JP3457910B2 - Glass ceramic substrate for information storage media - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for an information storage medium used in an information storage device, particularly improved super-smoothness of the substrate surface, high Young's modulus compatible with high speed rotation, low specific gravity characteristics and drive components. The present invention relates to a substrate for information storage medium such as a magnetic disk substrate made of glass ceramics having a thermal expansion characteristic that conforms to the above, a method for manufacturing the same, and an information storage medium using the same. In the present specification, the "information storage medium" is used as a hard disk of a personal computer or information recording for a network, and an information magnetic medium that can be used in a fixed hard disk, a removable hard disk, a card hard disk, a digital video camera, a digital camera. It means a disc-shaped information storage medium such as a storage medium.

[0002]

2. Description of the Related Art As personal computers become multimedia and large data such as moving images and voices are handled like digital video cameras and digital cameras, a large capacity magnetic information storage device is required. . As a result, the information magnetic storage medium tends to increase the bit and track densities and reduce the bit cell size in order to increase the areal recording density. To cope with this, as the size of the bit cell becomes smaller, the magnetic head comes to operate closer to the disk surface. In this way, when the magnetic head operates with respect to the information magnetic storage medium substrate in a low flying state or a contact state (contact),
As a technology for starting and stopping the magnetic head, adsorption prevention processing (texturing, etc.) is performed on a specific part of the information magnetic storage medium substrate (the unrecorded part on the disk inner diameter side or outer diameter side), and then the magnetic head is started and stopped. Technical development such as the landing zone method is important.

In the current information magnetic storage device, the magnetic head is in contact with the information magnetic storage medium substrate before the device is started, and when the device is started, the CSS (contact start) is repeated to levitate from the information magnetic storage medium substrate.・ Stop) system is used. At this time, if the contact surfaces of the two are mirror surfaces more than necessary, adsorption occurs and problems such as smooth rotation start and damage to the surface of the information magnetic storage medium occur due to an increase in the friction coefficient. As described above, the information magnetic storage medium substrate has a function of lowering the flying height of the magnetic head as the storage capacity increases and preventing the magnetic head from adsorbing on the information magnetic storage medium substrate.
Conflicting requirements are required. In response to these conflicting demands, development of a landing zone technology for producing a start / stop portion of a magnetic head in a specific area of an information magnetic storage medium substrate is under way. Furthermore, in opposition to these landing zone technologies, a ramp load technology has also been developed in which the magnetic head is brought into complete contact and the start / stop of the head is removed from the information magnetic storage medium substrate. Is becoming smoother.

Further, today, technological development is being made to speed up the information by rotating the information magnetic storage medium substrate of the magnetic storage device at high speed. However, due to the increase in the rotation speed of the substrate, bending and deformation Therefore, the substrate material is required to have a high Young's modulus. In addition to the current fixed type information magnetic storage device, information magnetic storage devices such as removable type and card type are under consideration and put into practical use, and their application to digital video cameras and digital cameras is being started.

Conventionally, aluminum alloys have been widely used as magnetic disk substrate materials. However, aluminum alloy substrates produce projections or spot-like irregularities on the surface of the substrate during the polishing process due to the effects of various material defects and become flat. Is not sufficient as a substrate for the high-density storage medium in terms of performance and smoothness, and the aluminum alloy is a soft material and has a low Young's modulus and surface hardness, so vibration is likely to be severely deformed when the drive rotates at high speed. That is, it has a drawback that it is difficult to cope with thinning. Further, the head is liable to be deformed and scratched, and the medium is damaged.

On the other hand, as materials for solving the problems of the aluminum alloy substrate, soda lime glass (SiO ₂ —CaO—Na ₂ O) and aluminosilicate glass (SiO ₂ —Al ₂ O ₃ —Na ₂ ) which are chemically strengthened glass are used. O) is known, but in this case, (1) polishing is performed after chemical strengthening, so that the instability factor of the reinforcing layer in thinning the disk is high. (2) Since the glass contains the Na ₂ O component as an essential component, the film forming characteristics are deteriorated, and it is necessary to perform a barrier coat treatment on the entire surface to prevent elution of Na ₂ O. There are drawbacks.

Further, some crystallized glasses are known for aluminum alloy substrates and chemically strengthened glass substrates. For example, the SiO ₂ —Li ₂ O—MgO—P ₂ O ₅ based crystallized glass described in USP 5,626,935 is:
Lithium disilicate (Li ₂ O · 2SiO ₂ ) as main crystal phase
And α-quartz (α-SiO ₂ ) and by controlling the spherical particle size of α-quartz (α-SiO ₂ ), the conventional mechanical texture and chemical texture are not used, and the surface roughness is obtained by polishing. Degree (Ra)
It is a very excellent material for the entire surface texture material of the substrate that can control the temperature in the range of 15 to 50Å, but the target surface roughness (Ra) of the present application is 9Å or less, more preferably less than 6Å. In addition, it is not possible to obtain a surface roughness to cope with the low flying height of the head in accordance with the rapid increase in recording capacity. Also, no discussion or suggestion has been made regarding the coefficient of thermal expansion.

In Japanese Unexamined Patent Publication No. 9-35234, SiO is disclosed.
₂ -Al ₂ O ₃ -Li ₂ in O-based glass, a magnetic disk main crystalline phase consists lithium disilicate (Li ₂ O · 2SiO ₂₎ and β- Supojuumen _{(Li 2 O · Al 2 O} 3 · 4SiO 2) Although a substrate for use is disclosed, this crystallized glass is a composition system having a relatively large content of Al ₂ O ₃ component, and at the same time, α-quartz (α-SiO ₂ ) and α-cristobalite (α -SiO ₂ ) crystals and other SiO ₂ -based crystals are significantly restricted from being precipitated. This crystallized glass has a center line average surface roughness obtained by polishing as a magnetic disk,
Although it is 20 Å or less, the center line average surface roughness disclosed in the embodiment is as rough as 12 to 17 Å and does not reach the above target. Therefore, it is possible to sufficiently reduce the flying height of the magnetic head as the storage capacity is improved. Can not do it. Further, the crystallization heat treatment temperature needs to be as high as 820 ° C. to 920 ° C., which hinders cost reduction and mass productivity.

International Publication No. WO97 / 01164 includes the above-mentioned JP-A-9-35234, and Al ₂
Although it is a crystallized glass for a magnetic disk in which the lower limit of the range of the O ₃ component is lowered and the crystallization heat treatment is performed at a low temperature (680 ° C. to 770 ° C.), the improvement effect can be said to be sufficient only by lowering the lower limit. In addition, the crystal phase of all the crystallized glasses disclosed in the examples is β-eucryptite (Li ₂ O).
・ Al ₂ O ₃ · 2SiO ₂ ) is deposited.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned drawbacks of the prior art and to sufficiently deal with the ramp load method (contact recording of a magnetic head) for high density recording. A glass-ceramic substrate for an information storage medium, which has good surface characteristics, has an improved relationship between high Young's modulus that can withstand high-speed rotation and specific gravity, and has thermal expansion characteristics that match each drive member, and a method for manufacturing the same, and An object is to provide an information storage medium using this substrate.

[0011]

Means for Solving the Problems As a result of extensive studies to achieve the above object, the present inventor has found that the main crystal phases are lithium disilicate (Li ₂ O.2SiO ₂ ) and α-quartz (α). -SiO ₂ ) crystal, and all the crystal grains are in the form of fine spherical particles, so they have excellent workability, and the surface obtained by polishing is more smooth, and has thermal expansion characteristics that match drive components. In addition, in comparison with the conventional glass ceramic substrate for the information storage medium, the glass ceramic for the information storage medium is more advantageous than the conventional glass ceramic substrate for the information storage medium in that it has both a high Young's modulus and a low specific gravity capable of supporting high-speed rotation of the information storage device. The inventors have found that they can be obtained and have reached the present invention. In particular, the glass-ceramic substrate for an information storage medium which achieves the object of the present invention is suitable for use in a ramp load system because of its surface smoothness.

That is, according to the first aspect of the invention, in the glass ceramic substrate for information storage medium, Young's modulus (GPa) / specific gravity is in the range of 37 to 50, and Al ₂ O _{3 is used.}
The content (weight percentage based on oxide) is 5.3% to 8%,
ZrO ₂ content is 0.5 to 5% (however,
A glass ceramic substrate for an information storage medium, characterized in that each component of F and Cl is not contained). The invention according to claim 2, wherein the glass ceramic has a Young's modulus of 95 to 120 GPa and a specific gravity of 2. The glass ceramic substrate for an information storage medium according to claim 1, wherein the glass ceramic substrate has a coefficient of thermal expansion of 4 to 2.6. 65 to 130x in the range of -50 to + 70 ° C
A range of 10 ^-7 / ° C.
2. The glass ceramics substrate for information storage medium according to any one of 2, wherein the invention according to claim 4 is the glass ceramics substrate, wherein the surface roughness Ra after polishing is
The (arithmetic average roughness) is 3 to 9Å or less, which is the glass ceramic substrate for an information storage medium according to any one of claims 1, 2 and 3, and The invention is characterized in that, in the glass-ceramic substrate, the main crystal phases thereof are lithium disilicate (Li ₂ O.2SiO ₂ ) and α-quartz (α-SiO ₂ ) crystals. The glass ceramic substrate for an information storage medium according to any one of claims 1, 3 and 4, and the invention according to claim 6 is substantially free of Na ₂ O and PbO. , 2, 3, 4, 5 is a glass-ceramic substrate for an information storage medium according to any one of claims 1, 2 and 3, wherein the crystal grain size (average) of the crystal phase is 0.05 μm to 0. 3. 30 μm, characterized in that The glass ceramic substrate for an information storage medium according to any one of 1, 2, 3, 4, 5, 6, and the invention according to claim 8, wherein the weight percentage of oxide reference is SiO ₂ 71 to. 81% Li ₂ O 8 to 11% K ₂ O 0 to 3% MgO 0.3 to 2% ZnO 0 to 1% P ₂ O ₅ 1 to 3% ZrO ₂ 0.5 to 5% TiO ₂ 0 to 3% Al ₂ O ₃ 5.3 to 8% Sb ₂ O ₃ 0.1 to 0.5% SnO ₂ 0 to 5% MoO ₃ 0 to 3% NiO 0 to 2% CoO 0 to 3% Cr ₂ O ₃ 0 to It contains each component in the range of 3%, and the main crystal phase is lithium disilicate (Li ₂ O · 2SiO ₂ ) and α-quartz (α-Si).
O ₂ ) crystal, claim 1, 2,
The glass ceramic substrate for an information storage medium according to any one of 3, 4, 5, 6 and 7, wherein the invention according to claim 9 is a crystallization heat treatment after melting / molding and gradually cooling a glass raw material. As conditions, nucleation temperature = 550 ° C. to 650 ° C.,
Nucleation treatment time = 1 to 12 hours, crystal growth temperature = 680
C. to 800.degree. C., heat treatment is carried out in the range of nuclear growth treatment time = 1 to 12 hours, and the surface roughness (Ra) after polishing is 9.ltoreq.9.ltoreq. 4,
The method for producing a glass-ceramic substrate for an information storage medium according to any one of 5, 6, 7, and 8,
The invention described in (1) is an information formed by forming a magnetic film and, if necessary, a base layer, a protective film, a lubricating layer, etc. on the glass ceramic substrate for an information storage medium according to any one of claims 1 to 8. It is a magnetic storage medium.

The reasons for limiting the physical characteristics, surface characteristics, main crystal phase and crystal grain size, and composition of the glass-ceramic substrate of the present invention to the above ranges will be described below. In addition, the composition is expressed on the basis of oxides as in the original glass.

First, Young's modulus and specific gravity will be described. As described above, in order to improve the recording density and the data transfer rate, the tendency of the information storage medium substrate to rotate at a high speed is progressing. To cope with this tendency, the substrate material is caused by the flexure at the time of the high speed rotation. It must have high rigidity and low specific gravity to prevent disk vibration. Further, when it is used for a head contact or a portable storage device such as a removable storage device, it is necessary to have sufficient mechanical strength, high Young's modulus and surface hardness.

However, if the specific gravity is large even if the rigidity is high, the weight is large at the time of high-speed rotation, so that the bending is generated and the vibration is generated. Conversely, if the rigidity is low even with low specific gravity, vibration similarly occurs. Therefore, it is necessary to balance the seemingly contradictory characteristics of high rigidity and low specific gravity, and the preferable range is Young's modulus (GPa) / specific gravity of 37 or more. A more preferable range is 39 or more, a still more preferable range is 41 or more, and a most preferable range is 43 or more. There is also a preferable range for rigidity, and even if the above specific range is satisfied even with a low specific gravity, at least 95 GPa or more is required from the viewpoint of the above-mentioned vibration generation problem, but it is considered from the viewpoint of workability and specific gravity of the substrate. Therefore, the upper limit needs to be 120 GPa or less. The same applies to the specific gravity. From the point of view of the vibration generation problem, even if the rigidity is high, it must be 2.6 or less, but if it is less than 2.4, the desired rigidity is not achieved in this type of glass ceramics. It is practically difficult to obtain the substrate. That is, the Young's modulus (GPa) / specific gravity is preferably 50 or less.

Next, regarding the coefficient of thermal expansion, as the recording density is improved, the positioning of the magnetic head and the medium is required to be highly accurate, so that high dimensional accuracy is required for each component of the medium substrate and the disk. It Therefore, the influence of the difference in the coefficient of thermal expansion from these components cannot be ignored, and the difference in the coefficient of thermal expansion must be minimized. Particularly, the thermal expansion coefficient of the components used for a small-sized magnetic information storage medium is about +90 to + 100 × 10 ⁻⁷ / ° C., and the substrate is required to have such a thermal expansion coefficient. Depending on the drive manufacturer, the coefficient of thermal expansion outside this range (around +70 to +125
A material having a front-back direction of 10 ⁻⁷ / ° C.) may be used for the component. For the above-mentioned reasons, the thermal expansion coefficient range must be determined so that the crystal system of the present invention can be widely compatible with the materials of the components to be used while striking the balance with the strength, and the range is from -50 to In the range of + 70 ° C,
It is preferably +65 to + 130 × 10 ⁻⁷ / ° C.
Further, the coefficient of thermal expansion is more preferably + 95 × 10 ⁻⁷ / ° C. or higher, and further preferably + 110 × 10 ⁻⁷ / ° C. or lower.

Next, regarding the crystal grain size of the main crystal phase and the surface characteristics of the substrate, as described above, as the areal recording density of the information storage medium increases, the flying height of the head becomes 0.025.
It is markedly lower than μm, and it is advancing toward the near-contact recording method or the contact recording method in which the contact is perfect. To meet this, the smoothness of the disk surface must be better than that of conventional products. . Even if an attempt is made to perform high-density input / output to / from a magnetic recording medium with the smoothness of the conventional level, input / output of magnetic signals cannot be performed due to the large distance between the head and the medium. Further, if the distance is reduced, the projection of the medium collides with the head, and the head or the medium is damaged. The surface roughness (Ra) is preferably 9 Å or less, and more preferably less than 6 Å, in order not to cause head damage or medium damage even at this extremely low flying height or in a contact state. For the same reason, the maximum surface roughness (Rmax) is preferably 100 Å or less, more preferably less than 72 Å.

In order to obtain the glass-ceramic substrate having the above-mentioned smoothness, the shape and grain size of the precipitated crystal grains are important factors. That is, the precipitated crystal particles are preferably fine spherical particles from the viewpoint of workability and surface roughness. Specifically, in order to obtain a desired surface roughness, the crystal grain size (average) is preferably 0.30 μm or less, and more preferably 0.2 μm or less. Also,
In order to obtain a desired Young's modulus, the crystal grain size (average) is 0.
It is preferably at least 05 μm.

Next, regarding the main crystal phase, various studies were conducted to realize the above-mentioned physical properties, thermal expansion coefficient, and surface roughness. As a result, lithium disilicate (Li ₂ O.2Si) was obtained.
The combination of O ₂ ) and α-quartz (α-SiO ₂ ) crystal phases was optimal.

Next, regarding the Na ₂ O and PbO components, when the precision and miniaturization of the magnetic film are improved, Na in the material is
_{When the 2} O component is contained, these ions are diffused in the magnetic film during the film forming process, which causes coarsening of the magnetic film particles and deterioration of the orientation. Therefore, these components are not substantially contained. This is very important. Further, it should not contain any PbO component which is environmentally unfavorable.

In addition, the information storage medium substrate is required to have a dense, homogeneous, and fine structure without defects such as crystal anisotropy, foreign matter, and impurities. By using the main crystal phase having a crystal shape (lithium disilicate and α-quartz), these requirements can be sufficiently satisfied.

Next, the reason why the composition range of the raw glass is limited as described above will be described below. The SiO ₂ component is composed of lithium disilicate (Li ₂ O · 2SiO ₂ ) and α-quartz (α) which are precipitated as a main crystal phase by heat treatment of the raw glass.
-SiO ₂ ) is an extremely important component for forming crystals, but if the amount is less than 71%, the precipitated crystals of the glass ceramics are unstable and the structure tends to coarsen, and if it exceeds 81%, the raw glass It becomes difficult to melt and mold.

The Li ₂ O component is a lithium disilicate (Li ₂ O.2) which is precipitated as a main crystal phase by heat treatment of the raw glass.
SiO ₂ ) is a very important component, but if the amount is less than 8%, it becomes difficult to precipitate the above-mentioned crystals and it becomes difficult to melt the raw glass, and if it exceeds 11%, the obtained crystals become The structure is unstable and the structure tends to be coarse, and the chemical durability is reduced.

The K ₂ O component is a component that improves the meltability of glass and prevents coarsening of precipitated crystals.
The amount of 3% or less is sufficient.

The MgO and ZnO components improve the meltability of the glass and at the same time prevent coarsening of the precipitated crystals. At the same time, the main crystal phase is lithium disilicate (Li).
₂ O ・ 2SiO ₂ ), α-quartz (α-SiO ₂ ), α
-Effective for precipitating each crystal particle of the quartz solid solution (α-SiO ₂ solid solution) into a spherical shape. Therefore M
The gO component is preferably 0.3% or more. Similarly, the ZnO component is more preferably 0.1% or more.
In addition, when the MgO and ZnO components are excessively contained, the obtained crystals are unstable and the structure is apt to coarsen.
The gO component is preferably 2% or less, more preferably 1% or less. Similarly, the ZnO component is preferably 2% or less, more preferably 1% or less. The sum of the components of MgO and ZnO is preferably 2% or less, more preferably 1% or less.

In the present invention, the P ₂ O ₅ component is indispensable as a crystal nucleating agent for glass, but if the amount is less than 1%, the crystal nucleation is insufficient and the precipitated crystal phase grows abnormally. If it exceeds%, devitrification of the raw glass is caused.

Like the P ₂ O ₅ component, the ZrO ₂ and TiO ₂ components function as crystal nucleating agents for glass, and at the same time, refine the precipitated crystals and improve the mechanical strength and chemical durability of the material. However, if the ZrO ₂ component is less than 0.5%, the above effect cannot be obtained, and the ZrO ₂ component is 5% or the TiO ₂ component is 3%.
If it exceeds, it becomes difficult to melt the raw glass, and ZrSi
Undissolved residue such as O ₄ will occur.

The Al ₂ O ₃ component is suitable for improving the chemical durability and mechanical hardness of glass ceramics. The types of precipitated crystals differ depending on the heat treatment conditions, but even if various heat treatment conditions are taken into consideration, Li ₂ O ・ 2S
In order to precipitate iO ₂ + α-quartz, Al ₂ O ₃
Should be less than 10%. Preferably 4-8%
Is the range.

The Sb ₂ O ₃ component is added as a fining agent during glass melting. If the amount is less than 0.1%, the above effect cannot be obtained, but 0.5% or less is sufficient.

The SnO ₂ and MoO ₃ components are effective as a coloring agent for glass ceramics, and in particular, they have a great effect on the detection of surface defects of products, and at the same time, LD excitation laser (Nd:
YAG, etc.) can be added to facilitate absorption. In addition, it has an excellent light-transmitting property in the glass state, which makes it easy to inspect the material before crystallization and is an important component found to cause coloring in crystallization.
It is sufficient that the content of ₂ components is within 5% and the content of MoO ₃ is within 3%.

The NiO, CoO and Cr ₂ O ₃ components are SnO.
_2, MoO ₃ ingredients as well as LD excitation laser used in the landing zone texture like: Although effective in increasing the absorption of (Nd YAG other), Toru in glassy state as SnO _2, MoO ₃ ingredients There is no light, each Ni
It is sufficient that the O component is within 2%, the CoO component is within 3%, and the Cr ₂ O ₃ component is within 3%.

Next, in order to manufacture the glass-ceramic substrate for an information storage medium according to the present invention, the glass having the above composition is melted, hot-formed and / or cold-worked, and then 550 ° C. to 650 ° C. Heat treatment at a temperature in the range of ℃ for 1 to 12 hours to form crystal nuclei, followed by 680 to 800
Crystallization is performed by heat treatment at a temperature in the range of ° C for about 1 to 12 hours.

The main crystal phase of the glass ceramic crystallized by the heat treatment is lithium disilicate (α-Li).
₂ O ・ 2SiO ₂ ) and α-quartz (α-SiO ₂ ).
It was a crystal, and the crystal grain size (average) of all the crystal phases was 0.05 μm or more and 0.30 μm or less, and the crystal shape was almost spherical particles.

Next, the heat-treated crystallized glass ceramics are lapped by a conventional method and then polished to obtain a surface roughness (Ra) of 3 Å or more and 9 Å or less, (R
A disc substrate material for information storage media having a max) of 100Å or less was obtained.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Next, preferred embodiments of the present invention will be described. Tables 1 to 4 show practical composition examples (Nos. 1 to 16 ) of the glass ceramic substrate for a magnetic disk of the present invention, and Table 5 shows comparative SiO ₂ -Li ₂ as a comparative composition example.
O-MgO-P ₂ O ₅ based glass ceramics (Comparative 1: U
(Described in SP 5,626,935), SiO ₂
-Al ₂ O ₃ -Li ₂ O glass ceramics (Comparative Example 2: disclosed in JP-A-9-35234) (Comparative Example 3: disclosed in International Patent Publication No. WO97 / 01164) , Composition of these glass ceramics, nucleation temperature, crystallization temperature, main crystal phase, crystal grain size (average), crystal grain shape, surface roughness formed by polishing (R
a), (Rmax), Young's modulus, specific gravity, Young's modulus (GP
a) / specific gravity and thermal expansion coefficient.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

[0042]

In each of the glasses of the above-mentioned examples of the present invention, raw materials such as oxides, carbonates and nitrates are mixed, and this is melted at a temperature of about 1350 to 1450 ° C. with a normal melting apparatus and stirred and homogenized. After being made into a glass, it was molded into a disk and cooled to obtain a glass molded body. And this is 550-650
After heat treatment at ℃ for about 1 to 12 hours to form crystal nuclei,
It was heat-treated at 800 ° C. for about 1 to 12 hours to be crystallized to obtain a desired glass ceramic. Then, the above-mentioned glass-ceramics are polished with an average grain size of 5 to 30 μm for about 10 minutes to 60 minutes.
After lapping for a minute, it was polished and finished with cerium oxide having an average particle size of 0.5 μm to 2 μm for about 30 minutes to 60 minutes.

As shown in Tables 1 to 7, the present invention and the comparative example of the conventional Li ₂ O--SiO ₂ glass ceramics have different main crystal phases or crystal particle diameters (average). Glass-ceramics include lithium disilicate (Li ₂ Si ₂ O ₅ ) and α-quartz (α-SiO ₂ ).
Of the glass ceramics of Comparative Examples 1, 2 and 3 are crystal particles having an average diameter.
Was as large as 0.5 μm or more. This particle size (average) affects the surface roughness after polishing and defects caused by falling off of crystal particles in the current trend of substrates that require more smoothness. Young's modulus,
Regarding the specific gravity and Young's modulus (GPa) / specific gravity, the present invention has a good Young's modulus (GPa) / specific gravity of 39 or more, while the glass ceramics of Comparative Examples 1, 2, and 3 have Young's modulus (GPa). ) / Specific gravity is less than 37, which is not sufficiently compatible with high-speed rotation drive use. Further, the coefficient of thermal expansion of the glass-ceramics of the present invention is 95 × 10 ⁻⁷ / ° C. or higher, whereas the glass-ceramics of Comparative Examples 1, 2 and 3 are low at 64 × 10 ⁻⁷ / ° C. or less, and particularly, The glass ceramics of Comparative Examples 2 and 3 have a crystalline phase (β-
Spodium, β-cristobalite crystal), it has a low expansion characteristic, and the difference in the coefficient of thermal expansion from the drive components becomes large, making it unsuitable as an information storage medium device as a substrate material for information storage medium.

On the glass ceramic substrate obtained in the above embodiment, a Cr intermediate layer (80 nm), a Co--Cr magnetic layer (50 nm), and SiC were formed by DC sputtering.
A protective film (10 nm) was formed. Then, a perfluoropolyether lubricant (5 nm) was applied to obtain an information storage medium. The information storage medium obtained by this can reduce the flying height of the head more than before because of its good smoothness, and by the ramp load method, even if the head and the medium perform input / output in a contact state, It was possible to input and output magnetic signals without causing head damage or media damage.

[0046]

As described above, according to the present invention, the surface smoothness characteristics corresponding to the high recording density and the high Young's modulus-specific gravity corresponding to the high speed rotation are solved while solving the above-mentioned drawbacks. It is possible to provide a glass-ceramic substrate suitable for a glass-ceramic substrate for an information storage medium, a method for producing the same, and an information storage medium using the same, which have both a good balance of properties and a thermal expansion characteristic that matches an information storage medium device. .

─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 11-41370 (32) Priority date February 19, 1999 (February 19, 1999) (33) Priority claim country Japan (JP) Preliminary Examination (56) Reference JP 10-1558034 (JP, A) JP 10-45426 (JP, A) JP 11-16143 (JP, A) JP 11-16142 (JP, A) JP 11-16151 (JP, A) JP 2000-143290 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C03C 1/00-14/00 G11B 5 / 62-5/858 WPI

Claims (10)

(57) [Claims] 1. Young's modulus (GPa) / specific gravity of 37 to 50
And the Al ₂ O ₃ content (weight percentage based on oxide) is 5.3% to 8%, and the ZrO ₂ content is 0.5 to 5%.
(However, each component of F and Cl is not included)
A glass-ceramic substrate for information storage media, characterized by: 2. Young's modulus = 95 to 120 GPa, specific gravity =
The glass-ceramic substrate for an information storage medium according to claim 1, wherein the glass-ceramic substrate is in the range of 2.4 to 2.6. 3. The information according to claim 1, wherein the coefficient of thermal expansion is in the range of 65 to 130 × 10 ⁻⁷ / ° C. in the range of −50 to + 70 ° C. Glass-ceramic substrate for storage media. 4. Surface roughness Ra (arithmetic mean roughness) after polishing
Is 3 to 9Å, Claims 1, 2, 3
A glass-ceramic substrate for an information storage medium according to any one of 1. 5. The main crystal phase is lithium disilicate (Li ₂ O).
· 2SiO ₂₎ and α- quartz (α-SiO ₂₎ characterized in that it is a crystalline, glass-ceramic substrate for an information storage medium according to any one of claims 1, 2, 3, 4. 6. The glass-ceramic substrate for an information storage medium according to claim 1, which is substantially free of Na ₂ O and PbO. 7. The crystal grain size (average) of the crystal phase is 0.05.
It is characterized by being in the range of μm to 0.30 μm.
2. A glass-ceramic substrate for information storage media according to any one of 2, 3, 4, 5, and 6. 8. A weight percentage of oxide, SiO ₂ 71 to 81% Li ₂ O 8 to 11% K ₂ O 0 to 3% MgO 0.3 to 2% ZnO 0 to 1% P ₂ O ₅ 1 〜3% ZrO ₂ 0.5 〜 5% TiO ₂ 0 〜 3% Al ₂ O ₃ 5.3 〜 8% Sb ₂ O ₃ 0.1 〜 0.5% SnO ₂ 〜 5% MoO ₃ 〜 3 % NiO 0 to 2% CoO 0 to 3% Cr ₂ O ₃ 0 to 3% are contained in the respective components, and the main crystal phase is lithium disilicate (Li ₂ O.2SiO ₂ ) and α-quartz (α). -Si
O ₂ ) crystal, claim 1, 2,
The glass-ceramic substrate for an information storage medium according to any one of 3, 4, 5, 6, 7. 9. The glass raw material is melted / molded and gradually cooled,
As the crystallization heat treatment condition, nucleation temperature = 550 ° C. to 65
0 ° C., nucleation treatment time = 1 to 12 hours, crystal growth temperature =
Heat treatment is performed at a temperature of 680 ° C. to 800 ° C. and a nucleus growth treatment time of 1 to 12 hours, and the surface roughness (Ra) after polishing =
Claims 1, 2, 3, characterized in that it is 9 Å or less.
4. A method for manufacturing a glass-ceramic substrate for an information storage medium according to any one of 4, 5, 6, 7, and 8. 10. An information magnetic comprising a glass ceramic substrate for an information storage medium according to claim 1, on which a magnetic film and, if necessary, an underlayer, a protective film, and a lubricating layer are formed. Storage medium.