JP2813157B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium having excellent storage stability.

[0002]

2. Description of the Related Art Conventionally, magnetic recording media have been widely used in the form of tapes, disks, drums or sheets. Such a magnetic recording medium usually forms a magnetic layer on a non-magnetic support such as a polyester film by applying a magnetic paint containing a magnetic powder and a binder as main components, and further forms a non-magnetic support on the non-magnetic support. It is manufactured by forming a back coat layer on the back surface.

However, in the above-described magnetic recording medium,
There is a problem that storage stability is poor, such as deterioration of electromagnetic conversion characteristics during storage. In order to solve such a problem, Japanese Patent Publication No. Hei 4-79046 proposes a magnetic recording medium in which the residual solvent amount and surface roughness of a magnetic layer are specified. However, at present, the above-mentioned problems have not been sufficiently solved, and a magnetic recording medium having further excellent storage stability has been demanded.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetic recording medium which has excellent electromagnetic conversion characteristics and whose electromagnetic conversion characteristics hardly decrease with time.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have provided a nonmagnetic support, a magnetic layer and a back coat layer, and the remaining of the back coat layer. It has been found that a magnetic recording medium having a solvent amount in a specific range can achieve the above object.

The present invention has been made on the basis of the above findings, and includes a nonmagnetic support, a magnetic layer provided on the surface side of the nonmagnetic support, and a magnetic layer provided between the nonmagnetic support and the magnetic layer.
An intermediate layer which is a magnetic recording medium having a back coat layer provided on the back surface of the non-magnetic support, the residual solvent content of the back coat layer, Oh in 5~ 15 00ppm
In addition, the present invention provides a magnetic recording medium characterized in that the thickness of the magnetic layer is 0.05 to 0.6 μm . Here, the “residual solvent amount” refers to both the residual solvent amount in the magnetic recording medium immediately after production and the residual solvent amount in the magnetic recording medium used and stored in a normal use and storage state.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic recording medium of the present invention will be described below in detail. First, a preferred configuration of the magnetic recording medium of the present invention will be described with reference to FIG. FIG.
The magnetic recording medium 1 of the present invention shown in FIG.
It comprises a magnetic layer 4 provided on the surface of the non-magnetic support 2 and a back coat layer 5 provided on the back surface of the non-magnetic support 2. Between the above-mentioned non-magnetic substrate 2 and the magnetic layer 4, the intermediate layer 3 is provided.

The magnetic recording medium of the present invention further comprises a non-magnetic support, an intermediate layer, a magnetic layer, and a back coat layer, as well as a non-magnetic support and an intermediate layer or a back coat layer. Other layers, such as a primer layer provided therebetween and another magnetic layer provided for recording a servo signal or the like corresponding to a hard system using a long wavelength signal, may be provided.

As the non-magnetic support used in the magnetic recording medium of the present invention, any known non-magnetic support can be used without any particular limitation. Specifically, a flexible film made of a polymer resin is used. And disks; Cu, Al, Z
Films, disks, cards, and the like made of nonmagnetic metals such as n, glass, ceramics such as porcelain, and ceramics can be used.

Examples of the polymer resin forming the flexible film and the disk include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycyclohexylene dimethylene terephthalate, and polyethylene bisphenoxycarboxylate; , Polyolefins such as polypropylene, cellulose acetate butyrate,
Cellulose derivatives such as cellulose acetate propionate, polyvinyl chloride, vinyl resins such as polyvinylidene chloride, or polyamide, polyimide, polycarbonate, polysulfone, polyetheretherketone, polyurethane, etc. Two or more can be used in combination.

In the magnetic recording medium of the present invention, the magnetic layer provided on the surface side of the non-magnetic support is an uppermost layer of the magnetic recording medium, that is, a layer provided as a layer located on the surface of the magnetic recording medium. It is formed by applying a magnetic paint on the non-magnetic support. When an intermediate layer described later is provided, the magnetic layer is formed by applying the magnetic paint on the intermediate layer. As the magnetic paint, a paint containing magnetic powder, a binder and a solvent as main components is preferably used.

Examples of the magnetic powder include a ferromagnetic metal powder mainly composed of iron and a hexagonal ferrite powder.

The coercive force of the ferromagnetic metal powder is 1600
~ 2500 Oe, preferably 1800 to 240
More preferably, it is 0 Oe. The coercive force of the hexagonal ferrite powder is preferably 1300 to 2300 Oe, and more preferably 1500 to 2200 Oe. When the coercive force of the ferromagnetic metal powder and the hexagonal ferrite are each less than the lower limit, the short-wavelength RF output is reduced due to easy demagnetization,
If the upper limit is exceeded, the head magnetic field becomes insufficient and the write performance becomes insufficient, and further the overwrite characteristics deteriorate. The saturation magnetization of the ferromagnetic metal powder is 100 to 180 emu / g.
Is preferable, and it is more preferable that it is 110-160 emu / g. The saturation magnetization of the hexagonal ferrite powder is preferably from 30 to 70 emu / g, and more preferably from 45 to 70 emu / g. When the saturation magnetization of the ferromagnetic metal powder and the hexagonal ferrite powder are each less than the lower limit, the output is reduced , and when the saturation exceeds the upper limit , each magnetic powder is The interaction between them becomes large, and as a result, the magnetic powder is in an agglomerated state, and it is difficult to obtain a desired output.
It is preferable to be within the above range.

Therefore, the coercive force of the magnetic layer containing the ferromagnetic metal powder is preferably 1800 to 2400 Oe,
More preferably, it is 1800-2300 Oe, and the coercive force of the magnetic layer containing the above hexagonal ferrite powder is preferably 1500-2200 Oe. The saturation magnetic flux density of the magnetic layer containing the ferromagnetic metal powder is preferably 3000 to 4500 gauss, more preferably 32 gauss.
The saturation magnetic flux density of the magnetic layer containing the hexagonal ferrite powder is preferably 1 to 4000 Gauss.
500-2500 gauss, more preferably 1600-2
500 gauss.

The ferromagnetic metal powder has a metal content of 7
0% by weight or more, and 80% by weight or more of the metal component is Fe.
Ferromagnetic metal powder. Specific examples of the ferromagnetic metal powder include, for example, Fe-Co, Fe-Ni,
Fe-Al, Fe-Ni-Al, Fe-Co-Ni, F
e-Ni-Al-Zn, Fe-Al-Si, and the like. The shape of the ferromagnetic metal powder is needle-like or spindle-like, and its major axis is preferably 0.05 to 0.25 μm,
More preferably, it is 0.05 to 0.2 μm, the preferred needle ratio is 3 to 20, and the preferred X-ray particle size is 130 to 2
It is desirably 50 ° and the specific surface area is 40 to 80 m ² / g.

Further, as the hexagonal ferrite powder, barium ferrite and strontium ferrite in the form of fine flat plate, and a part of their Fe atoms are Ti, C
magnetic powders substituted with atoms such as o, Ni, Zn, V, and the like. The shape of the hexagonal ferrite powder has a plate diameter of 0.02 to 0.09 μm and a plate ratio of 2 to 0.09 μm.
And a specific surface area of preferably 25 to 70 m ² / g.

Further, the magnetic powder in the magnetic coating material forming the magnetic layer may contain a rare earth element or a transition metal element, if necessary. In the present invention, in order to improve the dispersibility and the like of the magnetic powder,
The magnetic powder may be subjected to a surface treatment. The surface treatment is described in "Characterization of Powder Surfaces"; Acad
The method can be performed by a method similar to the method described in emic Press and the like, for example, a method of coating the surface of the magnetic powder with an inorganic oxide. At this time, as the inorganic oxide that can be used, Al ₂ O ₃ , Si
O ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ , Z
nO and the like. When used, they can be used alone or in combination of two or more. The surface treatment can be performed by an organic treatment such as a silane coupling treatment, a titanium coupling treatment, and an aluminum coupling treatment, in addition to the above method.

Examples of the binder include a thermoplastic resin, a thermosetting resin, and a reactive resin. When used, they can be used alone or as a mixture.
Specific examples of the binder include vinyl chloride resins,
Polyester, polyurethane, nitrocellulose, epoxy resin, etc .;
No. 2128, page 2, upper right column, line 19 to page 2, lower right column 1
Resins and the like described in line 9 are exemplified. further,
The binder may contain a polar group for improving dispersibility and the like. The amount of the binder used is 10
The amount is preferably about 5 to 100 parts by weight, particularly preferably 5 to 70 parts by weight, per 0 parts by weight.

Examples of the solvent include ketone solvents, ester solvents, ether solvents, aromatic hydrocarbon solvents, chlorinated hydrocarbon solvents, and the like. Solvents described in JP-A-57-162128, page 3, lower right column, line 17 to page 4, lower left column, line 10 can be used. The amount of the solvent used is preferably 80 to 500 parts by weight, more preferably 100 to 350 parts by weight, based on 100 parts by weight of the magnetic powder.

In addition, the above-mentioned magnetic paint contains additives commonly used in magnetic recording media such as a dispersant, a lubricant, an abrasive, an antistatic agent, a rust inhibitor, a fungicide, and a curing agent. It can be added as needed. As the above additives,
Specifically, it is described in page 2, upper left column, line 6 to page 2, upper right column, line 10 and page 3, upper left column, line 6 to page 3, upper right column, line 18 of JP-A-57-162128. And various additives.

In order to prepare the magnetic paint, for example, the magnetic powder and the binder are put into a Nauta mixer or the like together with a part of the solvent and premixed to obtain a mixture. After kneading with a kneader or the like, then diluting with a part of the solvent, dispersing using a sand mill or the like, mixing additives such as a lubricant, filtering, further curing agent such as polyisocyanate and the remaining. Examples thereof include a method of mixing a solvent.

The thickness of the magnetic layer is 0.05 to 0.6 μm.
m Ru Der. If the thickness of the magnetic layer is less than 0.05 μm, it becomes difficult to apply the magnetic layer uniformly, If it exceeds 6 μm, the thickness loss increases and the high-frequency output may decrease, which is not preferable.

The amount of residual solvent in the magnetic layer is 4000 pp
m, preferably 3000 ppm or less. If it exceeds 4000 ppm, the residual solvent may migrate from the magnetic layer to the back coat layer during storage or may cause tackiness, which is not preferable. still,
Here, ppm is based on weight.

The surface roughness of the magnetic layer is preferably from 2 to 10 nm, more preferably from 2.5 to 8 nm. If the surface roughness of the magnetic layer is less than 2 nm, the friction coefficient increases, which causes trouble in running. If it exceeds 10 nm, the output may decrease due to space loss, which is not preferable.

Further, the magnetic layer is preferably being coated, formed upon wetting of the intermediate layer.

In the magnetic recording medium of the present invention, the back coat layer provided on the back surface of the non-magnetic support is formed by applying a back coat paint on the back surface of the non-magnetic support. The back coat layer may be a layer having no magnetism or a layer having magnetism. When the back coat layer is a layer having no magnetism, the back coat paint forming the back coat layer is a non-magnetic back coat paint containing a nonmagnetic powder, a binder and a solvent as main components. Is preferably used.

The non-magnetic powder used in the non-magnetic back coat paint is not particularly limited as long as it is non-magnetic, but carbon black, graphite,
Titanium oxide, barium sulfate, zinc sulfide, magnesium carbonate, calcium carbonate, zinc oxide, calcium oxide, magnesium oxide, tungsten disulfide, molybdenum disulfide, boron nitride, tin dioxide, silicon dioxide, nonmagnetic chromium oxide, alumina, carbonized Silicon, cerium oxide, corundum, artificial diamond, non-magnetic iron oxide, garnet, garnet, silica, silicon nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, diatomaceous earth, dolomite, resinous powder, etc. Among them, carbon black, titanium oxide, barium sulfate, calcium carbonate, alumina, non-magnetic iron oxide and the like are preferably used. Further, the shape is not particularly limited, but specific examples include a spherical shape, a plate shape, an amorphous shape, and a needle shape. The size is 5 to 8 for spherical, plate-like and amorphous shapes.
00 nm, and the long axis length is 20
８００800 nm and the axial ratio is 3-20. Further, in order to improve the dispersibility of the non-magnetic powder, the non-magnetic powder may be subjected to the same surface treatment as that of the magnetic powder in the magnetic layer.

Examples of the binder used in the non-magnetic backcoat paint include thermoplastic resins, thermosetting resins, and reactive resins. When used, they may be used alone or as a mixture. it can.
Specific examples of the binder include vinyl chloride resins,
Polyester, polyurethane, nitrocellulose, epoxy resin, etc .;
No. 2128, page 2, upper right column, line 19 to page 2, lower right column 1
Resins and the like described in line 9 are exemplified. further,
The binder may contain a polar group for improving dispersibility and the like. The amount of the binder used is the amount of the nonmagnetic powder 1
The amount is preferably from 10 to 300 parts by weight, particularly preferably from 15 to 200 parts by weight, per 100 parts by weight.

Examples of the solvent used in the non-magnetic backcoat paint include ketone solvents, ester solvents, ether solvents, aromatic hydrocarbon solvents, and chlorinated hydrocarbon solvents. Examples of the solvent include a solvent described in JP-A-57-162128, page 3, lower right column, line 17 to page 4, lower left column, line 10, and the like. The amount of the solvent to be used is preferably 150 to 2000 parts by weight, more preferably 200 to 1500 parts by weight, based on 100 parts by weight of the nonmagnetic powder.

In addition, the above-mentioned non-magnetic back coat paints include inorganic powders other than the above non-magnetic powders; dispersants; lubricants; antistatic agents; rust inhibitors; Additives usually used for the back coat layer of the magnetic recording medium can be added as needed.

When the backcoat layer is a layer having magnetism, the backcoat paint for forming the backcoat layer is a backcoat paint having magnetism, comprising magnetic powder, a binder and a solvent as main components. Is preferably used.

As the magnetic powder used in the above-mentioned magnetic backcoat paint, a ferromagnetic powder is preferably used, and as the ferromagnetic powder, both a soft magnetic powder and a hard magnetic powder are preferably used. The soft magnetic powder is not particularly limited as long as it is a soft magnetic powder, but is preferably used for a so-called weak electric device such as a magnetic head or an electronic circuit. (Bottom) Magnetic properties and applications ”(Shokabo, 198
(4 years) Soft magnetic materials described on pages 368 to 376 can be used, and specific examples thereof include oxide soft magnetic powder. As the oxide soft magnetic powder, spinel type ferrite powder is preferably used, and as the spinel type ferrite powder, MnFe ₂ O ₄ , Fe ₃ O ₄ , CoF
e ₂ O ₄ , NiFe ₂ O ₄ , MgFe ₂ O ₄ , Li _0.5
Fe _2.5 O ₄ and, Mn-Zn ferrite, Ni-Zn
Ferrite, Ni-Cu ferrite, Cu-Zn ferrite, Mg-Zn ferrite, Li-Zn ferrite, Zn ferrite, Mn ferrite, and the like. In use, one kind thereof may be used alone, or two or more kinds thereof may be used in combination.

Further, as the soft magnetic powder, a metal soft magnetic powder or the like can be used. Examples of the metal soft magnetic powder include Fe-Si alloy and Fe-Al alloy (Alperm, Alf
enol, Alfer), permalloy (Ni-Fe-based binary alloy and a multi-component alloy to which Mo, Cu, Cr, etc. are added), sendust (Fe-Si-Al [9.6% by weight of Si, 5. 4% by weight of Al and the balance being Fe]), Fe—Co alloys and the like. In use, one kind thereof can be used alone, or two or more kinds thereof can be used in combination.

The coercive force of the above oxide soft magnetic powder is usually 0.1 to 150 Oe, and the saturation magnetization thereof is usually 30 to 9 Oe.
0 emu / g. The coercive force of the metal soft magnetic powder is usually 0.02 to 100 Oe, and the saturation magnetization is usually 50 to 100 Oe.
~ 500 emu / g.

The above soft magnetic powder can be produced, for example, as follows. That is, the metal soft magnetic powder can be obtained by a gas phase method. The oxide soft magnetic powder can be produced by a glass crystallization method, a coprecipitation firing method, a calcining method, a hydrothermal synthesis method, a sol-gel method, or the like.

The shape of the soft magnetic powder is not particularly limited, but specifically, it is preferably spherical, plate-like, or amorphous. The size is preferably 5 to 800 nm.

The hard magnetic powder includes a ferromagnetic metal powder, a hexagonal ferrite powder and the like. Examples of the ferromagnetic metal powder include a ferromagnetic metal powder mainly composed of iron in which the metal content is 70% by weight or more and 80% by weight or more of the metal content is Fe. Examples include, for example, Fe-Co, Fe-Ni, Fe
-Al, Fe-Ni-Al, Fe-Co-Ni, Fe-
Ni-Al-Zn, Fe-Al-Si and the like can be mentioned.
The hard magnetic powder includes iron oxide [FeO _x (4
/ 3 ≦ x ≦ 3/2 ) iron oxide ferromagnetic powder represented by], the FeO _x to Cr, Mn, Co, metal powder divalent metal is added, such as Ni, Co to the FeO _x Co-deposited FeO _x , chromium dioxide, or a metal powder obtained by adding a metal such as Na, K, Fe or Mn, a semiconductor such as P, or an oxide of the metal to the chromium dioxide. Can be Further, the shape of the hard magnetic powder,
Needle-shaped or spindle-shaped, the major axis length is preferably 0.05 to
It is preferably 0.25 μm, more preferably 0.05 to 0.2 μm, preferably a needle ratio of 3 to 20, and a preferred X-ray particle size of 130 to 250 °.

As the above hexagonal ferrite powder, barium ferrite and strontium ferrite in the form of fine flat plate, and part of their Fe atoms are Ti, C
magnetic powders substituted with atoms such as o, Ni, Zn, V, and the like. The shape of the hexagonal ferrite powder preferably has a plate diameter of 0.02 to 0.09 μm and a plate ratio of 2 to 7.

In addition, the above magnetic powder may, if necessary,
Rare earth elements and transition metal elements can be included. In the present invention, in order to improve the dispersibility and the like of the magnetic powder, the magnetic powder is subjected to the same surface treatment as the surface treatment applied to the nonmagnetic powder contained in the nonmagnetic intermediate layer. Can be.

Further, the above-mentioned magnetic backcoat paint comprises the above-mentioned magnetic powder and a binder, a dispersant, and a binder used for the above-mentioned non-magnetic backcoat paint for forming the above-mentioned nonmagnetic backcoat layer. It can be obtained by appropriately selecting and mixing a lubricant, a curing agent, a solvent and the like. Here, the amount of the binder used is preferably about 5 to 400 parts by weight, more preferably 10 to 300 parts by weight, based on 100 parts by weight of the magnetic powder. The amount of the solvent to be used is preferably 150 to 2500 parts by weight, more preferably 150 to 1500 parts by weight, based on 100 parts by weight of the magnetic powder.

In order to prepare the backcoat paint, for example, the above magnetic powder or nonmagnetic powder and the above binder are put into a Nauta mixer or the like together with a part of the solvent and premixed to obtain a mixture. The resulting mixture was kneaded with a continuous pressure kneader or the like, then diluted with a part of the solvent, dispersed using a sand mill or the like, mixed with additives such as a lubricant, filtered, and further subjected to filtration. It can be easily obtained by a method of mixing a curing agent such as isocyanate or the like and the remaining solvent.

Thus, in the magnetic recording medium of the present invention,
The residual solvent amount of the back coat layer is 5 to 1500 pp.
m.

[0043] Here, the residual solvent content of the back coat layer, to less than 5ppm is difficult manufacturing, when the residual solvent amount is more than 15 00Ppm, when the magnetic recording medium is a tape, the tape After winding, the magnetic layer adheres to the back surface of the tape to roughen the magnetic surface, and furthermore, if the adhesion is excessive, the magnetic surface may peel off or the tape may be cut off. And other problems such as curling.

The thickness of the back coat layer is 0.1 to 5
μm, more preferably 0.2 to 3 μm. If the thickness is less than 0.1 μm, uniform coating becomes difficult, and the durability may decrease. If the thickness exceeds 5 μm, cupping, curling, etc. occur, the head contact becomes poor, and the envelope characteristics are significantly reduced. Therefore, it is preferable to be within the above range.

Further, the intermediate layer provided between the nonmagnetic support and the magnetic layer in the magnetic recording medium of the present invention may be a layer having magnetism, even layer having no magnetic Good. When the intermediate layer is a layer having magnetism, the intermediate layer is a magnetic layer containing magnetic powder (hereinafter, referred to as “magnetic intermediate layer”), and the magnetic layer is formed on the non-magnetic support. It is formed by applying a magnetic paint containing powder. Further, when the intermediate layer is a layer having no magnetism, the intermediate layer is a non-magnetic layer containing no magnetic powder (hereinafter, referred to as a “non-magnetic intermediate layer”). It is formed by applying a non-magnetic paint on the body.

As the magnetic paint used for forming the magnetic intermediate layer, a paint containing magnetic powder, a binder and a solvent as main components can be preferably used.

As the magnetic powder used in the above-mentioned magnetic paint, any of the above-mentioned magnetic powders used in the above-mentioned magnetic backcoat paint can be appropriately selected and used.

As the above-mentioned non-magnetic paint used for forming the above-mentioned non-magnetic intermediate layer, a paint containing non-magnetic powder, a binder and a solvent as main components can be preferably used.

The non-magnetic powder used in the non-magnetic paint is not particularly limited as long as it is non-magnetic.
Carbon black, graphite, titanium oxide, barium sulfate, zinc sulfide, magnesium carbonate, calcium carbonate, zinc oxide, calcium oxide, magnesium oxide, tungsten disulfide, molybdenum disulfide, boron nitride, tin dioxide, silicon dioxide, non-magnetic oxidation Chromium, alumina,
Silicon carbide, cerium oxide, corundum, artificial diamond, non-magnetic iron oxide, garnet, garnet, quartzite,
Silicon nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, diatomaceous earth, dolomite, resinous powder, etc., among which carbon black, titanium oxide, barium sulfate, calcium carbonate, alumina, non-magnetic iron oxide And the like are preferably used. The shape of the non-magnetic powder may be spherical, plate-like, needle-like, or amorphous, and its size is preferably 5 to 200 nm in spherical, plate-like, or amorphous. Further, in the case of a needle-like material, it is preferable that the major axis length is 20 to 300 nm and the axial ratio is 3 to 20.

In the present invention, the nonmagnetic powder
Surface treatment to improve the dispersibility of the non-magnetic powder.
May be applied. The above-mentioned surface treatment is described in “Characterizati
on of Powder Surfaces "; described in Academic Press
Can be performed by the same method as
A method of coating the surface of the above non-magnetic powder with an inorganic oxide
Is mentioned. At this time, the above inorganic materials that can be used
As the oxide, Al_TwoO_Three, SiO_Two, TiO_Two, Z
rO _Two, SnO_Two, Sb_TwoO_Three, ZnO, etc.,
When used, use alone or as a mixture of two or more
be able to. In addition to the above methods,
Run coupling treatment, titanium coupling treatment and
This can be done by organic treatment such as luminium coupling treatment.
Can also be.

As the binder and the solvent used in the non-magnetic paint for forming the non-magnetic intermediate layer, the same binders and solvents as those used in the magnetic paint are used. The compounding ratio of the binder is preferably from 5 to 200 parts by weight, more preferably from 5 to 100 parts by weight, based on 100 parts by weight of the nonmagnetic powder. Further, the compounding ratio of the solvent is based on 100 parts by weight of the nonmagnetic powder.
It is preferably from 80 to 500 parts by weight, more preferably from 100 to 350 parts by weight.

The above non-magnetic paint includes a dispersant,
Lubricants, abrasives, antistatic agents, rust inhibitors, fungicides, and additives that are commonly used in magnetic recording media such as curing agents,
It can be added as needed. Specific examples of the additive include the same additives as those used in the above-described magnetic paint.

When the intermediate layer is provided, the thickness of the intermediate layer is preferably 0.2 to 5 μm, more preferably 0.5 to 4 μm, and more preferably 0.5 to 4 μm.
Most preferably, it is 3.5 μm. When the thickness is less than 0.2 μm, the strength of the obtained magnetic recording medium becomes weak, and when it exceeds 5 μm, the strength of the obtained magnetic recording medium becomes too strong, or cupping or curling occurs and the head contact decreases. Therefore, it is preferable to be within the above range.

The magnetic recording medium of the present invention is suitable as a magnetic tape such as an 8 mm video tape or a DAT tape, but can also be applied as another magnetic recording medium such as a floppy disk.

Next, an outline of a method for manufacturing the magnetic recording medium of the present invention will be described. First, on the non-magnetic support, so that the magnetic or non-magnetic coating material for forming the intermediate layer, and a magnetic coating for forming the magnetic layer is dried thickness of the intermediate layer and the magnetic layer serving as the thickness Simultaneous multilayer coating is performed by a wet-on-wet method to form a coating film of an intermediate layer and a magnetic layer. That is, the magnetic layer is preferably applied and formed when the intermediate layer is wet. Next, the coating film is subjected to a magnetic field orientation treatment, dried, calendered, and then further coated with the backcoat paint on the back surface of the nonmagnetic support to form a backcoat layer. And
Perform a drying process. Then, if necessary, for example, when obtaining a magnetic tape, 6 to 72 ° C. at 40 to 70 ° C.
After time aging, slit to desired width.

[0056] above Symbol simultaneous multilayer coating method, JP-A-5-73
No. 883, column 42, line 31 to column 43, line 31, etc., wherein the magnetic paint which forms the magnetic layer before the magnetic or non-magnetic paint which forms the intermediate layer dries A method of coating, wherein the interface between the intermediate layer and the magnetic layer is smooth and the surface properties of the magnetic layer are also good, so that the dropout is small, the high density recording can be supported, and the coating film can be formed. A magnetic recording medium having excellent durability of the (intermediate layer and the magnetic layer) can be obtained.

The magnetic field orientation treatment is performed before the magnetic or non-magnetic paint and the magnetic paint are dried. For example, when the magnetic recording medium of the present invention is a magnetic tape, the magnetic paint is treated with the magnetic paint. About 50 in the direction parallel to the coating surface
A method of applying a magnetic field of 0 Oe or more, preferably about 1000 to 10000 Oe, or a method in which the magnetic or non-magnetic paint and the magnetic paint are 1000 to 1000 in a wet state.
It can be performed by a method of passing through a 0 Oe solenoid or the like.

The calendering treatment can be performed by a super calendering method in which a metal roll and a cotton roll or a synthetic resin roll, a metal roll and a metal roll are passed between two rolls.

The drying treatment can be performed, for example, by supplying a heated gas (hot air). At this time, the drying degree of the coating film is controlled by controlling the temperature of the hot air and the supply amount (wind speed). Can be controlled. The drying of the magnetic layer (and the intermediate layer) can be performed in the same manner.

In the production of the magnetic recording medium of the present invention, a finishing step such as a polishing or cleaning step for the surface of the magnetic layer can be performed, if necessary. The application of the above-mentioned magnetic or non-magnetic paint and magnetic paint can also be carried out by a generally known sequential multilayer coating method.

The magnetic recording medium of the present invention is not particularly limited as long as the amount of the residual solvent in the back coat layer is 5 to 1500 ppm, but the amount of the residual solvent is adjusted within the above range as follows. can do.

In order to keep the amount of the residual solvent in the back coat layer in the above range, the solvent composition in the back coat paint,
It can be carried out by appropriately selecting and adjusting the application speed of the back coat paint, drying conditions (wind speed, temperature, etc.) and the like. Here, the solvent composition is preferably a composition containing at least one or more high-boiling solvents such as cyclohexanone. The coating speed is 50 to 800 m / m.
It is preferably in. The drying conditions are preferably such that the temperature of the hot air is 60 to 120 ° C., the wind speed is 10 to 35 m / sec, and the drying time is 1 to 60 seconds.

The residual solvent amount in the back coat layer is a value indicated according to a measuring method in Examples described later.

The amount of the solvent remaining in the magnetic layer can be set in the above-mentioned preferable range in the same manner as the amount of the solvent remaining in the back coat layer. Specifically, the solvent composition is preferably a composition containing at least one or more high-boiling solvents such as cyclohexanone. Also,
The above coating speed is preferably set to 50 to 800 m / min. Further, the drying conditions are as follows:
The temperature of hot air is 60-120 ° C and the wind speed is 10-35m / se
The drying time is preferably 1 to 60 seconds.

[0065]

Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

Reference Example 1 Using a magnetic paint A having the following composition and a back coat paint having the following composition, a magnetic tape was produced in accordance with the following [Method of producing a magnetic recording medium]. A magnetic tape as a magnetic recording medium in which a magnetic layer and a back coat layer were respectively formed by using the magnetic paint A and the back coat paint shown in FIG. When the coercive force and the saturation magnetic flux density of the magnetic layer formed using the magnetic paint A were measured according to the [measurement method] described later, the coercive force was 1880 Oe and the saturation magnetic flux density was 3510 gauss. Was.

Magnetic coating A : 100 parts by weight of acicular ferromagnetic metal powder mainly composed of iron Fe: Al: Ba: Si: Ni: Co (weight ratio) = 88: 2: 1: 1: 3: 5 Magnetic force: 1840 Oe, saturation magnetization: 134 emu / g Average major axis length: 0.12 μm, specific surface area: 58 m ² / g X-ray particle size: 150 °, axial ratio: 10 · alumina (average particle size 0.3 μm) 8 parts by weight・ 2 parts by weight of carbon black (average primary particle diameter: 20 nm) ・ 10 parts by weight of “MR-110” [trade name, manufactured by Zeon Corporation, sulfonic acid group-containing vinyl chloride polymer] ・ “UR-8700” 23 Parts by weight [Trade name, Toyobo Co., Ltd., sulfonic acid group-containing polyurethane resin] 2 parts by weight of 2-ethylhexyl stearate 2 parts by weight of palmitic acid 4 parts by weight of "Coronate L" [trade name, Nippon Polyurethane Polyisocyanate compound manufactured by Kogyo Co., Ltd.]-120 parts by weight of methyl ethyl ketone-80 parts by weight of toluene-40 parts by weight of cyclohexanone

Backcoat paint carbon black (average primary particle size 0.028 μm) 32 parts by weight Carbon black (average primary particle size 0.062 μm) 8 parts by weight “Nipporan 2301” [trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.] Polyurethane] 50 parts by weight Nitrocellulose (viscosity 1/2 second manufactured by Hercules Powder Co.) 20 parts by weight Polyisocyanate (trade name "D-250N" manufactured by Takeda Pharmaceutical Co., Ltd.) 4 parts by weight Copper Phthalocyanine 5 parts by weight Stearic acid 1 part by weight Methyl ethyl ketone 120 parts by weight Toluene 120 parts by weight Cyclohexanone 120 parts by weight

[Manufacture of Magnetic Recording Medium] The magnetic paint A was applied on the surface of a 7 μm thick polyethylene terephthalate film so that the dry thickness of the magnetic paint A was 2.5 μm. Was formed. Next, while the coating film is passed through a 5000 Oe solenoid while in a wet state, a magnetic field orientation treatment is performed.
Drying was performed for 40 seconds in a drying oven supplied at m / sec.
Next, after performing a calendering process at 85 ° C. and 350 kg / cm to form a magnetic layer, the backcoat paint is applied on the back surface of the nonmagnetic support so that the dry thickness becomes 0.5 μm, and the temperature is raised. 90 ° C hot air at a wind speed of 15m / sec
Was dried for 40 seconds in a drying furnace supplied by, and then wound up. After this, immediately 3.81mm width, 90m
The resulting tape was cut into lengths, and a magnetic tape was obtained. The obtained magnetic tape was loaded into a DAT cassette case to prepare a DAT cassette. The coating and calendering were performed on the same line (in-line method).

Regarding the obtained magnetic tape as a magnetic recording medium, the amount of the solvent remaining in the back coat layer was determined as follows.
The surface roughness, C / N characteristics and durability were evaluated. The results are shown in [Table 1].

[Measurement Method] ◎ Coercive Force and Saturation Magnetic Flux Density Regarding the magnetic layer coated on the non-magnetic support,
Only the magnetic layer is peeled off from the nonmagnetic support using an adhesive tape, the magnetic layer is punched into a predetermined size and shape, and the coercive force and the saturation magnetic flux density are measured using a vibrating magnetometer at an applied magnetic field of 10 kOe. Each was measured. ◎ Amount of residual solvent in back coat layer For the magnetic tape immediately after the above cutting, a tape with only the back coat layer obtained by peeling off only the magnetic layer using an adhesive tape, a sample of headspace gas chromatography The tube was filled and subjected to gas chromatographic analysis to measure the solvent concentration. At this time, the area of the separated magnetic layer was about 30 cm ² . The weight of the back coat layer alone was determined by subtracting the weight of the support from the weight of the tape on which only the back coat layer was formed.・ Sample temperature: 140 ° C. ・ Needle temperature: 165 ° C. ・ Injection time: 30 seconds ・ Column: “DB-1” (trade name) manufactured by J & W [inner diameter 0.25 mm, length 30 m, stationary phase 0.25 μm] Column temperature: 60 to 70 ° C. Detector: FID method Detector temperature: 220 ° C. Carrier gas: He, 14 psi The obtained chromatogram was calibrated based on the measurement results of the standard solution to determine the amount of residual solvent. . The total residual solvent amount for methyl ethyl ketone, toluene and cyclohexanone was defined as the residual solvent amount. ◎ Surface roughness of magnetic recording medium Surface roughness Ra The obtained magnetic recording medium was manufactured by Tokyo Seimitsu Co., Ltd.
The surface roughness Ra was measured using a surface roughness shape measuring instrument (trade name: Surfcom 553A) under the conditions of a needle radius of 2 μm, a load of 30 mg, a magnification of 200,000, and a cutoff of 3.81 mm (before storage). ). The temperature is 50 ° C. and the relative humidity is 90.
% After storing for 2 days in a cassette condition
a was also determined. Note that Ra (center line average roughness) is obtained by extracting a portion of the measurement length L from the roughness curve in the direction of the center line, setting the center line of the extracted portion as the X axis and the direction of the vertical magnification as the Y axis. When the curve is represented by y = f (x), the value obtained by the following equation is represented by [nm].

[0072]

(Equation 1)

C / N characteristics (Evaluation of DAT cassette) Using a DDS-1 drive (a DAT drive for data recording), a single 4.7 MHz wave was recorded on the obtained magnetic tape, and a reproduction output ( C) was observed with a spectrum analyzer, and the noise level was expressed as C / N as 3.7 MHz noise level (N) (before storage). Also,
The C / N after storage for 2 days at a temperature of 50 ° C. and a relative humidity of 90% was also determined. In addition, Comparative Example 2 (before storage) was used as a reference. ◎ Storage stability (error rate change rate) For the obtained magnetic tape, a 4.7 MHz signal was recorded over the entire length of the tape using a DDS-1 drive, reproduced, the error rate was measured, and the average value (full length) Average)
And this was set as the error rate before storage. In addition, the error rate after storage for 2 days under storage conditions of a temperature of 50 ° C. and a relative humidity of 90% was measured in the same manner, and the average value was obtained.
This was taken as the error rate after storage. Then, (error rate after storage) / (error rate before storage) was determined as an error rate change rate, and thereby the storage stability was evaluated. Incidentally, the lower the rise, the better the storage stability.

Hereinafter, other examples and comparative examples will be described. In the following Examples and Comparative Examples, the temperature and the speed of the hot air were adjusted to adjust the amount of the solvent remaining in the back coat layer.

[0075] except that the amount of the solvent remaining Reference Example 2 backcoat layer was prepared a magnetic tape so that 800 ppm, to create a magnetic tape in the same manner as in Reference Example 1, the obtained magnetic tape Reference < The same test as in Example 1 was performed and evaluated. [Table 1]
Shown in

Reference Example 3 The following magnetic paint B was used in place of the magnetic paint A to obtain a dry thickness of 2.5 μm.
m, a magnetic tape was prepared in the same manner as in Reference Example 1 except that the magnetic layer was formed by coating so as to obtain a magnetic tape, and the obtained magnetic tape was evaluated by performing the same test as in Reference Example 1. . The results are shown in [Table 1]. When the coercive force and the saturation magnetic flux density of the magnetic layer formed using the magnetic paint B were measured in the same manner as in Reference Example 1, the coercive force was 1,820 Oe and the saturation magnetic flux density was 1910 gauss.

[0077] magnetic paint B · hexagonal ferrite powder 100 parts by weight of (hexagonal plate-like Co-Ti substituted barium ferrite powder) coercivity; 1670Oe, saturation magnetization; 56emu / g average plate diameter; 0.06 .mu.m, plate ratio; 4 ・ Alumina (average particle diameter 0.2 μm) 5 parts by weight ・ Carbon black (average primary particle diameter 20 nm) 2 parts by weight ・ “MR-110” 6 parts by weight [Product name, manufactured by Nippon Zeon Co., Ltd., sulfonic acid group] -Containing vinyl chloride polymer]-13 parts by weight of "UR-8700" [trade name, manufactured by Toyobo Co., Ltd., sulfonic acid group-containing polyurethane resin]-1.5 parts by weight of 2-ethylhexyl stearate-Palmitic acid 5 parts by weight-"Coronate L" 4 parts by weight (trade name, Nippon Polyurethane Industry Co., Ltd., polyisocyanate compound)-Methyl ethyl ketone 60 parts by weight・ Toluene 40 parts by weight ・ Cyclohexanone 20 parts by weight

Example 4 Using the above magnetic paint A, the following magnetic paint (a), and the above back coat paint, a magnetic tape was produced according to the following <Method of producing a magnetic recording medium>. Thus, a magnetic tape as a magnetic recording medium having a magnetic layer, an intermediate layer, and a back coat layer formed by the magnetic paint A, the magnetic paint (a), and the back coat paint shown in Table 1 was obtained.
The obtained magnetic tape was tested and evaluated in the same manner as in Reference Example 1. The results are shown in [Table 1]. <Method of Manufacturing Magnetic Recording Medium> On the surface of a polyethylene terephthalate film having a thickness of 7 μm, the dry thickness of the magnetic paint A was 0.2 μm, and the dry thickness of the magnetic paint (a) was 2.3 μm. The magnetic paint A and the magnetic paint (a) are simultaneously applied to
Coatings of the magnetic layer and the intermediate layer were formed. Next, while the coating film was passed through a 5000 Oe solenoid while in a wet state, a magnetic field orientation treatment was performed, and a drying treatment was performed at 80 ° C. for 40 seconds. Next, a magnetic layer and an intermediate layer are formed by calendering under the conditions of 85 ° C. and 350 kg / cm, and a back coat paint is applied on the back surface of the non-magnetic support so as to have a dry thickness of 0.5 μm. After drying, it was wound up. Thereafter, the tape was immediately cut into 3.81 mm width and 90 m length to obtain a magnetic tape, and the obtained magnetic tape was loaded into a DAT cassette case to produce a DAT cassette.
The coating and calendering were performed on the same line (in-line method).

100% by weight of FeOx (4 / 3.ltoreq.X.ltoreq.3 / 2) coated with magnetic paint (a) [Saturation magnetization 81 emu / g, coercive force 910 Oe, average major axis length 0.2 μm, needle ratio 10, specific surface area 38 m ² / g] 2 parts by weight of carbon black (average primary particle diameter 20 nm) 10 parts by weight of “MR110” [trade name, manufactured by Zeon Corporation, sulfonic acid group-containing vinyl chloride polymer] -"UR8700" 23 parts by weight [Trade name, Toyobo Co., Ltd., sulfonic acid group-containing polyurethane resin]-2-ethylhexyl stearate 2 parts by weight-Palmitic acid 1 part by weight-"Coronate L" 4 parts by weight (product Name, Nippon Polyurethane Industry Co., Ltd., polyisocyanate compound] 60 parts by weight of methyl ethyl ketone 40 parts by weight of toluene 20 parts by weight of cyclohexanone

Example 5 Instead of the magnetic paint A, the magnetic paint B was dried at a dry thickness of 0.2 μm.
m to form a magnetic layer, and the following non-magnetic paint (b) instead of the magnetic paint (a) is applied to a dry thickness of 2.3 μm to form an intermediate layer. A magnetic tape was prepared in the same manner as in Example 4 except that the magnetic tape was formed, and the obtained magnetic tape was evaluated by performing the same test as in Reference Example 1. The results are shown in [Table 1]. Non-magnetic paint (b) In place of the above-mentioned Co-coated FeOx (4/3 ≦ X <3/2), TiO ₂ (manufactured by Ishihara Sangyo, trade name “TTO-55”)
B ", except that a specific surface area of 37 m ² / g) was used.

[0081] except that the amount of the solvent remaining Comparative Example 1 backcoat layer was prepared a magnetic tape so that the 2800 ppm, to create a magnetic tape in the same manner as in Reference Example 1, ginseng obtained magnetic tape
It was evaluated subjected to the same test as that considered in Example 1. The results are shown in [Table 1].

Comparative Example 2 The following magnetic paint C was used in place of the magnetic paint A and had a dry thickness of 2.5 μm.
m, a magnetic tape was prepared in the same manner as in Reference Example 1 except that the magnetic layer was formed by coating so as to obtain a magnetic tape, and the obtained magnetic tape was evaluated by performing the same test as in Reference Example 1. . The results are shown in [Table 1]. Magnetic paint C , needle-shaped metal powder mainly composed of iron 100 parts by weight [Fe: Al: Ba: Si: Ni: Nd: Co (weight ratio) = 89: 2: 1: 1: 1: 1: 5] Magnetic force: 1610 Oe, saturation magnetization: 141 emu / g Average major axis length: 0.15 μm, specific surface area: 51 m ² / g X-ray particle size: 180 °, axial ratio: 10 · alumina (average particle size: 0.3 μm) 8 parts by weight・ 2 parts by weight of carbon black (average primary particle diameter: 20 nm) ・ 10 parts by weight of “MR-110” [trade name, manufactured by Zeon Corporation, sulfonic acid group-containing vinyl chloride polymer] ・ “UR-8700” 23 Parts by weight [Trade name, Toyobo Co., Ltd., sulfonic acid group-containing polyurethane resin] 2 parts by weight of 2-ethylhexyl stearate 2 parts by weight of palmitic acid 4 parts by weight of "Coronate L" [Nippon Polyurethane Industry Co., Ltd.] Ltd.), a polyisocyanate compound] Methyl ethyl ketone 120 parts Toluene 80 parts Cyclohexanone

[0083] except that the amount of the solvent remaining Comparative Example 3 the back coat layer was prepared magnetic tape so that the 3600 ppm, to create a magnetic tape in the same manner as in Example 4, ginseng obtained magnetic tape
It was evaluated subjected to the same test as that considered in Example 1. The results are shown in [Table 1].

[0084] except that the amount of the solvent remaining Comparative Example 4 backcoat layer was prepared a magnetic tape so that the 2100 ppm, to create a magnetic tape in the same manner as in Example 5, ginseng obtained magnetic tape
It was evaluated subjected to the same test as that considered in Example 1. The results are shown in [Table 1].

[0085]

[Table 1]

As is clear from the results shown in Table 1,
Since the amount of the solvent remaining in the back coat layer is in the above range, the magnetic recording medium of the present invention is stored (when stored in the original state,
It can be seen that there is no decrease in the electromagnetic conversion characteristics during storage in a pancake state prepared by slitting and storage in a cassette state.

[0087]

The magnetic recording medium of the present invention has excellent electromagnetic conversion characteristics, does not decrease with time, and has excellent storage stability.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of a magnetic recording medium according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic recording medium 2 Nonmagnetic support 3 Intermediate layer 4 Magnetic layer 5 Back coat layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-310821 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G11B 5/704

Claims (3)

(57) [Claims] 1. A non-magnetic support, a magnetic layer provided on a surface side of the non-magnetic support , the non-magnetic support and the magnetic layer
An intermediate layer provided between a magnetic recording medium having a back coat layer provided on the back surface of the non-magnetic support, the residual solvent content of the back coat layer, 5~ 15 00pp
m, and the thickness of the magnetic layer is 0.05 to 0.6 μm . 2. The magnetic layer contains a ferromagnetic metal powder, and has a coercive force of 1800 to 2400 Oe and a saturation magnetic flux density of 3000 to 4500 gauss.
Or contains hexagonal ferrite powder,
The coercive force of the conductive layer is 1500 to 2200 Oe,
Characterized in that the bundle density is 1500 to 2500 Gauss
The magnetic recording medium according to claim 1, wherein 3. The magnetic layer is formed by applying a magnetic paint.
The magnetic layer is coated when the intermediate layer is wet.
2. The magnet according to claim 1, wherein the magnet is provided and formed.
Mind recording medium.