JP3044850B2 - Magnetic recording medium and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art With the progress of the information society, the capacity and density of information recording media have been increased. In the field of magnetic tapes as well, research and development aimed at increasing the density of recording media have been actively pursued, and several thin-film media have been proposed to meet this requirement. Co-Cr and the like have been widely studied as ultra-high density magnetic recording materials, and Co-Cr thin films (or Co-Cr thin films) have been studied.
Research and development using Ni-Cr thin films) have been conducted.
In addition, a recording medium (hereinafter referred to as 2) in which a magnetic Co—O (or Co—Ni—O thin film) is laminated on a Co—Cr thin film.
Research has been conducted with the aim of achieving both recording density characteristics and practical durability by using a layered medium).

As a method for manufacturing these thin-film magnetic recording media, a continuous winding vacuum evaporation method is superior to other methods, particularly in terms of productivity, and is very effective as a practical mass production method. In other words, the magnetic tape can be mass-produced by e-beam evaporation of the magnetic layer while the long polymer substrate runs along the peripheral surface of the cylindrical can. For example, Co
In forming the -Cr magnetic thin film, Co-Cr may be used as an evaporation material, and in forming the Co-O thin film, Co may be evaporated in an oxygen atmosphere.

[0004]

However, the above-described conventional magnetic recording medium and the method of manufacturing the same have a great problem to be solved in terms of material cost as well as medium characteristics. The ratio of the polymer substrate to the material cost is large, and an inexpensive substrate material has been required. In the Co-Cr-based magnetic recording media formed by the vacuum deposition method, polyamide or polyimide substrates have been used so far,
These super heat resistant polymer substrates are generally expensive materials, and relatively inexpensive polyethylene naphthalate substrates,
Further, it was necessary to design a medium such that sufficient magnetic properties could be obtained even when an inexpensive polyethylene terephthalate substrate was used.

[0005] The present invention is to solve the above problems,
An object of the present invention is to provide a magnetic recording medium excellent in recording / reproducing characteristics at a low material cost and a method for manufacturing the same.

[0006]

In order to achieve the above-mentioned object, the present invention provides a method for producing Co and Cr or Co, Cr and Ni on a substrate made of polyethylene terephthalate directly or through an underlayer in order from the substrate side. A first magnetic layer containing as a component, and a second magnetic layer containing Co and O or Co, Ni, and O as main components, wherein the magnetic anisotropy of the first magnetic layer is from the in-plane direction of the film. It is characterized in that it is 15 degrees or less and 5 degrees or more, and Co and Cr or Co, Cr and Ni as main components on the substrate made of polyethylene naphthalate directly or through an underlayer from the substrate side. And a second magnetic layer containing Co and O or Co, Ni and O as main components, and the first magnetic layer has a magnetic anisotropy of 30 from the in-plane direction of the film. Less than 15 degrees or more Is shall.

[0007]

According to the present invention, the anisotropy of the first magnetic layer made of Co-Cr or Co-Cr-Ni can be inclined in the direction of the film surface to increase the recording / reproducing efficiency. it can. However, if the separation between the columnar grains forming the first magnetic layer is insufficient, the coercive force decreases and the reproduction noise increases. The value of the coercive force depends on the vapor incident angle and the substrate temperature.In order to obtain the same coercive force, the higher the substrate temperature, the more the incident angle component closer to the normal direction of the film surface can be taken in. This is advantageous from the viewpoint of productivity. If the anisotropy of the first magnetic layer is excessively inclined in the direction of the film surface, the recording / reproducing characteristics in a short wavelength region are adversely affected. Therefore, it is necessary to form the first magnetic layer with an appropriate inclination.
A high-density magnetic recording medium using a low-cost substrate can be obtained by making the anisotropy of the first magnetic layer close to the optimum inclination within a range where the coercive force for low noise can be secured according to the heat resistant temperature of the substrate to be used. Obtainable.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional view of a magnetic recording medium according to an embodiment of the present invention. As shown in FIG. 1, a saturated magnetization 550 emu / m is formed as a first magnetic layer 2 on a substrate 1 made of a polymer material by electron beam evaporation. A cc Co-Cr layer was formed. The thickness of the first magnetic layer 2 is 120 nm. Subsequently, a Co—O layer having a thickness of 60 nm was formed as the second magnetic layer 3 by an electron beam evaporation method. The saturation magnetization of the second magnetic layer 3 is also 550 emu / cc. This was cut into a tape shape, and the recording / reproducing characteristics were evaluated using a ring head. The relative speed between the medium and the head was 3.8 m / s. The carrier (C) and noise (N) levels were measured under the above conditions. The measurement bandwidth was 30 kHz. The coercive force was measured using a vibrating sample magnetometer, and the direction of magnetic anisotropy was measured using a torque meter.

First, the case where polyethylene terephthalate is used as the substrate 1 will be described. Initial incidence angle is 90
The Co-Cr layer was formed as the first magnetic layer 2 with the final incident angle fixed at 20 degrees. In this case, the magnetic anisotropy of the first magnetic layer 2 was in the range of 5 to 15 degrees at θ shown in FIG. Can temperature from -20 ° C to 7
The film was manufactured by changing the temperature to 0 ° C., and the coercive force and the direction of magnetic anisotropy of the film were measured. The result is shown in FIG. When the can temperature was 60 ° C., thermal damage of the substrate 1 occurred during the vapor deposition, and the film surface became rough and the film could not be stably formed. Further, when the can temperature is 70 ° C., the thermal damage of the substrate 1 is further severe,
Film formation was not possible. Further, as can be seen from FIG. 3, the coercive force is 200 Oe or less when the initial incident angle is 60 degrees or less, but the coercive force is 400 Oe or more when the initial incident angle is 70 degrees or more. In the range of small coercive force, the direction of magnetic anisotropy is almost in the in-plane direction. On the other hand, when the coercive force is 400 Oe or more, the direction of magnetic anisotropy is in the range of 5 ° to 15 ° from the in-plane direction of the film. It is in.

Next, a case where polyethylene naphthalate is used as the substrate 1 will be described. The Co-Cr layer was formed as the first magnetic layer 2 by changing the initial incident angle from 90 degrees to 30 degrees and fixing the final incident angle to 20 degrees. In this case, the magnetic anisotropy of the first magnetic layer 2 was in the range of 15 to 30 degrees at θ shown in FIG. Can temperature is 50 ℃ ～ 13
The film was manufactured by changing the temperature to 0 ° C., and the coercive force and the direction of magnetic anisotropy of the film were measured. FIG. 4 shows the results. When the can temperature was 120 ° C., thermal damage to the substrate 1 occurred during the vapor deposition, and the film surface became rough and a stable film could not be formed. When the can temperature was 130 ° C., the substrate 1 was further severely damaged by heat, and film formation was impossible. As can be seen from FIG. 4, the coercive force is 300 Oe or less even when the can temperature is increased to 110 ° C. when the initial incident angle is 40 ° or less, but when the initial incident angle is 50 ° or more, the can temperature becomes 110 ° C. A coercive force of 400 Oe or more can be obtained even if it is less than or equal to. Also, the direction of magnetic anisotropy at a coercive force of 400 Oe or more was in the range of 5 to 30 degrees from the in-plane direction of the film, and especially when the initial incident angle was in the range of 70 to 50 degrees, it could not be obtained with the polyethylene terephthalate substrate. Anisotropy inclined by 15 degrees or more from the in-plane direction of the film can be obtained.

FIG. 5 shows the direction of the magnetic anisotropy of the first magnetic layer 2 and the electromagnetic conversion characteristics of the magnetic recording medium when the substrate 1 made of polyethylene terephthalate and the substrate 1 made of polyethylene naphthalate are used, respectively. It is a figure showing a relation. The recording wavelength was 1.5 μm. In FIG. 5, white circles and white triangles indicate the results when the substrate 1 made of polyethylene terephthalate was used, and black circles and black triangles indicate the results when the substrate 1 made of polyethylene naphthalate was used. Round As can be seen from FIG.
The carrier (C) level shown by (1) takes a re-high value when the anisotropic magnetic field is between 15 and 30 degrees from the in-plane direction of the film. Meanwhile, triangle
The noise (N) level indicated by indicates that the anisotropic magnetic field is 5
It is almost constant in a range inclined more than a degree and depends on the coercive force.
It is considered that the reason why the noise is high when the anisotropic magnetic field is almost in the film plane is that the magnetic separation at the columnar grain boundaries is small and the magnetization process of the domain wall mode is taken, and the noise is 10 degrees from the in-plane direction of the film. This suggests that there is a considerable gap in the magnetization process from the case where the anisotropic magnetic field is tilted.

As described above, according to the above embodiment, the first magnetic layer 2 containing Co and Cr as main components formed directly on the substrate 1 made of polyethylene terephthalate or in order from the substrate 1 side via the underlayer is provided. In the manufacturing process of the magnetic recording medium having the second magnetic layer 3 containing Co and O as main components, the magnetic anisotropy of the first magnetic layer 2 is set to 15 degrees or less and 5 degrees or more from the in-plane direction of the film. Therefore, a first magnetic layer 2 containing Co and Cr as main components formed directly on the substrate 1 made of polyethylene naphthalate or in order from the substrate side via an underlayer, and Co and O as main components In the manufacturing process of the magnetic recording medium having the second magnetic layer 3 including the magnetic layer, the magnetic anisotropy of the first magnetic layer 2 is set to 30 degrees or less and 15 degrees or more from the in-plane direction of the film, so that excellent recording / reproduction is achieved. Characteristic A magnetic recording medium having, polyamides, can be obtained at low cost than the substrate such as polyimide. FIG. 6 shows an outline of an apparatus used for carrying out the manufacturing method of the present invention. As shown in FIG. 6, a substrate 1 made of polyethylene terephthalate, which is longer than a feed shaft 4 in a vacuum, is mounted on a cylindrical can. The first magnetic layer 2 containing Co and Cr as main components and Co and O from the electron beam evaporation source 6 are deposited on the substrate 1 directly or through an underlayer by a vacuum evaporation method while running along the peripheral surface of 5. A second magnetic layer 3 containing as a main component is sequentially formed as shown in FIG.
Further, in the above-described manufacturing method, the angle between the initial incident vapor flow when forming the first magnetic layer 2 and the normal line of the substrate 1 is in the range of 90 to 70 degrees, and the peripheral surface of the cylindrical can 5 is formed. The substrate 1 made of polyethylene naphthalate, which is longer than the feed shaft 4 in a vacuum, is moved along the peripheral surface of the cylindrical can 5 by setting the temperature to 50 ° C. or lower, and the substrate 1 The first magnetic layer 2 containing Co and Cr as the main components and the second magnetic layer 3 containing Co and O as the main components are similarly shown in FIG. 1 from the electron beam evaporation source 6 directly or via the underlayer. As shown in the figure, the angle between the initial incident vapor flow and the normal line of the substrate 1 when forming the first magnetic layer 2 is in the range of 70 to 50 degrees, and the cylindrical can 5 is formed. The peripheral surface temperature of
By setting the temperature within the range of 0 ° C., a magnetic recording medium having excellent recording / reproducing characteristics can be manufactured.

In FIG. 6, 7 is a guide roll for the substrate 1, 8 is a take-up shaft, 9 is a mask for preventing the vapor flow from the electron beam evaporation source 6 from going to unnecessary parts, and 10 is a vacuum. The tank 11 is an exhaust system.

In the embodiment, the case where Co--Cr is used for the first magnetic layer 2 has been described.
When Ni—Cr is used, or when the second magnetic layer 3 is made of Co
Similar effects were obtained when Co-Ni-O was used instead of -O.

In the present invention, the second magnetic layer 3 may be formed of the same material in multiple layers. The first magnetic layer is made of polyethylene terephthalate.
Directly on a substrate made of polyethylene or polyethylene naphthalate
Instead, it may be formed via an underlayer. That is, the substrate
A non-magnetic oxide layer of Co or a non-magnetic layer of Co-Cr
The conductive layer is formed in advance by vacuum evaporation, etc.
A first magnetic layer may be formed on these nonmagnetic layers. This
These non-magnetic layers suppress the gas emitted from the substrate when forming the magnetic layer.
Control because of the variation of the moisture content of the substrate.
Product variation in recording and reproduction characteristics can be reduced.
There are advantages such as cutting. The thickness of the nonmagnetic underlayer is, for example, 3
３０30 nm.

In the present invention, the embodiment of the magnetic recording medium in the form of a magnetic tape has been described, but it goes without saying that the present invention can be applied to a magnetic recording medium in the form of a disk.

[0017]

As is apparent from the above embodiments, the magnetic recording medium and the method of manufacturing the same according to the present invention have Co and Cr or Co, Cr and Ni as main components on a substrate made of polyethylene terephthalate or polyethylene naphthalate. First magnetic layer, Co and O or Co, Ni and O
By forming the second magnetic layer whose main component is an incident angle within a certain range, a magnetic recording medium having excellent recording and reproducing characteristics can be manufactured at low material cost.

[Brief description of the drawings]

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

FIG. 2 is a view for explaining an angle of magnetic anisotropy of a first magnetic layer in the magnetic recording medium.

FIG. 3 is a characteristic diagram showing substrate temperature dependence of coercive force and direction of magnetic anisotropy at an initial incident angle when a substrate made of polyethylene terephthalate is used in the magnetic recording medium.

FIG. 4 is a characteristic diagram showing substrate temperature dependence of coercive force and direction of magnetic anisotropy at an initial incident angle when a substrate made of polyethylene naphthalate is used.

FIG. 5 shows the direction of the magnetic anisotropy of the first magnetic layer and the magnetic recording medium when a substrate made of polyethylene terephthalate or a substrate made of polyethylene naphthalate is used in one embodiment of the present invention. Diagram showing the relationship between electromagnetic conversion characteristics

FIG. 6 is a schematic diagram of an apparatus used to carry out a method for manufacturing a magnetic recording medium according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 1st magnetic layer 3 2nd magnetic layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-139920 (JP, A) JP-A-3-86913 (JP, A) JP-A-3-86914 (JP, A) JP-A-63-139 204513 (JP, A) JP-A-62-236136 (JP, A) JP-A-3-54719 (JP, A) JP-A-3-183014 (JP, A) JP-A-4-76813 (JP, A) JP-A-1-205716 (JP, A) JP-A-61-9821 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/66 G11B 5/85

Claims (4)

(57) [Claims] 1. A magnetic recording medium having a magnetic layer on a substrate made of polyethylene terephthalate directly or via an underlayer, wherein the magnetic layer mainly comprises Co and Cr or Co, Cr and Ni in order from the substrate side. A first magnetic layer containing Co and O or a second magnetic layer containing Co, Ni and O as main components, wherein the magnetic anisotropy of the first magnetic layer is from the in-plane direction of the film. A magnetic recording medium, wherein the angle is 15 degrees or less and 5 degrees or more. 2. A magnetic recording medium having a magnetic layer directly or via an underlayer on a substrate made of polyethylene naphthalate, wherein the magnetic layer comprises Co and C in order from the substrate side.
a first magnetic layer containing r or Co, Cr, and Ni as main components; and a second magnetic layer containing Co, O, or Co, Ni, and O as main components. A magnetic recording medium wherein the anisotropy is 30 degrees or less and 15 degrees or more from the in-plane direction of the film. 3. A method in which a substrate made of long polyethylene terephthalate is run in a vacuum along the peripheral surface of a cylindrical can by a vacuum deposition method on the substrate directly or via an underlayer. A first magnetic layer containing Cr and Ni as main components, Co and O or Co and Ni
And a second magnetic layer containing O as a main component in a method for manufacturing a magnetic recording medium, wherein an initial incident vapor flow at the time of forming the first magnetic layer and an incident angle formed by a normal to the substrate. Is within the range of 90 to 70 degrees, and the peripheral surface temperature of the cylindrical can is 50 ° C. or lower. 4. A method in which a substrate made of a long polyethylene naphthalate is run in a vacuum along the peripheral surface of a cylindrical can, and Co and Cr or Co or Co is deposited on the substrate directly or via an underlayer by a vacuum deposition method. And a first magnetic layer containing Cr and Ni as main components and a second magnetic layer containing Co and O or Co, Ni and O as main components in order. The angle of incidence between the initial incident vapor flow and the normal to the substrate when forming the magnetic layer is in the range of 70 to 50 degrees, and the peripheral surface temperature of the cylindrical can is 60 to 110 degrees Celsius. A method for manufacturing a magnetic recording medium, wherein