JPH10194785A - Production of glass substrate for information recording medium, and production of information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a glass substrate for an information-recording medium, containing a process for chemically reinforcing a glass substrate and a process for grinding the glass substrate, to preventing the adhesion of foreign particles causing a low flying height and a thermal asperity by performing at least one of processes in an atmosphere in which filtered and clean air is circulated. SOLUTION: This method for producing a glass substrate for an information recording medium contains a process for grinding the main surface of a glass substrate and a chemically reinforcing process for reinforcing the glass substrate by bringing the glass substrate into contact with a chemically reinforcing treatment liquid to replace a part of ions contained in the glass substrates with ions each having a larger diameter than that of each of the ions contained in the substrate. Therein, at least one of a washing process, the chemically reinforcing treatment process, a process for washing a chemically reinforcing treatment liquid, a drying process, an examination process, and a packaging and storing process is performed in a filtered and cleaned air-circulated atmosphere so that particles do not adhere to the glass substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium used as a recording medium for information processing equipment, and a method of manufacturing a substrate thereof.

[0002]

2. Description of the Related Art A magnetic disk is one of such information recording media. A magnetic disk is formed by forming a thin film such as a magnetic layer on a substrate, and an aluminum or glass substrate has been used as the substrate. However, in recent years, in response to the pursuit of higher recording density, the proportion of the glass substrate that can make the distance between the magnetic head and the magnetic recording medium smaller than that of aluminum has been gradually increasing.

[0003] The glass substrate which tends to increase in this manner is generally manufactured by chemically strengthening it to increase the strength so as to withstand an impact when mounted on a magnetic disk driver. In addition, the glass substrate surface is polished with high precision to achieve a high recording density so that the flying height of the magnetic head can be reduced as much as possible.

On the other hand, not only the glass substrate but also the magnetic head changes from a thin film head to a magnetic resistance (MR head).
Responding to high recording density.

[0005]

As described above, high flatness of the surface of a magnetic disk is indispensable for a low flying height required for a high recording density. In addition, when an MR head is used, a high flatness is required on the surface of the magnetic recording medium due to the problem of TA (thermal asperity). The thermal asperity is such that when a protrusion is present on the surface of a magnetic disk, the protrusion is affected by the MR head, and heat is generated in the MR head. This is a phenomenon that causes malfunction.

As described above, the demand for high flatness of the magnetic disk surface has been increasing day by day to reduce the flying height and to prevent the occurrence of thermal asperity. In order to obtain such high flatness of the magnetic disk surface, a substrate surface with high flatness is ultimately required. However, if the substrate surface is no longer polished with high precision, the high recording density of the magnetic disk can no longer be obtained. We have reached the stage where we cannot realize the realization. In other words, no matter how high the polishing accuracy, high flatness cannot be obtained if foreign matter adheres to the substrate. Needless to say, foreign matter has been conventionally removed, but foreign matter on the substrate, which has been conventionally allowed, is considered to be a problem at today's high-density level. Examples of such foreign matter include extremely fine iron powder that cannot be removed by ordinary cleaning. When a thin film such as a magnetic film is laminated with the iron powder adhered to the glass substrate, a protrusion is formed on the surface of the magnetic disk, which becomes a hindrance to lowering the flying height and preventing thermal asperity. The present invention
An object of the present invention is to prevent such minute iron powder from adhering to a glass substrate.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned object, and has ascertained why a fine iron powder adheres to a glass substrate. It was found that metals or metal oxides such as iron powder generated from manufacturing equipment or construction equipment were floating therein, and these floating substances were mixed into the chemical strengthening treatment liquid and adhered to the glass substrate.

A first configuration of the present invention comprises a step of polishing a main surface of a glass substrate and a step of bringing the glass substrate into contact with a chemical strengthening treatment solution to remove some ions contained in the glass substrate. A chemical strengthening step of strengthening the glass substrate by substituting ions in a processing liquid having an ion diameter larger than the ions, wherein the cleaning step after the final polishing step, the chemical strengthening step At least one of the steps of washing the chemical strengthening treatment solution, drying, inspecting, and packaging or storing the glass substrate for the information recording medium in a container is filtered so that particles do not adhere to the glass substrate. A method for producing a glass substrate for an information recording medium, wherein the method is performed in an atmosphere in which clean air is circulated.

In a second aspect of the present invention, a step of polishing a main surface of a glass substrate and a step of bringing the glass substrate into contact with a chemical strengthening treatment solution to remove some ions contained in the glass substrate. A chemical strengthening step of strengthening the glass substrate by substituting ions in a processing liquid having an ion diameter larger than the ions, wherein the cleaning step after the final polishing step, the chemical strengthening step At least one of the steps of washing, drying, inspecting, and packaging the glass substrate for information recording medium in a container,
A method for producing a glass substrate for an information recording medium, wherein the method is performed in an environment having a cleanliness of 1000 particles / cubic foot-meter or less of particles having a size of 00 microns.

A third configuration of the present invention is characterized in that clean air has a cleanliness of less than 1000 particles / cubic foot-meter of particles having a size of 0.3 to 100 microns. 2. The method for manufacturing a glass substrate for an information recording medium according to the above configuration 1.

In a fourth aspect of the present invention, the cleanliness of particles of 0.3 to 100 microns is 100 particles / cubic foot-meter or less.
Or the method for producing a glass substrate for an information recording medium according to 2 above.

A fifth aspect of the present invention is the method for manufacturing a glass substrate for an information recording medium according to the first or second aspect, wherein the cleanliness of the particles is not more than 50 particles / cubic foot-meter.

According to a sixth aspect of the present invention, there is provided a method for manufacturing a glass substrate for an information recording medium according to any one of the first to fifth aspects, wherein the particle cleanliness environment is specified.
A method for manufacturing an information recording medium, comprising performing cleaning after the final polishing step and chemically strengthening the glass substrate.

A seventh aspect of the present invention is the method for manufacturing a glass substrate for an information recording medium according to any one of the first to sixth aspects, wherein the glass substrate for the information recording medium is a glass substrate for a magnetic disk.

According to an eighth aspect of the present invention, in the information recording medium according to the seventh aspect, the glass substrate for a magnetic disk is a glass substrate used for a magnetic disk reproduced by a magnetoresistive head. Of manufacturing glass substrates for use.

A ninth aspect of the present invention is a method for manufacturing an information recording medium, wherein at least a recording layer is formed on a glass substrate obtained by the method for manufacturing a glass substrate for an information recording medium according to any one of the first to eighth aspects.

A tenth aspect of the present invention is the method for manufacturing an information recording medium according to the ninth aspect, wherein the recording layer is a magnetic layer.

The particles removed by the present invention include:
There are metal pieces such as fine iron powder, metal oxide pieces, glass chips, oil mist, silicon dust, fibers and the like. In essence, these sizes are intended to be used during the use of the information recording medium or in the manufacturing process. The preferred size range is
It is from 0.3 microns to less than 100 microns.
There is an effect even if the size is restricted to 1 micron to 100 microns. Even if the size is restricted to 10 to 100 microns, it can be used practically. .

As a method for increasing the cleanliness of particles, a method of covering dust-producing parts such as manufacturing equipment and construction equipment with a dustproof cloth, or a method using a clean booth system or a clean room system to achieve a predetermined cleanliness degree. In a controlled room, a cleaning step after final polishing, a chemical strengthening step, a cleaning step, a drying step, an inspection step, and a glass substrate packaging and packing step may be performed.

The step of increasing the cleanliness of the particles may be at least one of a cleaning step after final polishing, a chemical strengthening step, a cleaning step, a drying step, an inspection step, and a glass substrate packaging or packing step. It is better to do.
It is particularly effective to improve the cleanliness of the particles in the steps from the final polishing step to the chemical strengthening step. If particles adhere to the glass substrate at the stage of chemical strengthening, the part of the glass substrate under the particles will not be chemically strengthened, or the particles on the glass base will be strengthened by the chemical strengthening salt. This is because they adhere to the glass substrate and cannot be easily removed by washing in a later step. Therefore, the cleanliness of the glass substrate during and before the chemical strengthening step is particularly important.

The type, size, thickness and the like of the glass substrate are not particularly limited. Examples of the material of the glass substrate include aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, chain silicate glass, and glass ceramics such as crystallized glass. Can be

As the aluminosilicate glass, Si
O2: 62 to 75% by weight, Al2 O3: 5 to 15% by weight, L
i2O: 4 to 10% by weight, Na2O: 4 to 12% by weight, Z
rO2: contains 5.5 to 15% by weight as a main component, and the weight ratio of Na2O / ZrO2 is 0.5 to 2.0;
Chemical strengthening glass having a weight ratio of l2O3 / ZrO2 of 0.4 to 2.5 is preferred.

In order to eliminate projections on the surface of the glass substrate caused by undissolved ZrO 2, 57% to 74% of SiO 2, 0% to 2.8% of ZnO 2,
Al2O3 3-15%, LiO2 7-16%, Na2O
It is preferable to use glass for chemical strengthening containing 4 to 14%. The aluminosilicate glass or the like having such a composition increases the transverse rupture strength by chemical strengthening, has a deep compressive stress layer, and is excellent in Knoop hardness.

In the present invention, the surface of the glass substrate can be subjected to a chemical strengthening treatment by a low-temperature ion exchange method for the purpose of improving impact resistance, vibration resistance and the like.

The chemical strengthening method is not particularly limited as long as it is a conventionally known chemical strengthening method. For example, a low-temperature chemical strengthening method in which ion exchange is performed in a region not exceeding a transition temperature from the viewpoint of a glass transition point. Are preferred. Potassium nitrate,
Examples thereof include sodium nitrate, and a nitrate obtained by mixing them.

The glass substrate for an information recording medium according to the manufacturing method of the present invention can be used as a glass substrate for a magneto-optical disk which does not like fine particles, or as a disk substrate for an electro-optical disk such as an optical disk.

Next, the magnetic recording medium of the present invention will be described.

The magnetic recording medium of the present invention is obtained by forming at least a magnetic layer on the glass substrate for a magnetic recording medium of the present invention.

In the present invention, since particles that cause thermal asperity are not generated,
When manufacturing a magnetic recording medium by forming a magnetic layer etc. on a glass substrate, a convex part formed by particles that cause thermal asperity does not occur on the main surface of the glass substrate, at a higher level Head crash can be prevented. In particular, the function of the magnetoresistive head can be fully exploited for a magnetic recording medium that performs reproduction with the magnetoresistive head. In addition, the performance of a CoPt-based magnetic recording medium or the like that can be suitably used for a magnetoresistive head can be sufficiently brought out.

Similarly, on the recording / reproducing surface of the magnetic recording medium, no projection formed by particles causing thermal asperity does not occur, and head crash can be prevented at a higher level.

Further, there is no possibility that a particle such as a thermal asperity causes a defect in a film such as a magnetic layer to cause an error.

The magnetic recording medium usually has a predetermined flatness and surface roughness, and has an underlayer, a magnetic layer, a protective layer, It is manufactured by sequentially laminating a lubricating layer.

The underlayer in the magnetic recording medium of the present invention comprises:
It is selected according to the magnetic layer.

As the underlayer, for example, Cr, Mo, T
a, an underlayer made of at least one material selected from nonmagnetic metals such as Ti, W, V, B, and Al. In the case of a magnetic layer containing Co as a main component, it is preferable to use Cr alone or a Cr alloy from the viewpoint of improving magnetic properties. The underlayer is not limited to a single layer, and may have a multilayer structure in which the same or different layers are stacked. For example, Cr / Cr, Cr / CrMo, Cr / CrV, Cr
V / CrV, Al / Cr / CrMo, Al / Cr / C
r, a multilayer base layer of Al / Cr / CrV, Al / CrV / CrV and the like.

The material of the magnetic layer in the magnetic recording medium of the present invention is not particularly limited.

As the magnetic layer, for example, CoPt, CoCr, CoNi, CoNiCr, C
oCrTa, CoPtCr, CoNiPt, CoNi
CrPt, CoNiCrTa, CoCrTaPt, Co
A magnetic thin film such as CrPtSiO may be used. The magnetic layer is made of a non-magnetic film (for example, Cr, CrMo, Cr).
V, etc. to reduce noise (for example, CoPtCr / CrMo / CoPtCr, CoC
rTaPt / CrMo / CoCrTaPt).

As a magnetic layer corresponding to a magnetoresistive head (MR head) or a large magnetoresistive head (GMR head), Y, Si, rare earth elements, Hf, G
An impurity element selected from e, Sn, and Zn, or an element containing an oxide of these impurity elements is also included.

The magnetic layer has a structure in which magnetic particles such as Fe, Co, FeCo, and CoNiPt are dispersed in a nonmagnetic film made of ferrite, iron-rare earth, SiO2, BN, or the like. And the like. Further, the magnetic layer may have any of an inner surface type and a perpendicular type recording format.

The protective layer in the magnetic recording medium of the present invention is not particularly limited.

Examples of the protective layer include a Cr film, a Cr alloy film, a carbon film, a zirconia film, and a silica film. These protective films can be continuously formed with an underlayer, a magnetic layer, and the like by an in-line type sputtering apparatus. Also,
These protective films may have a single-layer structure or a multilayer structure composed of the same or different films.

In the present invention, another protective layer may be formed on the above protective layer or in place of the above protective layer. For example, in place of the above protective layer, colloidal silica fine particles are dispersed and applied to a Cr film after diluting tetraalkoxylan with an alcohol-based solvent, and then baked to form a silicon oxide (SiO2) film. May be.

The lubricating layer in the magnetic recording medium of the present invention is not particularly limited.

The lubricating layer is prepared, for example, by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a solvent such as freon, and applying it to the medium surface by dipping, spin coating, or spraying. It is formed by performing heat treatment.

[0044]

EXAMPLES The present invention will be described below more specifically based on examples.

Example 1 (1) Roughing Step First, a glass substrate made of aluminosilicate glass having a diameter of 96 mmφ and a thickness of 3 mm cut out from a sheet glass formed by a down-draw method with a grinding wheel was used.
Grinding with a relatively rough diamond wheel
It was molded to a diameter of 1.5 mm and a thickness of 1.5 mm. In this case, instead of the down-draw method, the molten glass may be directly pressed using an upper mold, a lower mold, and a body mold to obtain a disk-shaped glass body. Further, a float method may be used.

As the aluminosilicate glass, in terms of mol%, SiO 2 is 57 to 74%, ZnO 2 is 0 to 2.8%, Al 2 O 3 is 3 to 15%, and LiO 2 is 7 to 74%.
Glass for chemical strengthening containing 16% and 4 to 14% of Na2O as main components (for example, SiO2:
67.0%, ZnO2: 1.0%, Al2O3: 9.0%,
Glass for chemical strengthening containing 12.0% of LiO2 and 10.0% of Na2O as main components was used.

Next, both surfaces of the glass substrate were ground one by one with a diamond grindstone having a finer grain size than the grindstone. The load at this time was about 100 kg. As a result, the surface roughness of both surfaces of the glass substrate can be reduced to Rmax (JIS
B 0601) (about 10 μm).

Next, a hole is formed in the center of the glass substrate using a cylindrical grindstone, the outer peripheral end surface is also ground to a diameter of 95 mmφ, and then the outer peripheral end surface and the inner peripheral surface are subjected to predetermined chamfering. did. At this time, the surface roughness of the end face of the glass substrate was about 4 μm in Rmax.

(2) Mirror Finishing Process Next, the surface roughness of the end surface of the glass substrate is set to 1 μm by Rmax while rotating the glass substrate by brush polishing.
Polished to about 0.3 μm with Ra.

The surface of the glass substrate which had been subjected to the above-mentioned mirror polishing of the end face was washed with water.

(3) Sanding (Wrapping) Step Next, the glass substrate was sanded. This sanding step aims at improving dimensional accuracy and shape accuracy.
The sanding process was performed using a lapping device, and was performed twice while changing the grain size of the abrasive grains to # 400 and # 1000.

More specifically, first, the load L was set to about 100 kg using alumina abrasive grains having a grain size of # 400.
By rotating the internal rotation gear and the external rotation gear, both sides of the glass substrate housed in the carrier are surface-accurate 0-1 μm,
Lapping was performed to a surface roughness (Rmax) of about 6 μm.

Next, the particle size of the alumina abrasive grains was changed to # 1000.
Perform lapping instead of surface roughness (Rmax) 2μ
m.

The glass substrate that had been subjected to the sanding process was washed by sequentially immersing it in a washing bath of a neutral detergent and water.

(4) First Polishing Step Next, a first polishing step was performed. This first polishing step is intended to remove scratches and distortion remaining in the above sanding step, and was performed using a polishing apparatus.

More specifically, the first polishing step was carried out under the following polishing conditions using a hard polisher (cerium pad MHC15: manufactured by Speed Fam) as a polisher (polishing powder).

Polishing liquid: cerium oxide + water Load: 300 g / cm ² (L = 238 kg) Polishing time: 15 minutes Removal amount: 30 μm Lower platen rotation speed: 40 rpm Upper platen rotation speed: 35 rpm Gear rotation speed in the inner part: 14 rpm Outer gear rotation speed: 29 rpm

After the first polishing step, the glass substrate is
Immerse in each washing tank of neutral detergent, pure water, pure water, IPA (isopropyl alcohol), IPA (steam drying) sequentially,
Washed.

(5) Second Polishing Step Next, using the polishing apparatus used in the first polishing step, the polisher was changed from a hard polisher to a soft polisher (Polyak: manufactured by Speed Fam), and the second polishing step was performed. Carried out. The polishing conditions were the same as in the first polishing step, except that the load was 100 g / cm ² , the polishing time was 5 minutes, and the removal amount was 5 μm.

The steps after the second polishing step were performed in an atmosphere in which air filtered by a clean booth was circulated. Specifically, in the environment where the air cleaning degree is 800 particles / cubic foot meter of particles having a size of 2 to 4 microns, cleaning after the second polishing step, chemical strengthening, chemical strengthening treatment solution cleaning step, All steps of vapor drying and substrate packaging were performed.

First, the glass substrate after the second polishing step is sequentially immersed in each of washing tanks of a neutral detergent, a neutral detergent, pure water, pure water, IPA (isopropyl alcohol) and IPA (steam drying). , Washed. In addition, ultrasonic waves were applied to each cleaning tank.

(6) Chemical Strengthening Step Next, the glass substrate after the above-mentioned grinding, polishing and cleaning steps was subjected to chemical strengthening. Chemical strengthening is performed using potassium nitrate (60
%) And sodium nitrate (40%) were prepared, and the solution was heated to 400 ° C.
The cleaning was performed by immersing the cleaned glass substrate preheated to 00 ° C. for about 3 hours. In this immersion, in order to chemically strengthen the entire surface of the glass substrate, the immersion was performed in a state where a plurality of glass substrates were housed in a holder so as to be held at end faces.

As described above, by performing the immersion treatment in the chemical strengthening solution, the lithium ions and the sodium ions on the surface layer of the glass substrate become the sodium ions and the sodium ions in the chemical strengthening solution.
The glass substrate is strengthened by being respectively substituted by potassium ions.

The thickness of the compressive stress layer formed on the surface of the glass substrate was about 100 to 200 μm.

The glass substrate that has been chemically strengthened is
It was immersed in a water bath at a temperature of 10 ° C. and rapidly cooled and maintained for about 10 minutes. Thereafter, the product was dried by vapor, surface inspection was performed, and the product was packed in a case to complete the production.

The quenched glass substrate is heated to about 40 ° C.
The substrate was immersed in heated sulfuric acid and washed while applying ultrasonic waves.

The surface roughness Ra of the main surface of the glass substrate obtained through the above steps was 0.5 to 1 nm.

Further, when the glass surface was subjected to a close inspection, no particles causing thermal asperity were found. Specifically, a glass substrate having a diameter of 65 mm was left for 30 minutes, and then inspected with a laser scattering type surface defect inspection apparatus. As a result, it was found that 30 or less 1 micron particles were present. It is preferable that particles of 5 μm or more are removed from the glass substrate. Incidentally, in the conventional method, there were several hundred particles having a size of 10 to 100 μm, mainly the fine iron powder.

(7) Magnetic Disk Manufacturing Process A texture layer, a Cr underlayer, and a CrMo underlayer are formed on both surfaces of a glass substrate for a magnetic disk obtained through the above-described steps by using an in-line type sputtering apparatus by sputtering AlN. , A CoPtCrTa magnetic layer and a C protective layer were sequentially formed to obtain a magnetic disk.

A glide test was performed on the obtained magnetic disk. As a result, no hit (the head touches a projection on the magnetic disk surface) or crash (the head collides with the projection on the magnetic disk surface) was not recognized. . In addition, it was confirmed that no defect was generated in the film such as the magnetic layer due to the particles causing the thermal asperity. As described above, in this example, a disk could be manufactured magnetically with a high yield.

A reproduction test was performed on the magnetic disk of the present embodiment after the glide test with a magnetoresistive head. However, a malfunction of reproduction due to thermal asperity was observed for all of a plurality of samples (500 sheets). I was not able to admit.

Example 2 On both sides of the glass substrate for magnetic disk obtained in Example 1, Al (film thickness 50 Å) / Cr (100
0 Å / CrMo (100 Å), CoPtCr (120 Å) / CrMo (50 Å) / Co
A magnetic layer made of PtCr (120 Å),
A Cr (50 Å) protective layer was formed by an in-line type sputtering apparatus.

The above substrate is immersed in an organic silicon compound solution (a mixed solution of water, IPA and tetraethoxysilane) in which silica fine particles (particle size: 100 Å) are dispersed,
A protective layer having a texture function of SiO2 is formed by firing, and a lubricating layer is formed on the protective layer by dipping with a lubricant of perfluoropolyether to form a magnetic disk for an MR head. I got

When a glide test was conducted on the obtained magnetic disk, no hit or crash was recognized. It was also confirmed that no defect occurred in the film such as the magnetic layer. Furthermore, as a result of a reproduction test using a magnetoresistive head, no reproduction malfunction due to thermal asperity was recognized. In addition, there was no subsequent thermal asperity generated during use after a good magnetic disk was mounted on the magnetic disk driver.

Example 3 The underlayer was made of Al / Cr / Cr, and the magnetic layer was made of CoNiCr.
A magnetic disk for a thin film head was obtained in the same manner as in Examples 1 and 2, except that Ta was used.

It was confirmed that the above magnetic disk was the same as in the above embodiment.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not necessarily limited to the above embodiments.

For example, the type of the glass substrate and the type of the magnetic layer are not limited to those of the embodiment.

[0079]

As described above, according to the present invention, since the production of the glass substrate after the final polishing is performed in a clean atmosphere, particles which cause head crash and thermal asperity are generated. Therefore, it is possible to prevent a decrease in the reproduction function due to thermal asperity.

Further, it is possible to avoid a defect caused by particles which cause thermal asperity, and to obtain a higher quality magnetic recording medium with a higher yield.

Claims (10)

[Claims] A step of polishing a main surface of a glass substrate;
By contacting the glass substrate with the chemical strengthening treatment solution,
A chemical strengthening step of strengthening the glass substrate by replacing some of the ions contained in the glass substrate with ions in a processing solution having a larger ion diameter than the ions. In the above, at least one of a cleaning step after the final polishing step, the chemical strengthening step, a cleaning step of the chemical strengthening treatment liquid, a drying step, an inspection step, and a packaging step of packaging the information recording medium glass substrate or a container. Is carried out in an atmosphere in which filtered clean air is circulated so that particles do not adhere to the glass substrate. 2. A step of polishing a main surface of a glass substrate,
By contacting the glass substrate with the chemical strengthening treatment solution,
A chemical strengthening step of strengthening the glass substrate by replacing some of the ions contained in the glass substrate with ions in a processing solution having a larger ion diameter than the ions. In the above, at least one of a cleaning step after the final polishing step, the chemical strengthening step, a cleaning step of the chemical strengthening treatment liquid, a drying step, an inspection step, and a packaging step of packaging the information recording medium glass substrate or a container. And particles having a size of 0.3 to 100 microns are 10
A method for producing a glass substrate for an information recording medium, wherein the method is performed in an environment having a cleanness of not more than 00 pieces / cubic foot-meter. 3. The cleanness of clean air is from 0.3 to 10
2. The method for producing a glass substrate for an information recording medium according to claim 1, wherein the cleanliness of the particles having a size of 0 micron is 1000 particles / cubic foot / meter or less. 4. The method for producing a glass substrate for an information recording medium according to claim 1, wherein the cleanliness of the particles is 100 particles / cubic foot-meter or less. 5. The method for producing a glass substrate for an information recording medium according to claim 1, wherein the cleanliness of the particles is 50 particles / cubic foot-meter or less. 6. The cleaning after the final polishing step and the chemical treatment of the glass substrate under the environment of particle cleanliness specified in the method of manufacturing a glass substrate for an information recording medium according to claim 1. A method for manufacturing an information recording medium, comprising strengthening. 7. The method for producing a glass substrate for an information recording medium according to claim 1, wherein the glass substrate for an information recording medium is a glass substrate for a magnetic disk. 8. The method for manufacturing a glass substrate for an information recording medium according to claim 7, wherein the glass substrate for a magnetic disk is a glass substrate used for a magnetic disk reproduced by a magnetoresistive head. 9. A method for manufacturing an information recording medium, comprising forming at least a recording layer on a glass substrate obtained by the method for manufacturing a glass substrate for an information recording medium according to claim 1. 10. The method according to claim 9, wherein the recording layer is a magnetic layer.