TW494397B - Method for making a glass substrate for magnetic recording media - Google Patents

Abstract

This invention provides a method for making a glass substrate for magnetic recording media, which uses a polishing solution containing a CeO2-based abrasive having ≤ 1 wt.% and ≤ 0.5 μm average particle size D50, preferably ≤ 0.5 wt.% and ≤ 0.3 μm average particle size D50 during a fine polishing process of a crystallized glass substrate and a surface chemically-reinforced glass substrate for magnetic recording media; and a polishing cloth, which preferably uses a hard foamed urethane to polish and manufacture glass substrate for the application in magnetic recording media. This can easily obtain crystallized glass substrate for magnetic recording media with a smooth surface having extremely small surface roughness.

Description

494397 A7

V. Description of the Invention (1) [Technical Field] The present invention relates to a method for manufacturing a glass substrate for magnetic recording media. More specifically, it relates to a method that can produce a surface with homogeneity and surface defects (please read the note on the back first) ? Please fill in this page again.) A method for manufacturing a glass substrate for magnetic recording media with a smooth surface with extremely low surface roughness. (The magnetic recording media referred to herein are items such as magnetic tapes, magnetic disks, etc. that can be used to store computer or other data in the form of electrical signals.] [Background Art] With the increase in the capacity of magnetic disk recording devices, in order to increase the recording density There is a need for a magnetic recording medium substrate that can reduce the amount of floating of the magnetic head, and that has a good surface smoothness and few surface defects. In the past, a substrate for a magnetic recording medium having excellent surface smoothness has mainly been a substrate obtained by applying Ni-P plating to an aluminum alloy and subjecting the main surface of the plating to multi-stage polishing. Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs. However, in recent years, magnetic disk recording devices have also been used in portable personal computers such as laptops, and substrates for magnetic recording media that can withstand the impact of carrying them have begun. In order to improve the response speed of the magnetic disk recording device, high-strength magnetic recording medium substrates are required starting from the need to rotate the magnetic recording medium substrates at a high speed of 10,000 rpniU, and glass substrates have been used to meet these needs. Such a glass substrate for a magnetic recording medium mainly uses a strengthened glass substrate whose surface strength is enhanced by chemical strengthening of the surface, and a glass substrate obtained by melt molding is maintained at a high temperature of 600 to 800 ° C for a long time to make the crystal phase Partially precipitated crystallized glass substrate. This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) 1 311400 494397 A7

V. Description of the invention (2 J (Please read the note on the back? Matters before filling out this page) Surface chemically strengthened glass-breaking substrate, for example, after grinding, grinding, processing, and melt-forming a surface chemically strengthened glass substrate, A glass substrate immersed in a molten salt such as sodium nitrate or potassium nitrate to form a compressive stress layer on the surface to increase the breaking strength. The crystallized glass substrate, for example, is obtained by melting an amorphous glass obtained by melting it into a glass substrate. A glass substrate obtained by maintaining the temperature at a temperature of 6,000 to 800% by forming a mixed phase in which 40 to 80% of a crystalline phase and 20 to 60% of an amorphous phase coexist. However, 'in this case In the process of grinding and polishing of crystallized glass substrates or surface chemically strengthened glass substrates, especially in the process of fine polishing, when using conventional techniques, that is, using a suede type soft polishing cloth and a content of several mass% When the polishing liquid of Ce02 based abrasive material with an average particle size of 0 / m / m or less is ground, linear unevenness due to the bristles and eyelike shapes of the abrasive cloth occurs, and only unevenness can be obtained. The surface roughness achieved has a limit of about 3 5 A on the surface chemically strengthened glass substrate, and a limit of about 4.5 A on the crystallized glass substrate. Therefore, a glass substrate for magnetic recording media is desired. The required surface roughness of 3 A or less is extremely difficult. Clothing printed by employees of the Intellectual Property Bureau, Ministry of Economic Affairs, Consumer Cooperatives [Disclosure of Invention] The subject of the present invention is to provide an efficient and homogeneous production of polished surfaces, A method for manufacturing a glass substrate for a magnetic recording medium with few surface defects and a smooth surface with extremely low surface roughness. As a result of intensive studies on the above-mentioned subject, the present inventors have found that a glass for a magnetic recording medium is conventionally used in accordance with a conventional method. After the substrate is ground to a predetermined thickness, and polished as required, the paper size is subject to Chinese National Standard (CNS) A4 (21 × 297 mm) 2 311400 494397 A7 V. Description of the invention (3 ; (Please read the note on the back? Matters before filling out this page) In the polishing process, when using abrasive cloth, it is better to use Unexpectedly, when a hard abrasive cloth made of foamed polyurethane is polished using a polishing solution containing extremely fine Ce02-based abrasives at a very low concentration, it can be easily produced without bristles. The linear substrate with a linear line-shaped unevenness has a glass substrate with few surface defects and a surface roughness of 3 A or less, thereby completing the present invention. That is, the method for manufacturing a glass substrate for a magnetic recording medium of the present invention is characterized in that : In a polishing process of a glass substrate for a magnetic recording medium, a polishing liquid and a polishing cloth containing a Ce02-based polishing material having an average particle diameter D50 of 0.5% or less and 0.5 / zm or less are used for polishing. [Best Mode for Carrying Out the Invention] Hereinafter, the present invention will be described in detail. The Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs prints a processed glass substrate for manufacturing a magnetic recording medium glass substrate in accordance with the manufacturing method of the present invention, although as long as it has the strength required for a magnetic recording medium substrate or uses surface chemistry Any type of glass substrate that can provide the required strength for the substrate for magnetic recording media can be used for the strengthening treatment. However, in the current technology, it is better to use a crystallized glass substrate and a surface chemically strengthened glass substrate. The abrasive used in the polishing method of the present invention has an average particle diameter D5. Ce02-based fine particles having a size of 0.5em or less, preferably 0.35vm or less, and more preferably 0.2 // m or less. When using a polishing liquid containing an abrasive material with an average particle size greater than 0.5em to grind a glass substrate, the surface roughness becomes large, and a smooth surface with few surface defects and extremely low surface roughness cannot be produced as the object of the present invention Glass substrate. 311400 494397 A7 V. Description of the invention (4) The Ce02-based abrasive material that can be used for fine polishing in the manufacturing method of the present invention includes high-purity Ce02, a mixture of Ce02 and rare earth element oxides, and Ce A mixture of 〇2 and%, a solid solution composed of hafnium oxide and oxidized stone as disclosed in the specification of US Patent No. yam, and the like. Such a solid solution is particularly suitable for use in the present invention because it can be taken out as a commercially available product with extremely fine particles desired, and has good dispersibility in water. Such a solid solution is preferably a solid solution consisting of ytterbium oxide and oxidized silica in an amount of 0.1 to 10 parts by weight. The polishing liquid used for fine polishing in the manufacturing method of the present invention contains the above-mentioned ceo2-based abrasive material at 1% by weight or less, and more preferably Ce02-based abrasive material at 0.05% by weight or less. When the glass substrate is polished using a polishing solution containing CeO2f and a concentration of abrasive material in excess of 1% by weight, the surface roughness becomes large, and it is not possible to produce the surface roughness as low as the object of the present invention and the surface roughness is extremely low. The smooth surface of the glass substrate. Regarding the reason why the surface roughness of the glass substrate surface is extremely low by using a polishing liquid with a very low concentration of Ce02-based polishing material, although the explanation is not clearly understood at this point, it may be considered practical The concentration of the abrasive material required to effectively work in the grinding process is very low, and when there is an excessive amount of abrasive material in the polishing liquid, the surface roughness will be deteriorated. In the manufacturing method of the present invention, although the concentration of the polishing material in the polishing liquid is low, the polishing resistance and the processing resistance during polishing become large, but in order to reduce such resistance, the polishing liquid can be made in the same manner as in the conventional technology. Contains polymer additives or surfactants. Such polymer additives can use fibers, glycerin, etc., and surfactants can use anions and cations. The paper size is applicable to China National Standard (CNS) A4 (210 X 297 mm) A7 ------ B7_____ V. Description of the invention (5) Non-ionic surfactant, preferably fatty acid surfactant. In this case, it is not only to reduce the grinding resistance and processing resistance, but also to easily produce a glass substrate having a smooth surface with extremely low surface roughness. (Please read the precautions on the back before filling this page.) The fine polishing in the manufacturing method of the present invention uses a well-known two-side grinder and a well-known abrasive cloth to polish the glass substrate. Although the abrasive cloth used is not particularly limited, in order to improve the mechanical action in the mechanochemical action during grinding, a harder abrasive cloth is preferably used, and a harder abrasive cloth is preferably used in the past. Hard abrasive cloth made of foamed polyurethane used in the rough grinding (primary polishing) process. The hardness of this rigid polyurethane abrasive cloth is shown in several stages. Although the hardness can be used in any stage, it is from the viewpoint of preventing the corner slope of the glass substrate. It seems that the better is the one with the better hardness. Further, for the purpose of making the polishing liquid easy to flow, grooves having a width of 1 mm and a depth of 1 mm are provided in advance on the polishing side surface of the rigid polishing cloth made of foamed polyurethane at intervals of 30 to 50 mm. The thickness of the polishing cloth is preferably about 0.5 to 1.5 mm. Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs as mentioned above, when using lambskin-type soft abrasive cloth and abrasive liquid containing Ce02-based abrasive material with an average particle size of about 0.5 to 2 / zm At this time, although linear unevenness due to the direction of the bristles of the abrasive cloth occurs, only an uneven surface is obtained, but by using an average particle diameter D5G of 0.5 / zm or less containing 1% by weight or less, The polishing liquid of the Ce〇2 type polishing material can suppress the occurrence of linear unevenness caused by the bristles of the polishing cloth. Furthermore, by using such a polishing liquid in combination with the above-mentioned foamed polyurethane, Hard abrasive cloth can prevent the cause The paper size is applicable to China National Standard (CNS) A4 specification (210 X 297 mm) 5 imm A7 5. Invention description (6) (Please read the precautions on the back before filling this page) Occurrence of linear unevenness in the bristles of the abrasive cloth. Due to the line-shaped unevenness of the bristles of this abrasive cloth, although it is a small height difference that cannot be discerned in the ordinary visual inspection of the glass substrate, it can be clearly seen when the magnetic film is formed. . In addition, the linear irregularities caused by the bristles of the abrasive cloth are formed by a combination of a hard abrasive cloth and a polishing solution containing a common Ce02-based abrasive material having an average particle size of about G.5 to 2 " m. It can be reduced, but in this case minor surface defects still occur. Printed by the Consumers' Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs In the manufacturing method of the present invention, the grinding conditions other than the above, such as grinding pressure, rotation number, and grinding time, are not particularly limited as long as ordinary grinding processing can be performed. However, when the grinding pressure is too high, it may cause choking, eating or drinking, or damage to the glass substrate. Therefore, it is preferably performed at less than 100 g / cm2, and more preferably performed at 80 g / cm2 or less. When the number of rotations is too slow, squeaking sounds sometimes occur, and when the speed is too fast, the processing impedance sometimes becomes too large. Therefore, it is preferably about 15 to 60 rpm. In addition, although the polishing time is related to the number of rotations, when the time is too short, the improvement of the surface roughness tends to be insufficient, and even if the time becomes longer, a comparable effect cannot be obtained, so the better one is The grinding time (minutes) X number of revolutions (rpm) is set to about 150 to 1,000. Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Example 1 In accordance with the usual manufacturing procedure of a glass substrate for a magnetic recording medium, a glass-crystallized glass plate (manufactured by Ohara Co., Ltd. TS-10SX, quartz-crystobalite) was 70 to 80%, the rest is amorphous) internal and external diameter processing, grinding processing to make the external diameter This paper size applies Chinese National Standard (CNS) A4 specifications (210 X 297 public love) 6 ΤΓΤΪ0ΪΓ 494397 A7 V. Description of the invention (7) A plurality of donut-shaped substrates of 65 mm, an inner diameter of 20 mm, and a plate thickness of 0.68 mm. (Please read the note on the back? Matters before filling out this page) Next, 'Set 100 pieces of the doughnut substrate above on a 16B double-side grinder manufactured by Hamai Co., Ltd. and use rice made by Mitsui Metals Mining Co., Ltd. Raco 80l (CeO2 based abrasive material, average particle diameter D50 = 1.5 // m) as abrasive material, and MHC15 A (foamed urethane) manufactured by Rodunida as abrasive cloth The surface thickness is reduced by 15 / m to produce a crystallized glass substrate to be polished in the present invention. The 100 crystallized glass substrates obtained above were set on a 16B double-side grinder manufactured by Hamai Co., Ltd., and were made of CEP (100 parts by weight of hafnium oxide and 1 part by weight of silicon oxide i) manufactured by Mitsui Metals Mining Co., Ltd. Solid solution, with an average particle size of 0 = 0.2 // m), using a polishing solution containing 0.5% by weight of abrasive material, and using MHC15A (foamed urethane) manufactured by Rodunida for grinding The cloth was polished on both sides of the crystallized glass substrate under polishing conditions of a polishing pressure of 60 g / cm2, a rotation number of 30 rpm, and a polishing time of 20 minutes. Using A.F.M. (Atomic Force Microscope) to observe the surface of the polished crystallized glass substrate on the area of 2 // mx 2 / zm. The surface roughness (Ra and Rmax) printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. The results are shown in Table i. Comparative Example 1 Except that Mireku SO (average particle diameter D5 () = 1.0 / Z m; Ce0270%) manufactured by Mitsui Metals Mining Co., Ltd. was used instead of the CEP abrasive material used in Example i The rest was subjected to the same treatment as in Example 1 and the surface roughness of the surface of the crystallized glass substrate after polishing was observed in the same manner as in Example 1. The results are shown in Table 1. ‘The paper size is applicable to the Zhongguanjia Standard (CNS) A4 specification (210 X 297 male shame Γ-31140011 494397 A7 B7 V. Description of the invention (8) Table 1

Type of abrasive material Average particle size Ra Rmax Example 1 Comparative example 1 CEP Mireco SO 0.2 // m 1.0 / zm 2.0 A 4.5 A 52 A 110 A (Please read the note on the back first? Matters before filling out this page) It can also be understood from the data in Table 1 that the Ce02-based abrasive can be polished at a low concentration (less than 1% by weight) using an average particle size of 1.0 am (D50 is 0.5 "m or less), which has been conventionally used. The surface roughness of the surface of the crystallized glass substrate was sufficiently reduced. Examples 2 to 9 Except that the polishing conditions (polishing time, polishing pressure, and number of rotations) used in Example 1 were changed to those shown in Table 2, the rest were applied. The same treatment as in Example 1 was performed, and the surface roughness of the surface of the crystallized glass substrate after polishing was observed in the same manner as in Example 1. The results are shown in Table 2. Table 2

Grinding time Grinding pressure rotation number Ra Rmax Example 2 20 minutes 75g / cm3 30rpm 1.8 A 50 A Example 3 20 minutes 30g / cm3 30rpm 2.0 A 52 A Example 4 20 minutes 30g / cm3 50rpm 2.1 A 54 A Example 5 15 minutes 60g / cm3 40rpm 1.7 A 32 A Example 6 15 minutes 60g / cm3 30rpm 2, 2 A 54 A Example 7 15 minutes 60g / cm3 20rpm 2.1 A 55 A Example 8 10 minutes 60g / cm3 20rpm 2.4 A 56 A Example 9 5 minutes 60g / cm3 30rpm 3.0 A 80 A Examples 10 to 15 and Comparative Example 2 were printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs, except that the concentration of the CEP abrasive material used in Example 1 was changed to As shown in Table 3, and added at the concentration shown in Table 3 (with or without adding 7ΙΙ4ϋϋ) This paper size applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) 494397 A7 B7 V. Description of the invention (9 ) (Please read the note on the back? Matters before filling out this page} Situation) Fatty acid alkaloids (produced by Synergic Oils and Fats; MKP-98) are treated in the same manner as in Example 1 except that they are used as additives, and are the same as in Example 1. 1 Similarly, observe the surface roughness of the surface of the crystallized glass substrate after polishing. This result is shown in Table 3 together with the data of Example 1. Table 3

Abrasive material concentration NaOH concentration Ra Rmax Comparative example 2 2.0% by weight 0% by weight 4.8 A 120 A Example 1 0.5% by weight 0% by weight 2.0 A 58 A Example 10 0.1% by weight 1% by weight 1.6 A 33 A Example 11 0.1% by weight 0.5% by weight 1.5 A 30 A Example 12 0.1% by weight 0% by weight 1.8 A 52 A Example 13 0.01% by weight 1% by weight 1.5 A 32 A Example 14 0.01% by weight 0.5% by weight 1.6 A 34 A Implementation Example 15 0.005% by weight 1% by weight 1.5 A 29 A As can be understood from the data in Table 3, when the concentration of the abrasive in the polishing liquid is higher than 1% by weight, the surface of the surface of the crystallized glass substrate after polishing is rough When the concentration is very low, the surface roughness of the surface of the crystallized glass substrate after grinding can be reduced, and when the fatty acid petrolatum is applied as an additive, its lubricating effect can be used to reduce the surface roughness. Examples 16 to 18 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. In addition to setting the concentration of the CEP abrasive material used in Example 1 to 0.005% by weight, fatty acid alkaloids (manufactured by Synergy Fats and Oils) were added at a concentration of 1% by weight. ; MKP-98) is used as an additive, and the polishing cloth is changed to the one shown in Table 4 (MHC14E and Suba are made by Rodunida, N0038 are made of bellspun (stock) lambskin type), the rest are given and implemented The same treatment as in Example 1, and the surface of the crystallized glass substrate after grinding was observed in the same manner as in Example 1. The paper size of this paper applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) ¥ 311400 494397 A7 V. Description of the invention (10) Surface roughness. The results are shown in Table 4 together with the data of Example 15. Table 4

Abrasive cloth Ra Rmax Example 15 MHC15A 1.5 A 30 A Example 16 MHC14E 1.8 A 62 A Example 17 Suba 2,4 A 84 A Example 18 N0038 2.2 A 80 A (" Read the precautions on the back before filling in this (Page) It can also be understood from the data in Table 4 that polishing with a harder abrasive cloth can reduce the surface roughness of the crystallized glass substrate. Example 19 In accordance with the usual manufacturing procedure of a glass substrate for a magnetic recording medium, a surface-chemically strengthened lithium-silicate glass substrate (Asahi Glass Co., Ltd .: AH-1) was subjected to inner and outer diameters. Machining, grinding process' to produce a plurality of donut-shaped substrates with an outer diameter of 65mm, an inner diameter of 20mm, and a plate thickness of 0.68mm. Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. 100 tablets of the above doughnut substrates were set on a 16B double-sided grinder manufactured by Hamai Co., Ltd. and Mireku 801 (Ce02 manufactured by Mitsui Metals Mining Co., Ltd. was used. Is a polishing material, with an average particle diameter of D50 = 1.5 // m) as the polishing material, and using MHC15A (foamed urethane) manufactured by Rodunida as a polishing cloth to reduce the thickness of one side by 15 μ m to produce a surface chemically strengthened glass substrate which has been subjected to the polishing treatment in the present invention. The 100 pieces of surface chemically strengthened glass substrates obtained above were set on a 16B double-side grinder manufactured by Hamai Co., Ltd., and Mitsui metal paper I was not used in accordance with τ National Standard (CNS) A4 specification (21〇χ). 297 mm) -ΠΓ-mm— 494397 A7 B7 V. Description of the invention (11) CEP (Solid solution consisting of 100 parts by weight of hafnium oxide and 100 parts by weight of silicon oxide) produced by Mining Co., Ltd. The average particle diameter is D5. = 0.2 // m), using a polishing liquid containing 0.5% by weight of abrasive material, and using MHC14E (foamed urethane) manufactured by Rodunida as a polishing cloth, at a polishing pressure of 60 g / cm2, and the number of rotations Both surfaces of the surface chemically strengthened glass substrate were polished under polishing conditions of 30 rpm and a polishing time of 20 minutes. A.F.M. (Atomic Force Microscope) was used to observe the surface roughness (Ra and Rmax) of the surface of the chemically strengthened glass substrate after grinding on an area of 2 # mx 2 // m. The results are shown in Table 5. In addition, the line-like unevenness of the bristles was not visible on the surface at all. Comparative Example 3 Instead of using the CEP abrasive material used in Example 19, Mireku SO (average particle diameter D5G = 1_0 "m; CeO270%) manufactured by Mitsui Metals Mining Co., Ltd. was used, and bell spinning was used. The lambskin type N0038 was produced in place of MHC14E (foamed urethane), and the rest was treated in the same manner as in Example 19, and the surface of the surface of the chemically strengthened glass substrate after polishing was observed in the same manner as in Example 19 Roughness. The results are shown in Table 5. In addition, the bristles-like linear irregularities are visible on the surface. Table 5

Type of abrasive material, average grain Ra Ramax material of abrasive cloth Example 19 Comparative Example 1 Mirecu SO, 1.0 // m Foam urethane lambskin type 1.5 A 5.6 A 50 A 120 A From Table 5 It can also be understood from the data that by using a low concentration (1% by weight (please read the note on the back? Matters before filling out this page), printed by the Employees ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs

This paper size is applicable to China National Standard (CNS) A4 specification (21〇X 297 public love) 3114UU 494397 Α7 Β7 V. Description of the invention (below 12) Use an average particle size smaller than 1.0 // m used in the past (D50 is 0.5 // m or less) Ce02-based abrasives can sufficiently reduce the surface roughness of the surface of the surface chemically strengthened glass substrate. (Please read the precautions on the back before filling out this page.) Example 2 0 to 2 7 Except that the polishing conditions (polishing time, polishing pressure, and number of rotations) used in Example 19 were changed to those shown in Table 6, The rest was subjected to the same treatment as in Example 19, and the surface roughness of the surface of the surface chemically strengthened glass substrate after polishing was observed in the same manner as in Example 19. The results are shown in Table 6. Table 6

Grinding time Grinding pressure rotation number Ra Rmax Example 20 20 minutes 75g / cm3 30rpm 1.4 A 48 A Example 21 20 minutes 30g / cm3 30rpm 1.6 A 54 A Example 22 20 minutes 30g / cm3 50rpm 1.6 A 52 A Example 23 15 minutes 60g / cm3 40rpm 1.4 A 46 A Example 24 15 minutes 60g / cm3 30rpm 1.7 A 54 A Example 25 15 minutes 60g / cm3 20rpm 1.8 A 57 A Example 26 10 minutes 60g / cm3 20rpm 2.1 A 58 A Implementation Example 27 5 minutes 60 g / cm3 30 rpm 2.4 A 61 A Examples 28 to 33 and comparison Example 4 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs In addition to changing the concentration of the CEP abrasive material used in Example 19 to As shown in Table 7, fatty acid alkaloids (manufactured by Synergy Oils and Fats; MKP-98) were added (with or without addition) at the concentrations shown in Table 7 as additives, and the rest were treated in the same manner as in Example 19. The surface roughness of the surface of the chemically strengthened glass substrate after polishing was observed in the same manner as in Example 19. The results are shown in Table 7 together with the data of Example 19. This paper size applies Chinese National Standard (CNS) A4 specification (210 X 297 mm) 12 --ΤΓΠΠϋ- 494397 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 i. Description of the invention (13) Table 7

Abrasive material concentration NaOH concentration Ra Rmax Comparative Example 4 2.0% by weight 0% by weight 4.9 A 124 A Example 19 0.5% by weight 0% by weight 1.6 A 54 A Example 28 0.1% by weight 1% by weight 1.4 A 51 A Example 29 0.1% by weight 0.5% by weight 1.4 A 49 A Example 30 0.1% by weight 〇% by weight 1.5 A 52 A Example 31 0.01% by weight 1% by weight 1.3 A 53 A Example 32 0.01% by weight 0.5% by weight 1.4 A 50 A Implementation Example 33 0.005% by weight 1% by weight 1.4 A 52 A As can be understood from the data in Table 7, when the concentration of the abrasive in the polishing liquid is higher than 1% by weight, the surface of the surface of the chemically strengthened glass substrate after polishing is The surface roughness will be poor, and when the concentration is very low, the surface roughness of the surface of the chemically strengthened glass substrate after polishing can be reduced, and when fatty acid petrolatum is applied as an additive, its lubricating effect can be used to reduce the surface roughness. degree. Example 34 $ 36 In addition to setting the concentration of the CEP abrasive material used in Example 19 to 0.005% by weight, fatty acid alkaloid (produced by Synergy Oils and Fats; MKP-98) was added at a concentration of 1% by weight as an additive, and Except that the polishing cloth was changed to the one shown in Table 8 (MHC14E and Suba are made by Rodunida and N0038 are made of bellspun (strand) made of lambskin), the rest were given the same treatment as in Example 19 and implemented as In Example 19, the surface roughness of the surface of the surface chemically strengthened glass substrate after polishing was similarly observed. The results are shown in Table 8 together with the data of Example 33. ----------------- ^ ---- ^ --------- (Please read the notes on the back before filling this page) This paper size is applicable to China National Standard (CNS) A4 Specification (21 × 297 mm) 13

J114UU 494397 A7 B7 V. Description of the invention (14) Table 8

Abrasive cloth Ra Rmax Example 33 MHC15A 1.3 A 48 A Example 34 MHC14E 1.4 A 52 A Example 35 Suba 2.3 A 63 A Example 36 N0038 2.7 A 68 A It can also be understood from the data in Table 8 to use hard The surface roughness of the surface chemically strengthened glass substrate can be reduced by polishing with a polishing cloth. [Industrial Applicability] As described above, by polishing a crystallized glass substrate or a surface chemically strengthened glass substrate according to the manufacturing method of the present invention, it is easy to obtain magnetic properties with a smooth surface with extremely low surface roughness. A crystallized glass substrate for a recording medium. (Please read the precautions on the back before filling out this page.) Clothing printed by the Employees ’Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs This paper applies the Chinese National Standard (CNS) A4 (210 X 297 mm) 14 311400

Claims (1)

Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. 6. Patent application scope L-A manufacturing method of glass substrates for magnetic recording media, which is characterized by the following: The content of the glass substrates for magnetic recording media is finely polished. A polishing liquid of a Ce02-based polishing material having an average particle diameter Dm of 0.5 m or less and a polishing cloth to be polished. 2. Ik method according to item i of the patent application, in which the glass substrate for magnetic recording media is a crystallized glass cylinder + i Sakazo plate or a surface-reinforced glass substrate. 3. The manufacturing method of item j or 2 in the scope of patent application, and the production of 2 items, in which the average particle size D5G of 0.3 " m or less with a reduction method of 0.5 is used. A polishing solution for abrasive materials. 4. The manufacturing method according to item i or item 2 of the scope of patent application, wherein the Ce02-based abrasive material is a solid solution composed of 100 parts by weight of hafnium oxide and 0.1 to 10 parts by weight of silicon oxide. 5. According to the method of claim 3 in the patent application, the dry surface method is adopted, in which the Ce02 series abrasive material is a solid solution composed of 100 parts by weight of oxide and 0.1 to 10 parts by weight of gasified silicon. body. 6. Each method according to the scope of the patent application, or 2 .. I, wherein the grinding fluid contains fatty acid alkaloid as an additive. Grinding 7 · If the mm ° method of the scope of patent application No. 3, in which the grinding fluid contains fatty alkaloids as additives. 8. The method according to item 4 of the scope of the patent application, wherein the grinding fluid contains fatty aragonite as an additive. 9. If the patent application scope is J or 2 hard foamed ethyl urethane. "Method" Where the standard of grinding a private paper is applicable to the Chinese national standard y '?) I t— -I i SI 1 ii I nm ϋ · i ^ i ϋ .1 · nn I σσ, ϋ ϋ II i.— I (Please read the precautions on the back before filling this page) 15 311400 494397 A8 B8 C8 D8 VI. Application for patent scope 10. If the method of application for scope of patent application item 3, the abrasive cloth is rigid foamed amine formate (Please read the notes on the back and fill in this page) Printed by the Intellectual Property Bureau of the Ministry of Economic Affairs, Employee Consumer Cooperatives This paper is sized to the Chinese National Standard (CNS) A4 (210 X 297 mm) 16 311400