JPH10198945A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To offer a magnetic recording medium and its manufacturing method with suppressed oxidation of magnetic layer consisting of magnetic thin films. SOLUTION: This magnetic recording medium 10 provided with a magnetic layer 2 consisting of magnetic thin films on a non-magnetic supporting body 1 has a surface roughness Ra of 5.0nm or less on an opposite side face 5 of the magnetic layer side of the non-magnetic supporting body and has a surface roughness Ra of 5.0nm or less on a surface 6 on the magnetic layer side of the non-magnetic supporting body. For manufacturing it, it requires a process for manufacturing an raw roll of the non-magnetic supporting body, which has a surface roughness Ra of 5.0nm or less on the opposite side face of the magnetic layer side and on the opposite side face of the magnetic layer side on both end areas, a process of forming a magnetic layer by depositing magnetic particles on the area of the original cloth of the non-magnetic supporting body except both end area, and a process of winding in roll the raw roll of the non- magnetic supporting body, on which the magnetic layer has been formed.

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 (eg, a magnetic tape, a magnetic disk, etc.) having a magnetic layer made of a magnetic thin film provided on a non-magnetic support, and a method of manufacturing the same. is there.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a powder magnetic material such as an oxide magnetic powder or an alloy magnetic powder has been coated on a non-magnetic support by a vinyl chloride-vinyl acetate copolymer, a polyester resin, a urethane resin. A so-called coating type magnetic recording medium, which is formed by applying and drying a magnetic paint dispersed in an organic binder such as a polyurethane resin, is widely used.

On the other hand, magnetic recording media such as video tape recorders are required to have higher density recording in order to achieve higher image quality. For example, metals, Co-Ni alloys, Co-Ni alloys, Metal alloys such as Cr alloys, Co-O, etc., are plated (plated) or vacuum thin film forming technology (a so-called PVD technology such as a vacuum deposition method, a sputtering method, or an ion plating method) into polyester films, polyamides, polyimide films, etc. There has been proposed a so-called metal magnetic thin film type magnetic recording medium which is directly attached on a non-magnetic support.

The magnetic recording medium of the metal magnetic thin film type is excellent in coercive force and squareness ratio, and the thickness of the magnetic layer can be made extremely thin. Therefore, the thickness loss at the time of recording demagnetization and reproduction is extremely small. In addition to being excellent in electromagnetic conversion characteristics, there is no need to mix a binder, which is a non-magnetic material, into the magnetic layer, so that there are many advantages such as an increase in packing density of the magnetic material.

That is, a magnetic recording medium provided with a magnetic layer made of a metal magnetic thin film is considered to be the mainstream of high-density magnetic recording due to its superior magnetic properties.

Further, in order to improve the electromagnetic conversion characteristics of this type of magnetic recording medium and to obtain a larger output, when forming the magnetic layer of the magnetic recording medium, the magnetic layer is obliquely deposited. So-called oblique deposition is proposed,
Has been put to practical use.

[0007] Among such magnetic recording media, a vapor-deposited tape on which a magnetic layer is formed by a vacuum vapor-deposition method, particularly, has a high band-pass due to high production efficiency and stable characteristics (electromagnetic conversion characteristics and magnetic characteristics). Commercialization is progressing as an 8 mm tape, a digital micro tape (NT tape), a home digital video tape (DVC) and the like.

One of the problems in the production of these vapor-deposited tapes is an oxidation phenomenon of a magnetic layer (vapor-deposited layer) after a metal magnetic material is vapor-deposited.

[0009] This is because when a roll after vapor deposition (a roll-shaped non-magnetic support raw material on which a magnetic layer is formed: the same applies hereinafter) is stored in the air, the roll gradually becomes inward from the end face of the roll. Oxidation of the deposited layer proceeds.

FIG. 8 shows this state. FIG. 8 shows one surface of a raw material (roll) 50 in which a deposited layer (magnetic layer) 51 made of a metallic magnetic material is formed on a nonmagnetic support.

In the deposited layer 51, a region 53 where oxidation has occurred (oxidized region) 53 and a region where oxidation has not occurred (unoxidized region) 54 have different colors, and the boundary 55 thereof can be clearly observed with the naked eye. . Also, this boundary 55
The degree of oxidation of each of the regions 53 and 54 separated by is uniform. This boundary 55 is not observed immediately after the deposition of the metallic magnetic material, but proceeds from the end of the raw material (roll) 50 inward (in the direction of arrow A in the figure) with time,
Finally, both the left and right oxidation boundaries meet almost at the center of the web 50, and the boundary disappears and the entire surface is oxidized.

Thus, the oxidized area of the deposition layer is
In some cases, predetermined magnetic characteristics cannot be obtained, and normal recording and reproduction may be difficult. Therefore, the oxidation of the vapor deposition layer contributes to a decrease in the yield of the vapor deposition tape.

Here, the mechanism of the occurrence of oxidation in the deposited layer (magnetic layer) is not known in detail, but the following is known.

First, oxidation of the deposited layer does not occur when the roll is stored in an oxygen-free environment after the deposition of the magnetic material on the non-magnetic support substrate. Also, since the oxidation of the deposited layer proceeds from the end of the roll toward the inside,
It is considered that the oxidation of the deposited layer involves the invasion of oxygen from the end of the roll. Furthermore, the running surface side of the non-magnetic support (the side opposite to the side on which the deposited layer of the non-magnetic support is provided)
After the back coat layer is formed, the progress of oxidation is stopped even when the film is wound into a roll and stored.

Therefore, if the time from the deposition of the magnetic material to the formation of the back coat layer is shortened, the oxidation of the deposited layer can be minimized. However, aging (magnetic layer stabilization for the purpose of stabilizing the magnetic particles) can be achieved. The raw material after vapor deposition must be preserved over time), and there are manufacturing restrictions such as the formation of a back coat layer using a separate chamber and a different apparatus from the deposition of the magnetic material. At present, oxidation of the deposited layer to some extent is inevitable.

After forming the back coat layer,
Since oxidation does not proceed even when wound in a roll, it is considered that if the back coat layer is formed before depositing the magnetic material on the non-magnetic support, oxidation of the deposited layer can be avoided. In this case, the back coat layer may be peeled off or the non-magnetic support (base film) may be dissolved by heat generated during the deposition of the magnetic material, which is difficult to realize.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional situation, and its object is to provide:
An object of the present invention is to provide a magnetic recording medium in which oxidation of a magnetic layer made of a magnetic thin film is suppressed, and a method of manufacturing the same.

[0018]

As a result of intensive studies on the above-mentioned problems, the present inventor has found that a magnetic recording medium having a magnetic layer made of a magnetic thin film provided on a non-magnetic support has a non-magnetic recording medium. The surface roughness Ra of the upper and lower surfaces of the magnetic support is reduced, and the surface (particularly, the surface opposite to the side on which the magnetic layer is provided) is made extremely smooth, so that the oxidation of the magnetic layer composed of the magnetic thin film becomes possible. Can be suppressed.

That is, according to the present invention, in a magnetic recording medium having a magnetic layer made of a magnetic thin film provided on a nonmagnetic support, the surface of the nonmagnetic support opposite to the side on which the magnetic layer is provided is provided. Wherein the surface roughness Ra of the magnetic recording medium is 5.0 nm or less, and the surface roughness Ra of the surface of the non-magnetic support on which the magnetic layer is provided is 5.0 nm or less. , Referred to as the magnetic recording medium of the present invention.)
It is related to.

According to the magnetic recording medium of the present invention, there is provided a magnetic recording medium wherein a magnetic layer comprising a magnetic thin film (particularly a metal magnetic thin film) is provided on a non-magnetic support (base film). Has a surface roughness Ra of 5.0 nm or less (more preferably 2.0 nm or less) on the surface opposite to the surface on which the magnetic layer is provided, and the surface of the non-magnetic support on which the magnetic layer is provided. Has a surface roughness Ra of 5.0 nm or less (for example, 2.0 to 5.0 nm), so that it is possible to provide a magnetic recording medium (particularly a vapor-deposited tape) in which the oxidation of the magnetic layer composed of the magnetic thin film is suppressed. it can.

Here, the above-mentioned surface roughness Ra is determined by using an organic solvent containing an appropriate amount of fine particles in the upper surface (the surface on which the magnetic layer is provided) and / or the lower surface (the surface on which the magnetic layer is provided) of the nonmagnetic support. May be formed by coating and drying on the surface opposite to the side, or may be formed by previously containing fine particles in a non-magnetic support. Further, the surface roughness Ra of the upper and lower surfaces of the non-magnetic support may be zero, or may be a value close to zero as much as possible. If the fine particles are not contained in the non-magnetic support at all, such a value may be obtained. Become.

However, the value of the surface roughness Ra was measured using a surf coder ET-30HK manufactured by Kosaka Laboratories. The tip radius of the stylus was 2 μm, the weight was 10 mg, and the cut off period was 80 μm. The measurement was performed with a height magnification of 100,000 times and a measurement area of 250 μm × 25 μm. The surface roughness Ra indicates a center line average roughness, and is based on JIS surface roughness (B0601).

Next, an example of the magnetic recording medium of the present invention is shown in FIG.
This will be described with reference to FIG. FIG. 3 is a sectional view of a main part of the magnetic recording medium (evaporated tape) 10.

In FIG. 3, on a non-magnetic support (for example, polyethylene terephthalate: PET) 1, a magnetic layer 2 made of a metal magnetic thin film (for example, cobalt) is provided. A back coat layer 4 may be provided on the surface 5 of the non-magnetic support opposite to the surface 6 on which the magnetic layer 2 is provided.

Here, the surface roughness Ra on the surface 6 of the nonmagnetic support 1 is 5.0 nm or less (for example, 2.0 nm), and the surface roughness Ra on the surface 5 of the nonmagnetic support 1 is
Is 5.0 nm or less (especially 2.0 nm or less).

In a non-magnetic support (base film) used for a normal magnetic recording medium (particularly a magnetic recording medium of a metal magnetic thin film type, ie, a vapor-deposited tape), the surface on which the magnetic layer is provided (the surface in FIG. 3) 6) is designed to be significantly smoother than a coating type magnetic recording medium (for example, a magnetic tape) in consideration of the electromagnetic conversion characteristics and running durability, etc., but is opposite to the side on which the magnetic layer is provided. The surface on the side (surface 5 in FIG. 3: running surface) is much rougher than the surface on which the magnetic layer is provided (surface 6 in FIG. 3) within a range in which show-through to the magnetic layer and transfer of unevenness do not occur. Designed.

On the other hand, in the present invention, the surface roughness Ra of the surface of the non-magnetic support opposite to the surface on which the magnetic layer is provided (the surface 5 in FIG. 3: running surface) is defined as the non-magnetic support. By smoothing the surface of the support on which the magnetic layer is provided (surface 6 in FIG. 3) to a level equal to or less than the surface roughness Ra, an effect of preventing oxidation of the magnetic layer after the deposition of the magnetic material is exhibited. Is what you do.

In such a magnetic recording medium, in particular, the magnetic layer is not oxidized or hardly oxidized during the manufacturing process, so that deterioration of magnetic characteristics due to oxidation is suppressed, and the magnetic recording medium is excellent in magnetic characteristics and electromagnetic conversion characteristics. (Especially vapor deposition tapes).

Further, according to the present invention, when manufacturing a magnetic recording medium in which a magnetic layer composed of a magnetic thin film is provided on a non-magnetic support, the non-magnetic support is opposite to the side on which the magnetic layer is provided. The surface roughness Ra of the surface of the non-magnetic support and the surface of the non-magnetic support opposite to the surface on which the magnetic layer is provided are 5.0 nm or less in each of both end regions. Forming a magnetic layer, forming magnetic layers by depositing magnetic particles in regions other than the both end regions on the non-magnetic support raw material, and forming the magnetic layer on the non-magnetic support. A method of manufacturing a magnetic recording medium (hereinafter, referred to as a manufacturing method of the present invention), comprising a step of winding a raw material into a roll shape.

According to the production method of the present invention, a magnetic thin film (particularly a metal magnetic thin film) is formed on a non-magnetic support (base film).
When manufacturing a magnetic recording medium provided with a magnetic layer consisting of (particularly a vapor-deposited tape), a surface of the non-magnetic support opposite to the side on which the magnetic layer is provided, and a surface of the non-magnetic support A non-magnetic support raw material having a surface roughness Ra of 5.0 nm or less in each of both end regions (so-called “ears”) of the surface opposite to the surface on which the magnetic layer is provided is manufactured. Forming a magnetic layer by depositing magnetic particles (particularly metal magnetic particles) in a region other than the both end regions on the non-magnetic support raw material; and forming a non-magnetic support on which the magnetic layer is formed. And winding the non-magnetic support material into a roll, so that when the non-magnetic support material is wound into a roll, both end regions of the non-magnetic support material (where the magnetic layer is formed) Parts that are not covered, so-called "ears") Therefore, oxygen or an atmosphere containing oxygen (especially, air) does not enter the inside (that is, the magnetic layer side) from the above both end regions, and thus does not easily come into contact with the magnetic layer, thereby suppressing oxidation of the magnetic layer. be able to.

FIG. 2 shows this state. FIG. 2 is a schematic view of a main part of a part of both end regions of a non-magnetic support material provided with a magnetic layer composed of a magnetic thin film when the material is wound into a roll.

In the region 8 of FIG. 2, the non-magnetic support 1
a and the magnetic layer 2a form the medium 7a, and the non-magnetic support 1b and the magnetic layer 2b form the medium 7b, and the non-magnetic support 1c and the magnetic layer 2c form the medium 7c. The media formed by the body and the magnetic layer are stacked. This region 8 is a portion on which a back coat layer and the like are formed in the next manufacturing process and used as a magnetic recording medium.

The region 3 is both end regions. this is,
When depositing the magnetic material on the non-magnetic support, this is an area for preventing the magnetic material from scattering on portions other than the non-magnetic support (for example, the surface of the cooling can). As shown in FIG. 7, the non-magnetic support raw material after the formation of the magnetic layer is wound in a roll shape around a cylindrical core (cylinder).
In the both end regions (so-called ear portions) 3, the non-magnetic supports are non-magnetic supports 1a, non-magnetic supports 1b,.
Overlap like.

If the surface roughness Ra of the upper and lower surfaces of the non-magnetic support is within the above range, both surfaces (particularly, the side opposite to the side door on which the magnetic layer is provided) are extremely smooth. .. In the end regions 3, the non-magnetic supports 1 a, the non-magnetic supports 1 b,... Layer and the outside air can be shut off), so that oxidation of the magnetic layer can be suppressed and
Deterioration of magnetic properties due to oxidation is suppressed, and it is possible to manufacture a magnetic recording medium having excellent magnetic properties.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION In the magnetic recording medium (especially a magnetic tape) of the present invention and the manufacturing method of the present invention, the surface roughness of the surface of the non-magnetic support opposite to the side on which the magnetic layer is provided It is more desirable that Ra be 2.0 nm or less.

As will be described later in detail, for example, the surface roughness Ra of the surface (surface 6 in FIG. 3) of the nonmagnetic support on which the magnetic layer is provided is about 2.0 nm, When the surface roughness Ra of the surface (surface 5 in FIG. 3) opposite to the surface on which the layer is provided is about 5.0 nm, the non-magnetic support raw material provided with the magnetic layer is stored for a long time. Otherwise, the magnetic layer may be slightly oxidized. However, this oxidized area (for example, an area about 1 cm inside from the end) is small, and when the raw material is slit (cut) into a predetermined tape width (for example, 8 mm) to be taped, it is usually discarded. There is no problem because it is the part that is done.

Further, in the conventional manufacturing method, as shown in FIG. 2, even if the non-magnetic supports overlap each other at the end regions 3, the surface roughness Ra (particularly opposite to the side on which the magnetic layer is provided). It is probable that the non-magnetic supports did not adhere to each other in the both end regions 3 because the surface roughness Ra) of the side surface was relatively large, and a large amount of oxygen-containing atmosphere penetrated.

Of course, it depends on various factors such as the thickness of the non-magnetic support, the length of both end regions, the thickness of the magnetic layer, etc., but generally the opposite side of the non-magnetic support from the side on which the magnetic layer is provided. If the surface roughness Ra of the surface (surface 5 in FIG. 3) is 2.0 nm or less, the magnetic layer is hardly oxidized, so that a magnetic recording medium having extremely high magnetic properties can be obtained.

Further, in the magnetic recording medium of the present invention, it is preferable that the magnetic layer comprises a metal magnetic thin film formed by vapor deposition.

As described above, a magnetic recording medium (especially an evaporation tape) in which the magnetic layer composed of a metal magnetic thin film formed by evaporation (especially oblique evaporation) is provided on a nonmagnetic support,
It has excellent coercive force and squareness ratio, and the thickness of the magnetic layer can be made extremely thin.
Not only is it excellent in electromagnetic conversion characteristics at short wavelengths, but it also has many advantages, such as the ability to increase the packing density of magnetic materials because it is not necessary to mix a binder that is a nonmagnetic material in the magnetic layer. I have.

In such a magnetic recording medium of the metal magnetic thin film type, the metal magnetic thin film forming the magnetic layer is formed, for example, by oblique evaporation or vertical evaporation.
A metal thin film mainly composed of o, Ni, Fe or the like, or a metal thin film mainly composed of an alloy thereof can be used.

For example, ferromagnetic metals such as Fe, Co and Ni, Fe-Co, Co-Ni, Fe-Co-Ni, F
e-Cu, Co-Cu, Co-Au, Co-Pt, Mn
-Bi, Mn-Al, Fe-Cr, Co-Cr, Ni-
Cr, Fe-Co-Cr, Co-Ni-Cr, Fe-C
A ferromagnetic alloy such as o-Ni-Cr is exemplified. These may be a single layer film or a multilayer film.

Further, in addition to the in-plane magnetic recording metal magnetic film on which the above-mentioned material is deposited, a perpendicular magnetic recording magnetic thin film (Co-
Of course, a Cr alloy thin film, a Co—O-based thin film, etc.) can also be applied.

In this metal magnetic thin film, oxygen is used as an atmosphere at the time of vapor deposition for the purpose of improving the adhesion strength to the non-magnetic support (film) or improving the corrosion resistance and abrasion resistance of the ferromagnetic metal thin film itself. It is desirable to use a ferromagnetic thin film (ferromagnetic thin film containing oxygen) obtained in an atmosphere in which gas is dominant.

Further, in the manufacturing method of the present invention, it is sufficiently possible to form the magnetic layer composed of a metal magnetic thin film using a vacuum evaporation method.

As a means for forming the metal magnetic thin film, a vacuum evaporation method of heating and evaporating a ferromagnetic material under vacuum and depositing it on a nonmagnetic support is preferable. For example, a so-called PVD technique such as a sputtering method in which glow discharge is caused in an atmosphere containing argon as a main component and atoms on a target surface are struck by generated argon ions.

Here, an apparatus for manufacturing a magnetic recording medium that can be used in the manufacturing method of the present invention will be described with reference to FIG.

FIG. 4 schematically shows the configuration of a continuous winding type vapor deposition apparatus for forming a metal magnetic thin film applicable to the production method of the present invention.

This continuous winding type vapor deposition apparatus is configured for so-called oblique vapor deposition, and is placed in a vacuum chamber 26 in which the inside is in a vacuum state (for example, about 10 ⁻² Pa) in a counterclockwise direction (in the figure). Rotating in the direction of arrow Z), an evaporation source 17 for a metal magnetic thin film is arranged to face a cooling can 25 cooled to, for example, −20 ° C.

Then, the nonmagnetic support (raw material) 1 is moved from the supply roll 23 rotating counterclockwise in FIG.
In the direction, and while being moved along the peripheral surface of the cooling can 25, the evaporation material 20 heated and evaporated by the electron beam 19 from the evaporation source 17 is adhered to form a metal magnetic thin film,
Thereafter, it is wound on a winding roll 24. Guide rollers 21 and 22 are provided between the supply roll 23 and the cooling can 25 and between the cooling can 25 and the take-up roll 24, respectively. Can 2
A predetermined tension is applied to the non-magnetic support 1 running from 5 to the winding roll 24 so that the non-magnetic support 1 runs smoothly. A cooling device (not shown) is provided in the cooling can 25 so that deformation and breakage of the non-magnetic support due to heat during vapor deposition can be suppressed.

The evaporation source 17 is a container (for example, a crucible) 16
The above-mentioned metal magnetic material (for example, Co) is accommodated in the metal magnetic material 20. The metal magnetic material 20 is heated by irradiating the deposition source (metal magnetic material) with an electron beam 19 from the electron beam source 15 at an accelerated rate. Evaporate and adhere to the non-magnetic support 1 running along the peripheral surface of the cooling can 25 (evaporation)
Thus, a metal magnetic thin film is formed, and a magnetic recording medium (a raw material for a magnetic recording medium) is manufactured. At this time, a deposition-preventing plate 27 is provided between the vapor deposition source 17 and the cooling can 25, and a shutter 18 is provided so as to be adjustable in position, so that only vapor-deposited particles incident on the nonmagnetic support 1 at a predetermined angle are provided. Let it pass. Thus, the metal magnetic thin film is formed by the oblique deposition method.

Further, at the time of depositing such a metal magnetic thin film, oxygen gas is supplied to the surface of the non-magnetic support 1 through the oxygen gas inlet 28, whereby the magnetic properties, durability and weather resistance of the metal magnetic thin film are obtained. The performance is improved. In addition, in order to heat the evaporation source, in addition to the above-described heating means using an electron beam, for example, known means such as a resistance heating means, a high-frequency heating means, and a laser heating means can be used.

In the magnetic recording medium of the present invention and the manufacturing method of the present invention, a back coat layer is provided on the surface of the non-magnetic support opposite to the side on which the magnetic layer is provided. Is desirable.

In the non-magnetic support according to the present invention, particularly, the surface of the non-magnetic support opposite to the side on which the magnetic layer is provided (surface 5 in FIG. 3: running surface) has a surface roughness Ra = 5.
Since it is extremely smooth, that is, 0 nm or less, and further 2.0 nm or less, when it is taped in this state, for example, a large frictional force acts to deteriorate running properties in some cases. Therefore, by providing a back coat layer on this surface and providing the back coat layer with an appropriate surface roughness, it is possible to obtain a magnetic recording medium having excellent running properties.

As the back coat layer, as is well known, a non-magnetic pigment such as carbon or calcium carbonate may be dispersed in a binder such as polyurethane or a vinyl chloride-vinyl acetate copolymer. As is well known, an extrusion die coating method, a gravure method such as direct gravure, reverse gravure, and offset gravure, and other roll coating methods can be used.

In the manufacturing method of the present invention, it is preferable that the both end regions are regions between both ends of the non-magnetic support raw material and an inner position separated by several cm from the both ends.

Of course, it varies depending on the thickness of the non-magnetic support, the surface roughness of the non-magnetic support, the thickness of the magnetic layer, and the like. It is sufficient to set the area between both ends of the magnetic support raw material and an inner position several cm, especially about 2 cm away from the raw material.

Further, in the manufacturing method of the present invention, while transporting the non-magnetic support raw material, the magnetic particles are deposited in a region other than the both end regions by using a mask disposed close to the non-magnetic support raw material. It is desirable to form a magnetic layer.
Further, it is preferable that after depositing the magnetic particles, the non-magnetic support raw material on which the magnetic layer is formed is wound into a roll, and further, the non-magnetic support raw material on which the magnetic layer is formed is removed. It is sufficiently possible to store it in the rolled state until the next step.

Next, the above-described manufacturing method will be described with reference to FIGS. 5 to 7 show a flow of depositing metal magnetic particles on a non-magnetic support raw material to produce a non-magnetic support raw material provided with a magnetic layer composed of a metal magnetic thin film. .

FIG. 5 is a front view of the cooling can 25 in the continuous winding type vapor deposition apparatus shown in FIG. 4 when viewed from the front.

In FIG. 5, a non-magnetic support 1 (indicated by a dashed line) is conveyed by a cooling can 25 which rotates at a predetermined speed in the direction of arrow Z in FIG. . Then, the metal magnetic material is evaporated from the evaporation source by a heating means such as an electron beam,
The vaporized metal magnetic material enters through an opening 32 formed by a mask disposed in the vicinity of the cooling can 25 and is vapor-deposited on the non-magnetic support 1 to form a magnetic layer composed of a metal magnetic thin film. Here, the width of the opening 32 is designed to be slightly smaller (about several cm) than the width of the non-magnetic support 1, and when the metal magnetic material is deposited, the metal magnetic material is coated on the surface of a cooling can or the like. It is made to prevent vapor deposition on the substrate. Accordingly, on the non-magnetic support 1, there are formed a region 33 on which a magnetic layer is deposited and a region 34 (both end regions) where so-called ear magnetic metal material is not or hardly deposited.

The non-magnetic support 1 on which the vapor deposition region 33 and the both ends 34 called so-called ears are formed on the cooling can 25 is conveyed while vapor deposition is sequentially performed, and the metal cylinder 38 is wound on the take-up roll 24. Then, a non-magnetic support raw material 24a provided with a magnetic layer is formed in the form shown in FIG.

The raw material 24a thus produced is
As shown in FIG. 7, a rod 37 longer than the raw material 24a is inserted into a metal tube 38 of the raw material 24a, and is fixed on a base 36, so that external stress is not applied to the raw material 24a. Is stored until.

However, the next step may be a step of forming a back coat layer on the surface of the raw material 24a on the side opposite to the side on which the magnetic layer of the nonmagnetic support is provided. And
Although a step of forming a hard carbon film, a lubricant, or the like on the magnetic layer may be performed, a back coat layer is preferably formed in the next step from the viewpoint of suppressing oxidation of the magnetic layer.

Usually, there are manufacturing restrictions such as the formation of a back coat layer using a chamber and a separate apparatus different from the deposition of the magnetic material, and for the purpose of stabilizing (aging) the magnetic particles. Since it is desirable to leave the raw material after the magnetic layer deposition over time, it is possible to wind the non-magnetic support raw material provided with the magnetic layer in a roll shape and store it for a certain period of time. General.

In FIGS. 6 and 7, the material 24a
Although the magnetic layer is present on the outer surface of the raw material, the magnetic layer may be wound so that the magnetic layer is present on the outer surface of the raw material. Also,
At the time of forming the magnetic layer, a portion where the magnetic layer is not formed may be provided at the end of the non-magnetic support, and the outermost layer (outermost surface) may be made only of the non-magnetic support. It can also be prevented on the outermost surface side of the roll (raw material).

In the present invention, a conventionally known material can be used for the nonmagnetic support. For example, polymer materials such as polyesters, polyolefins, cellulose derivatives, vinyl resins, polycarbonates, polyamides, and polyimides are exemplified. Needless to say, a dispersant may be used in the non-magnetic support for the purpose of dispersing the fine particles.

In particular, polyesters are preferable. For example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytetramethylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalene diester Carboxylates and the like are typical examples. The form is not limited at all, and may be any form such as a tape form, a sheet form, and a drum form.

The non-magnetic support (especially a polyester film) which can be used in the present invention is a film obtained by forming the above-mentioned polymer compound by a known method (that is, a sheet or a cylinder obtained by melting the polymer compound). Extruded in a shape and stretched in at least one direction), a normal balance type, a uniaxially reinforced type in a machine axis direction or a direction perpendicular thereto, or a biaxially reinforced type. It is desirable that

Further, based on the magnetic recording medium of the present invention and the manufacturing method of the present invention, the upper and lower surfaces of the nonmagnetic support can be provided with different or identical surface roughnesses Ra, respectively. Ra is an organic solvent containing an appropriate amount of fine particles (eg, a resin coating solution of an emulsion, an aqueous coating solution, etc.) is applied to the upper and / or lower surface of the nonmagnetic support during or after the preparation of the nonmagnetic support. It may be formed by coating and drying and solidifying, or may be formed by previously containing fine particles in a non-magnetic support.
Further, the surface roughness Ra of the upper and lower surfaces of the non-magnetic support may be zero, or may be a value close to zero as much as possible,
Such a value is obtained when no fine particles are contained in the nonmagnetic support.

The fine particles include organic fine particles such as polystyrene, polymethyl methacrylate, methyl methacrylate copolymer, crosslinked product of methyl methacrylate copolymer, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, and benzoguanamine resin. Inorganic fine particles such as calcium carbonate (CaCO ₃ ), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), titanium dioxide, kaolin, talc, graphite, feldspar, molybdenum disulfide, carbon black, barium sulfate, etc. However, the present invention is not limited to these.

Examples of the solvent containing the fine particles include methyl cellulose, methyl methacrylate, methyl acrylate, acrylic polyester resin, polyvinyl alcohol and polyvinyl butyral.

For example, the fine particles have a particle size of about 20 nm.
When silica (SiO ₂ ) is contained in the solvent and applied to the non-magnetic support, projections having the fine particles as nuclei are 800
If it is about 10,000 / mm ² , the surface roughness Ra of this part will be about 2.0 to 3.0 nm. Further, it does not contain any projections having the fine particles as nuclei, or 1 to 4,000,000 particles /
When the thickness is about ² mm, the surface roughness Ra can be set to 2.0 nm or less. Furthermore, the surface roughness Ra is zero or as close to zero as possible when no fine particles are contained and only the nonmagnetic support is used.

In addition to such a method, the surface roughness Ra of the nonmagnetic support can be adjusted by various known methods. As described above, the surface roughness Ra of the nonmagnetic support is adjusted based on the present invention.
The surface roughness Ra of the surface (surface 5 in FIG. 3) of the nonmagnetic support opposite to the surface on which the magnetic layer is provided is 5.0 nm or less, and the magnetic layer of the nonmagnetic support is provided. The surface roughness Ra of the surface (surface 6 in FIG. 3) can be 5.0 nm or less, and the surface of the non-magnetic support opposite to the side on which the magnetic layer is provided (surface 5 in FIG. 3). Is preferably 2.0 nm or less, and the surface roughness Ra of the surface of the nonmagnetic support on which the magnetic layer is provided (surface 6 in FIG. 3) is preferably 2.0 to 5.0 nm.

In general, as a method for producing a non-magnetic support raw material, for example, a slit-shaped nozzle of a raw material tank containing a non-magnetic support material mainly containing polyethylene terephthalate in a molten state is used. There is a method in which a material is continuously discharged onto a cooling roll, and a film-shaped raw material of a non-magnetic support is sequentially formed while being stretched.

In the production method of the present invention, it is particularly desirable that the surfaces of both end regions (so-called ear portions) of the raw material of the non-magnetic support be smooth. When adjusting the surface roughness Ra of the upper and lower surfaces of the non-magnetic support, the raw material tank is partitioned by a partition plate or the like when manufacturing the above-mentioned non-magnetic support raw material, and the non-magnetic support for both end regions is formed. The magnetic support raw material and the non-magnetic support raw material for the region where the magnetic layer is provided are separately accommodated and discharged simultaneously from the slit, and the difference in surface roughness Ra between the both end regions and the region where the magnetic layer is provided is provided. May be provided as appropriate.

An appropriate amount of the nonmagnetic support is provided on the surface on which the magnetic layer is provided (surface 6 in FIG. 3) and / or on the surface opposite to the surface on which the magnetic layer is provided (surface 5 in FIG. 3). When adjusting the surface roughness Ra of the non-magnetic support by coating and drying a solvent containing fine particles, by applying the solvent only to the region where the magnetic layer of the non-magnetic support is provided,
Alternatively, by applying different solvents to the both end regions and the region where the magnetic layer is provided, the surface roughness Ra is applied to the both end regions and the region where the magnetic layer is provided.
It is also conceivable to provide a difference between them as appropriate.

The configuration of the magnetic recording medium of the present invention is not limited to this, but may be modified without departing from the scope of the present invention. For example, a protective film made of a hard carbon film or the like may be used if necessary. The formation of an undercoat layer, an adhesive layer, and the like, as well as a lubricant and a rust inhibitor made of perfluoropolyether or the like can be performed without any problem.

[0079]

EXAMPLES The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples.

Examples 1 to 6 and Comparative Examples 1 to 5 The surface roughness of the surface of the non-magnetic support opposite to the side on which the magnetic layer is provided (surface 5 in FIG. 3; hereinafter referred to as the running surface). R
a, and a plurality of nonmagnetic support raw materials (base film: the same applies hereinafter) having different surfaces on which the magnetic layer of the nonmagnetic support is provided (surface 6 in FIG. 3: hereinafter referred to as a magnetic surface). . However, the surface roughness Ra of the running surface and the magnetic surface is determined by coating a non-magnetic support with silica (SiO ₂ ) having a particle size of about 20 nm in various concentrations in a solvent (isopropyl alcohol). Adjusted. Here, the base film is a polyethylene terephthalate having a width of 600 mm, a length of 5000 m, and a thickness of 10 μm.

Table 1 below shows the surface roughness Ra of the running surface and the surface roughness Ra of the magnetic surface of the prepared base film.
However, the magnetic surface having a surface roughness Ra of 2.0 nm is similar to the surface roughness Ra of the non-magnetic support used in the Hi8 vapor deposition tape manufactured by Sony Corporation. The surface roughness Ra of the magnetic surface of the base film greatly affects the electromagnetic conversion characteristics and running durability of the magnetic recording medium (evaporated tape). If the value is too large, the electromagnetic conversion characteristics deteriorate. If too small, the running durability may be degraded.

The value of the surface roughness Ra was measured using a surf coder ET-30HK manufactured by Kosaka Laboratories. The tip radius of the stylus was 2 μm, the weight was 10 mg, and the cut off period was 80 μm. The measurement was performed with a height magnification of 100,000 times and a measurement area of 250 μm × 25 μm.

A magnetic layer was formed on each of the base films of Examples 1 to 6 and Comparative Examples 1 to 5 by depositing a metal magnetic material under the same conditions.

For this deposition, a deposition source (cobalt lump) 17 disposed in a crucible 16 was placed in a vacuum apparatus of 10 ⁻² Pa using the continuous winding type deposition apparatus shown in FIG. Was heated and dissolved by an electron beam 19 to evaporate and vaporize a vapor-deposited substance (cobalt) 20, which was vapor-deposited on a base film (polyethylene terephthalate). Further, at this time, both end regions (so-called ears) where direct vapor deposition was not performed were produced in a region 2 cm inside from the end of the base film.

The incident angle of the vapor deposition material at the time of vapor deposition is 90 to 45 degrees from the normal direction of the non-magnetic support raw material, the transport speed of the base film is 25 m / min, and the vapor deposition layer (magnetic layer)
Was 200 nm in thickness. During the vapor deposition, vapor deposition was performed while introducing oxygen gas from the gas inlet 28 at a rate of 800 cc / min.

[0086] The base film after the evaporation was wound in a vacuum into a metal cylinder having a diameter of 20 mm at a tension of 10 kg / 600 mm.

After the magnetic layer made of cobalt is provided on the base film made of polyethylene terephthalate in this way, as shown in FIG. 7, a rod 37 is inserted into a metal tube 38, and the base film provided with the magnetic layer is formed. (Raw cloth: the same applies hereinafter) and stored for 1 week in an atmosphere at a temperature of 25 ° C. and a humidity of 30% without applying external stress. One week later, how far the oxidation boundary position of the vapor deposition layer (magnetic layer) has progressed from the end of the vapor deposition region was measured for the left and right oxidation regions, and the average value is shown in Table 1 below in cm units.

Table 1 ────────────────────────────────── Deposition layer of base film (magnetic layer) ) Surface roughness of running surface Oxidation progress distance of surface roughness of magnetic surface Ra (nm) Ra (nm) (cm) ────────────────────── ──────────── Example 1 2.0 2.00 Example 2 1.1 2.00 Example 3 5.0 2.0 0.5 Example 4 2.0 3.5 0.3 Example 5 2.0 5.0 0.7 Example 6 0.5 2.00 Comparative Example 1 36.7 2.0 28.6 Comparative Example 2 24.6 2.0 19 .8 Comparative Example 3 11.3 2.0 5.2 Comparative Example 4 6.4 2.0 1.3 Comparative Example 5 2.0 6.0 1.1 ───────────────────── ─

Further, with respect to the raw materials of Examples 1 to 3, Example 6 and Comparative Examples 1 to 4 in which the surface roughness Ra of the magnetic surface of the base film was 2.0 nm, the back coat of the non-magnetic support was used.
Surface roughness Ra (the surface roughness R of the running surface)
FIG. 1 is a graph showing the change in the amount of oxidation of the magnetic layer (the oxidation progress distance of the deposited layer) according to a).

From Table 1 and FIG. 1, the smaller the surface roughness Ra of the running surface of the base film and the surface roughness Ra of the magnetic surface of the base film, the more the progress of oxidation can be suppressed.
That is, the surface roughness Ra of the running surface of the base film is 5.0.
When the surface roughness Ra of the magnetic surface of the base film is 5.0 nm or less (especially about 2.0 nm), oxidation of the magnetic layer (evaporation layer) hardly progresses.
Even when oxidation is slightly progressing (Example 3), if it is at this level, it is a portion that is usually discarded when slitting (cutting) to a predetermined tape width (for example, 8 mm) to form a tape. So there is no problem. In this case, after storing in the rolled state, measuring the boundary position of the magnetic layer oxidation at both ends, applying a back coat layer, further applying a lubricant on the magnetic layer, and slitting. May do it.

From the above results, it can be seen that particularly when the surface roughness Ra of the running surface of the base film is 2.0 nm or less, the oxidation of the deposited layer (magnetic layer) has not progressed at all.

This is because the running surface of the base film and the magnetic surface of the base film are smooth, so that the ears of the raw material are closely overlapped with each other, so that there is an effect of blocking oxygen from entering the vapor deposition layer (magnetic layer). It is thought to be. Therefore, it is appropriate to consider that the oxidation of the vapor deposition layer is caused by the invasion of oxygen in the cross-sectional direction from the end of the raw material.

That is, when producing a vapor-deposited tape on which a metallic magnetic material is vapor-deposited on a base film, a base film whose running surface is extremely smooth (surface roughness Ra = 5.0 nm or less, further 2.0 nm or less) is used. By doing so, when the base film (raw material) provided with the vapor-deposited layer is wound into a roll, the intrusion of an atmosphere containing oxygen (particularly air) from the cross section (end) of the raw material is prevented. Oxidation of the vapor deposition layer of the raw material can be suppressed. Surface roughness Ra of this running surface
Is preferably as close to zero as possible. In addition, if the oxidation of the deposited layer is suppressed in this manner, a magnetic recording medium (particularly a magnetic tape) having excellent magnetic characteristics, electromagnetic conversion characteristics, and the like does not occur due to deterioration of magnetic characteristics due to oxidation.

In this embodiment, since the base film (particularly, the running surface of the base film) is extremely smooth, even when the base film (raw material) provided with the vapor deposition layer is wound into a roll, In addition, the roughness of the running surface of the base film hardly affects the magnetic layer surface due to show-through, transfer, or the like, and it is considered that a magnetic recording medium having excellent electromagnetic conversion characteristics and running durability is obtained.

Although the present invention has been described with reference to the embodiment, the present embodiment can be further modified based on the technical idea of the present invention.

For example, in this embodiment, the surface roughness Ra of the magnetic layer is set to 5.
Although the thickness is set to 0 nm or less (especially 2.0 nm), the magnetic recording medium of the present invention and the present invention are also applicable to a digital video tape for home use (DVC) which requires a smoother surface roughness Ra of the magnetic surface than the vapor-deposited tape. Needless to say, it can be manufactured based on the manufacturing method described above.

Further, it is sufficiently possible to form the magnetic layer with a magnetic material made of an alloy or a magnetic material made of a metal oxide, instead of a metal magnetic material such as cobalt.

Further, the material, thickness and the like of the nonmagnetic support can be variously changed, and a back coat layer, a protective film, a lubricant and the like can be formed as required.

[0099]

According to the magnetic recording medium of the present invention, there is provided a magnetic recording medium in which a magnetic layer comprising a magnetic thin film (particularly a metal magnetic thin film) is provided on a non-magnetic support (base film). The surface roughness Ra of the surface of the magnetic support opposite to the side on which the magnetic layer is provided is 5.0 nm or less (further 2.0 nm or less), and the magnetic layer of the non-magnetic support is The surface roughness Ra of the surface to be provided is 5.
0 nm or less (for example, 2.0 to 5.0 nm),
It is possible to provide a magnetic recording medium (particularly a vapor-deposited tape) in which oxidation of the magnetic layer made of the magnetic thin film is suppressed.

According to the production method of the present invention, a magnetic thin film (particularly a metal magnetic thin film) is formed on a non-magnetic support (base film).
When manufacturing a magnetic recording medium provided with a magnetic layer consisting of (particularly a vapor-deposited tape), a surface of the non-magnetic support opposite to the side on which the magnetic layer is provided, and a surface of the non-magnetic support A non-magnetic support raw material having a surface roughness Ra of 5.0 nm or less in each of both end regions (so-called “ears”) of the surface opposite to the surface on which the magnetic layer is provided is manufactured. Forming a magnetic layer by depositing magnetic particles (particularly metal magnetic particles) in a region other than the both end regions on the non-magnetic support raw material; and forming a non-magnetic support on which the magnetic layer is formed. And winding the non-magnetic support material into a roll, so that when the non-magnetic support material is wound into a roll, both end regions of the non-magnetic support material (where the magnetic layer is formed) Parts that are not covered, so-called "ears") Because of the fit, oxygen or an atmosphere containing oxygen (especially air) penetrates into the inside (that is, the magnetic layer) from the above-mentioned both end regions and is less likely to come into contact with the magnetic layer, thereby suppressing oxidation of the magnetic layer. .

[Brief description of the drawings]

FIG. 1 is a graph showing the change in the amount of oxidation of a magnetic layer depending on the surface roughness Ra of the non-magnetic support on the side where a back coat layer is provided.

FIG. 2 is a schematic diagram of a main part of a part of both end regions of a non-magnetic support raw material provided with a magnetic layer formed of a magnetic thin film according to the manufacturing method of the present invention when the raw material is wound into a roll shape. .

FIG. 3 is a sectional view of a main part of the magnetic recording medium.

FIG. 4 is a schematic configuration diagram of a continuous winding type vapor deposition apparatus that can be used in the manufacturing method.

FIG. 5 is a front view of a cooling can in the continuous winding type vapor deposition apparatus based on the manufacturing method.

FIG. 6 is a schematic perspective view of a raw material wound into a roll based on the manufacturing method.

FIG. 7 is a schematic perspective view showing a storage state of a raw material wound in a roll shape based on the manufacturing method.

FIG. 8 is a schematic perspective view showing a state where a raw magnetic layer wound in a roll shape is oxidized based on a conventional manufacturing method.

[Explanation of symbols]

1, 1a, 1b, 1c, 1d: Non-magnetic support, 2, 2
a, 2b, 2c, 35, 51 ... magnetic layer, 3, 34, 52
... Both end regions (ears), 4) Back coat layer, 5, 6
... surface, 7a, 7b, 7c ... medium, 8, 33 ... area, 10
... magnetic recording medium, 15 ... electron beam generation source, 16 ... container (crucible), 17 ... evaporation source, 18 ... shutter, 19 ... electron beam, 20 ... evaporation material, 21, 22 ... guide roller, 23 ... supply roll, 24 ... take-up roll, 24a,
50: raw fabric, 25: cooling can, 26: vacuum chamber, 27 ...
Deposition plate, 28 ... gas inlet, 31 ... shaft, 32 ... opening,
36 ... table, 37 ... rod, 38 ... metal cylinder, 53 ... oxidized area,
54: unoxidized area, 55: boundary

Claims (12)

[Claims] 1. A magnetic recording medium in which a magnetic layer made of a magnetic thin film is provided on a non-magnetic support, the surface roughness of the surface of the non-magnetic support opposite to the side on which the magnetic layer is provided. A magnetic recording medium, wherein Ra is 5.0 nm or less, and surface roughness Ra of the surface of the nonmagnetic support on which the magnetic layer is provided is 5.0 nm or less. 2. The magnetic recording medium according to claim 1, wherein the surface of the non-magnetic support opposite to the side on which the magnetic layer is provided has a surface roughness Ra of 2.0 nm or less. 3. The magnetic recording medium according to claim 1, wherein said magnetic layer comprises a metal magnetic thin film formed by vapor deposition. 4. The magnetic recording medium according to claim 1, wherein a back coat layer is provided on a surface of the non-magnetic support opposite to a surface on which the magnetic layer is provided. 5. When manufacturing a magnetic recording medium in which a magnetic layer made of a magnetic thin film is provided on a non-magnetic support, a surface of the non-magnetic support opposite to a side on which the magnetic layer is provided is provided. And fabricating a nonmagnetic support raw material having a surface roughness Ra of 5.0 nm or less in each of both end regions thereof with respect to a surface of the nonmagnetic support opposite to the surface on which the magnetic layer is provided. Forming a magnetic layer by depositing magnetic particles in regions other than the both end regions on the non-magnetic support raw material; and rolling the non-magnetic support raw material on which the magnetic layer is formed. And a step of winding the magnetic recording medium into a magnetic recording medium. 6. The method according to claim 5, wherein the surface of the non-magnetic support opposite to the side on which the magnetic layer is provided has a surface roughness Ra of 2.0 nm or less. 7. The manufacturing method according to claim 5, wherein the both end regions are regions between both ends of the non-magnetic support raw material and an inner position separated by several cm from the both ends. 8. While transporting the non-magnetic support raw material,
The manufacturing method according to claim 5, wherein the magnetic layer is formed by depositing the magnetic particles in a region other than the both end regions by using a mask disposed in close proximity to the magnetic layer. 9. The method according to claim 8, wherein the non-magnetic support material on which the magnetic layer is formed is wound into a roll after the deposition of the magnetic particles. 10. The method according to claim 9, wherein the non-magnetic support substrate on which the magnetic layer is formed is stored in a rolled state until the next step. 11. The method according to claim 5, wherein the magnetic layer made of a metal magnetic thin film is formed by using a vacuum evaporation method. 12. The method according to claim 5, wherein a back coat layer is formed on a surface of the non-magnetic support opposite to a surface on which the magnetic layer is provided.