JPS63261517A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve an antistatic property, running performance and electromagnetic conversion characteristics by incorporating a copolymer contg. a specific intramolecular salt type unit as its copolymer component into the binder of a magnetic layer formed by dispersing ferromagnetic powder into the binder. CONSTITUTION:This magnetic recording medium includes a nonmagnetic base and the magnetic layer which is provided on the base and is formed by dispersing the ferromagnetic powder into the binder and the binder thereof contains the copolymer of the intramolecular salt type unit expressed by formula I as its copolymer component. In formula, R<1> denotes hydrogen or methyl group; R<2> denotes a divalent hydrocarbon group of 1-18C; R<3> and R<4> respectively independently denote a monovalent hydrocarbon group of 1-6C or hydroxyl hydrocarbon group; M<-> denotes -R<5>COO<->, -R<5>OH.OH<->, etc., (where R<5> is a divalent hydrocarbon group of 1-6C); (n) denotes 0 or 1. The antistatic property, running performance and electromagnetic conversion characteristics are thereby improved.

Description

[Detailed description of the invention] [Field of invention] The present invention relates to a novel magnetic recording medium.

[Background of the Invention] In general, y-Fe203, Co
A magnetic recording medium is used in which a magnetic layer in which ferromagnetic powder such as iron oxide, CrO2, or ferromagnetic metal fine powder is dispersed in a binder is provided on a nonmagnetic support.

Magnetic recording media tend to be charged with static electricity as they run (or rotate) at high speeds while coming into contact with various components of the running system, such as magnetic heads and balls. The layer contains antistatic agents such as carbon black and surfactants. Under normal conditions, such conventional methods can provide practically satisfactory antistatic drops, but especially under low humidity conditions. However, when increasing the amount of the general antistatic agent mentioned above in order to improve the antistatic performance of the magnetic layer, various adverse effects occur. do. In other words, when a large amount of carbon black is used, a decrease in magnetic properties, especially a decrease in residual magnetic density, and a deterioration of surface properties tend to occur, and when a large amount of surfactant is added, high temperature conditions In this case, the surfactant oozes out onto the surface of the magnetic layer (blooming), and the gap in the magnetic head tends to become clogged. Furthermore, there is a tendency for running properties to deteriorate at high temperatures. In addition, it can also be used to improve the electromagnetic conversion characteristics of magnetic recording media. #As long as it does not cause any negative effects, it is preferable to use as little additive as possible.

Based on these technical requirements, a quaternary binder is added to the binder of the magnetic layer.
An invention has already been disclosed that aims to improve the antistatic effect of a magnetic layer by introducing a specific functional group such as an ammonium group or an amide group (Japanese Patent Publication No. 55-2648, No. 6).
0-47648, JP 61-198418, JP 62-6429, JP 62-8329, etc.).

However, it cannot be said that binders into which these known functional groups are introduced necessarily provide a sufficient antistatic effect, especially when dispersing highly finely divided ferromagnetic powders, which have been attracting attention in recent years. In some cases, there is a problem that the dispersibility tends to be insufficient.

On the other hand, since vinyl chloride-based copolymers are often used as the resin component of the binder in the magnetic layer of magnetic recording media, this vinyl chloride-based copolymer is made of repeating units derived from vinyl chloride. In addition, it has been proposed to use a vinyl chloride copolymer into which a monomer containing a carboxylic acid group (including a sodium carboxylate group, hereinafter the same) such as maleic anhydride is introduced (JP-A-57 -442
27 and 59-1827), by introducing these binders, some improvement is seen in improving the dispersibility of ferromagnetic powder, but almost no effect is seen in terms of antistatic effect.

[Object of the Invention] An object of the present invention is to provide a novel magnetic recording medium exhibiting excellent characteristics.

Furthermore, the present invention mainly improves antistatic properties and running properties.

Another object of the present invention is to provide a magnetic recording medium with improved electromagnetic conversion characteristics.

An object of the present invention is to provide a magnetic recording medium with improved electromagnetic conversion characteristics, using particularly finely divided ferromagnetic powder as a magnetic material.

[Summary of the Invention] The present invention provides a magnetic recording medium comprising a non-magnetic support and a magnetic layer provided on the support in which ferromagnetic powder is dispersed in a binder, wherein the binder has the general formula : [However, 7111 represents hydrogen or methyl group, R
2 represents a divalent hydrocarbon group having 1 to 18 carbon atoms, R3 and R4 each independently represent a monovalent hydrocarbon group having 1 to 6 carbon atoms or a hydroxyl hydrocarbon group,
Between R3- is -R5COO-
1-R5-P-0-1t or -R50H-OH- (wherein, R5 is a divalent hydrocarbon group having 1 to 6 carbon atoms, and R
3 and R4 have the same meanings as above), n represents O or l]. .

[Effect of the Invention J The magnetic recording medium of the present invention has excellent antistatic properties, and also has improved running properties (particularly running durability at low humidity) and electromagnetic conversion characteristics. In addition, the binder containing the copolymer used in the present invention has a strong effect of uniformly dispersing the finely divided ferromagnetic powder. It is advantageous to apply it to

[Detailed Description of the Invention] The magnetic recording medium of the present invention has a basic structure in which a non-magnetic support and a magnetic layer made of ferromagnetic powder dispersed in a binder are provided on the non-magnetic support. It is something that you have.

In the present invention, any conventional nonmagnetic support can be used for the magnetic recording medium. Examples of materials forming the nonmagnetic support include various synthetic resin films such as polyethylene terephthalate, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamideimide, and polyimide, and metal foils such as aluminum foil and stainless steel foil. can be mentioned. The non-magnetic support generally has a thickness of 3 to 507 zm, preferably 5 to 3 zm.
A thickness of 0.01 m is used.

The nonmagnetic support may be provided with a backing layer on the side where the magnetic layer is not provided.

The magnetic recording medium of the present invention is one in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a nonmagnetic support as described above.

Examples of ferromagnetic powders that can be used in the present invention include those commonly used as ferromagnetic powders:
Ferromagnetic metal fine powder mainly composed of iron, y-F e 2
Examples of iron oxide-based ferromagnetic powders include iron oxide-based ferromagnetic powders such as 03 and Fe, Oa, and dissimilar metals such as Co-modified iron oxide, barium ferrite, strontium ferrite, and the like.

The ferromagnetic powder contained in the magnetic layer of the magnetic recording medium of the present invention is preferably a finely powdered modified iron oxide-based ferromagnetic powder and a fine ferromagnetic metal powder. This is because even ferromagnetic powder has a good dispersion state. In the case of ferromagnetic metal fine powder, it is preferable that the specific surface area is 42 m''/g or more (even 45 rn'/g or more), and the specific surface area of ferromagnetic powder made of different metals or iron oxides is preferably 30m''/g or more (even 4
0 m″/g or more).

An example of a ferromagnetic metal fine powder is one in which the metal content in the ferromagnetic metal fine powder is 75% by weight or more, and 80% by weight or more of the metal content is at least one type of ferromagnetic metal or alloy (e.g., Fe, Co, Ni, Fe-Co, Fe-Ni, C
o-Ni, Co-N1-Fe), and the metal content is 20
Within the range of weight% or less ↑ Other components (e.g. A, SL, S,
Sc, Ti, V, Cr, Mn, Cu, Zn, y.

Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, T
a, W, Re, Au, Hg, Pb, B, La, Ce, P
Mention may be made of alloys which may contain r, Nd%BL, P). Furthermore, the ferromagnetic metal component may contain a small amount of water, hydroxide, or oxide, and methods for producing these ferromagnetic metal fine powders are already known, and the ferromagnetic metal used in the present invention Ferromagnetic metal fine powder, which is an example of powder, can also be produced according to these known methods.

There are no particular restrictions on the shape of the ferromagnetic powder, but it is usually acicular,
Granular, dice-shaped, rice grain-shaped, plate-shaped, etc. are used. It is particularly preferable to use acicular-shaped ferromagnetic powder.The acicular ratio (short axis length:long axis length) of the acicular ferromagnetic powder is usually l:3 or more (preferably l:8 or more) It is.

The magnetic layer of the magnetic recording medium of the present invention contains a binder in an amount of usually 1 to 40 parts by weight (preferably 15 to 30 parts by weight) per 100 parts by weight of the ferromagnetic powder.

The binder for the magnetic layer of the magnetic recording medium of the present invention has the general formula: [where R1 represents hydrogen or a methyl group, and R2 represents a divalent hydrocarbon group having 1 to 18 carbon atoms (preferably 1 to 18 carbon atoms)]
to 6 fullkylene 7; R3 and R4 each independently represent a monovalent hydrocarbon group or a hydroxyl hydrocarbon group having 1 to 6 carbon atoms;

M″″ is -R5Coo″″, -R5-P-0-1 or -R50H・OH- (however, R5 is a divalent hydrocarbon group having 1 to 6 carbon atoms, and R3 and R4 are the same as above). (synonymous), n represents O or l] At least a copolymer containing an inner salt type unit as a copolymer component.

The above copolymer is preferably a copolymer containing a repeating unit derived from vinyl chloride, particularly a copolymer containing a repeating unit derived from vinyl chloride and a repeating unit derived from vinyl acetate. Other examples of preferable copolymerization components include carboxyl group-containing monomers, vinyl acetate, epoxy group-containing monomers, and sulfonic acid group-containing monomers.

The above-mentioned inner salt type unit is contained in the copolymer from 10-6 to
The content is preferably 1O-3 mol/g, and more preferably 1O-5 to 10-4 mol/g.

When the above-mentioned copolymer contains green-back units derived from vinyl chloride, the vinyl chloride-derived green-back units are usually contained in the copolymer in an amount of 60% by weight or more (preferably 80% by weight or more).

The degree of polymerization of the copolymer, which is a characteristic binder component of the present invention, is usually in the range of 200 to 600 (preferably 300 to 500). Further, a low molecular weight copolymer having a degree of polymerization of about 20 to 200 may be used in combination in an amount of about 20% by weight or less based on the above copolymer.

Such a copolymer can be prepared, for example, by combining a monomer inducing the repeating unit of the general formula with another reactive monomer (e.g., vinyl chloride) in accordance with a method for producing a normal vinyl chloride copolymer. ) can be produced by copolymerizing. Alternatively, after copolymerizing a heptamer such as acrylic acid, acrylic acid ester, methacrylic acid, or methacrylic acid ester with other monomers, the carboxyl group thereof can be obtained.

Alternatively, the inner salt type unit of the present invention may be introduced into the ester group.

The above binder has the general formula: % formula % [where R11 represents hydrogen or a methyl group, and 11
i12 represents a divalent hydrocarbon group having 2 to 18 carbon atoms, preferably a fullkylene group having 2 to 6 carbon atoms), 1
1113 and R14 each independently represent hydrogen or a monovalent hydrocarbon group having 1 to 6 carbon atoms;
-2 alkyl group), Z is RI
SCOOH, R15SO3H1R150S03 H, (
R15)2PO2Hl and (R150)2PO
N, N
- dialkylalkylenediamine derivative unit, and/
or [However, R21 represents hydrogen or a methyl group, 1 (22 represents a divalent hydrocarbon group having 2 to 12 carbon atoms (preferably an alkylene group having 2 to 6 carbon atoms), and R23 and R2J are each independently represents a monovalent hydrocarbon group having 1 to 6 carbon atoms, and 1 (25 represents a divalent hydrocarbon group having 1 to 12 carbon atoms, preferably an alkylene group having 1 to 6 carbon atoms)
, T represents hydrogen or a hydroxyl group, x- is R2'S
O3-, R260303- or (R26) 2 PO
2 (R26 is a monovalent hydrocarbon group having 1 to 18 carbon atoms (preferably an alkyl group having 1 to 12 carbon atoms) or a C 4 to 1
8) or NO
3- represents an N, N, N-trialkylalkylene diamine derivative unit and/or general formula:
32 represents a divalent hydrocarbon group having 2 to 18 carbon atoms (preferably an alkylene group having 2 to 6 carbon atoms), R33, R34
and R35 each independently represent a monovalent hydrocarbon group having 1 to 6 carbon atoms (preferably a methyl group and an ethyl group), and M is a divalent hydrocarbon group having 1 to 18 carbon atoms or any of the following: Group C-0-R36-0-11 (where R36 represents a monovalent hydrocarbon group having 2 to 18 carbon atoms or a polyethylene oxide residue having 4 to 18 carbon atoms), n represents O or l] The phosphoric acid ester type quaternary ammonium group unit represented by may be contained as a copolymerization component in an amount of about 10-6 to 10-3 mol/g.

As the binder, the above-mentioned copolymer can be used alone as a resin component, but in addition to this, it is preferable to use a resin commonly used as a resin component of magnetic recording media. Examples of polyurethane resins that are preferably used in combination with polyurethane resins include commonly used polyurethane resins, polyester polyurethane resins, and polyurethane resins having polar groups such as carboxylic acid groups, hydroxyl groups, or carboxylic acid groups. can be mentioned.

When a polyurethane resin is used, the weight ratio of the copolymer to the polyurethane resin is preferably within the range of 9:1 to 1:9.

In addition, it is preferable to use a hardening agent in addition to the above resin component. In particular, when using a ferromagnetic metal fine powder as the ferromagnetic powder, the use of a hardening agent makes it possible to use a ferromagnetic metal fine powder with low hardness. Nevertheless, a magnetic layer with high strength can be obtained. As the curing agent, polyisocyanate compounds that are normally used in the production of polyurethane resins are used.

When a curing agent is used, the weight ratio of the resin component to the curing agent is preferably within the range of 9:1 to 5:5.

The copolymer of the present invention may be cured with an electron beam by using it in combination with an electron beam curable resin.

In addition to being a binder for the magnetic layer, the copolymer of the present invention is also useful as a binder for a back layer or a resin material for an overcoat layer that may be provided on the surface of a magnetic layer.

The magnetic layer of the magnetic recording medium of the present invention generally contains an abrasive like a normal magnetic layer. Abrasive material is ferromagnetic powder 1
It is blended in an amount of 0.2 to 10 parts by weight per 00 parts by weight.

In addition to the above-mentioned abrasives, it is also preferable to contain conductive carbon black, a lubricant, and the like.

It is preferable to use a combination of a plurality of lubricants, such as a combination of an afrI agent that mainly acts during low-speed running and a lubricant that mainly acts during high-speed running.

Next, an example of the method for manufacturing the magnetic recording medium of the present invention will be described.

First, a magnetic paint is prepared by kneading ferromagnetic powder, a resin component, and, if necessary, an abrasive or the above-mentioned additives with a solvent. When preparing a magnetic paint, known additives such as a dispersant, an antistatic agent, and a lubricant may also be used.

The magnetic paint thus prepared is applied onto the aforementioned non-magnetic support. The coating can be applied directly onto the non-magnetic support, but it can also be applied onto the support via an adhesive layer or the like.

The magnetic layer is generally applied so that the thickness after drying is in the range of 0.5 to 1 OILm (preferably in the range of 1.5 to 7.0 #Lm).

A magnetic layer coated on a non-magnetic support is usually subjected to a treatment for orienting the ferromagnetic powder in the magnetic layer, that is, a magnetic field orientation treatment, and then dried. Further, the magnetic recording medium that has been subjected to surface smoothing treatment, etc., which is subjected to surface smoothing treatment if necessary, is then subjected to hardening treatment and blade treatment as desired, and then cut into a predetermined shape.

Next, Examples and Comparative Examples of the present invention will be shown. In the Examples and Comparative Examples, the expression "r part" indicates "heavy IsS: part."

[Video tape manufacturing method] Magnetic coating composition Co-F e O, (x-1,44) ferromagnetic powder (H
c: 9000s, specific surface area, 50m2/g average long axis length 0.25pm) l OO part Copolymer described in each example 15 parts polyester polyφ urethane resin (average molecular weight 120,000) 5 parts α-alumina (average particle Diameter: 0.1 parts) 5 parts 2-ethylhexyl stearate 1.5 parts myristic acid
2 parts carbon black (average particle size: 20 theory JL) 2 parts solvent (cyclohexanone/methyl ethyl ketone = 377) The above composition was mixed and dispersed for 5 hours using a sand grinder, and filtered using a filter having an average pore size of lpm. After that, a polyisocyanate compound (Coronate L-
75, manufactured by Nippon Polyurethane Co., Ltd.) and mixed to prepare a magnetic paint.

The obtained magnetic coating material was applied using a reverse roll onto the surface of a polyethylene terephthalate support having a thickness of 14 pm so that the thickness of the magnetic layer after drying was 4 pm.

The non-magnetic support coated with the magnetic paint is subjected to magnetic field orientation treatment using a 3000 Gauss magnet while the magnetic paint is still wet, and after drying, supercalender treatment, hardening treatment and blade treatment are performed. A videotape was produced by slitting it to a width of 2 inches.

[Example 1] Copolymer: Vinyl chloride/vinyl acetate/glycidyl methacrylate copolymer containing 5XIO-5 mol/g of a copolymer component represented by CH2-N-CH2COO"C)13 [Example 2] Polymer: Vinyl chloride/vinyl acetate/glycidyl methacrylate copolymer containing 5XlO-5 mol/g of copolymer component represented by CH2-N◆→CH2 OH number OH- CH3 [Example 3] Copolymerization represented by Vinyl chloride/vinyl acetate/maleic anhydride copolymer containing 5XlO-5 mol/g [Comparative Example 1] Vinyl chloride/vinyl acetate/glycidyl methacrylate that does not contain copolymer bimolecular inner salt type units as a copolymerization component Copolymer [Comparative Example 2] Copolymer: A quaternary ammonium group copolymer component represented by Coo-(-CH2廿N''-C2Is a Y2 H5 (y=c-) was added to 5X1
Lower margin of vinyl chloride/vinyl acetate/glycidyl methacrylate copolymer 1 containing 0-S mol/g [Comparative Example 3] 5X1 quaternary ammonium group copolymer component represented by 2 Hs (Y=H3O4-)
Vinyl chloride/vinyl acetate/glycidyl methacrylate copolymer containing 0-5 mol/g [Evaluation of video tapes] Various performances of the video tapes obtained in the above six examples were tested as follows.

6MHzVS: 6MHz video sensitivity (represents a relative value when the measured value on the videotape of Comparative Example 1 is set to 0 and 0 dB),
The larger the value, the better.

6 MHz C/N: Difference between the 6 MHz output and the modulation noise at 2 MHz full (the measured value on the videotape of Comparative Example 1 is 0.
(represents relative value when set to 0 dB).

The larger the value, the better.

Running performance: Driving performance at 5°C, 20% RH and 40°C, 80% RH, increased dropouts, screen shaking.

and jitter The evaluation symbols are as follows.

A: Good, B: Fairly good, C: Slightly poor Increase in dropout (Do): Increase in dropout during running at 5° C. and 20% RH was counted.

The evaluation symbols are as follows.

A: 5 pieces/min or less ゛B: 6 to 10 pieces/min C: 11 to 20 pieces/min Still Life Ni The still life at -10°C was measured by a conventional method.

The values obtained in each measurement are listed in Table 1.

Table 1 6MH2VS 6MHzC/N Driving Do Still (dB) (dB) Increase Life Example 1 1.2 13 A A50
Minute Example 2 1.4 1.4 A A40
Minute Example 3 1.8 1.9 A A60
Min Comparative Example to, o o, o c CS
Minute Comparative Example 20.2 0.2 B 815 Minute Comparative Example 30.5 0.6 B B20 Minute Patent Applicant Fuji Photo Film Co., Ltd. Attorney Patent Attorney Yasushi Yanagawa Man's Procedural Amendment Letter June 2, 1988 2. Name of the invention Magnetic recording medium 3. Relationship with the person making the amendment Patent applicant name (520) Fuji Photo Film Co., Ltd. 4 Agent address 8 Mitsuya Yotsuya Building, 2-14 Yotsuya, Shinjuku-ku, Tokyo
Floor 6: Number of inventions increased by amendment None 7: Subject of amendment: “Detailed Description of the Invention” column of the specification.

8. Contents of the amendment (1) In the 9th line of page 8 of the specification, amend ``r te'' to ``te''.

(2) "r carboxylic acid group" on page 17, line 5 from the bottom of the specification is corrected to "r sulfonic acid group".

Claims (1)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support and a magnetic layer provided on the support and formed by dispersing ferromagnetic powder in a binder, wherein the binder has the general formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [However, R^1 represents hydrogen or a methyl group, and R^
2 represents a divalent hydrocarbon group having 1 to 18 carbon atoms; R^3 and R^4 each independently represent a monovalent hydrocarbon group having 1 to 6 carbon atoms or a hydroxyl hydrocarbon group; M^- is , -R^5COO-, ▲Mathematical formulas, chemical formulas, tables, etc.▼, or -R^5OH・OH^- (However, R^5 is a divalent hydrocarbon group having 1 to 6 carbon atoms, and R ^3 and R^4 have the same meanings as above), n represents 0 or 1] Magnetic recording characterized in that it contains at least a copolymer containing an inner salt type unit as a copolymer component. Medium. 2. The magnetic recording according to claim 1, wherein the copolymer containing the inner salt type unit as a copolymerization component is a copolymer containing repeating units derived from vinyl chloride. Medium. 3. A patent claim characterized in that the copolymer containing the inner salt type unit as a copolymerization component is a copolymer containing repeating units derived from vinyl chloride and repeating units derived from vinyl acetate. The magnetic recording medium according to item 1. 4. The inner salt type unit is 10^-^ in the copolymer.
The magnetic recording medium according to claim 1, characterized in that the magnetic recording medium contains 6 to 10^-^3 mol/g. 5. The magnetic recording medium according to claim 1, wherein the binder contains a polyurethane resin in addition to the copolymer.