JPH10143859A - Substrate for magnetic recording medium and production of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to control the height of the projecting parts of laser marks to values of a specific range by irradiating a substantially flat nonmagnetic brittle substrate with a laser beam and forming plural sets of the laser marks having the projecting parts in at least part thereof on the surface of the substrate, then subjecting the parts inclusive of the laser marks to a heat treatment. SOLUTION: The laser marks 3 having the projecting parts in at least part are formed by irradiation with the laser on the part on the side to be formed with the magnetic layer 2 of the nonmagnetic brittle substrate 1 consisting of a glass material, glass ceramic material, ceramic material, etc. The magnetic layer 2 is a ferromagnetic alloy of a Co alloy system having, for example, 50 to 500A thickness and is formed by a sputtering method, etc. After the laser marks 3 are formed, the parts of the substrate 1 inclusive of the laser marks are heat treated. The substrate is heated up, is held at the temp. and is then lowered more gently as compared with the cooling temp. arising in a laser process, by which the height of the laser marks 3 is controlled to 10 to 500A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium substrate and a method for manufacturing a magnetic recording medium.

[0002]

2. Description of the Related Art A hard disk drive in which a magnetic recording medium is loaded has a magnetic recording medium, a magnetic recording head for performing magnetic recording / reproduction on at least the magnetic recording medium, a rotation of the magnetic recording medium, and the like. It comprises a mechatronic unit for driving the magnetic recording head and a signal processing unit for processing signals for recording and reproduction.

The disk-shaped magnetic recording medium (hereinafter, also referred to as a disk) records and reproduces data with an annular landing area where a magnetic recording head (hereinafter, also referred to as a head) is stationary and in contact with the disk by its function. It is divided into annular data areas. In general, a contact start / stop (CSS) method is used for operating a head in a hard disk drive.

In the CSS system, when the magnetic recording medium is stationary, the head is stationary and in contact with the landing area on the disk. When the disk starts rotating, the air flow generated by the viscosity of the surface of the disk and the air flows into the gap between the head and the disk, causing the head to fly. In this state, since the head glide on the disk through an extremely thin air layer, the head can smoothly move to a desired recording / reproducing position in the data area without making an undesired physical contact between the disk and the head. It can be moved at high speed. Also, after moving to the landing area, the head loses buoyancy by decelerating and stopping the rotation of the disk,
Touch and rest on the disc again.

In this hard disk drive, the head must be brought as close as possible to the disk in order to improve the recording density, and the disk surface is ultimately smooth in the data area where data is recorded and reproduced. Is required. Recently, the flying height of the head from the disk surface has been required to be 500 ° or less, more preferably 300 ° or less in order to achieve high recording density.

On the other hand, a frictional force acts between the disk and the head when they are stationary or in contact with each other.
If the surface of the disk is too smooth and this static friction is greater than the motor torque (called stiction), the disk cannot rotate. Also, if you try to forcibly rotate the disk with a larger motor torque against this large static friction force, the disk will be damaged due to unstable vibrations that occur when the head comes out of the suction state with the disk, etc. May be.

[0007] In order to overcome these problems, at least in the landing area, a method of reducing the frictional force between the disk and the head by actively applying a controlled roughness called a texture on the disk surface. Is adopted.

On the other hand, as a substrate for a disk,
Conventionally, an aluminum substrate plated with an alloy represented by NiP has been used.
A nonmagnetic brittle substrate represented by a glass material has been used because of its impact resistance and high rotation characteristics.

As described above, there are conflicting demands in the art for smoothing the surface to reduce the flying height and roughening the surface for stiction resistance. To fulfill these two conflicting requirements on a high level, experts in the art have proposed several useful techniques in texturing.

As a method for forming a well-controlled and homogeneous texture, a texture processing method using a laser (hereinafter referred to as a laser texture) is disclosed in
No. 275029, U.S. Pat. No. 5,620,221, U.S. Pat. No. 5,108,781 and JP-A-8-106630. The related technology is “A New LaserTex
turing Technique for High Performance Magnetic Dis
k Drives ”IEEE Trans.Mag., Vol.31, pp2946-2951,1995
Is described in detail.

[0011] These are intended for metals and metal alloys as laser processing materials. The mechanism of laser processing for these materials is that the laser irradiation produces a temperature distribution in the processing area, a corresponding surface tension distribution in the irradiation area, and rearrangement of the material corresponding to the surface tension, followed by It is said to be due to solidification, and no consideration has been given to the processing of brittle substrates such as glass substrates, glass ceramic substrates, and carbon substrates, which have different processing mechanisms, and no specific method has been proposed.

Japanese Patent Application Laid-Open No. 7-182655 discloses a laser processing method peculiar to a surface of a brittle material having a thermal shock limit fluence level, that is, a method of generating a hair line crack or a material ejection above it. We propose a method of forming a highly reproducible bump on the surface of a glass disk using a single laser pulse whose energy fluence is precisely controlled below the thermal shock fluence limit to be generated.

Japanese Patent Application Laid-Open No. Hei 7-182655 proposes a method of processing a brittle material having a different processing mechanism from that of a metal or an alloy. The height of the ridge changes greatly due to the slight change in the laser output because of the sharp change in the ridge formed by the processing of the ridge, making it difficult to form a ridge with high reproducibility. It is difficult to form a micro-height ridge required in the art with good reproducibility.

In recent hard disk drives, it is required that the head flies lower than before in order to achieve higher density. On the other hand, since the lowest possible flying height of the head is determined by the maximum height of the texture peak, it is required to control the height of the protrusion to 500 ° or less, more preferably 300 ° or less. In addition, in order to withstand the contact / sliding of the disk and the head during CSS, the minute laser marks constituting these textures also need to be strictly controlled in height variations.

[0015] The above proposal does not consider the control of the minute height of the laser mark in detail, and improves the precision of controlling the height of the laser mark to a minute height of 500 ° or less, preferably 300 ° or less. I feel the need.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a glass, glass ceramics, ceramics or other non-magnetic brittle substrate or a magnetic recording medium using the substrate, and in particular, to form a texture by irradiating a laser beam. The object of the present invention is to provide a method for manufacturing a magnetic recording medium substrate or a magnetic recording medium capable of accurately controlling the height of a laser mark constituting a texture to a desired minute height.

[0017]

SUMMARY OF THE INVENTION According to the present invention, a plurality of laser marks having at least partially convex portions are formed by irradiating a plurality of portions of a substantially flat non-magnetic brittle substrate with laser light. By forming a heat treatment on at least a portion of the substrate including the laser mark on the surface, the height H of the convex portion of the laser mark is set to 10 to 5
A method for manufacturing a substrate for a magnetic recording medium, characterized in that the method is controlled to be in the range of 00 °.

Further, according to the present invention, a plurality of laser marks having at least a portion having a convex portion are formed on the substantially flat nonmagnetic brittle substrate by irradiating the plurality of portions with a laser beam. A substrate manufacturing method for obtaining a substrate for a magnetic recording medium in which a height H of a convex portion of the laser mark is controlled in a range of 10 to 500 ° by subjecting at least a portion including the laser mark of the substrate to heat treatment. And a film forming step of forming a magnetic film and / or other necessary films on the surface of the substrate.

The present invention also relates to a method of manufacturing a magnetic recording medium having a magnetic film and other required films on a non-magnetic brittle substrate, wherein the laser beam is applied to a plurality of locations on the substantially flat surface of the non-magnetic brittle substrate. Forming a plurality of laser marks having a convex portion on at least a part of the surface by irradiating the surface, a film forming step of forming a magnetic film and or other required film on the surface, A heat treatment step performed in the film forming step, wherein the height H of the convex portion of the laser mark stored on the outermost surface after the film formation is controlled in the range of 10 to 500 ° by the heat treatment step. And a method for manufacturing a magnetic recording medium.

The present invention also relates to a method of manufacturing a magnetic recording medium having a magnetic film and other required films on a non-magnetic brittle substrate, wherein the laser beam is applied to a plurality of locations on the substantially flat surface of the non-magnetic brittle substrate. Forming a plurality of laser marks having a convex portion on at least a part of the surface by irradiating the surface, a film forming step of forming a magnetic film and or other required film on the surface, A heat treatment step to be performed after the film formation step, wherein the heat treatment step controls the height H of the convex portion of the laser mark stored on the outermost surface after the film formation in a range of 10 to 500 °. A method for manufacturing a magnetic recording medium is provided.

The heat treatment includes a step of raising the temperature from room temperature to a temperature T ₁ , a step of maintaining the temperature at T ₁ ,
A temperature lowering step from ₁ to room temperature.

Here, the nonmagnetic brittle substrate is a substrate made of a bulk material such as glass, glass ceramic (crystallized glass) or ceramics, or the above nonmagnetic brittle material having a thickness sufficient for forming a laser mark. Is laminated on another material substrate.

In the present invention, when the non-magnetic brittle substrate is made of glass, the heat treatment includes a step of raising the temperature from room temperature to a temperature T which does not exceed the annealing point of the glass, and a step of holding the glass at the temperature T. And a step of lowering the temperature from the temperature T to room temperature.

Here, the step of irradiating a laser beam onto a substantially flat surface of the nonmagnetic brittle substrate to form a plurality of laser marks having a convex portion on at least a part of the surface is performed by a laser. Also called a process. The laser process involves a temperature raising process by laser irradiation and a cooling process after stopping laser irradiation.

It is appropriate to select the cooling rate from the temperature T ₁ or T to the room temperature sufficiently lower than the cooling rate in the cooling step.

As a heating method in the heat treatment step,
A method using an electric furnace, an oven, infrared radiation, or the like can be used, and any of a convection type, a radiation type, and an electric type can be used.

The shape of the laser mark formed on the surface of the brittle substrate is preserved on the outermost surface through an underlayer, a magnetic film, a protective film, a lubricating film, etc. provided thereon.

In the present invention, the magnetic recording medium has a landing area and a data area, and the laser mark can be provided on the outermost surface of the substrate or the magnetic recording medium so that the laser mark exists only in the landing area. In the substrate or the magnetic recording medium of the present invention, a laser mark in which the height H of the convex portion of the laser mark is substantially lower in the data area than in the landing area can be provided.

Further, in the substrate or the magnetic recording medium of the present invention, a laser mark having a laser mark density substantially lower in a data area than in a landing area can be provided. The landing area is formed with a predetermined width in the inner peripheral area or the outer peripheral area of the donut-shaped disk-shaped magnetic recording medium.

The laser mark according to the present invention has various forms as shown in FIGS. 3 to 5 according to the change in irradiation energy, but has at least a part of a convex part, and the convex part after the heat treatment. Is in the range of 10 to 500 °.
The height H in the present invention is the height of the protrusion shown in FIGS.

When a non-magnetic brittle substrate such as glass or glass ceramic is irradiated with a laser beam, the temperature of the substrate material in the irradiated area rises and expansion occurs. In the cooling process after the laser light irradiation is stopped, as in the art, when the laser irradiation area is smaller than the substrate or the magnetic recording medium, the surrounding cold and large heat capacity causes the irradiation area to have a smaller area. The temperature drops rapidly, and the bulge generated by the expansion cannot be sufficiently alleviated and remains after cooling. The height of the bulge generated by this expansion depends on the depth of the laser irradiation area, that is, the irradiation energy of the laser.

FIG. 6 shows the relationship between the laser irradiation amount of the soda aluminosilicate glass material and the height of the laser mark. FIG. 6 shows the degree to which the change in the irradiation energy of the laser is converted into the change in the height of the laser mark. That is, the slope of the curve of the graph determines the variation of the height of the laser mark with respect to the variation of the irradiation energy of the laser. It is generally accepted that the output of a laser varies over time. On the other hand, in the art,
Fluctuations in the height of the laser mark as a texture of the magnetic recording medium are required to be strictly controlled for stable low flying of the head. In FIG. 6, the slope of the curve is smallest at a height near 400 °, and is 100 ° to 200 °.
The largest in height.

Therefore, in order to suppress variations in the height of the laser mark, the height of the laser
The irradiation energy may be selected so as to be close to 0 °, but this does not always coincide with the required laser mark height determined by the drive design (head flying height). Therefore, in order to obtain a laser mark of a required height with the height variation controlled to a minimum, a height control factor is required in addition to the irradiation energy.

According to the present invention, a plurality of lasers having a small height variation are selected by selecting an irradiation energy level at which a variation in the height of a laser mark formed with respect to a variation in the irradiation energy upon laser beam irradiation is small. forming a mark, when the height of the laser marks is higher than the required height, process heating to the temperatures T ₁ or T in laser marking, holding step at temperatures T ₁ or T and temperatures T ₁ or T By performing a heat treatment including a slow temperature lowering step, a laser mark having a required height and a small variation in height is obtained.

[0035]

FIG. 1 is a schematic diagram showing a cross section of a magnetic recording medium manufactured by the manufacturing method of the present invention, and 1 is a non-magnetic brittle substrate. As such a substrate, a substrate made of a glass material, a glass-ceramic material, or a ceramic material is preferable, but other non-magnetic brittle substrates such as a carbon substrate whose laser mark formation mechanism is considered to be the same as these can also be used. . In addition, a material obtained by coating the above materials on a substrate of another material can also be used.

In order to avoid undesired physical contact between the head and the surface of the substrate and to suppress the range of variation in the height of the laser mark, the surface of the substrate must have a roughness of less than 10 ° prior to the laser irradiation. It is desirable to perform mirror polishing.

In the method for manufacturing a recording medium shown in FIG. 1, a laser mark 3 having at least a part of a convex portion was formed by laser irradiation on a portion of the nonmagnetic brittle substrate 1 on which the magnetic layer 2 was formed. Thereafter, a heat treatment is performed on at least the portion of the substrate including the laser mark, so that the height H of the convex portion of the laser mark 3 is controlled in the range of 10 to 500 °. Generally, the convex portion on the surface of the base is called a ridge, and the height of the convex portion is called the ridge height or the height of the laser mark. The lower limit 10 ° of the height H is determined by the fact that the presence of the laser mark is substantially distinguishable from the roughness of the substrate surface, and when the height H is less than 10 °, suppression of stiction by the laser mark is performed. No effect can be expected. The upper limit is also determined by the head flying height required by the art, since the height of the laser mark directly determines the minimum possible flying height of the head.

The magnetic layer 2 generally has a thickness of 50 to 500
Ｃｏ is a Co alloy-based ferromagnetic alloy and is formed by a sputtering method, a vacuum evaporation method, or the like. The configuration in the present invention is:
At least a magnetic layer is provided on the non-magnetic brittle substrate, but a barrier layer for corrosion resistance and an underlayer film for controlling the growth of the magnetic layer may be provided between the non-magnetic brittle substrate and the magnetic layer. . As the barrier layer, a Cr-based or Ti-based material is preferable. Further, NiP or Cr-based material is used for the underlayer.

A protective film can be provided on the magnetic layer 2. As the protective film, a carbon film, a hydrogenated carbon film, a carbon nitride film, a hydrogenated carbon film containing nitrogen, a carbide film such as TiC and SiC, and an oxide film such as ZrO ₂ are used. A lubricating film, for example, a perfluoropolyether-based lubricant is formed on the protective film by 5 to 50 °.
The thickness is provided.

The heat treatment after the formation of the laser mark is performed not only before forming the magnetic layer and other necessary films, but also simultaneously with forming the magnetic layer or other necessary films, for example, a protective film. It can be performed, or can be performed after formation of those films.

The laser mark of the present invention formed on a brittle substrate is stored on the outermost surface through a barrier layer, an underlayer, a magnetic layer, a protective film, a lubricating film, etc. provided thereon, and the head and the disk are This contributes to a reduction in the frictional force between them.

FIG. 2 shows an example of the configuration of an apparatus for irradiating a nonmagnetic brittle substrate with a laser to form a laser mark on the surface, but the present invention is not necessarily limited to this. Reference numeral 4 denotes a YAG / Q-switched pulse laser. By arranging a nonlinear element inside the resonator,
Radiation energy having a wavelength of 532 nm, which is the second harmonic of the fundamental wave of YAG (wavelength 1.064 μm), is obtained as an output.

The laser output to be used is guided to the nonlinear element 6 by the folding mirror 5, and the laser energy of the fourth harmonic (wavelength 266 nm) is obtained by wavelength conversion.

[0044] As a laser, in addition to the YAG laser may be a laser having a wavelength in the absorption range of the material to be processed, a solid laser such as YLF or YVO _4, an excimer laser or a carbon dioxide laser, such as argon laser extensive When the non-magnetic brittle substrate is made of glass, the glass material has strong absorption in the infrared region having a wavelength of 3 μm or more and the ultraviolet region having a wavelength of 300 nm or less. laser,
4th harmonics such as YLF laser and YVO ₄ laser,
Alternatively, it is preferable to use an excimer laser, a second harmonic or ultraviolet region of a visible region of an argon laser, or a carbon dioxide laser.

In order to obtain a discrete laser mark, in addition to the Q-switch pulse laser, a continuous wave (C
W) The laser can be modulated by EOM or AOM to form a pulse, or collective exposure can be performed through a mask.

The laser beam passes through an attenuator 7 for controlling the irradiation energy and a folding mirror 8 to an opening 9 for shaping the laser beam into a desired shape, and further controls the intensity distribution of the energy on the recording surface. To the expander 10. The laser light is guided to the surface of the brittle substrate 14 via the X-axis galvanometer mirror 11, the Y-axis galvanometer mirror 12, and the objective lens 13. Multiple laser marks on the substrate, concentric, spiral,
Other arbitrary patterns are formed by driving the X and Y two-axis galvanomirrors controlled between the pulse laser and the repetition frequency.

The plurality of laser marks are formed by a method of deflecting a laser beam by driving the X-axis galvanometer mirror 11 and the Y-axis galvanometer mirror 12 described above.
Under a laser beam whose position is fixed, a spindle with a brittle substrate is rotated, and during the rotation, the spindle moves in a controlled radial direction to form a spiral,
Alternatively, concentric laser mark rows can be formed. In the above, instead of moving the spindle, the laser beam may be moved in the radial direction to be replaced.

[0048]

According to the present invention, regarding the formation mechanism of a ridge generated by laser processing of a non-magnetic brittle substrate, the present inventor described Dimensional C
hanges Caused in Glass by Heating Cycles (AQTool,
DBLioyd and GEMerritt: J.Res.Nat.Bur.Stand., 5,6
27, 1930). In other words, when the glass material is heated to a high temperature by the irradiation of laser energy and the volume expands (density decreases), and subsequently cooled, the volume contracts (increases density) and returns in the process of cooling. It is known that the material does not completely return to its original density.

A bulge (laser mark) formed on a glass substrate as a result of being heated by laser irradiation, raised in temperature, and expanded.
After the laser irradiation is stopped, the glass material is rapidly cooled due to the large heat capacity of the non-laser-irradiated area around it, so that the thermal equilibrium of the glass material cannot be maintained. Also estimates that the ridges are not sufficiently mitigated and the ridges remain. And
It is considered that the protruding portion facing outward from the substrate surface is generated as the sum of the volume increase in the depth region heated and heated by the laser (referred to as the altered region by the laser).

On the other hand, when the irradiation energy is further increased, the high temperature portion of the irradiation region exceeds the material evaporation temperature, and the material starts to evaporate. At this stage, the mechanism of the ridge formation due to the volume increase and the evaporation mechanism of the material in the high temperature part of the irradiated part (in the case of the focused laser energy, the central part) are simultaneously progressing, A crater-shaped laser mark with constriction is obtained.

The mechanism of the bulge formation of glass and glass ceramics is that the denatured region generated as a result of the response to the energy of the laser rises in temperature and expands (density reduction) and then undergoes a non-equilibrium quenching process. The degree of preservation of the low-density state (uplift) is considered to be related to the speed of the cooling process.

The holding temperature T or T ₁ of the heat treatment in the present invention, the holding time, and the cooling rate in the cooling step are selected so that the protrusions remaining on the substrate by the heat treatment are alleviated and the required height is obtained. When the non-magnetic brittle substrate is made of glass, the heat treatment in the present invention raises the temperature (T) which does not exceed the annealing point of the glass by reheating the ridge (laser mark) generated by the laser process and remaining on the substrate. By raising the temperature (heating step), maintaining the temperature at T (holding step), and then slowly lowering the temperature (cooling step) as compared with the cooling rate generated in the laser process, it acts to alleviate the uplift, and as a result, the laser The height of the laser mark formed by the process can be controlled to the height required in the art.

[0053]

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

A laser mark was formed on a glass substrate using a laser texture processing apparatus shown in FIG.
The glass substrate used was the same as the soda aluminosilicate glass used in FIG. The shape of the laser mark was a simple convex shape as shown in FIG. 3, and the height of the protrusion was (the height of the laser mark) 420 °. The height is measured by AFM (atomic force microscope) (the same applies hereinafter). The process parameters at the time of laser processing are as follows.

Laser wavelength λ = 266 nm, pulse repetition frequency = 5 kHz, laser irradiation energy per pulse = 1.3 μJ laser pulse width = 65 ns
c, focal length of the objective lens = 150 mm, beam waist diameter = 15 μm.

A glass substrate (sample without heat treatment in Table 1 below) having a laser mark formed on the surface under the above-described conditions is inserted into an electric furnace, and the temperature is lowered to room temperature after being maintained at a predetermined holding temperature for a predetermined holding time. (Examples 1 to 5).
The time required to lower the temperature from the holding temperature to room temperature is about 10 minutes. The time of 10 minutes is a sufficiently long time as compared with the cooling time for returning to the room temperature from the stop of the laser beam irradiation (it is said to be about several hundred nsec). It is much slower than the cooling rate when returning. Comparative Example 1 was performed without heat treatment.
Using the laser texture processing device of FIG.
A laser mark of 40 ° was obtained. The projection height in Table 1 is an average value, and σ / projection height is the ratio (%) of σ to the average value when the variation in projection height is represented by a standard deviation σ.

Compared to Comparative Example 1 in which the height of the protrusion was 340 ° without heat treatment, the height of the protrusion was 420 ° using the irradiation energy at a level where the fluctuation of the height of the laser mark formed with respect to the fluctuation of the irradiation energy was small. It can be seen that the variation in the protrusion height of about 340 ° (Examples 1 and 2) obtained by forming the heat treatment and heat-treating it is small.

[0058]

[Table 1]

The glass substrate used in this example has a strain point temperature of about 455 ° C. and an annealing point of about 520 ° C. At a temperature at which the holding temperature exceeded the strain point temperature of 455 ° C., a rapid decrease in the projection height was observed. In addition, the effect of reducing the height of the protrusions increases as the holding time increases, and increases as the holding time approaches the strain point temperature. The selection of the holding temperature and the holding time is appropriately selected depending on the difference between the height of the laser mark before the heat treatment and the required height of the laser mark after the heat treatment.

[0060]

The present invention has the following excellent effects. (1) The height of a laser mark as a texture can be formed with high precision in a very small area (500 ° or less, more preferably 300 ° or less), and the flying of the head is facilitated. (2) Since the variation in the height of the laser mark as the texture is suppressed to be small, the recording capacity can be improved by achieving both low flying of the head and CSS durability.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an embodiment of a magnetic recording medium according to the present invention.

FIG. 2 is a block diagram of a laser texture processing apparatus that can be used in the method of the present invention.

FIG. 3 is a schematic cross-sectional view of a laser mark formed with a relatively low irradiation energy.

FIG. 4 is a schematic cross-sectional view of a laser mark formed with moderate irradiation energy.

FIG. 5 is a schematic cross-sectional view of a laser mark formed with a relatively high irradiation energy.

FIG. 6 is a graph of an example showing laser processing characteristics of a soda aluminosilicate glass substrate.

[Explanation of symbols]

 1: non-magnetic brittle substrate 2: magnetic layer 3: laser mark 4: YAG-Q switch pulse laser second harmonic output 5: folding mirror 6: nonlinear element 7: attenuator 8: folding mirror 9: aperture 10: expander 11 : X-axis galvanometer mirror 12: Y-axis galvanometer mirror 13: Objective lens 14: Non-magnetic brittle substrate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Atsushi Takenaka 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd.

Claims (5)

[Claims] A plurality of laser marks having at least a part of which are convex by irradiating a plurality of portions of the substantially flat non-magnetic brittle substrate with a laser beam; A method for manufacturing a substrate for a magnetic recording medium, wherein a height H of a convex portion of the laser mark is controlled in a range of 10 to 500 ° by performing a heat treatment on at least a portion including the laser mark of the substrate. 2. A plurality of laser marks having a convex portion at least in part by irradiating a plurality of portions of a substantially flat non-magnetic brittle substrate with a laser beam; Performing a heat treatment on at least a portion of the substrate including the laser mark to obtain a magnetic recording medium substrate in which the height H of the convex portion of the laser mark is controlled in a range of 10 to 500 °; Forming a magnetic film and / or other necessary films on the surface of the substrate. 3. A method of manufacturing a magnetic recording medium having a magnetic film and other required films on a non-magnetic brittle substrate, wherein a plurality of portions of the surface of the substantially flat non-magnetic brittle substrate are irradiated with laser light. Forming a plurality of laser marks having a convex portion on at least a part of the surface, forming a magnetic film and / or other necessary films on the surface, and forming the film on the surface. Wherein the height H of the convex portion of the laser mark stored on the outermost surface after the film formation is controlled in the range of 10 to 500 ° by the heat treatment step. Manufacturing method of recording medium. 4. A method for manufacturing a magnetic recording medium having a magnetic film and other necessary films on a non-magnetic brittle substrate, wherein a plurality of portions of the surface of the substantially flat non-magnetic brittle substrate are irradiated with laser light. Forming a plurality of laser marks having a convex portion on at least a part of the surface, forming a magnetic film and / or other necessary films on the surface, and forming the film on the surface. And the height H of the convex portion of the laser mark stored on the outermost surface after the film formation by the heat treatment step.
Is controlled in the range of 10 to 500 °. 5. A non-magnetic brittle substrate made of glass, wherein a heat treatment step is performed from room temperature to a temperature T which does not exceed the annealing point of the glass; a holding step of holding the temperature T;
5. The method according to claim 1, further comprising a step of lowering the temperature from room temperature to room temperature.