JP3006334B2 - Manufacturing method of magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium and, more particularly, to a method for producing a back layer having excellent running stability, conductivity, light shielding properties, and surface smoothness.

[0002]

2. Description of the Related Art Generally, magnetic recording media such as high-grade video tapes, digital audio tapes, and computer tapes have a back layer provided on a surface opposite to a magnetic surface with respect to a support. The back layer is required to provide running stability, an antistatic effect, and a light shielding effect for detecting the end of the tape. For this reason, generally, the back layer has a color.
It has been practiced to disperse Bon Black to impart conductivity and light shielding properties.

In recent years, as the recording density has increased, the smoothness of the magnetic layer has progressed, and the demand for smoothness has also increased in the back layer. That is, if the smoothness of the back layer is not sufficient, the unevenness of the back layer is transferred to the magnetic layer, causing problems such as dropout and a decrease in the SN ratio. Further, with the recent thinning of magnetic tapes, demands for the conductivity and light-shielding properties of the back layer are increasing.

In order to obtain sufficient smoothness, conductivity and light-shielding properties in the back layer, it is necessary to disperse carbon black having a relatively small particle size in a high concentration and high concentration. Large surface area and oil absorption. Therefore, as a disperser having a high shearing force, for example, a method of using a roll mill, a kneader or the like to perform pre-mixing to crush strong aggregated particles of carbon black has been adopted. -Without sufficient adsorption of high molecular weight components such as-, sufficient smoothness cannot be obtained,
In addition, the fluidity of the paint and the stability over time of the paint that are sufficient for thin film coating have not been obtained.

[0005]

SUMMARY OF THE INVENTION In order to solve these problems, as a result of investigations aimed at obtaining a highly dispersed state of a filler containing carbon black required for a back layer of a magnetic recording medium, The following method for producing a magnetic recording medium has been invented.

[0006]

SUMMARY OF THE INVENTION The present invention is a method of manufacturing a magnetic recording medium having a magnetic layer and a back layer on opposite sides of a support. First, a basic organic dye compound represented by the following general formulas (1) and (2) is kneaded and dispersed with a filler containing carbon black as a component of the back layer to form a solid chip. At this time, it is desirable that a solvent of 15% by weight or less as a solvent remains in the chip. Then, it has been found that the above problem can be solved by dissolving the mixture in a solvent and then dispersing the mixture in a sand mill to form a backcoat paint.

General formula (1)

[0008]

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[0009] wherein, Q; organic pigment residue, X; direct _{bond, -CONH-Y 2 -, -} SO 2 NH-Y
₂ - or _{-CH 2 NHCOCH 2 NH-Y 2} -, (Y 2; an optionally substituted alkylene group or an arylene group) Y _1; -NH- or -O-, (Y ₃ ; —NH— or —O—), or n = 1
R ₁ , R ₂ ; each independently may be a substituted or unsubstituted alkyl group, or at least a heterocycle may be formed by R ₁ and R ₂ .

M represents an integer of 1 to 6; n represents an integer of 1 to 4; General formula (2)

[0011]

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Wherein Q: organic dye residue X; direct bond, -CONH-Y _1- , -SO ₂ NH-Y
₁ -, or _{-CH 2 NHCOCH 2 NH-Y 1} - (Y 1; an optionally substituted alkylene group or an arylene group) Y; substituent represented by the following formula

[0013]

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[Wherein, R₁, R_Two; Independently substituted or unsubstituted al
Kill group or R₁And R _TwoForms at least a heterocyclic ring with
May be. Y_TwoA hydrogen atom, a halogen atom, ─NO_Two, ─NH_TwoAlso
Or SO_ThreeH is shown.

K: an integer of 1-4, m; an integer of 1-6,
n; represents an integer of 1 to 4; The organic dye residues in the above general formula include phthalocyanine dyes, azo dyes, anthraquinone dyes, quinacridone dyes, dioxazine dyes, anthrapyrimidine dyes, anthanthrone dyes, indanthrone dyes, and flavanthrone. Dyes, perylene dyes, perinone dyes, thioindigo dyes,
Pigments or dyes such as isoindolinone dyes and triphenylmethane dyes.

[0016] The binder may be selected from known materials conventionally used for magnetic recording media, for example, polyurethane elastomer, nitrified cotton, vinyl chloride, vinyl chloride-vinyl acetate copolymer, vinylidene chloride copolymer, and the like. Epoxy resin, polyamide resin, acrylate resin, methacrylic resin, polyester resin, urethane resin or
There are mixtures of these resins.

The roll mill of the present invention includes two rolls. It is only necessary to paint the components of the back layer containing the organic dye compound with a disperser such as a sand mill.
A sufficient shearing force to crush the agglomerated particles of carbon cannot be obtained, and the desired quality cannot be obtained. In addition,
In the method of making solid chips using a mill, carbon can be crushed into primary particles by high shear force.
The finely divided carbon is not accompanied by sufficient adsorption of high molecular weight components and cannot be said to be in a stable dispersed state. According to the present invention, the presence of an organic dye compound under a high shearing force in a roll mill enables the adsorption of a high molecular weight component sufficient to prevent reagglomeration of carbon, thereby improving quality and productivity. Has been found to be able to achieve improvement.

The organic dye compound in the present invention may be simply mixed with the filler and the binder containing carbon black at the time of roll mill dispersion, but the organic dye compound and the binder are dispersed before the roll mill dispersion. By preliminarily heating and mixing in a dissolved state, not only the affinity between the basic substituent of the organic dye compound and the polar group of the binder is improved, but also it is uniform and prompt with the filler such as carbon. , The quality and productivity are improved.

The mixing ratio of the organic dye compound and the binder is 0.1 part to 30 parts by weight with respect to 100 parts by weight of the binder.
Parts by weight are preferred. The mixing ratio of the filler containing carbon black was 100 parts by weight of the above-mentioned mixture.
50 to 150 parts by weight are preferred. The surface smoothness of the back layer formed by adding the organic dye compound represented by the general formula and fatty acids such as stearic acid, palmitic acid and oleic acid and metal salts of fatty acids or other known surfactants in combination. It is possible to further enhance the performance.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments. In the example,
“Parts” and “%” are “parts by weight” and “% by weight”, respectively. Example 1 Cobalt-containing γ-Fe ₂ O ₃ 100 parts Vinyl chloride resin (MR-110, Nippon Zeon Co., Ltd.) 10 parts Urethane resin (Nipporan 2301, Nippon Polyurethane Co., Ltd.) 10 parts Alumina 5 parts Toluene 120 parts Methyl ethyl ketone 120 parts Cyclohexanone 60 parts 3 parts of an isocyanate compound (Coronate L, Nippon Polyurethane Co., Ltd.), 1 part of myristic acid, and 1 part of n-butyl stearate are added to a magnetic coating material obtained by dispersing the above composition by a sand mill, and a thickness of 10 μm is added. After coating, orientation, and drying on a polyethylene terephthalate support, mirror finishing by calendering was performed to form a magnetic coating film having a thickness of 3 μm.

Next, the following composition was heated and stirred at 60 ° C. for 1 hour in a stirring vessel to obtain a solution of the organic dye compound. (Solution of organic dye compound) Nitrified cotton (Cellline FM200S, Daicel Chemical Industries, Ltd.) 100 parts Urethane resin (Nipporan 2301, Nippon Polyurethane Co., Ltd.) 100 parts Organic dye compound 5 parts

[0022]

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The following composition containing the obtained solution was added to
Using a mill, the mixture was processed 20 times to obtain solid chips. Dissolved solution of organic dye compound 205 parts Carbon black (average primary particle diameter 17 mμ) 100 parts Next, the obtained chip was dissolved in a resin and a solvent and dispersed using a sand mill to obtain a backcoat paint. Further, 20 parts of Coronate L was added, coated on the surface opposite to the magnetic layer and dried to form a back layer having a thickness of 0.7 μm, and then cut into イ ン チ inch width to prepare a magnetic tape.

Chip (solid content: 94%) 170 parts Nitrified cotton (Cell Line FM200S, Daicel Chemical Industries, Ltd.) 100 parts Urethane resin (Nipporan 2301, Nippon Polyurethane Co., Ltd.) 50 parts Methyl ethyl ketone 400 parts Toluene 400 parts Cyclohexanone 200 Part Example 2 A magnetic recording medium was obtained in the same manner as in Example 1 except that the organic dye compound was changed to Chemical formula 8.

[0025]

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Example 3 A magnetic recording medium was obtained in the same manner as in Example 1, except that the organic dye compound was changed to Chemical formula 9.

[0027]

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Example 4 A magnetic recording medium was obtained in the same manner as in Example 1 except that the organic dye compound was changed to Chemical Formula 10.

[0029]

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Example 5 A magnetic recording medium was obtained in the same manner as in Example 1 except that the organic dye compound was changed to Chemical formula 11.

[0031]

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Example 6 A magnetic recording medium was obtained in the same manner as in Example 1, except that the organic dye compound was changed to Chemical formula 12.

[0033]

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Example 7 A magnetic recording medium was obtained in the same manner as in Example 1, except that the organic dye compound was changed to Chemical formula 13.

[0035]

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Comparative Example 1 A magnetic tape was prepared in the same manner as in Examples 1 to 7, except that the organic dye compound was omitted from the method of manufacturing the back layer composition in Examples 1 to 7. Comparative Example 2 In the process for producing the back layer compositions of Examples 1 to 7, Chemical Formula 7 was used as an organic dye compound, and the mixture was subjected to sand mill dispersion and magnetic recording.
Created

The center line surface roughness Ra, 6 of the back layer of the magnetic tape prepared in Examples 1 to 7 and Comparative Examples 1 and 2 above.
Table 1 shows the results of measuring the 0 ° specular reflectance, the surface electrical resistance, and the abrasion resistance, and the results of evaluating the coating fluidity and the temporal stability of the back layer composition. The center line surface roughness Ra was measured with a stylus type surface roughness measuring instrument at a cutoff value of 0.08 based on JIS-B-0601-1982. The abrasion resistance was determined by observing the degree of scratching after running 200 passes with a tape running tester.

As is clear from Table 1, the coating material obtained by kneading and dispersing the organic dye compound according to the present invention and a carbon book using a roll mill to form a solid chip and then forming a coating has excellent fluidity and stability over time. It can be seen that the back layer coated with is excellent in smoothness and abrasion resistance.

[0039]

[Table 1]

[0040]

According to the present invention, by improving the dispersibility of carbon black, a back layer having good surface smoothness is formed, and the characteristics required for a magnetic recording medium are improved.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-248177 (JP, A) JP-A-4-79018 (JP, A) JP-A-3-214425 (JP, A) JP-A-62-1987 134824 (JP, A) JP-A-62-18623 (JP, A) JP-A-62-6435 (JP, A) JP-A-62-3342 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) G11B 5/84 G11B 5/704 CA (STN) CAOLD (STN) REGISTRY (STN) WPIDS (STN)

Claims (2)

(57) [Claims] 1. A method for producing a magnetic recording medium having a magnetic layer and a back layer on opposite sides of a support, comprising: a filler containing an organic dye compound having a basic terminal group and carbon black; and a binder. A method for manufacturing a magnetic recording medium, comprising kneading and dispersing into a solid chip using a roll mill, forming a coating, and applying a coating to form a back layer. 2. An organic dye compound having a basic terminal group.
Is represented by the following general formula (1) or (2).
A method for manufacturing a magnetic recording medium. General formula (1)[Wherein, Q: organic dye residue, X: direct bond, -CONH-Y_Two−, −SO_TwoNH-Y
_Two-Or -CH_TwoNHCOCH_TwoNH-Y_Two−, (Y_TwoAn alkylene group or an ant which may have a substituent
-Lene group) Y₁-NH- or -O-,(Y_Three-NH- or -O-), or n = 1
In the case of, it may be -NH-XQ, R₁, R_Two; Independently substituted or unsubstituted al
Kill group or R₁And R_TwoForms at least a heterocyclic ring with
May be. m represents an integer of 1 to 6; n represents an integer of 1 to 4; General formula (2)[Wherein Q: organic dye residue X; direct bond, -CONH-Y₁−, −SO_TwoNH-Y
₁-Or -CH_TwoNHCOCH_TwoNH-Y₁− (Y₁An alkylene group or an ant which may have a substituent
-Ylene group) Y; a substituent represented by the following formulaEmbedded image[Where R₁, R_Two; Independently substituted or unsubstituted al
Kill group or R₁And R _TwoForms at least a heterocyclic ring with
May be. Y_TwoA hydrogen atom, a halogen atom, ─NO_Two, ─NH_TwoAlso
Or SO_ThreeH is shown. k; an integer of 1 to 4, m; an integer of 1 to 6, n; an integer of 1 to 4
Represents a number. ]