JP4698546B2 - Method for manufacturing glass substrate for magnetic disk, method for manufacturing magnetic disk - Google Patents

Description

  The present invention relates to a method for manufacturing a glass substrate for a magnetic disk, a method for manufacturing a magnetic disk, a glass substrate for a magnetic disk, and a magnetic disk.

  In recent years, with the advancement of information technology, information recording technology, particularly magnetic recording technology, has made remarkable progress. An aluminum substrate has been widely used as a substrate for a magnetic recording medium such as an HDD (Hard Disk Drive) which is one of the magnetic recording media. However, with the miniaturization, thinning, and high recording density of magnetic disks, glass substrates are gradually being replaced with glass substrates that are superior in substrate surface flatness and substrate strength compared to aluminum substrates. In particular, there is a demand for mounting on mobile phones, digital cameras, portable music players, and the like, and magnetic disks are required to be further downsized and have higher recording density.

  Texture processing by tape polishing has been widely adopted in magnetic disks using an aluminum substrate as a technique for controlling the magnetic head adsorption performance and the magnetic disk recording density in the conventional CSS (Contact Start Stop) method. It was. The CSS system is a system in which a magnetic head is brought into contact with a CSS zone provided on a magnetic disk when the magnetic disk is not rotating, and is placed on standby. The CSS needs to have a certain degree of surface roughness in order to prevent adsorption of the magnetic head in standby.

Under such circumstances, Patent Document 1 (Japanese Patent Laid-Open No. 4-238116) describes a so-called cross texture configuration in which the angle formed by the texture marks from the circumferential direction of the magnetic disk is 5 ° to 30 °. ing. According to Patent Document 1, the above configuration allows obtaining excellent CSS characteristics without deteriorating electromagnetic conversion characteristics. In addition, Patent Document 2 (Japanese Patent Laid-Open No. 4-349218) is excellent by combining a circular texture mark oriented in the circumferential direction and a cross texture shifted from the circumferential direction of 2 ° to 40 ° (cross texture). Both the electromagnetic conversion characteristics and the magnetic head adsorption prevention by the CSS method can be achieved.
JP-A-4-238116 JP-A-4-349218

However, recently, in order to effectively use the main surface of the magnetic disk, a LUL (Load UnLoad) method (load unload method) has been used instead of the conventional CSS method. The LUL method is a method in which the magnetic head is retracted to a ramp (tilted portion) provided outside the magnetic disk. As described above, since the CSS method requires a certain degree of surface roughness, it has been difficult to promote smoothing. However, by adopting the LUL method, the entire surface of the magnetic disk can be used as a recording area. The surface of the magnetic disk need not be provided with an uneven shape, and the surface of the magnetic disk can be extremely smoothed.

  Further, as the magnetic recording technology has been increased in density, the magnetic head has been changed from a thin film head to a magnetoresistive head (MR head) and a large magnetoresistive head (GMR head). However, the GMR head has high sensitivity and high recording density, and if the head and the substrate are separated from each other, information on adjacent recording bits is picked up. Therefore, it is necessary to keep the flying height of the magnetic head low.

  Under these circumstances, the flying height of the magnetic head is required to be reduced, and the flying height of the magnetic head from the substrate is narrowed to about 8 nm. If the flying height of the magnetic head is reduced, a head crash failure or thermal asperity failure may occur. The head crash failure is a failure in which the magnetic head collides with the convex portion of the magnetic disk and is damaged. Thermal asperity failure means that the magnetoresistive element is heated by adiabatic compression or contact of air when the magnetic head passes over a minute convex or concave shape on the magnetic disk surface while flying. This is a failure that causes a read error. Therefore, for a magnetic head equipped with a magnetoresistive element, it is required to make the surface of the magnetic disk smooth and flat and to have a very high level of uniformity so as not to have an abnormal uneven shape.

  Here, in the LUL method, an uneven shape is not necessary, but when a Co alloy magnetic layer is employed, the orientation of the magnetic crystal grains can be controlled by the surface shape of the substrate. That is, since the magnetic crystal grains are easily aligned in the normal direction with respect to the substrate surface, the axial direction of the grains can be concentrated in the circumferential direction by forming grooves in the circumferential direction (track direction). Therefore, it is meaningful to form a texture even in the LUL method.

  However, similarly to the texture, when there is a scratch (concave defect) on the glass substrate, the orientation of the same magnetic crystal particle is affected. And since the recording bit length has become shorter as the recording density of magnetic disks increases, the output drops below the specified value and the recording bits are lost if the orientation of the magnetic crystal grains is distorted due to scratches. It's starting to end up. This is a major obstacle to commercializing a high recording density HDD. Further, the texture processing is to polish the glass substrate in the circumferential direction while rotating the glass substrate, and it is easy to generate circumferential scratches. For this reason, the texture processing has a problem that signal errors (negative modulation) that are continuous in the reading and writing directions are likely to occur.

  The conventional techniques disclosed in the above-mentioned Patent Document 1 and Patent Document 2 are mainly concerned with the prevention of head adsorption in the CSS system by cross texture and the durability of the magnetic head by removing abnormally high convex shape, and the electromagnetic conversion characteristics It is configured for the purpose of minimizing the deterioration of the. This does not take into consideration the prevention of scratches on the magnetic disk required in the low flying height region of the magnetic head in the LUL system.

  Accordingly, an object of the present invention is to prevent the occurrence of negative modulation in texturing and to enhance the orientation of magnetic crystal grains to increase the recording density of a magnetic disk.

In order to solve the above problems, a typical configuration of a method for manufacturing a glass substrate for a magnetic disk according to the present invention is for a disk-shaped magnetic disk used in a magnetic disk mounted on a load-and-load magnetic recording apparatus . In the method for manufacturing a glass substrate, a step of forming a first texture having a locus intersecting at a predetermined angle with respect to a circumferential direction by repeatedly moving a polishing head in a radial direction relative to a rotating substrate; Forming a second texture having a trajectory intersecting the circumferential direction at an angle different from that of the first texture, in this order, and the intersecting angle of the first texture with respect to the circumferential direction of the second texture It is characterized by being larger than the crossing angle with respect to the circumferential direction.

  According to the said structure, since the process of forming the 1st texture with a big intersection angle draws the locus | trajectory of a random direction, it can prevent a deep scratch. Even if scratches are generated, since they are inclined with respect to the circumferential direction, negative modulation can be minimized. Furthermore, by drawing a trajectory in a random direction, it is possible to reduce the micro-waveness, to improve the low flying height of the magnetic head and to ensure stability.

  Then, in the step of forming the second texture with a small intersection angle, the occurrence of scratches is suppressed because the convex foreign matter has already been removed, and the surface roughness in the circumferential direction is close to the circumferential direction. And the prevention of crash failure and thermal asperity in the low flying height region can be achieved.

The intersection angle of the first texture with respect to the circumferential direction is preferably 0.1 ° or more, and the intersection angle of the second texture with respect to the circumferential direction is preferably smaller than 0.1 °. Furthermore, the intersection angle of the first texture with respect to the circumferential direction is preferably 0.2 ° or more. By setting this range, it is possible to achieve both prevention of circumferential scratching and high recording density. The magnetic head is preferably used for a magnetic disk having a flying height of 8 nm or less. This is because stability can be ensured even for a magnetic head with a low flying height.

  A typical configuration of the magnetic disk manufacturing method according to the present invention is to form at least a Co alloy-based magnetic layer on the surface of the magnetic disk glass substrate obtained by the above magnetic disk glass substrate manufacturing method. It is characterized by. By using a Co alloy system for the magnetic layer, the orientation of the magnetic crystal grains can be controlled by the texture on the glass substrate. Here, in particular, since the crossing angle of the second texture with respect to the circumferential direction is small, the orientation in the circumferential direction can be improved, and the recording density of the magnetic disk can be increased.

  A typical configuration of a glass substrate for a magnetic disk according to the present invention is a disk-shaped glass substrate for a magnetic disk, wherein a first texture having a trajectory intersecting at a predetermined angle with respect to the circumferential direction, and a circumferential direction. A second texture having a trajectory intersecting at an angle different from that of the first texture, the second texture is applied on the first texture, and the intersection angle of the first texture with respect to the circumferential direction Is larger than the crossing angle with respect to the circumferential direction of the second texture.

  A typical configuration of the magnetic disk according to the present invention is characterized in that at least a Co alloy-based magnetic layer is provided on the magnetic disk glass substrate.

  According to the present invention, it is possible to prevent the occurrence of negative modulation in texture processing, increase the orientation of magnetic crystal grains, and increase the recording density of a magnetic disk.

  Embodiments of a magnetic disk glass substrate and a magnetic disk manufacturing method according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining the state of the tape polishing device and the texture, FIG. 2 is a diagram for explaining the texture shape observed by the inspection device, and FIG. 3 is a diagram for explaining the evaluation results obtained by changing the intersecting angle between the circumferential direction and the texture. FIG. Note that dimensions, materials, and other specific numerical values shown in the following examples are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified.

  FIG. 1 is an explanatory view of a main part of the tape polishing apparatus. In the figure, a glass substrate 1 is a disk-shaped glass substrate for a magnetic disk, is supported by a spindle 10 and is driven to rotate at a predetermined speed. A polishing liquid containing an abrasive is discharged from the slurry nozzle 11 and supplied to a polishing head composed of a polishing tape 12 and a roller 13. The polishing tape 12 is wound around a roller 13, and the roller 13 presses the polishing tape 12 against both main surfaces of the glass substrate 1. The polishing tape 12 is wound up in a direction opposite to the rotation direction of the glass substrate 1 at a contact portion with the glass substrate 1, and a new surface always contacts the glass substrate 1. As a result, the main surface of the glass substrate 1 is rubbed and polished to form a circumferential texture.

  Further, by allowing the spindle 10 and the polishing tape 12 to swing relatively in the axial direction of the roller 13 (radial direction of the glass substrate), a cross texture or a spiral shape having a predetermined angle with respect to the circumferential direction. Form a texture. At this time, the texture locus (intersection angle with respect to the circumferential direction) is adjusted by adjusting the rotation speed of the glass substrate 1 (rotation speed of the spindle 10) and the relative oscillation cycle of the spindle 10 and the polishing tape 12. Can be adjusted.

  The material and shape of the polishing tape 12 are not particularly limited, and examples thereof include a flocking tape, a woven fabric tape, and a non-woven fabric tape. Examples of the tape fiber material include plastic fibers such as polyester and nylon. The abrasive contained in the polishing liquid is not particularly limited as long as it is an abrasive grain used for polishing a glass substrate such as diamond abrasive grains, alumina, cerium oxide, colloidal silica, or a mixture thereof. Good.

  Here, in the present embodiment, two types of textures having different intersection angles of the texture locus with respect to the circumferential direction are formed. That is, first, the first texture 20 having a large intersection angle α is formed, and then the second texture 21 having a small intersection angle β is formed.

  FIG. 2 shows a texture shape observed by an optical reflection type fine defect inspection apparatus MicroMax (VISION PSYTEC). 2A is an example in which a texture according to the present embodiment is applied, FIG. 2B is an example in which only a texture having a large intersection angle is applied as Comparative Example 1, and FIG. The example which gave only the texture with a small angle is shown. MicroMax is an evaluation device that visualizes reflected light, and represents a texture scratch having a deep concave shape in a white portion. Referring to FIG. 2C, a texture having a small intersection angle forms many continuous deep scratches. Referring to FIG. 2B, a texture having a large intersection angle has almost no deep scratches. Recognize. Then, referring to FIG. 2A, it is understood that when a texture having a small intersection angle is applied after a texture having a large intersection angle, a large continuous one is not formed.

  According to the inventor's consideration, when a glass substrate is polished with a tape, first, if there is a convex foreign material on the glass substrate, the convex foreign material is removed by tape polishing and floated as a contamination. To do. At this time, when the crossing angle is small, it is considered that floating contaminants are sandwiched between the glass substrate 1 and the polishing tape 12 and there is no escape space, and scratches are formed on the glass substrate 1. This scratch generates a signal error (negative modulation) that is continuous in the circumferential direction, that is, the read / write direction (track direction). Negative modulation is a signal error that is counted when a high-frequency signal (for example, 300 kfci) is written on one track, when a predetermined number of output recording bits that are less than or equal to the average output continue. .

  However, when the crossing angle is large, a trajectory in a random direction is drawn. Therefore, it is considered that the contamination is quickly dropped from between the glass substrate 1 and the polishing tape, so that a deep scratch is not formed on the glass substrate 1. Even if a scratch is generated, since it is inclined with respect to the circumferential direction, signal errors continuous in the read / write direction can be minimized.

Furthermore, by drawing a trajectory in a random direction, it is possible to reduce the micro-waveness, to improve the low flying height of the magnetic head and to ensure stability. Microwaveness is a quantity that expresses a waviness with a period as a height, and is expressed in units of arithmetic average roughness (Ra) and root mean square roughness (Rq). In the present embodiment, the micro-waveness is the average height (average) of micro-waviness obtained by the following relational expression when the period of micro-waviness is 2 μm to 4 mm when the substrate surface is measured by non-contact laser interferometry. Value) Ra ′ is preferably 0.4 nm or less.

  In the step of forming the second texture having a small intersection angle, the occurrence of scratches can be suppressed because the convex foreign matter has already been removed. In addition, since the angle is close to the circumferential direction, the surface roughness in the circumferential direction is reduced, and the prevention of crash failure and thermal asperity in the low flying height region can be achieved. Furthermore, since the crossing angle is small, the orientation of the magnetic crystal grains in the circumferential direction can be improved, and the recording density of the magnetic disk can be increased.

  As will be described later, it is preferable that the intersection angle of the first texture with respect to the circumferential direction is 0.1 ° or more and the intersection angle of the second texture with respect to the circumferential direction is smaller than 0.1 °. Furthermore, the intersection angle of the first texture with respect to the circumferential direction is preferably 0.2 ° or more.

[Example]
Examples of a glass substrate for a magnetic disk and a method for manufacturing the magnetic disk to which the present invention is applied will be described below. This glass substrate for magnetic disk and magnetic disk are 0.85 inch type disk (inner diameter 6 mm, outer diameter 21.6 mm, plate thickness 0.381 mm), 1.0 inch type disk (inner diameter 7 mm, outer diameter 27.4 mm, It is manufactured as a magnetic disk having a predetermined shape such as a plate thickness of 0.381 mm) and a 1.8 inch type magnetic disk (inner diameter of 12 mm, outer diameter of 48 mm, plate thickness of 0.508 mm). Further, it may be manufactured as a 2.5 inch type disc or a 3.5 inch type disc.

(1) Shape processing step and first lapping step First, the melted aluminosilicate glass was molded into a disk shape by direct pressing using an upper die, a lower die, and a barrel die to obtain an amorphous plate glass. The aluminosilicate glass is a glass containing an alkali metal element having a network-like glass skeleton made of SiO and a structure containing aluminum as a modifying ion. In addition to direct pressing, a disk-shaped glass substrate for a magnetic disk may be obtained by cutting a sheet glass formed by a downdraw method or a float method with a grinding wheel. As the aluminosilicate _glass, SiO 2: 58 to 75 _{wt%, Al} 2 O 3: _{5~23 wt%,} Li 2 O: 3 to 10 _wt%, Na 2 O: 4 to 13 principal component weight% Chemically strengthened glass contained as

  Next, both main surfaces of the plate glass were lapped to form a disk-shaped glass base material. The lapping process is a grinding process in which a lapping platen is pressed against the main surface of the sheet glass and roughed.

(2) Cutting process (coring, forming)
Next, an inner hole was formed in the center using a cylindrical diamond drill (coring). Then, the inner peripheral end face and the outer peripheral end face were ground with a diamond grindstone and subjected to predetermined chamfering (forming).

(3) End surface polishing process Next, the end surface of the glass substrate was mirror-polished by a brush polishing method. By this end surface polishing step, the end surface of the glass substrate was processed into a mirror surface state capable of preventing generation of particles and the like.

(4) Second Lapping Step Next, a second lapping process was performed on both main surfaces of the obtained glass substrate in the same manner as in the first lapping step. By performing this second lapping step, it is possible to remove in advance the fine unevenness formed on the main surface in the cutting step and end surface polishing step, which are the previous steps, and shorten the subsequent polishing step on the main surface. Will be able to be completed in time.

  In the second lapping step, # 1000 is selected as the grain size of the abrasive grains, the flatness of the main surface is 3 μm, the surface roughness Rmax is about 2 μm, and the arithmetic average roughness Ra is about 0.2 μm (Rmax and Ra are According to Japanese Industrial Standard (JIS) B0601). Rmax and Ra were measured with an atomic force microscope (AFM) (Digital Instruments Nanoscope). The flatness is measured by a flatness measuring device, and is the distance (height difference) between the highest part and the lowest part of the substrate surface in the vertical direction (direction perpendicular to the surface).

(5) 1st grinding | polishing process of a main surface First, the 1st grinding | polishing process was given as a grinding | polishing process of a main surface. The primary purpose of this first polishing step is to polish the main surface in advance prior to the second polishing step (mirror polishing step), which is the next step, and to remove scratches and distortions remaining on the main surface in the lapping step described above. To do.

  In the first polishing step, 100 to 200 glass substrates were polished at once by a double-side polishing apparatus capable of polishing. This double-side polishing apparatus performs polishing by sandwiching a large number of glass substrates with an upper surface plate and a lower surface plate through a polishing cloth and relatively moving them by a planetary gear mechanism. A hard resin polisher was used as the polishing cloth in the first polishing step. As the abrasive, cerium oxide abrasive grains were used, and those having a maximum particle size of 3.5 μm, an average value of 1.1 μm, and a D50 value of 1.1 μm were mixed in water.

  The glass substrate which finished this 1st grinding | polishing process was immersed in each washing tank of neutral detergent, a pure water, and IPA (isopropyl alcohol) one by one, and was wash | cleaned.

(6) Second polishing step for main surface Next, a second polishing step was performed as a polishing step for the main surface. The purpose of this second polishing step is to finish the main surface into a mirror surface. In the second polishing step, mirror polishing of the main surface was performed using a soft foam resin polisher, specifically, foamed polyurethane, as the polishing cloth, using the same double-side polishing apparatus as in the first polishing step.

  Colloidal silica abrasive grains having a grain diameter of 40 nm were prepared as abrasives, and a polishing liquid was prepared by adding water, sulfuric acid as a total dissociating inorganic acid, and tartaric acid as an organic acid as a chemical solution having a buffering action. The content of silica in the polishing liquid is preferably 5 to 40% by weight. In this example, it was 10% by weight. The balance in the polishing liquid is ultrapure water.

(7) Cleaning step after mirror polishing The glass substrate after the second polishing step was immersed in an aqueous NaOH solution having a concentration of 3 to 5 wt% to perform alkali cleaning. The cleaning was performed by applying ultrasonic waves. Furthermore, it wash | cleaned by immersing in each washing tank of neutral detergent, a pure water, a pure water, IPA, and IPA (steam drying) sequentially. Note that ultrasonic waves were applied to each cleaning tank.

(8) Chemical strengthening process Next, the glass substrate which finished the above-mentioned lapping process and polishing process was chemically strengthened. For chemical strengthening, a chemical strengthening solution prepared by mixing potassium nitrate (60%) and sodium nitrate (40%) is prepared, and the chemically strengthened solution is heated to 375 ° C., and the cleaned glass substrate is preheated to 300 ° C. And was immersed in the chemical strengthening solution for about 3 hours. In this immersion, in order to chemically strengthen the entire surface of the glass substrate, it was performed in a state of being housed in a holder so that a plurality of glass substrates were held at the end surfaces.

  Thus, by immersing in the chemical strengthening solution, the lithium ions and sodium ions in the surface layer of the glass substrate are replaced with sodium ions and potassium ions in the chemical strengthening solution, respectively, and the glass substrate is strengthened. The thickness of the compressive stress layer formed on the surface layer of the glass substrate was about 100 μm to 200 μm.

  The glass substrate that had been subjected to the chemical strengthening treatment was immersed in a 20 ° C. water bath and rapidly cooled, and maintained for about 10 minutes. And the glass substrate which finished quenching was immersed in the concentrated sulfuric acid heated at about 40 degreeC, and was wash | cleaned. Further, the glass substrate after the sulfuric acid cleaning was cleaned by immersing in a cleaning bath of pure water and IPA (isopropyl alcohol) sequentially.

(9) Tape grinding | polishing process Next, tape grinding | polishing was performed with respect to the glass substrate wash | cleaned by said (8) using the tape grinding apparatus (refer FIG. 1) demonstrated above. At this time, as shown to Fig.3 (a), it experimented by the structure of Examples 1-7 and Comparative Examples 1-4 by changing the intersection angle of the circumferential direction and a texture variously. In Examples 1 to 7, the intersection angle of the first texture with respect to the circumferential direction is 0.1 ° or more, and the intersection angle of the second texture with respect to the circumferential direction is smaller than 0.1 °. Comparative Example 1 has only the first texture (see FIG. 2B), Comparative Example 2 has only the second texture (see FIG. 2C), and Comparative Example 3 has the first texture. The intersection angle is smaller than the second texture, and in Comparative Example 4, both the first texture and the second texture have a small intersection angle. In addition, the numerical value of the crossing angle in the figure is an angle measured at a position of a radius of 22 mm of a 2.5 inch type disk.

  After the tape polishing was completed, the surface of the glass substrate in each example and comparative example was in a clean mirror state. There were no foreign objects on the surface that could hinder the flying of the magnetic head or cause thermal asperity failure. That is, a flat and smooth high-rigidity glass substrate for a magnetic disk was obtained.

  A magnetic disk of the longitudinal magnetic recording system was manufactured using the glass substrate for a magnetic disk manufactured as described above.

(11) Magnetic disk manufacturing process A CrTi layer, a CoW underlayer, a CoPtCrB magnetic layer, and a hydrogenated carbon protective layer are formed on an in-line type sputtering apparatus on the magnetic disk glass substrate obtained through the above-described processes. Then, a perfluoropolyether lubricating layer was formed by a dip method to produce a magnetic disk. Although this configuration is an example of the configuration of the in-plane magnetic disk, a magnetic layer or the like may be configured as a perpendicular magnetic disk.

[Evaluation]
A recording / reproducing test was performed on the magnetic disks having the configurations of the examples and the comparative examples obtained by the above manufacturing method. Then, as shown in FIG. 3 (a), the magnetic anisotropy coefficient OR (Mrt) = Mrt (circumferential direction) / Mrt (radial direction), the scratch occurrence rate, and the negative modulation count were evaluated. It was.

  First, referring to FIG. 3A, Comparative Example 3 in which the second texture has a large intersection angle and Comparative Example 1 in which the second texture is not applied (that is, the state where the first texture has a large intersection angle) are obtained. , OR value is low. On the other hand, in the other examples and comparative examples, the second texture is constant at 0.01 °. However, as can be seen from FIG. FIG. 3B is a graph visualizing the value of OR with respect to the intersection angle of the first texture. From this, it is understood that the second texture as the texture final step preferably has a small intersection angle. From the experimental results, it can be seen that the intersection angle of the second texture with respect to the circumferential direction is preferably smaller than 0.1 °.

  FIG. 3B is a graph visualizing the scratch occurrence rate and the negative modulation with respect to the intersection angle of the first texture. As can be seen from the figure, as the crossing angle of the first texture is increased, the scratch occurrence rate and the negative modulation count are significantly reduced. From the experimental results, it can be seen that the crossing angle of the first texture with respect to the circumferential direction is preferably 0.1 ° or more, and more preferably 0.2 ° or more.

  As described above, according to the present invention, the first texture having a large intersection angle with respect to the circumferential direction and the second texture having a small intersection angle are formed in this order, thereby preventing deep scratches in the circumferential direction. Thus, it is possible to increase the orientation of the magnetic crystal grains while minimizing negative modulation and to increase the recording density of the magnetic disk. Further, the micro-waveness can be lowered and the surface roughness can be reduced, so that the flying height and stability of the magnetic head can be reduced, and the crash failure and the thermal asperity can be prevented in the low flying height region.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention can be used as a method for manufacturing a glass substrate for a magnetic disk, a method for manufacturing a magnetic disk, and a magnetic disk.

It is a figure explaining the state of a tape grinding | polishing apparatus and a texture. It is a figure explaining the texture shape observed with the inspection apparatus. It is a figure explaining the result evaluated by changing the intersection angle of the circumference direction and a texture.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Glass substrate 10 ... Spindle 11 ... Slurry nozzle 12 ... Polishing tape 13 ... Roller 20 ... 1st texture 21 ... 2nd texture

Claims (5)

In the method of manufacturing a disk-shaped glass substrate for a magnetic disk used for a magnetic disk mounted on a load-and-load magnetic recording apparatus,
Forming a first texture having a trajectory that intersects the circumferential direction at a predetermined angle by repeatedly moving the polishing head in a radial direction relative to the rotating substrate;
Forming a second texture consisting of trajectories intersecting at a different angle from the first texture with respect to the circumferential direction in this order,
A method of manufacturing a glass substrate for a magnetic disk, wherein an intersection angle of the first texture with respect to a circumferential direction is larger than an intersection angle of the second texture with respect to a circumferential direction.   2. The magnetism according to claim 1, wherein the crossing angle of the first texture with respect to the circumferential direction is 0.1 ° or more, and the crossing angle of the second texture with respect to the circumferential direction is smaller than 0.1 °. A method for producing a glass substrate for a disk.   2. The method of manufacturing a glass substrate for a magnetic disk according to claim 1, wherein an angle of intersection of the first texture with respect to the circumferential direction is 0.2 [deg.] Or more.   The method for manufacturing a glass substrate for a magnetic disk according to any one of claims 1 to 3, wherein the flying height of the magnetic head is used for a magnetic disk of 8 nm or less.   A magnetic disk manufacturing method comprising: forming a magnetic layer of at least a Co alloy system on a surface of a glass substrate for a magnetic disk obtained by the method for manufacturing a glass substrate for a magnetic disk according to claim 1. Method.