JPH043319A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To improve electromagnetic conversion characteristics, traveling stability and traveling durability for high density recording by forming a magnetic layer containing fatty acid and fatty acid ester of the magnetic coating liquid and fatty acid and fatty acid ester of an overcoating layer. CONSTITUTION:A magnetic coating liquid comprising dispersion of ferromagnetic powder, binder, fatty acid and fatty acid ester is applied on a nonmagnetic supporting body, and dried. Then fatty acid and fatty acid ester is applied thereon as a overcoating layer. Thus, the magnetic layer contains fatty acid and fatty acid ester of the coating liquid and fatty acid and fatty acid ester of the overcoating layer. Thereby, the obtd. medium has higher electromagnetic conversion characteristics, traveling stability and traveling durability. Especially, still durability is improved with reduction of video head clogging, and the medium has high traveling stability even after storage with lapse of time.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a magnetic recording medium and a method for manufacturing the same, and particularly a magnetic recording medium that has excellent electromagnetic conversion characteristics and running durability in high-density recording (short wavelength recording). This invention relates to a magnetic recording medium and its manufacturing method.

(Prior Art and its Problems) In recent years, magnetic recording media have been widely used as audio tapes, video tapes, computer magnetic tapes, and the like. The magnetic recording medium is tf! It is required to have excellent characteristics in various characteristics such as i-conversion characteristics and running durability. In particular, excellent electromagnetic conversion characteristics and good running characteristics are extremely important requirements, and it is necessary to achieve both of the above characteristics so that they are both excellent.

However, recently, high image quality such as 5-VH3 and High Eight
High-quality sound systems are being considered, and systems such as high-definition, digitally recorded videotapes, and high-density floppy disks are being considered, and the demand for higher density is increasing. In order to achieve such high density, the surface of the magnetic column layer should have, for example, a center line average roughness (Ra).
It is necessary to make it ultra-smooth with a thickness of Ion- or less, preferably 5 nm or less.

Therefore, instead of the conventional smoothing process using a combination of metal rolls and elastic rolls, a calendering process using a combination of metal rolls and metal rolls is used to improve surface properties and reduce noise. A method for manufacturing magnetic recording media with higher C/N and higher recording density was disclosed in Japanese Patent Application Laid-Open No. 1986-
It is disclosed in No. 230623.

However, even if this method smoothes the surface properties of the magnetic layer surface and improves the electromagnetic conversion characteristics, the running properties and durability of the magnetic layer are insufficient. It has not been possible to put into practical use a smoothing treatment technique for media using a combination of the above-mentioned metal rolls.

Generally speaking, when the surface of a magnetic tape is made smooth, the friction coefficient of the contact between the magnetic layer and the device system increases while the magnetic tape is running, and as a result, the magnetic layer of the magnetic recording medium is damaged after short-term use. In extreme cases, the magnetic layer may peel off.

In particular, in the case of a video tape, since the video head and the magnetic recording medium run in contact with each other at high speed, the ferromagnetic powder and/or binder easily fall off from the magnetic layer, which can cause clogging of the magnetic head. Therefore, in a magnetic recording medium having a smooth magnetic tape surface, it is desired to improve the runnability and durability of the magnetic layer. When treated to make it ultra-smooth, the coefficient of friction increases significantly, and improving the runnability and durability of the magnetic layer has become a major issue, and improvements have been strongly desired.

The present invention has an ultra-smooth magnetic layer surface, and has excellent running properties.
The present invention proposes a method for manufacturing a highly durable magnetic recording medium, and provides a magnetic recording medium that is extremely effective in the fields of high-density magnetic recording such as high-definition and digital recording.

Conventionally, in order to improve the running performance and durability of these magnetic recording media, methods of adding various lubricants to magnetic coating liquids (for example, Japanese Patent Publication No. 49-39402, Japanese Patent Publication No. 39-26793, Japanese Patent Publication No. 5) have been proposed.
No. 1-39081, No. 39-28367, No. 41-1
8065), a method of applying a lubricant to the surface of the magnetic layer (for example, Japanese Patent Publication No. 59-39810, Japanese Patent Publication No. 56-135)
No. 27), or a method of impregnating a lubricant (for example,
Japanese Unexamined Patent Publication No. 52-24503) has been proposed. However, with these methods, it is no longer possible to achieve both advanced TIFI conversion characteristics, runnability, and durability, as ultra-smooth magnetic surfaces are now required to have good runnability and durability.

(Objective of the Invention) Therefore, the present invention provides excellent electromagnetic conversion characteristics, especially in high-density recording (short wavelength recording), as well as running stability and running durability, especially still durability, video head clogging, and after storage over time. An object of the present invention is to provide a magnetic recording medium with improved running stability and a method for manufacturing the same.

(Structure of the Invention) That is, the above object of the present invention is to provide a magnetic recording medium having a magnetic layer mainly containing ferromagnetic powder and a binder on a non-magnetic support, in which the magnetic layer is coated with a magnetic coating before coating. This is achieved by a magnetic recording medium characterized by containing fatty acids and fatty acid esters contained in a liquid, and having fatty acids and fatty acid esters overcoated on a magnetic layer after forming a magnetic coating on a non-magnetic support. be able to.

Further, the above object of the present invention is to provide a method for manufacturing a magnetic recording medium in which a magnetic layer is coated on a non-magnetic support, which mainly includes a magnetic coating formed by mixing and dispersing a ferromagnetic powder, a binder, a fatty acid, and a fatty acid ester. This can be achieved by a method for manufacturing a magnetic recording medium, which comprises coating a liquid onto a non-magnetic support, drying it, and then overcoating the coating film with a fatty acid and a fatty acid ester.

That is, according to the present invention, a magnetic coating liquid containing fatty acids and fatty acid esters is applied onto a non-magnetic support, the magnetic surface is made ultra-smooth by calendering, and by overcoating fatty acids and fatty acid esters, an extremely smooth surface is formed. It has a magnetic surface with a high degree of filling, and the output is improved, the C/N ratio is also improved, and excellent electromagnetic conversion characteristics, running performance, and durability are obtained.

In the method of adding lubricants such as fatty acids and fatty acid esters to the magnetic coating liquid, if the amount added is small, sufficient runability and durability cannot be obtained, and if the amount of fatty acids added is large, the lubricants in the magnetic coating liquid The dispersion stability of the magnetic material decreases and agglomeration of the magnetic material progresses, making it impossible to obtain good electromagnetic conversion characteristics, or part of the binder adsorbed to the magnetic material is replaced by fatty acids, causing the binder-magnetic material to deteriorate. It is presumed that this is to weaken the interfacial force between the wheels, but it also makes it easier for scratches to occur during driving and reduces durability. Furthermore, if the amount of fatty acid ester added is large, there is a problem that plasticization of the magnetic layer becomes large and durability becomes weak, or that bath rolls etc. are stained during web handling in the manufacturing process up to overcoat.

In a method in which lubricants such as fatty acids and fatty acid esters are not added to the magnetic coating liquid and are coated on the surface of the magnetic layer, running properties and durability deteriorate due to storage over time after magnetic tape production. This is because the inside of the magnetic layer is not saturated with lubricant and a lubricant concentration gradient with the surface of the magnetic layer occurs, so the applied lubricant is absorbed into the magnetic layer during storage over time, and the lubricant on the surface of the magnetic layer is absorbed. It is presumed that because the amount present decreases, sufficient lubricating function cannot be exhibited. In order to prevent these problems, it was proposed in JP-A No. 5 that the aging of the lubricant should be accelerated by heat treatment after application.
No. 6-13527, however, the heat treatment increases the number of manufacturing steps by one, increasing the manufacturing cost, and the heat treatment causes the magnetic tape to deform. In particular, in the case of high-density recording video tapes, the tape is thin and easily deforms, which is undesirable because the contact of the tape to the video head fluctuates, causing output fluctuations.

In order to solve these drawbacks of the prior art, in the present invention, a part of the fatty acid and fatty acid ester used as a lubricant is added to the magnetic coating liquid, and the remaining lubricant is overcoated on the magnetic layer. The total amount of fatty acids and fatty acid esters required to ensure durability could be reduced. What is particularly effective in improving durability is the fluid lubrication function, and since fatty acid ester is effective for this, by adding it to the magnetic coating liquid and using an overcoat together,
This is presumed to be because the fatty acid ester was localized on the surface of the magnetic layer. Further, the present invention is effective in reducing the coefficient of friction during repeated running, and furthermore, the sliding noise, which is a problem in video heads, is reduced.

Furthermore, in the production method of the present invention, if the ratio of fatty acids and fatty acid esters in the overcoating lubricant is the same as the ratio of fatty acids and fatty acid esters added to the magnetic coating liquid, these lubricants can be used in common. , there is an advantage that the lubricant preparation process can be done all at once.

The present invention will be explained in detail below.

The fatty acids used in the present invention preferably have a total carbon number of 12 to 26, particularly 14 to 20, as they are effective in improving running properties and durability. Preferred specific examples of these include lauric acid, myristic acid, and palmitic acid. fatty acids such as stearic acid, isostearic acid, arachidic acid, behenic acid, tetracosanoic acid, hexacosanoic acid, oleic acid, linoleic acid, linolic acid, eicoic acid, elaidic acid, and erucic acid, and particularly preferably myristic acid, These are palmitic acid, stearic acid, isostearic acid, behenic acid, oleic acid, and erucic acid.

The fatty acids used in the magnetic coating liquid and the fatty acids to be overcoated may be the same or different, or each may be a mixture of two or more fatty acids.

The fatty acid ester used in the present invention has a total number of carbon atoms of 16 to
36, particularly 18 to 26, is effective in improving running performance and durability and is preferred. Preferred specific examples of these include methyl, ethyl, propyl, butyl, and 5ec fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, arachidic acid, oleic acid, eicoic acid, elaidic acid, and erucic acid. -butyl, amyl, 1so-amyl, hexyl, 2-ethylhexyl, heptyl, octyl, 1so-octyl, decyl, 1
so-decyl, 1so-tridecyl, 1so-7tyl,
Straight-chain or branched alkyl esters such as oleyl and 1so-stearyl, or alkoxy esters such as methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl, butoxyethoxyethyl, and butoxyethoxyethoxyethyl are particularly preferred. Examples include butyl myristate, octyl myristate, propyl valmitate, butyl stearate, octyl isostearate, oleyl oleate, and the like.

The fatty acid ester used in the magnetic coating liquid and the fatty acid ester to be overcoated may be the same or different, or each may be a mixture of two or more fatty acid esters.

In the present invention, the amount of fatty acid used in the magnetic coating liquid is preferably 0.1 to 3 parts by weight, more preferably 0.3 to 2 parts by weight, based on 100 parts by weight of the ferromagnetic powder. In addition, the amount of fatty acid ester used in the magnetic coating liquid is 1 part of the ferromagnetic powder.
The amount is preferably 0.1 to 2 parts by weight, more preferably 0.3 to 1.5 parts by weight.

In the magnetic coating liquid of the present invention, the ratio of fatty acids and fatty acid esters, which are lubricant components, is as follows:
Preferably 0.5 to IO parts by weight, more preferably 1 to 5 parts by weight
Parts by weight of fatty acid ester are used.

In the overcoat liquid of the present invention, the ratio of fatty acid and fatty acid ester, which are lubricant components, is preferably 0.5 to 10 parts by weight, preferably 1 part by weight, per 1 part by weight of fatty acid.
~5 parts by weight of fatty acid ester is used.

The coating amount of the lubricant to be overcoated is preferably 5 to 300 mg/f of the lubricant component.

More preferably 10 to 50 mg/rrf.

The lubricant used in the magnetic coating liquid is 10 to 80% by weight of the total amount of lubricant used in the magnetic layer, preferably 30 to 7% by weight.
It is 0% by weight.

The above magnetic recording medium of the present invention can be manufactured by satisfying the following conditions (1) to (4).

■ The ferromagnetic powder contained in the magnetic layer has a specific surface area of 35 nf/g or more and a crystallite size of 30 nm by BET method.
0 Å or less, preferably a specific surface area of 45n? /
More preferably, it is a ferromagnetic alloy powder and has a specific surface area of 55rd/g or more as measured by the BET method.

100n(σ) decreases when it exceeds 7g, so a range of 55 to 100rr?/g is practically preferable.

■ The content ratio of the ferromagnetic powder and the binder in the magnetic layer is 10 to 30 parts by weight, preferably 18 to 30 parts by weight, of the binder per 100 parts by weight of the ferromagnetic powder, and the content of other additives is is less than the binder content.

(2) During the manufacture of magnetic recording media, the magnetic layer is calendered. Preferably, it is calendered with at least one pair of rigid rolls (eg, metal rolls having a center surface roughness (Ra) of about 2 Onam or less).

■ Glass transition temperature of the magnetic layer before the above calendar treatment'
rg (peak temperature of E') is lower than the calendering temperature by 30° C. or more, preferably by 50° C. or more.

In the method for producing a magnetic recording medium of the present invention, the method for overcoating with a lubricant includes coating and drying a magnetic paint on a non-magnetic support, and then (1) dissolving the lubricant in an organic abrasion. (2) A method of spraying the above-mentioned lubricant or its solution; (3) A method of passing a lubricant vapor through a support carrying the magnetic layer; (4) ) Methods include rubbing the aforementioned lubricant in solid form.

Among the above manufacturing methods, the preferred method is (1), and the coating methods include dip coating, gravure coating, extrusion coating, coating with a coil bar,
Examples include curtain coating, slide coating, and coating methods in which fibers impregnated with a lubricant solution are touched.

Although the order of overcoating the lubricant and calendering is not particularly limited, it is preferable to overcoat the lubricant after calendering. This is because it is directly connected and allows overcoating to be performed immediately after calendering without winding up.

The organic solvent that can be used for overcoating is one that is soluble in the lubricant, does not easily dissolve the coated magnetic layer, or does not damage the magnetic layer, and has a boiling point of 120°C or less. Preferably. Examples of specific organic solvents include ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, esters such as methyl acetate and ethyl acetate, alcohols such as methanol, ethanol, and propatool, pentane,
Hydrocarbons such as hexane, heptane, petroleum ether, ligroin, benzene, toluene, and xylene, and ethers such as ethyl ether, dioxane, and tetrahydrofuran can be used. Among these, preferred are those having a boiling point of 80°C or less, such as acetone, methyl ethyl ketone, ethyl acetate, and methanol. A mixed solvent of these may be used if necessary.

There are no particular restrictions on the non-magnetic support in the present invention,
Those commonly used can be used. Examples of materials forming the nonmagnetic support include various synthetic resin films such as polyethylene terephthalate, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamideimide, and polyimide, and metal foils such as aluminum foil and stainless steel foil. be able to.

The thickness of the nonmagnetic support is also not particularly limited, but is generally 2.5 to 100 μm, preferably 3 to 80 μm.

In addition, the surface roughness (Ra: optical interference type surface roughness) of the support is 0.05 m or less, preferably 0.02 m or less, more preferably 0.015 to 0.004, particularly 0.
．． Excellent effects can be achieved when a support with an excellent surface smoothness of 02- or less is used.

The ferromagnetic fine powder in the present invention includes conventionally known ferromagnetic fine powders, such as T-iron oxide ferromagnetic powder, Co-containing iron oxide ferromagnetic powder, ferromagnetic chromium dioxide fine powder,
Ferromagnetic metal or alloy fine powder, iron nitride-based ferromagnetic powder, orthogonal ferrite-based ferromagnetic powder such as barium ferrite, strontium ferrite, etc. can be used. Such ferromagnetic fine powder can be produced by a method known per se. In the present invention, the specific surface area measured by the BET method is 35 rrf/g or more, preferably 45 n
It is preferable to use a ferromagnetic powder having a crystallite size of 300 Å or less, preferably 250 Å or less.

There are no particular restrictions on the shape of the ferromagnetic powder, but it is usually acicular,
Granular, dice-shaped, rice grain-shaped, plate-shaped ones, etc. can be used.

The binder for the magnetic layer in the present invention may be any of the known thermoplastic resins, thermosetting resins, radiation-curable resins, reactive resins, and mixtures thereof, which have been conventionally used as binders for magnetic recording media. More preferably, the binder contains a substance that can be crosslinked or polymerized by radiation irradiation.

As the thermoplastic resin, acrylic acid ester 7/J
Rylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer,
Methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, vinyl chloride copolymer (details below), polyurethane resin (details below)
, urethane elastomer, nylon-silicon resin,
Nitrocellulose-polyamide resin, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, chlorovinyl ether acrylate copolymers, amino resins, and various synthetic rubber-based thermoplastic resins.

In addition, the above-mentioned thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and the molecular weight becomes extremely large when heated after coating and drying, such as phenol resin, Phenoxy resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, epoxy-polyamide resin, nitrocellulose melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, methacrylic Mixtures of acid salt copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycol/high molecular weight diol/triphenylmethane triisocyanate, polyamine resins and mixtures thereof, etc. It will be done.

Further, as the radiation-curable resin, a resin having at least one carbon-carbon unsaturated bond in the molecule that can be cured by radiation irradiation can be used. Examples of radiation-curable resins include using a compound having at least one carbon-carbon unsaturated bond in the molecule in the vinyl chloride copolymer or polyurethane resin as a copolymerization component during polymerization, or Examples include those manufactured by incorporating it by coalescence or reaction with a resin. The compound having at least one carbon-carbon unsaturated bond is preferably a compound containing at least one (meth)acryloyl group in the molecule,
Such compounds may further contain a glycidyl group or a hydroxyl group.

Furthermore, a compound that can be polymerized by radiation irradiation may be added to the binder. Examples of such compounds include (meth)acrylic esters, (meth)acrylamides, allyl compounds, vinyl ethers, and vinyl esters. Examples include vinyl heterocyclic compounds, N-vinyl compounds, styrenes, acrylic acid, methacrylic acid, crotonic acids, itacon #s, olefins, and the like. Particularly preferred compounds among these are - compounds containing two or more (meth)acryloyl groups in the molecule, such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate. ) acrylate, pentaerythritol tetra(meth)acrylate, a reaction product of polyisocyanate and poly(meth)acrylate, and the like.

The vinyl chloride copolymer has a softening temperature of 150
℃ or less and an average molecular weight of about 10,000 to 300,000 can be used.

Specific examples of preferred vinyl chloride copolymers include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-acrylic acid ester copolymer, vinyl chloride-glycidyl (meth) ) acrylate copolymer, or -303M group, -PO3
Vinyl chloride copolymers with compounds having Mg groups, -C00M groups, etc., vinyl chloride-vinyl acetate-vinyl alcohol copolymers, vinyl chloride-vinyl acetate-maleic acid-vinyl alcohol copolymers, vinyl chloride- Vinyl propionate-maleic acid copolymer, vinyl chloride-vinyl propionate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-acrylic acid copolymer, hinyl chloride-vinyl acetate-acrylic acid-vinyl alcohol copolymer, and Examples include oxidized copolymers of these.

In particular, vinyl chloride copolymers having polar groups such as carboxylic acid groups or their salts, sulfonic acid groups or their salts, phosphoric acid groups or their salts, amino groups, and hydroxyl groups are used to improve the dispersibility of magnetic materials. Preferred 6 Furthermore, as the polyurethane resin, a polyurethane resin produced from a polyol, a diisocyanate, and, if necessary, a chain extender, by a known method for producing polyurethane can be used.

The above polyols are, for example, compounds such as polyether diol, polyester diol, polycarbonate diol, and polycaprolactone diol.

Typical examples of the polyether diol include polyalkylene glycols such as polyethylene glycol and polypropylene glycol.

The above polyester diol can be synthesized, for example, by polycondensation of a dihydric alcohol and a dibasic acid, ring-opening polymerization of lactones, such as caprolactone, etc.
Typical dihydric alcohols include ethylene glycol, propylene glycol, butanediol, and 1,6-
Examples include glycols such as hexanediol and cyclohexane dimetatool. Furthermore, typical dibasic acids include adipic acid, pimelic acid, azelaic acid, sebacic acid, phthalic acid, and terephthalic acid.

Further, the polycarbonate diol has, for example, the following general formula (A-1) HO-R'-OH (A-1) [wherein R' is, for example, -(Ch)ll-(n is 3 to
14CH.

A polycarbonate diol with a molecular weight of 300 to 20,000 and a hydroxyl value of 20 to 300, synthesized by condensation or transesterification of a polyhydric alcohol represented by phosgene, chloroformate, dialkyl carbonate, or diaryl carbonate, or the polycarbonate diol and the following general formula (A-2) HOOC-R"-COOH (A-2) [wherein, R8 is an alkylene group having 3 to 6 carbon atoms,
1, 4-11,3- or 1.2-phenylene group or 1.4-11.3- or 1.2-cyclohexylene group] obtained by condensation with a dihydric carboxylic acid represented by
It is a polycarbonate polyester diol with a molecular weight of 400 to 30,000 and a hydroxyl value of 5 to 300.

Other polyols (for example, polyether polyol, polyester ether polyol) or polyester may be blended with the above polyol in an amount up to 90% by weight of the above polyol.

The polyisocyanate used to react with the above polyol to form polyurethane is not particularly limited, and commonly used polyisocyanates can be used.
For example, hexamethylene diisocyanate, tolylene diisocyanate, inphorone diisocyanate, 1.3
-xylylene diisocyanate, 1,4-xylylene diisocyanate, cyclohexane diisocyanate, toluidine diisocyanate, 2.4-tolylene diisocyanate, 2.6-) lylene diisocyanate, 4
, 4'-diphenylmethane diisocyanate, P-phenylene diisocyanate, m-phenylene diisocyanate, 1.5-naphthylene diisocyanate, 4.4-
Examples include diphenylmethane diisocyanate, 3,3-dimethylphenylene diisocyanate, dicyclohexylmethane diisocyanate, and the like.

Examples of the chain extender include the aforementioned polyhydric alcohols, aliphatic polyamines, alicyclic polyamines, and aromatic polyamines.

The above polyurethane is, for example, -COOM, -5o3
It may contain a polar group such as M, OP03M, -0M (where M represents a hydrogen atom, sodium, or potassium).

Further, the binder may further contain a compound having two or more isocyanate groups (polyisocyanate). Examples of such polyisocyanates include tolylene diisocyanate and 4,4'-diphenylmethane diisocyanate. , hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,
Isocyanates such as 5-diisocyanate, 0-toluidine diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, reaction products of these isocyanates and polyalcohols, and
Examples of the above polyisocyanates include polyisocyanates produced by condensation of these isocyanates.
Coronate, Coronate HL, Coronate H1 Coronate EH, Coronate 2030, Coronate 2031,
Coronate 2036, Coronate 3015, Coronate 3041, Coronate 2014, Millionate MR, Millionate MTL, DaltoSec 1350, DaltoSe7ri 2170, DaltoSesoku 228o, Shikinichi Pharmaceutical Industry, Takenate D-102, Takenate D-11O
N, Takenate D-200, Takenate D-202,
From Resident Bayer■, Sumidur N75, from West German Bayer AG, Desmodule 1 Desmodule IL, Desmodule N, Desmodule HL, from Dainippon Ink & Chemicals ■, Parnock-D850, Parnock-
It is sold under product names such as D802.

The mixing ratio of the ferromagnetic powder and the binder in the magnetic layer of the magnetic recording medium of the present invention is preferably 10 to 30 parts by weight of the binder per 100 parts by weight of the ferromagnetic powder.

When the magnetic layer is calendered during production of the magnetic recording medium of the present invention, the glass transition temperature Tg (peak temperature of E') of the magnetic layer before calendering is preferably 30°C or more higher than the calendering temperature. It is preferable that the temperature is maintained at a value lower than 50°C.

Generally, the above Tg is preferably 60°C or less, particularly 40°C or less. In order to maintain the above Tg under the above conditions, the type and amount of the binder to be used must be appropriately selected,
It is only necessary to adjust the amount of cutting remaining in the magnetic layer. In particular,
When a substance that can be crosslinked or polymerized by radiation irradiation is used as the binder, the Tg can be easily adjusted.

In addition to the ferromagnetic fine powder and binder, the magnetic layer of the magnetic recording medium of the present invention may contain various other additives, such as carbon black, fillers, abrasives, dispersants, antistatic agents,
A lubricant etc. can be contained. The content of these various additives is preferably lower than the content of the binder.

As the carbon blank, known carbon blacks such as furnace black, color black,
Any carbon black can optionally be used, such as acetylene black.

Carbon black whose surface is partially grafted may be used, and the average particle size is about 30 to 1000.
It is preferable to use r+- carbon black,
Fine particle carbon black and coarse particle carbon black may be used together.

There are no particular restrictions on the filler, and for example, the filler may have an average particle size of 0. O1-0.8- range, preferably 0.06-0
．． Commonly used granular fillers in the range of 4 m can be used. Examples of the above-mentioned fillers include particles of tungsten disulfide, calcium carbonate, titanium dioxide, magnesium oxide, zinc oxide, calcium oxide, lithopone and talc, which may be used alone or in mixtures. be able to.

The abrasive contained in the magnetic layer in the present invention includes:
For example, α-alumina, fused alumina, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond, α-iron oxide, garnet, emery (main components: corundum and magnetite), garnet, silica, silicon nitride, nitride Typical examples include boron, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, tripoly, diatomaceous earth, and dolomite from the viewpoint of durability of the magnetic layer of the magnetic recording medium. In particular, it is preferable to use a combination of one to four types of abrasives having a Mohs hardness of 6 or more.

The average particle size of the abrasive is 0.005-5-1, especially 0.005-5-1.
It is preferable that it is 05-2-.

Dispersants include fatty acids having 9 to 22 carbon atoms (e.g., caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, lilunic acid, stearolic acid); Metal soaps consisting of the above fatty acids and alkali metals (e.g. lithium, sodium, potassium) or alkaline earth metals (e.g. magnesium, calcium, barium), esters of the above fatty acids and part of the hydrogen atoms of their compounds; Compounds completely substituted with fluorine atoms, amides of the above fatty acids, aliphatic amines, higher alcohols, polyalkylene oxide alkyl phosphates, alkyl phosphates, alkyl borates, sarcosinates, alkyl ether esters, trialkyl When using a dispersant, which may include known dispersants such as polyolefin oxy quaternary ammonium salts and lecithin, it is usually used in an amount of 0.00% per 100 parts by weight of the binder used.
It is used in a range of 0.05 to 20 parts by weight.

As antistatic agents, conductive fine powder such as carbon black graft polymer; natural surfactants such as saponin; nonionic surfactants such as alkylene oxide type, glycerin type and glycidol type; higher alkylamines, quaternary Cationic surfactants such as ammonium salts, salts of pyridine and other heterocyclic compounds, phosphonium or sulfoniums; anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric acid ester groups Agents include amphoteric surfactants such as amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, and the like. When the above-mentioned conductive fine powder is used as an antistatic agent, it is used in an amount of, for example, 0.2 to 20 parts by weight per 100 parts by weight of the binder, and when a surfactant is used, it is used in an amount of 0.2 to 20 parts by weight. 1
-10 parts by weight.

In addition to the fatty acids and fatty acid esters used as lubricants in the present invention, examples of lubricants include higher alcohols, mineral oils, animal and vegetable oils, olefin low polymers, α-olefin low polymers, and silicone oil. , graphite fine powder, molyfdenum disulfide fine powder, Teflon fine powder, and other known lubricants and plastic lubricants.

There are no particular restrictions on the solvent used for crosstalk, and solvents that are normally used in preparing magnetic paints can be used.

There is no particular restriction on the kneading method, and the order of addition of each component can be set as appropriate.

For the preparation of magnetic paints, conventional mixing machines such as two-roll mills, three-roll mills, ball mills, pebble mills, thoron mills, sand grinders, Szegv
ari) Attritor, high speed impeller dispersion machine, high speed stone mill, high speed impact mill, disper, kneader
1. High-speed mixers, homogenizers, ultrasonic dispersers, etc. can be mentioned.

It should be noted that the above-mentioned additives such as dispersants, antistatic agents, lubricants, etc. are not described with the strict limitation that they only have 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.

In addition, detergent dispersants, viscosity index improvers, pour point depressants,
Foam stoppers and the like can also be added.

The viscosity of the magnetic paint prepared in this way is usually 60
~200 ps.

Although it is possible to apply the magnetic paint directly onto the non-magnetic support, it is also possible to apply it via an adhesive layer or by applying physical treatment (for example, corona discharge treatment, etc.) on the non-magnetic support. It can also be applied onto a non-magnetic support after being subjected to electron beam irradiation treatment.

Examples of coating methods on non-magnetic supports include air doctor coating, blade coating, rod coating, extrusion coating, air knife coating, squeeze coating, impregnation coating,
reverse roll coat, transfer roll coat,
Methods such as gravure coating, kiss coating, cast coating, spray coating, and spin cording can be used, and methods other than these can also be used.

Simultaneous multilayer coating (@et on wet method) may be used.

The coating thickness is preferably such that the thickness of the magnetic layer of the finally obtained magnetic recording medium is within the range of 2 to 10 mm.

Generally, the coating layer thus applied is subjected to a magnetic field orientation treatment in an undried state to orient the ferromagnetic fine powder contained in the magnetic layer. The magnetic field orientation treatment can be performed according to a conventional method.

Next, the coating layer is subjected to a drying process and dried to form a magnetic layer. The drying step is usually carried out by heating the coating layer at 50 to 120°C, and the heating time is generally 10 seconds to 5.
It is a minute.

After drying, the magnetic layer is usually subjected to surface smoothing treatment.

The surface smoothing treatment is carried out by calendering. This calendering preferably includes a step of heating and pressurizing using at least one pair (two stages), preferably three or more stages of rigid rolls. As the roll, for example, a metal roll having a center surface roughness (Ra: cutoff value, 0.25 m) of about 2 h or less, more preferably about 10 ns or less is preferable. Examples of the rigid roll include various steel rolls. Examples include rolls with hard chrome plating or ceramic coating on the surface, and rolls with a cemented carbide surface. Before and/or after the step of using at least one pair of rigid rolls, a step of using a combination roll of a rigid roll and an elastic roll used in normal calendering may be provided.

The above calendering process is performed at a temperature in the range of 50 to 110°C and a linear pressure in the range of 50 = 1000 kg/cm (preferably 100 to 400 kg/cm, more preferably 200 kg/cm).
~350 kg/cm2), and if the calendering conditions are outside the above range, the magnetic recording medium of the present invention cannot be manufactured. If the above processing conditions are lower than the above range, a magnetic recording medium with excellent electromagnetic conversion characteristics and running characteristics cannot be manufactured, and if the above processing conditions are higher than the above range, the magnetic recording medium may be deformed or the rigidity may be reduced. The roll may be damaged.

After the surface smoothing treatment as described above, radiation treatment or heat treatment is performed as appropriate, and the magnetic recording medium is cut into a desired shape.

As the radiation irradiated in the above-mentioned radiation treatment, electron beams, gamma rays, beta rays, ultraviolet rays, etc. can be used, but electron beams are preferable. The electron beam irradiation is performed using an electron beam accelerator. This electron beam irradiation causes a polymerization reaction in the binder component of the magnetic paint coated on the non-magnetic support and hardens it.

The electron beam to be irradiated generally has an accelerating voltage of 100 to 500 kV, preferably 150 to 300 kV. Further, the absorbed dose is generally 1.0 to 20 megarans, preferably 2 to 10 megarans. If the accelerating voltage is less than 100 kV, the curing reaction of the magnetic layer may not proceed completely due to insufficient energy.
If it exceeds 500 kV, the applied energy becomes excessive than the energy used for the polymerization reaction, which may have an adverse effect on the magnetic layer and the nonmagnetic support.

In addition, if the absorbed dose is less than 1.0 megarads, the curing reaction may not proceed sufficiently and the strength of the magnetic layer may not be sufficient. On the other hand, if the absorbed dose exceeds 20 megarads, the energy efficiency decreases and the magnetic layer becomes unsatisfactory. This is not only economical, but also generates heat in the irradiated object, which may deform the nonmagnetic support.

In the present invention, the radiation (electron beam) irradiation step described above allows the hardening process of the magnetic layer to be significantly shortened compared to a normal heat hardening process. Furthermore, the amount of solvent used during manufacturing can be significantly reduced, and since the quality is stabilized immediately after manufacturing, the product can be shipped immediately.

In the present invention, it is preferable to irradiate the radiation after applying the magnetic paint and calendering as described above.
It is also possible to carry out calender treatment after irradiation. Alternatively, it is also possible to irradiate one more time.

A known back layer may be provided on the surface of the non-magnetic support on which the magnetic layer is not provided.The back layer may be made of, for example, carbon black and a Mohs hardness of 5.
The thin film layer is made of a binder in which the above inorganic filler particles are dispersed and has a thickness of 0.6 mm or less.

(Effects of the Invention) The present invention contains fatty acids and fatty acid esters in a magnetic coating liquid, and after forming a magnetic layer, overcoats the magnetic layer with fatty acids and fatty acid esters. Since it is possible to control the amount present and not unevenly distributed, still durability is prevented from deteriorating even when stored in harsh environmental conditions such as high temperature and high humidity, and the video head remains stable even after repeated use. A magnetic recording medium was obtained in which clogging was prevented and the electromagnetic conversion characteristics were extremely excellent.

(Example) Next, Examples and Comparative Examples of the present invention will be shown.

In each case, "part J" indicates "part by weight."

[Example 1] Ferromagnetic alloy powder (composition: Fe94%, Zn4%, Ni2%, He1
5000e, crystallite size 200 people) was ground for 10 minutes in an open kneader. Next, vinyl chloride/
Vinyl acetate/glycidyl methacrylate (86/9
/5 weight ratio) compound with hydroxyethyl sulfonate sodium salt added to a copolymer (SOsNa group content -6Xl0-'eq/g.

Epoxy group content = 10-'eq/g, average molecular weight = 3
0.0OO) 10 parts 60 parts of methyl ethyl ketone was added and kneaded for 60 minutes. Then, 5OJa group-containing urethane resin (UR8200 manufactured by Toyobo) (solid content) 10
Part polishing Cutox particle size 0.3. s) 2
Part carbon black (particle size 40nm) 2
100 parts of methyl ethyl ketone and 100 parts of toluene were added and dispersed in a sand mill for 120 minutes. To this was added 5 parts of polyisocyanate (Coronate 3041 manufactured by Nippon Polyurethane) (solid content) and 50 parts of lubricant A (see Table 1), methyl ethyl ketone, and after stirring and mixing for another 20 minutes, a filter having an average pore size of 1- A magnetic paint was prepared by using and filtering the powder.

The obtained magnetic coating material was applied to the surface of a polyethylene terephthalate support having a thickness of 1O- by using a reverse roll so that the thickness after drying was 3.0-.

A non-magnetic support coated with magnetic paint is magnetically aligned with a 3000 Gauss magnet while the magnetic paint is not dry.
After further drying, metal roll - metal roll - metal roll -
Calendar treatment using a combination of elastic roll-metal roll-elastic roll-metal roll was carried out at a speed of 100 s/win.
After conducting at a linear pressure of 300 kg/cm and a temperature of 90°C, 3
It was slit to a width of 74 inches.

Lubricant B is applied to the magnetic layer surface of the videotape thus created.
(See Table 1) A 374-inch videotape sample was prepared by gravure coating a solution of 50 parts of methyl ethyl ketone so that the coating amount of lubricant B after drying was 30 mg/rrf.

[Examples 2 to 3, Comparative Examples 1 to 4] In Example 1, except that lubricant A used in the magnetic paint and lubricant B used in the overcoat liquid were changed as shown in Table 1. A 3/4 inch videotape sample was prepared in the same manner as in Example 1.

The following performance evaluation was performed on the 374-inch videotape sample prepared as described above.

(1) Electromagnetic conversion characteristics: The above videotape is a VTR (manufactured by Sony: DV
A 32 MHz signal was recorded and played back using the Rlo.

The relative playback output of the videotape was measured when the playback output of 32MFI2 recorded on the reference tape (Comparative Example 1) was set as OdB.

(2) Running properties: The magnetic surface of the obtained videotape was brought into contact with a stainless steel pole at a tension (TI) of 50g and a wrapping angle of 180°, and under these conditions, the videotape was run at a speed of 3.3cm/see. The tension (T:) required to run the vehicle was measured.

Based on this measured value, the friction coefficient μ of the videotape was determined using the following equation.

μm1/π·ffi, (Tl/TI) The friction coefficient was measured at 25° C. and 70% RH.

(3) Durability: The VTR described above was tested in a still state, and the time required for the reproduction output to reach 50% of the recorded signal was measured (this is referred to as the still durability time). At this time, Unloadi
The ng function has been disabled.

(4) Repeatability: A 90-minute long videotape was repeatedly run 200 times, the video output was continuously recorded, and the degree of clogging of the video head was examined, and the dirt on the video head was visually observed. , evaluated according to the following evaluation criteria.

○ No stains were observed.

Δ There was some dirt on it.

× There was a lot of dirt.

(5) Preservability: The friction coefficient (μ value) of the videotape stored at 50° C. and 80% RH for one week was measured to evaluate the preservability.

The results obtained are shown in Table-1.

As is clear from the results in Table 1, the magnetic recording medium of the present invention has excellent electromagnetic conversion characteristics with high reproduction output and a coefficient of friction (
It exhibited excellent running performance with a low value) and excellent durability with a long still life time.

In addition, the video head does not get dirty or clogged even after repeated running, and it also has excellent storage stability, with no increase in the coefficient of friction even when stored in harsh environmental conditions such as high temperatures. Indicated.

On the other hand, in the magnetic recording media of comparative examples, fatty acids and fatty acid esters were used in the magnetic coating liquid and no overcoat liquid was used (Comparative Example 1), and conversely, fatty acids and fatty acid esters were used in the overcoat liquid and the magnetic coating When no lubricant was used (Comparative Example 2), the performance was inferior to that of the magnetic recording medium of the present invention.

Furthermore, when fatty acids were used in the overcoat liquid without being used in the magnetic paint (Comparative Example 3), and fatty acid esters were used in the magnetic paint without being used in the overcoat liquid (Comparative Example 4). However, their performance was inferior to that of the magnetic recording medium of the present invention.

From the above, it can be seen that only the magnetic recording medium of the present invention satisfies excellent electromagnetic conversion characteristics, runnability, and durability.

Claims (2)

[Claims] (1) In a magnetic recording medium having a magnetic layer mainly containing ferromagnetic powder and a binder on a non-magnetic support, the magnetic layer contains fatty acids and fatty acid esters contained in the magnetic coating liquid before coating. A magnetic recording medium comprising a fatty acid and a fatty acid ester overcoated on a magnetic layer after forming a magnetic coating on a non-magnetic support. (2) In a method for manufacturing a magnetic recording medium in which a magnetic layer is coated on a non-magnetic support, ferromagnetic powder, a binder,
A magnetic recording medium characterized in that a magnetic coating liquid formed by mixing and dispersing fatty acids and fatty acid esters is applied onto a non-magnetic support, and after drying, fatty acids and fatty acid esters are overcoated on this coating film. Production method.