WO2008062847A1

WO2008062847A1 - Glass for information recording medium substrate

Info

Publication number: WO2008062847A1
Application number: PCT/JP2007/072590
Authority: WO
Inventors: Tetsuya Nakashima; Kensuke Nagai; Kei Maeda
Original assignee: Asahi Glass Company, Limited
Priority date: 2006-11-22
Filing date: 2007-11-21
Publication date: 2008-05-29
Also published as: JPWO2008062847A1; CN101541696A; MY157935A; JP5396859B2

Abstract

Provided is a glass having a high glass transition point to be used for an information recording medium substrate. The glass for the information recording medium substrate contains the following oxides in mol percentage; an SiO2 of 55-75%, Al2O3 of 1-12%, MgO of 2-15%, CaO of 0-1.5%, Na2O or K2O of 1-20% and TiO2 of 0-8%. When the glass contains BaO, the content is 2% or less, when it contains Li2O, the content is 1% or less and when it contains ZrO2, the content is 0.5% or less. The glass transition point of the glass is 600°C or higher.

Description

Specification

Glass for information recording medium substrate

Technical field

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

Background art

[0002] Glass substrates are widely used as substrates for information recording media, particularly as magnetic disk (node disks) substrates. As glass substrates for magnetic disks, they are chemically strengthened and chemically strengthened! / Something exists.

Non-chemically strengthened glass substrates for magnetic disks include SiO -A1 O -Li O-

2 2 3 2

One made of Na 2 O—K 2 O—TiO glass has been proposed (see Patent Document 1).

2 2 2

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-161597 (Table;! To 12)

Disclosure of the invention

Problems to be solved by the invention

[0004] The glass of Patent Document 1 has a maximum glass transition point (Tg) of 567 ° C. When this glass is used for a glass substrate for a magnetic disk, the temperature at which a magnetic layer is formed on the glass substrate. As a result, the coercive force of the magnetic layer may not be increased.

An object of the present invention is to provide a glass for an information recording medium substrate and a glass substrate for an information recording medium using the same, which can solve such problems.

Means for solving the problem

[0005] In the present invention, SiO is 55 to 75% and Al 2 O is 1 to 12 in terms of mol% based on the following oxides.

2 2 3

%, MgO 2 ~; 15%, CaO 0 ~;! · 5%, Na O or K 2 O in total;! ~ 20%, Ti

twenty two

When O is contained in an amount of 0 to 8% and BaO is contained, the content is 2% or less, and Li O is contained.

2 2 If it contains, its content is 1% or less, and if it contains ZrO, its content is 0.5

2

Provided is a glass for an information recording medium substrate that is not more than%.

Also provided is a glass substrate for information recording medium comprising the glass for information recording medium substrate. To do.

The invention's effect

[0006] According to the present invention, a glass for an information recording medium substrate having a Tg of 600 ° C or higher can be obtained.

Further, it is possible to obtain a glass for an information recording medium substrate or a glass substrate for an information recording medium that has high strength, a low density, or that can be float formed.

In addition, since a glass substrate for information recording media having high weather resistance can be obtained, the surface properties of the glass substrate change significantly during inventory, and films such as a base film, a magnetic film, and a protective film formed on the substrate. The problem of easy peeling is less likely to occur.

In addition, since a glass substrate for information recording media can be produced without performing chemical strengthening treatment, the number of processes can be reduced, and the problem of contamination on the substrate surface after chemical strengthening treatment can be solved.

BEST MODE FOR CARRYING OUT THE INVENTION

[0007] The Tg of the glass for an information recording medium substrate of the present invention (hereinafter referred to as the glass of the present invention) is preferably 600 ° C or higher! If the temperature is lower than 600 ° C, the force for sufficiently increasing the heat treatment temperature for forming the magnetic layer cannot be achieved, and it may be difficult to increase the coercivity of the magnetic layer. More preferably, it is 610 ° C or higher, particularly preferably 620 ° C or higher.

[0008] The average linear expansion coefficient at 50 to 350 ° C of the glass of the present invention (alpha) is preferably on 70 Χ 10_ ⁷ / ° C or less. 70 X In 10_ ⁷ / ° less than C, the thermal expansion coefficient of the metal hub attached to the substrate (typically ^{70 X 10- 7 ~; 100 X} 10- 7 / ° C) difference between the increases, of the substrate Cracking is likely to occur. More preferably 75 X 10_ ⁷ / ° C or more, particularly preferably 80 X 10 _ ⁷ / ° C or more. Further, alpha is typically less than 95 X 10- ⁷ / ° C.

[0009] The glass of the present invention has its liquidus temperature as T and the temperature at which the viscosity becomes 10 ⁴ P (poise) as T.

In the case of L 4, (T−T) is preferably less than 50 ° C. (T — T) is over 50 ° C

L 4 L 4

Float molding may be difficult, and is preferably less than 40 ° C, particularly preferably less than 30 ° C.

The temperature T at which the viscosity of the glass of the present invention becomes 10 ² P is preferably 1700 ° C or lower.

2

If T exceeds 1700 ° C, it may be difficult to melt or clarify the glass. [0010] The glass substrate for magnetic disk is used for 2.5 inch substrate (glass substrate outer diameter: 65mm) used for notebook computers, etc. and portable ΜΡ3 player, etc. 1. 8 inch substrate

(Glass substrate outer diameter: 48mm) is widely used, and the market is expanding year by year. On the other hand, low-cost supply is required. The glass used for such glass substrates is preferably suitable for mass production.

Mass production of sheet glass is widely performed by continuous molding methods such as the float method, fusion method, and downdraw method. As described above, the glass of the present invention can be made into a glass that can be float formed, for example. Suitable for production.

[0011] The density of the glass of the present invention is preferably 2.50 g / cm ³ or less, more preferably 2.

48 g / cm ³ or less, particularly preferably 2. 47 g / cm ³ or less.

[0012] The glass substrate for information recording medium of the present invention (hereinafter referred to as the glass substrate of the present invention) is a generally circular glass plate made of the glass of the present invention. An example of the information recording medium is a magnetic disk.

[0013] When the glass substrate of the present invention is held in a water vapor atmosphere at 120 ° C and 2 atm for 20 hours, the number of deposits existing on the surface and having a size of 10 m or more N force / cm ² or less

L

Or the number of deposits with a size of 1 m or more but less than 10 m N force 0 ⁵ pieces / cm ² or less

S

Preferably it is below. For N force pieces / cm ² or N force pieces / cm ²

L S

Deposits (white dust) are generated on the surface of the glass substrate during substrate stock, and films such as the base film, magnetic film, and protective film formed on the glass substrate are easily peeled off. This deposit is considered to be a reaction product that has been generated and adhered to the glass substrate due to the effects of water in the air or carbon dioxide, and cannot be removed by wiping. N is more preferably 0.8 / cm ² or less, particularly preferred

L

Or 0.5 piece / cm ² or less. N is more preferably 0.8 × 10 ⁵ pieces / cm ² or less, particularly preferably

Preferably it is 0.6 x 10 ⁵ pieces / cm ² or less.

[0014] The crack occurrence rate of the glass of the present invention is preferably 70% or less. If it exceeds 70%, the glass strength may be insufficient. More preferably, it is 60% or less, particularly preferably 50% or less.

The crack occurrence rate is obtained as follows. That is, in a room controlled at 23 ° C and a relative humidity of 70%, the mirror polished glass with a thickness of !! ~ 2mm and a size of 4cm x 4cm A Vickers indenter is driven into the surface of the lath plate with a load of 500 g, and the number of cracks generated from the four apexes is measured. This measurement is repeated 10 times, and 100 X (total number of cracks generated) / 40 is defined as the crack occurrence rate.

When the crack generation rate is small, the glass surface is not easily scratched, so that stress concentration does not occur, and brittle fracture does not occur or decreases with weak stress that is difficult.

[0015] The method for producing the glass and the glass substrate of the present invention is not particularly limited, and various methods can be applied. For example, the raw materials of each component that are usually used are prepared so as to have a target composition, and this is heated and melted in a glass melting kiln. Homogenize the glass by publishing, stirring, adding a clarifying agent, etc., forming into a sheet glass of a specified thickness by methods such as the well-known float method, press method, fusion method, and downdraw method, and after slow cooling, as necessary After processing such as polishing ij and polishing, a glass substrate having a predetermined size is formed. As the molding method, a float method suitable for mass production is particularly suitable. Further, continuous molding methods other than the float method, that is, the fusion method and the downdraw method are also suitable.

[0016] Next, the composition of the glass of the present invention will be described using mol% display.

SiO is a component that forms a glass skeleton and is essential. Less than 55% in glass

2

It becomes easy to be scratched, and T rises and the glass becomes unstable. Preferably 58% or more

L

More preferably, it is 60% or more, particularly preferably 62% or more, typically 64% or more, and more typically 65% or more. If it exceeds 75%, the high-temperature viscosity rises and it becomes difficult to melt the glass. Preferably it is 72% or less, More preferably, it is 71% or less.

[0017] Al 2 O is essential as it has the effect of increasing Tg and improving weather resistance. Less than 1%

twenty three

Small effect. Preferably it is 1.5% or more, more preferably 2% or more, and particularly preferably 2.5% or more. If it exceeds 12%, the high-temperature viscosity will increase, making it difficult to melt the glass.

L

Too high. It is preferably 10% or less, more preferably 8% or less, particularly preferably 7% or less, and typically 6.5% or less.

[0018] MgO is an essential component with the effect of increasing α while maintaining weather resistance, scratching the glass, and improving glass solubility. If it is less than 2%, the effect is small. Preferably it is 5% or more, more preferably 7% or more, and most preferably 8% or more. Above 15%, TL becomes too high. Preferably it is 14% or less, more preferably 13% or less [0019] CaO is not essential! /, But may be contained up to 1.5% in order to increase α while maintaining the weather resistance or to improve the solubility of the glass. 1. If it exceeds 5%, the glass may be damaged. It is preferably 1% or less, more preferably less than 0.5%, typically 0.3% or less.

[0020] Na 2 O and K 2 O have the effect of increasing α and improving the solubility of glass.

twenty two

It is an ingredient and must contain at least one of them. Na O and K O content

If the total amount of Na 2 + K 2 O is less than 1%, the effect is small. Preferably over 2%, more preferred

twenty two

It is preferably 5% or more, particularly preferably 7% or more, and typically 10% or more. If it exceeds 20%, the weather resistance is lowered and the glass transition point is lowered. It is preferably 17% or less, more preferably 15% or less, particularly preferably 14% or less, and typically 13.5% or less. Typically, NaO is 2 to 8%, K? Is 3 to 10%.

twenty two

SiO force is over 0%, Al O force is 0% or less, Na O + K O is over 2% and 17% or less.

2 2 3 2 2

preferable.

[0021] TiO is not an essential component, but it increases Tg, weather resistance, or glass melting.

2

It has the effect of improving the dissolvability and may be contained up to 8%. Above 8%, T becomes too high

L

There is a risk that phase separation phenomenon is likely to occur. Preferably it is 7% or less, more preferably 6% or less, particularly preferably 5% or less. In case of containing TiO

2

The content is preferably 1% or more. More preferably, it is 1.5% or more, particularly preferably 2% or more, and most preferably 3% or more.

Total content of MgO and TiO MgO + TiO is preferably 10% or more

twenty two

. If it is less than 10%, the glass may be easily damaged, or the high-temperature viscosity may increase, making it difficult to dissolve the glass. MgO + TiO is typically over 13%

2

Yes

Typically, SiO is 62 to 72%, Al O is 2 to 8%, MgO is 7 to 14%, Na O + K

2 2 3 2 2

〇 is 10-14%, 1 〇 is 0-6%.

2

[0022] The glass of the present invention consists essentially of the above components, but may contain other components as long as the object of the present invention is not impaired. In that case, the total content of the other ingredients is preferred. Or 10% or less, more preferably 5% or less, and typically 2% or less. For example, even if it contains up to 2% of total fining agents such as SO, Cl, AsO, SbO, SnO

3 2 3 2 3 2

Although it is good, it is preferable not to contain As 2 O 3, Sb 2 O 3, or SnO.

2 3 2 3 2

It also contains up to 3% B 2 O in order to improve the solubility and stability of the glass.

twenty three

Good.

However, it is preferable that B 2 O is not substantially contained from the following viewpoints. Snow

twenty three

In other words, when BΟ coexists with the alkali metal oxide component, the alkali borate compound with low vapor pressure is used.

twenty three

It becomes easy to form an object, and the same component is very easily volatilized from the glass melt. As a result, inconsistencies such as striae occur, causing glass quality to deteriorate, and at the same time, the volatile matter is condensed into the brick material used in the glass melting furnace, and the strength of the volatile matter is significantly reduced. Since problems such as enormous costs occur, it is preferable that BO is not substantially contained when it is desired to suppress such problems.

twenty three

[0023] In some cases, SrO or BaO may be contained in a total range of 4% or less in order to increase α while maintaining the weather resistance and to improve the solubility of the glass. If it exceeds 4%, the glass may be easily damaged. Preferably it is 2% or less. However, when it contains BaO, its content must be 2 mol% or less.

It should be noted that when it is desired to make the glass more difficult to be damaged, SrO is not contained or even if it is contained, it is preferably less than 0.1%. In such a case, BaO is not contained, and even if it is contained, it is preferably less than 0.1%.

Contains up to 1% Li 2 O to increase α or improve glass solubility

2

Also good. If it exceeds 1%, Tg will be low, the weather resistance will be lowered, or the glass will be easily damaged. Typically not more than 0.6%, but it is often preferred not to contain substantially

Yes

To increase Tg, ZrO may be contained up to 0.5%. 0. Above 5%, glass is damaged

2

It becomes easier.

[0024] When CaO, SrO or BaO is contained, the molar ratio of MgO content to (total content of MgO, CaO, SrO and BaO): (MgO) / (MgO + CaO + SrO + BaO) is Preferably it is 0 · 6 or more. If it is less than 0.6, the glass tends to be damaged. [0025] The total content of Li 0, Na 2 O, and KO is R ′ 2 O, and the alkaline earth metal oxide

2 2 2 2

Where the total content of RO is RO, the molar ratio of R'O to (R'O + RO), that is, (R'O)

2 2 2

/ (R, O + RO) is preferably 0.25-0.75. Outside this range, the weather resistance is

2

It may decrease, make you feel weak, or damage the glass. More preferably, it is 0.3 to 0.7.

含有 When Ο is contained, Κ Ο content and total of Li 0, Na O and Κ Ο

2 2 2 2 2

The molar ratio of K 0 / (Li O + Na O + K Ο) is preferably 0.2 or more.

2 2 2 2

Yes. If it is less than 0.2, Tg may be lowered or the weather resistance may be lowered. More preferably, it is 0.3 or more, particularly preferably 0.4 or more.

Since oxides of atoms with atomic numbers larger than Ti (such as V) may easily damage the glass, the total content of these oxides should be 0.5% or less. Force S is preferred. More preferably, it is 0.3% or less, particularly preferably 0.2% or less, and most preferably 0.1% or less.

Example

[0026] The composition of the raw materials of each component is shown in mol% in the columns up to SiO power and ZrO in the table.

twenty two

And dissolved in a platinum crucible at a temperature of 1550-; 1600 ° C for 3-5 hours. For melting, a platinum stirrer was inserted into the molten glass and stirred for 2 hours to homogenize the glass. Next, the molten glass was poured out, formed into a plate shape, and gradually cooled. In the table, RO is the total content of MgO, CaO, SrO and BaO (unit: mol%), R and O are Li

2

0, Na O and Κ content Omicron: shows the total (unit mol ^_0/0).

2 2 2

The glasses of Examples 1-11 are examples, and the glasses of Examples 12-25 are comparative examples.

! [0027] One glass plate thus obtained /, Te, and the cracking incidence (unit:%), the glass transition point Tg (Unit: ° C), thermal expansion coefficient "(unit: X 10- ⁷ / ° c), liquidus temperature T (unit: ° C), viscosity 10 ⁴ P

L

Temperature T (unit: C), temperature T (unit: C) at which the viscosity becomes 10 ² P, N (unit: piece / unit)

4 2 L

cm ² ), N (unit: 10 ⁵ pieces / cm ² ), and density (unit: g / cm ³ ) were measured. result

S

Are shown in the table below, and the methods for measuring Tg, α, T, T, T, N and N are shown below. In addition

L 4 2 L S

In the “table”, items indicated by “one” were not measured.

Tg: Using a differential thermal dilatometer, with quartz glass as the reference sample, from room temperature to 5 ° C / min The elongation of the glass when the temperature is raised is measured to the temperature at which the glass is softened and no longer stretched, i.e., to the yield point. did.

[0028] a: Using a differential thermal dilatometer, the elongation of the glass was measured up to the yield point when the temperature was raised from room temperature at a rate of 5 ° C / min using quartz glass as a reference sample. 50 from the expansion curve

The average linear expansion coefficient at ˜350 ° C. was calculated.

[0029] T: The glass is crushed into about 2 mm glass grains in a mortar, and the glass grains are placed in a platinum boat.

L

And heat-treated in a temperature gradient furnace for 24 hours. The maximum temperature of the glass grains on which crystals were deposited was defined as the liquidus temperature.

T, T: Measured with a rotational viscometer.

4 2

[0030] Ν, Ν: Thickness 〜 ~ 2mm, 4cm X 4cm size glass plate both sides mirror polished, charcoal

L S

After washing with calcium acid and neutral detergent, place it in a super accelerated life tester (unsaturated pressure tacker TPC-410, Tabai Espec Co., Ltd.) in a water vapor atmosphere at 120 ° C and 2 atm. Let stand for hours. The surface of the surface of the glass plate taken out was observed with a differential interference microscope, and the number of deposits with a size of 10 m or more and the number of deposits with a size of 1 m or more and less than 10 Hm were counted.

[0031] [Table 1]

2]

3]

Industrial applicability

It can be used for manufacturing information recording media substrates such as magnetic disk substrates and information recording media such as magnetic disks. It should be noted that the entire contents of the Japanese Patent Application 2006-315122, filed on November 22, 2006, the text of claims, drawings and abstract are cited herein, and the description of the present invention is disclosed. It is included as an indication.

Claims

The scope of the claims

[I] In terms of mol% based on the following oxide standards, SiO is 55 to 75%, Al 2 O ;! to 12%, MgO

2 2 3

2-15%, CaO 0 ~;! · 5%, Na O or K 2 O in total;! ~ 20%, TiO 0 ~ 8%

2 2 2 content and BaO content is 2% or less.

2

If the content of ZrO is 1% or less, the content is 0.5% or less.

2

Glass for information recording medium substrate.

[2] SiO force over 0%, Al O force over 0%, Na O + K O over 2% over 17%

2 2 3 2 2

Item 2. The glass for an information recording medium substrate according to Item 1.

[3] SiO force 2 to 72%, Al 2 O force ¾ to 8%, MgO 7 to 14%, Na 2 O + K 2 O 10 to 14

2 2 3 2 2

2. The glass for an information recording medium substrate according to claim 1, wherein the glass has a TiO power of 3 to 6%.

2

[4] The information recording medium substrate according to claim 1, 2 or 3, wherein MgO + TiO power is S10% or more.

2

Glass.

[5] It contains CaO, SrO or BaO, and the molar ratio between the MgO content and the total content of MgO, CaO, SrO and BaO is 0.6 or more; Glass for recording information recording medium substrate.

[6] The glass for an information recording medium substrate according to any one of claims 1 to 5, wherein the CaO content is less than 0.5%.

[7] The total content of Li 0, Na O and Κ Κ is R '0, the alkaline earth metal oxide content.

2 2 2 2

When the total content is RO, the molar ratio of R'O to (R'O + RO) is 0.25—0.75.

twenty two

Claims 1-6 The glass for information recording medium substrates in any one of.

[8] Containing K 2 O, and the mole of K 2 O and the sum of the contents of Li 0, Na 2 O and Κ

2 2 2 2 2

The glass for an information recording medium substrate according to any one of claims 1 to 7, wherein the ratio is 0.2 or more.

[9] An information recording medium substrate according to any one of claims 8 to 8, which does not substantially contain 実質

twenty three

Glass.

10. The glass for an information recording medium substrate according to any one of claims 1 to 9, wherein the glass transition point is 600 ° C or higher.

[II] 50 to 350 ° information recording medium glass substrate according to any one of claims 1 to 10 average linear expansion coefficient at C is 70 X 10_ ⁷ / ° C or more. When the liquidus temperature is T and the temperature at which the viscosity is 10 ⁴ Ρ is Τ, (Τ-)) is 50 ° C.

L 4 L 4 Claim;! To 11! /, Glass for information recording medium substrate according to any one of the above.

13. The information recording medium substrate glass according to claim 1, wherein the density is 2.50 g / cm ³ or less.

A glass substrate for an information recording medium comprising the glass for an information recording medium substrate according to any one of claims 1 to 13.