JPH0562163A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic tape, a magnetic disk, and a magnetic drum with improved durability and running property by allowing a magnetic layer to retain phosphoric acid triester when forming a magnetic layer on a non- magnetic support as a magnetic recording medium. CONSTITUTION:After forming a magnetic layer on a support, phosphoric acid triester which is shown by [(RO)m(RfO)3-n]P is retained at it, where R within the expression is a non-saturated fat carbon hydride group, Rf is fluorine substituent alkyl group, and n is an integer ranging from 0 to 3. Concretely speaking, a ferromagnetic metal thin film which is 0.2mum in thickness consisting of Co-Ni- O is formed on polyethylene telephthalate film which is for example 10mum in thickness, it is dipped into a 0.2% freon liquid solution of [(C18H33O)2CF3(CF2)6 CH2-]P, it is dried and then a protection layer is formed, and then it is cut for obtaining a video tape. In this manner, even if the tape is slid on a magnetic head repeatedly, it does not leave the tape easily, a continuous lubrication operation is fully achieved, and a magnetic layer is not worn out or damaged.

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 such as a magnetic tape, a magnetic disc or a magnetic drum having a magnetic layer on a non-magnetic support.

[0002]

2. Description of the Related Art This type of magnetic recording medium is in sliding contact with a magnetic head or the like at a large relative speed during recording and reproduction,
In order to improve durability, it is necessary to improve wear resistance of the magnetic layer, and stable running properties are required for proper recording and reproduction.

In particular, a magnetic recording medium having a ferromagnetic metal thin film type magnetic layer and a coating type magnetic layer containing a metal magnetic powder has a higher magnetic recording medium than an oxide recording medium using an oxide type magnetic powder as a magnetic material. While it has excellent density recording characteristics, it has a large coefficient of friction between the magnetic layer surface and the magnetic head, and the hardness of the magnetic material is low, so the magnetic layer is easily worn and damaged.
Improving durability and runnability is a major issue.

Therefore, in the past, as a lubricity protective layer on the magnetic layer, a film made of a lubricant such as an aliphatic compound such as fatty acid or fatty acid ester, or a fluorine compound such as perfluoroalkyl polyether was used. By forming it, a means for reducing the coefficient of friction on the surface and improving durability and running property is adopted (Japanese Patent Publication No. 56-3060).
No. 9, No. 60-10368, JP-A No. 60-10902.
No. 8, No. 61-11926, etc.).

[0005]

However, in the above-mentioned lubricity protective layer, since the interaction between the lubricant component and the surface of the magnetic layer is weak, the sliding contact with the magnetic head at the time of recording / reproducing results in early magnetic properties. There is a problem that the layer is separated from the surface of the layer, and sufficient durability and runnability cannot be imparted.

In view of the above situation, it is an object of the present invention to provide a magnetic recording medium having excellent durability and runnability.

[0007]

The inventors of the present invention have conducted extensive studies in order to achieve the above object, and as a result, have made a specific phosphorous triester present on the surface or / and inside of the magnetic layer. In this case, the friction coefficient with respect to the magnetic head is remarkably reduced, and even if the phosphorus phosphite triester slides repeatedly on the magnetic head, it does not easily come off and exerts a good lubricating effect continuously, which causes wear of the magnetic layer. The inventors have found that a magnetic recording medium having excellent durability and runnability can be obtained by preventing damage and damage, and have completed the present invention.

That is, the present invention provides a magnetic recording medium having a magnetic layer on a non-magnetic support, wherein the above-mentioned magnetic layer has the following general formula (I): [(RO) _n (R _f O) _{3 -n} ] P ... (I) (wherein R is an unsaturated aliphatic hydrocarbon group, R _f is a fluorine-substituted alkyl group, and n is an integer of 0 to 3) The present invention relates to a magnetic recording medium characterized in that

[0009]

The phosphite triester used in the present invention has an excellent lubricating action and a strong adsorptivity to the magnetic layer, and even if the magnetic layer holding it has repeatedly slidably contacted the magnetic head. It is difficult to separate, and the above lubricating action is continuously exerted over a long period of time to prevent abrasion and damage of the magnetic layer, so that the running property and durability of the magnetic recording medium are remarkably improved.

Such phosphite triesters are represented by the above-mentioned general formula (I), and n in the above formula is 0 or 3 (that is, all three groups are unsaturated as shown by R above). An aliphatic hydrocarbon group or a fluorine-substituted alkyl group represented by R _f above), where n in the above formula is 1
Or those having 2 (that is, those having both the groups represented by R and R _f above) are particularly preferable.

That is, the fluorine-substituted alkyl group described above exerts an excellent lubricating action by the fluorine atom, while the unsaturated aliphatic hydrocarbon group lowers the freezing point of the phosphorous triester to lower the temperature of the magnetic recording medium. The form containing both of these groups is the most preferable because it has the effect of making the running property particularly good.

The unsaturated aliphatic hydrocarbon group represented by R preferably has about 6 to 20 carbon atoms, and the fluorine-substituted alkyl group represented by R _f preferably has about 4 to 10 carbon atoms.

The magnetic recording medium of the present invention has a coating-type magnetic layer formed by coating a non-magnetic support with a magnetic coating material containing an oxide-based magnetic powder or metal magnetic powder and a binder and drying the coating. And a ferromagnetic metal thin film type magnetic layer formed by depositing a ferromagnetic metal on a non-magnetic support by means such as vacuum deposition, ion plating, sputtering, and plating. The phosphorous acid triester is usually applied to the surface of the magnetic layer as a protective layer, but when the magnetic layer is of a coating type, it can be contained inside the surface of the magnetic layer. It may be held in both.

A general phosphoric acid ester compound, which has been widely used for forming a pressure resistant film on a magnetic layer, is gradually hydrolyzed, and a strong acid generated causes a metal of a magnetic material to be formed. There was a problem of corroding and thermal decomposition. However, the above-mentioned phosphite triester used in the present invention can form a strong protective film on the magnetic layer without the above-mentioned problems of corrosion and thermal decomposition. The applicability to the magnetic layer and the ferromagnetic metal thin film type magnetic layer is great.

To form a protective layer of phosphite triester on the surface of the magnetic layer, the phosphite triester is dissolved in a suitable solvent such as Freon, and the magnetic layer is dipped in this solution and dried. Alternatively, this solution may be applied or sprayed on the surface of the magnetic layer and dried to form a film. Further, in order to contain the above-mentioned phosphorous acid triester in the coating type magnetic layer, the above-mentioned phosphorous acid triester may be blended in the magnetic paint used for forming this magnetic layer. The amount of the phosphite triester retained in the magnetic layer is preferably about 0.5 to 50.0 mg / m ^2, and if it is too small, the desired action and effect will not be fully exhibited, and conversely, it will be large. If it is too much, it may cause a drop in output of the magnetic recording medium or dropout.

The metal magnetic powder contained in the coating type magnetic layer includes Fe powder, Co powder, Fe-Co alloy powder, Fe-Ni alloy powder, Fe-Co-Ni alloy powder and the like. As the oxide-based magnetic powder, γ-Fe ₂ O
₃ powder, Fe ₃ O ₄ powder, Co-containing γ-Fe ₂ O ₃ powder, Co-containing Fe ₃ O ₄ powder, CrO ₂ powder, Ba ferrite powder and the like. The ferromagnetic metals used for the ferromagnetic metal thin film type magnetic layer include Fe, Co, Ni, and C.
o-Ni alloy, Co-Cr alloy, Co-P alloy, Co-
There are Ni-P alloys and the like.

As the binder in the coating type magnetic layer, for example, vinyl chloride resin, fibrin resin, polyurethane resin, acetal resin, butyral resin, polyester resin, radiation curable resin A low molecular weight polyisocyanate compound as a cross-linking agent is used. In addition, various additives such as an abrasive, a lubricant, an antistatic agent, a dispersant, a filler, and a coloring agent may be appropriately added to the coating-type magnetic layer, if necessary.

The types of magnetic recording medium to which the present invention is applied include magnetic tape having a synthetic resin film such as polyester film as a base, magnetic disk having a disk as a base, and magnetic drum having a drum as a base. It includes various forms that are in sliding contact with the magnetic head during reproduction.

[0019]

In the magnetic recording medium according to the present invention, the specific phosphite triester retained in the magnetic layer does not easily come off even when repeatedly slidingly contacted with the magnetic head at the time of recording / reproducing, and has a continuous excellent lubricating action. As a result, the friction of the sliding contact portion is small, the wear and damage of the magnetic layer are unlikely to occur, and excellent durability and running performance are exhibited.

[0020]

EXAMPLES Next, examples of the present invention will be specifically described in comparison with comparative examples. In the following, parts and% mean parts by weight and% by weight, respectively.

Example 1 A polyethylene terephthalate film having a thickness of 10 μm was placed in a vacuum vapor deposition apparatus and a Co—Ni alloy (Co: Ni = 80: 2) was used in an atmosphere of an oxygen gas pressure of 5 × 10 ⁻⁵ torr.
0) is evaporated by heating and vapor-deposited obliquely on the film to form Co—Ni—O having a thickness of 0.2 μm.
m ferromagnetic metal thin film was formed.

Next, this was converted into [(C ₁₈ H ₃₃ O) ₂ CF
₃ (CF ₂ ) ₆ CH ₂ O] P (dinoylyl monopentadecafluorooctyl phosphite) was dipped in a 0.2% freon solution, dried to form a protective layer, and then cut into 8 mm width. Then, a video tape was produced.

EXAMPLE 2 [CF ₃ (CF ₂ ) ₆ CH was used as the phosphorous acid triester.
_A video tape was produced in the same manner as in Example 1 except that ₂ O] ₃ P (tripentadecafluorooctyl phosphite) was used.

Example 3 A video tape was prepared in the same manner as in Example 1 except that (C ₁₈ H ₃₃ O) ₃ P (trilinoleyl phosphite) was used as the phosphite triester.

Example 4 α-Fe magnetic powder (average major axis diameter 0.2 μm, average axis ratio 10) 80 parts Vinyl chloride resin (trade name MR-110 manufactured by Zeon Corporation) 12 parts Polyurethane resin (Japan Polyurethane) Kogyo Co., Ltd., trade name N-2309) 4 parts Trifunctional low molecular weight isocyanate compound 2 parts (Nippon Polyurethane Industry Co., Ltd. trade name Coroneto L) Cyclohexanone 65 parts Toluene 65 parts

A magnetic paint was prepared by mixing and dispersing the above composition in a ball mill for 100 hours.
A magnetic layer was formed by coating on a polyethylene terephthalate film having a thickness of 3 μm so that the thickness after drying was 3 μm, and dried to form a magnetic layer on the magnetic layer in the same manner as in Example 1. After forming the protective layer, it was cut into a width of 8 mm to prepare a video tape.

Comparative Example 1 A ferromagnetic metal thin film was formed in the same manner as in Example 1, and this was immersed in a 0.2% isopropyl alcohol solution of stearic acid and dried to form a protective layer. A video tape was produced by cutting into a width of 8 mm.

Comparative Example 2 A ferromagnetic metal thin film was formed in the same manner as in Example 1, and 0.2% Freon of perfluoroalkylpolyether (Fuombrin Z-DOL, trade name, manufactured by Ikuten Montefluos Co., Ltd.) was used. After dipping in a solution and drying to form a protective layer, it was cut into a width of 8 mm to prepare a video tape.

Comparative Example 3 A ferromagnetic metal thin film was formed in the same manner as in Example 1, and the thin film was formed of (C ₁₈ H ₃₇ O) ₃ P (tristearyl phosphite).
It was dipped in a 2% isopropyl alcohol solution, dried to form a protective layer, and cut into 8 mm width to prepare a video tape.

Comparative Example 4 A magnetic layer was formed in the same manner as in Example 4, and this was used as Comparative Example 3.
After immersing in the same isopropyl alcohol solution as above and drying to form a topcoat layer, it was cut into a width of 8 mm to prepare a video tape.

With respect to each of the video tapes of Examples 1 to 4 and Comparative Examples 1 to 4 described above, the coefficient of friction, the jitter characteristic and the actual running durability were measured in the following manner. The results of these measurements are shown in Table 1 below.

<Friction coefficient> Surface roughness 0.2 s, outer diameter 4 mm
A video tape was wrapped around the cylindrical pin of No. 1 at a wrap angle of 150 degrees, a load of 21 g was applied, and the same portion was repeatedly fed at a feed rate of 1.4 cm / sec, and the friction coefficient at the 100th feed was measured.

<Jitter characteristics> A video tape is mounted on the video deck, the video signal is recorded and reproduced, and the interval of the horizontal synchronizing signal of 15.75 KHz at the time of reproduction is read.
The deviation of the interval of the horizontal synchronizing signal in the second was measured.

<Actual Running Durability> A video tape was mounted on a video deck, a video signal was recorded, and running was repeated in a playing state, and the number of running times until the playback output was reduced by 3 dB from the expected value was measured. ..

[0035]

[Table 1]

Next, each of the video tapes of Examples 1 to 4 and Comparative Examples 1 to 4 was tested for 8-mode sheer durability. Test method is 13m of recorded tape
And select "Fast forward → Fast forward search → Rewind search"
CH → (play) pose → fast-forward search → (record) pose →
A series of operations "fast forward → rewind" is repeated as one pass, and the reproduction output is measured every 100 passes, 200 passes, 300 passes, 400 passes, 500 passes, and the output reduction value with respect to the initial output I checked. The results are shown in Table 2 below.

[0037]

[Table 2]

From the results of Tables 1 and 2, the video tape of the present invention (Examples 1 to 1) provided with a protective layer of a phosphorous acid triester having an unsaturated aliphatic hydrocarbon group or a fluorine-substituted alkyl group. 4) is a video tape having a protective layer of a conventional general lubricant (Comparative Examples 1 and 2) and a video tape having a protective layer of phosphite triester different from that of the present invention (Comparison). Compared to Examples 3 and 4), the friction coefficient and jitter are small, the actual running durability is very good, and the 8-mode shuttle durability is remarkably good, and the running property and durability are extremely excellent. it is obvious.

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer on a non-magnetic support, wherein the magnetic layer has the following general formula (I); [(RO) _n (R _f O) _3-n ] P (I) (wherein R is an unsaturated aliphatic hydrocarbon group, R _f is a fluorine-substituted alkyl group, and n is an integer of 0 to 3) and a phosphite triester is retained. Magnetic recording medium.