JP2000290039A - Glass for recording medium free from permanent strain and hard disk using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten specific rigidity and to suppress warps when the glass is processed to a thin film by calculating the value of R2 of regression straight line by using the measured value of the coefficient of thermal expansion of the glass in a specific temp. range and controlling the glass composition so that the value of R2 becomes higher than the specific value. SOLUTION: The value of R2 of the regression straight line is calculated by substituting the measured value of the coefficient of thermal expansion of the glass in the temp. range of (Tg-20)/2 to (Tg-20) deg.C. The glass composition is selected so that the value of R2 becomes not less than 0.9. In the formula, X is temp; Y is coefficient (%) of thermal expansion; n is number of measurements. The composition of the glass is selected from at least one of the group of Ca-Al-Si-O-N-system, Mg-Al-Si-O-N-system, Y-Al-Si-O-N-system, Ce-Al-Si-O-N-system, La-Al-Si-O-N-system, Gd-Al-Si-O-N-system, Mg-Si-O-N- system and Ca-Si-O-N-system. It becomes possible to produce a hard disk substrate free form permanent strain by using the glass mentioned above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to glass suitable as a disk material for a recording medium such as a magnetic disk and a hard disk substrate using the glass.

[0002]

2. Description of the Related Art In the field of magnetic disk drives, technical developments are being made more and more rapidly in order to improve recording density and transfer speed. In particular, recently, there is an urgent need to increase the rotation speed of a disk with the aim of improving the transfer speed, and a high specific rigidity disk material that does not vibrate even during high speed rotation is desired.
The specific rigidity of a conventionally used aluminum disk (hereinafter referred to as aluminum substrate) is 26.7 (Young's modulus:
72 GPa / density: 2.7 g / cm ³ )
It is said that a specific rigidity more than twice that of use at a high speed rotation of up to 000 rpm is required. However, in order to double the specific rigidity of the aluminum substrate, there is only a method such as compounding with ceramics (MMC) or the like, and the practical possibility is low in terms of cost.

On the other hand, a glass disk (hereinafter, a glass substrate) used in a 2.5-inch size has attracted attention because it has a high specific rigidity. For example, many attempts have been made to improve the Young's modulus by heat-treating the glass at an appropriate temperature to precipitate a crystal phase having a high Young's modulus to form glass ceramics. For example, JP-A-6-3294
No. 40, JP-A-8-111024, JP-A-8
Japanese Patent No. 221747 discloses an example in which lithium dioxide crystals and α-quartz crystals are precipitated. Japanese Patent Application Laid-Open No. 9-77531 discloses an example in which spinel crystals are precipitated to increase the Young's modulus to 109 to 144 Gpa and the specific rigidity to 36 to 47.

[0004] However, although the specific rigidity of the glass itself is increased by crystallization, the glass has a composite structure of a hard crystal phase and a soft glass phase. There is a disadvantage that it is difficult to obtain a mirror surface.

On the other hand, as a measure for improving the specific rigidity of the glass itself, a method of adding a rare earth element which is expected to improve the Young's modulus of the glass is also known. However, the addition of rare earths increases the Young's modulus of the glass and at the same time increases the specific gravity. As a result, the specific rigidity does not improve as expected.

Therefore, as a measure for improving the Young's modulus without significantly increasing the specific gravity of the glass, there is an oxynitride glass in which oxygen in the glass is replaced with nitrogen. Japanese Patent Laying-Open No. 10-1327 discloses an example in which oxynitride glass is used as a disk substrate. Since the Young's modulus shown in the examples of the invention of the publication is extremely high at 139 to 185 Gpa and the specific gravity is relatively low at 2.9 to 3.4 g / cm ³ , the specific rigidity is 47 to 55. Extremely high values have been obtained. However, when a disk is actually manufactured using the oxynitride glass disclosed so far, the warp of the disk is as large as about 50 μm, and the disk cannot be actually used as a magnetic disk.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to significantly reduce the warpage generated when processing into a thin plate with high specific rigidity. Another object of the present invention is to provide a recording medium glass and a hard disk substrate using the glass.

[0008]

According to the present invention, (Tg
−20) / 2 ° C. to (Tg−20) ° C. Substituting the measured value of the thermal expansion in the temperature range, the R ² value of the regression line calculated from the following equation (1) is 0.9 or more. A glass for a recording medium free from the characteristic permanent distortion is provided.

[0009]

(Equation 2)

(Where X: temperature (° C.), Y: thermal expansion (%), n: the number of measurements) At this time, the glass is a Ca—Al—Si—O—N system,
Mg-Al-Si-ON, Y-Al-Si-ON
System, Ce-Al-Si-ON system, La-Al-Si-
ON-based, Gd-Al-Si-ON-based, Mg-Si-
It is desirable that the glass composition has at least one composition selected from the group consisting of ON-based and Ca-Si-ON-based, and the preferred glass composition ranges are as follows.

First, the glass is made of Ca-Al-Si-O-
In oxynitride glass represented by N, C
The metal components of a, Al, and Si are in the hatched portion in the composition diagram shown in FIG. 1, and the nonmetal components of O and N are 5 eq% ≦ N ≦ 25 eq% and O + N = 1.
00eq%.

In the oxynitride glass represented by Mg—Al—Si—O—N, the metal components of Mg, Al, and Si are in the hatched portion in the composition diagram shown in FIG. 5eq% for metal components
≦ N ≦ 25 eq% and O + N = 100 eq%.

[0013] In the oxynitride glass represented by Y-Al-Si-ON, the metal components of Y, Al, and Si are in the hatched portion in the composition diagram shown in FIG. For the metal component, 5eq% ≦ N
≦ 25 eq% and O + N = 100 eq%.

In the oxynitride glass represented by Gd-Al-Si-ON, the metal components of Gd, Al, and Si are shown in the hatched portion in the composition diagram shown in FIG. 5eq% for metal components
≦ N ≦ 25 eq% and O + N = 100 eq%.

In the oxynitride glass represented by Ce—Al—Si—O—N, the metal components of Ce, Al, and Si are shown in the hatched portion in the composition diagram shown in FIG. 5eq% for metal components
≦ N ≦ 25 eq% and O + N = 100 eq%.

By using the glass specified as described above, a hard disk substrate without permanent distortion is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive studies conducted by the present inventors, it has been found that the warpage that occurs when glass is processed into a thin plate shape is caused by permanent distortion that occurs in the glass manufacturing process. It has been found that the warpage of the disk can be greatly reduced by reducing the permanent distortion, and the present invention has been accomplished. That is, in the glass for a recording medium of the present invention, the measured value of the thermal expansion in the temperature range of (Tg-20) / 2 ° C. to (Tg-20) ° C. is substituted into the formula (1).
Wherein the R ² value of the regression line calculated from is not less than 0.9. When the R ² value calculated from the above formula (1) is less than 0.9, the residual stress in the glass increases, and the flatness of the glass disk when processed into a thin plate is 10 μm.
m or more, and cannot withstand actual use as a hard disk substrate. The R ² value is more preferably 0.99 or more. Such glass for recording media is
For example, in the cooling process after melting the glass in the manufacturing process,
100 ° C / h in the temperature range from 1,100 ° C to 700 ° C
r or a cooling rate of 1,100
It can be obtained by, for example, a method in which the temperature is maintained within a temperature range of from 700C to 700C for 10 minutes or more. Note that the heat treatment is not necessarily performed in the cooling step after melting the glass. For example, the heat treatment may be performed by heating again after the melting and cooling steps of the glass.

Further, the glass for a recording medium of the present invention is preferably made of Ca--Al--Si--O--N in view of specific rigidity and workability.
System, Mg-Al-Si-ON system, Y-Al-Si-O
-N system, Ce-Al-Si-ON system, La-Al-S
i-ON system, Gd-Al-Si-ON system, Mg-S
i-ON-based, Ca-Si-ON-based, preferably comprises at least one composition selected from the group consisting of:
Further, the nitrogen content as a non-metal component is reduced to 5 eq% <N ≦ 25.
eq% and O + N = 100eq%, C
a, Mg, Y, Gd, and Ce based compositions are shown in FIGS.
A more excellent effect can be obtained by setting the inside of the hatched portion shown in FIG. That is, Ca, Mg, Y, G
In each of d and Ce-based recording medium glasses, in the case of a composition outside the hatched portion in the figure, the glass is crystallized or foamed, and the surface roughness after final polishing becomes 10 μm or more. This is because it may not be suitable as a hard disk substrate.

Hereinafter, the present invention will be described in more detail with reference to Examples, but it should be understood that the present invention is not limited to these Examples.

[0020]

Examples SiO ₂ , Al ₂ O ₃ , CaC were used to obtain glass compositions having the equivalent% compositions shown in Tables 1 and 2.
O ₃ , MgCO ₃ , AlN, Y ₂ O ₃ , La ₂ O ₃ , Gd
After weighing and mixing predetermined amounts of ₂ O ₃ and CeO ₂ , the glass composition was melted at 1,650 ° C. under a nitrogen atmosphere. Next, cooling was performed under the cooling conditions shown in Tables 1 and 2, and a rod-shaped glass having a diameter of 4 mm x a length of 20 mm and a diameter of 95 mm x a thickness of 1.
A 2 mm disk was made. The R ² value and the amount of warpage of these glasses were measured by the following methods. The results are shown in Tables 1 and 2.

(R ² value of regression line) Using a rod-shaped glass having a diameter of 4 mm and a length of 20 mm, the thermal expansion from room temperature to 1,200 ° C. in a nitrogen atmosphere was measured by a compression probe type thermal expansion measuring instrument. Was measured. From these measured values, the R ² value of the regression line was calculated from the above equation (1) by substituting the measured values of the thermal expansion in the temperature range of (Tg-20) / 2 ° C. to (Tg-20) ° C. .

(Surface Roughness and Warpage Amount)
A 95 mm x 1.2 mm thick disk is cut using an edge grinder
The inner and outer diameters were chamfered. Raw plate as carrier
Fixed, containing 20wt% alumina with average particle size of 20μm
Using a double-side polishing machine "18B" having a cast iron surface plate
40 rotations, polishing pressure 100gf / cm^TwoIn primary
Went. Next, 20 wt% of alumina having an average particle size of 8 μm
% Under the same conditions as the primary lap using a cast iron platen containing
The next lap was done. After washing, hard foam polyurethane
A pad is stuck on the surface plate, and the average particle size is 2μm
Using a polishing liquid containing 20 wt%
Using, rotation speed 30rpm, polishing pressure 250gf / cm^Two
The primary polishing was performed under the following conditions. After simple cleaning, nap
Attach a soft polyurethane pad with a layer to the surface plate,
Polishing liquid containing 20 wt% of cerium oxide having an average particle size of 1 μm
Using the above double-side polishing machine, the number of rotations is 25 rpm
m, polishing pressure 200gf / cm ^TwoSecondary polish under the conditions of
And finished to a 0.8 mm thick disk. This de
The surface roughness of the disk is measured using a contact surface roughness meter,
Disk warpage is measured using a non-contact surface profiler
did.

[0023]

[Table 1]

[0024]

[Table 2]

Examples 1 to 14 in which the R ² value is 0.9 or more
In the glass for recording medium, the warpage amount was 5 μm or less, which is an excellent result. On the other hand, in the glass for recording media of Comparative Examples 1 to 6 in which the R ² value was less than 0.9, the warpage amount was 17 μm or more. It was not practical.

Next, when the nitrogen content is 5 eq% ≦ N ≦ 25 e
Ca, Mg, Y, Gd and Ce in the range of q%
Was studied for a suitable composition.

Nitrogen was added to the equivalent% composition shown in Table 3.
Ca-based, Mg-based, Y-based, Gd-based and Ce-based samples containing 0 and 20 eq% were prepared. The preparation method of the sample is Ca
CO ₃ , MgCO ₃ , Y ₂ O ₃ , CeO ₂ , Gd ₂ O ₃ , Al ₂
O ₃ , SiO ₂ , and Si ₃ O ₄ were weighed in predetermined amounts, mixed by a ball mill, dried, and formed into a predetermined shape by CIP molding. Then, it melted and cooled at 1750 degreeC in a BN crucible, and obtained glass. Tables 4 and 8 show the respective cooling conditions. In the table, M is the above Ca, Mg, Y, Gd, C
e, for example, Example E-1
Includes five examples in which each of M, Ca, Mg, Y, Gd, and Ce is used alone or in combination at 10 eq%. “M = 0” indicates that the oxynitride glass does not contain these metals.

[0028]

[Table 3]

For glasses having the compositions shown in Table 3, R
^{The binary} value, the amount of warpage, and the surface roughness were investigated. 10 eq of nitrogen
Table 5 shows the results of the glass containing 20% nitrogen, and 20 eq of nitrogen.
Tables 9 to 11 show the results of the glasses containing%, respectively.

[0030]

[Table 4]

[0031]

[Table 5]

[0032]

[Table 6]

[0033]

[Table 7]

[0034]

[Table 8]

[0035]

[Table 9]

[0036]

[Table 10]

[0037]

[Table 11]

Next, the R ² value, the amount of warpage, and the surface roughness of the glass when the composition shown in Table 12, that is, the nitrogen content was changed to 5, 25, 30 eq%, were examined. The examination results are shown in Tables 13 to 15.

[0039]

[Table 12]

[0040]

[Table 13]

[0041]

[Table 14]

[0042]

[Table 15]

According to Tables 13 to 15, in the case of E-34 to E-37 in which the nitrogen content is 5, 25 eq%, any metallic element type glass is excellent in R ² value, warpage amount and surface roughness. Met. On the other hand, E having a nitrogen content of 30 eq%
The glass of -38, 39 was slightly inferior in surface roughness to E-34 to E-37 having a small nitrogen content.

Next, a base plate was prepared with the composition of E-37, and a disk was prepared in the same manner as described above. The resulting disc was examined for surface roughness (Ra), Young's modulus, density, and hardness. Table 16 shows the results.

[0045]

[Table 16]

As shown in Table 16, the nitrogen content was 25 e
All the discs with q% show excellent surface roughness and high Young's modulus, and are suitable as discs for high-speed rotation. Oxynitride glasses containing rare earth elements such as Y, Ce and Gd have high Young's modulus, but also have high densities, so that from the viewpoint of improving non-rigidity, Ca-based or Mg-based oxynitride Glass is preferred.

(Si, Al, Ca, O, N) = (30,
50, 20, 75, and 25) are shown in Table 1.
7, and the glass (Tg: 950)
C) from 465 to 930 in a nitrogen atmosphere.
The thermal expansion up to ° C. was measured with a compression probe type thermal expansion meter. The results are shown in Table 17.

[0048]

[Table 17]

[0049]

As described above, according to the present invention, it is possible to obtain a glass substrate in which permanent distortion is suppressed and the warpage of a disk is greatly reduced. In addition, a homogeneous glass substrate suitable as a disk can be obtained, and the needs for high recording density, high transfer speed, and high-speed rotation of a hard disk can be met.

[Brief description of the drawings]

FIG. 1: Ca—Al in the case of 5 eq% ≦ N ≦ 25 eq%
FIG. 3 is a composition diagram of metal components of Ca, Al, and Si in the oxynitride glass represented by —Si—O—N.

FIG. 2 shows Mg—Al when 5 eq% ≦ N ≦ 25 eq%
FIG. 3 is a composition diagram of metal components of Mg, Al, and Si in the oxynitride glass represented by —Si—O—N.

FIG. 3 shows Y—Al— when 5 eq% ≦ N ≦ 25 eq%.
FIG. 3 is a composition diagram of metal components of Y, Al, and Si in an oxynitride glass represented by Si—O—N.

FIG. 4 Gd-Al when 5 eq% ≦ N ≦ 25 eq%
The composition diagram of the metal component of Gd, Al, and Si in the oxynitride glass represented by -Si-ON.

FIG. 5: Ce—Al when 5 eq% ≦ N ≦ 25 eq%
The composition diagram of the metal component of Ce, Al, and Si in the oxynitride glass represented by -Si-ON.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazutaka Kunii 1-5-5 Takatsukadai, Nishi-ku, Kobe City Inside Kobe Research Institute, Kobe Steel Ltd. (72) Inventor Nobuhiro Hara 1-chome, Takatsukadai, Nishi-ku, Kobe-shi No. 5-5 Kobe Steel, Ltd. Kobe Research Institute F-term (reference) 4G062 AA18 BB01 CC10 DB01 DB02 DB03 DB04 DC01 DD01 DD06 DE01 DF01 EA01 EA10 EB01 EC01 ED01 ED02 ED03 ED04 EE01 EE02 EE03 EE04 FA01 EB01 FC01 FD01 FE01 FF01 FG01 FH01 FJ01 FJ02 FJ03 FK01 FK02 FK03 FK04 FL01 FL02 FL03 FL04 GA01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH03 KK KK JJ JJ JJ KK KK FA00

Claims (8)

[Claims] 1. (Tg-20) / 2 ° C. to (Tg-20)
℃ glass permanent undistorted recording medium, wherein R ² value of the regression line calculated from the following equation by substituting the measured values of the thermal expansion in the temperature range (1) is 0.9 or more. (Equation 1) (Where X: temperature (° C.), Y: thermal expansion (%), n: number of measurements) 2. The method according to claim 1, wherein the glass is Ca—Al—Si—O—.
N-based, Mg-Al-Si-ON-based, Y-Al-Si-
ON-based, Ce-Al-Si-ON-based, La-Al-
Si-ON-based, Gd-Al-Si-ON-based, Mg-
The glass for a recording medium according to claim 1, comprising at least one composition selected from the group consisting of Si-ON-based and Ca-Si-ON-based. 3. The glass according to claim 1, wherein the glass is Ca—Al—Si—O—N.
Oxynitride glass represented by the formula:
The metal components of 1 and Si are in the shaded portion in the composition diagram shown in FIG. 1, and the nonmetal components of O and N are 5 eq% ≦ N ≦ 25 eq% and O + N = 100 e.
The glass for a recording medium according to claim 2, which is q%. 4. The glass according to claim 1, wherein the glass is Mg—Al—Si—O—N.
Mg, A, which was an oxynitride glass represented by
The metal components of l and Si are in the shaded portion in the composition diagram shown in FIG. 2, and the nonmetal components of O and N are 5 eq% ≦ N ≦ 25 eq% and O + N = 100 e.
The glass for a recording medium according to claim 2, which is q%. 5. The oxynitride glass represented by Y—Al—Si—O—N, wherein Y, Al,
The metal components of Si are shown in the hatched portions in the composition diagram shown in FIG. 3, and the nonmetal components of O and N are
5 eq% ≦ N ≦ 25 eq%, and O + N = 100 eq%
The glass for a recording medium according to claim 2, which is: 6. The method according to claim 1, wherein the glass is Gd-Al-Si-O-N.
Oxynitride glass represented by the formula: Gd, A
The metal components of 1 and Si are in the shaded portion in the composition diagram shown in FIG. 4, and the nonmetal components of O and N are 5 eq% ≦ N ≦ 25 eq% and O + N = 100 e.
The glass for a recording medium according to claim 2, which is q%. 7. The method according to claim 1, wherein the glass is Ce—Al—Si—O—N.
In the oxynitride glass represented by
The metal components of 1 and Si are in the shaded portion in the composition diagram shown in FIG. 5, and the nonmetal components of O and N are 5 eq% ≦ N ≦ 25 eq% and O + N = 100 e.
The glass for a recording medium according to claim 2, which is q%. 8. A hard disk substrate using the glass according to claim 1.