JP3024908B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention enables high-density recording.
In particular, it relates to a magnetic recording medium having excellent output characteristics.

[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, in recent years, there has been a demand for high-density recording along with miniaturization of magnetic recording media. In order to respond to such demands, for example, attempts to improve coercive force and saturation magnetization, Proposals have been made to reduce the thickness. Further, in order to meet the demand for a high quality magnetic recording medium in addition to the above-mentioned demand, a magnetic recording medium having particularly excellent output characteristics is strongly desired. Accordingly, it is an object of the present invention to provide a magnetic recording medium capable of high-density recording and having particularly excellent output characteristics.

[0003]

As a result of various studies, the present inventors have found that a magnetic recording medium in which the surface areas of powders contained in the non-magnetic layer and the powder contained in the magnetic layer and their ratios are in specific ranges, It has been found that the above object can be achieved.

[0004] The present invention has been made based on the above findings, and comprises a non-magnetic support, at least a non-magnetic layer provided on the magnetic support, and a magnetic layer provided on the non-magnetic layer. Wherein the non-magnetic layer and the magnetic layer are wet-
The magnetic recording medium odor formed by down-wet method
Te, the nonmagnetic layer and the magnetic layer contains the their respective powders, the powder contained in the magnetic layer is ferromagnetic
Including metal powder, the powder contained in the non-magnetic layer is
Total surface area α _{1 of} all powders contained per unit volume in the magnetic layer including nonmagnetic oxide powder (total surface area of all powders /
The total volume of the magnetic layer) [m ² / cm ³ ] is 130 <α ₁ <
180, and the total surface area α ₂ (total surface area of all powders / total volume of the non-magnetic layer) [m ² / cm ³ ] of all powders contained in the non-magnetic layer per unit volume is 100 < α ₂ <160
In and, alpha ₁ / alpha ₂ is _{0.8 <α 1 / α 2 <} 1.3, it is intended to provide a magnetic recording medium characterized.

Hereinafter, the magnetic recording medium of the present invention will be described in detail. As shown in FIG. 1, the magnetic recording medium according to the present invention includes a non-magnetic support 1, a non-magnetic layer 2 provided on the magnetic support 1, and a magnetic layer 3 provided on the non-magnetic layer 2. And, if necessary, a nonmagnetic support 1
The back coat layer 4 is provided on the back surface of the.

The non-magnetic support 1 comprises at least a matrix component or a matrix component and a filler component.

The matrix component is made of a thermoplastic resin or the like. Examples of the thermoplastic resin include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycyclohexylene dimethylene terephthalate, and polyethylene bisphenoxycarboxylate; Polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose acetate butyrate and cellulose acetate propionate; vinyl resins such as polyvinyl chloride and polyvinylidene chloride; or polyamides, polyimides, polycarbonates, polysulfones, polyether ethers Ketone, polyurethane and the like are used. These resin components can be used alone or in combination.

[0008] The filler component is used for controlling the surface property and running property of the outer surface of the nonmagnetic support to a predetermined value. The same as the non-magnetic powder described later used for the formation may be mentioned, but the particle size is preferably 0.8 μm or less, more preferably 0.01 to 0.5 μm.
And its content (blending amount) is preferably 5
% By weight, more preferably 0.001 to 2% by weight.

In the present invention, the filler component may be subjected to a surface treatment in order to improve the dispersibility and the like of the filler component. The above-mentioned surface treatment
zation of Powder Surfaces "; a method similar to the method described in Academic Press, etc.,
For example, there is a method of coating the surface of the filler component with an inorganic oxide. At this time, the inorganic oxide that can be used includes Al ₂ O ₃ , SiO ₂ , TiO _2
2 , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ , ZnO and the like. When used, they can be used alone or as a mixture 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 alumina coupling treatment, in addition to the above method.

Here, a preferable thickness of the whole non-magnetic support is 1 to 300 μm. Further, the nonmagnetic support may have a layer structure of two or more layers of an upper layer and a lower layer, and the upper layer and the lower layer may have different surface roughness.

The non-magnetic layer provided on the non-magnetic support is a layer formed by applying a non-magnetic paint on the non-magnetic support. As the non-magnetic paint used for forming the non-magnetic layer, a paint comprising a powder, a binder and a solvent, or a paint comprising the binder and the solvent is preferably used. Here, the specific surface area of the powder used for the non-magnetic paint is preferably 1 to 1000 m ^2.
/ G, more preferably 5 to 800 m ² / g.

[0012] powder used in the non-magnetic coating, include non-magnetic oxide powder. As the non-magnetic oxide powder, but it if not particularly limited nonmagnetic and acid titanium, acid zinc, calcium oxide, magnesium oxide, Two <br/> tin oxide, silicon dioxide, the non-magnetic chromium oxide , Alumina ,
Acid cerium, corundum, nonmagnetic iron oxide, garnet, garnet, quartzite, Quai picolinimidate earth and the like, medium-<br/> But acid titanium, Alumina, iron oxide or the like of the non-magnetic preferably Used. If necessary, other than non-magnetic oxide powder
Non-magnetic powder such as carbon black, graphite
G, barium sulfate, zinc sulfide, magnesium carbonate, carbonic acid
Calcium, tungsten disulfide, molybdenum disulfide,
Boron nitride, silicon carbide, artificial diamond, silicon nitride,
Molybdenum carbide, boron carbide, tungsten carbide, carbonized
Titanium, dolomite, resinous powder and the like are used. Further, above the non-magnetic oxide powder, in order to improve the dispersibility and the like of the non-magnetic oxide powder may be subjected to a surface treatment described above non-magnetic oxide powder.

When the nonmagnetic layer contains a nonmagnetic oxide powder, the nonmagnetic oxide powder preferably has a particle size of 0.001 to 3 μm, more preferably 0.005 to 2 μm.
μm, most preferably 0.005 to 1.0 μm.
Further, the non-magnetic oxide powder is preferably contained in the non-magnetic layer formed by applying the non-magnetic paint, preferably in the range of 5-99.
It is desirable that the non-magnetic paint is incorporated in the above-mentioned non-magnetic paint so that it is contained in an amount of 30 to 95% by weight, more preferably 50 to 95% by weight.

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.
As the binder, specifically, a vinyl chloride resin, polyester, polyurethane, nitrocellulose,
Epoxy resins, acrylic resins and the like are listed. In addition, in JP-A-57-162128, page 1, upper right column 1
Resins and the like described in line 9 to page 19, lower right column, line 19 and the like can be mentioned. Further, the binder may contain various functional groups and polar groups for crosslinking and improving dispersibility. The amount of the binder used is preferably about 5 to 100 parts by weight based on 100 parts by weight of the nonmagnetic oxide powder,
It is particularly preferred to be 5 to 70 parts by weight.

Examples of the solvent include a ketone solvent, an ester solvent, an ether solvent, an aromatic hydrocarbon solvent, and a chlorinated hydrocarbon solvent. Solvents described on page 3, lower right column, line 17 to page 4, lower left column, line 10 of JP-A-57-162128 are exemplified.

The above-mentioned non-magnetic paint includes a usual magnetic recording medium such as a dispersant, a lubricant, an abrasive, an antistatic agent, a rust inhibitor, a fungicide, and a curing agent such as an amine compound or an acid anhydride. The additives used in the above can be added as necessary. 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 exemplified. .

To prepare the above non-magnetic paint, for example,
The non-magnetic oxide powder and the binder are put into a Nauta mixer or the like together with a part of the solvent and preliminarily mixed to obtain a mixture, and the obtained mixture is kneaded by a continuous pressure kneader or the like, and then the mixture is kneaded. After dilution with a part of the solvent and dispersion treatment using a sand mill or the like, a method of mixing an additive such as a lubricant, filtering, and further mixing the remaining solvent, curing agent and the like can be mentioned.

The magnetic layer provided on the nonmagnetic layer is a layer formed by applying a magnetic paint on the nonmagnetic layer. As the magnetic paint used for forming the magnetic layer, a paint containing powder, a binder, and a solvent as main components is preferably used. Here, the specific surface area of the powder used in the magnetic paint is preferably 1 to 1000 m ² /
g, more preferably 5 to 800 m ² / g. Examples of the powder used in the magnetic paint include a magnetic powder and other powders. Above the magnetic powder include ferromagnetic metal powders. Ferromagnetic iron oxide, ferromagnetic diacid as required
Chromium oxide may be contained.

The ferromagnetic iron oxide is FeOx (1.33).
.Ltoreq.x.ltoreq.1.5) to which metals such as Cr, Mn, Co, and Ni are added. Further, the ferromagnetic chromium dioxide, Na the CrO ₂ or the CrO _2, K, F
Metals such as e and Mn, oxides of the metals, and nonmetallic elements such as P can be used. The ferromagnetic metal powder includes a ferromagnetic metal powder having a metal content of 70% by weight or more and a metal content of at least 80% by weight is at least one ferromagnetic metal (for example, Fe, Co, Ni, or the like). . Specific examples of the ferromagnetic metal powder include, for example,
Fe-Co, Fe-Ni, Fe-Al, Fe-Ni-A
1, Co-Ni, Fe-Co-Ni, Fe-Ni-Al
-Zn, Fe-Al-Si and the like.

In addition, the magnetic powder may include, if necessary,
Rare earth elements and transition metal elements can be included. Further, if necessary, barium ferrite on a micro flat plate and magnetic powder in which a part of Fe atoms thereof are replaced with atoms such as Ti, Co, Zn, and V can be used. As the other powder, the same powder as the nonmagnetic powder can be appropriately selected and used. In addition, the above magnetic
The conductive powder is preferably 5-99% by weight, more preferably 3% by weight, in the magnetic layer formed by applying the magnetic paint.
It is desirable that the compound is contained in an amount of 0 to 95% by weight, most preferably 50 to 95% by weight. Incidentally, the magnetic powder <br/>, in order to improve the dispersibility and the like of the magnetic powder may be subjected to surface treatment described above.

As the binder and the solvent used in the magnetic paint, the same binders and solvents as those used in the non-magnetic paint can be used. Also,
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. Further, the above-mentioned additives used for the above-mentioned non-magnetic paint can also be added to the above-mentioned magnetic paint.

In order to prepare the above magnetic paint, for example, the above magnetic powder and the above binder are put into a Nauter mixer or the like together with a part of the solvent and premixed to obtain a mixture, and 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 polyisocyanate, acid anhydride and amine. Examples thereof include a method of mixing a curing agent such as a compound and the remaining solvent. In the magnetic recording medium according to the present invention, the dry thickness of the magnetic layer is preferably 0.05 to 1.5 μm, more preferably 0.05 to 1.2 μm, and most preferably 0.1 to 0.1 μm.
And the dry thickness of the nonmagnetic layer is preferably 0.5 to 4 μm, more preferably 0.5 to 3.5 μm.
m, most preferably 0.5 to 3 μm.

Thus, in the magnetic recording medium of the present invention, the total surface area α ₁ [m ² / cm ³ ] of all powders contained in the magnetic layer per unit volume is 130 <α ₁ <180, Preferably 135 <α ₁ <180, more preferably 135
<Α ₁ <175, and the total surface area α ₂ [m ² / cm ³ ] of all powders contained in the nonmagnetic layer per unit volume is 10
0 <α ₂ <160, preferably 105 <α ₂ <160,
More preferably, 105 <α ₂ <155, and α ₁ / α
₂ is 0.8 <α ₁ / α ₂ <1.3, preferably 0.8
5 <α ₁ / α ₂ <1.3, more preferably 0.85 <α
₁ / α ₂ <1.25. The above α ₁ , α ₂ and α ₁ /
When alpha ₂ is outside the above range, the surface deteriorates output decreases.

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, the non-magnetic paint and the magnetic paint are subjected to simultaneous multi-layer coating by a wet-on-wet method so that the dry thickness of the non-magnetic layer and the magnetic layer becomes the above-mentioned thickness, respectively. A coating film of a non-magnetic layer and a magnetic layer is formed. Then, for the coating,
After performing a magnetic field orientation treatment, a drying treatment is performed and the film is wound. Thereafter, a calender treatment is performed if necessary, and then 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 disclosed in JP-A-5-73.
No. 883, column 42, line 31 to column 43, line 31, etc., wherein the magnetic paint for forming the magnetic layer is applied before the nonmagnetic paint for forming the nonmagnetic layer dries. A method in which the interface between the non-magnetic layer and the magnetic layer is smoothed and the surface properties of the magnetic layer are also improved, so that dropout is small, high-density recording can be performed, and a coating film (magnetic layer And a non-magnetic layer) having excellent durability.

The magnetic field orientation treatment is performed before the magnetic paint is dried. For example, when the magnetic recording medium of the present invention is a magnetic tape, the magnetic paint is oriented in a direction parallel to the magnetic paint application surface. About 500 Oe or more, preferably about 1000
It can be performed by a method of applying a magnetic field of 10000 Oe, a method of passing a magnetic paint through a solenoid of 1000〜１０10000 Oe or the like in a wet state, or the like.

[0027] The drying treatment is carried out, for example, at 30 to 120 ° C.
In this case, the degree of drying of the coating film can be controlled by controlling the temperature of the gas and the supply amount of the gas.

The above-mentioned calendering treatment can be performed by a super calendering method in which two rolls such as a metal roll and a cotton roll or a synthetic resin roll, a metal roll and a metal roll are passed. Also,
The conditions of the calendering treatment are as follows.
５００500 kg / cm.

The back coat layer provided as necessary is provided on the back surface of the non-magnetic support (the surface on which the non-magnetic layer and the magnetic layer are not provided). This is obtained by applying the back coat paint used for forming the coat layer on the non-magnetic support. The backcoat paint is obtained by appropriately selecting and mixing the nonmagnetic powder, binder, dispersant, lubricant, curing agent, solvent, and the like described in detail in the nonmagnetic paint. The above-mentioned back coat paint can be prepared by a generally known method for producing a back coat paint.

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. Further, the application of the non-magnetic paint and the magnetic paint can also be carried out by a generally known sequential coating method.

[0031]

EXAMPLES 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>

[Preparation of Magnetic Coatings A to F, Non-Magnetic Coatings G to M, and Back Coating Coatings] In each of the following coating formulations, components excluding polyisocyanate, fatty acid, and fatty acid ester were added together with a part of the solvent. The mixture was charged into a Nauta mixer and preliminarily mixed to obtain a mixture, and the obtained mixture was kneaded by a continuous pressure kneader. Then, each was diluted with a part of the solvent, and dispersed by a sand mill. Then, the fatty acid and the fatty acid ester were mixed, filtered, and the remaining solvent and the polyisocyanate were further mixed to obtain a magnetic coating material A.
To F, non-magnetic paints G to M, and a back coat paint were obtained.

(Blending of magnetic paints A to F) Magnetic paints A to F
Were as shown in the following [Table 1].

[0035]

[Table 1]

In the table, the metal powder, carbon 1, carbon 2, alumina, binder, lubricant and solvent are as follows.・ Metal powder; needle-shaped metal magnetic powder mainly composed of iron (Fe: A
l: Ca: Si: Ni: Co = 85: 2: 1: 1: 3:
8, coercive force 1860 Oe, saturation magnetization 137 emu / g,
The average major axis length 0.1 [mu] m, a specific surface area of 60 m ² / g) · Carbon 1; specific surface area 200 meters ² / g · Carbon 2; specific surface area 1000 m ² / g · alumina; average particle size 0.3 [mu] m, a specific surface area of 11m ² / g Binder: sulfonic acid group-containing vinyl chloride resin (sulfonic acid group content: 1.5 × 10 ⁻⁴ eq / g), sulfonic acid group-containing polyurethane (GPC number average molecular weight: 2500)
0, sulfonic acid group content 1.9 × 10 ⁻⁴ eq / g), and polyisocyanate [Nihon Polyurethane Industry Co., Ltd.
Manufactured, trade name "Coronate L"] [weight ratio 10:10:
4] Lubricant; n-butyl stearate and stearic acid (weight ratio 1: 1) Solvent: methyl ethyl ketone, toluene and cyclohexanone (weight ratio 1: 1: 1)

(Blending of non-magnetic paints G to M) Non-magnetic paint G
The compositions of ＭM were as shown in Table 2 below.

[0038]

[Table 2]

In the table, α-Fe ₂ O ₃ , TiO ₂ , carbon 1, carbon 2, alumina, binder, lubricant and solvent are as follows. Α-Fe ₂ O ₃ ; average major axis length 0.07 μm, specific surface area 39 m ² / g ・ TiO ₂ ; rutile type, average particle diameter 0.03 μm, specific surface area 41 m ² / g ・ carbon 1; [Table 1 • Carbon 2; same as carbon 2 in [Table 2] • Alumina: average particle diameter 0.3 μm, specific surface area 11 m ² / g • Binder: vinyl chloride resin containing sulfonic acid group (sulfonic acid group) Content 1.5 × 10 ⁻⁴ eq / g), sulfonic acid group-containing polyurethane (GPC number average molecular weight 2500
0, sulfonic acid group content 1.9 × 10 ⁻⁴ eq / g), and polyisocyanate [Nihon Polyurethane Industry Co., Ltd.
Manufactured, trade name "Coronate L"] [weight ratio 10:10:
4] Lubricant; n-butyl stearate and stearic acid (weight ratio 1: 1) Solvent: methyl ethyl ketone, toluene and cyclohexanone (weight ratio 1: 1: 1)

(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 K.K.) 20 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 Parts 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

[Production of Magnetic Recording Medium] The non-magnetic coating material G and the magnetic coating material A were dried on the surface of a non-magnetic support (polyethylene terephthalate film, film thickness: 10 μm) in a thickness of 2.5 μm and 0.2 μm, respectively. Simultaneous multi-layer coating was performed by a wet-on-wet method so as to have a thickness of 3 μm to form a coating film of a nonmagnetic layer and a magnetic layer. Next, the coating film was passed through a 5000 Oe solenoid while in a wet state to perform a magnetic field orientation treatment, dried at 80 ° C., and wound up. Then, 85 ° C, 350kg
After performing a calendering process under the condition of / cm to form a non-magnetic layer and a magnetic layer, a back coat paint is applied on the back surface of the magnetic support so as to have a dry thickness of 0.5 μm.
After performing a drying treatment at 0 ° C., it was wound up. Then 5
Aging treatment was performed at 0 ° C. for 16 hours, slit to a 3.81 mm width, and a 3.81 mm wide magnetic tape was obtained. The output (4.7 MHz) of the obtained magnetic tape was measured according to the following measuring method. The results are shown in [Table 3].

[Measurement Method] Output (4.7 MHz) The obtained 3.81 mm wide magnetic tape was loaded into a DAT cassette to obtain a test DAT tape cassette. The obtained test DAT tape cassette was inserted into MediaLogic.
Product name "Tape Evaluator Mode"
l 4500 ”and 4.7M on the magnetic tape
Hz signal was recorded and the output (reproduced output) when this was reproduced was measured. The recording wavelength of 4.7 MHz is 0.6.
It was 7 μm.

<Example 2 and Comparative Examples 1 to 5> The procedure of Example 1 was repeated except that the magnetic paint and the non-magnetic paint shown in Table 1 were used as the magnetic paint and the non-magnetic paint, respectively. The magnetic tape thus obtained was evaluated according to the method of Example 1. The results are shown in [Table 3].

[0044]

[Table 3]

[0045]

As described above, the magnetic recording medium of the present invention can have a high density and has particularly excellent output characteristics.

[Brief description of the drawings]

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

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-17042 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/842 G11B 5/70

Claims (1)

(57) [Claims] A non-magnetic support, at least a non-magnetic layer provided on the magnetic support, and a magnetic layer provided on the non-magnetic layer, wherein the non-magnetic layer and the magnetic layer Ue
In the magnetic recording medium formed by Tsu preparative-on-wet method, the non-magnetic layer and the magnetic layer contains the their respective powders, the powder contained in the magnetic layer is strong Including magnetic metal powder
The powder contained in the non-magnetic layer is a non-magnetic oxide
It includes a powder (total volume of the total surface area / the magnetic layer of Zenkonatai) total surface area alpha ₁ of the total powder the magnetic layer contains per unit volume [m ²
/ Cm ³ ] is 130 <α ₁ <180, and the total surface area α _{2 of} all powders contained in the non-magnetic layer per unit volume (total surface area of all powders / total volume of the non-magnetic layer)
[M ² / cm ³ ] is 100 <α ₂ <160, and α ₁ / α ₂ is 0.8 <α ₁ / α ₂ <1.3.