JPS63263630A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium with which high output and high S/N are obtd. by increasing the squareness ratio of a magnetic layer to >=0.82 and specifying the surface roughness thereof to <=0.013mum. CONSTITUTION:The magnetic layer 2 is formed on a base 1 consisting of Al, glass, etc., and a back coat layer 3 is formed on the rear face thereof. The magnetic layer 2 contains carbon black, lubricant (Si oil) and antistatic agent (graphite) in addition to ferromagnetic powder such as gamma-Fe2O3. A polishing material having <=0.4mum average grain size may otherwise be incorporated therein at <=20pts.wt. of the magnetic powder. Polyurethane and phenoxy resin and/or vinyl chloride copolymer are incorporated as a binder resin into this powder to improve the dispersibility of the magnetic powder and to increase the mechanical strength thereof. The binder resin used in the magnetic layer 2 is also used for the layer 3 and SrO2 particles are added thereto. The magnetic powder is treated with Al or Al compd. to improve the dispersibility. Good electromagnetic conversion characteristics are obtd. and running performance and running durability are improved if the squareness ratio is increased to >=0.82 and the surface roughness is kept at 0.01-0.013mum according to this constitution.

Description

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

BACKGROUND OF THE INVENTION Generally, magnetic recording media such as magnetic tapes are manufactured by applying a magnetic paint made of magnetic powder, binder resin, etc. onto a support and drying it.

In these magnetic recording media, especially video tapes,
A technique for increasing the specific surface area (BET value) of magnetic powder is known for high-density recording.

However, as the specific surface area increases, the magnetic powder becomes finer, so the squareness ratio (residual magnetic flux density/
It is inevitable that the saturation magnetic flux density will decrease and the electromagnetic conversion characteristics such as output will deteriorate. Moreover, when the specific surface area is increased,
The surface roughness of the magnetic layer is reduced, making it easier to achieve a smooth surface, but it requires processing to achieve such surface properties (dispersion of magnetic powder, etc.), which does not improve productivity.
A problem arises in that the running durability is rather deteriorated.

OBJECT OF THE INVENTION An object of the present invention is to provide a magnetic recording medium that not only provides high output and high S/N, but also has good productivity and excellent durability.

26. Structure of the invention and its effects, ie, 11. The present invention relates to a magnetic recording medium having a magnetic layer having a squareness ratio of 0.82 or more and an average surface roughness of 0.013 μm or less.

According to the present invention, attention is paid to the squareness ratio of the magnetic layer, and based on the recognition that this greatly influences the important electromagnetic conversion characteristic, especially the residual magnetic flux density, the squareness ratio is set to 0.82 or more, which is the conventional value ( (usually less than 0.81). With this squareness ratio, the residual magnetic flux density can be increased especially to 1500G.
auss or higher, and it becomes possible to solve the above-mentioned problems. In other words, the combined output, S
/N etc. can be improved. This squareness ratio is 0.8
It should be 2 or more, but more preferably 0.83 or more.

In addition to this, in the present invention, the average surface roughness R of the magnetic layer is
a) (Average roughness or height of center line of surface unevenness) to 0.0
Although it is limited to 13 μm or less and includes cases where the surface is relatively rough, good electromagnetic conversion characteristics are maintained even with such surface roughness, and at the same time, a relatively rough surface improves running performance and driving performance. It was found that the durability was improved. Moreover, Ra may be relatively large (0,013μ
m or less), the surface properties of the magnetic layer do not need to be so strict, and the productivity of the medium is improved accordingly. This Ra is 0.
It should be less than 0.01311m, but furthermore 0.010~
0.013 is good, lower limit is o, oos, or 0.0
It may be set as 08.

Just go. In addition, if the magnetic powder is surface-treated in advance, for example with aluminum or an aluminum compound, the dispersibility (and corrosion resistance) of the magnetic powder will improve, resulting in a high residual magnetic flux density (in other words, a high square shape). ratio) can be obtained. In particular, even if a magnetic powder with a large specific surface area is used, the above-mentioned pre-dispersion technology and surface treatment technology will result in good dispersion, and this can be utilized to achieve the squareness ratio of the present invention. .

The magnetic recording medium of the present invention has, for example, as shown in FIG.
A magnetic layer 2 is provided on a support 1. Further, an 80 layer 3 is provided on the opposite side of the magnetic layer 2. Although this BC layer may be provided, it is not necessary to provide it. The magnetic powder used for the magnetic layer 2, especially the ferromagnetic powder, is γ-Fe.
203, co-containing r-Fe203, Fe 304, C
Iron oxide magnetic powder such as Fe 304 containing o: Fe, Ni
s 00% Fe-Ni-Co alloy, Fe-Mn-Zn
Alloy, Fe-M1-Zn alloy, F, e-Co-
'Ni-Cr alloy, Fe-Go-Ni-P alloy, Go-
Ni alloy etc., Fe.

Metal magnetic powder mainly composed of N1% Co, etc.: cr
Examples include various ferromagnetic powders such as Q2. In addition, magnetic ff2
In addition to the carbon black mentioned above, lubricants (such as silicone oil, graphite, molybdenum disulfide,
Tungsten disulfide, monobasic fatty acids with 12 to 20 carbon atoms (e.g. stearic acid), and monobasic fatty acids with 3 to 4 carbon atoms.
0 fatty acid esters, etc.), antistatic agents (e.g. graphite), etc. may also be added. Non-magnetic abrasive particles may also be added, including alumina (α-AjzO3 (
Corundum), artificial corundum, fused alumina, silicon carbon, chromium oxide, diamond, artificial diamond, garnet, emery (main components: corundum and magnetite), etc. are used. The content of this abrasive material is preferably 20 parts by weight or less based on the magnetic powder, and the average particle diameter is preferably 0.5 μm, more preferably 0.4 μm or less.

Furthermore, at least polyurethane can be used as the binder resin for the magnetic layer, which can be synthesized by reacting polyol and polyisocyanate. If a phenoxy resin and/or a vinyl chloride copolymer is contained together with polyurethane, the dispersibility of the magnetic powder will be improved when applied to a magnetic layer, and its mechanical strength will be increased. However, if only the phenoxy resin and/or vinyl chloride copolymer is used, the layer becomes too hard, but this can be prevented by containing polyurethane, and the adhesion to the support or base layer is improved. In addition to the above, cellulose resins, thermoplastic resins, thermosetting resins, reactive resins, and electron beam curable resins may be used as the binder resin.

Furthermore, the binder resin used for the magnetic layer 2 may be used for the 80 layer 3, and the non-magnetic particles added may also be 5i02.1k.
12203 etc. may be used.

Furthermore, the magnetic recording medium shown in FIG. 1 is one in which an undercoat layer (not shown) is provided between the magnetic layer 2 and the support 1 (
Alternatively, the undercoat layer may not be provided (the same applies hereinafter), or the support may be subjected to corona discharge treatment.

The material of the support 1 may be plastic such as polyethylene terephthalate or polypropylene, AI, or Zn.
Metals such as glass, BN, Si carbide, ceramics such as porcelain and earthenware, etc. are used.

Furthermore, above. When forming the magnetic layer by coating, it is desirable to add a predetermined amount of a polyfunctional isocyanate as a crosslinking agent to the coating material in order to strengthen the magnetic layer. In addition to the polyfunctional polyisocyanates mentioned above, examples of such crosslinking agents include triphenylmethane triisocyanate, tris-(
Preferred are p-isocyanate (phenyl) thiophosphite and polymethylenenate. Note that when the magnetic layer is cured by electron beam irradiation or the like, the addition of the isocyanate compound may be omitted, but it may be added.

FIG. 2 shows other magnetic recording media.
A 6C layer 4 is provided on the magnetic layer 2 of the illustrated medium. This 00 layer 4 is provided to protect the magnetic layer 2 from damage, etc., and for this purpose, it needs to have sufficient slipperiness.

Therefore, as the binder resin for the 00 layer 4, the urethane resin used for the above magnetic F32 is used (preferably in combination with a phenoxy resin and/or a vinyl chloride copolymer). The surface roughness of the 00 layer 46 is particularly related to color S/N: Ra≦0.01 part m, Rmax≦0.13. cr
It is better to set it to m. In this case, the surface roughness of the support 1 is R
It is desirable to set a faO, 011m, Rmax≦0.13 μm, and to use a smooth support 1.

FIG. 3 shows a magnetic recording medium configured as a magnetic disk, in which a magnetic M2.00 similar to that described above is applied to both sides of the support 1.
Layers 4 are provided, and the 00 layer 4 may contain a binder resin containing the above-mentioned urethane resin as a main component.

E, Example Hereinafter, the present invention will be explained with reference to specific examples.

However, in the following, "parts" represent parts by weight.

First, a magnetic paint having the following composition was prepared.

Cor-Fe zo3 (BET35rrr/g)1
00 parts vinyl chloride vinyl acetate copolymer (VAGH: u, c, c, manufactured by Co., Ltd.) 1
0 parts polyurethane (Nistan 5701 manufactured by Gutdrich) 10 parts myristic acid 1 part butyl stearate 1 part alumina
5 part lecithin
3 part carbon black
5-part cyclohexanone
100 parts methyl ethyl ketone 1
00 parts toluene 100
Part This composition was pre-treated with Ni-Goo to pre-disperse the magnetic powder, then thoroughly stirred and mixed in a ball mill, and then mixed with a polyfunctional isocyanate (Coronet manufactured by Nippon Polyurethane Co., Ltd.).
After adding 5 parts of L), the mixture was filtered through a filter with an average pore size of 1 μm. The obtained magnetic paint was applied to the surface of a polyethylene terephthalate (PET) base having a thickness of 14 μm to a dry thickness of 5 μm.

Thereafter, the surface of the magnetic layer was treated with a super calender roll, and the paint for the BCC period with a hot composition was coated on the opposite side of the magnetic layer to a dry thickness of 1 μm.

Carbon black 40 parts Titanium oxide (average particle size 0.4 μm) 10 parts Nitrocellulose 25 parts N-2301 (
Made by Nippon Polyurethane) 25 parts Coronate L ()
10 parts cyclohexanone 400 parts methyl ethyl ketone 250 parts toluene
250 parts A wide magnetic film having a magnetic layer and a BC layer of a predetermined thickness was obtained in this way, and this was wound up.

This film was cut to a length of 12.65 mm to create a magnetic tape for video. The squareness ratio of this tape is 0.82
As mentioned above, the Ra of the magnetic layer was 0.01.

When the squareness ratio and Ra of the tape produced by this method were varied, the results shown in the table below were obtained. However, evaluation items are measured and displayed according to the following standards.

Squareness ratio: Measure the ratio between the residual magnetic flux density and the saturated magnetic flux density of the sample film after coating (without calendering) under a magnetic field of 5k
Measured using VSM at Oe.

Decrease in RF output after running durability test: The tape was recorded and played 200 times at room temperature and humidity.
The output difference of RF ratio output after 200 times of initial RF ratio output is d
BDisplay in small units. + means that the output after 200 times is greater than the RF ratio output at the first reproduction.

4M using a VTR deck for measuring RF output
The RF specific output at Ilz was measured.

Lumi S/N: Measuring device is Shibatsu noise meter
(925D/1), Example Tape 3 was used as a reference tape (OdB), and the difference with respect to the reference tape (OdB) was expressed. Bypass filter is 4.2M) Iz, low pass 74) Lt - 10k Hz i? went. The VTR is JVCHR-
DI20 was used.

Chroma S/N: Same as RF output.

(The following margins are continued on the next page.) From these results, it can be seen that all the tapes based on the present invention have excellent electromagnetic conversion characteristics and good running durability characteristics.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the invention, and FIGS. 1, 2, and 3 are enlarged cross-sectional views of a portion of a magnetic recording medium from each side. In addition, in the symbols used in the drawings, 2...
. . . Magnetic layer 3 . . . Back coat layer (BC layer).

Claims (1)

[Claims] 1. Squareness ratio is 0.82 or more, average surface roughness is 0.013
A magnetic recording medium having a magnetic layer of μm or less.