JP5840958B2 - Surface flattening method of glass disk - Google Patents

Description

  The present invention relates to a glass disk surface flattening method for flattening the outer peripheral surface of a glass disk used as an information recording medium substrate or the like.

  Conventionally, glass substrates made of glass are used in addition to aluminum discs for aluminum as information recording medium substrates for HDDs (hard disk drives). The glass disk for HDD is required to have a nanoscale flatness of about 5 nm in terms of Ra as the surface roughness of its recording surface and outer peripheral surface in order to stabilize the rotational operation during rotational driving. In general, such flatness is obtained by performing mechanical polishing using diamond abrasive grains or the like on a molded glass disk so that the Ra value of the glass disk becomes about 100 nm, and then cerium oxide is used. It is obtained by applying the used chemical mechanical polishing (CMP) (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 11-129155 JP 2009-94345

  By the way, the above-described CMP needs to use cerium oxide known as a so-called rare metal as an abrasive. Cerium oxide is very expensive because its country of origin is limited, etc. From the viewpoint of reducing manufacturing cost, a proposal of a method that can realize nanoscale flatness without using CMP is proposed. Is desired.

  In order to solve such a problem, Patent Document 2 discloses a surface flattening method for flattening the surface of a substrate such as a disk using near-field light. In this surface planarization method, a substrate such as a disk is placed in a chamber to which an etching gas such as fluorine gas is supplied, and light having a wavelength longer than the absorption edge wavelength of the etching gas is irradiated. This generates near-field light on the minute projections formed on the surface of the substrate and dissociates the etching gas through a non-adiabatic process based on the near-field light, thereby selecting only the minute projections on the surface of the substrate. Etching can be performed.

  However, in the surface flattening method disclosed in Patent Document 2, it is necessary to use an etching gas such as a fluorine gas, and therefore it is necessary to work in consideration of toxicity to the human body and danger during handling. There is.

  In addition, the polishing rate per unit of CMP is on the order of 10 to 50 nm / min, the etching rate per unit time by the method of Patent Document 2 is on the order of 100 nm / hour, and in order to obtain nanoscale flatness In addition, there is a problem that long work is required.

  Therefore, the present invention has been devised in view of the above-described problems, and the object of the present invention is to realize nanoscale flatness in a short time without using CMP or etching gas. An object of the present invention is to provide a method for flattening the surface of a glass disk.

  In order to solve the above-mentioned problems, the present inventor has invented the following method for flattening the surface of a glass disk after intensive studies.

A glass disk surface flattening method according to a first aspect of the present invention is a glass disk surface flattening method for flattening an outer peripheral surface of a glass disk to a nano-order , wherein a light absorbing material is applied to the outer peripheral surface of the glass disk. And applying the light absorbing film to the light absorbing film while moving the light irradiation range to the light absorbing film at a relatively constant speed along the circumferential direction of the glass disk. A continuous irradiation step of irradiating continuous wave laser light, and in the continuous irradiation step, thermal stress is generated in the outer peripheral portion of the glass disk by light absorption of continuous wave laser light in the light absorbing film, The outer peripheral portion of the glass disk is broken along the circumferential direction based on thermal stress.

  According to a second aspect of the present invention, there is provided the glass disk surface flattening method according to the first aspect, wherein in the continuous irradiation step, the continuous wave laser is applied to the light-absorbing film while the glass disk is rotated at a constant speed around a central axis. By irradiating light, the light irradiation range with respect to the light absorptive film is moved relatively at a constant speed along the circumferential direction of the glass disk.

  According to a third aspect of the present invention, there is provided the glass disk surface flattening method according to the first aspect, in the continuous irradiation step, in a state where the oscillation source of the continuous wave laser light is rotated at a constant angular velocity around the central axis of the glass disk. By irradiating the light absorbing film with continuous wave laser light, the light irradiation range with respect to the light absorbing film is moved at a relatively constant speed along the circumferential direction of the glass disk.

  According to the first to third inventions, CMP and etching gas are performed only by performing a simple procedure of irradiating a glass disk with continuous wave laser light after forming a light absorbing film on the outer peripheral surface of the glass disk. Nanoscale flatness can be realized without using. In particular, since CMP is not required, cerium oxide as a rare metal required for CMP is not required, and nanoscale flatness can be realized at a very low cost. In addition, it is possible to obtain nano-order flatness in a very short time on the outer peripheral surface of the disk.

(A) is a top view which shows the structure of a glass disc, (b) is an expanded sectional view of the outer peripheral part. It is a figure which shows an example of the schematic structure of the surface planarization apparatus used with the surface planarization method which concerns on 1st Embodiment. It is a figure for demonstrating the surface planarization method which concerns on 1st Embodiment. It is a perspective view for demonstrating the light irradiation range of a continuous wave laser beam. It is a perspective view which shows the state in the middle of fracture | rupturing the outer peripheral part of a glass disc by application of the surface planarization method which concerns on 1st Embodiment. It is a figure for demonstrating the surface planarization method which concerns on the modification of 1st Embodiment.

  Hereinafter, an embodiment for carrying out a method for flattening a surface of a glass disk to which the present invention is applied will be described in detail with reference to the drawings.

  As shown in FIG. 1, a glass disk 1 (hereinafter referred to as a disk 1) to which the present invention is applied is formed in a disk shape as a whole, and a pair of main surfaces 11 on both upper and lower sides thereof, The outer peripheral surface 12 provided in the outer peripheral side of a pair of main surface 11 is provided. The disk 1 is formed, for example, such that its thickness is 0.6 mm to 2 mm and its diameter is 45 mm to 200 mm. In the first embodiment, the outer peripheral surface 12 of the disk 1 includes a vertical surface 12 a parallel to the vertical direction, and a chamfer surface 12 b as an inclined surface provided between the vertical surface 12 a and the main surface 11. The disk 1 is used as an information recording medium substrate such as an HDD substrate.

  The material of the disk 1 is not particularly limited as long as it is a glass material. For example, aluminosilicate glass, soda lime glass, ceramic glass, or the like is used.

  In the surface flattening method according to the present invention, a continuous irradiation step S2 described later is performed using a surface flattening apparatus 3 as described below.

  As shown in FIG. 2, the surface flattening device 3 according to the first embodiment includes an illumination optical system 31 that irradiates the disk 1 with continuous wave laser light, and a spindle 34 that rotates the disk 1.

  In the first embodiment, the illumination optical system 31 is a laser light source 32 that oscillates continuous wave laser light, and a light irradiation range adjustment that adjusts the light irradiation range of the continuous wave laser light oscillated from the laser light source 32 to the glass disk 1. And a collimating lens 33 as means.

  The laser light source 32 oscillates continuous wave laser light having a predetermined wavelength based on control by a driving power source (not shown). The continuous wave laser light oscillated from the laser light source 32 can adjust the light irradiation range on the glass disk 1 by adjusting the position of the collimating lens 33 in the first embodiment. The means for adjusting the light irradiation range of the continuous wave laser light is not limited to the one using only such a collimating lens 33.

  The spindle 34 is configured so that the disk 1 can be mounted. The spindle 34 is configured so that the disk 1 can be rotated around the central axis at a constant speed by driving a motor (not shown).

  Next, the surface flattening method according to the present invention will be described.

  The surface flattening method according to the present invention includes a coating step S1 and a continuous irradiation step S2.

  In the coating step S1, a light absorbing film 2 is formed by applying a light absorbing material to the outer peripheral surface 12 of the disk 1 as shown in FIG. As the light absorbing material, a material having a high absorptance with respect to the wavelength of the continuous wave laser light emitted from the illumination optical system 31 is selected. From such a point of view, for example, a material containing various coloring compounds including a black compound as a pigment or dye is used as the light absorbing material. Examples of the black compound include carbon black. The light-absorbing material is applied in a state where it is dissolved in an organic solvent such as an aromatic, alcohol, or fatty acid. Examples of the method for applying the light-absorbing material include application by a roll coater, brush coating, spraying, and the like, in addition to coating by a writing instrument such as a pen with a built-in ink containing the light-absorbing material.

  In the continuous irradiation step S2, as shown in FIGS. 3B and 4, the light-absorbing film 2 on the outer peripheral surface 12 of the disk 1 is irradiated with a continuous wave laser beam. The continuous wave laser beam 42 is irradiated from the illumination optical system 31 in the first embodiment, and the wavelength thereof is longer than the absorption edge wavelength of the glass material that is the material of the disk 1 so that the disk 1 is not photoexcited. Is used. As an example of this wavelength, since a general glass material has an absorption edge wavelength of about 400 nm, the continuous wave laser light 42 has a wavelength longer than the absorption edge wavelength, for example, a wavelength of 532 nm. Is used.

  In this continuous irradiation step S2, as shown in FIG. 4, the light-absorbing film 2 is moved to the light-absorbing film 2 while moving the light-irradiating range 41 relative to the light-absorbing film 2 at a relatively constant speed along the circumferential direction of the disk 1. On the other hand, continuous wave laser light 42 is irradiated. In the first embodiment, by irradiating the light-absorbing film 2 with the continuous wave laser light 42 while rotating the disk 1 around the central axis at a constant speed, the light irradiation range 41 for the light-absorbing film 2 is set. Move relatively at a constant speed. At this time, in the first embodiment, the disk 1 is rotated at a constant speed by the rotational drive of the spindle 34. Further, the rotational speed of the disk 1 at this time is, for example, 5 rpm to 20 rpm.

  By irradiating the light absorbing film 2 with the continuous wave laser light 42 in this way, light energy is converted into thermal energy by light absorption of the continuous wave laser light 42 in the light absorbing film 2. As a result, the outer peripheral portion 13 of the disk 1 is heated using the light absorbing film 2 as a heat source, as shown in FIG. Compressive thermal stress is generated by being constrained by this part, and tensile thermal stress is generated in a part away from the outer peripheral surface 12 of the disk 1 due to this compressive thermal stress.

  At this time, as a result of examination by the present inventor, the light irradiation is performed after adjusting the output power of the continuous wave laser light to the entire light irradiation range 41 so that a sufficient amount of heat is given to the outer peripheral portion 13 of the disk 1. When the range 41 is relatively moved along the circumferential direction of the disk 1, as shown in FIGS. 3C and 5, based on the tensile thermal stress generated in the outer peripheral portion 13 of the disk 1, It has been found that the outer peripheral portion 13 is broken along the circumferential direction. The fracture piece 15 formed by this fracture has a constant radial thickness of the disk 1.

  Further, when the light-absorbing film 2 is irradiated with continuous wave laser light while the moving speed of the light irradiation range 41 is kept constant, the fracture surface 14 formed after the fracture has a nano-order surface roughness. It was found that it was (Ra). This is because the continuous wave laser beam having a stable output power is irradiated while moving the light irradiation range 41 at a constant speed, so that the disk 1 is continuously fixed along the circumferential direction of the outer peripheral portion 13. This is probably because heat was given.

  In this way, in order to break the outer peripheral portion 13 of the disk 1 along the circumferential direction, the output power of the continuous wave laser beam is set to a certain level or more so that a sufficient amount of heat is given to the outer peripheral portion 13 of the disk 1. There is a need to. The output power of the continuous wave laser beam that satisfies these conditions is the wavelength of the continuous laser beam, the light absorption rate of the light absorbing film 2, the dimensional conditions such as the thickness and diameter of the disk 1, and the disk 1 Since it changes according to conditions, such as a glass material and the moving speed of the light irradiation range 41, it adjusts so that sufficient calorie | heat amount may be given in relation to these conditions.

  Further, when the outer peripheral portion 13 of the disk 1 is broken along the circumferential direction in this way, the portion of the outer peripheral surface 12 of the disk 1 through which the light irradiation range 41 has passed is continuously broken. For this reason, when the light-absorbing film 2 is formed over the entire circumference of the outer peripheral portion 13 of the disk 1, the outer peripheral surface 12 of the disk 1 is kept in a state where the outer peripheral surface 12 of the disk 1 is irradiated with continuous wave laser light. When the light irradiation range 41 is moved over one circumference, the outer peripheral portion 13 of the disk 1 is broken along the entire circumference.

  Note that the coating step S1 and the continuous irradiation step S2 may be performed continuously during the constant speed rotation of the disk 1, or the continuous irradiation step S2 may be performed after the coating step S1 is completed.

  According to the above, the light-absorbing film 2 is formed on the outer peripheral surface 12 of the disk 1 and then a simple procedure of irradiating the disk 1 with continuous wave laser light is performed without using CMP or etching gas. Nanoscale flatness can be realized. In particular, since CMP is not required, cerium oxide as a rare metal required for CMP is not required, and nanoscale flatness can be realized at a very low cost.

  Further, only by moving the light irradiation range 41 over the outer peripheral surface 12 of the disk 1, the outer peripheral portion 13 of the disk 1 is broken over the entire circumference along the circumferential direction, and the nano-order surface is formed over the entire circumference. A rough fracture surface 14 is obtained. The moving speed of the light irradiation range 41 is, for example, about 5 to 20 rpm in terms of the rotational speed of the disk 1 and is about several seconds per round of the outer peripheral surface 12 of the disk 1. For this reason, the application of the present invention makes it possible to obtain nano-order flatness on the outer peripheral surface 12 of the disk 1 in a very short time.

  Although the chamfer surface 12b formed on the outer peripheral surface 12 of the disk 1 is also removed by the application of the present invention, the present processing technique for obtaining nano-order flatness on the outer peripheral surface 12 of the disk 1 is described. The invention can be used.

  As mentioned above, although the example of embodiment of this invention was demonstrated in detail, all the embodiment mentioned above showed only the example of actualization in implementing this invention, and these are the technical aspects of this invention. The range should not be construed as limiting.

  For example, in the above-described embodiment, the disk 1 is rotated at a constant speed around the central axis in order to move the light irradiation range 41 with respect to the light-absorbing film 2 at a relatively constant speed along the circumferential direction of the disk 1. However, as shown in FIG. 6, the illumination optical system 31 serving as the oscillation source of the continuous wave laser light may be rotated at a constant angular speed around the central axis of the disk 1.

  Hereinafter, the effects of the present invention will be further described with reference to examples.

  In this example, the effect of the present invention was confirmed by actually using the surface flattening method according to the present invention.

  As the disk 1, a disk having a shape as shown in FIG. 1 was used. The disk 1 had a diameter of 63.5 mm and a wall thickness of 0.635 mm, and the material thereof was ceramic glass. As the surface flattening device 3, the one as shown in FIG. 2 was used, and as the laser light source 32, one having a wavelength of 532 nm and an output power of 15 W was used. The collimating lens 33 has a focal length f of 80 mm, and the distance between the collimating lens 33 and the disc 1 is set so that the light irradiation range on the disc 1 coincides with the overall length of the outer peripheral surface 12 of the disc 1 in the thickness direction. Was 125 mm.

  In the coating step S1, an ink containing carbon black is used as the light absorbing material, and the light absorbing film 2 is formed by applying the ink to the outer peripheral surface 12 of the disk 1 with a pen in which the ink is built. It was decided. The light absorbing film 2 is formed over the entire periphery of the outer peripheral portion 13 of the disk 1.

  In the continuous irradiation step S2, the light-absorbing film 2 is irradiated with the continuous wave laser beam 42 while the disk 1 is rotated at a constant speed of 8.3 rpm by the spindle 34.

  As a result, as shown in FIG. 3 (c), the outer peripheral portion 13 of the disk 1 was broken along the entire circumference. Further, the fracture surface 14 formed by this fracture had a surface roughness Ra value of 0.99 nm and a nano-order flatness. In addition, the time required for breaking the outer peripheral portion 13 of the disk 1 over the entire circumference is 7.2 seconds.

  As another test condition, the test was performed under the condition that the output power was 6 W and the rotation speed of the disk 1 was 1.5 rpm. As a result, it took about 40 seconds to break the outer peripheral portion 13 of the disk 1 over the entire circumference. Further, the fracture surface 14 formed by this fracture had the same surface roughness as when the output power was 15 W.

DESCRIPTION OF SYMBOLS 1 Glass disk 2 Light absorption film | membrane 3 Surface planarization apparatus 11 Main surface 12 Outer peripheral surface 13 Outer peripheral part 14 Fracture surface 15 Fracture surface 31 Illumination optical system 32 Laser light source 33 Collimating lens 34 Spindle 41 Light irradiation range 42 Continuous wave laser light

Claims (3)

In the glass disk surface flattening method for flattening the outer peripheral surface of the glass disk to the nano order ,
A coating step of coating a light-absorbing material on the outer peripheral surface of the glass disk to form a light-absorbing film;
A continuous irradiation step of irradiating the light absorbing film with a continuous wave laser beam in a state where the light irradiation range with respect to the light absorbing film is moved at a relatively constant speed along the circumferential direction of the glass disk; Have
In the continuous irradiation step, thermal stress is generated in the outer peripheral portion of the glass disk by light absorption of continuous wave laser light in the light absorbing film, and the outer peripheral portion of the glass disk is aligned along the circumferential direction based on the thermal stress. A method for flattening the surface of a glass disk, wherein In the continuous irradiation step, the light-absorbing film is irradiated with continuous-wave laser light in a state in which the glass disk is rotated at a constant speed around a central axis, whereby a light irradiation range for the light-absorbing film is changed to the glass. The method for flattening the surface of a glass disk according to claim 1, wherein the glass disk is moved relatively at a constant speed along a circumferential direction of the disk. In the continuous irradiation step, the light absorption film is irradiated with continuous wave laser light while the oscillation source of the continuous wave laser light is rotated at a constant angular velocity around the central axis of the glass disk, thereby absorbing the light. The surface flattening method for a glass disk according to claim 1, wherein the light irradiation range with respect to the conductive film is moved relatively at a constant speed along the circumferential direction of the glass disk.

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