JP2003146703A - Method for manufacturing glass substrate for information recording medium, and holder for holding chemical reinforcing treatment liquid used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a glass substrate for an information recording medium by which the occurrence of a defect after chemical strengthening is suppressed and improvement in the yield is achieved, and to provide a holder for holding chemical reinforcing treatment liquid used for the same. SOLUTION: The glass substrate for the information recording medium is immersed into a chemical reinforcing treatment liquid obtained by heating and melting salt, part of ions contained in the composition of the glass substrate is substituted by ions in the treatment liquid having a larger ionic radius than that of the former ion, and thereby the glass substrate is chemically reinforced. The chemically reinforced glass substrate is pulled up from the treatment liquid, and cooled at a temperature at which the molten salt solidifies, i.e., a temperature below the melting point of the molten salt, at a cooling rate of 10 to 200 degrees deg.C/min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass substrate for an information recording medium for use in an information recording medium such as a magnetic disc, a magneto-optical disc, an optical disc which is a magnetic recording medium of an information recording device such as a hard disk. The present invention relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, the above glass substrate for information recording medium (hereinafter, also simply referred to as a glass substrate) is formed into a disc shape by cutting a glass plate. Further, the surface of the glass substrate is polished, and then the glass substrate is subjected to a chemical strengthening treatment by being immersed in a chemical strengthening treatment liquid obtained by heating and melting a molten salt such as potassium nitrate. Normal,
This chemical strengthening treatment is performed by immersing the plurality of glass substrates together with the chemical strengthening holder in the chemical strengthening treatment liquid in a state where the plurality of glass substrates are accommodated in the chemical strengthening holder.

As shown in FIGS. 5 and 6, the chemical strengthening holder 80 is composed of a metal case 81 and four substantially rod-shaped support members 82 installed inside the case 81. ing. On the outer peripheral surface of the support member 82, a plurality of projections 83 in the shape of an abacus ball are projected. Support recesses 84 are formed between the protrusions 83, and the inner bottom surface of the support recess 84 is formed flat. Then, the peripheral edge portion of the glass substrate 90 is engaged with the supporting concave portion 84 of each supporting member 82, whereby the chemical strengthening holder 80 has a plurality of glass substrates 90 inside.
Is configured so that it can be accommodated and held vertically.

FIG. 7 is a schematic view of a chemical strengthening furnace for performing the chemical strengthening process. The chemical strengthening furnace 70 has a vertically long rectangular box shape, and a lower half portion thereof is a chemical strengthening portion 71 and an upper half portion thereof is a preheating / cooling portion 72. The top plate of the chemical strengthening furnace 70 is a lid that can be opened and closed. The chemical strengthening section 71
A chemical strengthening treatment liquid is stored inside. The chemical strengthening treatment liquid is heated by a heater (not shown) arranged around the chemical strengthening section 71. And preheating
The temperature inside the cooling unit 72 is higher than room temperature due to the heat from the chemical strengthening unit 71.

When performing the chemical strengthening process in the above chemical strengthening furnace 70, the chemical strengthening holder 80 is housed in a cage 80a having a plurality of glass substrates 90 in a cage shape. When performing the chemical strengthening treatment, the glass substrate 90 is put into the chemical strengthening furnace 70 from the lid together with the chemical strengthening holder 80 and the cage 80a, and is preheated by being retained in the preheating / cooling unit 72 for a certain period of time. After that, the chemical strengthening holder 80 and the cage 80a
At the same time, it is lowered to the chemical strengthening section 71 and immersed in the chemical strengthening treatment liquid for a predetermined time to be chemically strengthened.

As shown by the chain double-dashed line in FIG. 7, the glass substrate 90 after being chemically strengthened is pulled up from the chemical strengthening treatment liquid to the preheating / cooling section 72 together with the chemical strengthening holder 80 and the cage 80a. Is temporarily stopped, and then gradually cooled for a predetermined time. Then, the glass substrate 90 is transported to the next cleaning step for the purpose of removing the molten salt, which solidifies and adheres to the surface of the glass substrate 90 during slow cooling.

[0007]

However, in the above-mentioned chemical strengthening treatment, as shown in FIGS. 5 and 6, the chemical strengthening portion 71 to the chemical strengthening holder 80 and the cage 80 are removed.
When a is pulled up, the inner surface of the supporting recess 84 and the glass substrate 9
The chemical strengthening treatment liquid remains in the gap 85 with the surface of 0. The remaining molten salt in the chemical strengthening treatment liquid slowly solidifies according to the slow cooling time when slowly cooling the glass substrate 90, and at this time, the inner surface of the supporting recess 84 and the glass substrate 90.
A tensile stress is exerted between them by contracting their volume while in contact with the surface of the. When the tensile stress acts in this way, distortion, undulation, unevenness, etc. occur on the surface of the glass substrate 90 that is heated and softened during the chemical strengthening treatment, and these become defects. In the above conventional chemical strengthening treatment, such defects occur at a high rate, so that there is a problem that the yield cannot be improved.

The present invention has been made by paying attention to the problems existing in such a conventional technique. An object of the invention is to provide a method for manufacturing a glass substrate for an information recording medium, which can suppress the occurrence of defects after the chemical strengthening treatment and can improve the yield, and a chemical strengthening holder used for the method. Especially.

[0009]

In order to achieve the above object, the invention of a method for producing a glass substrate for an information recording medium according to claim 1 is a chemical strengthening treatment liquid obtained by heating and melting a molten salt. After dipping a disk-shaped glass substrate into the glass substrate, and then chemically strengthening the glass substrate by replacing some of the ions contained in the composition of the glass substrate with ions in a chemical strengthening treatment liquid having an ion radius larger than the ion The glass substrate is pulled up from the chemical strengthening treatment liquid, and the temperature at which the molten salt solidifies the glass substrate and the cooling rate is 10 to 200 ° C.
It is characterized in that it is cooled so that it becomes / min.

According to the invention of a method for manufacturing a glass substrate for an information recording medium described in claim 2, in the invention described in claim 1, in the chemical strengthening treatment, a frame-shaped or box-shaped metal case, A holder for chemical strengthening provided with a plurality of plate-shaped metal supporting members provided inside the case and a plurality of supporting recesses provided on the surface of each supporting member is used, and each supporting recess is made of glass. The glass substrates are accommodated in the case by engaging the peripheral portions of the substrates with each other and supporting the glass substrates with the plurality of supporting members, and in this state, the glass substrates are chemically strengthened together with the chemical strengthening holder. It is characterized in that it is immersed in a treatment liquid to chemically strengthen it.

The invention for a holder for chemically strengthening a glass substrate for an information recording medium described in claim 3 is used in the method for manufacturing a glass substrate for an information recording medium according to claim 2, and accommodates a plurality of glass substrates. A holder for chemical strengthening that is used by immersing it in a chemical strengthening treatment liquid together with the glass substrate in a held state, the chemical strengthening treatment liquid remaining on the surface of the glass substrate when the glass substrate is pulled out from the chemical strengthening treatment liquid. Of the molten salt therein, the weight of the molten salt present in the gap between the inner surface of the supporting recess and the surface of the glass substrate is V (mg),
The heat capacity of the support member around the support recess is A (JK
^-1 ), V × A is 0.005 to 20 (mg · J
・ K ⁻¹ ) is set.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. As shown in FIGS. 1 and 3, a metal case 11 that constitutes the chemical strengthening holder 10 is formed in a rectangular frame shape with both upper and lower surfaces opened, and three support members 12 are provided inside the case 11. Is installed so as to extend in the longitudinal direction. Each of the supporting members 12 is formed of a rectangular thin metal plate, and a plurality of supporting recesses 13 are cut out so as to form a sawtooth shape at one long side edge thereof. The three support members 12 each have a plurality of support recesses 13 directed inwardly of the case 11, and when viewed from the longitudinal direction, two of the three support members 12 are located substantially in the center of both sides of the case 11. One of them is arranged substantially at the center of the lower end of the case 11.

The metal forming the case 11 and the supporting member 12 is preferably one having heat resistance and corrosion resistance. Examples of such a metal include SUS3
00 series stainless steel, nickel alloys such as Inconel,
Examples thereof include titanium. Among them, nickel alloys such as stainless steel and Inconel are easily available, and are easier to process than welding, such as welding, pressing, and cutting, as compared with titanium, and thus are preferable as materials for the case 11 and the supporting member 12.

The information recording medium glass substrate 21 is formed into a disk shape having a circular hole at the center by cutting a sheet-shaped glass plate, and its surface is smoothed by polishing. It is supposed to be. As the material of the glass substrate 21, a float method, a down draw method,
Examples thereof include soda lime glass, aluminosilicate glass, borosilicate glass, and crystallized glass produced by the redraw method or the pressing method. In addition, the glass substrate 21 formed into a disk shape has its end faces ground so that the outer dimensions and the inner diameter have a predetermined length, and after grinding, the outer and inner edge corners are ground to chamfer. Has been done.

As shown in FIGS. 1 and 2, the glass substrate 2
1 is placed vertically and is housed in a case 11 with its lower end and both ends supported by a support member 12. Case 1
The glass substrate 21 in the state of being accommodated in 1 is restricted from moving in the extending direction of the support member 12 by engaging the peripheral edge portions thereof with the support recesses 13 of the support members 12.

The glass substrate 21 is subjected to a chemical strengthening treatment in order to improve impact resistance, vibration resistance, heat resistance and the like required as an information recording medium. This chemical strengthening treatment means, for example, monovalent metal ions such as lithium and sodium contained in the composition of the glass substrate 21 and having a larger ionic radius than that of monovalent metal ions such as potassium. Replaced with glass substrate 2
In this method, a compressive stress is applied to the surface of No. 1 to strengthen it.

FIG. 4 is a schematic view of a chemical strengthening furnace for subjecting the glass substrate 21 to the above chemical strengthening treatment. The chemical strengthening furnace 30 is formed in the shape of a vertically long rectangular box, and the top plate of the chemical strengthening furnace 30 serves as a lid that can be opened and closed.
1. The upper half part is a preheating part 32 so as to be arranged above the chemical strengthening part 31. Further, the chemical strengthening section 31 and the preheating section 32 communicate with each other.

Inside the chemical strengthening section 31, a chemical strengthening treatment liquid obtained by heating and melting a molten salt is stored. Examples of the molten salt include potassium nitrate, sodium nitrate, silver nitrate, etc., or a mixture of at least two of them. The chemical strengthening treatment liquid is heated by a heater (not shown) arranged around the chemical strengthening section 31. The temperature of the chemical strengthening treatment liquid at this time is preferably about 50 to 150 ° C. lower than the strain point of the glass forming the glass substrate 21.
More preferably, the temperature of the chemical strengthening treatment liquid is about 350 to 400 ° C. Then, the internal temperature of the preheating section 32 is higher than room temperature due to the heat from the chemical strengthening section 31.

When the chemical strengthening process is performed, a plurality of glass substrates 21 are accommodated and held in the holder 10, and a plurality of the holders 10 are accommodated in a cage 33 made of a metal. Has been done. The cage 33 is made of a metal having heat resistance and acid resistance, such as SU.
Examples include S300 series stainless steel, nickel alloys such as Inconel, and titanium. Then, the glass substrate 21
Moves the cage 33 from the lid of the preheating unit 32 to the chemical strengthening unit 31.
By placing the holder 10 and the cage 33 in the inside
It is also immersed in the chemical strengthening treatment liquid.

The glass substrate 21 is placed in the chemical strengthening furnace 30 described above.
When the chemical strengthening process is performed on the glass substrate 21, the plurality of glass substrates 21 housed in the cage 33 together with the holder 10 in the state of being housed in the holder 10 are first temporarily stopped by the preheating unit 32 and then preheated for a predetermined time. To be done. After that, the glass substrate 21 is transferred into the chemical strengthening section 31 together with the holder 10 and the cage 33 and immersed in the chemical strengthening treatment liquid heated to about 350 to 400 ° C. for a predetermined time, so that a plurality of sheets are chemically strengthened at the same time. . Then, after the glass substrate 21 is chemically strengthened, the glass substrate 21 is pulled out from the chemical strengthening treatment liquid together with the holder 10 and the cage 33, and cooled to almost room temperature.

As shown in FIGS. 1 and 2, when the glass substrate 21 is pulled out from the chemical strengthening treatment liquid, the glass substrate 2
The chemical strengthening treatment liquid remains in the gap 14 between the surface of the peripheral edge portion of No. 1 and the inner surface of the support recess 13 of the holder 10 due to its surface tension. The remaining molten salt in the chemical strengthening treatment liquid gradually solidifies when the glass substrate 21 is cooled. At this time, the molten salt is absorbed on the surface of the glass substrate 21 and the supporting recesses 13.
By contracting the volume while applying a tensile stress to the inner surface of the glass substrate 21, an attempt is made to generate defects such as distortion, waviness, and unevenness on the surface of the glass substrate 21 in a heated and softened state.

In order to suppress the defects of the glass substrate 21 generated when the molten salt is solidified, the glass substrate 21 pulled up from the chemical strengthening treatment liquid is a chemical strengthening furnace as shown by a chain double-dashed line in FIG. Without being stopped inside 30, it is quickly taken out from the lid part of the preheating part 32. And
The glass substrate 21 after the chemical strengthening has a temperature at which the molten salt solidifies outside the chemical strengthening furnace 30, that is, a melting point (28
It is rapidly cooled to a temperature of about 0 to 350 ° C.) or lower to almost room temperature. That is, by rapidly cooling the glass substrate 21, the time during which the tensile stress of the molten salt acts on the surface of the glass substrate 21 is shortened.
The generation of the distortion of 1 is suppressed.

When the glass substrate 21 is rapidly cooled as described above, the cooling rate is 10 to 200 ° C./min. When the cooling rate is less than 10 ° C./min, the time for the tensile stress of the molten salt to act on the surface of the glass substrate 21 becomes long, and defects such as distortion, waviness, and unevenness occur in the glass substrate 21. If the cooling rate is higher than 200 ° C./min, the glass substrate 21 will be cracked, chipped, or cracked by the rapid cooling.

When the glass substrate 21 is left in an atmosphere at room temperature for rapid cooling, if the room temperature is 5 to 30 ° C.,
The cooling time is preferably 5 to 20 minutes. 5-30
If the cooling time is set to less than 5 minutes in an atmosphere of ° C, the glass substrate 21 may suffer from defects such as cracks, chips, and cracks due to rapid cooling. When the cooling time is longer than 20 minutes, the tensile stress of the molten salt acts on the surface of the glass substrate 21 for a long time, which may cause defects in the glass substrate 21.

In addition, in the holder 10, the action of the tensile stress of the molten salt on the surface of the glass substrate 21 is caused by adjusting the size of the supporting recess 13 or changing the material of the supporting member 12. It is being reduced.

First, by adjusting the size of the supporting recess 13, the residual amount of the molten salt in the supporting recess 13 is reduced. When the weight of the molten salt remaining in the support recess 13 is V, the weight V is preferably adjusted to 0.5 to 14 mg. If the weight V is less than 0.5 mg, the gap between the glass substrate 21 and the supporting recess 13 becomes narrower, and the glass substrate 21 and the supporting member 12 during the chemical strengthening treatment.
It is not possible to secure sufficient escape for the amount of thermal expansion, and the glass substrate 21 may be damaged. If the weight V is more than 14 mg, it becomes difficult to reduce the action of the tensile stress of the molten salt on the surface of the glass substrate 21, and the glass substrate 21 may be distorted.

It is also effective to solidify the molten salt in the shortest possible time. The time until the molten salt solidifies is the glass substrate 21 and the supporting member 12 around the molten salt.
It is thought to be affected by the heat capacity of. Generally, the smaller the heat capacity of the glass substrate 21 and the supporting member 12, the easier it is to heat and the easier they are to cool. Then, by reducing the heat capacities of the glass substrate 21 and the supporting member 12, heat is rapidly transferred from the molten salt to the glass substrate 21 or the supporting member 12, and the heat of the molten salt is transferred from the glass substrate 21 or the supporting member 12. It becomes easy to radiate heat, and it is possible to shorten the time until the molten salt solidifies.

Here, it should be emphasized that the glass substrate 21 satisfies various conditions required as an information recording medium rather than the influence of the heat capacity on the molten salt. Therefore,
In this embodiment, it is assumed that the heat capacity of the support member 12 is reduced to shorten the time until the molten salt is solidified.

When the range in which the supporting member 12 affects the molten salt around the supporting recess 13 is H,
The weight of the range H of the supporting member 12 is W, and the supporting member 12 is
When the specific heat of the material used for is Q, the heat capacity A in the range H can be calculated by the product of the weight W and the specific heat Q. Although this heat capacity A is affected by the values of the weight W and the specific heat Q, it is preferably greater than 0 (J · K ⁻¹ ) and less than 2 (J · K ⁻¹ ) and more preferably 0.1 to It is 1.5 (J · K ⁻¹ ). It is almost impossible to set the heat capacity A to 0 (J · K ⁻¹ ) or less, and when it is 2 (J · K ⁻¹ ) or more, the solidification time of the molten salt cannot be made sufficiently short. . The range H in this embodiment is, as shown in FIG.
Of the pair of protrusions 13a that are adjacent to each other with 3 in between, it is considered that the distance is from the center of one protrusion 13a to the center of the other protrusion 13a.

From the above, in order to efficiently reduce the effect of the tensile stress of the molten salt on the surface of the glass substrate 21,
A method of reducing the weight V of the remaining molten salt and reducing the heat capacity A around the supporting recess 13 is effective. Therefore, it is necessary to set the support member 12 so that the product of the weight V and the heat capacity A is as small as possible when the support member 12 is formed. And V × A is 0.001 to 20 (mg
・ J ・ K ^-1 ). Preferably, V × A is 0.001 to 1 (mg · J · K ⁻¹ ). If V × A is less than 0.001 (mg · J · K ⁻¹ ), the holder 10 cannot support the glass substrate 21 sufficiently, or the glass substrate 21 is damaged. Further, when it is larger than 20 (mg · J · K ⁻¹ ), it is not possible to sufficiently reduce the action of the tensile stress of the molten salt on the surface of the glass substrate 21.

The acceleration of the glass substrate 21 which is obtained by quenching after the chemical strengthening using the holder 10 as described above is preferably 0.5 to 5 m / sec ² . Here, the acceleration will be described. Acceleration is an index value indicating defects such as strain, large irregularities, and rapid undulations existing on the surface of a glass substrate. This acceleration is the second derivative of the distance that the contact terminal moves in the direction intersecting the moving direction up to that point when the contact terminal is moved at a constant speed while being in contact with the surface of the glass substrate. It is calculated from the absolute value of the calculated value.
That is, as the glass substrate 21 has a lower acceleration value, the glass substrate 21 has fewer defects and has higher quality. It is difficult to make this acceleration less than 0.5 m / sec ^2, and it is difficult to improve the yield, and it becomes 5 m / s.
If it is higher than ec ² , the rotation of the information recording medium becomes unstable, and the head for reading information from the information recording medium collides with such defects.

The effects exerted by the above embodiment will be described below. According to the method for manufacturing a glass substrate for an information recording medium of the embodiment, the glass substrate 21 is pulled out from the heated chemical strengthening treatment liquid and then rapidly cooled at a cooling rate of 10 to 200 ° C./min. Therefore, when the molten salt in the chemical treatment liquid is solidified, the time during which the tensile stress of the molten salt acts on the glass substrate 21 can be shortened. Therefore, the surface of the glass substrate 21 after the chemical strengthening treatment is distorted, undulated,
Occurrence of defects such as unevenness can be suppressed, and the yield can be improved.

Further, by using the holder 10, it is possible to perform a chemical strengthening treatment on a plurality of glass substrates 21. Therefore, the yield can be favorably improved while suppressing the occurrence of defects in the glass substrate 21 after the chemical strengthening treatment.

In addition, the support member 12 of the holder 10
Is the weight V of the molten salt remaining in the supporting recess 13 and the supporting recess 1.
The product of the heat capacity A around 3 is 0.001 to 20 (mg.
J · K ⁻¹ ). This allows
The molten salt remaining in the supporting recess 13 can be solidified in a short time, and the time during which the tensile stress of the molten salt acts on the glass substrate 21 can be shortened. Therefore, it is possible to suppress the occurrence of defects in the glass substrate 21 after the chemical strengthening treatment, and it is possible to improve the yield.

[0035]

EXAMPLES Next, the above-mentioned embodiment will be described more concretely with reference to Examples and Comparative Examples. (Evaluation of cooling rate) Diameter 65 mm and thickness 0.635 mm
The glass substrate formed in the disk shape was subjected to a chemical strengthening treatment using a holder. After that, in Examples 1 and 2, the holder 10 having the saw-toothed support member 12 shown in FIG. 2 was used, and the cooling rate was 25 ° C./min and 200, respectively.
The glass substrate was cooled at a rate of ° C / min. Further, in Example 3, the supporting member 82 shown in FIG. 6 uses the abacus ball-shaped holder 80, and the glass substrate is cooled at the cooling rate of 25 ° C./min. Further, in Comparative Example 1, the abacus ball-shaped holder 80 was used, and the glass substrate was cooled at a cooling rate of 4 ° C./min.
Then, the acceleration of the glass substrates produced in Examples 1 to 3 and Comparative Example 1 was measured. The results are shown in Table 1.

[0036]

[Table 1] From the results of Table 1, the glass substrates of Examples 1 to 3 had an acceleration of 0.5 to 6 m / sec ² . On the other hand, the glass substrate of Comparative Example 1 has an acceleration of 7
˜15 m / sec ^2, which is higher than those of Examples 1 to 3. Further, when comparing Example 3 and Comparative Example 1 in which the supporting recesses 13 of the supporting member 12 have the same shape, Example 3 having a high cooling rate was lower in acceleration than Comparative Example 1. Furthermore, when Example 1 and Example 2 were compared, the acceleration of Example 2 having a higher cooling rate was low. As a result, the cooling rate was 10 than that of Comparative Example 1 in which the cooling rate was less than 10 ° C./min.
It was shown that high-quality glass substrates can be obtained in Examples 1 to 3 at a temperature of ℃ / min or more. Furthermore, it has been shown that higher quality glass substrates can be obtained by increasing the cooling rate. (Evaluation of Support Member) Next, using a glass substrate having the same size as the evaluation of the cooling rate, Examples 4 to 6 and Comparative Example 2 were used.
In 3 and 3, the holder supporting member was changed, the weight V of the remaining molten salt and the heat capacity A were changed, and the acceleration of the obtained glass substrate was measured. In addition, in Examples 4 to 6 and Comparative Examples 2 and 3, the cooling rate of the glass substrate was 10 ° C. /
It was set to min. The results are shown in Table 2.

[0037]

[Table 2] From the results of Table 2, in Examples 4 to 6, V × A was 0.2 (mg
・ J.K ^-1 ) or less, which is generally low, and the obtained glass substrate has an acceleration of 8 or less, and a high-quality glass substrate was obtained. On the other hand, Comparative Examples 2 and 3 have V × A higher than 20 (mg · J · K ⁻¹ ) and an acceleration of 6 or more, which are obviously inferior in quality as compared with Examples 4 to 6. Became. As a result, it was shown that a high quality glass substrate can be obtained by setting the value of V × A of the supporting member of the holder used to be 20 (mg · J · K ⁻¹ ) or less.

The embodiment can be modified and embodied as follows. The quenching of the glass substrate 21 is performed by using an inert gas such as nitrogen gas or helium gas as a coolant and leaving the glass substrate 21 in the atmosphere of this coolant or by spraying the coolant on the glass substrate 21. Good. With this configuration, the rapid cooling can be efficiently performed without affecting the glass substrate 21.

In the embodiment, the support recess 13 of the support member 12 has a sawtooth shape, but the support member may be configured as follows. That is, the support member is formed by bending a rectangular thin plate so that the cross-sectional shape when viewed in the longitudinal direction is an arc shape. A plurality of protrusions are formed in a wavy shape in the longitudinal direction on the bulging side surface of the support member, and support recesses are provided between the protrusions.
The support member is attached to the case 11 such that the bulging surface of the support member faces the inside of the case 11. Since this support member has an arc-shaped cross section as viewed in the longitudinal direction, the contact area with the peripheral edge of the glass substrate 21 is small. Furthermore, since the molten salt that is about to remain in the supporting recess can be poured out along the arc of the supporting recess, the amount of residual molten salt can be reduced. Therefore, it is possible to suppress the occurrence of defects in the glass substrate 21 after the chemical strengthening treatment, and it is possible to improve the yield.

The supporting recess 13 may be chamfered by polishing the corners of its peripheral edge so that the peripheral edge has a blade shape. With this structure, the area of the inner surface of the support recess 13 can be reduced, and the amount of residual molten salt can be reduced.

Further, the technical idea which can be understood from the above embodiment will be described below. The manufacturing of the glass substrate for an information recording medium according to claim 1 or 2, wherein the cooling of the glass substrate is performed by holding the glass substrate in air under an atmosphere of 5 to 30 ° C for 5 to 20 minutes. Method. With this structure, it is possible to effectively suppress the occurrence of defects in the glass substrate after the chemical strengthening treatment.

The weight V of the molten salt existing between the inner surface of the supporting recess and the surface of the glass substrate is 0.5 to 14 mg.
The chemical strengthening holder for a glass substrate for an information recording medium according to claim 3, wherein With this configuration, it is possible to reduce the residual amount of the molten salt in the supporting recess.

The support member is formed of a thin rectangular plate, and a plurality of sawtooth-shaped support recesses are cut out at the long side edges thereof, and chamfering is performed by polishing the corners of the periphery of the support recesses. The chemical strengthening holder for a glass substrate for an information recording medium according to claim 3, wherein the peripheral portion is formed to have a blade shape. With this configuration, it is possible to reduce the residual amount of the molten salt in the supporting recess.

The support member is formed by bending a rectangular thin plate so that the cross-sectional shape when viewed in the longitudinal direction becomes an arc shape, and a plurality of protrusions are wavy in the longitudinal direction on the surface of the bulging side. By forming so that
The holder for chemical strengthening of a glass substrate for an information recording medium according to claim 3, characterized in that a supporting recess is provided between each protrusion. With this configuration, it is possible to reduce the residual amount of the molten salt in the supporting recess.

A glass substrate for an information recording medium manufactured by using the chemical strengthening holder according to claim 3, wherein the acceleration is 0.5 to 5 m / sec ^2. Glass substrate for recording media. With this structure, it is possible to obtain a high-quality glass substrate with few surface defects.

A glass substrate for an information recording medium manufactured by the method for manufacturing a glass substrate for an information recording medium according to claim 1 or 2, wherein the acceleration is 0.5.
A glass substrate for an information recording medium, characterized in that the glass substrate is about 5 m / sec ² . With this structure, it is possible to obtain a high-quality glass substrate with few surface defects.

A chemical strengthening holder which is used in a chemical strengthening process in manufacturing a glass substrate for an information recording medium and is used by being immersed and held in a chemical strengthening treatment liquid together with a plurality of glass substrates in a state of being held. It has a frame-like or box-like shape, and a case for accommodating a glass substrate inside thereof, and a plate-like or rod-like shape that is installed inside the case and supports the glass substrate accommodated in the case. A plurality of metal supporting members for holding the glass substrate between the supporting members by providing a supporting recess on the surface of the supporting member and engaging the peripheral edge of the glass substrate with the supporting recess. Of the molten salt of the chemical strengthening treatment liquid that precipitates on the surface of the glass substrate when the glass substrate is pulled out from the chemical strengthening treatment liquid, the inner surface of the supporting recess and the glass substrate When the weight of the molten salt existing in the gap with the surface is V (mg) and the heat capacity of the supporting member around the supporting recess is A (J · K ⁻¹ ), V × A is 0.0.
A holder for chemical strengthening of a glass substrate for an information recording medium, which is set to be 05 to 20 (mg · J · K ⁻¹ ). When configured in this manner, it is possible to suppress the occurrence of defects in the glass substrate after the chemical strengthening treatment, increase the processing amount of the glass substrate per unit time,
The yield can be improved.

[0048]

As described in detail above, the present invention has the following effects. According to the invention of the method for manufacturing a glass substrate for an information recording medium described in claim 1, it is possible to suppress the occurrence of defects in the glass substrate after the chemical strengthening treatment and to improve the yield.

According to the invention of the method for manufacturing a glass substrate for an information recording medium described in claim 2, in addition to the effect of the invention described in claim 1, generation of defects in the glass substrate after the chemical strengthening treatment is suppressed. In addition, the yield can be improved satisfactorily.

According to the invention of the holder for chemical strengthening of the glass substrate for information recording medium described in claim 3, it is possible to suppress the occurrence of defects in the glass substrate after the chemical strengthening treatment and to improve the yield. You can

[Brief description of drawings]

FIG. 1 is a front view showing a state in which a glass substrate is housed in a holder according to an embodiment.

FIG. 2 is a side view showing the support member of the embodiment.

FIG. 3 is a perspective view showing a chemical strengthening holder.

FIG. 4 is a conceptual diagram showing a chemical strengthening furnace according to an embodiment.

FIG. 5 is a front view showing a state in which a glass substrate is housed in a holder of a conventional example.

FIG. 6 is a partially cutaway side view showing a conventional supporting member.

FIG. 7 is a conceptual diagram showing a conventional chemical strengthening furnace.

[Explanation of symbols]

10 ... Holder for chemical strengthening, 11 ... Case, 12 ... Support member, 13 ... Support recess, 14 ... Gap, 21 ... Glass substrate.

Claims (3)

[Claims] 1. A disk-shaped glass substrate is immersed in a chemical strengthening treatment liquid obtained by heating and melting a molten salt, and a part of ions contained in the composition of the glass substrate has a larger ionic radius than the ion. After chemically strengthening the glass substrate by substituting ions in the chemical strengthening treatment liquid, the glass substrate is pulled out of the chemical strengthening treatment liquid, and the temperature at which the molten salt solidifies the glass substrate and the cooling rate is 10 to 10. 200 ° C /
A method of manufacturing a glass substrate for an information recording medium, which comprises cooling the glass substrate to a minimum temperature. 2. In the chemical strengthening treatment, a frame-shaped or box-shaped metal case, a plurality of plate-shaped metal support members installed inside the case, and a surface of each support member. Using a holder for chemical strengthening provided with a plurality of supporting recesses respectively provided in, by supporting the glass substrate with a plurality of supporting members by engaging the peripheral portion of the glass substrate to each supporting recess The glass substrate for an information recording medium according to claim 1, wherein the substrates are housed in a case, and in this state, the plurality of glass substrates are chemically strengthened by being immersed in a chemical strengthening treatment liquid together with a chemical strengthening holder. Manufacturing method. 3. The chemical strengthening used in the method for manufacturing a glass substrate for an information recording medium according to claim 2, wherein a plurality of glass substrates are accommodated and held, and the glass substrate is immersed in a chemical strengthening treatment liquid together with the glass substrate. A holder for use in a molten salt in the chemical strengthening treatment liquid remaining on the surface of the glass substrate when the glass substrate is pulled out from the chemical strengthening treatment liquid, and a gap between the inner surface of the supporting recess and the surface of the glass substrate. When the weight of the molten salt existing in the support is V (mg) and the heat capacity of the support member around the support recess is A (J · K ⁻¹ ), V × A is 0.005 to 20 (mg · J ·). A holder for chemical strengthening of a glass substrate for an information recording medium, characterized in that it is set to be K ⁻¹ ).