JPH01100727A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent surface characteristics and durability and excellent magnetic characteristics, electromagnetic conversion characteristics, etc., by using a specific vinyl chloride copolymer as the binder of a magnetic layer. CONSTITUTION:The vinyl chloride copolymer contg. a ternary amine and at least one kind of a phosphoric acid group, sulfonic acid group, sulfuric acid group, and carboxyl group is used as the binder. A vinyl chloride resin is constituted by introducing these polar groups into the side chain of the vinyl chloride copolymer. The binder, therefore, exhibits extremely high affinity to magnetic powder and has the good dispersibility of even, for example, ultrafinely ground magnetic powder and magnetic powder having a large magnetization quantity. The durability and surface characteristics of the resultant magnetic recording medium are improved and the excellent electromagnetic conversion characteristics are obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium such as a magnetic tape, and more particularly to a binder contained in a magnetic layer formed on a non-magnetic support. This is related to the improvement of

[Summary of the invention]

The present invention provides a magnetic recording medium in which a magnetic layer consisting mainly of ferromagnetic powder and a binder is formed on a non-magnetic support. By using a beer chloride copolymer having a polar group and an acidic polar group, the dispersibility of the magnetic powder and the surface properties of the magnetic layer are improved, and the durability of the resulting magnetic recording medium is improved.
The aim is to improve magnetic properties, electromagnetic conversion properties, etc.

[Conventional technology]

In recent years, magnetic recording media, especially magnetic recording media for VTRs (video tape recorders), have been required to have improved magnetic properties and electromagnetic conversion properties in order to obtain high playback output even when recording at short wavelengths. There is.

As a countermeasure, efforts have been made to make the magnetic powder particles finer and to increase the magnetic force, and there is a strong tendency to increase the packing density of the magnetic powder in the magnetic layer, the so-called backing density.

On the other hand, conventionally used binders for magnetic recording media include vinyl chloride-vinyl acetate copolymer, vinyl chloride-propionic acid copolymer, and vinyl chloride-vinyl acetate copolymer.
Examples include vinyl chloride-based binders such as vinyl alcohol copolymers, among which the hydroxyl groups of vinyl alcohol contribute to the dispersibility of magnetic powder, and the active hydrogen of the hydroxyl groups reacts with isocyanate compounds to form a crosslinked structure. Vinyl chloride-vinyl acetate-vinyl alcohol copolymers are widely used because of their ability to form and increase the mechanical strength of coating films.

However, due to the increase in specific surface area due to the finer particles of magnetic powder and the increase in cohesive force due to higher magnetic force, the above-mentioned binders cannot provide satisfactory dispersibility and surface properties, and buffing of magnetic powder is difficult. It has also become difficult to increase king density.

Therefore, the durability, magnetic properties, and electromagnetic conversion properties were also insufficient. Alternatively, methods such as using a surfactant as a dispersant have been considered, but in this case, since the surfactant is a low molecular weight, the presence of this surfactant in the magnetic layer causes the powder to become powdery. Problems have arisen in terms of mechanical strength and durability, such as falling off and plumping due to changes over time.

Under these circumstances, there is a need for a binder that can further improve these properties. Techniques have been proposed in which polymers into which polar groups such as metal salts, acidic sulfuric esters or alkali metal salts thereof, carboxylic acids or alkali metal salts thereof are introduced are used as binders.

However, although the binders produced by these technologies show some effect in improving dispersibility compared to conventional binders that do not have polar groups introduced, The performance with respect to powder was insufficient and lacked practicality.

[Problem that the invention seeks to solve]

As described above, there is no known binder that exhibits sufficient dispersibility even for ultrafine magnetic powder, and magnetic recording media using this ultrafine magnetic powder do not meet the specified durability and T61 characteristics. , it was difficult to ensure electromagnetic conversion characteristics.

Therefore, the present invention was proposed in order to eliminate the above-mentioned drawbacks in the technical field, and provides a binder that can further improve the dispersibility of magnetic powder, and improves surface properties and durability. The purpose of the present invention is to provide a magnetic recording medium with excellent magnetic properties, electromagnetic conversion properties, etc.

[Means for solving problems]

The inventors of the present invention have conducted intensive research over a long period of time in order to achieve the above-mentioned objectives, and have found that the phosphoric acid group in the side chain has a high coating viscosity but has high affinity and improves dispersibility.

Acidic polar groups such as sulfonic acid groups, sulfate groups, and carboxyl groups are combined with basic polar groups of tertiary amines, which have the effect of further improving dispersibility and durability, into vinyl chloride copolymers. The present invention was completed based on the knowledge that by introducing the two, the effects of both are synergistically exhibited, and a magnetic layer with extremely excellent dispersibility and durability can be provided. The present invention has been obtained based on the above-mentioned findings, and provides a magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a non-magnetic support. 3 amine and a vinyl chloride copolymer having at least one of a phosphoric acid group, a sulfonic acid group, a sulfuric acid group, and a carboxyl group.

In the present invention, the vinyl chloride resin contained in the binder has a polar group (a tertiary amine and at least one of a phosphoric acid group, a sulfonic acid group, a sulfuric acid group, and a carboxyl group) in the side chain of the vinyl chloride copolymer. It introduces the general formula, (CHzCH) i→X+r-f-Y)W-(Z
12 (In the formula, X represents a monomer having a vinyl group copolymerizable with vinyl chloride, Y represents a monomer having a vinyl group and tertiary amine copolymerizable with vinyl chloride, and Z is copolymerizable with vinyl chloride. vinyl group, phosphoric acid group, sulfonic acid group,
Represents a monomer having at least one of a sulfate group and a carboxyl group, and i, j, ni, j! represents the degree of polymerization, respectively. In addition, in the above-mentioned section, each component of the compound is described as being arranged in a regular order for convenience, but in addition to the case shown in the above-mentioned section, each component is arranged in regular proportions. Of course, they may be arranged repeatedly or randomly.

Here, the degree of polymerization (i+j+
+j2) is preferably within the range of 100≦(i+j++1≦1000. If this value is less than 100, the durability of the resulting coating film will deteriorate, and if it exceeds 1000, the solvent will The solubility in the paint deteriorates, making it difficult to form into a paint.

The vinyl chloride component contained in the vinyl chloride copolymer preferably accounts for 30 to 95% by weight. If this value is less than 30% by weight, durability will deteriorate;
If it exceeds 5%, thermal deterioration is likely to occur.

The amount of the tertiary amine introduced into the vinyl chloride copolymer is preferably 0.001 rm mol/g or more, and the amount of phosphoric acid group or sulfonic acid group introduced into the vinyl chloride copolymer is preferably 0.001 rm mol/g or more. The amount of at least one of , sulfate group, and carboxyl group introduced is also preferably 0.00111 mol/g or more. The combined content of tertiary amine and at least one of phosphoric acid group, sulfonic acid group, sulfuric acid group, and carboxyl group is 0.01 to 1.0 m mol/
It is preferable that it is within the range of g.

If this value is less than 0.01 m mol/g, the dispersibility deteriorates; If it exceeds Om mol/g, the solubility in the solvent will decrease and at the same time the moisture resistance during coating film formation will deteriorate.

Next, the monomers X, Y, and Z will be explained in order.

First, the monomer X mentioned above includes vinyl acetate, vinyl alcohol, maleic acid, and maleic anhydride.

Acrylic acid, acrylic ester, methacrylic acid.

Examples include methacrylic acid ester, acrylonitrile, vinylidene chloride, vinyl propionate, and hydroxyl group-containing monomers such as 2hydroxyethyl methacrylate, 2hydroxyethyl acrylate, and 2hydroxypropyl acrylate. These are added as appropriate from the viewpoints of solubility in solvents, improvement of crosslinking properties, improvement of coating film strength, etc., and two or more types may be used as a mixture.

Next, regarding the monomer Y, the tertiary amine constituting the monomer Y-t- is represented by -NR1 (R represents a compound having 1 to 12 carbon atoms), such as the following substances. can be mentioned.

i) R' CHz=CCOOCCHt)J(Rh ii) R' CHi=CCOO(CHzhN(R)tiii)
R' CHz=CCONH(CHz) KN (R) ziv
) Fl' CHt=CCONH(Cut) sN (R) z (wherein R represents an alkyl group having 1 to 3 carbon atoms,
R' represents hydrogen or a methyl group, respectively. ) etc.

In addition, phosphoric acid groups, sulfonic acid groups, which constitute monomer Z,
A sulfate group and a carboxyl group represent an alkyl group and a phenyl group, respectively. ) 5-0 SO! .

-3OJ, -COOH, and examples include the following substances.

■ CHz=CHCNHC(CHs) zcHzs(h
H■ HOOCCH=CHCOOH By copolymerizing these monomers Y and Z with the vinyl chloride monomer, monomer X, etc., a radial group can be introduced into the vinyl chloride copolymer.

Further, phosphoric acid groups, sulfonic acid groups, sulfuric acid groups, carboxyl groups, etc. can also be introduced into vinyl chloride by the following method.

After copolymerizing with vinyl chloride a monomer having a double bond and active hydrogen that can be copolymerized with vinyl chloride, a group that can react with active hydrogen, a phosphoric acid group, and a sulfone fI! A method of modifying with a compound having at least one of a group, a sulfate group, and a carboxyl group in the molecule.

Double bonds and active hydrogen (
Examples of the hexamer having a group (which may be a group capable of reacting with chlorine) include (in the formula, X represents H or CH), and vinyl alcohol.

In addition, as a compound having a group capable of reacting with active hydrogen and a hydrophilic polar group in the molecule, for example, C1-1(O
ll)z, CIGHz-j:(Oll)z, C
j! -3OJ.

CjICHz-5OJ, Cl0SlhH, fJcl
lt-OSO3H.

CI! Phosphoric acid group, sulfonic acid group, sulfuric acid group in molecules such as -COOH and C41CHz-COOH.

Examples include compounds containing a carboxyl group and chlorine.

Alternatively, in addition to the above-mentioned chlorine, compounds having an isocyanate group, an epoxy group, or an aziridinyl group can also be used as the group capable of reacting with active hydrogen.

As described above, at least one of phosphoric acid groups, sulfonic acid groups, sulfuric acid groups, and carboxyl groups can be introduced into the vinyl chloride copolymer.

Furthermore, alkali metal bases such as phosphoric acid groups, sulfonic acid groups, sulfuric acid groups, and carboxyl groups may be introduced into the vinyl chloride copolymer for the purpose of improving coating viscosity.Introduction of these basic polar groups The method uses the above-mentioned phosphoric acid group, sulfonic acid group,
This can be carried out in the same manner as the method for introducing acidic polar groups such as sulfate groups and carboxyl groups.

The above-mentioned tertiary amine, phosphoric acid group, and sulfonic acid group.

A vinyl chloride copolymer containing at least one of a sulfuric acid group and a carboxyl group may be used in combination with other binders. Such binders include those conventionally used as binders for magnetic recording media. are available, and
Vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, bimol chloride-acrylonitrile copolymer,
Acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride , vinylidene chloride
Acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenol resin, epoxy resin, thermosetting polyurethane resin, Examples include urea resins, melamine resins, alkyd resins, urea-formaldehyde resins, and mixtures thereof.

Among these, polyurethane resins, polyester resins, acrylonitrile butadiene copolymers, etc., which are said to impart flexibility, are preferred.
Functional isocyanate compound.

If a reaction product of 1 mole of trimethylolpropane and 3 moles of tolylene diisocyanate is used in combination, durability etc. can be further improved. In any case, the polar group equivalent (molecular weight per polar group) of at least one of the tertiary amine, phosphoric acid group, sulfonic acid group, sulfuric acid group, and carboxyl group in these binders is 1, 000～
It is preferably within the range of 100.000; if this value exceeds too, ooo, no effect can be expected;
If it is less than 000, the effect will not change much, but problems will arise in terms of moisture resistance.In the magnetic recording medium of the present invention, the magnetic layer is made by dispersing, for example, ferromagnetic powder in the above-mentioned binder and dissolving it in an organic solvent. It is formed by applying the prepared magnetic paint onto the surface of a non-magnetic support.

Here, the material for the non-magnetic support may be any material that is normally used in this type of magnetic recording medium, such as polyesters such as polyethylene terephthalate, polyolefins such as polyethylene, polypropylene, etc. cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate polyimide, polyamide, and polyamideimide, paper, aluminum, and metals such as 1Ji1. , light alloys such as aluminum alloys and titanium alloys, ceramics, and single crystal silicon. The form of this non-magnetic support is as follows:
film, tape.

Any of sheet disks, cards, drums, etc. may be used.

Moreover, any ordinary ferromagnetic powder can be used as the ferromagnetic powder used in the magnetic layer. Therefore, ferromagnetic powders that can be used include ferromagnetic iron oxide particles,
Examples include ferromagnetic chromium dioxide, ferromagnetic alloy powder, macrogonal barium ferrite fine particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles include -S2Fed.

When expressed as
0), magnetite (F e O,x = 1.33)
and solid solutions thereof (F e 011 , 1.33 <
x < 1.50).Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force.Cobalt-containing iron oxides can be roughly divided into two types: doped type and coated type. There are different types.

The above-mentioned ferromagnetic chromium dioxide may include Cry, or Ru for the purpose of improving coercive force.

A material containing at least one of Sn, Te, Sb, Fe, Ti, V, Mn, etc. can be used.

As a ferromagnetic alloy powder, V er + Co * N
i.

Fe-Co, Fe-Ni, Fe-Co-Ni.

Co-Ni, Fe-Co-B, Fe-Go-Cr-B,
Mn-B1. Mn-Al, Fe-Go-V, etc. can be used, and AIl, S
i, Ti, Cr, Mn, Cu.

A metal component such as Zn may also be added.

In addition to the binder and ferromagnetic powder, the magnetic layer also contains additives such as a dispersant, a lubricant, an abrasive, an antistatic agent,
These dispersants, lubricants, etc. may be added with rust preventive agents, etc.
Any conventionally known abrasives, antistatic agents, and rust preventives can be used.

The constituent materials of the magnetic layer described above are prepared as a magnetic paint by dissolving it in an organic solvent and coated on a non-magnetic support.The solvent for the magnetic paint may be acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Ketone solvents, methyl acetate, ethyl acetate, butyl acetate,
Ethyl lactate.

Ester solvents such as acetic acid glycol monoethyl ether, glycol ether solvents such as glycol dimethyl ether, glycol monoethyl ether, dioxane, etc.
Aromatic hydrocarbon solvents such as benzene, toluene and xylene, aliphatic hydrocarbon solvents such as hexane and heptane, methylene chloride, ethylene chloride, carbon tetrachloride,
Examples include organic chlorine compound solvents such as chloroform, ethylene chlorohydrin, and dichlorobenzene.

[Effect]

Phosphate group introduced into vinyl chloride copolymer.

At least one of a sulfonic acid group, a sulfuric acid group, and a carboxyl group
The acidic polar group consisting of seeds has excellent dispersibility and durability. Further, the basic polar group of the tertiary amine introduced into the vinyl chloride copolymer can be made into a practical binder by adding clay as a binder.

By using both of these properties together, a synergistic effect is exhibited, and even when ultrafine magnetic powder or magnetic powder with a large amount of magnetization is used, good dispersibility is expected, and workability is improved. It also improves.

(Examples) Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

First, a vinyl chloride resin was prepared. That is, butyl acrylate and 2-hydroxyethyl acrylate are used as the monomer X copolymerizable with vinyl chloride, and the following a) to e) are used as the monomer Y copolymerizable with vinyl chloride. (CHi)z
e) CH! =CHCNHC(CH3)ICH! 5O
3He) A resin was also prepared in which a substance represented by the formula HOOCCH=CHCOOH was selected, and an alkali metal sulfonic acid salt was introduced in addition to a tertiary amine and an acidic polar group. The above alkali metal sulfonic acid salt has the following formula: CHz=CHCHZOCOCIC11tCOOC+ 2
It is expressed as Htt03Na.

Table 1 shows the types and contents of the four polar groups added to the vinyl chloride copolymer.

(The following is a blank space) Table 1: Using the above-mentioned Resin 1, a magnetic coating composition was prepared according to the following composition.

Ferromagnetic metal iron powder 670 parts by weight (specific surface area 45rdIg, axial ratio 11-13) Vinyl chloride copolymer resin 1100 parts by weight Carbon black
35 parts by weight CrZO! particle
60 parts by weight olive oil
7 parts by weight methyl ethyl ketone 3
50 parts by weight cyclohexanone 35
0 parts by weight Toluene 350 parts by weight The above composition was kneaded and dispersed for 20 minutes in a ball mill, and then 28 parts by weight of an isocyanate compound (Desmodur L, manufactured by Bayer) was added and dispersed under high-speed shearing to obtain a magnetic paint.

This magnetic paint was applied to one side of a polyethylene terephthalate film with a thickness of 14 μm and a surface roughness of 0.03 μm to a dry thickness of 4 μm.
．． The sample tape was coated to a thickness of 0 μm, then oriented in a 2500 Gauss DC magnetic field, dried at 80° C., supercalendered, and cut into a 172-inch width to prepare a sample tape.

Sample tapes were prepared in the same manner as in Example 1, except that Resin 2 to Resin 9 were used in place of Resin 1 in Example 1.

' 1 to 6 4 Resin 10 to Resin 13 instead of Resin 1 in Example 1
A sample tape was prepared in the same manner as in Example 1 except for the following.

Surface gloss, powder removal, and paint viscosity were measured for each sample tape obtained.

Note that the above surface gloss was measured using a glossy needle at an incident angle of 75".
, and the reflection angle was 75°. In addition, powder fall is 6
After running the shuttle 100 times for 0 minutes, the amount of powder falling onto the head drum, guide, etc. was visually observed and evaluated using a point deduction method. The results are shown in Table 2.

As is clear from Table 2, the tertiary amine and phosphoric acid group,
By using a vinyl chloride copolymer containing acidic polar groups such as sulfonic acid groups, sulfuric acid groups, and carboxyl groups as a binder, surface gloss and powder removal are improved overall compared to when this is not used. I understand that.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Vinyl chloride copolymer with excellent dispersibility and durability, low in phosphoric acid groups, sulfonic acid groups, sulfuric acid groups, and carboxyl groups (all 1 type) and tertiary amine as a polar group, which further improves dispersibility and durability. Since coalescence is used as a binder for the magnetic layer,
Both effects are exerted synergistically, and it exhibits a very high affinity for magnetic powder, resulting in good dispersibility even for ultrafine magnetic powder or magnetic powder with a large amount of magnetization. Therefore, the durability of the magnetic recording medium obtained is 1
The surface properties are improved and the electromagnetic conversion characteristics are also extremely excellent.

Claims (1)

[Claims] A magnetic recording medium in which a magnetic layer mainly consisting of ferromagnetic powder and a binder is formed on a non-magnetic support, wherein the binder comprises a tertiary amine, a phosphoric acid group, and a sulfonic acid group. ,
A magnetic recording medium comprising a vinyl chloride copolymer having at least one of a sulfate group and a carboxyl group.