JPS63164018A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability of a titled medium by incorporating two kinds of carbon blacks and specific ester into a magnetic layer. CONSTITUTION:Two kinds of the carbon blacks and the ester expressed by the formula are added to the magnetic layer essentially consisting of magnetic powder and resin binder. Two kinds of the carbon blacks refer to the carbon (A) having 10-50mmu average single grain size and the carbon (B) having 200-1,000mmu average single grain size. The compounding ratio thereof by weight is confined to A<B. In the formula, R1, R2 denote a satd. alkyl of 1-25C having a straight chain or branch, R3 denotes a(n) (un) satd. alkyl of 7-29C having a straight chain or branch. The medium such as floppy disk having the excellent durability is obtd. if the medium is constituted in the above-mentioned manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media. Specifically, the present invention relates to a magnetic recording medium with excellent durability.

[Conventional technology and problems]

Magnetic recording media are generally made by applying magnetic paint consisting of magnetic powder, binder resin, organic solvent, and other necessary components onto a substrate such as polyester film. Since the magnetic layer is easily abraded due to violent sliding contact with the head, jacket liner, etc., a magnetic layer with low abrasion (and excellent durability) is required.

Therefore, as a measure to improve the wear resistance of the magnetic layer, various lubricants are mixed into the magnetic layer.

Conventionally used lubricants include fatty acids, oleyl oleate, butoxyte stearate, fatty acid amides, liquid paraffin, wax, and the like. however,
At present, these lubricants cannot be said to be satisfactory in terms of performance. For example, oleyl oleate, butoxide stearate, etc. are insufficient for improving the durability of media, while fatty acids such as stearic acid and oleic acid, and hydrocarbon-based lubricants such as liquid paraffin are effective in improving durability. Although effective, it has poor compatibility with the resin binder, and when used in large quantities, it bleeds from the surface of the magnetic layer and tends to stain the head.

On the other hand, carbon black is usually blended into the magnetic layer of a magnetic recording medium such as a floppy disk. It is believed that the main purpose of incorporating carbon black is to prevent static electricity in the magnetic layer and to provide light-shielding properties required for magnetic recording media. In order to satisfy this purpose, several carbon black blending systems have been proposed.

By the way, as a result of studies conducted by the present inventors, it has become clear that changing the type of carbon black can change the durability of the magnetic recording medium.Furthermore, when various combinations of lubricant and carbon black are used, It has also been found that durability can change accordingly. Therefore, it is considered important to find an optimal combination of these.

In particular, recently, devices equipped with magnetic recording media such as floppy disks have been increasingly used outdoors, and magnetic recording media that are highly durable even under various environmental changes have been required along with the devices. .

[Means for solving problems]

The present inventors have arrived at the present invention as a result of intensive research to obtain a magnetic recording medium that is imparted with good lubricity and has significantly improved durability even under a wide range of use environments.

That is, the present invention provides a magnetic recording medium having a magnetic layer mainly composed of magnetic powder and a resin binder, in which the magnetic layer is carbon black (a-1) having an average single particle size of 10 to 50 mμ. and the average single particle size is 200-100
Carbon black consisting of carbon black (a-2) of 0 mμ and having a blending weight ratio of (a-2) > (a-1), (bl) following formula (1) (wherein, R7 and R are A straight chain or branched saturated alkyl group having 1 to 25 carbon atoms (however, the sum of the carbon numbers of R1 and R2 is 22 to 34); R3 is a straight chain or branched saturated or unbranched alkyl group having 7 to 29 carbon atoms; The present invention provides a magnetic recording medium characterized by containing an ester compound represented by:

In the present invention, carbon black (a-1) having an average single particle size of 10 to 50+ mμ and carbon black (a-2) having an average single particle size of 200 to 1000 mμ are used together as carbon black. However, it is necessary to make (a-2) larger than (a-1) in the weight mixing ratio of both. Further, as long as the average single particle size of carbon black is within the above range, a plurality of carbon blacks may be appropriately selected and blended. The blending amount of these carbon blacks is (a
The total amount of -1) and (a-2) is 8 to 25% of the magnetic powder.
It is preferable to mix it so that it becomes % by weight.

Further, in the present invention, it is necessary to use a specific ester compound represented by the above formula (1), and this compound is thought to mainly act as a lubricant. Further, the ester compound and various compounds conventionally used as lubricants may be used together. Compounds that can be used in combination include higher fatty acids such as oleic acid, palmitic acid, stearic acid, and behenic acid, and linear or low molecular weight branched fatty acids such as oleyl oleate, tridecyl stearate, isocetyl stearate, and eicosyl myristate. Examples include fatty acid esters having groups, fatty acid alkoxy esters such as butoxyethyl stearate and butoxyisopropyl stearate, fatty acid amides, paraffin, and wax. One type or two or more of these can be used in combination, but when used in combination, the ester compound represented by the formula (1) is 100 parts by weight in total.
It is preferable that the amount is 0 parts by weight or more. The lubricant is usually used in an amount of 1 to 5% by weight based on the magnetic powder.

The magnetic powder according to the present invention is fine needle-shaped rF.
Metal oxides such as etch, Fe1g4, Crow, as well as Co-coated 7-Fetch, CO-doped 7-Fe,
0. γ-FezO: +, iron metal powder, barium ferrite in the form of microplates, and some of its Fe atoms are Ti + Co, Zn, V, Nb, etc. or 2 types, etc.
Magnetic powder substituted with more than one species, Co, Fe-Co, F
Examples include ultrafine powder of metal or alloy such as e-Ni.

Among these, iron metal powder has particularly poor chemical stability, so to improve it, nickel, cobalt, titanium, silicon,
A small amount of aluminum or the like in the form of metal atoms, salts, or oxides may be added or the surface may be treated, and these may also be used. In order to stabilize iron metal powder, a thin oxide film may be formed on the surface in a weakly oxidizing atmosphere, and metal powder treated in this manner may also be used.

Examples of resin binders that can be used in the present invention include polyurethane, polyester, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, polyacrylonitrile, nitrile rubber, epoxy resin, alkyd resin,
Polyamide, polyacrylic ester, polymethacrylic ester, polyvinyl acetate, polyvinyl butyral,
Examples include vinylidene chloride, vinylidene chloride copolymer, nitrified cotton, maleic acid-modified vinyl chloride/hinyl acetate copolymer, and ethyl cellulose. Although these may be used alone, two or more types are usually used in combination. Further, in order to adjust the hardness of the resin, a desensitizing agent or a curing agent may be added.

The amount of the resin binder is generally 15 to 60 parts by weight per 100 parts by weight of the magnetic powder. Even if the resin binder has the highest binding strength, if the amount is less than 15 parts by weight, the strength of the magnetic coating will be weak and the adhesive strength between the substrate and the magnetic coating will be insufficient. On the other hand, if the amount is more than 60 parts by weight, the concentration of magnetic powder in the magnetic coating film becomes small, which is disadvantageous because the reproduction output decreases. Furthermore, the properties of the coating film may deteriorate.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 The following mixture was kneaded in a sand mill for about 15 hours.

Thereafter, 7 parts of a polyisocyanate compound (trimethylolpropane triisocyanate) was added to prepare a magnetic paint.

Next, this coating material was applied onto a 75-thick polyethylene terephthalate film so that the dry film thickness was 1.5 μm, and after drying, calendering was performed. Further, this was left at 60° C. for 4 days to undergo a hardening reaction, and then punched out into a disk shape, the surface polished and enclosed in a jacket to produce a floppy disk.

A durability test was conducted by loading this disk into a floppy disk accelerated durability test drive under the test conditions below. By measuring the running time until the playback output reached 70% of the initial value, Durability was evaluated.

The results are shown in Table 1.

Test conditions> ■ First, the temperature was 5°C and the humidity was 30χR,H for 8 hours.

■ Gradually increase the temperature and humidity until 40℃ and 8℃ after 4 hours.
0χR,H.

■ Hold at 40℃, 80χR,H, for 8 hours.■ Gradually lower the temperature and humidity, and after 4 hours, hold at 5℃, 30χR,H.
, so that

■ Repeat this from now on.

Example 2 In Example 1, 1 part by weight of carbon black with an average single particle size of 20 rmμ, and an average single particle size of 3011
4 parts by weight of 1μ, 1 part of average single particle size 350mμ
A floppy disk was manufactured in the same manner as in Example 1 except that 0 parts by weight was used, and its durability test was conducted.

The results are shown in Table 1.

Example 3 In Example 1, 4 parts by weight of carbon black with an average single particle size of 15 mμ, and an average single particle size of 350 n+
Using 11 parts by weight of μ, 4.0 parts by weight of tridecyl stearate was used instead of a lubricant consisting of 2-decyltetradecyl oleate, tridecyl stearate and valmitic acid.
A Frompy disk was produced in the same manner as in Example 1 except that 2.0 parts by weight of isocetyl stearate and 2.0 parts by weight of 2-decyltetradecyl palmitate were used, and its durability test was conducted. .

The results are shown in Table 1.

Example 4 In Example 1, 8 parts by weight of carbon black with an average single particle size of 20 mμ, and an average single particle size of 3301μ
Example 1 except that 10 parts by weight of 2-octylhexadecyl isostearate, 4.5 parts by weight of eicosyl myristate and 2.0 parts by weight of butoxyethyl stearate were used as lubricants. A floppy disk was manufactured in the same manner as above, and its durability was tested.

The results are shown in Table 1.

Comparative Example 1 In Example 1, 5 parts by weight of carbon black with an average single particle size of 20 taμ, and 5 parts by weight of carbon black with an average single particle size of 62 t
A floppy disk was manufactured in the same manner as in Example 1 except that 4 parts by weight of aμ was used, and its durability was tested.

The results are shown in Table 1.

Comparative Example 2 In Example 2, 5 parts by weight of carbon black with an average single particle size of 20 ta μ, and 5 parts by weight of carbon black with an average single particle size of 25 μ
A floppy disk was manufactured in the same manner as in Example 1 except that 5 parts by weight of the same material was used, and its durability test was conducted.

The results are shown in Table 1.

Comparative Example 3 In Example 1, butyl stearate 8 was used as a lubricant.
A floppy disk was manufactured in the same manner as in Example 1 except that parts by weight were used, and a durability test was conducted.

The results are shown in Table 1.

Comparative Example 4 In Example 4, oleyl oleate 8 was used as a lubricant.
A floppy disk was manufactured in the same manner as in Example 4 except that parts by weight were used, and its durability test was conducted.

The results are shown in Table 1.

Table 1

Claims (1)

[Scope of Claims] 1. In a magnetic recording medium having a magnetic layer mainly composed of magnetic powder and a resin binder, the magnetic layer comprises (a) carbon black (a- 1) and average single particle size of 200 to 1000 mμ
(b) The following formula (1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ...(1) {In the formula, R_1 and R_2 have 1 to 25 carbon atoms (however, R
The sum of the carbon numbers of _1 and R_2 is 22 to 34) is a linear or branched saturated alkyl group, and R_3 is a saturated alkyl group having 7 to 7 carbon atoms.
It is a saturated or unsaturated alkyl group having 29 straight or branched chains. } A magnetic recording medium characterized by containing an ester compound represented by the following.