JPH03192516A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve traveling durability and electromagnetic conversion characteristics by incorporating aniline black with carbon black into a magnetic layer. CONSTITUTION:Aniline black is incorporated with carbon black into a magnetic layer. By incorporating aniline black with carbon black into the magnetic layer, such an effect can be obtained that the aniline black suppresses reduction of pH caused by oxide compds. on the surface of carbon black, and thereby, it suppresses reduction in structure. By this method, dispersibility and conductivity of carbon black can be improved, and traveling property and electromagnetic conversion characteristics of the medium can be adequately improved. It is preferable that the carbon black used has BET specific surface area between >=100 m<2>/g and <300 m<2>/g, and <160 ml/100 g DBP oil absorption. Since this type of carbon black disperses well in a magnetic coating material, the obtd. medium has little noise and is suitable for high density recording.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium with excellent running durability and electromagnetic conversion characteristics.

[Conventional technology]

Magnetic recording media are usually made by coating magnetic powder on a substrate such as a polyester film along with a binder resin. In order to reduce the frictional resistance of the magnetic layer and to reduce electrical resistance and prevent charging, Generally, carbon black is incorporated into the magnetic layer. (Unexamined Japanese Patent Publication No. 59-
No. 16141, JP-A No. 58-211321, JP-A-Sho 5
(No. 8-218039, Japanese Patent Publication No. 53-20203, Japanese Patent Publication No. 54-9041, Japanese Patent Publication No. 57-4968) [Problems to be Solved by the Invention] However, this type of conventionally used carbon black, It is difficult to disperse in a stracture structure, and the dispersibility varies depending on the type of binder resin used, and the dispersibility in polyurethane resins is particularly poor.

For this reason, it is necessary to increase the dispersion time of carbon black,
It is also possible to improve the dispersibility of carbon black by reducing the carbon black content, but if the dispersion time of carbon black is increased, the magnetic powder in the dispersion is often damaged ( This not only does not improve the electromagnetic conversion characteristics of the magnetic recording medium, but also causes the problem that the magnetic powder becomes over-fractionated due to long-term dispersion and re-agglomerates in the magnetic paint. If it is not introduced, good conductivity will not be obtained and durability will also decrease.

[Means to solve the problem]

This invention was made as a result of various studies to solve this problem, and by incorporating aniline black in combination with carbon black into the magnetic layer, the dispersibility of carbon black is improved and the conductivity is improved. It has good running durability and electromagnetic conversion characteristics.

The aniline black used in this invention is a compound obtained by oxidative condensation of aniline, and when used together with carbon black to contain it in the magnetic layer, the aniline black suppresses the decrease in pH caused by the surface acidic compounds of the carbon black, and suppresses the strafe formation. In order to suppress the decrease in carbon black, the dispersibility of carbon black is improved, the conductivity is improved, and the running durability and electromagnetic conversion characteristics are sufficiently improved.

Further, carbon black used in combination with aniline black is not particularly limited, but has a specific surface area of 100 r in BET value.
rr/g or more and less than 300rrf/g, and the oil absorption is 160mI in DBP value! , /100g is preferably used. Since this type of carbon black is well dispersed in the magnetic paint, noise can be sufficiently reduced and high-density recording can be performed satisfactorily. Therefore, the chroma S/N and lumi S/N can be sufficiently improved, and the surface resistivity of the magnetic layer can be lowered,
In addition to suppressing the occurrence of dropouts, the friction coefficient of the magnetic layer can be lowered to sufficiently improve running durability. In particular, it is possible to reduce the decrease in output during running at high temperatures, and it is also possible to reduce calendar stains and head clogging.

Specific examples of such carbon blacks include, for example, manufactured by Columbia Carbon Co., Ltd.; Raben 1035, Raben 1255, Raben 1000, Raben 2000,
Manufactured by Cabot; Black Pearl Zoo L1 Black Burls 1000, Black Pearls 900, Monarch 80
0, manufactured by Mitsubishi Kasei Corporation, CF-9, etc.

In order to improve the dispersibility of carbon black and sufficiently improve electromagnetic conversion characteristics and running durability, the mixing ratio of aniline black and carbon black used together in this way is determined by the weight ratio of aniline black to carbon black. It is preferable that the ratio is within the range of 1:10 to 4:10. The amount of aniline black and carbon black blended within this range should be 20 parts by weight or less per 100 parts by weight of magnetic powder in total, and 0.1 to 100 parts by weight per 100 parts by weight of magnetic powder. It is preferable that the amount is 6 parts by weight; if the amount added is small, the antistatic effect will decrease.
On the other hand, if the amount is too large, the degree of filling of the magnetic powder in the magnetic layer decreases, the surface properties of the magnetic layer deteriorate, and the electromagnetic conversion characteristics deteriorate.

In order to incorporate such aniline black and carbon black into the magnetic layer, it may be carried out according to a conventional method. A magnetic paint may be prepared by mixing and dispersing the necessary components, and this magnetic paint may be applied onto a substrate such as a polyester film by any means such as roll coating, and dried.

Here, as the magnetic powder, 1-Fe, O, powder, Fe
, O, powder, CO-containing 1-Fe, 0. Powder, Co-containing F
e, O, powder, Cry, powder, Fe powder, Co powder, F
Various conventionally known magnetic powders such as e-Ni powder and barium ferrite powder are widely used.

In addition, binder resins include vinyl chloride-vinyl acetate copolymers, cellulose resins, polyvinyl butyral resins, urethane resins, polyester resins, epoxy resins, OH groups, 000H groups, NH groups in molecules, etc. Any of those commonly used in magnetic recording media can be used, such as acrylic acid resins and isocyanate compounds having functional groups that are reactive with epoxy groups such as SH groups and SH groups.

The organic solvents are particularly limited to those suitable for dissolving the binder resin used, such as cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, benzene, toluene, xylene, dimethyl sulfoxide, tetrahydrofuran, dioxane, etc. They can be used alone or in a mixture of two or more.

Note that various commonly used additives such as dispersants, abrasives, lubricants, etc. may be appropriately added to the magnetic paint.

〔Example〕

Next, embodiments of the invention will be described.

Example I Co-containing r Feze3 B00 parts by weight hinyl chloride-vinyl acetate-90 maleic anhydride copolymer (manufactured by Nippon Zeon Co., Ltd.; 400X110A) Polyurethane resin (manufactured by Nippon Zeon Co., Ltd.; 400X110A) Carbon black (manufactured by Nippon Zeon Co., Ltd., N-2304) BET ratio surface 40 square footage 140
dlg, oil absorption 114mf/100g) Aniline black 10 (average particle size 0.5 μm) Alumina (average particle size 0.7 μ”) 15 // Valmitic acid 8 Stearic acid -
n-Butyl 8 Methyl ethyl ketone 800 Toluene
800 After mixing and dispersing the above composition in a ball mill for 80 hours, 5 parts by weight of a polyfunctional isocyanate compound (Coronet L, manufactured by Nippon Polyurethane Industries, Ltd.) was further added and mixed and dispersed to prepare a magnetic paint. This magnetic paint was applied onto a 14 μm thick polyester film to a dry thickness of 5 μm, mirror-finished, and then cut to a predetermined width to produce a magnetic tape.

Example 2 In the composition of the magnetic paint in Example 1, vinyl chloride-vinyl acetate-maleic anhydride copolymer was replaced with vinyl chloride resin (manufactured by Nippon Zeon Co., Ltd.: MR-110, molecular weight:
11000, epoxy group: 8.14X 10-' equivalent/
A magnetic tape was produced in the same manner as in Example 1, except that the same amounts of hydroxyl group: 4.11X 10-' equivalent/g and sulfonic acid group: 5.82X 10-' equivalent/g were used.

Example 3 In the composition of the magnetic paint in Example 1, the BET specific surface area was 140 rrf/g, and the oil absorption amount was 114 mJ2/100 g.
Instead of carbon black, BET specific surface area 35M/
g, carbon black manufactured by Cabot with an oil absorption capacity of 91 mA/100 g; except that the same amount of Sfuring V was used.
A magnetic tape was produced in the same manner as in Example 1.

Example 4 In the composition of the magnetic paint in Example 1, the BET specific surface area was 140rrf/g and the oil absorption amount was 114mj! /100g
Instead of carbon black, BET specific surface area is 250 bo/g and oil absorption is 170 mj! /100g Colombian
A magnetic tape was produced in the same manner as in Example 1, except that the same amount of carbon black C-975 manufactured by Carbon Co., Ltd. was used.

Example 5 In the composition of the magnetic paint in Example 1, the same amount of barium ferrite (average particle size 0.09 μm, average thickness 0.0075 pm, average plate ratio 12) was used instead of CO-containing -Feze3. A magnetic tape was produced in the same manner as in Example 1.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1 except that aniline black was omitted from the composition of the magnetic paint in Example 1.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 2, except that aniline black was omitted from the composition of the magnetic paint in Example 2.

Comparative Example 3 A magnetic tape was produced in the same manner as in Example 3 except that aniline black was omitted from the composition of the magnetic paint in Example 3.

Comparative Example 4 A magnetic tape was produced in the same manner as in Example 4, except that aniline black was omitted from the composition of the magnetic paint in Example 4.

Comparative Example 5 A magnetic tape was produced in the same manner as in Example 5, except that aniline black was omitted and the amount of carbon black used was changed from 40 parts by weight to 100 parts by weight in the composition of the magnetic paint in Example 5.

Comparative Example 6 A magnetic tape was produced in the same manner as in Example 5 except that aniline black was omitted and the amount of carbon black was changed from 40 parts by weight to 5 parts by weight in the composition of the magnetic paint in Example 5.

Regarding the magnetic tapes obtained in each example and comparative example,
Still durability, lumi S/N, chroma S/N, and electrical resistance of the magnetic layer surface were tested and measured using the following methods. Also,
In order to examine running durability, RF output reduction and powder falling were tested and measured using the following method.

Steel Durability〉 The obtained magnetic tape is incorporated into a VHS cassette to create a VTR that is a partially improved version of Hitachi's Massfuchs Z-70.
A certain video signal was recorded and played back using the deck, and the time until the playback output of a still image decreased by 2 dB was measured.

<RF output reduction> Record a 4 MHz signal, use a VTR deck for RF output measurement, and heat the resulting magnetic tape at room temperature for 20 minutes.
Recording and reproduction were repeated 0 times, and the difference between the RF output at the first time and the RF output after 200 times was examined.

Dust removal> Using Hitachi's MassFux Z-70, the obtained magnetic tape was recorded and played 200 times at room temperature, and the dirt on the magnetic tape running part inside the deck was visually observed. The evaluation was rated as (O) when no stains were observed, (△) when faint stains were observed, and (×) when stains were clearly observed.

<Lumi S/N> Using a noise meter made by Shibatsu Co., Ltd. as a measuring instrument, the bypass filter was measured at 4.2 MH2 and the low-pass filter was measured at 10 KHz. Examples 1 to 4 and Comparative Examples 1 to
4 is expressed using Example 1 as a standard (OdB), and Example 5 and Comparative Examples 5 to 6 are expressed using Example 5 as a standard (OdB), and is expressed as a comparative value with respect thereto.

<Chroma S/N> Record the chroma signal on the obtained magnetic tape, measure the noise part of the reproduced signal using an RF output measurement deck,
Examples 1 to 4 and Comparative Examples 1 to 4 are based on Example 1 (O
dB), and Example 5 and Comparative Examples 5 and 6 are expressed as comparative values with respect to Example 5 as a standard (odd).

Electrical Resistance> Two rod-shaped metal electrodes whose cross section is a quarter of a circle with a radius of 1 cm are separated by 81 cm, and the magnetic layer surface of the magnetic tape is placed in contact with these electrodes at right angles. Suspend weights of 50 g each from both ends of the
A measurement voltage of v was applied to these electrodes, the resistance value was measured, and the electrical resistance of the surface of the magnetic layer was investigated.

Table 1 below shows the results.

Table 1 [Effects of the Invention] As is clear from Table 1 above, the magnetic tapes obtained in Example Processes to 5 have better still durability and RF output decrease, powder falling,
Lumi S/N and chroma S/N are both good, and the surface electrical resistance of the magnetic layer is small. Therefore, the magnetic recording medium obtained by this invention has good electrical conductivity, and is excellent in durability and electromagnetic conversion characteristics. It can be seen that

Claims (1)

[Claims] 1. A magnetic recording medium characterized in that the magnetic layer contains aniline black together with carbon black. 2. The carbon black has a specific surface area of 100 in BET value.
Less than m^2/g and oil absorption amount is 160ml in DBP value
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is carbon black of less than /100g.