JP2002352422A - Glass substrate for information recording medium and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass substrate and a method for manufacturing the same, for an information recording medium in which the optimization of the unevenness of the surface of the glass substrate contributes to narrowing the flying height, and, at the same time, does not give rise to a head crash and a thermal asperity. SOLUTION: In the glass substrate for the information recording medium for use in an information recording apparatus such as a hard disk, a texture treatment by etching is performed for the surface layer of the glass substrate, and then, an abnormal projection which is inevitably formed by the etching treatment is removed by a scrubbing surface treatment. The scrubbing surface treatment is performed by sandwiching the doughnut-like glass substrate 1 between rolls of sponge 2, and by performing the scrubbing along the circumferential direction of the glass substrate 1 while rotating the glass substrate 1 and the rolls of sponge 2, respectively. The roll of sponge 2 consist of a surface layer 4 and an under layer 3, in which the hardness of the surface layer 4 is of Asker C hardness of 40-100 of the Standard SRISO101 of the Society of Rubber Industry, Japan.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a glass substrate for an information recording medium and a method for manufacturing the same, and more particularly, to a glass substrate for an information recording medium used for an information recording device such as a hard disk and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, digitization of information has been remarkable, and various information recording apparatuses for recording the information have been developed and manufactured. Improvements in these devices have been steadily progressing, and the information recording capacity and the recording / reproducing speed are improving at a rate of about 10% per year. In such a situation, a hard disk is the most widely used information recording device at present, and its improvement speed is higher than other devices.

[0003] In a hard disk, information is recorded and reproduced by a magnetic head on an information recording layer formed on a substrate for an information recording medium (hereinafter simply referred to as a "substrate").
At present, hard disks of a system called CSS or ramp load are generally used. The CSS method is a method called a contact start / stop method in which a magnetic head glides over a data zone of a disk while the substrate is rotating, and glides over the CSS zone of the substrate when the substrate starts or stops moving. It is. here,
The CSS zone of the substrate refers to a portion of the substrate (mainly provided along the inner or outer periphery) where uniform irregularities of several tens nm order are intentionally provided. The ramp load method is a method in which the magnetic head glides over the substrate while the substrate is rotating, and the magnetic head is stored in the storage position when the substrate stops. In the ramp load method, a CSS zone is unnecessary due to its mechanism. In recent years, what is called a contact method in which a magnetic head and a substrate are always in contact has been studied.

In the CSS method and the ramp load method, the magnetic head glides on the surface (information recording area) at intervals of several tens of nm (hereinafter referred to as "flying height") while the substrate is rotating. Therefore, it is necessary to reduce the flying height in order to embody high density information recording. However, if the surface unevenness of the substrate is large, the magnetic head and the projection on the substrate surface collide during rotation, and the possibility of head crash increases. Further, even if a head crash does not occur, a so-called thermal asperity may occur, in which the magnetic head detects an abnormal signal due to the heat due to the collision and malfunctions. Particularly recently, high sensitivity MR heads or GMR heads have become mainstream, and the problem of thermal asperity has become more serious.

Conventionally, it has been thought that head crush and thermal asperity caused by collision with a convex portion can be avoided by reducing the unevenness of the information recording area. Therefore, the higher the surface smoothness, the higher the performance of the substrate. Was considered to be. As a typical technique for shaving a surface unevenness to form a smooth surface, a method of finishing polishing using a suede (artificial leather), that is, a method of forming a smooth substrate by shaving off a surface layer (Japanese Patent Application Laid-Open No. 2000-2000) No. 53450), and a method of removing impurities and irregularities on the substrate surface by scrub cleaning using a sponge such as PVA to smooth the substrate (Japanese Patent Application Laid-Open No. 2000-149249). . As a scrubbing apparatus, a method has been proposed in which a substrate is sandwiched between sponges in the form of a roller in a substrate for use in cleaning both sides of a wafer (Japanese Patent Application Laid-Open No. H11-288911).

[0006]

However, the prior art has the following problems. That is, recently, the flying height is set extremely low in order to increase the recording density, and the substrate surface is moderately roughened so as not to apply excessive resistance to the magnetic head when the glide head contacts the substrate. Processing (hereinafter referred to as “texture processing”) has been performed, and it has been difficult to selectively remove abnormal projections and foreign substances adhering to the substrate surface on the substrate subjected to the texture processing. .

For example, when scrubbing is performed with a soft sponge such as a polyvinyl formal sponge or a polyurethane sponge, it is difficult to remove abnormal projections and strongly adhered foreign substances generated during texturing. Alternatively, if an attempt is made to remove abnormal projections that protrude under severe conditions such as a high pressure and a high rotational speed for a long time, there is a problem that the texture is excessively scraped off.

[0008] In addition, in the case of polishing or finish polishing using a polishing machine, there is a problem that the texture is excessively removed because the substrate surface layer is removed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to contribute to a reduction in flying height by optimizing irregularities on the surface of a glass substrate, and at the same time, to reduce a pad crash. Another object of the present invention is to provide a glass substrate for an information recording medium that does not cause thermal asperity and a method for manufacturing the same.

[0010]

According to a first aspect of the present invention, there is provided a method of manufacturing a sponge having a surface of a glass substrate having a hardness of 40 to 100 as Asker C of Japan Rubber Association Standard SRISO101. The surface of the glass substrate is scrubbed in the circumferential direction.

According to the manufacturing method of the first aspect, the surface of the glass substrate has a surface layer having a hardness of the Japan Rubber Association Standard SR.
Since the scrub surface treatment is performed in the circumferential direction of the glass substrate using a sponge of ISO 101 ASKER C of 40 to 100, the outermost surface portion (the portion in contact with the glass substrate) of the sponge is hardened microscopically and macroscopically. Supplied, while contacting the sponge so that the contact portion shape is linear or strip-shaped in the radial direction of the glass substrate, forcibly rotating the glass substrate fixed at the inner peripheral edge, and scrubbing in the circumferential direction, Abnormal protrusions and strongly adhered foreign substances caused by uneven etching of the glass substrate can be removed, and as a result,
A glass substrate for an information recording medium and an information recording medium having excellent surface cleanliness and in-plane uniformity can be manufactured.

A manufacturing method according to a second aspect is characterized in that, in the manufacturing method according to the first aspect, the glass substrate is chemically strengthened before the scrub surface treatment.

According to the manufacturing method of the second aspect, since the scrub surface treatment is performed after the glass substrate is chemically strengthened, the operation and effect of the manufacturing method of the first aspect can be reliably achieved.

According to a third aspect of the present invention, in the manufacturing method of the first or second aspect, after the scrub surface treatment, the glass substrate is washed with an alkaline aqueous solution having a pH of 8 or more.

According to the third aspect of the present invention, after the scrub surface treatment, the glass substrate is washed with an alkaline aqueous solution having a pH of 8 or more, so that abnormal projections due to uneven etching are removed. Redeposition can be prevented.

According to a fourth aspect of the present invention, in the manufacturing method according to the first or second aspect, after the scrub surface treatment, the glass substrate is washed with an acidic aqueous solution having a pH of 4 or less, and then the alkaline aqueous solution having a pH of 8 or more. It is characterized by being washed by using.

According to the fourth aspect of the present invention, after the scrub surface treatment, the glass substrate is washed with an acidic aqueous solution having a pH of 4 or less, and then washed with an alkaline aqueous solution having a pH of 8 or more. While forming the texture while suppressing the occurrence of abnormal protrusions,
The abnormal projection can be removed to prevent re-adhesion.

According to a fifth aspect of the present invention, in the manufacturing method according to any one of the first to fourth aspects, the glass substrate is fixed at an inner peripheral portion and forcibly rotated during the scrub surface treatment. It is characterized by the following.

According to the manufacturing method of the fifth aspect, at the time of the scrub surface treatment, the glass substrate is fixed at the inner peripheral portion and is forcibly rotated, so that the glass substrate can be smoothly and stably rotated.

According to a sixth aspect of the present invention, in the method of any one of the first to fifth aspects, the surface of the glass substrate is textured before the scrub surface treatment. I do.

According to a seventh aspect of the present invention, there is provided a glass substrate for an information recording medium manufactured by the manufacturing method according to any one of the first to sixth aspects. A bearing height BH04 on the surface of the glass substrate having a contact ratio of 0.4% as measured by an atomic force microscope is 2 to 7 nm, and a bearing height BH04 in a radial direction on the surface of the glass substrate;
Is characterized by having an in-plane variation of 0 to 1 nm.

According to the glass substrate for an information recording medium of the present invention, the bearing height B on the surface of the glass substrate whose contact ratio measured by an atomic force microscope is 0.4%.
Since H04 is 2 to 7 nm and the in-plane variation of the bearing height BH04 in the radial direction of the surface of the glass substrate is 0 to 1 nm, the flying height is reduced, and at the same time, the occurrence of head crash and thermal asperity is prevented. be able to.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a glass substrate and a method of manufacturing the same according to an embodiment of the present invention will be described in detail. However, the present invention is not limited to such an embodiment.

The glass substrate according to the embodiment of the present invention comprises:
It is used as a substrate for an information recording medium used in an information recording device such as a hard disk. Although the base material of the substrate is not particularly limited, glass and crystallized glass having high surface smoothness, easy surface processing, high elasticity, rigidity, and strength are preferable. For example, SiO ₂ , Na ₂ O,
Soda-lime glass mainly composed of CaO, SiO ₂ ,
_{Al 2 O 3, Na 2 O} , aluminosilicate glass mainly composed of Li ₂ O, Polo silicate glass, Li ₂ O-S
Chemical strengthening of iO ₂ -based glass, Li ₂ O-Al ₂ O ₃ -SiO ₂ -based glass, RO-Al ₂ O ₃ -SiO ₂ -based glass, etc., containing ZrO ₂ , TiO ₂ , SrO, etc. as other components Glass, crystallized glass without chemical strengthening, and the like. The modification of the surface layer of the glass substrate may include, but is not limited to, a case where a compressive stress layer is formed on the surface of the glass substrate by chemical strengthening.

Hereinafter, the manufacturing process of the glass substrate for the information recording medium will be described in detail.

The glass which is the base material for producing the base plate may be made by any method as long as it is a sheet-like glass, for example, by a float method formed into a predetermined thickness on a molten metal. Glass, a down-draw method using gravity, or a sheet of ingot glass formed by a redraw method may be used.

Circular processing First, the outer diameter of the sheet-like glass of the aluminosilicate composition produced by the above float method is slightly larger than the outer diameter of the product dimensions using a cemented carbide (or diamond) cutter, and the inner diameter is the product. Circular processing was performed by simultaneously cutting slightly smaller than the dimensions. By simultaneously cutting the outer diameter and the inner diameter in this manner, a donut-shaped glass substrate having a good concentricity between the outer diameter and the inner diameter (hereinafter simply referred to as a “glass substrate”).
Is obtained.

As another method of obtaining a donut-shaped glass substrate, after cutting only the outer diameter, the inner diameter may be cut using a cylindrical diamond grindstone, or the outer diameter may be reduced to a desired size by a pressing method. It may be prepared, and only the inner diameter may be perforated with a diamond grindstone.

Edge / Chamfering (End / Chamfer Grinding) Next, in order to accurately adjust the outer and inner diameters of the glass substrate to the product dimensions, the inner and outer peripheries of the glass substrate are ground and chamfered. Processed. In this end face processing, grinding was performed in two stages of # 325 and # 500 using a grindstone to which diamond abrasive grains were adhered. Simultaneously with the grinding, a grinding wheel was prepared so that a predetermined shape of the product appeared, and the inner and outer circumferences of the glass substrate were chamfered. Of course, the end face processing and the chamfering processing may be performed simultaneously or separately.

The number of diamond abrasive grains may be different depending on the required quality. Also,
As long as the dimensions are close to the product dimensions during the circular processing, two-stage grinding is not required, and only one stage may be used.

After the edge / chamfering process, the edge / chamfered surface of the glass substrate was polished with a cerium abrasive to smooth the roughness of the edge / chamfered surface.

Lapping (rough polishing) Next, prior to precision polishing of the main surface of the glass substrate, the glass substrate is made uniform in thickness to improve flatness and undulation, and to remove defects on the surface. Then, a lapping process (rough polishing process) was performed on the main surface of the glass substrate with a polishing machine.
In this rough polishing, a slurry in which alumina abrasive grains are dissolved in water so as to have a concentration of about 20% by mass is supplied between a metal platen of a polishing machine and a glass substrate, and the upper and lower surfaces of the glass substrate are cleaned. The glass substrate was polished in two stages of rough grinding and rough processing using two types of alumina abrasive grains, # 600 and # 1000.

This rough polishing may be performed before the end face / chamfering processing, and the first step rough grinding is performed before the end face / chamfer processing, and the second step rough polishing is performed before the end face / chamfering processing.・ It may be performed after chamfering.

In this rough polishing, since the speed of polishing the glass substrate is high, the thickness of the glass substrate is reduced to near the product size. If the glass substrate is thin,
It is not necessary to perform rough polishing in two stages, and single-stage rough polishing using fine abrasive grains may be used. Further, in the present embodiment, the glass substrate is polished using a method based on loose abrasive polishing, but a method in which the upper and lower surfaces of the glass substrate are ground using a fixed grindstone in which diamond abrasive grains or alumina abrasive grains are embedded. May be used.

After the rough polishing, the glass substrate was washed with water or a detergent so that the abrasive used for polishing was not carried into the next step. At the time of this cleaning, an ultrasonic wave having an appropriate frequency was applied to the glass substrate in order to easily remove the abrasive adhered to the surface of the glass substrate, and the cleaning was performed. Rough polishing is performed by the above method, but this step can be omitted depending on the required degree of flatness and undulation.

Primary Polishing Next, the main surface of the glass substrate was subjected to primary polishing using a cerium abrasive for the purpose of removing roughness and cracks on the surface by the coarse polishing. In this primary polishing, a cerium abrasive having an average particle size of about 1.5 μm containing cerium oxide and lanthanum oxide as main components was used, and dissolved in water so that the concentration of the cerium abrasive was about 20% by mass. The slurry was supplied to a polishing machine to polish the glass substrate. On the polishing machine, a urethane foam-based polishing pad impregnated with cerium oxide was adhered to the surface in contact with the glass substrate, and the upper and lower surfaces of the glass substrate were simultaneously polished by the polishing pad. In this polishing, a polishing pad was operated by applying a load of about 5 kg to the polishing pad until the glass substrate had a predetermined thickness.

Even after the primary polishing, the glass substrate was washed with water or a detergent so as not to carry the abrasive into the next step. In this cleaning, too, an ultrasonic wave having an appropriate frequency was applied to the glass substrate so that the abrasive adhered to the surface of the glass substrate was easily removed, and the cleaning was performed.

Secondary polishing Next, in order to make the main surface of the glass substrate a required smooth surface, precision polishing was performed as secondary polishing. In this secondary polishing process, cerium oxide and lanthanum oxide are the main components as in the primary polishing process, and free polishing is performed using a cerium polishing agent and a suede type polishing pad with a smaller particle size than the polishing agent used in the primary polishing. Grain polishing was performed. At the time of polishing, if a too large load is applied to the glass substrate, fine scratches called fine scratches will be attached to the main surface of the glass substrate.

After the secondary polishing, the glass substrate was cleaned by the following method to remove the abrasive. In other words, if an abrasive or the like remains on the surface of the glass substrate, it will firmly adhere to the surface in the next chemical strengthening step. Therefore, instead of simply washing with water and detergent, the surface is rubbed with a soft resin. The kimono was mechanically removed, and an appropriate combination of an acidic aqueous solution, an alkaline aqueous solution, and pure water was performed, and precise washing was performed while applying ultrasonic waves.

Texture treatment A texture treatment method for a glass substrate can also be realized by controlling the working conditions in a known mechanical polishing method more precisely. However, in the case of a glass substrate using glass or crystallized glass as a base material, the surface of the glass substrate is roughened by etching, so that the texture can be textured by a simpler method. In an etching process, the surface of a multi-component glass substrate should theoretically be uniformly etched, and abnormal projections (protrusions that are abnormally high compared to the surrounding minute projections) should not be formed. Even after the treatment, abnormal projections may be present on the surface of the glass substrate. That is, generally, in the surface layer of the glass substrate, the composition is not necessarily uniform when viewed microscopically, and the abrasive is strongly pressed against the surface of the glass substrate during polishing, and adheres or is embedded.
There is a portion like a lid on the surface of the glass substrate.
Therefore, there are portions on the surface of the glass substrate that are well-dissolved in the etching solution and portions that are not so. As a result, uneven etching may progress and abnormal projections may be generated. Further, on a chemically strengthened glass substrate, a foreign substance such as a metal may be strongly attached to the surface of the glass substrate during the chemical strengthening, or abnormal projections may be formed. The surface of the glass substrate that has been subjected to the texture processing has irregularities as indicated by reference numeral 10 in FIG.

Such abnormal projections can be suppressed by appropriately adjusting the conditions of the chemical treatment, the polishing conditions before the chemical treatment, and the chemical strengthening conditions. However, scrub cleaning (scrub surface treatment) described later after the texture treatment is performed. By doing so, abnormal projections can be removed more reliably. When the chemical strengthening is performed after the texture treatment, the abnormal projection can be more reliably removed by performing the scrub surface treatment after the chemical strengthening step.

Hereinafter, the scrub surface treatment will be described in more detail.

Scrub Surface Treatment Step The scrub surface treatment step is not particularly limited as long as it is after the texture treatment, but the scrub surface treatment is carried out in a state where many large foreign substances such as abrasives are present on the glass substrate surface. When this step is performed, foreign matter is rubbed against the glass substrate surface to easily cause scratches. Therefore, the step is preferably in a step of higher cleanliness, that is, a step after the cleaning step. In addition, when the chemical strengthening treatment is performed after the texture treatment, foreign substances such as iron adhere during chemical strengthening. Therefore, if the scrub surface treatment is performed after the chemical strengthening treatment, the abnormal protrusions can be more reliably removed. Therefore, it is more preferable. In order to more completely remove metallic foreign matter and the like on the surface of the glass substrate, washing with an acidic aqueous solution may be performed after the chemical strengthening treatment and before performing the scrub surface treatment.

Scrub Surface Treatment Method / Apparatus When used as an information recording medium, the magnetic head flies in the circumferential direction. It is preferred to scrub along, i.e., in the circumferential direction.

In this embodiment, as shown in FIGS. 1 (a) and 1 (b), a schematic configuration diagram of a scrub surface treatment method is shown in which a textured donut-shaped glass substrate 1 is used as a pair of cylinders. The glass substrate 1 and the roll-shaped sponge 2 are sandwiched between the roll-shaped sponges 2, and are scrubbed in the circumferential direction of the glass substrate 1 while rotating the glass substrate 1 and the roll-shaped sponge 2 as indicated by arrows in the figure. The roll-shaped sponge 2 includes a surface layer 3,
It consists of a portion 4 other than the surface layer 3 (hereinafter referred to as "underlayer 3"), and rotates around the rotation center axis as shown by the arrow in the figure.

The method and apparatus for circumferentially scrubbing the surface of a glass substrate using a roll-shaped sponge 2 are not particularly limited as long as the contact surface between the glass substrate 1 and the roll-shaped sponge 2 is linear or strip-shaped. Instead, a commercially available scrub cleaning device may be used. Further, as shown in FIGS. 2A and 2B, a method in which the glass substrate 1 is sandwiched between a pair of tape-shaped sponges 5 instead of the roll-shaped sponge 2 and the glass substrate 1 and the tape-shaped sponge 5 are rotated. And the like. The tape-shaped sponge 5 includes a tape-shaped surface layer 6 and a base layer 7, and rotates along a cylindrically rotatably supported resin roll 8 as indicated by an arrow in the drawing.

When the glass substrate 1 is sandwiched between roll-shaped sponges 2 to perform a scrub surface treatment, the method of rotating the glass substrate 1 includes a method of rotating the inner peripheral portion of the glass substrate 1 by chucking and a method of rotating the glass substrate 1. A method in which a driving unit (a roll or a belt) is brought into contact with the outer peripheral portion to rotate the glass substrate 1 or a method in which the glass substrate 1 is rotated by giving a speed difference to the rotation of the roll-shaped sponge 2 to be sandwiched.
As described in Japanese Patent Application Laid-Open No. H11-288911, in the method in which the roller is brought into contact with the outer peripheral portion of the glass substrate 1 and rotated, irregular sliding phenomenon and chatter are likely to occur between the outer peripheral portion and the roller. Radial texture spots are likely to occur due to the scrub surface treatment. In particular, if excessive scrub is applied to a portion, the portion becomes texture unevenness. Therefore, when a uniform scrub surface treatment is performed on the surface of the textured glass substrate 1, the glass substrate 1 can be smoothly and stably. From the viewpoint of turning to
Preferably, a method of chucking (fixing) the inner peripheral edge (inner peripheral portion) and forcibly rotating the inner peripheral edge (inner peripheral portion) so as not to cause slippage.

Sponge used for scrub surface treatment The hardness of the surface layer 3 of the roll-shaped sponge 2 used for scrub surface treatment is determined by the Japan Rubber Association Standard SRISO101.
If the Asker C is 40 or more, it is preferable to appropriately adjust the scrub conditions, because abnormal protrusions can be satisfactorily removed without excessively shaving the texture. The underlayer 3 is
There is no particular limitation on the type, hardness, thickness, and number of layers. Further, the method of bonding the surface layer 3 and the base layer 4 is not particularly limited. The surface layer 3 may be directly formed on the underlayer 4, or the underlayer 4 and the surface layer 3 may be separately formed and then bonded with an adhesive such as a double-sided tape.

When the glass substrate 1 is sandwiched between the tape-shaped sponges 5, a material that does not extend to the underlayer 3 is selected in order to prevent the tape-shaped sponge 5 from stretching and loosening. It is preferable to provide a layer that does not stretch. As an example, there is a tie or the like in which a sponge having a two- or three-layer structure which is easily stretched is formed or attached on a nylon tape having a thickness of about 0.5 mm which is hardly stretched (FIG. 2).

The kind of the resin constituting the surface layer 3 is not particularly limited, but the 100% modulus of the resin is 45 kg / cm.
^{If it is 2} or more and 250 kg / cm ² or less, it is preferable to adjust the scrub conditions as appropriate so that abnormal protrusions can be removed without excessively shaving the texture. That is, it is estimated that if the 100% modulus of the resin is 45 kg / cm ² or more, the outermost surface of the sponge becomes microscopically hard, and the ability to remove abnormal protrusions is increased. If a hard resin having a 100% modulus exceeding 250 kg / cm ² is used, the glass substrate itself is easily damaged.
kg / cm ² or less is preferable.

As the sponge material, urethane resin is preferably used from the viewpoint of cleanliness. In the case of urethane resin, if the type of resin is fixed, the larger the modulus of 100%, the higher the proportion of hard crystal parts (softer). The proportion of the amorphous part decreases). That is, the outermost surface of the sponge becomes harder in a transparent manner.

There are various types of urethane resins depending on their starting materials, and typical examples include polyester-based polyurethane, polyether-based polyurethane, polycarbonate-based polyurethane, and copolymer-type polyurethane thereof. Polycarbonate-based polyurethane and polyurethane of copolymerized tire of carbonate and ester are superior in chemical resistance compared to ester-based and ether-based, and the microscopic hardness of the outermost surface of the sponge when used in an alkaline solution, etc. It is preferable in that it can be maintained.

The structure of the surface layer 3 of the roll-shaped sponge 2 is as follows.
The sponge is not particularly limited as long as it is a sponge (foam). However, it is preferable to form a continuous foam having an average opening diameter of 30 μm or more, because abnormal projections can be removed well without excessively shaving the texture. The reason why the abnormal protrusions are selectively removed is not well understood, but it is estimated that if the average opening diameter is 30 μm or more, the abnormal protrusions and the sponge surface are efficiently contacted during the scrub. If the average opening diameter is larger than 150 μm, the surface layer 3 is easily worn and the durability is reduced.

The thickness of the surface layer when forming an open cell having an average opening diameter of 30 μm or more is not particularly limited.
When the opening is exposed by shaving the surface after continuous foaming, in order to uniformly form the average opening diameter, 0.3 to
It is preferable to set it to about 1.0 mm.

Scrubbing liquid The above scrubbing surface treatment is preferably performed using a scrubbing liquid. Scrubbing liquid is not particularly limited, pure water, electrolytic ionized water, ozone water, hydrogenated water, acidic aqueous solution, alkaline aqueous solution, or a chelating agent, a surfactant,
What added salts can be used.

In order to remove abnormal protrusions caused by uneven etching, it is more preferable to use an alkaline aqueous solution which chemically attacks glass bonding. When an alkaline aqueous solution is used, an electrostatic repulsion acts between the removed abnormal projection and the glass substrate, which is also preferable from the viewpoint of preventing the removed abnormal projection from reattaching. Although the concentration of the alkaline aqueous solution is not particularly limited, it is preferable to use the alkaline aqueous solution at pH 8 or higher because the effect of preventing re-adhesion is significantly increased at pH 8 or higher.

When the removed abnormal protrusions are foreign matters such as abrasives and metals, they can be dissolved and removed by appropriately adjusting the acidic aqueous solution. Further, when scrub cleaning is performed with an acidic aqueous solution, a texture can be formed while suppressing the occurrence of abnormal projections. Although the details of this mechanism are unknown, it is presumed that roughening of the glass substrate due to chemical etching and removal of abnormal protrusions occur simultaneously.
For such a reason, it is preferable to use an acidic aqueous solution.
The concentration of the acidic aqueous solution is not particularly limited, but the effect of the chemical etching treatment is improved at pH 4 or less. The scrub surface treatment using an acidic aqueous solution and the scrub surface treatment using an alkaline aqueous solution may be performed in combination.

Although the temperature of the scrubbing liquid is not particularly limited,
It is preferable to use in a temperature range of 10 ° C. to 50 ° C. in consideration of gagging such as evaporation of the scrubbing liquid.

Washing Solution after Scrub The washing solution after scrubbing is not particularly limited, and pure water, electrolytic ionized water, ozone water, hydrogenated water, acidic aqueous solution, alkaline aqueous solution, or a chelating agent, a surfactant, and salts are added thereto. Those added can be used. In particular, an alkaline aqueous solution is preferable because the electrostatic repulsion acts between the foreign matter and the glass substrate 1 so that the alkaline aqueous solution can be washed while preventing reattachment.
Even when the foreign matter adheres to the glass substrate 1 very strongly, the degree of foreign matter adhesion is weakened by scrub surface treatment, completely lifted off by chemical etching treatment with an acidic aqueous solution, and the system is prevented from being re-adhered by an alkaline aqueous solution. Since it can be carried out, it is more preferable to perform treatment with an acidic aqueous solution after the scrub surface treatment and then with an alkaline aqueous solution.

The type of the acidic aqueous solution is not particularly limited, and may be a weak acid such as acetic acid. However, hydrofluoric acid, hydrosilicofluoric acid, sulfuric acid, hydrochloric acid, nitric acid, sulfamic acid, which has a strong etching action on glass, or A strong acid such as phosphoric acid is preferable in promoting the etching of the surface of the glass substrate 1.

The type of the alkaline aqueous solution is not particularly limited, and potassium hydroxide, sodium hydroxide, ammonia,
Any alkaline aqueous solution such as trimethylammonium hydride can be used as long as it is an alkaline raw material that dissolves in water. The concentration of the alkaline aqueous solution is pH 8
Since the effect of preventing re-adhesion is remarkably increased as described above, it is preferable to use at pH 8 or more. It is also preferable to add a commercially available synthetic alkali detergent in addition to a surfactant and a chelating agent in order to enhance the washing effect.

The scrub surface treatment according to the embodiment of the present invention can be used to effectively remove irregularities, foreign matters, and stains even on the glass substrate 1 on which no texture is formed.

An information recording medium is formed by sequentially forming at least a base film, a magnetic film, and a protective film on the textured glass substrate 1. If necessary, a shield layer may be provided between the glass substrate 1 and the base film, or a multilayer structure may be provided by providing a buffer layer or a shield layer for each layer.

Then, the glass substrate for an information recording medium is incorporated into an information recording device such as a hard disk by a known method. The types, thicknesses, and film forming means of the base film, the magnetic film, and the protective film are not particularly limited.

When the glass substrate 1 is used, it is preferable to use NiAl as the shield layer and a Co-based alloy as the base film in order to ensure excellent information recording / reproducing characteristics and film adhesion. As a film forming means, a sputtering method is usually used, and according to this method, the surface irregularities of the glass substrate 1 are maintained as they are. Note that by applying a tape burnishing process after the film formation, foreign substances and dirt attached to the protective film can be removed. Since the information recording medium directly reflects the irregularities on the surface of the glass substrate, head crash and thermal asperity are likely to occur even if the flying height is reduced.

As described above, scrub surface treatment is performed to solve the problems of head crash and thermal asperity, and the surface irregularities of the optimized glass substrate 1 are evaluated based on a predetermined standard. The evaluation criteria for the irregularities on the surface of the glass substrate 1 include an average surface roughness Ra, a ten-point average surface roughness Rz, and the like. In the present invention, a bearing height described below is used.

Hereinafter, the bearing height will be described with reference to FIG.

FIGS. 3A and 3B are conceptual diagrams of the irregularities on the surface of the glass substrate 1 subjected to the texture processing. FIG. 3A shows the irregularities on the surface of the glass substrate, and FIG. 3B shows A in FIG. -A
It is a line sectional view, and (c) is a BB line sectional view of Drawing 3 (a).

In FIG. 3, reference numeral 10 denotes the surface unevenness of the glass substrate 1, and reference numeral 11 denotes a bearing ratio of 0.4%.
12 shows a slice surface (reference surface) with a bearing ratio of 50%, and 13 shows a cut surface of a convex portion of the surface of the glass substrate 1 in the slice surface.

The bearing height focuses only on the projections on the surface of the glass substrate 1 and evaluates the irregularities on the surface of the glass substrate 1 based on the criteria for evaluating the shape of the projections.
Specifically, the contact ratio of the irregularities on the surface of the glass substrate 1 is 5
0% is the reference height, and the height when the contact ratio is 0.4%: bearing height (BH04) is 2 to 7 n
The evaluation criterion is whether or not it is within the range of m. Here, the contact ratio is a value represented by a bearing ratio, and is measured by an atomic force microscope (AFM). The bearing ratio is the ratio of the cut surface of the convex portion of the glass substrate surface to the slice surface when the glass substrate surface is sliced on a certain plane. Therefore, the case where the contact ratio is 50% is a ratio in which the cut surface of the convex portion occupies half of the slice surface in the slice surface (FIG. 3C). When the slice plane in the case of the contact ratio of 50% is set as the reference plane and this slice plane is moved in parallel to the tip direction of the projection, the contact ratio gradually decreases. And the contact area is 0.4% (FIG. 3).
(B)) is the distance moved until the contact ratio is 0.4%
Corresponds to the height BH04. That is, when the distance moved on the slice surface is 2 to 7 nm until the contact ratio becomes 50% to 0.4%, it is found that the glass substrate can solve the problems of head crash and thermal asperity. Was.

FIG. 4 briefly shows the relationship between the bearing ratio and the bearing height together with a typical example of the present invention.

Such an evaluation criterion was found and introduced for the first time by many experiments of the present inventors on the irregularities of the glass substrate surface and analysis of the results. In other words, in the relationship between the magnetic head and the glass substrate surface, as a result of a detailed comparison of the contact characteristics and flight stability of the magnetic head, the bearing height on the glass substrate surface is directly related to the flight stability of the magnetic head. It starts with finding out that it is a certain parameter. In this regard, BH04 produced a number of different information recording media, each of which was reduced to 26.7 kPa (200 Torr) under reduced pressure.
In r), a fixed point flying test of the magnetic head was performed. A part of the result is shown in FIG. Generally, the flying height of the magnetic head becomes smaller as the environmental pressure decreases, so that the magnetic head and the glass substrate are more likely to come into contact under reduced pressure. Therefore, the test under reduced pressure is regarded as a kind of acceleration test regarding head crash proof strength.

Regarding the CSS method, various studies have been made on the irregularities on the surface of the glass substrate.
A suitable range based on various parameters such as a, Rmax, maximum projection height Rp, projection density, projection height or projection size has been proposed. Here, the maximum protrusion height Rp is the maximum value of the protrusion observed in the measurement area of 20 μm × 20 μm.

However, these studies are for optimization of friction and wear in the CSS zone.
It does not consider the flight stability or thermal asperity of the magnetic head in the data zone when flying low.

As shown in FIG. 5, if BH04 is at or below 2 nm, a head crash will occur within several hours if BH04 is less than 2 nm. It is considered that this is because when BH04 becomes smaller than 2 nm, the flight stability of the magnetic head rapidly decreases. On the other hand, when BH04 exceeds 7 nm, the probability of occurrence of a head crash due to collision with a protruding projection increases, and the frequency of occurrence of thermal asperity also increases.

BH04 preferably has a thickness of 3 to 6.5 nm, more preferably 3.5 to 6.0 nm. The lower limit is set to 3 or 3.5 nm or more because the above glass substrate 1
This is because there is a foreign matter removal step called tape burnish when processing the information recording medium into an information recording medium, so that a shaving allowance is left there. With the lower limit set higher as described above, the production yield of the glass substrate having the target performance is improved. On the other hand, by setting the upper limit to be low, even if the design value of the flying height is low, the frequency of occurrence of head crash can be reduced. Further, the reliability of the information recording device can be improved even in a severe environment with a low atmospheric pressure such as a high mountain.

Further, the irregularities on the surface of the glass substrate were determined to have a contact ratio of 0.
It is preferable that the height BH01 at 1% is 2 to 10 nm. This is because when BH01 exceeds 10 nm, the probability of occurrence of a head crash increases, as proved in the examples described later. Normally, BH0
1 ≧ BH04.

[0078]

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

First, a glass substrate for an information recording medium shown in Table 1 was manufactured through the following steps.

[0080]

[Table 1]

Example 1 Processing Step Aluminosilicate glass (Si) formed by a float method
O ₂ : 66.0 mol%, Al ₂ O ₃ : 11.0 mol
%, Li ₂ O: 8.0 mol%, Na ₂ O: 9.0 mol
%, MgO: 2.4 mol%, CaO: 3.6 mol
%, K ₂ O: 0.2 mol%, SrO: 2.0 mol
%) Using a diamond cutter to obtain an outer diameter of 96 mm.
φ and an inner diameter of 24 mmφ were cut at the same time to obtain a donut-shaped glass substrate.

Next, in order to accurately adjust the outer and inner diameters of the doughnut-shaped glass substrate to the product size, the inner and outer peripheries of the glass substrate were ground and chamfered. In this end face processing, grinding was performed in two stages of # 325 and # 500 using a grindstone to which diamond abrasive grains were attached.
At the same time as the grinding, a grinding wheel was prepared so that a predetermined shape of the product was obtained, and chamfering was performed on the inner and outer circumferences of the glass substrate. After this edge / chamfering process, the edge / chamfered surface of the glass substrate was polished with a cerium abrasive to smooth the roughness of the edge / chamfered surface.

Lapping (Coarse Polishing) Step Alumina abrasive grains are dissolved in water to a concentration of about 20% by mass to form a slurry, and the slurry is supplied between a metal platen of a polishing machine and a glass substrate. The upper and lower surfaces of the glass substrate were simultaneously polished. # 600 and # 1 as alumina abrasives
The glass substrate was polished in two stages of rough grinding and rough processing using two types of 000. After this rough polishing, cleaning was performed using water or a detergent so that the polishing agent used for polishing was not carried into the next step. At the time of this cleaning, in order to make it easy to remove the abrasive attached to the glass substrate surface, about 48 kHz
Cleaning was performed by applying ultrasonic waves of 1 W / cm ² to the glass substrate.

Primary polishing step A cerium abrasive having an average particle size of about 1.5 μm and containing cerium oxide and lanthanum oxide as main components was dissolved in water so that the concentration of the cerium abrasive became about 20% by mass. The slurry was supplied to a polishing machine to polish the glass substrate. On the polishing machine, a urethane foam-based polishing pad impregnated with cerium oxide was adhered to the surface in contact with the glass substrate, and the upper and lower surfaces of the glass substrate were simultaneously polished by the polishing pad. In this polishing, a polishing pad was operated by applying a load of about 5 kg to the polishing pad until the glass substrate had a predetermined thickness. After the primary polishing, the glass substrate was washed with water or a detergent so as not to carry the abrasive into the next step. Also in this cleaning, in order to make it easy to remove the abrasive adhered to the glass substrate surface, about 48 kHz, 1 W / cm ² ultrasonic wave was applied to the glass substrate for cleaning.

Secondary polishing process The main component is cerium oxide and lanthanum oxide, which are the same as those used in the primary polishing process, and are released using a cerium abrasive having a smaller particle size than the abrasive used in the primary polishing and a suede-based polishing pad. Abrasive polishing was performed. At the time of polishing, if a too large load is applied to the glass substrate, fine scratches called fine scratches will adhere to the main surface of the glass substrate.

Even after the secondary polishing, the glass substrate was cleaned by applying ultrasonic waves of about 48 kHz and 1 W / cm ² to remove the attached abrasive.

Washing / texture treatment step Washing with a shower of pure water to remove the polishing agent weakly adhering to the surface of the glass substrate, and then placing it in a bath of 0.01% by mass hydrofluoric acid solution hardened at 50 ° C. The glass substrate was immersed for 1 minute and irradiated with about 48 kHz, 1 W / cm ² ultrasonic waves for 1 minute. Thereafter, a commercially available alkaline solution (pH 11: RBS2 manufactured by Chemical Products Co., Ltd.) maintained at 40 ° C.
5) Immerse the glass substrate in the bath for 1 minute,
Ultrasonic waves of 1 W / cm ² were applied for 1 minute. The glass substrate was pulled out of the bath of the alkaline solution, immersed in a pure water bath and rinsed to remove the alkaline solution. Finally, the glass substrate was rinsed three times in a pure water bath, immersed in a bath of isopropyl alcohol, irradiated with ultrasonic waves of about 48 kHz for 2 minutes, and then dried in isopropyl alcohol vapor for 1 minute.

Chemical strengthening step The glass is immersed in a mixed molten salt of 40% of the first grade sodium nitrate and 60% of the first grade potassium nitrate.
For 3 hours to carry out ion exchange for chemical strengthening. The sample after the chemical strengthening was gradually cooled, and the strengthening salt attached to the glass substrate was washed away in a pure water bath.

[0089]Scrub surface treatment (removal of abnormal protrusions) Subsequently, urethane sponge (hardness (Asker C) = 1)
0, thickness = 10mm)
Surface layer (hardness (Asker C) = 75, resin 10)
0% Modulus = 200 kg / cm^Two, Average opening diameter = 1
00 μm, thickness = 0.6 mm, continuous foam type)
Cut the sponge into strips and paste with double-sided tape
Spirally around a cylindrical roll and scrub
For sponge. Rotated while holding at the inner edge
Glass substrate between the two sponges
For 10 seconds. At this time, the glass base
The rotation speed of the plate is 300 rpm, and the pressure of the sponge is 392.
00Pa (400gf / cm ^Two) And pH 11 hydroxyl
An aqueous solution of potassium iodide is placed between the glass substrate and the sponge every minute.
The feed was 30 ml.

After the final cleaning step , the glass substrate was immersed in a 0.01 wt% sulfuric acid bath maintained at 40 ° C. for 1 minute, and was immersed at about 48 kHz, 1 W / cm
The ultrasonic wave of No. ² was irradiated for 1 minute. The glass substrate was pulled out of the sulfuric acid bath, immersed in a pure water bath and rinsed to remove the acidic aqueous solution. Further, a commercially available alkaline solution (pH 11: R manufactured by Chemical Products Co., Ltd.) maintained at 40 ° C.
The glass substrate was immersed in a bath of BS25) for 1 minute,
kHz, and irradiated for 1 minute ultrasound 1W / cm ^2. The glass substrate was pulled out of the bath of the alkaline solution, immersed in a pure water bath and rinsed to remove the alkaline solution. Finally, the glass substrate is rinsed three times in a pure water bath, immersed in a bath of isopropyl alcohol, and irradiated with ultrasonic waves of about 48 kHz for 2 hours.
After irradiating for 1 minute, it was dried in isopropyl alcohol vapor for 1 minute.

Film-forming step A NiAl seed layer, a CrMo underlayer, a CoCrPt magnetic layer and a C-based protective film are sequentially formed on this glass substrate by a sputtering method, and a perfluoropolyether-based lubricant is further applied by a dipping method. And an information recording medium was manufactured.

(Example 2) A sponge used in the scrub surface treatment step was a polycarbonate polyurethane surface layer (hardness (Asker C) = 75, on a YAC tape woven with nylon / polyester mixed yarn). A sponge having a resin 100% modulus = 200 kg / cm ² , an average opening diameter = 100 μm, a thickness = 0.6 mm, and a continuous foam type) is adhered, and the sponge is applied to both surfaces of a glass substrate. The process was performed under the same conditions as in Example 1 except that the shape of the contact portion to the glass substrate was changed to a strip shape by pressing the resin from the outside with a resin roll, thereby obtaining Example 2.

Example 3 Example 3 was carried out under the same conditions as in Example 1 except that the scrub surface treatment step was performed before the chemical strengthening step.

(Example 4) In the finishing washing step after the scrub surface treatment step, the treatment was performed under the same conditions as in Example 1 except that the treatment was performed only with an alkaline aqueous solution instead of the acidic aqueous solution treatment and the alkaline aqueous solution treatment. , Respectively.

(Example 5) In the finish cleaning step after the scrub surface treatment step, the treatment was performed under the same conditions as in Example 1 except that the treatment was performed only with pure water instead of the treatment with the acidic aqueous solution and the alkaline aqueous solution. , Respectively.

Embodiment 6 As a method of holding and rotating the glass substrate in the scrubbing step, the outer periphery of the glass substrate is held by a roller, and the roller in contact with the outer periphery of the glass substrate is rotated to rotate the glass. The processing was performed under the same conditions as in Example 1 except that the substrate was rotated (the glass substrate was sandwiched between a pair of roll-type sponges having a length longer than the diameter of the glass substrate, and the glass substrate was rotated at about 200 rpm). And Example 6.

Example 7 Example 7 was carried out under the same conditions as in Example 1 except that a sponge having a surface layer of Asker hardness of 40 was used as a sponge used in the scrub surface treatment step.

Comparative Example 1 A sponge used in the scrub surface treatment step was not a roll type, but a cup-shaped planar sponge, and the substrate was rotated by rotating the sponge at 300 rpm. The process was performed under the same conditions as in Example 1 to obtain Comparative Example 1.

(Comparative Example 2) [0099] Comparative Example 2 was performed under the same conditions as in Example 1 except that a sponge having a surface layer having an Asker hardness of 30 was used as a sponge used in the scrub surface treatment step.

(Comparative Example 3) As a sponge used in the scrub surface treatment step, a cylindrical roll having a thickness of 10 mm was used.
The process was performed under the same conditions as in Example 1 except that a wound VF sponge was used, and Comparative Example 3 was obtained.

Evaluation of Shape of Glass Substrate Abnormal protrusions and textures of the glass substrates of Examples 1 to 6 and Comparative Examples 1 to 3 were measured by using a scanning probe microscope: AFM.
(Nanoscope IIIa manufactured by Digital Instruments) and measured using a tapping mode. As the index of the abnormal protrusion, the maximum protrusion height Rp, the number of protrusions having a height of 20 nm, and the height 1
The number of protrusions at 0 nm was measured. Here, Rp represents the maximum projection height observed in the measurement area of 20 μm × 20 μm. The number of protrusions having a height of 10 or 20 nm indicates the number of protrusions in the measurement area. From the existence probability, the number of protrusions was adjusted so that the AFM viewing area became 0.01 mm ² in total.

In order to evaluate the distribution in the radial direction, the above measurement was performed at the following places on the donut-shaped glass substrate.

3 mm from inner edge to outer edge
Location moved 5 mm from inner edge to outer circumference Intermediate point between inner edge and outer edge Location moved 1 mm from outer edge to inner circumference Move 3 mm from outer edge to inner circumference As an index of the texture, the bearing height BH0, which is the height when the contact ratio of the surface unevenness of the glass substrate is 50% and the contact ratio is 0.4%, is set as the reference height.
4 was used. The contact ratio is a value represented by a bearing ratio, and the bearing ratio is a ratio of a cut surface of a convex portion of a glass substrate surface to a slice surface when the glass substrate is sliced on a certain plane. When the slice plane in the case of the contact ratio of 50% is set as the reference plane and this slice plane is moved in parallel to the tip direction of the projection, the contact ratio gradually decreases. The distance moved until the contact area becomes 0.4% corresponds to the height BH04 when the contact ratio is 0.4%.

We have determined that the bearing height of the glass substrate surface is a parameter directly related to the flight stability of the magnetic head (the magnetic head does not contact the glass substrate surface during flight), BH04 is 2n
It has been found that when the diameter is smaller than m or when the diameter exceeds 7 nm, the probability of occurrence of head crash increases and the frequency of occurrence of thermal asperity also increases. It is estimated that when BH04 is smaller than 2 nm, the flight stability of the magnetic head is rapidly reduced, and when BH04 is larger than 7 nm, the probability of occurrence of a head crash due to collision with a protruding projection increases. BH04 produced a number of different information recording media, each of which was subjected to a reduced pressure of 26.7 kPa (200 T
Table 2 shows the results of the fixed point flying test of the magnetic head performed at orr).

[0105]

[Table 2]

Performance Evaluation of Information Recording Medium The information recording medium was subjected to a pressure reduction of 26.7 kPa (200 kPa).
(Torr), a fixed point levitation test was performed to evaluate the time until the head crashed. In order to evaluate the radial distribution, the above-mentioned test was performed at the following places on the donut-shaped glass substrate.

3 mm from inner edge to outer edge
Moved location Intermediate point between inner peripheral edge and outer peripheral edge Location moved 1 mm from outer peripheral edge toward inner circumference BH04, Rp, number of 10 nm protrusions, radial distribution of time to head crash FIGS. 6 to 9 It was shown to.

From Examples 1 to 7, when the hardness (Asker C) of the sponge surface layer is larger than 40, there are no protrusions of 10 nm and 20 nm over the in-plane radial direction, and Rp is 10 n.
It can be seen that a texture with a uniform height and good in-plane homogeneity with a BH04 of 2 to 7 nm and an in-plane variation of BH04 of less than 1 nm can be obtained. In such a glass substrate, the time until head crash is 1
When the time was 00 hours or more, good characteristics as an information recording medium were exhibited.

Comparative Example 1 shows that when the sponge used for scrub cleaning is a cup-shaped planar sponge, the asperity in the inner peripheral portion of the glass substrate cannot be sufficiently removed. In the inner circumference, BH04 becomes larger than 7 nm, and Rp
Became larger than 10 nm, HTO became about 7 nm, and several to several tens of 10 nm protrusions / 0.01 mm ^{2 were} present. Comparing the time required until head crash, in Comparative Example 1, the time until head crash is shorter near the center of the glass substrate than in Example 1. This tendency is that when the sponge is in contact with the glass substrate at the inner peripheral portion of the glass substrate, the contact is likely to occur in the cup-shaped flat sponge due to its structure, and the inner peripheral portion is weaker than the outer peripheral portion. It is presumed that the relative speed becomes smaller.

Also, when comparing the time until head crash at the center of the glass substrate, it can be seen that head crash occurs in Comparative Example 1 earlier than in Example 1. This is presumed to be because the cup-shaped planar sponge rubs almost perpendicularly to the circumferential direction, whereas in the first embodiment, it rubs in the circumferential direction, that is, the same direction as the head flight direction.

Comparative Example 2 shows that when the hardness (Asker C) of the sponge surface layer used for scrub cleaning is smaller than 40, abnormal protrusions cannot be removed, and BH04 also becomes larger than 7 nm. 10 hours before head crash
It did not reach 0 hours.

As can be seen from Comparative Example 3, when scrubbing was performed using a PVF sponge, abnormal protrusions could not be removed, and BH04 was not removed.
It turns out that it becomes larger than nm. The time to head crash did not reach 100 hours.

By comparing Examples 1 and 2, it is found that the same performance can be obtained in terms of asperity removal ability and texture control ability regardless of whether the scrub surface treatment method is a roll brush method or a tape method. I understand.

By comparing Examples 1 and 3, when the chemical strengthening step is included, it is preferable that the scrub surface treatment step is performed after the chemical strengthening step, because the asperity removing ability and the texture controlling ability are more excellent. You can see that.

By comparing Example 1 with Examples 3 and 4, in the finish cleaning step after the scrub surface treatment step, an acidic aqueous solution treatment and an alkaline aqueous solution treatment are performed in terms of asperity removal ability and texture control ability. This is more preferable and preferable, and then it is preferable to perform an alkaline aqueous solution treatment.

By comparing Example 1 with Example 6, the scrub surface treatment method is based on the method of rotating the glass substrate by rotating the holding roller while holding the glass substrate at the outer periphery. A head crash occurred earlier than in a method in which the substrate was chucked at the periphery and the substrate was rotated stably and smoothly. This is presumed to be because a sliding phenomenon occurred between the glass substrate and the roller, and when viewed microscopically, radial irregularities occurred in the texture of the glass substrate in the radial direction.

[0117]

As described above in detail, according to the manufacturing method of the first aspect, the surface of the glass substrate has a hardness of 40 according to Asker C of the Japan Rubber Association Standard Standard SRISO101.
The surface of the glass substrate is scrubbed in the circumferential direction using a sponge of ~ 100, so that the outermost surface of the sponge (the portion in contact with the glass substrate) is microscopically hard and macroscopically supple, and the shape of the contact portion Non-uniform etching of the glass substrate by forcibly rotating the glass substrate fixed at the inner peripheral edge and scrubbing in the circumferential direction while contacting the sponge so that it becomes linear or strip-shaped in the radial direction of the glass substrate As a result, it is possible to remove abnormal protrusions and strongly adhered foreign substances caused by the above, and as a result, it is possible to manufacture a glass substrate for an information recording medium and an information recording medium having excellent surface cleanliness and in-plane uniformity. .

According to the manufacturing method of the second aspect, before the scrub surface treatment, the glass substrate is chemically strengthened, so that the operation and effect of the manufacturing method of the first aspect can be reliably achieved.

According to the manufacturing method of the third aspect, after the scrub surface treatment, the glass substrate is washed with an alkaline aqueous solution having a pH of 8 or more, so that abnormal projections due to non-uniform etching are removed. Redeposition can be prevented.

According to the manufacturing method of the fourth aspect, after the scrub surface treatment, the glass substrate is washed with an acidic aqueous solution having a pH of 4 or less, and then with an alkaline aqueous solution having a pH of 8 or more. The texture can be formed while suppressing the generation of projections, and the abnormal projections can be removed to prevent re-adhesion.

According to the manufacturing method of the fifth aspect, the glass substrate is fixed at the inner peripheral portion and forcedly rotated during the scrub surface treatment, so that the glass substrate can be smoothly and stably rotated.

According to the glass substrate for an information recording medium of the present invention, the bearing height B on the surface of the glass substrate whose contact ratio measured by an atomic force microscope is 0.4%.
H04 is 2 to 7 nm, and the in-plane variation of the bearing height BH04 in the radial direction of the surface of the glass substrate is 0 to 1 nm. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a scrub surface treatment method,
(A) is a longitudinal sectional view, (b) is a side view.

FIG. 2 is a schematic explanatory view of another modified example of the scrub surface treatment method of FIG. 1, where (a) is a longitudinal sectional view,
(B) is a side view.

3A and 3B are conceptual diagrams of irregularities on the surface of a glass substrate 1 on which a texture process has been performed, where FIG. 3A shows irregularities on the surface of the glass substrate, and FIG. 3B shows a line AA in FIG. It is sectional drawing, (c) is BB sectional drawing of FIG.3 (a).

FIG. 4 is a typical relationship diagram between a bearing ratio and a bearing height.

FIG. 5 is a correlation diagram between a bearing height BH04 and a head crash.

FIG. 6 is a diagram showing the distribution of the bearing height BH04 in the radial direction.

FIG. 7 is a diagram showing the distribution of the maximum protrusion height Rp in the radial direction.

FIG. 8 is a diagram showing a radial distribution of the number of protrusions of 10 nm or more.

FIG. 9 is a diagram showing a relationship between a time until a head crash and a measurement place.

FIG. 10 is a schematic view of a conventional scrub surface treatment method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Roll-shaped sponge 3, 6 Surface layer 4, 7 Underlayer 5 Tape-shaped sponge 8 Resin roll 10 Irregularities of glass substrate surface 11 Slice surface with bearing ratio 0.4% 12 Slice surface with bearing ratio 50% (reference) 13) Cut surface of the convex part of the glass substrate surface in the slice plane 21 Sponge

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B24B 1/00 B24B 1/00 D C03C 17/38 C03C 17/38 (72) Inventor Minami Akihide Osaka 4-7-28 Kitahama, Chuo-ku, Osaka-shi F-term (reference) in Nippon Sheet Glass Co., Ltd. 5D112 AA02 GA02

Claims (7)

[Claims] 1. The surface of a glass substrate is made of Asker C having a hardness of 40-100 according to Japan Rubber Association Standard SRISO101.
A method for producing a glass substrate for an information recording medium, wherein a scrub surface treatment is performed in a circumferential direction of the glass substrate using a sponge. 2. The method according to claim 1, wherein the glass substrate is chemically strengthened before the scrub surface treatment. 3. The method according to claim 1, wherein after the scrub surface treatment, the glass substrate is washed with an alkaline aqueous solution having a pH of 8 or more. 4. The method according to claim 1, wherein after the scrub surface treatment, the glass substrate is washed with an acidic aqueous solution having a pH of 4 or less, and then washed with an alkaline aqueous solution having a pH of 8 or more. Method. 5. The manufacturing method according to claim 1, wherein the glass substrate is fixed at an inner peripheral portion and is forcibly rotated during the scrub surface treatment. 6. The method according to claim 1, wherein a texture treatment is performed on a surface of the glass substrate before the scrub surface treatment. 7. A glass substrate for information recording manufactured by the manufacturing method according to claim 1, wherein a contact ratio measured by an atomic force microscope is 0.
4% bearing height B on the surface of the glass substrate
A glass substrate for an information recording medium, wherein H04 is 2 to 7 nm, and in-plane variation of a bearing height BH04 in a radial direction of a surface of the glass substrate is 0 to 1 nm.