JPS6310316A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve an electromagnetic conversion characteristic and running durability by incorporating an ester compd. having a mercapto group into a magnetic layer. CONSTITUTION:The magnetic layer formed by dispersing ferromagnetic powder into a binder is provided on a nonmagnetic base to form this recording medium. The magnetic layer contains the ester compd. having the mercapto group, above all, the compd. expressed by HS(CH2)mCOO(CH2)nCH3 (n; >=7 and <=20 integer, m: >=1 and <=20 integer). The magnetic recording medium which has the excellent electromagnetic conversion characteristic and exhibits the stable running durability in spite of a change in temp. and humidity is thus obtd.

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 electromagnetic conversion characteristics and running durability.

[Conventional technology]

In magnetic recording media, there is an increasing demand for high-density recording, and it is known that one way to solve this problem is to make the surface of the magnetic layer smooth.

However, when the surface of the magnetic layer is made smooth, the friction coefficient of the contact between the magnetic layer and the device system increases while the magnetic recording medium is running. As a result, the magnetic layer of the magnetic recording medium may be damaged or the magnetic layer may be damaged after a short period of use. Layers tend to peel off.

Sometimes, in video tapes, the magnetic layer must be placed under harsh conditions such as in still mode, and when used under such conditions, ferromagnetic powder tends to fall off from the magnetic layer, which can clog the magnetic head. It can also be the cause of

Conventionally, a method of adding abrasives (hard particles) such as corundum, silicon carbide, or chromium oxide to the magnetic layer has been proposed as a measure to improve the running durability of the magnetic layer. When an abrasive is added to the magnetic layer for the purpose of improving durability, the effect of the addition is unlikely to be apparent unless the abrasive is added in a fairly large amount.

However, a magnetic layer with a large amount of abrasive added causes significant wear on magnetic heads, etc., and also goes against the purpose of smoothing the magnetic layer and improving electromagnetic conversion characteristics, so it is not a desirable method. I can not say.

It has also been proposed to add a fatty acid or an ester of a fatty acid and an aliphatic alcohol to the magnetic layer as a lubricant to reduce the coefficient of friction.

However, with the recent spread of portable video tape recorders and flexible disk drive devices for personal computers, various usage conditions for magnetic recording media are expected, such as use at low temperatures or use at high temperatures and high humidity. . Therefore, magnetic recording media must be stable so that their running durability does not change under various expected conditions, but conventionally known lubricants are not sufficient. Ta.

In particular, in video tapes and floppy disks, as the recording wavelength becomes shorter and the size of the recording medium becomes smaller due to the compression of the track width, the magnetic material is becoming more ferromagnetic than the conventional iron oxide-based ferromagnetic powder. Alloy powders have come to be commonly used, and magnetic powders of smaller size have also come to be used.

Although such rapid miniaturization of magnetic particles allows relatively excellent electromagnetic conversion characteristics to be obtained, it has been difficult to simultaneously improve running durability.

Therefore, the present inventors conducted intensive studies on lubricants that would eliminate the above-mentioned drawbacks, and found that ester compounds having a mercapto group, and especially among ester compounds having a mercapto group, H8(CH2)mCOO(CH2)n
CHs (n: an integer from 7 to 23, m: from 7 to 2
The present inventors have discovered that when a magnetic layer contains an integer of 0 or less, stable running durability can be obtained even when used under harsh conditions such as high temperature and high humidity, and low temperature and low humidity. Ta.

[Purpose of the invention]

The present invention is characterized by providing a magnetic recording medium with improved electromagnetic conversion characteristics and running durability.In particular, the present invention provides a magnetic recording medium that has excellent electromagnetic conversion characteristics and is stable even when changes in temperature and humidity occur. The object of the present invention is to provide a magnetic recording medium that exhibits excellent running durability.

[Structure of the invention]

The present invention relates to a magnetic recording medium comprising a magnetic layer in which ferromagnetic powder is dispersed in a binder on a non-magnetic support. The present invention relates to a magnetic recording medium characterized by containing an ester compound represented by:

HS (CH2)m C00(CH2) n CH3(
(m: an integer of 7 or more and 20 or less) (m: an integer of 7 or more and 20 or less) The magnetic recording medium of the present invention contains a ferromagnetic powder, a binder, and an ester compound represented by the following general formula on a nonmagnetic support. A magnetic layer is provided which has two basic structures.

As the nonmagnetic support used in the present invention, commonly used nonmagnetic supports can be used.

Examples of materials forming the nonmagnetic support include various composite resin films such as polyethylene terephthalate, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamideimide, and polyimide, and metal foils such as aluminum foil and stainless steel foil. be able to. In addition, the thickness of the non-magnetic support is generally 3 to 10 μm.
m, preferably 3 to 30 μm.

The nonmagnetic support may be provided with a backing layer (backing layer) on the side where the magnetic layer is not provided.

The magnetic layer of the magnetic recording medium of the present invention must contain an ester compound having a mercapto group.

Any ester compound having a mercapto group can be used. For example, one or more of the hydrogen atoms bonded to carbon in an ester compound produced by any combination of saturated/unsaturated fatty acids and saturated/unsaturated aliphatic alcohols is replaced with SH. If the material has a lubrication effect, it will exhibit an effective lubricating effect. Among these compounds, compounds represented by the following general formula are particularly preferred.

H8(CH2)mCOO(CH2)nCHa (n: an integer of 7 or more and 23 or less) (m: an integer of 7 or more and 20 or less) n is preferably 13 or more, more preferably 77 or more. m is preferably / to /j.

The amount of this ester compound added is preferably θ, O/wt% to /0,0 wt%, more preferably 0.0!, based on the ferromagnetic powder. wt% to twt%.

Specific examples of these ester compounds are as described below. However, it is not limited to these.

H8CI-(2COO(CH2)7CHsH8CH2C
OO(CH2)sCHa HS CH2COO(CH2) 9 CH5H8CH2
COO(CH2)xocHaH8CH2COO(CH2
)11CH3H8CH2C00 (CI-12)12CH
3H3CH2Coo(CH2)13CHaH8CH2C
OO(CH2)14CHaH8CH2Coo(CH2h
5CH3 H8CH2COO(CH2)16CH3H8CH2CO
O(CH2)17CH3H8CH2COO(CH2)1
8CH3H8CH2COO(CH2)1gCH3H8C
H2C00(CH2)20 CH3H8CH2C00(
CH2)21 CH3H8CH2C00(CH2)22
CI-13H8CH2Coo (CH2)23CH3H
S CH3COO(CH2) 7 CH5H8CHaC
OO(CH2)scH3 H8CHsCOO(CH2)eCHa H8CH3Coo(CH2)10CHaH8CH3Co
o(CH2hICH3 H8CH3COO(CH2)12CH3H8CH3,C
C00(CH2)13CH3H8CH3COO(CH2
)14CH3H8CH3Coo(CH2hsCH aH3CH3Coo(CH2)16CH3H8CHsC
oo(CH2h7CH aH8CH3COO(CH2)18CH3H8CH3C
OO(CH2)19CH3H8CH3COO(CH2)
20CH3H8CH3COO(CH2)21CHaH8
CH3COO(CH2)22CH3H8CH3COO(
CH2) 23 For those with CH3 greater than or equal to Hiroshi, illustrations will be omitted.

There are no particular limitations on the ferromagnetic powder used in the present invention. In addition to ferromagnetic alloy powder, γ-Fe20a/Fe3O4/Co modified iron oxide C002, modified 7 (lithium 7 elite, modified strontium ferrite, etc.) can be mentioned.

There is no particular restriction on the shape of the ferromagnetic powder, but needle-like, granular, dice-like, rice-grain-like, and plate-like shapes are usually used. The specific surface area of this ferromagnetic powder is 2m2/S
' The above is preferable in terms of electromagnetic conversion characteristics.

The binder forming the magnetic layer can be selected from binders commonly used in magnetic recording media. Examples of binders include:
Vinyl chloride/vinyl acetate copolymer, [Formula 1=”Nil, hinyl acetate copolymer with maleic acid and/or acrylic acid, vinyl chloride/vinyritine chloride copolymer, vinyl chloride/acrylonitrile copolymer ,
Examples include ethylene/vinyl acetate copolymers, cellulose derivatives such as nitrocellulose resins, acrylic resins, polyvinyl acetal resins, polyvinyl butyral resins, epoxy resins, phenoxy resins, polyurethane resins, polycarbonate polyurethane resins, and the like.

The total binder content in the magnetic J- of the magnetic d-recording medium of the present invention is usually 10-1 parts by weight per 100 parts by weight of the ferromagnetic powder.
00 parts by weight, preferably 20 to 0 parts by weight.

The magnetic layer of the magnetic recording medium of the present invention further includes mo/
O--S hardness! It is preferable to contain the above inorganic particles.

The inorganic particles used are not particularly limited as long as they have a Mohs hardness of 5 or more. Examples of inorganic particles with a Mohs hardness of 5 or more include A1203 (Mohs hardness), Ti0 (Mohs hardness),
), Ti02 (same J, J-).

S A02 (same 7), 5nOz (same a, t), cr2
03 (same as above) and α-Fe20a (same as above), and α-Fe20a (same as above), and these may be used alone or in combination.

Particularly preferred are inorganic particles having a Mohs' hardness of 500 s or more. When relatively soft inorganic particles with a Mohs hardness lower than j are used, the inorganic particles easily fall off from the magnetic layer and have almost no abrasive action on the head.
Head clogging is likely to occur, and running durability is also poor.

The content of the inorganic particles is usually in the range of o, i to 20 parts by weight, preferably in the range of 7 to 70 parts by weight, based on 100 parts by weight of the ferromagnetic powder.

In addition to the above-mentioned inorganic particles, the magnetic layer preferably contains carbon black (particularly one having an average particle size of 10 to 300 nm).

Next, an example of a method for manufacturing the magnetic recording medium of the present invention will be described.

First, a magnetic powder, a binder, the above-mentioned ester compound having a mercapto group, and if necessary, other fillers,
Additives are mixed with a solvent to prepare magnetic paint. As the solvent used in the crosstalk, a solvent commonly used for preparing magnetic paints can be used.

There is no particular restriction on the kneading method, and the order of adding the specific volume components can be set as appropriate.

For the preparation of magnetic paints, conventional mixing machines such as two-roll mills, three-roll mills, whole mills, pebble mills, thoron mills, sand grinders, zegvariator lighters,
Examples of high-speed inks include a Lar disperser, a high-speed stone mill, a high-speed impact mill, a disperser, a kneader-1 high-speed mixer, a homogenizer, and an ultrasonic disperser.

When preparing a magnetic paint, known additives such as dispersants, antistatic agents, lubricants, etc. can also be used.

Examples of dispersants include fatty acids having 72 to 72 carbon atoms (e.g.
caprylic acid, capric acid, lauric acid, myristic acid,
/ (lumilinic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, lylinic acid, stearolic acid), a gold plate consisting of the above fatty acids and an alkali metal (e.g. lithium, sodium, potassium, barium) Soaps, esters of the above fatty acids and compounds in which some or all of the hydrogen atoms in these compounds have been replaced with fluorine atoms, amides of the above fatty acids, aliphatic amines, higher alcohols, polyalkylene oxide alkyl phosphates, alkyl phosphates, alkyl phosphors Mention may be made of known dispersants such as acid esters, sarcosinate L alkyl ether esters, trialkyl polyolefins, oxy≠primary ammonium salts and lecithin.

When using a dispersant, the ferromagnetic powder 7 usually used
It is used in a range of 0.7 to 10 parts by weight per 00 parts by weight.

Examples of antistatic agents include conductive fine powders such as carbon black and carbon black graft polymers; natural surfactants such as saponins; nonionic surfactants such as alkylene oxides, glycerins, and glycidols; higher alkyl amines. cationic surfactants such as μ-class ammonium salts, salts of pyridine and other heterocyclic compounds, phosphoniums or sulfoniums;
Anionic surfactants containing acidic groups such as carzene acid sulfonic acid, phosphoric acid, sulfuric ester groups, and phosphoric ester groups; amphoteric surfactants such as amino acids, amino acids, aminosulfonsanes, and sulfuric or phosphoric esters of amino alcohols; Agents, etc. can be mentioned. When using the above conductive fine powder as an antistatic agent, for example, ferromagnetic powder io
o used in the range of 0.7-10 parts by weight,
When a surfactant is used, it is similarly used in a range of 0.12 to 10 parts by weight.

Examples of additional lubricants include monobasic fatty acids having 72 to 2θ carbon atoms, such as the fatty acids mentioned above, high-grade alcohols, butyl stearate, and sorbitan oleate, and monobasic fatty acids having 3 to 2θ carbon atoms. Esters consisting of 20 monohydric or polyhydric alcohols, mineral oils, animal and vegetable oils, olefin low polymers, fatty acid amides, silicone oils, modified silicone oils,
In addition to alkylene oxide adducts of fatty acids, known lubricants and plastic lubricants such as fine graphite powder, fine molybdenum disulfide powder, and fine tetrafluoroethylene polymer powder can be mentioned.

Note that the above-mentioned additives such as dispersants, antistatic agents, and lubricants are not strictly limited to having only the above-mentioned effects; for example, if the dispersant is a lubricant, Alternatively, it may act as an antistatic agent. Therefore, it goes without saying that the effects of the compounds exemplified by the above classifications are not limited to those listed in the above classifications, and when using substances that have multiple effects, it is necessary to The amount is preferably determined in consideration of its effects.

The magnetic paint thus prepared is coated on the non-magnetic support described above. Coating can be done directly onto the support, but it can also be applied onto a non-magnetic support via an adhesive layer or the like.

Examples of coating methods on non-magnetic supports include air doctor coating, blade coating, rod coating, extrusion coating, air knife coating, Swiss coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, and cast coating. , spray coating and stain/coat methods, and methods other than these can also be used.

Further, details of the method of dispersing the above-mentioned ferromagnetic powder and binder and the method of coating it on a support are described in various publications such as JP-A-1+-≠601I and J-KOK-2IROZ.

The thickness of the magnetic layer coated in this manner is generally in the range of about 0.0 to 1101 t after drying, usually /,
It is applied so that the thickness is in the range of j to 7.0 μm.

When a magnetic recording medium is used in the form of a tape, the magnetic layer coated on the non-magnetic support is usually subjected to a treatment for orienting the ferromagnetic powder in the magnetic layer, that is, a magnetic field orientation treatment, and then dried. The magnetic recording medium, which has been subjected to surface smoothing treatment, etc., if necessary, is then cut into a desired shape.

〔Example〕

Next, examples of the present invention will be shown. Note that "parts" in the examples indicate "parts by weight."

[Example 1] After cross-dispersing the following composition for a tie time using a ball mill, 5 parts of polyincyanate was added thereto, and after cross-dispersing for another 7 hours, it was filtered using a filter having an average pore size of 7 μm. , a magnetic paint was prepared. The obtained magnetic paint was dried so that the thickness after drying was ≠ θμm.
The coating was applied onto the surface of a polyethylene terephthalate support having a thickness of 10 μm using a reverse roll.

Magnetic paint composition l 7- Ferromagnetic alloy powder (composition: Fe rehiro%, Zn4t% +
Nt-2%; anti-magnetic crab/! 000e; surface area j
11n9/rrL2) 100 parts vinyl chloride/vinyl acetate/maleic anhydride copolymer (manufactured by Nippon Zeon ■≠OOX/ioA.

Polymerization degree Hiro 00) 72 parts Abrasive material (α-alumina, average particle size 3 μm) 5 parts Ester compound having a mercapto group (listed in Table 1) Stearic acid 7 parts Carbon black (average particle size Hiro (7 parts m) 2 Part methyl ethyl ketone 300 parts The non-magnetic support coated with the magnetic paint was oriented in a magnetic field with a 3000 Gauss magnet while the magnetic paint was not dry, and after drying, it was subjected to soot and e-calender treatment, and then 1 m wide. Ixa-/t- videotape was produced by slitting the tape into Ixa-/t-videotape.

A 7 MHz signal was recorded on the videotape obtained as described above using a VTR (Fuji Photo Film ■: FUJIX-r) and played back. The relative playback output of the videotape was measured when the 7MHz playback output recorded on the reference tape (Comparative Example 1) was set as OdB.

The obtained videotape is brought into contact with the tension (Tl) of stainless steel pole roller 1Of (wrapping angle 1ro0),
Under these conditions, the tension (T2) required to run the videotape at a speed of 3.3 cm/s was measured. Based on this measured value, the friction coefficient μ of the videotape was determined using the following calculation formula.

(Listed in Table 1) tt-=l/π-1n (T2/T 1) The friction coefficient test was as follows: a, 20°C, 7°%RH, b, ≠
The test was carried out under two conditions: o 0C and tochi RH.

〔Effect of the invention〕

As is clear from the results in Table 1, Examples using the ester compound having a mercapto group of the present invention/~! It can be seen that the reproduction output is high in both conditions, and the friction coefficient is low in both conditions a and b.

On the other hand, it can be seen that when only fatty acids or esters are used without using the compound of the present invention, the regeneration output is low and the friction coefficient is large especially under high temperature and high humidity (condition b). .

Claims (2)

[Claims] (1) A magnetic recording medium comprising a magnetic layer in which ferromagnetic powder is dispersed in a binder on a non-magnetic support, characterized in that the magnetic layer contains an ester compound having a mercapto group. magnetic recording media. (2) A magnetic recording medium comprising a magnetic layer in which ferromagnetic powder is dispersed in a binder on a non-magnetic support, characterized in that the magnetic layer contains a compound represented by the following general formula. A magnetic recording medium according to claim (1). HS(CH_2)_mCOO(CH_2)_nCH_3 (n: an integer from 7 to 23) (m: an integer from 1 to 20)