JPS62112216A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To simultaneously improve the traveling durability and electromagnetic transducing characteristic of the titled medium by incorporating the specified amt. of acicular Cr2O3 having <=1.0mum major axis and <=0.1mum minor axis into the magnetic powder of a magnetic layer and a incorporating polyurethane or a vinyl chloride resin each contg. a metallic sulfonate group as a binder. CONSTITUTION:The vinyl chloride resin contg. the metallic sulfonate group has -SO3M linked to the copolymer and the polyurethane contg. the metallic sulfonate group has -SO3M linked to the polymer. The total amt. of the binder is regulated to 10-100pts.wt., based on 100pts.wt. ferromagnetic powder. The Cr2O3 is the acicular dichromium trioxide having <=1.0mum major axis, <=0.1mum minor axis, and 5-20 acicular ratio and the content is controlled to 1-20wt% of the magnetic powder contained in the magnetic layer. The acicular Cr2O3, ferromagnetic powder such as ferromagnetic alloy powder, the binder, and other fillers, as necessary, are kneaded along with a solvent to obtain a magnetic paint. The paint is coated on a carrier, the magnetic field is oriented, and then the paint is dried to form the magnetic recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording medium in which a magnetic layer is coated on a non-magnetic support, and particularly to a magnetic recording medium with improved running durability.

[Conventional technology]

Conventionally, r-F
A magnetic recording medium is used in which a magnetic layer in which ferromagnetic powder such as I1.203, C-containing iron oxide, chromium dioxide, or ferromagnetic alloy powder is dispersed in a binder is coated on a non-magnetic support. ing. Recently, the density of such magnetic recording media has increased,
With the increase in S/N, magnetic materials are being made into finer particles, but as the particles become finer, the abrasiveness of the magnetic materials decreases, and for this reason, magnetic recording media using such magnetic materials are The running durability of the vehicle deteriorates. Moreover, this slope is remarkable when a ferromagnetic alloy powder with low hardness is used.

[Problem that the invention seeks to solve]

As a measure to prevent such deterioration of running durability, conventionally, granular 0Aj1203. It has been proposed to add abrasives such as SiC, Cr2O3, etc. to the magnetic layer, but adding a large amount of such abrasives may cause deterioration or dispersion of the magnetic field orientation of the magnetic recording medium and the filling dust of the magnetic powder. The problem is a decrease in electromagnetic conversion characteristics due to deterioration of surface properties accompanied by deterioration.

In addition, reducing the amount of abrasive added to improve the surface properties improves the electromagnetic characteristics, but the friction coefficient of the magnetic layer increases.
Problems such as sticking during running and poor running properties of the magnetic recording medium occur.

Therefore, an object of the present invention is to simultaneously improve the running durability and electromagnetic conversion characteristics of a magnetic layer, and to provide a magnetic recording medium with improved running properties.

[Failure to solve the problem]

The present applicant has previously developed an acicular inorganic material having a major axis diameter of 1.0 μm or less, a minor axis diameter of 071 μm or less, an acicular ratio of 5 to 20, and a Mohs hardness of 5 or more as a means for achieving the above object. proposed to use it as an abrasive (patent application Sho 6O-62).
968).

As a result of repeated research to achieve the above-mentioned objects and to obtain a magnetic recording medium with improved running properties, the present invention has found that, among the abrasive materials proposed for the above-mentioned light, in particular, acicular Cr2O3 having the above-mentioned properties,
The present invention has been achieved by discovering that the running durability and electromagnetic conversion characteristics of the magnetic layer can be significantly improved by dispersing it together with magnetic powder using a specific binder to form a magnetic counterfeit.

That is, the present invention provides a magnetic recording medium having a magnetic layer containing magnetic powder dispersed in a binder on a non-magnetic support, the magnetic layer having a major axis diameter of 1. Oμm or less, short axis diameter 0.1μ
m or less, containing acicular Cr203 with an acicular ratio of 5 to 20 from 1 to 20 times per weight per magnetic powder, and containing polyurethane or vinyl chloride resin containing a sulfonic acid metal base as a binder. This is a magnetic recording medium characterized by:

The present invention will be explained in detail below.

The present invention can also be applied to magnetic recording media using conventionally commonly used iron oxide-based ferromagnetic powders, CO-containing iron oxide-based ferromagnetic powders, and chromium dioxide (CrO2)-based ferromagnetic powders; however, so-called ferromagnetic alloy powders , "The specific surface area of \j is 25m27g
It is particularly effective when using the above ferromagnetic alloy powder. That is, the hardness of ferromagnetic alloy powder is lower than that of other ferromagnetic powders, and magnetic recording media using this powder tend to have low abrasiveness and poor running durability. However, by applying the present invention, These problems can be effectively solved.

The nonmagnetic support used in the present invention is not particularly limited, and any commonly used nonmagnetic support can be used. Examples of materials forming the non-magnetic support include polyethylene terephthalate (PET), polyzolopyrene, polycarbonate, polyethylene naphthalate, polyamide, polyamideimide, ? Various synthetic resin films such as Liimide,
and metal foils such as aluminum foil and stainless steel foil.

The thickness of the nonmagnetic support is also not particularly limited, but is generally 5 to 5011 m, preferably 5 to 60 m.

The non-magnetic support may be provided with a single layer (/S layer) on the side on which the magnetic layer described below is not provided.

The magnetic recording medium of the present invention is one in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a nonmagnetic support as described above.

The ferromagnetic powder used in the magnetic layer of the present invention includes fine ferromagnetic alloy powder containing iron as a main component, γ-Fe 203 TF
e304. In addition to Go-modified ferromagnetic iron oxide CrO2, there are modified barium ferrite and 7-modified strontium 7-elite, but the 7N invention is a ferromagnetic alloy powder containing iron, cobalt or nickel, and whose specific surface area is 25 m2/g. K is particularly effective when the above ferromagnetic alloy powders are used as ferromagnetic powders.

As an example of this ferromagnetic alloy powder, the metal content in the ferromagnetic alloy powder is 75% by weight or more, and 80% by weight or more of the metal content is dust of at least one kind of ferromagnetic metal or alloy, and the metal content is Mention may be made of alloys that may contain other components within a range of 20% or less. Also,
The ferromagnetic metal may contain a small amount of water, hydroxide, or oxide. Methods for producing these ferromagnetic metal powders are already known, and ferromagnetic alloy powder, which is a typical example of the ferromagnetic powder used in the present invention, can also be produced according to these known methods.

When using ferromagnetic alloy powder, there are no particular restrictions on its shape, but needle-like, granular, dice-like, rice-grain-like, and plate-like shapes are usually used.

The specific surface area (S BET) of this ferromagnetic alloy powder is 42
m2/y, preferably greater than or equal to 45I
It is preferable to use 112/8 or more.

The sulfonic acid metal base-containing vinyl chloride resin used in the present invention refers to other monomers that can be polymerized with vinyl chloride,
For example, a copolymer with vinyl acetate, vinylitine chloride, acrylonitrile, styrene, acrylic ester, etc. is 18o3M (M is Li, Na.

The p, -3o3M group is preferably 5mof4 or less relative to the moi number of the monomer used to form this copolymer.

Moreover, the average molecular weight of this copolymer is preferably 5,000 to 100,000. In addition, the vinyl chloride content of this resin is 80 to 90w.
t%, and other copolymerizable components are preferably 20 to 1 Qwt%.

The sulfonic acid metal base-containing urethane used in the present invention is a polymer of 18o3M (M is Ll , represents Na, K,
(preferably Na) is bonded thereto. -8
The o3M group is preferably contained in an amount of 0.2 to 10 equivalents, more preferably 0.3 to 8 equivalents, per molecule of the polyurethane. Moreover, the average molecular weight of this polyurethane is preferably 5,000 to 100,000.

Preferred polyurethanes include organic dibasic acids such as phthalic acid and adipic acid; glycols such as ethylene glycol, fluoropylene gelicol, and butylene glycol;
Reactive polyester preferably having an average molecular weight of 600 to 6000, obtained by reaction with polyhydric alcohols such as trimethylolpropane, hexanetriol, pentaerythritol, and cyclohexane-1,4-diol, and phenols such as bisphenol A. alone or in combination; or obtained by reacting propylene oxide, ethylene oxide, etc., preferably,
A reactive polyether with an average molecular t600 to 6000,
Tolylene diisocyanate, alone or in combination, 4.4'
Examples include polyester polyurethanes obtained by reacting with isocyanates such as -diphenylmethane diisocyanate and hexamethylene diisocyanate, polyether polyurethanes alone or as a mixture, or combinations thereof.

Furthermore, a low molecular weight polyisocyanate compound having a plurality of isocyanate groups and a molecular weight of 150 to 2000 is used as a binder.
By incorporating this low molecular weight, l? The amount of the IJ isocyanate compound added is preferably 5wt4 to 100wt of the total binder amount. A low-molecular polyisocyanate compound is an incyanate monomer having a plurality of incyanate groups, a multimer thereof, or a combination of these monomers or multimers with a compound such as the polyhydric alcohol. Includes adduct bodies. As incyanate monomer,
For example, ethanediocyanate, 2.2.4-)limethylpentane diincyanate, ω,ω'-diincyanate 1,3-dimethylpenzole, ω,ω'-
Examples of diisocyanates include 1,2-dimethylcyclohexane diincyanate, naphthalene-1,4-2 incyanate, and triphenylmethane-4,4',4''-triisocyanate.

In the present invention, the polyurethane having the -803M group and the vinyl chloride type 1 fat may be used alone or in combination, and the total weight of the binder is preferably 10 to 90 inches, more preferably 15 to 85 inches. .

Moreover, polyurethane and vinyl chloride resins excluding the above -8o and M groups can also be used in combination as binders.

In addition, as binders that can be used in combination in the present invention, commonly used thermoplastic resins, thermosetting resins, reactive resins, and the like can be used. These resins can be used alone or in combination.

Thermoplastic resins generally have an average molecular weight of 10,000 to 2.
00,000 and a polymerization degree of about 200 to 2,000. Examples of such thermoplastic resins include acrylic resins, cellulose derivatives, various synthetic thermoplastic resins, polyvinyl fluoride, polyamide resins, polyvinyl butyrate, styrene/butadiene copolymers, and polystyrene resins. These can be used alone or in combination.

Thermosetting resins or reactive resins are generally resins with an average molecular weight of 20 or less in the coating liquid state, and resins whose molecular weight becomes almost infinite due to a condensation reaction or an addition reaction after coating. be done. However, when these resins are thermosetting resins, it is preferable that the resins do not soften or dissolve due to heating during the process leading to curing. Examples of such resins include phenol/
Formalin/nogelac resin, phenol/formalin/resol resin, phenol/furfural resin, xylene/formaldehyde resin, urea resin, melamine resin, drying oil-modified alkyd resin, phenol resin-modified alkyd resin, maleic acid resin-modified alkyd resin, Examples include combinations of saturated polyester resins, epoxy resins, and curing agents, and these can be used alone or in combination.

The amount is generally in the range of 10 to 100 parts by weight, preferably in the range of 15 to 50 parts by weight, per 100 parts by weight of the total binder ferromagnetic powder.

Cr2O3 used in the present invention has a major axis diameter of 1.0 μm or less,
It is acicular chromium sesquioxide with a minor axis diameter of 0.1 μm or less and an acicular ratio of 5 to 200. Long axis diameter is 0.1 to 0.95μm1
Short axis diameter is 0402~0.09μm, needle ratio is 8~15
Particularly preferred is Cr203.

When the long axis diameter of Cr2O used as an abrasive is larger than 1.0 μm and the short axis length is larger than 0.1 μm, and when the acicular ratio of Cr2O3 is smaller than 5 or larger than 20, Cr, 03 The dispersibility of 1.1 and the electromagnetic conversion characteristics are not sufficiently improved.

Furthermore, it may have an adverse effect on the magnetic field orientation treatment of the ferromagnetic powder, and the electromagnetic conversion characteristics of the resulting magnetic recording medium may not be improved.

Note that the upper limit values of the long axis length and the short axis length defined in the present invention are Cr2O contained in the magnetic layer.

means the upper limit of each average value of the major axis length and minor axis length.

The numerical values in each preferable range also have the same meaning.

The above-mentioned Cr2O3 used in the present invention has a Mohs hardness of about 9.

The acicular Cr2O used in the invention can be produced, for example, by the following known method.

That is, a mixture of CrO3 and Cr2o3 is dispersed in water to form a water-dispersed slurry, and this is subjected to a hydrothermal reaction in an autoclave at a temperature of 550 to 670°C and a pressure of 600 to 500 atm. , 700-9
00C, preferably 800-850C, by heating in live air.

is obtained. In addition, Cr obtained by partially reducing CrO3
2(CrO4)3 may be used as the starting material.

In the present invention, the above-mentioned acicular Cr2O3 is contained in an amount of 1 to 20% by weight, preferably 2 to 1% by weight of the ferromagnetic powder contained in the magnetic layer.
It is contained in the magnetic layer so as to have a weight width of 5%.

The magnetic recording medium of the present invention has the above-mentioned acicular Cr2O3 in the magnetic layer.
Although it is not necessary to add other abrasives because it contains -C, other commonly used abrasives may also be added as long as it does not interfere with achieving the object of the present invention. It is.

Similarly, other commonly used particulate particles (e.g., average particle size Q, I' as an antistatic agent) 15 to 0.2μ, as long as they do not impede the achievement of the objects of the present invention.
It is also possible to add m.

When forming the magnetic layer of the magnetic recording medium of the present invention, first, the above-mentioned acicular Cr2O, ferromagnetic powder such as ferromagnetic alloy powder, the above-mentioned binder, and other granular fillers are added as necessary. It is formed by kneading a magnetic paint with a solvent, coating it on a support, applying field orientation, and then drying it.

As the solvent used during kneading, a solvent commonly used in the manufacture of magnetic paints can be used.

As for the kneading method, a method commonly used for kneading magnetic paints can be used. The size and order of addition of each component can be set as desired.

Various techniques are known for preparing magnetic paints, and these known techniques can be used as desired in the production of the present magnetic recording medium.

When preparing a magnetic paint, known additives such as dispersants, antistatic agents, lubricants, etc. can also be used.

Examples of dispersants include fatty acids having 12 to 18 carbon atoms, metal soaps made of the above fatty acids and alkali metals or alkaline earth metals, esters of the above fatty acids, and compounds in which some or all of the hydrogen atoms of the above fatty acids are replaced with fluorine atoms. Substituted compounds, amides of the above fatty acids, aliphatic amines, higher alcohols, polyalkylene oxide alkyl phosphates, alkyl phosphates, alkyl borates,
Known dispersants such as sarcosinates, alkyl ether esters, trialkyl polyolefin oxy quaternary ammonium salts and lecithin can be mentioned. When a dispersant is used, it is usually used in an amount of 0.5 to 2.0 parts by weight per 100 parts by weight of the binder used.

Examples of antistatic agents include natural surfactants; nonionic surfactants; cationic surfactants; anionic surfactants containing acidic groups such as calzenic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, and ester phosphate groups; Agents: Examples include amphoteric activators such as amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, and the like. When a conductive fine powder such as carbon black is used as an antistatic agent, it is used in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder, and a surfactant is used. In some cases, it is used in a range of 0.1 to 10 parts.

Examples of lubricants include the above-mentioned fatty acids, higher alcohols, fatty acids consisting of monobasic fatty acids with 12 to 20 carbon atoms, such as butyl stearate, and sorbitan oleate, and monohydric or polyhydric alcohols with 6 to 20 carbon atoms. esters,
In addition to mineral oils, animal and vegetable oils, olefin low polymers and α-olefin low polymers, known lubricants such as fine graphite powder and lubricants for plastics can be mentioned.

The amount of lubricant added can be arbitrarily determined according to known techniques.

Note that the above-mentioned additives such as dispersants, antistatic agents, and lubricants are not strictly limited to having only the above-mentioned effects; for example, if the dispersant is a lubricant, Alternatively, it may act as an antistatic agent. Therefore, it goes without saying that the effects of compounds etc. exemplified by the above classifications are not limited to those listed in the above classifications, and when using substances that have multiple effects, the amount of is preferably determined by considering the action and effect of the substance.

The magnetic paint thus prepared is coated on the above-mentioned non-magnetic support according to a known method. Coating is usually done directly onto the non-magnetic support. However, it can also be applied onto a non-magnetic support via an adhesive layer or the like.

There is no particular limit to the thickness K of the magnetic layer coated in this way, but the thickness after drying is generally in the range of about 0.5 to 10 μm, usually in the range of 1.5 to ZO μm. be done.

A magnetic layer coated on a 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. Also, if necessary, surface smoothing treatment is performed. The magnetic recording medium that has been subjected to surface smoothing treatment is then cut into a desired shape.

Next, Examples and Comparative Examples of the present invention will be shown. Note that "parts" in Examples and Comparative Examples indicate "parts by weight."

[Example 1] A slurry obtained by dispersing a weight mixture of CrO2 and Cr203 in water was heated to a temperature of 650°C in an autoclave.
A hydrothermal reaction (reaction time: 5 hours) was carried out under conditions of temperature and pressure of 600 atm to obtain acicular Cry2. This temperature is 8
Acicular Cr203 was obtained by heating at 00° C. for 2 hours in air.

The obtained acicular Cr, 03 was classified and used.

Next, a magnetic paint having the composition shown below was prepared and coated on a polyethylene terephthalate nonmagnetic support having a thickness of 10 μm so that the thickness of the magnetic layer after drying was 6.0 μm.

Magnetic paint composition Ferromagnetic alloy powder 100 parts (Fe-N
i alloy, N1 approximately 5% by weight) (Specific surface area (S-BETI: 45 m"/g) Vinyl chloride/vinyl acetate/maleic anhydride copolymer (vinyl chloride resin) 12 parts (manufactured by Nippon Zeon Co., Ltd.: 400x
110A) Polyurethane 8 parts (-8o3Na group 1 equivalent/molecule (molecule t: approx. 5000
0) Polyisocyanate 8 parts (Nippon Polyurethane Co., Ltd.: Coro $-) L) Methyl ethyl ketone 150 parts A non-magnetic support coated with magnetic paint was subjected to a-field orientation treatment while the magnetic paint was not dry. After further drying, perform calendering, 8wI
An 8 mm videotape was produced by slitting the tape into m@.

As the magnetic properties of this videotape, the B-H curve (B:
The magnetic flux density, H: external magnetic field, is measured and obtained, and from this value the angle p2 ratio (Br/Bm, (Br: maximum residual magnetic flux density,
Bm: maximum magnetic flux density]) was determined.

The obtained videotape was recorded on a video recorder (F'tJJI
3. Recorded and played back a 5MHz signal using X-8)
When the playback output of 5MH2 recorded on the reference tape (8mm video CHF obtained in Comparative Example 1 below) is taken as QdB, the relative S/NXF++ raw output of the above video tape and the playback output drop of 100pass7i are calculated. It was measured.

The video recorder described above was run repeatedly to determine the number of runs until the magnetic head became clogged.

The surface light selectivity was determined by measuring the total reflectance at an incident angle of 45° and a reflection angle of 45° using a standard light selectivity meter. Cry2 standard tape value 1
It was set at 50 inches. The foot measuring device used was a digital standard color difference photometer AUD-CH-GV3 manufactured by Suga Test Instruments.

Comparative Example 1 A videotape was produced in the same manner as in Example 1, except that polyurethane without -5o3Na groups and granular Cr203 (size 050 μm) were used.

Comparative Example 2 In Example 1, the vinyl chloride resin was changed to -8O3N a
55 mol% of Cr2O3 in granular form (size 0.
A videotape was produced in the same manner except that 30/Im) was used instead.

Example 2 A videotape was produced in the same manner as in Example 1, except that the vinyl chloride resin was replaced with one having 5 mol of 1803 Na.

Comparative Example 5 A videotape was produced in the same manner as in Example 1 except that the polyurethane was replaced with a polyurethane having no 18o3Na group.

jt Chu Vitari 4 Real Ni? In 7111, vinyl chloride type @! A videotape was produced in the same manner except that I'n was replaced with -So, one having 5 mol% of Na groups, and Cr2O3 was replaced with one having a major axis diameter of 0.08 .mu.m and a minor axis diameter of 0.02 .mu.m.

Example 6 In Example 1, the vinyl chloride Aφ1 fat was replaced with -S O3N
Cr2O3 is added to the one having 5 mol% of a group with a major axis diameter of 0.
．． A videotape was produced in the same manner except that the tape was replaced with one having a length of 9 μm and a short axis diameter of 007 μm.

Comparative Example 5 A videotape was produced in the same manner as in Example 6 except that Cr2O3 was replaced with one having a long sleeve diameter of 1.2 μm and a short axis diameter of 0.06 μm.

Comparative Example 6 A videotape was produced in the same manner as in Example 6 except that the amount of Cr2O3 added was changed to 0.5 parts.

Example 4 A video tape was manufactured in the same manner as in Example 6, except that the amount of Cr2O3 added was changed to 25 parts. Example 5 A video tape was manufactured in the same manner as in Example 6, except that the amount of Cr203 added was changed to 15 parts. Manufacture tape/ζ.

Comparative Example 7 A videotape was produced in the same manner as in Example 6 except that the amount of Cr2O3 added was 25 parts.

Comparative Example 8 A videotape was produced in the same manner as in Example 6 except that both the vinyl chloride resin and the polyurethane were changed to those without 18O3Na groups, Cr2O3 was used in granular form (size 0.3 μm), and the amount added was changed to 15 parts. was manufactured.

Comparative Example 9 In Example 1, instead of acicular Cr2O3, acicular Cl
-1!203 (long axis diameter: 0.3 μm, needle ratio: 1/1
A videotape was produced in the same manner except that the same portion of 5) was used.

The results are shown in the table below. In the table, "actual" indicates "example" and "ratio" indicates "comparative example."

(Effects of the Invention) As is clear from the above results, in the present invention, specific acicular Cr2O3, polyurethane having a sulfonic acid metal base, and vinyl chloride resin were mixed at 1゜mh, b
It is possible to obtain a magnetic recording medium which has excellent surface properties and electrical conversion characteristics of 1.2 degrees and has improved running durability.

;]4 2″゛6゜7゜8゜Procedure Ill v-E 9','=r Date of 1986, 4th Office Attorney Name of magnetic recording medium: (520) Fuji Photo Film Number of inventions to be added by 1 due to stock interest amendment: 0 Counterparts of the amendment: Contents of the amendment in the "Detailed Description of the Invention" column of the description: of the description 1. The column of Detailed Description of the Invention J is amended as follows.

(1) Specification u4 page 18 line 11 [”, “Weight?11
Compound 1 is corrected as IF early mixture-1.

(2) Circular, page 20, line 10, “Relative S/Nj
Delete.

(3) Same book, page 20, line 12, 1. " followed by "Also, the C/N is set to 5MHz (with the playback output and 4M1z
Insert:

(4) Same i'! ] In the table on page 24, at the top of the third block from the right, Is/Nj is corrected to "C/N".

Claims (1)

[Claims] In a magnetic recording medium having a magnetic layer containing magnetic powder dispersed in a binder on a non-magnetic support, the magnetic layer has a major axis diameter of 1.0 μm or less, a minor axis diameter of 0.1 μm or less, and an acicular ratio. 5
~20 acicular Cr_2O_3 to the magnetic powder 1 to 2
1. A magnetic recording medium characterized in that it contains 0% by weight and a polyurethane or vinyl chloride resin containing a sulfonic acid metal base as a binder.