JP2013211068A - Method for manufacturing glass substrate for information recording medium, and polishing liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing glass substrates for information recording media, even when reducing a polishing step such as not performing a coarse polishing step of performing polishing with a polishing liquid containing cerium oxide, having substantially high smoothness and substantially suppressing an occurrence of end face sagging.SOLUTION: The method for manufacturing glass substrates for information recording media includes a polishing step of moving a glass substrate 10 and a polishing pad 15 relative to each other, with a polishing liquid 16 supplied thereto and polishing the surface of the glass substrate 10. The polishing liquid 16 used is a polishing liquid containing a silica sol in which colloidal silica with an average particle size of 5-15 nm is dispersed, and the average particle size of the colloidal silica in the polishing liquid 16 is 20-30 nm.

Description

  The present invention relates to a method for producing a glass substrate for an information recording medium, and a polishing liquid.

  2. Description of the Related Art Information recording apparatuses that record information on an information recording medium by using magnetism, light, photomagnetism, or the like are known. A typical example of such an information recording apparatus is a hard disk drive apparatus. A hard disk drive device is a device that magnetically records (writes) information on a magnetic disk (hard disk) as an information recording medium having a recording layer formed on a substrate, and reproduces (reads) the recorded information. is there. As a base material of such an information recording medium, a so-called substrate, a glass substrate is preferably used.

  Further, the hard disk drive device floats the magnetic head with respect to the magnetic disk without contacting the magnetic disk when information is recorded on or read from the magnetic disk. It is known that the recording density can be improved by reducing the flying height of the magnetic head. In recent years, the recording density of magnetic disks has been increased, and the flying height of the magnetic head has been reduced to about several nanometers. For these reasons, in order to further reduce the flying height of the magnetic head and increase the recording density, it is required that the glass substrate for the information recording medium has high smoothness.

  Such a glass substrate for information recording media is manufactured by cutting a glass base plate (glass blanks) obtained from molten glass and then polishing it. Specifically, a method of subjecting a cut glass base plate to a rough polishing step of polishing with a polishing liquid containing cerium oxide and then a precision polishing step of polishing with a polishing liquid containing colloidal silica. Etc. Thus, the glass substrate for information recording media with high smoothness was obtained by performing grinding | polishing process in multiple times.

  Moreover, the method of patent document 1, etc. are mentioned. Patent Document 1 includes a finish polishing step of polishing the surface of a glass substrate for a magnetic recording medium with a slurry containing two types of abrasive grains, and arithmetic on the surface of the glass substrate polished by the finish polishing step. A method of manufacturing a glass substrate for a magnetic recording medium is described in which the average roughness (Ra) is controlled within a range of ± 0.05 nm at 1.0 nm or less. According to Patent Document 1, it is disclosed that the surface roughness of a glass substrate can be easily and accurately controlled in a stable state.

JP 2010-192041 A

  A glass substrate for an information recording medium having high smoothness can be easily obtained by performing the polishing process a plurality of times as in the rough polishing step and the precision polishing step as described above. However, the polishing process multiple times has a problem that the cleaning process becomes complicated. In particular, when cerium oxide is used, since it has a relatively high affinity with glass, there is a problem that it tends to remain on the glass base plate.

  In addition, as described above, along with the further increase in density in recent years, there may be a problem such as a small adhesion that has not been a problem so far. Polishing without using relatively high components is required.

  Therefore, the present inventors have reduced the number of polishing steps, for example, polishing with two types of polishing agents without performing a rough polishing step of polishing with a polishing liquid containing cerium oxide in order to achieve one polishing. It was examined to perform a polishing process using a liquid. Specifically, the invention described in Patent Document 1 is not intended for single polishing, but uses a slurry containing two types of abrasive grains having different particle diameters as described in Patent Document 1. We examined the application of the final polishing.

  However, a glass substrate with sufficiently high smoothness cannot be obtained by the method of performing a polishing step using a polishing liquid containing two kinds of abrasives. According to the study by the present inventors, this is presumed that the surface of the glass substrate is damaged by the abrasive having a large particle diameter. That is, it was guessed that the smoothness depends on a polishing agent contained in the polishing liquid having a large particle diameter.

  Further, it is conceivable to polish with a polishing liquid containing an abrasive having a relatively small particle size. In such a case, since the polishing rate is low, in order to obtain sufficient smoothness, the time required for polishing becomes longer. In addition, the polishing of the glass base plate tends to preferentially proceed with the polishing pad hitting the edge more than the center, so when polishing for a long time, the vicinity of the edge is more than the center of the glass substrate. So-called end face sagging that is preferentially polished occurs.

  The present invention has been made in view of such circumstances, and even if the polishing step is reduced, such as not performing a rough polishing step for polishing with a polishing liquid containing cerium oxide, the smoothness is sufficiently high, and the end face is drooped. An object of the present invention is to provide a method for producing a glass substrate for an information recording medium in which the occurrence of the above is sufficiently suppressed. Moreover, it aims at providing the polishing liquid used in the manufacturing method of the glass substrate for information recording media.

  In the method for manufacturing a glass substrate for an information recording medium according to an aspect of the present invention, the glass base plate and the polishing pad are relatively moved while the polishing liquid is supplied onto the glass base plate, and the glass A polishing step of polishing the surface of the base plate, the polishing liquid comprising a silica sol in which colloidal silica having an average particle diameter of 5 to 15 nm is dispersed, and the average particle diameter of the colloidal silica in the polishing liquid is 20 A polishing liquid having a thickness of ˜30 nm is used.

  According to such a configuration, if the polishing step is performed, a glass substrate having sufficiently high smoothness can be produced at a relatively high polishing rate without performing another polishing step. That is, a glass substrate for an information recording medium in which smoothness is sufficiently high and occurrence of edge drooping is sufficiently suppressed even if the polishing step is reduced, such as by not performing a rough polishing step for polishing with a polishing liquid containing cerium oxide. Can be manufactured.

Moreover, in the manufacturing method of the glass substrate for information recording media, it is preferable that the maximum value of the polishing pressure in the polishing step is 140 to 180 g / cm ² .

  According to such a configuration, the smoothness can be further improved and the occurrence of end face drooping can be further suppressed.

  In the method for manufacturing a glass substrate for an information recording medium, the polishing step comprises polishing a glass base plate having a surface roughness of 0.1 to 0.5 μm in arithmetic average roughness Ra as the glass base plate. It is preferable that it is a process to perform.

  According to such a configuration, the smoothness can be further improved and the occurrence of end face drooping can be further suppressed.

  In the method for manufacturing the glass substrate for information recording medium, it is preferable to use a suede pad as the polishing pad.

  According to such a configuration, the smoothness can be further improved and the occurrence of end face drooping can be further suppressed.

  Further, the polishing liquid according to another embodiment of the present invention is a polishing liquid used for manufacturing a glass substrate for an information recording medium by polishing the surface of a glass base plate, and has an average particle diameter of 5 to 15 nm. The colloidal silica is dispersed in a silica sol, and the average particle size of the colloidal silica in the polishing liquid is 20 to 30 nm.

  According to such a configuration, when used for polishing the surface of the glass base plate, a glass substrate for information recording medium having sufficiently high smoothness can be produced at a relatively high polishing rate. Therefore, even if the polishing step is reduced, such as not performing a rough polishing step for polishing with a polishing liquid containing cerium oxide, the smoothness is sufficiently high, and the occurrence of edge droop is sufficiently suppressed. Can be manufactured.

  According to the present invention, even if the polishing step is reduced, such as not performing a rough polishing step for polishing with a polishing liquid containing cerium oxide, the smoothness is sufficiently high, and the occurrence of end face sagging is sufficiently suppressed. A glass substrate for a medium can be manufactured.

It is a schematic sectional drawing which shows an example of the grinding | polishing apparatus used at the grinding | polishing process in the manufacturing method of the glass substrate for information recording media which concerns on this embodiment. It is a top view which shows the glass base plate used with the manufacturing method of the glass substrate for information recording media concerning this embodiment. It is a partial cross section perspective view which shows the magnetic disc which is an example of the information recording medium using the glass substrate for information recording media manufactured by the manufacturing method of the glass substrate for information recording media concerning this embodiment.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

  In the method for manufacturing a glass substrate for an information recording medium according to this embodiment, the glass base plate is moved by relatively moving the glass base plate and the polishing pad in a state where a polishing liquid is supplied onto the glass base plate. A polishing step of polishing the surface of the silica, and the polishing liquid contains a silica sol in which colloidal silica having an average particle diameter of 5 to 15 nm is dispersed, and the average particle diameter of the colloidal silica in the polishing liquid is 20 to 30 nm. A polishing liquid is used.

  According to such a manufacturing method, if the polishing step is performed, a glass substrate having sufficiently high smoothness can be manufactured at a relatively high polishing rate without performing another polishing step. Even if this polishing process is performed as a precision polishing process and the rough polishing process is not performed by polishing with a polishing solution containing cerium oxide, even if the polishing process is reduced, the smoothness is sufficiently high, and the occurrence of edge dripping is sufficiently high. A suppressed glass substrate for an information recording medium can be produced.

  Moreover, the manufacturing method of the glass substrate for information recording media which concerns on this embodiment will not be specifically limited if the said grinding | polishing process is provided. Specifically, the polishing step is not particularly limited except that the polishing step is as described above, and any conventional manufacturing method may be used. Moreover, in the conventional general manufacturing method, it is common to perform multiple times of polishing including a rough polishing step and a precision polishing step as a polishing step for polishing the main surface. As described above, the polishing step according to the present embodiment can produce a glass substrate with sufficiently high smoothness at a relatively high polishing rate. Therefore, in the present embodiment, the polishing step is performed as a precision polishing step. The polishing step according to the embodiment may be performed, and the rough polishing step may be omitted.

  Here, the polishing process in the method for manufacturing the glass substrate for information recording medium according to the present embodiment will be described.

  The polishing step is not particularly limited as long as it is the above-described polishing step. Specifically, it is a step of polishing the surface of the glass base plate by relatively moving the glass base plate and the polishing pad while supplying the polishing liquid onto the glass base plate. And as the polishing liquid, a polishing liquid containing a silica sol in which colloidal silica having an average particle diameter of 5 to 15 nm is dispersed and adjusted so that the average particle diameter of the colloidal silica in the polishing liquid is 20 to 30 nm. Use.

  The average particle diameter here can be measured using a dynamic light scattering device or the like.

  First, the polishing liquid used in this polishing step is not particularly limited as long as it is as described above.

  Specifically, first, the silica sol contained in the polishing liquid is one in which colloidal silica having an average particle diameter of 5 to 15 nm is dispersed, and one in which colloidal silica having an average particle diameter of 5 to 8 nm is dispersed. preferable. If the average particle size of the colloidal silica contained in the silica sol is too small, the polishing rate tends not to be sufficiently increased even if the average particle size of the colloidal silica in the polishing liquid is within the above range. Therefore, there is a tendency that end face sagging is likely to occur. Further, if the average particle size of the colloidal silica contained in the silica sol is too large, even if the average particle size of the colloidal silica in the polishing liquid is within the above range, the polishing properties tend not to be sufficiently improved. Therefore, there is a tendency that the occurrence of scratches on the surface cannot be sufficiently suppressed. From these facts, if the average particle size of the colloidal silica contained in the silica sol is not too small or too large, the polishing property can be sufficiently improved while maintaining the polishing rate.

  And the colloidal silica in polishing liquid is the polishing liquid adjusted so that an average particle diameter may not be 5-15 nm but 20-30 nm.

  Such colloidal silica having an average particle diameter of 20 to 30 nm in the polishing liquid is a collection of a plurality of colloidal silicas having an average particle diameter of 5 to 15 nm when in a silica sol state. This aggregated state is considered to be a relatively weak aggregated state that disperses as soon as an impact or the like is applied.

  Then, the polishing step according to this embodiment, in which polishing is performed with such a relatively weakly agglomerated colloidal silica, has a relatively large particle diameter of colloidal silica, so that a somewhat high polishing rate can be ensured. it is conceivable that. In addition, since the aggregation state is relatively weak, it is considered that generation of scratches such as when polishing with an abrasive having a relatively large particle diameter is suppressed, and high smoothness can be secured. Therefore, it is considered that a glass substrate with high smoothness can be produced while ensuring a relatively high polishing rate.

  Further, if the average particle size of the colloidal silica in the polishing liquid is too small, the polishing rate tends not to be sufficiently increased even if the average particle size of the colloidal silica contained in the silica sol is within the above range. Therefore, there is a tendency that end face sagging is likely to occur. This is considered due to the fact that the aggregated state is too weak. Further, if the average particle size of the colloidal silica in the polishing liquid is too large, even if the average particle size of the colloidal silica contained in the silica sol is within the above range, the polishing properties tend not to be sufficiently improved. Therefore, there is a tendency that the occurrence of scratches on the surface cannot be sufficiently suppressed. From these facts, if the average particle size of the colloidal silica in the polishing liquid is not too small or too large, the polishing property can be sufficiently improved while maintaining the polishing rate.

  Next, a method for preparing the polishing liquid will be described.

  As the method for preparing the polishing liquid, a polishing liquid containing silica sol in which colloidal silica having an average particle diameter of 5 to 15 nm is dispersed and having an average particle diameter of 20 to 30 nm in the polishing liquid is prepared. If it can do, it will not be specifically limited. Specifically, a method of including a silica sol in which colloidal silica having an average particle diameter of 5 to 15 nm is dispersed and further adjusting the average particle diameter of the colloidal silica in a polishing liquid to 20 to 30 nm. Etc. The polishing liquid is also referred to as polishing slurry.

  More specifically, for example, an additive such as a pH adjuster such as an acid, a dispersant, and a flocculant is added to a silica sol in which colloidal silica having an average particle size of 5 to 15 nm is dispersed, By adjusting, the method of adjusting so that the average particle diameter of the said colloidal silica in polishing liquid may be 20-30 nm is mentioned. The colloidal silica in the polishing liquid is a collection of a plurality of colloidal silicas in the silica sol, and is considered to be relatively weakly aggregated. This method is considered to be a method of adjusting the amount of additive added so as to obtain an appropriate aggregation state.

  As the method for preparing the polishing liquid, among the above methods, a method of adding a pH adjusting agent such as an acid is preferable. Moreover, as the method, the method of adjusting pH of polishing liquid to about 1-3 is mentioned. This method has little adverse effect on the polishing properties, and the adjustment of the colloidal silica particle diameter is easy.

  The pH adjuster is not particularly limited as long as the particle diameter of colloidal silica can be adjusted. Specific examples include inorganic acids, organic phosphonic acids, and carboxylic acids from the viewpoint of preventing damage to the surface of the glass substrate, that is, reducing scratches. Examples of the inorganic acid include nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, tripolyphosphoric acid, and sulfamic acid (amidosulfuric acid). It is done. Examples of the organic phosphonic acid include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), and diethylenetriaminepenta. (Methylenephosphonic acid), ethane-1,1, -diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1, 2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, And α-methylphosphonosuccinic acid. Examples of the carboxylic acid include aminocarboxylic acids such as glutamic acid, picolinic acid, and aspartic acid, citric acid, tartaric acid, oxalic acid, nitroacetic acid, maleic acid, oxaloacetic acid, formic acid, acetic acid, glycolic acid, lactic acid, and propane. Examples include acid, hydroxypropanoic acid, butyric acid, benzoic acid, glycine, succinic acid, glutaric acid, adipic acid, fumaric acid, itaconic acid, malic acid, isocitric acid, phthalic acid, nitrotriacetic acid, and ethylenediaminetetraacetic acid. Among these, it is preferable to use an inorganic acid and an organic phosphonic acid from the viewpoint of preventing damage to the surface of the glass substrate, that is, from the viewpoint of reducing scratches. Moreover, as an inorganic acid, phosphoric acid, nitric acid, and a sulfuric acid are preferable, and nitric acid is more preferable. As the organic phosphonic acid, HEDP, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), and diethylenetriaminepenta (methylenephosphonic acid) are preferable, HEDP and aminotri (methylenephosphonic acid) are more preferable, and HEDP is further. preferable. That is, it is particularly preferable to use nitric acid and HEDP.

  Further, the polishing liquid contains the silica sol and an additive for adjusting the particle diameter of colloidal silica, which is added as necessary, and other components such as components generally contained in the polishing liquid. Ingredients may be included.

  Next, a polishing apparatus used in the polishing process will be described.

  The polishing apparatus used in this polishing step is not particularly limited as long as it is a polishing apparatus used for manufacturing a glass substrate for an information recording medium. Specifically, there is a polishing apparatus 11 as shown in FIG. FIG. 1 is a schematic cross-sectional view showing an example of a polishing apparatus used in a polishing step in the method for manufacturing a glass substrate for information recording medium according to the present embodiment.

  A polishing apparatus 11 as shown in FIG. 1 is an apparatus capable of simultaneously polishing both surfaces of the main surface of a glass base plate. The polishing apparatus 11 includes an apparatus main body 11a and a polishing liquid supply unit 11b that supplies a polishing liquid (polishing slurry) to the apparatus main body 11a.

  The polishing main body 11a includes two surface plates 12 and 13 disposed to face each other. The positional relationship between the respective surface plates is not limited to the upper and lower sides. For example, of the two surface plates, the surface plate disposed on the upper side is the upper surface plate 12, and the surface plate disposed on the lower side is This is referred to as the lower surface plate 13. That is, the polishing main body 11a includes a disk-shaped upper surface plate 12 and a disk-shaped lower surface plate 13, and they are arranged at intervals in the vertical direction so that they are parallel to each other. Then, the disk-shaped upper surface plate 12 and the disk-shaped lower surface plate 13 rotate in directions opposite to each other.

  A polishing pad 15 for polishing both the front and back surfaces of the glass base plate 10 is attached to each of the opposing surfaces of the disk-shaped upper surface plate 12 and the disk-shaped lower surface plate 13.

  A plurality of rotatable carriers 14 are provided between the disk-shaped upper surface plate 12 and the disk-shaped lower surface plate 13. The carrier 14 is formed with a plurality of base plate holding holes 51, and the glass base plate 10 can be fitted into the base plate holding holes 51 and disposed. As the carrier 14, for example, 100 base plate holding holes 51 may be formed, and 100 glass base plates 10 may be fitted and arranged. If it does so, 100 glass base plates can be processed by one process (1 batch).

  The carrier 14 sandwiched between the surface plates 12 and 13 through the polishing pad 15 is the same as the lower surface plate 13 with respect to the center of rotation of the surface plates 12 and 13 while rotating while holding the glass base plate 10. Revolve in the direction. The disk-shaped upper surface plate 12 and the disk-shaped lower surface plate 13 can be operated by separate driving. In the polishing apparatus 11 operating in this way, the polishing liquid 16 is supplied between the upper surface plate 12 and the glass base plate 10 and between the lower surface plate 13 and the glass base plate 10, respectively. The glass base plate 10 can be polished. The polishing liquid 16 is the above-described polishing liquid.

  Further, the polishing liquid supply unit 11 b includes a liquid storage unit 110 and a liquid recovery unit 120. The liquid reservoir 110 includes a liquid reservoir main body 110a and a liquid supply pipe 110b having a discharge port 110e extending from the liquid reservoir main body 110a to the apparatus main body 11a. The liquid recovery part 120 was extended from the liquid recovery part main body 120a, the liquid recovery pipe 120b extended from the liquid recovery part main body 120a to the apparatus main body 11a, and from the liquid recovery part main body 120a to the polishing liquid supply part 11b. And a liquid return pipe 120c.

  Then, the polishing liquid 16 put in the liquid storage unit main body 110a is supplied from the discharge port 110e of the liquid supply pipe 110b to the apparatus main body part 11a, and from the apparatus main body part 11a through the liquid recovery pipe 120b, the liquid recovery part main body 120a. To be recovered. The recovered polishing liquid 16 is returned to the liquid storage part 110 via the liquid return pipe 120c, and can be supplied again to the apparatus main body part 11a.

  Here, the case where the recovered polishing liquid is used in a circulating manner (circulation use) has been described. However, the polishing liquid used for polishing is not recovered, but a new polishing liquid is used. The case of using a liquid (use of pouring) may be used. Further, polishing may be performed by pouring the polishing liquid after polishing by circulation. The reason why the polishing liquid is used by pouring is that, if polishing sludge (polishing waste) generated by polishing is present in the polishing liquid, the surface of the glass substrate may be damaged. If the average particle size of the colloidal silica dispersed in the silica sol and the average particle size of the colloidal silica in the polishing liquid are within the above ranges, respectively, the circulation use and the pouring use are changed. Also good.

The polishing pad used in the polishing step is not particularly limited as long as it is used in the polishing step when manufacturing the glass substrate for information recording medium. Among these, a polishing pad used in a precision polishing step in a general method for manufacturing a glass substrate for information recording media is preferable. Specifically, a suede pad etc. are mentioned, for example. The suede pad is a suede type soft foamed resin pad whose surface (polishing layer) is made of a soft foamed resin such as soft foamed polyurethane. The suede pad is a polishing pad in which bubbles are open to the surface (pad surface), and there are relatively many soft walls separating the bubbles. And it is preferable that the hardness of the pad surface of a polishing pad is 80-84 by Asker C hardness. Moreover, it is preferable that the diameter (open diameter) of the bubble open | released by the pad surface is 20-80 micrometers. Moreover, it is preferable that the density of the polishing layer arrange | positioned on the surface of a polishing pad is 0.55-0.62 g / m < ³ >. Further, a so-called non-buffing polishing pad in which the pad surface of the polishing pad is not buffed is preferable.

Moreover, as polishing conditions in the said polishing process, it is preferable that the maximum value of the pressure (polishing pressure) which presses a polishing pad to a glass base plate is 140-180 g / cm < ² >. When the polishing pressure is too low, it tends to be difficult to increase the polishing rate. Therefore, there is a tendency that end face sagging is likely to occur. Further, if the polishing pressure is too high, it tends to be difficult to improve the polishing properties. From these facts, if the polishing pressure is not too low or too high, the polishing property can be further improved while maintaining the polishing rate.

  Moreover, the glass base plate provided to the said grinding | polishing process will not be specifically limited if it is a glass base plate used as grinding | polishing object when manufacturing the glass substrate for information recording media. It is not necessary to have a high smoothness subjected to a rough polishing step, such as a glass base plate used in a precision polishing step in a general method for manufacturing a glass substrate for information recording media, and is used for a rough polishing step. It may be a glass base plate. That is, according to the manufacturing method according to the present embodiment, an information recording medium glass substrate can be manufactured by performing the polishing step in the present embodiment without performing the rough polishing step.

  Moreover, it is preferable that the surface roughness of the glass base plate used for the said grinding | polishing process is low. For example, the arithmetic average roughness Ra is preferably 0.1 to 0.5 μm. Examples of the glass base plate satisfying such Ra include those obtained by adjusting the conditions of the grinding step performed before the polishing step. If this surface roughness is too high, the processing time in the polishing process will be prolonged, and end face sagging tends to occur. In addition, when the surface roughness is too low, it may be difficult to set conditions in the grinding process, or it may be necessary to devise a separate polishing process before the main polishing process.

  By performing the polishing step as described above, as described above, even if the polishing step is reduced, a glass substrate for an information recording medium is produced that has sufficiently high smoothness and occurrence of end face sagging sufficiently suppressed. be able to.

  Moreover, as a manufacturing method of the glass substrate for information recording media which concerns on this embodiment, the said grinding | polishing process should just be provided, but the other process may be provided. For example, a method including a disk machining process, a grinding process (lapping process), an internal / external grinding process, an end surface polishing process, a chemical strengthening process, a polishing process (polishing process), and a cleaning process can be used. And each said process may be performed in this order, and a chemical strengthening process may be performed after a grinding | polishing process. Furthermore, a method including steps other than these may be used. Moreover, a grinding | polishing process performs the said grinding | polishing process.

  The disk processing step is a step of processing the raw glass into a disk-shaped glass base plate 10 in which a through hole 10a is formed in the center so that the inner periphery and the outer periphery are concentric circles as shown in FIG. is there. Specifically, a glass melting step in which raw glass is melted in a melting furnace to form molten glass, a forming step in which the molten glass is formed into a disc-shaped glass base plate, and the formed disc-shaped glass base plate The coring process which forms the through-hole 10a in the center part of this, and is processed into the disk shaped glass base plate 10 as shown in FIG. 2 etc. is provided. FIG. 2 is a top view showing a glass base plate used in the method for manufacturing a glass substrate for information recording medium according to the present embodiment.

The glass melting step is not particularly limited as long as raw glass can be melted in a melting furnace to obtain molten glass. The starting glass is not particularly limited, for _example, SiO 2, _Na 2 O, and soda-lime glass composed mainly of _{CaO, SiO 2, Al 2 O} 3, and ^R ₁ in 2 O (wherein, ^{R 1} is , K, Na, or Li.) Aluminosilicate glass, borosilicate glass, Li ₂ O—SiO ₂ glass, Li ₂ O—Al ₂ O ₃ —SiO ₂ containing an oxide represented by Glass, R ² O—Al ₂ O ₃ —SiO ₂ glass (wherein R ² represents Mg, Ca, Sr, or Ba). More specifically, for example, a glass composition, SiO ₂ is 55 to 75 wt%, _Al 2 _{O 3} is 5 to 18 wt%, Li ₂ O is 1 to 10 mass%, Na ₂ O is 3 to 15 mass %, K ₂ O is 0.1 to 5% by mass, MgO is 0.1 to 5% by mass, and CaO is 0.1 to 5% by mass. Among these, aluminosilicate glass and borosilicate glass are preferable in that they are excellent in impact resistance and vibration resistance. Moreover, it does not specifically limit as a melting method of raw material glass, Usually, the method of fuse | melting the said glass raw material at high temperature by well-known temperature and time is employable.

  The forming step is not particularly limited as long as the molten glass can be formed into a disk-shaped glass base plate. Specifically, the press process etc. which form a disk shaped glass base plate by press molding molten glass are mentioned. The forming step is not limited to the pressing step, and may be a step of, for example, cutting a sheet glass formed by a downdraw method or a float method with a grinding stone to produce a disk-shaped glass base plate. The float method is, for example, a method in which a molten liquid obtained by melting a glass material is poured onto molten tin and solidified as it is. Since the obtained glass base plate is a free surface of glass and the other surface is an interface between glass and tin, the smoothness is high, for example, the arithmetic average roughness Ra is 0.001 μm. The following mirror surface is provided. Moreover, as a thickness of a glass base plate, a 0.95 mm thing is mentioned, for example. In addition, the surface roughness of a glass base plate or a glass substrate, for example, Ra or Rmax, can be measured using a general surface roughness measuring machine.

  Moreover, the said coring process is a process of giving the coring process which forms the through-hole 10a in the center part of the disk shaped glass base plate formed at the said formation process. By doing so, the disk-shaped glass base plate 10 in which the through-hole 10a was formed in the center part as shown in FIG. 2 is obtained. The coring process is not particularly limited as long as it is a drilling process that forms a through hole in the center of the glass base plate. For example, a method of forming a through-hole in the center of the glass base plate by grinding with a core drill having a diamond grindstone or the like in the cutter portion, a cylindrical diamond drill, or the like can be used. By doing so, a through hole is formed in the center of the glass base plate, and an annular glass base plate is obtained in plan view.

  By the disk processing step, for example, the outer diameter r1 is 2.5 inches (about 64 mm), 1.8 inches (about 46 mm), 1 inch (about 25 mm), 0.8 inches (about 20 mm), etc., and the thickness is Disc-shaped glass base plates of 2 mm, 1 mm, 0.63 mm, etc. are obtained. Further, when the outer diameter r1 is 2.5 inches (about 64 mm), for example, the inner diameter r2 is processed to 0.8 inches (about 20 mm).

  The grinding step (lapping step) is a step of processing the glass base plate to a predetermined plate thickness. Specifically, for example, a step of grinding (lapping) both surfaces of the glass base plate can be mentioned. By doing so, the parallelism, flatness and thickness of the glass base plate are adjusted. Further, this lapping step may be performed once or twice or more. For example, when it is performed twice, the parallelism, flatness and thickness of the glass base plate are preliminarily adjusted in the first lapping process (first lapping process), and glass is used in the second lapping process (second lapping process). Finely adjust the parallelism, flatness and thickness of the base plate. Moreover, when performing a grinding process twice, you may perform a 1st lapping process and a 2nd lapping process continuously, but perform the inside-and-outside grinding process mentioned later and an end surface grinding | polishing process between these processes. Also good.

  The grinding apparatus used in the grinding process is not particularly limited as long as it can be used as a grinding apparatus used in the grinding process in the method for producing a glass substrate for information recording medium. Specifically, it is the same as the polishing apparatus used in the polishing step, and includes a resin sheet (grinding sheet) using diamond as a fixed abrasive instead of the polishing pad.

  In addition, examples of the first lapping step include a step in which the entire surface of the glass base plate has a substantially uniform surface roughness. Moreover, as a grinding sheet used at a 1st lapping process, it is preferable to use that whose average particle diameter of a fixed abrasive is 6-12 micrometers, for example. In the first lapping step, when the arithmetic average roughness Ra of the glass base plate is measured at a plurality of locations, the difference between the minimum value and the maximum value of Ra obtained is about 0.01 to 0.4 μm. It is preferable to do.

  In addition, examples of the second wrapping step include a step in which a glass base plate from which defects such as large undulations, chips, and cracks are removed can be obtained. Moreover, as a grinding sheet used at a 2nd lapping process, it is preferable to use that whose average particle diameter of a fixed abrasive is 0.5-4 micrometers, for example, and it is preferable to use a 1-2 micrometers thing. Moreover, it is preferable that Rmax of the obtained glass base plate shall be 0.5-2 micrometers in the said 2nd lapping process. Moreover, it is preferable that Ra shall be 0.1-0.5 micrometer. If the surface of the glass base plate after the second lapping step is too rough, it is difficult to obtain a glass substrate having sufficiently high smoothness even if the polishing step is performed. In addition, the glass base plate after the second lapping step is preferably as smooth as possible, that is, as Ra is small, but in the lapping step, about 0.01 μm is the limit, and 0.01 μm is the limit. This is considered to be the lower limit value of the arithmetic average roughness Ra of the glass base plate after the second lapping step.

  The inner / outer grinding step is a step of grinding the outer peripheral end surface and the inner peripheral end surface of the glass base plate. Specifically, the process etc. which grind the outer peripheral end surface and inner peripheral end surface of a glass base plate with grinding wheels, such as a drum-shaped diamond grindstone, are mentioned.

  The said end surface grinding | polishing process is a process of grind | polishing the outer peripheral end surface and inner peripheral end surface of a glass base plate. Specifically, a plurality of glass base plates subjected to the inner and outer grinding steps, for example, about 100, are stacked and laminated, and in this state, the outer peripheral end surface and the inner peripheral end surface are polished using an end surface polishing machine. And the like.

  The said chemical strengthening process is not specifically limited, Specifically, the process etc. which immerse a glass base plate in a chemical strengthening liquid (strengthening process liquid) and form a chemical strengthening layer in a glass base plate are mentioned. By performing such a process, a chemical strengthening layer can be formed in the surface of a glass base plate, for example, a 5 micrometer area | region from the glass base plate surface. And by forming a chemical strengthening layer, impact resistance, vibration resistance, heat resistance, etc. can be improved.

  More specifically, in the chemical strengthening step, by immersing the glass base plate in a heated chemical strengthening treatment liquid, alkali metal ions such as lithium ions and sodium ions contained in the glass base plate are potassium having a larger ion radius. It is carried out by an ion exchange method for substituting alkali metal ions such as ions. Due to the strain caused by the difference in ion radius, compressive stress is generated in the ion-exchanged region, and the surface of the glass base plate is strengthened. That is, it is considered that the reinforcing layer is suitably formed on the glass base plate by this chemical strengthening step.

  The chemical strengthening treatment liquid is not particularly limited as long as it is a chemical strengthening treatment liquid used in the chemical strengthening step in the method for producing a glass substrate for a magnetic information recording medium. Specifically, for example, a melt containing potassium ions, a melt containing potassium ions and sodium ions, and the like can be given.

  Examples of these melts include melts obtained by melting potassium nitrate, sodium nitrate, potassium carbonate, sodium carbonate, and the like. Among these, it is preferable to use a combination of a melt obtained by melting potassium nitrate and a melt obtained by melting sodium nitrate from the viewpoint of low melting point and preventing deformation of the glass base plate. At that time, a melt obtained by melting potassium nitrate and a melt obtained by melting sodium nitrate are preferably mixed in approximately the same amount.

  The said washing | cleaning process is a process of wash | cleaning a glass base plate. It is preferable that the washing process is appropriately performed after each process. Moreover, scrub cleaning is mentioned as a final cleaning process which cleans the glass substrate grind | polished by the said grinding | polishing process among the said washing | cleaning processes, for example. Scrub cleaning is a wet physical cleaning method in which the scrub member and the glass substrate are relatively moved while the scrub member is pressed against the glass substrate while supplying a cleaning liquid to the surface of the glass substrate. . By doing so, dirt on the surface of the glass substrate can be scraped off. The apparatus for scrub cleaning (scrub cleaning apparatus) is not particularly limited as long as it is an apparatus capable of scrub cleaning an information recording medium glass substrate. Specifically, a roll scrub cleaning device in which the scrub member is a cylindrical roll scrub, a cup scrub cleaning device in which the scrub member is a cup type, and the like can be given.

  In addition, the glass base plate or the glass substrate before the cleaning step such as the final cleaning step is kept in contact with the liquid in order to prevent foreign matter from adhering to the surface. It is preferable.

  Further, as the final cleaning step, it is preferable to perform ultrasonic cleaning after scrub cleaning.

  In addition, after the final cleaning, the glass substrate is dried. Examples of the drying method include drying with IPA vapor, spin drying, and hot water drying.

  Next, a magnetic recording medium using the glass substrate for information recording medium manufactured by the method for manufacturing the glass substrate for information recording medium according to the present embodiment will be described.

  FIG. 3 is a partial cross-sectional perspective view showing a magnetic disk as an example of a magnetic recording medium using the glass substrate for information recording medium manufactured by the method for manufacturing the glass substrate for information recording medium according to the present embodiment. This magnetic disk D includes a magnetic film 102 formed on the main surface of a circular glass substrate 101 for an information recording medium. For the formation of the magnetic film 102, a known method is used. For example, a formation method (spin coating method) for forming the magnetic film 102 by spin-coating a thermosetting resin in which magnetic particles are dispersed on the glass substrate 101 for information recording medium, Examples thereof include a forming method for forming the magnetic film 102 by sputtering (sputtering method) and a forming method for forming the magnetic film 102 on the glass substrate 101 for information recording medium by electroless plating (electroless plating method). The thickness of the magnetic film 102 is about 0.3 to 1.2 μm when the spin coating method is used, and is about 0.04 to 0.08 μm when the sputtering method is used. In some cases, the thickness is about 0.05 to 0.1 μm. From the viewpoint of thinning and densification, film formation by sputtering is preferable, and film formation by electroless plating is preferable.

The magnetic material used for the magnetic film 102 can be any known material and is not particularly limited. The magnetic material is preferably, for example, a Co-based alloy based on Co having high crystal anisotropy in order to obtain a high coercive force and Ni or Cr added for the purpose of adjusting the residual magnetic flux density. More specifically, CoPt, CoCr, CoNi, CoNiCr, CoCrTa, CoPtCr, CoNiPt, CoNiCrPt, CoNiCrTa, CoCrPtTa, CoCrPtB, CoCrPtSiO, and the like whose main component is Co can be given. The magnetic film 102 has a multilayer structure (for example, CoPtCr / CrMo / CoPtCr, CoCrPtTa / CrMo / CoCrPtTa, etc.) divided by a nonmagnetic film (for example, Cr, CrMo, CrV, etc.) in order to reduce noise. May be. Magnetic material used for the magnetic layer 102, in addition to the magnetic material, ferrite or iron - may be a rare earth, also, Fe in a non-magnetic film made of _SiO 2, BN, etc., Co, FeCo, CoNiPt and the like A granular material having a structure in which the magnetic particles are dispersed may be used. In addition, for recording on the magnetic film 102, either an inner surface type or a vertical type recording format may be used.

  In order to improve the sliding of the magnetic head, the surface of the magnetic film 102 may be thinly coated with a lubricant. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a freon-based solvent.

Furthermore, an underlayer or a protective layer may be provided on the magnetic film 102 as necessary. The underlayer in the magnetic disk D is appropriately selected according to the magnetic film 102. 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. For example, in the case of the magnetic film 102 containing Co as a main component, the material of the underlayer is preferably Cr alone or a Cr alloy from the viewpoint of improving magnetic characteristics. Further, the underlayer is not limited to a single layer, and may have a multilayer structure in which the same or different layers are stacked. Examples of such an underlayer having a multilayer structure include multilayer underlayers such as Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, and NiAl / CrV. Examples of the protective layer that prevents wear and corrosion of the magnetic film 102 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 continuously formed with the underlayer and the magnetic film 102 by an in-line sputtering apparatus. These protective layers may be a single layer, or may be a multi-layer structure composed of 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, instead of the protective layer, a SiO ₂ layer may be formed on the Cr layer. Such a SiO ₂ layer is formed by dispersing and applying colloidal silica fine particles in a tetraalkoxysilane diluted with an alcohol-based solvent on the Cr layer and further baking.

  In such a magnetic recording medium based on the information recording medium glass substrate 101 according to the present embodiment, the information recording medium glass substrate 101 is formed with the above-described composition. Can be done by sex.

  In addition, although the case where the glass substrate 101 for information recording media in this embodiment was used for a magnetic recording medium (magnetic disk) was demonstrated above, it is not limited to this, For information recording media in this embodiment The glass substrate 101 can also be used for magneto-optical disks, optical disks, and the like.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[Example A: Examples 1 to 4, Comparative Examples 1 to 4]
In Example A, the result of examining the polishing liquid used in the polishing step is shown.

  First, a method for preparing a polishing liquid used in the polishing step will be described.

(Preparation of polishing liquid)
First, silica sol (manufactured by Nissan Chemical Industries, Ltd.) was prepared.

  And the silica sol in each Example and a comparative example used the thing with the average particle diameter of the colloidal silica currently disperse | distributed in the silica sol in the value shown in Table 1. Specifically, the Snow Tech series manufactured by Nissan Chemical Industries, Ltd. is used, Snowtex XS as a silica sol having an average particle diameter of 5 nm, Snowtex S as a silica sol having an average particle diameter of 10 nm, and Snow as a silica sol having an average particle diameter of 20 nm. Tex 20 was used. The silica sol having an average particle diameter of 2 nm was obtained by classifying Snowtex XS, and the silica sol having an average particle diameter of 15 nm was obtained by classifying Snowtex 20.

  Next, HEDP and nitric acid were added to the silica sol so that the average particle size of the colloidal silica in the polishing liquid was the average particle size shown in Table 1. In some cases, the average particle diameter of colloidal silica in the polishing liquid may be adjusted to the average particle diameter shown in Table 1 by filtering each polishing liquid with a filter. By doing so, the polishing liquid (polishing slurry) used by the grinding | polishing process in each Example and a comparative example was obtained.

  In addition, the average particle diameter here is an average particle diameter measured using the dynamic light scattering apparatus DLS-6500 made from Otsuka Electronics Co., Ltd.

(Glass substrate manufacturing method)
First, the disk processing process was performed using the aluminosilicate glass whose glass transition temperature Tg is 600 degreeC as raw material glass. Specifically, the raw glass was melted by a known method, and the obtained molten glass was press-molded to obtain a disk-shaped glass base plate. And the through-hole was formed in the center part of a glass base plate using the core drill provided with the diamond grindstone. By doing so, a glass base plate (the outer diameter r1 was 68 mm, the inner diameter r2 was 18 mm, and the thickness was 1.3 mm) as shown in FIG. 2 was produced.

Next, the 1st lapping process was performed. Specifically, the surface of the glass base plate was ground (lapped) using a polishing machine (manufactured by HAMAI). At that time, a resin sheet using diamond as a fixed abrasive and having an average particle diameter of 10 μm was used. The processing conditions were a load of 100 g / cm ² , an upper surface plate rotation speed of 30 rpm, and a lower surface plate rotation speed of 10 rpm.

  Next, an internal / external grinding process was performed. Specifically, the outer peripheral end surface and the inner peripheral end surface of the glass base plate subjected to the first lapping step were ground with a drum-shaped diamond grindstone. By doing so, the outer diameter r1 became 65 mm and the inner diameter r2 became 20 mm.

  Next, an end face polishing process was performed. Specifically, 100 glass base plates subjected to the inner and outer grinding steps were stacked and laminated, and in this state, polishing of the outer peripheral end face and the inner peripheral end face was polished using an end face polishing machine.

Next, the second lapping process was performed. Specifically, the surface of the glass base plate was ground (lapped) using a polishing machine (manufactured by HAMAI). At that time, a resin sheet using diamond as the fixed abrasive grains and having an average particle diameter of 3 μm was used. The processing conditions were a load of 100 g / cm ² , an upper surface plate rotation speed of 30 rpm, and a lower surface plate rotation speed of 10 rpm. By doing so, the surface roughness of the glass base plate was 3 μm for Rmax and 0.3 μm for Ra.

  The surface roughness was measured by the method described later.

Next, a chemical strengthening step was performed. Specifically, first, a mixed melt obtained by melting potassium nitrate (KNO ₃ ) and sodium nitrate (NaNO ₃ ) was prepared. In addition, this mixed melt was a mixture prepared by heating the mixture so that the mixing ratio of potassium nitrate and sodium nitrate was 1: 1 by mass to 400 ° C. Then, with the mixed melt kept at 400 ° C., the washed glass base plate was immersed in the mixed melt for 40 minutes.

Next, a polishing process was performed. Specifically, the surface of the glass base plate was polished (polished) using a polishing machine (manufactured by HAMAI). At that time, a suede pad was used as a polishing pad. As processing conditions, the maximum value of the load (polishing pressure) was 120 g / cm ² , the rotation speed of the upper surface plate was 30 rpm, and the rotation speed of the lower surface plate was 10 rpm.

  Next, a final polishing step was performed. Specifically, after scrub cleaning, ultrasonic cleaning was performed.

  Then, it rinsed with the pure water and made it IPA dry.

  And the glass substrate obtained in this way was evaluated by the following methods.

(Surface roughness Ra)
The surface roughness Ra of the obtained glass substrate was measured as follows.

  First, it measured using the surface roughness measuring machine (SE3500 by Kosaka Laboratory Ltd.). If Ra obtained at that time was 0.1 μm or more, the value was adopted as it was. If the obtained Ra is less than 0.1 μm, the atomic force microscope AFM (Dimension V manufactured by Veeco) was used to measure a range of 1 μm × 1 μm by 256 scans, and the obtained results From this, the surface roughness Ra was calculated.

  In addition, Ra in the middle of manufacture was also measured by the same method. Further, Rmax measured at that time was also measured by the same method as Ra.

(The end face)
The edge of the glass substrate obtained was measured using OSA 7120 manufactured by OSA Candela. At that time, the amount of droop (nm) at a point where the distance R from the center was 32.1 mm was measured.

(Evaluation)
From the above measurement results, when Ra was 1.9 mm or less and the end face was 800 nm or less, it was evaluated as “「 ”. In addition, when Ra was 2.1 mm or less and the end face was 1000 nm or less, it was evaluated as “◯”. Further, when Ra was less than 2.3 mm and the end face was less than 1200 nm, it was evaluated as “Δ”. Further, when Ra was 2.3 mm or more, or the end face was 1200 nm or more, it was evaluated as “x”.

  An evaluation result is shown with the average particle diameter of the colloidal silica in a silica sol, and the average particle diameter of the colloidal silica in a polishing liquid.

  As can be seen from Table 1, when using a polishing liquid containing a silica sol in which colloidal silica having an average particle diameter of 5 to 15 nm is dispersed and having an average particle diameter of colloidal silica in the polishing liquid of 20 to 30 nm (implementation) In Examples 1 to 4), the surface roughness Ra of the obtained glass substrate was smaller than that in the case of using a polishing liquid other than this (Comparative Examples 1 to 4), and the occurrence of surface dripping was suppressed.

  Further, even when the average particle size of the colloidal silica in the polishing liquid is 20 to 30 nm, the average particle size of the colloidal silica in the raw silica sol is not 5 to 15 nm (Comparative Example 1 and Comparative Example 2). However, as compared with Examples 1 to 4, Ra was large or the effect of suppressing surface dripping was low.

  Further, even when the average particle size of the colloidal silica in the raw material silica sol is 5 to 15 nm, the average particle size of the colloidal silica in the polishing liquid is not 20 to 30 nm (Comparative Example 3 and Comparative Example 4). However, as compared with Examples 1 to 4, Ra was large or the effect of suppressing surface dripping was low.

  From these facts, it was found that the average particle diameter of colloidal silica in the silica sol and the average particle diameter of colloidal silica in the polishing liquid both affect Ra and the surface dripping.

[Example B: Examples 1, 5 to 7]
In Example B, the result of examining the polishing pressure in the polishing step is shown.

(Example 5)
Example 5 is the same as Example 1 except that the maximum value of the load (polishing pressure) in the polishing process is changed to 140 g / cm ² .

(Example 6)
Example 6 is the same as Example 1 except that the maximum value of the load (polishing pressure) in the polishing process is changed to 180 g / cm ² .

(Example 7)
Example 7 is the same as Example 1 except that the maximum value of the load (polishing pressure) in the polishing process is changed to 200 g / cm ² .

  And evaluation similar to the evaluation in Example A is performed, and the result is shown in Table 2 together with the polishing pressure.

As can be seen from Table 2, when the maximum value of the polishing pressure is 140 to 180 g / cm ² (Examples 5 and 6), the pressure is too low (Example 1) or too high. From (Example 7), the surface roughness Ra of the obtained glass substrate was small, and the occurrence of surface dripping was suppressed. From this, it was found that the maximum value of the polishing pressure is preferably 140 to 180 g / cm ² .

[Example C: Examples 1, 8 to 10]
In Example C, the result of examining the surface roughness Ra (surface roughness Ra before the polishing process) of the glass base plate subjected to the polishing process is shown.

(Example 8)
Example 8 is the same as Example 1 except that the lapping process is performed such that the surface roughness Ra of the glass base plate obtained by the second lapping process is 0.1 μm. That is, the surface roughness Ra of the glass base plate subjected to the polishing process was 0.1 μm.

Example 9
Example 9 is the same as Example 1 except that the lapping process is performed such that the surface roughness Ra of the glass base plate obtained by the second lapping process is 0.5 μm. That is, the surface roughness Ra of the glass base plate subjected to the polishing process was 0.5 μm.

(Example 10)
Example 10 is the same as Example 1 except that the lapping process is performed such that the surface roughness Ra of the glass base plate obtained by the second lapping process is 1 μm. That is, the surface roughness Ra of the glass base plate subjected to the polishing process was 1 μm.

  And evaluation similar to the evaluation in Example A is performed, and the result is shown in Table 3 with the surface roughness Ra of the glass base plate used for a grinding | polishing process.

  As can be seen from Table 3, when the surface roughness Ra before the polishing process is 0.1 to 0.5 μm (Examples 1 to 3), the surface roughness Ra before the polishing process exceeds 0.5 μm ( From Example 10), the surface roughness Ra of the obtained glass substrate was small, and the occurrence of surface dripping was suppressed. From this, it was found that the surface roughness Ra before the polishing step is preferably 0.1 to 0.5 μm.

DESCRIPTION OF SYMBOLS 10 Glass base plate 11 Polishing apparatus 101 Glass substrate for information recording media 102 Magnetic film

Claims (5)

With the polishing liquid supplied on the glass base plate, the glass base plate and the polishing pad are moved relative to each other, and a polishing step for polishing the surface of the glass base plate is provided.
The polishing liquid includes a silica sol in which colloidal silica having an average particle diameter of 5 to 15 nm is dispersed, and a polishing liquid having an average particle diameter of the colloidal silica in the polishing liquid of 20 to 30 nm is used. A method for manufacturing a glass substrate for an information recording medium. In the polishing step, the maximum value of the polishing pressure, 140~180g / cm ² a method of manufacturing a glass substrate for information recording medium according to claim 1.   The said grinding | polishing process is a process of grind | polishing the glass base plate whose surface roughness is 0.1-0.5 micrometer by arithmetic mean roughness Ra as said glass base plate. A method for producing a glass substrate for an information recording medium.   The method for manufacturing a glass substrate for an information recording medium according to claim 1, wherein a suede pad is used as the polishing pad. A polishing liquid used for polishing a surface of a glass base plate to produce a glass substrate for an information recording medium,
Including a silica sol in which colloidal silica having an average particle diameter of 5 to 15 nm is dispersed;
A polishing liquid, wherein the colloidal silica in the polishing liquid has an average particle diameter of 20 to 30 nm.

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