JPS63168825A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which can realize high-density recording and has excellent corrosion resistance and dispersibility by incorporating specific iron-aluminum magnetic powder and carbon black into a magnetic layer. CONSTITUTION:The iron-aluminum magnetic powder and the carbon black are incorporated into the magnetic layer. The Fe-Al magnetic powder in which the content of Al is specified to 0.5wt.%-20% with respect to Fe is used as the magnetic powder in this case. The magnetic powder, therefore, exhibits the high corrosion resistance intrinsic to the Fe-Al powder and has good dispersibility. The corrosion resistance and dispersibility are extremely poor if the content of Al is below 0.5% and the electromagnetic conversion characteristic us deteriorated if the content exceeds 20%. Since the carbon black is slightly lowered in BET value to >=15m<2>/g and <50m<2>/g, the coefft. of friction thereof is decreased and the light shielding property is improved. In addition, the oil absorption thereof is confined to <110ml/100g and, therefore, the surface roughening of the medium is obviated even if the amt. of the carbon black to be added is increased.

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. It is manufactured by applying a magnetic paint consisting of magnetic powder, binder resin, etc. onto a support and drying it.

These magnetic recording media, especially video tapes, satisfy several of the characteristics of the medium, such as conductivity, coefficient of friction, surface properties (i.e., electromagnetic conversion characteristics), and abrasion resistance (nicarbonate). Conventionally, the technique of using black in combination with
Those disclosed in Japanese Patent Publications No. 58-218039, No. 58-211321, Japanese Patent Publication No. 53-20203, Japanese Patent Publication No. 54-9041, Japanese Patent Publication No. 57-4968 are known.

In addition, in JP-A No. 61-144727, fatty acids with a melting point of less than 50°C, 5
Fatty acids and fatty acid esters with a temperature of 0°C or higher, an average particle size of 60 to 120 fiμ, and a DBP oil absorption of 100
A magnetic recording medium containing carbon black of m/1009 or less is shown.

However, in conventional media, there is no limitation on the composition of the ferromagnetic alloy powder combined with carbon black, although there is a regulation on its specific surface area.

However, in recent years, video tapes have been used in a wide variety of ways due to the shift to portable video tapes, and the conditions for their use vary.

Therefore, video tapes are required to have high resistance to contact.

Among ferromagnetic alloys where corrosion resistance is generally a problem,
Iron-aluminum based ferromagnetic alloy powder has good corrosion resistance. Further, although ferromagnetic alloy powder generally has poor dispersibility, iron-aluminum ferromagnetic alloy powder has good dispersibility.

Furthermore, in conventional media, the combination of iron oxide-based magnetic powder added to the magnetic layer and carbon black is common;
There are almost no combinations with ferromagnetic alloy powders.

The purpose of the present invention is to realize high-density recording, have excellent corrosion resistance and dispersibility, and without deteriorating electromagnetic conversion characteristics.
The objective is to improve running durability, prevent calendar dirt, reduce dropouts caused by calendar dirt, reduce head clogging, and increase running durability under high and low temperatures.

21 Structure of the invention and its effects, that is, the present invention has an aluminum content of 0.5% by weight to
Iron-aluminum magnetic powder of 20% by weight, specific surface area of 15 m'/f or more in BET value, 50v? A magnetic recording medium in which a magnetic layer (2) contains carbon black having a DBP value of less than /9 and an oil absorption amount of less than /100.

According to the present invention, as the magnetic powder, F/-M magnetic powder is used, the M content of which is specified as 0.5% by weight (hereinafter simply expressed as %) to 20% of Fe. , Fe-A
It exhibits the high corrosion resistance characteristic of the L series, and also has good dispersibility.

This is extremely important for realizing high-density recording, since even if the specific surface area of the magnetic powder is increased, its dispersibility can be sufficient. Moreover, in this case,
It is extremely important that the M content of the magnetic powder is limited to a specific range of 0.5 to 20%;
If it is less than 2%, the corrosion resistance and dispersibility will be very poor;
On the other hand, if it exceeds 0%, the proportion of M increases too much and the electromagnetic conversion characteristics deteriorate. It is desirable that the M content is within the above-mentioned range, from 2 liters to 8%.

However, in addition to the M content within the above range, other components other than M may also be contained.

In the present invention ζ:, the above-mentioned "wt%" of the aluminum content refers to the magnetic powder that is an alloy of At and/or its compounds (for example, At, O,) with F as a product component. , M atoms (e.g. At, O,
When added as F.
It means the weight ratio expressed relative to all atoms of the component. Therefore, for example, when the M content is 1% by weight, it means that the weight is 1:1 when the total Fe atomic weight is 100.

In addition, in the present invention (:), the magnetic powder used may have a specific surface area of 40yy//f or more in BIT value,
In this case, C2 can be filled in the magnetic layer at high density.

Furthermore, according to the present invention, the BIT value and oil absorption amount of carbon black in the magnetic layer are within the above-mentioned specific ranges, so that high electromagnetic conversion characteristics such as Lumi S/N and Chroma 8/N can be achieved. It has low dropout, low friction coefficient of the magnetic layer, excellent running durability, little loss of output especially when running at high temperature, high humidity and low temperature, and also reduces calendar stains and head clogging. In other words, since the BIT value of carbon black is set to be lower than 15-/f and less than 5 oi/, the coefficient of friction is reduced and the light-shielding property is also improved.Moreover, its oil absorption is 110sd7100.
Since it is less than 2, the surface of the medium will not be roughened even if the amount added is increased. Furthermore, this carbon black ζ-Y improves running durability, especially durability under high temperatures.

In the present invention (2), in order to obtain the above effects, the amount of carbon black added is preferably 10 parts by weight or less, preferably 0.1 to 6 parts by weight, per 100 parts by weight of magnetic powder. is even better.

Carbon blacks that can be used in the present invention include Sterling V (manufactured by Cabot Co., Ltd.: BET value 35 w?/f1 oil absorption 91-/100 F), R-420 (manufactured by Columbia Carbon Co., Ltd.: BET value 25 ml/f, oil absorption Amount 7
8sml/100f) etc.

In addition, in the above, "r specific surface area" refers to the surface area per unit weight, and is a physical quantity that is completely different from the average particle size. For example, even if the average particle size is the same, the specific surface area is large, Some have small specific surface areas.
To measure the specific surface area, for example, first, the powder is heated at around 250°C for 30 to 60 minutes while being degassed to remove what is adsorbed to the powder, and then introduced into a measuring device and filled with nitrogen. The initial pressure is set to 0.5 kf/-, and the adsorption measurement is performed using nitrogen at a liquid nitrogen temperature (-195°C) (a specific surface area measurement method generally referred to as the &E,T method).

For details, see J, Am@, Chem, Soc, 6
0 309 (1938) This specific surface area (BET
As a measuring device for the value), it is possible to use the "powder measuring device (Canterthorpe)" jointly manufactured by Digestion Battery (1) and Digestion Ionics (2). A general explanation of the specific surface area and its measurement method can be found in “Powder Measurement J.
(J, M DALLAVALIJ, CI, YDEX
) Co-authored by RR Jr., translated by others; published by Sangyo Toshosha)
Pages 70-1171, Nihon Kagaku complete edition, Maruzen ■ 1966 4
In the above-mentioned "Chemistry Handbook", the specific surface area is simply described as surface area (i/gr), but in this specification (2) it is the same as the specific surface area. ) Also, regarding the above ° “Oil absorption @ (DBP method)” ζ:
Pigment powder 100g1=D B P (Dibutyl
phthalate) little by little, observe the state of the pigment while kneading, and find the point where the pigment forms a single lump from the dispersed state.The number of DBP is the DBP.
Oil absorption amount.

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, a BC 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 in the magnetic layer 2, especially the ferromagnetic powder, is Fe − with an M content of 0.5 to 20% as described above.
A2 alloy powder is used.

However, other than AL, N1, Co, P, Mn, Zn.

A small amount of Cr or the like may be added. Moreover, in the magnetic layer 2,
In addition to the above-mentioned carbon black, lubricants such as silicone oil, graphite, molybdenum disulfide, tungsten disulfide, monobasic fatty acids having 12 to 20 carbon atoms (such as stearic acid) and carbon blacks having 3 to 26 carbon atoms, A fatty acid ester consisting of a monohydric alcohol, etc.), an antistatic agent (for example, graphite), etc. may be added. Also,
Non-magnetic abrasive particles may also be added, including alumina (such as α-A40m (corundum)), artificial corundum, fused alumina, silicon carbide, chromium oxide, diamond, artificial diamond, garnet, and emery (main component). :
corundum and magnetite) etc. are used. The content of this abrasive material is preferably less than the weighted part of the magnetic powder C, and the average particle size is preferably O, Sμ or less, and more preferably 0.4μ 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 when applied to the magnetic layer ζ is improved and its mechanical strength is increased. However, if only the phenoxy resin and/or the beer 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.

Further, the carbon black according to the present invention used in the magnetic layer 2 may also be added to the BC layer 6.

Further, the magnetic recording medium shown in FIG. 1 may be provided with an undercoat layer (not shown) between the magnetic layer 2 and the support 1, or may not be provided with an undercoat layer (not shown). Same below).
The support may also be subjected to corona discharge treatment.

In addition, the material of the support body 1 includes plastics such as polyethylene terephthalate and polypropylene, At, and Zn.
Metals such as glass, BN, Sl carbide, ceramics such as porcelain and earthenware, etc. are used.

In addition, when coating and forming the above-mentioned magnetic layer, etc., it is desirable to add a predetermined amount of 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-(
p-isocyanate (phenyl) thiophosphite, polymethylene polyphenylisocyanate, and the like.

Methylene diisonanate type and tolylene diisocyanate type are preferable. 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 C20C layer 4 is provided on the magnetic layer 2 of the medium shown in the figure.

This 00 layer 4 is provided to protect the magnetic layer 2 from damage, etc., and therefore needs to have sufficient lubricity. Therefore, as the binder resin for the 00 layer 4, the urethane resin used for the magnetic layer 2 described above is used (preferably in combination with a phenoxy resin and/or a vinyl chloride copolymer). The surface roughness of 00 layer 4 is particularly high for color S/
In relation to N, Ra≦0.01μTsuru, Rmax50.13
It is better to set it to μs. In this case, it is desirable to use a smooth support 1 with a surface roughness of Ra≦0.01μs and Rmax≦0.13μ+l+.

FIG. 6 shows a magnetic recording medium configured as a magnetic disk, with magnetic layers 2.00 similar to those described above on both sides of the support 1.
Layers 4 are provided, and each of the layers 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 (2), "parts" represent parts by weight.

Examples 1 to 5 At content is 0.5.3.0.5.0.8.0.20.
Using 0% by weight iron-aluminum ferromagnetic alloy powder,
And as carbon black, R-420 (manufactured by Columbia Carbon Co., Ltd.: BET value 25W?/f, oil absorption 78
wt/toof) to prepare the following magnetic powder-containing composition.

Iron-aluminum ferromagnetic alloy powder 80 parts Polyurethane resin and Tuboran 2304 (manufactured by Nippon Polyurethane)
5-part phenoxy resin (PKHH: manufactured by Union Carbide →
Part 2 Vi/f'7
4 parts α-aluminum oxide (abrasive)
4 parts carbon black (R-420: manufactured by Columbia Carbon) 3 parts cyclohexanone 200 parts toluene
30 parts methyl ethyl ketone
30 parts of the composition according to the above formulation was thoroughly stirred and mixed in a ball mill, and a polyfunctional isocyanate (Coronate L: manufactured by Nippon Polyurethane) was added as a binder curing agent.
After adding 3 parts by weight of
It was coated onto a polyethylene terephthalate film in a micrometer size and subjected to supercalender treatment.

Next, the following back coat paint was prepared.

Carbon black 50 parts Nitrocellulose (Seltsuba: manufactured by Kankasei) zo part Polyurethane resin and Tuboran 2304: manufactured by Nippon Polyurethane)
20 parts Polyison Anate (Coronate L: manufactured by Nippon Polyurethane) 101
Methyl ethyl ketone 2001 toluene
200I This composition was dispersed in a ball mill for 5 hours, and two coats were dried to form a back coat layer on the back surface of the support having the magnetic layer to a dry thickness of 0.5 μm.

The above-mentioned wide magnetic tape film was cut into two 8 ml pieces to produce five types of 8 m video tapes as samples for the examples, each of which was designated as Example tapes 1 to 5. 8 of these
11II videotape cassette and the characteristics were measured.

Example 6 As carbon black, Sterling V (manufactured by Capot Co., Ltd.: BET value 35-/f oil absorption 9) was used instead of R-420.
Except for using 3 parts by weight of 1mg7100F), the same process as in Example 6 was added to produce an 8m wide videotape,
This 8 mm videotape was designated as Example Tape 6.

Comparative Example 1 Example 1 to
A videotape with a width of 8 m was prepared by applying the same treatment as in No. 5, and this 8m videotape was designated as Comparative Example Tape 1.

Comparative Example 2 The same treatment as in Examples 1 to 5 was carried out, except that iron-aluminum ferromagnetic alloy powder with an At content of 25.0 atomic weight t% was used instead of the alloy powder in Examples 1 to 5. In addition, an 8-width videotape was prepared, and this 8-inch videotape was designated as Comparative Example Tape 2.

Comparative Example 3 An 8-inch wide videotape was produced by applying the same treatment as in Example 6 except for carbon black R-420,
This 8vm videotape was designated as Comparative Example Tape 6.

Comparative Example 4 +22B (carbon black instead of R-420)
Manufactured by Mitsubishi Kasei: BET value 55dl'? , oil absorption 131
A videotape having a width of 8+w+ was prepared by carrying out the same process as in Example 6, except that 3 parts by weight of 3 parts by weight of 3 parts by weight of 3 parts by weight of 8cm wide videotape was used as Comparative Example Tape 4.

Comparative Example 5 R-MT- instead of R-420 as carbon black
P (manufactured by Columbian Carbon: BET value 8dl?,
In addition to using 3 parts by weight of oil absorption (36+ml/1oof),
A video tape having a width of 811,111 mm was prepared by applying the same processing as in Example 3, and this was designated as Comparative Example Tape 5, which was an 8 m video tape.

Comparative Example 6 Regal 5 was used instead of R-420 as carbon black
00 R (manufactured by Capot: BET value 86m”/f.

Oil absorption: 65 Wt/10 Qf) was used in a triple barrel.

FIG. 4 shows the results of measuring the performance of the tape obtained as described above. However, evaluation items are measured and displayed according to the following standards.

(,) Saturation magnetization: The saturation magnetization of the sample tape is shown in Gaussian units.

(b) Saturation magnetization after storage: sample tape at 60°C, 80R
The saturation magnetization after being left for one week in an atmosphere of H% (relative humidity) is expressed in Gauss.

(c) Residual rate of saturation magnetization: sample tape at 60°C, 80R
The saturation magnetization measured after being left in an H% atmosphere for one week corresponds to what percentage of the saturation magnetization measured before being left.

(d) Squareness ratio: The ratio between the residual magnetic flux density and the saturation magnetic flux density of the coated sample film (without calender treatment) was measured using a VSM with a measuring magnetic field of 5 KOs.

(a) Glossiness: The glossiness of the sample film after coating (without calender treatment) was measured at an incident angle of 60' perpendicular to the coating direction, and expressed with the standard plate as 100%.

(f) Still durability: Still image playback output is 2dB...
・Indicates the time required for the temperature to drop in minutes.

(2) Calendar stain: temperature 80℃, linear pressure 200㎡/c
After 20,000 m calender treatment with In, stains on the surface of the metal roll were visually observed.

○: No dirt △: Faint ζ: Stain ×: Obvious dirt (h) D, O, (54): A 100% white level signal is recorded, and the attenuation of the Radup output to the video during playback is 12 dB. , dropout with a duration of 5 μsec or more was measured by dropout count for 10 minutes, and the average value per minute was determined.

(i) R after driving durability test (Durability)
F output decrease: Record and play the tape 200 times at normal temperature and humidity, and display the output difference in RF specific output after the first 200 RF specific outputs in dB. + means that the output after 200 times is greater than the RF ratio output at the first reproduction.

(j) Powder removal after Durabsttty: After recording and reproducing the tape 200 times at normal temperature and normal humidity, wipe off the dirt on the tape running part in the deck and visually judge the degree of dirt.

○: No stains △: Slightly contaminated .

(4RF output using a VTR deck for measuring RF output)
The RF specific output at MHz was measured, and Example Tape 6 was shown as a reference tape after being played back 100 times (unit: dB).

(e) Lumi S/N: A noise meter (925D/1) manufactured by Sibaku Co., Ltd. was used as a measuring device, and Example Tape 6 was used as a reference tape (OdB), and the difference was expressed with respect to the reference tape (OdB).
The bypass filter was set to 4.2 MHz, and the low pass filter was set to 10 kHz. VTR is JVCHR-D12
Use 0.

(,) Chroma S/N: Same as RF output.

From Figure 4, which summarizes the above results, it can be seen that both tapes of the present invention (two tapes) have excellent electromagnetic conversion characteristics, and have good properties such as running durability at high and low temperatures, calendar staining, and dropout. I understand.

Next, in the above, the At content in the magnetic powder and the Lumi S/
The relationship between N and the residual rate of saturation magnetization after storage was investigated, and the results were as shown in FIGS. 5 and 6. As can be seen from these two figures, from the point where the At content exceeds 20%, the Lumi S/N (this trend changes to RF specific output Chroma S/N).
The same applies to N), and the residual rate of saturation magnetization after storage rapidly deteriorates when the At content becomes less than 0.5%. Therefore, it can be seen that the At content of the Fe-AL magnetic powder as the magnetic powder should be in the range of 0.5 to 20%.

Next, the correlation between the oil absorption amount of carbon black added in Example 1 and tape properties will be examined. FIG. 7 shows a graph in which the vertical axis represents Lumi EIN and the horizontal axis represents the oil absorption amount of carbon black. From this graph, the oil absorption amount of the added carbon black is 11011! It can be seen that the lumi S/N (this tendency is the same for the RF specific output chroma S/N) decreases rapidly when it is higher than g/100r.

As can be seen from this result, the oil absorption amount of carbon black must be 110tR in order to avoid deterioration of electromagnetic conversion characteristics.
Must be less than t/100f.

Also, in the same way (Niji, BI of carbon black to be added)
Let's look at the correlation between T and tape characteristics. FIG. 8 shows a graph in which the vertical axis shows the RF output decrease and the horizontal axis shows the BET (logarithm display). From this, the electromagnetic conversion characteristics, D, 0. (5μ8) The range of BET values for carbon black that satisfies both characteristics is 15dl 1 or more and 50rr? It should be less than /f.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIGS. 1, 2, and 3 are enlarged cross-sectional views of a portion of a magnetic recording medium on each side, and FIG. Figures 5 and 6 are graphs showing changes in characteristics depending on the At content of magnetic powder, and Figures 7 and 8 are graphs showing each characteristic when the physical quantity of carbon black is changed. This is a graph showing the drawings.
......Magnetic layer 3...
... Back coat layer (BC layer). Agent Patent Attorney Hiroshi Aisaka Figure 5 Figure 6, mt student Hn74? °tsu′τ
Yes (% 1 Figure 7 Figure 8 (spontaneous) Procedure Neho 1986 (Z) to 1986 (8861) Patent Application No. 315170 2, Name of Invention Magnetic Recording Medium 3, Person Making Amendment Case Relationship Patent applicant address: 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name:
(127) Roku Konishi Photo Industry Co., Ltd. 4, Agent address: 2-4-11 Shibasaki-cho, Tachikawa-shi, Tokyo FINE Building Equipment 0425-24-541115 6. Number of inventions increased by amendment (1), Specification 1st line from the bottom of page 2, 1st line of page 3,
Page 3, line 3, page 3, line 10 from the bottom, page 4, line 8
line, “touch resistance” in the sixth line from the bottom of the fourth page of the same page is “corrosion resistance”
I will correct each. One or more -

Claims (1)

[Claims] 1. Iron-aluminum magnetic powder with an aluminum content of 0.5% to 20% by weight, a specific surface area of 15 m^2/g or more and less than 50 m^2/g in BET value, and an oil absorption amount A magnetic recording medium in which a magnetic layer contains carbon black having a DBP value of less than 110 ml/100 g.