JPS58158032A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve surface characteristics and durability by mixing carbon black and fatty acid as well as fatty acid ester and a polishing agent in combination at a specific ratio and incorporating said mixture in a magnetic layer. CONSTITUTION:1-20wt% (Based on the weight of a magnetic material) carbon of about <=10mmu average particle size, 0.1-3wt% (based on the weight of the magnetic material) fatty acids and fatty acid ester such as stearic acid, aluminum stearate or the like and 1-15wt% (based on the weight of the magnetic material) a polishing agent of >=6 Mohs hardness such as Cr2O3 are incorporated in a magnetic layer for magnetic recording consisting of the magnetic material and a binder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium with improved surface properties and durability.

In recent years, there has been a strong demand for higher densities in magnetic recording media, and the rapid development of home video tapes in particular has become well known to general consumers.

2-hour format → 6-hour format on VH8 VTR, Beta-f
1→'l −+ 5−+ on ormat VTR 4.
Ultra-compact VT using 5-hour type and 2-inch tape
The appearance of R "CvC" was largely supported by efforts to increase the density of magnetic tapes through subsequent improvements.

However, the conventional techniques are no longer able to adequately meet the demand for higher tape densities.

In other words, in order to increase the density of a tape, smoothing of the surface of the magnetic layer and presence of magnetic material in a uniformly dispersed state within the magnetic layer are important factors. Merely using techniques such as strengthening the conditions or improving the direction of magnetic liquid dispersibility will result in deterioration of the strength and durability of the tape magnetic layer.

In addition, carbon black with an average primary particle size of several tens of mp is usually mixed into the magnetic recording material mainly for the purpose of preventing static electricity, for example, about 5 to 10% by weight based on the magnetic material. As is well known, black has fine particles compared to general pigments and is therefore difficult to disperse, degrading the magnetic dispersibility of the magnetic recording medium and the surface properties of the coating film. If dispersion is strengthened by examining dispersion conditions, the durability of the magnetic layer of the magnetic recording material will deteriorate even if the coating surface becomes smooth.

The present inventors have conducted detailed studies on this point and have arrived at the present invention.

That is, the present invention improves both the surface properties and the durability of a magnetic recording material at the same time. (a) 1 to 20% by weight of carbon black with an average particle size of 10 mμ or less based on the magnetic material,
←) Fatty acids and fatty acid esters are each 0 for magnetic materials.
The present invention relates to a magnetic recording material characterized by an abrasive of 1 to 3% by weight and (iii) a Mohs hardness of 6 or more.

The carbon black used in the present invention may have an average particle size of approximately 10 mμ or less, such as Royal 5pectra manufactured by Colombian Carbon Co., Ltd.
(7m, u) I Neo 5pect
ra Mark 1 (8mμ) 11 tt [(
9mμ) ” ?' I[[
(10mμ) I 5uper 5pectra (
9mμ) II 5uperba
(11m, u) etc. are preferable, and by using such fine particles of carbon black, the surface properties of the magnetic recording medium are improved.

The amount of carbon black used is 1 to 2 per magnetic material.
It is preferably 0% by weight, more preferably 3 to 15% by weight, and even more preferably 5 to 10% by weight.

As the fatty acid in the present invention, ordinary saturated and unsaturated fatty acids can be used. Specific examples include lauric acid, palmitic acid, myristic acid, stearic acid, behenic acid, and instearic acid.

Of course, these may be used in combination if necessary.

The fatty acid ester is preferably one consisting of a monobasic fatty acid and m alcohols, and specific examples include ethyl stearate, butyl stearate, amyl stearate, butyl palmitate, hexyl laurate, butyl laurate, butyl myristate, etc. There is.

The amount of fatty acids and fatty acid esters used is 100% of the magnetic material.
It is preferably 0°1 to 3 wt%, more preferably α3 to 2 wt%.

It is necessary to use both fatty acids and fatty acid esters in combination in order to maintain good durability such as VTR runnability and stale life.

The abrasive is effective for durability such as VTR running performance and stale life, and preferably has a Mohs hardness of 6 or higher, and is 0r203.
．． Alumina, SiC! Ordinary abrasive particles such as , MgO, etc. can be used, and the particle size thereof is preferably 1 μ or less, particularly preferably 0.2 to α8 μ. The amount used is preferably 1 to 15 wt based on the magnetic material.

As the non-magnetic support, any material that can be used for ordinary magnetic recording materials such as polyethylene terephthalate, triacetylcellulose, polyethylene naphthalate, polyamide, polyimide, etc. can be used, and At-deposited polyester film, carbon black and/or the like can be used. Or a back coat layer mainly consisting of other inorganic extender pigments (
A film provided on the diamagnetic side can be used.

As shown in the examples, the surface roughness is measured by the center line average roughness Ra
Those having a molecular weight of 0.03 or less are particularly suitable for the purpose of improving the surface properties of the magnetic recording medium of the present invention.

In order to further improve the surface properties of the magnetic recording medium, carbon black may be front-sheeted together with a magnetic material, a binder, and an organic solvent. Similarly to carbon black, the amount of front coating of each magnetic substance and binder can be adjusted as necessary. Normally, for magnetic materials, it often gives more favorable results if the entire amount is subjected to frontal treatment.

It is essential to carefully consider the type and amount of binder and set the front bonding conditions. When only the surface smoothness of the magnetic layer is of interest, it is preferable to add the entire amount of carbon black to the front. However, when the electrical resistance of the magnetic layer surface is required to be below a certain value, only a portion of the carbon black is added. In many cases, it is better to remove the amount at the front and use the remaining amount in the subsequent process. More details will be specifically described later in Examples.

The front-line method includes a three-roll mill, a pressure kneader, an oven kneader, and a '7. The use of -1-121 goo is preferred, but the method is not limited to these, and almost any method that can be used for kneading ordinary pigments can be applied.

As a solvent for front rinsing, acetic acid esters such as ethyl acetate and butyl acetate, Ml! ! In addition, most of the solvents normally used in magnetic tapes, including ketones such as cyclohexano/etc., can be used.

As a magnetic material, 7-Fe2O31F61304,0
! r021 Cobalt-added γ-”203 * Cobalt-added Feox.

In addition to oxides such as (X-1,33~1.'5), Fe-N
Metal powders such as i, Fe-Ni-Co, etc. can also be used.

As a binder, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, carboxyl group-containing salt-vinyl acetate copolymer,
Vinyl alcohol-containing salt vinyl acetate copolymer, polyvinylidene chloride, vinylidene chloride-acrylonitrile copolymer, nitrocellulose and other cellulose derivatives, acrylonitrile-butadiene rubber, styrene-butadiene rubber, polyester, epoxy resin, polyincyanate,
Any material that can be used for ordinary magnetic recording materials, such as polyamide, can be used.

As lubricants other than fatty acids and fatty acid esters, paraffin, liquid paraffin, silicone oil, fatty acid-modified silicone, fluorine-based oils such as Kreitx-Difloil, ketone wax graphite, solid lubricants such as MoB2, etc. can be used.

If necessary, plasticizers such as DBF (dibutyl phthalate) and TPP (triphenyl phosphate), and dispersants such as lecithin and tenguchi may be mixed into the magnetic layer.

The magnetic recording body of the present invention obtained in this manner has the following advantages.

■ The surface smoothness of the magnetic layer is excellent, resulting in less modulation noise.

■ The tape has excellent durability when repeatedly run on a VTR.

■ Long stay life.

Examples of the present invention will be specifically described below.

Example 1 Cellulose propionate 13N
ipo1 1432 (Nippon Zeon synthetic rubber) 2
Amyl stearate 1 Stearic acid 1 Butyl acetate/MEK-171 mixed solvent Appropriate amount After rough dispersion of these compositions except for Coronate L using a stirrer, thorough fine dispersion treatment was performed using a sand grinder to obtain excess fractions. It was canceled just before it happened. The hardening agent Coronate L was added to the liquid using a stirrer and the resulting magnetic liquid was stirred, and the viscosity of the obtained magnetic liquid was adjusted to a viscosity of 60 poise using a mixed solvent.

Filter the liquid using a filter. After that, the above magnetic liquid was applied to a 15μ thick polyethylene terephthalate film (Raα033μ) using a reverse method, and the magnetic material was oriented in the coating direction (lengthwise direction) using a lenoid, and then using a super calendar, The surface smoothing treatment of the magnetic layer was carried out under the conditions of a temperature of 80° C., an inter-roll nip linear pressure of 280 kg/cm, and a speed of 60 m/min. This was cut into A-inch width to obtain a VHEI videotape (sample size 1).

Comparative example 1 Cellulose propionate 13Ni
pol 1432 completed
2 Coronate L6 Liquid paraffin Dibutyl acetate/MEK = 1/1 mixed solvent Appropriate amount These compositions were coarsely and finely dispersed in the same manner as in Example 1,
The obtained magnetic liquid was made to have a viscosity of 60 voids, and the steps after coating were carried out in the same manner as in Example 1 to obtain Sample &2.

Example 2 Samples 3 to 5 were obtained by changing the type of carbon black to the following in Example 1.

Example 3 Samples-6 to II in which the amount of carbon black was changed as follows in Example 1! Example 11 was obtained in the same manner as in Example 1 except for the following.

Comparative Example 2 In Example 1, the type of carbon black was changed to the following, and Comparative Sample Collections 12 to 14 were obtained.

Comparative Example 5 Comparative samples 15 to 17 were obtained in the same manner as in Example 1, except that the lubricant "stearic acid and amyl stearate" was replaced with the following.

Example 4 Samples Nn18 to 21 in Example 1 were obtained by replacing stearic acid and amyl stearate with the following.

Example 5 Samples Nos. 22 to 26 were obtained in the same manner as in Example 1 except that the following was used as the polishing agent Or203.

Example 6 The following samples lV&127~ were prepared in the same manner as in Example 1 except that non-magnetic supports with different surface properties were used.
I got 30.

Example 7 In Example 1, carbon black was kneaded (ie, front kneaded) with the magnetic material, cellulose propionate, and mixed solvent in an open kneader. Cellulose propionate was used as a 20% by weight solution using a mixed solvent as a solvent.

Further, the front line mixed solvent was gradually added while visually observing the cross-wire condition, and when the load current reached almost the maximum (in this example, after 30 minutes), the addition was stopped, and the treatment was continued for an additional 60 minutes. After the front line is finished, cross-wire treated products, Cr2O3, N
1pol 1432J, stearic acid, and amyl stearate were roughly dispersed together with a mixed solvent using a stirrer.

The rest of the steps were carried out in the same manner as in Example 1, and sample volume 61 was obtained.

Example 8 Half the amount of carbon black (2.5% by weight) in Example 1
The mixture was mixed with a magnetic material, cellulose propionate, and a mixed solvent in an open kneader (ie, front mixing).

After that, the kneaded product, 0r203, N1pol
1432J, the remaining amount of carbon black (in powder form), stearic acid, and amyl stearate were coarsely dispersed with a mixed solvent, and the other conditions were the same as in Example 7.
I got 2.

Example 9 In the same manner as in Example 1, carbon black was subjected to open knee goo treatment together with the magnetic material, cellulose propionate (8% by weight), and a mixed solvent. The remaining amount of cellulose propionate (5% by weight) was added as a 20% by weight solution in the rough dispersion step. Sample-33 was obtained in the same manner as in Example 7.8.

The evaluation results for samples Nos. 1 to 33 are shown in Table 1.

Sample No. 1 is according to the present invention, and when compared with Sample No. 2 of the prior art, which has a large size of carbon black, the tape magnetic layer surface properties (Ra), modulation noise, VTR100A running performance, and stay life are as follows. It can be seen that Sample No. 1 according to the present invention is superior in all characteristics.

Samples II & 13 to 5 are also samples according to the present invention and have different sizes of carbon particles, but the one with fine particles (sample number 3) tends to be better in terms of Ra and modulation noise, and the overall sample positive Similar to 1, it is significantly superior to comparison sample 2.

Samples 6 to II & 111 are the same as in Example 1 except that the amount of carbon black added was changed. If the addition amount is as low as 0.5% by weight as in sample positive 6, the VTR running performance and stale life will be insufficient.
If the amount added is as high as 30% by weight as in Example 1, it is unfavorable in terms of stay life and modulation noise, and the amount added is preferably in the range of 1 to 20% by weight.

Further, l1lk112 to l1lk114 are samples obtained by changing the carbon black to a conventional size in Example 1 according to the present invention, but both Ra and modulation noise are significantly inferior to those of the present invention.

-15 is Sample NQ1 with amyl stearate removed, -16 with stearate/acid removed, and No. 17 with both removed.

No. 15 has insufficient VTR running performance and stale life. Although Ii & 116 has a slightly better stay life than No. 15, it is conversely worse in terms of VTR runnability, indicating that both fatty acids and fatty acid esters are essential to the present invention.

-17 has an extremely short life in both VTR running performance and stay life, which poses a serious problem in practical use.

Collections 18 to 21 are examples according to the present invention, fatty acids,
Although the type and amount of fatty acid ester were changed, the results showed almost the same good results as Samples II & 11.

Samples 11 & 122-26 are sample number 1 0r20
This is an abrasive using other abrasives in addition to No. 3.

II & 126, which does not use abrasives, and 25, which uses abrasives with a Mohs hardness of 5.5, have poor VTR running performance and stale life, as well as poor modulation noise. This is pottery 2
The Ra of both 6.25 is the same as other ridges 22 to 24.1, and there are scratches and scratches on the magnetic layer, indicating that the video head stains were caused by scratches on the tape magnetic layer. Therefore, when the head surface was observed under a microscope after the VTR running test, a small amount of brown stain was observed. It has been shown that abrasives having a Mohs hardness of 6 or more have shown preferable results.

Floors 27 to 30 are samples obtained in the same manner as IVllll except that the nonmagnetic support was replaced with one of various smoothness. The surface properties of the magnetic layer show a good correspondence with the surface properties of the support, and when a smooth support is used (the smoothness increases as you go from 27 to 60), the magnetic layer Ra also becomes smaller, and Modulation noise is also reduced.

In NQ27-30 using a support with RaO of 0.030 or less, -1. using a support with Ra of 0.033. Since the modulation noise is further reduced than the Ra of the non-magnetic support is 0.
030 or less is more preferable in order to achieve the object of the present invention.

Figures 31 to 33 are carbon blacks subjected to front-line treatment. In both cases, the Ra and modulation noise are even better than that of sample ridge 1, and it is clear that the frontal treatment is effective in further improving the surface properties, which is the objective of the present invention.

Looking at the fronting conditions and results in detail, -32, where half the amount of carbon black was added to the front, and tI & 1, where the entire amount of carbon black was added to the front.
31 has a better surface smoothing effect, but Nn3
It can be seen that even more favorable results can be obtained if the amount of binder (cellulose propionate) during front printing is set more appropriately as shown in 3. In this way, establishing the front-line conditions is extremely important in order to obtain better results.

An outline of the above evaluation method is as follows.

a, Center line average roughness Ra of tape magnetic layer and support surface
; The centerline average roughness of cutoff 0.08 wh was determined using Model I 5E-3AK manufactured by Koita Research Institute.

b. Modulation noise: 5MHz sine wave signal with relative velocity 5.
8 m/8El (!VH8VTR made by Victor Japan)
The output when recording and reproducing with the HR-360 (1) was analyzed using a spectrum analyzer, and N in FIG. 1 was calculated in dB (with a sample interval of 2 as the standard).

c. VTR running performance; VH8 system VT manufactured by Victor Japan
R (HR-3600) was placed in a thermo room set at 40° C. and 60° RH, the tape was run repeatedly, and the number of passes in which running abnormality (tape stickiness) occurred was determined.

d.Still life; HR-3600 is set to the still state, and the time until the image disappears is determined. The environmental conditions were both room temperature and harsh 5°C.

FIG. 2 shows modulation noise in a comparative example according to the prior art and several examples according to the present invention.

The implementation sample NQ1 according to the present invention is preferable because it has less noise than the comparative samples (11!12) according to the prior art.

Sample-60 using a smooth support is even more preferred. In Example 1, a sample 26 containing no abrasive was given.
There is also a lot of noise.

[Brief explanation of the drawing]

FIG. 1 is a graph showing a method for evaluating modulation noise of a magnetic recording medium in the present invention, and FIG. 2 is a graph showing modulation noise in the present invention and a comparative example. Agents 1) Akira’s agent Ryo Hagiwara −

Claims (3)

[Claims] (1) From magnetic material and binder on a non-magnetic support
A magnetic recording material coated with a magnetic layer comprising: 0) 1 to 20% by weight of carbon with an average particle size of about 10 mμ or less based on the magnetic material; (b) fatty acids and fatty acid esters are magnetically 0.1 to 3% by weight of each abrasive with a Mohs hardness of 6 or more to the magnetic body.
15% by weight, a magnetic recording body characterized by comprising: (2) Center line average roughness Ra of non-magnetic support is 0.05μ
The magnetic recording body according to claim 1, which is as follows. (3) The magnetic recording material according to claim 1, which contains a part or all of carbon black as a front layer.