JPS58189826A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a titled medium having good durability and travelability in a metallic tape using metallic powder as ferromagnetic powder by contg. 1-15wt% nonmagnetic power based on the weight of ferromagnetic metallic powder and 0.1-5wt% fatty acid ester based on the weight of the ferromagnetic metallic powder and further forming a magnetic layer to <=0.03mu surface roughness. CONSTITUTION:Nonmetallic powder is added at 1-15wt%, more preferably 2- 10wt% more particularly preferably 3-7wt% based on the weight of ferromagnetic metallic powder. If the content of the nonmetallic powder is smaller than the abovementioned range, the tape is vulnerable to flaw and damage by heads, and causes head clogging, thus resulting in the failure in outputting and the decrease in S/N. Ester is added at 0.1-5wt%, more preferably 0.2-4wt%, more particularly preferably 0.4-3wt% based on the weight of the ferromagnetic metallic powder. If the amt. to be added is too small, the durability of the magnetic layer cannot be assured. The surface roughness of the magnetic layer is preferably <=0.03mu, more preferably <=0.025mu and more particularly preferably <=0.02mu.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic recording media, and more particularly to improving the video characteristics of so-called metal tapes using metal powders as ferromagnetic powders.

A magnetic recording medium is composed of a nonmagnetic support such as a polyethylene terephthalate film, a polycarbonate film, a polyimide film, etc., and a magnetic layer provided thereon, which mainly consists of ferromagnetic powder and a binder.

Examples of ferromagnetic powders include conventionally used iron-based fine powders, and ferromagnetic metals that have recently been used to improve magnetic recording density and reproduction output due to their high saturation magnetization and coercive force. There are powders etc.

Nine-sulfur recording tape (so-called metal tape), which uses ferromagnetic metal powder, has a lower recording density than conventional iron oxide tape, so its practical use has been seriously considered in recent years for video applications. iru. V for metal tape fttC
A prototype model in which the Ti-L is miniaturized and integrated with a camera has been proposed. In such a system, the recording density is assumed to be more than twice that of the current VH8 system and β system, the diameter of the head cylinder will be approximately 1/cm compared to the current one, and the head/tape relative speed will be approximately 1/cm. There is. Accordingly, the recording wavelength is also halved, and is estimated to be approximately F, 4μ.

Under such conditions, the image quality for recording and playback is comparable to the current VH8/β7.
It is required to be as good as the stem. Therefore, when testing under the same conditions, the C/N ratio (ratio of reproduced signal output/modulation noise when PM carrier waves are recorded) is required to be at least +jdB for VH8/β tape.

In order to meet this requirement, the medium needs to have a uniform condition, which causes gaps.

The distance between the tape and the head [(f) is desired to be smaller as the recording density becomes higher and the recording wavelength (λ) becomes shorter when considering spacing loss.

Ninth, the surface properties of the magnetic layer are required to be bulkier. When the surface properties become high and the magnetic layer becomes smooth, (1) the contact resistance with the guide parts in the TR, the cylinder, and the mechanical parts in the cassette becomes high, making it difficult for the tape to run stably.

If the running of the tape becomes unstable, not only will the quality of the material deteriorate, but the tape will also become more easily damaged, leading to problems with durability.

By using metal magnetic powder, the output during short wavelength recording must be kept in consideration of the above-mentioned spacing loss, etc., and noise 'J! t, 16〈It is necessary to do so.

For this purpose, it is advantageous that the magnetic layer has high surface properties.

A uniform fraction of magnetic powder particles is also important for surface properties.

As mentioned above, in order to obtain a metal tape with a high recording density and high video characteristics with a length of e length of /μ or more, the following table [l[
] Requires a magnetic layer with stable footing and magnetic properties.
- The durability of the conventional V) is or β must be maintained.
S1 magnetic tape has a new innovation not found in iron oxide tape.
An issuance fee is required.

The object of the present invention is to provide a magnetic recording medium with good video characteristics, and to provide a magnetic recording medium for video having a magnetic layer with good durability. Thirdly, it is an object of the present invention to provide a video recording medium with good running properties.

As a result of various attempts to achieve the above object, the inventors of the present invention discovered that the magnetic layer contains a ferromagnetic metal powder with a ratio of 1 Om''/gr or more and a non-magnetic powder with a Mohs hardness of 4 or more. The above object is achieved by containing /~/jwt% of the magnetic powder, fatty acid ester of 0.j-jet's of the ferromagnetic powder, and by setting the surface roughness of the magnetic layer to 0.03 μm or less. I have found that it can be achieved.

Although the method for producing the ferromagnetic metal powder used in the present invention is not particularly limited, it can be produced, for example, by the following method.

(1) A method of thermally decomposing an organic acid salt of a ferromagnetic metal and reducing it with a reducing gas.

(2) A method for reducing acicular oxyhydroxides, acicular oxyhydroxides containing other metals, or acicular iron oxides obtained from these oxyhydroxides.

(3) Method of evaporating ferromagnetic metal sound in low pressure inert gas.

(4) A method of thermally decomposing a metal carbonyl compound.

(5) A method of electrodepositing ferromagnetic metal powder using a mercury cathode and then separating it from mercury.

(6) A method in which a ferromagnetic powder is obtained by reducing a metal salt capable of producing a ferromagnetic substance using a reducing substance (borohydride compound, hypophosphite, hydrazine, etc.) in an aqueous solution.

In the present invention, the ferromagnetic metal powder produced by the above-mentioned methods (2), (3), and (6) is easy to use, and the powder obtained by the namefu method (2) is second to none in terms of cost and quality. desirable. (9) When producing the ferromagnetic metal powder of the present invention, it is desirable to provide an oxide film on the surface of the particles in order to improve the chemical stability of the fine metal powder.

The composition of the ferromagnetic metal powder is pc, Fe-N's? e-
Pure iron such as N1-Go, alloy, and further improves properties by adding 8% CXN5 Al-, S1% P%8, T
It is also possible to contain a small amount of non-magnetic or non-magnetic elements such as I, Cr, Mu, Cu, and Zn. The particle size is generally difficult to determine because it has a good shape with several 100 angstrom spherical particles connected like a necklace, and six acicular particle shapes running together.

The present inventors have found that the ratio and area measured by the N2 gas adsorption method using the BET method is a very narrow indicator for improving the properties targeted by the present invention. In order to achieve the object of the present invention, J o m ” / 9 or more, preferably J
z m ” / 9 or more, especially preferably 3 m ”
/ f. If the specific surface area is small, the output may not be sufficient or the noise may be high, making it impossible to achieve the desired video characteristics. Coercive force of ferromagnetic metal powder (
HC) is 1000 to 0000e, and the saturation magnetization (0m) is preferably /20emμ/f or more.

Another important point of the present invention is the use of a non-magnetic powder with a Mohs hardness of 4 or more and a fatty acid ester under the conditions described below.

Non-magnetic powders with a Mohs hardness of 4 or higher include alumina, titanium oxide, silicon carbide, chromium oxide, corundum, diamond, silica, iron oxide, garnet, zirconia,
There are various oxides, nitrides, carbides, and ferrides such as aluminum nitride, silicon nitride, boron nitride, and boron carbide. The average particle diameter is preferably 0.01-jμ, particularly preferably 0./-jμ. The amount of such non-magnetic powder added is 7 to 1/Jwt, preferably 2 to 1 Jwt, of the ferromagnetic metal powder.
0 wt%, %K [L< is 3 to 7 WtLs. If there is not enough non-magnetic powder, the tape will be scratched by the head and the tape will be damaged, the head will fail and no output will be output, or the noise will be large and the 8/N will be low. or On the other hand, if it is too large, the saturation magnetization of the magnetic layer will be low, resulting in a low output, or the surface properties of the magnetic J- will be low, resulting in a large amount of noise and a low S/N ratio. Furthermore, this also causes the problem of increased wear on the head. A non-magnetic powder with a hardness of 4 or more is suitable for magnetic I- to maintain an appropriate polishing effect on video heads. You can say that. The addition method is that it can be added from the beginning of the crosstalk dispersion process along with the magnetic material, or it can be added in the middle.i! ! is to distribute it uniformly within the magnetic layer.

Examples of fatty acid esters include linear alkyl alcohols having more than one carbon number, such as ethyl, butyl, amyl, and ofnal;
Coethylhexyl, cohephthyl undefur @
Chain alkyl alcohols or alcohols with ether bonds such as butoxyethyl and saturated fats such as valmitic acid, stearic acid, myristic acid, and lafric acid.
; Olein cough button unsaturated fat fls alkyl group m-
An ester compound obtained by an esterification reaction with a fatty acid is used.

Its attachment/JD t is o, i-twt of ferromagnetic metal powder
capsule, preferably 00λ to 30%, particularly preferably 0.
This is ~Jwt-. @Magnetic with still mode for viewing still images with less! − Durability cannot be guaranteed. On the other hand, if there is too much fecal matter, the magnetism will become soft, and it will be easier to cause radish I reading during normal driving, or stick-slip phenomenon will occur, making it difficult to drive properly. become unable to do so.

Also, it is important that fatty acids are added to the rolls to ensure smooth running of the tape, but that the sludge with the fatty acid esters does not exceed the iowts of the ferromagnetic metal #powder. If it exceeds 1 OWt, the magnetic layer becomes soft, resulting in low durability and poor surface properties, resulting in high noise and low S/N.

In the present invention, in addition to satisfying the above-mentioned material selection conditions, it is important to have the surface properties of the magnetic layer equal to or higher than the level of the magnetic layer in order to achieve the objective m. According to the inventors' experiments, J
Cutoff value 0 defined by IS-Boiaot item 5
．． The surface roughness when defined by the centerline average roughness of λzmm is 0. OJμF, preferably 0.0ko! It has been found that a value of F or less than μ, particularly desirably less than F of 0.0λμ is sufficient.

If the specific surface area of the magnetic material is within the above conditions, the surface properties of the magnetic layer can be increased by appropriately selecting conditions such as the dispersion process and molding process of the magnetic powder, and the purpose can be achieved within the above conditions. Is possible.

If the surface roughness is too large, the output cannot be made high due to spacing loss with the head, or the video 8/N cannot be made very high due to increased noise. On the other hand, when the surface roughness becomes extremely high and the roughness becomes very small, the coefficient of friction between the magnetic layer and the cassette parts and (2) Tf'L parts becomes large and the footing property becomes low.

The above ferromagnetic powder is kneaded with a binder to form a magnetic coating liquid.

The binder used in the present invention is not particularly limited, and may include conventionally used thermoplastic resins, thermosetting resins, reactive resins, or mixtures thereof.

Examples of these binders include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer,
Vinyl chloride-acrylonitrile co-electropolymer, acrylic wrinkle ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic acid ester-
Acrylonitrile co-electrolyte, methacrylic version ester-4
Vinylidene chloride co-N8, methacrylic acid ester-styrene 1i combination, urethane elastomer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose 04, styrene/-butadiene! 1 unit, polyester resin, various synthetic rubber-based thermoplastic resins, phenol-formalin-based resins, formaldehyde-based resins, urea resins, nosimine resins, various lucid-based resins, epoxy resins and various curing agents with terminal isocyanates. There are thermosetting resins and reactive resins such as. The mixing ratio of ferromagnetic metal powder and binder, preferably l[
Violet ratio: powder 100K to binder l~λ! It is.

Examples of organic solvents for crosstalk dispersion include ketones such as methyl ethyl ketone and cyclosanone, alcohols, esters such as ethyl acetate and dityl acetate, benzene, toluene,
Aromatics such as xylene 41143, and 4 others! carbon chloride,
Organic solvents such as chlorinated hydrocarbon solvents such as chloroform can be included.

As the non-magnetic support, synthetic resins (for example, polyester, vinyl thread polymers, and Rululose derivatives), non-magnetic metals, paper, etc. can be used, and the forms thereof are films, tapes, sheets, etc.

The magnetic layer coated on the support is subjected to a smoothing treatment (for example, a smoothening treatment before drying or a calendering treatment after drying) to reduce the magnetic properties such as 8/N.

The additives, supports, and manufacturing methods exemplified above are described in Japanese Patent Publication Shojj-Jjf No. 0.

According to the present invention, a metal tape with high video characteristics can be obtained. In other words, by using a fine ridged powder with a large specific surface area and further increasing the surface properties of the magnetic layer, it is possible to reduce the gap loss with the head, suppress the low F of the output, and reduce the modulation noise. It is possible to raise the video by 8/Nt.

The shape of ferromagnetic metal powder may be the remains of acicular particles of iron oxide, or a chain of spherical particles, or the particle size may vary due to the formation of voids in the dehydration root during the reaction process. It's hard to decide. The inventors of the present invention have concluded from their experiments that the specific surface area correlates well with the properties of magnetic l-.

Although video characteristics can be ensured by selecting the ferromagnetic metal powder and controlling the surface properties of the magnetic layer, it becomes difficult to run the resulting tape in a VTR. Furthermore, it has been found that if a magnetic material with a large specific surface area is selected, the durability of the magnetic layer 1- is lowered, and the magnetic layer is more likely to be destroyed in the low output F still mode due to head clogging 9.

It has been found that these problems can be alleviated by adding fatty acids and fatty acid esters as in the method of the present invention.

As described above, according to the present invention, it is possible to obtain a metal tape with high video characteristics and guaranteed runnability and durability.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, "parts" in the examples indicate "parts by weight."

Examples 1 to 3 Acicular α-F e OOH containing jwt- cobalt
obtained by thermal decomposition of 9α-F・, 0. A black ferromagnetic metal powder was obtained by converting it into water. Before taking this powder out of the furnace, check the il inside the furnace! Gradual oxidation treatment was performed by gradually increasing the elementary partial pressure. The magnetic properties and specific surface area of this powder are shown in Table 1. The specific surface area was changed by selecting the conditions for forming the acicular α-Fe00H.

Table 1 The above ferromagnetic metal powder 300@ and the following composition were dispersed in a ball mill for 10 hours.

Polyester polyurethane (reaction product with ethylene adiide and p-)lylene diincyanate, styrene equivalent average molecular weight of approximately 730,000) Jj-based vinyl-vinyl acetate-maleic anhydride copolymer (v-leic acid containing Amount 3.Owt, -degree of polymerization approx. oo) JOs α-Alumina 11 parts Carbon black Js Zotyl acetate
JOO part methyl isobutyl keto/
After the partial dispersion of JOO, fatty acids (3 parts of oleic acid and 3 parts of palmitic acid) and fatty acid ester (parts of amyl stearate) are added according to each example, and the mixture is stirred for ~30 minutes. Furthermore, the triisocyanate compound [an adduct of 3 mol of tolylene diisocyanate and 1 mol of trimethylolpropane (molecular sum approximately 740.NCO content/J
, Jwt, -1 Part name: 7JVIt, manufactured by Bayer, G0 [Desmodur L-7jJ] - Ethyl acetate solution was added and dispersed with high speed shear for 7 hours to prepare a magnetic coating liquid.

The obtained coating liquid was applied onto a polyethylene terephthalate film having a thickness of i+ and zμ so that the dry film thickness was 0μ.

Then, it was oriented in a direct T&magnetic field and dried by blowing an ioo'c hot air stream. After drying, it was calendered and slit to a width of l/inch to obtain a magnetic tape for video. The rutted coating layer is J, 3 and 9.

The magnetic properties are measured values using a loss 1EII magnetic flux needle (*product name: "VsM-1 type" manufactured by Kyodo Industry).

The video physical properties were determined by a VHa type VTR (Matsu F' Brewery Manufacturing Co., Ltd., product name: INV) whose recording/playback head was modified with Sendust alloy.
-1100'') is the measured value of the reproduction output at MHz. The standard tape is VH8 tape T/CO OE (manufactured by Fuji Photo Film ■). Table 1 shows the custom tapes for each example.

Table λ shows the surface roughness, magnetic customization, and electromagnetic variation characteristics of the magnetic tape obtained at that time.

While we showed +ti which is easy to overcome, the ratio #fl'll/
~λ, Meng, did not even reach 0 dtl.

The running performance is towing, such as 8ttck 5lip etc.
4 did not always show.

Also, when playing in still mode, the playback time is 30 minutes or more.
4 It was rebirth without wealth.

From the above, it can be seen that the surface roughness of the non-magnetic powder with a 7-th fracture Fit of 1 or higher and the fatty acid ester magnetic layer satisfies the graininess of the method of the present invention, and the ratio of the ferromagnetic metal powder is 3 parts m/I in width.
It can be seen that if it is less than lr, it is a small amount of light according to the electromagnetic conversion characteristic oii.

In "Example 4 to 6 Fruitful Examples", α-alumina was added to 2 parts (Comparative Example 3), 1 part (Example 3), 10 parts (Example 4), and 21 parts (Example 4).
), or add 10 copies (comparative cleverness) and perform the same operation.9. As the amount of α-alumina increased, the roughness of the peaks became larger and the video output ri decreased, and in the comparative example≠, the surface roughness was more than θ, 0 reference μ or more than 10 samples dB, and the object of the present invention could not be achieved. . As the amount of α-alumina added decreases, the video output increases, but head clogging becomes more likely to occur, and in Comparative Example J, it is difficult to obtain a proper C value for the magnetic conversion characteristics.

Examples 7 to 9 In Example λ, amylstearate total o, 2 parts (comparative example), o, j parts (Example 7), 3 parts (Example R), r
20 parts (Example 1) or 20 parts (Comparative Example t) were added and the same operation was performed.

In the comparison vINJ j, the durability of the magnetic layer in still mode was extremely low, and the head clogged in less than 7 minutes, resulting in no output.

In addition, in Comparative Example B with a large amount of added IJO11, the runnability with a regular bamboo was low and a stick-slip phenomenon occurred.

Example 10 Jakufu super-imitation particle powder (manufactured by Vacuum Metallurgy) t-300 made by evaporating metal with the composition Fe/CO=I r/l j (heavy electric ratio) in a low-pressure inert gas Perform coulometric part ipH
/ ~ Made into magnetic tape with the same recipe and under the same conditions as 3. The specific surface area of the powder was J t m ”/g r. The surface roughness of the tape was 0.0 colμ, and HcJJ,
/j10 (Qe) Brjroo (Gaussian) squareness ratio was 0.7λ.

The video characteristics, runnability, and durability all met the objectives of the present invention.

Patent Applicant Fuji Photo Film Co., Ltd. Procedural Amendment 1. Display of 19 cases 1939 Patent Application No. 7L/
j> 2. Name of the invention Magnetic recording medium 3. Relationship with the person making the amendment Patent applicant Address: 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Address: 21112+ Nishimakan, Minato-ku, Tokyo 1()0; No. 30 Koi, Sha Film Co., Ltd. East 5 Headquarters Shinwa (+06) 2537 Table Subject of amendment Column 6 of "Detailed Description of the Invention" of the specification Amendment on#.

(1) Seventh true J line of the present specification “rr+j/fJ−≠About 1
m2/f or more.”

(2) Specifications of this application! Correct the line f-8/J to 1'-8/N ratio.

(3) Correct the ``I didn't say it'' to ``I didn't show it.''

that's all

Claims (1)

[Claims] In a magnetic recording medium provided by coating a magnetic layer mainly composed of ferromagnetic metal powder and a binder on a non-magnetic support, the ferromagnetic metal powder has a specific surface area of JOm 71 or more, and the magnetic layer contains a non-magnetic powder with a Mohs hardness of 4 or more and a fatty acid ester, 1 of the non-magnetic powder is 1~/jWt9G of the ferromagnetic metal powder, and 1 of the fatty acid ester is 0.1 of the ferromagnetic metal powder. /-jwt smooth, and furthermore, the table dIJ roughness of the damage no is 0. A magnetic recording medium characterized in that it is OJμ.