JPS6011371B2 - Method for manufacturing magnetic recording material - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of manufacturing a magnetic recording medium.

More specifically, the present invention relates to a method of manufacturing a magnetic recording medium having multiple magnetic layers. Magnetic recording bodies are generally manufactured by providing a magnetic layer on a flexible or hard nonmagnetic support.

The magnetic layer generally consists of a mixture of magnetic powder and a binder, and is provided on a non-magnetic support by coating or plating, with the former being the most common. The magnetic layer thus provided on the support is usually a single layer. However, in recent years, in order to develop magnetic tapes particularly suitable for short-wavelength recording and high-performance tapes that require uniform output over a wide frequency band, magnetic recording bodies having magnetic layers with various multilayer configurations have been proposed. Ta.

From a structural point of view, in order to obtain uniform output,
For example, U.S. Patent No. 2,691,072;
No. 13; No. 2,941,901; Special Publication No. 37-22
No. 18; Japanese Patent Publication No. 40-5351; U.S. Patent No. 3,761
, No. 311; Tokusekki No. 48-31907.

Furthermore, US Pat. No. 2,647,954 aims to achieve a similar effect in which the coercive force is continuously varied in the thickness direction. Japanese Patent Publication No. 39-8106 and U.S. Pat.
There is a method shown in issues such as No. 6,94. Other examples of tapes that take into consideration the mechanical properties of tapes include:
No. 3678 and JP-A-47-18508. In addition, US Pat. No. 3,676,217 and US Pat.
No. 41,901, Japanese Patent Publication No. 48-81093, Special Seki No. 4
7-37903 etc. Examples of methods proposed for use in multiple recording media include Japanese Patent Publication No. 43-185 and US Pat. No. 3,328,195.

Other Special Publications No. 48-28681, Actual Publications No. 34-18
No. 135, etc., it is stated that characteristics such as S/N are improved.

The common method for forming these multilayer magnetic layers was to apply the lower magnetic layer first, then dry it, then apply the upper layer and let it dry.
-9 So No. 03 proposes a simultaneous multilayer coating method in order to reduce modulation noise due to irregular formation on layer boundaries that is likely to occur with such sequential coating. ◇Generally, when multilayer magnetic layers are provided by coating Apart from the problem of irregular formation on layer boundaries, there is no doubt that simultaneous multilayer coating is superior to sequential coating in terms of production efficiency.

However, the simultaneous multilayer coating method disclosed in Tokukan Sho 48 Yama 98803 belongs to the so-called bead coating method, and the thickness of the formed coating film is determined by the thickness of the coating film that is to be coated on the tip of the liquid container. Because it is determined by the clearance between For example, in the production of photographic light-sensitive materials, this clearance is on the order of several hundred micrometers, which does not pose much difficulty in operation, but in the production of magnetic recording media, this clearance is on the order of several tens of micrometers. Not only does this tend to cause problems when the band-shaped support passes through it, but also, in the case of magnetic recording media, the thickness of the support is extremely thin, so the band-shaped support comes into contact with the tip of the genitals and breaks. However, it has been difficult to put it into practice in practice due to the major problem of the magnetic recording medium.An object of the present invention is to provide a method for manufacturing a magnetic recording medium having a novel multi-layered magnetic layer.The present invention Another object of the present invention is to provide a method for manufacturing a multilayer magnetic recording medium with excellent orientation.Another object of the present invention is to provide a method for manufacturing a multilayer magnetic recording medium with excellent orientation. It is an object of the present invention to provide a method for manufacturing a magnetic body.An object of the present invention is to form a multilayer free-falling curtain in which two or more magnetic coating liquids constituting a magnetic layer are superimposed, and to apply a magnetic field in the free-falling curtain portion. This is achieved by applying the two or more magnetic coating liquids onto the surface of the strip-like support being conveyed across the free-falling curtain.

The present inventors have already formed a free fall curtain of a magnetic coating liquid consisting of at least a ferromagnetic metal and a binder according to Japanese Patent Application No. 51-96675. We proposed a method for manufacturing magnetic recording materials by applying a coating liquid to a support, and applied the so-called curtain coating liquid to the manufacturing of magnetic recording materials, which had previously been prevented from being put to practical use because a stable curtain film could not be formed. This was made possible by applying an orienting magnetic field to the curtain film.

According to this method, the liquid film made of the magnetic coating liquid is stretched in the falling direction of the free-falling curtain, so the orientation is dramatically improved, and the orientation of the magnetic particles deep in the magnetic layer is also insufficient. It can be seen that the effect can be obtained.

However, in general, magnetic coating liquids have strong chicken tropism, and unless they are made to have a relatively high viscosity, agglomeration tends to occur, and it is said that medium to low viscosity coating liquids, which are necessary to form a thin curtain film, are difficult to dissolve. Due to its properties, it is not only possible to form a stable curtain film, but also the amount of coating required for manufacturing magnetic recording media is much smaller than that required for manufacturing photosensitive materials. The presence of such particles also hindered the formation of a stable curtain film.

Moreover, in a magnetic recording medium having multiple magnetic layers,
Generally, it is required that the total thickness of the multilayer magnetic layer be equal to or even larger than the thickness of the magnetic layer of a conventional single-layer magnetic recording material, so the thickness of each magnetic layer is The thickness of the magnetic layer must necessarily be smaller than that of a single magnetic layer. Therefore, when manufacturing a magnetic recording medium having multiple magnetic layers like this, in which a magnetic coating liquid is coated layer by layer by the curtain coating method, the amount of solvent is increased more than necessary to coat the coating liquid constituting each layer. There is no other choice but to maintain the stability of the curtain film by increasing the amount of coating. However, when increasing the amount of coating liquid in this way, it is necessary to improve the drying ability or otherwise increase the conveyance of the support to increase the thickness of the coating film applied on the support. Unless a method is adopted to reduce the amount of magnetic material, it will not be possible to manufacture a magnetic recording medium having multiple magnetic layers. However, the former method is clearly not economical, and the latter method is prone to various troubles as the coating speed increases, and both have their own defects. In contrast, in the present invention, since a superimposed free-falling curtain is formed of two or more magnetic coating liquids constituting a multilayer magnetic layer, even if the coating amount of the magnetic coating liquid forming each magnetic layer is reduced, The amount of coating solution flowing in a free-falling curtain is the sum of the coating amounts of the magnetic coating solutions constituting two or more magnetic layers. This has the remarkable effect of making it possible to stabilize the membrane.

According to the present invention, not only Tsubaki Gansho 51-96675
Needless to say, the effect of improving the orientation disclosed in the specification of the present invention can also be obtained.

In the present invention, "without forming one folded free-fall curtain by all of the magnetic coating liquids constituting the multilayer magnetic layer, two or more superimposed free-fall curtains made of two or more magnetic coating liquids are provided, and the first Two or more magnetic coating solutions are applied to the support using a second free-falling curtain, and two or more magnetic coatings are applied using a second free-falling curtain while the thus obtained magnetic layer is still wet or after drying. You may apply the liquids in a superimposed manner and repeat the same operation. However, the method of forming one free-falling curtain with all the magnetic coating liquids is the best way to apply the magnetic coating liquids in a manner that reduces the amount of each magnetic coating liquid applied and the overall amount. As mentioned above, it is preferable to reduce the amount of coating as described above.Furthermore, after the first multilayer magnetic layer is dried, the second multilayer magnetic layer is coated on top of it. If this method is used, modulation noise is likely to occur at the interface between the first and second multilayer magnetic layers, so this is not a preferred mode.In this way, two or more magnetic coating liquids form a superimposed free-falling curtain. However, it has been confirmed that when the free-falling curtain collides with a support and multiple magnetic layers are provided on the support, each magnetic layer maintains its own individual layer without mixing with each other. Then, a first multilayer magnetic layer is coated by forming a superimposed free-falling curtain composed of two or more magnetic coating liquids, and while this multilayer magnetic layer is still wet, two or more other magnetic coating liquids are applied. It has been found that even in the case of sequential coating in which a superimposed free port curtain is formed and the magnetic layers are layered and coated on the multilayer magnetic layer, each magnetic layer similarly maintains its individual layer without mixing with each other. Hereinafter, embodiments of the present invention will be explained based on the accompanying drawings.

FIG. 1 is a schematic diagram of a magnetic coating liquid coating device showing an embodiment of the present invention, and FIG. 2 is a schematic perspective view thereof.

In FIGS. 1 and 2, two types of magnetic coating liquids are supplied to the coating head 3 through nozzles la, lb and pipes 2a, 2b, and then to pockets 4a, 4b provided over almost the entire width of the coating head 3. The fluid is sent to eliminate the dynamic pressure during supply, and then passes through the slots 5a and 5b provided over the entire width of the coating head 3, and then the bimagnetic coating is applied within the slit 6 provided over the entire width of the coating head 3. The liquids merge and exit the drop application head 3 in superimposed layers, forming a superimposed multilayer free fall curtain 7.

Both ends of the free-falling curtain 7 are supported by guide rods 8a and 8b, and consideration is given to preventing contracted flow and further increasing the stability of the free-falling curtain 7. Since the free-falling curtain 7 of the magnetic coating liquid is generally unstable as described above, it is desirable to provide guide rods 8a and 8b. Furthermore, an air-core solenoid coil 9 (
Not shown in FIG. ) is provided, and a magnetic field is applied in the falling direction of the free-falling curtain 7 to orient it. On the other hand, a band-shaped support 10 is conveyed in the direction of the arrow so as to cross this free-falling curtain 7, and the magnetic coating liquid in the free-falling curtain 7 that has passed through the orienting magnetic field collides with the band-shaped support 1. The coating is carried out, and two folded magnetic layers 11 and 12 are formed on the strip-shaped support 10. Upstream of the free-falling curtain 7, an air shield 13 (not shown in FIG. 2) is provided to remove the air flow entrained by the strip support 10' and impair the stability of the free-falling curtain 7. Care has been taken to ensure that this does not occur. Furthermore, the conveyance path of the belt-shaped support 10 is also a free-falling curtain 7.
The direction is changed just before the free-falling curtain 7, thereby preventing the entrained airflow from impairing the stability of the free-falling curtain 7. Furthermore, the free-falling curtain 7 is provided to extend beyond the width of the strip-shaped support 10, and is intended to prevent thick coating of the coating film, which is generally likely to occur at the ends in the width direction (hereinafter referred to as "edges"). There is. The uncoated magnetic coating liquid is collected by a known collection device (
(not shown) and reused as necessary. The strip-shaped support 10 carrying the magnetic layers 11 and 12 thus provided is supported by a packing roll 14 while
Sent to drying process. Here, in order to further enhance the orientation effect, an auxiliary orientation magnet (not shown in FIG. 2) 15 may be provided. It goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways.
For example, in the above embodiment, an extrusion type coating head is used as the coating head, but other coating heads such as those disclosed in Japanese Patent Publication No. 49-24133, such as a slide type coating head, may also be used. etc. can also be used. If a slide-type coating head is used, it is necessary to arrange it to prevent evaporation of the binder in the magnetic coating liquid. Further, in the embodiment described above, the width of the free port lower curtain 6 is set larger than the width of the band-shaped support 10 to prevent thick coating on the ears, but it is not necessary to do this, and the free port lower curtain It is also possible to apply the coating while keeping the width of No. 6 within the range of the width of the strip-shaped support 10.

In this case, thick coating tends to occur at the ears, so in order to prevent this, some bristles are attached to the lower ends of the guide bars 8a and 8b as disclosed in Japanese Patent Publication No. 49-35447. A brush made of the material, a strip made of a flexible elastic material, etc. may also be provided. Furthermore, the free falling curtain 8
A line (
Hereinafter, it will be referred to as the "Yabushi line."

) is generally stretched by the belt-shaped support 10 and forms a curve that swells toward the downstream side of the belt-shaped support 10 as it approaches the center of the belt-shaped support 10. As a result, the free-falling curtain 7 tends to entrain the airflow entrained by the strip-shaped support 1, making the free-falling curtain 7 unstable and causing air bubbles in the coating film, especially when the coating speed is increased. , in extreme cases, it may even result in a patchy area, so in May 1970
As shown in the application specification of the patent blinking A) (applicant: Fuji Photo Film Co., Ltd.) dated May 23, the magnetic force of the orientation magnetic field is set to different values upstream and downstream of the free port curtain 7, or the guide It is preferable to frame the grooves 8a and 8b in the direction of movement of the band-shaped support 10 to control the connecting line so that it becomes a straight line. Further, in the embodiment described above, the magnetic layer is two layers, but it goes without saying that the present invention is not limited to two layers and may be applied to three or more layers.

Further, as for the method of applying the magnetic field, an air-core solenoid is preferable from the viewpoint of stability of the curtain film, but permanent magnets having opposing magnetic poles can also be used.

In the present invention, the initial falling velocity of the magnetic coating liquid supplied to the free-falling curtain is desirably about 20 skins/sec or less, preferably about 15 skins/sec or less.

If it is more than this, the stability of the curtain film will decrease, which is not preferable. For example, curtain film formation by gravity provides desirable results. In the present invention, the falling distance of the curtain film is desirably set in a range of about 3 arcs to about 40 arcs.

Although it depends on the surface tension of the magnetic coating liquid, if the falling distance exceeds about 40 skin, the falling speed of the magnetic coating liquid becomes excessive as a result of acceleration due to gravity, and the thickness of the curtain film becomes too thin. becomes easy to tear into sagging shapes. Further, if the diameter is less than about 5 degrees, especially less than about 3 degrees, it becomes difficult to arrange the magnet. In the present invention, the supply rate of the magnetic coating liquid is approximately 0.7 cc/s per width of the free-falling curtain.
ec or more, especially about lcc/sec or more is required in order to form a stable curtain film. In the present invention, the viscosity of the magnetic coating liquid is preferably about 1 to about 10 p.

When the ratio p is less than about 1, the dispersion of the magnetic particles tends to be poor, and when the ratio p exceeds about 10, it becomes difficult to form a thin curtain film. The strength of the magnetic field applied in the present invention is also related to the coercive force of the magnetic particles, but
It is desirable that it be 00 Oe or more, preferably 500 Oe or more.

If it is less than this, the orientation will deteriorate. In addition, at least ⅓ or more of the free fall length of the curtain film passes through the strength of the magnetic field described above, and the stability of the curtain film also decreases. The thickness of the magnetic layer to be applied in the present invention is:
Under wet conditions, 100 r or less and 5 florets or more are suitable.

In addition, the conveyance speed of the belt-shaped support to be coated is determined by the desired coating amount (
determined by the coating film thickness) and the supply amount of the magnetic coating liquid,
An arc/sec to 700c/sec is desirable. Regarding the manufacturing method of the magnetic coating liquid used in the present invention, Japanese Patent Publication No. 35-1
5, 39-26794, 43-186, 47-28
No. 043, No. 47-28045, No. 47-28046,
47-27048, 47-31445, 48-11
162, No. 48-21331 L48-33 Spot No. 3, Soviet Patent Specification No. 308,033, and other publications. The magnetic coating liquids described in these documents contain ferromagnetic powder, binder, and coating solvent as main components, and may also contain additives such as dispersants, lubricants, abrasives, and antistatic agents. As the ferromagnetic fine powder of the present invention, ferromagnetic iron oxide, ferromagnetic chromium dioxide, ferromagnetic alloy powder, etc. can be used.

Is the above ferromagnetic iron oxide a general formula? x when expressed in eo wide
The value is 1.33SxSI. 50 ferromagnetic iron oxides, namely maghemite (y-Fe203, x=1.
．． 33), magnetite (Fe304, x: 1.50)
and these bertolide compounds (Fe○×, 1.33
<×<1.50).

The above x value is
13×(trivalent amemiC%)}×turbidity.

It is shown by the formula.

A divalent metal may be added to these ferromagnetic iron oxides.

Divalent metals include Cr, Mn, Co, Ni, Cu, Z
n, etc., and mic% of 0 to 1 melon with respect to the above iron oxide
It is added within the range of

The above ferromagnetic chromium dioxide contains 2 of C and Na,
K, Ti, V, Mn, Fe, Co, Ni, Tc, Ru,
Cr02 to which 0 to 2% of metals such as Sn, Ce, and Pb, semiconductors such as P, Sb, and Te, or oxides of these metals are added is used. The acicular ratio of the above ferromagnetic iron oxide and ferromagnetic chromium dioxide is about 2'1 to 20'1, preferably 5/1 or more, and the average length is 0.2 to 2.0 m.
A range of 0.3 to 1.5 m is effective. The above ferromagnetic alloy powder has a metal content of 75 M.% or more, and a metal content of 8 skin t. % or more of at least one ferromagnetic metal (i.e. Fe, Co, Ni, Fe
-Co, Fe-Ni, Co-Ni or Co-Ni-F
e), and there are two metal parts. % or less, preferably 0.5-5M. % is AI, Si, S, SC, Ti
, V, Cr, Mm, Cu, Zn, Y, Mo, Rh, Pd
, Ag, Sn, Sb, Te, song, Ta, W, Re, Au
, Hy, Pb, Bi, La, Ce, Pr, Nd, B, P
It has a composition such as, and may also contain small amounts of water, hydroxide, or oxide.

Specifically, Special Publication No. 36-5515, No. 37-482
No. 5, No. 39-500, No. 39-10307, No. 44-14090, No. 45-18372, No. 47-22062, No. 47-22513, No. 46-284
No. 66, No. 46-38755, No. 47-4286,
No. 47-12422, No. 47-17284, No. 47
11850 plan, No. 47-18573, No. 48-39
No. 63y, U.S. Pat. No. 3,026,215;
No. 1,341; No. 3,100,194; No. 3,242
, No. 005: 3,389 No. 014: British Patent 752
, No. 65; No. 782, 762: No. 1,007, 32
No. 3; French Patent No. 1,107,654; West German Published Patent (OB) No. 1,281,334, etc.

As the binder for the magnetic coating liquid used in the present invention, a conventionally known thermoplastic resin, thermosetting raw resin, reactive resin, or a mixture thereof can be used.

As a thermoplastic resin, the softening temperature is 150q0 or less, the average molecular weight is 10,000 to 200,000, and the degree of polymerization is about 20.
0 to 200 varnish, such as vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer combination, ester acrylate styrene copolymer, ester methacrylate acrylonitrile copolymer,
Methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butadiene copolymers, polyester resins, amino resins, various synthetic rubber thermoplastic resins (polybutadiene, poly chloroprene, polyisoprene, styrene-butadiene copolymer, etc.) and mixtures thereof. Examples of these resins are given in Japanese Patent Publication No. 37-16877, 39-12528.
No. 39-19282, No. 40-5349, 40-12
No. 0907, No. 41-9463, No. 41-1405,
41-16985, 42-6428, 42-116
No. 21, No. 43-4623, No. 43-15206, 44
-288 number, 44-17947, 44-18232
No. 45-1402, No. 45-14500, No. 47-18573, No. 47M22063, No. 47-22064
No. 47-22068, 47-22069, 47-22070, 48-27886, U.S. Patent No. 3,14
No. 4,352: No. 3,419 No. 42: No. 3,499
No. 789: Described in No. 3,713,887.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating solution, but when added after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, phenol formalin novolac resin, phenol formalin resol resin,
Phenol/furfural resin, xylene/formaldehyde resin, urea resin, melamine resin, drying oil-modified alkyd resin, carbonic acid resin-modified alkyd resin, maleic acid resin-modified alkyd resin, unsaturated polyester resin,
Epoxy resin and curing agent (polyamine, acid anhydride, polyamide resin, etc.), terminal isocyanate polyester moisture-curing resin, terminal isocyanate polyether moisture-curing resin, polyisocyanate bleed polymer ( 1 obtained by reacting a diisocyanate with a low molecular weight triol
Compounds having 3 or more isocyanate groups in the molecule,
diisocyanate trimers and tetramers), polyisocyanate prepolymers and resins containing active hydrogen (polyester polyols, polyether polyols, acrylic acid copolymers, maleic acid copolymers, 2-hydroxyethyl methacrylate copolymers, hydroxystyrene copolymers, etc.), and mixtures thereof.
Examples of these resins include Japanese Patent Publication Nos. 39-8103, 40-19779, 41-7192, 41-8016, 4
No. 1-14275, No. 42-1817y, No. 43-120
No. 81, No. 44-28023, No. 45-14501, 4
5-24902, 46-13103, 47-220
No. 65, No. 47-22066, No. 47-22067, 4
7-22072, 47-22073, 47-280
45, 47-28048, 47-28922, U.S. Patent No. 3,144,353: U.S. Pat. No. 3,320,09; U.S. Pat.
No. 3,781,21; described in No. 3,781,211.

These binders may be used alone or in combination, and other additives may be added.

The mixing ratio of the ferromagnetic powder and the binder is in the range of 10 parts by weight of the ferromagnetic powder to 8 to 15 parts by weight of the binder, preferably 10 to 100 parts by weight, and more preferably 12 to 6 parts by weight. used in In addition to the binder and ferromagnetic fine powder described above, additives such as a dispersant, a lubricant, an abrasive, and an antistatic agent may be added to the magnetic coating liquid.

Dispersants include caprylic acid, capric acid, lauric acid,
Fatty acids with 12 to 18 carbon atoms such as myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, stearolic acid (R, COO, R, is a fatty acid with 11 to 17 carbon atoms) alkyl or alkenyl group); alkali metal (Li, Na, K
) or alkaline earth metals (Mg, Ca, Ba); fluorine-containing compounds of the above fatty acid esters; amides of the above fatty acids: polyalkylene oxide alkyl phosphate esters; lecithin; Alkyl polyolefin oxy quaternary ammonium salts (alkyl having 1 to 5 carbon atoms, olefin being ethylene, propylene, etc.) are used.

In addition, higher alcohols having 1 or more carbon atoms and sulfuric acid esters can also be used. These dispersants are added in an amount of 0.5 to 20 parts by weight based on the weight of the binder 10. Regarding these, special public
No.-2836y, No. 44-17945, No. 48-74
No. 41, No. 48-15001, No. 48-15002, No. 48-16363, No. 50-14121, US Pat. No. 3,387,993; US Pat. No. 3,470,021, etc. As lubricants, conductive column fine powders such as carbon black, graphite, and carbon black graft polymers; inorganic fine powders such as molybdenum disulfide and tungsten dioxide; polyethylene, polypropylene, polyethylene vinyl chloride copolymers, polytetrafluoroethylene, etc. Plastic fine powder: olefin polymer;
Unsaturated aliphatic hydrocarbon that is liquid at room temperature (a compound in which an n-olephylle double bond is bonded to the terminal carbon, approximately 20 carbon atoms)
; Kawabata's monobasic fatty acid with 12 to 2 carbon atoms and 3 to 1 carbon atoms
Fatty acid esters consisting of two monohydric alcohols can be used.

These lubricants are used in amounts of 0.2 to 100 parts by weight of binder.
It is added in an amount of 2 parts by weight. Regarding these, Tsubaki Kosho 41-180 Nezumi, No. 43-2388y, 46-40
No. 461, No. 47-15621, No. 47-18482
No. 47-28043, No. 47-32001, No. 50-5042, U.S. Patent No. 3,470,021: No. 3,492,235: No. 3,497,411; No. 3
, 523 086; 3,625,760: 3.
No. 630,772: No. 3,642,539; “IBM
Technical DisclosmeBulle
tin"Vol.9, No.7, Pa bag 779 (196
December 2006); “ELEK-TRONIK” 1961, No. 12, Pa bag 38 losses, etc. are listed. Commonly used polishing materials include fused alumina, silicon carbide chromium oxide, zircon (ZrSi04), aluminum phosphate (AIP04), and cerium oxide (CI02).
), boron carbide (B4C), aluminum borate (AI
BQ), Spinel (MgA1204) Rutile, Anatase (all Tj02), Diasurpol (Q-Mountain 00)
H), corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main components: corundum and magnetite), etc. are used.

These abrasives have a Mohs hardness of 5 or more and an average particle diameter of 0.05 to 5 m, particularly preferably 0.1 to 2 Am. These abrasives are added in an amount of 0.5 to 2 parts by weight based on the cloud content of the binder 10. Regarding these, Taruko 47-185
No. 72, No. 48-i5003, No. 48-15004 (U.S. Patent No. 3,617,378), No. 49-3940
No. 2, No. 50-9401, U.S. Patent No. 3,007,80
No. 7; No. 3,041,196: No. 3,293,066
No. 3,630,91; No. 3,687,725; British Patent No. 1,145,34y; West German Patent (DT
-PS) No. 853,211: Described in PS No. 1,101,000. Antistatic agents include conductive fine powder such as carbon black, graphite, and carbon black graft polymer; natural surfactants such as saponin; nonionic surfactants such as alkylene oxide, glycerin, and glycidol; higher alkyl Cationic surfactants such as amines, quaternary ammonium salts, pyridine and other heterocycles, phosphonium or sulfoniums; carboxylic acid, sulfonic acid, phosphoric acid, sulfate ester groups,
Anionic surfactants containing acidic groups such as phosphate ester groups:
Ampholytic active agents such as amino/acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of aminoalcohols, etc. are used.

The above conductive fine powder is added in an amount of 0.2 to 2 parts by weight, and the surfactant is added in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the binder.

Some of the conductive fine powders and surfactant compounds that can be used as antistatic agents include Hakama Kosho Nos. 46-22726, 47-24881, 47-26882, and 4
No. 8-15440, No. 48-126761, U.S. Patent 2
, No. 271,623, No. 2,240,472, No. 2,
No. 288,226, No. 2,676,122, No. 2,6
No. 76,924, No. 2,676,975, No. 2,69
No. 1,566, No. 2,727,860, No. 2,730
, No. 498, No. 2,742, 37y, No. 2,739,
No. 891, No. 3,068,101, No. 3,19F 4
No. 84, No. 3,201,253, No. 3,210,19
No. 1, No. 3,294,540, No. 3,415,649
No. 3,441,413, No. 3,442,654, No. 3,475,174, No. 3,545,974,
West German Patent Publication (OLS) No. 1,942,665, British Patent No. 1,077,317, OLS No. 1,198,45, etc., "Synthesis of Surfactants and Their Applications" by Ryoheiike Oda (Enoki) Shoten 1964 edition);A. M. Schwartz & J.
．． W. "Surf S Active Agents" by IJ Bay (Interscience Publications, Inc. 195 Western edition); J. P. ``Encyclopedia of Surf S Active Agency, Volume 2'' by Sisley (Chemical Publications Company)
It is described in books such as "Surfactant Handbook" 6th edition (Sangyo Tosho Co., Ltd., December 20, 1964);

These surfactants may be added alone or in combination.

These are used as antistatic agents, but are sometimes used for other purposes, such as dispersion, improving magnetic properties,
It may also be used to improve lubricity and as a coating aid.
Organic solvents used during coating include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propanol, and butanol; methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and acetic acid. Ester series such as glycomonoethyl ether; ether, glycol dimethyl ether, glycol monoethyl ether,
Glycol ethers such as dioxane; tars (aromatic hydrocarbons) such as pen pen, toluene, and xylene; chlorine such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. Carbonized hydrocarbons and the like can be used.

The magnetic coating liquid used in the present invention is prepared by kneading and dispersing ferromagnetic metal powder, a binder, a dispersant, a lubricant, an abrasive, an antistatic agent, a coating solvent, and the like.

In kneading, the ferromagnetic metal powder and each of the above-mentioned components are fed into a kneading machine either simultaneously or individually one after another.

For example, there is a method in which ferromagnetic metal powder is first added to a solvent containing a dispersant and kneaded for a predetermined period of time to form a magnetic coating liquid. Various kneaders are used for kneading and dispersing the magnetic coating liquid.

For example, two roll mill, three roll mill, ball mill,
Veple Mill, Thoron Mill, Sand Glider, Szeg
vari attritor, high speed inveler dispersion machine, high speed stone mill, high speed impact mill, disperser, kneader,
These include high-speed mixers, homogenizers, and ultrasonic dispersers. The technology regarding kneading and dispersion is described by T. C. “Paint FlOWandPigment, Di” by PATTON
John Wiley (1964)
& Sons, Inc.).

Also, U.S. Patent Nos. 2,581,414 and 2,855,
It is also mentioned in No. 156. Supports used in the present invention include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate;
Polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, plastics such as polycarbonate: Cu,
A non-magnetic metal foil such as AI or Zn is used. The appropriate thickness of these supports is 2 to 125 mm, preferably about 3 to 100 mm.

The above-mentioned support may be coated with a so-called backcoat on the opposite side to the side on which the magnetic layer is provided (i.e., it has a back layer) for the purpose of preventing static electricity, preventing transfer, preventing wow and flutter, etc. ).

Regarding backcoats, for example, U.S. Patent No. 2,804,
No. 401, No. 3,293 No. 066, No. 3,617, 3
No. 78, No. 3,062,676, No. 3,734,77
No. 2, No. 3,476,596, No. 2,643,048
No. 2,803,556, No. 2,887,462, No. 2,923,642, No. 2,997,451,
No. 3,007,892, No. 3,041,196, No. 3,115,420, No. 3,166,688, No. 3
, 761, 311, etc.

The magnetic layer provided on the support according to the invention is sent to a drying step and dried by a stream of air.

The drying temperature depends on the solvent used in the coating solution, but is generally about 50 to 120 qoC, preferably 70 to 100 qo,
Particularly preferably 80 qo to 90 qo. The flow rate of drying air is approximately 1 to 5 mm, preferably approximately 2 to 3 mm.
The suitable drying time is approximately 3 seconds to 10 minutes, preferably approximately 1 to 5 minutes. It is desirable that the dried magnetic layer is subjected to surface smoothing treatment.

In general, the curtain coating method can form a coating film with excellent surface properties, but in the case of a magnetic coating liquid, due to its composition, it may not be possible to obtain sufficient smoothness by itself, and the magnetic recording medium Since strict accuracy is required for the smoothness, it is desirable to further perform a smoothing process. Surface smoothing treatment is
After drying, calendering is usually performed using a smoothing sheet.

In the case of calendering, it is preferable to carry out the supercalendering method in which the material is passed between two rolls such as a metal roll and a cotton roll or a synthetic resin (for example, nylon) roll.

The conditions for the super calendar are about 25 to 100.
Preferably at an inter-roll pressure of 30 to 70 k9/g, about 3
At a temperature of 5 to 100 °C, preferably 40 to 80 qo,
It is preferable to carry out the process at a processing speed of ~200 machines/min.
Temperature and pressure above these upper limits have an adverse effect on the magnetic layer and non-magnetic support. Also, the processing speed is about 5M/
If it is less than min, the effect of surface smoothing cannot be obtained, and about 20
If it is more than 0 skin/min, the processing operation becomes difficult. These surface smoothing treatments are described in U.S. Patent No. 2,688,567.
No. 2,998,325: No. 3,783,023: West German Published Patent Application (DT-OS) No. 2,405,222;
It is described in Samurai Kaisho No. 49-153631, No. 50-10337, etc.

The method using a smoothing sheet is a method of smoothing the magnetic layer by bringing it into surface contact with a maneuverable sheet while the magnetic layer is in a dry, unsolidified state.

In the present invention, the composition of the magnetic coating liquid constituting each magnetic layer can be selected as described above to suit the respective purpose.

Here, as the coating solvent used for each magnetic coating liquid during coating, it is necessary to select the same or compatible solvent for each magnetic coating liquid applied at the same time in order to prevent agglomeration. Furthermore, it is required to be a solvent for the binder contained in each magnetic coating liquid. Further, the abrasive does not necessarily have to be contained in each magnetic coating liquid, and if necessary, it may be contained only in the magnetic coating liquid constituting the outermost surface.

If necessary, the lubricant may be included only in the magnetic coating liquid constituting the outermost surface, and if necessary, the lubricant may be included in the magnetic coating liquid constituting any of the magnetic layers if it has the property of oozing into other magnetic layers. It may be contained only in the liquid or only in the magnetic coating liquid constituting some magnetic layers.

It goes without saying that it may be included in each magnetic coating liquid. It is not necessary to include the curing agent in all the magnetic coating liquids, and if necessary, it may be contained only in the magnetic coating liquid constituting the outermost layer.

Furthermore, in the case of magnetic recording media for audio and video,
It is desirable to prepare each magnetic coating solution so that the coercive force of each magnetic layer gradually increases from the layer in contact with the support to the outermost layer. In particular, the coercive force of the outermost layer is 1.2 of the coercive force of the bottom layer. It is preferable to make it more than double.

(U.S. Patent No. 2,691,072, U.S. Patent No. 2,643,
No. 130, No. 3,676,217, No. 3,761,
No. 311, No. 3,775,178, Special Publication No. 37-2
No. 218, No. 39-23678, etc.) For multiplex recording, Tsubaki Kosho No. 43-185, U.S. Pat. No. 3,328
, No. 195, the coercive force of the lower magnetic layer may be made higher than that of the upper layer. Examples will be given below in order to make the effects of the present invention more clear.

In the examples, all parts are by weight.

Examples Two types of compositions having the compositions shown in Table 1 were treated as follows to obtain two types of magnetic coating liquids (
1) and (b) were prepared.

Table 1 (1) Average long axis diameter 0.50 m, acicular ratio 10:1, saturation magnetization 351em ↓ Sobon r-Fe203 (2) Maghemite (saturation magnetization 360em riso gun, acicular ratio 6: 1. Cobalt-adsorbed iron oxide (cobalt content: 2.7 wt.) obtained by treating iron oxide (average major axis diameter: 0.40 mm) with cobalt hydroxide in an alkaline aqueous solution and washing with water at 150°C.
(3) Polyesters synthesized from adipic acid, terephthalic acid, equiethylene glycol, diethylene glycol, butylene glycol, etc., are urethanized with 4,4'-sophenylmethane diisocyanate, etc.

Styrene equivalent heavy charge average molecular weight approximately 13,000. (4) Copolymerization ratio 83:17 (many moles), degree of polymerization approximately 450. (5
) AZ203, average particle size 0.5 m. The compositions shown in Table 1 were kneaded, placed in a ball mill and dispersed for 2 hours, and then mixed with a 75M% ethyl acetate solution of an adduct of polyisocyanate (3 mol of tolylene diisocyanate and 1 mol of trimethylolpropane). Bayer AG's "Desmodur L-7" with an NCO content of 13.
5 parts to paint (1) and 7.5 parts to paint (0), further dispersed at high speed for 1 hour, filtered through a filter with an average pore size of 2 m, and finally methylisobutyl Adjust the viscosity to 3&p with ketone and apply magnetic coating liquid (1), (0).
I got it.

The thus obtained magnetic coating liquids (1) and (0) were applied by each method shown in Table 2 so that the magnetic coating liquid (1) was the lower layer and the magnetic coating liquid (b) was the upper layer.

Table 2 (6) Doctor coating method: Magnetic coating liquid (1) is applied using the Doctor Fried method, dried, calendered, stored at 50°C for 48 hours, allowed to harden, and then reapplied to the magnetic coating liquid plate. was applied using the Dr.Frede method, dried, and calendered.

Here, the falling speed of the free-falling curtain is 3 skin/
sec, and the amount of the coating liquid was controlled by adjusting the cap length of the nozzle and the amount of each coating liquid supplied to the nozzle.

The magnetic field was applied from an air-core solenoid with an air-core part length of 15 mm, the strength of the magnetic field was 1250 oelsted direct current, and the orientation direction was the falling direction of the free-falling curtain (#1
, #2) or in the longitudinal direction (#3, #4) on the strip support.
, #5). In addition, the free fall distance was set to 20 feet. The support has a width of 300mm, a thickness of 23mm, and a surface roughness of 0.
A polyethylene terephthalate film with a diameter of 15 m was used and the film was run at a speed of 180 m/min.

In samples #1 and #2, stable coating was performed, but in #3, the curtain film was unstable, and the film thickness was non-uniform and easily fluctuated.

Further, the curtain film of #4 was even more unstable than that of #3, and the curtain film was easily broken and became so-called sagging. #5 uses a different coating method and was able to achieve stable coating. The wide support provided with the magnetic layer was cut in the longitudinal direction into 1/2 width and 3.81 width to obtain a magnetic tape.

When the electromagnetic conversion characteristics and BH characteristics of the five types of magnetic tapes thus obtained were investigated, the results shown in Table 3 were obtained.

Here, bias position 120%, equalizer 5
It was set to 0 rsec. Table 3 (7) Since the coatings were not averaged, the BH properties show average values.

Video output and audio output fluctuated so much that it was impossible to measure them. (8) Output by 4MHz non-bias recording. Measurements were made using a 1/2" wide tape.

*5 is the standard. (9) Output by 400Hz bias recording.

Measured using a 3.81 skin width tape.

*5 is the standard. In Table 3, comparing #1 and #3, it can be seen that according to the present invention, the squareness ratio is significantly improved and the output, especially the audio output, is significantly increased.

Although #2 had a smaller amount of coating liquid than #1, the curtain film was still stable.

However, in #3, in which no magnetic field was applied to the curtain film itself, the curtain film was unstable even if the amount of coating liquid was large, and in #4, in which the amount of coating liquid was reduced, good coating could not be achieved. . #1 and #2 according to the present invention have excellent electromagnetic conversion characteristics and BH characteristics, even though the number of steps is far fewer than that of #5, which is made by repeating the conventional doctor coating method. It has been found.

In addition, when we examined the cross section of the magnetic layer using an electron microscope, we found that
It was observed that #1 and #2 had much better orientation over the entire magnetic layer than #3.

[Brief explanation of drawings]

1 and 2 are schematic diagrams of a curtain coating device showing an embodiment of the present invention, and FIGS. 3 and 4 are diagrams showing the magnetic field application position in the embodiment, respectively. la, lb...nozzle, 2a, 2b...pipe, 3...
Application head, 4a, 4b...pocket, 5a, 5b
...Slot, 6...Slit, 7...Free fall curtain, 83, 8b...Guide shank, 9...
Air-core solenoid coil, 10... Band-shaped support, 11
, 12...Magnetic layer, 13...Air shield, 14...Packing roll, 15...Orienting magnet. Multi-box *2 Evil fin 3 figure 4th spot

Claims (1)

[Claims] 1. A method for manufacturing a magnetic recording material having multiple magnetic layers, in which a multilayer free-falling curtain is formed by superimposing two or more magnetic coating liquids constituting the magnetic layer, and a magnetic field is applied in the free-falling curtain portion. . A method for producing a magnetic recording material, comprising: providing two or more magnetic layers by coating and superimposing the two or more magnetic coating liquids on the surface of the strip-shaped support being conveyed across the free-falling curtain.