
The average coefficient of linear expansion was measured for each sample of crystallized glass produced by performing heat treatment for crystal precipitation on the above heat treatment schedule.
The average linear expansion coefficient is measured by measuring the distribution of the average linear expansion coefficient on the surface having the maximum area (in-plane direction distribution) and the distribution of the average linear expansion coefficient in the direction perpendicular to the surface having the maximum area (plate thickness). Direction distribution).
The results are shown in Table 1. As can be seen from the above, the thermal expansion coefficient uniformity of the crystallized glass bulk was improved in the production method of the present invention.

In addition, the in-plane average linear expansion coefficient (CTE) distribution graph in Example 1, Comparative Example 1 and Comparative Example 2 is shown in FIG. 3, and the CTE distribution graph in the plate thickness direction in Example 2 and Comparative Example 2 is shown in FIG. Show.
FIG. 3 is an in-plane direction distribution, and is a graph when the in-plane CTE distribution is seen in a direction perpendicular to the drawing direction at the time of glass forming (the width direction of the strip-formed glass material).
FIG. 4 is a graph showing the CTE distribution in the plate thickness direction of the glass material formed into a strip, that is, the central portion of the forming plate at the time of glass forming from the upper surface to the lower surface.

In FIG. 3, when the pattern of the in-plane distribution of the CTE of Comparative Example 1 as a conventional heat treatment schedule is seen, the CTE for both ends is low and the center CTE is high, which is a large variation. This is because the effect of retaining the heat of the spilled glass at the time of glass forming remains in the central part, and the end part is due to the rapid cooling. For this reason, the state of the nuclei is inevitably different, and this is the difference.
Moreover, in the comparative example 2, it is the example which crystallized about the glass which performed the end part burner heating for the moldability improvement of the both ends. An increase in CTE at the end is confirmed due to the influence of heating, and as in Comparative Example 1, there is a large variation.
On the other hand, the CTE of Example 1 according to the present invention is almost the same value in a straight line, and it can be seen that the thermal expansion coefficient in the in-plane direction is very stable.

  FIG. 4 shows the CTE distribution in the thickness direction of Example 2 and Comparative Example 2. In the comparative example, an abrupt heat exchange phenomenon due to contact with the mold and an influence of nucleation generation due to the effect of internal heat storage are seen in the upper and lower parts, and the distribution of CTE greatly changes in the thickness direction. On the other hand, in Example 2, such a change in the CTE value was not observed at all, and a very uniform value was obtained.

  Next, for Example 1 and Comparative Example 1, when the crystal grain size of the main crystal phase was measured and the crystal grain size distribution was calculated, it was 0.02 μm in Example 1 and 3 μm in Comparative Example 1. Thus, also about the particle size of a precipitation crystal | crystallization, it turns out that the crystallized glass manufactured by the manufacturing method of this invention has high uniformity.

  As described above, according to the manufacturing method of the present invention, the final CTE in the crystallized glass bulk can be stabilized by the stable precipitation of the first phase regardless of the difference in the state of the base glass (difference in nuclei, etc.). I can plan. Accordingly, this makes it possible to produce a crystallized glass having a very high uniformity of physical properties in the bulk body with a high yield.

Claims (12)

  A method for producing crystallized glass, wherein when the yield point of the original glass is At (° C.), the pre-crystallization step of heat-treating the original glass in a temperature range of At (° C.) to (At + 120) ° C., and crystallization A method for producing crystallized glass comprising at least a crystallization step of performing a heat treatment at a temperature higher than that of the pre-crystallization step after the pre-step.   The manufacturing method of the crystallized glass of Claim 1 which has the nucleation process heat-processed at temperature lower than the pre-crystallization process before the pre-crystallization process.   The method for producing crystallized glass according to claim 1 or 2, wherein a heat treatment time in the pre-crystallization step is 1h to 20h, and a heat treatment time in the crystallization step is 1h to 20h.   The method for producing crystallized glass according to any one of claims 1 to 3, wherein a heat treatment time in the nucleation step is 1h to 20h.   The crystallization according to any one of claims 1 to 4, wherein a first crystal phase is precipitated in the pre-crystallization step, and the first crystal phase is transformed into a second crystal phase in the crystallization step. Glass manufacturing method.   The crystallized glass contains lithium disilicate as a crystal phase and at least one selected from α-quartz, α-quartz solid solution, α-cristobalite, and α-cristobalite solid solution. To 5. The method for producing a crystallized glass according to any one of 5 to 5.   The method for producing crystallized glass according to claim 5, wherein the first crystal phase contains lithium monosilicate. The composition of the raw glass is a mass percentage based on oxide,
SiO ₂ 60~80%,
Li ₂ O 5-15%,
K ₂ O 0-5%,
MgO + ZnO + SrO + BaO 1-10%,
P ₂ O ₅ 0.5~5%,
ZrO ₂ 0-7%,
Al ₂ O ₃ 1-15%,
The manufacturing method of the crystallized glass of Claims 1-7 containing each component of these. The composition of the raw glass is a mass percentage based on oxide,
CeO ₂ 0-2%,
SnO ₂ 0-2%,
Sb ₂ O ₃ 0-2%,
The manufacturing method of the crystallized glass in any one of Claim 1 to 8 containing each component of these. The crystal grain size distribution of the main crystal phase is in the range of 0.05 μm or less, and in the plane having the maximum area, the distribution width of the average linear expansion coefficient of the plane is 0 × 10 ⁻⁷ ° C. ^{−1 to} 3 × 10 ^−7. A crystallized glass article having a temperature of ⁻¹ .   The crystallized glass article according to claim 10, comprising at least one selected from lithium disilicate and α-quartz, α-quartz solid solution, α-cristobalite, α-cristobalite solid solution as a crystal phase. Oxide-based mass percentage
SiO ₂ 60~80%,
Li ₂ O 5-15%,
K ₂ O 0-5%,
MgO + ZnO + SrO + BaO 1-10%,
P ₂ O ₅ 0.5~3%,
ZrO ₂ 0-7%,
Al ₂ O ₃ 1-15%,
The crystallized glass article of Claim 10 or 11 containing each component of these.