JP2002145641A - Crystallized glass substrate for information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystallized glass substrate which has a high thermal expansion coefficient in spite of its low corrosion by alkali metal components and has good workability. SOLUTION: This crystallized glass substrate for an information recording medium contains each component of, by weight, 65 to 70% SiO2, 5 to 10% Al2O3, 4 to 8% Li2O, 1 to 5% ZrO2 and 1 to 3% P2O5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystallized glass substrate suitable for a substrate used for an information recording medium such as a magnetic disk, an optical disk and a magneto-optical disk.

[0002]

2. Description of the Related Art A magnetic recording apparatus such as a computer is mainly composed of a magnetic recording medium having a magnetic disk as a substrate and a magnetic recording / reproducing head. Among them, as a substrate for a magnetic disk, an aluminum substrate, a glass substrate and the like have been put to practical use. Among them, a glass substrate has received the most attention because of its excellent surface smoothness and mechanical strength. As such a glass substrate, a chemically strengthened glass substrate in which the surface of the glass substrate is strengthened by ion exchange, and a crystallized glass substrate in which a crystal component is precipitated on the substrate to strengthen the bond are known.

However, there is a problem that the chemically strengthened glass substrate cannot be made high in strength and high in rigidity due to its material properties. On the other hand, a crystallized glass substrate has attracted attention as a material for compensating for the disadvantages of an aluminum substrate and a chemically strengthened glass substrate.

[0004] Such a crystallized glass substrate is disclosed in JP-A-11-16142, JP-A-11-16143, and JP-A-10-226532.
No., JP-A-9-208260, Lithium disilicate crystal
A crystallized glass substrate in which (Li ₂ O · 2SiO ₂ ) is a main crystal phase has been proposed.

Also, Japanese Patent Application Laid-Open Nos. 9-100137 and 6-206736
Japanese Patent Application Laid-Open Publication No. H11-157210 proposes a crystallized glass substrate having a crystal of either mullite or cordierite as a main crystal phase.

[0006]

The crystallized glass in which the lithium disilicate crystal (Li ₂ O.2SiO ₂ ) is the main crystal phase has a high expansion coefficient. There is a characteristic that the thermal expansion coefficient is close to that of the stainless steel material used as the chucking member.
Therefore, when these crystallized glass substrates are incorporated into a device as a magnetic disk, the substrate is hardly broken even when heated by a motor or the like for rotating the disk. However, crystallized glass in which lithium disilicate crystal (Li ₂ O.2SiO ₂ ) is the main crystal phase,
There is a problem that the corrosion (particularly, the amount of movement of the alkali metal component from the substrate) is very large. If the amount of movement of the alkali metal component is large, the alkali metal component erodes the protective layer and the magnetic recording layer formed on the crystallized glass substrate, lowering the smoothness of the magnetic disk, and reducing the protective layer and the magnetic recording layer. Deformation and deterioration will occur.

On the other hand, a crystallized glass substrate having any of the above-mentioned mullite and cordierite crystals as a main crystal phase has a low alkali metal component corrosion, but has a low coefficient of thermal expansion. When incorporated into a device as a magnetic disk, the substrate may be broken by being heated by a motor or the like for rotating the disk. In addition, a crystallized glass substrate having either mullite or cordierite as a main crystal phase has a problem in that the workability upon smoothing is extremely poor.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a crystallized glass substrate having a low coefficient of corrosion with respect to an alkali metal component and having a high coefficient of thermal expansion and good workability.

[0009]

In order to achieve the above object, a crystallized glass substrate for an information recording medium according to claim 1 is characterized by containing the following components in% by weight: SiO ₂ 65 w% or more, 70 w% or less, Al ₂ O ₃ 5 w% or more, 10 w% or less, Li ₂ O 4 w% or more, 8 w% or less, ZrO ₂ 1 w% or more, 5 w% or less, P ₂ O ₅ 1 w% or more Less than 3w%.

[0010]

Embodiments of the present invention will be described below. The crystallized glass substrate of the present embodiment contains the following components by weight.

SiO ₂ 65 w% or more, 70 w% or less, Al ₂ O ₃ 5 w% or more, 10 w% or less, Li ₂ O 4 w% or more, 8 w% or less, ZrO ₂ 1 w% or more, 5 w% or less, P ₂ O ₅ 1w% or more and 3w% or less.

In a system having the above-mentioned glass component, Si
O ₂ is a glass-forming oxide and is a component of cristobalite, cristobalite solid solution, quartz, and quartz solid solution precipitated as a main crystal phase. However, in the present embodiment, Si
If O ₂ is less than 65% by weight, the above-mentioned crystals are difficult to precipitate, which is not desirable. On the other hand, if the content of SiO ₂ exceeds 70% by weight, the melting temperature is increased and the devitrification is increased.

Al ₂ O ₃ is a glass intermediate oxide, and when lithium aluminum silicate or lithium aluminosilicate solid solution is precipitated as a sub-crystal phase, it is a constituent component of these crystal phases. However, in the present embodiment, Al ₂ O ₃ is 5
If less than w%, mechanical strength and chemical durability cannot be obtained. On the other hand, if the content of Al ₂ O ₃ exceeds 10% by weight, the melting temperature increases, and the meltability and devitrification deteriorate.

Since Li ₂ O works as a flux, it improves the stability during production. Further, when lithium aluminosilicate, lithium aluminosilicate solid solution, lithium zinc silicate, and lithium zinc silicate solid solution are precipitated as sub-crystal phases, they are constituents of these crystal phases.
However, in the present embodiment, if Li ₂ O is less than 4% by weight, the meltability deteriorates. On the other hand, when Li ₂ O exceeds 8% by weight, crystal phases such as lithium monosilicate (Li ₂ O · SiO ₂ ) and lithium disilicate (Li ₂ O · 2SiO ₂ ) are precipitated as a crystal layer. This is not desirable because the corrosion value of the alkali metal component increases and elution of the alkali metal component from the substrate occurs.

ZrO ₂ functions effectively as a crystal nucleating agent and also functions as a glass-modified oxide. But second
In the embodiment, if ZrO ₂ is less than 1% by weight, necessary crystal nuclei are not formed. In addition, the chemical durability and migration resistance are reduced, affecting the magnetic recording layer. On the other hand, if it exceeds 5% by weight, the melting temperature becomes high and the glass tends to be devitrified, so that melt molding becomes difficult. In addition, the crystal grains become coarse or the precipitated crystal phase changes, making it difficult to obtain the desired characteristics. A fine and uniform crystal structure cannot be obtained, and a smooth surface required as a magnetic disk substrate in polishing cannot be obtained.

P ₂ O ₅ is a nucleating agent that functions as a flux and precipitates silicate-based crystals, and is an important component for uniformly depositing crystals throughout the glass. However, in the present embodiment, if P ₂ O ₅ is less than 1% by weight, necessary crystal nuclei are not formed. In addition, the chemical durability and migration resistance are reduced, affecting the magnetic recording layer.
On the other hand, if it exceeds 3% by weight, the melting temperature becomes high and the glass tends to be devitrified, so that melt molding becomes difficult. In addition, the crystal grains become coarse, the precipitated crystal phase changes, and it becomes difficult to obtain the required characteristics, and a smooth surface required as a magnetic disk substrate during polishing cannot be obtained. Further, the reactivity with the furnace material at the time of melting increases, and the devitrification also increases, so that the productivity at the time of melt molding decreases. In addition, the stability of the glass structure is reduced, and the elution of the alkali metal component is likely to occur.

The manufacturing method will be described below. Raw materials containing the composition of the main components of the finally produced glass substrate are sufficiently mixed at a predetermined ratio, and the mixture is put into a platinum crucible or a brick crucible and melted. After melting, it is poured into a mold to form a rough shape. This is annealed to room temperature. Then, 50
The primary heat treatment temperature (nucleation temperature) of 0 to 600 ° C. and the primary treatment time (nucleus formation time) are maintained (heat treatment), and crystal nuclei are generated. Subsequently, a secondary heat treatment temperature (nucleus growth temperature) of 600 to 750 ° C. and a secondary treatment time (nucleus growth time)
And crystal nucleus growth is performed. By cooling this, the desired crystallized glass is obtained.

By subjecting this to grinding and polishing to a desired shape and thickness, it can be used as a crystallized glass substrate.

The crystallized glass substrate of the present embodiment satisfies the following conditional expression (1).

Co <150 (1) where, Co: the amount of movement of the alkali metal component with respect to water per 2.5 inch disk substrate [ppb].

Conditional expression (1) defines the range of the transfer amount of the alkali metal component from the substrate to water. Corrosion value of alkali metal component is the elution amount of alkali metal component to water per 2.5 inch disk substrate [ppb]
It is represented by If the amount of movement exceeds 150 [ppb], the protective layer and the magnetic recording layer formed on the crystallized glass substrate are eroded by the alkali metal component, and the smoothness of the magnetic disk is reduced. Also, the deterioration of the magnetic recording layer becomes remarkable, which is not desirable. In particular, in a crystallized glass substrate existing in a region where the amount of movement exceeds 150 [ppb], the elution amount of the alkali metal component is too large, and the protective layer and the magnetic recording layer formed on the substrate are eroded. Notable and undesirable.

The crystallized glass substrate of the present embodiment satisfies the following conditional expression (2). 70 <CTE <150 (2) where CTE: coefficient of thermal expansion at 25 ° C to 100 ° C [× 10 ^-7 /
° C].

Conditional expression (2) is a condition relating to thermal expansion and defines a range that the crystallized glass substrate should satisfy as a numerical range of a thermal expansion coefficient [× 10 ⁻⁷ / ° C.] at 25 ° C. to 100 ° C. It is. In recent years, with the improvement in recording density of magnetic recording media, high precision is required for the positioning of the magnetic head and the magnetic recording medium (crystallized glass substrate).
High dimensional accuracy is required not only for crystallized glass substrates but also for various components. Furthermore, in order to maintain the dimensional accuracy, the difference in the coefficient of thermal expansion between the crystallized glass substrate and the various components has become more significant. In the case of a magnetic recording apparatus, various components are often formed of a stainless steel-based metal material, and usually have a value of a thermal expansion coefficient at 25 ° C to 100 ° C [× 10 ⁻⁷ / ° C] of 90 to 100 ×. 10 ⁻⁷ / ° C. Therefore, the thermal expansion coefficient of the crystallized glass substrate also
It is desirable to correspond to this range. That is, the conditional expression
If the upper and lower limits of (2) are exceeded, the coefficient of thermal expansion between the various components becomes too large, so that not only dimensional accuracy cannot be maintained, but in the worst case, the crystallized glass substrate may be broken. Yes, not desirable.

The crystallized glass substrate of the present embodiment satisfies the following conditional expression (3). 1.0 <P / PLi <1.5 (3) Where, P: surface smoothness value when cerium oxide (average particle size: 0.5 μm) is used as an abrasive and polished at a pressure of 100 g / cm ² , and 3Å Grinding / polishing allowance [μg / min] per unit time when achieving the following conditions: PLi: When grinding and polishing a lithium disilicate-based crystallized glass substrate under the same conditions, set the surface smoothness value to 3Å. Grinding / polishing allowance [μg / min] per unit time to achieve.

Conditional expression (3) defines the processing rate for a conventional lithium disilicate-based crystallized glass substrate. If the lower limit of conditional expression (3) is exceeded, it will not be superior to the conventional lithium disilicate-based crystallized glass substrate. If the upper limit of conditional expression (3) is exceeded, the probability of breakage during processing (the occurrence of cracks, focus, scratches, etc.) will increase rapidly, which is not desirable.

The crystallized glass substrate of the present embodiment satisfies the following conditional expression (4). 28 <E / ρ <36 (4) where E: Young's modulus [GPa]; ρ: Specific gravity.

Conditional expression (4) defines the ratio between the Young's modulus and the specific gravity, and determines the resonance frequency inherent to the crystallized glass substrate mainly by expressing the physical characteristics of the substrate.
If the lower limit of the conditional expression (4) is exceeded, the value of the resonance frequency becomes too small, causing a problem of resonance with the magnetic recording device, and lowering the rigidity, which is not desirable. Conversely, if the value exceeds the upper limit of the conditional expression (5), the resonance frequency becomes too large, and it becomes impossible to use the design resources of the magnetic recording device that can be used for general purposes. In particular, by satisfying the range of the conditional expression (4), it is possible to set the resonance frequency range higher than the resonance frequency range of the aluminum substrate which has conventionally been a problem, and substantially equal to the resonance frequency range of a general glass material as a general-purpose substrate. Since it becomes possible, the manufacturing apparatus can be shared, which is desirable also from the viewpoint of reducing the cost of the magnetic recording apparatus.

In the crystallized glass substrate of the present embodiment defined by the above-mentioned essential components, the above-mentioned conditional expressions (1) to (5)
The range of (4) is optimized as follows. 30 <Co <100 (1a) 80 <CTE <150 (2a) 1.0 <R / RLi <1.5 (3a) 28 <E / ρ <33 (4a) % By weight. By adding the following components, it is possible to adjust the value of E / ρ by adjusting the values of the Young's modulus E [GPa] and the specific gravity ρ. ZnO acting as a flux may be added. ZnO is
Aids uniform crystal precipitation. In addition, when zinc zinc silicate or a lithium zinc silicate solid solution precipitates as a sub-crystal phase, ZnO becomes a constituent component of these crystal phases. However, in this embodiment, if the content of ZnO is less than 0.1% by weight, the crystal homogenization cannot be sufficiently improved. On the other hand, ZnO
Exceeds 5% by weight, the glass becomes stable, crystallization is suppressed, and it becomes difficult to obtain the required strength.

MgO acting as a flux may be added. M
By adding gO, granular crystals can be aggregated to form a crystal particle mass. However, if it is less than 0.5% by weight, the working temperature range is narrowed, and the chemical durability of the glass matrix phase is not improved. On the other hand, if MgO exceeds 5% by weight, other crystal phases will precipitate, making it difficult to obtain the required strength. By adding MgO, the Young's modulus E tends to increase and the value of ρ tends to decrease. Therefore, the value of E / ρ increases, and the resonance frequency tends to increase.

[0030] CaO acting as a flux may be added. C
aO can form a high melting property and a stable crystal phase. If the content of CaO is less than 0.5% by weight, the meltability cannot be sufficiently improved. Conversely, if it exceeds 5% by weight, the glass becomes stable, crystallization is suppressed, and it becomes difficult to obtain the required strength.
By adding CaO, the Young's modulus E tends to increase and the value of ρ tends to decrease. Therefore, E
The value of / ρ will increase and the resonance frequency will tend to increase.

BaO acting as a flux may be added. B
aO can form a high melting property and a stable crystal phase. If the content of BaO is less than 0.5% by weight, sufficient melting property cannot be improved. Conversely, if it exceeds 10% by weight, the glass becomes stable, crystallization is suppressed, and it becomes difficult to obtain the required strength.
By adding BaO, the Young's modulus E tends to decrease, and the value of ρ tends to increase rapidly. Therefore, the value of E / ρ decreases, and the resonance frequency tends to decrease.

SrO acting as a flux may be added. S
rO can form a high melting property and a stable crystal phase. If SrO is less than 0.5% by weight, sufficient melting property cannot be improved. Conversely, if it exceeds 10% by weight, the glass becomes stable, crystallization is suppressed, and it becomes difficult to obtain the required strength.
By adding SrO, the Young's modulus E tends to decrease and the value of ρ tends to increase. Therefore, E
The value of / ρ will decrease and the resonance frequency will tend to decrease.

[0033] Y ₂ O ₃ acting as a flux may be added.
However, if Y ₂ O ₃ is less than 0.1% by weight, sufficient rigidity improvement cannot be obtained. When Y ₂ O ₃ exceeds 5% by weight, crystal precipitation is suppressed, sufficient crystallinity cannot be obtained, and desired characteristics cannot be achieved. By adding Y ₂ O ₃ , the Young's modulus E tends to increase rapidly and the value of ρ tends to decrease.
Therefore, the value of E / ρ increases, and the resonance frequency tends to increase.

Sb ₂ O _3, which acts as a fining agent, may be added. Sb ₂ O ₃ improves stability during production. Where S
If b ₂ O ₃ is 2 w% or less, it is sufficient. If it exceeds 2 w%, crystallization of the glass becomes unstable, so that the precipitated crystal phase cannot be controlled, and it becomes difficult to obtain the required characteristics.

[0035]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The glass compositions of the crystallized glass substrates of the respective examples are all expressed in terms of weight% (w%) on an oxide basis, and the nucleation temperature / time and nucleus growth temperature shown in the table by the above-mentioned production method. -It becomes a crystallized glass substrate by being processed and processed according to time.

The abbreviation of the crystal phase shown in each table is Crist.
Represents cristobalite, α-Q represents α-quartz, LAS represents lithium aluminum silicate, LZS represents lithium zinc silicate, L2S represents lithium disilicate, and SS represents a solid solution.

Tables 1 and 2 show the glass compositions of the crystallized glass substrates of Examples 1 to 18 in terms of% by weight, together with the respective production conditions. Further, Tables 3 and 4 show as Examples 19 to 36 crystallized glass substrates manufactured by changing the nucleus growth temperature for the same glass compositions as in Examples 1 to 18. In addition, Tables 5-6
On the other hand, for the same glass composition as in Examples 1 to 18, crystallized glass substrates manufactured by changing the nucleus growth time were used in Examples 37 to
Indicated as 54.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

[Table 4]

[0042]

[Table 5]

[0043]

[Table 6]

Tables 7 and 8 show the glass compositions of the crystallized glass substrates of Examples 55 to 74 in% by weight, together with the respective production conditions. Tables 9 to 10 show, as Examples 75 to 94, crystallized glass substrates manufactured by changing the nucleus growth temperature for the same glass compositions as Examples 55 to 74. In addition, Table 11
In Example 12, a crystallized glass substrate manufactured by changing the nucleus growth time for the same glass composition as in Examples 55 to 74 was used in Example 95.
114114.

[0045]

[Table 7]

[0046]

[Table 8]

[0047]

[Table 9]

[0048]

[Table 10]

[0049]

[Table 11]

[0050]

[Table 12]

Tables 13 and 14 show the glass compositions of the crystallized glass substrates of Examples 115 to 134 in% by weight, together with the respective production conditions. Tables 15 and 16 show, as Examples 135 to 154, crystallized glass substrates manufactured by changing the nucleus growth temperature for the same glass compositions as Examples 115 to 134. Further, Tables 17 to 18 show, as Examples 155 to 174, crystallized glass substrates manufactured by changing the nucleus growth time for the same glass compositions as Examples 115 to 134.

[0052]

[Table 13]

[0053]

[Table 14]

[0054]

[Table 15]

[0055]

[Table 16]

[0056]

[Table 17]

[0057]

[Table 18]

Tables 19 to 20 show the glass compositions of the crystallized glass substrates of Examples 175 to 194 by weight%, together with the respective production conditions. In Tables 21 and 22, crystallized glass substrates manufactured by changing the nucleus growth temperature for the same glass compositions as in Examples 175 to 194 are shown as Examples 195 to 214. Further, Tables 23 to 24 show, as Examples 215 to 234, crystallized glass substrates manufactured by changing the nucleus growth time for the same glass compositions as Examples 175 to 194.

[0059]

[Table 19]

[0060]

[Table 20]

[0061]

[Table 21]

[0062]

[Table 22]

[0063]

[Table 23]

[0064]

[Table 24]

In Tables 25 to 26, the glass compositions of the crystallized glass substrates of Examples 235 to 254 are shown in% by weight, and are shown together with the respective production conditions. Tables 27 to 28 show, as Examples 255 to 274, crystallized glass substrates manufactured by changing the nucleus growth temperature for the same glass compositions as Examples 235 to 254. Further, Tables 29 to 30 show, as Examples 275 to 294, crystallized glass substrates manufactured by changing the nucleus growth time for the same glass composition as Examples 235 to 254.

[0066]

[Table 25]

[0067]

[Table 26]

[0068]

[Table 27]

[0069]

[Table 28]

[0070]

[Table 29]

[0071]

[Table 30]

Tables 31 to 32 show the glass compositions of the crystallized glass substrates of Examples 295 to 314 in% by weight, together with the respective production conditions. Tables 33 to 34 show, as Examples 315 to 334, crystallized glass substrates manufactured by changing the nucleus growth temperature for the same glass compositions as Examples 295 to 314. Further, Tables 35 to 36 show, as Examples 335 to 354, crystallized glass substrates manufactured by changing the nucleus growth time for the same glass compositions as Examples 295 to 314.

[0073]

[Table 31]

[0074]

[Table 32]

[0075]

[Table 33]

[0076]

[Table 34]

[0077]

[Table 35]

[0078]

[Table 36]

Tables 37 to 38 show the glass compositions of the crystallized glass substrates of Examples 355 to 363 in terms of% by weight, together with the respective production conditions. Further, Tables 39 to 40 show, as Examples 373 to 390, crystallized glass substrates manufactured by changing the nucleus growth temperature for the same glass compositions as Examples 355 to 363. Further, Tables 41 to 42 show, as Examples 391 to 408, crystallized glass substrates manufactured by changing the nucleus growth time for the same glass compositions as Examples 355 to 363.

[0080]

[Table 37]

[0081]

[Table 38]

[0082]

[Table 39]

[0083]

[Table 40]

[0084]

[Table 41]

[0085]

[Table 42]

The following table shows, as a comparative example, a crystal glass substrate having a conventional lithium disilicate-based crystal as a main crystal phase.

[0087]

[Table 43]

[0088]

As described above in detail, according to the present invention, a crystallized glass substrate having a high expansion coefficient and a good workability with a low corrosion rate with respect to an alkali metal component can be provided.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4G062 AA11 BB01 DA06 DB03 DC01 DD03 DE01 DF01 EA03 EB01 EC01 ED01 EE01 EF01 EG01 FA01 FB01 FC03 FD01 FE01 FF01 FG01 FH01 FJ01 FK01 FL01 GA01 GA10 GB01 H01H01H01H01H01H01H01 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM27 NN29 NN34 QQ02 QQ03 5D006 CB04

Claims (1)

[Claims] 1. A crystallized glass substrate characterized by containing the following components in weight%: SiO ₂ 65 w% or more, 70 w% or less, Al ₂ O ₃ 5 w% or more, 10 w% or less, Li ₂ O 8 w% or less at 4 w% or more, 5 w% or less at ZrO ₂ 1 w% or more, and 3 w% or less at P ₂ O ₅ 1 w% or more.