JP2001097739A - Production method of crystallized glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of crystallized glass capable of reducing the fluctuation of coefficient of thermal expansion corresponding with respect to the fluctuation of crystallizing temperature by retaining material glass at a specific nucleation temperature and then retaining at the crystallizing temperature to crystallize at least an α-quartz phase. SOLUTION: The material glass is retained at a nucleation temperature and then retained at a crystallization temperature to crystallize the material glass for depositing at least its α-quartz phase. In this case, the nucleation temperature is adjusted at 620-680 deg.C, and as a result, the difference Δα between the maximum and the minimum of coefficients of thermal expansion of the crystallized glass obtained by crystallizing in a range, a standard crystallizing temperature ±10 deg.C, is controlled to Δα<=10×10-7/k.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing crystallized glass.

[0002]

2. Description of the Related Art For magnetic disk applications, crystallized glass having a coefficient of thermal expansion around room temperature of 60 to 130 × 10 ⁻⁷ / k, preferably 60 to 90 × 10 ⁻⁷ / k is required. In order to improve the recording density, it is essential to reduce the flying height of the magnetic head. Therefore, a smooth surface is required for the magnetic disk. In order to increase the coefficient of thermal expansion of the so-called LAS-based crystallized glass to 60 × 10 ⁻⁷ / k or more, it is necessary to precipitate crystals having a large coefficient of thermal expansion.
Crystals having a large coefficient of thermal expansion include cristobalite,
Although there are tridymite and α-quartz, it is advantageous to use α-quartz which easily precipitates as fine crystals to obtain a smooth surface.

[0003]

However, α-quartz precipitated in crystallized glass is very sensitive to the heat treatment temperature, and the coefficient of thermal expansion of crystallized glass varies considerably due to a slight temperature difference. The number of defective products increases, which is not suitable for mass production.

Japanese Patent Publication No. 6-29152 discloses P ₂ O
Disclosed is a crystallized glass containing α-cristobalite and lithium disilicate as main crystals containing ₅ and MgO as essential components. In this patent, it is described that the thermal expansion coefficient is excellent in stability with respect to the crystallization temperature, because α-cristobalite is precipitated. JP 11
JP-A-16151 and JP-A-11-16143 disclose crystallized glass for a magnetic disk having α-quartz and lithium disilicate as main crystals. This patent does not describe the stability of the coefficient of thermal expansion with respect to the crystallization temperature. In addition, since α-quartz is precipitated in an aggregated form, the center line average surface roughness Ra after precision polishing is
Is relatively large. JP-A-10-226532 discloses that the main crystal is lithium disilicate and the sub crystal is α-
A quartz crystallized glass for a magnetic disk is disclosed.
In this patent, nucleation occurs at 550-600 ° C. JP-A-7-101750 discloses that P ₂ O ₅ and T
The iO ₂ was an essential component, the main crystal of α- quartz and lithium disilicate glass-ceramics is disclosed. Although it is described that the thermal expansion coefficient has excellent stability with respect to the crystallization temperature, the lithium metasilicate phase has poor weather resistance and is not suitable for magnetic disk applications.

It is an object of the present invention to maintain the raw glass at a nucleation temperature and then at a crystallization temperature to crystallize the raw glass, in which case at least the α-quartz phase is precipitated. Is to reduce the variation of the coefficient of thermal expansion with respect to the variation of

[0006]

SUMMARY OF THE INVENTION The inventor of the present invention has proposed a method of maintaining a raw glass at a nucleation temperature and then at a crystallization temperature to crystallize the raw glass, wherein at least an α-quartz phase is precipitated. In the method for producing glass frit, by setting the nucleation temperature to 620-680 ° C., the heat of the crystallized glass obtained when crystallizing at a temperature within ± 10 ° C. with respect to the reference crystallization temperature is obtained. the difference Δα between the maximum value and the minimum value of the expansion coefficient of 10 × 10 ^- found that can be controlled to below ⁷ / k, have reached the present invention.

Here, the reference crystallization temperature is a target crystallization temperature in the production process of crystallized glass. In an actual mass production process, the crystallization temperature of each product is at least ±
There is an error of about 10 ° C. Δα is the coefficient of thermal expansion α of the crystallized glass obtained when the original glass is crystallized at each crystallization temperature within a range of ± 10 ° C. with respect to the reference crystallization temperature.
Is a difference between the maximum value and the minimum value, and is an index indicating the variation of the thermal expansion coefficient α at the time of manufacture. The coefficient of thermal expansion α is −
It is a coefficient of thermal expansion in a temperature range of 50 ° C-+ 70 ° C.

[0008] The present invention is based on the following findings.

Generally, nucleation during crystallization is usually performed in a temperature range as high as about 30 to 40 ° C., which is the glass transition point. The present inventors have found that, when nucleation is performed at various temperatures in crystallized glass on which α-quartz is precipitated, the amount of α-quartz deposited changes according to the nucleation temperature, and peaks at about 610 ° C. Was found.

This point will be described with reference to the graph of FIG. The horizontal axis of the graph in FIG. 1 is the nucleation temperature, and the vertical axis is the thermal expansion coefficient α. As the nucleation temperature increased, the thermal expansion coefficient α increased, peaked at about 610 ° C., and at temperatures higher than this, the thermal expansion coefficient α gradually decreased.

On the other hand, when the crystallization temperature rises, the precipitation amount of the α-quartz phase in the crystallized glass increases, and the thermal expansion coefficient α tends to increase.

Conventionally, nucleation is usually performed at a nucleation temperature of 610 ° C. or less, ie, a nucleation temperature in a region where the slope of the graph is positive in FIG. 1, and then maintained at a predetermined crystallization temperature for a predetermined time. Was. It has been discovered that such a method amplifies the variation of the coefficient of thermal expansion α with the variation of the crystallization temperature.

In a heat treatment apparatus such as an electric furnace, the set nucleation temperature and crystallization temperature are
Usually, an error of about ± 10 ° C. occurs.
At this time, when the nucleation temperature is higher than the set value, the crystallization temperature is rarely lower than the set value, and usually both are higher or lower than the respective set values.

Therefore, conventionally, when the nucleation temperature is higher than the set value, the precipitation amount of α-quartz increases as described above. At the same time, when the crystallization temperature becomes higher than the set value, the precipitation amount of α-quartz also increases. For this reason, the precipitation amount of α-quartz in the crystallized glass as a whole became larger than the target value, and the thermal expansion coefficient α of the glass increased. Also, when the nucleation temperature is lower than the set value, the precipitation amount of α-quartz is lower than the target value, and when the crystallization temperature is lower than the set value, the precipitation amount of α-quartz is also lower. I do. For this reason, the thermal expansion coefficient α of the crystallized glass decreased.

On the other hand, according to the present invention, the nucleation temperature is 620-680 ° C. That is, a nucleation temperature higher than 610 ° C. at which the amount of precipitated α-quartz increases most is used. In this temperature range, as the nucleation temperature rises, the amount of precipitated α-quartz decreases.

That is, when the nucleation temperature is higher than the set value, the precipitation amount of α-quartz decreases as compared with the target value. At the same time, when the crystallization temperature becomes higher than the set value,
The precipitation amount of α-quartz increases as compared with the target value. For this reason, as a whole, the variation of the precipitation amount of α-quartz in the crystallized glass from the target value is reduced. Similarly, when the nucleation temperature is lower than the set value, the precipitation amount of α-quartz increases from the target value. Decrease.
For this reason, the variation of the amount of precipitated α-quartz in the crystallized glass from the target value is reduced as a whole.

Therefore, according to the present invention, the maximum and minimum values of the thermal expansion coefficient of the crystallized glass obtained when crystallizing at a temperature within the range of ± 10 ° C. with respect to the reference crystallization temperature are determined. the difference Δα can be reduced, and in particular 10 × 10 ^- could be controlled below ⁷ / k.

If the nucleation temperature is lower than 620 ° C., the above-mentioned effects cannot be obtained. When the nucleation temperature exceeds 680 ° C., the nucleation action becomes insufficient, the α-quartz phase does not sufficiently precipitate, and the thermal expansion coefficient α decreases. The nucleation temperature is preferably 640 ° C. or higher, more preferably 670 ° C. or lower.

The crystallization temperature is preferably set at 700-740 ° C. Thereby, the α-quartz phase can be appropriately precipitated, whereby the coefficient of thermal expansion can be set to a desired value.

The crystal phase of the crystallized glass is not particularly limited, but preferably includes a lithium disilicate phase, and more preferably a petalite phase, in addition to the α-quartz phase.

At this time, it is preferable that each crystal quantitative value by the Rietveld quantitative method is in the following range, whereby the thermal expansion coefficient in the range of -50 ° C to 70 ° C is 60 to
It could be adjusted to about 130 × 10 ⁻⁷ / k. 5% by weight ≦ Petalite phase ≦ 45% by weight 25% by weight ≦ Lithium disilicate phase ≦ 45% by weight 5% by weight ≦ α-quartz phase ≦ 40% by weight

Particularly, by precipitating more petalite phases than the α-quartz phase, the coefficient of thermal expansion in the range of -50 ° C. to 70 ° C. is adjusted to about 60 to 90 × 10 ⁻⁷ / k. Was completed. In addition, it was found that by precipitating the petalite phase as the main crystal, the surface roughness after precision polishing of the crystallized glass was reduced. Further, by increasing the amount of crystals of the petalite phase, the amount of lithium eluted is significantly reduced.

The composition of each crystal phase in the crystallized glass is more preferably as follows. 20 wt% ≦ Petalite phase ≦ 40 wt% 25 wt% ≦ lithium disilicate phase ≦ 45 wt% 10 wt% ≦ α-quartz phase ≦ 25 wt%

The crystallinity of the crystallized glass of the present invention is 65
% By weight or more, more preferably 75% by weight or more.

The method for producing the crystallized glass of the present invention is, of course, not limited, but may be, for example, as follows.

By setting the amount of SiO _{2 in} the raw glass to 70% by weight or more, crystal grains can be refined, and
By adjusting the content to 0% by weight or less, the raw glass can be easily melted. More preferably, the amount of SiO ₂ is greater than or equal to 72% by weight and less than or equal to 77% by weight.

If the amount of Al ₂ O ₃ in the raw glass is less than 5% by weight, the α-quartz phase does not precipitate and the coefficient of thermal expansion of the crystallized glass decreases. Al ₂ O ₃ content of 10% by weight
If it exceeds, the solubility of the glass will deteriorate. More preferably, the amount of Al ₂ O ₃ is at least 6.5% by weight;
5% by weight or less.

By setting the amount of Li ₂ O to 7% by weight or more, more preferably 8% by weight or more, a desired crystal phase can be deposited. If the amount of Li ₂ O exceeds 10% by weight, the crystal grains become coarse.

If the amount of P ₂ O ₅ is less than 1% by weight, desired crystals do not precipitate. When the amount of P ₂ O ₅ exceeds 3% by weight, the crystallized glass is devitrified, and the crystal grains are likely to be coarse. More preferably, the amount of P ₂ O ₅ is not more than 2% by weight.

K ₂ O can be contained in an amount of 0 to 3% by weight. K ₂ O lowers the melting temperature of the glass. In order to exert this effect, the content is more preferably 1% by weight or more. On the other hand, if the content of K ₂ O exceeds 3% by weight, the α-quartz phase does not precipitate, the coefficient of thermal expansion decreases, and the crystal grains become coarse. More preferably, K ₂ O
Is not more than 2% by weight.

It is preferable to contain 0 to 3% by weight of CaO and 0 to 3% by weight of BaO. These lower the melting temperature of the raw glass. If the amounts of CaO and BaO each exceed 3% by weight, no crystals will precipitate. More preferably, the amounts of CaO and BaO are each 1.5% by weight or less.

Preferably, ZnO is contained in an amount of 0 to 3% by weight. ZnO lowers the melting temperature of the raw glass.
If the amount of ZnO exceeds 3% by weight, the crystallized glass tends to be devitrified. More preferably, the amount of ZnO is at most 1.5% by weight.

It is preferable that ZrO ₂ be contained in an amount of 0 to 6% by weight. ZrO ₂ refines the crystal. ZrO ₂
When the amount exceeds 6% by weight, no α-quartz phase is precipitated. More preferably, the amount of ZrO ₂ is at least 1% by weight,
4% by weight or less.

It is preferable that Sb ₂ O ₃ be contained in an amount of 0 to ₂ % by weight. Sb ₂ O ₃ degass the glass. Sb ₂
The amount of O ₃ saturates at 2% by weight. More preferably,
The amount of Sb ₂ O ₃ is 0.1% by weight or more and 1% by weight or less.

It is preferable that Nb ₂ O ₅ be contained in an amount of 0 to 6% by weight. When Nb ₂ O ₅ is added, when the crystallization temperature changes, the change in the coefficient of thermal expansion decreases. Nb ₂
If the amount of O ₅ exceeds 6% by weight, the crystal grains become coarse. More preferably, the amount of Nb ₂ O ₅ is not more than 2% by weight.

Other components can be contained in the crystallized glass of the present invention. First, TiO ₂ , SnO ₂ ,
A noble metal fluoride such as platinum can be contained alone or as a mixture of two or more.

As ₂ O ₃ may be contained in an amount of 0 to 2% by weight. This is a fining agent for melting glass. B ₂
O _3, may contain 0-3 wt%.

In producing the raw glass, the respective raw materials containing the respective metal atoms are mixed so as to correspond to the above weight ratio, and the mixture is melted. The raw materials include oxides, carbonates, nitrates, phosphates of each metal atom,
A hydroxide can be exemplified. In addition, as an atmosphere for heat treatment and crystallization of the raw glass, an air atmosphere, a reducing atmosphere, a steam atmosphere, a pressurized atmosphere, or the like can be selected.

Further, when the raw glass is heated in the above-mentioned manufacturing method, the generation of crystal nuclei is advanced by controlling the temperature rising rate in a temperature region of at least 500 ° C. to 50 to 300 ° C./hour. Is preferred.

The crystallization temperature at which a large amount of the petalite phase precipitates varies depending on the composition of the raw glass. When the crystallization temperature is high, the petalite phase is converted to the α-quartz phase, and a large amount of the α-quartz phase tends to precipitate. When the crystallization temperature is low, the petalite phase does not convert to the α-quartz phase, and a large amount of the petalite phase tends to precipitate.

In the step of precision polishing of the above-mentioned crystallized glass material with abrasive grains, a substrate for a magnetic disk can be prepared by polishing by a known precision polishing method such as so-called lapping or polishing. On the main surface of the magnetic disk substrate of the present invention, a base treatment layer, a magnetic film, a protective film, and the like can be formed, and a lubricant can be applied on the protective film.

[0042]

EXAMPLES (Manufacture of glass parent) Compounds containing each metal were mixed so that the weight ratio of various metal oxides shown in Tables 1 and 3 was obtained. 250 g of this mixture was put in a 200 cc platinum crucible and heat-treated at 1400 ° C. for 5.5 hours to melt. After the temperature of the furnace was lowered to 1350 ° C. and maintained for one hour, the raw glass was poured into a carbon mold and molded. After annealing at 500 ° C. for 1 hour, the resultant was gradually cooled to obtain a disk-shaped parent glass.

From this parent glass, a plate-like sample having dimensions of 5 × 30 × 0.85 mm in thickness was cut out. Both surfaces of the plate-like sample were finished with a # 400 grindstone.

(Crystallization Step) Each plate-like sample was crystallized in a nitrogen atmosphere while being sandwiched between carbon plates having a thickness of 5 mm. The crystallization schedule was as follows: the temperature was raised at 200 ° C./hour to each nucleation temperature shown in Tables 1 and 3;
Hold for about 5 hours, and until each crystallization temperature shown in Tables 1 and 3,
The temperature was raised at 0 ° C./hour, kept at each crystallization temperature for 2 to 5 hours, and lowered to room temperature at 200 ° C./hour.

(Identification of Crystal Phase) X-ray output 50 kV / 30
A 0 mA X-ray diffractometer (RINT 2500) was used (2θ = 10-60 °, step width 0.02 °, Fix)
ed Time 10 seconds, slit DS = SS = 0.5
°, RS = 0.15 °). An optical system including a Ge (111) curved monochromator was provided on the incident side of the X-ray diffraction apparatus. By the Rietveld analysis method using alumina as an internal standard sample (analysis software: "RIETAN"),
The crystallization ratio of each crystal phase in the crystallized glass was determined. "RI
The quantification of crystals by ETAN was performed by F. Izumi.
pl. Crystallogr. ", 20,411 (1987).

As a result, petalite (Li ₂ O.Al ₂
O ₃ · 8SiO ₂ ), lithium disilicate (Li ₂
O.2SiO ₂ : described as “L2S”, α-quartz (chemical formula SiO ₂ ), spodium (Li ₂ Al ₂ S)
Crystals such as i ₈ O ₂₀ ) and cristobalite (chemical formula: SiO ₂ ) were observed.

(Measurement of Thermal Expansion Coefficient α) A plate sample having a size of 5 × 30 × 0.85 mm in thickness after crystallization was cut into a measurement sample having a length of 20 mm. The coefficient of thermal expansion of the test sample was measured in a range of -75 ° to + 110 ° using a thermal expansion coefficient measuring device (“TD5000S” manufactured by Mac Science). The coefficient of thermal expansion up to + 70 ° C was calculated based on -50 ° C. The coefficient of thermal expansion reacts sensitively to minute changes in the crystallization temperature. Therefore, Tables 2 and 4
Is the average value of α of three measurement samples crystallized at (the crystallization temperatures shown in Tables 1 and 3) ± 10 ° C.

Further, “Δα” in Tables 2 and 4 is (Table 1,
This is the difference between the maximum value and the minimum value of α for three samples crystallized at each crystallization temperature shown in Table 3) ± 10 ° C.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

In Example 1-4, the main crystal phase was petalite and lithium disilicate, and the sub-crystal phase was α-quartz. Thermal expansion coefficient α is 68~85 × 10 ^{- 7} / k
In it, [Delta] [alpha] is 10 × 10 ^- were less than ⁷ / k.

In Example 5, the main crystal phase was lithium disilicate and α-quartz, and the sub crystal phase was petalite. The α coefficient of thermal expansion 101 × 10 ^- a ⁷ / k, [Delta] [alpha] is 3 × 10 ^- was ⁷ / k.

From Examples 1, 3, and 4 and Comparative Examples 1 and 3, Δ
The alpha 10 × 10 ^- in order to below ⁷ / k should be nucleation temperature in the range of six hundred twenty to six hundred eighty ° C..

Example 1 and Comparative Example 1 have the same composition.
The crystal phase hardly changes. However, when the nucleation temperature is 6
When the temperature was 20 to 680 ° C, Δα was small, and when the nucleation temperature was 590 ° C, Δα was significantly increased.

Example 2 and Comparative Example 2 or Example 5 and Comparative Example 4 have the same composition. However, if the nucleation temperature was not 620-680 ° C., Δα increased.

FIG. 1 shows the relationship between the nucleation temperature and the coefficient of thermal expansion α when the composition of Example 1 was used (the crystallization temperature was 710 ° C.). When the nucleation temperature exceeds 620 ° C., the thermal expansion coefficient α decreases with respect to the temperature. In each of the crystallized glasses of Example 2-5 and Comparative Example 1-4, almost the same tendency was observed.

[0059]

As described above, according to the present invention, the raw glass is held at the nucleation temperature and then at the crystallization temperature to crystallize the raw glass, and at least the α-quartz phase is formed. During the precipitation, the fluctuation of the thermal expansion coefficient with respect to the fluctuation of the crystallization temperature can be reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the nucleation temperature of the crystallized glass of Example 1 and the coefficient of thermal expansion α.

Continued on front page F-term (reference) 4G062 AA11 BB01 CC09 DA07 DB03 DC01 DD03 DE01 DE02 DE03 DF01 EA03 EB01 EC01 EC02 EC03 EE01 EE02 EE03 EF01 EG01 EG02 EG03 FA01 FA10 FB01 FC01 FC02 FC03 FD01 F01 FG01 F01 FG01 F01 FG01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ04 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM27 NN29 QQ02 QQ06 QQ08

Claims (6)

[Claims] 1. A process for producing crystallized glass, wherein the raw glass is kept at a nucleation temperature and then kept at a crystallization temperature to crystallize the raw glass, and at least an α-quartz phase is precipitated. By setting the nucleation temperature to 620-680 ° C., the maximum value of the coefficient of thermal expansion of the crystallized glass obtained when crystallized at a temperature within the range of ± 10 ° C. with respect to the reference crystallization temperature, the difference Δα between the minimum value 10 × 10 ^- and controls below ⁷ / k, method for producing the crystallized glass. 2. The method according to claim 1, wherein the crystallization temperature is 690-750 ° C. 3. The method according to claim 1, wherein the crystallized glass has a petalite phase, a lithium disilicate phase and an α-quartz phase. 4. The method for producing crystallized glass according to claim 3, wherein the quantitative value of each crystal by the Rietveld quantitative method is within the following range. 20 wt% ≦ Petalite phase ≦ 40 wt% 25 wt% ≦ lithium disilicate phase ≦ 45 wt% 10 wt% ≦ α-quartz phase ≦ 25 wt% 5. The crystallized glass according to claim 4, having the following oxide composition. 70 wt% ≦ SiO ₂ ≦ 80 wt% 5 wt% ≦ Al ₂ O ₃ ≦ 10 wt% 7 wt% ≦ Li ₂ O ≦ 10 wt% 1 wt% ≦ P ₂ O ₅ ≦ 3 wt% 0 wt% ≦ K ₂ O ≦ 3% by weight 0% by weight ≦ CaO ≦ 3% by weight 0% by weight ≦ BaO ≦ 3% by weight 0% by weight ≦ ZnO ≦ 3% by weight 0% by weight ≦ ZrO ₂ ≦ 6% by weight 0% by weight ≦ Sb ₂ O ₃ ≦ 2% by weight 0% by weight ≦ Nb ₂ O ₅ ≦ 6% by weight 6. The crystallization according to claim 1, wherein the thermal expansion coefficient at -50 ° C. to + 70 ° C. is 60 to 130 × 10 ⁻⁷ / k. Glass manufacturing method.