JP4092407B2 - Recording medium, recording apparatus, and recording medium manufacturing method - Google Patents

Description

The present invention relates to a method for protecting the surface of a substrate provided with a functional surface layer with a lubricating film, and to a functional substrate provided with such a lubricating film on the functional surface layer. In particular, the present invention relates to a recording medium provided with a recording film as a functional surface layer and a protective film formed on the surface. Specifically, the present invention relates to a recording medium in which a lubricating film is formed on a protective film, a recording apparatus provided with such a recording medium, and a method for manufacturing such a recording medium.
This application claims the priority based on the Japan patent application 2005-234322 for which it applied on August 12, 2005, The whole content of this application is used as reference in this specification.

Miniaturization of a substrate having a functional surface layer is in progress. For example, with the recent increase in capacity of recording media, the size and precision of magnetic recording apparatuses equipped with a recording magnetic disk (hereinafter simply referred to as “magnetic disk”) are being advanced. For example, recently, the gap between the recording head and the magnetic disk has reached only 10 nm. A DLC (diamond-like carbon) film is formed on the surface of the magnetic disk and the surface of the recording head as a protective film for protecting the two surfaces against contact and sliding. In recent years, the thickness of such a protective film has been reduced to about 2 to 3 nm.
The surface of the protective film (DLC film) is coated with a lubricant that exhibits a lubricating action against contact sliding between the head and the disk, thereby forming a lubricating film. The thickness of the lubricating film has been reduced to 1.5 nm to 2 nm so far, and has already reached the level of a monomolecular film (single layer film).

  In the magnetic recording apparatus having the precise configuration as described above, the ratio of the lubricant in the mechanical gap between the recording head and the magnetic disk is increasing. For this reason, the behavior and form of the lubricant (Conformation), the surface flow characteristics (Spreading) of the lubricant, and the like have greatly affected the reliability and durability of the magnetic recording apparatus. In other words, the reliability, durability, and the like of the recording medium and the magnetic recording apparatus including the medium can be improved by well controlling the characteristics of the lubricant, the shape of the lubricating film, and the like.

Specifically, in such a thin lubricating film, the function of being bonded to the solid (disk or head) surface with sufficient strength to prevent direct contact with the opposing solid (head or disk) surface (ie, Self-sustainability is required. At the same time, when the molecular film (lubricating film) breaks, the function of self-repairability (self-repairability) is required that allows the lubricant in the surrounding area to flow at a sufficient speed and repair the broken part. The However, the above self-holding function is a characteristic related to the immobility of the lubricating film, while the self-repairing function is a characteristic related to the fluidity of the lubricating film. Although it is generally difficult to satisfy such conflicting requirements, there is a strong demand for further improvement of the performance of the magnetic recording apparatus.
In this regard, for example, Japanese Patent Application Laid-Open No. 7-57245 discloses a substance having a polar group formed on a protective film of a magnetic disk in which regions having different surface energies are formed concentrically, pits, or spirally. It is disclosed that by forming a lubricating film made of a lubricant, it is possible to obtain a magnetic disk that has high wear resistance and is difficult to disperse lubricant due to disk rotation.

Accordingly, the present invention was created to solve the conventional problems related to a recording apparatus in which a recording medium (also referred to as a storage medium) such as a magnetic disk as described above can be mounted, and an object of the present invention relates to a lubricating film. It is to provide a recording medium that realizes both the self-holding function (fixability) and the self-repairing function (fluidity) at a high level. Another object is to provide a recording apparatus and a recording medium manufacturing method capable of mounting such a recording medium.
In addition, the improvement to the recording medium disclosed here is applied to a base material having a functional surface layer and a lubricating film in the same manner as the recording medium, and the functional group has improved the functional surface protection performance by the lubricating film. The purpose is to provide materials.

One recording medium provided by the present invention to solve the above problems has the following characteristics.
A recording medium (for example, a magnetic disk) comprising a substrate, a recording film (for example, a magnetic film) formed on the substrate, and a protective film formed on the recording film, the protective film A lubricating film formed of a predetermined lubricant is provided on the top. The lubricating film itself forms a microscopic uneven structure. At least a part of the lubricant in the concave part maintains fluidity that allows the convex part to flow, and when the lubricant in a part of the convex part is physically lost, the flow It is characterized in that at least a part of the deleted part is compensated by moving a part of the lubricant maintaining the property to the convex part.

In the recording medium having the above structure, a microscopic uneven structure composed of a lubricating film is formed on the surface of the protective film. For this reason, pinpoint lubrication (pinpoint surface protection) of only the convex portions is performed on the recording head. In other words, the concave / convex structure reduces the contact area with the recording head (typically contacts only at the top of the convex portion) and reduces the adhesion force (meniscus force) that adversely affects the fixing property of the lubricating film. Can be made. That is, the recording medium of the present invention has a microscopic structure (the concavo-convex structure) having an excellent self-holding function.
Also, when a part of the lubricant on the convex part (particularly the top) is lost due to contact of the recording head, etc., a part of the lubricant in the concave part moves (climbs up to the convex part), thereby At least part of the convex deletion is compensated. That is, the recess has a function of a lubricant storage tank for the lubricant. Therefore, the recording medium of the present invention has a high self-repair function.

In a preferred aspect of the recording medium of the present invention, the convex portion in the concavo-convex structure is formed in advance at a site where an energy ray (energy ray) capable of improving the binding force of the lubricant is artificially irradiated to the lubricant film in advance. In addition, the recess in the concavo-convex structure is formed at a site where the energy beam was not irradiated.
Preferably, the energy beam to be irradiated is at least one light beam selected from the group consisting of ultraviolet light, infrared light, and laser light, an ion beam, or an electron beam.
In the concavo-convex structure formed by irradiation of these light beams, ion beam or electron beam, the lubricant constituting the convex portion (that is, the portion irradiated with the energy beam) has high fixability and high self-holding. Characteristics are realized.

In another preferred embodiment of the recording medium of the present invention, the convex portion is formed in a bowl shape having a width of 0.5 μm to 600 μm sandwiched between the concave portions. It is particularly preferable that the maximum level difference (height difference) in such a concavo-convex structure is at least 0.2 nm (more preferably at least 0.5 nm).
By forming the convex portion in such a form, the contact area between the recording medium (protective film) and the recording head can be further reduced, and the adhesion force (meniscus force) can be further reduced.

In another preferred embodiment of the recording medium of the present invention, a striped pattern having the concavo-convex structure is formed on the lubricating film.
According to the present invention, it is possible to provide a recording medium in which such a striped pattern is arbitrarily formed. Therefore, the function / performance desired according to the application can be realized in a specific part of the protective film.

In a particularly preferred aspect of the recording medium of the present invention, the lubricating film is formed of a polar lubricant.
By irradiating the protective film composed of this type of lubricant with the energy beam, the recording medium of this aspect has a concavo-convex structure with a large step that is excellent in a self-holding function and a self-repairing function.

As another aspect, the present invention provides a method for suitably manufacturing any of the recording media (for example, magnetic disks) disclosed herein.
That is, a recording medium manufacturing method (for example, a magnetic disk manufacturing method) of the present invention includes a base material, a recording film (for example, a magnetic film) formed on the base material, and a protective film formed on the recording film. Is a method for manufacturing a recording medium. This method can (1) apply a predetermined lubricant on the protective film to form a lubricating film, and (2) improve the binding force of the lubricant in a predetermined pattern on the protective film. Irradiating with energy rays, (a) a convex part formed at a site irradiated with the energy beam, and (b) a concave part formed at a site where the energy beam was not irradiated, At least a part of the lubricant constituting the concave part maintains fluidity that allows flow to the convex part, and the fluidity is maintained when a part of the lubricant of the convex part is physically lost. Forming a microscopic concavo-convex structure comprising a concave portion characterized in that at least a part of the missing portion is compensated by moving a part of the lubricant to the convex portion.

By such a method, it is possible to manufacture a recording medium that is excellent in both the two functions that are inherently contradictory, the self-holding function and the self-repairing function.
Further, by performing the energy beam irradiation in a predetermined pattern, a concavo-convex structure (also referred to as a texture at the nm level) can be formed (patterned) in a desired pattern. Therefore, according to the method disclosed herein, the area ratio between the convex region and the concave region, the anisotropy of the concave / convex pattern (texture) can be arbitrarily adjusted, and further, the method can be fixed over a wide range of the recording medium. Can adjust and control the property (self-holding function) and fluidity (self-healing function). That is, according to the recording medium manufacturing method of the present invention, a recording medium having a functional surface (protective film) having a target function / performance can be easily manufactured.
For example, in the present invention, the energy beam irradiation can be performed with a pattern corresponding to the pattern so that a striped pattern having the concavo-convex structure is formed on the lubricating film.

In a preferred embodiment of the recording medium manufacturing method of the present invention, the protective film is at least one light selected from the group consisting of ultraviolet light, infrared light, and laser light, or an ion beam, or an electron beam. Are irradiated in a predetermined pattern.
By this type of irradiation with a high energy beam, an ion beam or an electron beam, a convex portion having a high self-holding characteristic can be formed.
Particularly preferably, the protective film is irradiated in a predetermined pattern with vacuum ultraviolet light in an inert gas atmosphere.

In another preferred embodiment of the method for producing a recording medium of the present invention, the protective film is irradiated with the energy beam in a linear form having a width of 0.5 μm to 600 μm, and a ridge-like convex corresponding to the linear irradiated part is obtained. Forming part. Particularly preferably, the irradiation amount of the energy beam is controlled so that the maximum level difference in the concavo-convex structure is at least 0.2 nm (or at least 0.5 nm).
By irradiating the energy beam in such a form, an uneven structure that can reduce the contact area between the recording medium (protective film) and the recording head and reduce the adhesion force (meniscus force) on the protective film surface. Can be formed.

In a particularly preferred embodiment of the recording medium manufacturing method of the present invention, a polar lubricant is used as the lubricant. As the lubricant having such polarity, it is particularly preferable to use a fluorine-based lubricant having at least one polar group.
By irradiating the lubricant film composed of such a lubricant with the energy beam, a recording medium having a concavo-convex structure with a large step which is excellent in a self-holding function and a self-repairing function can be manufactured.

The present invention also provides a recording apparatus (for example, a magnetic recording apparatus) provided with any of the recording media disclosed herein.
As described above, the recording apparatus of the present invention (for example, a recording apparatus in which the recording medium of the present invention is rotatably mounted) includes the recording medium excellent in the self-holding function and the self-repairing function. Realized.

  The improvements provided by the present invention are also applicable to functional substrates other than recording media. That is, the present invention relates to a method for protecting a surface of a substrate having a functional surface layer (for example, the surface of various probes or sensors) with a lubricating film, and such a lubricating film is formed on the functional surface layer. For functional substrates (eg, various probes or sensors, or other micromachines). That is, the functional base material provided by the present invention includes a functional surface layer formed on the base material, and a lubricating film formed with a predetermined lubricant on the functional surface layer. . The lubricating film itself constitutes a microscopic concavo-convex structure, and at least a part of the lubricant in the concave portion maintains fluidity capable of flowing to the convex portion, and the convex portion When a part of the lubricant is physically deleted, a part of the lubricant that maintains the fluidity moves to the convex portion, so that at least a part of the deleted part is compensated.

  Such a functional base material includes a base material main body and a functional film formed on the base material main body to give a predetermined lubricant to form a lubricating film, and the functional surface The layer is irradiated with energy rays that can improve the binding force of the lubricant in a predetermined pattern, and (a) a convex portion formed at a site irradiated with the energy rays, and (b) irradiation of the energy rays. A recess formed in a portion where the recess has not been performed, wherein at least a part of the lubricant constituting the recess maintains fluidity capable of flowing to the projection and lubricates a part of the projection A concave portion characterized in that, when the agent is physically deleted, a part of the lubricant that maintains the fluidity is moved to the convex portion to compensate at least a part of the defective portion; Forming a microscopic relief structure comprising: Some preferred embodiments of this method are as described above for the production of the recording medium.

FIG. 1 is a plan view schematically showing an example of a magnetic recording apparatus including a magnetic disk, which is a typical example of the present invention. FIG. 2 is a cross-sectional view showing an example of the structure of the magnetic disk of the present invention. FIG. 3 is a plan view schematically showing an example of the concavo-convex structure formed on the lubricating film of the magnetic disk of the present invention. FIG. 4 is a plan view schematically showing an example of the concavo-convex structure formed on the lubricating film of the magnetic disk of the present invention. 5A to 5F are diagrams schematically illustrating an example of a concavo-convex structure formed on the lubricating film of the magnetic disk of the present invention. FIG. 5A is a diagram for explaining the rotating direction of the magnetic disk, the sliding direction of the head, and the rotating air flow direction, and FIG. 5B is an example of a circumferential stripe pattern along the sliding direction. FIG. 5C shows an example of a radial stripe pattern perpendicular to the sliding direction, FIG. 5D shows an example of an oblique stripe pattern along the rotating air flow direction, and FIG. ) Shows an example of an oblique stripe pattern orthogonal to the sliding direction. FIG. 5F is an explanatory diagram showing each vector component (orthogonal component, inward component) constituting the rotating air flow direction. 6A to 6E are diagrams schematically illustrating an example of a concavo-convex structure (two-dimensional pattern) formed on the lubricating film of the magnetic disk of the present invention. FIG. 6A is a diagram for explaining the rotating direction of the magnetic disk, the sliding direction of the head, and the rotating air flow direction. FIG. 6B shows an example of a two-dimensional pattern (isotropic lattice pattern). FIG. 6C shows another example of a two-dimensional pattern (an anisotropic lattice pattern), FIG. 6D shows another example of a two-dimensional pattern (a depression pattern), and FIG. E) is an explanatory view showing another example (a plateau pattern) of a two-dimensional pattern. FIG. 7 is a graph showing the change in state of “film thickness redistribution” with the passage of time after UV irradiation at the irradiation boundary. The horizontal axis is the distance (d; mm), and the vertical axis is the thickness (h; nm) of the lubricating film. The plot lines in the figure are 0.5 hours (0.5 h), 6 hours (6 h), 12 hours (12 h), 24 hours after UV irradiation from the top in the UV non-irradiated region (Without UV; right side of the graph) 24h) and 48 hours (48h) later. FIG. 8 is a diagram schematically illustrating the redistribution of the film thickness after UV irradiation at the irradiation boundary. FIG. 9 is a schematic diagram illustrating a state of UV irradiation in the first embodiment. FIG. 10 is a graph showing the change in state of “film thickness redistribution” with the passage of time after UV irradiation at the irradiation boundary. The horizontal axis is the distance (d; mm), and the vertical axis is the thickness (h; nm) of the lubricating film. The plot lines in the figure are 0.5 hours (0.5 h), 6 hours (6 h), and 12 hours (12 h) after UV irradiation in the UV non-irradiated region (Without UV; the ellipse formation part on the right side of the graph). , 24 hours (24 h), 48 hours (48 h) later. FIG. 11 is a graph showing a change in “redistribution step” with time after UV irradiation at the irradiation boundary. The horizontal axis represents time (t: time), and the vertical axis represents the square value of the redistribution step (h _d ² ; nm ² ). FIG. 12 is a graph showing the relationship between the formation state of the “redistribution step” at the irradiation boundary and the UV irradiation time. The horizontal axis represents the UV irradiation time (t: seconds), and the vertical axis represents the redistribution level difference (h _d ; nm). FIG. 13 is a schematic diagram illustrating a state of UV irradiation in the third embodiment. FIG. 14 is an image obtained by visualizing, using an optical surface analyzer, the state change of the concavo-convex structure over time after UV irradiation at the site irradiated with UV that has passed through a linear slit having a slit width of 100 μm. (A), FIG. 14 (B), FIG. 14 (C), FIG. 14 (D), FIG. 14 (E) and FIG. 14 (F) are 0.5 hours, 1 hour, 3 hours after UV irradiation, respectively. It is an image when 9 hours, 24 hours and 48 hours have passed. FIG. 15A and FIG. 15B show optical surface analysis of the concavo-convex structure in the portion irradiated with UV that has passed through the slit of slits of 100 μm (FIG. 15A) and slits of 20 μm (FIG. It is the image visualized using the apparatus. FIG. 16A and FIG. 16B are diagrams showing a lubricant depletion state on the surface of the lubricating film by sliding the glass ball in Example 4, and FIG. 16 (A) is slid parallel to the uneven texture (stripe formation direction). FIG. 16B is an image obtained by visualizing the state in which the moving trace is formed using an optical surface analyzer, and FIG. 16B shows the state in which the sliding trace is formed perpendicular to the uneven texture (stripe formation direction). It is the image visualized using the surface analyzer. FIG. 17 is a graph showing changes in the film thickness of the lubricant deposition site (buttock) with the passage of time after sliding the glass ball in Example 4. The horizontal axis is the elapsed time (t; time), and the vertical axis is the deposition material (ΔS;%). FIG. 18 is a graph showing the change in film thickness of the lubricant depletion site (groove portion) over time after sliding the glass ball in Example 4. The horizontal axis is elapsed time (t; time), and the vertical axis is depletion charge (ΔS;%).

Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than those specifically mentioned in the present specification, and matters necessary for concrete implementation of the present invention (for example, the form of a part not related to the present invention in the magnetic recording apparatus and the magnetic recording apparatus The method of use) can be grasped as a design matter of those skilled in the art based on the common general technical knowledge in the field. The present invention can be implemented based on the contents disclosed in the present specification and common general technical knowledge in the field. For example, since an optical recording apparatus (also referred to as an optical storage apparatus) using a method in which a recording head is moved close to a recording medium has been recently studied, the present invention is not limited to a magnetic recording apparatus and the present invention is applied to an optical recording apparatus. May be applied.
The shape of the recording medium is not particularly limited, and may be a plate shape having various outer shapes and sizes, or a cylindrical shape such as a photosensitive drum of a copying machine, in addition to a typical disk shape.

Hereinafter, the present invention is specifically described by taking a recording medium (specifically, a magnetic disk) as an example of a functional base material provided by the present invention. A recording medium (for example, a recording medium that converts time information and spatial information by a close relative motion between the recording head (that is, the recording head itself is a component that can be included in the functional base material in this specification) and the recording medium (for example, Needless to say, the present invention can be applied to a magnetic recording medium and an optical recording medium), and a recording apparatus and a recording medium manufacturing method using the same.
A substrate having a functional surface that forms an electrostatic latent image, such as a photosensitive drum of a copying machine, is also included in the recording medium (functional substrate).

The magnetic disk provided by the present invention irradiates the protective film of the magnetic disk with ultraviolet light or other high-energy rays, thereby providing a convex portion that contacts the recording head and fluidity that can be supplied to the convex portion. The magnetic disk is characterized in that a concave-convex structure (chemical and microscopic texture) including a concave portion having a protective agent (lubricant) to be held is formed on the protective film. Therefore, there are no particular restrictions on the other components / structures of the magnetic disk and the constituent members of the magnetic recording apparatus other than the magnetic disk of the magnetic recording apparatus provided with the magnetic disk.
The magnetic recording apparatus 1 provided by the present invention may have a conventional configuration as shown in FIG. 1 when viewed macroscopically. That is, the magnetic recording apparatus 1 of one form shown in FIG. 1 roughly includes a case 3 that accommodates main components therein, a magnetic disk 10 accommodated in the case 3, and a recording magnetic head 2. Is provided. The magnetic disk 10 is attached to a spindle 4 that is rotated by a motor (not shown), and is rotated at a predetermined rotational speed. On the other hand, the recording magnetic head 2 is attached to the actuator 6 via the arm portion 8. At this time, the gap between the recording magnetic head 3 and the magnetic disk 10 can be 50 nm or less (for example, about 10 nm). Further, a not-illustrated backbone portion of the arm portion 8 is connected to the voice coil motor 7, whereby the recording magnetic head 3 is rotated and positioned.

FIG. 2 is a cross-sectional view showing an example of the configuration of a magnetic disk provided by the present invention. As shown in this figure, the magnetic disk 10 has a base material (substrate) 12 made of a metal such as an aluminum alloy, or amorphous glass or crystallized glass. A plating layer 13 (for example, nickel-phosphorus electroless plating) is formed on the surface of the substrate 12 by an electroless plating method or the like. A chromium underlayer 14 is formed on the surface by sputtering or the like. Further, a magnetic film 15 made of a cobalt alloy or the like is formed on the surface of the underlayer 14 by sputtering or the like (although not particularly limited, the bit interval is 30 to 35 nm and the thickness is about 10 to 50 nm, for example, 15 to 20 nm). Is formed.
A carbonaceous protective film, preferably a DLC protective film 16 (thickness 10 nm) is formed on the surface of the magnetic film 15 by performing a plasma CVD method while supplying a source gas such as methane gas or by an ion beam deposition method. Hereinafter, for example, 2 to 3 nm) is formed. Preferably, in order to improve the bonding between the surface of the carbonaceous (preferably made of DLC) protective film 16 and the lubricating film (lubricant) described later, a treatment for introducing a functional group into the surface of the carbonaceous protective film 16 is performed. Good. For example, an adsorption site can be generated in the vicinity of the introduced nitrogen atom by nitriding the surface layer of the carbonaceous protective film 16.

Thus, on the carbonaceous (preferably DLC) protective film 16, a predetermined lubricant is dipped (that is, a method in which the disk 10 is immersed in a solution containing the predetermined lubricant (polymer)) or the like. A lubrication film 17 formed by coating is formed.
In the practice of the present invention, such a lubricant film 17 can be used without any particular restriction on a lubricant (polymer) that has been conventionally used to form this type of lubricant film. For example, various perfluoropolyethers (PFPE) and perfluoroalkyl compounds that are used to form this type of lubricating film can be used.
Preferably, for example, the following linear main chain structure (1):
X-CF ₂ -[(OCF ₂ -CF ₂ ) m-[(OCF ₂ ) n] -O-CF ₂ -Y
(1)
(Here, m and n are real numbers and m / n is approximately 2/3. X and Y represent end groups.)
Perfluoropolyethers having the following are preferred. For example, (1). Nonpolar polyether (trade name “Fomblin Z”) in which terminal groups X and Y are each F, (2). Polar polyether (trade name “Fomblin Zdol”) in which the end groups X and Y are each CH ₂ —OH, (3). A polar polyether (trade name “Fomblin Zteraol”) in which the end groups X and Y are each CH ₂ —O—CH ₂ C (OH) H—CH ₂ OH, (4). A polar polyether (trade name “Fomblin Zdiac”) in which the end groups X and Y are each CH ₂ —COOH, (5). Terminal groups X, Y are each _{CH 2 -O-CH 2 - (} C 6 H 3) = O 2 = CH 2 in which the polarity of the polyether (trade name "Fomblin AM3001"), (6). A polar polyether having a terminal group X of CH ₂ —OH and a terminal group Y of CH ₂ O (N ₃ P ₃ ) [O (C ₆ H ₄ ) —CF ₃ ] ₅ (trade name “Moresco A20H” ), And the like.
Of these, the use of a polymer having polarity (that is, having at least one polar group at a terminal group or the like) is preferable. Examples of the terminal functional group (polar group) include a sulfone group or a metal salt or other hydrophilic group in addition to the hydroxyl group and carboxyl group listed here. By bonding such a terminal functional group (polar group) to a functional group contained on the surface of the DLC protective film 16, the lubricating film 17 having excellent fixability (self-holding function) can be formed.
Typically, the lubricant as described above is diluted with a suitable solvent, for example, a hydrofluoroether solvent (for example, 3M product (trade name): HFE-7200, Dupon product (trade name): VertrelXF). Then, the lubricating film 17 having an appropriate film thickness can be easily formed by immersing the manufactured magnetic disk in the obtained solution and pulling it up at a predetermined speed or pouring out the solution.

Next, a predetermined energy beam is irradiated onto the lubricating film in a desired pattern to form the concavo-convex structure having the above-described contents.
The type of energy ray employed in the practice of the present invention is not particularly limited as long as energy capable of forming a desired uneven structure can be imparted to the lubricating film.
For example, as the energy rays to be irradiated, at least one light ray selected from the group consisting of ultraviolet light (especially vacuum ultraviolet light having a wavelength region of approximately 100 to 200 nm is preferable), infrared light, and laser light, heat rays, Examples include actinic radiation, radiation, electromagnetic radiation, and radiation.
Particularly preferable energy rays for forming the concavo-convex structure are high-density and high-energy rays, such as ultraviolet light (particularly vacuum ultraviolet light), infrared light, laser light of various wavelengths, ion beams, electron beams, and the like. Can be mentioned.
As a light source for generating ultraviolet light, for example, a low-pressure mercury lamp (for example, Sen Special Light Source Company product: SUV110GS-36, 110W) can be mentioned. This type of mercury lamp has spectral peaks at wavelengths of 184.9 nm and 253.7 nm. Although not particularly limited, a disk sample is placed on the stage, the low-pressure mercury lamp (SUV110GS-36, 110W) is separated from the disk sample by an appropriate distance (for example, 50 mm), and the stage is moved at an appropriate speed (for example, 3.3 mm / By reciprocating with an appropriate width (for example, 50 mm) in s), the entire magnetic disk can be irradiated with ultraviolet light almost uniformly. Examples of other suitable light sources include dielectric barrier discharge excimer lamps (for example, Ushio Corporation product: USER20-172B). The excimer lamp has a spectral peak at a wavelength of 172 nm, and the nominal irradiation intensity at a distance of 5 mm from the lamp house surface to the disk surface can be about 10 mW / cm ² . Such ultraviolet light can particularly promote the binding force of a lubricant having an ultraviolet light functional type polarity (for example, the above-mentioned Fomblin AM3001 (trade name) having a benzene ring at the terminal).
Irradiation with ultraviolet rays or other energy rays can be performed in an air atmosphere, but is preferably performed in an inert gas atmosphere such as nitrogen or argon.

For example, the concavo-convex structure having a predetermined pattern can be easily performed by applying a lithography technique using a UV mask having a predetermined pattern. For example, the magnetic disk is irradiated with ultraviolet light or the like through a mask having a pattern in which transparent regions (slits) and opaque regions (masks) are alternately arranged in a striped pattern, and the binding state of the lubricant is changed according to the pattern. Can be distributed.
Alternatively, a desired pattern can be drawn by scanning a high energy beam using an elaborate XY or XYZ stage device and / or a laser beam scanning device.

As a typical pattern form to be formed on the lubricating film 17, an ultraviolet light irradiation portion 24 (that is, a convex portion forming portion 24) and a circumferential direction (circumferential striped pattern) of the magnetic disk 20 as shown in FIG. The form by which the ultraviolet light non-irradiation site | part 22 (namely, recessed part formation part 22) is formed alternately is mentioned. Further, as shown in FIG. 4, in the radial direction (radial stripe pattern) of the magnetic disk 30, an ultraviolet light irradiation part 34 (that is, the convex part forming part 34) and an ultraviolet light non-irradiation part 32 (that is, the concave part forming part 32). Is formed alternately.
Alternatively, in implementing the present invention, it is possible to design and implement a suitable pattern that can exhibit the desired performance and function in consideration of the application and operation mode of the magnetic disk.
This will be described in detail below.

The main three factors relating to the tribological characteristics of the recording head 2 and the magnetic disk 10 are the following three factors regarding the fixing property and fluidity of the lubricating film. The first factor is the characteristic in the circumferential direction induced by the direct sliding between the head and the disk, or the air pressure in the flying surface of the recording head 2 floating on the disk 10. The second factor is a characteristic in the radial direction in which the head 2 and the disk 10 are worn by being scraped in the radial direction from the surface by direct contact sliding. And the 3rd factor is the characteristic which goes to the diagonal outer periphery direction driven by the rotation airflow which goes to an outer periphery direction.
Therefore, in the approach related to such tribological characteristics, the optimum pattern of the concavo-convex structure exists by the combination of these three factors.
As a typical pattern corresponding to these factors, a circumferential stripe pattern as shown in FIG. 5 (FIG. 5B), a radial stripe pattern (FIG. 5C), and parallel to the direction of the rotating airflow (FIG. 5D). Alternatively, there is a skew pattern that is orthogonal (FIG. 5E). Here, it does not mean that the directions are strictly matched.
The present inventor has clarified that the flow in the parallel direction is faster in the vicinity of the surface of the disk 10 and the flow is slower in the orthogonal direction by the evaluation tests so far. Therefore, the flow direction can be adjusted and controlled by utilizing this anisotropic flow characteristic. For example, in the oblique stripe pattern (orthogonal) shown in FIG. 5E, if the direction of the rotating air flow is slightly inclined relative to the stripe, the upward component is generated along the stripe and the lubricant is moved upward. The effect to be generated will occur. That is, it has an inward component that is directed in the inner circumferential direction (FIG. 5F).

Furthermore, a two-dimensional pattern as shown in FIG. For example, in a two-dimensional isotropic lattice pattern as shown in FIG. 6B, an isotropic characteristic is obtained on average. In such an arrangement configuration of the convex portion forming portion 54 and the concave portion forming portion 52, the so-called concave portion 52 which is a lubricant non-fixed region functioning as a lubricant storage tank is divided, so that the fluidity is lowered. It has the feature. A two-dimensional anisotropic lattice pattern as shown in FIG. 6C is preferable. This pattern has the feature that the fixing property and fluidity can be adjusted in accordance with the magnitude and direction of the acting force by imparting anisotropic characteristics.
Further, in the two-dimensional recessed pattern formed by arranging the convex portion forming portion 54 and the concave portion forming portion 52 as shown in FIG. 6D, the concave portion 52 that is a lubricant non-fixed region that functions as a lubricant storage tank is divided. In addition, the convex portion 54 which is the lubricant fixing region is continuous, and can be a lubricating film having a high fixability. That is, it has a feature of high self-holding function.
On the contrary, in the two-dimensional plateau pattern formed by the arrangement configuration of the convex portion forming portion 54 and the concave portion forming portion 52 as shown in FIG. 6E, the convex portion 54 that is the lubricant fixing region is discontinuous, and the surroundings The recess 52 has a certain height. For this reason, it is effective in reducing the adhesion force (meniscus force) due to the effect of reducing the contact area with the magnetic head 2. Further, the concave portion 52 which is a lubricant non-fixed region functioning as a lubricant storage tank is continuous, and it has a feature that surface flow by sliding or rotating air flow is easy.
As described above, according to the present invention, an uneven structure having a pattern suitable for exerting desired characteristics (self-holding function and / or self-repairing function) according to the intended use and usage of the magnetic disk is provided. And a magnetic recording device comprising such a magnetic disk can be provided.

The concavo-convex structure formed by the present invention is characterized in that the concavo-convex step (height difference) gradually expands at a specific portion after applying ultraviolet light or other energy rays to the lubricating film 17. Typically, as will be described later in the examples, the protrusion is formed in a bowl shape having a width of 0.5 μm to 600 μm sandwiched between the recesses, and the maximum step of the uneven structure is 0.2 nm or more (preferably 0). .5 nm or more).
That is, in the magnetic disk manufactured according to the present invention, a concavo-convex structure is formed in which the height difference gradually increases at the boundary portion between the energy ray irradiated portion and the non-irradiated portion (hereinafter referred to as “irradiation boundary portion”) after the energy ray irradiation. (Hereinafter, this phenomenon is referred to as “redistribution of film thickness”). FIG. 7 is a graph showing this, and FIG. 8 is a diagram for schematically explaining the redistribution of the film thickness.
Although described in detail in the examples described later, a lubricating film 17 having a film thickness of about 3.7 nm is formed on the DLC protective film 16 by dipping (however, the lubricant is the above-mentioned polyether having the trade name Fomblin AM3001). Subsequently, the lubricant film 17 was irradiated with ultraviolet light in a predetermined pattern for 20 seconds using a dielectric barrier discharge excimer lamp (not shown) and the patterning mask 9.
FIG. 7 is a graph showing the enlargement of the uneven step at the irradiation boundary (position at a distance of 20 mm from the center of the magnetic disk). As is clear from the figure, 0.5 hours, 6 hours, and 12 after UV irradiation. It can be seen that as the time, 24 hours, and 48 hours elapse, the unevenness level increases.

This phenomenon (redistribution of film thickness) can be explained as follows (however, it is not limited to this explanation).
That is, when the lubricant molecules flow from the non-irradiated region 17B of ultraviolet light toward the irradiated region 17A (redistribution flow), the valley of the non-irradiated region 17B becomes deeper, while the valley of the irradiated region (convex portion 17A). The mountain rises. As shown in FIG. 8, the non-irradiated region 17B of ultraviolet light serves as a tank for storing the fluid lubricant 18B, and the lubricant 18B is supplied from here (recessed portion 17B) to the irradiated region 17A. You can see that the mechanism is working.
Since this flow is a phenomenon that occurs after irradiation with ultraviolet light, in this specification it is referred to as redistribution flow of the lubricant molecules 18B.
Although not particularly limited, in the lubricating film 17 formed by the dip method, the length of the region in which such redistribution of the film thickness (that is, the diffusion length of the lubricant) is approximately 0.6 mm. It can be seen that it is within (600 μm). Here, as a parameter for evaluating the performance of redistribution, a + b obtained by adding the peak height a and the valley depth b at the irradiation boundary is defined as a “redistribution step”.

On the other hand, the time transition of the film thickness in the non-irradiation region 17B and the irradiation region 17A excluding the irradiation boundary is compared. As shown in FIG. 7, in the irradiation region 17A, the film thickness decreases immediately after irradiation, but the subsequent change disappears. On the other hand, in the non-irradiation region 17B, the film thickness gradually decreases with time. This indicates that, in the irradiation region 17A, the bonding between the lubricant molecules is promoted by the ultraviolet light irradiation, and the film thickness is slightly decreased and the lubricating film is stabilized. On the other hand, in the non-irradiated region 17B, such stabilization is not performed, indicating that the fluid lubricant is maintained as it is and gradually decreases with time.
As is clear from the above knowledge, the magnetic disk according to the present invention is characterized in that a concavo-convex structure having a step (height difference) is formed at the irradiation boundary irradiated with ultraviolet light or other energy rays. It is a disk.

  Hereinafter, the present invention will be described in detail on the basis of some examples. However, the present invention is not intended to be limited to the contents of these examples.

<Example 1-1>
A 3-inch diameter magnetic disk on which a base film, a magnetic film, and a DLC protective film were previously formed in accordance with a conventional method was prepared. The DLC protective film was a hydrogenated amorphous carbon (a-CH) film formed by a CVD method and had a thickness of about 4.5 nm. The arithmetic average roughness was Ra = 0.36 nm. Next, a lubricating film was formed on the protective film.
As the lubricant, polar perfluoropolyether (here, PFPE having an average molecular weight of 4300 g / mol having a piperonyl group at the terminal, trade name Fomblin AM3001) was used. This lubricant was diluted in a hydrofluoroether solvent (trade name: HFE-7200) to a concentration of 0.2 wt%. The disk was half immersed in this lubricant diluted solution (pickup speed 2.0 mm / S), and a lubricating film was formed on the half surface of the disk. The film thickness of the lubricating film measured with a scanning ellipsometer (product of Fibrabo: MARY-102) was about 3.5 nm. From this, it can be seen that the lubricating film produced in this example is a multilayer film of a fixed layer and a fluidized layer. That is, since the molecular diameter when the lubricant (PFPE) molecule is represented by a spherical model is 2.8 nm, the fixed layer made of the lubricant having a fixed thickness corresponding to the monomolecular film (2.8 nm). Is the thickness. On top of that, there is a layer made of a flowable lubricant having a thickness of 0.7 nm as a fluidized bed through which molecules can flow.

After 25 minutes from the formation of the lubricating film, as shown in FIG. 9, the photomask 9 having a predetermined pattern is used in the nitrogen atmosphere chamber to correspond to the photomask 9 on the lubricating film of the magnetic disk 60. The pattern was irradiated with vacuum ultraviolet light. As an ultraviolet light generation light source, a dielectric barrier discharge excimer lamp (product of USHIO INC .: USER20-172B, wavelength 172 nm, intensity 10 mW / cm ² ) was used. At this time, the distance from the lamp house surface to the disk 60 surface was set to 5 mm, and the ultraviolet light irradiation time was set to 20 seconds. In the disk 60 shown in FIG. 9, a nearly half of the upper part of the disk covered with the mask 9 is the formation part 60 </ b> A of the lubricating film 17, and the disk 60 including a part covered with the mask 9. The lower half of the lower portion is the lubricating film non-formed portion 60B.
Thus, the film thickness of the lubricating film was measured using the above scanning ellipsometer when 0.5 hours, 6 hours, 12 hours, 24 hours and 48 hours had elapsed after irradiation with ultraviolet light. The results are shown in FIG. Further, FIG. 7 is an enlarged view of a measurement result in the vicinity of the irradiation boundary (a point where the horizontal axis distance d in FIG. 10 is 20 nm).
The results are as described above, and a film thickness redistribution phenomenon in which the uneven step height increases as time passes can be confirmed at the irradiation boundary. The maximum step (height difference) at the irradiation boundary after 48 hours was 0.5 nm or more (typically 0.5 to 0.6 nm).

Moreover, the change of the “redistribution step” with the passage of time after UV irradiation was examined. The results are shown in FIG. The vertical axis of this figure represents the square of “redistribution level difference”.
As is clear from this figure, the square value of the redistribution step increased linearly with the elapsed time by 9 hours after UV irradiation. It can be seen that the change thereafter becomes gradual and that an equilibrium state is reached after 24 hours. That is, it can be seen that the height of the convex portion at the irradiation boundary becomes constant when a predetermined time elapses.
In addition, the measurement values up to 9 hours were linearly approximated by the least square method under the constraint condition passing through the origin of this figure and indicated by a solid line. The slope of the straight line in the figure represents the diffusion coefficient. Here, it is 1.65 × 10 ⁻¹⁷ m ² / s, which is much smaller than the diffusion coefficient (10 ⁻¹¹ to 10 ⁻¹² m ² / s) of the lubricant (Fomblin AM3001) on the magnetic disk surface. I understand.

<Example 1-2>
Next, the same magnetic disk as that prepared in Example 1-1 was used, and a single-layer lubricating film was formed on the DLC protective film.
That is, the same treatment as in Example 1-1 was performed except that a lubricant dilution obtained by adding a lubricant to a hydrofluoroether solvent so that the lubricant concentration was 0.13 wt% was used for protection. A thin lubricating film with a thickness of 2.1 to 2.2 nm as a single layer film (monomolecular film) was formed on the film.
Subsequently, the ultraviolet light irradiation treatment was performed under the same conditions as in Example 1-1 except that the ultraviolet light irradiation time was set to 5 seconds. As a result of measuring the film thickness of the lubricating film at the time when 0.5 hours, 6 hours, 12 hours, 24 hours, and 48 hours had passed after the ultraviolet light irradiation using the scanning ellipsometer, Example 1-1 was obtained. Similar to the multilayer film, a thin redistribution phenomenon in which unevenness steps increase with time in the vicinity of the irradiation boundary portion of the thin lubricating film at a single layer film (monomolecular film) level was confirmed. Although detailed data is not shown, the maximum step (height difference) at the irradiation boundary after 48 hours was 0.2 nm or more (typically 0.2 to 0.3 nm).

<Example 2>
Next, the same treatment as in Example 1-1 was performed except that the ultraviolet light irradiation time was changed to 5 seconds, 10 seconds, 20 seconds, 30 seconds, and 40 seconds. The value of “redistribution step” for each UV irradiation time was calculated based on the measured value of the scanning ellipsometer. The results are shown in FIG. As shown in the figure, the redistribution level increases with the irradiation time, and takes a maximum value in 20 seconds in this embodiment. On the other hand, when the UV irradiation time is longer than 30 seconds, redistribution flow does not occur. That is, under the conditions of this example, the irradiation time of 20 seconds was almost the optimum time for forming the concavo-convex structure.
Similarly, the same treatment as in Example 1-2 was performed except that the ultraviolet light irradiation time was changed to 5 seconds, 10 seconds, and 20 seconds, and for each UV irradiation time for the lubricating film that was the single-layer film. The value of “redistribution step” was calculated based on the measured value of the scanning ellipsometer. As a result, detailed data is not shown, but under the conditions of this example, the irradiation time of 5 seconds is almost the optimal time for forming the concavo-convex structure, and redistribution flow does not occur when the irradiation time reaches 20 seconds. It was.

<Example 3>
As is clear from the above description, according to the present invention, a desired uneven pattern (texture) can be obtained by applying the characteristics of the uneven structure formed at the irradiation boundary between the ultraviolet light irradiation region and the non-irradiation region. Can be formed. At this time, the width of the irradiation region (for example, the width of the light transmission slit when using a photomask) of the ultraviolet light (or other light beam, ion beam or electron beam, or other energy beam) is used as the lubricant molecule. Forming a striped pattern of lubricant composed of peaks (convex) and valleys (concave) by making the distance less than the diffusion distance (the width of the region where the convex or concave portions appear at the irradiation boundary) Can do. Although not particularly limited, the width of the linear irradiation region (for example, the width of the light transmission slit of the mask) is preferably 0.6 mm or less in the case of the multilayer film made of the lubricant used here. In the case of a single layer film having a thickness of 2.8 nm, 0.5 mm or less is preferable.
Hereinafter, an embodiment related to this will be described.

As schematically shown in FIG. 13, a mask 79 in which light transmission slits with slit widths of 100 μm and 20 μm are formed in a linear stripe shape and a letter (NAGOYA U.) shape is prepared. Based on the technique, the surface of the lubricating film of the magnetic disk 70 having the lubricating film formed on the entire surface was irradiated with ultraviolet light through the mask 79.
Thereafter, the change in film thickness with time was measured with a scanning ellipsometer in the same manner as in the above example. At the same time, the surface state was directly visualized using an optical surface analyzer (Candela Instruments product: OSA5130). The results are shown in FIGS.
FIG. 14 is an image of a portion irradiated with UV that has passed through a linear slit having a slit width of 100 μm, and (a) to (f) are 0.5 hour, 1 hour, 3 hours, and 9 hours after UV irradiation, respectively. , 24 hours and 48 hours, the image of the surface of the irradiation boundary and the height difference are shown. FIG. 15 is an image of a portion irradiated with UV that has passed through a character slit having a slit width of 100 μm (FIG. 15 a) and a slit width of 20 μm (FIG. 15 b). It is. From these images, the convex part is formed in a bowl shape with a width of 0.5 μm to 600 μm sandwiched between the concave parts (for example, 20 μm, 100 μm), and the maximum step of the concavo-convex structure is 0.2 nm or more ( For example, 0.7 nm and 0.8 nm) were confirmed.
As is clear from these drawings, according to the present invention, a magnetic disk having a concavo-convex structure of a desired pattern can be manufactured.

<Example 4>
Next, an embodiment of the self-repair function of the magnetic disk provided by the present invention will be described.
In this example, a DLC protective film in which nitrogen was added to the surface of a hydrogenated amorphous carbon (a-CH) film was used. Further, nonpolar PFPE (trade name Fomblin Z03) was used as a lubricant. Then, the same processing is performed using the same photomask as in Example 3 above, and the uneven structure (texture) of the striped pattern (height difference: 0.2 to 0.3 nm) having a slit width of 100 μm is formed on the lubricating film. Formed.
Next, while rotating the disk, a glass ball was slid in a predetermined direction on the surface (lubricant film), and a lubricant depletion test was performed. The result visualized by the optical surface analyzer is shown in FIG. The darkly colored region in the drawing indicates a portion where the lubricant that has been worn out and removed by sliding of the glass ball is deposited to form a raised ridge. On the other hand, the light-colored area indicates a portion where the lubricant is depleted to form a groove. FIG. 16 (a) shows an example in which sliding traces are formed in parallel to the uneven texture (stripe formation direction) (parallel sliding), and FIG. This shows a case in which sliding traces are formed perpendicularly to the (forming direction) (orthogonal sliding). By the way, from the viewpoint of the restoration flow of the lubricant, in the case of parallel sliding (FIG. 16a), the flow direction of the lubricant flows in a direction perpendicular to the direction of the uneven texture (stripe formation direction). Conversely, in the case of orthogonal sliding (FIG. 16b), the flow direction of the lubricant is parallel flow that flows in a direction parallel to the direction of the uneven texture (stripe formation direction).

Next, the restoration properties of the lubricant after such sliding wear was examined. Here, regarding the restoration characteristics, if there is anisotropy corresponding to the direction of formation of the uneven texture, it can be said that the texture formation is effective from the viewpoint of fixability and fluidity. As a control, the restorative properties of a lubricating film on which a concavo-convex texture was not formed were contacted and slid with a glass ball were simultaneously examined.
Specifically, the above-described scanning ellipsometer was used to examine changes in the film thickness of the lubricant deposition site (groove) and the lubricant depletion site (groove) over time after sliding the glass ball. The results are shown in FIG. 17 (saddle part) and FIG. 18 (groove part).
As is clear from these figures, it was confirmed that the disk on which the uneven texture was formed had a better self-healing function than the disk on which the uneven texture as a control was not formed. In addition, anisotropy was observed in the repair characteristics of both the deposit part (the ridge part) and the depletion part (the groove part).

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
For example, in each of the above-described embodiments, a vacuum mask is used to irradiate vacuum ultraviolet light using a photomask having a predetermined pattern of light transmission slits, and an uneven texture corresponding to the pattern is formed on the lubricating film. It is not limited to such a method. For example, a predetermined pattern may be drawn by scanning with a laser beam or an ion beam, or the shape of the energy beam may be shaped and directly irradiated to the lubricating film with a predetermined pattern.
In addition, the production conditions for forming the concavo-convex structure according to the present invention on the lubricating film, such as the irradiation time and irradiation intensity of ultraviolet light and other energy rays, are the recording medium constituting base material (disk substrate etc.) and the lubricant used. What is necessary is just to change suitably according to the kind (height difference etc.) of the uneven structure to form or the uneven structure to form. The production conditions such as the optimal irradiation time and irradiation intensity (for example, the distance between the recording medium and the light source) can be easily determined for each object by performing a simple preliminary experiment.

According to the present invention, the surface layer of the base material provided with the functional surface layer can be appropriately protected by the lubricating film. Therefore, for example, it is possible to provide a recording medium such as a magnetic disk, an optical disk, or a photosensitive drum with improved durability.

Claims (16)

A recording medium comprising a substrate, a recording film formed on the substrate, and a protective film formed on the recording film,
On the protective film, a lubricating film formed of a predetermined lubricant is provided,
The lubricating film itself constitutes a microscopic uneven structure,
Here, at least a portion of the lubricant in the concave portion maintains fluidity that allows flow to the convex portion, and when a part of the lubricant in the convex portion is physically lost, A recording medium characterized in that at least a part of the deleted part is compensated by moving a part of the lubricant that maintains fluidity to the convex part.   The convex portion in the concavo-convex structure is formed in advance at a site where an energy ray that can improve the binding force of the lubricant to the lubricating film is artificially irradiated, and the concave portion in the concavo-convex structure is the energy beam The recording medium according to claim 1, wherein the recording medium is formed at a site where no irradiation is performed.   The recording medium according to claim 2, wherein the irradiated energy beam is at least one light beam selected from the group consisting of ultraviolet light, infrared light, and laser light, an ion beam, or an electron beam.   The recording medium according to claim 1, wherein the convex portion is formed in a bowl shape having a width of 0.5 μm to 600 μm sandwiched between the concave portions.   The recording medium according to claim 1, wherein a maximum step in the uneven structure is at least 0.2 nm.   The recording medium according to claim 1, wherein the lubricating film has a striped pattern formed of the concavo-convex structure.   The recording medium according to claim 1, wherein the lubricating film is formed of a lubricant having polarity.   A recording apparatus comprising the recording medium according to claim 1. A method for producing a recording medium comprising a substrate, a recording film formed on the substrate, and a protective film formed on the recording film:
(1) Applying a predetermined lubricant on the protective film to form a lubricating film; and (2) Improving the binding force of the lubricant in a predetermined pattern on the lubricating film formed on the protective film. Irradiate energy rays that can be
(A) a convex portion formed at a site irradiated with the energy beam;
(B) a recess formed in a portion where the energy ray was not irradiated, wherein at least a part of the lubricant constituting the recess maintains fluidity capable of flowing to the protrusion, and When a part of the lubricant in the convex part is physically deleted, a part of the lubricant that maintains the fluidity moves to the convex part to compensate at least a part of the defective part. A recess characterized by
Forming a microscopic relief structure comprising:
Including the method.   The at least one light ray selected from the group consisting of ultraviolet light, infrared light, and laser light, an ion beam, or an electron beam as the energy ray is applied to the protective film in a predetermined pattern. the method of.   The method according to claim 10, wherein the protective film is irradiated in a predetermined pattern with vacuum ultraviolet light in an inert gas atmosphere. The lubricating film formed on the protective film is irradiated with the energy rays in a linear shape having a width of 0.5 μm to 600 μm to form a bowl-shaped convex portion corresponding to the linear irradiation site. The method in any one of.   The method according to any one of claims 9 to 12, wherein an irradiation amount of the energy beam is controlled so that a maximum step in the uneven structure is at least 0.2 nm.   The method according to claim 9, wherein the energy beam irradiation is performed in a pattern corresponding to the pattern such that a striped pattern including the concavo-convex structure is formed on the lubricating film.   The method according to claim 9, wherein a lubricant having polarity is used as the lubricant. The method according to claim 15 , wherein a fluorine-based lubricant having at least one polar group is used as the polar lubricant.