JPH10105954A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which has improved adhesion between a carbon substrate and a magnetic layer, etc., and has improved magnetic characteristics. SOLUTION: The magnetic recording medium 1 constituted by providing at least ground layers 3, 3' and the magnetic layer 4 on the carbon substrate 2 is provided with a first ground layer 3 consisting of Cr directly on the carbon substrate 2 and a second ground layer 3' consisting of Cr or a Cr alloy between the first ground layer 3 and the magnetic layer 4. Further, no texture layer is provided between the first base layer 3 and the magnetic layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium mounted on a fixed magnetic disk drive or the like, and more particularly, to a magnetic recording medium having improved magnetic properties and improved adhesion between a substrate and a magnetic layer. It is about.

[0002]

2. Description of the Related Art A carbon substrate for a magnetic recording medium can be obtained by curing and baking a carbonaceous resin such as a phenolic resin and then performing a surface processing step.
The magnetic recording medium is used for cleaning the substrate, forming a magnetic layer, etc.,
Obtained through an inspection process and the like. However, if the cleaning of the substrate prior to the formation of the magnetic layer or the like is insufficient, the film adhesion between the substrate and the magnetic layer or the like deteriorates due to dirt present on the substrate surface.
Therefore, ultra-precision cleaning of the substrate is required, but as a result, the production cost is increased and excessive production control is required. In addition, there is a case where dirt cannot be completely removed even by performing ultra-precision cleaning.

Japanese Patent Application Laid-Open No. 8-180362 discloses a magnetic recording medium comprising a carbon substrate and a film made of a carbide-forming metal and a texture film made of an Al-carbide-forming metal alloy. Zr or the like is mentioned as a bite forming metal. However, among these carbide-forming metals, those having a high gas-adsorbing property, such as Zr, react with a gas derived from organic dirt present on the substrate and become inert, making it difficult to form a carbide, and In some cases, film adhesion could not be obtained.

Accordingly, an object of the present invention is to provide a magnetic recording medium in which the adhesion between a carbon substrate and a magnetic layer or the like is improved and the magnetic characteristics are improved.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that two specific underlayers are provided between a substrate and a magnetic layer, and a texture is provided between the underlayer and the magnetic layer on the substrate side. It has been found that by not providing a layer, a magnetic recording medium capable of achieving the above object can be obtained.

The present invention has been made based on the above findings. In a magnetic recording medium comprising at least an underlayer and a magnetic layer provided on a carbon substrate, a first underlayer made of Cr is directly provided on the carbon substrate. Is provided,
A second underlayer made of Cr or a Cr alloy is provided between the first underlayer and the magnetic layer, and there is no texture layer between the first underlayer and the magnetic layer. The above object has been achieved by providing a magnetic recording medium characterized by the following.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the magnetic recording medium of the present invention will be described below with reference to the drawings. Here, FIG.
FIG. 1 is a schematic diagram showing a structure of a first embodiment of a magnetic recording medium of the present invention.

The magnetic recording medium 1 of the embodiment shown in FIG. 1 is disk-shaped, and has a first underlayer 3 provided on a substrate 2 and a second underlayer 3 'provided thereon. Yes,
Further, a magnetic layer 4 and a protective layer 5 are further provided thereon in this order. Further, a lubricant layer 6 is provided on the protective layer 5.
Is provided.

The substrate 2 is a carbon substrate and is formed of a carbonaceous material such as glassy carbon and amorphous carbon. The carbon substrate is, for example,
It is obtained by sandwiching a carbonaceous raw material such as a phenol resin between two glass plates and hardening, punching it into a predetermined shape, for example, a disk shape, and further firing. Further, it can also be obtained by slicing a columnar carbon material obtained by carbonizing a carbonaceous material such as pitch by hot isostatic pressing (HIP) to a predetermined thickness.

The surface of the substrate 2 is made smooth (for example, by applying a center line average roughness Ra
= 0.1 to 0.3 nm), but may have a certain number or pore diameter.
The reason for this is that the openings are covered by the formation of the first underlayer 3 described later, and the adhesion to the magnetic layer and the like does not decrease. For example, in the present invention, even when the substrate 10 has about 100 holes / mm ² or less in the surface thereof with a hole diameter of 10 μm or less, it is used at a level of film adhesion that does not cause a problem as a substrate for a magnetic recording medium. It is possible, but not limited to this range. 100 holes /
If it exceeds mm ² , the thickness of the first underlayer 3 required to cover the openings becomes excessively large, and as a result, the effect of improving the adhesion is reduced. In addition, the diameter of the opening is 10 μm.
The same result is obtained even if m is exceeded. If there are apertures,
The number is desirably about 1 to 80 pieces / mm ^2.
If it is about 50 / mm ^{2, the} level is almost the same as in the case where there is no opening, and therefore it is more desirable. In this specification, the term “open hole” means a micropore (micropore) existing on the surface of the substrate. Note that the number of openings can be measured by observation with a scanning electron microscope (SEM) or an optical microscope. Further, the magnetic recording medium of the present invention is
When used as an S (contact start and stop) type magnetic recording medium, a texture (unevenness) may be formed in a predetermined region of the substrate surface as described later.

As shown in FIG. 1, a first underlayer 3 is provided directly on the substrate 2. The first underlayer 3
Is formed of Cr, and its thickness is preferably 1 to 50 nm, more preferably 2 to 25 nm, in order to obtain a sufficient level of film adhesion. The first underlayer 3 is formed by a thin film forming means such as vacuum evaporation or sputtering.

As shown in FIG. 1, a second underlayer 3 ′ is formed directly on the first underlayer 3. The second underlayer 3 'is made of Cr or a Cr alloy. When the second underlayer 3 'is formed of a Cr alloy, the Cr alloy may be, for example, C
r-based binary alloys (CrTi, CrTa, Cr
V, CrMo) can be used. The concentration of Cr in the Cr alloy is preferably from 50 to 99 atomic% from the viewpoint of coercive force, S / N ratio, and film adhesion.
More preferably, it is 0 atomic%. The thickness of the second underlayer 3 ′ is preferably 1 to 50 nm from the viewpoint of the balance between the coercive force of the medium and the S / N ratio, and is preferably 2 to 30 nm.
Is more preferable. The second underlayer 3 ′
For example, it is formed by thin film forming means such as vacuum evaporation or sputtering.

In the magnetic recording medium of the present invention, if the first underlayer 3 and the second underlayer 3 'are provided between the carbon substrate and the magnetic layer, the film of the substrate and the magnetic layer etc. The reason why the adhesion and the magnetic properties are improved is not necessarily clear, but is presumed to be as follows. That is, since the first underlayer 3 directly formed on the carbon substrate 2 is formed of Cr, the first underlayer 3 is formed from the interface between the substrate 2 and the first underlayer 3. A layer of carbide (chromium carbide) is formed on the inside of No. 3, thereby improving the adhesion between the two. In particular, even if a gas derived from the organic dirt on the substrate is generated, Cr does not easily react with the gas, so that carbide is effectively formed.
On the other hand, Cr has the effect of controlling the crystallinity of the material forming the magnetic layer and improving the magnetic properties of the magnetic layer due to its crystal system. Therefore, the first underlayer 3 made of Cr
It is thought that if the magnetic layer is formed directly on the film, both the film adhesion and the magnetic characteristics are improved. However, according to detailed studies by the present inventors, it has been found that the magnetic characteristics are not sufficiently improved.
The reason for this is that even if a magnetic layer is formed directly on the first underlayer 3, the crystal state of the first underlayer 3 at the interface between the two is not a pure Cr crystal state. It is considered that the crystal state is disturbed due to the formation of carbide in the underlayer 3 and the crystal state is not sufficient to improve the magnetic properties of the magnetic layer ( According to the study of the present inventors, the thickness of the Cr layer was set to 30.
Even at about 00 °, it has been found that crystal disorder is caused on the surface by the formation of carbides). Therefore, when separate Cr layers (that is, the first underlayer 3 and the second underlayer 3 ′ in the magnetic recording medium of the present invention) are used, the two functions of the Cr layer are as follows.
That is, it is considered that the improvement of the film adhesion and the improvement of the magnetic properties of the magnetic layer are separately exhibited by each layer.
In fact, as is apparent from the examples described later, the film thickness is set to 30.
Forming two Cr layers having a thickness of 150 ° and 200 °, respectively, improves the film adhesion and magnetic properties, compared to forming a single Cr layer of 00 °. Further, in the present embodiment, since the texture (irregularity) layer is not provided between the first underlayer 3 and the magnetic layer 4, the second underlayer is formed from above the first underlayer 3. The crystallinity and the crystal grain size are not largely disturbed over the underlayer 3 ′, and the design of the underlayers 3 and 3 ′ becomes easy. Furthermore, in the present embodiment, since the second underlayer 3 ′ made of the same material as the first underlayer 3 is directly formed on the first underlayer 3,
The crystallinity of the second underlayer 3 'is improved, and the magnetic properties of the magnetic layer are further improved.

As shown in FIG. 1, the second magnetic layer 3 '
On top of this, a magnetic layer 4 is provided. As a material constituting the magnetic layer 4, a Co alloy is preferable in terms of magnetic properties, crystallinity with the second magnetic layer 3 ', corrosion resistance, and the like.
In particular, CoCr-based alloys, further CoCrPt-based alloys, especially CoCrPtX (where X is B, Ta, Au, T
i, C, Ni, W, La, Ce, Pr, Nd, Pm, S
m, Eu, Li, Si, Ca, As, Y, Zr, Nb,
Or one or more metals selected from Mo, Ru, Rh, Ag, Sb and Hf). The thickness of the magnetic layer 4 is preferably from 1 to 100 nm from the viewpoint of a balance between high coercive force and output.
More preferably, it is 80 nm. The magnetic layer 4 includes:
For example, it is formed by thin film forming means such as vacuum evaporation or sputtering.

On the magnetic layer 4, a protective layer 5 is provided. As the protective layer 5, a layer formed from a substance usually used for a magnetic recording medium can be used without any particular limitation. In particular, a protective layer formed from a substance containing carbon or Si is preferably used. Above all,
Diamond-like carbon or amorphous carbon,
SiO ₂ , SiC and the like are preferable because of their excellent durability. The protective layer 5 may be formed, for example, by sputtering in an atmosphere in which hydrogen or methane gas is mixed in argon gas, or may be formed from a carbon-based material using CVD (chemical vapor polymerization). Is also good. The thickness of the protective layer 5 is 1 to 3 from the viewpoint of the balance between wear resistance and electromagnetic conversion characteristics.
It is preferably 50 nm, more preferably 2 to 25 nm. The protective layer 5 is formed by a thin film forming means such as vacuum evaporation or sputtering.

On the protective layer 5, a lubricant layer 6 is provided. The lubricant constituting the lubricant layer 6 can be used without any particular limitation as long as it is usually used for a magnetic recording medium. In particular, a fluorine-containing lubricant having perfluoropolyether as a basic skeleton or a fatty acid skeleton Is preferably used. Above all, Fomblin Z-do
Fluorine-containing lubricants such as 1 and Z-03 (manufactured by Ausimont) are preferred. The thickness of the lubricant layer 6 is 1 to 8 in view of the balance between lubrication performance and prevention of stiction of the magnetic head.
The angle is preferably 0 °, more preferably 5 to 25 °.

Next, a preferred method of manufacturing the magnetic recording medium shown in FIG. 1 will be described focusing on the formation of the first underlayer 3 and the second underlayer 3 '. The magnetic recording medium shown in FIG. 1 is formed on a substrate 2 having been subjected to a predetermined surface treatment (polishing, grinding, washing, etc.) by a thin film forming means such as vacuum evaporation or sputtering. The second underlayer 3 ′, the magnetic layer 4, and the protective layer 5 are formed and laminated in this order. In particular, when forming the first underlayer 3 and the second underlayer 3 ′, first, the first underlayer 3 is formed to have a predetermined thickness, and then the formation of the layers is temporarily stopped. Then, the inside of the device is returned to the atmospheric pressure, and then a second underlayer 3 'is formed. By forming the first underlayer 3 and the second underlayer 3 'using such a method, the effects of improving the film adhesion and the magnetic properties are separately and effectively exerted on the respective underlayers. Can be done. The first underlayer 3 and the second underlayer 3 ′ formed by using such a method can be obtained by observing the cross section of the magnetic recording medium with, for example, an electron microscope or the like. Is confirmed to exist.

Next, second, third and fourth embodiments of the magnetic recording medium of the present invention will be described with reference to the drawings. Here, FIGS. 2, 3 and 4 are schematic diagrams (each corresponding to FIG. 1) showing the structure of the second, third and fourth embodiments of the magnetic recording medium of the present invention, respectively. In the second, third, and fourth embodiments, only the portions that are different from the first embodiment will be described, and the same portions will not be described in detail, but will be described in detail in the first embodiment. Is applied as appropriate. 2, 3, and 4, the same members as those in FIG. 1 are denoted by the same reference numerals.

In the magnetic recording medium 1 according to the embodiment shown in FIG. 2, T is applied between the first underlayer 3 and the second underlayer 3 '.
A layer 7 made of a metal selected from the group consisting of i, W, Mo, Zr and V or an alloy thereof is formed. Since these metals and their alloys have the function of improving the magnetic properties of the magnetic layer 4, the provision of the layer 7 improves the adhesion between the first underlayer 3 and the second underlayer 3 '. The magnetic properties of the magnetic layer 4 can be improved without any loss.
On the other hand, these metals have the ability to form carbide, but since the first underlayer 3 is present in the lower layer, carbon is not dispersed (diffused) in the layer 7. The effect of improving the magnetic properties is not hindered. The layer 7 is made of, in particular, Ti or an alloy thereof, for example, TiCr, CrV,
It is preferable to be formed from CrMo or the like. Also,
When the layer 7 is formed from an alloy of the above metals, the concentration of the above metals in the alloy is preferably about 50 to 99% by weight. The thickness of the layer 7 depends on the coercive force and S /
It is preferably 1 to 100 nm from the viewpoint of the N ratio, and 2
More preferably, it is 30 nm. The layer 7 is formed by thin film forming means such as vacuum evaporation or sputtering.

The magnetic recording medium 1 of the embodiment shown in FIG.
The magnetic recording medium is the same as the magnetic recording medium shown in FIG. 2 except that the texture (irregularities) 13 is formed directly on the surface of the substrate 2 and the first underlayer 3 is formed directly thereon. Is a point. When the texture 13 is formed directly on the surface of the substrate 2, the first underlayer 3 directly provided thereon functions as a buffer layer, and the cause of the disorder of the crystallinity of the second underlayer 3 'is eliminated. As a result, even when a texture is formed on the magnetic recording medium, the crystallinity of the material forming the magnetic layer 4 is improved, and the magnetic characteristics are further improved.

As a method of directly forming a texture on the surface of the substrate 2, a method of irradiating a laser beam as described in, for example, JP-A-6-290452 is preferable from the viewpoint of less generation of processing dust. However, other methods such as a method using a polishing tape, a method of thermally oxidizing the surface of the substrate, and the like can also be used. The center line average roughness Ra of the substrate 2 on which the texture is formed is 8 to 100 °.
And more preferably 10 to 50 °.

The magnetic recording medium 1 of the embodiment shown in FIG.
The magnetic recording medium is the same as the magnetic recording medium shown in FIG. 2 except that a texture (irregularity) layer 14 is formed on the magnetic layer 4. Since the texture layer is formed above the magnetic layer 4, the first and second underlayers 3,
The texture can be formed on the magnetic recording medium without deteriorating the crystallinity of 3 ′ and the magnetic layer 4 without deteriorating the magnetic properties and without decreasing the film adhesion. The texture layer 14 preferably has the function of a protective layer. Examples of the material having such a function include, for example, Si as used in Examples described later.
After coating the magnetic layer 4 with fine particles of O ₂ by spin coating, a silica-containing polysilicate-based film formed by heat treatment can be used. The center line average roughness Ra of the texture layer 14 is preferably from 8 to 100 °, and more preferably from 10 to 50 °.

Although the magnetic recording medium of the present invention has been described based on the preferred embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. . For example, in the magnetic recording medium of the embodiment shown in FIG. 1, the texture may be formed directly on the surface of the substrate 2 as in the magnetic recording medium shown in FIG. Further, in the magnetic recording medium of the embodiment shown in FIG. 1, a texture layer may be formed on the magnetic layer 4 similarly to the magnetic recording medium shown in FIG. In the magnetic recording medium of the embodiment shown in FIGS. 2 to 4, two or more layers 7 may be provided. Further, in the magnetic recording medium of the embodiment shown in FIGS. 1 to 4, layers capable of improving various performances of the magnetic recording medium of the present invention may be provided between the respective layers as needed.

[0024]

The following examples illustrate the effectiveness of the present invention. However, it goes without saying that the scope of the present invention is not limited to such an embodiment.

Example 1 A glassy carbon substrate was subjected to ultrasonic cleaning in pure water at room temperature for 15 seconds, then immersed in pure water at 80 ° C. for 15 seconds, and then pulled up at a speed of 1 mm / s.
Then it was dried. Next, the substrate was placed in a stationary facing type sputtering apparatus, and film formation was continuously performed by the following procedures (1) to (5) under the condition of an Ar gas pressure of 2 mTorr. (1) The substrate temperature is heated to 180 ° C. by a lamp heater. (2) A Cr layer as a first underlayer is Ar gas pressure of 2 mTo.
A film is formed to a thickness of 15 nm at rr. (3) A Cr layer is formed as a second underlayer with an Ar gas pressure of 2 mTo.
A film is formed to a thickness of 20 nm at rr. (4) A CoCrPtB layer is formed as a magnetic layer with an Ar gas pressure of 2 m.
A film is formed to a thickness of 30 nm by Torr. (5) A carbon layer is formed to a thickness of 9 nm as a protective layer at a mixed gas pressure of Ar and hydrogen (total pressure) of 5 mTorr.
The bias voltage in the sputtering was -100 volts. After taking out the substrate from the sputtering device and performing burnishing with a polishing tape, Fomblin z-dol (manufactured by Ausimont) is applied on the protective layer by dip coating to a thickness of 2 nm, A magnetic disk was obtained.

The magnetic disk thus obtained was evaluated for film adhesion by the following method.
VSM (vibrating sample magnetometer) manufactured by Toei Industry Co., Ltd.
Were used to measure the magnetic properties [Hc, Brt, squareness ratio (S and S ^* )] of the magnetic disk. Table 1 shows the results. <Evaluation of film adhesion>
After leaving it for 100 days under the conditions of 85 ° C. and 85 RH%, it was taken out, and a 1.5 cm × 1.5 cm cellophane tape [No. 4
05, registered trademark, manufactured by Nichiban Co., Ltd.] was attached to four places of the magnetic disk so that air bubbles did not enter. Then, slowly pull up the cellophane tape vertically,
The area where film peeling occurred was measured. The evaluation was 10
The average value of the disks was determined based on the following criteria. ◎: The film peeling area is less than 5% of the cellophane tape area ○: The film peeling area is 5% or more and less than 10% of the cellophane tape area △: The film peeling area is 10% or more of the cellophane tape area

Embodiment 2 The second underlayer in Embodiment 1 was formed from CrTi (Cr: 90 at%), the thickness was 15 nm, and the thickness of the magnetic layer was 28 nm. A magnetic disk was obtained in the same manner as in Example 1. The same evaluation and measurement as in Example 1 were performed on the obtained magnetic disk. Table 1 shows the results.

[Embodiment 3] A layer made of Ti (film thickness: 10) between the first underlayer and the second underlayer in the first embodiment.
nm), and the thickness of the second underlayer is set to 15 nm.
A magnetic disk was obtained in the same manner as in Example 1 except that the thickness of the magnetic layer was changed to 28 nm. The same evaluation and measurement as in Example 1 were performed on the obtained magnetic disk. Table 1 shows the results.

Example 4 Prior to the formation of the first underlayer in Example 3, the surface of the substrate was textured using a polishing tape. The processing conditions are as follows.・ Abrasive tape: Nippon Micro Coating # 4000
Flat type ・ Tape feed speed: 400 mm / min ・ Processing pressure: 2.2 kg / cm ²・ Tape swing speed: 460 reciprocations / min ・ Work rotation speed: 50 rpm ・ Processing time: 10 seconds ・ Polishing solution: JS602 manufactured by Johnson The surface shape of the substrate obtained by 3% by weight texture was Ra = 25.
３６36 nm, Rp (centerline maximum height) = 29-52 nm
Met. Except for this, a magnetic disk was obtained in the same manner as in Example 3. The same evaluation and measurement as in Example 1 were performed on the obtained magnetic disk. Table 1 shows the results.

Example 5 A magnetic disk was prepared in the same manner as in Example 3 except that an SiO ₂ layer which also functions as a texture layer in addition to the carbon layer was formed as the protective layer in Example 3. Obtained. The SiO ₂ layer is
Tetraethoxysilane, water (4 moles relative to the amount 1 mol in terms of SiO ₂ in tetraethoxysilane), hydrochloric acid (0.1 mole relative to the amount 1 mol in terms of SiO ₂ in tetraethoxysilane), A solution obtained by dissolving and dispersing silica having an average particle diameter of 40 nm (0.4 mol per 1 mol of SiO ₂ in tetraethoxysilane) in isopropyl alcohol is applied by spin coating.
It is formed by heat treatment at 00 ° C. for 1 hour. The S
Ra of the iO ₂ layer was 15 ° and Rp was 100 °. The same evaluation and measurement as in Example 1 were performed on the obtained magnetic disk. Table 1 shows the results.

Comparative Example 1 A magnetic disk was obtained in the same manner as in Example 1 except that a layer (thickness: 25 nm) made of Zr was formed instead of the first underlayer in Example 1. The same evaluation and measurement as in Example 1 were performed on the obtained magnetic disk. Table 1 shows the results.

Comparative Example 2 A magnetic disk was fabricated in the same manner as in Example 1 except that the first and second underlayers in Example 1 were replaced with a single layer of Cr (thickness: 35 nm). Obtained.

Comparative Example 3 A magnetic disk was obtained in the same manner as in Comparative Example 2, except that the thickness of the layer having a Cr thickness in Comparative Example 2 was changed to 300 nm. The same evaluation and measurement as in Example 1 were performed on the obtained magnetic disk. Table 1 shows the results.

[0034]

Comparative Example 4 A magnetic disk was prepared in the same manner as in Example 1 except that a texture layer made of Al-Si (1 atomic%) was formed between the first and second underlayers in Example 1. I got In addition, the texture layer has an Ar pressure of 2 mTorr.
The thickness was 10 nm, and the center line average roughness Ra was 3.5 nm.

[0035]

[Table 1]

As is clear from the results shown in Table 1, the magnetic recording medium of the present invention in which the first and second underlayers formed of specific materials are provided on a carbon substrate (Example 1)
5) have better film adhesion than the magnetic recording medium provided with only one underlayer (Comparative Example 1). Further, the magnetic disk of Comparative Example 2 consisting of only one Cr layer having the same thickness as the total thickness of the Cr layer of Example 1, and the thickness of the Cr layer being about 10% of the total thickness of the Cr layer of Example 1 The film adhesion of the magnetic disk of Comparative Example 2, which was twice as large, did not reach the film adhesion of the magnetic disk of Example. Furthermore, the film adhesion of the magnetic disk of Comparative Example 4, in which the texture layer was formed between the first and second underlayers, did not reach the film adhesion of the magnetic disk of Example. Also,
Reflecting the good adhesion, the magnetic recording media of Examples 1 to 5 were superior in magnetic properties to the magnetic recording media of Comparative Examples 1 to 4.

[0037]

According to the magnetic recording medium of the present invention, the adhesion between the substrate and the magnetic layer and the like are improved and the magnetic properties are improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a structure of a first embodiment of a magnetic recording medium of the present invention.

FIG. 2 is a schematic diagram (corresponding to FIG. 1) showing the structure of a second embodiment of the magnetic recording medium of the present invention.

FIG. 3 is a schematic diagram (corresponding to FIG. 1) showing the structure of a third embodiment of the magnetic recording medium of the present invention.

FIG. 4 is a schematic diagram (corresponding to FIG. 1) showing the structure of a fourth embodiment of the magnetic recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic recording medium 2 Substrate 3 First underlayer 3 'Second underlayer 4 Magnetic layer 5 Protective layer 6 Lubricant layer

Claims (6)

[Claims] 1. A magnetic recording medium comprising at least an underlayer and a magnetic layer provided on a carbon substrate, wherein a first underlayer made of Cr is provided directly on the carbon substrate. Cr between the underlayer and the magnetic layer
Or a second underlayer made of a Cr alloy is provided,
And a magnetic recording medium having no texture layer between the first underlayer and the magnetic layer. 2. The method according to claim 1, wherein the carbon substrate has a pore size of 1 on its surface.
It has 100 holes / mm ² or less of 0 μm or less,
The magnetic recording medium according to claim 1. 3. The magnetic recording medium according to claim 1, wherein the second underlayer is provided directly on the first underlayer. 4. One or more layers comprising a metal selected from the group consisting of Ti, W, Zr, V and Mo or an alloy thereof are provided between the first underlayer and the second underlayer. The magnetic recording medium according to claim 1, wherein: 5. The magnetic recording medium according to claim 1, wherein a texture is formed directly on the surface of the carbon substrate. 6. The magnetic recording medium according to claim 1, wherein a texture layer is formed on the magnetic layer.