JP2006134370A - Metallic thin film type magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic thin film type magnetic recording medium wherein high recording density and thinness are attained, satisfactory rigidity is secured and stable recording and reproduction characteristics can be obtained. <P>SOLUTION: In the metallic thin film type magnetic recording medium 100 having reinforcing layers 2a and 2b constituted of a material selected from a metal, a semimetal, an alloy, their oxides and composites on both surfaces of a long non-magnetic supporting body 1 and provided with a magnetic layer 3 constituted of a ferromagnetic metallic thin film on the reinforcing layer 2a of one surface and a back coat layer 5 on the reinforcing layer 2b of the other surface, a reinforcement coefficient obtained by multiplying total film thickness of the reinforcing layers 2a and 2b by a Young's modulus of the material which constitutes the reinforcing layers 2a and 2b is ≥22,700 Pa m and a B/M ratio obtained by dividing the film thickness of the reinforcing layer 2b on the back coat layer 5 side by the total film thickness of the magnetic layer 3 and the reinforcing layer 2a on the magnetic layer 3 side is 0.25 to 2.22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a metal thin film type magnetic recording medium, and in particular, a video tape for long-time recording, in which a reinforcing layer is provided on a long nonmagnetic support for the purpose of improving the mechanical strength of the magnetic recording medium. The present invention also relates to a thin metal thin film magnetic recording medium for high-density magnetic recording suitable for a large-capacity tape streamer.

  Conventionally, as magnetic recording tapes such as audio tapes and video tapes, magnetic powder such as oxide magnetic powder or alloy magnetic powder is coated on a non-magnetic support with a vinyl chloride-vinyl acetate copolymer, polyester resin, urethane. 2. Description of the Related Art A so-called coating type magnetic recording medium is widely known which is obtained by applying and drying a magnetic paint prepared by dispersing in various binders such as resins and polyurethane resins.

  On the other hand, along with the recent increase in demand for high-density recording, metal magnetic materials such as Co—Ni alloys, Co—Cr alloys, and Co—O are plated, vacuum deposited, sputtering, ion-plated. A so-called metal thin film type magnetic recording medium has been proposed in which a magnetic layer is formed directly on a nonmagnetic support or via an extremely thin adhesive layer by a vacuum thin film forming technique such as a ting method.

  Further, in order to improve electromagnetic conversion characteristics and obtain a larger output, a method of forming a magnetic layer by oblique deposition in which the magnetic layer is obliquely deposited is proposed, and the magnetic layer is formed by this method. The magnetic recording medium has been put to practical use as a vapor deposition tape for a high-band 8 mm video tape recorder and a digital video tape recorder.

  Such a metal thin film type magnetic recording medium is excellent in coercive force and squareness ratio, and since the magnetic layer can be formed in a very thin layer, it has excellent electromagnetic conversion characteristics in a short wavelength region, and also has recording demagnetization and reproduction. The thickness loss at the time is remarkably small, and unlike the coating-type magnetic recording medium, since the binder which is a nonmagnetic material is not mixed in the magnetic layer, the packing density of the ferromagnetic metal particles can be increased. Has advantages.

  In the metal thin film type magnetic recording medium described above, a protective layer is formed on the magnetic layer in order to improve durability, running property, etc., or a back coat is formed on the main surface opposite to the magnetic layer forming surface. It is usual to form a layer.

In a metal thin film type magnetic recording medium, the surface tends to be further smoothed in order to reduce the spacing loss corresponding to the high density recording.
However, when the surface of the magnetic layer becomes smooth, the contact area with the magnetic head increases, so that the frictional force increases and the shear stress generated in the magnetic layer increases. In order to protect the magnetic layer from such severe sliding conditions, it is important to form a protective layer on the magnetic layer.

  In addition, the backcoat layer lowers the dielectric constant of the surface of the non-magnetic support, prevents running defects due to charging, improves the durability of the non-magnetic support, and prevents scratches due to friction with the running head. It has a function of protecting or protecting against friction between magnetic tapes.

  By the way, with a tape-like magnetic recording medium used for a video tape recorder, further downsizing and longer recording time are desired along with downsizing of a video cassette in which the magnetic recording medium is stored. In addition, with the recent increase in the amount of information, it is desired to increase the capacity of magnetic recording media for tape streamers. As a method for improving the recording capacity per cassette, there are a method for increasing the recording density to increase the amount of information that can be recorded on the magnetic recording medium, and a method for winding around one cassette by reducing the thickness of the magnetic recording medium. There are techniques to increase the amount of tape. In particular, since the latter method does not require changing the recording format, it can be used to increase the capacity of an existing magnetic recording medium format.

  The most effective method for reducing the thickness of the magnetic tape is to thin the polymer film, which is a nonmagnetic support. The thickness of a conventional non-magnetic support (polyethylene terephthalate (PET) film) is, for example, about 7 to 10 μm for an 8 mm tape application of a home video tape recorder, and 5 to 7 μm for a tape streamer application for computer data backup. However, it was desired that the thickness be 5 μm or less.

  However, the rigidity of the non-magnetic support is related to the Young's modulus and thickness of the non-magnetic support. However, if the thickness of the non-magnetic support is reduced, the rigidity of the non-magnetic support is significantly reduced and the durability is increased. Tend to deteriorate. In addition, the magnetic recording medium using the non-magnetic support whose durability has been deteriorated as described above is likely to be deformed during running on a video tape recorder or a drive, and wrinkles, breaks, etc. are likely to occur. In particular, if the rigidity in the width direction of the tape-like nonmagnetic support is remarkably reduced, when a magnetic recording medium is constructed using this nonmagnetic support, the contact between the magnetic tape and the magnetic head becomes worse, and as a result As a result, fluctuations in reproduction output occurred, and stable recording / reproduction characteristics could not be obtained.

  Therefore, it has been studied to use a polyamide (PA) film as a nonmagnetic support. Since PA film has the characteristics of superior Young's modulus and heat resistance compared to PET film, the thickness of non-magnetic support can be made thinner than before, and video cassette tape can be recorded for a long time. As a magnetic recording medium corresponding to an increase in the capacity of a tape streamer, it is attracting attention.

  However, since the rigidity is proportional to the cube of the thickness, for example, in order to obtain the same rigidity by halving the thickness of the support, the Young's modulus of the material of the nonmagnetic support must be 8 times. . Therefore, the mechanical strength is insufficient only by changing the material of the nonmagnetic support.

  Further, PA films are more expensive than conventionally used PET films and polyethylene naphthalate (PEN) films, and are not suitable for mass production and sales as nonmagnetic support materials for magnetic tapes.

  In order to compensate for this, a technique has been proposed in which a strengthening layer is formed on a polymer film, which is a non-magnetic support, by vacuum thin film formation technology, thereby reducing the thickness of the magnetic recording medium and maintaining appropriate mechanical strength ( For example, see Patent Documents 1 and 2.) The reinforcing layer is remarkably superior in mechanical strength than a polymer film having the same thickness, and even a small thickness is effective. As a result, the magnetic recording medium can be made thinner.

JP 2002-358629 A Japanese Patent Laid-Open No. 11-283234

  However, with the recent change of reproducing magnetic heads from inductive heads to magnetoresistive heads (MR heads) and giant magnetoresistive heads (GMR heads) for the purpose of improving recording density, In order to prevent saturation, it is necessary to reduce the thickness of the magnetic layer. For example, in the product using the vapor deposition tape, the magnetic layer of the consumer DV tape using the inductive head is about 200 nm, whereas the magnetic layer of the MMV tape using the MR head is about 50 nm. As a result, even the magnetic tape provided with the reinforcing layer as described above may deteriorate in durability. In this case, if the reinforcing layer is simply thickened, a problem may occur in the recording / reproducing characteristics.

  The present invention has been made in view of the above-described problems in the prior art, and is a metal that can achieve further high recording density and thickness, and sufficient rigidity can be secured to obtain stable recording / reproduction characteristics. An object of the present invention is to provide a thin film magnetic recording medium.

  The present invention provided to solve the above-described problems has a reinforcing layer made of a material selected from metals, metalloids and alloys, and oxides and composites thereof on both sides of a long nonmagnetic support. And a metal thin film type magnetic recording medium comprising a magnetic layer made of a ferromagnetic metal thin film on the reinforcing layer on one side and a backcoat layer on the reinforcing layer on the other side, wherein the total of the reinforcing layers The reinforcing coefficient obtained by multiplying the film thickness and the Young's modulus of the material constituting the reinforcing layer is 22700 Pa · m or more, and the thickness of the reinforcing layer on the backcoat layer side is set to the magnetic layer and the magnetic layer side. A B / M ratio obtained by dividing by the total film thickness of the reinforcing layer is a metal thin film type magnetic recording medium characterized in that it is 0.25 or more and 2.22 or less (claim 1).

  In order to solve the above-mentioned problems, the present invention provides a reinforcing layer made of a material selected from a semimetal and an alloy, and an oxide and a composite thereof on one main surface of a long nonmagnetic support. In the metal thin film type magnetic recording medium having a magnetic layer made of a ferromagnetic metal thin film on the other main surface, obtained by multiplying the thickness of the reinforcing layer and the Young's modulus of the material constituting the reinforcing layer The reinforcement coefficient is 22700 Pa · m or more, and the B / M ratio obtained by dividing the film thickness of the reinforcement layer by the film thickness of the magnetic layer is 0.25 or more and 2.22 or less. It is a metal thin film type magnetic recording medium.

Here, in the invention of claim 1 or 2, the thickness of the nonmagnetic support is preferably 2 μm or more and 5 μm or less.
In the invention of claim 1 or 2, the thickness of the magnetic layer is preferably 20 nm or more and 90 nm or less.

According to the present invention, the magnetic layer is thinned and the nonmagnetic support is thinned, and the recording density per unit volume is improved as a magnetic recording medium, while sufficient rigidity as a magnetic recording medium is achieved. Therefore, running stability and contact with the magnetic head can be improved, and the shape of the magnetic recording medium can be maintained well.
In addition, since the reinforcing layers are formed on both main surfaces of the nonmagnetic support, the nonmagnetic support constituting the magnetic recording medium is expensive even when it is made thin while using a conventional inexpensive material. Mechanical strength can be maintained without using a non-magnetic support made of a raw material, and the manufacturing cost of the metal thin film type magnetic recording medium can be reduced.

The configuration of the first embodiment of the metal thin film type magnetic recording medium according to the present invention will be described below.
FIG. 1 is a schematic sectional view of a metal thin film type magnetic recording medium of the present invention.
The metal thin film type magnetic recording medium 100 has a reinforcing layer made of a material selected from metals, metalloids and alloys, and oxides and composites thereof formed on a nonmagnetic support 1 by a vacuum thin film forming technique. 2a, 2b, and a magnetic layer 3 formed by a vacuum thin film forming technique using a ferromagnetic metal or an alloy thereof on the reinforcing layer 2a or formed by a wet coating process technique. A back coat layer 5 formed by a wet coating process technique is provided on the reinforcing layer 2b on the opposite surface side.

Here, the thicknesses of the reinforcing layers 2a and 2b and the magnetic layer 3 are t _2a (nm), t _2b (nm) and t _m (nm), respectively, and the Young's modulus of the material constituting the reinforcing layers 2a and 2b is E. Then, the following relational expression is established in the metal thin film type magnetic recording medium of the present invention.

(T _2a + t _2b ) × E ≧ 22700 Pa · m (1)
0.25 ≦ t _2b / (t _2a + t _m ) ≦ 2.22 (2)

In the above formula (1), a product obtained by multiplying the total film thickness (t _2a + t _2b ) of the reinforcing layers 2a and 2b and the Young's modulus E of the material constituting the reinforcing layers 2a and 2b is referred to as a reinforcing coefficient k. In the above equation (2), the thickness t _2b of the reinforcing layer 2b on the backcoat layer 5 side is divided by the total thickness (t _2a + t _m ) of the magnetic layer 3 and the reinforcing layer 2a on the magnetic layer 2 side. This is called the B / M ratio.

  The Young's modulus E referred to in the present invention may be a numerical value obtained by measuring a bulk material made of the material constituting the reinforcing layers 2a and 2b. That is, the Young's modulus obtained by measuring the deflection and elongation of the bulk material may be used.

  Hereafter, each layer which comprises the metal thin film type magnetic recording medium 100 of this invention is demonstrated in detail.

  The nonmagnetic support 1 has a long shape, and any known material that is usually used as a base for a magnetic tape can be applied. For example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytetramethylene terephthalate, poly-1,4-cyclohexylenedimethylene terephthalate, polyethylene 2,6-naphthalene dicarboxylate, polyethylene-p-oxybenzoate, polyamide (PA) etc. can be mentioned. In particular, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are preferable from the viewpoint of availability of materials and good workability. These polyesters may be homopolyesters or copolyesters.

  In conventional magnetic tapes, the nonmagnetic support is usually 5 to 15 μm thick to maintain mechanical strength and ensure running stability, but methods other than improving the strength of the nonmagnetic support itself Therefore, if the mechanical strength during running of the magnetic recording medium can be obtained, the nonmagnetic support can be made thinner. From this viewpoint, in the metal thin film type magnetic recording medium 100, the nonmagnetic support 1 can be 5 μm or less, for example, 4 μm.

  The bending stiffness of the nonmagnetic support 1 can be calculated from the Young's modulus and thickness of the nonmagnetic support 1. Further, when layers of various materials are formed on both main surfaces of the nonmagnetic support, the bending rigidity of the nonmagnetic support 1, the thickness of the layer to be formed, the Young's modulus, and the thickness of the nonmagnetic support 1 Can be calculated taking into account the parameters obtained from

  When bending stress is applied to the nonmagnetic support 1, one main surface side of the nonmagnetic support 1 is shrunk and the other main surface side is stretched. Therefore, the expansion and contraction of the nonmagnetic support 1 can be prevented. The bending rigidity will be improved. At this time, high bending rigidity can be obtained by forming a layer having high rigidity on the outermost side, and further forming layers having high rigidity on the outermost side of both main surfaces of the nonmagnetic support 1.

Therefore, in order to improve the bending rigidity, it is effective to form layers (strengthening layers) for imparting rigidity to both main surfaces of the nonmagnetic support 1.
For example, even when a polyester film having a thickness of about 4 μm is used as the nonmagnetic support 1, the reinforcing layers 2a and 2b are formed by selecting the constituent materials and adjusting the Young's modulus, and further, the reinforcing layers 2a and 2b. By controlling the thickness, the rigidity can be increased and a nonmagnetic support having a bending rigidity comparable to that of the polyamide film can be obtained.

  On the other hand, when the thickness of the polyester film such as polyethylene terephthalate is more than 5 μm, the effect of improving the bending rigidity by the reinforcing layers 2a and 2b is reduced. Since this is generally proportional to the cube of the thickness, when the polyester film, that is, the nonmagnetic support 1 is thickened, the rigidity of the nonmagnetic support 1 itself is improved, and the rigidity of the reinforcing layers 2a and 2b is increased. This is because the improvement rate is relatively decreased.

Further, since the polyester film having a thickness of less than 2 μm basically has a bending rigidity of the film itself that is too low, the metal thin film type magnetic recording medium 100 can be used even if the rigidity is improved by the reinforcing layers 2a and 2b. A practically sufficient rigidity as a non-magnetic support constituting the film cannot be obtained.
From the above, it is preferable that the thickness of the nonmagnetic support 1 constituting the metal thin film type magnetic recording medium 100 of the present invention is 2 to 5 μm.

  The reinforcing layers 2a and 2b are formed on both sides of the main surface of the nonmagnetic support 1 by a vacuum thin film forming technique, and are selected from metals, metalloids and alloys, and oxides and composites thereof. Formed by material.

  Materials constituting the reinforcing layers 2a and 2b include Al, metals such as Cu, Zn, Sn, Ni, Ag, Co, Fe, and Mn, semimetals such as Si, Ge, As, Sc, and Sb, and the like. The oxide can be applied. In addition, alloys of these metals and metalloids include Fe—Co, Fe—Ni, Co—Ni, Fe—Cu, Co—Cu, Co—Au, Co—Y, Co—La, Co—Pr, and Co. -Gd, Co-Sm, Co-Pt, Ni-Cu, Mn-Bi, Mn-Sb, Mn-Al, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co-Cr, Ni-Co-Cr The oxides of these metals, metalloids and alloys can be easily obtained by introducing oxygen gas at the time of vapor deposition, for example. In addition, examples of composites of these metals, metalloids, and alloys include Fe-Si-O, Si-C, Si-N, Cu-Al-O, Si-N-O, and Si-C-O. It is done.

The film thicknesses of the reinforcing layers 2a and 2b are set so as to satisfy the above relational expressions (1) and (2). In other words, reinforcing layer 2a, to select the material constituting the 2b, material of Young's modulus E and the above equation from the thickness t _m of the magnetic layer 3 (1), in a range that satisfies (2), reinforcing layer 2a, The film thicknesses t _2a and t _2b of _2b are set. At this time, in view of productivity and the like, it is preferably formed to a thickness of 20 to 200 nm.

FIG. 2 shows a schematic diagram of an example of a vapor deposition apparatus 10 for forming the reinforcing layers 2 a and 2 b of the metal thin film type magnetic recording medium 100.
In the vapor deposition apparatus 10, a feed roll 13 and a take-up roll 14 are provided in a vacuum chamber 11 that is evacuated from the exhaust ports 21 and 22 to be in a vacuum state, and a nonmagnetic support is provided therebetween. 1 is made to run sequentially.

  A cooling can 15 is provided between the feed roll 13 and the take-up roll 14 while the nonmagnetic support 1 travels. The cooling can 15 is provided with a cooling device (not shown) to suppress thermal deformation or the like due to a temperature rise of the nonmagnetic support 1 running on the peripheral surface.

The nonmagnetic support 1 is sequentially fed from the feed roll 13, further passes through the circumferential surface of the cooling can 15, and is taken up by the take-up roll 14.
A predetermined tension is applied to the non-magnetic support 1 by the guide rolls 16 and 17 so that the non-magnetic support 1 runs smoothly.

  In the vacuum chamber 11, a crucible 18 is provided below the cooling can 15, and the film forming material 19 is filled in the crucible. On the other hand, an electron gun 20 for heating and evaporating the film forming material 19 filled in the crucible 18 is provided on the side wall of the vacuum chamber 11. The electron gun 20 is disposed at a position such that the electron beam B emitted from the electron gun 20 is applied to the film forming material 19 in the crucible 18. Then, the film forming material 19 evaporated by the irradiation of the electron beam B is deposited on the surface of the nonmagnetic support 1 to form the reinforcing layer 2a or the reinforcing layer 2b.

  The reinforcing layers 2a and 2b are made of, in addition to the above-described vacuum deposition method, an ion plating method in which the film forming material is evaporated in the discharge, or argon ions generated by glow discharge in an atmosphere containing argon as a main component. It can be formed by a so-called PVD technique such as sputtering that knocks out atoms on the surface. It can also be formed by wet coating process technology.

  The magnetic layer 3 can be formed by directly depositing a ferromagnetic metal material on the reinforcing layer 2a. As the ferromagnetic metal material, any conventionally known metal or alloy can be used. . For example, ferromagnetic metals such as Fe, Co, and Ni, and ferromagnetic alloys such as CoNi, FeCo, FeCoNi, FeCu, CoCu, CoAu, CoPt, MnBi, MnAl, FeCr, CoCr, NiCr, FeCoCr, CoNiCr, and FeCoNiCr. . The magnetic layer 3 may be a single layer film or a multilayer film of the above ferromagnetic metal material.

Furthermore, between the reinforcing layer 2 a and the magnetic layer 3, or between the metal magnetic thin films in the case of a multilayer film, an intermediate layer is formed by Cr or the like in order to improve the adhesion between layers or control the coercive force. It may be formed.
Further, the vicinity of the surface of the magnetic layer 3 may be an oxide in order to improve the corrosion resistance and the like.

  The film thickness of the magnetic layer 3 is preferably 20 nm or more and 90 nm or less, and may be set according to the reproducing magnetic head (MR head, GMR head).

  The magnetic layer 3 is preferably formed by the vapor deposition apparatus shown in FIG. In this case, the crucible 18 is filled with the ferromagnetic metal material instead of the film forming material 19. Then, the ferromagnetic metal material evaporated by the irradiation of the electron beam B is deposited on the surface of the reinforcing layer 2a of the nonmagnetic support 1, and the magnetic layer 3 is formed.

  A shutter 23 is disposed between the cooling can 15 and the crucible 18 and in the vicinity of the cooling can 15 so as to cover a predetermined region of the nonmagnetic support 1 that runs on the peripheral surface of the cooling can 15. The shutter 23 allows the evaporated ferromagnetic metal material to be deposited obliquely on the nonmagnetic support 1 within a predetermined incident angle range.

  Further, when the magnetic layer 3 is vapor-deposited, oxygen gas is supplied to the surface of the nonmagnetic support 1 by an oxygen gas introduction tube 24 provided through the side wall portion of the vacuum chamber 11. 3 is improved in magnetic properties, durability, and weather resistance.

A protective layer 4 is usually formed on the magnetic layer 3 in order to ensure good corrosion resistance and running durability.
As a material for forming the protective layer 4, any conventionally known material that is generally used as a protective layer for a metal magnetic thin film can be applied. Examples thereof include _{carbon, CrO 2, Al 2 O 3} , BN, Co _{oxide, MgO, SiO 2, Si 3} O 4, SiN X, SiC, SiN X -SiO 2, ZrO 2, TiO 2, TiC, and MoS etc. be able to. These single-layer films or multilayer films may be used. In particular, the protective layer 4 based on carbon is excellent in durability, corrosion resistance, and productivity.

  If the protective layer 4 is formed too thick, the loss due to spacing increases. If the protective layer 4 is too thin, the wear resistance and corrosion resistance deteriorate, so it is desirable to form the protective layer 4 to a thickness of about 4 to 12 nm. .

  The protective layer 4 can be formed by a known vacuum film forming technique, and can be formed by, for example, a CVD method using a plasma CVD continuous film forming apparatus 300 shown in FIG.

  The plasma CVD continuous film forming apparatus 300 shown in FIG. 3 is provided with a feed roll 333 and a take-up roll 334 in a vacuum chamber 331 that is evacuated from an exhaust system 330 to be in a vacuum state. The to-be-processed object 340 on which the reinforcing layers 2 a and 2 b and the magnetic layer 3 are formed is sequentially fed from the feed roll 333, passes through the peripheral surface of the cylindrical rotatable counter electrode can 335, and is wound on the take-up roll 334. It is made to wind up. A guide roll 336 is disposed between the feed roll 333 and the counter electrode can 335, and between the counter electrode 335 and the take-up roll 334, respectively, and applies a predetermined tension to the object 340 to be processed. The processing body 340 is made to travel smoothly.

A reaction tube 337 made of, for example, Pyrex (registered trademark) glass or plastic is provided below the counter electrode can 335.
Further, in the reaction tube 337, there is provided a gas introduction tube 341 having one end inserted through the bottom of the reaction tube 337 and the other end led out of the vacuum chamber 331. A film forming gas is introduced into the reaction tube 337 from the gas inlet 341.
Further, a discharge electrode 338 made of a metal mesh or the like is incorporated in the reaction tube 337. A predetermined potential, for example, a voltage of 500 to 2000 V, is applied to the discharge electrode 338 by a power source 339 provided outside.

  In plasma CVD continuous film forming apparatus 300 having the above-described configuration, glow discharge is generated between electrode 338 and counter electrode can 335 by applying a voltage to electrode 338. Then, the film forming gas introduced into the reaction tube 337 is decomposed by the generated glow discharge and deposited on the object to be processed 340.

  When a carbon compound gas is introduced as a film forming gas and decomposed in plasma by this CVD method, it has excellent wear resistance, corrosion resistance, and surface coverage, and has a smooth surface shape and high dielectric constant. Hard carbon called diamond-like carbon can be stably deposited to a thickness of 10 nm or less.

In this case, as the carbon compound, any conventionally known materials such as hydrocarbon, ketone, and alcohol can be used. In addition, a high-frequency bias voltage is used for decomposition in plasma. Further, at the time of plasma purification, Ar, H ₂ or the like may be introduced as a gas for promoting the decomposition of the carbon compound.

In addition, in order to improve the film hardness and corrosion resistance of diamond-like carbon, the carbon may be in a state of reacting with nitrogen or fluorine, and the diamond-like carbon film may be a single layer or a multilayer. Further, at the time of plasma generation, it is also possible to form a film in a state where a gas such as N ₂ , CHF ₃ , CH ₂ F ₂ or the like is used alone or appropriately mixed in addition to the carbon compound.

Further, the protective layer 4 may be formed by applying the magnetron sputtering apparatus 400 shown in FIG.
In the magnetron sputtering apparatus 400 shown in FIG. 4, a supply roll 439 and a take-up roll 440 are provided in a chamber 431 that is brought into a vacuum state by a vacuum pump 432, and the supply roll 439 and the take-up roll 440 are provided with A target object 450 in which the reinforcing layers 2a and 2b and the magnetic layer 3 are formed on the nonmagnetic support 1 is made to travel sequentially.
A cylindrical rotating counter electrode cooling can 435 is provided in the middle of the object 450 traveling from the supply roll 439 to the take-up roll 440.

  A guide roll 441 is disposed between the supply roll 439 and the cooling can 435, and between the cooling can 435 and the take-up roll 440, respectively, and applies a predetermined tension to the object 450 to be processed. 450 is made to travel smoothly.

In the chamber 431, a target 436 is provided at a position facing the cooling can 435.
The target 436 is a material for the protective layer 4 and, for example, carbon is used.

These targets 436 are supported by a backing plate 437 constituting a cathode electrode.
A magnet 438 that forms a magnetic field is disposed on the back surface of the backing plate 437.

In the magnetron sputtering apparatus 400, when the protective layer 4 is formed, the inside of the chamber 431 is decompressed to about 10 ⁻⁴ Pa by the vacuum pump 432, and then the valve 433 for exhausting to the vacuum pump 432 side is adjusted. Control the exhaust speed. On the other hand, Ar gas is introduced from the gas introduction pipe 434 so that the degree of vacuum is about 0.8 Pa, for example.

  Then, while introducing Ar gas from the gas introduction pipe 434, a voltage of about 3000 V is applied with the cooling can 435 as an anode and the backing plate 437 as a cathode, and a state in which a current of about 1.4 A flows is maintained. By applying this voltage, the Ar gas is turned into plasma, and the ionized ions collide with the target 436, so that atoms are ejected from the respective materials.

  At this time, since a magnetic field is formed in the vicinity of the target 436 by the magnet 438 disposed on the back surface of the backing plate 437, the ionized ions are concentrated in the vicinity of the target 436.

  Then, the atoms ejected from these targets 436 are fed out from the magnetic tape roll in the direction of the arrow shown in the figure, and adhere to the magnetic layer 3 of the object 450 that travels along the outer peripheral surface of the cooling can 435. In this way, the target object 450 on which the protective layer 4 is formed is taken up by the take-up roll 440.

The back coat layer 5 is formed for the purpose of imparting running stability on the reinforcing layer 2b opposite to the surface on which the magnetic surface 3 is disposed. This material may be any material as long as it is generally used. For example, _{carbon, CrO 2, Al 2 O 3} , BN, Co _{oxide, MgO, SiO 2, Si 3} O 4, SiN 4, SiC, SiN 4, SiO 2, ZrO 2, TiO 2, TiC , and the like . The back coat layer 5 may be a single layer film or a multilayer film. Furthermore, the film is usually formed by mixing and coating with an organic binder, but the binder may be any.

  In the metal thin film type magnetic recording medium 100 of the present invention, it is desirable to form the lubricant layer 6 by coating the outermost layer on the magnetic layer 2 forming surface side with a lubricant or a rust preventive agent. At this time, any lubricant can be used as long as it is generally used as a magnetic recording medium. In particular, the main skeleton is preferably a fluorocarbon, alkylamine, alkyl ester, or the like. The lubricant layer may be formed on the outermost layer on the backcoat layer 5 forming surface side.

Next, the configuration of the second embodiment of the metal thin film type magnetic recording medium according to the present invention will be described.
FIG. 5 is a schematic cross-sectional view of the metal thin film type magnetic recording medium of the present invention.
The metal thin film type magnetic recording medium 200 includes a reinforcing layer 2b made of a material selected from a semimetal and an alloy, and oxides and composites thereof on one main surface of the nonmagnetic support 1, and the other main surface. A magnetic layer 3 made of a ferromagnetic metal thin film is provided on the surface. That is, the present invention is such that the thickness of the reinforcing layer 2a is set to 0 (the reinforcing layer 2a is omitted) in the first embodiment shown in FIG. 1, and the other configurations are the same as those in the first embodiment. Is the same.
The metal thin film type magnetic recording medium of the present invention is required to satisfy the following relational expression.

t _2b × E ≧ 22700 Pa · m (3)
0.25 ≦ t _2b / t _m ≦ 2.22 (4)

Here, what is obtained by multiplying the thickness t _2b of the reinforcing layer 2b by the Young's modulus E of the material constituting the reinforcing layer 2b in the above equation (3) is the reinforcing coefficient k, and the back in the above equation (4) The B / M ratio is obtained by dividing the film thickness t _2b of the reinforcing layer 2b on the coat layer 5 side by the film thickness t _m of the magnetic layer 3.

  The nonmagnetic support 1, the reinforcing layer 2b, the magnetic layer 3, the protective layer 4, the back coat layer 5, and the lubricant layer 6 may have the same configuration as the first embodiment, and the formation method may be the same.

  Next, the metal thin film type magnetic recording medium of the present invention will be described with specific examples and comparative examples, but the metal thin film type magnetic recording medium of the present invention is not limited to the following examples. .

[Example 1]
As the nonmagnetic support 1, a PET film having a thickness of 4.5 μm and a width of 150 mm was prepared, and the metal thin film type magnetic recording medium 100 shown in FIG. 1 was produced under the following conditions.

A reinforcing layer 2 a (on the magnetic layer 3 side) was formed on one of the main surfaces of the nonmagnetic support 1.
The reinforcing layer 2a was formed under the following vapor deposition conditions by vacuum vapor deposition using the vapor deposition apparatus 10 shown in FIG. Cu was used for the film forming material 19.
(Deposition conditions)
・ Film forming material: Cu100wt%
-Incident angle: 45 ° to 10 °
・ Degree of vacuum during deposition: 2.0 × 10 ⁻² Pa
-Strengthening layer 2a film thickness: 100 nm
Further, a reinforcing layer 2b (back coat layer side) was formed to a thickness of 80 nm on the opposite surface of the nonmagnetic support 1 under the same conditions.
The film thickness of the reinforcing layers 2a and 2b is measured by embedding the sample with a visible light curable resin (D-800), preparing a cross-sectional sample by a microtome method, and observing with a transmission electron microscope (TEM). It is a thing.

According to the above equation (1), the strengthening coefficient k was 23360 Pa · m. The Young's modulus of Cu was 12.98 × 10 ¹⁰ Pa.

Next, the magnetic layer 3 was formed on the reinforcing layer 2a using the vapor deposition apparatus 10 shown in FIG. 2 under the following vapor deposition conditions.
(Deposition conditions)
・ Metal magnetic material: Co100wt%
-Incident angle: 45 ° to 10 °
・ Introduced gas: Oxygen gas ・ Oxygen introduced amount: 3.3 × 10 ⁻⁶ m ³ / sec
・ Degree of vacuum during deposition: 2.0 × 10 ⁻² Pa
Magnetic layer 3 film thickness: 50 nm

From the above formula (2), the B / M ratio was 0.53.
The order of forming the reinforcing layers 2a and 2b and the magnetic layer 3 is not necessarily limited to the above. For example, after forming the reinforcing layer 2a, the magnetic layer 3 is formed thereon, and then the magnetic layer 3 is formed. The reinforcing layer 2b may be formed on the main surface of the nonmagnetic support 1 opposite to the above.

Next, the protective layer 4 was formed on the magnetic layer 3.
As the protective layer 4, a diamond-like carbon layer was formed by plasma CVD under the following conditions.
(Protective layer deposition conditions)
-Reaction gas: Toluene-Reaction gas pressure: 10Pa
・ Introduction power: Direct current (DC) 1.5 kV
-Protective layer 4 film thickness: 10 nm

  Next, the back coat layer 5 was formed on the surface layer (reinforced layer 2b) opposite to the surface on which the magnetic layer 3 was disposed for the purpose of imparting running stability. Here, the backcoat layer 5 having a thickness of 0.4 μm was formed by mixing and applying carbon together with an organic binder.

  Next, a lubricant made of fluorocarbon as a main skeleton and modified with a tertiary amine was applied to each of the outermost layers on the magnetic layer 3 forming surface side and the back coat layer 5 forming surface side. As the fluorocarbon, a product name “Demnam” manufactured by Daikin Industries, Ltd. was used, and dimethyldecylamine was used as the tertiary amine so as to have a salt structure.

  Finally, it was cut into 6.35 mm width and 8 mm width to obtain a sample of a metal thin film type magnetic recording medium.

[Examples 2 to 6]
In Example 1, the thicknesses of the reinforcing layers 2a and 2b are 100, 100 nm (Example 2), 75, 125 nm (Example 3), 50, 125 nm (Example 4), and 50, 175 nm (Example 5), respectively. 150, 50 nm (Example 6), and samples were produced under the same conditions as in Example 1 except that.

[Examples 7 and 8]
In Example 1, the thicknesses of the reinforcing layers 2a and 2b are set to 0, 180 nm (Example 7) and 0, 200 nm (Example 8) (that is, the configuration shown in FIG. 5), and the film thickness of the magnetic layer 3 is set. The sample was manufactured under the same conditions as in Example 1 except that the thickness was 90 nm.

[Examples 9 and 10]
In Example 1, the material constituting the reinforcing layers 2a and 2b is Al (the film forming material 19 is Al 100 wt%), and the respective film thicknesses are 100, 300 nm (Example 9), 150, 250 nm (Example 10). Other than that, a sample was produced under the same conditions as in Example 1. The Young's modulus of Al was set to 7.03 × 10 ¹⁰ Pa.

[Comparative Examples 1 and 2]
In Example 1, the thicknesses of the reinforcing layers 2a and 2b were 100, 50 nm (Comparative Example 1), 180, and 40 nm (Comparative Example 2), respectively, and samples were manufactured under the same conditions as in Example 1.

[Comparative Example 3]
In Example 1, the reinforcing layers 2a and 2b were omitted, and a sample was manufactured under the same conditions as in Example 1 except that.

[Comparative Examples 4 and 5]
In Example 1, the thicknesses of the reinforcing layers 2a and 2b were set to 0, 100 nm (Comparative Example 4) and 0, 200 nm (Comparative Example 5), respectively, and samples were manufactured under the same conditions as in Example 1.

[Comparative Examples 6-8]
In Example 1, the thicknesses of the reinforcing layers 2a and 2b were 100, 0 nm (Comparative Example 6), 200, 0 nm (Comparative Example 7), and 300, 0 nm (Comparative Example 8), respectively. Samples were prepared under the same conditions.

[Comparative Example 9]
In Example 1, the thickness of the reinforcing layers 2a and 2b was set to 0,250 nm, the thickness of the magnetic layer 3 was set to 90 nm, and the sample was manufactured under the same conditions as in Example 1.

[Comparative Examples 10-12]
In Example 1, the material constituting the reinforcing layers 2a and 2b is Al (the film forming material 19 is Al 100 wt%), and the respective film thicknesses are 70, 250 nm (Comparative Example 10), 100, 175 nm (Comparative Example 11), Samples were prepared under the same conditions as in Example 1 except for 250 and 50 nm (Comparative Example 12).

[Comparative Examples 13 and 14]
In Example 10, the thicknesses of the reinforcing layers 2a and 2b were 0, 300 nm (Comparative Example 13), 400, and 0 nm (Comparative Example 14), respectively, and samples were manufactured under the same conditions as in Example 10.

[Comparative Example 15]
In Example 10, a sample was prepared under the same conditions as in Example 10 except that the thickness of the reinforcing layers 2a and 2b was set to 0,350 nm and the thickness of the magnetic layer 3 was set to 90 nm.

[Reference Examples 1 and 2]
In Example 1, the nonmagnetic support 1 is a PA film (thickness: 4.5 μm), the reinforcing layers 2a and 2b are omitted, and the thickness of the magnetic layer 3 is 100 and 50 nm, respectively. Samples were prepared under the same conditions.

  About the sample produced as mentioned above, it measured and evaluated by the method shown below. The characteristics per RF and the error rate were evaluated using a cassette containing a 6.35 mm wide sample in an actual magnetic recording medium modified from Sony Corporation AIT drive SDX-500C. .

(1) Cupping When a sample with an 8 mm width is left standing with the magnetic layer 3 facing upward, the cross-sectional shape of the sample is curved so that the magnetic layer 3 side is concave (the back coat layer 5 side is convex). A (+) cupping is defined, and a curved state such that the magnetic layer 3 side is convex (back coat layer 5 side is concave) is defined as minus (−) cupping.
In the cupping measurement, the absolute value of the cupping amount is the difference in height (mm) between the bottom and end of the recess for plus cupping, and the height difference (mm) between the apex and end of the protrusion for minus cupping. The plus amount in the case of plus cupping and the minus amount in the case of minus cupping were used as the amount of cupping.
In addition, as the cupping evaluation, a case where the absolute value of the measured cupping amount was less than 0.8 was regarded as good evaluation, and a case outside this range was regarded as poor evaluation.

(2) Flexural rigidity (loop stiffness)
The strength against bending of the sample in the longitudinal direction of the tape was measured as bending stiffness. Specifically, both ends of the cut 8 mm width sample were bonded together to form a loop with a circumference of 4 mm, and the repulsive force at 0.5 mm indented into this loop was measured as an index of bending stiffness.
The ratio of the bending rigidity of Reference Example 1 was determined as the bending rigidity ratio.

(3) Characteristics per RF (AIT deck)
A signal having a recording wavelength of 0.5 μm was recorded on the sample while the sample was running, and then the envelope characteristics of the RF signal due to head reproduction were monitored with an oscilloscope. Here, the characteristic per RF is the ratio of the width (B) of the deteriorated RF signal to the width (A) of the normal RF signal, and is calculated by the following equation. For the width (B) of the deteriorated RF signal, the worse one of the track length entrance and exit was used. In the evaluation, the case where the characteristic per RF was 90% or more was considered good.
(Characteristics per RF) = B / A x 100 (%)

(4) Error rate (AIT deck)
The sample was run and the block error rate was measured.

  The results are shown in Table 1.

  In Reference Examples 1 and 2, in the case of the non-magnetic support of the polyamide film, there is no problem in each characteristic when the thickness of the magnetic layer 3 is 100 nm, but when the magnetic layer thickness is reduced to 50 nm, It can be seen that the characteristics per RF cannot be obtained due to the deterioration of the mechanical strength, and the error rate also deteriorates. Similarly, in Comparative Example 3 using a non-magnetic support of PET film having no reinforcing layer and low strength, the characteristics per RF are low and the error rate is not good.

  On the other hand, in the metal thin film type magnetic recording media of Examples 1 to 6 according to the present invention, the reinforcing layers are formed on both surfaces of the nonmagnetic support even when the nonmagnetic support of the PET film having low strength is used. As a result, bending rigidity, RF contact characteristics, and error rate are improved.

In Comparative Example 1, since the reinforcement coefficient is small, the bending rigidity is low, the characteristics per RF are deteriorated, and the error rate is deteriorated. Further, in Comparative Example 2, the enhancement coefficient was satisfied, but the B / M ratio was small and out of the appropriate range, so that the amount of cupping was large and the RF contact characteristics deteriorated.
In Comparative Examples 4 and 5, the cupping amount increases with minus cupping as the B / M ratio increases, and in Comparative Examples 6 to 8, the cupping amount increases with plus cupping as the B / M ratio decreases. I understand that. Among them, Comparative Example 4 satisfies the B / M ratio, but the reinforcement coefficient is small and out of the appropriate range. Like Comparative Example 1, the characteristics per RF are deteriorated and the error rate is deteriorated. Further, Comparative Examples 5, 7, and 8 satisfied the strengthening coefficient, but the B / M ratio was out of the proper range, and the amount of cupping was increased as in Comparative Example 2, resulting in poor RF contact characteristics.
In Examples 7 and 8, it was confirmed that even when only the reinforcing layer on the backcoat layer side was used, if the reinforcing coefficient and the B / M ratio were set to predetermined values, good characteristics could be obtained. In other words, it can be seen that the presence of the reinforcing layer 2b on the backcoat layer 5 side is more effective for improving the characteristics per RF than the reinforcing layer 2a on the magnetic layer 3 side. However, if the reinforcing layer 2b on the backcoat layer side is made too thick as in Comparative Example 9, the B / M ratio becomes excessively large and falls outside the proper range, resulting in poor cupping.
From the above, in order to prevent deterioration of characteristics per RF and to set the cupping amount to an appropriate value, it is necessary to set the strengthening coefficient and the B / M ratio to predetermined values.

  Examples 9 and 10 and Comparative Examples 10 to 15 are examples in which the reinforcing layer is made of Al. Al has lower mechanical strength than Cu, but the same effect can be obtained by setting the strengthening coefficient and the B / M ratio to predetermined values.

  As described above, according to the metal thin film type magnetic recording medium of the present invention, by forming appropriate reinforcing layers on both sides of the non-magnetic support or on the back coat layer side, a thin layer magnetic layer such as a medium for MR heads is formed. Even a non-magnetic support of low-priced PET film with weak mechanical strength can maintain sufficient mechanical strength, improve the per-RF characteristics and error rate deterioration, and achieve a high-capacity, high-performance, highly reliable magnetic recording medium It was confirmed that it could be realized.

It is sectional drawing which shows the structure in 1st Embodiment of the metal thin film type magnetic recording medium based on this invention. It is the schematic of the vapor deposition apparatus for producing the magnetic layer and reinforcement layer which comprise the metal thin film type magnetic recording medium of this invention. It is the schematic of a plasma CVD continuous film forming apparatus. It is the schematic of the magnetron sputtering apparatus for reinforcement | strengthening layer formation which comprises the metal thin film type magnetic recording medium of this invention. It is sectional drawing which shows the structure in 2nd Embodiment of the metal thin film type magnetic recording medium based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic support body, 2a, 2b ... Strengthening layer, 3 ... Magnetic layer, 4 ... Protective layer, 5 ... Backcoat layer, 10 ... Evaporation apparatus, 11 ... Vacuum chamber, 13 ... feed roll, 14 ... winding roll, 15 ... cooling can, 16, 17 ... guide roll, 18 ... crucible, 19 ... film forming material, 20 ... Electron gun, 21,22 ... Exhaust port, 23 ... Shutter, 24 ... Oxygen gas introduction tube, 100,200 ... Metal thin film type magnetic recording medium, 300 ... Continuous plasma CVD Film forming apparatus, 330 ... exhaust system, 331 ... vacuum chamber, 333 ... feed roll, 334 ... winding roll, 335 ... counter electrode, 336 ... guide roll, 337 ...・ Reaction tube, 338 ... electrode, 339 ... DC power supply, 340 ... Processing body, 341 ... discharge gas inlet, 400 ... magnetron sputtering device, 431 ... chamber, 432 ... vacuum pump, 433 ... valve, 435 ... cooling can, 436, 466 ..Target, 437, 467 ... backing plate, 438, 468 ... magnet, 439 ... supply roll, 440 ... take-up roll, 441 ... guide roll, 450 ... target object

Claims (4)

It has a reinforcing layer made of a material selected from metals, metalloids and alloys, and oxides and composites thereof on both sides of a long non-magnetic support, and further has a ferromagnetic layer on the reinforcing layer on one side. A metal thin film type magnetic recording medium comprising a magnetic layer made of a metal thin film and having a backcoat layer on the reinforcing layer on the other surface
The reinforcement coefficient obtained by multiplying the total film thickness of the reinforcement layer and the Young's modulus of the material constituting the reinforcement layer is 22700 Pa · m or more,
The B / M ratio obtained by dividing the thickness of the reinforcing layer on the backcoat layer side by the total thickness of the magnetic layer and the reinforcing layer on the magnetic layer side is 0.25 or more and 2.22 or less. A metal thin film type magnetic recording medium. A ferromagnetic metal thin film is provided on one main surface of a long nonmagnetic support, comprising a reinforcing layer made of a material selected from a semimetal and an alloy, and oxides and composites thereof. In a metal thin film type magnetic recording medium comprising a magnetic layer comprising:
The reinforcement coefficient obtained by multiplying the film thickness of the reinforcement layer and the Young's modulus of the material constituting the reinforcement layer is 22700 Pa · m or more,
A metal thin film type magnetic recording medium, wherein a B / M ratio obtained by dividing the thickness of the reinforcing layer by the thickness of the magnetic layer is 0.25 or more and 2.22 or less.   3. The metal thin film type magnetic recording medium according to claim 1, wherein the nonmagnetic support has a thickness of 2 μm or more and 5 μm or less. 3. The metal thin film magnetic recording medium according to claim 1, wherein the magnetic layer has a thickness of 20 nm or more and 90 nm or less.

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