JPH043321A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electromagnetic conversion characteristics and traveling property from low temp. to high temp. by incorporating a specified acyloin compd. into a magnetic layer. CONSTITUTION:The magnetic recording medium has a magnetic layer comprising a ferromagnetic powder dispersed in a binder, formed on a nonmagnetic supporting body, and acyloin compd. expressed by formula I is incorporated into the magnetic layer. Thereby, the obtd. medium has higher electromagnetic conversion characteristics and traveling property from low temp. to high temp. In formula, one of R1 and R2 is a satd. or unsatd. chain aliphatic hydrocarbon group of 9 - 23 carbon number, and the other is a satd. or unsatd. chain aliphatic hydrocarbon group of 5 - 23 carbon number.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic recording medium comprising a nonmagnetic support and a magnetic layer.

(Prior Art) A magnetic recording medium basically consists of a non-magnetic support and a magnetic layer made of ferromagnetic powder dispersed in a binder provided on the non-magnetic support. ing.

In recent years, magnetic recording media have been widely used as recording tapes, video tapes, floppy disks, etc., and are required to have various characteristics depending on their use.

Nowadays, video tapes have high video output and excellent original picture playback ability! It is required that the tape has excellent magnetic conversion properties and also has good properties in terms of tape running properties and the like.

In particular, video tapes used for 8mm video, which have recently been put into practical use, are used under harsher conditions than conventional video tapes, so the above-mentioned characteristics essentially required for video tapes are not met. , a higher level than that of conventional videotape is required.

In particular, recent magnetic recording media such as 8mm video tapes have highly smooth magnetic layer surfaces in order to reduce spacing loss between the magnetic head and the magnetic layer surface and improve electromagnetic conversion characteristics. It is becoming more and more popular.

However, when the surface of the magnetic layer is smoothed, the friction coefficient of the magnetic layer increases, causing a problem in that squeaking noise (so-called tape squeal) occurs when the magnetic head or other running system contacts the magnetic layer. There is.

By the way, in order to lower the friction coefficient of the magnetic layer and improve the running properties of the magnetic recording medium, a method has been adopted in which a lubricant is contained in the magnetic layer.

The use of various substances as lubricants has been proposed, such as compounds containing fatty acids, fatty acid esters, silicone oils, and the like.

Although these lubricants have a certain degree of effectiveness in the normal use of conventional magnetic recording media, for example, they use extremely fine ferromagnetic metal powder, and For 8 mm video tapes with high smoothness, it may not be possible to sufficiently reduce the coefficient of friction of the magnetic layer.

In other words, measures to improve the running properties of magnetic recording media are sufficient for magnetic recording media, such as 8 mm video tapes, which are required to have various properties at a higher level than conventional ones. I can't say that.

In order to solve these problems, monoketone compounds were known (Japanese Patent Laid-Open No. 158026/1983), and a magnetic recording medium containing a diketone represented by the following general formula [I1] in the magnetic layer was proposed (Japanese Patent Laid-Open No. 158026/1983). (Sho 62-95731).

R' -〇〇-Co-R” [II] However,
One of R1 and R2 is a saturated or unsaturated chain aliphatic hydrocarbon group having 9 to 23 carbon atoms, and the other is a saturated or unsaturated chain aliphatic hydrocarbon group having 5 to 23 carbon atoms. It is.

However, in such diketones, because the polar Co groups are adjacent to each other, the adsorption force of Co groups on the magnetic layer surface is stronger than that of monoketones, but the behavior tends to be similar to that of monoketones, and the lubricant is dense. The lubricity is not sufficiently exhibited at the beginning of running due to the formation of rough spots and sparse areas, and the temperature at 23°C to 40°C
Although it shows good lubricity in a temperature range of about 0.degree. C., it sometimes does not show sufficient lubricity at temperatures as low as 5.degree. C. or as high as 60.degree.

(Object of the Invention) The first object of the present invention is to provide a novel magnetic recording medium.

A second object of the present invention is to provide a magnetic recording medium that has improved running properties mainly at low to high temperatures and also has good electromagnetic conversion characteristics.

(Structure of the Invention) That is, the above object of the present invention is to provide a magnetic recording medium having a non-magnetic support and a magnetic layer in which ferromagnetic powder is dispersed in a binder provided on the support. This can be achieved by a magnetic recording medium characterized by containing an acyloin compound represented by the following general formula (1).

H R'-Co-C-R" (5 to 23 saturated or unsaturated chain aliphatic hydrocarbons.) More preferably, the object of the present invention is that the magnetic recording medium contains a fatty acid having a carbon number of 12 to 22; This can be achieved by a magnetic recording medium characterized by containing an ester of a fatty acid having a carbon number in the range of 12 to 22 and an aliphatic alcohol having a carbon number in a range of 1 to 5.

More preferably, the above object of the present invention has a non-magnetic support, a magnetic layer in which ferromagnetic powder is dispersed in a binder provided on one surface of the support, and a magnetic layer provided with a binder provided on the other surface. A magnetic recording medium having a bank layer in which a filler is dispersed, characterized in that the magnetic layer and the hack layer contain a diketone represented by the general formula [r]. I can do it.

Preferred embodiments of the present invention are as follows.

(1) The content of the diketone represented by the above general formula [I] in the magnetic layer is 0.0 parts by weight per 100 parts by weight of the ferromagnetic powder.
A magnetic recording medium characterized in that the content is 1 part by weight or more.

(2) The content of the diketone represented by the above general formula [I] in the magnetic layer is 0.0 parts by weight per 100 parts by weight of the ferromagnetic powder.
A magnetic recording medium characterized in that the amount is in the range of 2 to 5 parts by weight.

(3) A magnetic recording medium characterized in that R' and R2 are the same saturated or unsaturated chain aliphatic swollen hydrogen group having 9 to 23 carbon atoms.

(4) The total content of fatty acids and fatty acid esters contained in the magnetic layer is 0.00 parts by weight per 100 parts by weight of the ferromagnetic powder.
A magnetic recording medium characterized in that the amount is within a range of 0.02 to 10 parts by weight.

(5) The magnetic layer is characterized in that the ratio of the content of the compound represented by the general formula [N to the total weight content of fatty acids and fatty acid esters is within the range of 1:2 to 1:8. magnetic recording medium.

(6) A magnetic recording medium characterized in that the ferromagnetic powder is a fine ferromagnetic metal powder having a specific surface area of 42rrf/g or more.

That is, in the present invention, by including an acyloin compound having a ketone group and a hydroxyl group in the molecule in the magnetic layer, running properties from low to high temperatures are significantly improved, and the 111 magnetic conversion characteristics are also improved.

The reason why the magnetic recording medium containing the acyloin compound of the present invention exhibits particularly good running properties and durability is not necessarily clear, but it is presumed that it is due to the presence of ketones and hydroxyl groups. In other words, ketones have a better affinity for components constituting the magnetic layer, such as ferromagnetic powder or binder, than compounds that do not have polar groups such as intramolecular [-Co-] bonds. It is considered to have both lubricity and adsorption properties because it has a high retention property, and because it has hydroxyl groups, it reacts with polyisocyanate and binders.

This adsorption is not just adsorption due to Van der Waals force, but because it is bonded through a chemical reaction, it is not just a temporary adsorption or desorption. Therefore, it has extremely excellent durability from the initial stage to long-term use. It is also thought that it exhibits excellent lubrication properties.

The magnetic recording medium of the present invention basically has a structure in which a non-magnetic support and a magnetic layer made of ferromagnetic powder (ferromagnetic material) dispersed in a binder are provided on the support. .

The material forming the non-magnetic support can be one that is normally used as a material for the non-magnetic support of magnetic recording media.

Examples of the material include polyethylene terephthalate, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamideimide, polyimide, and metal foils such as aluminum foil and stainless steel foil.

The non-magnetic support generally has a thickness of 3 to 50 μm, preferably 5 μm.
~30 μm thick.

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

The magnetic recording medium of the present invention is one in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a nonmagnetic support as described above.

Examples of ferromagnetic powders include γ-Fe20. , Fe3O4
Metal oxide-based ferromagnetic powder such as C.

Examples include modified metal oxide-based ferromagnetic powders such as γ-Fe, O, etc. containing γ-Fe, O, etc., and ferromagnetic metal fine powders containing ferromagnetic metals such as iron as a main component.

In particular, it is preferable to use ferromagnetic metal fine powder.

When using a ferromagnetic metal fine powder, the ferromagnetic metal fine powder is a ferromagnetic metal fine powder containing iron, cobalt or nickel, and its specific surface area (S BET) is 42rr.
It is preferable to use fine ferromagnetic metal powder with a particle size of r/g or more (particularly preferably 45 n?/g or more). If the specific surface area of the ferromagnetic metal fine powder is smaller than 42 m/g,! Magnetic conversion characteristics may not be sufficiently improved.

As an example of this ferromagnetic metal fine powder, the metal content in the ferromagnetic metal fine powder is 75% by weight or more, and the metal content is 8% by weight.
0% by weight or more of at least one ferromagnetic metal or alloy (e.g., Fe, Co, Nis Fe-Co-Fe-N
i, Co-Ni.

Co-N1-Fe), and other components (eg, A1, Si, S) within a range of 20% by weight or less of the metal content.

Sc, Ti, V, Cr, Mn, Cu, Zn, Y.

Mo, Rh, Pd, Ag, 5nSSb, Te.

Ba, Ta, W, Re, Au, Hg, Pb, Bi.

Mention may be made of alloys which may contain La, Ce, Pr, Nd, B, P). Furthermore, the ferromagnetic metal component may contain a small amount of water, hydroxide, or oxide, and methods for producing these ferromagnetic metal fine powders are already known, and the ferromagnetic metal used in the present invention Fine metal powder can also be produced according to these known methods.

There is no particular restriction on the shape of the ferromagnetic metal fine powder, but needle-like, granular, dice-like, rice-grain-like, and plate-like shapes are usually used. In particular, it is preferable to use needle-shaped ones.

As the binder, commonly used binders can be used. Examples of resins used include cellulose derivatives,
Vinyl chloride/vinyl acetate copolymer resin containing a third component such as vinyl chloride/vinyl acetate/maleic anhydride copolymer, vinyl chloride/vinyl acetate copolymer resin, vinylidene chloride resin, polyester resin, acrylic resin, Examples include polyvinyl acetal resin, polyvinyl butyral resin, phenoxy resin, epoxy resin, butadiene-acrylonitrile copolymer resin, polyurethane resin, and urethane epoxy resin, which can be used alone or in combination.

Furthermore, when using the binder of the present invention, it is preferable to use a polyisocyanate compound in combination.Since the polyisocyanate compound reacts to form a three-dimensional network crosslinked structure, the strength of the magnetic layer is high. be.

The polyisocyanate compound can be selected from commonly used polyisocyanate compounds.

The binder used in the present invention is generally a ferromagnetic powder of 100%
It is used in an amount of 10 to 100 parts by weight, preferably 15 to 50 parts by weight.

The magnetic layer of the magnetic recording medium of the present invention contains a compound (acyloin compound) represented by the following general formula (1).

H R'-Co-C=R" [I] In the above general formula, at least one of R1 and R2 must be a saturated or unsaturated chain aliphatic hydrocarbon group having 9 to 23 carbon atoms. In addition, the other one must be a saturated or unsaturated chain aliphatic hydrocarbon group having 5 to 23 carbon atoms, and in particular, a chain aliphatic hydrocarbon group having 9 carbon atoms as above.
-23 saturated or unsaturated chain aliphatic hydrocarbon groups are preferred. However, the number of carbon atoms in R1 and R2 does not need to be the same, and the number of carbon atoms of different types is 9 to 23.
It may be a saturated or unsaturated chain aliphatic hydrocarbon group within the range of . A magnetic recording medium containing an acyloin compound in which both R1 and R2 are saturated or unsaturated chain aliphatic hydrocarbon groups outside this range cannot improve running performance.

In the present invention, the acyloin compound is preferably contained in an amount of 0.01 parts by weight or more, and preferably in a range of 0.01 to 5 parts by weight, based on 100 parts by weight of the ferromagnetic powder contained in the magnetic layer. It is particularly preferable that If the content of the acyloin compound is less than 0.01% by weight, the coefficient of friction on the surface of the magnetic layer may not be sufficiently reduced.

Examples of such acyloin compounds include H Cq H+q Co CC9HI9, 0H C1H33Co CC+aHz.

H C+bHx3 COCCI? H x H CI? Compounds such as Hs s COCC+ q Hx s, H Cz s Ha and COCC23Ha 7 can be mentioned.

The method for synthesizing the acyloin compound of the present invention is as follows.
Ru.

According to Hans Ley's method, 46 g of metallic sodium with a purity of 99.7% was placed in a reactor with 2.71' of toluene, stirred at 105° C. at a speed of 1800 rpm, and the air inside was sufficiently replaced with nitrogen. From, methyl caprate 186. A solution obtained by dissolving 1 g (1 mol, 1 mol was also used in the case of other esters) in the same amount of toluene was added dropwise in about 90 ml, and then 60 ml was added.
Continue stirring. After the reaction was completed, it was neutralized with 13% dilute sulfuric acid in a nitrogen stream, separated, and the toluene layer was washed with water.
% sodium carbonate solution to remove as much fatty acid as possible, add an appropriate amount of 50% methanol aqueous solution to break the emulsion, leave it at 40°C or less, separate the liquid, rinse with water, and rinse with water.
Distill toluene. The crude asoloin thus obtained was recrystallized from 99% ethanol. Toluene was used as the recrystallization solvent when methyl valmitate was used.

In addition to the above-mentioned acyloin compound, the magnetic layer contains 12 carbon atoms.
fatty acids within the range of ~22 and carbon numbers between 12 and 22
It is preferable to include an ester of a fatty acid within the range of 1 to 5 carbon atoms and an aliphatic alcohol having 1 to 5 carbon atoms.

When containing fatty acids and fatty acid esters in addition to the above-mentioned acyloin compounds, the total content of fatty acids and fatty acid esters should be 0.02 to 1.0% per 100 parts by weight of the ferromagnetic powder.
It is preferable to set it within the range of 0 parts by weight.

Further, the ratio of the content of the acyloin compound contained in the magnetic layer to the total weight content of fatty acids and fatty acid esters is usually set within the range of 1:2 to 1:8.

In addition to the above binder, ferromagnetic powder, acyloin compound, and optionally added fatty acids and fatty acid esters, the magnetic layer of the magnetic recording medium of the present invention contains commonly used dispersants, other lubricants, It may also contain additives such as stabilizers, abrasives and antistatic agents.

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

In the magnetic recording medium of the present invention, a magnetic coating material is prepared by dispersing ferromagnetic powder, a binder, an acyloin compound, and the above-mentioned additives used as desired in a commonly used organic solvent such as methyl ethyl ketone or cyclohexanone. However, it can be manufactured by coating this magnetic paint on a non-magnetic support, drying it, and cutting it. usually,
The magnetic layer is attached by coating directly on the non-magnetic support,
It is also possible to attach it via an adhesive layer or an undercoat layer. Alternatively, it can be manufactured by applying a magnetic paint, subjecting this coated layer to a magnetic field alignment treatment before drying, and then passing through a drying process, a surface smoothing process, and a curing process. Methods for preparing magnetic coating materials, coating methods, magnetic field orientation treatment methods, drying methods, surface smoothing treatment methods, curing methods, etc. are already known, and the magnetic recording medium of the present invention can also be manufactured according to these methods.

The magnetic recording medium of the present invention has a low coefficient of friction on the surface of the magnetic layer,
Shows good running performance.

Therefore, it exhibits good running properties even on magnetic recording media with very smooth magnetic layer surfaces, such as 8 mm video tapes, and at the same time ensures good contact between the smooth magnetic layer and the magnetic head. Therefore, it has the advantage of exhibiting high playback output.

It should be noted that the magnetic recording medium of the present invention is not limited to 8 mm video tapes, but can of course be used as magnetic recording media such as ordinary video tapes, audio tapes, magnetic tapes for computers, and floppy disks. .

(Effects of the Invention) The present invention includes an acyloin compound having a ketone group and a hydroxyl group in the molecule in the magnetic layer, so that the ketone group has a high affinity with the ferromagnetic powder and the binder, and has a high retention property in the magnetic layer. The durability of the magnetic layer is improved because the hydroxyl group reacts with the hardening agent polyisocyanate.

Therefore, even under low temperature and low humidity conditions of 5°C and 30%, 40°C and 80%
It has a low coefficient of friction even under high-temperature conditions of %RH, and also solves problems such as playback output and tape squeal.

(Example) Next, Examples and Comparative Examples of the present invention will be shown. In addition, in the Examples and Comparative Examples described below, the expression "parts" represents "parts by weight."

[Example 1] After cross-dispersing the following composition for 48 hours using a ball mill, 5 parts of polyisocyanate (manufactured by Bayer AG, Desmodur L) was added thereto, and after further cross-dispersing for 1 hour, an average of 18 m A magnetic paint was prepared by filtration using a filter with a pore size. The obtained magnetic paint was coated on the surface of a 10 μm thick borie-ethylene terephthalate support using a reverse roll so that the thickness of the magnetic layer after drying was 4.0 μm.

Blue 11-grade ferromagnetic metal fine powder (Constitution: Fe94%, Zn4
%, N4 2%, Hc: 15000e, specific surface area: 54+d/g) 100 parts vinyl chloride/hinyl acetate/maleic anhydride copolymer (Nippon Zeon ■, 400X110A degree of polymerization: 400) 12 parts Formula [I
] Acilloin compound (R', R' is C+tHss) 1 part α
-A1.03 (average particle size 40 μm) 5 parts carbon black (average particle size 40 μm) 2 parts stearin #1 2 parts butyl stearate 2 parts methyl ethyl ketone 300 parts In the undried state, it was subjected to magnetic field orientation treatment using a 3000 Gauss magnet, and after drying, it was subjected to supercalender treatment and slit to a width of Bf1 to produce an 8 mm video tape.

A 7 MHz signal was recorded and played back on the videotape obtained as described above using a video recorder (FUJIX-8). The relative playback output of the videotape was measured when the 7MHz playback output recorded on the reference tape (8 mm video tape obtained in Comparative Example 2) was set as OdB.

50g of the obtained videotape and stainless steel pole (
The tension (T2) required to run the tape at a speed of 3.33/min under these conditions was measured under the conditions of 5°C and 30% RH. (Conditions and conditions of 40°C and 80% RH (conditions ■)
I did it.

At this time, the first sliding was expressed as [friction coefficient A], and the 100th sliding was expressed as [friction coefficient B]. From these measured values, the friction coefficients μ, (condition (■)) and μ2 (condition (■)) of the videotape were determined using the following formulas.

μ (+, 2) = 1/win (Tz/T+) Also, 30 rolls of manufactured 8mm video tape were run on the above video recorder, and the number of rolls of tape at which tape squeal occurred during the running test was calculated. I looked into it.

Table 1 shows the playback output, friction coefficients A and B (conditions ■ and conditions ■), and the number of turns at which tape squeal occurred.

In the Examples and Comparative Examples described below, the reproduction output, friction coefficient (Condition I, Condition TJ), and tape squeal were measured under the above conditions.

[Example 2] In Example 1, instead of the acyloin compound in which R1 and Rz are both Ct7H3s, R1 is C+iH*z, R
An 8 mm video tape was produced in the same manner except that an acyloin compound in which 2 is C, H, , etc. was used.

The obtained tape playback output, friction coefficient (condition ■, condition ■
) and the number of turns of tape in which tape squeal occurred are listed in Table 1.

[Example 3] An 8 mm video tape was produced in the same manner as in Example 1 except that the amount of the acyloin compound was changed to 5 parts.

The obtained tape playback output, friction coefficients A and B (condition I,
Condition (2) and the number of turns of tape in which tape squeal occurred are listed in Table 1.

[Example 4 In Example 1, are R1 and R2 both CI? Hs
An 8 mm video tape was produced in the same manner except that an acyloin compound in which both R1 and R2 were Cq H+q was used instead of the acyloin compound in which R1 and R2 were Cq H+q.

The obtained tape playback output, friction coefficients A and B (condition I,
Condition (2) and the number of turns of tape in which tape squeal occurred are listed in Table 1.

[Example 5] In Example 1, instead of the acyloin compound in which R1 and R2 are both C+-rHxs, R1 and Ro are both C
An 8 mm video tape was produced in the same manner except that an acyloin compound of z 3 Ha q was used.

The obtained tape playback output, friction coefficients A and B (condition I,
Condition (2) and the number of turns of tape in which tape squeal occurred are listed in Table 1.

[Comparative Example 1] An 8 mm video tape was produced in the same manner as in Example 1 except that the acyloin compound was not used.

The obtained tape playback output, friction coefficients A and B (condition I,
Condition (2) and the number of turns of tape in which tape squeal occurred are listed in Table 1.

[Comparative Example 2] In Example 1, R1 and R2 are both C+ q H3s
In place of the acyloin compound where R1 and R2 are both C? 8 in the same manner except that H+s diketone was used.
Manufactured millimeter video tape.

The obtained tape playback output, friction coefficients A and B (conditions ■,
Condition (2) and the number of turns of tape in which tape squeal occurred are listed in Table 1.

As is clear from the results in Table 1, the general formula [I] of the present invention
Examples 1 to 5 using the acyloin compound represented by
Like H, it has a low friction coefficient at low temperatures and low humidity and high temperatures and high temperatures, has good tape squeal, and has high playback output.

On the other hand, when the acyloin compound of the present invention is not used or when a diketone is used, the friction coefficient especially at the 100th pass increases, and tape squeal and reproduction output can be sufficiently improved.

Claims (2)

[Claims] (1) In a magnetic recording medium having a non-magnetic support and a magnetic layer in which ferromagnetic powder is dispersed in a binder provided on the support, the magnetic layer is represented by the following general formula [I]. A magnetic recording medium characterized by containing an acyloin compound. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] (However, R^1 and R^2 have one carbon number of 9 to 2
3 saturated or unsaturated chain aliphatic hydrocarbon group,
The other one is a saturated or unsaturated chain aliphatic hydrocarbon having 5 to 23 carbon atoms. ) (2) The magnetic recording medium may contain a fatty acid having a carbon number of 12 to 22, a fatty acid having a carbon number of 12 to 22, and an aliphatic alcohol having a carbon number of 1 to 5. The magnetic recording medium according to claim (1), characterized in that it contains an ester of.