JP2005222630A - Coating material to form non-magnetic layer and coating material to form back layer on magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing method of carbon blacks which are excellent in dispersibility, stability, and physical properties for the coated film for improving the flatness and the physical properties of the film of the non-magnetic layer and the back layer of a multi layered magnetic recording medium. <P>SOLUTION: This is a coating material for a magnetic recording medium to form a non-magnetic layer and a magnetic layer in this order on a surface of a base plate and to form a back layer on the other surface. This coating material is a non-magnetic layer forming paint which contains adsorption processed carbon blacks obtained by processing carbon blacks and an organic dye derivative having acidity or a basic fuctional group or a triazine derivative having acidity or a basic fuctional group in liquid. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a nonmagnetic layer-forming coating material or a back layer-forming coating material used for a magnetic recording medium.

  In recent years, with increasing recording capacity and image quality of magnetic recording media, particularly data storage tapes and video tapes, higher recording density has been achieved by shortening the recording wavelength and narrowing the recording track width. Various improvements have been made to improve the recording characteristics of the magnetic recording medium, such as improving the magnetic characteristics of the ferromagnetic powder and smoothing the surface. As the wavelength is shortened, the problem of self-demagnetization loss and thickness loss that the output decreases as the thickness of the magnetic layer increases is increasing, and the magnetic layer has been required to be thinner.

  However, if the magnetic layer is thinned, it is easily affected by the support and deteriorates the electromagnetic conversion characteristics. For this reason, a so-called multilayer coating type magnetic recording medium in which a nonmagnetic layer and a magnetic layer are laminated in this order on a support is increasingly used. As a result, the surface shape of the support hardly appears on the surface of the magnetic layer, and the smoothness of the magnetic layer thin film can be improved. Currently, the end of a magnetic tape of a magnetic recording medium such as a video tape is detected by detecting a difference in light transmittance. If the light transmittance of the magnetic recording layer increases due to the thinning of the magnetic recording medium and the formation of fine particles of the ferromagnetic powder dispersed in the magnetic recording medium, it becomes difficult to detect the end of the tape. The light transmittance is reduced by adding black or the like. Further, if the surface electrical resistance value of the magnetic recording medium is high, cutting scraps, dusts and the like adhere to the surface of the magnetic recording medium during the manufacture and use of the magnetic recording medium due to charging, and as a result, the dropout increases. Therefore, carbon black is also used for the purpose of reducing the surface electrical resistance value of the magnetic recording medium.

On the other hand, the magnetic recording tape is provided with a back layer for the purpose of imparting running stability. Also in the back layer, carbon black is used for preventing charging due to the decrease in surface electrical resistance and detecting the end of the magnetic tape.
As described above, carbon black plays an important role in both the non-magnetic layer and the back layer in the multilayer magnetic recording medium. However, in order to perform the function while smoothing the surface of the magnetic layer, the carbon black is finely dispersed. There is a need to. However, the finer the carbon black, the more difficult it is to stabilize the dispersion. If the smoothness of the coating surface of the formed nonmagnetic layer or back layer is insufficient, the smoothness of the magnetic layer thin film may be disturbed. This leads to deterioration of recording characteristics.

  Accordingly, various studies have been conducted to improve the dispersibility of carbon black used for the nonmagnetic layer and the back layer. Patent Document 1 contains carbon black and a specific organic dye compound in the back layer, and Patent Document 2 contains carbon black and a specific organic dye compound in Patent Document 2, thereby improving the dispersibility of carbon black and improving smoothness. It is disclosed.

JP 61-224136 A JP-A-1-232524

  However, simply using these organic dye compounds as a dispersant may not provide sufficient smoothness or stability over time of the paint, especially when applied with aged paint. There were problems such as limited time limit and storage environment. As an action mechanism of this organic dye derivative, an organic dye derivative having a polar functional group and a resin having a reverse polarity to the functional group of the organic dye derivative form a salt by acid-base interaction and dissolve in the solvent, It is considered that this salt is adsorbed to carbon black using the organic dye portion as an adsorption site, and the resin layer exhibits a steric repulsion effect to stabilize the dispersion of carbon black. In this method using an organic pigment derivative, since the resin for coating can be used as a dispersion resin as it is in most cases, there is no compatibility problem caused by the dispersant, and the versatility is excellent. However, when used in combination with a resin in a non-aqueous system, the organic dye portion is also solvated, so the solubility of the organic dye derivative is high, the adsorption rate to carbon black is poor, and the surface required for dispersion stabilization In order to achieve the coverage, it is necessary to increase the treatment amount of the organic dye derivative, and as a result, the unadsorbed organic dye derivative increases. This unadsorbed organic dye derivative has adverse effects such as reduced stability over time, reduced smoothness, adverse effects such as water resistance and bleed, reduced pot life due to the action of a curing agent such as isocyanate compounds, and decreased coating strength. There was a case.

  The present invention provides a method for treating carbon black that is excellent in dispersibility, paint stability, and coating film physical properties in order to enhance the smoothness and coating film physical properties of the nonmagnetic layer and back layer of the multilayer magnetic recording medium. is there.

That is, the present invention is a coating for forming a nonmagnetic layer of a magnetic recording medium having a nonmagnetic layer and a magnetic layer laminated in this order on one side of a support and having a back layer on the other side. An organic dye derivative having an acidic or basic functional group or a triazine derivative having an acidic or basic functional group and carbon black in a liquid, an organic dye skeleton part of the organic dye derivative or a triazine part or triazine of the triazine derivative When the derivative has an aryl group or an anthraquinone residue, the adsorption treatment is performed in such an amount that the adsorption area when the triazine part and the aryl group or anthraquinone residue part are assumed to be adsorption sites is 50% or more of the BET specific surface area of carbon black. A paint for forming a nonmagnetic layer, comprising adsorption-treated carbon black.
The present invention also provides a coating for forming a back layer of a magnetic recording medium having a magnetic layer on one side of the support and a back layer on the other side, the coating having an acidic or basic functional group. An organic dye derivative or a triazine derivative having an acidic or basic functional group and carbon black, and the organic dye skeleton part of the organic dye derivative or the triazine part or triazine derivative of the triazine derivative has an aryl group or an anthraquinone residue. In the case, it is characterized in that it contains an adsorption-treated carbon black that is adsorbed in an amount such that the adsorption area is 50% or more of the BET specific surface area of the carbon black, assuming that a triazine moiety and an aryl group or an anthraquinone residue moiety are adsorption sites. The back layer forming coating.
Furthermore, the present invention is a coating composition for forming a nonmagnetic layer or a coating composition for forming a back layer in which the amount of unadsorbed organic dye derivative or triazine derivative is 0.005 g or less per 1 g of carbon black. Furthermore, the present invention is a coating for forming a non-magnetic layer or a coating for forming a back layer, wherein the adsorption treatment uses a media-type disperser. Furthermore, the present invention is a coating composition for forming a nonmagnetic layer or a coating composition for forming a back layer, comprising a resin having a functional group having a polarity opposite to that of the functional group of the organic dye derivative or the triazine derivative.
The present invention also provides a magnetic recording medium having a nonmagnetic layer or a back layer formed from the above-mentioned paint.

  The adsorption-treated carbon black in the present invention has excellent dispersibility, a non-magnetic layer-forming coating material and a back-layer-forming coating material having excellent smoothness and stability over time, and a coating film for the non-magnetic layer and the back layer. A magnetic recording medium with improved strength and excellent smoothness and running durability can be provided.

  The present invention will be described in detail below. The magnetic recording medium of the present invention has a magnetic layer on one side of a nonmagnetic support, a back layer on the opposite side, and a nonmagnetic layer and a magnetic layer are laminated in this order on one side of the nonmagnetic support. There is a so-called multilayer magnetic recording medium having a back layer on the opposite surface.

  As the support in the present invention, polyethylene terephthalate, polyethylene naphthalate, synthetic resin films such as polyamide, polyamideimide, polyimide and polycarbonate, metal films such as aluminum and stainless steel, and various papers that are currently widely used for magnetic recording media can be used. The thickness is 1.0 to 200 microns, preferably 2 to 20 microns. As a method of laminating the nonmagnetic layer and the magnetic layer on the support, the magnetic layer is provided while the nonmagnetic layer and the magnetic layer are wet or simultaneously, or after the nonmagnetic layer is applied. There are a so-called wet-on-wet method that is sequential wet coating and a wet-on-dry method in which a magnetic layer is provided after the nonmagnetic layer is dried.

The magnetic layer in the present invention can be obtained by applying and drying a magnetic paint in which ferromagnetic powder is dispersed in a binder, or by forming a metal thin film by vapor deposition or sputtering. The ferromagnetic powder is not particularly limited as long as it has magnetic properties such as metal magnetic powder, iron oxide, iron carbide, barium ferrite, and the shape can be arbitrarily selected from spherical, needle-like, plate-like and the like. These ferromagnetic powders may be surface-treated with an inorganic compound or an organic compound as necessary. The magnetic layer can contain carbon black and additives such as conventionally known lubricants, abrasives, and dispersants. The metal thin film formed by vapor deposition or sputtering includes those made of ferromagnetic metals such as Fe, Co, and Ni, and alloys thereof, and may be a single layer or a multilayer. Further, a protective film by sputtering, CVD method or the like may be formed on the upper layer of the vapor deposition layer, and a conventionally known lubricating layer may be formed.
The nonmagnetic layer in the present invention has a nonmagnetic powder containing at least carbon black and a binder resin, and examples of nonmagnetic powder other than carbon black include inorganic materials such as metal oxides, metal carbonates, metal nitrides, and metal carbides. There are compounds. Specific examples include titanium oxide, iron oxide, zinc oxide, tin oxide, magnesium oxide, zirconium oxide, barium sulfate, calcium carbonate, alumina, silica, silicon nitride, silicon carbide and the like. The average particle size of these nonmagnetic powders is 5 nm to 1000 nm, but 10 nm to 500 nm is particularly preferable. When the nonmagnetic particles are spherical, the average particle size is preferably 80 nm or less, and when they are acicular particles, the average major axis is preferably 300 nm or less. These nonmagnetic powders may be surface-treated with an inorganic compound or an organic compound as necessary. In particular, it is preferable to carry out coating treatment with one or more selected from hydroxides or oxides of aluminum and hydroxides or oxides of silicon. The nonmagnetic layer can contain conventionally known additives such as lubricants, abrasives, and dispersants.

  The back layer in the present invention has at least carbon black and a binder resin, and one or more nonmagnetic powders other than carbon black may be used. Examples of nonmagnetic powders include graphite, titanium oxide, iron oxide, zinc oxide, tin oxide, magnesium oxide, zirconium oxide, barium sulfate, calcium carbonate, alumina, silica, silicon nitride, silicon carbide, and the like. In addition, by combining two or more types of carbon black or nonmagnetic powder having an average primary particle size of 10 to 50 nm and carbon black or nonmagnetic powder having an average primary particle size of 50 to 500 nm, the friction coefficient is adjusted and smoothness and running properties are adjusted. Can be balanced. Further, the back layer may contain conventionally known additives such as a dispersant, a lubricant and an antifungal agent.

As the binder resin used for the nonmagnetic layer, magnetic layer, and back layer, conventionally known resins used for magnetic recording media can be used. For example, polymers or copolymers containing vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid ester, acrylonitrile, styrene, vinyl vinylal, vinyl acetal, etc. as structural units, polyurethane resins, polyester resins, phenol resins , Epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicon resins, and nitrified cotton. Preferred binders are vinyl chloride resins, polyurethane resins, nitrified cotton, phenoxy resins, polyvinyl butyral resins, alone or in combination, particularly preferably polyurethane resins or combinations of nitrified cotton and polyurethane resins, vinyl chloride resins and polyurethane. It is a combination of resins. As the polyurethane resin, known ones such as polyester polyurethane, polyether polyurethane, polycarbonate polyurethane, polycaprolactone polyurethane can be used. The -COOM These binder _{resins, -SO 3 M, -OSO 3 M} , -PO (OM) 2 (M per above hydrogen or an alkali metal), - OH, -NRn (R is hydrogen or a hydrocarbon ), At least one polar group selected from an epoxy group, a shobetaine group and the like is preferably introduced. Moreover, you may introduce | transduce into these binders the unsaturated group bridge | crosslinked with an ultraviolet-ray or an electron beam. These resins may be combined with a polyisocyanate as a crosslinking agent. Polyisocyanates include tolylene diisocyanate, 4-4 ′ diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, orthotoluidine diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate and the like, and isocyanates blocked with so-called blocking agents. In addition, products of these isocyanates and polyalcohols, polyisocyanates formed by condensation of isocyanates, and the like can be used. These isocyanates are three-dimensionally cross-linked by reacting with the polar group in the binder, and have the effect of increasing the strength and durability of the coating film.

  Various carbon blacks such as commercially available furnace black, channel black, thermal black, and acetylene black can be used as the carbon black subjected to the adsorption treatment used in the present invention. Carbon black that has been subjected to various pretreatments (gas phase plasma treatment, liquid phase oxidation treatment, etc.) that are usually performed can also be used. Further, the carbon black used in the present invention may be in the form of a powdery product or a granular product.

  In view of the adsorptivity and desorption properties of the organic dye derivative or triazine derivative, neutral carbon having fewer surface functional groups is preferred. Further, the particle size of carbon black is preferably 5 to 1000 nm, and particularly preferably 10 to 500 nm, as in the particle size range of carbon black used for ordinary inks and paints. However, the particle size referred to here indicates an average primary particle size measured with an electron microscope or the like, and the physical property values are generally used to represent the physical characteristics of carbon black.

The organic dye derivative having a basic functional group and the triazine derivative having a basic functional group used in the present invention are represented by the following general formula (1) or (3).
General formula (1)

式中の記号は下記の意味を表す。
Ｑ₁；有機色素残基、アントラキノン残基またはアミノ基を有するアリール基
Ｘ_１；直接結合，−ＣＯＮＨ−Ｙ_２−，−ＳＯ₂ ＮＨ−Ｙ_２- または−ＣＨ₂ ＮＨＣＯＣＨ₂ＮＨ−Ｙ_１ −（Ｙ_２；置換基を有してもよいアルキレン基またはアリーレン基を表す。アリーレン基の例としてはフェニレン基、ナフチレン基等がある。）
Ｙ_１；−ＮＨ−または−Ｏ−
Ｚ_１；水酸基、アルコキシ基または下記一般式（２）で示される基で、ｎは１〜４の整数を表す。またｎ＝１の場合、−ＮＨ−Ｘ_１−Ｑ_１であってもよい。
Ｒ_１、Ｒ_２；それぞれ独立に置換もしくは無置換のアルキル基
ｍ；１〜６の整数
一般式（２）

The symbol in a formula represents the following meaning.
Q ₁ ; aryl group having an organic dye residue, anthraquinone residue or amino group X ₁ ; direct bond, —CONH—Y ₂ —, —SO ₂ NH—Y ₂ — or —CH ₂ NHCOCH ₂ NH—Y ₁ — (Y ₂ represents an alkylene group or an arylene group which may have a substituent. Examples of the arylene group include a phenylene group and a naphthylene group.)
Y ₁ ; —NH— or —O—
Z ₁ ; a hydroxyl group, an alkoxy group or a group represented by the following general formula (2), and n represents an integer of 1 to 4. In the case of n = 1, it may be —NH—X ₁ -Q ₁ .
R ₁ and R ₂ ; each independently a substituted or unsubstituted alkyl group m; an integer of 1 to 6 General Formula (2)

式中の記号は下記の意味を表す。
Ｙ₃；−ＮＨ−または−Ｏ−
Ｒ_３、Ｒ_４；それぞれ独立に置換もしくは無置換のアルキル基またはＲ_３とＲ_４ とが一体となって形成されたヘテロ環。
ｏ；１〜６の整数。
一般式（３）
Ｑ₂−（−Ｘ_２−Ｙ_４）_ｐ
式中の記号は下記の意味を表す。
Ｑ₂；有機色素残基またはアントラキノン残基
Ｘ_２；直接結合、−ＣＯＮＨ−Ｙ_５−，−ＳＯ₂ＮＨ−Ｙ_５−または−ＣＨ₂ＮＨＣＯＣＨ₂ＮＨ−Ｙ_５−（Ｙ_５は置換基を有してもよいアルキレン基またはアリーレン基を表す。アリーレン基の例としてはフェニレン基、ナフチレン基等がある。）
Ｙ_４；下記一般式（４）で示される基
ｐ；１〜４の整数。

一般式（４）

The symbol in a formula represents the following meaning.
Y ₃ ; —NH— or —O—
R ₃ and R ₄ each independently a substituted or unsubstituted alkyl group or a heterocycle formed by combining R ₃ and R ₄ together.
o; an integer of 1-6.
General formula (3)
_{Q 2 - (- X 2 -Y} 4) p
The symbol in a formula represents the following meaning.
Q ₂ ; organic dye residue or anthraquinone residue X ₂ ; direct bond, —CONH—Y ₅ —, —SO ₂ NH—Y ₅ — or —CH ₂ NHCOCH ₂ NH—Y ₅ — (Y ₅ represents a substituent) Represents an alkylene group or an arylene group which may have an example, and examples of the arylene group include a phenylene group and a naphthylene group.
Y ₄ ; group p represented by the following general formula (4); an integer of 1 to 4.

General formula (4)

式中の記号は下記の意味を表す。
Ｒ_５、Ｒ_６；それぞれ独立に置換もしくは無置換のアルキル基。
ｑ；１〜６の整数。

The symbol in a formula represents the following meaning.
R ₅ and R ₆ each independently represents a substituted or unsubstituted alkyl group.
q; an integer of 1 to 6.

Examples of the organic dye residue in Q ₁ of the general formula (1) and Q ₂ of (3) include phthalocyanine dyes, azo dyes, quinacridone dyes, dioxazine dyes, anthrapyrimidine dyes, anthanthrone dyes, Examples include pigments or dyes such as danslon dyes, flavanthrone dyes, perylene dyes, perinone dyes, thioindico dyes, isoindolinone dyes, and triphenylmethane dyes. Examples of the aryl group having an amino group in Q ₁ of the general formula (1) include an aminophenyl group and an aminonaphthyl group. At this time, in addition to the amino group, the benzene ring can be substituted at other substitutable positions. You may have a substituent in any one of a halogen group, an amino group, a nitro group, a hydroxyl group, a carboxyl group, a sulfonic acid group, an alkoxy group, a substituted or unsubstituted alkyl group.

The organic dye derivative having an acidic functional group and the triazine derivative having an acidic functional group used in the present invention are represented by the following general formula (5) or (6).
General formula (5)

式中の記号は下記の意味を表す。
Q₃；有機色素残基、またはアントラキノン残基、または置換基を有していてもよい複素環、または置換基を有していてもよい芳香族環
R₇；−Ｏ−Ｒ_８、−ＮＨ−Ｒ_８、ハロゲン基、−Ｘ_３−Ｒ_８、−Ｘ_４−Ｙ_６−Ｚ_２（R₈は水素原子または置換基を有していてもよいアルキル基、アルケニル基を表す。）
X₃；−ＮＨ−、−Ｏ−、−ＣＯＮＨ−、−ＳＯ_２ＮＨ−、−ＣＨ_２ＮＨ−、−ＣＨ_２ＮＨＣＯＣＨ_２ＮＨ−または−Ｘ_５−Ｙ_６−Ｘ_６−（Ｘ_５及びＸ_６はそれぞれ独立に−ＮＨ−または−Ｏ−を表す。）
X₄；−ＣＯＮＨ−、−ＳＯ_２ＮＨ−、−ＣＨ_２ＮＨ−、−ＮＨＣＯ−または−ＮＨＳＯ_２−
Y₆；炭素数２０以下で構成された、置換基を有してもよいアルキレン基、あるいは置換基を有してもよいアルケニレン基、あるいは置換基を有してもよいアリーレン基。アリーレン基の例としてはフェニレン基、ナフチレン基等がある。
Z₂；−ＳＯ_３Ｍ、−ＣＯＯＭ（Mは１〜３価のカチオンの１当量を表す。）

The symbol in a formula represents the following meaning.
Q ₃ ; an organic dye residue, an anthraquinone residue, an optionally substituted heterocyclic ring, or an optionally substituted aromatic ring
R ₇ ; —O—R ₈ , —NH—R ₈ , a halogen group, —X ₃ —R ₈ , —X ₄ —Y ₆ —Z ₂ (R ₈ may have a hydrogen atom or a substituent. Represents an alkyl group or an alkenyl group.)
_{X 3; -NH -, - O} -, - CONH -, - SO 2 NH -, - CH 2 NH -, - CH 2 NHCOCH 2 NH- or _{-X 5 -Y 6 -X 6 - (} X 5 and X ₆ each independently represents —NH— or —O—.
_{X 4; -CONH -, - SO} 2 NH -, - CH 2 NH -, - NHCO- or -NHSO ₂ -
Y ₆ ; an alkylene group which may have a substituent, an alkenylene group which may have a substituent, or an arylene group which may have a substituent, which is composed of 20 or less carbon atoms. Examples of the arylene group include a phenylene group and a naphthylene group.
Z ₂ ; —SO ₃ M, —COOM (M represents one equivalent of a monovalent to trivalent cation)

Examples of the organic dye residue in Q ₃ of the general formula (5) include phthalocyanine dyes, azo dyes, quinacridone dyes, dioxazine dyes, anthrapyrimidine dyes, ansanthrone dyes, indanthrone dyes, and flavanthrones. Pigments or dyes such as dyes, perylene dyes, perinone dyes, thioindico dyes, isoindolinone dyes, and triphenylmethane dyes

Examples of the heterocyclic ring or aromatic ring in Q ₃ of the general formula (5) include thiophene, furan, pyridine, pyrazole, pyrrole, imidazole, isoindoline, isoindolinone, benzimidazolone, benzthiazole, benztriazole, and indole. Quinoline, carbazole, acridine, benzene, naphthalene, anthracene, fluorene, phenanthrene and the like.
General formula (6)
Q ₄ − (− X ₇ −Z ₃ ) _r
The symbol in a formula represents the following meaning.
Q ₄ ： Organic dye residue or anthraquinone residue
X _7; direct _{bond, -NH -, - O -,} - CONH -, - SO 2 NH -, - CH 2 NH -, - CH 2 NHCOCH 2 NH- or _{-X 8 -Y 7 -X 9 - (} X ₈ and X ₉ each independently represent —NH— or —O—, and Y ₇ represents an alkylene group or an arylene group which may have a substituent, examples of the arylene group include a phenylene group and a naphthylene group. There is.)
Z ₃ ; —SO ₃ M, —COOM (M represents one equivalent of a monovalent to trivalent cation)
r; an integer from 1 to 4

Examples of the organic dye residue in Q ₄ of the general formula (6) include phthalocyanine dyes, azo dyes, quinacridone dyes, dioxazine dyes, anthrapyrimidine dyes, ansanthrone dyes, indanthrone dyes, and flavanthrones. Pigments or dyes such as dyes, perylene dyes, perinone dyes, thioindico dyes, isoindolinone dyes, and triphenylmethane dyes

  The disperser used for the adsorption treatment is not particularly limited. For example, a paint conditioner (manufactured by Red Devil), a ball mill, a sand mill (such as “Dyno mill” manufactured by Shinmaru Enterprises), an attritor, a pearl mill (Such as “DCP mill” manufactured by Eirich), coball mill, basket mill, homomixer, homogenizer (such as “Creamix” manufactured by M Technique), wet jet mill (“Genus PY” manufactured by Genus, “Nanomizer manufactured by Nanomizer”) Or the like. In view of cost, processing capability, etc., it is preferable to use a media type dispersing machine. As the media, glass beads, zirconia beads, alumina beads, magnetic beads, stainless beads, etc. can be used.

  When the organic dye derivative or triazine derivative having an acidic group is treated, the adsorption treatment is dissolved in water or a basic aqueous solution having a pH of about 7 to 11. Preferably it is pH 8-10. Adsorption treatment proceeds by adding, mixing and dispersing carbon black in the derivative aqueous solution.

  Examples of bases added to dissolve organic dye derivatives or triazine derivatives having an acidic group include metal hydroxides such as alkali metals, salts obtained by the reaction of weak acids and strong bases, ammonia, amine group-containing organic compounds, etc. A compound that is dissolved in water and exhibits basicity can be used. Alkali metal hydroxides, ammonia, and amine group-containing organic compounds are preferred.

  The amount of base added to dissolve the organic dye derivative or triazine derivative having an acidic group can be 0.1 to 10 equivalents relative to the amount of acidic functional group contained in the organic dye derivative or triazine derivative. More preferably, it is 0.5-5 equivalent, and 1-2 equivalent is especially preferable.

  In the case of a basic organic pigment derivative or triazine derivative, it is dissolved in water or an acidic aqueous solution having a pH of about 3-7. Preferably it is pH 3-5. Adsorption treatment proceeds by adding and mixing and dispersing carbon black in the aqueous derivative solution.

  Acids for dissolving organic dye derivatives or triazine derivatives having a basic functional group include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, salts of inorganic compounds obtained by the reaction of strong acids and weak bases, carboxylic acids and sulfonic acids. A compound that shows acidity when dissolved in water, such as an acid, can be used. Organic acids are preferred, and carboxylic acids are particularly preferred.

  The amount of acid added to dissolve the organic dye derivative or triazine derivative having a basic group may be added in an amount of 0.1 to 10 equivalents relative to the amount of the basic functional group contained in the organic dye derivative or triazine derivative. I can do it. 0.5-5 equivalent is preferable and 1-2 equivalent is especially preferable.

  The concentration of the organic dye derivative or triazine derivative aqueous solution having acidic and basic functional groups is 1 to 100 mmol / L, and preferably 1 to 50 mmol / L. More preferably, it is 5-20 mmol / L.

  The slurry concentration of the aqueous dispersion of carbon black depends on the characteristic values unique to carbon black, such as the surface functional group amount of carbon black, and the acid amount and base amount added to dissolve the organic dye derivative or triazine derivative. Since it fluctuates, it is not particularly limited, but 5 to 15% is preferable.

  The carbon black adsorption treatment is preferably carried out in an aqueous solution in view of the simplicity of the treatment, but it can also be carried out in a non-aqueous solvent solution as long as it has solubility in organic dye derivatives or triazine derivatives.

In order to achieve stable dispersion, it is necessary to coat the surface of carbon black with more organic dye derivatives or triazine derivatives to increase the affinity with the resin. Specifically, when an organic dye derivative or triazine derivative portion is considered as an adsorption site, it is necessary to adsorb an amount that is 50% or more of the BET specific surface area of carbon black. For example, in the case of using a phthalocyanine derivative, calculation is performed assuming that the molecular occupation area per molecule of the phthalocyanine residue is 106 ² , and hereinafter, the molecular occupation area per molecule of the benzimidazolone residue is calculated by the same calculation method. is 111Å ^2, molecular area per molecule triazine residues and aryl groups was calculated as 55 Å ^2.

  The saturated adsorption amount of the organic dye derivative or triazine derivative with respect to carbon black is a value calculated from the BET adsorption specific surface area of carbon black and the molecular occupation area per molecule of the organic dye derivative or triazine derivative. Each derivative is considered to adsorb as a single layer on the carbon black surface.

In the present invention, carbon black is treated with an organic dye derivative or triazine derivative corresponding to 50% or more of the saturated adsorption amount derived by calculation. The carbon black obtained by the present invention is characterized in that an organic dye derivative or triazine derivative having an actually measured adsorption amount of 50% or more with respect to the saturated adsorption amount is adsorbed.
The actually measured adsorption amount is a value obtained by centrifuging the adsorbed slurry to sediment the adsorbed carbon black and measuring the absorbance of the supernatant. A general-purpose spectrophotometer can be used for measuring the absorbance (for example, V570-DS manufactured by JASCO Corporation).

  The carbon black adsorbed by the disperser is desirably refined to a dispersed particle size of 0.5 μm or less, preferably 0.2 μm or less in order to exhibit its performance. The dispersed particle size here is an average particle size (D50 value) measured by a general particle size distribution meter, for example, a dynamic light scattering type particle size distribution meter (for example, “Microtrac UPA” manufactured by Nikkiso Co., Ltd.). is there.

  Since the unadsorbed organic dye derivative or triazine derivative-resin salt is in a dissolved state, there is a concern about adverse effects on water resistance, bleed, etc. even after it is made into a coating, and it is cured in a cured coating with an isocyanate compound, etc. When used in applications that require high coating strength, durability, and durability, such as magnetic recording media, the concentration of organic dye derivatives or triazine derivatives, Adjusting the amount of carbon black and adjusting the amount of unadsorbed organic dye derivative or triazine derivative to 0.005 g or less per 1 g of carbon black as a condition that 90% or more of the charged organic dye derivative or triazine derivative is adsorbed. desirable. According to this method, it is not necessary to remove the unadsorbed organic dye derivative or triazine derivative by operations such as centrifugation and ultrafiltration, and a treated carbon black having no problems such as water resistance and bleed is obtained at low cost. Can do.

  When this adsorption-treated carbon black is used for a multilayer magnetic recording medium, it may be used after removing water, and the adsorption-treated carbon black composition has a reverse polarity to the functional group of the organic dye derivative or triazine derivative. It is possible to obtain a fine dispersion by adding and mixing a varnish containing a resin having a functional group while heating, adding a paint-based solvent, and removing water.

  When water is removed and used as a powder, the water dispersion after adsorption treatment is neutralized with an aqueous solution that has a reverse polarity to the functional group of the treated organic dye derivative or triazine derivative and is insolubilized. And then filtering. Acids as neutralizers include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, inorganic compounds such as salts obtained by the reaction of strong acids and weak bases, carboxylic acids, organic acids such as sulfonic acids, etc. Can be used. Organic acids are preferred, and carboxylic acids are particularly preferred. Bases as neutralizers dissolve in water, such as metal hydroxides such as alkali metals and alkaline earth metals, salts obtained by the reaction of weak acids and strong bases, ammonia, amine group-containing organic compounds, metal alkoxides, and the like. Thus, a compound showing basicity can be used. Alkali metal hydroxides, ammonia, amine group-containing compounds and alkali metal metal alkoxides are preferred, and ammonia and amine-containing compounds are particularly preferred.

  The adsorption-treated carbon black obtained by the present invention is dispersed and adjusted with a solvent or a known resin solution used for the above-mentioned magnetic recording medium to obtain a non-magnetic forming coating for a magnetic recording medium and a coating for forming a back layer. Can do. In this case, it is preferable that the resin used has a reverse polarity to the acidic and basic functional groups of the organic dye derivative or triazine derivative subjected to the adsorption treatment.

  The resin having an acidic or basic functional group and having a functional group opposite in polarity to the organic dye derivative or triazine derivative is a resin containing an amino group or a resin containing an acidic functional group. The amino group-containing resin is at least one selected from amine-modified resins or polymer dispersants. Examples of amine-modified resins include amine-modified polyvinyl resins, amine-modified acrylic resins, amine-modified polyester resins, and amine-modified polyurethanes. There are resins. The acidic functional group is a carboxylic acid, phosphoric acid, sulfonic acid or the like or a salt thereof, and the resin containing these acidic functional groups is one selected from these acidic functional groups, such as polyvinyl resins, acrylic resins, polyester resins. And a modified polyurethane resin or the like, or at least one selected from polymer dispersants. As the polymer dispersant, a conventionally known one having an acid value or an amine value used in paints and inks can be used. Examples of commercial products of these polymer dispersants include Solspers series manufactured by Avicia, BYK series manufactured by BYK Chemie. A resin having a polarity opposite to that of these organic dye derivatives or triazine derivative dyes has a structure in which the functional group of the organic dye derivative or triazine derivative adsorbed on carbon black is ionically bonded, and the surface of carbon black is coated with the resin. The dispersibility of carbon black is considered to be improved, and the amount of resin added is preferably 1 to 5 times, particularly preferably 1.1 to 2 times the amount of neutralizing the functional group of the organic dye derivative or triazine derivative. .

  As a method for producing the coating material for forming a nonmagnetic layer or the coating material for forming a back layer of the present invention, a production process using a conventionally known kneader or disperser can be used. Examples of dispersers to be used include a two roll mill, a three roll mill, a pressure kneader, a continuous kneader, a sand mill, an agitator mill, a super mill, a coball mill, a shot mill, a pin mill, an attritor, a hep mill, an extruder, a Henschel mixer, A super mixer, dissolver, ultrasonic disperser, or the like can be used alone or in combination of two or more.

  EXAMPLES Next, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not specifically limited to an Example. In each example, unless otherwise specified, “parts” represents parts by weight, and “%” represents percent by weight. In addition, chemical structural formulas of organic dye derivatives and triazine derivatives used in Examples and Comparative Examples are shown below.

Monarch 800 (manufactured by Cabot Corporation: BET specific surface area 210 m ² / g) 25 g, copper phthalocyanine derivative 2.8 g represented by the general formula (7) and ion-exchanged water 74.8 g were charged into a 225 cc glass bottle, mixed, and then pH adjusted. Dimethylethanolamine was added so as to be = 9.5, and dispersion was performed for 1 hour using a paint shaker using zirconia beads as a medium. The obtained adsorption-treated carbon black aqueous dispersion was heated and dried in a hot air oven at 105 ° C. to obtain adsorption-treated carbon black A. Moreover, it dilutes with ion-exchange water until the carbon black density | concentration of a carbon black water dispersion is set to 1%, and carbon black is sedimented for 1 hour at 50000 rpm using an ultracentrifuge (the Hitachi Koki Co., Ltd. product: 70P-72). The supernatant was passed through a 0.5 μm membrane filter, and then the absorbance was measured to determine the concentration of the copper phthalocyanine derivative in the supernatant. The adsorption amount of the copper phthalocyanine derivative was determined from the difference between the supernatant concentration and the charged amount. When the adsorption amount is 0.52 mg / m ² and the area occupied by copper phthalocyanine is 1.06 × 10 ⁻¹⁸ m ² , the surface coverage is 51%. The amount of unadsorbed copper phthalocyanine derivative per 1 g of carbon black is 0.0028 g.
General formula (7)

[Creation of nonmagnetic layer]
α-iron oxide (average major axis 0.10 μm, BET value: 55 m 2 / g, PH = 6) 80 parts Adsorbed carbon black A 20 parts Amine-modified vinyl chloride resin 12 parts Polyurethane resin 30% solution (UR made by Toyobo Co., Ltd.) -8300) 20 parts α-alumina (average particle size 0.2 μm) 5 parts Myristic acid 1 part Butyl stearate 1 part Methyl ethyl ketone 100 parts Toluene 50 parts Cycloheixanone 50 parts After the above composition was dispersed in a sand mill, 5 parts of isocyanate (Coronate L, manufactured by Nippon Polyurethane) was added to obtain a coating for a nonmagnetic layer. The nonmagnetic layer was applied to a 9 μm thick polyethylene terephthalate support and then dried to form a nonmagnetic layer.

[Creation of paint for back layer]
Adsorption treated carbon black A 100 parts Large particle size carbon black (primary particle diameter 270 nm) 3 parts Amine modified vinyl chloride resin 49 parts Polyurethane resin 30% solution (UR-8300 manufactured by Toyobo Co., Ltd.) 110 parts Methyl ethyl ketone 310 parts Toluene 310 parts Cyclohae 120 parts of Sanon After the above composition was dispersed with a sand mill, 20 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was added to obtain a coating material for a back layer. The back layer coating is applied to the opposite surface on which the non-magnetic layer is formed and dried to form a back layer of about 0.6 μm, then cured at 60 ° C. for 24 hours, and cut into ½ inch widths to form a coating tape. did.

Monarch 800 (manufactured by Cabot Corporation: BET specific surface area 210 m ² / g) 25 g, copper phthalocyanine derivative 3.3 g represented by the general formula (8), and ion-exchanged water 75.5 g were charged into a 225 cc glass bottle, mixed, and then mixed. Acetic acid was added so as to be = 5, and dispersion was performed for 1 hour using a paint shaker using zirconia beads as a medium. The obtained adsorption-treated carbon black aqueous dispersion was heated and dried in a hot air oven at 105 ° C. to obtain adsorption-treated carbon black B. The adsorption amount obtained by the same operation as in Example 1 was 0.62 mg / m ² , and the surface area coverage was 52% when the molecular occupation area of copper phthalocyanine was 1.06 × 10 ⁻¹⁸ m ^2. Become. The amount of unadsorbed copper phthalocyanine derivative per 1 g of carbon black is 0.0018 g.
General formula (8)

[Creation of nonmagnetic layer]
α-iron oxide (average major axis diameter: 0.10 μm, BET value: 55 m 2 / g, PH = 6) 80 parts Adsorbed carbon black B 20 parts S0 ₃ Na group-containing vinyl chloride resin 12 parts S0 ₃ Na group-containing polyurethane resin 30 % Solution (UR-8300 manufactured by Toyobo Co., Ltd.) 20 parts α-alumina (average particle size 0.2 μm) 5 parts Myristic acid 1 part Butyl stearate 1 part Methyl ethyl ketone 100 parts Toluene 50 parts Cycloheixanone 50 parts After dispersion with a sand mill, 5 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was added to obtain a coating for a nonmagnetic layer. The nonmagnetic layer was applied to a 9 μm thick polyethylene terephthalate support and then dried to form a nonmagnetic layer.

[Creation of paint for back layer]
Adsorbed carbon black B 100 parts Large particle size carbon black (primary particle diameter 270 nm) 3 parts 70% wet nitrified cotton (Celnova BTH1 manufactured by Asahi Kasei Co., Ltd.) 70 parts SO ₃ Na group-containing polyurethane resin 30% solution (UR- manufactured by Toyobo Co., Ltd.) 8300) 10 parts Methyl ethyl ketone 300 parts Toluene 300 parts Cycloheixanone 120 parts After the above composition was dispersed in a sand mill, 20 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was added to obtain a coating material for a back layer. The back layer coating is applied to the opposite surface on which the non-magnetic layer is formed and dried to form a back layer of about 0.6 μm, then cured at 60 ° C. for 24 hours, and cut into ½ inch widths to form a coating tape. did.

Legal 250R (manufactured by Cabot: BET specific surface area 50 m ² / g) 30 g, 1.5 g of triazine derivative represented by the general formula (9) and 68 g of ion-exchanged water were charged into a 225 cc glass bottle, mixed, and then adjusted to pH = 5. Acetic acid was added so that the dispersion was performed for 1 hour using a paint shaker using zirconia beads as a medium. The obtained adsorption-treated carbon black aqueous dispersion was heated and dried in a hot air oven at 105 ° C. to obtain adsorption-treated carbon black C. The adsorption amount obtained by the same operation as in Example 1 was 0.90 mg / m ² , and the surface coverage was 77% when the occupied area of the triazine moiety and the aryl group was 5.5 × 10 ⁻¹⁹ m ^2. It becomes. Further, the unadsorbed triazine derivative per 1 g of carbon black is 0.005 g.
General formula (9)

次に実施例２の非磁性層用塗料の作成、バック層用塗料の作成において吸着処理カーボンブラックＢを吸着処理カーボンブラックＣに変えた以外は同様の方法で非磁性層塗料及びバック層用塗料を作成し、塗布テープを作成した。

Next, the nonmagnetic layer coating material and the back layer coating material were prepared in the same manner as in Example 2 except that the adsorption-treated carbon black B was changed to the adsorption-treated carbon black C in the creation of the coating material for the nonmagnetic layer and the coating material for the back layer. And coated tape was prepared.

Monarch 800 (manufactured by Cabot Corporation: BET specific surface area 210 m ² / g) 25 g, benzimidazolone derivative 2.8 g represented by the general formula (10) and ion-exchanged water 75.5 g were charged into a 225 cc glass bottle and mixed. Acetic acid was added so that pH = 5, and dispersion was performed for 1 hour using a paint shaker using zirconia beads as a medium. The obtained adsorption-treated carbon black aqueous dispersion was heated and dried in a hot air oven at 105 ° C. to obtain adsorption-treated carbon black D. The amount of adsorption obtained by the same operation as in Example 1 is 0.52 mg / m ² , and when the molecular occupation area of benzimidazolone is 1.11 × 10 ⁻¹⁸ m ² , the surface coverage is 51%. Become. The amount of unadsorbed benzimidazolone derivative per 1 g of carbon black is 0.0028 g.
General formula (10)

次に実施例２の非磁性層用塗料の作成、バック層用塗料の作成において吸着処理カーボンブラックＢを吸着処理カーボンブラックＤに変えた以外は同様の方法で非磁性層塗料及びバック層用塗料を作成し、塗布テープを作成した。

Next, the nonmagnetic layer coating material and the back layer coating material were prepared in the same manner as in Example 2 except that the adsorption-treated carbon black B was changed to the adsorption-treated carbon black D in the creation of the coating material for the nonmagnetic layer and the coating material for the back layer. And coated tape was prepared.

[Comparative Example 1]
Monarch 800 (manufactured by Cabot Corporation: BET specific surface area 210 m ² / g) 25 g, copper phthalocyanine derivative 2.0 g represented by the general formula (7) and ion-exchanged water 74.8 g were charged into a 225 cc glass bottle, mixed, and then mixed. Dimethylethanolamine was added so as to be = 9.5, and dispersion was performed for 1 hour using a paint shaker using zirconia beads as a medium. The obtained adsorption-treated carbon black aqueous dispersion was heated and dried in a hot air oven at 105 ° C. to obtain adsorption-treated carbon black E. The adsorption amount obtained by the same operation as in Example 1 is 0.37 mg / m ² , and the surface coverage is 36% when the area occupied by copper phthalocyanine is 1.06 × 10 ⁻¹⁸ m ^2. . Moreover, the non-adsorbed copper phthalocyanine derivative per 1 g of carbon black is 0.0023 g.
Next, the nonmagnetic layer coating material and the back layer coating material were prepared in the same manner as in Example 1 except that the adsorption-treated carbon black A was changed to the adsorption-treated carbon black E in the creation of the coating material for the nonmagnetic layer and the coating material for the back layer. And coated tape was prepared.

[Comparative Example 2]
In the preparation of the coating for the nonmagnetic layer of Example 1, adsorption treatment carbon black A, 20 parts were replaced with Monarch 800, 18 parts and the copper phthalocyanine derivative represented by the general formula (7) and 2 parts in the same manner. A coating for the nonmagnetic layer was prepared. Further, in the preparation of the back layer coating material of Example 1, adsorption treatment carbon black A, 100 parts were replaced with Monarch 800, 90 parts and a copper phthalocyanine derivative represented by the general formula (7) and 10 parts in the same manner. A paint for the back layer was prepared. A coating tape was prepared in the same manner as in Example 1 using the obtained nonmagnetic coating material and back layer coating material. As a result of obtaining the adsorption amount and the surface coverage by the same operation as in Example 1 except that toluene was used to dilute the carbon black concentration to 1% using the obtained paint, the paint for the nonmagnetic layer was obtained. Was an adsorption amount of 0.32 mg / m ² and a surface coverage of 31%, and the back layer coating material had an adsorption amount of 0.35 mg / m ² and a surface coverage of 34%. At this time, the amount of unadsorbed copper phthalocyanine derivative per gram of carbon black is 0.044 g for the nonmagnetic layer coating material and 0.038 g for the back layer coating material.

[Comparative Example 3]
In the preparation of the nonmagnetic layer coating material of Example 2, adsorption treatment carbon black B, 20 parts was replaced with Monarch 800, 17, 67 parts and a copper phthalocyanine derivative represented by the general formula (8), 2.33 parts. A nonmagnetic layer coating material was prepared in the same manner. Further, in the preparation of the back layer coating material of Example 1, the adsorption-treated carbon black B, 100 parts, was replaced with Monarch 800, 88.34 parts and a copper phthalocyanine derivative represented by the general formula (8), 11.66 parts. A coating material for the back layer was prepared in the same manner. A coating tape was prepared in the same manner as in Example 1 using the obtained nonmagnetic coating material and back layer coating material. As a result of obtaining the adsorption amount and the surface coverage by the same operation as in Example 1 except that toluene was used to dilute the carbon black concentration to 1% using the obtained paint, the paint for the nonmagnetic layer was obtained. The adsorption amount was 0.41 mg / m ² and the surface coverage was 34%, and the back layer coating material had an adsorption amount of 0.45 mg / m ² and a surface coverage of 37%. At this time, the amount of unadsorbed copper phthalocyanine derivative per gram of carbon black is 0.046 g for the nonmagnetic layer coating material and 0.037 g for the back layer coating material.

[Comparative Example 4]
A similar method except that 20 parts of adsorption treated carbon black B, 195.05 parts of legal 250R and triazine derivative represented by the general formula (9), 0.95 parts were replaced in the preparation of the coating for the nonmagnetic layer of Example 2. The coating for the nonmagnetic layer was made with Further, in the preparation of the back layer coating material of Example 2, adsorption treatment carbon black B, 100 parts was replaced with legal 250R, 95.24 parts and the triazine derivative represented by the general formula (9), 4.76 parts. The coating material for the back layer was prepared by the method described above. A coating tape was prepared in the same manner as in Example 1 using the obtained nonmagnetic coating material and back layer coating material. As a result of obtaining the adsorption amount and the surface coverage by the same operation as in Example 1 except that toluene was used to dilute the carbon black concentration to 1% using the obtained paint, the paint for the nonmagnetic layer was obtained. The adsorption amount was 0.42 mg / m ² and the surface coverage was 36%, and the back layer coating material had an adsorption amount of 0.40 mg / m ² and a surface coverage of 34%. At this time, the amount of unadsorbed triazine derivative per gram of carbon black is 0.029 g for the nonmagnetic layer coating material and 0.030 g for the back layer coating material.

[Comparative Example 5]
Legal 250R (manufactured by Cabot: BET specific surface area 50 m ² / g) 30 g, triazine derivative 0.8 g represented by the general formula (9), and ion-exchanged water 68 g were charged in a 225 cc glass bottle, mixed, and then adjusted to pH = 5. Acetic acid was added so that the dispersion was performed for 1 hour using a paint shaker using zirconia beads as a medium. The obtained adsorption-treated carbon black aqueous dispersion was heated and dried in a hot air oven at 105 ° C. to obtain adsorption-treated carbon black F. The adsorption amount obtained by the same operation as in Example 1 was 0.50 mg / m ² , and the area coverage of the triazine moiety and the aryl group was 5.5 × 10 ⁻¹⁹ m ² , and the surface coverage was 43%. It becomes. Further, the unadsorbed triazine derivative per 1 g of carbon black is 0.0017 g.
Next, the nonmagnetic layer coating material and the back layer coating material were prepared in the same manner as in Example 2, except that the adsorption-treated carbon black B was changed to the adsorption-treated carbon black F in the creation of the coating material for the nonmagnetic layer and the coating material for the back layer. And coated tape was prepared.

[Comparative Example 6]
In the preparation of the nonmagnetic layer coating material of Example 2, adsorption-treated carbon black B, 20 parts were replaced with Monarch 800, 18.0 parts and benzimidazolone derivative represented by the general formula (10), 2.0 parts Prepared a coating for the non-magnetic layer in the same manner. Further, in the preparation of the back layer coating material of Example 2, the adsorption-treated carbon black B, 100 parts, was replaced with Monarch 800, 90.0 parts and 10.0 parts of the benzimidazolone derivative represented by the general formula (10). A coating material for the back layer was prepared in the same manner. A coating tape was prepared in the same manner as in Example 1 using the obtained nonmagnetic coating material and back layer coating material. As a result of obtaining the adsorption amount and the surface coverage by the same operation as in Example 1 except that toluene was used to dilute the carbon black concentration to 1% using the obtained paint, the paint for the nonmagnetic layer was obtained. The adsorption amount was 0.36 mg / m ² and the surface coverage was 36%, and the back layer coating material had an adsorption amount of 0.40 mg / m ² and a surface coverage of 39%. At this time, the amount of unadsorbed benzimidazolone derivative per gram of carbon black is 0.036 g for the nonmagnetic layer coating material and 0.027 g for the back layer coating material.

  The coating films for the nonmagnetic layer and the back layer of the coating tapes prepared in Examples 1 to 4 and Comparative Examples 1 to 6 were evaluated, and the coating for the nonmagnetic layer and the coating for the back layer were evaluated by the methods described below.

  [Center line average roughness]: The surface of the nonmagnetic layer and the back layer was measured with a stylus type surface roughness meter (stylus diameter of 1 micron) at a cutoff value of 0.08 based on JIS-B-0601-1982. The center line average roughness Ra was determined. The smaller Ra is, the smoother it is. Further, Ra was measured for each of the coating film on which the coating tape was prepared immediately after the coating was prepared and the coating film on which the coating tape was prepared after storing the coating material at 40 ° C. for 1 month.

  [Coating Young's Modulus]: For each of the tape coated with a nonmagnetic layer and a back layer, the tape coated with only the nonmagnetic layer, and the support coated with none, the stress elongation characteristics were measured with a tensile tester, and the initial rise From the inclination and the film thickness, the Young's modulus of each of the nonmagnetic layer coating film and the back layer coating film was determined. The coating film Young's modulus can be seen as a measure of the coating film strength, and the higher the coating film strength, the higher the coating film strength.

  [Back layer running durability]: The friction coefficient between the back layer surface and the SUS304 guide pin was measured with a tape running tester. The coefficient of friction after traveling 100 passes at a winding angle of 180 degrees and the scratched state of the back layer surface after traveling were evaluated. A mark in which almost no scratches were observed on the back layer after running, a mark in which some scratches were observed, and a mark in which a number of scratches were observed were indicated as x.

  [Coating stability]: The increase rate of the viscosity of the coating material after storing the coating material for the nonmagnetic layer and the coating material for the back layer at 40 ° C. for 1 month was determined from the viscosity after aging / initial viscosity. About paint viscosity, after adjusting liquid temperature to 25 degreeC, the value after 60 rpm for 1 minute was measured in BL type viscometer.

  The above evaluation results are summarized in Table 1. As is apparent from Table 1, the use of the adsorption-treated carbon black according to the present invention greatly improves the temporal stability of the non-magnetic layer coating material and the back layer coating material. Equivalent paint fluidity and coating film smoothness were obtained. In addition, the coating film obtained by applying and curing these coatings showed improved coating strength for both the non-magnetic layer coating film and the back layer coating film, and showed excellent running durability for the back layer.

  The present invention is not limited to magnetic recording media such as data storage tapes and digital broadcasting VTR tapes that require high-density recording, and can be used in various fields such as other recording media containing carbon black, display materials, and functional materials.

Claims (6)

A coating for laminating a nonmagnetic layer and a magnetic layer in this order on one side of a support and forming a nonmagnetic layer of a magnetic recording medium having a back layer on the other side. An organic dye derivative having a functional functional group or a triazine derivative having an acidic or basic functional group and carbon black, wherein the organic dye skeleton part of the organic dye derivative or the triazine part or triazine derivative of the triazine derivative is an aryl group or In the case of having an anthraquinone residue, an adsorption-treated carbon black that has been adsorbed in an amount that makes the adsorption area 50% or more of the BET specific surface area of the carbon black assuming that the adsorption site is a triazine moiety and an aryl group or an anthraquinone residue. A nonmagnetic forming paint characterized by containing. A coating for forming a back layer of a magnetic recording medium having a magnetic layer on one side of the support and a back layer on the other side, the coating comprising an organic dye derivative having an acidic or basic functional group or When the triazine derivative having an acidic or basic functional group and carbon black are in a liquid, the organic dye skeleton part of the organic dye derivative or the triazine part or triazine derivative of the triazine derivative has an aryl group or an anthraquinone residue. And an adsorbed carbon black that is adsorbed in an amount such that the adsorbed area is 50% or more of the BET specific surface area of the carbon black, assuming that the aryl group or anthraquinone residue is an adsorbed site. Paint. The paint according to claim 1 or 2, wherein the amount of the unadsorbed organic dye derivative or triazine derivative is 0.005 g or less per 1 g of carbon black. The paint according to any one of claims 1 to 3, wherein a media-type disperser is used for the adsorption treatment. The paint according to any one of claims 1 to 4, comprising a resin having a functional group having a reverse polarity to the functional group of the organic dye derivative or the triazine derivative. A magnetic recording medium having a nonmagnetic layer or a back layer formed of the paint according to claim 1.