JPH01173320A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the still durability of a medium and to decrease head wear by adding MgAl2O4 powder to a magnetic layer. CONSTITUTION:The magnetic layer of the title medium is formed essentially of magnetic powder (A) and binder (B) and is further added with the MgAl2O4 powder (C) as well. The component C is a polishing agent having a spinel type crystal structure, for which the powder having a desired particle size can be used in a prescribed amt. Ferromagnetic iron oxide (e.g.: Co-deposited gamma iron oxide), etc., are usable for the component A. A vinyl chloride copolymer and polyurethane, etc., may be used in combination for the component B. Further, a lubricating agent, antistatic agent, rust inhibitor, etc., can be added to the magnetic layer.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium having a magnetic layer mainly composed of magnetic powder and a binder on a non-magnetic support. The present invention also relates to improvement of head wear (amount of head wear that occurs when a magnetic recording medium is run).

[Summary of the invention]

The present invention provides a magnetic recording medium in which a magnetic layer mainly composed of magnetic powder and a binder is formed on a non-magnetic support, in which MgA1. By incorporating O, powder, it is intended to improve still durability and reduce head wear.

[Conventional technology]

In recent years, especially in magnetic recording media such as video tapes,
With the enhancement of functions such as still image (still) and slow motion of VTR, the magnetic layer is It has become necessary to strengthen the

Conventionally, in order to satisfy the above requirements, a measure has been proposed in which non-magnetic inorganic material powder is added to the magnetic layer of a magnetic recording medium. Examples of the non-magnetic inorganic material powder added to the magnetic layer include chromium oxide, alumina, titanium oxide, α-iron oxide, zinc oxide, silica, resin beads, etc., and the effects of adding these to the magnetic layer Various studies have been made regarding this.

[Problem that the invention seeks to solve]

However, when these non-magnetic inorganic material powders are added to the magnetic layer, although some improvement is seen in terms of improving the durability of the magnetic layer, the effect is still not sufficient.

On the other hand, since the non-magnetic inorganic material powder mentioned above is very hard, the non-magnetic inorganic material powder added to the magnetic layer has a negative effect on the running system when the magnetic recording medium is run, causing damage to the magnetic head. This has led to problems such as increased wear on the magnetic head and increased wear on the magnetic head.

Therefore, the present invention has been proposed in view of the above-mentioned conventional situation, and an object of the present invention is to provide a magnetic recording medium that can improve still durability and reduce head wear. It is.

[Means for solving problems]

As a result of intensive research to achieve the above-mentioned object, the present invention etc. has discovered that Mg is used as a non-magnetic inorganic material powder to be added to the magnetic layer.
It has been found that AlzO powder is effective and that adding this MgAJ204 powder improves still durability and has the effect of reducing head wear.

The present invention has been made based on the above findings, and provides a magnetic recording medium in which a magnetic layer mainly composed of magnetic powder and a binder is formed on a non-magnetic support.
g Alz Oa powder is contained therein.

MgAl! used in this invention! , 04 powder is
It is an abrasive having a spinel crystal structure, has an excellent magnetic layer reinforcing function, and is compatible with binder resin. Further, by appropriately regulating the particle size and content of the MgA1zo4 powder, excellent effects on headwear can be exhibited.

Therefore, M g A 122 with a predetermined particle size
By containing a predetermined amount of 04 powder in the magnetic layer, the excellent magnetic layer reinforcing function is fully exhibited, and the effects of improving still durability and reducing head wear are simultaneously satisfied.

Here, it is preferable to use the average particle diameter of the above M g Al t O4 powder within the range of 0.1 to 0.8 μm; if it is less than 0.1 μm, the still durability will deteriorate, and the If it is larger than .8 μm, spacing loss will occur, adversely affecting electromagnetic conversion characteristics, and head wear will become too large.

Further, the amount added to the magnetic layer is preferably within the range of 0.5 to 25 parts by weight per 100 parts by weight of the magnetic powder in the magnetic layer.
The effect of adding t Oa powder is not exhibited, and if the amount is more than 25 parts by weight, the headwear will become too large.

The magnetic layer containing the above-mentioned M g A 1 t O4 powder is usually prepared by mixing and dispersing the above-mentioned M g A 1 z Oa powder together with a magnetic powder, a binder component, an organic solvent, and other additives to form a magnetic paint. It is formed by preparing it, coating it on a non-magnetic support, and drying it.

Here, as the binder, any conventionally widely used binder resin can be used, such as vinyl chloride-
Vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer L, vinyl chloride-vinyl acetate-malein i1M polymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer Polymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, thermoplastic polyurethane resin, polyvinyl fluoride, vinylidene chloride-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. Among these binder resins, especially in the magnetic recording medium of the present invention, it is preferable to use a combination of a vinyl chloride copolymer and a polyurethane resin as the binder.

The vinyl chloride copolymer has a degree of polymerization of 100 to 7.
For example, vinyl monomers such as vinyl chloride, vinyl acetate, vinyl propionate, vinyl alcohol, methyl vinyl ether, isobutyl vinyl ether, and cetyl vinyl ether, and methyl (meth)acrylate.

Ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)allylate.

Butyl (meth)acrylate, lauryl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl methacrylate.

Acrylic monomers such as 2-hydroxyethyl acrylate and acrylic esters, vinylidene chloride.

A copolymer of one or more types of vinylidene yarns such as vinylidene fluoride can be used.

Further, the vinyl copolymer may be copolymerized with another monomer having a double bond that can be copolymerized with the vinyl compound. As such a monomer, for example, 1.3
-Butadiene monomers such as butadiene, maleic acid,
Maleic anhydride, diethyl maleate, butylbenzyl maleate, di-2-hydroxyethyl maleate,
Dimethyl itaconate, styrene, α-methylstyrene,
p-methylstyrene, acrylonitrile, ethylene.

Examples include propylene.

On the other hand, polyurethane resins are obtained by the reaction of polyhydroxy compounds and polyisocyanates.
It is preferable to use long chain diols with a molecular weight of about 500 to 500, short chain diols with a molecular weight of about 50 to 500, and organic diisocyanates as the polyhydroxy compound and polyisocyanate that are the main components of the resin, and as the polyurethane resin, It is preferable to use one having a molecular weight of about 5,000 to 80,000.

The long-chain diols are broadly classified into, for example, polyester diols, polyether diols, polyether ester glycols, and the like. Specific examples of polyester diols include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, or lower alcohol esters thereof, ethylene glycol, 1.3-
Propylene glycol, 1,4-butylene glycol,
1゜6-hexane glycol, diethylene glycol,
Examples include polyester diols obtained by reacting neopentyl glycol, ethylene oxide adducts of bisphenol A, etc., or mixtures thereof, and lactone-based polyester diols obtained by ring-opening polymerization of lactones such as ε-caprolactone. It will be done. Examples of polyether diol include polyethylene glycol,
Examples include polypropylene ether glycol, polytetramethylene ether glycols, and copolymerized polyether glycols thereof. Examples of polyether ester glycols include polyester glycols obtained by reacting the above polyalkylene ether glycol as a polyol component with an aliphatic or aromatic dicarboxylic acid.

If the molecular weight of this long-chain diol is too small, the urethane group concentration of the resulting polyurethane resin will be too high, resulting in poor resin flexibility and poor solubility in solvents, making it difficult to use as a binder for magnetic recording media. Not very desirable for use.

Also, when the molecular weight of the long chain diol is too large,
Since the long-chain diol content in the resin becomes too large and the urethane group concentration becomes relatively very low, the abrasion resistance and heat resistance of the resin decrease.

Examples of the short chain diols include ethylene glycol, propylene glycol, 1,4-butylene glycol, 1.
6-hexane glycol, aliphatic glycol such as neopentyl glycol, or ethylene oxide adduct or propion oxide adduct of bisphenol A;
There are aromatic diols such as ethylene oxide adducts of hydroquinone, and these can be used alone or in mixtures in various ratios depending on the properties of the polyurethane resin.

Furthermore, glycerin, ethylene oxide adduct of glycerin, 2-methylpropane-1,2,3-)liol, 4-[bis(2-hydroxyethyl))-2-hydroxypenkune, 3-methylpentane-1, 3,5-
triol, L2,6-hexandriol, ■-bis(2-hydroxyethyl)amino-2 propatool,
It is also possible to use a triol such as a propion oxide adduct of jetanolamine.

Examples of the organic diisocyanate include aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, tophenylene diisocyanate, p-phenyl diisocyanate, and 2,4-tolylene diisocyanate. , 2.6-tolylene diisocyanate, diphenylmethane diisocyanate, 3.3-dimethoxy-4,4''-biphenylene diisocyanate, 3
, 3'-dimethyl-4,4'-biphenylene diisocyanate, 4I4'-diisocyanato diphenyl ether, 1,5-naphthalene diisocyanate, 2,4-naphthalene diisocyanate and other aromatic diisocyanates, 1 .3-diisocyanatomethylcyclohexane, 1
．． 4-diisocyanatomethylcyclohexane, 4,4
-Diisocyanate Examples include alicyclic diisocyanates such as dicyclohexylmethane and isophorone diisocyanate.

In addition, the polyurethane resin referred to in the present invention includes polyurea resin and polyurethane urea resin in addition to the above-mentioned polyurethane resin. The above-mentioned polyurea resin and polyurethane urea resin are obtained by replacing part or all of the organic diisocyanate constituting the polyurethane resin with an organic diamine.

Further, the vinyl chloride copolymer and polyurethane resin described above can also be used in combination with the other resins mentioned above.

A hydrophilic polar group may be introduced into the vinyl chloride copolymer or polyurethane resin or other binder used in combination for the purpose of further improving dispersibility. The above-mentioned hydrophilic polar groups include -3O,M group, -osozh
group, -PO(OM')z group, -C00M group, -NR3X
group, -NR,.)IX group (where M represents a hydrogen atom or an alkali metal atom, M" represents a hydrogen atom, an alkali metal atom or a hydrocarbon atom, R represents an alkyl group, and X represents a halogen, respectively. ) etc.

In the magnetic recording medium of the present invention, the magnetic layer is formed by coating the surface of the non-magnetic support with a magnetic paint prepared by, for example, dispersing ferromagnetic powder in the above-mentioned binder and dissolving it in an organic solvent.

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, cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonate, polyimide,
Plastics such as polyamide and polyamideimide, paper,
Examples include metals such as aluminum and W4, light alloys such as aluminum alloys and titanium alloys, ceramics, and single crystal silicon. Examples of the forms of this non-magnetic support include film and tape.

It may be a sheet, disk, card, drum, etc.

Furthermore, any ordinary magnetic powder can be used for the magnetic layer. Therefore, usable magnetic powders include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powders, hexagonal barium ferrite a particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles are those having an X value in the range of 1.33≦X≦1.50 when expressed as general FeOx, that is, maghemite (γ-Peso).

X=1.50), Magnephyte (Fe, Ja,
X = 1.33) and their solid solutions (FeOx, 1
．． 33<X<1.50). Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. There are two types of cobalt-containing iron oxide: doped type and deposited type.

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

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

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

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

-Ni, Fe-Co-B, Fe-Co-Cr-B.

Mn-B1. Mn-Aj! , Fe-Co-V, etc. can be used, and A/! can be used to improve various properties of these. ,
Metal components such as Si, Ti, Cr, Mn, Cu, and Zn may be added.

Furthermore, in addition to the above-mentioned binder and magnetic powder, the above-mentioned magnetic layer also contains dispersants, lubricants, abrasives, etc., which are commonly used as additives.
Antistatic agents, rust inhibitors, etc. may be added.

Examples of solvents for magnetic paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, methyl acetate, and ethyl acetate.

Ester systems such as butyl acetate, ethyl lactate, glycol acetate monoethyl ether, glycol dimethyl ether,
Glycol monoethyl ether, glycol ethers such as dioxane, benzene.

Examples include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane and heptane, and chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene. .

[Effect]

Although there is a contradictory relationship between still durability and head wear, MgAltO is used as a reinforcing agent for the magnetic layer.
Powder a not only functions as a reinforcing agent, but also has the effect of reducing headwear due to its own properties and compatibility with the binder.

Therefore, still durability and head wear can be satisfied at the same time even in complicated traveling mechanisms such as still, slow motion, and high speed traveling.

〔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.

100 parts by weight of magnetic powder (specific surface area 4Qrrr/g, Co-adhered γ iron oxide) binder
10 parts by weight (maleic acid-containing vinyl chloride-vinyl acetate copolymer, manufactured by Denki Kagaku Co., Ltd.)
Product name R-45>Binder
10 parts by weight (polyurethane, manufactured by Nippon Polyurethane Co., Ltd.)

Product name N-2304) Lubricant (butyl stearate) 2 parts by weight Antistatic agent 2 parts by weight (carbon, manufactured by Cabosoto, product name Palcan XC-72) Abrasive (MgApz04 + particle size 0.5.crm)
5 parts by weight Solvent (methyl ethyl ketone) 120 parts by weight Solvent (methyl isobutyl ketone) 60 parts by weight Solvent (toluene) 60 parts by weight The above composition was mixed in a ball mill for 48 hours and after filtering with a filter, 2 parts by weight of Coronae) L Part was added. 30
After a few minutes, this was applied onto a polyethylene terephthalate film having a thickness of 16 μm so that the film thickness after drying was 6 μm. Next, after performing a magnetic field orientation treatment, it was dried and rolled up. After calendering this, it is further hardened and 1/2
A sample tape was prepared by slitting it into inch width pieces.

12-7 In the composition of the magnetic paint, the abrasive Mg/l, the particle diameter of 0°, the added amounts of vinyl chloride copolymer and urethane resin were changed as shown in Table 1, and the other changes were as shown in Example A sample tape was prepared in the same manner as in Example 1.

This MflL top The composition of the magnetic paint, the type and particle size of the abrasive.

Sample tapes were prepared in the same manner as in Example I except that the amounts of vinyl chloride copolymer and urethane resin added were changed as shown in Table 1.

Table 1 shows the types of abrasives used in Examples 1 to 7 and Comparative Example 1, and the amounts of vinyl chloride copolymers and urethane resins added.

Table 1 For each sample tape obtained, the reproduction output, still characteristics, and headwear were measured.

Note that the above reproduction output was determined by recording a 4 MHz signal and then measuring the reproduction output.

In addition, the above still characteristics are as follows: 4°2Mf on the sample tape
A video signal of 1z was recorded, and the time until the playback output attenuated to 50% was taken as the time.

Furthermore, the headwear is made by Sony, product name NV-8.
25°C using a 200° videotape recorder.

The wear depth of the magnetic head was measured and determined after running 100 times in an environment of 6% RH.

The measurement results are shown in Table 2.

(The following is a blank space) Table 2 As is clear from the above Table 2, Example 1 according to the present invention
- In each of the sample tapes of Example 7, head wear was significantly suppressed.

Furthermore, as is clear from the measurement results of each sample tape in Examples 6 and 7, the influence of the binder resin used in the magnetic layer is also large; When resin was used, satisfactory values for head wear were obtained, but still durability deteriorated. On the other hand, in Examples 1 to 5, both reproduction output and still durability were good.

On the other hand, the sample tape of Comparative Example 1 using a conventionally used non-magnetic inorganic material was unsatisfactory in terms of still durability and head wear.

〔Effect of the invention〕

As is clear from the above description, in the present invention, MgAJ20. Since powder is added, it is possible to simultaneously satisfy the contradictory effects of keeping headwear small and increasing still time.

Patent applicant: Sony Corporation Agent: Patent attorney: Akira Koike Same old material Sakae Same as Sage Masaru Procedural amendments issued) March 24, 1986

Claims (1)

[Claims] A magnetic recording medium comprising a magnetic layer mainly composed of magnetic powder and a binder formed on a non-magnetic support, characterized in that the magnetic layer contains MgAl_2O_4 powder.