JP4446683B2 - Glass substrate for magnetic recording media - Google Patents

Glass substrate for magnetic recording media Download PDF

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Publication number
JP4446683B2
JP4446683B2 JP2003145583A JP2003145583A JP4446683B2 JP 4446683 B2 JP4446683 B2 JP 4446683B2 JP 2003145583 A JP2003145583 A JP 2003145583A JP 2003145583 A JP2003145583 A JP 2003145583A JP 4446683 B2 JP4446683 B2 JP 4446683B2
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Prior art keywords
glass
magnetic recording
glass substrate
recording medium
temperature
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JP2004043295A (en
Inventor
淳史 倉知
昭浩 小山
信行 山本
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Hoya株式会社
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    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00Glass compositions
    • C03C3/04Glass compositions containing silica
    • C03C3/076Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C03C3/085Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
    • C03C3/087Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass substrate useful for a magnetic recording medium having high heat resistance and capable of imparting a greater degree of strengthening to chemical strengthening treatment by ion exchange.
[0002]
[Prior art]
Glass has excellent properties not found in other materials such as high surface smoothness and large surface hardness, and is suitable for substrates for information recording media such as hard disk drives (magnetic recording devices).
[0003]
However, glass has a drawback that it tends to cause cracks and cracks. As countermeasures, so-called strengthening treatment has been performed by applying compressive stress to the surface by rapid cooling or ion exchange. Among these, the chemical strengthening treatment by ion exchange is suitable for a substrate material that requires very high dimensional accuracy because the deformation of the glass is extremely small.
[0004]
Japanese Patent No. 2837134 discloses, in mass%, 62 to 75% of SiO 2, 5 to 15% of Al 2 O 3, 4 to 10% of Li 2 O, 4 to 12% of Na 2 O, and 5 0.5 to 15% of ZrO 2 and the weight ratio of Na 2 O / ZrO 2 is 0.5 to 2.0, and the weight ratio of Al 2 O 3 / ZrO 2 is 0.4 to 2 A glass substrate for recording information is disclosed from a chemically strengthened glass obtained by subjecting a chemically strengthened glass of .5 to ion exchange treatment with a molten salt containing Na ions and / or K ions.
[0005]
This glass has the disadvantage that the heat resistance of the glass itself is low even when subjected to a chemical strengthening treatment by ion exchange. As the recording density increases in recent years, the layer structure of the magnetic material formed on the substrate is becoming more complex and sophisticated, and it is necessary to increase the substrate temperature when forming the layer. In particular, a magnetic material for perpendicular magnetic recording, which is expected to become the mainstream in the future, requires a particularly high temperature (for example, 400 ° C. or more) during film formation. There has been a problem of deformation. For example, in a general manufacturing process of glass for a magnetic disk substrate, the glass surface is polished. Since pressure is applied to the glass surface during polishing, residual stress is generated on the glass surface. When the glass in such a state is exposed to a high temperature, thermal relaxation of the residual stress occurs and protrusions are formed on the surface, so that the surface becomes rough.
Further, the glass is warped or deformed by heat at high temperatures.
[0006]
Japanese Patent Application Laid-Open No. 9-2836 discloses that the composition is mass%, SiO 2 50 to 65%, Al 2 O 3 5 to 15%, Na 2 O 2 to 7%, K 2 O 4 to 9%, Na 2 O + K 2. There is disclosed a glass substrate for a magnetic disk obtained by chemically strengthening glass composed of O7 to 14%, MgO + CaO + SrO + BaO in a total of 12 to 25%, and ZrO 2 1 to 6%. Although this glass substrate has high heat resistance, the centrifugal force of a magnetic disk drive (HDD) that uses a recent magnetic recording medium rotated at high speed, the recording head is retracted when the magnetic recording medium is stopped, and the magnetic recording medium is rotated. There is a problem that the strength is insufficient to withstand the collision between the recording medium and the recording head in the so-called load / unload method.
[0007]
[Problems to be solved by the invention]
The present invention has been made as a technical problem to solve the above-mentioned problems. For example, when a magnetic recording medium is produced, the glass surface is roughened even when subjected to a high-temperature treatment step, or the glass is deformed. Will never happen. It is another object of the present invention to provide a glass substrate for a magnetic recording medium in which a large mechanical strength can be obtained by chemical strengthening treatment by ion exchange.
[0008]
[Means for Solving the Problems]
Claim 1 is essentially expressed as mass%, SiO 2 60-70%.
Al 2 O 3 5-20%
Li 2 O + Na 2 O + K 2 O 5-25%
Li 2 O 0-1%
Na 2 O 3-18%
K 2 O 0~9%
MgO + CaO + SrO + BaO 5-20%
MgO 0-10%
CaO 1-15%
SrO 0-4.5%
BaO 0-1%
TiO 2 0-1%
ZrO 2 0 to 1%
The average thermal expansion coefficient in the range of −50 to 70 ° C. is at least 70 × 10 −7 / ° C., and the average thermal expansion coefficient in the range of 50 to 350 ° C. is at least 80 × 10 −7 / ° C. It is a glass substrate for magnetic recording media characterized by the above.
[0009]
According to the glass substrate for a magnetic recording medium according to claim 1, even when subjected to high temperature heating when forming the magnetic recording layer on the glass surface, the glass does not deform, and the surface of the substrate is rough due to heat. In addition, a smooth surface can be maintained without generating irregularities due to alkali elution on the substrate surface.
According to the glass substrate for a magnetic recording medium according to claim 1, since the expansion coefficient approximates that of a metal, particularly stainless steel, even if it is attached to a metal rotating shaft of the magnetic recording apparatus and rotated at high speed. The generated heat does not change dimensions or warp in the glass. Therefore, the glass does not deviate from the rotation axis during rotation, and the head position shifts during disk drive. There is a feature that no problems occur.
[0010]
Claim 2 is the glass substrate for a magnetic recording medium according to claim 1,
The composition is expressed in mass%, essentially SiO 2 60-70%
Al 2 O 3 8-15%
Na 2 O + K 2 O 11-18%
Na 2 O 8-16%
K 2 O 0~3.5%
MgO + CaO + SrO 7-14%
MgO 2-5%
CaO 3 to 7.5%
SrO 0-4.5%
ZrO 2 0 to 1%
A glass substrate for a magnetic recording medium having the following composition:
[0011]
According to the glass substrate for a magnetic recording medium according to claim 2, even when subjected to high temperature heating when forming the magnetic recording layer on the glass surface, the glass is not further deformed, and the substrate is further heated. The surface is not roughened, and further, unevenness caused by alkali elution is not further generated on the substrate surface, and a smooth surface can be maintained at a high level.
[0012]
A third aspect of the present invention is the glass substrate for a magnetic recording medium according to the first or second aspect, wherein the glass transition point of the glass substrate is at least 560 ° C.
[0013]
According to the glass substrate for a magnetic recording medium according to claim 3, even when heated in a molten salt when chemically strengthening the glass substrate or when heated when forming the magnetic recording layer on the glass substrate, Warpage can be prevented from occurring in the glass substrate. Further, when the magnetic recording layer is formed, it is possible to suppress the formation of protrusions due to alkali elution on the glass surface.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. The reasons for limiting the composition of the glass composition constituting the glass substrate for a magnetic recording medium of the present invention will be described. In the following description, “%” is mass%.
[0015]
SiO 2 is a main component constituting glass, and when the ratio is less than 60%, the heat resistance and chemical durability of the glass deteriorate. On the other hand, if it exceeds 70%, the viscosity of the glass at a high temperature becomes high and melting and molding become difficult. Consequently, the proportion of SiO 2 needs to be 60 to 70%.
[0016]
Al 2 O 3 is an essential component that improves the heat resistance and chemical durability of the glass and further facilitates chemical strengthening. If the proportion is less than 5%, these effects do not sufficiently appear. On the other hand, when the ratio exceeds 20%, the liquidus temperature of the glass increases, and the formability into a plate shape deteriorates. Therefore, the ratio of Al 2 O 3 needs to be 5% or more and 20% or less. In order to achieve a good balance between the heat resistance (glass transition point) and chemical durability of the glass, it is more preferably 8% or more and 15% or less.
[0017]
Li 2 O, Na 2 O, K 2 O (hereinafter collectively referred to as R 2 O) lowers the viscosity of the glass to facilitate melting and lowers the liquidus temperature to form into a plate shape. It is a component that increases the average thermal expansion coefficient. In order to obtain these effects, the total of the three components needs to be 5% or more. On the other hand, if the total of these components exceeds 25%, the heat resistance of the glass deteriorates, and further the chemical durability deteriorates. Therefore, the total amount of Li 2 O, Na 2 O, K 2 O needs to be 5 to 25%. Furthermore, in order to balance the heat resistance and chemical durability of the glass in a balanced manner, the total amount of these is preferably 11% or more and 18% or less.
[0018]
Li 2 O is among other R 2 O, is a component for improving the strength of glass by Li ions are replaced with Na ions, K ions, etc. other cations in the molten salt. However, when the content is increased, there is a drawback that the heat resistance of the glass is impaired. Therefore, the ratio of Li 2 O needs to be 1% or less, and it is more preferable that the amount is substantially the amount of impurities.
[0019]
Na 2 O is a component that improves the strength of the glass by being replaced with other cations such as K ions in the molten salt. Further, among R 2 O, raw materials can be easily obtained at low cost, and it is preferable from the viewpoint of the raw material cost of glass to increase the proportion of R 2 O. If the ratio is less than 3%, it becomes difficult to obtain chemically strengthened glass having strength, and the effect is not sufficiently exhibited.
From this point of view, it is more preferably 8% or more. On the other hand, if the content exceeds 18%, the heat resistance of the glass is greatly impaired, so it is necessary to make it 18% or less. In order to ensure the heat resistance of the glass more reliably, it is preferably 15% or less.
[0020]
K 2 O has the advantage that heat resistance is hardly impaired in R 2 O. However, if the ratio exceeds 9%, the compressive stress necessary for securing the strength cannot be formed on the glass surface in the chemical strengthening by the ion exchange treatment with the commonly used potassium nitrate molten salt. Therefore, the proportion of K 2 O needs to be 0% to 9%, and more preferably 0 to 3.5%.
[0021]
MgO, CaO, SrO, and BaO (hereinafter collectively referred to as RO) are components that lower the viscosity of the glass and facilitate melting. In addition, the contribution is small compared with R 2 O, but it has the effect of increasing the average thermal expansion coefficient. In order to obtain these effects, the total of the four components needs to be 5% or more, and preferably 7% or more. On the other hand, if the total of these components exceeds 20%, it becomes difficult to chemically strengthen the glass to make a tempered glass, so it is necessary to make it 20% or less. If it exceeds 14%, the devitrification temperature of the glass rises, and it becomes difficult to directly form the glass plate by the float manufacturing method in which the molten glass is directly introduced into the molten tin bath from the glass melting furnace and formed into a plate shape. It is not preferable. Therefore, the total amount of RO is more preferably 7% or more and 14% or less from the viewpoint that it can be chemically strengthened glass and that a glass plate can be directly formed by a float manufacturing method.
[0022]
MgO has the advantage that it is difficult to adversely affect chemical strengthening in RO, but has a strong tendency to increase the devitrification temperature of glass. Therefore, the ratio of MgO needs to be 0 to 10%, and it is preferable to contain 2 or more from the viewpoint of maintaining the chemical properties of the glass, and 5% or less from the viewpoint of suppressing the devitrification phenomenon of the glass. Is preferred.
[0023]
CaO is an essential component that improves the solubility by suppressing the adverse effect on chemical strengthening compared to SrO, without significantly affecting the devitrification temperature of glass among ROs. If it is less than 1%, the effect is not sufficiently exhibited, but if it exceeds 15%, the devitrification temperature of the glass rises and the glass moldability deteriorates. Therefore, the content of CaO needs to be 1 to 15%. It is preferable to set it to 3% or more from the viewpoint of ensuring glass solubility and ensuring glass solubility. Moreover, it is preferable to set it as 7.5% or less from a viewpoint which suppresses that the devitrification temperature of glass becomes high.
[0024]
SrO has the advantage of not increasing the devitrification temperature among ROs, but has the property of hindering the movement of alkali (R 2 O) in the glass, so that if it exceeds 4.5%, chemical strengthening becomes difficult. Further, when the glass is contained in a large amount, the density becomes high. Therefore, the ratio of SrO needs to be 4.5% or less.
[0025]
BaO has the advantage of not increasing the devitrification temperature, especially among ROs, but has the property of preventing the movement of alkali in the glass among ROs. Therefore, when the content is increased, chemical strengthening by ion exchange of the glass becomes possible. It becomes difficult. Further, when the glass is contained in a large amount, the density becomes high. In addition, barium raw materials are deleterious and difficult to handle. Therefore, the ratio of BaO needs to be 1% or less, and it is more preferable that the amount is substantially impurity.
[0026]
TiO 2 is a component that improves the solubility without lowering the heat resistance of the glass, but if its proportion exceeds 1%, the devitrification temperature of the glass increases and the formability deteriorates. In general, glass containing TiO 2 is difficult to recycle because the glass is colored yellow by coexistence with iron in the glass due to iron contained as impurities in the glass raw material. Therefore, the ratio of TiO 2 needs to be 1% or less, and it is more preferable that the amount is substantially the amount of impurities.
[0027]
ZrO 2 is a component that improves the heat resistance of the glass. However, if the proportion exceeds 1%, the devitrification temperature of the glass increases and the formability into a plate shape deteriorates. Therefore, the ratio of ZrO 2 needs to be 1% or less.
[0028]
In addition to the above components, for example, Sb 2 O 3 , As 2 O 5 , SO 3 , SnO 2 , F contained in the fluorine compound as a glass refining agent for the purpose of defoaming at the time of melting, coloring of the glass Various components such as transition metal compounds such as Fe 2 O 3 , CoO, and NiO, and impurities derived from industrial glass raw materials can be included within a range not exceeding 0.5 mass%.
[0029]
In the glass composition, when the glass component is selected within the range of the above-described content ratio, and the glass working temperature and the glass devitrification temperature are expressed in (° C.), the value of the working temperature−the value of the devitrification temperature ≦ − If it is made into the relationship of 17, it can be set as preferable glass when performing the direct shaping | molding of the glass plate by the float manufacturing method which introduce | transduces a molten glass directly on a molten tin bath from a glass melting furnace, and shape | molds into a plate shape. .
[0030]
Since the glass composition has a glass transition point of at least 560 ° C., for example, even when subjected to a heating step when a magnetic recording layer is formed on a glass substrate by a sputtering film formation method, the glass composition does not change in quality. It is suitable as a substrate for a perpendicular magnetic recording medium at a high temperature. The higher the glass transition point, the higher the temperature treatment is possible, so the higher the glass transition point, the better, but 700 ° C. or less is preferable in a practical range.
[0031]
The glass composition has an average coefficient of thermal expansion of at least 70 × 10 −7 / ° C. in the range of −50 to 70 ° C. and an average coefficient of thermal expansion in the range of 50 to 350 ° C. of at least 80 × 10 −7 / ° C. For this reason, even if it is used by being bonded and fixed to a metal material having a large thermal expansion such as stainless steel, the occurrence of cracks in the glass due to the difference in expansion of the material due to temperature change, and consequently the destruction does not occur. In terms of the phenomenon of glass dimension expansion / contraction due to temperature changes, for example, even when the recording track of the magnetic recording medium is narrowed, tracking errors due to thermal expansion differences from the metal structure material can be suppressed or avoided. The glass composition of the present invention is a glass composition having an expansion coefficient substantially equal to that of a metal material, and is characterized by having a larger expansion coefficient than conventional glass. Therefore, the upper limit of the average thermal expansion coefficient is not particularly limited, but is preferably 110 × 10 −7 / ° C. or less at 50 to 350 ° C. in a practical range .
[0032]
The glass composition is brought into contact with a molten salt containing a monovalent cation having an ionic radius of Na or more at a temperature below the glass transition temperature, such as potassium nitrate, a mixed salt of potassium nitrate and sodium nitrate, and the surface is compressed by ion exchange. Strength can be increased by applying stress. Therefore, it is suitable for a high-speed rotation type hard disk drive (HDD). Since the glass substrate obtained from the glass composition of the present invention can ensure sufficient strength even if the thickness is reduced, it can be used, for example, for a substrate for a panel such as a liquid crystal display device, or for a liquid crystal projector or a projector. It can also be used for a reflecting mirror of a used light source lamp, a glass substrate for a solar cell, and the like.
[0033]
【Example】
Hereinafter, the present invention will be described in detail with examples. Glasses of Examples 1 to 18 of the glass composition of the present invention were produced by melting experiments, and the melting temperature, working temperature, glass transition point, linear expansion coefficient, specific gravity, Young's modulus, cracks of the obtained glass were obtained. Tables 1 to 4 show the results of measuring the pressure at an occurrence rate of 50%. Further, as comparative examples, glass disclosed in Example 3 of Japanese Patent No. 2837134 and glass disclosed in Example 1 of Japanese Patent Laid-Open No. 9-2836 were prepared by melting experiments. 2 as shown in Table 4.
[0034]
Production of the glasses of Examples 1 to 18 and Comparative Examples 1 and 2 and measurement of physical properties of the obtained glasses were carried out according to the following procedures.
[0035]
[Table 1]
[0036]
[Table 2]
[0037]
[Table 3]
[0038]
[Table 4]
[0039]
(Production of glass substrate for magnetic recording medium)
First, silica, alumina, lithium carbonate, sodium carbonate, potassium carbonate, basic magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, oxidation, which are ordinary glass raw materials, so as to have the glass compositions shown in Tables 1 to 4 Glass raw materials (batch) were prepared using titanium and zirconium oxide. The prepared batch was kept at 1550 ° C. for 4 hours using a platinum crucible and heated in an electric furnace to form molten glass, which was poured out on an iron plate outside the furnace and cooled to form a glass block. After this glass was held at 650 ° C. for 30 minutes in an electric furnace, the furnace was turned off and gradually cooled to room temperature to obtain a sample glass.
[0040]
The sample glass was processed into a cylindrical shape having an outer diameter of 5 mm and a length of 15 mm, and an average thermal expansion coefficient and a glass transition point were measured using a differential thermal dilatometer (Rigaku Corporation Thermoflex TMA8140).
[0041]
The sample glass was pulverized, passed through a 2380 μm sieve, and the glass particles remaining on the 1000 μm sieve were immersed in ethanol, ultrasonically cleaned, and then dried in a thermostatic bath. After placing 25 g of the glass particles on a platinum boat having a width of 12 mm, a length of 200 mm, and a depth of 10 mm so as to have a substantially constant thickness, the glass particles are kept in an electric furnace having a temperature gradient of 930 to 1180 ° C. for 2 hours. The glass was taken out from the furnace, and the devitrification generated inside the glass was observed with a 40-fold optical microscope, and the highest temperature at which devitrification was observed was defined as the devitrification temperature.
[0042]
The sample glass was cut into a donut shape having an outer diameter of 68 mm and an inner diameter of 20 mm, ground with alumina abrasive grains, and mirror-polished on both sides of the glass with cerium oxide abrasive grains (surface roughness Ra: 2 nm or less; JIS B 0601-1994). To obtain a glass substrate (disk) for a magnetic recording medium having a thickness of 0.635 mm. The disc was washed with a commercially available alkaline detergent and then subjected to a chemical strengthening treatment by dipping in a potassium nitrate molten salt heated to 440 ° C. for 10 minutes.
In Comparative Example 1 having a low glass transition point, the composition and temperature of the salt were adjusted to the conditions disclosed in Japanese Patent No. 2837134, and the mixed melting of 60% potassium nitrate and 40% sodium nitrate heated to 385 ° C. Chemical strengthening was performed by dipping for a minute. These discs were washed again with a commercially available alkaline detergent to obtain a magnetic recording medium substrate. A load of 50 to 2000 gf was applied to the recording surface portion of this substrate using a diamond indenter (a quadrangular pyramid indenter having a facing angle of 136 degrees) of a micro Vickers hardness tester (Akashi MVK-G2), and 50% around the indentation. The pressure at which vertical cracks occur was measured with the probability of.
[0043]
Moreover, the analysis of the glass composition was performed by using a wet chemical glass analysis method, an atomic absorption spectrophotometry method, or the like.
[0044]
Specific gravity was measured by Archimedes method, and Young's modulus was measured according to JIS R 1602 (elastic modulus test method of fine ceramics).
[0045]
The average thermal expansion coefficient at -50~70 ° C. embodiment of the present invention is in the range of 71 to 82 × 10 -7 / ° C., it was all 70 × 10 -7 / ℃ above.
[0046]
As shown in Table 1 to Table 4, the glass transition points of Examples 1 to 18 in the present invention are all 560 ° C. or higher, and heat resistance is high with respect to Comparative Example 1 having a glass transition point of 491 ° C. It is excellent as a member that undergoes high temperature use and high temperature processes.
[0047]
The load at which the crack occurrence probability of the glasses after the chemical strengthening treatment of Examples 1 to 18 of the present invention is 50% is 800 gf or more, which is larger than the glass of Comparative Example 1 disclosed as a high heat resistant glass. Has a value. From this, it can be seen that the glass having the glass composition of the present invention has both high heat resistance and a high degree of chemical strengthening.
[0048]
In contrast, the glass of Comparative Example 1 has a glass transition point as high as 615 ° C. and heat resistance, but since the pressure value at a crack occurrence rate of 50% is as small as 100 gf, it has high heat resistance and large chemical strengthening strength. It does not have (crack resistance). Further, the glass of Comparative Example 2 has a large value at which the crack occurrence probability is 50% and the load exceeds 2000 gf. However, since the glass transition point is as low as 491 ° C., as in Comparative Example 1, it has high heat resistance and large chemical. It does not have both strengths.
[0049]
Examples 8 to 15 and 18 are useful in that the value of the working temperature—the value of the devitrification temperature is −17 ° C. or more, and the glass sheet can be formed by the float manufacturing method without causing devitrification.
[0050]
(Preparation of magnetic recording medium)
Next, using the glass substrate for magnetic recording medium shown by the glass composition of Example 12 , Comparative Example 1 and Comparative Example 2, a magnetic recording medium was produced as follows. Sample glass is cut into a donut shape having an outer diameter of 68 mm and an inner diameter of 20 mm, polishing of the inner and outer end faces, grinding with alumina abrasive grains on both front and back surfaces (surface to be the recording surface), and polishing with cerium oxide abrasive grains, Mirror polishing (surface roughness Ra: 2 nm or less; JIS B0601-1994) was performed to obtain a glass having a thickness of 0.635 mm.
[0051]
After these glass substrates were washed with a commercially available alkaline detergent, the glasses of Example 12 and Comparative Example 2 were chemically strengthened by immersion in potassium nitrate molten salt heated to 440 ° C. for 4 hours, and further commercially available alkaline. Wash again with detergent. About the glass of the comparative example 1, after wash | cleaning using a commercially available alkali detergent, it was immersed in the mixed molten salt of potassium nitrate 60% and sodium nitrate 40% by mass for 4 hours, and was chemically strengthened, and also a commercially available alkali detergent was used. Used to wash. The obtained glass substrate was heated to 400 ° C., and a Cr film as an underlayer, a Co—Cr—Ta alloy film as a recording layer, and a carbon film as a protective layer were sequentially formed by a sputtering film forming method. Further, a perfluorocarbon-based lubricating oil was applied to the protective layer to obtain a magnetic recording medium.
[0052]
The obtained magnetic recording medium was subjected to a rotational driving test using a test apparatus according to a sealed magnetic recording apparatus (HDD). In the rotational drive test, the magnetic recording medium was mounted and fixed so as to fit into a stainless steel rotating shaft having a radius slightly smaller than the inner peripheral radius of the magnetic recording medium, and the magnetic recording medium was 416.7 times / second (25,000 rpm). ). As a result, the glass of Comparative Example 1 was damaged during rotation which was considered to be due to insufficient chemical strengthening strength, but the magnetic recording media of Example 12 and Comparative Example 2 did not cause such damage. .
[0053]
Next, a fixed point floating test and a continuous seek test were performed on the magnetic recording medium. The fixed point levitation test was performed for 24 hours under a reduced pressure of 26.7 kPa, and the presence or absence of a head crash was observed with an optical microscope. The continuous seek test was performed at a flying height of 15 nm, 166.7 times / second (10,000 rpm) for 1,000 hours, and the presence or absence of a head crash was examined with an optical microscope. In the magnetic recording medium using the glass substrate obtained from the sample glass of Example 12 and Comparative Example 1, no head crash error occurred. In contrast, the glass substrate obtained from the sample glass of Comparative Example 2 frequently had head crash errors in which the recording head collided with the recording surface. The reason why such a difference has occurred is not clearly understood, but if the heat resistance of the glass is large, the warp deformation due to softening does not occur even when the glass is heated to a high temperature in the film forming process of the magnetic recording film, and further by polishing. It is thought that this is because minute distortions on the formed glass surface are not thermally relaxed, and the alkali component (R 2 O) in the glass does not precipitate on the surface and form minute protrusions.
[0054]
In addition, when the recording head runs on a magnetic recording surface at a short distance or while touching momentarily, if there are minute protrusions on the glass surface, more frictional heat is generated, so this heat is a thermal noise. Therefore, it is not preferable.
[0055]
【The invention's effect】
The glass substrate for a magnetic recording medium of the present invention obtained by disc processing a glass plate made of a glass composition has high heat resistance even when subjected to high temperature heating when forming a magnetic recording layer on the glass surface. Therefore, a smooth surface finished in a mirror surface can be maintained without causing deformation, and without generating a projection-like product due to alkali elution on the substrate surface.
[0056]
In addition, the coefficient of expansion is close to that of metals, especially stainless steel, so even if it is mounted on a metal rotating shaft of a magnetic recording device and rotated at high speed, dimensional changes due to generated heat and cracking damage due to vibration The occurrence of problems such as these can be prevented.
[0057]
A glass base plate for obtaining a glass substrate for a magnetic recording medium of the present invention is obtained by selecting a glass composition within a predetermined range and selecting a glass working temperature and a devitrification temperature so as to satisfy a predetermined relationship. Glass melted in a melting furnace can be directly guided onto a tin bath and formed into a plate shape.

Claims (3)

  1. Essentially SiO 2 60-70%, expressed in mass%
    Al 2 O 3 5-20%
    Li 2 O + Na 2 O + K 2 O 5-25%
    Li 2 O 0-1%
    Na 2 O 3-18%
    K 2 O 0~9%
    MgO + CaO + SrO + BaO 5-20%
    MgO 0-10%
    CaO 1-15%
    SrO 0-4.5%
    BaO 0-1%
    TiO 2 0-1%
    ZrO 2 0 to 1%
    The average thermal expansion coefficient in the range of −50 to 70 ° C. is at least 70 × 10 −7 / ° C., and the average thermal expansion coefficient in the range of 50 to 350 ° C. is at least 80 × 10 −7 / ° C. A glass substrate for a magnetic recording medium, characterized in that
  2. In the glass substrate for magnetic recording media according to claim 1,
    The composition is expressed in mass%, essentially SiO 2 60-70%
    Al 2 O 3 8-15%
    Na 2 O + K 2 O 11-18%
    Na 2 O 8-16%
    K 2 O 0~3.5%
    MgO + CaO + SrO 7-14%
    MgO 2-5%
    CaO 3 to 7.5%
    SrO 0-4.5%
    ZrO 2 0 to 1%
    The glass substrate for magnetic recording media characterized by having the composition:
  3.   The glass substrate for a magnetic recording medium according to claim 1 or 2, wherein the glass transition point of the glass substrate is at least 560 ° C.
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Families Citing this family (36)

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Publication number Priority date Publication date Assignee Title
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WO2012131824A1 (en) 2011-03-31 2012-10-04 日本板硝子株式会社 Glass composition suitable for chemical strengthening and chemically strengthened glass article
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JP6042875B2 (en) * 2012-03-29 2016-12-14 Hoya株式会社 Glass for magnetic recording medium substrate, glass substrate for magnetic recording medium and use thereof
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