JPH01245422A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the desorption of a binder from magnetic powder so as to improve the dispersibility of the magnetic powder and to decrease the dislodgment thereof by incorporating a vinyl chloride compd. having a residual aminocarboxylic acid in the molecule as the binder to constitute a magnetic layer. CONSTITUTION:The magnetic layer 2 essentially consisting of the magnetic powder and the binder is provided on a nonmagnetic base 1 and the vinyl chloride compd. having the residual aminocarboxylic acid in the molecule is incorporated as the binder therein. The vinyl chloride compd. prepd. by introducing the residual aminocarboxylic acid as a polar group into the side chain of the vinyl chloride compd. is used as the vinyl chloride compd. to be incorporated into the binder. The desorption of the binder from the magnetic powder is thereby prevented and the dispersibility of the magnetic powder is improved and the dislodgment thereof is decreased.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to magnetic recording media such as magnetic tapes, and in particular to improvement of the durability of an aI magnetic layer formed on a non-magnetic support and This invention relates to improving the dispersibility of magnetic powder blended into a magnetic layer.

[Summary of the invention]

The present invention creates a magnetic paint with excellent viscosity characteristics by containing a vinyl chloride copolymer having aminocarboxylic acid residues in the molecule as a binder constituting the magnetic layer, and also creates a magnetic paint with excellent viscosity characteristics. The objective is to prevent the detachment of the binder, improve the dispersibility of the magnetic powder and reduce the shedding, improve the deterioration of the magnetic conversion characteristics of 1, and improve the durability of the magnetic coating film.

[Conventional technology]

Kl magnetic recording media are moving toward higher density recording year by year. Under these circumstances, in the magnetic layer, magnetic powder with an extremely fine particle size is highly dispersed in the binder resin, and the surface of the magnetic layer is mirror-finished to improve the t [transformation characteristics]. At the same time, it is required to improve the durability of magnetic coatings.

That is, in the above magnetic recording medium, how well the magnetic powder contained in the magnetic layer is dispersed in the paint;
How to bond well with the binder is a very important issue.

Conventionally, vinyl chloride-based copolymers such as vinyl chloride-vinyl acetate copolymers have been widely used as binders for magnetic recording media as described above, but they are insufficient in terms of bonding strength with magnetic powder. However, this resulted in deterioration of the dispersibility of the magnetic powder.

Therefore, as a method to solve the above problems, a so-called dispersant (for example, a surfactant) or a compound having both an alkyl group (lipophilic group) and a hydrophilic group such as a fatty acid is added to the magnetic paint, and the dispersion By bonding the parent wood group of the dispersant or fatty acid with the parent wood group of the magnetic powder, and further bonding the lipophilic group of the dispersant or fatty acid with the lipophilic group in the binder, the magnetic powder and the binder are combined. It has been proposed to improve the durability and paternity of the magnetic powder by combining the two.

However, in this method, due to the action of the dispersant, the binder that was bonded to the magnetic powder is released into the container, leading to deterioration of the dispersibility of the magnetic powder, and the lipophilic group of the surfactant has polarity. Therefore, the bonding force with the binder is very weak and the interface reinforcing function is not fully demonstrated. The activator was deposited on the surface of the coating film, resulting in a significant lack of durability of the coating film.

On the other hand, in recent years, a method has been proposed in which carboxylic acid is introduced into the binder as a polar group in the form of phthalic anhydride or phthalic acid. A technology has been proposed that combines these functions. However, as mentioned above, when carboxylic acid is introduced as a polar group using phthalic acid, etc., although it works well against magnetic powders with basic surfaces, it works well against CFL powders with neutral or acidic surfaces. This results in extremely poor dispersibility.

Furthermore, the above-mentioned binder containing four major carboxylic acids tends to increase the viscosity of the paint, which poses a problem in terms of practicality.

(Problems to be Solved by the Invention) As mentioned above, in the field of magnetic recording media, there are problems such as the insufficiency of the binder used and the polar group added thereto, the relationship between the polar group and the surface characteristics of the magnetic powder, etc. Due to this, various practical characteristics remain unsatisfactory.

Therefore, the present invention was proposed in view of the above-mentioned conventional situation, and aims to prevent the detachment of the binder from the magnetic powder, improve the dispersibility of the magnetic powder, and reduce the detachment. The purpose is to provide a magnetic recording medium with excellent electromagnetic conversion characteristics and durability.

[Means to solve the problem]

As a result of intensive research to achieve the above object, the present inventor used a vinyl chloride copolymer as the binder resin and introduced aminocarboxylic acid residues into it to improve the affinity between the magnetic powder and the binder. It has been found that the dispersibility of the magnetic powder and the durability of coating are significantly improved.

The present invention has been made based on the above findings, and as shown in FIG. The magnetic recording medium is characterized in that the binder contains a vinyl chloride copolymer having aminocarboxylic acid residues in the molecule.

The present invention also provides a non-magnetic support (1
1) with a magnetic layer (12) on one side and 4 holes 1 on the other side.
A back coat layer (13
) may be applied to a 10-ki recording medium.

In the present invention, the vinyl chloride copolymer contained in the binder is the vinyl chloride copolymer side! An aminocarboxylic acid residue is introduced into j″4 as a polar group, and the general formula % formula %) (in the formula, X represents a polar group containing an aminocarboxylic acid residue,
In addition, Y represents a heptad containing a vinyl group copolymerizable with vinyl chloride, and i and j each represent the degree of polymerization.
) is a compound represented by In addition, in the above general formula (
Y) does not necessarily represent one type of monomer, but may be a combination of several types of monomers, and the monomer Y itself may have various functional groups or polar groups.

In the above general formula, each component of the compound is described for convenience as being arranged in a regular manner. Of course, they may be arranged or randomly arranged.

In the above compound, the aminocarboxylic acid residue that is the polar group It is a compound that simultaneously has both groups in the molecule, for example, in addition to aminocarboxylic acid residues containing -Nils group and -COO11 group, -N11 group and -COO group.
Iminocarboxylic acid residues containing H5 and ・N-1 and -COO
Pyridine carboxylic acid residues including II5 are also included.

Examples of the above aminocarboxylic acid residue include ■-Nil
(C1h) -COOH o-N11. C,I,I,C,0,01,. . 1゜■＞
Examples include various residues that are introduced into the binder resin in the form of N-(C112), COO11O-N"'10011), etc.

Any of the conventionally known introduction methods can be used to introduce these various 7-minocarboxylic acid residues into vinyl chloride copolymers. Consists of monomers contained in
This resin can be introduced by copolymerizing it with other vinyl resins or monomers represented by Y in the general formula.

Compound (binder) synthesized by the method described above
In the above, the vinyl chloride component greatly contributes to the strength of the coating and the solubility in the solvent. In other words, if the degree of polymerization i of the vinyl chloride component is smaller than loo, the desired coating strength cannot be obtained. Moreover, if i is larger than 1000, the solubility in the solvent will deteriorate. Therefore, it is preferable that the degree of polymerization i is 100 to 1000.

Furthermore, the vinyl component in which an aminocarboxylic acid residue is introduced into the side chain as a polar group X contributes to improving the dispersibility of the magnetic powder, but the effect is insufficient if the degree of polymerization k is less than 0.05. On the other hand, even if the degree of polymerization k is greater than 10, the effect of improving dispersibility does not change much and problems arise in terms of moisture resistance. It is necessary to set it to 0.05-10 degree.

In addition to the copolymerizable monomers mentioned above, vinyl acetate, vinyl alcohol, maleic acid, maleic anhydride, acrylic acid, etc. , acrylic ester, methacrylic acid, methacrylic ester, acrylonitrile, vinylidene chloride, vinyl propionate, HEMΔ
, 1 (EA, glycidyl acrylate, glycidyl methacrylate, etc.) can be copolymerized as a heptamer Y having a vinyl group that can be copolymerized with vinyl chloride. 503M, -0303M, -1: (ON) □, -C
OOM.

Polar groups such as -Nllz, -NRII, -NRx (M in the above polar groups is H.

), -011, -511, -1, j-, q11□, which represents alkali metals such as Na and Ka, quaternary ammonium salts, etc.
It may contain functional groups such as.

Furthermore, in the vinyl chloride monomer, -011, glycidium
′・-ma””・-°゛“・”゛“* R;jr:'!4
)□ゝ, T'i, /h Graft polymerization may be carried out with a compound containing a carboxylic acid residue.

The vinyl chloride copolymer into which the aminocarboxylic acid residue shown above has been introduced may be used in combination with other binders. Such resins may be used as binders for recording media. Any of those conventionally used can be used, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer,
Vinyl chloride-vinylidene chloride copolymer, vinyl chloride-
Acrylonitrile copolymer 1. Acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer, thermoplastic polyurethane resin, polyvinyl fluoride, vinyl chloride - Nylidene-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral.

Cellulose derivatives, styrene-butadiene copolymers, polyester resins, phenolic resins, epoxy resins, thermosetting polyurethane resins, urea resins.

Binder resins such as melamine resins, alkyd resins, urea-formaldehyde resins or mixtures thereof may be mentioned. In addition, when these binders are polymerized, it is preferable that the polar group equivalent of the aminocarboxylic acid residue (molecule Wk per polar group) is within the range of 1000 to 100000. If the equivalent amount exceeds 100,000, no effect can be expected, and if it is less than 1,000, 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 formed, for example, by coating the surface of a nonmagnetic support with a magnetic paint prepared by dispersing comagnetic powder in the above-mentioned binder and combing it with an organic solvent.

The magnetic powder dispersed in the binder to constitute the magnetic paint includes ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, '7M
Examples include +11 alloy powder, hexagonal barium ferrite fine particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles are those whose X value is in the range of 1.33≦X≦1.50 when expressed by the -i formula FeQx, that is, magnetite (γ-Pe103).

X=1.50), magnetite (FaxOn, X
= 1.33) and their solid solutions (FaOx, 1.
33 < There are two types.

2. As the ferromagnetic chromium dioxide, CrCh or Ru may be added to these for the purpose of improving coercive force.

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

Examples of the ferromagnetic alloy powder include Fe, Co, and Ni.

Fe-Co, Fo-Ni, Fe-Go-Ni, C.

-Ni, Fe-Go-B, Fe-Co-Cr-1'3°Mn-B1. Mn-80, Fe=co-V, etc. can be used, and A1. S
Metal components such as i, Ti, Cr, Mn, Cu, and Zn may be added.

the above! Examples of organic solvents used when forming the 11-layer layer include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and acetic acid glycol monoethyl ether. Ester types, glycol ether types such as glycol dimethyl ether, glycol monoethyl ether, and dioxane, aromatic hydrocarbons such as benzene, toluene, and xylene, aliphatic hydrocarbons such as hexane and heptane, and methylene chloride.

Ethylene chloride, carbon tetrachloride, chloroform.

Examples include chlorinated hydrocarbons such as ethylene chlorohydrin and dichlorobenzene.

In addition to the above-mentioned binder and magnetic powder, the above-mentioned magnetic layer contains a dispersant, a lubricant, an abrasive, and an antistatic agent, which are usually used as additives constituting the magnetic layer of a magnetic recording medium. , a rust preventive agent, etc. may be added. When adding these things, it is preferable to add them within a range that does not inhibit the effect of introducing the aminocarboxylic acid residue into the binder.

In particular, the fatty acid used for the purpose of imparting lubricity to the tiling layer and improving the durability of the magnetic layer usually has a carbon number of 10.
The above fatty acids are used. The fatty acid may be any fatty acid that is normally used in this type of magnetic recording medium, and includes saturated fatty acids, unsaturated fatty acids, and the like. Specific examples of the above fatty acids include capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, valmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, and serotinic acid. acids, hebucconic acid, montanic acid, melisic acid, oxeric acid, undecylic acid, oleic acid, elaidic acid, cetoleic acid, erucic acid, brassicic acid, linoleic acid, linuric acid, arachidonic acid, stearolic acid, etc. .

These fatty acids have a non-polar alkyl group in their structure, so they have a weak bonding force with the binder, but if the surface of the magnetic powder is basic, the fatty acids preferentially is adsorbed, significantly deteriorating the durability of the paint film. However, in the magnetic recording medium of the present invention, since an aminocarboxylic acid residue is introduced into the binder resin, it is strongly bonded to the magnetic powder that has basic active sites. Therefore, the magnetic powder is well bonded to the aminocarboxylic acid residue without adsorption of fatty acids, thereby improving the dispersibility of the magnetic powder. Furthermore, since the fatty acid exists alone in the magnetic layer, it can exhibit a good lubricating effect.

The material for the non-magnetic support forming the magnetic layer as described above may be any material that is normally used in this type of magnetic recording medium (e.g., polyesters such as polyethylene terephthalate, Polyolefin necks such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate, and polyvinyl chloride.

Vinyl resins such as polyvinylidene chloride, polycarbonate, polyimide, polyamide, polyamideimide, PP
Plastics such as S, paper, metals such as aluminum, copper, etc.
Examples include light alloys such as aluminum alloys and titanium alloys, ceramics, and single crystal silicon. The forms of this non-magnetic support include films, tapes, sheets, disks, and cards.

Any drum or the like may be used.

(Function) The aminocarboxylic acid residues introduced into the vinyl chloride copolymer in the present invention are multidentately coordinated on the surface of the Gfi powder and bond very strongly to the magnetic powder, especially when neutral or It has a remarkable effect on the dispersibility of magnetic powder with acidic surface properties and the reinforcing properties of the paint film interface.

In addition, because aminocarboxylic acid residues strongly adsorb to the surface of the neutral or acidic powder, various additives with proton-donating atomic groups such as fatty acids are adsorbed to the magnetic powder. As a result, a coating film is completed without losing dispersion stability or interfacial reinforcement, and a coating film with high magnetic properties, high surface gloss, and excellent durability is completed.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

Compatible alloy powder (specific surface area 40rrr/g) 10
0 parts Vinyl chloride-vinyl acetate copolymer 10 parts by weight Polyurethane resin (N-2304)
10 parts by weight Dimethyl silicone oil 1 part by weight Lecithin 1 part by weight C
r, 0. 2 parts by weight Methyl ethyl ketone 100 parts by weight Methyl isobutyl ketone 50 parts by weight Toluene
50 parts by weight of the magnetic paint having the above composition was mixed in a ball mill for 48 hours, filtered through a filter, a curing agent was added, and 3 parts by weight were mixed.
After mixing for 0 minutes, this was applied onto a polyethylene terephthalate film having a thickness of +4.5 μm so that the thickness after drying would be 6 μm, and after magnetic field orientation, it was dried and wound up.

After calendering this, cut it into 1/2 inch width.
A sample tape was made.

According to the above method, the type of the polar group X introduced into the vinyl chloride-vinyl acetate copolymer was changed as shown in Table 1, and Examples 1 to 9 and Comparative Examples 1 to 2 were prepared. went.

(Left below) For each sample tape obtained, the surface gloss, powder removal, and magnetic properties were as follows: magnetic flux density of 11 m, squareness ratio Rs.
was measured. The above gloss was measured using a gloss meter at an incident angle of 60°.
, the reflectance at a reflection angle of 60° was measured. In addition, for dust removal, visually observe the amount of powder falling on the head drum, guide pins, etc. after running the shuttle 100 times for 60 minutes, and score 0 if there is almost no dust falling off, and score 0 if there is a very large amount of dust falling. It was evaluated as 15 points.

Furthermore, the magnetic properties were measured in a magnetic field of 2500 Gauss. The results are shown in Table 2.

(Leaving space below) Table 2 As is clear from Table 2 above, the magnetic layer using a binder in which aminocarboxylic acid residues are introduced into the vinyl copolymer has high gloss and extremely low powder fall-off. At the same time, the magnetic properties are improved.

(Effects of the Invention) As is clear from the above explanation, in the Gil recording medium according to the present invention, aminocarboxylic acid residues are introduced into the vinyl chloride copolymer contained as a binder. Aminocarboxylic acid residues bond very strongly to magnetic powder, and even when fatty acids are mixed into the binder, the vinyl chloride copolymer does not separate, making it particularly suitable for magnetic powders with neutral or acidic surface properties. The powder has a remarkable effect on paternity and IF-reinforcement of the coating film interface.

Furthermore, since the vinyl chloride polymer into which aminocarboxylic acid residues have been introduced has a low viscosity, it becomes a magnetic paint with excellent fluidity.

Therefore, by using this binder to form the magnetic layer of a 611-magnetic recording medium, it is possible to prevent the binder from separating from the magnetic powder, improve the dispersibility of the magnetic powder, reduce the shedding, and improve electromagnetic conversion. It is possible to provide magnetic recording media with improved characteristics deterioration and excellent durability of the magnetic coating film.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a magnetic recording medium to which the present invention is applied. FIG. 2 is a schematic cross-sectional view showing another example of the configuration of a magnetic recording medium to which the present invention is applied. 1.11... Non-&II support 2.12... 651 layer 13... Back coat layer Patent applicant Sony Corporation representative Patent attorney Kodo Koike Materials Sakae Sa'yi Katsudai 1 Figure 2

Claims (1)

[Claims] In a magnetic recording medium having a magnetic layer mainly composed of magnetic powder and a binder on a non-magnetic support, the binder may contain a vinyl chloride copolymer having an aminocarboxylic acid residue in the molecule. Features of magnetic recording media.