JP2000143282A - Glass composition, substrate for information recording medium using same and information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-cost glass composition having a high elastic modulus (Young's modulus), a high rigidity (elastic modulus/density) and high surface smoothness and easy to mold, to obtain a substrate which effectively suppresses deflection and vibration when it is used in an information recorder and to obtain an information recording medium. SOLUTION: This glass composition contains, by mol, 55-65% SiO2, 0.5-6% Al2O3, 12-22% Li2O, 0-5% Na2O, 0.1-10% TiO2, 0-3% ZrO2, 0-8% MgO, 0-18% CaO, 0-5% SrO and 5-18% RO (RO=MgO+CaO+SrO) and does not substantially contain Y2O3 and oxides of lanthanoids.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass composition having a high modulus of elasticity, and more particularly to a glass composition having excellent surface smoothness and suitable for a substrate for an information recording medium requiring a high modulus of elasticity. Furthermore, the present invention relates to a substrate for an information recording medium and an information recording medium using the glass composition.

[0002]

2. Description of the Related Art Information recording devices such as magnetic disks include:
There is a continuing demand for shortening access time and increasing recording capacity, and as one means for achieving this, increasing the speed of rotation of an information recording medium (hereinafter simply referred to as a “recording medium”) has been considered. . However, since the recording medium substrate itself is deflected, the resonance increases when the rotation speed is increased, and the possibility of collision between the recording medium and the magnetic head increases.
Since this collision causes a reading error or a crash of the magnetic head, it is difficult for the currently used recording medium to reduce the gap between the magnetic head and the recording medium to some extent.

Therefore, in order to increase the rotation speed of the recording medium and reduce its resonance, the elastic modulus (Young's modulus) and Young's modulus of the recording medium substrate (hereinafter simply referred to as “substrate”) are divided by the density. It is necessary to increase the value of rigidity.

The aluminum alloy most commonly used as a substrate so far has an elastic modulus of 71 GPa and a rigidity of 26 GPa · cm ³ / g, and cannot cope with a high-speed rotation of 10,000 rpm or more. Although the Young's modulus and rigidity can be increased by increasing the thickness of the substrate, increasing the thickness of the substrate is against the development trend because the size of the device is a trend of the times.

On the other hand, a substrate using chemically strengthened glass is superior to an aluminum substrate in that it has a higher elastic modulus and a lower density. However, a substrate obtained by ion-exchanging commercially available soda lime glass in a molten potassium salt has an elastic modulus of about 72 GPa and a rigidity of about 29 GPa · cm ³ / g.

As a substrate of high rigidity other than chemically strengthened glass, a substrate using crystallized glass having an elastic modulus of 90 GPa and a rigidity of 38 GPa · cm ³ / g is commercially available. However, crystallized glass has a disadvantage that since crystals precipitate inside, crystal irregularities remain on the surface after polishing, and the surface smoothness is inferior to a chemically strengthened glass substrate.

Japanese Patent Application Laid-Open No. Hei 10-81542 discloses an SiO ₂ —Al ₂ O ₃ —RO-based glass (where R is a divalent metal), in which Al ₂ O ₃ or 20 mol% or more is used. A substrate material containing at least MgO is disclosed. But,
This glass substrate material has a problem that it has a high liquidus temperature and is difficult to mold, and is not suitable for high-speed rotation because of its high density.

[0008] International Publication WO98 / 55993 states that
A glass substrate having a Young's modulus of 100 GPa or more and a liquidus temperature of 1,350 ° C. or less is disclosed. However, when the liquidus temperature is 1,350 ° C., devitrification easily occurs, and it is difficult to stably obtain a high-quality substrate.

[0009]

As for the information recording apparatus, it is necessary to further increase the speed of the rotation of the substrate, and it is expected that the demand for thinning the substrate with the downsizing of the apparatus will be further increased. Therefore, there is a need for a glass composition that is a material for a substrate having a high elastic modulus and rigidity, is easy to mold, and is suitable for mass production.

Therefore, the present invention provides a glass composition which has high elastic modulus (Young's modulus), rigidity (elastic modulus / density) and surface smoothness, is easy to mold, and is inexpensive. An object is to provide a substrate and a recording medium that effectively suppress vibration.

[0011]

Means for Solving the Problems To achieve the above object,
For example, the glass composition according to the first aspect of the present invention has a composition
Percent, silicon dioxide (SiO_Two): 55-65%,
Aluminum oxide (Al_TwoO_Three): 0.5 to 6%, lithium oxide
(Li_TwoO): 12-22%, sodium monoxide (Na _TwoO): 0
~ 5% titanium dioxide (TiO_Two): 0.1 to 10%, dioxide
Ruconium (ZrO_Two): 0-3%, magnesium oxide (Mg
O): 0-8%, calcium oxide (CaO): 0-18%, acid
Strontium bromide (SrO): 0-5%, RO (RO = MgO + CaO + Sr
O): contains 5 to 18% and contains yttrium oxide (Y_TwoO_Three) And
And lanthanoid oxides
You.

The glass composition of the invention according to claim 2 is
In composition mole percent, silicon dioxide (SiO_Two): 55-6
2%, aluminum oxide (Al_TwoO_Three): 2 to 6%, lithium oxide
Um (Li_TwoO): 12-20%, sodium monoxide (Na_TwoO):
1-4%, titanium dioxide (TiO_Two): 0.5 to 5%, dioxide
Ruconium (ZrO_Two): 0-2.5%, magnesium oxide (M
gO): 2-6%, calcium oxide (CaO): 5-10%, acid
Strontium bromide (SrO): 0-5%, RO (RO = MgO + CaO + Sr
O): contains 8 to 18% and contains yttrium oxide (Y_TwoO _Three) And
And lanthanoid oxides
You.

[0013] The glass composition of the invention according to claim 3 comprises:
The invention according to claim 1 or 2, wherein the content of SrO is 0.5 to 5%.

The glass composition of the invention according to claim 4 is
The invention according to any one of claims 1 to 3, in which contains substantially no ZrO _2.

[0015] The glass composition of the invention according to claim 5 comprises:
In the invention according to any one of claims 1 to 4, Al
The content of ₂ O ₃ is 5 to 6%.

[0016] The glass composition of the invention according to claim 6 comprises:
The invention according to any one of claims 1 to 5, wherein Li
The ratio of Na ₂ O to ₂ O is 1/20 to 1/5, and the ratio of MgO to CaO is 1/4 to 1/1.

The glass composition of the invention according to claim 7 comprises:
In the invention according to any one of claims 1 to 6, the elastic modulus represented by Young's modulus is 90 GPa or more, and the rigidity represented by Young's modulus / density is 30 GPa · cm ³ / g or more.

The glass composition of the invention according to claim 8 is
The invention according to any one of claims 1 to 7 is formed into a plate by a float method.

The glass composition of the invention according to claim 9 is as follows:
In the invention according to any one of claims 1 to 8, the strength is increased by immersion in a heated molten salt to ion-exchange an alkali component near the surface.

According to a tenth aspect of the present invention, there is provided a substrate for an information recording medium using the glass composition according to any one of the first to ninth aspects.

A recording medium according to the present invention uses the substrate according to the present invention.

[0022]

Embodiments of the present invention will be specifically described below. In addition,% is mol percent (mol%)
Represents

SiO ₂ is a main component constituting glass, and if its content is less than 55%, the chemical durability of glass deteriorates. On the other hand, if it exceeds 65%, the required elastic modulus cannot be obtained. Therefore, the content of SiO ₂ is 55
% To 65%, from the viewpoint of water resistance.
2% is more preferred.

Al ₂ O ₃ is a component that improves the elastic modulus and rigidity of the glass and also improves the water resistance of the glass.
If the content is less than 0.5%, these effects are not sufficiently exhibited. On the other hand, if the content exceeds 6%, the liquidus temperature rises and the moldability deteriorates. Therefore, the content of Al ₂ O ₃ needs to be 0.5% to 6%. In order to increase the elastic modulus, it is preferable to contain as much as possible within a range not exceeding 6%, more preferably 2% or more, and even more preferably 5% or more.

Li ₂ O is a component that improves the elastic modulus and rigidity of the glass and lowers the melting temperature. If the ratio is less than 12%, the elastic modulus and rigidity are insufficient. On the other hand, if it exceeds 22%, the weather resistance and acid resistance of the substrate deteriorate. Therefore, the content of Li ₂ O needs to be 12 to 22%, and particularly preferably 12 to 20% from the viewpoint of water resistance.

Na ₂ O is a component that lowers the melting temperature and lowers the liquidus temperature to enhance the formability. But 5%
If it exceeds 3, the required elastic modulus cannot be obtained, and furthermore, the weather resistance and the acid resistance deteriorate. If it exceeds 4%, the effect of lowering the liquidus temperature is reduced. Therefore, the content of Na ₂ O needs to be 0 to 5%, and more preferably 1 to 4%.

[0027] The ratio of Na ₂ O with respect to _{Li 2 O (Na 2 O /} Li
_When 2O) is 1/20 to 1/5, the liquidus temperature can be kept low while the elastic modulus is kept high, which is particularly advantageous in the production of a glass composition.

TiO ₂ is a component for improving the elastic modulus, rigidity and weather resistance of glass. However, if the content exceeds 10%, the liquidus temperature is increased and the formability is deteriorated. However, when the content is 0.5 to 5%, the effect of lowering the liquidus temperature and improving the moldability is exhibited. Therefore, the content of TiO ₂ is preferably 0.1 to 10%, and 0.5 to 10%.
~ 5% is more preferable.

ZrO ₂ is a component that improves the modulus of elasticity, rigidity and weather resistance of glass. However, if its content exceeds 3%, the liquidus temperature of the glass increases and the moldability deteriorates. In addition, even if it is 3% or less, it may precipitate as fine crystals, and if the content exceeds 2.5%, the possibility increases.
Therefore, the content of ZrO ₂ needs to be 3% or less,
It is preferable that the content is not more than 2.5%, and further, it is not substantially contained.

MgO is a component that increases the modulus of elasticity, rigidity and meltability of glass. When its content exceeds 8%,
The liquidus temperature of the glass increases, and the moldability deteriorates. Therefore, the content of MgO needs to be 8% or less. Further, the content is more preferably 2 to 6%.

CaO is a component that enhances the modulus of elasticity, rigidity and meltability of glass. However, if it exceeds 18%, the liquidus temperature of the glass rises and the devitrification resistance deteriorates. Therefore, Ca
The content of O needs to be 18% or less. Also, 5
More preferably, it is 10%.

SrO is a component that increases the elastic modulus of glass, but when contained in a large amount in glass, the density increases. Therefore, the content of SrO needs to be 5% or less.
Further, SrO has a great effect of lowering the liquidus temperature of glass, and when contained at 0.5% or more, the effect of improving the moldability while maintaining the elastic modulus is well exhibited. Therefore, the content of SrO needs to be 0 to 5%, and more preferably 0.5 to 5%.

Also, the total content (RO) of MgO + CaO + SrO is 5
If it is less than 18%, the elastic modulus and rigidity are insufficient, and if it exceeds 18%, the liquidus temperature of the glass increases, and the moldability deteriorates. Therefore, the total amount of RO needs to be 5-18%,
18% is more preferred.

Further, the ratio of MgO to CaO (MgO / Ca
When O) is 1/4 to 1/1, the liquidus temperature can be kept low while the elastic modulus is kept high, which is particularly advantageous in the production of a glass composition.

[0035] Y ₂ O ₃ and lanthanoid oxides are generally known as effective components for improving the elastic modulus. But,
Even if these are contained in a small amount, the density of the glass is greatly increased. Furthermore, since it is expensive, the distribution amount is small, and there is concern about supply, it is not suitable as a composition component of a glass composition to be mass-produced.
As described above, since the substrate is required to be inexpensive and thin, it is preferable that these components are not contained in the substrate. Therefore, the content of Y ₂ O ₃ and the lanthanoid oxide must be substantially 0%, that is, 0.1% or less in total. The lanthanoid refers to a rare earth element having an atomic number of 57 to 71. The chemical properties of these elements are similar to those of lanthanum with atomic number 57.

Here, "substantially not contained" means that it is not intentionally added, and is excluded from the case where it is contained as an impurity in the glass raw material or the case where it is contained so as not to affect the glass properties. It does not do.

In addition to these components, for the purpose of coloring, refining upon melting, or as impurities, for example, As
Other components such as ₂ O ₃ , Sb ₂ O ₃ , SO ₃ , SnO ₂ , Fe ₂ O ₃ , Cl, F and K ₂ O may be added up to a total of 3%.

As a molding method of the glass composition, any of known methods such as a press method, a down-draw method, and a float method can be used. Since the glass composition has a low liquidus temperature, it has excellent moldability, and is particularly suitable for production by a float method. In the float method, a uniform sheet glass composition having a thickness excellent in surface smoothness is produced in large quantities,
An inexpensive production material that is easy to process in each application is provided.

Since the glass composition contains Na ₂ O and Li ₂ O, it is chemically strengthened by immersing it in a molten salt containing ions having a larger ionic radius. This ion exchange produces a surface compressive stress, which provides the glass composition with high breaking strength.

The use of the glass composition is not particularly limited, and the glass composition can be used for various uses requiring the above-mentioned properties. For example, when used as architectural glass, the characteristic that the elastic modulus is high and it is hard to break is effectively exhibited. On the other hand, when used as a substrate, the elastic modulus and the rigidity are higher than those of the conventional substrate, so that the effect is obtained that the deflection is small and the problem due to resonance hardly occurs. Therefore, a recording medium using this glass composition is particularly suitable for a high rotation type information recording device.

In a hard disk widely used as an information recording apparatus at present, the recording medium is 4,000 to 10,000.
Rotating at 000 rpm, the distance (flying height) between the magnetic head and the recording medium is set on the order of 10 nanometers. In the future, it is inevitable that the rotation speed of the recording medium will be higher and the flying height will be smaller, so increasing the elastic modulus and rigidity of the substrate will be extremely important in terms of meeting the quality requirements of the next generation. Have. The glass composition having the above composition has an elastic modulus represented by Young's modulus of 90 GPa or more and a rigidity (Young's modulus /
Density) is 30 GPa · cm ³ / g or more, and the elastic modulus is improved by about 20 GPa and the rigidity is improved by 20% or more as compared with the conventional aluminum substrate. Therefore, if the substrate is made of this glass composition, the same flying height can be maintained even at 10,000 rpm or more.

For processing the glass composition into a substrate, a conventional method for producing a glass substrate can be used as it is. Therefore, if this glass composition is used, no new capital investment is required, and a high-performance substrate can be easily and inexpensively manufactured. Further, in processing a substrate into a recording medium, a conventional manufacturing method can be used as it is.

[0043]

The present invention will be described more specifically below with reference to examples and comparative examples.

Examples 1 to 20 and Comparative Examples 1 to
6) Ordinary glass raw materials such as silica and alumina, so that the content of each of the components shown in Tables 1 and 2 below are obtained.
Batches were prepared using lithium carbonate, sodium carbonate, basic magnesium carbonate, calcium carbonate, strontium carbonate, titania and zirconia. The prepared batch was held at 1,550 ° C. for 4 hours using a platinum crucible, and then poured out onto an iron plate. 650 of this glass
After holding for 30 minutes in an electric furnace set to ° C., the furnace was turned off and allowed to cool to room temperature to produce each sample glass.

In Comparative Examples 1 and 2, two types of glass compositions commercially available as substrates were used.
Are two kinds of glass compositions disclosed in JP-A-10-81542, and Comparative Examples 5 and 6 are WO98 / 5.
This is a reproduction of the glass composition disclosed in Japanese Patent No. 5993. The properties of these sample glasses were measured by the following methods.

[Measurement of Elastic Modulus] The sample glass was cut and each surface was mirror-polished to produce a 5 × 30 × 30 mm plate sample. The elastic modulus of each sample was calculated by an ultrasonic method using a sing-around transmitter.

[Measurement of Density] The above-mentioned sample glass was measured by the Archimedes method.

[Measurement of rigidity] The rigidity was calculated from the measurement results of the elastic modulus and the density.

[Measurement of liquidus temperature] The above sample glass was pulverized and passed through a 2,380 μm sieve to obtain 1,000 μm
Immerse the glass particles remaining on the screen in ethanol in ethanol,
After ultrasonic cleaning, it was dried in a thermostat. 25 g of the glass particles were placed 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.
After holding in a gradient furnace at 1,180 ° C. for 2 hours, the glass was taken out of the furnace, and the devitrification generated inside the glass was observed with a 40 × optical microscope. The maximum temperature at which devitrification was observed was defined as the liquidus temperature. did.

[0050]

[Table 1]

[0051]

[Table 2]

Each of the glass compositions of Examples 1 to 20 had an elastic modulus of 90 GPa and a rigidity of 35 GPa · cm ³ / g or more. In contrast, the glasses of Comparative Examples 1 and 2 each had an elastic modulus of 72 GPa and a rigidity of less than 30 GPa · cm ³ / g. This indicates that a glass composition having a high modulus of elasticity and high rigidity can be reliably obtained with the content of each composition component of the present invention.

The devitrification temperatures of Examples 1 to 20 are mostly 1,000 ° C. or less, whereas the devitrification temperatures of Comparative Examples 3 to 6 all exceed 1,180 ° C. From this, it can be seen that a glass composition having good moldability can be reliably obtained with the content of each composition component of the present invention. There is a large difference between the liquidus temperature described in International Publication WO98 / 55993 and the liquidus temperatures of Comparative Examples 5 and 6. This is due to the method of measuring the liquidus temperature, especially the holding time in the molten state. It is thought to be due to the difference. The devitrification of glass tends to increase with the retention time in the molten state, and the low liquidus temperature in WO 98/55993 is presumed to be due to the short retention time after melting. Therefore, the glass compositions of Comparative Examples 5 and 6 need to be processed in a short time from melting to molding, and are not suitable for a float method requiring a long time for molding.

The densities of the glass compositions of Examples 1 to 20 were as follows:
Both 2.75 g / cm ³ or less, much is 2.6 g / cm ³ or less. On the other hand, in Comparative Examples 3 to 5, 2.8 g /
cm ³ and in particular Comparative Example 5 highest and 2.88 g / cm ^3. Glass composition of Comparative Example 5 Y ₂ O ₃ from that contained 6%, Y ₂ O ₃ or when containing a lanthanoid oxide density it can be seen that high. A medium containing these composition components puts a burden on the driving device and increases the power consumption of the device. In Comparative Example 6, the characteristics could not be measured because molding was impossible.

[Manufacture and Evaluation of Substrate and Medium] The glass compositions of Examples 1 to 20 were cut into donut shapes having an outer diameter of 95 mm and an inner diameter of 20 mm, and ground and polished. JISB 0601-19;
94) to obtain a disk having a thickness of 1.2 mm.

KNO ₃ : NaNO heated to 380 ° C.
_The substrate was immersed for 1 hour in a mixed molten salt of ₃ = 80: 20 for chemical strengthening to obtain a substrate. Using this substrate, a recording medium was produced as follows. On the substrate, Cr was formed as a base layer, Co-Cr-Ta was formed as a recording layer, and C was formed as a protective layer by sputtering. Further, a lubricating layer was formed to obtain a recording medium.

The recording medium obtained in this way is incorporated into a hard disk by a conventional method, and the flying height 15n
m and were continuously operated at 10,000 and 12,000 rpm, respectively. In the media of any of the examples, no collision with the magnetic head was detected, and no problem of crash of the magnetic head occurred.

[0058]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the present invention, since the composition component is appropriate, an inexpensive glass composition having high elastic modulus (Young's modulus) and rigidity and good moldability can be easily obtained. .

According to the second aspect of the present invention, since the composition components are more suitable, it is possible to reliably obtain a high-rigidity / high-modulus glass composition which is easy to produce.

According to the third aspect of the present invention, since the content of SrO is limited, the formability of the glass composition can be improved while maintaining the elasticity.

According to the fourth aspect of the invention, substantially
Since it does not contain ZrO ₂ , zirconia can be prevented from precipitating as fine crystals during glass melting, and a high-rigidity, high-modulus glass composition having high surface smoothness can be obtained.

According to the fifth aspect of the present invention, since the content of Al ₂ O ₃ is 5 to 6%, it is possible to reliably obtain a high-rigidity / high-modulus glass composition having an appropriate liquidus temperature. Can be.

According to the invention of claim 6, Na ₂ O / Li
_Since the ratio of 2O and MgO / CaO is appropriate, a high-rigidity / high-modulus glass composition which can be easily formed by lowering the liquidus temperature can be obtained.

According to the seventh aspect of the present invention, since the glass composition has a high elastic modulus and rigidity, it can sufficiently cope with thinning of the substrate and further high-speed rotation of the medium.

According to the eighth aspect of the present invention, an inexpensive plate-like high-rigidity / high-modulus glass composition having a high surface smoothness can be obtained since it is formed by the float method.

According to the ninth aspect of the present invention, since the glass is chemically strengthened, a glass composition having both high elastic modulus and strength can be obtained.

According to the tenth aspect of the present invention, since the glass composition having high rigidity and high elastic modulus is used, it is possible to obtain a substrate which can be made thin and hardly bend even at high speed rotation.

According to the eleventh aspect of the present invention, since a substrate having a high rigidity and a high elastic modulus is used, it is possible to obtain a medium capable of increasing the storage capacity of the information recording apparatus and shortening the access time.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shoichi Kishimoto 3-5-11 Doshomachi, Chuo-ku, Osaka-shi, Osaka Inside Nippon Sheet Glass Co., Ltd. (72) Inventor Nobuyuki Yamamoto 3 Doshomachi, Chuo-ku, Osaka-shi, Osaka No. 5-11, Nippon Sheet Glass Co., Ltd.

Claims (11)

[Claims] 1. A composition molar percentage of silicon dioxide (SiO ₂ ) 55 to 65% aluminum oxide (Al ₂ O ₃ ) 0.5 to 6% lithium oxide (Li ₂ O) 12 to 22% sodium monoxide (Na) ₂ O) 0-5% Titanium dioxide (TiO ₂ ) 0.1-10% Zirconium oxide (ZrO ₂ ) 0-3% Magnesium oxide (MgO) 0-8% Calcium oxide (CaO) 0-18% Strontium oxide ( SrO) 0~ 5% RO (RO = MgO + CaO + SrO) contains 5 to 18% yttrium oxide (Y ₂ O _3), and lanthanoid oxides essentially glass compositions without the. 2. Compositional percent by mole: silicon dioxide (SiO ₂ ) 55-62% aluminum oxide (Al ₂ O ₃ ) 2-6% lithium oxide (Li ₂ O) 12-20% sodium monoxide (Na ₂ O) ) 1-4% titanium dioxide (TiO ₂₎ 0.5 to 5% zirconium oxide (ZrO ₂₎ 0 to 2.5% of magnesium oxide (MgO). 2 to 6% calcium oxide (CaO) 5 to 10% strontium oxide ( SrO) 0~ 5% RO (RO = MgO + CaO + SrO) contains 8-18% yttrium oxide (Y ₂ O _3), and lanthanoid oxides essentially glass compositions without the. 3. The glass composition according to claim 1, wherein the content of SrO is 0.5 to 5%. 4. The method according to claim 1, wherein the composition is substantially free of ZrO _2.
The glass composition according to any one of the above. 5. The glass composition according to claim 1, wherein the content of Al ₂ O ₃ is 5 to 6%. 6. The ratio of Na ₂ O to Li ₂ O is from 1/20 to 1
The glass composition according to any one of claims 1 to 5, wherein the ratio of MgO to CaO is １ ／ to 1/1. 7. The glass composition according to claim 1, wherein an elastic modulus represented by Young's modulus is 90 GPa or more, and a rigidity represented by Young's modulus / density is 30 GPa · cm ³ / g or more. object. 8. The glass composition according to claim 1, which is formed into a plate by a float method. 9. The method according to claim 1, wherein the alkali component near the surface is ion-exchanged by immersion in a heated molten salt to increase the strength.
9. The glass composition according to any one of items 8 to 8. 10. A substrate for an information recording medium using the glass composition according to claim 1. Description: 11. An information recording medium using the substrate according to claim 10.