JPH09168880A - Laser texture device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase power and power density of a laser beam by synthesizing in polarization the laser beams from two semiconductor laser light sources in an optical system. SOLUTION: Light beams emitted from a semiconductor laser light source are converted to a parallel beam bundle by a collimators 21-A, 21-B, then made incident from two different directions on a PBS (polarizing beam splitter) 23 and synthesized in polarization. The resultant beams are converged by a converging mechanism 22 and emitted to a projection-formed surface on a base board 3 rotatably supported by a base board rotating mechanism. Each laser light source is driven by a driving electric circuit 28. The laser beam, which is emitted from a semiconductor laser module 2 to a texture machining surface, is controlled to have the energy (output) capable of forming the target projections.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a texture device used in the manufacturing process of a magnetic recording medium, and more particularly to a texture device using laser light.

[0002]

2. Description of the Related Art Usually, a magnetic recording medium (hard disk)
Is textured for the purpose of reducing the friction coefficient during CSS (contact start / stop).
By the way, in order to improve the magnetic recording density, it is required to reduce the flying height of the head, and smoothness is required in the magnetic recording area of the disk. Conventionally, since the texturing is mechanically performed, it is difficult to control the height of the protrusions formed by the texturing, and since the texturing is performed on the entire surface of the disc, the texturing in the recording area is performed with a low head. It is disadvantageous for realizing the flying height. For this reason, zone texture processing has been proposed in which texture is applied only to the CSS area. Further, as a texture method, a method of forming projections or depressions by laser irradiation is being proposed.

[0003]

By the way, in the case of performing texture processing by laser irradiation, it is necessary to precisely irradiate a laser beam having necessary energy in a pulsed manner on a hard disk substrate in a narrow range. Therefore, a high output laser and a condenser lens are required. However, high-power lasers represented by Ar gas lasers and YAG solid-state lasers are expensive, increase the cost of the entire processing apparatus, and are insufficient in terms of pulse condition controllability. Further, the laser light source / device is also large.
In this respect, the semiconductor laser has an advantage that it is relatively inexpensive and small, and further, since the repetition frequency and the duty can be controlled in a wide range, the texture processing conditions can be finely controlled, which is industrially extremely advantageous.

However, the semiconductor laser has a relatively low output, and when the texture is performed by laser irradiation, sufficient output for forming the protrusion cannot be obtained depending on the use conditions.

As a method of increasing the output power of the semiconductor laser, there is a method of arranging the light emitting surfaces in an array, increasing the stripe width, and the like. In addition, the condensing area when condensing and irradiating the hard disk substrate with the laser light is increased. Therefore, in order to increase the output without increasing the light emitting area of the semiconductor laser chip, it is necessary to study and develop the structure and composition of the chip itself.

The present invention has been made in view of the current state of the art described above, and uses a low-cost and small-sized semiconductor laser and devises an optical system to provide a high-power laser beam. It is an object of the present invention to provide a laser texture device that enables industrially advantageous laser texture to a magnetic recording medium by taking out the laser beam and then narrowing the laser beam diameter. In the following description, a laser texture using a semiconductor laser may be referred to as a semiconductor laser texture. That is, the gist of the invention of the present application is that the surface of a non-magnetic substrate, a magnetic layer, or another layer of a magnetic recording medium having at least a magnetic layer on a non-magnetic substrate and optionally other layers provided on the surface. A laser texture device for concentrating and irradiating a conductor laser beam to perform a texturing process, comprising: a substrate supporting means for supporting the non-magnetic substrate; and first and second laser beams having two different polarization planes. A laser light unit for outputting, a polarization combining unit for receiving the first and second laser lights and combining the polarized lights to output a combined light, and collecting the combined light for the non-magnetic substrate and the magnetic layer. Or a laser texture device having a condensing means for irradiating the surface of another layer.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The apparatus of the present invention can be used for texture processing of a magnetic recording medium having at least a magnetic layer on a non-magnetic substrate. That is, for the purpose of improving various characteristics of the magnetic recording medium, an underlayer is provided on the surface of the substrate, a protective film or a lubricant layer is provided on the magnetic layer, and an intermediate layer is provided between the underlayer and the magnetic layer. Various layer configurations have been proposed such as provision of layers and multilayer magnetic layers, but the present device can be used without depending on these layer configurations. In the following description,
The non-magnetic substrate may be simply referred to as a substrate.

In using the laser texture apparatus of the present invention, an aluminum alloy substrate, a glass substrate or a silicon substrate is preferably used as the substrate, but other metal substrates such as copper and titanium, carbon substrate, ceramic substrate or A resin substrate can also be used. As the silicon substrate, a silicon alloy substrate obtained by adding a trace element for increasing the strength to silicon can be used in addition to a pure silicon substrate. The substrate is usually formed in a disk shape, but may be in another shape, for example, a card shape.

Although it is possible to form a magnetic recording medium by directly forming a magnetic layer on the surface of the substrate, it is possible to form an underlayer on the surface of the substrate and form the magnetic layer via the underlayer. Many. As this underlayer, a nonmagnetic underlayer made of Ni-P alloy is suitable, and such underlayer is usually formed by electroless plating or sputtering. The thickness of the underlayer is 50 to 20,000 nm, preferably 100.
˜15,000 nm.

C is provided between the magnetic layer and the substrate or the underlayer.
It is preferable to provide an intermediate layer such as an r layer and a Cu layer. The thickness of the intermediate layer is usually 20 to 200 nm, preferably 50 to 200 nm.
100 nm.

The magnetic layer (magnetic recording layer) is made of Co-P or Co.
-Ni-P, Co-Ni-Cr, Co-Ni-Pt, C
o-Cr-Ta, Co-Cr-Pt, Co-Cr-Ta
It is composed of a ferromagnetic alloy thin film such as -Pt-based alloy and is formed by a method such as electroless plating, electroplating, sputtering or vapor deposition. The thickness of the magnetic recording layer is usually 30 to 7
It is about 0 nm.

A protective layer is preferably provided on the surface of the magnetic recording layer. The protective layer is a carbon film, hydrogenated carbon film, T
A method such as vapor deposition, sputtering, plasma CVD, ion plating, wet method, etc., which includes a carbide film such as iC and SiC, a nitride film such as SiN and TiN, and an oxide film such as SiO, Al ₂ O ₃ , and ZrO. Is formed by. As the protective layer, a carbon film or a hydrogenated carbon film is particularly preferable.

A lubricant layer may be further provided on the surface of the protective layer. However, when a magnetic head having a layer of diamond-like carbon on the slider surface is used, the tribological property between the magnetic head and the magnetic recording medium is improved, and therefore the protective layer is not always necessary. As the lubricant, for example, a fluorinated liquid lubricant is preferably used, and the lubricant layer is usually formed on the surface of the protective layer by a dipping method or the like.

The present invention is an apparatus for subjecting a surface of either a non-magnetic substrate or each layer to a laser beam for converging and applying a texturing process in the production of the above magnetic recording medium. The surface on which the protrusion is formed by the texturing means the surface on the side where the magnetic recording medium comes into contact with the magnetic head.

Laser texturing in the use of the apparatus of the present invention is preferably performed on the underlayer (Ni-P layer) on the substrate, but is performed on the surface of any layer up to the protective layer under substantially the same conditions. Can also form a desired protrusion. Of course, the surface of the final magnetic recording medium can be textured. The laser light may be either continuous laser light or pulsed laser light, but pulsed laser light is usually used.

The substrate is usually used after being mirror-finished (polished). Then, an underlayer (for example, Ni
In the case of using a substrate provided with -P underlayer), the surface of the underlayer is mirror-finished. Also, when using these substrates, prior to the formation of protrusions by irradiation of laser light,
It is also possible to previously form a low-height projection by subjecting the entire surface of the substrate to a slight mechanical texture. Such a mechanical texture has the following effects.

That is, when the height and density of the projections formed by the irradiation of the laser beam are small, that is, when the magnetic recording medium and the magnetic head are partially in contact with each other, the mirror-finished substrate is simply used. Compared with, sticking is less likely to occur and the coefficient of friction is also smaller. In addition, the conditions for forming protrusions, which will be described later, can be widened, which is particularly preferable for mass production.

In the present invention, a semiconductor laser is used as the laser light source of the device. The semiconductor laser is a high power gas laser represented by Ar gas laser, YAG / YL.
Compared with solid-state lasers typified by F lasers and various lasers, the cost is low, and the device as a whole has the advantage of being relatively small. However, on the other hand, the semiconductor laser has weaker power than a high-power gas laser typified by an Ar gas laser and a solid-state laser typified by a YAG / YLF laser.

Usually, in order to focus the semiconductor laser light, the laser light oscillated from one semiconductor laser light oscillation source is passed through a collimator to be parallel light, and the parallel light is passed through a focusing objective lens.

The feature of the present invention resides in that linearly polarized laser beams emitted from two semiconductor laser beam oscillation sources are polarized and combined and then condensed by a condensing mechanism. By polarization combining two light sources, it is possible to increase the power of the parallel light flux before focusing compared to the case where one light source is used, and even if a semiconductor laser is used, the power is further increased. It is possible to irradiate the laser with high laser power, that is, with high power density.

Specifically, polarization combining is possible by using an optical element that combines and outputs lights having different polarization planes and makes light having a predetermined polarization plane incident on this optical element. A polarization beam splitter (PBS) or a birefringent crystal can be given as an element having such a property.

These elements are provided for light incident from two directions.
It has the property of synthesizing and outputting the orthogonal components of the planes of polarization. Therefore, in order to maximize the combined power, it is desirable to enter linearly polarized light whose polarization planes are orthogonal to each other.

Two lights whose polarization planes are orthogonal to each other may be produced by arranging the light source itself as such or by using an optical element such as a λ / 2 plate for changing the polarization plane.

In the laser texture using the device of the present invention, laser light from a semiconductor laser module optically designed such that the output on the irradiation surface is 70 mW or more and the focused spot diameter is 3 μm or less is applied to the projection forming surface. Irradiation is preferred. The above output is preferably 200 mW
As described above, more preferably 250 to 500 mW. The size of the spot diameter is usually N.V. of the lens used. A.
From the numerical aperture and the size of NFP (near field pattern), it is roughly estimated by the following formula. The spot diameter in the present invention means the diameter of a perfect circle (in the case where the spot is elliptical, the major diameter and the minor diameter) at which the intensity is reduced to "one square of e" of the maximum intensity at the light center. means.

(Spot diameter) = (Short diameter or long diameter in NFP) × (NA of collimator lens) / (NA of objective lens)

Further, it is preferable that the pulsed laser light from the semiconductor laser module according to the present invention is used and irradiation is performed under the conditions of a repetition frequency of 10 kHz to 4 MHz and a duty of 1 to 50%. The preferable range of the repetition frequency is 20 kHz to 300 kHz, and the preferable range of the duty is 2 to 10%. In the present invention, by using a semiconductor laser as the laser light source,
Since the repetition frequency and duty can be controlled in a wide range, it is industrially extremely advantageous in that the texture processing conditions can be finely controlled.

The laser texture is a substrate supporting mechanism for supporting a substrate and a light beam emitted from a semiconductor laser light oscillation source is made into a parallel light flux, and the light condensed by the light converging mechanism is moved relatively. , The parallel light beam is scanned on the projection forming surface on the substrate. The portion irradiated with the laser light and its periphery are physically deformed to form protrusions (unevenness). Then, the zone texture is possible by irradiating the CSS zone of the magnetic recording medium with laser light to perform the texture processing.

When the substrate has a disk shape, it is desirable that the substrate can be rotatably supported by the substrate supporting mechanism. The rotation speed in this case is usually 100 to 10000 rpm, preferably 100 to 7200 rpm, and more preferably 120.
~ 900 rpm. Further, the formation pattern of the protrusions can be arbitrarily selected, and as an example, a track interval: about 5 μm, a protrusion pitch interval: about 1
0 μm can be mentioned.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a laser texture device of the present invention will be described. FIG. 1 is an overall explanatory view of an example of a laser texture device of the present invention. Note that FIG. 1 shows a configuration in which the substrate is disk-shaped and the substrate support mechanism rotatably supports the substrate.

As shown in FIG. 1, the laser texture apparatus of the present invention comprises a substrate rotating mechanism (1), a semiconductor laser module (2), and a projection forming surface on the substrate for scanning a bundle of parallel rays of light. It comprises a substrate (3) rotatably supported by a substrate rotating mechanism and a relative moving mechanism (4) between the semiconductor laser module (2).

In FIG. 1, two substrate rotating mechanisms (1) are illustrated, but the number is arbitrary. Further, although the relative movement mechanism (4) is constituted by the horizontal movement mechanism of the semiconductor laser module (2), it may be constituted by the horizontal movement mechanism (not shown) of the substrate rotation mechanism (1). Further, the semiconductor laser module (2) may be provided with a vertical movement mechanism to adjust the focus.

The substrate rotating mechanism (1) is usually composed of a spindle motor, and the substrate (3) is supported by the rotating shaft of the spindle motor and moved at a constant rotation speed or linear velocity. As the moving mechanism (4), for example, a linear slider is preferably used. The semiconductor laser module (2) is mounted on the moving mechanism (4) and is reciprocally moved in the horizontal direction by the plurality of substrate rotating mechanisms (1), (1) ... At a constant speed.

In consideration of productivity, the moving mechanism (4) is normally moved at an increased speed when moving from one substrate (3) to another substrate (3). For such speed control, it is also possible to mount another moving mechanism on the moving mechanism (4) so that one moves between the substrates and the other moves for forming a protrusion. .

The above apparatus is usually provided with a timing control section (5) for controlling the modulation timing of laser light as means for forming protrusions in a fixed pattern with the same or different intervals. That is, for example, when the protrusions are formed at the same intervals that are usually adopted, the substrate (3) is moved at a constant rotation speed and a constant speed by the constant speed operation of the substrate rotating mechanism (1) and the moving mechanism (4). In this case, the distance between the protrusions in one track formed on the substrate surface becomes wider toward the outer circumference. Therefore, the timing control unit (5) confirms the position of the substrate, controls the modulation timing (irradiation time) of the laser light based on the signal, and makes the intervals of the protrusions formed on the substrate surface constant.

The timing control section (5) is composed of a computer, a position detecting mechanism, necessary interfaces and the like. As the position detecting mechanism, for example, a laser displacement meter, an encoder, or the like can be used. The speed of the substrate rotating mechanism (1) and the moving mechanism (4) may be controlled without controlling the modulation timing of the laser light.

FIG. 2 shows a first configuration example of the semiconductor laser module (2). In the figure, the double circle (◎) shown in the route indicates a wave whose polarization plane is orthogonal to the paper surface
→) shows a wave whose plane of polarization is parallel to the plane of the paper.
In this configuration example, two semiconductor laser light sources (20-A, 20-B) that output linearly polarized light are arranged such that the polarization planes of emitted light are orthogonal to each other. Light emitted from the semiconductor laser light source is converted into a parallel light flux by a collimator (21-A, 21-B), and then PBS (polarization beam splitter) is used.
It is incident on (23) from two different directions, and the polarized waves are combined. The combined light is condensed by the condensing mechanism (22) and is applied to the projection forming surface on the substrate (3) which is rotatably supported by the substrate rotating mechanism (1) shown in FIG. Each laser light source is driven by a driving electric circuit (28).

In this configuration example, the PBS (23) has a cube shape, but as described above, another shape such as a plate shape may be used. Similarly, PBS (polarization beam splitter) is used as an optical component for polarization combination.
Besides (23), it is also possible to use a birefringent crystal. As the birefringent crystal, any shape such as a prism shape or a flat shape can be used.

Further, in this embodiment, focus error detection including a non-polarization beam splitter (24), a cylindrical lens (25), an objective lens (26) and a four-division photodiode (27) is used for autofocus control by detecting a return term. A vessel (FED) is provided. The non-polarizing beam splitter (24) may have a shape other than the cube shape shown in FIG. 2, for example, a plate shape.

In this embodiment, the non-polarizing beam splitter (24) is provided for autofocusing.
The higher the transmittance, the larger the power for converging and irradiating the hard disk substrate is desirable, and the reflectance of about several percent is necessary for extracting as return light for AF. On the other hand, it is desirable that the absorptance of the non-polarizing beam splitter is zero. The laser light incident on the non-polarizing beam splitter is transmitted, absorbed, and reflected at a ratio corresponding to the transmittance, reflectance, and absorptance thereof, and the sum of these ratios is 1 (100%). . Transmittance is 90-99
% Is desirable. It should be taken into consideration that the transmittance, reflectance and absorptance of all the above optical components depend on the wavelength.

Each semiconductor laser light source (chip or Can) (20-A, 20-B) has an output of 80 mW or more, a major axis of the spot diameter of 8 μm or less, and a minor axis of 4 μm.
It is preferably optically designed to have an elliptical or perfect circle NFP (near field pattern) of μm or less. Such conditions are usually AlGaAs laser, InG
aAs laser, InGaAsP laser, AlGaInP
This can be achieved by using a semiconductor device (laser diode) such as a laser. Among these, A
An lGaAs laser or an InGaAs laser is preferable because of its high output.

Collimator lens (21-A, 21-B)
Is in the range of 0.3-0.5. A. It is preferable that it is configured by a collimator lens having

In order to effectively extract the power of the laser light, the collimator lens and other lenses are preferably provided with an antireflection film (AR coat) matched to the wavelength of the laser light used.

As the objective lens (22) as the condensing mechanism, the N.V. A. An objective lens for condensing is preferable. Then, for example, the semiconductor laser light sources (20-A, 20-B) and the collimators (21, 2) are provided at a place other than above the substrate rotating mechanism (1) shown in FIG.
1-A, 21-B) and PBS (23) are installed, the optical path can be changed by combining a total reflection mirror with the focusing objective lens.

Since the output of the semiconductor laser is weaker than that of a high-power gas laser typified by an Ar gas laser, the objective lens (22) has a function of narrowing down the laser light when irradiating to increase the output per area. The light collecting mechanism (22) is
Usually, an autofocus (AF) system is used in combination, but as the AF system, various methods other than the astigmatic difference method can be adopted.

In the semiconductor laser module of the present invention, a means for preventing the influence of the return light from the textured surface (nonmagnetic substrate, underlayer, magnetic layer or surface of the magnetic recording medium) on the light source is added. preferable. The two semiconductor laser light sources (20-A, 20-B) normally oscillate a pulsed laser light by controlling ON / OFF of the driving electric circuit (28). And its modulation timing (irradiation time)
Are appropriately controlled by the timing controller (5) shown in FIG.

The laser light emitted from the semiconductor laser module (2) to the textured surface is controlled to have energy (output) capable of forming a target projection. The specific output depends on the material of the substrate surface, the irradiation time on the substrate surface, and the like. The semiconductor laser module of the present invention is preferably optically designed such that the output on the textured surface is 70 mW or more and the spot diameter is 3 μm or less. A particularly preferable range of the spot diameter is 0.05 to 2 μ
m. The output of the laser light is usually 100 to
Adjusted to 500 mW.

FIG. 3 is a diagram showing a second configuration example of the semiconductor laser module (2). The present configuration example is different from the configuration in FIG. 2 only in that a collimator lens (21) is provided after the polarization beam splitter (23) and the laser light is converted into a parallel light flux after polarization combination.

Basically, the same constituent elements as in the constitution of FIG. 2 can be used, but the N.M. of the collimator lens (21) is used.
A. The lower limit may be about 0.1 depending on the size of optical components such as PBS and birefringent crystal. Basically N. A. Those of 0.3 to 0.5 are preferable.

The shape of the protrusion obtained by the texturing is a three-dimensional surface structure analysis microscope (device name "ZYGO").
Is observed by Normally, the protrusion height is 5 to 100 nm
The projection width is about 0.5 to 5 μm. In addition, the height of the above-mentioned protrusion is determined according to JIS surface roughness (B0601-198).
The height of the protrusion when the center line of the roughness curve defined by 2) is used as a reference.

Two semiconductor laser light sources as shown in FIG.
Also, the mode of the increase in power was investigated using the module having PBS. The semiconductor laser light source has a wavelength of 860 nm, and the collimator lens has an N.V. A. = 0.3
Was used. As a result, compared with the output of one laser beam (= 90 mW) emitted from the collimator lens, each collimated two laser beams are polarized by the PBS and combined by 1.84 times (= 166 m).
W) was obtained.

[0050]

According to the present invention, among the lasers used as the laser texture device, the advantage is that it is relatively inexpensive and compact, but on the other hand, when using a semiconductor laser with insufficient power, two semiconductors are used in the optical system. The power and the power density of the laser light emitted from the semiconductor laser module can be increased by polarization polarization combining the laser light from the laser light source.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a laser texture device according to the present invention.

FIG. 2 is the first of the semiconductor laser modules in FIG.
Diagram showing configuration example

FIG. 3 is a second part of the semiconductor laser module shown in FIG.
Diagram showing configuration example

[Explanation of symbols]

 1 substrate support mechanism 2 semiconductor laser module 3 substrate 4 moving mechanism 5 timing controller

Claims (4)

[Claims] 1. A semiconductor laser beam is provided on a surface of a non-magnetic substrate, a magnetic layer or another layer of a magnetic recording medium which has at least a magnetic layer on a non-magnetic substrate and is provided with another layer if necessary. A laser texturing device for converging and irradiating a non-magnetic substrate with a substrate, and a laser beam for outputting a first and a second laser beam having two different planes of polarization. Means, a polarization combining means for receiving the first and second laser lights, performing polarization combination, and outputting combined light; and collecting the combined light to collect the non-magnetic substrate, the magnetic layer, or another layer. Laser texture device having a condensing means for irradiating the surface of the laser. 2. The laser texture device according to claim 1, wherein the laser light output means is two semiconductor laser light sources arranged such that the polarization planes of the output light are different. 3. The polarized light beam is provided corresponding to the first and second laser lights, obtains a bundle of parallel rays from the first and second laser lights, and uses the polarized light as the first and second laser lights. 2. The method further comprising collimator means for supplying the synthesizing means.
The described laser texture device. 4. The laser texture device according to claim 1, wherein the polarization beam combiner is a PBS (polarizing beam splitter) or a birefringent crystal.