JP2820913B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a magnetic recording medium having excellent electromagnetic conversion characteristics and 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 is usually manufactured by applying a magnetic paint containing a magnetic powder and a binder as main components on a non-magnetic support such as a polyester film. In recent years, in particular, there has been a demand for a magnetic recording medium to have a smaller size and a higher recording density. In order to meet such demands, for example, a magnetic recording medium having a multilayer structure in which another magnetic layer or a nonmagnetic layer is provided as an intermediate layer between a magnetic layer and a nonmagnetic support has been proposed.

[0003] However, the above-mentioned magnetic recording medium has a problem that the electromagnetic conversion characteristics and its storage stability are poor, and more specifically, there is a problem that the electromagnetic conversion characteristics decrease during storage. In order to solve such problems, Tokuho 4
JP-A-79046 proposes a magnetic recording medium in which the residual solvent amount and surface roughness of the magnetic layer are specified, but the magnetic recording medium proposed in the publication still sufficiently solves the above-mentioned problems. Did not. In particular, the magnetic recording medium proposed in this publication relates to a so-called single-layer type magnetic recording medium that does not have the above-mentioned intermediate layer, and solves the above-mentioned problem in a magnetic recording medium having a multilayer structure. Since this was not the object, the above-mentioned problem in the magnetic recording medium having a multilayer structure has not yet been sufficiently solved. That is, in the magnetic recording medium having a multilayer structure proposed in the past, the above-mentioned problem has not been sufficiently solved, and a magnetic recording medium having a multilayer structure and excellent electromagnetic conversion characteristics and storage stability has been demanded. It is the current situation.

Accordingly, it is an object of the present invention to provide a magnetic recording medium which is excellent in electromagnetic conversion characteristics and further has excellent storage stability such that the electromagnetic conversion characteristics during storage are little reduced.

[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, an intermediate layer, and a magnetic layer. It has been found that a magnetic recording medium having a thickness, a specific center line surface roughness, and a specific residual solvent amount can achieve the above object.

The present invention has been made based on the above findings, and comprises a non-magnetic support, an intermediate layer located on the non-magnetic support, and a magnetic layer as the uppermost layer located on the intermediate layer. In the magnetic recording medium provided, the thickness of the magnetic layer is 0.05 to 0.6 μm, the center line surface roughness of the magnetic layer is 2 to 10 nm, and the residual solvent amount of the magnetic layer is: An object of the present invention is to provide a magnetic recording medium characterized by having a concentration of 5 to 3000 ppm.

[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.

A magnetic recording medium 1 of the present invention shown in FIG. 1 has a non-magnetic support 2, an intermediate layer 3 on the non-magnetic support 2, and a magnetic layer as an uppermost layer on the intermediate layer 3. Layer 4
Consists of A back coat layer 5 is provided on the back surface of the nonmagnetic support 2 as necessary.

In the magnetic recording medium of the present invention, in addition to the non-magnetic support, the intermediate layer, the magnetic layer and the back coat layer, the magnetic recording medium further comprises 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 1 used in the magnetic recording medium of the present invention, a generally known non-magnetic support can be used without any particular limitation. Films and disks; Cu, Al,
Films, disks, cards, and the like made of non-magnetic metals such as Zn, ceramics such as glass, porcelain, and porcelain can be used.

Examples of the polymer resin for forming the flexible film or 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 backcoat layer provided on the back surface of the nonmagnetic support as necessary can be formed by using a known backcoat paint without any particular limitation.

In the magnetic recording medium of the present invention, the intermediate layer located on the nonmagnetic support may be a layer having magnetism or a layer having no magnetism. 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,
A non-magnetic layer containing no magnetic powder (hereinafter referred to as a "non-magnetic intermediate layer"), which is formed by applying a non-magnetic paint on the non-magnetic support.

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 magnetic 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. (Lower) Magnetic Properties and Applications ”(Shokabo, 1984), pp. 368-376, and specifically include oxide soft magnetic powders. As the oxide soft magnetic powder, spinel-type ferrite powder is preferably used, and as the spinel-type ferrite powder, MnF
e ₂ O ₄ , Fe ₃ O ₄ , CoFe ₂ O ₄ , NiFe ₂ O
_{4, MgFe 2 O 4, Li} 0.5 Fe 2.5 O 4 and, Mn-
Zn-based ferrite, Ni-Zn-based ferrite, Ni-C
u-based ferrite, Cu-Zn-based ferrite, Mg-Zn
Ferrite, Li-Zn ferrite, Mn ferrite, Zn ferrite, and the like. In use, one kind thereof may be used alone, or two or more kinds thereof may be used in combination.

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 oxide soft magnetic powder is usually 0.1 to 150 Oe, and the saturation magnetization 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 of the soft magnetic powder is 0.0
It is preferably from 0.01 to 0.2 μm.

The hard magnetic powder includes hard magnetic gold.
Powder, hard magnetic oxide powder, hexagonal ferrite powder, etc.
Is mentioned. The hard magnetic 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.
And hard magnetic metal powder mainly composed of iron.
Specific examples of the magnetic metal powder include, for example, Fe-Co,
Fe-Ni, Fe-Al, Fe-Ni-Al, Fe-C
o-Ni, Fe-Ni-Al-Zn, Fe-Al-Si
And the like. Further, as the hard magnetic oxide powder,
FeO_xIron oxide based represented by (4/3 ≦ x ≦ 3/2)
Ferromagnetic powder, FeO_xCr, Mn, Co, Ni, etc.
Iron oxide powder to which a divalent metal of_xTo C
oCo-deposited FeO deposited _x, Chromium dioxide, also
Is gold such as Na, K, Fe or Mn on the chromium dioxide.
Semiconductors such as metals and P or oxides of the metals are added
Oxide powder. The hard magnetic metal
The shape of powder and hard magnetic oxide powder is needle-like or spindle-like
The major axis length is preferably 0.05 to 0.25 μm,
More preferably, it is 0.05 to 0.2 μm, and it is preferable.
The needle ratio is 3 to 20, and the preferred X-ray particle size is 130 to 2
Desirably, it is 50 °.

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 preferably has a plate diameter of 0.02 to 0.09 μm and a plate ratio of 2 to 7.

Further, the magnetic powder in the magnetic coating material for forming the magnetic intermediate layer may contain a rare earth element or a transition metal element, if necessary. In the present invention, the magnetic powder may be subjected to a surface treatment in order to improve the dispersibility and the like of the magnetic powder. The above-mentioned surface treatment is called “Characterization of Powder Surfaces”;
The method can be performed by a method similar to the method described in Academic 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 ,
SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb
Examples thereof include ₂ O ₃ and ZnO, and when used, they can be used alone or as a mixture of two or more. The surface treatment, in addition to the above method, silane coupling treatment,
Organic treatment such as titanium coupling treatment and aluminum coupling treatment can also be performed.

The binder used in the magnetic paint for forming the magnetic intermediate layer may be a thermoplastic resin,
Thermosetting resins, reactive resins, and the like can be used, and when used, they can be used alone or as a mixture. Specific examples of the binder include vinyl chloride resin, polyester, polyurethane, nitrocellulose, epoxy resin, and the like.
No. 28, page 19, upper right column, line 19 to page 2, lower right column, line 19, and the like. Further, the binder may contain a polar group for improving dispersibility and the like. The mixing ratio of the binder is 100
5 to 200 parts by weight, preferably 5 to 1 part by weight, is preferred.
00 parts by weight is more preferred.

The solvent used in the magnetic coating material for forming the magnetic intermediate layer includes ketone solvents, ester solvents, ether solvents, aromatic hydrocarbon solvents, and chlorine solvents. And the like. Specifically, solvents described in JP-A-57-162128, page 17, lower right column, line 17 to page 4, lower left column, line 10 are used. be able to. The mixing ratio of the solvent is 80 to 500 parts by weight based on 100 parts by weight of the magnetic powder.
Part by weight is preferred, and 100 to 350 parts by weight is more preferred.

The magnetic paint for forming the magnetic intermediate layer includes a dispersant, a lubricant, an abrasive, an antistatic agent,
Additives commonly used in magnetic recording media, such as rust inhibitors, fungicides, and curing agents, can be added as needed. As the above additives, specifically, JP-A-57-
Various additives described in page 162128, 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 can be mentioned. .

As the non-magnetic paint used for forming the non-magnetic intermediate layer, a paint mainly containing a non-magnetic powder, a binder and a solvent 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, in order to improve the dispersibility and the like of the nonmagnetic powder, the nonmagnetic powder may be subjected to the same surface treatment as the surface treatment performed on the magnetic powder contained in the magnetic intermediate layer. it can.

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.

Further, 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.

The thickness of the intermediate layer is 0.2 to 5 μm.
m, more preferably 0.5 to 4 μm, and most preferably 0.5 to 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.

In the magnetic recording medium of the present invention, the magnetic layer located on the intermediate layer 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 thereon. As the magnetic paint, a paint containing magnetic powder, a binder and a solvent as main components is preferably used.

As the magnetic powder, the above-mentioned ferromagnetic metal powder mainly composed of iron used in the above-mentioned magnetic intermediate layer,
Alternatively, the same as the above hexagonal ferrite powder is used. In the present invention, in order to improve the dispersibility and the like of the magnetic powder, the magnetic powder can be subjected to the same surface treatment as the surface treatment applied to the magnetic powder contained in the magnetic intermediate layer. .

The coercive force of the ferromagnetic metal powder is 1600
~ 2500 Oe, preferably 1800 to 240
More preferably, it is 0 Oe. Further, the coercive force of the hexagonal ferrite powder is preferably from 1300 to 2300 Oe, and more preferably from 1500 to 2200 Oe.
When the coercive force of the ferromagnetic metal powder and the hexagonal ferrite are respectively less than the above lower limits, the short-wavelength RF output is reduced because of easy demagnetization. Is insufficient, the writing ability is insufficient, and the overwrite characteristics are further deteriorated. The saturation magnetization of the ferromagnetic metal powder is preferably from 100 to 180 emu / g, and more preferably from 110 to 160 emu / g. The saturation magnetization of the hexagonal ferrite powder is 30 to
It is preferably 70 emu / g, more preferably 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 filling rate of the magnetic powder is reduced, the output is reduced, and when the upper limit is exceeded. Therefore, it is necessary to reduce the binder, the interaction between the magnetic powders increases, and as a result, the magnetic powders are in an agglomerated state, and it is difficult to obtain a desired output. Is preferred.

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 hexagonal ferrite powder is preferably 1500-2200 Oe, more preferably 15-20 Oe.
It is 00-2100 Oe. The saturation magnetic flux density of the magnetic layer containing the ferromagnetic metal powder is preferably 300
0-4500 gauss, more preferably 3200-400
0 gauss, and the saturation magnetic flux density of the magnetic layer containing the hexagonal ferrite powder is preferably 1500 to 25.
00 gauss, more preferably 1600 to 2500 gauss.

The binder and the solvent used in the magnetic coating material forming the magnetic layer are the same as the binder and the solvent used in the magnetic or non-magnetic coating material forming the intermediate layer. be able to.
The amount of the binder used is preferably about 5 to 100 parts by weight based on 100 parts by weight of the magnetic powder.
It is particularly preferred to use 0 parts by weight. The amount of the solvent used is 80 to 5 parts by weight based on 100 parts by weight of the magnetic powder.
It is preferably 00 parts by weight, more preferably 100 to 350 parts by weight.

[0036] The magnetic coating material may contain additives commonly used in magnetic recording media such as dispersants, lubricants, abrasives, antistatic agents, rust inhibitors, fungicides, and curing agents. 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 above magnetic paint, for example, the above magnetic 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 obtained mixture is continuously added. After kneading with a pressure 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, and further curing agent such as polyisocyanate and remaining And the like.

Thus, in the magnetic recording medium of the present invention,
The thickness of the magnetic layer is 0.05 to 0.6 μm, preferably 0.08 to 0.5 μm, and the center line surface roughness (Ra) of the magnetic layer is 2 to 10 nm, preferably 2.5 to ~
8 nm, and the residual solvent amount of the magnetic layer is 5 to 300
0 ppm, preferably 20 to 2000 ppm.
The above “ppm” is based on weight. 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.

If the thickness of the magnetic layer is less than 0.05 μm, uniform coating becomes difficult, and the durability may decrease. If it exceeds 0.6 μm, the thickness loss increases,
Output characteristics are degraded and overwrite characteristics are degraded. Further, if the center line surface roughness of the magnetic layer is less than 2 nm, a running trouble such as an increase in friction coefficient occurs. If the thickness exceeds 10 nm, output characteristics deteriorate due to space loss. Further, the residual solvent amount of the magnetic layer is 5 pp.
m is practically difficult, and if it exceeds 3000 ppm, when the magnetic recording medium is in the form of a tape, the magnetic layer and the back surface of the tape are adhered to each other after winding the tape, and the magnetic surface is roughened. If the adhesion is excessive, there are problems such as peeling of the magnetic surface and breakage of the tape, and curling of the tape when the magnetic recording medium is a tape.

When the magnetic layer contains a ferromagnetic metal powder, the magnetic layer has a coercive force of 1800 to 2400 Oe.
When the saturation magnetic flux density is 3000 to 4500 Gauss, or when the magnetic layer contains hexagonal ferrite powder, the coercive force of the magnetic layer is 1500 to 2200O.
When the magnetic flux density is e and the saturation magnetic flux density is 1500 to 2500 Gauss, it is preferable that the magnetic layer is applied and formed when the intermediate layer is wet.

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, a magnetic or non-magnetic coating material for forming the intermediate layer and a magnetic coating material for forming the magnetic layer on the non-magnetic support are wetted such that the dry thicknesses of the intermediate layer and the magnetic layer are respectively the above-mentioned thicknesses.・ Simultaneous multilayer coating is performed by an on-wet method to form a coating film of the intermediate layer and the magnetic layer. That is, the magnetic layer is preferably applied and formed when the intermediate layer is wet. Next, after performing a magnetic field orientation treatment on the coating film, a drying treatment is performed and the film is wound. Thereafter, after performing a calendering treatment, a back coat layer is further formed as necessary. Then, if necessary, for example, when obtaining a magnetic tape, 40 to 7
Aging treatment is performed at 0 ° C. for 6 to 72 hours, and slit to a desired width.

The above simultaneous multi-layer coating method is described in 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 above drying treatment can be performed, for example, by supplying a heated gas. At this time, the degree of drying of the coating film can be controlled by controlling the temperature of the gas and the amount of the supplied gas.

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 back coat layer provided as necessary is provided on the back surface of the non-magnetic support (the surface on which the intermediate layer and the magnetic layer are not provided). It is obtained by applying the back coat paint used for forming the layer on the non-magnetic support.

In the manufacture 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.

In the magnetic recording medium of the present invention, the thickness of the magnetic layer is 0.05 to 0.6 μm, the center line surface roughness (Ra) of the magnetic layer is 2 to 10 nm, There is no particular limitation as long as the amount of the residual solvent is 5 to 3000 ppm, but the center line surface roughness and the amount of the residual solvent can be adjusted within the above-described range as described below.

In order to make the center line surface roughness of the magnetic layer fall within the above range, the solvent composition in the magnetic paint, drying conditions (wind speed, temperature, etc.) of the magnetic paint, calendar conditions (speed, pressure, roll temperature, etc.) The amount of the solvent remaining in the magnetic layer can be adjusted to the above range by adjusting the solvent composition in the magnetic paint, the coating speed of the magnetic paint, and the drying conditions (wind speed). , Temperature, etc.) are appropriately selected and adjusted. here,
The solvent composition is preferably a composition containing at least one or more high-boiling solvents such as cyclohexanone. The drying conditions are preferably such that the temperature of the hot air is 60 to 120 ° C., the air speed is 5 to 35 m / sec, and the drying time is 1 to 60 seconds. The calender conditions are as follows: a calender speed of 50 to 300 m / min and a pressure of 50 to 4 m / min.
Preferably, the roll temperature is 50 kg / cm and the roll temperature is 60 to 120 ° C. The coating speed is 50 to 800.
m / min is preferable.

The above-mentioned center line surface roughness (Ra) and the above-mentioned residual solvent amount are values shown in accordance with the measuring method described in Examples described later.

[0052]

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.

Example 1 Using a magnetic paint A having the following composition and a magnetic paint (a) having the following composition, and using a back coat paint having the following composition as a back coat paint, A magnetic recording medium is produced by manufacturing a magnetic tape according to the method described above, and forming an intermediate layer with the magnetic paint (a) shown in Table 1 and a magnetic layer as the uppermost layer with the magnetic paint A. As a magnetic tape. 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

Magnetic paint (a) 100 parts by weight of Mn-Zn ferrite (saturation magnetization 62 emu / g, coercive force 64 Oe, average particle diameter 0.04 μm) Carbon black (average primary particle diameter 20 nm) 2 parts by weight MR110 "10 parts by weight [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 parts by weight of 2-ethylhexyl stearate 1 part by weight of palmitic acid 4 parts by weight of "Coronate L" (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd., polyisocyanate compound) 84 parts by weight of methyl ethyl ketone 56 parts by weight of toluene・ 28 parts by weight of cyclohexanone

(Blending of back coat 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, Nippon Polyurethane Industry Co., Ltd. Polyurethane manufactured by Co., Ltd.) 50 parts by weight Nitrocellulose (having a viscosity of 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 140 parts by weight Toluene 140 parts by weight Cyclohexanone 140 parts by weight

[Production of 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 0.5 μm and the dry thickness of the magnetic paint (a) was 2.0 μm. The magnetic paint A and the magnetic paint (a) were applied by a simultaneous multilayer coating method at a line speed of 100 m / min to form a magnetic layer and an intermediate layer. Then, the coating film was wet in a wet state
e, the magnetic field orientation treatment was performed by passing through a solenoid, and drying was performed for 30 seconds in a drying furnace in which hot air at a temperature of 90 ° C. was supplied at an air velocity of 15 m / sec. Next, 90 ° C, 350k
After forming a magnetic layer and an intermediate layer by performing a calendering treatment under the condition of g / cm, 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 at 0 ° C., it was wound up. After this, immediately 3.
The tape was cut to a width of 81 mm and a length of 90 m to obtain a magnetic tape.
An AT cassette was prepared. The coating and calendering were performed on the same line (in-line method).

With respect to the obtained magnetic tape as a magnetic recording medium, the amount of residual solvent, the center line surface roughness,
The C / N characteristics and durability were evaluated. The results are shown in [Table 1].

[Measurement Method] 保 Coercive Force and Saturation Magnetic Flux Density For the magnetic layer coated on the non-magnetic support and the intermediate layer, only the magnetic layer was separated from the non-magnetic support and the intermediate layer using an adhesive tape. Is peeled off, the magnetic layer is punched into a predetermined size and shape, and an applied magnetic field of 10 k is applied using a vibrating magnetometer.
In Oe, the coercive force and the saturation magnetic flux density were measured, respectively. Amount of residual solvent The magnetic tape immediately after the above cutting was peeled off only the magnetic layer using an adhesive tape. Next, after the weight of the peeled magnetic layer was measured, the magnetic layer was filled in a sample tube of a head space gas chromatography while being adhered to an adhesive tape, and subjected to gas chromatography analysis to measure the solvent concentration. At this time, the area of the separated magnetic layer was about 30 cm ²
And・ 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, name 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. ◎ Center line surface roughness of magnetic recording medium Center line surface roughness Ra The obtained magnetic recording medium was manufactured by Tokyo Seimitsu Co., Ltd.
Using a surface roughness shape measuring instrument "Surfcom 553A", center line surface roughness Ra under the conditions of a needle radius of 2 μm, a load of 30 mg, a magnification of 200,000, and a cutoff of 0.08 mm.
Was measured (before storage). The temperature is 50 ° C and the humidity is 9
Ra after storage in a cassette for 2 days under 0% storage conditions was also determined. The center line surface roughness Ra 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 longitudinal magnification as the Y axis. Is represented by y = f (x), the value obtained by the following equation is represented by [nm].

[0060]

(Equation 1)

C / N characteristics (Evaluation of DAT cassette) Using a DDS-1 drive (a DAT drive for recording data), a 4.7 MHz single 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 3 (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 amount of the solvent remaining in the magnetic layer was controlled to the value shown in Table 1 below by appropriately adjusting the temperature and the speed of the hot air. [Example 2] A magnetic paint A was applied to a dry thickness of 0.2 µm to form a magnetic layer.
Instead of the following magnetic paint (b), the dry thickness is 2.3 μm
A magnetic tape was prepared in the same manner as in Example 1 except that the intermediate layer was formed by applying the magnetic tape in such a manner as described above, and the obtained magnetic tape was tested and evaluated in the same manner as in Example 1. The results are shown in [Table 1]. 100 parts by weight of FeOx (4/3 ≦ X <3/2) coated with magnetic paint (b) Co (saturated magnetization 81 emu / g, coercive force 910 Oe, average major axis length 0.2 μm, needle ratio 10, ratio) Surface area 38 m ² / g) ・ Carbon black (average primary particle diameter 20 nm) 2 parts by weight ・ “MR110” 10 parts by weight [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 parts by weight of 2-ethylhexyl stearate 1 part by weight of palmitic acid 4 parts by weight of "Coronate L" (trade name, Japan Polyurethane isocyanate compound manufactured by Polyurethane Industry Co., Ltd.]-90 parts by weight of methyl ethyl ketone-60 parts by weight of toluene-30 parts by weight of cyclohexanone

Example 3 Instead of the magnetic paint A, the following magnetic paint B was applied to a dry thickness of 0.2 μm to form a magnetic layer, and the magnetic paint (a) was dried to a dry thickness of 0.2 μm. 2.3
A magnetic tape was prepared in the same manner as in Example 1 except that the intermediate layer was formed by coating to a thickness of μm, and the obtained magnetic tape was evaluated by performing the same test as in Example 1. The results are shown in [Table 1]. When the coercive force and saturation magnetic flux density of the magnetic layer formed using the magnetic paint B were measured in the same manner as in Example 1, the coercive force was 1820 Oe.
The saturation magnetic flux density was 1910 gauss.

Magnetic coating B : 100 parts by weight of hexagonal ferrite powder (hexagonal plate-shaped Co-Ti-substituted barium ferrite powder) Coercive force: 1670 Oe, saturation magnetization: 56 emu / g Average plate diameter: 0.06 μm, plate ratio; 4 ・ Alumina (average particle size 0.2 μm) 5 parts by weight ・ Carbon black (average primary particle diameter 20 nm) 2 parts by weight ・ “MR-110” 7 parts by weight [trade name, manufactured by Nippon Zeon Co., Ltd., sulfonic acid group] -Contained vinyl chloride polymer]-"UR-8700" 15 parts by weight [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-4 parts by weight of "Coronate L" (trade name, polyisocyanate compound manufactured by Nippon Polyurethane Industry Co., Ltd.)-84 parts by weight of methyl ethyl ketone・ Toluene 56 parts by weight ・ Cyclohexanone 28 parts by weight

Example 4 Instead of the magnetic paint A, the above magnetic paint B was applied to a dry thickness of 0.2 μm to form a magnetic layer, and the following magnetic material was used in place of the magnetic paint (a). A magnetic tape was prepared in the same manner as in Example 1 except that the intermediate layer was formed by applying the paint (C) of No. 3 so that the dry thickness became 2.3 μm. Were tested and evaluated. The results are shown in [Table 1]. Magnetic paint (c) 50 parts by weight of hexagonal ferrite powder (hexagonal barium ferrite, coercive force: 1680 Oe, saturation magnetization: 57 emu / g, average plate diameter: 0.06 μm, plate ratio: 4) 50 parts by weight of α-Fe ₂ O ₃ (major axis length: 0.15 μm, axial ratio: 8, specific surface area: 52 m ² / g) ・ Alumina (average particle size: 0.3 μm) 7 parts by weight ・ Carbon black (average) 2 parts by weight (primary particle diameter: 20 nm) 11 parts by weight of a vinyl chloride copolymer (MR-110, trade name, manufactured by Zeon Corporation) 13 parts by weight of polyurethane resin (UR-8200, trade name, Toyobo Co., Ltd.) -"Coronate HX" 3 parts by weight (trade name, polyisocyanate compound manufactured by Nippon Polyurethane Industry Co., Ltd.)-2 parts by weight of butyl stearate-2 parts by weight of myristic acid-84 parts by weight of methyl ethyl ketone Toluene 56 parts Cyclohexanone 28 parts by weight

Example 5 The magnetic paint A was dried at a dry thickness of 0.2.
μm to form a magnetic layer, and in place of the magnetic paint (a), the following non-magnetic paint (d) 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 1 except for the above, and the obtained magnetic tape was tested and evaluated in the same manner as in Example 1. The results are shown in [Table 1]. Non-magnetic paint (d) Instead of Mn-Zn ferrite, TiO ₂ (trade name “TTO-55B”, manufactured by Ishihara Sangyo, specific surface area: 37 m ² /
Except that g) was used, it was the same as the above magnetic paint (a).

Example 6 Instead of the magnetic paint A, the magnetic paint B was applied to a dry thickness of 0.2 μm to form a magnetic layer, and the non-magnetic paint was replaced with the magnetic paint (a). A magnetic tape was prepared in the same manner as in Example 1 except that the paint (d) was applied to a dry thickness of 2.3 μm to form an intermediate layer, and the obtained magnetic tape was the same as in Example 1. A test was performed and evaluated. The results are shown in [Table 1].

[Comparative Example 1] The magnetic paint A was dried at a dry thickness of 2.0.
A magnetic tape according to Example 1, except that the magnetic layer was formed by coating to a thickness of 0.5 μm to form a magnetic layer, and a magnetic paint (a) was applied to a dry thickness of 0.5 μm to form an intermediate layer. And the same test as in Example 1 was performed on the obtained magnetic tape to evaluate. The results are shown in [Table 1].

Comparative Example 2 A magnetic tape was prepared in the same manner as in Example 2 except that the magnetic tape was manufactured so that the calender temperature was 70 ° C. and the amount of the residual solvent in the magnetic layer was 350 ppm. The same test as in Example 1 was performed on the magnetic tape and evaluated. The results are shown in [Table 1].

[Comparative Example 3] The amount of solvent remaining in the magnetic layer was 310.
A magnetic tape was prepared in the same manner as in Example 2 except that the magnetic tape was manufactured so as to be 0 ppm, and the obtained magnetic tape was evaluated by performing the same test as in Example 1. The results are shown in [Table 1].

[Comparative Example 4] The amount of the solvent remaining in the magnetic layer was 380.
A magnetic tape was prepared in the same manner as in Example 6 except that the magnetic tape was manufactured to be 0 ppm, and the obtained magnetic tape was evaluated by performing the same test as in Example 1. The results are shown in [Table 1].

[Comparative Example 5] The residual solvent amount of the magnetic layer was 320
A magnetic tape was prepared in the same manner as in Example 5 except that the magnetic tape was manufactured to be 0 ppm, and the obtained magnetic tape was evaluated by performing the same test as in Example 1. The results are shown in [Table 1].

Comparative Example 6 The amount of the solvent remaining in the magnetic layer was 400
A magnetic tape was prepared in the same manner as in Example 6 except that the magnetic tape was manufactured to be 0 ppm, and the obtained magnetic tape was evaluated by performing the same test as in Example 1. The results are shown in [Table 1].

[Comparative Example 7] The magnetic paint A was dried to a thickness of 2.0.
μm, the non-magnetic paint (d) has a dry film thickness of 0.5 μm, and the residual solvent amount of the magnetic layer is 800 pp.
A magnetic tape was prepared in the same manner as in Example 5, except that the value was changed to m, and the obtained magnetic tape was evaluated by performing the same test as in Example 1. The results are shown in [Table 1].

[0075]

[Table 1]

As is clear from the results shown in [Table 1],
The magnetic recording medium of the present invention has excellent electromagnetic conversion characteristics because the thickness of the magnetic layer, the center line surface roughness and the amount of the remaining solvent are in the above ranges, and during storage (during slitting during storage in the original state). It can be seen that the deterioration of the electromagnetic conversion characteristics during storage in the prepared pancake state and storage in the cassette state is small.

[0077]

The magnetic recording medium of the present invention has excellent electromagnetic conversion characteristics and has little decrease in the electromagnetic conversion characteristics during storage.

[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

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-60359 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5/70 G11B 5/704

Claims (6)

(57) [Claims] 1. A magnetic recording medium comprising a non-magnetic support, an intermediate layer located on the non-magnetic support, and a magnetic layer as an uppermost layer located on the intermediate layer, wherein the thickness of the magnetic layer is The magnetic layer has a center line surface roughness of 2 to 10 nm and the magnetic layer has a residual solvent amount of 5 to 3000 ppm. Medium. 2. The magnetic layer according to claim 1, wherein the magnetic layer contains a ferromagnetic metal powder, the coercive force of the magnetic layer is 1800 to 2400 Oe, and the saturation magnetic flux density is 3000 to 4500 gauss. 2. The magnetic recording medium according to 1. 3. The magnetic layer contains a hexagonal ferrite powder, and has a coercive force of 1500 to 220.
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a saturation magnetic flux density of 1500 to 2500 Gauss. 4. The magnetic recording medium according to claim 2, wherein the magnetic layer is applied and formed when the intermediate layer is wet. 5. The intermediate layer has a thickness of 0.2 to 5 μm.
m.
Magnetic recording medium. 6. The intermediate layer according to claim 1 , wherein the magnetic layer is a soft magnetic material.
Magnetic coating containing powder or hard magnetic powder, binder and solvent
Is a magnetic layer formed by
The mixing ratio of the solvent in 100 parts by weight of the magnetic powder
80 to 500 parts by weight based on the weight
Item 6. The magnetic recording medium according to any one of Items 1 to 5.