JP5353715B2 - Packaging method of glass substrate for information recording medium - Google Patents

Abstract

Disclosed is a method for packaging a glass substrate, for an information recording medium, that does not newly cause adherence of foreign matter on the surface of the glass substrate during storage or transportation. The method comprises a hermetically sealing step of hermetically sealing an opening of a packaging member so that a support, which holds a glass substrate for an information recording medium, is hermetically sealed in a space containing a lower alcohol.

Description

The present invention relates to a packaging how the glass substrate for an information recording medium.

  Conventionally, as a magnetic disk substrate, an aluminum alloy is used for a stationary type such as a desktop computer or a server, and a glass substrate is generally used for a portable type such as a notebook computer or a mobile computer. However, since an aluminum alloy is easily deformed and has insufficient hardness, it cannot be said that a substrate using the aluminum alloy has sufficient smoothness on the surface of the substrate after polishing. In addition, a substrate using an aluminum alloy has a problem that the magnetic film easily peels from the substrate when the head contacts the magnetic disk. Therefore, glass substrates with little deformation, good smoothness, and high mechanical strength are expected to be widely used not only for portable devices but also for stationary devices and other household information devices in the future. ing.

  By the way, the recording capacity of the magnetic disk can be increased as the distance between the magnetic head and the surface of the magnetic disk is decreased. However, if the distance between the magnetic head and the surface of the magnetic disk is reduced, if the surface of the glass substrate has abnormal protrusions or foreign matter adheres to it, the magnetic head may collide with the protrusions or foreign objects on the magnetic disk. Arise. Therefore, in order to reduce the distance between the magnetic head and the magnetic disk surface and increase the recording capacity of the magnetic disk, it is necessary to eliminate abnormal protrusions and foreign matter adhesion on the surface of the glass substrate. Therefore, the glass substrate surface is smoothed by a polishing process (also referred to as a polishing process) in which the glass substrate surface is polished with an abrasive such as cerium oxide. For example, the surface roughness is Rmax from 2 nm to 6 nm, and the arithmetic average roughness Ra. Is smoothed to a level of 0.2 nm to 0.4 nm. Thereafter, the surface is cleaned with an isopropyl alcohol or ultrapure water in a cleaning process.

  However, the glass substrate surface thus ultra-cleaned is in an active state in which foreign substances such as particle dust in the atmosphere are easily adsorbed. For this reason, it has been proposed to perform the polishing process and later in a clean room, but when the manufacturing equipment for depositing a magnetic film or the like on the glass substrate surface to make a magnetic disk is away from the manufacturing location of the glass substrate, it was manufactured. When shipping a glass substrate to a customer, the glass substrate needs to be packed, stored and transported.

When storing and transporting the glass substrate, in Patent Document 1, the holder holding a certain number of glass substrates is vacuum packed using a laminate film so that no foreign matter adheres to the glass substrate surface. A method of storing and transporting as a package has been proposed.
JP 2006-151435 A

  However, even when a magnetic disk is manufactured using a glass substrate that has been packed, stored and transported using the method of Patent Document 1, the magnetic head collides with foreign matter on the surface of the magnetic disk, causing a head crash. There was a problem that the yield did not increase.

  When investigating the cause of foreign matter adhesion on the glass substrate surface, there is no foreign matter at a level that causes head crashes on the glass substrate surface before packing, but head crashes on the glass substrate surface that has been unpacked after packing and transportation. A new level of foreign matter was observed. From this, even if the method of Patent Document 1 is used, it can be seen that foreign matter adheres to the surface of the glass substrate in the state of the package.

  Therefore, the present invention has been made in view of the situation as described above, and a first object thereof is a manufacturing facility that manufactures a magnetic recording medium by packing, storing, and transporting a glass substrate for an information recording medium. A method for packing a glass substrate for an information recording medium, a glass substrate packing body for an information recording medium, and a glass substrate for an information recording medium, in which new foreign substances do not adhere to the surface of the glass substrate during storage and transportation even after delivery. It is in providing the manufacturing method of.

  A second object of the present invention is to produce a magnetic recording medium having good characteristics by using a glass substrate for information recording medium that has been conveyed by such a glass substrate package for information recording medium. Another object of the present invention is to provide a method for manufacturing a magnetic recording medium.

  Said subject is solved by the following structures.

1.
A holding step of holding the glass substrate for information recording medium on a holder;
A packaging step of packaging the holding body holding the glass substrate for information recording medium with a packaging member;
To seal the glass substrate for the information recording medium held by the holding member in a space containing a lower alcohol, have a, a sealing step of sealing the opening of said covering member,
In the sealing step, the lower alcohol is adjusted so that the concentration of the lower alcohol in the atmosphere of the space in which the holder holding the glass substrate for information recording medium inside the packaging member is sealed after sealing is in the range of 3 to 100 ppm. after filling the gas concentration is adjusted to the space inside the packaging member is performed by sealing the opening of the covering member, a concentration of a lower alcohol of the space after sealing is Ru 3~100ppm der A method for packing a glass substrate for an information recording medium.

2 .
2. The method for packing a glass substrate for an information recording medium according to the item 1, wherein the lower alcohol is at least one selected from the group consisting of methanol, ethanol, propanol, butanol, and pentanol.

3 .
3. The method for packing a glass substrate for an information recording medium according to 1 or 2 , wherein, in the sealing step, the pressure in a space in which the holder holding the glass substrate for the information recording medium is sealed is reduced.

4 .
4. The method for packing a glass substrate for an information recording medium according to 3 above, wherein the atmospheric pressure is reduced to a range of 200 to 600 hPa.

5 .
5. The method for packing a glass substrate for an information recording medium according to any one of 1 to 4 , wherein the sealing step is performed in a working chamber in which the concentration of the lower alcohol in the atmosphere is adjusted.

According to the packaging method and packaging body for a glass substrate for information recording media of the present invention, foreign matter floating inside the packaging body or foreign matter generated inside the packaging body during transportation is attached to the surface of the glass substrate during storage and transportation. The glass substrate can be delivered to a manufacturing facility for manufacturing a magnetic recording medium in an ultra-clean state after washing without wearing. Therefore, when manufacturing a magnetic recording medium using the glass substrate for information recording media packed by such a packing method, it is possible to manufacture a magnetic recording medium in which the occurrence of head crashes is suppressed.

It is a figure which shows the whole structure of the glass substrate for information recording media. It is a figure which shows the example of the magnetic recording medium provided with the magnetic film on the front main surface of the glass substrate for information recording media. It is a manufacturing process figure explaining the process in manufacture of the glass substrate for information recording media. It is process drawing for demonstrating the process of the packing method which concerns on this invention. It is a schematic diagram which shows an example of a scrub cleaning apparatus. It is the schematic which shows the holding body for hold | maintaining a glass substrate. It is the side view which looked at the state which stored the glass substrate in the storage container from the connecting plate side. It is the schematic which shows the glass substrate package for information recording media which concerns on this invention.

Explanation of symbols

1 Glass substrate for information recording media (glass substrate)
2 Magnetic film 5 Hole 7a Glass substrate surface (front main surface)
7b Glass substrate surface (back main surface)
10t outer peripheral end surface 20t inner peripheral end surface 10a, 10b sponge roller 20 nozzle 30 cleaning liquid 60 storage container 61 upper lid 63 fixing member 64 holding plate 65, 66 side plate 67, 68 connecting plate 69 bottom plate 70 rib 71 groove 200 packaging member 201 opening 300 information Glass substrate package for recording medium 600 Holder D Magnetic disk

  Although the present invention will be described based on the illustrated embodiment, the present invention is not limited to the embodiment.

  FIG. 1 shows the overall configuration of a glass substrate for information recording medium (hereinafter also referred to as a glass substrate) 1. As shown in FIG. 1, the glass substrate 1 has a donut-like disk shape with a hole 5 formed in the center. 10t is an outer peripheral end surface, 20t is an inner peripheral end surface, 7a and 7b are glass substrate surfaces, 7a is a front main surface, and 7b is a back main surface. FIG. 2 is a diagram showing an example of a magnetic recording medium (hereinafter also referred to as a magnetic disk) D provided with a magnetic film 2 on the front main surface 7a of the glass substrate 1 shown in FIG. The magnetic film 2 can also be provided on the back main surface 7b.

  FIG. 3 shows a manufacturing process diagram of an embodiment of a method for manufacturing a glass substrate for an information recording medium according to the present invention. The glass melted in the glass melting step is formed into a disk shape in the press molding step, and after forming a hole in the center in the coring step, the surface is polished in the first lapping step. After grinding to a predetermined inner / outer diameter and polishing the end face, the surface is re-polished in the second lapping step. Next, after chemically strengthening the glass substrate surface, the glass substrate surface is inspected through a polishing process and a cleaning process, packed in a packing process, and shipped as a glass substrate package for an information recording medium.

  Next, the glass substrate package for the information recording medium is conveyed, and the glass substrate for the information recording medium is taken out from the glass substrate package for the information recording medium at the shipping destination, and at least a magnetic layer is formed on the surface of the glass substrate for the information recording medium. A magnetic recording medium is manufactured by forming

  A method for packing a glass substrate for an information recording medium according to the present invention will be described with reference to FIG. FIG. 4 is an exploded process diagram of the packing process. The glass substrate that has finished the cleaning process of FIG. 3 is inspected for scratches and foreign matter on the surface of the glass substrate in the inspection process, and then holds a predetermined number of glass substrates on the holder as a holding process. Next, this holding body is packaged by a packaging member such as a laminate film in a packaging process. In the sealing step, the opening of the packaging member is sealed and packed. In this packaging method, lower alcohol is contained in the space inside the sealed packaging member. By containing the lower alcohol, a thin layer in which the lower alcohol component is adsorbed is formed on the surface of the glass substrate inside the package. When such a thin layer adsorbing a lower alcohol component is formed on the surface of the glass substrate, the activity of the glass substrate surface that has been in an active state after the cleaning process is lowered, and adhesion of foreign substances in the atmosphere is suppressed. Therefore, foreign matter floating inside the package and foreign matter generated inside the package during transportation are less likely to adhere to the glass substrate surface during storage and transportation, and the magnetic recording medium manufacturing facility maintains a clean surface. Can be delivered to.

  The concentration of the lower alcohol contained is preferably 3 to 100 ppm. When the concentration of the lower alcohol contained in the space inside the sealed packaging member is less than 3 ppm, the generation of the adsorption layer of the alcohol component becomes somewhat insufficient, and the effect of suppressing the adhesion of foreign matters is reduced. Also, if the concentration of the lower alcohol exceeds 100 ppm, the alcohol adsorbing layer is not uniformly formed, resulting in uneven drying on the substrate surface after removal, and aggregation of foreign matter occurs in the uneven drying portion, resulting in a problem size. There is a possibility.

  The lower alcohol is preferably at least one selected from the group consisting of methanol, ethanol, propanol, butanol and pentanol. These lower alcohols have a very high affinity with the glass surface and tend to form a thin film layer on the glass surface. Since the lower alcohol can be easily detached from the glass surface by heating, it can be easily removed before forming the magnetic recording layer, and a high-quality magnetic recording medium can be produced.

  In the sealing step in the method for packing an information recording medium glass substrate according to the present invention, it is preferable to reduce the pressure of the space in which the holder holding the information recording medium glass substrate is sealed. By reducing the pressure, foreign matter in the space inside the packaging member can be removed to some extent, which is preferable.

  Moreover, it is preferable to reduce the pressure in the space inside the packaging member to a range of 200 to 600 hPa. When the pressure is less than 200 hPa, pressure is applied to the package due to atmospheric pressure, and foreign matter is generated inside due to friction between the constituent members, friction, and the like, and easily adheres to the substrate surface. Moreover, in order to endure atmospheric pressure, it is necessary to raise the intensity | strength of a package, and it becomes unfavorable because the weight increases and the manufacturing cost increases. On the other hand, if it exceeds 600 hPa, a great effect cannot be obtained in terms of removing foreign matters inside the packaging member, which is not preferable.

  Further, in the method for packing an information recording medium glass substrate according to the present invention, the sealing step of sealing the opening of the packaging member is such that the holder holding the glass substrate for information recording medium inside the packaging member is sealed after the sealing. It is preferable to seal the space after filling the space inside the packaging member with a gas whose concentration of the lower alcohol is adjusted so that the concentration of the lower alcohol in the space to be in the range of 3 to 100 ppm. The pre-adjusted gas lower alcohol concentration P1 ppm is that the gas pressure to be filled is XhPa, the pressure inside the sealed packaging member is YhPa, and the lower alcohol you want to contain in the sealed space inside the packaging member When the concentration of P2 is P2 ppm, it can be calculated by P1 = P2 × (X / Y).

  The filling method for filling the space inside the packaging member with the gas whose concentration of lower alcohol has been adjusted in advance is not particularly limited, but at least the sealing step for sealing the opening of the packaging member has a lower alcohol concentration in the atmosphere. It is preferably performed in a controlled working chamber. As the concentration of the lower alcohol in this atmosphere, the lower alcohol concentration P1 calculated by the above formula is used.

  By performing the sealing step in such an atmosphere, the concentration can be adjusted to a predetermined concentration without using a filling means that fills the space inside the packaging member with a gas whose concentration of lower alcohol has been adjusted in advance. . Moreover, it is preferable that the work room is a clean room. In this way, by sealing the packaging member in a clean room in which the concentration of the lower alcohol is adjusted in advance, the gas contained in the space inside the packaging member can be easily within a predetermined lower alcohol concentration range, It is possible to suppress the entry of foreign matter into the space inside the packaging member.

  As another method of filling the space inside the packaging member with a gas whose concentration of lower alcohol has been adjusted in advance, for example, a holding body that holds a glass substrate for an information recording medium packaged by a packaging member in a decompression chamber. After that, the inside of the decompression chamber is decompressed, and after that, a gas (for example, air) in which the concentration of the lower alcohol is adjusted in advance is introduced and adjusted to a predetermined pressure, and then the opening of the packaging member is sealed. Also good. Alternatively, a lower alcohol having a predetermined concentration may be contained in a gas heavier than air (for example, nitrogen gas), filled with the gas with the opening of the packaging member facing upward, and then the opening may be sealed.

The manufacturing method of the glass substrate for information recording media will be described in more detail with reference to the manufacturing process diagram of FIG.
(Glass melting process)
First, a glass material is melted as a glass melting step. As a material of the glass substrate, for example, soda lime glass mainly composed of SiO ₂ , Na ₂ O, CaO; mainly composed of SiO ₂ , Al ₂ O ₃ , R ₂ O (R = K, Na, Li) Aluminosilicate glass; borosilicate glass; Li ₂ O—SiO ₂ glass; Li ₂ O—Al ₂ O ₃ —SiO ₂ glass; R′O—Al ₂ O ₃ —SiO ₂ glass (R ′ = Mg) , Ca, Sr, Ba) and the like can be used. Among these, aluminosilicate glass and borosilicate glass are particularly preferable because they are excellent in impact resistance and vibration resistance.
(Press molding process)
Next, as a press molding process, molten glass is poured into the lower mold and press molded with the upper mold to obtain a disk-shaped glass substrate precursor. The disk-shaped glass substrate precursor may be produced by cutting a sheet glass formed by, for example, a downdraw method or a float method with a grinding stone, without using press molding.

There is no limitation on the size of the glass substrate. For example, there are glass substrates of various sizes such as an outer diameter of 2.5 inches, 1.8 inches, 1 inch, and 0.8 inches. Further, the thickness of the glass substrate is not limited, and there are glass substrates having various thicknesses such as 2 mm, 1 mm, and 0.63 mm.
(Coring process)
The press-molded glass substrate precursor is pierced at the center by a coring process. In the drilling, a hole is drilled in the center by grinding with a core drill or the like equipped with a diamond grindstone or the like in the cutter part.
(First lapping process)
Next, as a first lapping step, both surfaces of the glass substrate are polished to preliminarily adjust the overall shape of the glass substrate, that is, the parallelism, flatness and thickness of the glass substrate.
(Inner and outer diameter precision machining process)
Next, as the inner / outer diameter processing step, the inner and outer diameters are processed by grinding the outer peripheral end surface and the inner peripheral end surface of the glass substrate with a grinding wheel such as a drum-shaped diamond.
(End polishing process)
A plurality of glass substrates that have undergone the inner and outer diameter processing steps are stacked and laminated, and in this state, the outer peripheral surface and the inner peripheral surface are polished using an end surface polishing machine.
(Second wrapping process)
Further, both surfaces of the glass substrate are polished again to finely adjust the parallelism, flatness and thickness of the glass substrate.

  As the polishing machine for polishing the front and back surfaces of the glass substrate in the first and second lapping processes, a known polishing machine called a double-side polishing machine can be used. The double-side polishing machine includes a disk-shaped upper surface plate and a lower surface plate that are arranged vertically so as to be parallel to each other, and rotate in opposite directions. A plurality of diamond pellets for polishing the main surface of the glass substrate are attached to the opposing surfaces of the upper and lower surface plates. Between the upper and lower surface plates, there are a plurality of carriers that rotate in combination with an internal gear provided in an annular shape on the outer periphery of the lower surface plate and a sun gear provided around the rotation axis of the lower surface plate. The carrier is provided with a plurality of holes, and a glass substrate is fitted into the holes. The upper and lower surface plates, the internal gear and the sun gear can be operated by separate driving.

  The polishing operation of the polishing machine is such that the upper and lower surface plates rotate in opposite directions, and the carrier sandwiched between the surface plates via the diamond pellets rotates with the surface plate holding a plurality of glass substrates. Revolves in the same direction as the lower surface plate with respect to the center of rotation. In such an operating polishing machine, the glass substrate can be polished by supplying a grinding liquid between the upper surface plate and the glass substrate, and the lower surface plate and the glass substrate.

When using this double-side polishing machine, the load on the surface plate applied to the glass substrate and the rotation speed of the surface plate are adjusted as appropriate according to the desired polishing state. The load in the first and second lapping steps is preferably 60 g / cm ² to 120 g / cm ² . Further, the rotation speed of the surface plate is preferably about 10 to 30 rpm, and the rotation speed of the upper surface plate is preferably about 30 to 40% slower than the lower surface rotation speed. If the load on the surface plate is increased and the rotation speed of the surface plate is increased, the amount of polishing increases, but if the load is increased too much, the surface roughness will not be good, and if the rotation speed is too high, the flatness will be good. Not. Further, when the load is small and the rotation speed of the surface plate is slow, the polishing amount is small and the production efficiency is lowered.

  When the second lapping process is completed, defects such as large waviness, chipping and cracks are removed, and the surface roughness of the main surface of the glass substrate is about 2 μm to 4 μm for Rmax and about 0.2 μm to 0.4 μm for Ra. Is preferable. By setting it as such a surface state, it can polish efficiently by a 1st polishing process through the following chemical strengthening process process.

  In the first lapping step, roughly large undulations, chips and cracks are efficiently removed so that the second lapping step can be performed efficiently. For this reason, it is preferable to use diamond pellets of # 800 mesh to # 1200 mesh which are coarser than # 1300 mesh to # 1700 mesh used in the second wrapping. The surface roughness at the time when the first lapping step is completed is preferably such that Rmax is 4 μm to 8 μm and Ra is about 0.4 μm to 0.8 μm.

  In addition, as a method for polishing the glass substrate, a method in which a pad is attached to the polishing surfaces of the upper and lower surface plates and a polishing liquid containing an abrasive is supplied for polishing can be used. Examples of the abrasive include cerium oxide, zirconium oxide, aluminum oxide, manganese oxide, colloidal silica, and diamond. These are dispersed in water and used as a slurry. The pad is divided into a hard pad and a soft pad, but can be appropriately selected and used as necessary. Examples of the hard pad include pads made of hard velor, urethane foam, pitch-containing suede, etc., and examples of the soft pad include pads made of suede, velor, etc.

  A polishing method using a pad and a polishing agent can cope with rough polishing to precision polishing by changing the particle size of the polishing agent and the type of the pad. Therefore, in the first lapping step and the second lapping step, the abrasive material, abrasive particle size, and pad are appropriately combined so that the above-mentioned surface roughness can be obtained by efficiently removing large undulations, chips, cracks, etc. Can respond.

  Moreover, it is preferable to perform the washing | cleaning process for removing the abrasive | polishing agent and glass powder which remained on the surface of the glass substrate after the 1st and 2nd lapping process.

It should be noted that the polishing machines used in the first lapping process and the second lapping process have the same configuration, but it is preferable to perform polishing using different polishing machines prepared exclusively for the respective processes. This is because the dedicated diamond pellets are pasted, so that the replacement is a large-scale operation, and complicated operations such as resetting the polishing conditions are required, resulting in a reduction in manufacturing efficiency.
(Chemical strengthening process)
Next to the second lapping step, as a chemical strengthening treatment step, the glass substrate is immersed in a chemical strengthening solution to form a chemical strengthening layer on the glass substrate. By forming the chemical strengthening layer, impact resistance, vibration resistance, heat resistance and the like can be improved.

  In the chemical strengthening process, by immersing the glass substrate in a heated chemical strengthening solution, alkali metal ions such as lithium ions and sodium ions contained in the glass substrate are converted into alkali metal ions such as potassium ions having a larger ion radius. It is carried out by the ion exchange method of substituting. Compressive stress is generated in the ion-exchanged region due to the distortion caused by the difference in ion radius, and the surface of the glass substrate is strengthened.

  There is no restriction | limiting in particular in a chemical strengthening process liquid, A well-known chemical strengthening process liquid can be used. In general, a molten salt containing potassium ions or a molten salt containing potassium ions and sodium ions is generally used. Examples of the molten salt containing potassium ions and sodium ions include potassium and sodium nitrates, carbonates, sulfates, and mixed molten salts thereof. Among these, from the viewpoint that the melting point is low and deformation of the glass substrate can be prevented, it is preferable to use nitrate.

  The chemical strengthening treatment liquid is heated to a temperature higher than the temperature at which the above components melt. On the other hand, when the heating temperature of the chemical strengthening treatment liquid is too high, the temperature of the glass substrate is excessively increased, and the glass substrate may be deformed. For this reason, the heating temperature of the chemical strengthening treatment liquid is preferably lower than the glass transition point (Tg) of the glass substrate, more preferably lower than the glass transition point −50 ° C.

  In addition, in order to prevent the occurrence of cracks and fine cracks in the glass substrate due to thermal shock when immersed in the heated chemical strengthening treatment liquid, the glass substrate is placed in a preheating tank prior to immersion in the chemical strengthening treatment liquid. You may have the preheating process heated to predetermined temperature.

  The thickness of the chemically strengthened layer is preferably in the range of about 5 μm to 15 μm in view of improving the strength of the glass substrate and shortening the time of the polishing process. When the thickness of the reinforcing layer is within this range, a glass substrate having good impact resistance, which is flatness and mechanical strength, can be obtained.

The shapes of the outer peripheral edge portions of the front main surface 7a and the back main surface 7b after the chemical strengthening treatment step are almost the same as those before the chemical strengthening treatment step, and the chemical strengthening layer of about 5 μm to 15 μm is formed on the entire surface of the glass substrate. It is in a state of being placed almost uniformly.
(Polishing process)
Next, a polishing process is performed.

  In the polishing process, the surface of the glass substrate is precisely finished, and the shape of the outer peripheral end of the main surface is polished to a predetermined shape. The polishing step may be one step, but two steps are preferable.

  First, in the first polishing step, the surface roughness is improved and the shape of the present invention is finally efficiently improved so that the surface roughness finally required in the second polishing step can be efficiently obtained. Polishing can be obtained.

  The polishing method uses a polishing machine having the same configuration as the polishing machine used in the first and second lapping processes except that a pad and a polishing liquid are used instead of the diamond pellets and the grinding liquid used in the lapping process.

  The pad is preferably a hard pad having a hardness A of about 80 to 90, for example, urethane foam. When the pad hardness becomes soft due to heat generated by polishing, the shape change of the polished surface increases, so it is preferable to use a hard pad. The abrasive is preferably used in the form of a slurry by dispersing cerium oxide or the like having a particle size of 0.6 to 2.5 μm in water. The mixing ratio of water and abrasive is preferably about 1: 9 to 3: 7.

The load on the glass substrate by the surface plate is preferably 90 g / cm ² to 110 g / cm ² . The load applied to the glass substrate by the surface plate greatly affects the shape of the outer peripheral edge. When the load is increased, the inner side of the outer peripheral end portion tends to decrease and increase toward the outer side. Further, when the load is reduced, the outer peripheral end portion tends to become close to a plane and the surface sagging increases. The load can be determined while observing such a tendency.

  In order to improve the surface roughness, it is preferable that the rotation speed of the surface plate is 25 rpm to 50 rpm, and the rotation speed of the upper surface plate is 30% to 40% slower than the rotation speed of the lower surface plate.

  The polishing amount is preferably 30 μm to 40 μm depending on the above polishing conditions. If it is less than 30 μm, scratches and defects cannot be removed sufficiently. On the other hand, when it exceeds 40 μm, the surface roughness can be in the range of Rmax from 2 nm to 60 nm and Ra from 2 nm to 4 nm.

  The second polishing step is a step of further precisely polishing the surface of the glass substrate after the first polishing step. The pad used in the second polishing step is a soft pad having a hardness of about 65 to 80 (Asker-C) softer than the pad used in the first polishing step, and it is preferable to use, for example, urethane foam or suede. As the abrasive, cerium oxide or the like similar to that in the first polishing step can be used, but it is preferable to use an abrasive having a finer particle size and less variation in order to make the surface of the glass substrate smoother. An abrasive having an average particle diameter of 40 nm to 70 nm is dispersed in water to form a slurry and used as a polishing liquid. The mixing ratio of water and abrasive is preferably about 1: 9 to 3: 7.

The load on the glass substrate by the surface plate is preferably 90 g / cm ² to 110 g / cm ² . The load applied to the glass substrate by the surface plate greatly affects the shape of the outer peripheral edge as in the first polishing step, but the shape cannot be changed as efficiently as the first polishing step because the polishing rate is slow. The change in the shape of the outer peripheral end due to the load adjustment is the same as in the first polishing step, and when the load is increased, the inner side of the outer peripheral end tends to decrease and increase outward. Further, when the load is reduced, the outer peripheral end portion tends to become close to a plane and the surface sagging increases. In order to obtain the shape of the outer peripheral end, the load can be determined while observing such a tendency. The rotation speed of the surface plate is preferably 15 rpm to 35 rpm, and the rotation speed of the upper surface plate is preferably 30% to 40% slower than the rotation speed of the lower surface plate.

  As described above, the polishing conditions in the second polishing step are adjusted to obtain the shape of the outer peripheral edge, and the surface roughness is set to the range of Rmax from 2 nm to 6 nm and Ra from 0.2 nm to 0.4 nm. be able to.

The polishing amount is preferably 2 to 5 μm. When the polishing amount is within this range, minute defects such as minute roughness and undulation generated on the surface and minute scratches generated in the process so far can be efficiently removed.
(Washing process)
Next, after the polishing process is finished, the abrasive or foreign matter adhering to the glass substrate surface is cleaned in the cleaning process.

  The cleaning method is not particularly limited, but scrub cleaning will be described as an example.

  An example of the scrub cleaning apparatus is shown in FIG. The scrub cleaning apparatus of FIG. 5 sandwiches the glass substrate 1 at the nip portion between sponge rollers 10a and 10b, which are a pair of rotating rollers that are in pressure contact with each other. While dripping or spraying in the vicinity of the contact portion with the substrate 1, the pair of sponge rollers 10a and 10b are rotated in opposite directions, and at the same time, the glass substrate 1 is also rotated to clean the entire front and back surfaces of the glass substrate 1. To do. The rotation of the glass substrate 1 of the glass substrate 1 is driven by using one of the three support rollers 60 as a drive roller and the other two as driven rollers.

  As cleaning conditions for scrub cleaning, the rotation speeds of the two rollers 10a and 10b may be the same or different rotation speeds as required. The rotation speed of the roller is generally in the range of 100 to 1000 rpm, and more preferably in the range of 300 to 500 rpm. The rotation speed of the glass substrate G is generally in the range of 50 to 500 rpm, and more preferably in the range of 100 to 300 rpm. The supply rate of the cleaning liquid 30 is generally in the range of 10 to 1000 ml / min, more preferably in the range of 50 to 500 ml / min. The scrub cleaning time is generally in the range of 5 to 150 seconds, more preferably in the range of 10 to 100 seconds.

  As the scrub member, it is of course possible to use a conventionally known brush or pad in addition to the sponge roller shown in FIG.

  The sponge rollers 10a and 10b are not particularly limited. For example, cellulose sponge, polyvinyl alcohol sponge, urethane foam, ethylene-vinyl acetate copolymer (EVA) sponge, melamine foam, resin foam such as polyethylene foam, natural rubber, and natural rubber. (NR) sponge, chloroprene rubber (CR) sponge, ethylene-propylene rubber (EPDM) sponge, rubber-based sponge such as butadiene-acrylonitrile rubber sponge, and the like. Among these, the sponge portion is preferably made of a resin-based sponge, that is, made of resin as a main material. The resin is preferably a hydrophilic polymer such as polyurethane, melamine resin, cellulose, or polyvinyl alcohol. As a result, the ability to retain dirt and the like by the sponge part and the carrying ability of the cleaning liquid can be made more excellent, and the contact area with the glass substrate is increased, thereby further improving the ability to remove dirt. Further, hydrogen peroxide solution can be added to the sponge to improve the hydrophilicity of the sponge surface and enhance the ability to remove dirt.

  In addition, it is preferable that adjacent air holes communicate with each other in the sponge portion. As a result, a larger amount of dirt and cleaning liquid can be accommodated in the pores of the porous body constituting the sponge part, and the ability to retain dirt and the like by the sponge part and the ability to carry the cleaning liquid can be improved. .

  The porosity of the sponge portion is preferably 20 to 80%, and more preferably 30 to 70%. As a result, it is possible to make the sponge portion have desirable properties such as strength and elasticity, and more excellent ability to retain dirt and the like and support capability of the cleaning liquid by the sponge portion.

  The hardness of the sponge portion is preferably 30 to 70 °, and more preferably 35 to 55 °. Accordingly, it is possible to make the sponge portion have desirable properties such as strength and elasticity, and more excellent ability to retain dirt and the like by the sponge portion and support capability of the cleaning liquid. Here, the hardness means a value measured in accordance with JIS K7312.

  In order to effectively remove the abrasive or foreign matter on the surface of the glass substrate, it is preferable to bring the glass substrate into contact with the same liquid as the above-described cleaning liquid before scrub cleaning. There is no particular limitation on the time of contact, but it is preferable to bring the abrasive or foreign matter firmly adhered to the surface of the glass substrate into contact for 10 minutes or more in order to be lifted by some erosion action by the liquid. On the other hand, the longer the contact time of the glass substrate with the liquid, the easier the removal of abrasives and foreign substances from the glass substrate surface. However, the productivity of the glass substrate decreases, so the preferred contact time is in the range of 5 to 30 minutes. It is. From the viewpoint of preventing foreign matter from adhering to the surface of the glass substrate, it is recommended to keep the glass substrate in contact with the liquid until immediately before scrub cleaning.

  The glass substrate surface is brought into contact with the liquid in such a manner that the glass substrate is immersed in a container in which the liquid is stored, the liquid is sprayed on the glass substrate, or the cloth impregnated with the liquid is coated on the glass substrate. A conventionally well-known form, such as a form, can be adopted. Among these, a mode in which the glass substrate is immersed in the liquid is preferable in that the entire surface of the glass substrate can be reliably and uniformly brought into contact with the liquid.

  In this way, scrub cleaning is performed, and the abrasive and foreign matter adhering to the glass substrate surface are removed.

Next, the cleaning liquid remaining on the glass substrate surface is removed using IPA or the like, and the substrate surface is dried. For example, a water rinse cleaning process is performed on the glass substrate after scrub cleaning for 2 minutes to remove the cleaning liquid residue. Next, an IPA (isopropyl alcohol) cleaning process is performed for 2 minutes to remove water on the substrate. Finally, an IPA (isopropyl alcohol) vapor drying step is performed for 2 minutes, and the liquid IPA adhering to the substrate is removed while being removed by the IPA vapor. The substrate drying process is not limited to this, and a method generally known as a glass substrate drying method such as spin drying or air knife drying may be used.
(Inspection process)
After the cleaning process, as a final inspection, the glass substrate is visually inspected for flaws, chips, foreign matters, etc., and those having no abnormality are selected.
(Packing process)
The glass substrate having no abnormality in the inspection process is packed by the packing process shown in FIG. The packaging process has three processes: a holding process for holding the glass substrate on the holding body, a packaging process for packing the holding body holding the glass substrate with the packaging member, and a process for sealing the opening of the packaging member. Yes. First, as a holding step, the glass substrate is held on a holding body. As a holding body used in this holding step, a holding body 600 as shown in FIG. 6 can be used. FIG. 6 is an exploded perspective view showing the entire holding body 600. The holding body 600 includes a storage container 60 that stores a plurality of glass substrates 1, an upper lid 61, and an upper lid 61, and includes a fixing member 63 that fixes the glass substrate 1 stored in the storage container 60. The fixing member 63 has a holding plate 64 that suppresses the outer peripheral end of the glass substrate 1. The configuration of the holding body 600 is not limited to the above configuration, and may be any configuration that can hold a plurality of glass substrates 1.

  The storage container 60 includes side plates 65 and 66, connecting plates 67 and 68 having U-shaped openings connecting the side plates 65 and 66, and a bottom plate 69 constituting a lower portion of the storage container 60. A plurality of ribs 70 are formed on the inner wall of 66 at a predetermined interval wider than the thickness of the glass substrate 1. By forming the plurality of ribs 70 in this manner, a plurality of grooves 71 that support the glass substrate 1 at predetermined intervals in the thickness direction are formed.

  The storage container 60, the upper lid 61, the fixing member 63, and the holding plate 64 constituting the holding body 600 are mainly made of a resin material. In manufacturing these, a resin molding method can be used as an example. In this resin molding step, general resins such as various polyolefins such as polyethylene and polypropylene, polyvinyl chloride, and Teflon (registered trademark) can be used. In particular, when the resin is produced by an injection molding method, examples of the resin include polycarbonate, polyamide, thermotropic liquid crystal polymer (LCP), polyether ether ketone (PEEK), polyether ketone (PEK), and PEEK alloy resin (for example, PEEK / thermotropic liquid crystal polymer, PEEK / polybenzimidazole (PBI), etc.), polybenzimidazole (PBI), polyphenylene sulfide (PPS), polyethersulfone (PES), polyetherimide (PEI), polytetrafluoroethylene ( A fluororesin such as PTFE) can be used. Moreover, it can also create in the groove | channel of a predetermined shape using a grinding wheel.

  FIG. 7 is a side view of the state in which the glass substrate 1 is stored in the storage container 60 as viewed from the connecting plate 67 side. The glass substrate 1 is supported by a pair of grooves 71 arranged to face each other. The distance between the inner walls of the side plates 65 and 66 is slightly larger on the upper opening side than the outer diameter of the glass substrate 1 so that the glass substrate 1 can be inserted from above. Moreover, the space | interval of the inner wall of the side plates 65 and 66 becomes narrow as it approaches the lower bottom plate 69 side, and is contacting with the outer peripheral edge part of the glass substrate 10 by P1 and P2 of the groove | channel 71.

  In this manner, a predetermined number of glass substrates 1 are stored in the storage container 60, and the lid is covered with the upper cover 61 to which the fixing member 63 in FIG.

  Next, the holding body 600 holding the glass substrate is packaged by the packaging member 200 as a packaging process, and further, as the sealing process, the opening 201 of the packaging member 200 is sealed, and the information shown in FIG. A glass substrate package 300 for a recording medium is produced.

  The packaging member may be any material that has an excellent barrier property against lower alcohol. Specifically, a packaging member in which a metal film or an oxide film is provided on a plastic film is preferable. Moreover, since the opening part of a packaging member is sealed, the packaging member which can be easily sealed by thermocompression using a laminator is preferable, and the laminate film which gave aluminum vapor deposition to films, such as a polypropylene, polyester, nylon, is preferable.

  In the sealing step, it is preferable to reduce the pressure in the space inside the packaging member, and it is more preferable to reduce the pressure to a range of 200 to 600 hPa. This pressure reduction can be performed by adjusting the air pressure in the space inside the packaging member to the above range using a vacuum pump when the laminator film is thermocompression bonded.

  Further, in the working chamber for performing the packing process, the concentration of the lower alcohol in the atmosphere is adjusted so that the concentration of the lower alcohol contained in the space inside the sealed packaging member is in the range of 3 to 100 ppm. It is preferable. By performing the packing process in such a work environment, the concentration of the lower alcohol inside the glass substrate package 300 for the information recording medium can be easily adjusted to a predetermined concentration.

  The concentration of the lower alcohol in the information recording medium glass substrate package 300 can be measured after a dummy package having an alcohol detector is prepared and sealed. As another method, the prepared package may be placed in a vacuum device and opened in the vacuum device, and the concentration of the lower alcohol in the vacuum device may be measured. In particular, the measuring method is not limited, and a general measuring device can be used.

  In addition, it is more preferable to perform from a washing | cleaning process to a packing process in the clean room where the density | concentration of the lower alcohol of atmosphere was adjusted. Further, the cleanliness in the clean room is preferably class 50,000 or less, and more preferably 10,000 or less, when defined as the number of particles of 0.5 μm or more present in an atmosphere of 1 cubic foot. By setting it as such a cleanliness | purity, the foreign material adhering to the glass substrate surface during the manufacturing process of the glass substrate for information recording media can further be reduced.

  In addition, after the packaging step of FIG. 4, the holding body holding the glass substrate for information recording medium wrapped with the packaging member is once put in the decompression chamber, and after that, the decompression chamber is decompressed, After introducing a gas whose concentration is adjusted (for example, air) and adjusting the pressure to a predetermined pressure, the opening of the packaging member may be sealed in the decompression chamber.

  Also, a gas heavier than air (for example, nitrogen gas) containing a predetermined concentration of lower alcohol is prepared, and the gas is filled with the opening of the packaging member facing upward, and the opening is then used with a laminator. Then, the pressure may be reduced to a predetermined pressure and sealed.

  As described above, the glass substrate package 300 for an information recording medium is manufactured and stored for a certain period, and then transferred to a manufacturing facility for manufacturing a magnetic recording medium.

  Next, a magnetic recording medium using the glass substrate produced as described above will be described.

  Hereinafter, a magnetic recording medium will be described with reference to the drawings.

  FIG. 2 is a perspective view of a magnetic disk as an example of a magnetic recording medium. In the magnetic disk D, a magnetic film 2 is directly formed on the surface of a circular glass substrate 1 for an information recording medium.

  The glass substrate for information recording medium is taken out from the packaged glass substrate for information recording medium, and a magnetic film is formed on the surface of the glass substrate for information recording medium.

  As a method for forming the magnetic film 2, a conventionally known method can be used. For example, a method in which a thermosetting resin in which magnetic particles are dispersed is spin-coated on a substrate, or a method by sputtering or electroless plating is used. A method is mentioned. The film thickness by spin coating is about 0.3 μm to 1.2 μm, the film thickness by sputtering is about 0.04 μm to 0.08 μm, and the film thickness by electroless plating is 0.05 μm to 0.1 μm. From the viewpoint of thinning and densification, film formation by sputtering and electroless plating is preferable.

The magnetic material used for the magnetic film is not particularly limited, and a conventionally known material can be used. However, in order to obtain a high coercive force, Ni having a high crystal anisotropy is basically used, and Ni or A Co-based alloy to which Cr is added is suitable. Specific examples include CoPt, CoCr, CoNi, CoNiCr, CoCrTa, CoPtCr, and CoNiPt containing Co as a main component, CoNiCrPt, CoNiCrTa, CoCrPtTa, CoCrPtB, and CoCrPtSiO. The magnetic film may have a multilayer structure (for example, CoPtCr / CrMo / CoPtCr, CoCrPtTa / CrMo / CoCrPtTa) that is divided by a non-magnetic film (for example, Cr, CrMo, CrV, etc.) to reduce noise. Addition to the above magnetic material, ferrite, iron - rare-earth or be in a non-magnetic film made of _{SiO 2, BN Fe, Co,} FeCo, etc. granular structure magnetic particles are dispersed, such CoNiPt Also good. Further, the magnetic film may be either an inner surface type or a vertical type recording format.

  In addition, a lubricant may be thinly coated on the surface of the magnetic film in order to improve the sliding of the magnetic head. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a freon-based solvent.

  Furthermore, you may provide a base layer and a protective layer as needed. The underlayer in the magnetic disk is selected according to the magnetic film. Examples of the material for the underlayer include at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni. In the case of a magnetic film containing Co as a main component, Cr alone or a Cr alloy is preferable from the viewpoint of improving magnetic characteristics. Further, the underlayer is not limited to a single layer, and may have a multi-layer structure in which the same or different layers are stacked. For example, a multilayer underlayer such as Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, or NiAl / CrV may be used.

Examples of the protective layer that prevents wear and corrosion of the magnetic film include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer. These protective layers can be formed continuously with an in-line type sputtering apparatus, such as an underlayer and a magnetic film. In addition, these protective layers may be a single layer, or may have a multilayer structure including the same or different layers. Note that another protective layer may be formed on the protective layer or instead of the protective layer. For example, in place of the protective layer, tetraalkoxysilane is diluted with an alcohol-based solvent on a Cr layer, and then colloidal silica fine particles are dispersed and applied, followed by baking to form a silicon dioxide (SiO ₂ ) layer. It may be formed.

  By using the magnetic recording medium manufactured by using the magnetic recording medium manufacturing method as described above, the occurrence of head crash can be suppressed and the operation of the magnetic head during high-speed rotation can be stabilized.

  The glass substrate for an information recording medium of the present invention is not limited to a magnetic recording medium, and can be used for a magneto-optical disk or an optical disk.

(Examples 1 to 19)
(1) Glass melting and press molding process Aluminosilicate glass having a Tg of 480 ° C. was used as a glass material, and the molten glass was press molded to produce a blank material (outer diameter 68 mm, thickness 1.3 mm).
(2) Coring process Next, the circular hole (diameter 18mm) was opened in the center part of the glass substrate using the cylindrical diamond grindstone.
(3) 1st lapping process Both surfaces of the glass substrate were grind | polished using the grinder (made by HAMAI).

As polishing conditions, diamond pellets of # 1200 mesh were used, the load was 100 g / cm ² , the upper platen was rotated at 30 rpm, and the lower platen was rotated at 10 rpm.

The thickness of the obtained glass substrate was 0.9 mm, and the surface roughness was Rmax of 1.5 μm and Ra of 1.0 μm.
(4) Inner / Outer Diameter Precision Machining Step Inner / outer diameter processing was performed with a drum-shaped diamond grindstone to obtain an inner diameter of 20 mm and an outer diameter of 65 mm.
(5) End surface polishing process Step 100 glass substrates obtained by finishing the inner and outer processing steps were stacked, and the inner and outer end surfaces were polished using an end surface polishing machine.

Nylon fibers having a diameter of 0.2 mm were used for the brush bristles of the polishing machine. As the polishing liquid, cerium oxide having a particle diameter of 3 μm was used. The surface roughness of the inner peripheral end surface of the obtained glass substrate was 0.3 μm for R and 0.03 μm for Ra.
(6) Second lapping process Both surfaces of the glass substrate were polished using a polishing machine (manufactured by HAMAI).

As polishing conditions, diamond pellets of # 1200 mesh were used, the load was 100 g / cm ² , the upper platen was rotated at 30 rpm, and the lower platen was rotated at 10 rpm.

As for the surface roughness of the obtained glass substrate, Rmax was 3 μm and Ra was 0.3 μm.
(7) Chemical strengthening treatment step Next, a chemical strengthening treatment step was performed by immersing the glass substrate in a chemical strengthening treatment solution. As the chemical strengthening treatment liquid, a mixed molten salt of potassium nitrate (KNO ₃ ) and sodium nitrate (NaNO ₃ ) was used. The mixing ratio was 1: 1 by mass ratio. The temperature of the chemical strengthening treatment liquid was 400 ° C. and the immersion time was 40 minutes.
(8) Polishing Step Next, as a first polishing step, a polishing machine (manufactured by HAMAI) was used, and urethane foam having a hardness A of 80 degrees was used for the pad. As the abrasive, cerium oxide having an average particle diameter of 1.5 μm was dispersed in water and used as a slurry. The mixing ratio of water and abrasive was 2: 8. The load was 100 g / cm ² , the upper platen was rotated at 30 rpm, and the lower platen was rotated at 10 rpm. The polishing amount was 30 μm.

  As for the surface roughness of the obtained glass substrate, Rmax was 30 nm and Ra was 3 nm.

Next, as a second polishing process, a polishing machine (manufactured by HAMAI) was used, and urethane foam having a hardness A of 70 degrees was used for the pad. As the abrasive, cerium oxide having an average particle diameter of 60 nm was dispersed in water and used as a slurry. The mixing ratio of water and abrasive was 2: 8. The load was 90 g / cm ² , the upper platen was rotated at 30 rpm, and the lower platen was rotated at 10 rpm. The polishing amount was 3 μm.

As for the surface roughness of the obtained glass substrate, Rmax was 5 nm and Ra was 0.3 nm.
(9) Cleaning Step After the second polishing step, scrub cleaning was performed with the cleaning device shown in FIG. As the cleaning liquid, scrub cleaning was performed using a hydrogen peroxide solution having a hydrogen peroxide concentration of 0.5 mass%. The cleaning liquid was supplied by spraying in an amount of 100 ml per minute continuously from 3 seconds before the start of scrub cleaning until the end of scrub cleaning. A polyvinyl alcohol sponge was used as the sponge for the scrub member. The porosity was 50% and the hardness was 45 ° (JIS K7312). The number of rotations of the sponge rollers 10a and 10b was 300 rpm. The rotation speed of the glass substrate 1 was 200 rpm. The glass substrate after scrub cleaning is subjected to a water rinse cleaning process for 2 minutes, followed by an IPA (isopropyl alcohol) cleaning process for 2 minutes, and finally an IPA (isopropyl alcohol) vapor drying process for 2 minutes for drying. It was.
(10) Inspection process After the cleaning process, the glass substrate was visually inspected for adhesion of scratches, chips, foreign matters, etc., and those that clearly showed scratches, chips, or deposits were removed.
(11) Packing process The number of foreign materials with a height of 10 nm or more attached to the glass substrate surface was counted on the surface of the glass substrate after the inspection process using a micro defect measuring machine (ODT: RZ350) manufactured by Hitachi High-Technologies Corporation. Evaluation was made before packing.

  After performing the pre-packaging evaluation, the packing was performed by the packing process shown in FIG. First, as a holding step, 25 glass substrates were held on the holding body 600 shown in FIG. Polycarbonate was used as the resin material for the holder 600. Next, the holding body 600 holding the glass substrate is packaged by the packaging member 200 as a packaging process, and further, as the sealing process, the opening 201 of the packaging member 200 is sealed, and the information shown in FIG. A glass substrate package 300 for a recording medium was produced. As the packaging member, a laminate film obtained by depositing aluminum on a polypropylene film (film thickness: 40 μm) was used. Further, as a laminator in the sealing step, a vacuum bagging device manufactured by Fuji Impulse Co., Ltd. was used, and the pressure inside the packaging member was reduced to a pressure shown in Table 1 and sealed.

The cleaning process, inspection process, and packing process were performed in a clean room of cleanliness class 100. The atmosphere in the clean room contained IPA (isopropyl alcohol) in propanol as the lower alcohol. The concentration of IPA in this atmosphere was adjusted so that the concentration of IPA contained in the space inside the sealed packaging member was the value shown in Table 1.
(Example 20)
In Example 10, a glass substrate package for an information recording medium was prepared in the same manner as in Example 10 except that methanol was used instead of the lower alcohol in the clean room instead of IPA.
(Example 21)
In Example 10, a glass substrate package for an information recording medium was prepared in the same manner as in Example 10 except that ethanol was used in place of the lower alcohol in the clean room instead of IPA.
(Example 22)
In Example 10, a glass substrate package for an information recording medium was prepared in the same manner as in Example 10 except that butanol was used instead of the lower alcohol in the clean room instead of IPA.
(Example 23)
In Example 10, a glass substrate package for an information recording medium was prepared in the same manner as in Example 10 except that the lower alcohol in the clean room was changed to IPA and pentanol was used.
(Comparative Example 1)
In Example 10, the concentration of the lower alcohol in the clean room in which the cleaning process is performed is not adjusted, and the inspection process and the packaging process are performed in a clean room different from the cleaning process, and the concentration of the lower alcohol in the separate clean room is 0 ppm. Otherwise, a glass substrate package for an information recording medium was prepared in the same manner as in Example 10. The lower alcohol concentration inside the produced package of Comparative Example 1 was 0 ppm.
(Evaluation method)
As described above, the glass substrate packagings for information recording media of Examples 1 to 23 and Comparative Example 1 were prepared and stored in a cleanliness class 100 room for 24 hours. Then, in a clean room of cleanliness class 100, the glass substrate package for the information recording medium is opened, and the surface of the glass substrate is applied to the surface of the glass substrate using a micro defect measuring machine (ODT: RZ3500) manufactured by Hitachi High-Technologies Corporation. The number of adhering foreign matters having a height of 10 nm or more was counted and evaluated after packing storage. Specifically, in Examples 1 to 23 and Comparative Example 1, the number of foreign matters before packing each glass substrate was subtracted from the number of foreign matters after packing and the number of increased foreign matters was calculated. Next, the increase number for 25 sheets for each glass substrate package for information recording media was totaled. This total number is less than 5 rank 7, rank 5 to less than 7 rank 6, rank 7 to less than 10 rank 5, rank 10 to less than 15 rank 4, rank 15 to less than 20 rank 3, 20 or more and less than 30 were ranked 2, and 30 or more were ranked 1. When the total number is 30 or more, the yield of the glide tester on the magnetic disk is deteriorated, so that less than 30 is required as a product.

  Moreover, one glass substrate was taken out from the glass substrate package produced in Examples 1 to 23 and the comparative example, and a 0.1 μm magnetic layer was formed on the surface to produce a magnetic recording medium. The magnetic material used was formed of CoNi on the front main surface by sputtering. The yield of this magnetic recording medium was evaluated using a glide tester device (model number RQ7800 manufactured by Hitachi High-Tech).

  The evaluation results are shown in Table 1.

  From the results of Table 1, when Examples 1 to 23 and Comparative Example 1 are compared, the lower alcohol is contained in the space inside the sealed packaging member. It can be seen that the yield is high and the adhesion of foreign matter during storage is suppressed. In addition, Examples 1 to 23 show that the concentration of the lower alcohol contained is preferably in the range of 3 to 100 ppm with less adhesion of foreign matters. Moreover, when Examples 5-15 are compared, it turns out that the adhesion of the foreign material at the time of storage is reduced by reducing the pressure of the space inside the packaging member to the range of 200 to 600 hPa.

Claims (5)

A holding step of holding the glass substrate for information recording medium on a holder;
A packaging step of packaging the holding body holding the glass substrate for information recording medium with a packaging member;
To seal the glass substrate for the information recording medium held by the holding member in a space containing a lower alcohol, have a, a sealing step of sealing the opening of said covering member,
In the sealing step, the concentration of the lower alcohol is such that the concentration of the lower alcohol in the atmosphere of the space in which the holder holding the glass substrate for information recording medium inside the packaging member is sealed after sealing is in the range of 3 to 100 ppm. after There filling the conditioned gas to the space inside the packaging member is performed by sealing the opening of said covering member, the concentration of the lower alcohol of said space after sealing, 3～100Ppm der Rukoto A method for packing a glass substrate for an information recording medium. The method for packing a glass substrate for an information recording medium according to claim 1 , wherein the lower alcohol is at least one selected from the group consisting of methanol, ethanol, propanol, butanol, and pentanol. The method for packing an information recording medium glass substrate according to claim 1 or 2 , wherein, in the sealing step, the pressure in a space in which the holder holding the glass substrate for information recording medium is sealed is reduced. The method for packing a glass substrate for an information recording medium according to claim 3 , wherein the pressure is reduced to a range of 200 to 600 hPa. The method for packing a glass substrate for an information recording medium according to any one of claims 1 to 4 , wherein the sealing step is performed in a working chamber in which the concentration of the lower alcohol in the atmosphere is adjusted.