JPS5843816B2 - Jikiki Loc Tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and particularly to the structure of a magnetic recording layer in a magnetic recording tape.

As a recording medium for various types of information such as audio, images, and digital signals, there is a magnetic recording medium in which a magnetic recording layer containing fine ferromagnetic powder dispersed in a binder is coated on a nonmagnetic support. Various types of magnetic recording materials, such as magnetic tapes such as audio tapes, video tapes, and memory tapes, as well as magnetic sheets, magnetic disks, and magnetic drums, are widely used depending on their form, purpose, and performance.

In recent years, there has been a demand for increasing the recording density of these magnetic recording media, and as one means of achieving this, magnetic recording media that have a two-layered magnetic layer structure to more efficiently record a target signal have been attracting attention.

Conventionally, there have been many examples in which the magnetic recording layer has two or more layers, and in particular, the coercive force of the upper layer is thicker than that of the undercoat.
No. 691072, No. 3676217, Special Publication No. 37-2
No. 218, JP-A-47-31602, JP-A No. 50-318
No. 04 and No. 50-46103 are known, and an example of an upper layer having smaller coerciveness than the lower layer is US Pat. No. 3328.
No. 195, Japanese Patent Publication No. 43-185, etc.

In particular, the so-called 4-head type video tape for VTR, which is currently the standard for broadcast video tape recorders (hereinafter referred to as broadcast VTR), was published in Japanese Patent Application Laid-open No. 4.
There is an example described in No. 8-31907.

Conventionally, video tapes used in broadcast VTRs are generally made of maghemite (γ-Fe2) on a polyester base.
Video tapes formed by coating one layer containing O3) or CrO2 as the main magnetic fine powder for recording are widely used.

In a 4-head type VTR, a video signal 1, an audio signal 2, a control signal 3, etc. are recorded on the magnetic layer of the video tape as shown in FIG.

As is clear from FIG. 1, the video track 1, the control track 3, and the audio track 2 are arranged approximately at right angles.

Therefore, if the magnetic field orientation is applied in the width direction of the tape, the squareness ratio (Br/Bm) in terms of the magnetic properties in the width direction increases, which is desirable for recording and reproducing video signals, but It is clear that the directional squareness ratio becomes smaller, making it unfavorable for recording and reproducing audio signals.

On the other hand, it is clear that if the magnetic field is oriented in the longitudinal direction of the tape, it is desirable for recording and reproducing audio signals, but not for recording and reproducing video signals.

In view of the special nature of two-way recording required for video tapes for 4-head VTRs, we developed a 4-head VT with a single magnetic layer.
Magnetic field orientation technology is an important point in R video tapes.

For this purpose, Special Publication No. 41-2065, No. 43-2
Technologies such as No. 1251 have been developed.

Furthermore, another technique is a 4-head V consisting of two magnetic layers.
A videotape for TR has been proposed.

As examples thereof are described in West German Patent (DT-AS) No. 1190985 and Japanese Patent Application Laid-Open No. 48-31907, the structure is such that the upper layer is oriented by a magnetic field mainly in the width direction, and the lower layer is oriented by a magnetic field mainly in the longitudinal direction. .

In addition, video signals with short wavelengths are mainly recorded in the magnetic layer of the upper layer oriented close to the width direction, and audio signals with long wavelengths are mainly recorded in the magnetic layer of the lower layer oriented in the longitudinal direction. In particular, it seeks to significantly improve audio characteristics compared to conventional single-layer videotape.

However, in such a two-layer videotape,
As in West German patent (DT-AS) +190985,
The coercive forces of the upper layer and the lower layer are almost the same, or JP-A-48-
31907, when the coercive force of the upper layer is larger than the coercive force of the lower layer, the audio recording and playback characteristics will be different compared to a conventional videotape using a single magnetic layer with the same coercive force as the upper layer. Compatibility deteriorates.

The reason for this will be explained below.

That is, conventional single-layer video tapes for four-head VTRs are mainly oriented in the magnetic field at an angle of about 200 to 45 degrees from the width direction, and are designed to place more importance on the recording and reproducing characteristics of video signals than on audio signals.

In this case, the longitudinal magnetization curve (B-H curve) is the second
As shown in the figure, it is inferior to the magnetization curve in the width direction (Figure 3).

FIGS. 2 and 3 are graphs showing general magnetization curves (B-H curves) of conventional 4-head video tapes.
FIG. 2 shows the B-H curve in the length direction, and FIG. 3 shows the B-H curve in the width direction.

In Figures 2 and 3, B is the magnetic flux density (Gauss
), H is the magnetic field (0ersted), △Br/△H
indicates the slope of the BH curve.

Especially in Figures 2 and 3, the slope of the B-H curve (△
Br/ΔH) is smaller when oriented in the longitudinal direction (FIG. 2) than when oriented in the width direction (FIG. 3).

Therefore, as mentioned above (West German Patent (DT-AS) 119
0985 and JP-A-48-31907, the audio recording and playback characteristics are mainly strongly influenced by the underlying magnetic recording layer, so the peak of the audio bias curve is as shown in Figure 4 when compared with the conventional single-layer videotape. As shown in FIG.

Furthermore, when the above two types of multilayer video tapes are used at a bias current suitable for conventional single layer video tapes, the audio frequency characteristics of the video tapes are improved in the low frequency portion, as shown in Figure 5. .

FIG. 4 is a graph showing the audio bias curves of the three types of video tapes mentioned above, and FIG. 5 shows the audio frequency characteristics of the three types of video tapes at the optimum bias current for conventional single layer video tapes.

In Figures 4 and 5, A is a conventional single-layer videotape, B is a conventional multilayer videotape in which the upper and lower layers have the same He, and C is a conventional multilayer videotape in which the upper layer has a higher He than the lower layer. Show tape.

As is clear from FIGS. 4 and 5, even with a multi-layered 4-head VTR videotape, depending on how the coercive force is selected,
It turns out that the compatibility (audio characteristics) with conventional single-layer videotape changes.

So far, we have specifically explained the audio characteristics, but since the very near surface of the magnetic layer (approximately 1 μm or less) contributes effectively to the video recording and playback characteristics, the upper layer magnetic layer has magnetic characteristics similar to those of conventional single-layer video tape. If the videotape has a recording layer, it will not be affected much by the magnetic properties of the underlying layer and there is no risk of compromising compatibility.

The foregoing has described a video tape for a four-head VTR having a two-layer structure with a magnetic recording layer having approximately the same thickness as a conventional single-layer video tape.

On the other hand, one way to improve magnetic recording density is to reduce the thickness of the magnetic recording layer.

In the case of commonly used single-layer video tapes, when the thickness of the magnetic layer is reduced, the optimum current value for the audio bias shifts to a smaller value, resulting in a difference from the optimum current value when the magnetic layer is not thinned. becomes larger, and compatibility tends to deteriorate.

In a multi-layered video tape, video signals with relatively short wavelengths are mainly recorded on the upper layer of the magnetic tape, and audio signals with relatively long wavelengths are mainly recorded on the upper layer and the lower layer.

Therefore, in order to reduce the layer thickness while maintaining optimum recording current compatibility for both video signals and audio signals, a multilayer structure as described below according to the present invention is effective.

As mentioned above, examples of making the coercive force of the lower layer larger than the coercive force of the upper layer include U.S. Pat.
No. 3-185 is known, but the former has a lower layer coercive force of 8 to 10 times, and the latter has a lower layer coercive force of 2 to 5 times. They are different in scope and also have different purposes.

The object of the present invention is to provide a two-layer videotape as described above, which has video and audio recording and playback characteristics compatible with conventional single-layer videotape, and which achieves a significant improvement in audio characteristics. In particular, among the two-layered magnetic recording layer, the coercive force of the lower layer is greater than 1 times the coercive force of the upper layer,
The characteristic is that it is less than twice.

That is, in the present invention, a lower magnetic recording layer is provided on a non-magnetic support, and an upper magnetic recording layer is further provided on top of the lower magnetic recording layer, and the lower and upper magnetic recording layers contain fine ferromagnetic powder and a binder. In a magnetic recording tape that is a magnetic recording layer, (1) (A) the coercive force of the lower magnetic recording layer is greater than or equal to twice that of the upper magnetic recording layer, and (B) the coercive force of the upper magnetic recording layer is greater than or equal to twice that of the upper magnetic recording layer; A magnetic device characterized in that the magnetic field orientation of the lower magnetic recording layer is applied in the longitudinal direction of the magnetic recording tape, and the magnetic field orientation of the upper magnetic recording layer is applied mainly in the width direction of the magnetic recording tape. and (2) (A) the coercive force of the lower magnetic recording layer is greater than or equal to twice the coercive force of the upper magnetic recording layer, and (q the lower and upper magnetic recording layers). A magnetic recording tape characterized in that a magnetic field orientation of 1 is applied in the longitudinal direction of the magnetic recording tape.

In the present invention, by making the coercive force of the lower layer larger than the coercive force of the upper layer, even when the lower layer is oriented in the longitudinal direction by a magnetic field, the audio bias of the two-layer type 4-head VTR video tape is different from that of the conventional single-layer type video tape. Compatibility in current, frequency characteristics, etc. can be provided.

In the case of a VTR, audio signals are recorded and reproduced at long wavelengths, so when the two-layer structure is used, especially if the upper layer is less than 3 μm thick, the characteristics of the lower magnetic recording layer will be very strong (it will be affected first). As stated above.

However, if the coercive force of the lower layer is larger than that of the upper layer, even if the optimum point of the audio bias shifts to a shallower direction due to the magnetic field orientation of the lower layer being in the longitudinal direction, this will be offset by the effect of the coercive force, resulting in a single-layer videotape. The above-mentioned discovery was made by discovering that it is possible to make the frequency characteristics almost the same, and that the audio output can be significantly improved while maintaining compatibility of frequency characteristics.

Furthermore, not only for 4-head broadcast video tapes but also for helical scanning VTR video tapes, when the magnetic recording layer is made thinner as described above, the optimum audio bias current value generally shifts to a shallower direction. Similarly, by making the coercive force of the lower layer of the two-layer structure larger than that of the upper layer, the shift of the bias point toward a shallower direction due to the thinning of the magnetic recording layer can be offset, and the result is almost the same as that of a single-layer videotape. made it possible to

Therefore, it is clear that it is possible to improve the audio output while maintaining compatibility in frequency characteristics.

In this case, it is important that the magnetic properties of the upper layer be approximately the same as those of the conventional single-layer type in order to maintain compatibility in recording and reproducing characteristics of video signals.

Therefore, in the two-layer videotape of the present invention, particularly for use in a four-head VTR, the coercive force of the upper layer must be 3750e or less, that is, almost the same as that of a conventional single-layer videotape.

In addition, the ferromagnetic fine powder currently used in helical scanning video tapes is magnetite (γ
-Fe2O3), magnetite (Fe304), Berthollide Iron Oxide
, FeOx11.33<x<1.50), Co-containing magmamite, Co-containing magnetite, co-fertolide iron oxide, chromium dioxide (CrO2), etc., so the coercive force has a wide range of 250 to 14000e. Although there is no need to specifically limit the coercive force, in the case of the two-layer structure of the present invention, it is necessary to make the coercive force of the lower layer larger than the coercive force of the upper layer.

A particularly preferable coercive force of the upper layer is 300 to 7000e.

On the other hand, in order to ensure compatibility of audio characteristics in currently used VTRs and tape recorders, in the case of the two-layer structure of the present invention, the coercive force of the lower layer must be less than twice the coercive force of the upper layer. is necessary.

Furthermore, broadcast videotape, helical scanning V
Not only for TR video tapes, but when trying to improve the recording density by thinning the magnetic recording layer, it is possible to reduce the thickness of the magnetic recording layer to less than i while maintaining compatibility with conventional tapes. This is not practical due to mechanical constraints due to the running characteristics of the VTR.

This also eliminates the need for the coercive force of the lower layer to be less than twice that of the upper layer for the purpose of the present invention.

The method for manufacturing the magnetic recording tape of the present invention will be explained below.

Methods for manufacturing magnetic recording tapes having a two-layer structure are described, for example, in Japanese Patent Publication Nos. 37-2218, 39-23678, 31602-1982 (USP 3761311), and 4
No. 7-37903, No. 48-31907 (USP
3775178), US Patent No. 50-31804, US Patent No. 2643130, US Patent No. 2647954, US Patent No. 29419
No. 01, No. 3676217, West German patent (DT-AS)
It is described in No. 1190985, No. 1238072, etc.

The magnetic recording layer of the present invention is formed by dissolving, kneading, and dispersing the compositions of the lower layer and upper layer described later in an organic solvent, applying the lower magnetic layer on a non-magnetic support as each coating solution, drying, and then forming the upper layer. Apply the magnetic layer and dry.

The treatment for orienting the magnetic powder in each magnetic layer can be carried out after the lower magnetic layer and the upper magnetic layer are coated and before they are dried.

Further, the surface of each magnetic layer can be smoothed after drying.

The method for orienting magnetic powder described above is also described in the patents listed below.

For example, US Pat. No. 1,949,840; US Pat. No. 2,796,359;
No. 3001891; No. 3172776; 3416949
No. 3473960; 3681138; Special Publication No. 32-3427; 39-2
No. 8368; No. 40-23624; No. 40-23625; No. 41-13181; No. 48-13043; No. 48-3
No. 9722, etc.

Specifically, this is carried out by applying an alternating current or direct current magnetic field of approximately 500 to 200 Gauss to the magnetic recording layer immediately after coating until it is completely dry.

In addition, in the case of (B) of the present invention, that is, when the upper layer is in the width direction and the lower layer is in the longitudinal direction, the lower layer is in the range of 0 to 30 degrees with respect to the longitudinal direction of the magnetic recording tape, and the upper layer is in the magnetic recording tape. It is preferable that the orientation is in the range of 300 to 900 with respect to the longitudinal direction of the recording tape.

On the other hand, in the case (e) of the present invention, that is, when both the upper layer and the lower layer are oriented in the longitudinal direction, it is preferable that the upper layer and the lower layer are both oriented in the range of 0 to 300 with respect to the longitudinal direction of the magnetic recording tape. .

Furthermore, it has been confirmed that preferable results can be obtained if the thickness of the magnetic recording layer of the magnetic recording tape of the present invention is approximately 0.5 to 4 .mu.m thick for the upper layer and 20 .mu.m thick for the lower layer.

Regarding the manufacturing method of the magnetic paint used in the present invention,
-15.39-26794, 43-186, 47-
No. 28043, No. 47-28045, No. 47-28046
No. 47-28048, No. 47-31445, 48-
No. 11162, No. 48-21331, No. 48-33683
No. 3, USSR Patent Specification No. 308033, and other publications.

The magnetic paints described in these documents mainly contain ferromagnetic powder, binder, and coating solvent, and may also contain additives such as dispersants, lubricants, abrasives, and antistatic agents.

The ferromagnetic fine powder used in the present invention includes γ-Fe2O
3. Co-containing γ-Fe2O3, Fe3O4, Co-containing Fe3O4, bertolide compound of r-Fe203 and Fe3O4 (FeOx, 1.33<x<1.50)Co
Bertolide compound of γ-Fe2O3 and Fe3O4 (FeOx, 1.33<x<1.50), CrO2,
Co-N1-P alloy, Co-Ni-Fe alloy, C.

-Ni-Fe-B alloy, Fe-Ni-Zn alloy, Fe-
Mn-Zn alloy, Fe-Co-N1-P alloy, Ni
-Co alloy and other known ferromagnetic fine powders can be used, specifically, Japanese Patent Publication Nos. 44-14090 and 45-18372.
No. 47-22062, No. 47-22513, No. 46-28466, No. 46-38755, No. 47-
No. 4286, No. 47-12422, No. 47-1728
No. 4, No. 47-18509, No. 47-18573,
No. 39-10307, No. 48-39639, U.S. Patent No. 3026215; No. 3031341; No. 3100
No. 194; No. 3242005; No. 3389014;
British Patent No. 752659; British Patent No. 782762; British Patent No. 100
No. 7323: French Patent No. 1107654; West German Published Patent No. 0L81281334, etc.

The particle size of these ferromagnetic fine powders is about 0.2 to 1 micron in length, and the length/width ratio is about 1/1 to 20/1.

As the binder used in the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used.

As a thermoplastic resin, the softening temperature is 150°C or less, the average molecular weight is 10,000 to 200,000, and the degree of polymerization is about 200 to 2.
For example, 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, acrylic ester Styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer Coalescence, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butadiene copolymer, polyester resin, chlorovinyl ether acrylic ester copolymer Polymer resins, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof are used.

Examples of these resins are given in Japanese Patent Publication No. 37-6877, 39-
No. 12528, No. 39-19282, No. 40-5349, No. 40-20907, No. 41-9463, No. 41-14
No. 059, No. 41-16985, No. 42-6428, 4
No. 2-11621, No. 43-4623, No. 43-1520
No. 6, No. 44-2889, No. 44 17947, No. 44-18232, No. 45-14020
No. 45-14500, No. 47-18573, 47-
No. 22063, No. 47-22064, No. 47-22068
No., 4722069, 47-22070, 4827
No. 886, U.S. Patent No. 3,144,352: No. 341,942
No. 0; No. 3499789; No. 3713887.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less after coating, and 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, examples include 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, malein. Acid resin-modified alkyd resin, unsaturated polyester resin, epoxy resin and curing agent (polyamine, acid anhydride, polyamide resin, etc.), terminal incyanate polyester moisture-curing resin, terminal incyanate polyether moisture-curing resin, polyisocyanate Prepolymers (compounds having three or more incyanate groups in one molecule obtained by reacting diisocyanate and low molecular weight triol, diisocyanate trimers and tetramers), polyisocyanate prepolymers and resins containing active hydrogen (polyester polyols) , polyether polyol, acrylic acid copolymer, maleic acid copolymer, 2-hydroxyethyl methacrylate copolymer, parahydroxystyrene copolymer, etc.), and mixtures thereof.

Examples of these resins are given in Japanese Patent Publication No. 39-8103, 40-
No. 9779, No. 41-7192, No. 418016, 41
-14275, 42-18179, 43-1208
No. 1, No. 44-28023, No. 45-14501, 45
-24902, 46-13103, 47-2206
No. 5, No. 47-22066, No. 47-22067, 47
-22072, 47-22073, 47-2804
No. 5, No. 4728048, No. 47-28922, U.S. Patent No. 3144353; No. 3320090; No. 3437
No. 510; No. 3597273; No. 3781210;
It is described in No. 3781211.

These binders may be used alone or in combination;
Other additives may be added.

The mixing ratio of the ferromagnetic powder and the binder is 10 to 400 parts by weight, preferably 30 to 200 parts by weight, per 100 parts by weight of the ferromagnetic powder.

In addition to the above-mentioned binder and fine ferromagnetic powder, additives such as a dispersant, a lubricant, an abrasive, and an antistatic agent may be added to the magnetic recording layer.

In addition to the above-mentioned binder and fine ferromagnetic powder, additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, etc. may be added to the magnetic recording layer by selecting the upper layer or the lower layer.

Dispersants include caprylic acid, capric acid, lauric acid,
Fatty acids with 12 to 18 carbon atoms (R1C0OH,
R1 is an alkyl or alkenyl group having 11 to 17 carbon atoms): a metal soap consisting of an alkali metal (Li, Na, etc.) or an alkaline earth metal (Mg, Ca, Ba) of the above fatty acid; the above fatty acid ester fluorine-containing compounds; amides of the aforementioned fatty acids; polyalkylene oxide alkyl phosphates; lecithin; trialkyl polyolefin oxy quaternary ammonium salts (alkyl has 1 to 5 carbon atoms, olefins include ethylene, propylene, etc.); etc. is used.

In addition, higher alcohols having 12 or more carbon atoms and sulfuric esters may also be used.

These dispersants are used in an amount of 0.5 to 100 parts by weight of the binder.
It is added in an amount of 20 parts by weight.

Regarding these, Special Publication No. 39-28369, No. 44-
No. 17945, No. 48-7441, No. 48-1500
No. 1, No. 48-15002, No. 48-16363,
No. 50-4121, U.S. Patent No. 3,387,993; No. 3
It is described in No. 470021, etc.

Examples of lubricants include dialkylpolysiloxane (alkyl has 1 to 5 carbon atoms), dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkylmonoalkoxypolysiloxane (alkyl has 1 to 5 carbon atoms, alkoxy has 1 to 4 carbon atoms), phenylpolysiloxane, fluoroalkylpolysiloxane (alkyl has 1 to 5 carbon atoms)
Conductive fine powder such as carbon black, graphite, carbon black graft polymer, etc. Inorganic fine powder such as molybdenum disulfide, tungsten disulfide: Polyethylene, polypropylene, polyethylene vinyl chloride copolymer, polytetrafluoro Fine plastic powder such as ethylene; α-olefin polymer;
Unsaturated aliphatic hydrocarbon that is liquid at room temperature (a compound in which an n-olefin double bond is bonded to the terminal carbon, approximately 20 carbon atoms)
; Monobasic fatty acids with 12 to 20 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 20 parts by weight.

Regarding these, Special Publication No. 4323889, No. 46-4
No. 0461, No. 47-15621, No. 47-1848
No. 2, No. 47-28043, No. 47-30207,
No. 47-32001, No. 48-7442, No. 49-
No. 14247, No. 50-5042, U.S. Patent No. 3470
No. 021 ° No. 3492235: No. 3497411 °
No. 3523086; No. 3625760 ° No. 3630
No. 772; No. 3634253 ° No. 3642539;
No. 3687725
alDisclosure Bulletin //
VOI, 9, &7, Page 779 (1966 1
February); “ELEKTRONIK, 1961, 12
, Page 380, etc.

Commonly used abrasive materials include fused alumina,
silicon carbide chromium oxide, corundum, artificial corundum,
Diamond, man-made diamond.

Garnet, emery (main ingredients: corundum and magnetite), etc. are used.

These abrasives have a Mohs hardness of 5 or more and an average particle size of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm.

These abrasives are used in an amount of 0.5 to 100 parts by weight of the binder.
It is added in an amount of 20 parts by weight.

Regarding these, Special Publication No. 47-18572, No. 48-
No. 15003, No. 48-15004 (U.S. Pat. No. 361
No. 7378), No. 49-39402, No. 50-940
No. 1, US Patent No. 3007807; US Patent No. 3041196; US Patent No. 3293066; US Patent No. 3630910;
No. 7725; British Patent No. 1145349; West German Patent (DT-PS) No. 853211; British Patent No. 1101000.

Carbon black, graphite,
Conductive fine powder such as carbon black graft polymer; Natural surfactant such as saponin; Nonionic surfactant such as alkylene oxide type, glycerin type, glycidol type; Higher alkylamines, quaternary ammonium salts, pyridine and other complexes Cationic surfactants such as rings, phosphoniums or sulfoniums: carboxylic acids,
Anionic surfactants containing acidic groups such as sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric ester groups; amphoteric surfactants such as diamino acids, aminosulfonic acids, and sulfuric or phosphoric esters of amino alcohols; and the like.

The above conductive fine powder is added in an amount of about 0.5 to 15 parts by weight, and the surfactant is added in an amount of about 0.2 to 5 parts by weight per 100 parts by weight of the binder.

Some examples of surfactant compounds that can be used as antistatic agents are disclosed in Japanese Patent Publication Nos. 46-22726 and 47-248.
No. 81, No. 47-26882, No. 48-15440, No. 48-26761, U.S. Patent No. 2271623,
No. 2240472, No. 2288226, No. 2676
No. 122, No. 2676924, No. 2676975,
No. 2691566, No. 2727860, No. 2730
No. 498, No. 2742379, No. 2739891,
No. 3068101, No. 3158484, No. 3201
No. 253, No. 3210191, No. 3294540,
No. 3415649, No. 3441413, No. 3442
No. 654, No. 3475174, No. 3545974,
Including West German Patent Publication (OLS) No. 1942665, British Patent No. 1077317, OLS No. 1198450, etc.
"Synthesis of Surfactants and Their Applications" by Ryohei Oda et al. (Maki Shoten 1964 edition); "Surface Active Agents" by A. M. Schwartz & J. W. Peiri (Interscience Publications Inc. 1958 edition) ; J. P. Sisley, "Encyclopedia of Surf S Active Agents, Volume 2" (Chemical Published Company 1964)
2015 edition): It is listed on the bottom of the 6th edition of "Surfactant Handbook" (Sangyo Tosho Co., Ltd., December 20, 1960).

The magnetic powder and the above-mentioned binder, dispersant, lubricant, abrasive, antistatic agent, solvent, etc. are kneaded to form a magnetic paint.

For mixing, the magnetic 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 magnetic powder is first added to a solvent containing a dispersant and mixed with each other for a predetermined period of time to form a magnetic paint.

Various kneaders are used to mix and disperse the magnetic coating liquid.

For example, two roll mill, three roll mill, ball mill,
Pebble Mill, Thoron Mill, Sand Glider-1S ze
gvari attritor, high speed impeller disperser, high speed stone mill, high speed impact mill, dispy, kneader
1 High-speed mixer homogenizer, ultrasonic disperser, etc.

The technology related to crosstalk dispersion is described in P. by T. C. TATTON.
a1nt Flow and PigmentDi
” (1964, John Wi
published by Ley & Sons).

It is also described in US Pat. No. 2,581,414 and US Pat. No. 2,855,156.

Methods for applying the magnetic recording layer onto the support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, and spray coating. can be used, and other methods are also possible, and detailed explanations of these can be found in "Coating Engineering" published by Shokusen Shoten, pages 253-277.
(published on March 20, 1972).

In the magnetic recording material of the present invention, a magnetic layer is coated on a non-magnetic support by the above-described coating method, dried, and this process is repeated to form two magnetic layers by a continuous coating operation.

Also, JP-A No. 48-98803 (West German patent DT-O
As described in German Patent No. 82309159) and German Patent No. 48-99233 (West German Patent No. DT-AS2309158), two magnetic layers may be simultaneously provided by a multilayer simultaneous coating method.

Organic solvents used during coating include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propatool, and butanol; methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, Ester systems such as acetic acid glycol monoethyl ether: ether, glycol dimethyl ether, glycol monoethyl ether,
Glycol ethers such as dioxane: Tars (aromatic hydrocarbons) such as benzene, toluene, and xylene: Chlorinated hydrocarbons such as methylene chloride, ethylene chloride, tetracarbon L chloroform, ethylene chlorohydrin dichlorobenzene, etc. Items can be used by selecting the upper layer or lower layer.

The magnetic recording layer is formed on the nonmagnetic support using the composition and method described above.

The materials used for this non-magnetic support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polycarbonate. Ru.

Since these non-magnetic supports are used as magnetic tapes in the present invention, they are flexible and have a thickness of approximately 1 to 1 microns.
The diameter of the door is approximately 00μm, preferably 2 to 50μm, particularly preferably 3 to 25μm.

The width of the magnetic tape is manufactured in the form of a wide sheet, and is slit to any width such as 2 inches, 4 inches in 3 layers, 2 inches in 1 layer, 4 inches in 1 layer, 3.81 mm, etc. depending on the purpose of use. .

By such a method, a magnetic layer coated on a non-magnetic support is subjected to a treatment for orienting the magnetic powder in the layer as described above, and then the formed magnetic layer is dried.

Further, the magnetic recording body of the present invention is manufactured by subjecting it to surface smoothing processing and cutting it into a desired shape, if necessary.

In particular, in the present invention, it has been found that by subjecting the magnetic recording layer to surface smoothing treatment, a magnetic recording body with a smooth surface and excellent wear resistance can be obtained.

The drying temperature of the magnetic layer is approximately 50 to 100°C, preferably 70 to 100°C, particularly preferably 80 to 90°C, and the air flow rate is 1 to 5 kl/m', preferably 2 to 3 kl/m'.
-, the drying time is about 30 seconds to 10 minutes, preferably 1
~5 minutes.

The surface smoothing process after drying of each of the magnetic layers described above is carried out by calendering, smoothing sheet, or the like.

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 (eg, nylon) roll.

Super calendar conditions are approximately 25-50kg/crf
At a pressure between the rolls of L and a temperature of about 35 to 150°C, 5 to
Preferably, it is carried out at a processing speed of 120 m/min.

Temperature and pressure above these upper limits have an adverse effect on the magnetic layer and non-magnetic support.

Further, if the processing speed is less than about 5 m/mvt, the surface smoothing effect cannot be obtained, and if it is more than about 120 m/min, the processing operation becomes difficult.

These surface smoothing treatments are described in US Pat. No. 26,885.
No. 67; No. 2998325; No. 3783023; OLS No. 2405222;
It is described in No. 53631, No. 50-10337, etc.

The magnetic recording tape of the present invention has harmonized video and audio characteristics compared to conventional single-layer magnetic recording tapes due to the difference in coercive force between the two-layered magnetic recording layer and the orientation direction of the ferromagnetic fine powder. It is possible to provide an excellent magnetic recording tape having good compatibility in audio bias current, frequency characteristics, etc.

The present invention will be explained in more detail below using examples.

It will be readily understood by those skilled in the art that the components, proportions, order of operations, etc. shown herein may be modified without departing from the spirit of the invention.

Therefore, the invention should not be limited to the examples below.

In addition, in the following examples, all parts indicate parts by weight.

Example 1 Ferromagnetic fine powder 100 parts (maghemite, average particle size: 0.45 μm) Vinyl chloride vinyl acetate copolymer [copolymerization ratio 80:20 (weight ratio) polymerization degree 450] 10 parts polyurethane resin (adipic acid, Reaction product of polyester consisting of diethylene glycol and butanediol and diphenylmethane diisocyanate, molecular weight: approx. 30,000) 25 parts carbon black 8 parts dimethylpolysiloxane (degree of polymerization: approx. 60) 0.1 part methyl ethyl ketone toluene 250 parts (7:3)
Volume ratio) Mixed solvent The above magnetic coating solution was cross-dispersed in a ball mill for 48 hours, coated on a polyethylene terephthalate film with a thickness of 24 μm to a dry thickness of 12.5 μm, and statically heated at 2000 Oe with a solenoid coil. After passing through a magnetic field to orient the maghemite in the magnetic layer in the longitudinal direction of the film, it was dried, and the formed magnetic layer was subjected to calender roll treatment (surface polishing treatment) to smooth the surface.

This will be referred to as sample 1-1. In the same manner as Sample &1-1, form the first magnetic layer (lower layer) for a door with a dry thickness of 11 μm, and then form a second magnetic layer (upper layer) on top of this so that the door has a dry thickness of 1.5 μm. was applied using the same magnetic paint as the lower layer.

This is passed through a static magnetic field of 20,000 e by a solenoid coil arranged at an angle of 3,000 to the width direction of the tape to orient the maghemite in the upper magnetic layer at an angle of 300 from the width of the film, and then dried. The formed upper magnetic layer is subjected to calender roll treatment to smooth the surface.
A multilayer magnetic tape was manufactured.

Sample consideration 1- with the coercive force (He) of the lower layer being
2. Sample Al with the same He content in the upper and lower layers
3. Sample 1-4 with lower He
shall be.

The above sample shoes 1-1 to 1-4 are each 2 inches (
50.8 mm) to make a videotape for a 4-head broadcast VTR (VR20
00 type, manufactured by Ampex Corp., the magnetic properties were measured at 1+B using a tape running speed of 38 cm/see.

Table 1 shows the results. From the results in Table 1 above, 4
In the case of video tapes for head broadcasting VTRs,
When Comparing 2 and 1-3 with 1-1, both maintain compatibility in video characteristics while improving audio characteristics.

However, A1-3 with the same Hc in the upper and lower layers
In particular, it was found that the output at high frequencies (10 KHz) was relatively lower than the output at low frequencies (400 Hz), and it was found to be incompatible with the conventional (Al l) audio frequency characteristics. did.

In addition, this tendency is further emphasized in Tsuta 1-4, in which the upper layer He is more intense than the lower layer He, and the compatibility with conventional (Al l) audio characteristics is found to be even worse than in Tsuta 13. did.

On the other hand, in &1-2 of the present invention, the video characteristics are of the conventional type (Al
l), while maintaining compatibility with low frequency (400Hz) and high frequency (10KH) audio characteristics.
z) Both are uniformly significantly improved, and compatibility with A1-1 is also good, and shoes 1-1, &1-3, and &1-
It turned out to be better than any of the 4 types.

From the above facts, the lower layer is oriented in the length direction of the magnetic tape, the upper layer is oriented in the width direction of the magnetic tape, and the He in the lower layer is oriented in the direction of H in the upper layer.
The magnetic tape of the present invention (AI 2), which is more similar to e than the conventional single layer type (1-1) and multilayer type (A, 1 3, A
It was confirmed that this material had better properties than 1-4).

Example 2 Ferromagnetic fine powder (Co-containing magmamite average particle size 0.45μ Co content 1.5 atomic%) 100 parts Vinyl chloride vinyl acetate copolymer [Copolymerization ratio 80:20 (weight ratio)] , degree of polymerization 450] 10 parts Polyurethane resin [reaction product of polyester consisting of adipic acid, diethylene glycol and butanediol and diphenylmethane diisocyanate, molecular weight: approx. 30,000, 1 25 parts carbon black dimethylpolysiloxane (degree of polymerization: approx. 60) 8 0.1 parts 250 parts of a mixed solvent of methyl ethyl ketone and toluene (7:3 volume ratio) After coating the Co-containing magmamite film in the magnetic layer in a longitudinal direction by passing it through a static magnetic field of 20,000 e by a solenoid coil, it is dried, and the formed magnetic layer is rolled with a calendar roll. treated to smooth the surface.

This will be referred to as sample A2-1.

The dry thickness of the magnetic layer was 4.5 in the same manner as sample A2-1.
Manufactured magnetic tape for μ doors.

This will be referred to as sample A2-2.

In the same manner as Sample 2-1, the first magnetic layer (lower layer) was applied to a dry thickness of 3.5 μm, oriented, dried, and calender rolled to form a lower magnetic layer. A second magnetic layer (upper layer) is coated on top using the same magnetic paint as the lower layer so that the dry thickness is 1.0 μm, and the multilayer magnetic layer is oriented in the longitudinal direction, dried, and calendered in the same way as the lower layer. manufactured the tape.

Each of the above sample shoes 2-1 to 2-3 is slit into 2-inch (1.27 mm) pieces, each part is made into a 2-inch wide video tape, and each part is made into a 2-inch EIAJ unified type (helical scan type). ) VTR (HV-1101CR
1 Made by Toshiba, tape running speed: 19 cm/sec
, ) was used to measure the magnetic properties.

Table 2 shows the results.

From the results in Table 2 above, it can be seen that for 1/2 inch wide helical scanning videotape, thin layer conventional (
It was found that although the video characteristics of A2 2) were almost the same as the conventional type (A2-1), the audio characteristics were significantly degraded due to the thinner magnetic layer.

On the other hand, the video characteristics of the magnetic tape (A2 3) of the present invention are the same, and the audio characteristics are less thick and thinner than the conventional magnetic tape (A2 3).
Although it is the same as 2), it has been significantly improved, and it has been found that it exhibits almost the same characteristics as the thick conventional type (A2 1).

Based on the above facts, the magnetic tape (A2 3) of the present invention, in which the upper and lower layers are oriented in the length direction of the magnetic tape, and the He in the lower layer is more dense than the He in the upper layer, is a conventional single-layer type (JFy
, 21 and A22).

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of magnetic recording patterns recorded on a video tape in a 4-head VTR, in which 1 indicates a video track, 2 an audio track, and 3 a control track. FIGS. 2 and 3 are graphs showing general magnetization curves (B-H curves) of conventional 4-head video tapes.
FIG. 2 shows the B-H curve in the length direction, and FIG. 3 shows the B-H curve in the width direction. In Figures 2 and 3, B is the magnetic flux density (Gauss
), H is the magnetic field (0ersted), △Br/△H
indicates the slope of the BH curve. FIG. 4 is a graph showing the audio bias curves of three types of video tapes, and FIG. 5 shows the audio frequency characteristics of the three types of video tapes at the optimum bias current for conventional single layer video tapes. In Figures 4 and 5, A is a conventional single-layer videotape, B is a conventional multilayer videotape in which the upper and lower layers have the same He, and C is a conventional multilayer videotape in which the upper layer has a higher He than the lower layer. Show tape.

Claims (1)

[Claims] 1. A lower magnetic recording layer is provided on a non-magnetic support, and an upper magnetic recording layer is further provided on top of the lower magnetic recording layer, and the lower and upper magnetic recording layers mainly contain ferromagnetic fine powder and a binder. In a magnetic recording tape having a magnetic recording layer, (4) the coercive force of the lower magnetic recording layer is greater than or equal to twice that of the upper magnetic recording layer, and (B) the coercive force of the lower magnetic recording layer is greater than or equal to twice that of the upper magnetic recording layer; A magnetic recording characterized in that the magnetic field orientation of the magnetic recording layer is applied in the longitudinal direction of the magnetic recording tape, and the magnetic field orientation of the upper magnetic recording layer is applied mainly in the width direction of the magnetic recording tape. tape. 2. A lower magnetic recording layer is provided on a non-magnetic support, and an upper magnetic recording layer is further provided on top of the lower magnetic recording layer, and the lower and upper magnetic recording layers are magnetic recording layers mainly composed of ferromagnetic fine powder and a binder. In a certain magnetic recording tape, (4) the coercive force of the lower magnetic recording layer is greater than or equal to twice the coercive force of the upper magnetic recording layer, and (C) the lower and upper magnetic recording layers What is claimed is: 1. A magnetic recording tape characterized in that a magnetic field is oriented in the longitudinal direction of the magnetic recording tape.