DE4224227A1 - Magnetic recording medium - comprising substrate with high Young's modulus, undercoat and ferromagnetic powder coat contg. binder, used esp. for durable tape - Google Patents

Abstract

Magnetic recording medium has a nonmagnetic substrate (I) with an undercoat (II) and then a magnetic coat (III) of ferromagentic powder and binder (IV) on at least one side. The sum of the Young's modulus in the machine direction (MD) and transverse direction (TD) of (I) is 1400 kg/sq. cm or more than the adhesion between (I) and (III) is 90 g or more. Pref. (II) is produced from a polyester contg. a naphthalene ring and opt. also a polyurethane. (I) pref. consists of polyethylene naphthalate, polyimide or polyamide, esp. polyethylene-2,6-naphthalene, and the coating soln. for (III) contains at least 20 (wt.)% cyclohexanone (V) w.r.t. total solvent. (IV) includes resin(s) with functional sulphonic, phosphoric or phosphonic acid, epoxide or OH gp(s).. USE/ADVANTAGE - The medium is useful e.g. for magnetic tape. It is suitable for long-term recording and has excellent electromagnetic and running properties and excellent durability, with unvarying high output. Sepn. of powder at the edge during running and drop-outs are avoided

Description

The invention relates to a magnetic recording medium which is suitable for long-term recording, with excellent electromagnetic properties, excellent running properties ten and excellent durability can be obtained, ins particular being a precipitation of powder from the edge or the edge during the travel of the magnetic recording medium and the Dropout are decreased.

The invention also relates to an improvement in the adhesion between between a non-magnetic carrier such as polyethylene naphthalate (PEN), polyimide and polyamide and a magnetic layer or back layer in the magnetic recording medium, for example a magnetic tape. In particular, the invention relates to a magnet table recording medium that has an invariant high output supplies, an increase in the dropout is prevented and an out has excellent running stability.

Generally used as a magnetic recording medium for audio equipment, video equipment, or a computer (e.g. discs, memory tapes), a magnetic record tion medium comprising a non-magnetic carrier having a applied thereon magnetic layer containing a finely divided tes powder of a ferromagnetic material (for example a fine ferromagnetic powder), which in a binder dis Pergiert is used.

These conventional magnetic recording media included hitherto a resin such as polyurethane and a polyester resin dissolved in an organic or aqueous solvent based on a or both sides of the non-magnetic carrier is pulled up. There is no undercoating layer between them magnetic carrier or a backing layer provided to the adhesion between the non-magnetic support and the To improve magnetic layer or back layer. Accordingly various resins have been reviewed regarding their use in the Underclass examined. These resins are disclosed in JP-B-47-22 071, JP- A-49-46 406, JP-A-51-1 35 971 and JP-A-55-7865 (the name "JP-A" means an "Unexamined Published Japanese Patent Application ") and JP-B-49-10 243, JP-B-49-11 612, JP-B-51-1745 and JP-B-63-29 331 (the term "JP-B" means an "examined Japanese Patent Publication ").

In recent years it has been required that this magneti between recording media a high recording density Provide. For this purpose, the size was required of the finely divided ferromagnetic powder material to ver reduce the size of the metal powder, reduce the Pac to increase the thickness of the magnetic record medium and reduce the surface of the magnetic Recording medium to a high degree, etc., in order to achieve a height res signal / noise ratio and a reduced noise level to accomplish. It is also used to improve record voltage density and image quality necessary, the speed of the Writing and reading of the magnetic recording medium in the VTR or modify the recording system ren (i.e. move from an analog system to a digital system walk). For a Helicalscan VTR, the speed is of the head cylinder 5400 rpm or more. To the magnetic open drawing medium with such a high output or an excellent one drew usability for a high speed To equip sliding movement, it is essential to have a sufficient Running stability for the magnetic recording medium to si to avoid damaging the VTR barrel system. To fillers such as carbon black and abrasives are used for this purpose a Mohs hardness of 8 or more is used. This filling Substances are in JP-A-59-1 93 533, JP-A-59-1 86 125, JP-A-59-1 91 133, JP-A-59-1 89 831, JP-A-59-63029, JP-A-63-1 68 821, JP-A-63-1 68 822 and JP-A-1-1 85 821.

Such magnetic recording media have the large size Disadvantage that when the thickness of this magneti is reduced between recording media to achieve recording with high density, the polyethylene terephthalate, previously considered not magnetic carrier was used, a too low Young's modulus has sufficient strength to run in a VTR to secure. Therefore, polyethylene naphthalate, polyamide and Polyimide films have been proposed as non-magnetic supports. To for high output ultra smoothing (Ra: 5 nm or less (Cut off value: 0.25 mm) according to JIS B 0601) it is necessary to get this non-magnetic carrier too smooth. In doing so, however, the adhesion is destroyed, even if conventional agents can be used for the underlayer, since the contact surface is reduced. In particular, the Case of VTRs with a speed exceeding 1800 RPM ability for the cylinder heads to record at high density, the magnetic layer or back layer of the non-magnetic Carrier detached, so that an increase in the dropout stress takes place at the belt edge.

In other words, in the prior art, Ver use of a polyethylene naphthalate, polyamide or polyimide films as a thin non-magnetic carrier (thickness: 11 µm or less) it is extremely difficult to achieve sufficient adhesion of the To obtain magnetic layer or back layer. this is the Reason that the surface of the magnetic layer and the not magnetic carrier must be extremely smoothed (Ra: 5 nm or less and Ra: 15 nm or less (cut off va lue): 0.25 mm) to ensure a high output, and with Durch Implementation of this measure will be the contact surfaces of the two Layers are reduced so that it becomes impossible to achieve a significant te adhesion. It is known that a binder with high strength, containing a functional group, in particular which is used for a ferromagnetic metal powder. This is a case in point where sufficient adhesion is not available between the high-strength magnetic layer and the high-strength carrier.

It has been suggested many times as a non-magnetic carrier for the magnetic layer in the magnetic recording medium Polyethylene-2,6-naphthalate (hereinafter often referred to as "PEN" be draws). However, PEN has a low tear stiffness, so that a slight tear at a break point can be done. In particular, PEN tapes are easily broken, if they are slashed or damaged by the guards poles or cylinders in the video deck (VTR). Therefore, PEN proved useless in practice.

On the other hand, JP-A-1-1 06 319 proposes a magnetic recording medium with a Young's modulus of 400 kg / mm ² or more for the magnetic layer and a percentage elongation for the magnetic layer at break of 3% or more.

This tried to increase the durability for the side of the magnet layer to enlarge. Since, however, polyethylene terephthalate is used as a carrier, the shelf life is spontaneously limited. It also shows decreased output reproducibility and low envelope flatness and created video head contamination and significant edges damage.

The invention is therefore based on the object of a magnetic Recording medium with a high output and high record power density that continues to run excellent possesses stability.

Another object of the invention is to provide a magneti cal recording medium that is extremely good Running stability, combined with a reduced peeling of the Magnetic layer or back layer of the non-magnetic Vehicles and an extremely diminished increase in dropout or dropout Owns head pollution.

This task is accomplished by a magnetic recording medium solved according to claim 1.

The subclaims relate to advantageous configurations of a such magnetic recording medium.

The invention therefore provides a magnetic recording medium, comprising an underlayer arranged on at least one side of a non-magnetic carrier and a magnetic layer arranged thereon, containing at least one ferromagnetic powder and a binder, the non-magnetic carrier being the sum of Young’s modulus in the length direction (tape direction or machine direction) and Young's modulus in the width direction (transverse direction) of 1400 kg / mm ² or more and the adhesive force between the non-magnetic carrier and the magnetic layers is in the range of 90 g or more.

That is, in order to provide a magnetic recording medium with a high recording density and further an ultra-smoothing of the surface and a reduction in the thickness, that a non-magnetic carrier with a high strength according to the invention is used, the sum of the Young ' s modulus in the length direction and the Young's modulus in the width direction of the non-magnetic carrier in the range of 1400 kg / mm ² or more. However, in the invention described above, there were two problems to be overcome.

One of the two problems can be seen in the phenomenon that the DO (dropout) occurs easily by using a non-magne table support with a high strength, so that the C / N (Carrier / Noise Ratio) is decreased. It is believed, that this problem is generated by the decrease in adhesive strength between the non-magnetic support and the magnetic layer, especially due to the decrease in adhesive strength between the not high strength magnetic carrier and the magnetic layer, caused by using a solvent with a high Polarity, like a cyclohexanone in a coating solution for the magnetic layer.

The other problem is that there is a weak tear inadequate reproductive output and inadequate quality Low wrap flatness is created when a polyethylene lenterenaphthalate (PEN) as a high-strength, non-magnetic carrier ger is used.

According to the invention, the first problem can be solved by Creation of an adhesive force between the non-magnetic carrier ger and the magnetic layer of 90 g or more, with the adhesive force is measured by fixing a magnetic tape on a Carrier plate, the magnetic tape to a width of 1/2 Inch (1.27 cm) and tape ("Splicing Tape "manufactured by 3M Co., Ltd.) on the magnetic tape is brought and then folded back to 180 ° under the condition supply of 23 ° C and 65% RH. This can preferably be mentioned first te problem can be overcome in that a polyester, contain tend to use a naphthalene ring as the material for the underlayer, is used.

The second problem described above can be overcome by providing one or more magnetic layers on a polyethylene naphthalate support, arranging the upper and lower magnetic layers, limiting the Young's modulus in the length direction of the entire magnetic layer to 700 kg / mm ² or more and limiting the percent elongation at break for the entire magnet layer to 2% or more.

The thin magnetic tape that enables long-term recording can obtain excellent mechanical properties by using a magnetic carrier in which the sum of Young's modulus in the length direction and Young's modulus in the width direction is 1400 kg / mm ² or more. With the present invention, the difficulties encountered in the prior art, ie a remarkably folded edge, DO (dropout), C / N (carrier / noise ratio) and contamination of the video head, due to the use of such a carrier, are prevented by setting the adhesive force between the non-magnetic support and the magnetic layer to 90 g or more, preferably 100 g or more. Furthermore, the above-described difficulties occurring in the prior art can be overcome by using a polyethylene naphthalate (PEN), polyamide or polyimide film as a non-magnetic carrier, by using a polyester containing a naphthalene ring, with a strong adhesive force and excellent th solvent resistance to cyclohexanone in the underlayer, by using a resin having a functional group as a binder, which is incorporated into the magnetic layer to improve the dispersibility of the ferromagnetic powder, or by using a cyclohexanone solvent to further improve the dispersibility of the ferromagnetic powder Powder to improve. The invention further provides both flexibility and toughness by combining the aforementioned high strength base (ie, a high strength beam) with multiple magnetic layers. In particular, the invention overcomes the weakness of the tear strength of PEN by combining PEN with several magnetic layers.

The invention will be further developed from the following embodiments explained.

The above objects of the invention can be achieved by incorporating a poly containing a naphthalene ring esters in the sub-layer described above.

The polyester containing a naphthalene can effectively Adhesive force between the non-magnetic carrier and the Ma Provide a wet layer of 100 g or more through strongly attaching a high strength base such as one Polyethylene naphthalate, polyamide and polyimide base to Mag net shift.

The object on which the invention is based is achieved by a magnetic recording medium, the non-magneti cal carriers at least polyethylene naphthalate, polyamide and Po is lyimide, and the coating solution of the magnetic layer Cyclohexanone solvent in an amount of 10% by weight or contains more, based on the total weight of the solvent.

In the invention, it is necessary that the magnetic layer be a contains ferromagnetic powder that is dispersed therein and is tightly packed. To ensure the dispersibility of the ferromag To improve chemical powder, a binder with a functional group such as sulfonic acid group, phosphoric acid regruppe, phosphonic acid group and epoxy group preferably ver turns. At this point, it is preferred to use cyclohexanone a high polarity is incorporated into the binder that has such a functional group in an amount of 10% by weight or more, based on the total weight of the binder allow strong gluing.

The above objects of the invention can be achieved with a magnetic recording medium in which the underlayer is a layer comprising a naphthalene-containing poly contains ester and / or a polyurethane, provided that the Polyurethane does not contain naphthalene.

The above object of the invention will continue solved by a magnetic recording medium in which the at least one binder incorporated in the magnetic layer Contains resin which has at least one functional group, selected from the group comprising a sulfonic acid, Phos phosphoric acid, phosphonic acid and epoxy groups.

The object underlying the invention can also be achieved by a magnetic recording medium, comprising a sublayer drawn on both sides of a non-magnetic carrier, a magnetic layer applied to one sublayer, containing at least one ferromagnetic powder and a binder and also one the other sub-layer applied back layer, containing at least one inorganic powder and a binder, wherein the sub-layers comprise a polyester containing a naphthalene ring, and the non-magnetic carrier a sum of the Young's modulus in the length direction and the Young's modulus in the width direction of 1400 kg / mm ² or more.

In the magnetic recording medium of the present invention, the thickness of the underlayer is preferably 5 nm (mμ) to 1000 nm (mμ). The total thickness of the magnetic recording medium is preferably 13.5 µm or less. The non-magnetic carrier is preferably made of at least one of poly ethylene naphthalate, polyimide and polyamide. The magnetic layer preferably consists of one or more magnetic layers. The magnetic layer preferably has a Young's modulus in the longitudinal direction of 700 kg / mm ² or more in total, and the percentage elongation at break of the entire Mag netschicht is 2% or more, provided that the percentage elongation at break is 1% or more if the magnetic layer is a single layer comprising a magnetic metal powder.

In particular, the above includes non-magnetic Carrier polyethylene-2,6-naphthalate.

The magnetic layer preferably consists of a carrier-side A magnetic layer containing a ferromagnetic powder Iron oxide containing cobalt with a crystallite size of 350 Å or less and an outer magnetic layer a ferromagnetic powder of an alloy with a crystal lit size of 250 Å or less.

According to a preferred embodiment of the invention, a A magnetic recording medium comprising a Magnetic layer obtained by coating on a smooth, non-magnetic carrier (Ra: 15 nm or less (cutoff value (cut off value): 0.25 mm) according to JIS B 0601), made of Polyethylene naphthalate, polyamide or polyimide with a higher Strength as a known polyethylene terephthalate, a mag netic solution containing at least one ferromagnetic Powder, binders, carbon black, abrasives and a cyclohexanone Solution in an amount of 10 wt% or more based on the Weight of solvent, with a layer of a naph thalin ring-containing polyester between the non-magneti between carrier and the magnetic layer is created to a Improvement in adhesive strength, a thinner base (i.e. a thin res magnetic medium) and excellent running durability or to create stability. The recording density is increased by Improved creation of a thinner base. The strength of the magnetic recording medium is obtained by using of polyethylene naphthalate, polyamide or polyimide. Furthermore is a layer of a naphthalene ring containing polyester between the non-magnetic support and the magnetic layer provided a drastic improvement in adhesive strength too obtained so that the magnetic layer may fall out or peel off can be prevented by the non-magnetic carrier. Up to At this point there were sub-layers containing polyethylene naphthalate or a naphthalene ring suggested individually (for example, in JP-A-55-7865). The inventive com However, bination can produce unpredictable beneficial effects.

The invention eliminates the insufficient mechanical strength of a non-magnetic PEN carrier that is itself a weak one Has tear resistance, compensates for, as does tear resistance Improved performance of the entire magnetic recording medium becomes, and continues to be a thin magnetic recording medium created, which allows long-term recording and excellent running durability and excellent electro possesses magnetic properties by controlling the formation of the Magnetic layer in such a way that the breakage level is so tight is set as described above.

In other words, according to the invention, there is good flexibility strength and hardness created by creating a magnetic Layer, preferably several magnetic layers with one high Young′s modulus and high elongation at break to get the best To create use for PEN, d. i.e., the insufficient tear to compensate for PEN. This leads to considerable Improvements in output reproducibility, wrapping Envelope flatness, contamination of the video head and the edge conditions. In the prior art, a higher one means Flexibility a lower hardness. In contrast, with greater hardness decreases the strength. According to the invention a magnetic layer can be obtained which has both the ge desired hardness as well as flexibility supplies in order to a thinner to create a magnetic recording medium that has a long time allows recording and shows no peeling of the magnetic layer and has excellent running durability.

The magnetic recording medium according to the invention has a basic structure wherein a magnetic layer containing a ferromagnetic powder and a binder, on one not magnetic carrier is drawn or piled up.

The magnetic recording medium of the present invention can be used different solid and liquid lubricants in the magnetic layer and may further contain a magnetic layer or a Backing layer containing a non-magnetic powder (e.g. carbon black, an inorganic powder, an abrasive tel, a solid lubricant) and / or a binder on the Surface of the non-magnetic carrier opposite the Magnetic layer.

The magnetic recording medium of the present invention can corro sion inhibitors, anti-fungal agents, anti static agents, non-magnetic powders, dyes, organ magnetic compounds, dispersants, etc. in addition to the, to be incorporated into the magnetic layer contain lubricants. The Magnetic recording medium according to the invention can consist of several Ren magnetic layers with the same or different ferromagne table powders.

According to a preferred embodiment of the invention comprises a magnetic recording medium having a magnetic layer by coating on a non-magnetic support made of poly ethylene naphthalate, polyamide and polyimide with a higher Fe strength as polyethylene terephthalate, a magnetic solution, containing at least one ferromagnetic powder, a binder medium, carbon black and an abrasive as well as a cyclohexanone lo solvents in an amount of preferably 10% by weight or more, based on the total weight of the solvent, with a Layer of a polyester containing a naphthalene ring between between the non-magnetic substrate and the magnetic layer is arranged to improve the adhesive strength, a thinner Base (magnetic medium) and excellent running durability and create stability. In particular, includes the magnetic Coating solution a solvent with strong solvent power, such as cyclohexanone, in an amount of preferably 10% by weight or more based on the total weight of the solvent and in particular 10 to 70% by weight, based on the total weight of the solvent, so that the ferromagnetic powder in a Kneaded binder with high strength and high elasticity and can be dispersed therein.

In the invention, the improvement of the adhesive force can be effective Achieve sam by creating a layer of one, a naphtha linring-containing polyester between the non-magnetic Support and the magnetic layer, and preferably shows one Naphthalene ring-containing polyesters resistance to via cyclohexanone.

The reason for this phenomenon is not known. From the point of view from the fact that this resin is in a certain sense Degree has aqueous properties and a structure that is similar to that of the resin contained in the non-magneti between carrier and the magnetic coating solution is, it can be explained that the affinity between the not magnetic carrier and the dispersed resin is increased and the The structure and strength of the underlayer are therefore that of Carrier and the dispersed resin is similar. However, details are unknown about this.

As a polyester which can be used in the invention, containing a Naphthalene ring can be a polyester with a linear structure are preferably used. Examples of such polyesters around contain one of the monomer units of at least 3 contains selected from the group consisting of an alkali metal salt of sulfonic acid, polyalkylene glycol, 1,4-naphthalenedi carboxylic acid, 2,5-naphthalenedicarboxylic acid and 2,6-naphthalenedicar acidic acid in an amount of 50% by weight or more. Such a poly ester can be a diol, a terephthalic acid, and isophthalic acid Contain adipic acid.

As polyalkylene glycol, ethylene glycol, diethylene glycol, tri ethylene glycol and others can be used.

1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, etc. can be used.

As a sulfonic acid, the alkali metal salt of which is contained in the polyester can hold is 4-sulfonaphthalene-2,7-dicarboxylic acid, 4-Sul phonaphthalene-2,5-dicarboxylic acid, 4-sulfonaphthalene-2,6-dicarbon acid, sulfoterephthalic acid, sulfoisophthalic acid, etc. are used become.

The synthesis of these polyesters is the same as for the production of polyethylene terephthalate feasible. At for example, a predetermined amount of naphthalenedicarbon acid and glycol to a temperature of 140 to 280 ° C in Ge are heated in the presence of an ester exchange catalyst, and the the resulting alcohol is then distilled off. The Reaction system is at a temperature of 200 to 310 ° C and polymerized in the presence of a pressure of 0.01 to 40 mmHg a polymerization catalyst, phosphoric acid and phosphori ger acid to obtain the desired polyester.

The thickness of the layer of a contain a naphthalene ring the polyester that is between the non-magnetic support and of the magnetic layer is preferably 5 to 1000 nm (mµ). If the value is below the specified range lies, the adhesive force between the non-magnetic Trä decreases ger and the magnetic layer. In contrast, if the If the value is above the specified range, the hardness of the magnetic recording medium increased, thereby undesirable Effects occur. Between the non-magnetic carrier and the magnetic layer may be composed of a layer from a mixture of a naphthalene ring containing Po lyesters and a polyurethane, a polyester or a po polyester polyurethane or several of these components can be ent be arranged holding layers.

In this case it is in combination with one of the naphthalene ring-containing polyester resin to be used preferably water soluble. Examples of polyurethane, polyester, and of the polyester polyurethane, which in combination with the one Naphthalene ring containing polyesters are useful described below.

Examples of polyurethanes include polyurethane elastomers such as "DN 4805" (manufactured by Nippon Polyurethane Co., Ltd.) and "Pandex" (manufactured by Dainippon Ink Co., Ltd.); Examples for polyester include polyesters such as "Vylon" (manufactured by Toyobo Co., Ltd.) obtained by converting 0.5 to 40 mol% of a dicarbon containing a sulfonic acid metal base acid or its ester and 60 to 99 mol% of a dicarboxylic acid or an ester thereof with a glycol component; Examples for polyester polyurethanes include a polyester consisting from adipic acid and glycol (i.e. from reactants obtained are made by adding an adipic acid based polye sters with TDI or MDI and by reacting an ester of poly caprolactone with TDI or MDI).

The total thickness of the underlayer, regardless of whether it is made of a single layer or two or more layers is preferably 5 to 1000 nm (mμ), in particular 50 up to 500 nm (µm), in total. The effect according to the invention occurs especially when the entire thickness of the magnetic tape, comprising a layer of one containing a naphthalene ring Polyester placed between the non-magnetic support, including polyethylene naphthalate, polyimide or polyamide and a magnetic layer, is in the range of 13.5 µm or less. In the case that the total thickness of the magnetic tape is 13.5 µm or less is lower, the invention is particularly effective; i.e., in the Invention, the insufficient tape strength due to the nied igen thickness compensated by using a non-magneti cal carrier with a higher strength and a higher Out put is assured even if a cyclohexanone solution medium is used that the adhesive force between the carrier and the magnetic layer is reduced.

The sub-layer according to the invention can optionally not be contain magnetic powder. Such a non-magnetic one Powder can be an inorganic powder with an average A grain size of 50 to 5000 Å, like spherical silica (e.g. organosilica), spherical carbon and platelet-like silica. Such a non-magnetic pulse ver can be used in an amount of 0.1 to 100% by weight, based on the resin contained in the underlayer can be used. To one to ensure high output, a ferromagnetic powder, especially a ferromagnetic metal powder, effectively incorporated are set. In the case of a magnetic recording medium, around containing a backing layer made from a non-magneto tied powder and a binding agent and applied to the upper surface of a non-magnetic carrier opposite the Magnetic layer, a layer of a can be a naphthalene ring containing polyester advantageously between the non-magneti be arranged between the carrier and the back layer.

If the sub-layer consists of two or more layers, is the layer of a poly containing a naphthalene ring esters preferably on the side of the non-magnetic layer arranged, between the non-magnetic carrier and the Mag net layer, and a layer of polyurethane, polyester or Polyester polyurethane is preferably on the side of the magnet arranged between the non-magnetic carrier and layer the magnetic layer. The one on the side of the magnetic layer The underlying undercoat can be created by applying Layers of polyurethane, polyester and polyester polyurethane, alone or as a mixture.

In a preferred embodiment according to the invention the magnetic recording medium has a magnetic layer which is obtained by coating on a non-magnetic Carrier made of polyethylene naphthalate, polyamide or polyimide, a magnetic solution containing at least a ferromagnetic powder, a binder, carbon black and a Abrasives and a cyclohexanone solvent in one Amount of 10% by weight or more, the binder being preferred wise contains at least one resin, containing at least one functional group selected from the group consisting of a sulfonic acid, phosphoric acid, phosphonic acid, epoxy and Hydroxyl group.

The resin containing such a functional group can be used preferably a vinyl chloride resin, vinyl chloride acetate resin, poly urethane resin or polyester resin. Such a resin can be found preferably in an amount of 50% by weight or more, preferably 60% by weight or more based on the total weight of the resin (Binder) can be used.

The non-magnetic carrier that has the specified value of the Sum of a Young's module in the length direction and one Young's module is fulfilled in the width direction, which is not magnetic cal carrier including the underlayer. The sum of the You ng's moduli of the non-magnetic carrier is the sum of Values of Young's moduli, determined from the voltage and the An increased from origin F (0.5) value = 0.5% elongation according to ASTM D 882-81. The Young's module in the length direction of the entire magnet stratum can be calculated from the compound law the Young's modulus of the entire magnetic recording medium and the Young's modulus of the non-magnetic carrier from the voltage and the rise from the origin at the F (0.5) value = 0.5% elongation according to ASTM D 882-81. The percent elongation at The fracture of the entire magnetic layer is the stretching elongation that appears voltage when the magnetic recording medium is in the foregoing The tensile test mentioned is placed under tensile stress. The mes Solution is at a temperature of 23 ° C at a relative Humidity of 50% and an expansion rate of 10% / min leads. As a measuring device, "Tensilon" manufactured by Toyo is used Baldwin Co., Ltd. is used.

In the magnetic recording medium according to the invention, the adjustment or adjustment of the sum of the Young's modulus in the length direction and the Young's modulus in the width direction of the non-magnetic carrier including an underlayer to 1400 kg / mm ² or more and the percentage elongation at breakage of the whole magnetic layer to 2% or more by appropriately selecting the formulations for the non-magnetic support, the underlayer, the solvent for the magnetic coating solution, and so on.

The Young's modulus in the length direction of the entire magnetic layer is preferably 700 kg / mm ² or more.

The facilities for setting the Young's module in the longitudinal direction to 700 kg / mm ² or more and the elongation at break of the entire magnetic layer to 2% or more are not specifically limited. The following exemplary measures can preferably also be used:

• (i) Increasing the degree of packing of the components, such as the ferromagnetic powder; and
• (ii) Arranging the magnetic layer in a multi-layer structure and changing the thickness of the magnetic layer on the support side (hereinafter referred to as "lower magnetic layer") and the outermost magnetic layer (hereinafter referred to as "upper magnetic layer"

An example of measure 1) includes a physical loading act, for example calendering the formed magnet layer.

Calendering is carried out at a roller pressure of 100 up to 500 kg / cm, preferably 200 to 350 kg / cm, of a roller unit temperature of 50 to 120 ° C, preferably 70 to 100 ° C and one Processing rate from 50 to 500 m / min, preferably 100 to 350 m / min. Examples of rolls that can be used in calendering include metal rollers, cotton rollers, and plastic rollers. Be metal rollers are preferably used.

Regarding measure 2) is the thickness of the upper magnetic layer in the range from 0.1 to 1.0 µm, preferably 0.3 to 0.7 µm and the thickness of the lower magnetic layer ranges from 1.5 to 4.0 µm, preferably 2.0 to 3.0 µm, the total thickness being the entire magnetic layer in the range from 1.6 to 5.0 µm, preferably wise 2.3 to 3.7 µm.

If the thickness of the upper magnetic layer is less than 0.1 µm the output is reduced in the shortwave range. If the thickness of the lower magnetic layer exceeds 4.0 µm, The effects of the multi-layer construction cannot suffice accordingly manifest and lower the output in the long-wave region rich unfavorable.

The thickness of the non-magnetic support (including the underlayer) is 2.5 to 11 µm. The thickness of the back layer is 0.2 to 1.0 µm, preferably 0.3 to 0.7 µm. The thickness of the entire magnetic recording medium is accordingly 6.8 to 13.5 μm, preferably 7.5 to 12.4 μm. The non-magnetic carrier used in the invention has a sum of Young's modulus in the length direction and Young's modulus in the width direction of 1400 kg / mm ² or more. The Young's modulus in the length direction is preferably 500 kg / mm ² or more, and the Young's modulus in the width direction is preferably 1000 kg / mm ² or less. In particular, the PEN shows a Young's modulus of 700 kg / mm ² or more in MD (tape direction) (ie in the length direction) and a Young's modulus of 800 kg / mm ² or less in TD (transverse direction) (ie in the width direction ). The adaptation or the adjustment of the Young's modulus of the entire magnetic layer is preferably carried out by separately setting the Young's modulus of the lower magnetic layer and the upper magnetic layer.

According to the invention, the elastic modulus of the upper magnetic layer is preferably greater than that of the lower magnetic layer. The modulus of elasticity or Young's modulus of the upper magnetic layer is preferably 1100 kg / mm ² or more, in particular 1300 kg / mm ² or more, in MD (machine direction) and the Young's modulus of the lower magnetic layer is preferably 600 kg / mm ² or more, especially 800 kg / mm ² or less, in MD (machine direction).

In this case, the Young's modulus is the upper magnetic layer greater than that of the lower magnetic layer and the friction by virtue of the sliding part of the upper magnetic layer on the Mag net head can be diminished to the external force generated by the magnetic recording medium is received to min change. At the same time, if the Young's module of the lower Magnetic layer is lower or smaller than that of the above ren magnetic layer covered by the magnetic recording medium external force received through the lower magnetic layer disper yawed and transferred to the carrier to an external Force (concentration of tension) on PEN (the one smaller Tear resistance), and thus makes it possible becomes, the tear strength of the entire magnetic record to increase the medium.

In other words, by combining a soft and flexi blen magnetic layer with a buffer effect as the lower layer, with a hard and durable magnetic layer as the top layer and furthermore with PEN, which has a high Young's modulus, can provide a thinner magnetic recording medium be, which has excellent running durability and excellent Excellent electromagnetic properties and a long-term record has the ability to be created.

Ferromagnetic powders useful for the invention include γ-Fe ₂ O ₃ , cobalt-containing (coated, modified, doped) γ-Fe ₂ O ₃ , Fe ₃ O ₄ , cobalt-containing (coated, modified, doped) Fe ₃ O ₄ , γ -FeO _x , cobalt-containing (coated, modified, doped) γ-FeO _x (x = 1.33 to 1.50), CrO ₂ , etc. In particular, a ferromagnetic metal powder of a single metal or an alloy such as iron, iron -Alloy, Fe-Co alloy, Fe-Co-Ni alloy, Fe-Co-Ni-P alloy, Fe-Co-Ni-B alloy, Fe-Ni-Zn alloy, Ni-Co alloy and Co-Ni-Fe alloy are preferably used. The grain size of these ferromagnetic metal powders is in the range of about 0.005 to 1 µm, and the long axis (length) / short axis (width) ratio is in the range of 1/2 to 15/1. The ferromagnetic metal powders have a specific surface area of 35 to 80 m ² / g, preferably 48 to 70 m ² / g, a coercive force (Hc) of 1250 to 2500 Oe, a water content of 0.1 to 2% by weight and a pH of 3 to 11 (5 g magnetic material / 100 g).

These ferromagnetic powders can have a corrosion effect bitor, surface treatment agent, dispersant, lubricant agent, antistatic agent or the like in a solution agents are treated before dispersing so that they do this Absorb funds for the appropriate purposes.

The magnetic recording medium of the present invention includes a magnet placed on a non-magnetic carrier layer comprising such a fer dispersed in a binder Contains romagnetic powder. The inventive magnetic The recording medium may further be other than the above elements described (e.g. Sr, Pb, Mn, Cd, Al, Si, Na, K, Ti, Cu, Zn, S) for the purpose of improving magnetic properties or as impurities in one Amount of 10,000 ppm or less. In particular, this includes fer romagnetic metal powder on the surface of which an aluminum or silicone compound as an oxidation stabilizer (corrosion inhibitor) layer in an amount of 1 to 10% by weight, based on on the weight of the metal component.

In the context of the invention, ferromagnetic metal powders are useful Lich. Such ferromagnetic metal powder may comprise a ferromagnetic metal powder which contains iron (α-iron), cobalt or nickel to increase its effects. Such ferromagnetic powders preferably comprise a ferromagnetic alloy powder having a specific surface area of 48 m ² / g or more and a coercive force of 1300 to 2500 Oe, preferably 1500 to 1800 Oe. Specific examples of such ferromagnetic alloy powders include powder of an alloy having a metal content of 60% by weight or more, with 70% by weight or more of the metal component being at least one ferromagnetic metal or an alloy (e.g. Fe, Fe-Co, Fe- Co-Ni, Co, Ni, Fe-Ni, Co-Ni, Co-Ni-Fe) and 40% by weight or less, preferably 20% by weight or less of the metal component which is the other component (for example, Al , Si, S, Sc, Ti, V, Cr, Mn, Cu, Zn, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta, W, Re, Au, Hg, Pb, Bi , La, Ce, Pr, Nd, B, P); a powder of iron nitride; and a powder of iron carbide. In particular, the metallic iron preferably contains Al, Si or Cr in its surface layer alone or in admixture in order to improve its strength. Furthermore, the ferromagnetic metal can contain a small amount of water, hydroxide, oxide, alkali metal elements (for example Na, K) or alkaline earth metal elements (for example Mg, Ca, Sr). Processes for producing these ferromagnetic metal powders are known. The ferromagnetic alloy powder as a typical example of a ferromagnetic powder which can be used in the invention can be produced by means of these known methods.

The examples for making the ferromagnetic alloy powders include the following procedures:

• a) a process comprising the reduction of a compound law th organic acid salt (mainly of an oxalate) with a reducing gas, such as hydrogen;
• b) a method comprising reducing iron oxide with a reducing gas, such as hydrogen, to iron or to obtain Fe-Co grains;
• c) a method comprising the thermal decomposition of a Metal carbonyl compound;
• d) a method comprising the reduction of an aqueous Lö Solution of a ferromagnetic metal with a reduction agents such as sodium borohydride, hydrophosphite and hydrazine;
• e) a method comprising the electro-precipitation of a ferro magnetic metal powder on a mercury cathode and subsequent separation of the ferromagnetic metal powder from the mercury cathode; and
• g) a method comprising evaporating a metal in an inert gas atmosphere at low pressure to make a fine to obtain distributed metal powder.

The ferromagnetic powder useful in the invention is not specifically limited in shape, but may usually needle-shaped, granular, cube-shaped, elip be soidal or platelet-shaped. This ferromagnetic alloy Powder powders preferably have a σs of 100 to 210 emu / g. The crystallite size of this ferromagnetic metal powder be preferably carries 100 to 300 Å. Regarding the needle ratio ses, is the ratio of long axis / short axis before preferably 3/1 to 15/1. Preferred examples include a kubi cal, hexahedral and octahedral shapes.

Plate-like ferromagnetic metal powders are present preferably a ratio: diameter / thickness: 3/1 to 30/1. At games for such ferromagnetic alloy powders are in JP- A-53-70 397, 58-1 19 609, 58-1 30 435, 59-80 901 and 59-41 453, JP-B- 61-37,761 and U.S. Patents 4,447,264, 4,791,021, and 4,931,198 described.

According to the invention, the lower magnetic layer may preferably cobalt-containing iron oxide grains with a crystallite size of 350 Å or less, preferably 250 to 300 Å, and the upper magnetic layer may preferably be ferromagnetic Alloy powder with a crystallite size of 250 Å or less ger, preferably 150 to 200 Å, included to form a multilayer design to get the excellent electromagnetic Properties shows.

The iron oxide containing cobalt has a specific surface area of 25 to 70 m ² / g, preferably 32 to 50 m ² / g, according to the BET method. If the specific surface area of the iron oxide containing cobalt is less than 25 m ² / g, the surface of the magnetic recording medium cannot be sufficiently smoothed. On the contrary, if the specific surface area of the iron oxide containing cobalt ^{exceeds 70 m 2} / g, the dispersion becomes difficult. For the same reasons, the average length of the long axis of the iron oxide grains containing cobalt is preferably 0.25 µm or less, more preferably 0.95 to 0.23 µm, and the crystallite size thereof is preferably in a range of 350 Å or less. The cobalt-containing iron oxide preferably exhibits a σs that is as high as possible. However, it is difficult to find an iron oxide containing cobalt with a σs value of more than 80 emu / g (1 emu / g = 1 A · m ² / kg).

The ferromagnetic alloy powder has a specific surface area of 35 to 80 m ² / g, preferably 40 to 70 m ² / g, measured by the BET method. If the specific surface area of the ferromagnetic alloy ^{powder is less than 35 m 2} / g, the surface of the magnetic recording medium cannot be sufficiently smoothed and grain noise is increased, which destroys the electromagnetic properties of the medium. On the contrary, if the specific surface area of the ferromagnetic alloy ^{powder exceeds 80 m 2} / g, the preparation of the dispersion becomes difficult. For the same reasons, the average length of the long axis of the ferromagnetic alloy powder is preferably 0.25 μm or less, particularly 0.05 to 0.23 μm, and the crystallite size thereof is preferably 25 nm or less. The ferromagnetic alloy powder has a σs value that is as high as possible. However, it is difficult at the moment to find a ferromagnetic alloy powder which has a σs value of more than 180 emu / g.

A non-magnetic carrier which can be used for the invention is preferably selected from a polyethylene naphthalate (PEN), Polyamide and polyimide. If one contains a naphthalene ring tender polyester is selected for the underlayer, the Adhesive strength between the carrier and the backsheet increased become. In addition, a coating solution can be used for the magnet layer containing a cyclohexanone solvent in an amount of 10 wt% or more based on the total weight of the solution means, contains and which is able to dissolve a binder in it, improve the dispersibility of the ferromagnetic powder and the adhesive force between the magnetic layer and the sub Strengthen layer, as the underlayer compared to the cyclohex anon-solvent resistant.

Examples of PEN to be used in the invention include Polyester compositions which essentially reflect the nature of the PEN retained, such as polyethylene-2,6-naphthalene dicarboxylate homopolymer, a copolymer containing ethylene-2,6- naphthalenedicarboxylate in an amount of 70% by weight or more as a repeating unit and a mixture of these with different polymers (PEN content: 70% by weight or more).

PEN can be produced by polycondensation of ethylene glycol, Dimethyl 2,6-naphthalenedicarboxylate, etc. Glycols other than Ethylene glycols can be used.

The PEN carrier can be produced by biaxially orienting a not oriented film. A PEN carrier with a desired Modulus of elasticity (Young's modulus) can be produced by suitable Selecting the unoriented film, the molecular weight weight of the PEN contained therein, the stretching temperature and the Extent of stretching.

The PEN carrier may contain a lubricant such as finely divided grains of an inorganic material (e.g. SiO ₂ , TiO ₂ , Al ₂ O ₃ , ZnO, MgCO ₃ , CaCO ₃ ) and an inert organic material (sorbitan, thyroid).

If within the scope of the invention a polyamide or polyimide carrier is used, such a polyimide or polyamide may be an im State of the art used. For example, Apical (manufactured by Kanegafuchi Chemical Industry Co., Ltd.) and a polyimide (manufactured by Mitsubishi Chemical Corpora tion) described in JP-A-60-15 436 is useful as the polyimide and polyparaphenylene phthalamide can be used as the polyamide.

The carrier made from these materials can be applied to the same way as when using PEN. The surface roughness of this carrier can be the same Way can be set as with PEN.

The magnetic layer according to the invention is not one-sided layered construction or two-layer construction limited, consisting of an upper layer and lower layer, but can also be three or contain more layers. The coating of the magnet shift can be carried out using known measures, like these for example in "Progress of Coating Technique", published by Sogogÿutsu Center (1988). In the case of a multi-layer construction, successive coatings can be used treatment process or simultaneous coating process alone or can be used in combination.

Examples of a multilayer coating method include following procedures:

• 1. a coating method comprising coating a lower magnetic layer by a gravure coater device, a roll coater, a blade mount coating device, an extrusion coating device tung, etc., which are conventionally used for Be layers of a magnetic coating solution, the dry Nening the material and then coating a top ren magnetic layer by an extrusion coater carrier printing type device as in JP-B-1-46 186, JP-A-60-2 38 179 and JP-B-2-265672;
• 2. a coating method comprising coating a lower magnetic layer by means of a gravure coating direction, roller coating device, blade coating processing device, extrusion coating device, etc., the conventional for coating with a magnetic Coating solution can be used and subsequent Coating an upper magnetic layer by means of an extrusion Carrier pressure type ion coater as shown in FIG JP-B-1-46 186, JP-A-60-2 38 179 and JP-A-2-2 65 672 are described while the lower magnetic layer is wet;
• 3. a coating method comprising coating all of them Licher magnetic layers at the same time by means of a Be layering head, the two or more passage slots for the coating solutions as disclosed in JP-A-63- 88 080, JP-A-3-17 971 and JP-A-2-2 65 672; and
• 4. a coating method comprising coating all of them Licher magnetic layers at the same time by means of an extrusion ion coater with a backup roller as described in JP-A-2-1 74 965.

To avoid the destruction of the electromagnetic properties of the magnetic recording medium due to agglomeration To prevent the ferromagnetic powder, the coating can processing solution in the coating head, preferably with shear force (Shearing) can be applied using a method described in JP-A-62-95 174 and JP-A-1-2 36 968 is described.

As in the magnetic layer and back layer of the fiction according to the magnetic recording medium to be incorporated medium can be any thermoplastic resin, thermosetting resin, reactive resin or their mixture can be used.

As the thermoplastic resin, usable is one which is one Glass transition temperature from -100 to 150 ° C and a weight average molecular weight from 5,000 to 100,000 preferably 5,000 to 50,000.

Specific examples of a usable thermoplastic resin zes include polymers or copolymers included as an ingredient subunits vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid ester, vinylidene chloride, Acrylni tril, methacrylic acid, methacrylic acid ester, styrene, butadiene, Ethylene, vinyl butyral, vinyl acetal, vinyl ether, etc., polyure than resin and various rubber resins.

Examples of thermosetting resins and reactive resins include sen phenolic resins, epoxy resins, phenoxy resins, polyurethane resins, Urea resins, melamine resins, reactive acrylic resins, formaldehyde resins, silicone resins, epoxy-polyamide resins, mixtures of polyes sterols and isocyanate prepolymers, mixtures of polyester polyol and polyisocyanate and mixtures of polyurethanes and Polyisocyanates.

These resins are described in "Handbook of Plastics", published Published by Asakura Shoten.

Furthermore, known resins can be used by Electron beams are hardened. Hence, resins are what contain an acrylic acid group built therein, for this Purpose usable. These resins and their manufacturing processes are described in detail in JP-A-62-2 56 219.

The above resins can be used alone or in their com bination can be used. Preferred examples of a combination tion of resins include a combination of at least one Resin selected from the group consisting of a vinyl chloride rid resin, vinyl chloride-vinyl acetate resin, vinyl chloride-vinylace tat-vinyl alcohol resin and vinyl chloride-vinyl acetate-maleic acid anhydride with a polyurethane resin and a combination of these Resins with polyisocyanate.

Specific examples of the polyurethane resin include known ones Resins such as polyester-polyurethane, polyether-polyurethane, poly ether-polyester-polyurethane, polycarbonate-polyurethane, poly ester-polycarbonate-polyurethane and polycaprolactone-polyurethane.

In order to create better dispersibility and durability for all binders described therein, binders which have at least one functional group are selected from the group consisting of SO ₃ M, an epoxy group, -OSO ₃ M, -COOM, -P = O (OM) ₂ , -OP = O (OM) ₂ (in which M denotes a hydrogen atom or an alkaline metal base), -OH, -NR ₂ , N⁺R ₃ (in which R denotes a hydrocarbon group), SH and CN preferably by one Copolymerization or addition reaction incorporated. The amount of the functional group is 1 × 10 ^-1 to 1 × 10 ^-8 mol / g, preferably 1 × 10 ^-2 to 1 × 10 ^-6 mol / g. _{-SO 3} M, -OP = O (OM) ₂ , -P = O (OM) ₂ and epoxy groups are particularly preferred.

As the vinyl chloride copolymer, one containing an epoxy group is preferably used. Examples of a vinyl chloride copolymer containing an epoxy group include a vinyl chloride copolymer containing vinyl chloride, epoxy, -SO ₃ M- repeating units.

In general, such a vinyl chloride copolymer has a number Average molecular weight from 15,000 to 60,000.

The production of a vinyl chloride copolymer in which Epoxygrup pen and -SO ₃ M groups are incorporated can be carried out by mixing sodium 2- (meth) acrylamide-2-methylpropanesulfonate containing a reactive double bond and -SO ₃ Na as functional le Group, with glycidyl acrylate at a low temperature and then polymerizing the mixture with vinyl chloride at a temperature of 100 ° C or less under pressure.

Besides, a production method can be used comprising producing a vinyl chloride copolymer containing a polyfunctional -OH group such as vinyl chloride-vinyl acetate-vinyl alcohol copolymer obtained by saponifying a copolymer of vinyl chloride and vinyl acetate and then reacting it with ClCH ₂ CH ₂ SO ₃ M (a dehydrochlorination, where M represents a hydrogen atom or an alkaline metal base to introduce a functional group into the copolymer). When introducing an epoxy group using the hydrochlorination reaction, epichlorohydrin is usually used.

The vinyl chloride copolymer can contain further monomers. Examples of such monomers include vinyl ethers (e.g. Methyl vinyl ether, isobutyl vinyl ether, lauryl vinyl ether), α-Mo noolefin (for example ethylene, propylene), acrylic acid esters (for example methyl (meth) acrylate, (meth) acrylic acid ester, ent holding a functional group such as hydroxyethyl (meth) acrylate), an unsaturated nitrile (e.g. (meth) acrylonitrile), an aromatic vinyl (e.g. styrene, methyl styrene) and a vinyl ester (e.g. vinyl acetate, vinyl propio nat).

The introduction of a functional group into another resin as a vinyl chloride resin, for example into a polyurethane resin, can be done by the same measures as above be wrote.

Examples of binders usable in the invention include VAGH, VYHH, VMCH, VAGF, VAGD, VROH, VYES, VYNC, VMCC, XYHL, XYSG, PKHH, PKHJ, PKHC and PKFE (manufactured by Union Carbi de); MPR-TA (manufactured by Nisshin Chemical Industries, Co., Ltd.); 1000W, DX80, DX81, DX82 and DX83 (manufactured by The Electro Chemical Industrial Co., Ltd.); MR100, MR100 and 400X110A (manufactured by Japanese Zeon Co., Ltd.); Nip plan 2301, N2302 and N2304 (manufactured by Nippon Polyurethane Co., Ltd.); Pandex T-5105, T-R3080, T-5201, Burnock D-400, D-210-80, Crisvon 6109 and Crisvon 7209 (manufactured by Dainippon Ink And Chemicals, Inc.); Vylon UR8200, UR8300, RV530 and RV280 (manufactured by Toyobo Co., Ltd.); Daipheramin 4020, 5020, 5100, 5300, 9020, 9022 and 7020 (manufactured by Dainichiseika Co., Ltd.); MX5004 (manufactured by Mitsubishi Chemical Corpo ration) and Sunprene SP-150 (manufactured by Sanyo Chemical Industries Co., Ltd.) and Salan F310 and F210 (manufactured by Asahi Chemical Industry Co., Ltd.).

Examples of polyisocyanates which can be used in the invention grasp isocyanates such as tolylene diisocyanate, 4-4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naph thalin-1,5-diisocyanate, o-toluidine isocyanate, isophorone diisocyanate nat and triphenylmethane triisocyanate, reaction products of these Isocyanates with a polyalcohol and polyisocyanates, which by Condensation of isocyanates can be produced. Such isocya nate are commercially available under the trade name Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate MR and Millionate MTL (manufactured by Nippon Polyurethane Co., Ltd.); Takenate D-102, Takenate D-110N, Takenate D-200 and Take nate D-202 (manufactured by Takeda Chemical Industries, Ltd.); Desmodur L, Desmodur IL, Desmodur N and Desmodur HL (manufactured by Sumitomo Bayer Co., Ltd.). These isocyanates can alone can be used. Two or more of these are isocyanates usable so that the difference in curing reactivity usable between them.

The amount of binder to be incorporated into the magnetic layer is in the range from 15 to 30% by weight, preferably 18 to 25 % By weight based on the weight of the ferromagnetic powder. The amount of binder to be incorporated into the backing layer means is 50 to 200 wt .-%, preferably 70 to 150 wt .-%, based on the weight of the non-magnetic powder.

The magnetic layer in the invention may optionally be an Ad ditive containing, for example, antistatic agents (at for example carbon black), abrasives, coloring agents, lubricants and Dispersants.

Furnace black, thermal black, color black, acetylene black or can be used similarly. The carbon black used in the invention can be surface treated with a dispersant, with a resin may be grafted, or its surface may be partially be graphitized. Carbon black can be added to a binder before adding it the magnetic coating solution can be dispersed. These Carbon blacks can be used alone or in combination.

The soot inhibits the electrification of the upper magnet layer, put the coefficient of friction of the upper magnet layer and supply the upper magnetic layer with a Light shielding effect or improve the strength of the top Magnetic layer. Different soots have different wes kungen. Therefore, these carbon blacks can be appropriately selected obviously of any type, amount and combination depending on the purpose and the desired characteristics, such as grain size, Oil absorption, electrical conductivity and pH. The DBP Oil absorption ranges from 30 to 500 ml / 100 g.

With regard to the carbon blacks to be used in the invention, reference is made taken on the "Handbook of Carbon Black", published by Carbon Black Kyokai.

Regarding the abrasive to be used in the invention is α-alumina with an α-conversion of 90% or more, β-alumina, Silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, syn thetic diamond, silicon nitride, silicon carbide, titanium carbide, Titanium oxide, silicon dioxide, boron nitride, etc., individually or in com bination usable.

Specific examples of abrasive usable in the invention Medium include AKP-20, AKP-30, AKP-50 and HIT-50 (manufactured by Sumitomo Chemical Co., Ltd.); G5, G7 and 5-1 (manufactured by Nippon Chemical Industrial Co., Ltd.); 100ED and 140ED (manufactured by Toda Kogyo K.K.).

These abrasives can be in a binder before adding to it the magnetic coating solution can be dispersed.

Examples of additives with a lubricating effect, more antistatic Effect, dispersing effect, plasticizing effect, etc. described below.

Examples of solid lubricants include molybdenum disulfide, tungsten disulfide, graphite, boron nitride, fluorinated graphite and carbon black.

Examples of organic lubricants include silicone oil, silicone oil, containing a polar group, silicone, which with an aliphati chemical acid is modified, fluorine-containing silicone, fluorine alcohol containing, fluorine containing ester, polyolefin, poly glycol, alkyl phosphate, alkali metal salt of an alkyl phosphate, Alkyl sulfate, alkali metal salt of an alkyl sulfate, polyvinyl ether, fluorine-containing alkyl sulfate, alkali metal salt of one fluorine-containing alkyl sulfate, monobasic aliphatic acid with 10 to 24 carbon atoms (the unsaturated bonds may contain or be branched), metal salts (for example Li, Na, K, Cu) monobasic aliphatic acids with 10 to 24 Carbon atoms, monovalent, divalent, trivalent, four valued, pentavalent and hexavalent alcohols (the unsaturated May contain bonds or be branched), alkoxy alcohol with 12 to 22 carbon atoms, monoaliphatic acid ester, dialiphatic acid ester or trialiphatic acid ester, made from a monobasic aliphatic acid with 10 up to 24 carbon atoms (which contain unsaturated bonds or branched), and any monovalent, two-valued tiger, trivalent, tetravalent, pentavalent and hexavalenti low alcohol with 2 to 12 carbon atoms (the unsaturated May contain bonds or be branched), aliphatic Acid ester of a monoalkyl ether of an alkylene oxide polymer tion product, aliphatic amides with 8 to 22 carbon atoms men and an aliphatic amine having 8 to 22 carbon atoms.

Specific examples of such organic lubricants include Lauric acid, myristic acid, palmitic acid, stearic acid, behen acid, butyl stearate, oleic acid, linoleic acid, linolenic acid, elaidic acid, octyl stearate, amyl stearate, isooctyl stearate, octyl myris tat, butoxyethyl stearate, anhydrosorbitan monostearate, anhydrosor bitan distearate, anhydrosorbitan tristearate, oleyl alcohol and Lauryl alcohol.

Nonionic surfactants that can be used in the invention Agents include alkylene oxide, glycerin, glycidol, and an additive cation product of alkylphenol ethylene oxide; cationic surface Active agents include cyclic amines, ester amides, quaters Nary ammonium salts, hydantoin derivatives, heterocyclic compounds dung, phosphonium or sulfonium compounds; anionic Surfactants with an acid group include carbon acid, sulfonic acid, phosphoric acid, sulfuric acid as well as one phosphorous acid ester; amphoteric surfactants include amino acid, aminosulfonic acid, sulfuric or phosphorous ge acid ester of an amino alcohol and alkyl betaine. This upper Surface-active agents are described in detail in "Surface Active Agent Binran ", Sangyo Tosho Co., Ltd.

These lubricants and surfactants can be used in any form cher type and quantity depending on the layer structure of the magnetic recording medium is suitably used become. For example, various configurations can be made be taken if the magnetic layer is made up of multiple layers consists. For example, aliphatic acids can be used with different melting points in the magnetic layer between the upper layer and the lower layer are built in to the Blooming of the material towards the surface of the magnetic layer Taxes. Esters with different boiling points or polarities can be used to control the blooming of the material on the Surface of the magnetic layer. The amount of surfactant Means can be used to increase the stability of the coating be like. The lubricant can essentially be incorporated in the middle layer than in the other layers to increase the lubricant effect. However, the invention is not limited with regard to the configurations.

To improve the dispersibility of the ferromagnetic powder in the To improve the upper magnetic layer, organic phosphorus will be used compounds are used, represented by the following formulas become:

(1) (RO) _n PO (OM) _3-n
(2) (RO) _n P (OM) _3-n
(3) (R) _n P (OM) _3-n
(4) RPO (OM) ₂

where mean:

R - a substituted or unsubstituted alkyl group with 4 to 16 carbon atoms, an alkenyl group or aryl group,
M - a hydrogen atom, alkaline metal or -N (R ¹ ) ₄ , in which R ^{1 is} an alkyl group having 1 to 6 carbon atoms and
n - an integer of 1 or 2.

The additives usable in the invention can completely or partially added to the system during the Her position of the magnetic layer, such as the coating solution solution for the lower magnetic layer, the coating solution solution for the upper magnetic layer and the coating solution for the back layer. For example, in the case of Her position of the magnetic coating solution with these additives a ferromagnetic powder before kneading den, can also be added to the system while kneading the ferro magnetic powder, the binder and the solvent can be added to the system during dispersing, added after dispersing or just before coating become.

As the organic solvent used for the dispersion, the Ver kneading or coating can be used in any Share of ketones, such as acetone, methyl ethyl ketone, methyl isobutylene clay, cyclohexanone, isophorone and tetrahydrofuran; Alcohols like Methanol, ethanol, propanol, butanol, isobutyl alcohol, isopro pyl alcohol and methylcyclohexanol; Esters, such as methyl acetate, Ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, Ethyl lactate and glycol monoethyl ether acetate; Ethers such as diethyl ether, tetrahydrofuran, glycol dimethyl ether, glycol monoethyl ether and dioxane; aromatic hydrocarbons, such as benzene, Toluene, xylene, cresol, chlorobenzene and styrene; chlorinated Koh hydrogen, such as methylene chloride, ethylene chloride, terachlor carbon, chloroform, ethylene chlorohydrin and dichlorobenzene; N, N-dimethylformamide and hexane can be used. Two or several of these solvents can be used in any proportion or in can be used in any ratio. These solvents can Impurities (for example polymerization products of these Solvents, water, starting materials) in a small amount Amount of 1 wt% or less.

The solvents are in an amount of 100 to 20,000 wt. Parts based on 100 parts by weight of the solids content of the magnetic coating solution or all of the solid content of the back coating solution and the coating solution for the lower layer, can be used. The magnetic solution preferably has a solids content of 10 to 40% by weight on. The coating solution for the back layer possesses preferably a solids content of 5 to 20% by weight. Watery Solvents (e.g. water, alcohol, acetone) can can be used in place of the organic solvents.

The organic solvents can preferably be cyclohexanone in an amount of 10% by weight or more (preferably up to 70% by weight) Wt .-%), based on the total weight of the solvent for the magnetic coating solution of the magnetic layer to increase the dispersibility of the ferromagnetic powder. If the magnetic layer consists of several layers, the total proportion of cyclohexanone in the various magneti different coating solutions within the above specifi adorned range, the proportion of cyclohexanone of the upper to the lower layer can be the same or different may, but is preferably higher than in the lower layer in the top layer to enhance the surface properties of the Mag secure net layer.

The formation of the magnetic layer can preferably be carried out are by means of a method comprising dissolving any a suitable combination of the above-mentioned together settlements in a cyclohexanone in an amount of 10 wt .-% or more, based on the total weight of the solvent, containing organic solvents to make a coating To obtain solution, coating the coating solution on a carrier, drying the material and then orienting animals of the material.

If the magnetic recording medium is used as a magnetic tape, the thickness of the support is 2.5 to 11 μm, preferably 3 to 10 μm. Preferably, the carrier is made of plastic such as polyethylene naphthalate, polyimide and polyamide. These carrier materials are described in detail in DE-33 38 854A, JP-A-59-1 16 926 and JP-A-61-1 29 731, as well as in US-A-4,388,368 and in Yukio Mitsuishi, "Seni to Kogo (Fiber and Industry) ", Volume 31, pages 50-55, 1975. If the magnetic recording medium is used as a video tape, the average surface roughness at the center line of the carrier surface is preferably 0.1 to 30 nm (cut-off value, cutoff value: 0.25 mm (according to JIS B 0601)). The Young's modulus (F5 value) of these carrier materials can be selected in the range from 2 to 50 kg / mm ² , both in the length direction and in the width direction, depending on the intended use.

The non-magnetic carrier can be a corona discharge, plasma treatment, treatment to facilitate adhesion, one Heat treatment, or subjected to dust resistance treatment before being covered with an underlayer or magnetic layer is layered.

The methods of dispersing and kneading are not specific fish limited. The order of adding the different Components (e.g. resin, powder, lubricant, solvent medium), the place where these components are found during the dis Perge or knead are added, the proportion of each Adding the same starting materials, the temperature when Dispersing (0 to 80 ° C), the moisture when dispersing etc. can be determined appropriately. The manufacture of the magneti between the coating solution and the coating solution for the Backing layer can be made with conventional kneading machines be carried out, for example with a two-roller mill, Three-roller mill, ball mill, pebble mill, Tron mill, a sand shredder, a Szegvari device, an attritor, high speed impeller, a dispersing device, Hochge speed stone mill, high speed pressure mill, Dispersing device, kneading device, high-speed Mixing device, ribbon mixer, a co-kneader, intensive mixer, Tumbler mixer, a homogenizing device, a single-axis Screw extruder, two-axis screw extruder and one Ultra sound wave dispersing device. In general, the Dis perge and knead continuously by means of a multitude of these dispersing devices and kneaders. The Dispersing and kneading techniques are described in detail in T. C. Patton, "Paint Flow and Pigment Dispersion," John Wiley & Sons, 1964, Shinichi Tanaka, "Kogyo Zairyo (Industrial Materi als) ", Volume 25, No. 37, 1977, as well as the reference cited therein put. As auxiliary materials to maximize the dispersing and Kneading effectiveness can be steel balls, steel beads, ceramic beads, Glass beads and organic polymer beads with a diameter from 0.05 mm to 10 cm can be used. These materials are not limited with regard to their sphere and are also in the US Patents 25 81 414 and 28 55 156 described. As part of the Invention, dispersing and kneading is carried out by means of Procedures that can be found in the above-mentioned references are written to a magnetic coating solution or Prepare coating solution for the back layer. The Hardeners and some of the additives mentioned (for example the aliphatic acid, phosphoric acid, phosphonic acid and the Sulphonic acid with high reactivity towards the ferromagneti powder, as well as their esters) can be added to the coating solution by means of an adding device, such as a mixing nozzle, directly in front are added to the coating.

The coating of the coating solution for the magnetic layer and the coating solution for the back layer on the Carrier can be adjusted by adjusting the viscosity of the coating solution carried out to 1 to 20,000 centistokes (at 25 ° C) with subsequent coating of the coating solution onto the carrier by means of an air knife, a blade, a Air knife, a squeeze coating process, immersion method driving, reverse roll coating process, transfer roll coating processing process, gravure coating process, a roller wear, a bar coating, spray coating, pour coating processing, forward roller coating, a curtain coating process, by extrusion coating or bar coating. This procedure Ren are described in more detail in "Coating Engineering", Asakura Shoten, pp. 253-277, March 20, 1971, and in "Progress of Coating Technique ", published by Sogogÿutsu Center, 30. April, 1988. The coating order for the coating solutions can be selected arbitrarily. The coating the sub-layers can be made continuously before coating the desired solutions can be carried out. If the magnet layer or backing layer made up of a plurality of layers consists, these layers can be simultaneous or consecutive be coated. These methods are in JP-A-57-1 23 532, JP- A-59-1 42 741, JP-A-59-1 65 239 and JP-B-62-37 451 are described.

The magnetic layer is then oriented with a thickness of about 1 to 100 μm on the carrier under a force of gravity of 500 to 5000 G in the desired direction (for example vertical direction, length direction, width direction, random direction, diagonal direction), the magnetic powder in the layer optionally is dried immediately in many stages at a temperature of 20 to 130 ° C. The resulting magnetic layer is then dried to a thickness of 0.1 to 4 µm. During this process, the carrier is usually at a rate of 10 m / min to 900 m / min through a plurality of drying zones, the temperatures of which are controlled to between 20 to 130 ° C, so that the resulting amount of solvent in the Lö Coating film reaches 0.01 to 40 mg / m ² . The magnetic layer and the backing layer thus obtained may be subjected to surface smoothing, if necessary, so that they have an average surface roughness on the center line of 0.001 to 0.3 µm (cut-off value: 0.25 mm (according to JIS B 0601)). Then, the material is cut into a desired shape to produce a magnetic recording medium of the present invention. These manufacturing methods may selectively include powder pretreatment and surface treatment, kneading and dispersing, coating, orienting, drying and smoothing, as well as heat treatment, EB treatment, surface roughening, cutting, winding, etc. These steps are preferably carried out sequentially are described in JP-B-40-23625, JP-B-39-28 368, JP-B-47-38 802, JP-B-48-11 336, JP-B-52-17 404, British Patent 11 91 424, JP-A-49-53 631, JP-A-50-1 12 005, JP-A-51-77 303, JP-A-60-70 532, JP-A-2-265 672 and US patents 34 73 960 47 28 569 and 47 46 542. The method described in JP-B-41-13 181 represents a functional and important technology in the prior art.

The cut magnetic recording medium is then made ßend wound on a plastic or metal roll. Right in front winding up or during the previous step the magnetic recording medium is preferred in terms of its Magnetic layer, backing layer, edge surface, base surface, painted and / or cleaned. The painting is used to remove bumps the surface of the magnetic recording medium with a to compensate for hard material, for example a sapphire line ge, razor blade, ultra hard blade, diamond blade and ceramic blade so that the surface is smoothed. The Mohs'sche Hardness of these blade materials is preferably 8 or more, but is not specifically limited and can be large enough be to remove the bumps from the surface of the magnetic Remove the recording medium. These materials are not necessarily in the form of a blade, but rather can also have a rectangular shape or a wheel shape, whereby the mate rialien if necessary on the periphery of a rotary cylinder ders are coated. The magnetic recording medium becomes by rubbing the surface of the magnetic layer, backsides layer, the edge surface, the back or the base with a non-woven fabric to remove dirt or a separate lubricant. examples for abrasive materials include various Vilene, herge manufactured by Japan Vilene Co., Ltd .; Toraysee and Ecsaine, here provided by Toray Industries, Inc .; Kimwipe, manufactured by Jujo Kimberly Co., Ltd .; different polishing tapes (lap ping tapes) manufactured by Fuji Photo Film Co., Ltd .; Not woven nylon fabrics, non-woven polyester fabrics, non-woven te rayon fabrics, acrylonitrile nonwoven fabrics, mixed nonwoven fabrics and tissue (pulp) paper. This mate materials for wiping or rubbing are in JP-B-46-39 309, JP-B- 58-46 768, JP-B-58-46 767, JP-A-56-90 429, JP-A-63-2 59 83O and JP-A- 1-2 01 824.

The magnetic characteristics of the magneti according to the invention between recording media include a squareness ratio nis of 0.77 or more, preferably 0.80 or more, in the Direction of travel of the tape when measured in a magnetic field of 5 KOe.

The invention is explained in more detail below with the aid of examples explained. All parts are to be understood as parts by weight.

example 1

A magnetic coating solution having a composition described later is prepared by kneading the composition (1) with an open kneader, adding the composition (2) to the material, dispersing the material with a sand mill, and then adding the composition (3) to the material before coating. The magnetic coating solution thus obtained is then coated onto a 7.0 micron thick non-magnetic polyethylene naphthalate carrier with an underlayer (polyester containing a naphthalene ring) (Young's module in MD (machine tape direction): 800 kg / mm ² ; Young's module in TD (transverse direction): 750 kg / mm ² ) in such an amount that the dry density of the magnetic layer is 2.5 µm.

The polyester containing a naphthalene ring (hereinafter referred to as "Naphthalene ring-containing polyester" is obtained th by reacting 1,6-naphthalenedicarboxylic acid, diethylene glycol, dimethyl isophthalate, ethylene glycol, polyethylene glycol and 5-sulfoisophthalic acid ethylene glycol ester in one weight ratio of 50/40/55/100/10 in line with the above named method. The underlayer is created by dissolving the egg NEN naphthalene ring-containing polyester in aqueous solution and then coating the coating solution on the Polyethylene naphthalate carrier with a dry thickness of 0.01 µm educated.

Composition of the magnetic coating solution

The one carrying the magnetic coating solution is non-magnetic cal carrier is then used for orientation in a magnetic field brought while the magnetic coating solution is still unge is drying. After drying, the material is subsequently calendered. A coating solution for the back is made prepared by adding the following composition (2) to following composition (1) before coating. The Beschich solution for the back layer is then applied to the Back of the non-magnetic carrier with a dry thickness of 0.6 µm coated. Then the material becomes a 1/2 inch wide slotted to make a Vi deobandes for example 1.

Composition of the coating solution for the back layer

Various examples are presented in the same way as in Bei game 1 except that various factors as shown in Table 1. The main factors are briefly described below.

Example 2-3

The thickness of the underlayer is increased.

Examples 4-5

The thickness of the underlayer is increased and the weight percent proportion of the cyclohexanone, based on the total weight of the Solvent in the magnetic coating solution reduced by changing the composition (2).

Example 6

The thickness of the underlayer is changed to 0.02 µm and the non-magnetic support is made of polyamide (provided that the thickness of the support is unchanged at 7 µm). The non-magnetic carrier has a Young's module in MD (tape direction) of 1300 kg / mm ² and a Young's module in TD (transverse ^{direction) of 1300 kg / mm 2} .

Example 7

The thickness of the underlayer is changed to 0.02 µm and the non-magnetic support is made of polyimide (provided that the thickness of the support is unchanged 7 µm). The non-magnetic carrier has a Young's module in MD (tape direction) of 800 kg / mm ² and a Young's module in TD (transverse ^{direction) of 800 kg / mm 2} .

Example 8

The factors shown in Table 1 are changed, and a vinyl chloride copolymer containing a phosphoric acid group in an amount of 2 x 10 ⁴ eq / g is used in place of the vinyl chloride copolymer resin (MR110).

Example 9

The proportion of cyclohexanone is reduced to 5%.

Example 10

The thickness of the underlayer and the amount of cyclohexanone are reduced.

Comparative example 1

Polyethylene terephthalate (PET) is used as the material for the non-magnetic carrier. The thickness of the carrier is 7 µm. The non-magnetic carrier has a Young's module in MD (tape direction) of 800 kg / mm ² and a Young's module in TD (transverse ^{direction) of 400 kg / mm 2} .

Comparative example 2

PEN undergoes a corona discharge without the presence of a sub layer exposed, and a magnetic layer is then piled up on it.

Example 11

The material of the lower layer is changed and a Phe polyester containing nyl ring (hereinafter referred to as "phenyl ring containing polyester ") is used. The phenyl ring-containing polyester is obtained by reacting Terephthalic acid, diethylene glycol, isophthalic acid and diol in a molar ratio of 50/50/10/120.

Example 12

An alkyl group is used as the material for the underlayer containing polyester (hereinafter referred to as "alkyl polyester" be draws). The alkyl polyester is made by reacting Adipic acid, diethylene glycol, isophthalic acid and diol in one obtained molar ratio of 50/50/10/120.

Comparative example 3

Untreated PEN is used.

These samples are then tested for the following properties th determined. The Young's modulus in MD and TD of the magnetic Carrier in Examples 2-5 and 8-12 and Comparative Examples play 2-3 was the same as in example 1:

1. Edge break

The tape sample 100 is used to determine the edge break Times played in a VTR and then regarding the Edge deformation investigated. The sample with no edges deformation is rated with 5 points. The sample with a slight edge deformation is rated with 4 points tet. The sample with some edge deformation is rated 3 Points rated. The sample with a raised edge defor mation is rated with 2 points and the samples with one significant edge deformation is rated with 1 point.

2. Adhesive strength

The tape slit 1/2 inch wide sample is attached to a carrier plate, and an adhesive tape ("Splicing Tape" manufactured by 3M Co., Ltd.) placed on the tape sample and then returned at 180 ° folded under the conditions of 20 ° C and 65% RH measure the adhesive strength of the tape sample.

3. Dropout (DO)

To determine the dropout, the tape was rehearsed 100 times played by a VTR and then regarding the DO measured by means of a DO counter.

4. C / N (carrier to noise ratio)

For the determination of C / N, the tape sample was tested 100 times played through a VTR and then C / N with measured by means of a noise meter.

The results are shown in Table 1.

The results in Table 1 show that the invention magnetic recording medium comprising PEN, polyimide or Polyamide as a non-magnetic carrier, a naphthalene ring containing polyester for the underlayer and a cyclohexa non-content of 10% or more in the magnetic coating solution has excellent adhesive strength, no edge breakage shows decreased DO and a high C / N value.

A magnetic coating solution having a composition described later is prepared in the same manner as in Example 1. The magnetic coating solution obtained in this way is naphthalate on a 7.0 micron thick non-magnetic polyethylene with a 0.02 micron thick sub-layer (naphthalene ring-containing polyester) applied (Young's modulus in MD (tape direction): 800 kg / mm ² ; Young 'S module in TD (transverse ^{direction): 750 kg / mm 2} ) drawn up or piled up in such an amount that the dry thickness of the magnetic layer is 3.0 μm.

The composition of the naphthalene ring-containing Po lyesters was the same as in Example 1. The underlayer is formed in the same manner as in Example 1.

Composition of the magnetic coating solution

Tabelle 2

Die in Tabelle 2 aufgeführten Ergebnisse zeigen, daß bei Ver­ wendung eines aus Polyethylennaphthalat hergestellten nicht magnetischen Trägers in der Erfindung, als Mittel für die Unter­ schicht ein einen Naphthalinring enthaltender Polyester verwend­ bar ist, allein oder in Kombination mit Polyurethan, um die Klebekraft für die Magnetschicht auf extrem wirksame Weise zu sichern. Es wird gefunden, daß ein interfaciales Abschälen dazu­ führt, daß die Magnetschicht vom nicht magnetischen Träger abge­ löst wird, selbst wenn die Klebekraft groß ist und ein nachtei­ liges Ablösen (Dropout) somit stattfindet. Wie vorstehend erläutert, schafft ein magnetisches Aufzeich­ nungsmedium, umfassend eine, auf einem nicht magnetischen Träger aufgebrachte Unterschicht und eine darauf angeordnete Magnet­ schicht, enthaltend wenigstens ein ferromagnetisches Pulver und ein Bindemittel, wobei die Unterschicht aus einem einen Haphtha­ linring enthaltenden Polyester hergestellt ist, und die Summe des Young′s Modul in Längenrichtung und des Young′s Modul in Breitenrichtung des nicht magnetischen Trägers 1400 kg/mm² oder mehr beträgt, einen hohen Output, eine hohe Aufzeichnungsdichte und eine extrem ausgezeichnete Laufhaltbarkeit. Insbesondere schafft die Erfindung ein magnetisches Aufzeichnungsmedium, das eine extrem ausgezeichnete Laufhaltbarkeit und ein vermindertes Ausfällen der magnetischen Schicht oder Rückseitenschicht vom nicht magnetischen Träger zeigt und gleichzeitig eine Erhöhung des Dropouts und der Kopfverschmutzung verhindert. Beispiel 19 Herstellung einer magnetischen Beschichtungslösung A (untere Schicht) CO-γ-FeO_x Pulver 100 Teile (x = 1,45; Koerzitivkraft: 800 Oe; @ spezifische Oberfläche: 43 m²/g; @ Kristallitgröße: 25 nm; durchschnittliche Länge der Längsachse: 0,2 µm) @ Vinylchloridharz 15 Teile (Additionsprodukt 86 : 14 Copolymeren von Vinylchlorid und Glycidylmethacrylat mit Natriumhydroxyethylsulfonat; @ SO₃Na: 6×10^-5 eq/g; Epoxygruppe: 10^-3 eq/g; Mw: 30 000) @ SO₃Na-enthaltendes Urethanharz 5 Teile ("UR8300", hergestellt durch Toyobo Co., Ltd.) (berechnet auf den Feststoffgehalt) Ruß (durchschnittliche Korngröße: 40 nm; DBP Ölabsorption: 60 ml/100 g) 3 Teile Polyisocyanat ("Coronate 3041", hergestellt durch Nippon Polyurethane Co., Ltd.) 6,7 Teile (berechnet auf den Feststoffgehalt) Butylstearat (industrielle Verwendung) 1 Teil Stearinsäure (industrielle Verwendung) 1 Teil Methylethylketon 250 Teile Cyclohexanon 100 Teile Unter diesen Zusammensetzungen werden andere Komponenten als Polyisocyanat und Stearinsäure mit einer Sandmühle 3 Stunden dispergiert. Anschließend werden Polyisocyanat und Stearinsäure zu der Dispersion zugegeben. Die Mischung wird für 15 Minuten anschließend dispergiert. Dann wird filtriert durch einen Filter mit einem durchschnittlichen Porendurchmesser von 1 µm zur Her­ stellung einer magnetischen Beschichtungslösung A.
Herstellung einer magnetischen Beschichtungslösung B (obere Schicht) Ferromagnetisches Legierungspulver 100 Teile (Metallkomponentenanteil (bezogen auf das Gewicht): Fe : Ni : Al=92 : 3 : 5; @ Sättigungsmagnetisierung: 122 emu/g; @ Koerzitivkraft: 1600 Oe; @ spezifische Oberfläche: 58 m²/g; @ Kristallitgröße: 20 nm; @ durchschnittliche Länge der Längsachse: 0,15 µm) @ Vinylchloridharz 10 Teile (Additionsprodukt eines 86 : 14 Copolymeren von Vinylchlorid und Glycidylmethacrylat mit Natriumhydroxyethylsulfonat; @ SO₃Na: 6×10^-5 eq/g; Epoxygruppe: 10^-3 eq/g; Mw: 30 000) @ Phenylphosphonsäure 2 Teile Methylethylketon 30 Teile Cyclohexanon 30 Teile Anschließend werden diese Komponenten 60 Minuten verknetet. Zu dieser Mischung werden dann folgende Komponenten zugegeben: SO₃Na-enthaltendes Polyurethanharz 10 Teile ("UR8200", hergestellt durch Toyobo Co., Ltd.) (berechnet auf den Feststoffgehalt) Schleifmittel (Al₂O₃; Korngröße: 0,3 µm 2 Teile Ruß (durchschnittliche Korngröße: 20 nm; DBP Ölabsorption: 250 ml/100 g) 2 Teile Methylethylketon/Toluol (1/1) 300 Teile Anschließend wird die Mischung mittels einer Sandmühle 120 Minu­ ten dispergiert. Zu der Mischung werden folgende Komponenten zugegeben: Polyisocyanat ("Coronate 3041", hergestellt durch Nippon Polyurethane Co., Ltd.) 5 Teile (berechnet auf den Feststoffgehalt) Butylstearat (industrielle Verwendung) 2 Teile Stearinsäure (industrielle Verwendung) 1 Teil Methylethylketon 50 Teile Die Mischung wird 20 Minuten gerührt und anschließend durch einen Filter mit einem durchschnittlichen Porendurchmesser von 1 µm filtriert zur Herstellung einer magnetischen Beschichtungslösung B. Herstellung der Beschichtungslösung C für die Rückseite Ruß (durchschnittlicher Korndurchmesser: 20 nm; 100 Teile DBP Ölabsorption: 200 ml/100 g) @ Tonerde (Korngröße: 0,2 µm) 1 Teil Nitrocellulose ("RS1/2", hergestellt durch Disel Ltd.) 50 Teile Urethanharz ("N-2301", hergestellt durch Nippon Polyurethane Co., Ltd.) 45 Teile (berechnet auf den Feststoffgehalt) Methylethylketon/Cyclohexanon 1000 Teile Anschließend werden diese Komponenten 3 Stunden mittels einer Sandmühle dispergiert. Zu der Dispersion werden folgende Kom­ ponenten zugegeben: Polyisocyanat ("Coronate 3041", hergestellt durch Nippon Polyurethane Co., Ltd.) 5 Teile (berechnet auf den Feststoffgehalt) Methylethylketon/Toluol 500 Teile Anschließend wird die Mischung 20 Minuten gerührt zur Herstel­ lung einer Beschichtungslösung C für die Rückseitenschicht. Die magnetische Beschichtungslösungen A und B werden im wesent­ lichen zur gleichen Zeit auf einen 8,0 µm dicken PEN-Träger (mit einer 0,01 µm dicken einen Naphthalinring enthaltenden Poly­ esterunterschicht; Young′s Modul in TD-Richtung: 816 kg/mm²; Young′s Modul in MD-Richtung: 612 kg/mm²) mittels eines Beschich­ tungskopfes mit zwei Durchgangsschlitzen für Beschichtungslösun­ gen aufgezogen, wie dies in der JP-A-2-2 65 672 beschrieben ist und zwar in solch einer Menge, daß die Trockendichte der unteren Schicht und oberen Schicht 3,0 µm und 0,6 µm beträgt. Der nicht magnetische Träger, auf den die magnetische Beschichtungslösun­ gen aufgezogen sind, wird anschließend in einem Magnetfeld bei 3000 G orientiert, während die magnetischen Beschichtungslösun­ gen ungetrocknet sind. Nach dem Trocknen wird das Material be­ schichtet mit der Beschichtungslösung C für die Rückseiten­ schicht auf seiner anderen Seite mittels eines Spulenstabs bis zu einer Trockendicke von 0,7 µm und anschließend getrocknet. Das Material wird kalandriert mittels einer Kombination aus Metallwalzen (Geschwindigkeit: 100 m/min; Lineardruck: 300 kg/cm; Temperatur: 90°C). Das Material wird anschließend hitzebehandelt bei einer Temperatur von 70°C über einen Zeit­ raum von 3 Tagen und anschließend zu einer Breite von 3/4 Inch geschlitzt. Die so erhaltenen Streifen werden einer Oberflächen­ behandlung unterzogen, die in JP-A-4-1 41 823 näher erläutert ist zur Herstellung einer Probe für Beispiel 19. Andere Proben wer­ den auf die gleiche Weise wie in Beispiel 19 hergestellt, mit der Ausnahme, daß die Faktoren gemäß Tabelle 3 geändert werden. Sämtliche Proben zeigen einen Young′s Modul in TD-Richtung von 816 kg/mm² für die Rückseitenschicht und die Klebekraft zwischen dem nicht magnetischen Träger und der Magnetschicht beträgt 190 g. Beispiel 20 und Vergleichsbeispiele 6, 7, 9, 10 Die Dicke der oberen und unteren Magnetschichten wird geändert. In Vergleichsbeispiel 9 wird bei einer Temperatur von 100°C kalandriert. In Vergleichsbeispiel 10 wird bei einer Temperatur von 70°C kalandriert. Vergleichsbeispiel 5 PET (Polyethylenterephthalat) mit einem Young′s Modul in TD- Richtung (Transversalrichtung) von 816 kg/mm² und einem Young′s Modul in MD-Richtung (Bandrichtung) von 612 kg/mm² wird ver­ wendet. Vergleichsbeispiel 8 Es ist keine Rückseitenschicht vorgesehen. Vergleichsbeispiel 11 Es ist eine einzige Magnetschicht, bestehend aus einer oberen Schicht vorgesehen. Vergleichsbeispiel 12 Es ist eine einzige Magnetschicht, bestehend aus einer unteren Schicht vorgesehen.

Tabelle 3

Diese Proben werden bezüglich folgender Eigenschaften unter­ sucht; die Ergebnisse sind in Tabelle 4 dargestellt. Meßverfahren 1) Elektromagnetische Eigenschaften Ein 32 MHz Signal wird aufgezeichnet und von einer Bandprobe mittels eines VTR ("DVR10", hergestellt durch Sony Corpora­ tion) reproduziert. Mit dem 32 MHz Output, reproduziert von dem Standardband (Beispiel 19) als 0 dB, wird der relative reproduzierte Output der Probe bestimmt. Das Verhältnis des Maximumoutputs zu dem Minimumoutput wird gemessen von der Umhüllungsoutput-Wellenform zur Bestimmung der Umhüllungs­ flachheit als Kopfkontakt. 2) Laufwiederholbarkeit Ein 64 Minuten dauerndes Band wird wiederholt 200fach durch ein VTR abgespielt. Der Videokopf wird anschließend bezüg­ lich einer Verschmutzung durch das Band untersucht. Das Band wird auch bezüglich der Kantenbedingungen untersucht. Verschmutzung des Videokopfes Ausgezeichnet es ist keine Verschmutzung zu beobachten Gut Verschmutzung beim Abreiben beobachtet Schwach Verschmutzung visuell beobachtet 3) Young′s Modul und Prozentuale Dehnung bei Bruch Der Young′s Modul für die gesamte Magnetschicht ist bere­ chenbar durch ein zusammengesetztes Gesetz vom Young′s Modul des Bandes und vom Young′s Modul des Trägers, bestimmt durch die Spannung und dem Anstieg vom Ursprung bei einem F (0,5)- Wert = 0,5% Dehnung gemäß ASTM D882-81. Die prozentuale Dehnung bei Bruch ist die erscheinende Streckdehnung in der Zugspannung des magnetischen Aufzeichnungsmediums beim vor­ stehend erwähnten Zugspannungstest. Die Messung wird bei einer Temperatur von 24°C, relativer Feuchtigkeit von 50% und einer Dehnungsrate von 10%/min durchgeführt. Das für die Messung eingesetzte Meßgerät ist ein "Tensilon", herge­ stellt durch Toyo Baldwin Co., Ltd.

Tabelle 4

Die in den Tabellen 3 und 4 wiedergegebenen Werte zeigen, daß das Vergleichsbeispiel 5 den spezifizierten Bereich der prozen­ tualen Dehnung bei Bruch und für den Young′s Modul der Magnet­ schichten erfüllt, jedoch schwache elektromagnetische Eigen­ schaften zeigt und eine beträchtliche Verschmutzung des Video­ kopfes und eine Beschädigung der Kanten infolge des nicht Vor­ handenseins von PEN festzustellen ist. Die Vergleichsbeispiele 6, 7, 9 und 11 zeigen eine prozentuale Dehnung bei Bruch von weniger als 2%. Vergleichsbeispiel 8 ist ein Beispiel, bei dem keine Rückseitenschicht vorhanden ist. Die Vergleichsbei­ spiele 10 und 12 sind Beispiele, welche den spezifizierten Be­ reich für den Young′s Modul der Magnetschichten nicht erfüllen. Vergleichsbeispiele Nr. 7 und 8 sind Beispiele mit einer ein­ zigen Schichtbauweise. Es ist offensichtlich, daß die Beispiele 19 und 20 gemäß der Erfindung ausgezeichnete elektromagnetische Eigenschaften und eine ausgezeichnete Laufhaltbarkeit im Ver­ gleich mit Vergleichsbeispielen Nr. 5-12 zeigen. Das erfindungsgemäße magnetische Aufzeichnungsmedium zeigt fol­ gende Effekte:

• 1) Die Dicke des magnetischen Aufzeichnungsmediums kann ver­ mindert werden, so daß ein Langzeitaufzeichnen möglich ist. Dies ermöglicht auch, das magnetische Aufzeichnungsmedium kompakt auszugestalten.
• 2) Das Magnetband ist steif genug, um einen guten Kopfkontakt zu schaffen, und zeigt ausgezeichnete elektromagnetische Eigenschaften.
• 3) Das Magnetband kann leicht und gut geschnitten werden, ver­ bunden mit einem verringerten Dropout und einer verringerten Fehlerquote.
• 4) Während des Laufs kann kaum Pulver aus den Kanten ausfallen, so daß eine Zunahme des Dropouts verhindert wird und die Fehlerquote verkleinert wird.
• 5) Das Magnetband zeigt keine Dehnung auf einer Seite während des Abspielens und behält seine ausgezeichneten elektroma­ gnetischen Eigenschaften nach wiederholter Verwendung bei.
• 6) Das Magnetband zeigt keinen Kantenbruch während des Laufs und besitzt eine ausgezeichnete Haltbarkeit in der Wiederho­ lung mit einer verminderten Zunahme des Dropouts und der Fehlerquote.
• 7) Das Magnetband ist gegenüber einer Wärmedeformation (geringe Wärmeschrumpfung) unempfänglich und verursacht nur ein ver­ mindertes Verdrehen.

The non-magnetic carrier with the magnetic coating solution drawn thereon is then subjected to orientation in a magnetic field, while the magnetic coating solution is undried. After drying, the material is calendered. The same coating solution as used for the back layer as in Example 1 is coated on the back of the non-magnetic support in a dry thickness of 0.6 µm. The material is then slit to a width of 1.27 cm (1/2 inch) to make video tape according to Example 13. Various samples are made in the same manner as described in Example 13, except that the agent for the sub-layer is changed according to Table 2. For these samples, a polyester containing a naphthalene ring, which corresponds to that in Example 1, is used. Example 14 A polyester containing naphthalene ring and a polyurethane ("Pandex", DIC) in a weight ratio of 1: 1 are used as the binder. Example 15 A polyester containing naphthalene ring and a polyisocyanate in a weight ratio of 1: 1 are used as the binder. Example 16 As a binder, a naphthalene ring-containing polyester and an epoxy resin ("Epolate", manufactured by Totokasei) are used in a weight ratio of 1: 1. Example 17 As a binder, a naphthalene ring-containing polyester and a vinyl chloride resin ("400 x 100A", manufactured by Japanese Zeon) are used in a weight ratio of 1: 1. Example 18 As an underlayer, a polyurethane resin ("Pandex", manufactured by DIC) is used. Comparative Example 4 An untreated PEN is used without an undercoat being present. These samples are then examined for adhesive strength and non-peelability. Adhesive strength An adhesive tape is applied to the sample and then folded back at an angle of 180 °. The sample is then measured with regard to the adhesive load. Non-peelability Cut = adhesive force is so great that the adhesive tape is cut,
Adhesive error = adhesive force is so great that the magnetic layer is destroyed,
Interfacial destruction = peeling occurs between the magnetic layer and the non-magnetic carrier, which shows the insufficient adhesive strength between the two. Rating Excellent: Adhesive strength is 90 g or more. Non-peelability is rated as "cut" or "defect in bonding". Good: Adhesive strength is 90 g or more. Inability to peel off is rated as "interfacial destruction". Weak: Adhesive strength is less than 90 g and non-peelability is rated as "interfacial destruction". The results are shown in Table 2.

Table 2

The results listed in Table 2 show that when using a non-magnetic carrier made of polyethylene naphthalate in the invention, a naphthalene ring-containing polyester is usable as a means for the lower layer, alone or in combination with polyurethane, to the adhesive force for the Secure magnetic layer in an extremely effective way. It is found that interfacial peeling leads to the magnetic layer being detached from the non-magnetic carrier, even if the adhesive force is high and a disadvantageous detachment (dropout) thus takes place. As explained above, provides a magnetic recording medium comprising an underlayer applied to a non-magnetic carrier and a magnetic layer disposed thereon, containing at least a ferromagnetic powder and a binder, the underlayer being made of a polyester containing a haphtha linring, and the sum of Young's modulus in the length direction and Young's modulus in the width direction of the non-magnetic medium is 1400 kg / mm ² or more, high output, high recording density and extremely excellent running durability. In particular, the present invention provides a magnetic recording medium which exhibits extremely excellent running durability and reduced precipitation of the magnetic layer or back layer from the non-magnetic medium, while preventing an increase in dropout and head contamination. Example 19 Preparation of magnetic coating solution A (lower layer) CO-γ-FeO _x powder 100 parts (x = 1.45; coercive force: 800 Oe; @ specific surface area: 43 m² / g; @ Crystallite size: 25 nm; average length of the longitudinal axis: 0.2 µm) @ Vinyl chloride resin 15 parts (Addition product 86: 14 copolymers of vinyl chloride and glycidyl methacrylate with sodium hydroxyethyl sulfonate; @ SO₃Na: 6 × 10 ^-5 eq / g; Epoxy group: 10 ^-3 eq / g; Mw: 30,000) @ SO₃Na-containing urethane resin 5 parts ("UR8300" manufactured by Toyobo Co., Ltd.) (calculated on the solids content) Carbon black (average grain size: 40 nm; DBP oil absorption: 60 ml / 100 g) 3 parts Polyisocyanate ("Coronate 3041" manufactured by Nippon Polyurethane Co., Ltd.) 6.7 parts (calculated on the solids content) Butyl stearate (industrial use) 1st chapter Stearic acid (industrial use) 1st chapter Methyl ethyl ketone 250 parts Cyclohexanone 100 parts Among these compositions, components other than polyisocyanate and stearic acid are dispersed with a sand mill for 3 hours. Then polyisocyanate and stearic acid are added to the dispersion. The mixture is then dispersed for 15 minutes. It is then filtered through a filter having an average pore diameter of 1 µm to prepare a magnetic coating solution A.
Preparation of magnetic coating solution B (upper layer) Ferromagnetic alloy powder 100 parts (Metal component content (based on weight): Fe: Ni: Al = 92: 3: 5; @ Saturation magnetization: 122 emu / g; @ Coercive force: 1600 Oe; @ specific surface area: 58 m² / g; @ Crystallite size: 20 nm; @ average length of the longitudinal axis: 0.15 µm) @ Vinyl chloride resin 10 parts (Addition product of an 86:14 copolymer of vinyl chloride and glycidyl methacrylate with sodium hydroxyethyl sulfonate; @ SO₃Na: 6 × 10 ^-5 eq / g; Epoxy group: 10 ^-3 eq / g; Mw: 30,000) @ Phenylphosphonic acid 2 parts Methyl ethyl ketone 30 parts Cyclohexanone 30 parts These components are then kneaded for 60 minutes. The following components are then added to this mixture: SO₃Na-containing polyurethane resin 10 parts ("UR8200" manufactured by Toyobo Co., Ltd.) (calculated on the solids content) Abrasive (Al₂O₃; grain size: 0.3 µm 2 parts Carbon black (average grain size: 20 nm; DBP oil absorption: 250 ml / 100 g) 2 parts Methyl ethyl ketone / toluene (1/1) 300 parts The mixture is then dispersed for 120 minutes using a sand mill. The following components are added to the mixture: Polyisocyanate ("Coronate 3041" manufactured by Nippon Polyurethane Co., Ltd.) 5 parts (calculated on the solids content) Butyl stearate (industrial use) 2 parts Stearic acid (industrial use) 1st chapter Methyl ethyl ketone 50 parts The mixture is stirred for 20 minutes and then filtered through a filter with an average pore diameter of 1 µm to prepare a magnetic coating solution B. Preparation of the coating solution C for the rear side Carbon black (average grain diameter: 20 nm; 100 parts DBP oil absorption: 200 ml / 100 g) @ Alumina (grain size: 0.2 µm) 1st chapter Nitrocellulose ("RS1 / 2" manufactured by Disel Ltd.) 50 parts Urethane resin ("N-2301" manufactured by Nippon Polyurethane Co., Ltd.) 45 pieces (calculated on the solids content) Methyl ethyl ketone / cyclohexanone 1000 parts These components are then dispersed for 3 hours using a sand mill. The following components are added to the dispersion: Polyisocyanate ("Coronate 3041" manufactured by Nippon Polyurethane Co., Ltd.) 5 parts (calculated on the solids content) Methyl ethyl ketone / toluene 500 parts The mixture is then stirred for 20 minutes to prepare a coating solution C for the back layer. The magnetic coating solutions A and B are essentially at the same time on an 8.0 micron thick PEN carrier (with a 0.01 micron thick polyester sublayer containing a naphthalene ring; Young's modulus in TD direction: 816 kg / mm ² ; Young's module in MD direction: 612 kg / mm ² ) by means of a coating head with two through slots for coating solutions drawn up, as described in JP-A-2-2 65 672 and in such an amount that the dry density of the lower layer and the upper layer are 3.0 µm and 0.6 µm, respectively. The non-magnetic support on which the magnetic coating solutions are drawn is then oriented in a magnetic field at 3000 G, while the magnetic coating solutions are undried. After drying, the material is coated with the coating solution C for the back layer on its other side by means of a coil bar to a dry thickness of 0.7 μm and then dried. The material is calendered by means of a combination of metal rollers (speed: 100 m / min; linear pressure: 300 kg / cm; temperature: 90 ° C). The material is then heat treated at a temperature of 70 ° C for a period of 3 days and then slit to a width of 3/4 inch. The strips thus obtained are subjected to a surface treatment which is explained in detail in JP-A-4-1 41 823 to prepare a sample for Example 19. Other samples are prepared in the same manner as in Example 19, with the exception that the factors according to Table 3 are changed. All samples show a Young's modulus in TD direction of 816 kg / mm ² for the back layer and the adhesive force between the non-magnetic carrier and the magnetic layer is 190 g. Example 20 and Comparative Examples 6, 7, 9, 10 The thickness of the upper and lower magnetic layers is changed. In comparative example 9, calendering is carried out at a temperature of 100.degree. In comparative example 10, calendering is carried out at a temperature of 70.degree. Comparative Example 5 PET (polyethylene terephthalate) with a Young's module in TD direction (transverse direction) of 816 kg / mm ² and a Young's module in MD direction (tape direction) of 612 kg / mm ² is used. Comparative Example 8 No back layer is provided. Comparative Example 11 A single magnetic layer consisting of an upper layer is provided. Comparative Example 12 A single magnetic layer consisting of a lower layer is provided.

Table 3

These samples are examined with regard to the following properties; the results are shown in Table 4. Measurement method 1) Electromagnetic properties A 32 MHz signal is recorded and reproduced from a tape sample by means of a VTR ("DVR10", manufactured by Sony Corporation). With the 32 MHz output reproduced from the standard tape (Example 19) as 0 dB, the relative reproduced output of the sample is determined. The ratio of the maximum output to the minimum output is measured from the envelope output waveform to determine the envelope flatness as a head contact. 2) Run repeatability A tape lasting 64 minutes is played back 200 times repeatedly by a VTR. The video head is then examined with respect to contamination from the tape. The tape is also examined for edge conditions. Soiling of the video head Excellent no pollution can be observed Well Soiling observed when rubbing off Weak Visually observed contamination 3) Young's modulus and percentage elongation at break The Young's modulus for the entire magnetic layer is calculable by a composite law of Young's modulus of the tape and Young's modulus of the carrier, determined by the tension and the increase from origin at an F (0.5) value = 0.5% elongation according to ASTM D882-81. The percentage elongation at break is the apparent elongation in tension in the tensile stress of the magnetic recording medium in the above-mentioned tensile stress test. The measurement is carried out at a temperature of 24 ° C., relative humidity of 50% and an elongation rate of 10% / min. The measuring device used for the measurement is a "Tensilon" manufactured by Toyo Baldwin Co., Ltd.

Table 4

The values shown in Tables 3 and 4 show that Comparative Example 5 meets the specified range of percent elongation at break and for the Young's modulus of the magnetic layers, but shows weak electromagnetic properties and considerable contamination of the video head and Damage to the edges as a result of the absence of PEN can be ascertained. Comparative Examples 6, 7, 9 and 11 show a percentage elongation at break of less than 2%. Comparative Example 8 is an example in which there is no back layer. The comparative games 10 and 12 are examples that do not meet the specified Be rich for the Young's modulus of the magnetic layers. Comparative Examples Nos. 7 and 8 are examples with a single layer structure. It is apparent that Examples 19 and 20 according to the invention show excellent electromagnetic properties and running durability as compared with Comparative Examples Nos. 5-12. The magnetic recording medium according to the invention exhibits the following effects:

• 1) The thickness of the magnetic recording medium can be reduced so that long-term recording is possible. This also enables the magnetic recording medium to be made compact.
• 2) The magnetic tape is stiff enough to make good head contact and exhibits excellent electromagnetic properties.
• 3) The magnetic tape can be easily and well cut, combined with a reduced dropout and a reduced error rate.
• 4) Hardly any powder can fall out of the edges during the run, so that an increase in the dropout is prevented and the error rate is reduced.
• 5) The magnetic tape shows no stretch on one side during playback and maintains its excellent electromagnetic properties after repeated use.
• 6) The magnetic tape shows no edge breakage during the run and has excellent durability in repetition with a reduced increase in dropout and error rate.
• 7) The magnetic tape is insensitive to thermal deformation (low heat shrinkage) and causes only a reduced twisting.

Claims (10)

1. A magnetic recording medium, comprising a least one side of a non-magnetic carrier brought up sublayer and a magnetic layer arranged thereon, comprising at least one ferromagnetic powder and a binder, characterized in that the sum of Young's modulus in the length direction and the Young's modulus in the width direction of the non-magnetic carrier is in the range of 1400 kg / mm ² or more and the adhesive force between the non-magnetic carrier and the magnetic layer is 90 g or more. 2. Recording medium according to claim 1, characterized in that that the underlayer contains a naphthalene ring tend polyester. 3. Recording medium according to claim 1, characterized in that that the non-magnetic carrier is made of one material is selected from polyethylene naphthalate, polyimide and polyamide and the coating solution of the magnetic layer Cyclohexanone in an amount of 20% by weight or more based on based on the total weight of the solvent. 4. Recording medium according to claim 1, characterized in that that the sub-layer containing a naphthalene ring Comprises polyester and a polyurethane. 5. Recording medium according to claim 1, characterized in that that the magnetic layer contains at least one resin which we has at least one functional group selected from a sulfonic acid, phosphoric acid, phosphonic acid, epoxy and a hydroxyl group. 6. A recording medium, characterized by a sub-layers arranged on both sides of the non-magnetic carrier and a magnetic layer arranged on one side, comprising at least one ferromagnetic powder and a binder, and a rear side arranged on the other side, comprising at least one inorganic Powder and a binder, wherein the sub-layer is made of a polyester containing a naphthalene ring and the sum of Young's modulus in the length direction and Young's modulus in the width direction of the non-magnetic carrier is 1400 kg / mm ² or more. 7. Recording medium according to claim 1, characterized in that that the thickness of the sub-layer 5 to 1000 nm (mµ) and the Total thickness of the magnetic layer is 13.5 µm or less. 8. Recording medium according to claim 1, characterized in that the non-magnetic carrier is made of a material Herge is selected from the group consisting of poly ethylene naphthalate, polyimide and polyamide, wherein the magnetic layer consists of one or more magnetic layers and the Young ' s module in the length direction of the entire magnetic layer is in the range of 700 kg / mm ² or more. 9. Recording medium according to claim 1, characterized in that the non-magnetic carrier is made of polyethylene-2,6-naphthalate, wherein the magnetic layer consists of one or more magnetic layers and the Young's modulus in the length direction of the entire magnetic layer 700 kg / mm ² or more and the elongation percentage at break of the entire magnetic layer is in the range of 2% or more. 10. Recording medium according to claim 1, characterized in that that the magnetic layer consists of a plurality of magnetic layers consists, comprising a magnetic layer on the carrier side, containing a ferromagnetic iron containing cobalt oxide powder with a crystallite size of 35 nm (350 Å) or less and an outer magnetic layer containing one ferromagnetic alloy powder with a crystallite size of 25 nm (250 Å) or less.