JPS62159334A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide the titled medium having an excellent electromagnetic conversion characteristic and excellent running property and running durability by forming a binder of a resin component which contains a copolymer contg. the repeating unit having -COOM bound via at least one carbon atom directly bound with the carbon atom constituting the main chain and the repeating unit derived from a vinyl chloride. CONSTITUTION:The binder is constituted of the resin component which contains the copolymer contg. the repeating unit having -COOM (M denotes a hydrogen atom or alkali metal atom) bound via at least one carbon atom directly bound with the carbon atom constituting the main chain and the repeating unit derived from the vinyl chloride. The carboxylic acid group which is not directly bound with the main chain of the copolymer constituting the binder is incorporated into the binder and since the carboxylic acid group is chemically stable, the cutting of side chains in the stage of preparing a magnetic coating compd. or the like is decreased and the dispersion condition of the ferromagnetic powder in a magnetic layer is extremely improved. The recording medium exhibits the excellent electromagnetic conversion characteristic as the squareness ratio of the magnetic layer is high and the surface of the magnetic layer is extremely smooth.

Description

[Detailed description of the invention] [4+11 fields] The present invention relates to a novel magnetic recording medium.

[Background of the Invention] Generally, γ-Fe20. , Co-containing iron oxide, Cry
A magnetic recording medium is used in which a magnetic layer in which ferromagnetic powder made of needle-like crystals such as fine ferromagnetic metal powder is dispersed in a binder is provided on a non-magnetic support.

Recently, there has been an increasing demand for particularly high-density recording, and these ferromagnetic powders have become increasingly finer.

- On the other hand, vinyl chloride copolymers are used as the resin component of the binder for the magnetic layer of magnetic recording media. Along with the pulverization of ferromagnetic powder, vinyl chloride-based copolymers are used in addition to repeating units derived from vinyl chloride, such as carboxylic acid groups such as maleic anhydride (containing sodium carboxylate groups, etc.). Vinyl chloride copolymers containing polar groups have come to be used. The polar groups of the vinyl chloride copolymer act to improve the affinity between the copolymer and the ferromagnetic powder. Then, not only the copolymer having this polar group but also the entire resin component containing this copolymer came to show good affinity with the ferromagnetic powder, and finally the ferromagnetic powder was dispersed in the magnetic layer. be able to improve the condition.

However, the carboxylic acid groups introduced using, for example, maleic anhydride are directly bonded to the side chains of the copolymer, and the copolymer does not have a simple linear structure; Since it generally has a complicatedly bent structure, the carboxylic acid group and the ferromagnetic powder particles may not be able to approach each other sufficiently due to the influence of this female body structure. In other words, such carboxylic acid groups give the copolymer an affinity for ferromagnetic powder! From the point of view of the effect of the system, it can be said that the purpose has not been fully achieved.

Therefore, it was proposed that the dispersion state of the ferromagnetic powder be modified by introducing a carboxylic acid group at a position away from the main chain of the ferromagnetic powder.
is JP-A-S 7-44227 tz and JP-A-Sho 59-18
No. 27- and other publications.

In order to introduce such a carboxylic acid group, for example, a copolymer containing vinyl chloride and vinyl alcohol is produced, and a hydroxyl group directly bonded to the main chain of the obtained vinyl chloride-based copolymer is added with, for example, monochloroethyl. Carboxylic acid and 0CN-
A method is used in which a hydroxyl group is reacted with a reactive carboxylic acid group-containing compound such as R-NHCOO(GH2) 2 GOOH. Therefore, the side chain having a carboxylic acid group and the main chain of the copolymer are bonded through a carbon-oxygen bond.

The carboxylic acid group introduced into the vinyl chloride copolymer in this form has a large effect on the dispersion of the ferromagnetic powder due to the distance between the main chain and the carboxylic acid group. It is less affected by the three-dimensional structure of
Shows good results.

However, according to the studies of the present inventors, the side chains introduced in this way can be used, for example, during long-time cross-dispersion during the preparation of magnetic paints, or when magnetic recording media are left in high-temperature, high-humidity conditions for long periods of time. When exposed to harsh conditions such as
There is a problem that a decomposition reaction is likely to occur in the vicinity of the m element bonded to the carbon p:(p) of the E chain and the 'E chain.

[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 II mainly aims to provide a magnetic recording medium with improved electromagnetic conversion characteristics.

Another object of the present invention is to provide a magnetic recording medium that has excellent electromagnetic change characteristics, as well as excellent running properties and running durability.

[9. Summary of Ming] 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, the binder comprising: ■ A subtraction unit having one COOM (M represents a hydrogen atom or an alkali metal atom r) bonded through at least one carbon atom directly bonded to a carbon atom constituting the chain, and vinyl chloride. A magnetic recording medium comprising a resin component containing a copolymer containing a repeating unit derived from the magnetic recording medium.

[Effects of the Invention] In the magnetic recording medium of the present invention, a carboxylic acid group that is not directly bonded to the copolymer constituting the binder is introduced, and the carboxylic acid group is chemically stable. Because of this, side chains are less likely to be broken when preparing magnetic paints, etc.
The dispersion state jE1 of the ferromagnetic powder in the magnetic paint and the magnetic layer prepared by applying the same becomes extremely good.

Therefore, the magnetic recording medium of the present invention exhibits excellent electromagnetic conversion characteristics because the squareness ratio of the magnetic layer is high and the surface of the magnetic layer is extremely smooth.

Furthermore, in the magnetic recording medium of the present invention, since the ferromagnetic powder is well dispersed in the magnetic layer, there are few lumps of ferromagnetic powder, and the bond between each particle of the ferromagnetic powder and the binder is strong. Therefore, the magnetic layer has high strength and exhibits good running durability.

Further, in the magnetic recording medium of the present invention, since the ferromagnetic powder is in a well-dispersed state in the magnetic layer, the gap formed by a plurality of adjacent ferromagnetic powder particles does not become excessively large, and a lubricant is applied to this gap. Since it is sequentially supplied to the surface of the magnetic layer without being retained, it exhibits good running properties.

[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.

As the nonmagnetic support for the magnetic recording medium in the present invention, commonly used nonmagnetic supports can be used. As an example of a magnetic support that forms a non-magnetic support.

Polyethylene terephthalate, polypropylene, polycarbonate, polyethylene naphthalate.

Examples include various synthetic resin films such as polyamide, polyamideimide, and polyimide, and metal foils such as aluminum foil and stainless steel foil.

The nonmagnetic support used generally has a thickness of 3 to 50 ILm, preferably 5 to 30 pm.

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 has a magnetic layer in which ferromagnetic powder is dispersed in a binder submerged in a non-magnetic support as described above.

In the present invention, commonly used ferromagnetic powders can be used. Examples of ferromagnetic powder include ferromagnetic metal fine powder containing five iron components, γ-Fe20.
Examples include iron oxide-based ferromagnetic powders such as Fe2, 04, and dissimilar metal/iron oxide-based ferromagnetic powders such as Co-modified iron oxide, barium ferrite, and strontium ferrite.

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 1 ferromagnetic metal fine powder, the specific surface area is 42rlf/g or more (or even 45rn'/g).
It is preferable that the specific surface area of the dissimilar metal/iron oxide-based ferromagnetic powder is 30 rn'/g or more (and more preferably 35 rn'/, hereinafter I:).

As an example of a ferromagnetic metal fine powder, the metal content in the ferromagnetic metal fine powder is 75 layers or more, and the metal content is 80 layers or more; , Fe, Co, Ni, Fe-Co, Fe-Ni,
Co-Ni, Co-N1~Fe), and the metal content is 2
Other components (e.g. All, Si,
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, Bi, P). In addition, water with a small ferromagnetic metal content,
It may also contain hydroxides or oxides, etc.
The manufacturing method of these ferromagnetic metal fine powders is already known and is described in Section 9 of this book. Ferromagnetic gold J, an example of ferromagnetic powder used in
The i1 fine powder can also be produced according to these known methods.

Further, the production of iron oxide-based ferromagnetic powder and dissimilar metal/iron oxide-based ferromagnetic powder is already known, and those used in the present invention 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. In particular, it is preferable to use acicular-shaped ferromagnetic powder.The acicular ratio (minor axis length:long axis length) of the acicular ferromagnetic powder is usually 1:3 or more (preferably 1:8 or more). .

The magnetic layer of the magnetic recording medium of the present invention usually contains 10 to 40 parts by weight (preferably 15 to 30!Tf parts) of a binder per 10 parts by weight of the ferromagnetic powder listed in L. .

The binder of the magnetic layer of the magnetic recording medium of the present invention is composed of a repeating unit having one COOM bonded through at least one carbon atom directly bonded to a carbon atom constituting one chain, and vinyl chloride. It is composed of a resin component containing a copolymer containing repeating units derived from the polymer.

The copolymer constituting the binder of the magnetic layer contains repeating monomers derived from vinyl chloride. This repeating position is usually contained in the copolymer in an amount of 60% by weight or more (preferably 80% by weight or more). When the amount is less than 60% by weight and 4%, the strength of the copolymer itself becomes low and the strength of the magnetic layer may not be sufficient.

An example of a repeating hierarchy having one COOM directly bonded to a carbon atom constituting one button contained in the copolymer through at least one carbon atom T is the formula described below. Examples include compounds represented by [II] and formula [II].

However, in L-warm formula [II and formula [II], R represents a hydrogen chain f- or a methyl group, and R1 and R2 are 1
~17 divalent aliphatic hydrocarbon group, M represents a hydrogen chain f- or an alkali metal atom, especially a straight chain aliphatic hydrocarbon group having 1 to 12 carbon atoms. is preferable, and by using a linear aliphatic hydrocarbon group, the free rotation of the carboxylic acid at the tip of the side chain is not inhibited, and it is higher than the ferromagnetic powder particles of the copolymer. It begins to show affinity.

1 for deriving the repeating unit represented by the above formula [11]
1:, Specific examples of the mer include carboxyl methyl acrylate and lO-carboxyl decyl acrylate, which can be used to form a middle A specific example is allyl acetate.

The repeating unit of letter L has a high stability compared to structure -L and the repeating tB position having a conventionally used carboxylic acid group.

In other words, a repeating unit having 1000M (hereinafter referred to as r) which is bonded to the carbon atom r constituting the chain through at least one carbon atom f directly bonded to the carbon atom r of the present invention. (sometimes written as "repeated honor") and vinyl alcohol and 0CN-R-N) ICOO (GH2)
When compared with conventionally used repeating units having a carboxylic acid group at the tip, such as the repeating trophic structure derived from 2GOON, conventional repeating units have carbon atoms constituting the main chain of the copolymer and In contrast, in the carboxylic acid-containing repeating unit of the present invention, the carbon atoms constituting one chain and the side chain are bonded through a carbon-carbon bond. They differ in that they are This difference mainly appears in the chemical stability of the copolymers. In other words, in conventional repeating units, bonds are often broken at this part. For example, if the side chain is broken during the preparation of magnetic paint, not only will the dispersibility of the ferromagnetic powder decrease, but also the copolymer itself will be damaged. The solubility of

On the other hand, the carbon-carbon bond of the carboxylic acid-containing repeating unit of the present invention is very stable, and the bond is rarely broken at this portion under normal conditions, so that the copolymer and ferromagnetic powder compatibility is preserved.

Furthermore, while many conventional repeating units contain a highly reactive nitrogen atom T in their side chains, the carboxylic acid-containing repeating unit of the present invention does not contain such a nitrogen atom T.
For example, it is said that it is stable with few decomposition reactions occurring even when it is left under harsh conditions for a long time, such as when preparing magnetic paint or when magnetic recording media are left under high temperature and high humidity conditions F for a long time. be able to.

In a copolymer containing a repeating unit derived from vinyl chloride and the above-mentioned repeating unit, the main chain and the carboxylic acid no^ are separated, so for example, the L@o cylindrical structure of the copolymer, etc. It is less affected by the ferromagnetic powder and shows a high affinity for the ferromagnetic powder. Therefore, the state of dispersion of the ferromagnetic powder in the magnetic layer is improved.

The content of the unreleased 11 carboxylic acid-containing repeating units in the copolymer is usually in the range of 0.1 to 10% by weight (preferably 0.2 to 8% by weight). If it is less than 0.1% by weight, the effect of introducing carboxylic acid groups may not be sufficiently exhibited, and the dispersion state of the ferromagnetic powder may not be sufficiently improved. Moreover, if the number of layers exceeds 10, the solubility of the copolymer in an organic solvent decreases, and as a result, the dispersion state of the ferromagnetic powder may not be sufficiently improved.

In addition, the above-mentioned copolymer contains one usually vinyl chloride in addition to a repeating unit derived from vinyl chloride and a repeating unit having a carboxylic acid ^ which is not directly bonded to carbon constituting one chain of the copolymer. Examples of other repeating units that may contain other repeating units contained in the copolymer include repeating units derived from vinyl acetate, and repeating units derived from maleic anhydride. , a repeating unit having a polar group such as a hydroxyl group or a sulfonic acid group, and a repeating unit having an epoxy group.

In particular, the humidity and heat stability of vinyl chloride is improved by introducing an epoxy group. However, the content of other repeating units in the copolymer is usually 1% or less.

Further, the degree of polymerization of the copolymer is usually within the range of 150 to 650 (preferably 200 to 600). Degree of polymerization is 15
If the copolymer is less than 0, the strength of the copolymer itself is not sufficient, so the running durability may not be sufficient, and if it exceeds 650, the dispersion state of the ferromagnetic powder may be poor. be.

Such a copolymer can be prepared, for example, by adding a monomer and vinyl chloride that induce the carboxylic acid-containing repeating unit of the present invention, and further other repeating units as necessary It can be produced by co-association with a compound that induces .

Does the binder use the above copolymer as a resin component? Although it can be used alone, it is preferable to use a resin commonly used as a resin component of magnetic recording media in combination. In particular, as a resin component, it is preferable to use a polyurethane resin in combination. Examples of polyurethane resins include commonly used polyurethane resins, polyester polyurethane resins, carboxylic acids, hydroxy acids,
Examples include polyurethane resins having polar groups such as (or carboxylic acid) and (etc.).

When a polyurethane resin is used, the ratio of the combination of the above compound and the polyurethane resin is 9:1 to 1:
It is preferable to set it within the range of 9.

In addition, it is preferable to use a hardening agent in addition to the resin components 1 to 1. In particular, when using a ferromagnetic metal fine powder as the ferromagnetic powder, the hardness of the ferromagnetic gold J11 fine powder can be reduced by using a hardening agent. A magnetic layer with high strength can be obtained despite the use of . As the curing agent, polyisocyanate compounds that are normally used in the production of polyurethane resins are used.

If a curing agent is used, the blending percentage of the resin component and curing agent
The quantitative ratio is preferably within the range of 9:1 to 5:5.

Usually, the magnetic layer of an undeveloped magnetic recording medium contains an abrasive. There is no particular restriction on the abrasive used, and any commonly used abrasive can be used. Ken,
The polishing material is usually 0.0 parts per 1.19 parts of 100% ferromagnetic powder.
．． 2 to 107K It is blended so that it is sized.

Further, in addition to the abrasive material listed in L, it is preferable to contain conductive carbon black, a lubricant, and the like.

As for the lubricant, it is preferable to use a combination of multiple 1171 lubricants, such as a combination of a lubricant that mainly acts when running at low speeds and a lubricant that mainly acts when running at high speeds.

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

First, prepare a magnetic paint by kneading 1 ferromagnetic powder and a resin component, and if necessary (if abrasive material or additives listed in L) with a solvent. Commonly used solvents can be used.

There is no particular restriction on the kneading method, and the order of addition of each component can be set as appropriate.

When preparing magnetic paint, 1 dispersant, ii? Known additives such as antistatic agents and lubricants may also be used.

The magnetic paint thus prepared is applied onto the aforementioned non-magnetic support. Coating can be performed 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 10 lm (preferably in the range of 1.5 to 7.0 lm).

The magnetic layer formed on the 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.Furthermore, if necessary, a surface digestion treatment is performed. The magnetic recording medium that has been subjected to surface smoothing treatment is then subjected to hardening treatment and blade treatment in steps q and then cut into a predetermined shape.

Next, Examples and Comparative Examples of the present invention will be shown. In addition, in the Examples and Comparative Examples, the expression "Part 1" indicates "R modified +, Part H".

[Example 1] The composition described in F was cross-dispersed for 3 hours using a sand grinder, and then filtered using a filter having an average pore diameter of 3 JLm to prepare a magnetic paint. The obtained magnetic paint was coated with a thickness of 7 gm so that the thickness of the magnetic layer after drying was 5.0 gm.
It was applied onto the surface of a JLm polyethylene terephthalate support using a reverse roll.

Xiu J11 Hongyu Co-modified 7-Fe0x (X = 1.45. Ca: 5% Le%, Hc:
Ei800e, needle ratio 1:12, specific surface area: 40rn
'/g) 100 parts Vinyl chloride copolymer 20 parts Polyester polyurethane resin (Molecular weight: 50,000) 5 parts α
-Ai 20 pieces (V average particle diameter = 0.5 final m) 2 parts myristic acid 3 parts dimethylpolysiloxane (degree of polymerization 60) 0.5 parts methyl ethyl ketone 180 parts cyclohexanone
60 parts However, the vinyl chloride-based resonance combination in L is a vinyl chloride/vinyl acetate e-carboxyl methyl acrylate copolymer (for polymerization, ratio = 86: 1)
3:1, polymerization degree 400).

The non-magnetic support coated with the magnetic paint was subjected to magnetic field alignment treatment using a 1000 Gauss magnet while the magnetic paint was still wet, and after drying, supercalender treatment and blade treatment were performed to obtain a width of 3.81 mm. A Phillips-type compact cassette tape (c-90) was produced by slitting.

Squareness ratio of the magnetic layer of the obtained cassette tape, surface gloss, maximum undistorted output (CMOL), saturation output (SQL), bias noise (BN), runnability, and dirt on the tape pad and magnetic head inside the device The degree of adhesion was measured. The results are shown in Table 1.

Note that the above measurements were performed as follows.

An external magnetic field (H
m) B r at 2 koe (159 kA/m)
/Bm value was measured.

Using a thin surface gloss meter (manufactured by Suga Testimonial A-, GK-45D) on Yugako, the gloss of the magnetic layer surface was measured, and the gloss of the black standard surface was 87%.
It was measured as

The measured maximum undistorted output (3% tertiary high frequency) at OL 315 Hz, and the value marked with 0 is a relative value when taken as MOLftOdB of the cassette tape manufactured in Comparative Example 1. In addition,
The measuring device was a TCK-777ESII model (manufactured by Sony ■).

The value expressed as 0 in which the saturation output of SQL 10 kHz was measured is a relative value when the SQL of the cassette tape manufactured in Comparative Example 1 is set to OdB. Note that the measuring device was the same model as above.

Bias noise (B) measured using the same model as above
The measured value expressed as 0 is a relative value when the bias noise (BN) of the cassette tape manufactured in Comparative Example 1 is set to OdB.

Running properties When the obtained cassette tape 50a was run 20 times back and forth using 50 commercially available cassette tape decks, the number of turns of the cassette tape at which running stopped was measured.

A: No stop cassette tape B: Stop cassette tapes 1 to 2a Degree of dirt adhesion After the above running test, the degree of dirt adhesion to the tape pad and magnetic head in the cassette deck was observed and evaluated according to the following criteria. .

A: There is no dirt attached B- There is a slight amount of dirt attached Cφ - There is some dirt attached although it is not a problem in actual use [Example 2] In Example 1, A Phillips-type compact cassette tape was produced in the same manner except that the vinyl chloride-based composite described below was used.

Vinyl chloride/vinyl acetate/carboxyl methyl acrylate copolymer copolymer ratio = 82:3:5, degree of concentration: 400 The same measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Example 3] A Phillips-type compact cassette tape was produced in the same manner as in Example 1, except that the vinyl chloride-based composite described below was used.

Vinyl chloride/vinyl acetate-10-carboxyldecyl acrylate copolymer copolymerization ratio=86:13:1 Degree of polymerization 400 The same measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Example 4] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described below was used.

Vinyl chloride/vinyl acetate allyl acetic acid copolymerization weight ratio = 86:13:1 Degree of polymerization 400 The same measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Example 5] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described below was used.

Vinyl chloride/vinyl acetate/carboxyl methyl acrylate copolymer 4
Ratio = 86:13:1 Degree of polymerization: 200 t'J The same type of measurements as in Example 1 were carried out on the cassette tape. The results are shown in Table 1.

[Example 6] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride-based composite described in F below was used.

Vinyl chloride/vinyl acetate carboxylic methyl acrylate copolymer weight ratio = 86:13:1 Degree of polymerization 600 The same measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Example 6] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described below was used.

Vinyl chloride e carboxyl methyl acrylate-glycidyl acrylate copolymer was copolymerized at Shukoku = 94:5:1, degree of polymerization: 400. The same measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Comparative Example 1] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described in F below was used.

Vinyl chloride/vinyl acetate/maleic anhydride copolymer weight ratio = 86:13:1 Degree of polymerization 400 The same measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

Table 1 Squareness Ratio Glossiness MOL SQL BN Runnability #
(X) (dB) (dB) (dB) Example 1 0.89 176 1.2 2.1~0.2
A A2 0.88 178 1.1 2.
2-0.3 A A3 0.89 1?5
1.3 1.8-0.3 A A4 0.90
1?6 1.3 2.0-0.3 A A5
0.90 178 +, 3 2.2-0.3
A BG 0.88 172 1.0 1
．． 7-0. I B A7 0.89 17?
1.2 2.3-0.5 A A Comparative Example 1 0.86 162 0.0 0.0 0. OB
C [Example 101 The composition in F was cross-dispersed for 5 hours using a sand grinder, filtered using a filter having an average pore size of lm, and then mixed with a polyisocyanate compound (Desmodur L-75 (Bayer)). Co., Ltd.)) and mixed to prepare a magnetic paint. The obtained magnetic paint was applied onto the surface of a polyethylene terephthalate support having a thickness of 104 m using a reverse roll so that the thickness of the magnetic layer after drying was 3.0 Lm.

Magnetic paint composition: Ferromagnetic totally refractory fine powder (components: Fe, Zn, An, Ha, 15000e,
Acicular ratio, 1:15, specific surface area, 60 m'/g) 100
Part 11! Vinyl chloride copolymer 10 parts Polyester polyurethane resin (sulfonic acid), (containing 0.5 weight 1118% IL average molecular weight: t:: 50,000) 10i α-A text, 03 (1. Average particle size: 0 .27 parts m) 3 parts stearic acid 2 parts butyl stearate 1 part conductive carbon ("1LEJ grain 7-diameter: 10 mg)
1 part methyl ethyl ketone 180 parts cyclohexanone 60 parts However,
The vinyl chloride/vinyl acetate/carboxyl methyl acrylate copolymer used in Example 1 was used as the vinyl chloride copolymer described in item (2).

The non-magnetic support coated with the magnetic paint is subjected to a magnetic field orientation treatment using a 3000 Gauss magnet in a state where the magnetic paint is not yet dried, and after drying, a super calender treatment, a hardening treatment and a blade treatment are carried out. An 8 mm video tape was produced by slitting the tape into mm $+i.

The squareness ratio 1 surface glossiness, C-S/N ratio, Y-S/N ratio, still life, runnability, and durability of the magnetic layer of the fully rolled video tape were measured, and the results are listed in Table 2. do.

Incidentally, the measurements described in F were performed as follows.

The external magnetic field (
Hm) B at 5 kOe (398 kA/m)
The magnitude of r/Bm was kept constant at Δ.

Surface gloss It was measured by the same method as above.

Recording wavelength of the videotape manufactured in C-S/N ratio comparative example 2: 0.7 MH
The S/N ratio was measured when the S/N ratio at z was expressed as OdB.

The measuring device is FUJ lX-8 (Fuji Photo Film)
tA).

Recording wavelength of the videotape manufactured in Y-S/N ratio comparative example 2: 5 MH
The S/N ratio was measured when the S/N ratio at z was expressed as OdB.

Note that the measuring device was FUJIX-8.

Still Life In still mode, the time required for the Y-S/N ratio of the image to decrease by 6 dB from the starting image was measured.

Note that the zero constant machine is FUJTX-8.

Running properties were evaluated based on the degree of jitter and skew during running according to the criteria described in F below.

A. Both jitter and skew are good. B. Jitter and skew are both increased, although it is not a problem in actual use. Durability After running 100 times, there is no jitter, kneeling, or dropout. The degree of increase was evaluated according to the following criteria.

A: No particular problem B: An increase that is not a problem in actual use C: An excessive increase is observed [Examples 9 to 14, Comparative Example 2] In Example 1O, F An 8 mm video tape was produced in the same manner as in Example 10, except that the vinyl chloride copolymer described in Section 11 was used.

The squareness ratio of the magnetic layer of the obtained videotape, the surface glossiness,
The C@S/N ratio, Y fist S/N ratio, still life, running performance, and durability were measured and the results are listed in Table 2.

Vinyl chloride copolymer used Example 9 Same as used in Example 2 10
Times used in Example 3 11 Same as those used in Example 4 12 Times used in Example 5 14 Times used in Example 6 14
Comparative example 2 used in Example 7
Those used in Comparative Example 1 are as follows:

Claims (1)

[Claims] 1. 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, in which the binder has a main chain A repeating unit having -COOM (M represents a hydrogen atom or an alkali metal atom) bonded through at least one carbon atom directly bonded to a constituent carbon atom, and a repeating unit derived from vinyl chloride. A magnetic recording medium comprising a resin component containing a copolymer containing. 2. A repeating unit with -COOM bonded through at least one carbon atom that is directly bonded to a carbon atom constituting the main chain has the formula ▲ Numerical formula, chemical formula, table, etc. (However, R represents a hydrogen atom or a methyl group, and R^
1 represents a divalent aliphatic hydrocarbon group of 1 to 17, M represents a hydrogen atom or an alkali metal atom), and/
Or, there are formulas▲mathematical formulas, chemical formulas, tables, etc.▼ (However, R represents a hydrogen atom or a methyl group, and R^
2. The magnetic recording medium according to claim 1, wherein 2 represents a divalent aliphatic hydrocarbon group of 1 to 17, and M represents a hydrogen atom or an alkali metal atom. 3. The magnetic recording medium according to claim 2, wherein R^1 and R^2 are divalent straight chain aliphatic hydrocarbon groups having 1 to 12 carbon atoms. 4. The content in the copolymer of repeating units having -COOM bonded through at least one carbon atom directly bonded to a carbon atom constituting the main chain is 0.1
2. The magnetic recording medium according to claim 1, wherein the content is in the range of 10% by weight. 5. The magnetic recording medium according to claim 1, wherein the degree of polymerization of the copolymer is within the range of 150 to 650. 6. A copolymer of repeating units derived from vinyl chloride. 2. The magnetic recording medium according to claim 1, wherein the content in the magnetic recording medium is 60% by weight or more. 7. The magnetic recording medium according to claim 1, wherein the resin component of the binder further contains a polyurethane copolymer.