JPH0991657A - Magnetic tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic tape having excellent head-touching property and good reproducing characteristics by forming a back coating film on the tape in such a manner that the surface roughness of the film satisfies specified characteristics. SOLUTION: This magnetic tape has a back coating film 3. The surface roughness (center line average toughness Ra) of the back coating film 3 satisfies the relation of (center average roughness Ra||)>(center average roughness Ra⊥), wherein Ra|| is roughness in the longitudinal direction and Ra⊥ is roughness in the width direction. Thereby, the obtd. tape has proper cupping property, excellent head-touching property, a smooth envelope and excellent reproducing characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal thin film type magnetic tape.

[0002]

A metal thin film type magnetic tape having a magnetic film or a back coat film formed by PVD (Physical Vapor Deposition) such as vapor deposition or sputtering is widely known. This metal thin film type magnetic tape is apt to cause cupping, which results in poor head touch and deteriorates recording / reproducing characteristics.

In order to solve this problem, it has been proposed to make a gap between the magnetic film and the back coat film to improve cupping. However, improvement in head touch is an important factor in terms of recording / reproducing characteristics, and further improvement is required. Therefore, it is an object of the present invention to provide a magnetic tape having a better head touch and excellent recording / reproducing characteristics.

[0004]

The object of the present invention is a magnetic tape provided with a back coat film, wherein the surface roughness (center line average roughness Ra) of the back coat film surface is in the longitudinal direction. It is achieved by a magnetic tape characterized in that surface roughness (centerline average roughness Ra‖)> surface roughness in the tape width direction (centerline average roughness Ra⊥) is satisfied.

A magnetic tape having a metal magnetic film on one side of the support and a back coat film on the other side,
The surface roughness (center line average roughness Ra) of the surfaces on both sides of the magnetic tape is the surface roughness in the longitudinal direction (center line average roughness Ra‖)> the surface width in the tape width direction (center line average roughness). It is achieved by a magnetic tape characterized by satisfying Ra⊥).

A magnetic tape having a metal magnetic film and a protective film on one surface side of the support and a back coat film on the other surface side, the surface roughness (center) of both surfaces of the magnetic tape. Achieved by a magnetic tape characterized in that the line average roughness Ra) satisfies the following: surface roughness in the longitudinal direction (centerline average roughness Ra‖)> surface width in the tape width direction (centerline average roughness Ra⊥). To be done.

In the magnetic tape of the present invention, it is more preferable that the surface roughness (center line average roughness Ra) of the surface of the back coat film satisfies 1.5 × Ra⊥ <Ra‖ <10 × Ra⊥. Further, it is more preferable that the surface roughness (center line average roughness Ra) on the metal magnetic film side satisfies 1.5 × Ra⊥ <Ra‖ <5 × Ra⊥.

Further, the above requirements are satisfied, and Ra / | on the surface of the back coat film is 0.2 to 200 nm (particularly 1.
5 to 30 nm), Ra⊥ is 0.1 to 100 nm (especially,
1 to 20 nm), and Ra on the metal magnetic film side is 0.2 to 200 nm (particularly 1.5 to 30 nm), Ra
A magnetic tape having a ⊥ of 0.1 to 100 nm (particularly 1 to 20 nm) is more preferable.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a magnetic tape provided with a back coat film, wherein the surface roughness (center line average roughness Ra) of the back coat film surface is the longitudinal surface roughness ( Centerline average roughness Ra‖)> surface roughness in the tape width direction (centerline average roughness Ra⊥).

A magnetic tape having a metal magnetic film on one side of the support and a back coat film on the other side,
The surface roughness (center line average roughness Ra) of both surfaces of the magnetic tape is the surface roughness in the longitudinal direction (center line average roughness Ra‖)> the surface roughness in the tape width direction (center line average roughness Ra). Sa Ra ⊥) is satisfied. A magnetic tape having a metal magnetic film and a protective film on one surface side of the support and a back coat film on the other surface side, the surface roughness (center line average roughness) of both surfaces of the magnetic tape. The surface roughness Ra) satisfies the following formula: surface roughness in the longitudinal direction (centerline average roughness Ra‖)> surface roughness in the tape width direction (centerline average roughness Ra⊥).

In particular, the surface roughness (center line average roughness Ra) of the back coat film surface is 1.5 × Ra⊥ <Ra‖ <10.
The condition of × Ra⊥ is satisfied. Further, the surface roughness (center line average roughness Ra) of the metal magnetic film side is 1.5 × Ra⊥ <Ra‖ <
The condition of 5 × Ra⊥ is satisfied. Further, the Ra ‖ of the surface of the back coat film is 0.2 to 200 nm and the Ra ⊥ is 0.1 to 100.
and Ra / | on the metal magnetic film side is 0.2 to 2
00 nm and Ra⊥ are 0.1 to 100 nm.

The magnetic tape support of the present invention may be magnetic or non-magnetic. Typical examples include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycyclohexylene dimethylene terephthalate, polyethylene bisphenoxycarboxylate, polyolefins such as polyethylene and polypropylene, cellulose acetate butyrate, cellulose acetate Examples thereof include cellulose derivatives such as pionate, vinyl-based resins such as polyvinyl chloride and polyvinylidene chloride, and non-magnetic plastic materials such as polyamide and polycarbonate. Of course, it is not limited to these. Also, various kinds of processing may be performed. For example, surface treatment is performed by corona discharge or other appropriate means. Further, polyester, polyurethane, oligomer or the like may be applied for improving the adhesiveness.

The surface roughness (centerline average roughness Ra) of both surfaces of the support is such that the surface roughness in the longitudinal direction (centerline average roughness Ra‖)> the surface roughness in the tape width direction (center) Line average roughness Ra⊥), especially on the backcoat film side, so that the condition of 1.5 × Ra⊥ <Ra‖ <10 × Ra⊥ is satisfied and Ra‖ is 0.2 to 200 n.
m, Ra⊥ is 0.1 to 100 nm, and further 1.5 × Ra⊥ <Ra‖ <5 × R on the metal magnetic film side.
to satisfy the condition of a⊥, and Ra‖ of 0.2 to 20
0 nm and Ra⊥ are 0.1 to 100 nm. For example, the plate ratio is 2 to 20, and the thickness is 0.00.
Plate-like particles of 1 to 0.1 μm (for example, BaO.6Fe ₂
When a coating material containing a binder resin (particularly a water-soluble polymer) in which ferrite such as O ₃ is dispersed is applied on a plastic film (support) and then stretched in the longitudinal direction, a support satisfying the surface profile described above is obtained. The body is obtained. The surface roughness on both sides may be the same or different. To make them different, the coating amount of the plate-like particles may be made different.

One or two or more metal magnetic films are provided on one surface side of the support having this surface profile by a PVD method such as oblique vapor deposition. Examples of the material forming the metal magnetic film include metals such as Fe, Co, and Ni, as well as Co—Ni alloys, Co—Pt alloys, and Co—Ni—P.
t alloy, Fe-Co alloy, Fe-Ni alloy, Fe-Co
-Ni alloy, Fe-Co-B alloy, Co-Ni-Fe-
A B alloy, a Co-Cr alloy, or those containing a metal such as Al is used. The metal magnetic film is a nitride film (for example, Fe-N-) using the above material.
O) or a carbonized film (for example, Fe—C—O). Since the film forming method is well known in the related art, detailed description thereof will be omitted.

When a metal magnetic film having a thickness of 500 to 3000 Å is provided, the surface roughness (center line average roughness Ra) of the surface of the metal magnetic film is affected by the surface profile of the base (support). Roughness in direction (centerline average roughness R
a‖)> surface roughness in the tape width direction (centerline average roughness Ra
⊥), especially 1.5 × Ra⊥ <Ra‖ <5 × Ra⊥,
Furthermore, Ra‖ is 0.2 to 200 nm and Ra⊥ is 0.1 to
It will be 100 nm.

A protective film is provided on the surface of the magnetic film, if necessary. As a material for forming this protective film,
For example, Al, Si, Ti, Cr, Zr, Nb, Mo, T
Oxides, nitrides, and carbides of metals such as a and W, diamond-like carbon, and boron nitride are used. The thickness of the protective film is 10 ~ 500Å, especially 30 ~ 2
It is about 00 °.

When a protective film having a thickness of about 10 to 500 Å is provided, the surface roughness (center line average roughness Ra) of the protective film surface is affected by the surface profile of the base (metal magnetic film). Roughness in the direction (centerline average roughness Ra
‖)> Surface roughness in the tape width direction (centerline average roughness Ra
⊥), especially 1.5 × Ra⊥ <Ra‖ <5 × Ra⊥,
Furthermore, Ra‖ is 0.2 to 200 nm and Ra⊥ is 0.1 to
It will be 100 nm.

A metal film type back coat film is provided on the other surface side of the support having the above surface profile by a PVD method such as vapor deposition. The back coat film has a thickness of 1000 to 5000Å, more preferably 1000 to 5000Å.
It is about 3500Å. Examples of the metal material forming the back coat film include Al, Zn, Sn, Ni, Ag,
Metals such as Fe and Ti are used. Also, Cu-Al-
X (where X is one or two or more selected from the group of Mn, Fe, Ni) alloys, Al-Si alloys,
A Ti alloy or the like is used. Cu-Al-X (however,
X is one or more selected from the group of Mn, Fe and Ni) and the Cu content in the alloy is 70 to 90
at%, Al content is 8 to 25 at%, Mn content is 0.5 to 4 at%, Fe content is 0.4 to 5 at%.
And the Ni content is 0.4 to 4 at%, Mn, F
It is preferable that the total content of e and Ni is 1 to 6 at%. Further, the Al content in the Al-Si alloy is 15 to
It is preferable that the Si content is 70 at% and the Si content is 15 to 70 at%. At the time of forming the back coat film, an oxidizing gas, oxygen ions or oxygen radical may be supplied to oxidize the surface layer portion of the metal-based film. Alternatively,
It is also possible to supply a highly reactive nitrogen compound, nitrogen ion or nitrogen radical so that the surface layer portion of the metal-based film is nitrided. Alternatively, a highly reactive carbon compound, carbon ion or carbon radical may be supplied to carbonize the surface layer portion of the metal-based film. It is preferable to supply a highly reactive carbon compound, carbon ion, or carbon radical to carbonize the surface layer portion of the metal-based film because it resembles the diamond-like carbon film.

When a metal film type back coat film having a thickness of 1000 to 5000 Å is provided, the surface profile of the back coat film (center line average roughness Ra) is affected by the surface profile of the base (support). Is the surface roughness in the longitudinal direction (centerline average roughness Ra‖)> the surface roughness in the tape width direction (centerline average roughness Ra⊥), especially 1.5 × Ra⊥ <R
a‖ <10 × Ra⊥, further Ra‖ is 0.2 to 200
nm and Ra⊥ are 0.1 to 100 nm.

The metal thin film type magnetic film or back coat film may be formed by forming the back coat film after forming the magnetic film. Conversely, the magnetic film may be formed after forming the back coat film. Alternatively, the films may be formed in almost the same process. Incidentally, in terms of steps, since a protective film such as a diamond-like carbon film is provided on the magnetic film, it is preferable to form the magnetic film after forming the back coat film.

After the metal magnetic film (protective film) or the back coat film is formed as described above, the film of the fluorine-based lubricant is dipped or ultrasonically sprayed at 20 to 70Å.
It is provided with a certain thickness. As the lubricant, for example,-(C (R)
F-CF ₂ -O) _p- (where R is a group such as F, CF ₃ , CH ₃ etc.), especially HOOC-CF ₂ (OC ₂ F ₄ ) _p (OCF ₂ ) _q -OCF ₂ -COOH,
F- (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ CF ₂ COOH carboxyl group-modified perfluoropolyether, HOCH ₂ -CF ₂ (OC ₂
F ₄ ) _p (OCF ₂ ) _q -OCF ₂ -CH ₂ OH, HO- (C ₂ H ₄ -O) _m -CH _2- (O-
C ₂ F ₄ ) _p (OCF ₂ ) _q -OCH _2- (OCH ₂ CH ₂ ) _n -OH, F- (CF ₂ CF ₂ C
F ₂ O) _n -CF ₂ CF ₂ CH ₂ OH, such as alcohol-modified perfluoropolyethers, or saturated hydrocarbon groups such as alkyl groups or unsaturated hydrocarbons on one side or part of the molecule Examples thereof include those having a hydrogen group, an aromatic hydrocarbon group, or other functional groups. Specifically, Montecatini's FOMBLIN Z DIAC and FOMBLII
Examples include NZ DOL and Daikin Industries' Demnum SA.

[0022]

[Embodiment 1] FIG. 1 is a schematic view of a first embodiment of an 8 mm VTR magnetic tape according to the present invention. In FIG. 1, 1 is about 6
It is a support having a thickness of μm. The support 1 had a plate ratio of 5 and a weight ratio of 0.01 μm of BaO.6Fe ₂ O ₃ plate particles of 0.5 part by weight, polyvinyl alcohol of 0.2 parts by weight, and water of 99 parts by weight. Mix the kneaded paint with BaO ・ 6F
e ₂ O ₃ tabular particles are about 10 million particles / mm ² (cross section TE
It was applied on both sides of a PET film having a thickness of 6 μm so as to obtain (from the M image), dried at 100 ° C., and stretched at a ratio of 2.5 times in the longitudinal direction and 1.1 times in the width direction. is there.

Numeral 2 is a 2000 Å thick Co metal magnetic film provided on the surface of the support having a specific surface profile by the stretching process by oblique vapor deposition. 3 is a 1000Å thick Cu-Al metal film (back coat film) provided on the surface of the support opposite to the Co metal magnetic film 2 by vapor deposition. Then, a 20Å-thick film of a fluorine-based lubricant (FOMBLINZ DIAC) is provided on the surface.

[0024]

Examples 2 to 5 The procedure of Example 1 was repeated except that the stretching ratio was changed. The stretching ratio is shown in Table-1.

[0025]

Embodiments 6 to 10 FIG. 2 shows an 8 mm VTR according to the present invention.
It is a schematic diagram of a sixth embodiment of a magnetic tape for use. The major difference between the magnetic tape of this example and the magnetic tape of Example 1 is that the magnetic tape of this Example has a diamond-like carbon film (protective film) of 100Å on the surface of the Co metal magnetic film 2.
4 is provided, and the other points are the same as those in the first embodiment, and thus detailed description will be omitted.

[0026]

Comparative Example 1 In Example 1, BaO.6Fe ₂ O ₃
The same procedure as in Example 1 was performed except that the coating material containing plate-like particles was not applied and a 2000 Å-thick Co metal magnetic film was provided on a 6-μm-thick PET film.

[0027]

[Comparative Example 2] The procedure of Example 1 was repeated except that the stretching ratio was changed. * -Indicates no stretching treatment.

[0028]

[Characteristics] Regarding the magnetic tapes obtained in each of the above examples, Ra‖ (centerline average roughness Ra in the longitudinal direction) and Ra⊥ (centerline average roughness in the width direction) of the surface of the magnetic film (protective film) and the back coat film. Ra) was examined, and the results are shown in Table 2.
In addition, the measurement of Ra (Ra‖, Ra⊥) is performed by Surfcom 30.
0B (manufactured by Tokyo Seimitsu Co., Ltd.), stylus 2 μmR, drive speed 0.03 mm / s, cutoff 0.08 mm, measuring length 0.8 mm (0.8 mm in the longitudinal direction for measuring Ra ∥).
m and Ra⊥ were measured under the condition that the width was 0.8 mm) and the number of measurements was 5 times.

Table 2 Backcoat Film Surface Roughness (nm) Magnetic Film (Protective Film) Surface Roughness (nm) Ra‖Ra⊥Ra‖ / Ra⊥Ra‖Ra⊥Ra‖ / Ra⊥ Example 1 8.6 3.1 2.7 8.6 3.2 2.7 Example 2 5.3 3.2 1.7 5.2 3.0 1.7 Example 3 24.6 3.2 8.2 24.5 3.0 8.2 Example 4 4.8 1.9 2.5 4.7 1.9 2.5 Example 5 2.9 1.8 1.6 2.9 1.8 1.6 Example 6 15.1 1.8 8.4 14.9 1.7 8.8 Implementation Example 7 20.9 1.9 11.0 20.0 1.8 11.1 Example 8 10.4 5.2 2.0 10.5 5.1 2.1 Example 9 29.2 5.3 5.5 29.0 5.2 5.6 Example 10 47.7 5.3 9.0 48.0 5.3 9.1 Comparative Example 1 1.8 1.8 1.0 1.8 1.8 1.0 Comparative Example 2 4.3 4.3 1.0 4.3 4.3 1.0 Also, the cupping r / a (r is the cupping height, a is the tape width) of the magnetic tape of each example was determined, the envelope was measured, and the precession rate thereof was investigated.
3 is shown.

Table 3 Cupping r / a Envelope Precession Rate (%) Example 1 0.09 5 Example 2 0.10 8 Example 3 0.12 10 Example 4 0.11 12 Example 5 0. 12 10 Example 6 0.13 8 Example 7 0.15 13 Example 8 0.14 15 Example 9 0.12 12 Example 10 0.11 13 Comparative Example 1 0.45 38 Comparative Example 2 0.31 42 According to this, the magnetic tape having the surface profile of the present invention has an appropriate cupping property, is excellent in head touch, and is excellent in reproducing characteristics as can be seen from the fact that the envelope is beautiful.

[0031]

The cupping is moderate, the head touch is excellent, and the envelope is beautiful.
It has excellent reproduction characteristics.

[Brief description of drawings]

FIG. 1 is a schematic view of a magnetic tape according to the present invention.

FIG. 2 is a schematic view of a magnetic tape according to the present invention.

[Explanation of symbols]

 1 support 2 metal magnetic film 3 back coat film 4 protective film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Sasaki 2606, Akabane, Kaiga, Haga-gun, Tochigi Kao Co., Ltd.Institute of Information Science Research (72) Inventor Katsumi Endo 2606, Akabane, Kaiga, Kaiga-cho, Haga-gun, Tochigi Company Information Science Laboratory

Claims (6)

[Claims] 1. A magnetic tape provided with a back coat film, wherein the surface roughness of the surface of the back coat film (center line average roughness R).
A magnetic tape characterized in that a) satisfies the following formula: surface roughness in the longitudinal direction (center line average roughness Ra‖)> surface width in the tape width direction (center line average roughness Ra⊥). 2. A magnetic tape in which a metal magnetic film is provided on one surface side of a support and a back coat film is provided on the other surface side, the surface roughness (center line average roughness) of both surfaces of the magnetic tape. The magnetic tape is characterized in that the surface roughness Ra) satisfies the following formula: surface roughness in the longitudinal direction (center line average roughness Ra‖)> surface width in the tape width direction (center line average roughness Ra⊥). 3. The surface roughness (center line average roughness Ra) of the surface of the back coat film satisfies 1.5 × Ra⊥ <Ra‖ <10 × Ra⊥. Magnetic tape. 4. The Ra / | on the surface of the back coat film is from 0.2 to.
It is 200 nm and Ra⊥ is 0.1-100 nm, The magnetic tape in any one of the Claims 1-3 characterized by the above-mentioned. 5. The magnetic tape according to claim 1, wherein the back coat film is of a metal film type. 6. The Ra of the metal magnetic film side surface is 0.2 to 2
The magnetic tape according to claim 2, wherein the magnetic tape has a thickness of 00 nm and a Ra⊥ of 0.1 to 100 nm.