JPH0532431A - Glass for chemical reinforcement - Google Patents

Abstract

PURPOSE:To provide a glass for chemical reinforcement, excellent in ion- exchange properties and capable of forming a chemically reinforced glass having a deep compressive stress layer, showing a high bending strength owing thereto and having a high Knoop hardness by ion-exchange and to provide a chemically reinforced glass produced therefrom. CONSTITUTION:The glass for chemical reinforcement in this invention is characterized by its composition containing 62-75wt.% SiO%2, 5-15wt/% Al2O3, 4-10wt.% Li2O, 4-12wt.% Na2O and 5.5-15wt.% ZrO2 so that the weight ratios of (Na2O)/(ZrO2) and (Al2O3)/(ZrO2) may be respectively 0.5-2.0 and 0.4-2.5. The chemically reinforced glass in this invention is characterized by chemical reinforcement of the glass using ion-exchange treatment in a treatment bath containing Na ion and/or K ion. By this invention, a watch cover, a base plate for information recording and a medium for information recording can be obtained by using the above-mentioned chemically reinforced glass.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemically strengthened glass, a chemically strengthened glass, a watch cover and an information recording substrate using the chemically strengthened glass.

[0002]

2. Description of the Related Art Conventionally, as a glass for chemical strengthening, JP-A-62-187140 discloses a glass of 64 to 7% by weight.
0% SiO ₂ , 14-20% Al ₂ O ₃ , 4-6%
Li ₂ O, 7-10% Na ₂ O, 0-4% Mg
Glasses containing O, 0-1.5% ZrO ₂ are disclosed.

The analysis value (% by weight) is 61.4.
% SiO ₂ , 16.8% Al ₂ O ₃ , 12.7% Na ₂ O, 3.6% K ₂ O, 3.7% MgO, 0.
Commercial glasses are known which contain 2% CaO and 0.8% TiO ₂ .

Further, US Pat. No. 4,156,755 discloses that 59 to 63% by weight of SiO ₂ , 10 to 1 are used.
3% Na ₂ O, 4-5.5% Li ₂ O, 15-23
% Al ₂ O ₃ , 2-5% ZrO ₂ and N
A glass having a weight ratio of a ₂ O / ZrO ₂ of 2.2 to 5.5 is disclosed.

By subjecting these chemically strengthening glasses to ion exchange treatment, alkali metal ions (eg, Li ions) in the glass have a larger ionic radius (eg, Na ions) in the ion exchange treatment bath.
Ions and K ions) are exchanged to obtain chemically strengthened glass.

The chemically strengthened glass thus obtained is used for, for example, a watch cover, but recently, it has been attempted to be applied to an information recording substrate such as a magnetic disk substrate, an optical disk substrate or a magneto-optical disk substrate. .

[0007]

When the above conventional glass for chemical strengthening is subjected to an ion exchange treatment, the ion exchange rate is slow and it is difficult to obtain an ion exchange layer (also called a compressive stress layer) having a sufficient depth. Inferior in bending strength. Moreover, since the Knoop hardness is low, the strength against fracture cannot be said to be sufficiently high.

Particularly when the chemically strengthened glass is applied to an information recording substrate such as a magnetic disk substrate, flaws which cannot be prevented by the manufacturer are likely to occur in the steps such as polishing and disk processing of the chemically strengthened glass. Even if the chemically strengthened glass having such a flaw is subjected to an ion exchange treatment, the compression applied layer formed on the glass surface by the ion exchange is shallow and the bending strength is low, so that the resulting chemically strengthened glass may be impacted. It is easy to destroy. Therefore, in order to obtain an information recording substrate that does not cause such destruction, it is necessary to deepen the compressive stress layer formed on the glass surface by ion exchange to increase the bending strength. Chemically strengthened glass obtained from glass has a shallow compressive stress layer,
Since the bending strength is low, it is insufficient for use as a substrate for recording information.

Therefore, a first object of the present invention is to provide a chemically strengthened glass obtained by ion exchange with a deep compressive stress layer, which has excellent ion exchange performance, and a high bending strength based on this, and a high Knoop. It is to provide a glass for chemical strengthening that can impart hardness.

A second object of the present invention is to provide a chemically strengthened glass by using the glass for chemically strengthening which achieves the first object.

A third object of the present invention is to provide a timepiece cover using the chemically strengthened glass which achieves the second object.

A fourth object of the present invention is to provide an information recording substrate by using the chemically strengthened glass which achieves the second object.

Further, a fifth object of the present invention is to provide the above-mentioned fourth object.
An object of the present invention is to provide an information recording medium using an information recording substrate that achieves the above object.

[0014]

The glass for chemical strengthening of the present invention which achieves the first object is 62 to 75% by weight.
% SiO ₂ , 5-15% Al ₂ O ₃ , 4-10% Li ₂ O, 4-12% Na ₂ O, and 5.5-15.
% 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 2.5. And

The chemically strengthened glass of the present invention which achieves the second object is chemically strengthened by subjecting the above glass for chemical strengthening to an ion exchange treatment in a treatment bath containing Na ions and / or K ions. It is characterized by

Further, the timepiece cover of the present invention which achieves the third object is characterized by using the above-mentioned chemically strengthened glass.

Furthermore, the information recording substrate of the present invention which achieves the fourth object is characterized by using the above chemically strengthened glass.

Further, an information recording medium of the present invention which achieves the above fifth object is characterized by using the above information recording substrate.

The present invention will be described in detail below. The reasons for limiting the composition of the glass for chemical strengthening of the present invention are as follows.

SiO ₂ is the main component forming the glass skeleton, and if it is less than 62%, the chemical durability deteriorates,
If it exceeds 75%, the melting temperature becomes too high. Therefore S
The proportion of iO ₂ is limited to 62-75%. It is particularly preferably 63 to 71%. Al ₂ O ₃ is contained in order to improve the ion exchange performance of the glass surface, but 5%
If it is less than less than this effect, the chemical durability is deteriorated and if it exceeds 15%, the devitrification resistance is deteriorated. Therefore, the proportion of Al ₂ O ₃ is limited to 5 to 15%. It is particularly preferably 7 to 14%.

Li ₂ O is an essential component for chemically strengthening the glass by being ion-exchanged mainly with Na ions in the ion-exchange treatment bath at the surface layer of the glass,
If it is less than 4%, the ion exchange performance is lowered, and if it exceeds 10%, both devitrification resistance and chemical durability are deteriorated. Therefore, the proportion of Li ₂ O is limited to 4 to 10%. It is particularly preferably 4 to 7%.

Na ₂ O is an essential component for chemically strengthening the glass by being ion-exchanged with K ions in the ion-exchange treatment bath at the surface layer of the glass, but if it is less than 4%, the devitrification resistance is low. When it exceeds 12%, the chemical durability deteriorates and the Knoop hardness decreases. Therefore Na ₂
The proportion of O is limited to 4 to 12%. It is particularly preferably 6 to 11%.

ZrO ₂ has the effect of increasing the Knoop hardness, and is required to be 5.5% or more in order to improve the chemical durability. However, if it exceeds 15%, it is not formed in the bottom of the melting furnace. The tendency to precipitate as a lysate becomes stronger. Therefore, the proportion of ZrO ₂ is limited to 5.5 to 15%. It is particularly preferably 6 to 12%. When the content of ZrO ₂ is large, the devitrification resistance of the glass is usually lowered, but the content of ZrO ₂ is 5.5 to 1
It is noteworthy that the glass of the present invention is excellent in devitrification resistance despite the relatively large amount of 5%.

In the glass for chemical strengthening of the present invention, N
a ₂ O / ZrO ₂ weight ratio and Al ₂ O ₃ / ZrO ₂
The weight ratio of is also limited to a predetermined range. That is, Na ₂
The weight ratio of O / ZrO ₂ needs to be 2.0 or less in order to increase the Knoop hardness and obtain excellent strength.
If it is less than 5, devitrification resistance deteriorates, so 0.5 to 2.
Limited to 0. A particularly preferable weight ratio of Na ₂ O / ZrO ₂ is 0.7 to 1.8.

The weight ratio of Al ₂ O ₃ / ZrO ₂ is
It is limited to 0.4 to 2.5 in order to maintain excellent devitrification resistance and ion exchange performance and obtain a stable and high-strength glass. A particularly preferred weight ratio of Al ₂ O ₃ / ZrO ₂ is
It is 0.6 to 2.0. The reason is that if it is less than 0.4, the glass becomes unstable, while if it exceeds 2.5, not only the compressive stress layer becomes thin and the transverse strength decreases, but also the Knoop hardness decreases. is there.

The glass for chemical strengthening of the present invention comprises, in addition to the above components, MgO, Zn within a range not impairing the characteristics of the present invention.
O, may contain or TiO ₂ and _{La 2 O 3, As 2 O} 3 usually used as a fining agent, Sb ₂ O _3, F and Cl and the like.

The glass for chemical strengthening of the present invention contains 15 glass raw materials prepared so that the composition thereof falls within the above range.
It is obtained by heating and melting at 00 to 1600 ° C. for 5 to 8 hours, casting the molten glass in a mold, and gradually cooling.

The obtained glass for chemical strengthening of the present invention has an excellent ion exchange performance, and a deep compressive stress layer based on the chemically strengthened glass obtained by ion exchange and a high bending strength based on the layer are obtained. Can add Knoop hardness.

Next, the chemically strengthened glass of the present invention will be described. This chemically strengthened glass is obtained by chemically strengthening the glass for chemical strengthening by ion exchange treatment in a treatment bath containing Na ions and / or K ions. Na
As the treatment bath containing ions and / or K ions, it is preferable to use a treatment bath containing sodium nitrate and / or potassium nitrate, but the treatment bath is not limited to nitrate, and sulfate, bisulfate, carbonate , Bicarbonate or halide may be used. When the treatment bath contains Na ions, the Na ions exchange ions with Li ions in the glass, and when the treatment bath contains K ions, the K ions exchange ions with Na ions in the glass. When the treatment bath further contains Na ions and K ions, these Na ions and K ions are ion-exchanged with Li ions and Na ions in the glass, respectively. By this ion exchange, alkali metal ions in the glass surface layer portion are replaced with alkali metal ions having a larger ionic radius, a compressive stress layer is formed in the glass surface layer portion, and the glass is chemically strengthened. As described above, the glass for chemical strengthening of the present invention has excellent ion exchange performance,
Since the compression stress layer formed by ion exchange is deep and has high bending strength, the chemically strengthened glass of the present invention has excellent fracture resistance.

The watch cover of the present invention uses the chemically strengthened glass obtained by processing the above-mentioned glass for chemical strengthening into the shape of the watch cover and then chemically strengthening it.

Further, the information recording substrate of the present invention uses the chemically strengthened glass obtained by processing the above-mentioned chemical strengthening glass into a shape of the information recording substrate such as a disk and then chemically strengthening it. Examples of the information recording substrate include a magnetic disk substrate, an optical disk substrate, and a magneto-optical disk substrate.

[0032]

【Example】

(Examples 1 to 6) These examples relate to the chemically strengthened glass and the chemically strengthened glass of the present invention. After using the oxides, carbonates, nitrates, hydroxides, etc. that are commonly used as raw materials, and weighing each raw material for each example so that the glass compositions shown in Tables 1 and 2 are obtained after melting and slow cooling. ,
Approximately 1.5 kg of the obtained raw material mixture was put into a 1 liter platinum crucible and heated at 1500 to 1600 ° C. for 5 to 8 hours to form a glass melt, which was stirred to perform defoaming and homogenization, and then the diameter. A glass for chemical strengthening was obtained by molding a rod having a length of 3 to 5 mm and a length of 60 mm by a pulling method. These rods were kept at 385-405 ° C. with KNO ₃ 60% and NaN.
By immersing in a treatment bath of a mixed salt of O ₃ 40% for 4 hours, Li ion and Na ion in the glass surface layer were ion-exchanged with Na ion and K ion in the treatment bath, respectively, to chemically strengthen them. In this way, 6 types of chemically strengthened glasses of Examples 1 to 6 were obtained.

Then, the Knoop hardness of the glass for chemical strengthening of each of the obtained examples, the depth of the compressive stress layer of the chemically strengthened glass, the bending strength, the liquidus temperature, the acid resistance and the water resistance were measured.

The Knoop hardness was measured according to the Japan Optical Glass Industry Association measurement standard JOGIS-09. In the glass after tempering, it is difficult to measure the Knoop hardness due to the presence of the compressive stress layer, and since the Knoop hardness has a proportional relationship before and after tempering, the Knoop hardness was measured with the glass before tempering. .
The depth and bending strength of the compressive stress layer were 0.
4 mm slices were cut out and measured using a polarization microscope. The liquidus temperature was measured using an inclined devitrification furnace. Acid resistance and water resistance are JOG measurement standard JOG
It measured based on IS-06.

The results are summarized in Tables 1 and 2. As a result, it was found that the glass for chemical strengthening of Examples 1 to 6 had a high Knoop hardness of 640 to 680, and the chemically strengthened glass obtained by subjecting the glass to ion exchange treatment had a higher Knoop hardness. . In addition, the present examples 1 to 6
The chemically strengthened glass has a high degree of ion exchange, the compressive stress layer is as deep as 200-260 μm, and the bending strength is 82-98 kg.
Since it is as high as f / mm ² , it has been found that it is sufficiently strong against deep cracks. From the results of Examples 1 to 6,
The smaller the weight ratio of Al ₂ O ₃ / ZrO ₂ is, the deeper the compressive stress layer is, and the ion exchange performance tends to increase.

In this embodiment, the liquidus temperature is 9
Since it was from 0 to 1150 ° C (devitrification was not observed in Examples 1 and 2), it was found that the devitrification resistance was sufficient for mass production.

The acid resistance and water resistance are respectively 0.
A preferable value was shown as 02 to 0.07% and 0.01 to 0.04%.

Comparative Examples 1 to 3 Comparative Example 1 shown in Table 2
Is the glass for chemical strengthening of Example 1 described in JP-A-62-187140, and Comparative Examples 2 and 3 are the commercially available glasses for chemical strengthening of the prior art. With respect to these glasses, production of chemically strengthened glass and measurement and evaluation of physical properties were performed in the same manner as in Examples 1 to 6 (however, Comparative Example 3
Is KNO ₃ 100% kept at 440 ℃ during chemical strengthening
Soak in the salt treatment bath for 16 hours to remove Na from the glass surface.
Ions were exchanged with K ions in the treatment solution). The results are shown in Table 2.

As a result, the glass of Comparative Examples 1 to 3 had a Knoop hardness of 57 compared with the glasses of Examples 1 to 6, respectively.
It was significantly inferior to 0,480,480 and the strength was small. Also, the compressive stress layer is 140 μm,
It was found to be as thin as 45 μm and 95 μm, inferior in ion exchange performance, and weak against deep cracks scratched on the glass surface.

[0040]

[Table 1]

[0041]

[Table 2]

(Embodiment 7) The glass for chemical strengthening obtained in the above-mentioned Embodiments 1 to 6 is cut and polished to have a desired shape as a watch cover, for example, opposing main surfaces are flat. It was molded into a disk shape, and then chemically strengthened by the method described in Examples 1 to 6 to obtain a watch cover using the chemically strengthened glass. The watch cover thus obtained also had the same physical properties and properties as the chemically strengthened glass of Examples 1 to 6.

(Embodiment 8) Regarding the glass for chemical strengthening obtained in the above-mentioned Embodiments 1 to 6, the shape of the magnetic disk substrate (outer diameter 130 mmφ, central hole diameter 40 mmφ, thickness 1.9).
mm disk shape) and then chemically strengthened by the method described in Examples 1 to 6 to obtain a magnetic disk substrate made of chemically strengthened glass. Even if these substrates were set on a disk rotating device and the substrates were rotated at 35,000 rpm, they were not destroyed. Even the disk with the film on this substrate did not break at the rotation of 35,000 rpm.

Example 9 A magnetic recording medium of the present invention was manufactured as follows. First, as shown in FIG. 1, the outer diameter is 1
On the surface of the magnetic disk substrate 1 obtained in Example 8 having a size of 30 mm, an inner diameter (hole diameter) of 40 mm and a thickness of 1.9 mm,
Underlayer 2 made of Cr (film thickness 2000 Å) and CoNiC by magnetron sputtering method
Ferromagnetic thin magnetic film 3 (thickness: 700 Å) made of r alloy and protective film 4 (thickness: made of carbon (C))
400 angstroms) were sequentially laminated to obtain a substrate 5 with a protective film.

Then, a lubricant (for example, AM2001 manufactured by Montedison Co., Ltd.) was dropped on the protective film 4 of the above-mentioned substrate 5 with a protective film, and a lubricating layer was applied by spin coating to obtain a magnetic recording medium. The obtained magnetic recording medium was excellent as a magnetic recording medium without breaking the substrate or peeling off the Cr underlayer.

[0046]

INDUSTRIAL APPLICABILITY As described above, the glass for chemical strengthening of the present invention has excellent ion exchange performance, and the chemically strengthened glass obtained by ion exchange has a deep compressive stress layer and a high resistance based on it. Folding strength and high Knoop hardness can be imparted. Therefore, from this glass for chemical strengthening, high-strength chemically strengthened glass, a timepiece cover, an information recording medium, and an information recording substrate can be obtained.

[Brief description of drawings]

FIG. 1 is a partially enlarged schematic view of a magnetic recording medium obtained in Example 9.

[Explanation of symbols]

1 ... Substrate for magnetic disk, 2 ... Underlayer, 3 ... Magnetic thin film,
4 ... Protective film, 5 ... Substrate with protective film

Claims (5)

[Claims] 1. 62 to 75% by weight of SiO ₂ , 5
15% of Al ₂ O _3, 4~10% of Li ₂ O, 4 to 1
It contains 2% Na ₂ O and 5.5 to 15% ZrO ₂ and has a Na ₂ O / ZrO ₂ weight ratio of 0.5 to 2.
Further, the weight ratio of Al ₂ O ₃ / ZrO ₂ is 0.
Glass for chemical strengthening, which is 4 to 2.5. 2. The glass for chemical strengthening according to claim 1,
A chemically strengthened glass that is chemically strengthened by ion exchange treatment in a treatment bath containing a ions and / or K ions. 3. A timepiece cover using the chemically strengthened glass according to claim 2. 4. An information recording substrate comprising the chemically strengthened glass according to claim 2. 5. An information recording medium comprising the information recording substrate according to claim 4.