JP4767939B2 - Method for manufacturing aluminum substrate for magnetic disk - Google Patents

Description

  The present invention relates to a method for manufacturing an aluminum substrate for a magnetic disk used as a base material of a recording medium of a magnetic disk device.

  In this specification, the term “aluminum” is used to include both aluminum and its alloys.

  An example of the aluminum substrate is a donut-shaped circular substrate (S ′) having a hole (10) formed in the center as shown in FIGS. 4 (A) and 4 (B). The aluminum substrate (S ′) has a chamfering angle (θ) and a chamfering length (L) at both edges in the plate thickness direction of the substrate (S ′) on the outer peripheral end surface (11) and the inner peripheral end surface (12). The chamfering process is performed at, and chamfered portions (13) and (14) are formed, respectively. The chamfering is performed, for example, by moving a cutting tool (not shown) along a path indicated by an arrow as shown in FIG. 5 in machining using an NC lathe.

  The aluminum substrate (S ′) thus chamfered is subjected to surface grinding of the storage surface (17) for storing magnetic data, nickel-phosphorus plating treatment, polishing processing for the purpose of smoothing the surface of the plating layer, and the like. The magnetic disk is processed through a plurality of processes.

  As shown in FIG. 2A, the delivery of the substrate (S ′) between the respective steps in the above manufacturing process is performed by chucking the peripheral portion of the aluminum substrate (S ′) with a jig (20) having a V-shaped cross section. Done.

Note that the following are related arts related to the chamfered portion of the peripheral end surface of the magnetic disk substrate. For example, a technique for preventing errors during recording / reproduction by attaching R to the chamfered part, a technique for preventing deterioration of the recording / reproducing function by attaching R to the chamfered part, and a film by attaching R to the chamfered part (See Patent Documents 1, 2, and 3).
JP 2002-100031 A (Claim 1 etc.) JP-A-10-154321 (Claim 8 etc.) JP-A-9-102122 (Claim 1 etc.)

  As shown in FIGS. 2 (A) and 2 (B), when the peripheral portion of the aluminum substrate (S) is chucked using a jig (20) having a V-shaped cross section, the end surface (11) of the chamfered portion (13) is obtained. The side corners (15 ') (15') are in contact with the jig (20). If the center line (P1) of the aluminum substrate (S ′) and the center line (P2) of the jig (20) coincide with each other as shown in FIG. ) Corners (15 ′) and (15 ′) have equal receiving surface angles.

  However, under actual operation, the center lines (P1) and (P2) of the two as shown in FIG. 2 (B) due to the slight displacement of the position of the aluminum substrate (S ′) and the approach posture of the jig (20). ) May shift. When the center line (P1) of the aluminum substrate (S ′) and the center line (P2) of the jig (20) are deviated, a difference occurs in the angle of the receiving surface of the left and right corners (15 ′) (15 ′) From the corners (15 ′) and (15 ′) on the end face side, scratches such as minute scratches may occur in the corner parts (18) and (18) on the storage face (17) side.

  If such a scratch exists on the aluminum substrate (S) or the magnetic disk substrate after nickel-phosphorus plating, a defective portion that cannot be read / written occurs, which causes a decrease in storage capacity and a crash of the read / write head. The product is inferior by product inspection.

  Recently, there is a strong demand for increasing the recording capacity of the magnetic disk substrate, and the recording density is increased or the area used as a storage area is widened. For this reason, it is necessary to eliminate minute scratches that have been allowed in the past and minute scratches in the inner and outer peripheral portions, particularly the outer peripheral portion, and there is a problem of deterioration in product yield.

  FIG. 2 shows the chucked state at the outer peripheral portion of the aluminum substrate (S ′), but the inner peripheral portion is also chucked by the similar jig (20), and the peripheral end surface of the chamfered portion (14). The jig may come into contact with the corner portions (16 ′) and (16 ′) on the (12) side, and the corner portion on the storage surface (19) side may be scratched.

  It is assumed that the above-mentioned scratch is caused by the chucking jig (20) coming into contact with the corners (15 ') (15'), (16 ') (16') at unequal angles. Is done. Eliminating slight deviations in the position of the aluminum substrate (S ') and the approach posture of the jig (20) is one solution to the problem, but there is a scratch on the chamfered side of the aluminum substrate (S'). A method for suppressing the occurrence is being sought. Each of the above-mentioned patent documents is to chamfer the chamfered portion, but does not show a relationship with scratches caused by chucking, and the substrate material is not a metal such as aluminum but glass.

  In view of the above-described technical background, an object of the present invention is to provide a method for manufacturing an aluminum substrate for a magnetic disk that can suppress the occurrence of scratches in a chamfered portion even if the contact angle with respect to a chucking jig varies.

That is, the manufacturing method of the aluminum substrate for magnetic disks of this invention has the following structure.
[1] A method of manufacturing an aluminum substrate for a magnetic disk using a donut-shaped aluminum substrate,
A step of forming chamfered portions on both edges in the plate thickness direction of the substrate for at least one of the outer peripheral end surface and the inner peripheral end surface of the substrate;
Processing the corner on the peripheral end surface side of the chamfered portion into a curved surface so that the radius of curvature (r) is 0.05 to 0.2 mm;
A step of chucking the curved surface processing portion with a jig having a V-shaped cross section and delivering the substrate to the next processing step;
Surface grinding the memory surface of the substrate;
A method for producing an aluminum substrate for a magnetic disk, comprising: performing nickel-phosphorous plating on a substrate in the order described above.

  [2] The step of forming the chamfered portion and the step of processing the corner portion into a curved surface are performed by machining, and the machining is performed from the chamfered portion to the peripheral end surface or from the peripheral end surface by moving the cutting tool. 2. The method for producing an aluminum substrate for a magnetic disk according to item 1, wherein the chamfered portion is continuously processed, and the cutting tool is moved in an arc shape at a corner between the chamfered portion and the peripheral end surface to form a curved surface. .

  [3] The method for manufacturing an aluminum substrate for a magnetic disk according to item 1 or 2, wherein the aluminum substrate is made of JIS A5086.

  According to the invention described in [1] above, it is possible to manufacture an aluminum substrate that can avoid stress concentration at the corners and prevent or suppress the occurrence of scratches during chucking. That is, even if the contact angle between the jig and the substrate varies during chucking, stress concentration on the corners is avoided and the generation of scratches is prevented or suppressed.

  According to the invention described in [2] above, an aluminum substrate that can prevent or suppress generation of scratches during chucking can be manufactured with the same number of man-hours as conventional substrate manufacturing.

  According to the invention described in [3] above, it is possible to manufacture a magnetic disk substrate that is excellent in terms of strength, plating ability, machinability and the like.

  FIG. 1 shows an embodiment of an aluminum substrate for a magnetic disk manufactured according to the present invention.

  The aluminum substrate (S) is a donut-shaped circular plate having a hole (10) in the center (refer to FIG. 4 (A), the overall shape of a conventional aluminum substrate (S ′)), an outer peripheral end surface (11), and On the inner peripheral end surface (12), chamfered portions (13) and (14) having a chamfering angle (θ) and a chamfering length (L) are formed on both edges in the plate thickness direction of the substrate (S). In these chamfered portions (13) and (14), the corner portions (15), (15), (16), and (16) on the peripheral end surface side are formed into curved surfaces having a curvature radius (r). In the figure, (17) is a storage surface for storing magnetic data, and (18) and (19) are corners on the storage surface (17) side of the chamfered portions (13) and (14).

  As shown in FIGS. 2A and 2B and FIG. 3, when the outer peripheral portion of the aluminum substrate (S) is chucked by a jig (20) having a V-shaped cross section, the circumference of the chamfered portion (13) is increased. It contacts the jig (20) at the corners (15) and (15) on the end face (11) side. FIG. 2A shows a state in which the center line (P1) in the thickness direction of the aluminum substrate (S) is coincident with the center line (P2) of the jig (20), and the opening of the jig (20) is shown. When the angle is (β1), the receiving surface angle of the jig (20) at the two corners (15) and (15) is equal to β1 / 2. On the other hand, FIG. 2B shows a state in which the center line (P1) of the aluminum substrate (S) is chucked at an angle (α) with respect to the center line (P2) of the jig, and two corner portions are shown. (15) The receiving surface angle in (15) is different by the inclination angle (α). 2 shows the chucked state at the outer peripheral portion of the aluminum substrate (S), the inner peripheral portion is also chucked by the similar jig (20), and the peripheral end surface ( 12) The jig contacts at the corners (16) and (16) on the side.

  In FIG. 3, the typical enlarged view of the contact part of one corner | angular part (15) of a chamfering part (13) and a jig | tool (20) is shown. In this figure, the chamfering angle (θ) of the aluminum substrate (S) is 25 °, and the opening angle (β1) of the jig (20) is 90 °. The solid line shows the case where the aluminum substrate (S) and the center lines (P1) (P2) of the jig (20) coincide, and the receiving surface angle (β2) is β1 / 2 = 45 °.

  In the aluminum substrate (S), the corners (15) and (16) on the peripheral end surfaces (11) and (12) side of the chamfered portions (13) and (14) are formed into curved surfaces. Therefore, the jig (20) is brought into contact with a larger area than the conventional angular corners (15 ′) and (16 ′), stress concentration is avoided, and a stable contact state is obtained. Further, as indicated by the alternate long and short dash line, even if the center lines (P1) and (P2) of both are shifted, the contact portion only moves on the same curved surface, and the stress concentration is avoided and stabilized by contacting with the curved surface. Contact state is obtained. In the illustrated example, the center line (P1) of the aluminum substrate (S) is inclined at an angle (α) from the center line (P2) of the jig (20), and the receiving surface angle (β3) of the jig (20) is β1. / 2-α, the chamfered portion (13) rotates in a direction approaching the jig (20), and the contact portion is shifted to the left in the drawing. Conversely, at the other corner (15) (not shown), the receiving surface angle is β1 / 2 + α, the chamfered portion (13) rotates and moves away from the jig (20), and the contact portion moves to the left. Misalignment as well as stress concentration during chucking is avoided. Similarly, stress concentration is avoided at the curved corner portion (16) of the inner peripheral portion (not shown). Thereby, in the aluminum substrate (S) of the present invention in which the corners (15) and (16) on the side of the peripheral end surfaces (11) and (12) of the chamfered portions (13) and (14) are formed in a curved surface, in the contact portion. It is presumed that stress concentration is avoided and the occurrence of scratches at the corners (18) and (19) on the memory surface (17) side is prevented or suppressed.

  In order to obtain a stable contact state with respect to a large inclination angle (α) at the corners (15) and (16) formed on the curved surface, it is effective to set the arc length of the curved surface long.

  Here, in view of the inclination angle that can occur in the normal manufacturing process, the arc length (M) of the effective contact region that enables stable chucking is set to a central angle of 40 ° (± 20 °) in a circle of radius (r). ), The arc length (M) is a numerical value shown in Table 1 below according to the set value of the radius (r). As shown in Table 1, the arc length (M) of the effective contact area increases in proportion to the radius of curvature (r), and the stability of chucking is improved. When the radius of curvature (r) is less than 0.05 mm, the arc length (M) is short and the effect of avoiding stress concentration is poor. On the other hand, when the radius of curvature (r) is increased, the arc length (M) is increased and the stress concentration avoidance effect is improved. However, the thickness of the normal aluminum substrate (S) is 0.635 to 1.27 mm, and the chamfer angle is increased. Considering that (θ) is 20 to 50 ° and the length (L) of the chamfered portions (13) and (14) is 0.13 to 0.21 mm, a length exceeding 0.2 mm is not realistic. Absent. Accordingly, the radius of curvature (r) at the corners (15) and (16) is preferably 0.05 mm to 0.2 mm. A particularly preferred radius of curvature (r) is 0.08 to 0.15 mm.

  Moreover, in the aluminum substrate of this invention, it is sufficient if the corners that come into contact with the chucking jig are formed in a curved surface. Accordingly, if the aluminum substrate is chucked only at one of the outer peripheral portion or the inner peripheral portion, only one of the aluminum substrates may be formed on a curved surface, and such an aluminum substrate is also included in the present invention.

  Moreover, although the aluminum which comprises the said aluminum substrate is not limited, JIS A5086 can be recommended. This is because the magnetic disk substrate can be excellent in terms of strength, plating property, machinability and the like.

  The chamfered portions (13) and (14) and the corner portions (15) and (16) formed on the curved surface can be formed by, for example, machining. In the machining process, as shown in FIG. 5, a cutting tool (not shown) is moved along a path indicated by an arrow (one chamfered portion-a peripheral end surface-the other chamfered portion) to chamfered portions (13) (14 ) Can be formed into a curved surface by moving the corners (15) and (16) so as to draw an arc. That is, the movement path from the peripheral end faces (11) and (12) to the chamfered parts (13) and (14) and the movement path from the chamfered parts (13) and (14) to the peripheral end faces (11) and (12) are arcuate. By doing so, the corner between these two surfaces can be formed into a curved surface. According to this method, it is not necessary to provide a separate process for forming the curved surface of the corner, and the aluminum substrate of the present invention can be manufactured with the same number of steps as in the prior art.

  The aluminum substrate (S) manufactured by the above-described method is formed into a magnetic disk by forming a magnetic layer after surface-grinding the storage surface (17). The magnetic disk uses an aluminum substrate with no scratches or a reduced number and size of scratches as a substrate, thereby suppressing defects in the magnetic layer, and thus corresponding to an increase in recording density and an expansion of a storage area. It can be. The kind of the magnetic layer is not limited, and examples thereof include a magnetic thin film such as nickel-phosphorus. The forming method can be exemplified by plating. Further, the magnetic layer in the present invention includes both a single layer and a multilayer, and further includes an underlayer and a surface protective layer.

  A large number of donut-shaped aluminum blanks (outer diameter: 95 mm, hole diameter: 25 mm, thickness: 1.27 mm) corresponding to JIS A5086 were prepared.

  The blank material was chamfered with a chamfering angle (θ) = 25 ° and a chamfering length (L) = 0.19 mm at the outer peripheral portion and the inner peripheral portion. The chamfering is performed by a cutting process using a cutting tool by an NC lathe, and the cutting tool (not shown) is moved along a path indicated by an arrow as shown in FIG. In this chamfering process, by moving the cutting tool in an arc shape, the corners (15) (15) (16) (16) on the end surface (11) (12) side of the chamfered part (13) (14) Was processed into a curved surface (see FIG. 1). The radius of curvature (r) of the corners (15) and (16) is 0.01 mm, 0.05 mm, 0.10 mm, 0.15 mm, and 0.20 mm, and five types of aluminum substrates having different curved corners ( S) was produced. However, the curvature radius (r): 0.01 mm is an extremely small curved surface that is unavoidably formed without setting the curvature radius (r) of the corner portion (15) in the machining process. In other words, it is an angular chamfer formed by conventional chamfering.

  Each manufactured aluminum substrate (S) was subjected to a chucking test using a V-shaped jig (20) having an opening angle (β) of 90 ° as shown in FIGS. Chucking is performed at a total of 6 locations, 3 locations on the outer periphery of the aluminum substrate (S) (peripheral positions on the outer periphery) and 3 locations on the inner periphery (three positions on the inner periphery). did. Then, a series of operations of chucking-moving-leaving was defined as one time, and this was repeated 150 times. The number of repetitions corresponds to five times the number of chucking performed in a normal magnetic disk substrate manufacturing process such as surface grinding of the storage surface (17), nickel-phosphorus plating treatment, and polishing of the plating layer. Table 1 shows the evaluation results according to the occurrence of scratches such as scratches.

  (Double-circle): The crack did not generate | occur | produce.

  ○: Slightly scratched, but to the extent that it is judged to be an acceptable product in normal product inspection.

  X: Scratches determined to be defective in normal product inspection occurred.

  From the results in Table 1, it was confirmed that the formation of scratches was suppressed by forming the corners of the chamfered portions that contact the chucking jig into curved surfaces.

  Next, with respect to the aluminum substrate evaluated as 評 価 or ○ in the evaluation of Table 1, that is, the aluminum substrate (S) formed with the curvature radius of the corner portion of the chamfered portion within the range of the present invention, the storage surface (17 ) Was subjected to surface grinding, and then a magnetic layer was formed to produce a magnetic disk. The magnetic layer is formed by degreasing, etching and zincate treatment by a conventional method, followed by a nickel sulfate bath using hypophosphite as a reducing agent, bath temperature 90 ° C., pH 4.5, treatment time 2. Nickel-phosphorus plating was performed under conditions of 0 hours, followed by washing with hot water, drying, heat treatment, and finishing polishing.

  When the surface state of the storage surface was observed with the optical interference type shape measuring apparatus for the above-described magnetic disk, no scratches of a level that would reduce the recording / reproducing function or the storage capacity occurred in any of the magnetic disks.

According to the present invention, an aluminum substrate for a magnetic disk that can suppress the occurrence of scratches on the chucking jig can be manufactured, and therefore, it can be applied to the manufacture of a magnetic disk.

It is principal part sectional drawing of one Embodiment of the aluminum substrate for magnetic discs of this invention. (A) and (B) are the partial front views which show the chucking state of an aluminum substrate. It is a schematic diagram which shows the contact part of an aluminum substrate and a jig | tool. It is the conventional aluminum substrate for magnetic discs, (A) is a fragmentary perspective view, (B) is principal part sectional drawing. It is explanatory drawing which shows the cutting process of a chamfer part.

Explanation of symbols

S, S '... Aluminum substrate for magnetic disk θ ... Chamfer angle r ... Radius of curvature L ... Chamfer length
10 ... hole
11… Outer end face
12 ... Inner peripheral edge
13,14… Chamfer
15,16… Corner on the end face side
17 Memory
18,19… The corner on the memory side

Claims (3)

A method of manufacturing an aluminum substrate for a magnetic disk using a donut-shaped aluminum substrate,
A step of forming chamfered portions on both edges in the plate thickness direction of the substrate for at least one of the outer peripheral end surface and the inner peripheral end surface of the substrate;
Processing the corner on the peripheral end surface side of the chamfered portion into a curved surface so that the radius of curvature (r) is 0.05 to 0.2 mm;
Using a jig having a V-shaped cross section, the curved surface processed portion is chucked at the outer periphery of the substrate at three locations on the outer periphery at three locations or at the inner periphery at three locations on the inner periphery. , The process of delivering the substrate to the next processing process,
Surface grinding the memory surface of the substrate;
A method for producing an aluminum substrate for a magnetic disk, comprising: performing nickel-phosphorous plating on a substrate in the order described above.   The step of forming the chamfered portion and the step of processing the corner portion into a curved surface are performed by machining, and the machining is performed by moving the cutting tool from the chamfered portion to the peripheral end surface, or from the peripheral end surface to the chamfered portion. 2. The method for producing an aluminum substrate for a magnetic disk according to claim 1, wherein the processing is performed continuously and the curved cutting tool is moved in an arc shape at a corner between the chamfered portion and the peripheral end surface to form a curved surface. The method for manufacturing an aluminum substrate for a magnetic disk according to claim 1, wherein the aluminum substrate is made of JIS A5086.

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