JP2002260216A - Glass substrate for information recording disk and information recording disk using the glass substrate - Google Patents

Abstract

(57) [Summary] [Problem] To provide a glass substrate for an information recording disk with improved quality. SOLUTION: By weight percentage, 50% or more and 70% or less of SiO ₂ , 10% or more and 25% or less of Al ₂ O ₃ , 1%
Ln ₂ O ₃ (Ln represents Pr, Nd, Sm or Eu) of not less than 8% and B ₂ O _{3 of not} less than 5% and not more than 15%;
0% to 13% of R ₂ O (R represents an alkali metal element). As a result, the visibility of the glass substrate is improved, and the occurrence of defects such as scratches and chips generated during processing of the glass substrate is reduced, and the defect of the glass substrate can be easily found in quality inspection and the like. Further, the influence of the glass substrate on the magnetization characteristics when processed into a magnetic disk or a magneto-optical disk can be reduced. In addition, separation of a layer or a film formed on the surface of the glass substrate can be suppressed. That is, the quality of the glass substrate can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a glass substrate for an information recording disk, and more particularly to a glass substrate suitable for a magnetic disk and the like.

[0002]

2. Description of the Related Art At present, magnetic disk devices and portable information are used as information recording media for general-purpose large-sized computers and personal computers, and as home servers for temporarily storing images distributed by digital signals. Magneto-optical disks and optical disks are used as recording media.

For example, in a magnetic disk drive, a 3.5-inch aluminum substrate has conventionally been used as a substrate for general-purpose or desktop personal computers, and mainly a portable notebook-type personal computer has been mainly used. A glass substrate with a size of 0.5 inches has been used. This glass substrate is harder and harder to deform than the aluminum substrate, and has excellent surface smoothness. For this reason, glass substrates have come to be applied to general-purpose 3.5-inch and 3-inch substrates instead of aluminum substrates. Also, glass substrates are being applied to information recording devices for small portable terminals such as 1.8-inch size and 1-inch size.

[0004] Further, demands for increasing the capacity of information recording devices and information recording media have been increasing, and in recent years, the annual rate of 10
The storage capacity is increasing at a rate of 0%. In order to cope with such an increase in the storage capacity, it is necessary to lower the flying height of the head of the recording unit with the increase in the density of information recorded on the disk. Therefore, the application of a glass substrate to the substrate of the information recording disk is expanding because the development of an information recording disk having a smoother recording surface is required.

[0005] Such a glass substrate has problems such as easiness of breaking, easy breaking and cracking which are inherent properties of glass. In order to solve such problems as the easiness of breaking glass, in a conventional glass substrate,
Chemical strengthening and crystallization are performed. However, with the chemically strengthened amorphous glass substrate, the surface of the glass substrate is roughened by the replacement of alkali ions in the chemical strengthening process, so the smoothness is lost, and the head flying height will be reduced in the future Difficult to do. Further, on the surface of the chemically strengthened glass substrate, the substituted alkali ions having a large ionic radius are chemically unstable, so that the glass substrate cleaning process and the film forming process on the glass substrate surface during the production process are performed. Alkali ions move to the surface of the substrate and precipitate during heat treatment, etc., and defects such as peeling or adhesion of the film or layer formed on the surface of the glass substrate and magnetic films formed on the surface of the glass substrate etc. There is a concern that the magnetic properties may deteriorate. In addition, even when the information recording disk is used for a long time or stored in a high-temperature and high-humidity environment, defects such as peeling or adhesion of the film or layer may occur, and alkali ions may migrate to the glass substrate surface. It is feared that the magnetic properties of the magnetic film and the like are deteriorated.

On the other hand, the crystallized glass substrate is in a state in which crystalline fine particles are generated in amorphous glass, and the polishing rate is reduced by the difference in hardness between the amorphous portion and the crystalline portion. Due to the difference, there has been a problem that it is difficult to create a recording surface having sufficient smoothness so as to be able to cope with a high density required for an information recording disk.

[0007] In order to solve the problems of such chemically strengthened and crystallized glass substrates, the inventors disclosed in Japanese Patent Laid-Open No.
No. 83531 proposes improving the mechanical strength by incorporating rare earth ions into a glass substrate. As a result, a glass substrate with sufficient strength can be obtained without chemical strengthening or crystallization,
The glass substrate surface is not roughened during the manufacturing or processing process of the information recording disk using the glass substrate, and the glass substrate surface is not roughened due to prolonged use or storage of the information recording disk. Smoothness can be maintained. That is, it is possible to produce a glass substrate having a recording surface with sufficient smoothness so as to be able to cope with the high density required for information recording disks.

[0008]

By incorporating rare earth ions into a glass substrate, a glass substrate having sufficiently high mechanical strength and sufficient smoothness can be manufactured. However, in the production of glass substrates and information recording disks, the suppression of defective products, the detection of defective products, the chemical durability, and the magnetic characteristics required when processed into magnetic disk devices and magneto-optical disks, etc. It is hard to say that it is sufficiently considered, and improvement of the quality as a glass substrate for an information recording disk is required from these viewpoints.

An object of the present invention is to improve the quality of a glass substrate for an information recording disk.

[0010]

According to the present invention, there is provided a glass substrate for an information recording disk comprising 50% to 70% by weight of SiO ₂ , 10% to 25% of Al ₂ O ₃ , and 1% by weight.
% Or more and 8% or less of Ln ₂ O ₃ (Ln represents Pr, Nd, Sm or Eu), and at least one of B ₂ O ₃ and R ₂ O (R represents an alkali metal element). Solves the above problem.

According to this structure, the glass substrate is appropriately colored by containing 1% or more and 8% or less of Ln ₂ O ₃ (Ln represents Pr, Nd, Sm or Eu). Since the transmittance can be set to a high value, bubbles and other contaminants in the glass substrate can be easily visually detected. Further, since the glass substrate is easily visible in the processing and cleaning steps of the glass substrate, the processing step of the information recording disk, and the like, processing defects such as damaging the glass substrate can be suppressed. In addition, when the glass substrate is used for a magnetic disk device, a magneto-optical disk, or the like, the amount of magnetization of the glass substrate can be reduced, and variations in magnetic characteristics can be reduced. That is, it is possible to suppress the occurrence of defects during the production of the glass substrate and the information recording disk, and further to reduce the variation in the magnetic characteristics, so that the quality of the glass substrate for the information recording disk can be improved.

It is preferable that Ln constituting Ln ₂ O ₃ be Pr, because the quality of the glass substrate for an information recording disk can be further improved.

Further, the weight percentage is 50% or more and 70% or more.
The following SiO ₂ and 10% or more and 25% or less of Al ₂ O
₃ , B ₂ O _{3 of} 5% or more and 15% or less, and 10% or more of 1
3% or less of R ₂ O (R represents an alkali metal element).

Further, in terms of weight percentage, 50% or more and 70% or less of SiO ₂ , 10% or more and 25% or less of Al ₂ O ₃ ,
Ln ₂ O _{3 of} 1% or more and 8% or less (Ln is Pr, Nd, S
m or Eu) and 5% to 15% of B ₂ O
₃ and 10% or more and 13% or less of R ₂ O (R represents an alkali metal element).

With such a structure, 5% or more and 15%
By containing the following B ₂ O ₃ and 10% or more and 13% or less of R ₂ O (R represents an alkali metal element), a striae and bubbles are reduced, and a sufficiently homogeneous glass substrate can be obtained. In addition, the film or layer formed on the surface of the glass substrate or on the recording surface due to precipitation of the alkali element on the surface of the glass substrate can be prevented from being separated, so that the quality of the glass substrate for an information recording disk can be improved.

Further, R ₂ O (R represents an alkali metal element) is composed of Li ₂ O, Na ₂ O, K ₂ O and
When the ratio of i ₂ O / Na ₂ O is 0.4 or more and 0.6 or less, peeling of a film or a layer formed on the surface of the glass substrate or the recording surface is surely suppressed, that is, It is preferable because the stability can be further improved and the quality of the glass substrate for the information recording disk can be further improved.

Further, the transmittance of visible light having a wavelength of 300 nm to 700 nm is 50% or more and 85% or less, and the magnetization when applying a magnetic field of 1 kOe is 3 × 10 ^−3.
If the glass substrate for an information recording disk is not more than emu / cc, bubbles and other contaminants in the glass substrate can be easily found by visual inspection, and the glass substrate processing and cleaning steps, and the information recording disk processing steps In such cases, the glass substrate is easily visible, and processing defects such as scratching the glass substrate can be suppressed. In addition, when a glass substrate is used for a magnetic disk device or a magneto-optical disk,
The amount of magnetization of the glass substrate can be reduced, and variations in magnetic characteristics can be reduced. That is, it is possible to suppress the occurrence of defects during the production of glass substrates and information recording disks,
Further, since the variation in the magnetic characteristics can be reduced, the quality of the glass substrate for the information recording disk can be improved.

The amount of the alkali element eluted into the hot water when immersed in 80 cc of 70 ° C. hot water for 24 hours is 0.1 mg.
/ L or less, a layer formed on the surface of the glass substrate or on the recording surface due to precipitation of an alkali element on the surface of the glass substrate can be prevented, and sufficient chemical stability can be obtained. Therefore, the quality of the glass substrate for an information recording disk can be improved.

If the information recording disk has any one of the above-mentioned glass substrates for an information recording disk and an information recording layer formed directly or via another layer on the surface of the glass substrate, the information recording disk By improving the quality of the glass substrate for use, the quality as an information recording disk can also be improved.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a glass substrate for an information recording disk to which the present invention is applied will be described below with reference to FIGS. FIG. 1 is a plan view showing a schematic configuration of a glass substrate for an information recording disk to which the present invention is applied. FIG. 2 is a sectional view showing a schematic configuration of a magnetic disk using a glass substrate to which the present invention is applied.
FIG. 3 is a perspective view showing a schematic configuration of a magnetic disk drive provided with a magnetic disk using a glass substrate to which the present invention is applied.

As shown in FIG. 1, the glass substrate 1 for an information recording disk of this embodiment has a diameter of 65 mm and a thickness of 0.1 mm.
This is a 635-mm 2.5-inch disk-shaped disk. In the center, when used as an information recording disk, the disk is mounted on a spindle or the like connected to a motor of a device that performs recording, reading, or reproducing. A circular through hole 3 having a diameter of 20 mmφ for fixing by an inner peripheral chuck or the like is formed. The corners of the inner peripheral surface and the outer peripheral surface are cut off and chamfered at 45 degrees to form a chamfer portion 5.

The production of such a glass substrate 1 is performed as follows. A raw material powder in an amount determined to have a desired glass composition is weighed and mixed, put in a platinum crucible, and melted at 1600 ° C. in an electric furnace. After the raw materials are sufficiently dissolved, the stirring blade is inserted into the glass melt in the crucible, and the
Stir for hours. Thereafter, the stirring blade was taken out and allowed to stand for 30 minutes, and then a glass melt was poured into a mold to obtain a glass block having a diameter of about 70 mmφ and a thickness of about 1 mm. The obtained glass block is reheated to the vicinity of the glass transition point of the glass, and is gradually cooled to remove a strain.

The glass block from which the distortion has been removed is cut out using a core drill so that the inner periphery and the outer periphery are concentric. Further, the chamfered portion 5 is formed by chamfering both corners of the inner peripheral surface and the outer peripheral surface with a diamond grindstone. As a result, a disk-shaped glass substrate 1 having the holes 3 is formed. Thereafter, both surfaces of the glass substrate 1 are roughly polished and then polished. After the polishing, the glass substrate 1 is washed with a cleaning agent and pure water to form the glass substrate 1 for an information recording disk. As described above, the glass substrate 1 for an information recording disk of the present invention has not been subjected to a strengthening process such as a chemical strengthening process or a crystallization process.

The creation of a magnetic disk will be described as an example of an information recording disk formed using such a glass substrate 1 for an information recording disk. The magnetic disk 7 is, as shown in FIG.
A particle size control layer 9 sequentially formed on the surface of the
It is composed of an orientation control layer 11, a magnetic film 13, a protective film 15, a lubricating film 17, and the like. The grain size control layer 9 controls the grain size of the magnetic film 13, and the orientation control layer 11 controls the orientation of the magnetic film 13. In this example, the particle size control layer 9 is made of NiAl
A 20-nm thick alloy film is formed. The orientation control layer 11 is formed of a CrMo-based alloy film with a thickness of 10 nm. The magnetic film 13 serving as the information recording layer is made of CoCrPrB.
A system magnetic film is formed with a thickness of 20 nm. Protective film 15
Has a film thickness of C of 4 nm. All of these layers or films were formed by a sputtering method. The lubricating film 17 was formed by a coating method after the end of the sputtering.

The characteristics, productivity, etc. of the glass substrate 1 for information recording disks of various compositions produced by such a method and the magnetic disk 7 having the magnetic film 13 formed on the glass substrate 1 were evaluated. The glass composition for improving the quality of glass was studied.

First, attention was paid to the types of rare earth elements to be added, and glasses having various compositions were produced. Table 1 shows the glass compositions and the characteristics of the glass substrate and the magnetic disk with respect to those glass compositions.

[0027]

[Table 1] In Table 1, aluminoborosilicate glass having the same composition and the same amount except for the type of the rare earth element was used. The amount of the rare earth oxide to be contained was kept constant at 2.8% by weight.
As characteristics of the glass substrate, micro Vickers hardness, transmittance of visible light, coloring property, and yield of the glass substrate were evaluated. The micro-Vickers hardness was applied to a glass substrate under the conditions of a load of 500 g and a load application time of 15 seconds,
An average value of 10 points was obtained. The transmittance of visible light was obtained by measuring a transmittance spectrum from a spectral transmittance curve of a wavelength from 300 nm to 700 nm using a spectrophotometer, and calculating the integrated value of the total transmittance of light in this wavelength range. The degree of coloring was visually evaluated to determine the degree of coloring. Colorless ones were evaluated as x, and colored ones were evaluated as ○. Yield is evaluated by using a device that inspects the glass substrate for the number of foreign substances using scattered light from laser light irradiation. Then, evaluation was made based on the ratio of non-defective products.

Further, as characteristics of the magnetic disk, magnetization, standard deviation of magnetization, recording / reproducing characteristics, and yield of the magnetic disk were evaluated. Further, the overall yield from the production of a glass block before processing to a glass substrate to the production of a magnetic disk was evaluated. The magnetization and the standard deviation of the magnetization are
The BH curve was measured by a vibrating sample magnetometer (VSM), and the background component of the hysteresis loop of the magnetic film was regarded as magnetism from the glass substrate, and the magnitude of the background component was evaluated. The magnetization and the standard deviation of the magnetization are the magnitude of the magnetization when 1 kOe is applied as a magnetic field.

In addition, the recording and reproducing characteristics of the magnetic disk were evaluated. Magnetic disk drive 1 used for evaluation of recording and reproduction characteristics
Reference numeral 8 denotes a magnetic disk 7, a spindle 19, a spindle motor (not shown), a magnetic head 21, an arm 23 of the magnetic head, a voice coil motor 25 for driving the head, a housing 27, etc., as shown in FIG. It is configured. A spindle motor (not shown), a voice coil motor 25, and the like are fixed to the housing 27. A spindle 19 is connected to a spindle motor (not shown), and the magnetic disk 7 is fixed to the spindle 19. The magnetic disk 7 has a spindle 19 driven by a spindle motor (not shown).
By the rotation of, the whole is rotated. On the other hand, the arm 23 is attached to the voice coil motor 25,
The magnetic head 21 is attached to the tip of the arm 23. The magnetic head 21 is a voice coil motor 2
The arm 23 is moved by driving the magnetic disk 5 to move on the recording surface of the magnetic disk 7 by a predetermined flying height.

A magnetic disk formed using glass substrates of various compositions was mounted on such a magnetic disk device 18, and a magnetic signal corresponding to ²⁰ Gb / in ² was recorded to evaluate magnetic recording / reproducing characteristics. This evaluation was performed on 150 magnetic disks, and the ratio of magnetic disks having sufficient recording / reproducing characteristics was determined as the magnetic disk yield. further,
The overall yield was evaluated from the yield of the glass substrate and the yield of the magnetic disk. ×, if the overall yield is less than 80%, ○, 90 if the yield is 80% or more and less than 90%
% Or more was evaluated as ◎.

As shown in Table 1, in the characteristics of the glass substrate, the micro Vickers hardness was about 650 or more in any of the glass substrates containing a rare earth element, which proved to be good. The transmittance of visible light was 80% or more in any of the glass substrates containing a rare earth element. Nd, Pr, Sm, Eu, H among rare earth elements
In the glass substrate containing any one of o and Er, sharp absorption due to the ff transition of rare earth was observed in the visible light region. Therefore, the transmittance is slightly lower than that of a glass substrate containing another rare earth element. However, Nd, Pr, Sm,
Because of the sharp absorption of Eu, Ho, and Er, clear coloring was observed on the glass substrate containing any one of Nd, Pr, Sm, Eu, Ho, and Er among the rare earth elements. In the evaluation by visual observation under an incandescent lamp, it was found that Pr was yellowish-green, Nd was purple, and Sm and Eu were very pale but yellow and pink, respectively. Er and Ho were also colored pink. The glass substrate containing another rare earth element was colorless and no coloring was observed.

When the yield of the glass substrate with respect to these substrates was evaluated, Pr, Nd, H
In the cases of o and Er, defects occurring during processing or cleaning, that is, defects due to damage such as scratches were smaller than those not colored, and the yield was 95% or more. This is because the colored glass substrate is easier to check visually than the transparent glass substrate in the processing step and the cleaning step, and is easy to handle. By suppressing the occurrence of damage,
It is considered that the yield has improved.

Although not shown in the table, a glass substrate having a high coloring property containing Ni was evaluated as a comparative example. The Ni-containing substrate had a transmittance of 47%.
It is difficult to find bubbles existing in the glass, or the components that make up the crucible when melting the raw materials of the glass substrate, that is, erosion of the furnace material into the glass. Yield was low due to the remaining.

Thus, a clear correlation is seen between the transmittance and the yield of the glass substrate and the magnetic disk. If the transmittance is less than 50%, bubbles remaining in the glass substrate and mixing of furnace materials are hard to be found, which causes a reduction in yield. Further, when the transmittance of the glass substrate exceeds 85%, the glass substrate becomes difficult to visually recognize, so that it is difficult to handle the glass substrate in processing and cleaning work, and processing defects such as accidental scratching increase. . Therefore,
The transmittance of the glass substrate is colored enough to be seen,
In addition, in order to obtain a glass substrate in which bubbles and furnace materials remaining in the glass substrate can be easily found, that is, defects can be easily found, the content needs to be 50% or more and 85% or less. further,
Rare earth elements added to the glass substrate to achieve such optical characteristics include Pr, Nd, Sm, Eu, and E.
r or Ho was found to be preferred. this house,
Pr, Nd, Er or Ho is more preferable because coloring is remarkable.

On the other hand, as shown in Table 1,
In the characteristics, the magnetization characteristics are Sc, of the rare earth elements,
Formed using a glass substrate containing any one of Y and La
In the magnetic disk, the magnitude of magnetization of the glass substrate is 1
0^-4on the order of emu / cc and other rare earth elements
Compared to magnetic disks formed using glass substrates containing
Thus, the amount of magnetization was extremely small. S as rare earth element
With a magnetic disk formed using a glass substrate containing m
Indicates that the magnetization shows a diamagnetic behavior, and -4 × 10
^-4emu / cc. Pr, N as rare earth elements
Formed using a glass substrate containing either d or Eu
1.0 to 3.0 × 10 ^-3emu
/ Cc.

Gd, Tb, Dy, H as rare earth elements
Glass substrate containing any one of o, Er, Tm, and Yb
In a magnetic disk formed by using^-3~ 2
× 10 ^-2emu / cc and the value of magnetization is other rare earth element
Was larger than the case where The difference in magnetization
When the standard deviation of the magnetization shown was evaluated, the magnitude of the magnetization
The larger the value, the larger the standard deviation of magnetization. This
This is because the larger the magnetization, the more the glass substrate
This indicates that the variation in magnetization is large. In particular,
Magnetization size is 3 × 10^-3G exceeding emu / cc
Any one of d, Tb, Dy, Ho, Er, Tm, and Yb
Magnetic disk using a glass substrate containing
In the disk, the standard deviation of magnetization is 1 × 10^-3emu / cc
As described above, the variation in the magnetic characteristics due to the glass substrate is large.
I got it.

[0037] Looking at the yield of the magnetic disk by the magnetic recording and reproducing characteristics, the magnetization is 3 × ^{10 -} below 3 emu / cc, the magnetic disk of a standard deviation of less than 1 × ¹⁰ -3 emu / cc in magnetization, sufficient The magnetic disk from which magnetic properties were obtained was as good as 90% or more. However, the magnetization is 3 ×
Exceeds 10 ⁻³ emu / cc and the standard deviation of magnetization is 1
For a magnetic disk having a capacity of × 10 ⁻³ emu / cc or more,
It was found that the yield was reduced to 80% or less.
This is because the magnetic properties of the glass substrate changed due to a slight solid-state difference of the rare earth element contained in the glass substrate, and the standard deviation became large, resulting in variations in recording when recording with a constant magnetic field. it is conceivable that.

Thus, the magnitude of the magnetization is 3 × 10 ^−3.
If it is less than emu / cc, a magnetic disk having a relatively small variation in magnetic recording / reproduction was obtained. Magnitude of 3
If it exceeds × 10 ⁻³ emu / cc, the dispersion of the magnetic recording / reproducing characteristics among the glass substrates increases, which is not preferable. Therefore, in order to reduce the influence of the glass substrate on the magnetization of the magnetic disk, the magnitude of the magnetization is 3 × 10 ^−3.
It is necessary to be less than emu / cc. Further, in order to obtain such magnetic characteristics, Sc, as a rare earth element,
It is preferable that any one of Y, La, Pr, Nd, Sm, and Eu is contained in the glass substrate.

The total yield was evaluated in consideration of the effect on the yield of the glass substrate and the effect of the magnetic characteristics on the recording / reproducing characteristics of the magnetic disk drive. As a result, both the effect on the yield of the glass substrate and the effect of the magnetic characteristics on the recording / reproducing characteristics showed satisfactory results, and any one of Pr, Nd, Sm, and Eu having an overall yield of 80% or more was obtained. If the glass substrate contains one as a rare earth element, the quality of the glass substrate can be improved. Furthermore, if a glass substrate containing Pr as a rare earth element that provides an overall yield of 90% is used, the quality of the glass substrate can be further improved.

Further, the relationship between the type of rare earth oxide and the amount of rare earth oxide added was examined. For coloring, Table 1
In the glass substrate containing a rare earth element which was transparent in the above, no change was observed in the transmittance of the glass substrate even when the content of the rare earth element was increased or decreased. For this reason, among the rare earth elements that colored the glass substrate, Pr, Er, and Sm were prepared with glass substrates having different contents, and the same examination as in Table 1 was performed. Table 2 shows the results of the study.

[0041]

[Table 2] When the content of Pr was changed, sample No. 1
The glass substrate containing 0.7% by weight of Pr ₂ O ₃ of No. 7 has low micro Vickers hardness and low mechanical strength of the glass, so there are many defects such as polishing scratches and spatters, and the yield of the glass substrate is 82. % Was low. Sample No. 1 containing 1% by weight of Pr ₂ O ₃ . 16, and Pr ₂ O ₃ at 1.5
No. 7% by weight. In Nos. 18 to 21, the micro Vickers hardness showed a high value, and both the coloring and the magnetic properties were sufficient. From this, the sample No. 16,
And sample no. For the glass substrates of Nos. 18 to 21, the total yield exceeded 90%, and good results were obtained.

On the other hand, as shown in sample No. 22, Pr ₂ O ₃
When the content exceeds 7% by weight, there is no problem with regard to coloring, but the magnetization of the magnetic disk is 3 × 10 ⁻³ em.
The value exceeded u / cc. For this reason, the variation in magnetization became large, and the yield of the magnetic disk was less than 80%, and a sufficient result was not obtained. Further, the sample No.
In a glass substrate having a Pr ₂ O ₃ content of 10.5% by weight, such as 23, rare earth elements in the glass are not uniformly dissolved in the glass, the number of defective products increases, and the yield is as low as 15%. It was not preferable as a glass substrate.

On the glass substrate containing Er as a rare earth element, the sample N having an Er ₂ O ₃ content of 0.5% by weight was used.
o. In 25, the micro Vickers hardness is small,
A glass substrate with sufficient strength could not be obtained, and the yield of the glass substrate was poor. At this time, the magnetization value of the magnetic disk was as high as 3.1 × 10 ⁻³ emu / cc, and the yield as the magnetic disk was also low. Er ₂ O ₃ content of 1
When the weight percentage is increased, the micro Vickers hardness increases and the transmittance decreases, so that the yield of the glass substrate increases, but the magnetization is still 3 × 1.
Since more than 0 ^-3 emu / cc, yield of the magnetic disk was bad. As described above, when Er is used as the rare earth element, the hardness and optical characteristics of the glass substrate,
It has been found that there is no composition range that simultaneously satisfies both magnetic properties as a magnetic disk.

For a glass substrate containing Sm as a rare earth element, the optical characteristics of the glass substrate are as follows: Sm ₂
When the O ₃ content is 2.5% by weight or more, the transmittance is 85%.
Below is the appropriate range. Magnetic properties of a magnetic disk, which was also a fair the _Sm 2 _{O 3} is contained 10% by weight, the content of _Sm 2 _{O 3} exceeds 10 wt% P
As in the case of r, the residual raw material remains in the glass, which is not preferable.

Similarly, rare earth elements such as Nd, Eu, H
When a glass substrate containing o was examined, the same results were obtained for Nd and Eu as for Sm, but when the content of Nd or Eu exceeded 8% by weight, the magnetic properties as a magnetic disk were Decreased, which was not preferable. Regarding Ho, as in the case of the glass substrate containing Er as a rare earth element, there was no composition range that satisfied both the optical characteristics of the glass substrate and the magnetic characteristics of the magnetic disk at the same time, so that a favorable result was not obtained.

As described above, Pr and N are rare earth elements.
By containing d, Sm, and Eu, and making the concentration of the rare earth oxide contained 1% by weight or more and 8% by weight or less, the optical characteristics of the glass substrate improve the visibility of the glass substrate and improve the visibility of the glass substrate. It is possible to reduce the occurrence of defects such as scratches and chips generated during processing, and to easily find defects such as bubbles, striae, foreign matter, scratches and chips in the glass substrate in quality inspection and the like. Furthermore, since the magnetization of the glass substrate can be reduced in the magnetic characteristics of a magnetic disk or a magneto-optical disk, the influence of the glass substrate on the magnetic characteristics of the magnetic disk or magneto-optical disk can be reduced. Therefore, the quality of the glass substrate can be improved.

Further, Pr is contained as a rare earth element,
The concentration of the rare earth oxide is 1.5% by weight to 5.2% by weight.
If it is below, the total yield is 90% or more, and the quality of the glass substrate can be further improved.

In the case other than the case where one of Pr and Nd is contained as the rare earth element, and when the Sm is contained as the rare earth element, the concentration of the rare earth oxide is not less than 2.5% by weight and 9%. Wt% or less, Eu as a rare earth element
Is contained, the concentration of the rare earth oxide is 2.5.
It may be not less than 8% by weight and not more than 8% by weight.

The rare earth elements Pr, Nd, S
If the content of m and Eu is less than 1% by weight, the mechanical strength of the glass substrate, such as the micro-Vickers hardness, decreases, or the transmittance becomes too high, and the yield of the glass substrate decreases. That is, defects due to scratches, sprinkling, etc. of the glass substrate are increased, and the quality of the glass substrate is reduced. On the other hand, when the content of the rare earth element is more than 8% by weight, the magnetization value of the glass substrate increases, and when processed into a magnetic disk or a magneto-optical disk, the variation in the magnetization characteristics of the magnetic disk or the magneto-optical disk is reduced. This is not preferable because it increases the quality of the glass substrate and the quality of a magnetic disk or a magneto-optical disk using the glass substrate. Further, when the content of the rare earth element is more than 8% by weight, the quality of the glass substrate is deteriorated because the raw material may remain in the glass, which is not preferable.

Next, in order to examine a glass composition suitable for a glass substrate for an information recording disk, the stability of the glass, the amount of alkali elution from the glass substrate, the micro Vickers hardness of the glass substrate surface, the ring strength, the high-temperature high-humidity test Table 3 shows the results of the examination. In each sample shown in Table 3, Pr was used as a rare earth element to be added. In addition,
In the glass compositions in Table 3, R ₂ O is Li ₂ O, Na ₂
The total alkali metal oxide content including O and K ₂ O is shown.

[0051]

[Table 3] Here, with respect to the stability of the glass, those in which bubbles, striae, foreign matter, etc. were remarkably observed after melting the glass were evaluated as x, and clear, homogeneous glass was obtained without bubbles, striae, foreign matter, etc. When it was, it was marked as ○. The amount of alkali eluted from the glass substrate was determined by placing each glass substrate as a sample in 80 ml of 70 ° C. pure water.
After immersion in the pure water, the amount of alkali components eluted from the glass substrate in the pure water was evaluated based on the concentration in the water. The ring strength is 22 m in outer diameter on the upper surface side of a 2.5 ″ glass substrate as a sample.
After placing an annular member of mφ and placing an annular member having an inner diameter of 63 mmφ and an outer diameter of 65 mmφ on the lower surface side of the glass substrate, a load was applied to these annular members to measure the breaking strength of the glass substrate. .

In the high-temperature and high-humidity test, a magnetic disk was manufactured using the obtained glass substrate in the same manner as described above, and the manufactured magnetic disk was mounted on a magnetic disk device as shown in FIG. When the percentage of drives in which a problem such as an increase in the error rate due to the high-temperature and high-humidity test occurred was 1% or more, X was marked, and when it was 1% or less, O was marked. High temperature and high humidity test
The test was performed under the conditions of a temperature of 60 ° C. and a humidity of 90% for 48 hours.

First, Li₂O, Na₂O, K₂Match O
Total alkali oxide amount (R in the table) ₂O) changed
The sample was designated as No. 3 in Table 3. 42 to 48. Sample No. 4
Low content of alkali metal oxides as in 2, 43
The melting temperature of the glass becomes too high,
At the melting temperature, striae and bubbles are often seen, and the raw material remains
Was confirmed. Sample No. Alkali metal acid like 44
When the content of the compound is 10% by weight, striae are not observed.
A homogeneous glass block was obtained. That is, Arca
Homogeneous glass if the oxide content is 10% by weight or more
Blocks are obtained.

On the other hand, as the amount of R ₂ O was increased, the amount of alkali elution gradually increased, and the micro Vickers hardness and the ring strength tended to decrease. Sample N
In the case of o.44 and 45 glasses, the alkali elution amount is 0.1 m.
g / l or less, and good results were obtained in the high-temperature and high-humidity test. Sample No. When a glass substrate having a content of R ₂ O of 46 to 48 exceeding 13% by weight is used,
In the high-temperature and high-humidity test of the magnetic disk drive, some error rates increased. This is presumably because an alkali element precipitated from the glass substrate on the surface of the glass substrate by holding the glass substrate in a high-temperature and high-humidity state, and an error occurred because the magnetic film was separated from the glass substrate.

As can be seen from the alkali elution amount and the results of the high temperature and high humidity test, the alkali elution amount was 0.1 mg.
By setting the ratio to / l or less, adhesion of the magnetic film or the like to the glass substrate is not impaired by precipitation of alkali on the surface of the glass substrate, so that an increase in the error rate can be suppressed. That is, peeling of a layer or a film formed on the surface of the glass substrate can be suppressed, so that the quality of the glass substrate can be improved. At this time, the alkali elution amount was 0.1 mg / l.
In order to make the content below, the content of the alkali metal oxide is 1
The content should be 0% by weight or more and 13% by weight or less.

Regarding the content of B ₂ O ₃ , sample No. 62
It examined from glass substrates, such as -64. Samples B ₂ O ₃ content exceeds 15 wt% No. In the glass substrate of No. 62, the glass became unstable and striae were remarkably generated, and a homogeneous glass substrate could not be obtained. Sample No. B content of 15 wt% of B ₂ O ₃ With the glass substrate of No. 63, a glass having stability was obtained, and a uniform glass substrate with few bubbles and stria was obtained. B ₂ O ₃ content of 4
% Of the sample No. In the case of the glass substrate No. 65, the chemical stability was lowered, and the alkali elution amount exceeded 0.1 mg / l.
On the other hand, in sample No. having a B ₂ O ₃ content of 5% by weight. In the glass substrate No. 64, since the alkali elution amount was less than 0.1 mg / l, the ratio of magnetic disk devices that failed in the high-temperature high-humidity test was relatively small, and a chemically stable glass substrate could be obtained. Was.

As described above, the content of B ₂ O ₃ is 5% by weight.
If it is less than 15% by weight, the alkali elution amount is 0.1%.
mg / l or less, peeling of a layer or a film formed on the surface of the glass substrate can be suppressed, and a clear and uniform glass substrate can be obtained, so that the quality of the glass substrate can be improved. When the content of B ₂ O ₃ is less than 5% by weight,
In a high-temperature and high-humidity test using a magnetic disk drive,
Increased error rates were scattered. When the content of B ₂ O ₃ exceeds 15% by weight, the glass stability of the glass substrate is lowered, and it is difficult to obtain a uniform glass substrate due to bubbles and striae.

Regarding the content of SiO ₂ , sample No. 49
It examined by the glass substrate, such as -54. Sample No. having a SiO ₂ content of 49.5% by weight. With 49 glass substrate, micro Vickers hardness and ring strength are not enough,
The quality was not sufficient as a glass substrate for an information recording disk. However, the sample No. As shown in 50 SiO ₂
Is 50% by weight or more, the micro Vickers hardness exceeds 650, so that the glass substrate was suitable. In addition, the sample No. If the content of SiO ₂ exceeds 70% by weight as in 54, the generation of air bubbles and the like during glass melting becomes remarkable, which is not preferable. On the other hand, sample N
o. When the content of SiO ₂ is 70% by weight as in 53,
A glass substrate free of bubbles, striae, and the like and having sufficient water resistance and mechanical strength was obtained.

As described above, the SiO_TwoContent is 50 weight
% Or more and 70% by weight or less,
Glass with sufficient water resistance and mechanical strength as a glass substrate
Substrate can be obtained. Note that SiO_TwoContent of
If it is less than 50% by weight, it may be difficult to use micro-Vickers strength
It is not preferable because mechanical strength is reduced. In addition, SiO _Two
If the content exceeds 70% by weight, bubbles and striae are generated.
However, it is difficult to obtain a clear and homogeneous glass, which is not preferable.

With respect to the content of Al ₂ O ₃ , 5
The study was conducted using glass substrates such as 9 to 65. Sample No.
In a glass substrate having an Al ₂ O ₃ content of 26% by weight, the melting temperature of the glass was too high and 1600 ° C.
Is undesirable because the glass material remains. However, the sample No. With a glass substrate having an Al ₂ O ₃ content of 25% by weight, a clear glass could be obtained. At this time, both the micro Vickers hardness and the ring strength showed sufficient values for a glass substrate. on the other hand,
Sample No. 1 having a content of Al ₂ O ₃ of 10% by weight. Even with a glass substrate of 60, both micro Vickers hardness and ring strength showed sufficient values as a glass substrate, and a clear glass substrate was obtained. However, the content of Al ₂ O ₃ is 9% by weight.
In the case of the glass substrate, inhomogeneity such as striae occurred in the glass, and a clear glass could not be obtained.

As described above, Al_TwoO₃Content of 10
If the amount is from 25% by weight to 25% by weight,
Having sufficient mechanical strength as a glass substrate
A stable glass substrate, that is, a clear and homogeneous glass
A substrate was obtained. In addition, Al _TwoO₃Content of 10 weight
%, A clear and homogeneous glass substrate cannot be obtained
Was. On the other hand, Al_TwoO₃Content exceeded 25% by weight
Sometimes, raw materials remain in the glass and clear glass
I couldn't get it.

Of the alkali metal oxides, Li₂O content
Amount and Na₂Focusing on the O content and the composition ratio
No. The study was performed using glass substrates such as 66 to 68. table
3 contains Li₂O / Na₂It is described as O ratio. L
i₂O / Na₂Sample No. with an O ratio of 0.62 66 of
On the glass substrate, Li eluted significantly from the glass substrate
And the alkaline elution amount is 0.1 mg / l
I was over it. Li ₂O / Na₂O ratio 0.38
Sample No. In the glass substrate No. 68, the sample No. 66 of
Na elutes significantly from glass substrate, contrary to glass substrate
And the alkali elution amount was 0.1 mg / l.
Was greatly exceeded. That is, the sample No. 66, 68
Glass substrates have a large amount of alkali
Layer formed on the surface of the glass substrate due to lack of chemical stability
Or peeling of the film is likely to occur. On the other hand, Li₂O / Na₂O ratio
Sample No. 0.46 For the 67 glass substrate,
Since the potash elution amount is 0.1 mg / l, sufficient chemical
Stability was obtained. Furthermore, Li₂O / Na₂O ratio
0.1 mg of alkali eluted even for samples with 0.57
/ L or less.

Therefore, the ratio of Li ₂ O / Na ₂ O is 0.1.
When the number is 4 or more and 0.6 or less, peeling of a layer or a film formed on the surface of the glass substrate can be further suppressed, and the quality of the glass substrate can be further improved.

As described above, the alkali elution amount was 0.1 mg.
/ L or less, or when the contained alkali metal oxide is 10% by weight or more and 13% by weight or less and the content of B ₂ O ₃ is 5% by weight or more and less than 15% by weight,
Since the separation of a layer or a film formed on the surface of the glass substrate can be suppressed and a clear and uniform glass substrate can be obtained, the quality of the glass substrate can be improved. Further, Li ₂ O / Na
_{When the} 2O ratio is 0.4 or more and 0.6 or less, peeling of a layer or a film formed on the surface of the glass substrate is reliably suppressed, and the quality of the glass substrate can be further improved.

As described above, 50% by weight is used.
% To 70% of SiO ₂ , 10% to 25% of Al ₂ O ₃ , and 1% to 8% of Ln ₂ O ₃ (Ln is P
r, Nd, Sm or Eu), B ₂ O ₃ and R ₂
A glass substrate including at least one of O (R represents an alkali metal element) is used. As a result, the visibility of the glass substrate is improved, and the occurrence of defects such as scratches and sprinkles that occur during processing of the glass substrate is reduced. In addition, bubbles, striae, foreign matter, and scratches in the glass substrate during quality inspection and the like are reduced. It is easy to find a defect such as a hang. Further, when used for a magnetic disk or a magneto-optical disk, since the magnetization of the glass substrate can be reduced, the influence of the glass substrate on the magnetization characteristics when processed into a magnetic disk or a magneto-optical disk can be reduced. Therefore, the quality of the glass substrate can be improved.

Further, if Ln constituting Ln ₂ O ₃ is Pr, the occurrence of defects can be further reduced, defects can be more easily found, and the magnetization when processed into a magnetic disk or a magneto-optical disk can be further improved. Since the influence on the characteristics can be further reduced, the quality of the glass substrate can be further improved.

Further, the transmittance of visible light having a wavelength of 300 nm to 700 nm is 50% or more and 85% or less, and the magnetization is 3 × 10 ⁻³ when a magnetic field of 1 kOe is applied.
Emu / cc or less also reduces the occurrence of defects,
The quality of the glass substrate can be improved from the viewpoint of facilitating finding defects and reducing the influence on the magnetic properties when processed into a magnetic disk or a magneto-optical disk.

Further, the weight percentage is 50% or more and 70% or more.
The following SiO ₂ and 10% or more and 25% or less Al ₂ O
₃ , 5% to 15% B ₂ O ₃ , 10% to 13
% Or less of R ₂ O (R represents an alkali metal element), a layer or a film formed on the surface of the glass substrate can be prevented from peeling off, and a clear and uniform glass substrate can be obtained. Therefore, the quality of the glass substrate can be improved.

[0069] Also, R ₂ O (R represents an alkali metal element) is composed of _{Li 2 O, Na 2 O,} K 2 O, and Li ₂
When the ratio of O / Na ₂ O is 0.4 or more and 0.6 or less, peeling of a layer or a film formed on the surface of the glass substrate is surely suppressed,
The quality of the glass substrate can be further improved. However, Rb, Cs, and Fr can be used as the alkali metal element, but there is a problem in handling because of being a radioactive isotope of Fr. In addition, Rb and Cs are rare elements, and there are problems in terms of availability and cost. Therefore, Li as an alkali metal element,
It is preferable to use Na and K.

Further, when immersed in 80 cc of hot water at 70 ° C. for 24 hours, the elution amount of the alkali element into the hot water is 0.1 m
Even when the amount is set to g / l or less, the quality of the glass substrate can be improved from the viewpoint of suppressing peeling of a layer or a film formed on the surface of the glass substrate.

Further, in weight percentage, 50% or more and 70%
The following SiO_TwoAnd 10% or more and 25% or less of Al_TwoO
_ThreeAnd Ln of 1% or more and 8% or less_TwoO_Three(Ln is Pr, N
d, Sm or Eu) and 5% or more and 15% or less of B
_TwoO_ThreeAnd R of 10% or more and 13% or less _TwoO (R is alkali
A metal element). Ma
Transmission of visible light with a wavelength of 300 nm to 700 nm
The rate is 50% or more and 85% or less, and a magnetic field of 1 kOe is marked.
Magnetization when applied is 3 × 10^-3less than emu / cc
When immersed in 80 cc of hot water at 70 ° C. for 24 hours.
The amount of alkaline element eluted in warm water is 0.1 mg / l or less.
A glass substrate is used. This reduces the occurrence of defects and
Easier discovery, and furthermore, magnetic disks and magneto-optical disks
The effect on the magnetic properties when processed into
Of the layer and film formed on the surface of the glass substrate
In all cases, the quality of the glass substrate can be improved.

However, when it is necessary to improve the quality only in terms of reducing the occurrence of defects, facilitating the detection of defects, and reducing the influence on the magnetic characteristics when processed into a magnetic disk or a magneto-optical disk, In the case where the quality needs to be improved only in the aspect of suppressing the peeling of the layer or the film formed on the surface of the glass substrate, the composition having the necessary composition and concentration on each surface may be used as described above. it can. Further, when it is necessary to improve the quality in terms of reducing the occurrence of defects, facilitating the finding of defects, and reducing the influence on the magnetic characteristics when processed into a magnetic disk or a magneto-optical disk, B ₂ O ₃ And R ₂ O (R represents an alkali metal element) affects the dissolution of the raw material powder,
It suffices to include at least one of them depending on the degree of required ease of melting. Furthermore, when it is desired to suppress the peeling of a layer or a film formed on the surface of the glass substrate with a glass substrate obtained by mechanically strengthening or crystallizing the mechanical strength of the glass substrate,
A structure in which a rare earth element is not contained in a glass substrate can be employed.

Further, in the information recording disk using the glass substrate for an information recording disk to which the present invention is applied, the quality and reliability of the information recording disk can be improved by improving the quality of the glass substrate.

[0074]

According to the present invention, the quality of a glass substrate for an information recording disk can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view of one embodiment of a glass substrate for an information recording disk to which the present invention is applied.

FIG. 2 is a cross-sectional view of one embodiment of a glass substrate for an information recording disk to which the present invention is applied.

FIG. 3 is a perspective view showing a schematic configuration of a magnetic disk device provided with a magnetic disk using a glass substrate for an information recording disk to which the present invention is applied.

[Explanation of symbols]

 Reference Signs List 1 glass substrate for information recording disk 3 through hole 5 chamfer part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Naito 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. No. 1 F-term in Hitachi Research Laboratory, Hitachi, Ltd. F-term (reference) 4G062 AA18 BB01 BB05 BB06 DA06 DB04 DC03 DC04 DD01 DE01 DF01 EA04 EB04 EC04 ED01 EE01 EF01 EG01 FA01 FA10 FB01 FC01 FD01 FE01 FF01 GA01 F01 FL01 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ05 JJ07 JJ10 KK01 KK02 KK03 KK04 KK05 KK07 KK10 MM27 NN01 NN33 NN34 5D006 CB04 CB06 CB04 CB06

Claims (9)

[Claims] 1. A weight percentage of 50% or more and 70% or less of SiO ₂ , 10% or more and 25% or less of Al ₂ O ₃ , 1% or more and 8% or less of Ln ₂ O ₃ (Ln is Pr, Nd , Sm
Or a glass substrate for an information recording disk, comprising: B ₂ O ₃ and at least one of R ₂ O (R represents an alkali metal element). 2. A weight percentage of 50% or more and 70% or less of SiO ₂ , 10% or more and 25% or less of Al ₂ O ₃ , 5% or more and 15% or less of B ₂ O ₃ , and 10% or more of 13% or less. % Of R ₂ O (R represents an alkali metal element) or less. In wherein weight percentages, and SiO ₂ 50% to 70%, 10% or more and 25% or less of _{Al 2 O 3, Ln 2 O} 3 of 8% with 1% (Ln is Pr, Nd , Sm
Or a glass substrate for an information recording disk, comprising 5% to 15% of B ₂ O ₃ and 10% to 13% of R ₂ O (R represents an alkali metal element). 4. The glass substrate for an information recording disk according to claim 1, wherein Ln constituting said Ln ₂ O ₃ is Pr. Wherein said R ₂ O (R represents an alkali metal element) is composed of _{Li 2 O, Na 2 O,} K 2 O, and Li ₂
4. The glass substrate for an information recording disk according to claim _{2, wherein} a ratio of O / Na ₂ O is 0.4 or more and 0.6 or less. 6. A visible light having a wavelength of 300 nm to 700 nm.
Transmittance is 50% or more and 85% or less and 1k
The magnetization when an Oe magnetic field is applied is 3 × 10 ^-3emu
/ Cc or less for an information recording disk glass substrate. 7. The amount of the alkali element eluted into the hot water when immersed in 80 cc of hot water at 70 ° C. for 24 hours is 0.1 mg.
/ L or less for an information recording disk glass substrate. 8. The transmittance of visible light having a wavelength of 300 nm to 700 nm is 50% or more and 85% or less, and 1 kOe.
Magnetization of 3 × 10 ⁻³ emu / c when a magnetic field of
c or less, and the amount of alkali element eluted into the hot water when immersed in 80 cc of 70 ° C. water for 24 hours is 0.1 mg.
/ L or less for an information recording disk glass substrate. 9. A glass substrate for an information recording disk according to any one of claims 1 to 8, and an information recording layer formed directly or via another layer on the surface of the glass substrate. Information recording disc.