JPH0430322A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability of the medium by incorporating a specific compd. into a magnetic layer, thereby well holding this compd. in the magnetic layer and maintaining the effect as a lubricant over a long period of time. CONSTITUTION:The compd. expressed by formula I (where X is an arom. group or alicyclic hydrocarbon group; R<1>, R<2> are 7 to 31C carbon-contg. group which may be the same group or the groups different from each other) is incorporated into the magnetic layer. The bivalent group: X existing in the dicarboxylic part of this compd. as aliphat. acid ester (dicarboxylate) consists of the arom. group or the alicyclic hydrocarbon group and, therefore, this X part is well held in the magnetic layer and the leaching to the surface hardly arises. The magnetic layer is thus strong to rubbing by a head, etc. Consequently, the effect as the lubricant is maintained over a long period of time and the durability thereof is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to magnetic recording media, such as magnetic disks and magnetic tapes.

BACKGROUND ART Conventionally, as a disk-shaped magnetic recording medium for still videos, computers, etc., there has been a magnetic recording medium in which a magnetic layer in which ferromagnetic alloy powder is dispersed in a binder is coated on a non-magnetic support. It is used. Recently, as the density and S/N of such magnetic recording media have increased, magnetic materials have been made into finer particles. Problems such as an increase in trombe out (Dlo), hend clogging, and a decrease in durability occur.

Furthermore, since the ferromagnetic alloy powder originally does not have very good dispersibility in the binder, it is actually difficult to obtain the expected electromagnetic conversion characteristics.

As a countermeasure against this, various lubricants are added to the magnetic layer, but with conventional lubricants, they leach onto the surface of the magnetic layer and cause roll stains during calendering, which reduces the durability of the magnetic layer. Electromagnetic conversion characteristics also deteriorate.

C.9 Purpose of the Invention An object of the present invention is to provide a magnetic recording medium that can prevent lubricant from seeping onto the surface of the magnetic layer and can achieve high electromagnetic conversion characteristics.

29. Constitution of the invention, that is, the present invention, has the following general formula: % formula % (However, X is an aromatic group or an alicyclic hydrocarbon group.R
1, R2 is a carbon-containing group having 7 to 31 carbon atoms,
They may be the same group or different groups. ) This relates to a magnetic recording medium in which the magnetic layer contains a compound represented by the following.

According to the magnetic recording medium of the present invention, a major feature is that the magnetic layer contains the above-mentioned compound. Group: Since X consists of an aromatic group or an alicyclic hydrocarbon group (however, these groups may have a substituent), this part of It has been found that the above-mentioned leaching to the surface is less likely to occur, and it is more resistant to rubbing by a head or the like. As a result, the effect as a lubricant lasts for a long period of time, which is extremely advantageous in improving the durability of magnetic disk media, which particularly requires severe durability. Further, even when producing media by calendering, the calendar rolls are not stained and the production is facilitated.

-COOR"), the lubricity is better than that of ordinary monocarboenoic acid esters. In the fatty acid ester of the present invention, R1 and R2 can be an alkyl group or an alkenyl group. The number of carbon atoms is preferably 11 to 21.

Moreover, the above-mentioned X may be a phenyl group or a cycloalkane such as cyclobenene-4-cyclohexane.

The amount of the fatty acid ester added is preferably 0.5 to 10.0 parts by weight, more preferably 1.0 to 5.0 parts by weight, per 100 parts by weight of the magnetic powder.

Note that other lubricants can also be used in combination with the fatty acid ester described above. Other such lubricants include
Examples include silicone oil, graphite, molybdenum disulfide, tungsten disulfide, and basic fatty acids (eg, stearic acid).

Magnetic powder used in the magnetic layer of the magnetic recording medium of the present invention,
In particular, ferromagnetic powders include 7 Feze3, Co-containing r-Fe, O+, Fe50. , Co-containing Fe: +0
Iron oxide magnetic powder such as 4; Fe, Ni, Co, Fe-Af system, Fe-Af-Ni system, Fe-AlCo system, Fe-
Af-Zn system, Fe-A/2Ca system, Fe-Ni-Co
system, Fe-Mn-Zn system, Fe-Ni system, Fe-N1-
Aff system, FeNi-Zn system, Fe-Co-N 1-
Cr-based, Fe-Co-N1-P-based, Co-Ni-based, etc., F
Examples include ferromagnetic powders such as metal magnetic powders containing e.g., Ni, Co, etc. as main components.

The magnetic powder preferably has a specific surface area (BET value) of 40 rrf/g or more. In particular, by using the above-mentioned ferromagnetic alloy powder having a specific surface area (BET value) of 42 rrf/g or more, the electromagnetic conversion characteristics are greatly improved.

In addition, the coercive force (coercive force) of ferromagnetic metal powder is usually 1
0000e or more (preferably 12000e or more).

Further, there is no particular restriction on the shape of the magnetic powder that can be used in the present invention, and for example, acicular, spherical, etc. can be used.

The magnetic layer may contain a vinyl chloride resin, a polyurethane resin, or a polyester resin as a binder, and may also contain a cellulose resin, a phenoxy resin, or a thermoplastic resin or thermosetting resin having a specific usage method. A reactive resin, an electron beam curable resin, etc. may be used in combination.

These binders include -3O,M, -0SO,M, C0
A negative functional group consisting of 0M, PO(OM')z, -0PO(OM' (where M is hydrogen or an alkali metal such as lithium, potassium, and sodium, and M' is an alkali metal such as hydrogen, lithium, potassium, and sodium). It is preferable to contain one or more groups (hydrophilic polar groups).These polar groups in the molecule improve the compatibility between the resin and the magnetic powder, thereby improving the dispersibility of the magnetic powder. In addition, it is possible to prevent agglomeration of the magnetic powder, thereby further improving the stability of the coating liquid, and in turn, improving the durability of the medium.

Regarding the introduction of the above polar group into polyurethane,
JP 5B-41565, JP 57-92422, JP 57-92423, JP 59-8127, JP 59
-5423, 59-5424, 62-1219
There are descriptions in publications such as No. 23, and these can also be used in the present invention.

The polyurethane resin improves the abrasion resistance of the magnetic layer and can also impart appropriate flexibility. When a vinyl chloride resin is used in combination with this polyurethane resin, the magnetic powder can be dispersed well and the mechanical strength of the magnetic layer can be improved.

In this case, the weight ratio of the vinyl chloride resin to the polyurethane resin is usually 80:20 to 20:80, preferably 70:30 to 40:60.

Regarding the introduction of polar groups into vinyl chloride resin,
JP-A-57-44227, JP-A No. 58-108052,
No. 59-8127, No. 60-101161, No. 60
-235814, 60-238306, 60-
No. 238371, No. 62-121923, No. 62-1
There are descriptions in publications such as No. 46432 and No. 62-146433, and these can also be used in the present invention.

In addition, non-magnetic abrasive particles other than those mentioned above may be added to the magnetic layer, such as alumina (αAI!z Os
(corundum, etc.), artificial corundum, fused alumina,
Silicon carbide, diamond, αFezes (hematite, artificial diamond, garnet, emery (main ingredients:
corundum and magnetite), etc. An antistatic agent such as carbon black, and a dispersant such as oleic acid or lecithin may be added to the magnetic layer.

The magnetic recording medium of the present invention, for example, a floppy disk, includes:
For example, as shown at 10 in FIG. 1, a magnetic layer 24 is provided on the screen of a non-magnetic support 21 via an intermediate layer 22 if necessary. If necessary, add an overcoat layer (
(not shown) may be provided on the magnetic layer.

The dry film thickness of the magnetic layer 24 is preferably 0.5 to 4.5 μm, and even more preferably 3.0 to 4.0 μm.

When providing the intermediate layer 22 under the magnetic layer, an undercoat layer may be formed by coating the various binders described above. This intermediate layer is provided as an adhesive layer or an undercoat layer for the purpose of improving the adhesiveness between the magnetic layer and the support and improving the electrical conductivity.

The material for the support 21 may include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and hycellulose diacetate, and plastics such as polycarbonate. can be mentioned. Furthermore, Cu,
Non-magnetic metals such as Al and Zn, glass, so-called new ceramics, etc. can also be used.

The thickness of the support formed using these materials is usually 1
It is within the range of 0 to 80 μm.

A magnetic layer is provided on at least one surface of the support, but usually the other surface also has a magnetic layer as described above. By providing magnetic layers on both sides in this manner, deformation (curling) of the magnetic disk can be effectively prevented. However, it is also possible to prevent curling by providing a hack coat layer on the back side.

Further, the magnetic recording medium of the present invention, for example as a magnetic tape, has a magnetic layer 24 on a non-magnetic support 21 such as polyethylene terephthalate, as shown in FIG. This is a structure in which a BC layer 23 is provided on the opposite surface.

The present invention may be applied to magnetic disks such as video floppies and data floppies for electronic still cameras, magnetic tapes, magnetic cards, and the like.

E, Example The present invention will be explained in detail below.

The components, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention.

The ingredients shown below are thoroughly kneaded and dispersed using a disper kneader and a ball mill, and then, immediately before application, a polyisocyanate compound (coronate) is added to the Nippon Polyurethane
Magnetic Paint CI] was prepared by adding and mixing 5 parts of Magnetic Paint CI).

100 parts by weight of Kozuki iron-aluminum ferromagnetic alloy powder (aluminum content = 4% by weight, specific surface area: 47 bo/g, coercive force (Hc): 12500e) 6 parts by weight of polyurethane resin (Toyo Boseki Co., Ltd.: U R-8200, containing SO3Na groups) Vinyl chloride copolymer 10 parts by weight (Nippon Zeon Co., Ltd.: MR110, containing 13O, Ni groups) Alumina oxide A12ch 10 parts by weight (
Average particle size: 20.4 μm) Carbon blank: 0.5 parts by weight (
Average particle diameter: 55 nm, BET specific surface area = 32 bo/g, DBP oil absorption: 180 d/100 g) Oleic acid 1 part by weight Lubricant [A]
(Things shown below) 1 part by weight cyclohexanone 100 parts by weight Methyl ethyl ketone 100 parts by weight Toluene
100 parts by weight of the obtained magnetic paint was filtered to remove poorly dispersed components, and coated on both sides of a polyethylene terephthalate film (thickness: 32 μm) using a reverse roll coater so that the dry thickness of each layer was 3.5 μm. After the solvent was removed under heating, a calendering process was carried out, followed by heat curing for the polyisocyanate compound.

After heating and curing, it was punched out into a disk shape of 2 inches in diameter and placed in a cassette to produce an electronic still video floppy.

Lubricant: Lubricant: C1? H3SCOO-(CHz) 3 CHI (A
-32) CI ff H3S COOCH9-COOC
+tHps (A) For each video floppy that was obtained at 33:1 or higher, the following performance evaluation was conducted and the results are shown in Table 1 below.

Durable commercially available electronic still video floppy recorder (AG8
00, manufactured by Matsushita Electric Industrial ■), the image signal is
In the still mode of the electronic still video floppy recorded on all 0 tracks, playback of 4 seconds of each track is continuously repeated from 1 to 50 tracks, and the playback output increases from the initial value to 3D.
The time taken until B decreased or until image quality deterioration such as dropout occurred in the reproduced image was measured. The results are shown in the table below.
Shown in 1.

In the same table, 500 hours or more means that the reproduction output did not decrease by 3 dB and the image quality did not deteriorate even after 500 hours of reproduction.

■Powder blowing refers to a condition in which white powder or oil appears on the surface when visually inspecting the medium after coating. ○ indicates no powder blowing, and × indicates powder blowing.

This refers to the case where black or brown stains are visually visible on the calender heat roll when continuous coating is performed for 3000 m of dirt on the left side.

○ indicates no stain, × indicates presence.

A 7 MHz sine wave signal was recorded using M VP-5500 manufactured by Danryo Kalanii ■, and the reproduced RF output was measured. The measured reproduced RF outputs are listed in Table 1 below as relative values to the gold reference values. The larger the RF specific output value, the better the electronic still video floppy.

(The following margins are continued on the next page.) Table (A) Table (B) From these results, by configuring a disk-shaped medium based on the present invention, it is possible to improve durability and prevent powder blowing on the disk surface. However, it is possible to provide a magnetic disk that can obtain high electromagnetic conversion characteristics and can also perform calendaring well.

1. Effects of the Invention As described above, the present invention contains the above-mentioned specific compound in the magnetic layer, so this compound is well retained in the magnetic layer and hardly leaches to the surface. This allows the lubricant to continue acting as a lubricant for a long period of time, which is very advantageous in improving the durability of the medium. Further, even when producing media by calendering, the calendar rolls are not stained and the production is facilitated.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an example of a disk-shaped medium according to the present invention;
FIG. 2 is a sectional view of an example of a magnetic tape. In addition, in the reference numerals shown in the drawings, 21...Nonmagnetic support 22...Intermediate layer 24...Magnetic layer. Agent Patent Attorney Hiro Osaka Condolence Diagram

Claims (1)

[Claims] 1. General formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, X is an aromatic group or an alicyclic hydrocarbon group, R
^1 and R^2 are carbon-containing groups having 7 to 31 carbon atoms, and may be the same group or different groups. ) A magnetic recording medium in which a magnetic layer contains a compound represented by: