JPH01176321A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide improved electromagnetic conversion characteristics, decreased drop-outs, improved still durability and decreased head wear by incorporating Al2O3 particles having a specific alphatization rate and average grain size into a magnetic layer. CONSTITUTION:The Al2O3 powder having 40-70wt.% alphatization rate and 0.3-0.8mum average grain size is incorporated into the magnetic layer. Namely, the hardness and dispersibility of the Al2O3 are controlled by specifying the alphatization rate of the Al2O3 powder, by which the drop-outs are effectively decreased, the still durability is improved and the head wear is decreased. The surface characteristic of the magnetic surface is improved and the spacing loss is decreased to improve the electromagnetic conversion characteristics by specifying the average grain size and content of the Al2O3 powder. In addition, the reciprocal effects of improving the still durability and decreasing the head wear are thereby simultaneously satisfied.

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. It's about improvement.

[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 an A1 having a predetermined gelatinization rate and average particle size is provided in the magnetic layer. ．． O
By incorporating particles, we aim to improve electromagnetic conversion characteristics and reduce dropouts, improve still durability, and further reduce head wear (magnetic head wear ff1 that occurs when a magnetic recording medium is run). This is what we are trying to achieve.

[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, 1. In order to ensure sufficient abrasion resistance (still durability) of the magnetic recording medium and to prevent damage to the magnetic layer of the magnetic recording medium due to contact with the magnetic head, it is now required to reinforce the magnetic layer. It has become.

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.

Among them, alumina, which is widely used as a non-magnetic inorganic material powder, is usually used with a gelatinization rate of around 90% by weight, and is extremely hard, has high abrasive power, and is extremely effective in cleaning magnetic heads. there were.

[Problem that the invention seeks to solve]

However, because alumina with a pregelatinization rate of around 90% by weight is obtained by firing at a very high temperature due to its manufacturing method, it has a very high affinity with dispersants and binders, and cannot be used in magnetic paints. This causes poor dispersion, resulting in deterioration of the electromagnetic conversion characteristics of the magnetic recording medium and dropouts.

Furthermore, when a large amount of alumina is added to improve the wear resistance of the magnetic layer, although the still durability etc. is improved, the magnetic head is damaged and the amount of wear increases due to the running of the magnetic recording medium. New problems are starting to arise.

Therefore, the present invention was proposed in view of the above-mentioned conventional situation, and it is possible to improve electromagnetic conversion characteristics, reduce dropouts, improve still durability, and further reduce head wear. The purpose of the present invention is to provide a magnetic recording medium with a high level of performance.

[Means for solving problems]

As a result of intensive research to achieve the above-mentioned objects, the present invention etc. has found that the non-magnetic inorganic material powder added to the magnetic layer has a gelatinization rate of 40 to 70% by weight and an average particle size of 0.3 to 0.8 μm. A
utos particles are effective, and by adding a predetermined amount of these A2□03 particles, it is possible to improve electromagnetic conversion characteristics and reduce dropouts, as well as improve still durability.
We have come to the conclusion that this technology has the effect of reducing headwear.

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. Rate 40-70% by weight.

It is characterized by containing 7i, 1*O, particles with an average particle size of 0.3 to 0.8 μm.

The Al□05 particles used in this invention have extremely many shapes (α, β, γ).

It is expressed as δ, etc., and A1□Q5 particles are usually a mixture of these shapes. Especially α type A120s1
Particles refer to very hard particles with a Mohs hardness of about 9. A used as an additive in the magnetic layer of the magnetic recording medium according to the present invention.
The ftOs particles have a pregelatinization rate of 40 to 40.
It is preferable that the amount is about 70% by weight.

When the gelatinization rate is lower than 40% by weight, Al! 0,
If the particles become too soft, they will lack effectiveness as an abrasive, and will also be very difficult to manufacture, resulting in poor dispersibility. If the magnetic head is overcoated, the sliding surface with the magnetic surface of the magnetic recording medium will be scraped, which will increase the amount of wear on the magnetic head, and will also deteriorate the dispersion properties. This will cause outs.

On the other hand, the average particle diameter of the AlltOs particles is 0.3 to 0.
．． It is preferable to use one within the range of 8 μm, and 0
．． If it is less than 3 μm, the effect of adding the AJgos particles described above cannot be obtained and it is not preferable in terms of still durability;
If it is larger, the sliding surface with the magnetic layer of the magnetic recording medium will be polished, resulting in larger head wear and deterioration of electromagnetic conversion characteristics due to spacing loss.

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, and if it is less than 0.5 parts by weight, A j! z 0
(If the amount is more than 25 parts by weight, the amount of contact between the magnetic layer of the magnetic recording medium and the sliding surface of the magnetic head, etc. increases, and Since the sliding surface is polished, head wear becomes large, and electromagnetic conversion characteristics deteriorate due to spacing loss.

Therefore, by containing a predetermined amount of Al2zO powder with a predetermined particle size and a pregelatinization rate of 40 to 70% in the magnetic layer, the dispersibility of the powder and the electromagnetic conversion characteristics can be improved. , it is possible to achieve effects such as reducing dropout, and simultaneously satisfy contradictory effects such as improving still durability and reducing head wear.

In addition, i20. Regardless of the particle shape of the powder, such as spherical, square, or distorted, the effect remains excellent.

The magnetic layer containing the A 1 t O-s powder as described above is
Usually, the above AIl□O5 powder is used as a magnetic powder, a binder component,
It is formed by mixing and dispersing an organic solvent and other additives to prepare a magnetic paint, 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, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester -Acrylonitrile copolymer, 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 Union,
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 particular, among the binder resins mentioned above, 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, 1-2hydroxyethylmethacrylate.

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

A copolymer of one or more vinylidene monomers 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 5000, short chain diols with a molecular weight of about 50 to 500, and organic diisocyanates as the polyhydroxy compound and polyisocyanate which are the main components of the resin, and as the polyurethane resin, It is preferable to use one having a molecular weight of about 15,000 to 80,000.

The above-mentioned long-chain diols are roughly divided into polyester diols, polyether diols, polyether ester glycols, etc. As polyester diols,
Specifically, for example, succinic acid, adipic acid, sebacic acid,
Aliphatic dicarboxylic acids such as azelaic acid, terephthalic acid,
Aromatic dicarboxylic acids such as isophthalic acid or lower alcohol esters thereof, ethylene glycol, 1,
Polyester diols obtained by reacting with 3-propylene glycol, 1,4-butylene gelylcol, 1゜6-hexane glycol, diethylene glycol, neopentyl glycol, or an ethylene oxide adduct of bisphenol A, or a mixture thereof; Examples include lactone-based polyester diols obtained by ring-opening polymerization of lactones such as ε-caprolactone. Examples of polyether diols include polyethylene glycol, 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 resulting polyurethane resin will have an excessively high toughness of 5 g, 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 resin contains too many long-chain diols 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-phthylene gelicol, 1.
There are aromatic diols such as BF-aliphatic glycols such as 6-hexane glycol and neopentyl glycol, ethylene oxide or propion oxide adducts of bisphenol A, and ethylene oxide adducts of hydroquinone, depending on the properties of the polyurethane resin. These can be used alone or in mixtures in various ratios.

Furthermore, glycerin, ethylene oxide adduct of glycerin, 2-methylpropane-1,2,3-triol, 4-[bis(2-hydroxyethyl))-2-hydroxypentane, 3-methylpentane-1,3, 5-triol, 1,2.6-hexane glycol, 1-bis(
It is also possible to use triols such as 2-hydroxyethyl)amino-2-propatol and a propion oxide adduct of jetanolamine.

Examples of the organic diisocyanate include aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, tophenylene diisocyanate, p-phenylene diisocyanate, 2.4-tolylene diisocyanate, and 2.4-tolylene diisocyanate. .6-tolylene diisocyanate, diphenylmethane diisocyanate, 383-dimethoxy-4,4°-biphenylene diisocyanate,
3,3"-dimethyl-4,4"-biphenylene diisocyanate, 4.4"-diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate, 2,4-
Aromatic diisocyanates such as naphthalene diisocyanate, 1,3-diisocyanatomethylcyclohexane,
1,4-diisocyanatomethylcyclohexane, 4.
Examples include alicyclic diisocyanates such as 4''-diisocyanate 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.

Furthermore, the vinyl chloride copolymer and polyurethane resin described above can also be used in combination with the other resins described 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 hydrophilic polar group is 503M! , -030,M group, -PO(OM')i group, -C00M group, -NR,X group, -NR,,HX group (where M is a hydrogen atom or an alkali metal atom, M" is a hydrogen atom , an alkali metal atom or a hydrocarbon atom, R represents an alkyl group, and X represents a halogen.

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, and cellulose acetate butyrate; vinyl resins such as polyvinyl chloride and polyvinylidene chloride; plastics such as polycarbonate, polyimide, polyamide, and polyamideimide;
Examples include paper, metals such as aluminum and copper, light alloys such as aluminum alloys and titanium alloys, ceramics, and single crystal silicon. The form of this non-magnetic support is film 1 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 powder, hexagonal barium ferrite 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 general formula FeOx, that is, magnetite (γ-Fez03).

X-1,50), magnetite (Fe304.
= 1.33) and their solid solutions (FeOx, 1.3
3 < There are two types.

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 ferromagnetic alloy powder include Fo, Co, and Ni.

Fa-Co, Fe-Ni, Fe-Co-Ni, C.

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

Mn-B1. Mn-A1! , Fe-Co-V, etc. can be used, and A1. S
Metal components such as i, 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 leclohexanone, 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]

By specifying the gelatinization rate of Altos powder, the A
β80. Powder hardness and dispersibility can be controlled, resulting in reduced dropouts, improved still durability, and reduced head wear.

In addition, by regulating the average particle diameter and content of AI, O, and powder, it is possible to improve the surface properties of the magnetic surface, reduce spacing loss, and improve electromagnetic conversion characteristics. It is possible to simultaneously satisfy contradictory effects such as improved durability and reduced head wear.

〔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.

Kasen Madaku magnetic powder 100 parts by weight (specific surface area 40 m/g, Co-adhered T iron oxide) binder
10 parts by weight (vinyl chloride-vinyl acetate copolymer).

Binder 10 parts by weight (Polyurethane, manufactured by Nippon Polyurethane Co., Ltd., manufactured by UCC Co., Ltd., trade name: VAGA).

Product name N-2304) Lubricant (butyl stearate) 2 mfi parts Antistatic agent 2 parts by weight (carbon, manufactured by Capot Co., Ltd., trade name Palcan XC-72) Abrasive agent 5 parts by weight Cal
1zOs + particle size 0.5 μm, gelatinization rate 70χ) 120 parts by weight of solvent (methyl ethyl ketone) 60 parts by weight of solvent (methyl isobutyl ketone) 60 parts by weight of solvent (toluene) The above composition was mixed in a ball mill for 48 hours and filtered with a filter. After that, 2 parts by weight of Coronate L was added. 30
After a few minutes, this was applied onto a polyethylene terephthalate film having a thickness of 14 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
Slit the sample tape to inch width and take a look at the sample tape [Takumi] In the composition of magnetic paint, the particle size of the abrasive Altos,
A sample tape was prepared in the same manner as in Example 1 except that the amount added and the gelatinization rate were changed as shown in Table 1.

ゞ1~f'4 In the composition of the magnetic paint, the particle size, addition amount, and gelatinization rate of AlzOs, which is an abrasive Q agent, were changed as shown in Table 1, and the other conditions were the same as in Example 1. A sample tape was prepared by the method.

Particle diameter of the abrasive used in Examples 1 to 5 and Comparative Examples 1 to 4. Table 1 shows the amount added and the gelatinization rate.

(The following is a blank space) Table 1 For each sample tape obtained, the reproduction output, dropout ffl, and still characteristics were measured.

The above reproduction output was determined by recording a 4MIIz signal and then measuring the reproduction output.

In addition, the dropout test measures the amount of dropouts that occur per minute of light by running the tape for a predetermined period of time.

Further, the still characteristics were determined by recording a video signal of 4.2 Mllz on a tape and measuring the time until the playback output attenuated to 50%.

The measurement results are shown in Table 2.

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 5, the reproduction output was improved, the still characteristics were improved, and the amount of dropout was also very small, showing good results.

On the other hand, the sample tape of Comparative Example 1 has very poor still characteristics due to its small particle size, and the sample tapes of Comparative Examples 2 to 4 are extremely hard with a gelatinization rate of 90%. Therefore, there is a large amount of dropout, making it impractical.

〔Effect of the invention〕

As is clear from the above explanation, in the present invention, 100 parts by weight of Altos powder with an average particle size of 0.3 to 0.8 μm and a gelatinization rate of 40 to 70% by weight is added to the magnetic layer. Since 0.5 to 25 parts by weight is added to the Al□0. Improving powder dispersibility, improving electromagnetic conversion characteristics,
While exhibiting effects such as reducing dropouts, it is also possible to simultaneously satisfy contradictory effects such as improving still durability and reducing head wear.

Hand 3 Seller Fusho 0;: (spontaneous) March 24, 1986

Claims (1)

[Claims] In a magnetic recording medium formed by forming a magnetic layer mainly composed of magnetic powder and a binder on a non-magnetic support, the magnetic layer contains a gelatinization rate of 40 to 70% by weight and an average particle size of 0.3 to 0. .8
A magnetic recording medium characterized by containing μm-sized Al_2O_3 particles.