JPS6159620A - Medium and method for magnetic recording - Google Patents

Abstract

PURPOSE:To obtain an excellent recording medium by providing a thin ferromagnetic metallic film consisting essentially of Co and org. top coat layer contg. a lubricating agent on a flexible substrate, providing a layer contg. an inorg. pigment, org. binder and lubricating oil on the other surface of the substrate and providing specific projections on the medium surface. CONSTITUTION:The thin ferromagnetic metallic film consisting essentially of Co and contg. oxygen and the org. top coat layer contg. the lubricating agent, preferably radiation curing lubricating agent and further antioxidant are provided on the flexible substrate. The back coat layer contg. the same lubricating agent as the lubricating agent of the top coat layer, inorg. pigment and the compsn. of a resin having >=2 unsatd. double bonds of the radiation curing type is further provided on the other surface of the substrate. The sticking of the top coat layer and the back coat layer when a tape is wound is thus prevented even after a long period. Particles having 30-300Angstrom grain size are further disposed on the substrate to provide 30-300Angstrom micro- projections at average >=10<5>/a<2> pieces for each 1mm<2> on the surface of the top coat layer with respect to the gap length amu of the magnetic head to be used. The magnetic recording medium having excellent running stability and electromagnetic conversion characteristic is obtd.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, particularly a metal thin film type magnetic recording medium and a magnetic recording method.

Prior art and its problems As magnetic recording media for video, audio, etc., media having a metal thin film type magnetic layer are being actively developed because of their compactness when wound into tapes.

The magnetic layer of such a metal thin film type medium is made of Co-based, Co--Ni-based, etc., formed by the so-called oblique evaporation method, in which MM is performed at a predetermined tilt angle with respect to the normal to the substrate due to # properties. A vapor deposited film is preferred.

Since the characteristics of such a medium are greatly degraded due to spacing loss, it is necessary to make the surface as smooth as possible.

However, if the surface is made too flat, friction will increase, causing problems with head touch and running surface.

By the way, in the total bending ITV film type media, the magnetic layer is 0.0
Since the medium is very thin (5 to 0.5 gm), the surface properties of the medium depend on the surface properties of the substrate.

For this reason, it has been proposed to provide relatively gentle protrusions, such as so-called wrinkle-like or earthworm-like protrusions, on the surface of the substrate (Japanese Unexamined Patent Publication No. 53-11GllS, etc.).

Also, JP-A-58-88227, JP-A No. 58-10022
No. 1 proposes that fine particles be placed on the surface of the substrate to create irregularities that can be observed at 50 to 400 times magnification with an optical microscope and whose height can be measured using a stylus-type surface roughness measuring device. ing.

However, even these are still insufficient in terms of physical properties such as running resistance, running durability, running stability, and electromagnetic conversion characteristics.

On the other hand, Japanese Patent Publication No. 39-2524.theta. proposes that a top coat layer made of an organic lubricant be provided on the surface of one ferromagnetic metal thin film layer to reduce running friction.

However, when organic lubricants are used, head clogging occurs when the feed agent does not reach the head. :
ITIJ” - a big problem.

This problem can be solved by forming a ferromagnetic metal oxide layer on the surface, and when the gap length of the magnetic head is auLm, the surface of the magnetic recording medium has a protrusion with a height of 30 to 300 people per l mm2 on average. This was greatly improved by using a ferromagnetic thin film having two or more 105/"a (Japanese Patent Application No. 111573/1983, etc.).

However, when storing magnetic recording media in a rolled manner, especially when stored under high temperature and high humidity, there is a transfer of lubricant between the back coat and top coat phase π, which causes head adhesion and clogging, and electromagnetic Disadvantages also arise in terms of conversion characteristics.

+! Purpose of the Invention The purpose of the present invention is to improve physical properties such as friction, running durability, and running stability in a metal thin film type magnetic recording medium and a magnetic recording method using the same, and to improve physical properties such as friction, running durability, running stability, etc., and to create a magnetic recording medium that does not cause any problems in terms of physical properties. In addition to eliminating adhesion and clogging within the range, we have also created a system that does not cause any problems in terms of electromagnetic conversion characteristics, and has also improved its durability and storage properties so that its physical properties do not deteriorate even when stored rolled. be.

Such objects are achieved by the invention described below.

That is, the first invention is.

A magnetic material with 12 thin ferromagnetic metal layers mainly composed of Co on one side of a flexible substrate, an organic top coat layer on the surface of the 119 thin ferromagnetic metal layers, and a back coat layer on the other side. In recording media.

The organic top coat layer contains a lubricant.

The back coat layer is lIl! Contains a mechanical pigment, an organic binder, and a lubricant, and has nine ferromagnetic metal fishing layers containing acid, and further has m5
When the gap length of the X head is defined as arm, the medium surface has an average of 105/a2 or more protrusions per square inch, and the protrusions have a height of 30 to 300 people.

The magnetic recording medium is characterized in that the organic top coat layer and the back coat layer contain substantially the same lubricant.

Moreover, the second invention is.

Ferromagnetic gold 1 whose main component is Go on one side of the flexible substrate
A magnetic recording medium is provided with iJ thin llI2 scrap, an organic top coat layer is provided on the surface of the ferromagnetic metal thin H wire layer, and a back coat layer is provided on the other surface.

In a magnetic recording method in which recording and reproduction are performed using a magnetic head, the topcoat Me contains a lubricant.

The back coat layer contains an inorganic pigment, an organic binder, and a lubricant.

and the 12 ferromagnetic metal thin layers contain oxygen, and furthermore, ra
Ap the gap length of the air head. When, the medium surface has an average of 105/a2 or more protrusions per l mm2,
Moreover, the magnetic recording method is characterized in that the protrusions have a height of 30 to 300 mm, and the top coat layer and the back coat layer contain substantially the same lubricant.

I] I Specific Structure of the Invention The magnetic recording medium of the present invention has a magnetic layer, a top coat layer, and a back coat layer, and protrusions are formed on the surface of the magnetic layer side. A magnetic recording method of the present invention uses such a medium and preferably a so-called amorphous head.

The specific structure of the magnetic recording medium and magnetic recording method of the present invention will be explained in detail below.

A. Magnetic Recording Medium The magnetic layer is a ferromagnetic metal thin film layer containing oxygen, and is particularly preferably a ferromagnetic alloy containing Co as a main component.

Further, the surface of this magnetic layer has protrusions having a predetermined height and a predetermined pitch.

The coating layer I± is composed of a lubricant or a composition containing a Pl lubricant.

It is preferable that it contains a) an iljJa agent + an antioxidant IF agent, or b) a radiation curable compound + a lubricant + an anti-intoxication agent.

In particular, C) a radiation-curable compound with a molecular weight of less than 2,000 + J + a lubricant and a lubricant-forming antioxidant.

d) one containing a radiation-curable phosphate ester antioxidant excavating lubricant; and e) one containing a radiation-curable phosphate ester antioxidant + radiation-cured ηJ compound + lubricant.

Also, in these, lubricants and/or antioxidants are radioactive MAM! Preferably, it is of the chemical form.

The coating layer contains an inorganic pigment, an organic pigment, and a lubricant. Preferably, the organic binder and lubricant are radiation-curable, and the organic binder is a composition of two or more resins having a predetermined molecular weight and an unsaturated two-claw bond.

The 1lflffi agent in the topcoat layer and the 11δ1 agent in the Hacco-1 layer are substantially the same.

Here, the term "substantially the same" refers to not only completely the same compounds but also those having substantially the same molecular moieties exhibiting lubricity.

In this case, if there are multiple molecular moieties that exhibit lubricity, or if there are molecular moieties that do not exhibit lubricity, they are substantially the same type.

More specifically, in relatively low-molecular compounds such as fatty acids, fatty acid esters, and alcohols, which will be described later, the number of carbon atoms is 2.
It includes compounds of the same type with different degrees.In addition, in polymer compounds such as silicone oil, the 5 molecular weight and the repeating method do not matter as long as the repeating units are the same.

In the radiation-curing type described below, the state of the polymer after curing does not matter as long as the molecular chains exhibiting lubricity are substantially the same.

In addition, in the case of an inorganic compound, the deviation of the composition etc. does not matter.

Furthermore, for metal soaps, the metal is not a problem.

And practically identical Jun like this? The Ij agent may be contained in the seven-layer coating layer and the top coat layer from the beginning.

The back coat layer and/or top coat layer may contain other lubricants.

If both layers further contain other lubricants, as long as one lubricant is substantially the same, the other lubricants may be the same or different) + Top coat layer and eight coat layer If one I11 lubricant, more preferably the main lubricant, is substantially the same, changes in the physical properties of both layers due to back mold transfer after winding and storage can be prevented.

It has an extremely high shelf life.

Below are (1) magnetic layer, (2) substrate, (3) protrusion, (4)
The magnetic recording medium of the present invention will be described in detail in terms of the top coat layer and (5)/back coat layer.

(1) Ia magnetic layer The ferromagnetic metal thin film layer as the magnetic layer in the invention is C
The main component is o, including 0, and further N as necessary.
It has f1 in which i and/or Cr are included.

That is, in a preferred embodiment, it may be made of Co alone, or it may be made of Co and Ni. When Ni is included, the Co/Ni ratio is preferably 1.5 or more.

Furthermore, Cr may be contained in the ferromagnetic metal thin layer 11!2.

When Cr is contained, electromagnetic conversion characteristics are improved, output and S/N ratio are improved, and film strength is also improved.

In such cases, Cr/Co or Cr/(Co
+Ni) has a gravity ratio of o, i or less, especially o,oot~0,
1. More preferably, it is 0.005 to 0.05.

Furthermore, O is contained in the ferromagnetic metal thin film.

The average amount of oxygen in a ferromagnetic metal thin film is an atomic ratio.

The atomic ratio of O/(Go or Co+Ni) is 0.5
Hereinafter, it is more preferably 0.05 to 0.5.

In this case, oxygen forms an oxide with the ferromagnetic metal (Co, Ni) on the surface of the ferromagnetic metal thin film layer. - That is, in one surface area, particularly in the range of 50 to 500 thickness, more preferably 50 to 200 thickness from the surface, a peak indicating an oxide is observed by Auger spectroscopy. The oxygen content of this oxide layer is about 0.5 to 1.0 in terms of atomic ratio.

In addition, such a ferromagnetic metal thin film may further contain other trace components, especially transition elements such as Fe, Mn, V, Zr,
Nb, Ta, Ti.

Zn, Mo, W, Cu, etc. may be included.

In a preferred embodiment, such a ferromagnetic metal thin film layer is composed of an aggregate of columnar crystal grains containing the above-mentioned Go as a main component.

In this case, the thickness of the first ferromagnetic metal thin film layer is 0.05 to 0.0.
5 gm, preferably 0.07 to 0.3 μm.

The columnar crystal grains have a length spanning almost the entire thickness direction of the thin film;

It is preferable that the inclination is within the range of 10 to 70' with respect to the normal to the main surface of the base.

Note that oxygen exists in the form of a compound on the surface of the columnar crystal grains in one surface portion, as described above.

Further, there is no particular restriction on the oxygen concentration gradient of the ferromagnetic metal thin film layer.

Further, it is preferable that the short axis of the crystal grains has a width of about 50 to 500.

Note that between the substrate and the ferromagnetic metal thin film layer.

If necessary, various known underlayers may be interposed.

Furthermore, if necessary, the five ferromagnetic metal thin film layers may be divided into a plurality of parts, and a non-cardiac gold scrap thin film layer may be interposed between them.

In the present invention, the magnetic layer is formed by electrolytic deposition.

Although ion blating or the like may be used, it is preferable to form by a so-called oblique vapor deposition method.

In this case, relative to the substrate normal. The minimum value of the incident angle of the vapor-deposited substance is preferably 20° or more.

When the incident angle is less than 20°, electromagnetic conversion characteristics deteriorate.

The vapor deposition atmosphere is usually an inert atmosphere such as argon, helium, vacuum, etc., and an atmosphere containing oxygen gas.
The pressure may be approximately -'X100 Pa, and the deposition distance, substrate conveyance direction, structure and arrangement of cans and masks, etc. may be the same as known conditions.

Then, by vapor deposition in an oxygen atmosphere, a metal oxide film is formed on the surface. Note that the oxygen gas partial pressure at which metal oxides are formed can be easily determined through experiments.

Note that in order to form a metal oxide film on one surface, various oxidation treatments are possible.

Applicable oxidation treatments include the following.

l) Dry treatment a, energetic particle treatment As described in Japanese Patent Application No. 140, 1987-78, oxygen is applied to the magnetic layer as energetic particles using an ion gun or a neutral gun in the latter stage of red and blue. .

b. Glow treatment 02, H20, 02+H20, etc. and Ar.

N2? An inert gas is used to generate plasma by glow discharge, and the surface of the magnetic film is exposed to this plasma.

C0 oxidizing gas Items that spray oxidizing gas such as oran or heated steam.

d, Heat treatment: Oxidation is performed by heating, heating temperature is 60-15
Around 0℃.

2) Wet treatment a: Anodizing, alkali treatment, C9 acid treatment, chromium a salt treatment, permanganate treatment, phosphate treatment, etc. are used.

d. Oxidizing agent treatment H2O2 etc. are used.

(2) No. (Board) The substrate on which such a ferromagnetic metal thin film layer is formed is not particularly limited as long as it is non-magnetic, but flexible substrates, especially resins such as polyester and polyimide, are used. Preferably, it is manufactured by

In addition, the thickness may be various, but especially 5.
It is preferable that it is 20 pm.

(3) Protrusions Fine protrusions are provided at a predetermined density on the surface of the magnetic recording medium of the present invention constructed as described above.

The fine protrusions are 30 to 300 people, more preferably 50 to 300 people.
It has a height of 250 people.

That is, the protrusions of the present invention cannot be observed with an optical microscope and measured with a stylus type surface roughness meter, but can be observed with a scanning electron microscope.

If the height of the protrusions exceeds 300 and becomes observable with an optical microscope, the electromagnetic conversion characteristics deteriorate and the running stability deteriorates.

Furthermore, if the number of participants is less than 30, there is no effective improvement in physical properties.

And its density is 105/a on average per l a+s2
2, more preferably 2XIO6/a2-1XIO9/
There are 2 pieces.

In this case, a represents the gap length of the magnetic head used in gm.

And a is 0.1-0.5 μm, especially O11-0°4
It is said to be the end.

In addition, the protrusion density is 105/a2 pieces/ma+2. Yori&f
Preferably 2x106/a2 pieces/. , less than 2, the physical properties deteriorate, such as increased noise and reduced running durability, and are not suitable for practical use.

Moreover, if it exceeds 109/a2 pieces/+u+2, the mold retention will be reduced and the effect on physical properties will be reduced.

In order to provide such protrusions, it is sufficient to cool the particles properly and arrange the particles on a plate.The particle size may be 30 to 300 people, especially 50 to 250 people, and this corresponds to the particle size. microscopic projections are formed.

The fine particles used are those commonly known as colloidal particles, such as s+o2 (=+c+Idarushiri force), A1203 (alumina sol), Mg.
O, T i 02 .

ZnO, Fe2O3, zirconia, CdO.

NiO, CaWO4, CaCo3.

BaCo3, CoCo3, BaTiO3°Ti (titanium platinum), Au, Ag, Cu.

Ni, Fe, various hydrosils, resin particles, etc. can be used.

In this case, it is particularly preferable to use inorganic substances.

Such fine particles may be prepared by forming a coating liquid using various solvents, coating this on the substrate, and drying it, or by applying a coating liquid containing various resins such as aqueous emulsions, etc., and drying it. You may.

In some cases, instead of disposing these coating liquids on the substrate, fine particles may be added to the top coat layer to form the protrusions.

Further, when a resin component is used, gentle protrusions may be provided to overlap the microprotrusions based on these fine particles, but this is usually not necessary.

(4) Top coat layer A predetermined top coat layer is provided on such a magnetic layer.

The top coat layer of the present invention contains a lubricant.

The lubricant used in the present invention is a lubricant conventionally used in this type of magnetic recording medium.

Although silicone oil, fluorine oil, fatty acids, fatty acid esters, paraffin, liquid paraffin, surfactants, etc. can be used, it is preferable to use fatty acids and/or fatty acid esters.

Fatty acids include caprylic acid and capric acid.

Fatty acids with 12 or more carbon atoms (RCoOH), such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolic acid, and stearolic acid.

For R, a full-kyl group having 11 or more carbon atoms or the like is used.

Further, alkaline or alkaline earth metal soaps made of these fatty acids may also be used.

Examples of fatty acid esters include fatty acid esters consisting of a monobasic fatty acid having 912 to 16 carbon atoms and a monohydric alcohol having 3 to 12 carbon atoms, and -i! having 17 or more carbon atoms. ! The total number of carbon atoms in basic fatty acid and juvenile fatty acid is 21.
A fatty acid ester consisting of a monohydric alcohol consisting of ~23 or the like is used.

As the silicone, those made of fatty acid-modified silicones and those partially fluorine-modified are used.

Examples of the alcohol include higher alcohols having carbon fi12 or more.

Further, the alcohol may be a sulfuric ester.

As the fluorine, those obtained by electrolysis, telomerization, oligomerization, etc. are used.

Furthermore, natural or synthetic surfactants such as lecithin,
Each ear coupling agent, graphite, molybdenum disulfide, stingray? Tungsten zeta oxide, etc. can also be used.

Among the lubricants, it is also advantageous to use radiation-curable types.

These suppress the transfer of the back mold to the ferromagnetic bacteria 11g, which prevents dropouts, reduces the difference in output depending on the inner and outer diameter when wound into a roll, and allows for online manufacturing. has the advantages of

Examples of radiation-curable lubricants include compounds having a molecular chain exhibiting 5M properties and an acrylic double bond in the molecule, such as acrylic esters, methacrylic esters, vinyl acetate esters, acrylic amide compounds, vinyl alcohol esters, Methyl vinyl alcohol ester, allyl alcohol ester, glyceride, etc.

The structural formula of these Nai 41 aggregates is CH2=CH-
CH2C0OR.

CH2=CHC0NHCH20CoR RCoOCH=CH2.

RCoOCH2-C1 (-CH2, etc., where R is a linear or branched saturated or unsaturated hydrocarbon group, and the number of carbon atoms is 7 or more, preferably 12 or more and 23 or less, and these are fluorine-substituted and You can also.

As a fluorine substituted product.

CnF2n, SOz NCH2CH2-1CnFnCH
2N) ICH2CH2-1C'2n-, oQco□ 2
°There are such things.

Preferred specific examples of these radiation-curable EL lubricants include stearic acid methacrylate (acrylate), stearyl alcohol methacrylate (acrylate),
Examples include glycerin methacrylate (acrylate), glycol methacrylate (acrylate), silicone methacrylate (acrylate), vinyl stearate, vinyl myristate, and the like.

It is preferable that the top coat layer of the present invention further contains an antioxidant.

The antioxidant used in the present invention may be any antioxidant as long as it prevents metal oxidation.

The antioxidants used in the present invention include 1) phenolic antioxidants, and 2) amine antioxidants.

3) Phosphorous antioxidant, 4) Sulfur-based antioxidant, 5) Organic acid, alcohol, ester-based antioxidant, 6) Quinone-based antioxidant, 7) Inorganic acid, a1. ! They are roughly divided into structural types such as antioxidants.

Here are some specific examples of various antioxidants.

■) As a phenolic antioxidant.

2.6-di-tert-butyl-p-crenol.

2.6-di-tert-butyl-phenol, 2.4-di-methyl-6-tert-butyl-phenol, butylhydroxyanisole.

2.2'-methylenebis(4-methylphenonol),
4.4'-butylidenebis(3-methyl-6-:, i-nibutylphenol), 4.4'-thiobis(3-methyl-6-tert-butylphenol), tetrakis[methylene-3(3,5-tert-butylphenol), 3-butyl-4-hypoxyphenylpropionate]methane, 1,1.3-1lis(2
-methyl-4-hydroquine-5-tert-butylphenyl)
Examples include butane, dibutylhydroquine tolueno, propyl gallate, guaiac butter, nordihydroguaiaretic acid, etc.

Radiation-curing types include monoglycol salicylate,
2.5-ditert-butylhydroquinone, 2.4-dihydroxyhensiphenone.

2.4.5-) Methacrylate and acrylate types such as lihydroxybutyrophenol and hydroquinone can be mentioned.

2) As an amine antioxidant.

phenyl-β-su7thylamine, α-naphthylamine 7,
N,N'-cy-tert-nibutyl-p-phenylenediamine,
Phenothiazine.

In addition to N,N'-diphenyl-p-phenylenediamine, alkanol 7! /n, phospholipids, etc.

Among amine-based materials, radiation-curable materials such as dimethylaminoethyl methacrylate and acrylate can be cited as radiation-curable materials.

3) As the phosphorus-based antioxidant, a radiation curing type or a non-radiation 1liI curing type is used.

The R of the phosphoric acid ester moiety includes an alkyl group, an alkylphenyl group, ethylene oxide, and #-propylene, and preferably has C of 1 to 26, more preferably 1 to 22.

The phosphoric acid esters include mono-, di-, and tri-type phosphoric acid esters, and may have a large mono- or di-component content, and tri-type phosphoric acid esters may be cut.

Moreover, phosphoric acid esters include those of NH4 type, methacrylate type, and acrylate type.

Specifically, triphenyl phosphite, triotadecyl phosphite, tridecyl phosphite, trilauryl trithiophosphite, hexamethylphosphoric triamide, butyl phosphate, cetyl phosphate, butquinethyl phosphate, etc. ,
2-ethylhexyl phosphate, β-chloroethyl phosphate, butoxyphosphate diethylamine salt,
Di(2-ethylhexyl) phosphate, ethylene glycol an7tophosphate, (2-hydroxyethyl) methacrylate phosphate, butyl hydroxy methacrylate e-phosphate, caprylic hydroxy methacrylate phosphate, myristyl hydroxy methacrylate phosphate, stearylhydroquine methacrylate phosphate, cetyl Hydroxy methacrylate phosphate, butylphenyl hydroxy methacrylate phosphate, amyl phenyl hydroxy methacrylate phosphate, nonylphenyl hydroxy methacrylate-phosphate, and their acrylate types, phenyl phosphate, other alcohols, and phenyl phosphates such as nonylphenyl, vanadium acids Examples include phosphoric acid esters such as phosphoric acid esters.

It is particularly suitably used in the top coat layer of the present invention. It is a radiation-curable phosphate ester.

The R of the ester moiety includes an alkyl group, an alkylphenyl group, other ethylene oxide, propylene oxide, and the R is preferably 01 to 26, more preferably 1 to 22), and NH4 type. However, it is a phosphoric acid ester having an acrylic, vinyl, or maleic double bond that is sensitive to ionization energy.

Phosphate esters include mono-2-di and tri-type phosphoric acid esters, and may have a large mono- or di-component, and tri-type esters may be cut.

Examples of these phosphate esters include (2-hydroxyethyl) methacrylate phosphate, butyl hydroxy methacrylate phosphate, caprylic hydroxy methacrylate and phosphate, myristyl hydroxy methacrylate triphosphate, stearyl hydroxy methacrylate phosphate, and cetyl hydroxy methacrylate phosphate. .

Examples include butylphenyl hydroxy methacrylate phosphate, amyl phenyl hydroxy methacrylate phosphate, nonylphenyl hydroxy methacrylate phosphate, and seven acrylate types thereof.

When using these radiation-curable phosphate esters,
Continuous processing is possible on top coat layer 52, and it can be processed online, which helps to save energy and reduce costs.Also, the coating is uniform, and it can be applied to m+, +'
An excellent effect can be obtained in which Z+ is often applied to Le 11.

4) Sulfur! Type 1 antioxidants include dilaurylthiodipropionate, dilaurylthiodipropionate, laurylstearylthiodipropionate, dimyrythrylthiodipropionate, distearyl β, β'-thiobutyrate, and 2-mercaptoben. In addition to imidasol and dilauryl sulfide, 4.4'-
Radiation-curing types such as methacrylates and acrylates of thio-bis(3-methyl-6-tert-butyl-phenol), 2.2' to thiobis(4-methyl-6-tert-butyl-phenol)':9 are mentioned. It will be done.

Moreover, these may contain ethylene oxide and propylene oxide.

5) As organic acid, alcohol, and ester antioxidants.

Examples include nrubitol, glycerin, propylene glycol, adipic acid, citric acid, and 7-scobic acid, and radiation-curable versions of these may also be used.

゛　　6) As a quinone antioxidant.

Hydroquinone, tocopherol, etc. are suitable, and among these, radiation-curable types may be used.

7) Phosphoric acid is a typical example of the inorganic acid and inorganic salt antioxidant.

Among the above-mentioned antioxidants, radiation-curable ones with an acrylic double bond in the molecule, such as heptanoglycol salicylate methacrylate (acrylate ), 4-q-butylcatechol methacrylate (7 acrylate), dimethylaminoethyl methacrylate (acrylate), ethyl hydroxy methacrylate (acrylate) phosphate, cetyl hydroxy phosphate methacrylate (acrylate).

Ste7lyl methacrylate (acrylate) phosphate, and phenyl types of the above, 2.2
” Thio-bis(4-methyl-6-tert-butyl-phenol) methacrylate (7-acrylate) and the like are preferred.

The phosphoric acid ester can be produced by any known method, including the method described in Japanese Patent Publication No. 57-44223.

Since the radiation curing inhibitor can be cured online to form a ferromagnetic thin film, there is no deterioration in surface properties due to back mold transfer due to curling during curing, and therefore there is no decrease in output.

As will be described later, the top coat of the ferromagnetic thin film is preferably 100 Å or less, and if it is thicker than this, the shape retention will deteriorate. Also, if it is too thick, the top coat layer will be scraped.

These words were discovered for the first time in this report. The use of a radiation-curing anti-aging agent not only prevents dropouts and reduces the difference in output between internal and external parts when wound into a roll, but also facilitates online manufacturing. This can undermine the processing effect that is possible.

The radiation-curable compounds used in the tomp coat layer of the present invention include acrylic acid, methacrylic acid, or acrylic double bonds such as ester compounds thereof, which have unsaturated double bonds exhibiting radical polymerizability, and diallylphthalate. It is possible to use resins that contain or introduce into the molecule of thermoplastic resin groups that can be crosslinked or polymerized and dried by radiation irradiation, such as heptalyl double bonds, maleic acid, unsaturated bonds such as maleic acid derivatives, etc. can.

Other usable polymer components include:

Examples of monomers include acrylic acid, methacrylic acid, and acrylamide.

Compounds with double bonds include various polyesters,
Polyols, polyurethanes, etc. can also be modified with compounds having acrylic double bonds. Furthermore, by blending a polyhydric alcohol and a polyhydric carboxylic acid as necessary, products with various molecular weights can be obtained.

The above are some of the radiation-sensitive resins,
These can also be used in combination.

(A) A plastic-like compound having a molecular weight of 5,000.100,000 and having two or more unsaturated double bonds that are curable by radiation or not curable by radiation.

CB) Molecule z3 that has one or more unsaturated double bonds that are curable by radiation or does not have radiation curability
There are rubber-like compounds with a molecular weight of ooo to 100,000, and (C) compounds with one molecule IJ of 200 to 3,000, which have one or more unsaturated double bonds that are curable by radiation.

These may be used alone or in the form of a mixture, and in the case of a mixture, these are particularly preferred.

(A) 20 to 70 wt%, (B) 20 to 80 wt%, (
C) A combination used in a proportion of 10 to 40% by weight.

In addition, the number of unsaturated double bonds in the compounds (A), (B), and (C) is 2 or more, preferably 5 or more for (A), 1 or more for (B), preferably 5 or more, and ( C) is 1 or more, preferably 3 or more.

The plastic-like compound (A) used in the present invention is one that generates radicals by radiation and produces a crosslinked structure.
It contains two or more unsaturated double bonds in its molecular chain, and can also be obtained by radiation-sensitizing a thermoplastic resin.

Specific examples of radiation-curable resins include acrylic double bonds such as acrylic acid, methacrylic acid, or their ester compounds, which exhibit radically polymerizable unsaturated double bonds, and allylic double bonds such as diacrylphthalate. Groups that can be crosslinked or polymerized and dried by radiation irradiation, such as tetrabonds, maleic acid, unsaturated bonds such as maleic acid derivatives, etc.
σr is a resin contained or contained in the molecule of plastic resin. Other compounds with unsaturated double bonds that undergo cross-linking polymerization upon radiation irradiation and have a molecular weight of 5,000-100,000
10,000 to aooooo can be used.

The following unsaturated polyester resins are examples of thermoplastic resins containing groups in their molecules that can be crosslinked or polymerized and dried by radiation irradiation.

Polyester compound 1 containing a radiation-curable unsaturated double bond in the molecular chain, for example, polyester compound 11 of (2) below! 21!
Yuwa polyester resin consists of ester bonds of ia and polyhydric alcohol, and has a polyester of 11! Examples include unsaturated polyester resins containing radiation-curable unsaturated double bonds in which part of the base acid is maleic acid.

The radiation-curable unsaturated polyester resin has a poly-Ij! Plain acid, fumaric acid, etc. are added to at least 1 C of the base acid component and at least 1 C of the polyhydric alcohol component, and dehydration or dealcoholization is carried out in a conventional manner, i.e., in the presence of a catalyst, at 180 to 200 °C under a nitrogen atmosphere. After the reaction, the temperature is raised to 240 to 280°C, and the reaction mixture is carried out under reduced pressure of 0.5 to 1 mmHg.

The content of maleic acid, fumaric acid, etc. in the acid component is 1 to 40 mol%, preferably 10 to 30 mol%, in view of crosslinking and radiation curability during production.

Examples of thermoplastic resins that can be modified into radiation-curable resins include the following.

(1) Vinyl chloride-based copolymer vinyl chloride-vinyl rubinyl alcohol copolymer,
Vinyl chloride-vinyl alcohol copolymer, vinyl chloride-
Vinyl alcohol-vinyl propionate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinyl acetate-terminal OH side chain alkyl group copolymer, and if U CC VROH, VYNC, VYBGX
, VERR, VYES, YMCA, VAC; I do.

(2) feed polyester TA41 with saturated poly-111 base acids such as former fucuric acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid;
Ethylene glycol, diethylene glycol, glycerin, trimethylolpropane, l, 2-propylene glycol, 1.3-butanediol, dipropylene glycol, 1°4-butadiol, 1,6-hexanediol, pentaerythritol, nrubitol, glycerin, neopentyl glycol, 1.4 Saturated polyester resins obtained by ester bonding with polyhydric alcohols such as cyclohexane dimetatool, or resins obtained by modifying these polyester resins with 5O3Nal (for example, Vylon 5
3S) is given as an example, and these are also subjected to radiation sensitivity modification in the same manner.

(3) Polyvinyl alcohol resin Polyvinyl alcohol, butyral resin, acetal resin, formal resin, and J (polymer) of these components. The wood groups contained in these resins are subjected to radiation-sensitive modification by the method described below. .

(4) Epoxy resin, phenoxy resin Epoxy resin 1 produced by the reaction of bisphenol A, epichlorohydrin, and methyl epichlorohydrin, such as Shell Chemical (Ebi: I-T 152.154, 828, 1001, 1004)
．． 1007), tau chemical acid (DEN431.DER
732, DER511, DER331).

Manufactured by Dai F3 Wood Ink Co., Ltd. (Ebiku ay 400, 800), phenoxy resin manufactured by UCC Corporation (PKHA, PKHC, APKHH), which is a high polymerization degree resin of the above epoxy, copolymer of brominated bisphenol A and epichlorohydrin, Dairoki Ink Kagaku Kogyo (Epicron 145, 152)
, 153.1120), etc.

Radiation sensitivity modification is performed using the epoxy groups contained in these resins.

(5) Various cellulose derivatives are used, but the particularly effective ones are nitrified cotton, cellulose acetobutyrate, ethyl cellulose,
Butyl cellulose, acetyl cellulose, etc. are suitable.

Radiation sensitivity modification is performed using the hydroxyl groups in the resin by the method described below.

Other resins that can be used for radiation sensitivity modification include polyfunctional polyester resins, polyether ester resins, polyvinylpyrrolidone resins and derivatives (PV
Acrylic resins containing at least one of P olefin copolymers), polyamide resins, polyimide resins, phenol resins, spiro 7secur resins, hydroxyl group-containing acrylic esters, and methacrylic esters as polymerization components are also effective. .

The compound having the same molecular weight as (B) used in the present invention is thermoplastic ester or brepolybute, or a radiation-sensitive modified version of these, and the latter is more effective.

Examples of elastomers or prepolymers are listed below.

(1) The use of polyurethane elastomer or prepolymer polyurethane has good abrasion resistance and good JD ZF properties to the base film, such as PET film. Valid for ¥.

Examples of urethane compounds include incyanate,
2.4-Toluene diisocyanate, 2.6-)Toluene diisocyanate, 1゜3-Toluene diisocyanate, 7)
, 1.4-xylene diisocyanate, 1.5-naphthalene diisocyanate, m-phenylene diisocyanate, P-7 enylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate,
4.4'-diphenylmethane diisocyanate, 3.3
” -dimethylbiphenylene diisocyanate, 4,4
'-biphenylene diisocyanate, hexamethylene diisocyanate, infron diincyanate, dicyclohexylmethanone incyanate, desmodur, and various polyvalent incyanates such as desmodur N.

Linear saturated polyesters (ethylene glycol, diethylene glycol, glycerin, trimethylolpropane, I,4-butanediol, 1,6-hexanediol, pentaerythritol, nlubitol 1, neopentyl glycol, 1,4-cyclohexane dimethyl) linear saturated polyethers (polyethylene glycol, Polyurethane elastomers and prepolymers made of polycondensates of various polyesters such as polypropylene glycol, polytetramethylene glycol), caprolactam, hydroxyl-containing acrylic esters, and hydroxyl-containing methacrylic esters are effective.

It is very effective to modify these urethane elastomers to make them radiation sensitive by reacting the terminal isocyanate (or hydroxyl group) with a monomer having an acrylic double bond or an allylic double bond. It is.

It also includes those containing OH, COOH, etc. as a polar group at the end.

(2) Acrylonitrile-butadiene copolymer elastomer A 7-acrylonitrile-butadiene copolymer prepolymer with a terminal hydroxyl group, which is commercially available as PolyBD Retainoresin manufactured by Sinclair Petrochemical Co., Ltd., or Hiker 1432J manufactured by Nippon Zeon Co., Ltd. The elastomer is particularly suitable as an elastomer component in which the double bond in butadiene forms a radical upon radiation and is polymerized.

(3) Polybutadiene elastomer A prepolymer having a low molecular weight terminal hydroxyl group, such as PolyBD Retained Resin R-15 manufactured by Claire Petrochemical Co., Ltd., is particularly suitable in terms of compatibility with thermoplasticity.

In R-15 prepolymer, the 5 molecule ends are hydroxyl 71
(Due to its sharp shape, it is possible to increase radiation sensitivity by adding an acrylic unsaturated double bond to the end of one molecule, making it more advantageous as a pinter.

In addition, polybutadiene cyclized product 1 CBR manufactured by Japan Synthetic Rubber Co., Ltd.
-M901 also has excellent properties due to its combination with thermoplastic resin.

Others, thermoplastic elastomer 8 and its prepolymer 7
- Suitable systems include styrene-butadiene rubber, chloride rubber, acrylic rubber, imprene rubber, and their cyclized products (ClR701 manufactured by Japan Synthetic Rubber Co., Ltd.), epoxy-modified rubber, internally plasticized saturated linear polyester (Toyobo Elastomers such as Heilon #300) can also be effectively used by subjecting them to the radiation sensitivity modification treatment described below.

Examples of the compound (C) having a radiation-curable undisturbed double bond used in the present invention include styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol acrylate, diethylene glycol dimethacrylate, and 1,6-hexane gelicol diacrylate. relay),
1.6-hexane gelicol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, polyfunctional oligoester acrylate (Aronix M-7100, M-5400,
5500, 5700 (Toagosei Co., Ltd.), acrylic modified products of urethane elastomer (Futoborane 4040), and products in which functional groups such as COOH are introduced into these products.

Next, an example of synthesis of a radiation-curable compound will be explained.

a) Synthesis of acrylic modified vinyl chloride vinyl acetate copolymer resin (radiation sensitive modified resin 111) Partially saponified vinyl chloride vinegar copolymer having OH groups (sFL degree of homopolymerization n-5)
00) Charge 750 parts of toluene, 1zso*a of toluene, and 5ooi of cyclohexanone into a 51 four-bottle flask, heat and dissolve, and heat to 80°C to ditolylene diisocyanate.
Hydroxyethyl methacrylate adduct*61.4
1 part, and further added 0.012 part of tin octylate, hydroquinone o, otz+iv, and heated at 80°C in a N2 stream.
The reaction is allowed to occur until the NGO reaction rate reaches 90%.

After the reaction is completed, the mixture is cooled and diluted with 1250 parts of methyl ethyl ketone.

(*Manufacturing method of tolylene diisocyanate (TD Rino 2- and droxyethyl methacrylate (2HEMA) adduct 348 parts of TDr in a N2 stream at 11 tr) 4 Tsuro 7
After heating to 80°C in a flask, 260 parts of 2-ethylene methacrylate, 0.07 part of tin octylate, and 0.05 part of hydroquinone were added while controlling cooling so that the temperature in each reaction vessel was 80 to 85°C. After dropping, 80℃
Stir for 3 hours to complete one reaction.

After the reaction is complete, take it out, cool it, and leave a white paste of T.
2HEMA of DI was obtained. ] b) Synthesis of acrylic modified product of Brachyral resin (radiation-sensitive modified resin) BM-5L00gll of Butyral Resin Building Block Chemical Co., Ltd. was charged into a 51 four-bottle flask with 191.2 parts of toluene and 71.4 parts of cyclohexanone, heated and dissolved at 80°C. After raising the temperature, add 7.4 parts of TDI's 2HEMA adduct*.
Furthermore, tin octylate o, ois part, hyde a quinone 0
015 parts of the mixture was added, and the mixture was allowed to react at 80° C. in a N2 stream until the NCo reaction rate reached 90% or more.

After the reaction is completed, the mixture is cooled and diluted with methyl ethyl ketone.

C) Synthesis of acrylic modified saturated polyester resin (radiation-sensitive modified resin) Saturated polyester resin (Vylon Rv-zoo manufactured by Toyobo Co., Ltd.
) Too part was heated and dissolved in 116 parts of Jlzz-7 and 116 parts of methyl ethyl ketone, and after raising the temperature to 80°C, 3.55 parts of TDI's 2HEMA adduct* was added, and further 0.007 parts of tin octylate and 0.007 parts of hydroquinone. Add part.

The reaction was carried out at 80°C in a N2 stream until the NCo reaction rate reached 90% or more.

d) i) Synthesis of modified acrylic epoxy resin (radiation-sensitive modified resin) Epoxy resin (Epicoat 1007 manufactured by Shell Chemical Co., Ltd.) 4
After heating and dissolving oog in 50 parts of toluene and 50 parts of methyl ethyl ketone, N,N-dimethylbenzyl 7min o,oo
sgB and 0.003 part of hydroquinone were added, the temperature was raised to 80°C, 69 parts of acrylic μm was added dropwise, and the mixture was allowed to react at 80°C until the acid value reached 5 or less.

ii) Synthesis of acrylic modified phenoxy resin (radiation-sensitive modified resin) 600 parts of a phenoxy resin having an OH group (PKHH: manufactured by UCC, molecule FF130000) and 1800 parts of methyl ethyl ketone were charged into 4 flasks, and heated and dissolved. After raising the temperature to 80°C, 6.0 parts of 2-hydroxyethyl methacrylate adduct of tolylene diisocyanate was added, and further 0.0 parts of tin octylate was added. OL2! , 0.012 part of hydroquinone was added, and the mixture was allowed to react at 80°C in a N2 stream until the NGO reaction rate reached 90%.

The molecular weight of this phenoxy modified product is 35,000. There is one double bond per molecule.

e) Synthesis of acrylic modified urethane elastomer (radiation-curable elastomer) 250 parts of a diphenylmethane diisocyanate (MDI)-based urethane prepolymer having terminal incyanate (Nipporan 3119 manufactured by Nippon Polyurethane Co., Ltd.), 32 parts of 2HHMA.
5 parts, hydroquinone 0.07 parts, tin octylate 0.
Pour 009 parts into a reaction vessel, heat to 80°C and dissolve, then TDI
43.5 parts were added dropwise while cooling so that the temperature inside one reaction vessel was 80 to 90°C, and after the dropwise addition was completed, the reaction was carried out at 80°C:
React until J95% or higher.

f) Synthesis of acrylic modified polyether-terminated urethane-modified elastomer (radiation-curable elastomer) Polyether PTG-500, 2 manufactured by Nippon Polyurethane Co., Ltd.
50 parts, 2HEMA 32.5 parts, hydroquinone 0.0
07 parts and 0.009 parts of tin octylate were placed in a reaction vessel.
After heating and dissolving at 80°C, 143.5 parts of TI) was added dropwise while cooling so that the temperature inside the reaction vessel was 80 to 90°C. After one drop was added, the reaction rate was 95% or more at 80°C. Make it react.

g) Synthesis of acrylic modified polybutadiene elastomer (radiation curable elastomer) Low molecular weight terminal water group polybutadiene polyBD Liquid Lensin R-15, 250 parts, manufactured by Sinclair Petrochemical Co., Ltd., 2HHMA32.
5 parts, 0.007g of hydroquinone! 1. Put 0.009 parts of tin octylate into a reaction vessel, heat and dissolve at 80°C,
43.5 parts of TDI is added dropwise while cooling the reaction vessel to a temperature of 80 to 90°C, and after one drop is added, the reaction is allowed to proceed at 80°C until the reaction rate reaches 95% or more.

It is known that some polymers disintegrate when irradiated with radiation, while others cause crosslinking between molecules.

Examples of substances that cause crosslinking between molecules include polyethylene, polypropylene, polystyrene, polyacrylic ester,
Polyacrylamide, Poly1! vinyl chloride, polyester, polyvinylpyrrolidone rubber, polyvinyl alcohol,
There is polyacrylene.

With such cross-linked polymers, the cross-linking reaction occurs even without the above-mentioned modification, so in addition to the above-mentioned modified products, these resins can be used as they are as top coat resins for radiation cross-linking. be.

Furthermore, according to this method, even a solvent-free resin that does not use a solvent can be cured in a short time, so such a resin can be used as a top coat.

In addition, as a functional group, alcohol type as a water @ group,
Also included are those containing aromatic, aliphatic, sulfonic acid groups, amine groups, ammonium groups, etc. as phenolic, phosphoric acid, and carboxylic acid groups. In particular, those having functional groups have better adhesion to the ferromagnetic fi film.

Particularly preferable combinations of the radiation-curable resin composition of the present invention include a vinyl chloride-vinyl acetate copolymer into which a partially saponified carboxylic acid has been introduced as the compound (A), vinyl chloride-vinyl acetate copolymer, and vinyl chloride-vinyl acetate copolymer. Vinyl alcohol-maleic acid copolymer, epoxy, phenoxy resin (preferably phthalic acid, isophthalic acid, terephthalic acid, adipic acid, sehesin Mk)
4) into which a carboxylic acid has been introduced) with a polyisocyanate compound, and an acrylic compound or a methacrylic compound having a functional group that is reactive with the incyanate group is reacted with a compound having an incyanate group. It is a compound that consists of

The compound (B) was obtained by reacting a polyol with an isocyanate compound. It is a compound obtained by reacting an isocyanate compound or a polyol (polyurethane elastomer, preferably one into which OH or COOH groups are introduced) with an acrylic compound or methacrylic compound having a functional group having monoreactivity.

The compound (C) is a polyfunctional (meth)acrylate monomer, oligoester acrylate, or a low molecular weight compound of CB).

Combinations of these are also included.

By using a radiation-curable compound, it has good adhesion to the ferromagnetic thin film, the top coat layer is reinforced with a polymer, the breaking strength of the coating film is increased, the coating film is strengthened, the top coat is less likely to wear off, and Durability during high-temperature running can be improved.

Therefore, it is possible to obtain a magnetic recording medium that has uniform characteristics in the length direction, with little dropout, and no curling during curing when wound into a roll.

If there is no polymer, it will be difficult to stop when running at high temperatures, there will be large scratches, and there will be adhesion.

Further, when a radiation-curable polymer is used, continuous processing is possible in manufacturing the top coat layer, and processing can be performed online, which is useful for energy saving and cost reduction.

Examples of radiation-curable molecules particularly preferably used in the top coat layer of the present invention, compounds having a molecular weight of less than 12,000, include acrylic, methacrylic, and Groups that can be crosslinked or polymerized and dried by radiation irradiation, such as acrylic double bonds such as those in ester compounds, allylic double bonds such as diallyl phthalate, and unsaturated bonds such as maleic acid and maleic m derivatives, are included in the molecule. Compounds with a molecular weight of less than 2,000 that are contained or introduced into the molecule can be used.

Those radiation-curable molecules FF12000 compounds include styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol methacrylate, 1,8-hexane glycol diacrylate, 1,6-hexane Sun glycolone methacrylate and the like can also be mentioned, but particularly preferred ones include N-vinylpyrrolidone, pentaerythritol letra-7 acrylate (methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), and trimethylolpropane. Diacrylate (methacrylate), 7-acrylate of phenol ethyleneoxide adduct (
methacrylate), an acrylic group (methacrylic, !l!i) on the pentaerythritol condensed ring represented by the general formula below
Or a compound with an ε-caprolactone-acrylic group.

A compound where m=1, a=2, and b=4 (hereinafter referred to as special pentaerythritol steel compound A).

m=1. A compound where a=3, b=3 (hereinafter referred to as special pentaerythritol 46 compound B), m=1. a=6, b
= o compound (hereinafter referred to as special pentaerythritol condensate C), m = 2. a=8. Compounds where b=o (hereinafter,
special pentaerythritol condensate).

and special acrylates represented by the general formula below.

1) (CH2=CHC0OH2) 3-CCH2
0H (4, special acrylate A) 2) (CH2=CHC00H2)3-CCH2o
t-t,.

(Special acrylate B) 3) (CH2=CHOC(C)C31(a),
-ocH2) 3-CCH,, CH3 (Special acrylate C) (Special acrylate D) (Special acrylate) E) (Special acrylate F) (16 out of n) (Special acrylate G) 8)
CH2=CHCoO-(CH2CH20)4-C
oCH=CH2 (Special acrylate H) (Special acrylate I) io) (Special acrylate J) 11) A AA-(X-Y+
X-A A: Acrino,
! Base (Special 7 Acrylate K) By using a radiation-curable compound with a molecular weight of less than 2000, it has good adhesion with a ferromagnetic thin film, and the top coat layer is reinforced by a compound with a molecular weight of less than 2000. , the breaking strength of the paint film is increased, the paint film is strengthened, there is less top coat abrasion, and the durability under high-temperature running is improved.
Therefore, it is possible to minimize dropouts and to
It is possible to obtain a magnetic recording medium that has uniform characteristics in the length direction without curling during curing in a cut-off form. If the radiation-curable compound with a molecular weight of less than 200 is not used, a stop occurs during high-temperature running, large scratches occur, and additional care is required. However, when a radiation-curable compound with a molecular weight of less than 200 is used, the crosslinking property increases. There is no scratching of the top coat, there is no clogging while driving, and still characteristics are improved.

In addition, compared to radiation-curable polymers, there are fewer scratches and clogging, and the still characteristics are improved, and since the molecular weight is lower than that of polymers, the viscosity is low and the coating film is uniform. Therefore, the i-magnetic conversion characteristic has a good envelope.

In the present invention, a radiation-curable compound having a molecular weight of less than 2,000 is used, but when the molecular weight is 2,000 or more, the frictional resistance tends to increase.

In addition, when using a radiation-curable molecule H2ooo ungrooved compound, iJx subsequent processing is possible in the manufacture of the top coat layer, and processing can be performed online, resulting in energy savings and
These compounds can be used alone or in mixtures to help reduce costs.

The method of forming a top coat layer on the surface of the ferromagnetic tII film is to mix a lubricant, an anti-oxidant, a radiation-curable compound, and other necessary trace components at the above-mentioned predetermined mixing ratio, and then dilute the mixture with a solvent. 1. There are methods such as applying a thin layer onto the ferromagnetic metal IIji film, or vaporizing the additive in the air, inert gas, or vacuum, and applying the vapor to the ferromagnetic metal surface. can do.

The thickness of the top coat layer is preferably 10 to 100. If it is too thick, it may cause poor mold retention or scratches. Also, if it is too thin, clogging will occur.

In this case, the thickness is preferably 10 to 50 people.

The resin compound, lubricant, and antioxidant contained in the top coat layer of the present invention are preferably radiation-curable ones.

In this case, the active energy rays used for crosslinking include electron beams using a radiation accelerator as a source, γ-rays using Co60 as a source, β-rays using 5r90 as a source, and X-ray generators as a source. X-rays or ultraviolet rays are used as a source.

In particular, as an irradiation source, it is advantageous to use radiation using a radiation heater from the viewpoints of controlling the absorbed dose, introducing it into the manufacturing process line, and shielding the TL radiation.

The characteristics of the radiation used when curing the top coat layer are to use a radiation accelerator with an accelerating voltage of 100-750 KV and a preferable tL<1i of 150-300 KV in terms of penetrating power, so that the absorbed dose is 0.5-20 Megarat. It is convenient to irradiate.

For the radiation curing of the present invention, a low-dose type radiation accelerator (electrocurtain system) manufactured by Energy Sciences, Inc. in the United States is used to shield secondary xya inside the accelerator when introduced into the tape coating processing line. He is extremely right-handed.

Alternatively, a van de Graaf type accelerator, which has been widely used for radiation acceleration, may be used.

Furthermore, during radiation crosslinking, it is important to irradiate the eight coat layer and the top coat layer with radiation in an inert gas flow such as N2 gas or He scum.

Irradiating the binder component with radiation in air is extremely disadvantageous because it inhibits radicals generated in the polymer due to radiation, such as O3, from working advantageously in the crosslinking reaction.

Therefore, the atmosphere of the area to be irradiated with active energy rays is
In particular, N2, He, Co, where the oxygen concentration is up to 5%
It is important to maintain the atmosphere in an inert gas atmosphere of grade 2.

The top coat layer of the present invention can also be cured with ultraviolet light by adding a photopolymerization sensitizer.

As the photopolymerization sensitizer, conventionally known ones may be used.For example,
Benzoin series such as benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin, α-chlordeoxybenzoin, ketones such as hensifhenone, acetophenone, bisdialkylaminohensifhenone,
Quinones such as anthraquinone and phenanthraquinone; sulfites such as benzyl disulfide and tetramethylthiuram monosulfide;

etc. can be mentioned.

Photopolymerized I81 sensitizer is 0.1-10% by weight based on solid content.
A range of is preferred.

As described above, the top coat layer of the present invention is a) flf1M
or (b) a radiation-curable compound, a lubricant, and an antioxidant, but the weight ratio is as follows: and 1:50 to 5:1, preferably ■:50 to l:
It is 1.

b) In the case of a radiation-curable compound (x), a lubricant (y), and an antioxidant C7,), the weight ratio is x:y=5
0:1-5:L.

y:z=1:50~5:1 More preferably x:y=50:1 to 1:l.

y+z=L: 50 to 1 Goe is preferred.

(5) Backcoat layer The backcoat layer of the present invention contains an inorganic pigment, an organic binder, and a lubricant.

Inorganic pigments include l) conductive carbon black and graphite;

2) 5i02. as an inorganic filler. TiO2, A-view 203
, Cr203. SiC, CaO1CaCo3, zinc oxide, goethite.

αFe2O3, talc, kaolin.

Examples include CaSO4, boron nitride, black salt fluoride, molybdenum disulfate, and ZnS.

Among them, CaCo3, kaolin, ZnO, Gesai), Z
nS and carbon are used.

How much of these inorganic pigments should be used?

Regarding 1), /<20 for parts of Ingu tool.
~200 parts by weight, and for 2) 10 to 300 parts by weight are appropriate.
- If the amount of inorganic pigment is too large, the coating film becomes brittle and has the disadvantage of increasing dropouts.

Conventionally, lubricants (including dispersants) are used in this type of back coat layer! ! Any of the same types can be used.

Caprylic acid, capric acid, lauric acid, myristic acid,
palmitic acid, stearic acid, behenic acid, oleic acid,
elaidic acid, linoleic acid, lylunic acid, stearolic acid, etc. 3 & i number 1 number 2 fatty acids (RCoOH, R is alkyl having 11 or more carbon atoms j!Ji); alkali gold Ffs (Lf, Na .

K, etc.) or alkaline earth metals (Mg, Ca.

Metal scrap soap consisting of Ba, etc.); Lecithin etc. are used.

In addition, higher alcohols having carbon atoms of 912 or more, sulfur esters thereof, surfactants, titanium coupling agents, silane coupling agents, etc. can also be used.

The amount of these lubricants (dispersants) is 1 to 20 parts by weight per 100 parts by weight of the binder! I! It is added in a certain amount.

Alternatively, the radiation curing type described above may also be used.

In addition to the above, lubricants include silicone oil, fluorine oil, paraffin, graphite, molybdenum disulfide,
Tungsten dioxide.

Monobasic fatty acids with 12 to 16 carbon atoms and 3 to 12 carbon atoms
fatty acid esters consisting of monohydric alcohols, monobasic fatty acids having 17 or more carbon atoms, and monohydric alcohols having 21 to 23 carbon atoms in total, including the number of carbon atoms in the fatty acid Ester etc. are used.

These lubricants have a ratio of 0 to 11 parts of binder.
It is added in an amount of 2 to 20 parts by weight.

In addition, as for other additives, any of those used in this type of coating can be used.

For example, as an antistatic agent, natural surfactants such as saponin; 7-ion surfactants such as alkylefluoride, glycerin, and glycidol; higher alkylamines, quaternary ammonium L1 salts, pyridine, and other complex Cationic surfactants such as rings, phosphoniums or sulfoniums; Anionic surfactants containing acidic groups such as carboxylic acids, sulfonic acids, phosphoric acids, sulfuric ester groups, phosphoric ester groups; Amino m-classes, aminosulfonic acids, Ampholytic activators such as sulfuric acid or phosphoric acid esters of amine alcohols are used.

The organic binder used in the back coat layer of the present invention is a thermoplastic, thermosetting or reactive resin conventionally used for magnetic recording media, or a mixture thereof.
From the viewpoint of the strength of the resulting coating film, curable resins, particularly radiation curable resins, are preferred.

The thermoplastic resin has a softening degree of 150°C or less, an average molecular weight of 10,000 to 200,000, and a polymerization degree of about 200.
~2000 or so.

For example, 11! Vinyl chloride-vinyl acetate Jl<li polymer (including those with carboxylic acid introduced), vinyl chloride-M acid vinyl rubinyl alcohol (polymer (including those with carboxylic acid introduced), vinyl chloride-vinylidene chloride copolymer , vinyl chloride-acrylonitrile copolymer, acrylic ester-7crylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, acrylic ester-styrene copolymer, methacrylic ester-acrylonitrile copolymer, methacrylic ester - Vinyldene chloride copolymer, methacrylic acid ester-styrene copolymer, 1/tan elastomer, nylon-silicon resin, nitrocellulose-polyamide resin, polyvinyl fluoride, vinylidene-7-crylonitrile IJs ffi
Coalescence, butadiene-7-crylonitrile copolymerization, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate, cellulose diacetate,
cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, chlorovinyl ether-acrylic acid ester copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof. used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating solution, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Moreover, among these resins, those that do not soften or melt until the resin is thermally decomposed are preferable.

Specifically, examples include phenol resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic resins, acrylic reaction resins, epoxy-polyamide resins, nitrocellulose melamine resins, and high molecular weight polyesters. mixtures of resins and incyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanates, polyamine resins, and mixtures thereof.

Particularly preferred are cellulose resins (nitrified cotton, etc.), vinyl chloride-vinyl acetate-vinyl alcohol copolymers, thermosetting resins consisting of a combination of urethane (using a curing agent), or vinyl chloride-vinyl acetate-vinyl alcohol. It consists of a radiation-curable resin consisting of a copolymer (including one introduced with carboxylic acid) or an acrylic modified vinyl chloride-vinyl acetate-vinyl accol copolymer (including one introduced with carboxylic acid) and urethane acrylate. be.

Regarding the radiation-curable resin, in addition to the above-mentioned preferred Ml combination, acrylic double bonds such as acrylic acid, methacrylic acid, or ester compounds thereof, which exhibit radically polymerizable unsaturated double bonds, diallyl phthalate, etc. Allyl double bond such as.

It is possible to use a thermoplastic resin containing or introducing into its molecule a group that can be crosslinked or polymerized by radiation irradiation, such as an unsaturated bond such as maleic acid or a maleic acid derivative.

Other usable binder components include monomers such as acrylic acid, methacrylic acid, and acrylamide.

As binders having double bonds, various polyesters, polyols, polyurethanes, etc. can be modified with compounds having acrylic double bonds. Furthermore, if necessary, by blending a polyhydric alcohol and a polycarboxylic acid, products with various molecular weights can be produced.

The above are some of the radiation-sensitive 81 fats.
These can also be used in combination.

Even more preferable.

(A) A plastic-like compound having a molecular weight of 5,000 to 1OO,000 and having two or more unsaturated double bonds that are curable by radiation.

(B) A rubber strip compound having one or more unsaturated double bonds that is curable by radiation or having a molecular weight of 3,000 to 100,000 that is not curable by radiation, and (C) An unsaturated compound that is curable by radiation. (A) 20 to 70% by weight of a compound having one or more double bonds with 1,200 to 3,000 molecules per molecule;

(B) 20 to 80% by weight, and (C) 10 to 40% by weight.

As a result, the breaking strength of the coating film is increased, the coating film is strengthened, there is less backcoat abrasion, there is no transfer of inorganic filler powder from the backcoat layer to the magnetic layer, so there is less dropout, and it can be rolled. A magnetic recording medium having uniform characteristics in the length direction without curling during curing in a wound form can be obtained.

In manufacturing the magnetic recording medium of the present invention, if the organic binder is a thermosetting type, the lubricant in the puncture coat layer is transferred to the magnetic thin film during the manufacturing process, resulting in an output drop due to unstable running as described above. However, one image may not appear, or the 'B rubbing level is still greatly insufficient.
'The A-type transfer causes the phenomenon that the ferromagnetic FJIkI is removed or destroyed, which is undesirable.

For this reason, it is conceivable to apply a top coat first, but this is often inconvenient because it is easily damaged during operation.

Furthermore, in the case of a thermosetting type, the difference in electromagnetic conversion characteristics between the inside and outside of the jumbo roll during thermosetting becomes a problem because of the back-type transition of the backcoat surface due to the tightness of the roll during stiffening.

On the other hand, in the case of radiation-curable resin, +1
! Sequential curing is possible, the curing time is short, there is no back mold transfer mentioned above, so dropouts can be prevented, and radiation curing and top coat processing can be performed online.

It is also useful for saving energy and reducing the number of personnel during manufacturing.
This also leads to cost reduction.

In terms of characteristics, in addition to dropouts caused by the tightness of the magnetic tape during thermosetting, there is no difference in output due to the lengthwise distance of the magnetic tape due to differences in pressure at the inner and outer diameters when it is wound into a roll. .

In the radiation-curable resin binder consisting of (A), (B) and (C), (A) alone lacks flexibility and CB) alone lacks elasticity; ) and (B), the destructive energy becomes large.

There is a limit to increasing the brittle energy, and (A)
This is probably because the hardness of (B) alone is low.

Under high temperature and humidity conditions, it became sticky and had high static friction.

On the other hand, by combining (A), CB) and (C), the crosslinking property increases, the tensile strength, breaking energy, and brittle energy of the binder increase, there is no bar or coat scraping, and the degree of hardening increases. This results in a strong coating film with high

Therefore, when it was stored at a high temperature of 50° C. and 80% for 5 days, no adhesion occurred, the coefficient of friction was low, and no distortion of one image occurred.

This is because the addition of (C) increased the crosslinking properties of the back coat film and increased the degree of curing.

By roughly adding (C) to (A) and (B), (
Compared to the case of a composition consisting only of A) and (B), (A) 4
Now it can be used even for low molecular weight substances. this is(
By introducing component (C) into a plastic-like material made of component A), the degree of hardening with improved plasticity has been improved, resulting in a tremendous amount of sexual energy that is unparalleled in viscoelasticity. It is something.

In the radiation curable resin binder of the present invention, (A)
If the molecular weight of (B) is less than 5,000, the coating film will become hard and the back coat will be severely scraped, and the electromagnetic conversion characteristics will also deteriorate;
Is it because of a minute nk defect? The 11ra conversion properties are degraded, and if (B) is radiation curable, the properties are degraded, resulting in a decrease in strength.

Regarding (C), when the molecular weight exceeds 3000, the crosslinking property decreases and the strength of the coating film decreases.

(A) is 10000~aoooo, CB) is 3000~
80000. (C) preferably has a molecular weight of 200 to 2,500. (B) is preferably radiation-curable because it increases crosslinking properties and increases coating film strength.

The blending ratio of (A), (B), and (C) is as follows: (A) is 20~
70ffi amount%, preferably 30 to 79ffi amount%, (B
) is 20 to 80% by weight, preferably 20 to 60% by weight,
weight) is 10 to 40% by weight, preferably 10 to 30% by weight.

The molecular weights of the compounds (A), (B), and (C) of the present invention are:
It is based on the number average molecular weight using the following measurement method.

*Measurement of average molecular Q of binder using GPC
(Get Permeation Chromatog
raphy) is a method of separating molecules in a sample based on their size in a mobile phase, and is a method of liquid chromatography in which a column is filled with a porous gal that acts as a molecular sieve.

To calculate the average molecular weight, use polystyrene of known molecular weight as a standard sample, and create a calibration curve from its elution time.

This calculates the average molecular weight in terms of polystyrene.

Assuming that a given polymer has Ni molecules with a molecular weight of 1 Mi in the substance, it can be expressed as follows.

The unsaturated double bonds in the compounds (A), CB), and (C) of the present invention are 2 or more, preferably 5 or more for (A), 1 or more for CB), preferably 5 or more, and ( C) is 1 or more, preferably 3 or more.

When the organic binder in the back coat layer of the present invention is radiation-curable, the same radiation-curable polymer as used in the top coat layer is used, and one combination of the types of resin compositions is used.

Regarding the manufacturing method, etc., all the examples given in the section of the top coat layer also apply to the back coat layer.

It is known that some polymers disintegrate when irradiated with radiation, while others cause crosslinking between molecules.

Examples of substances that cause crosslinking between molecules include pyriethylene, polypropylene, polystyrene, polyacrylic ester,
Examples include polyacrylamide, polyvinyl 41J, polyester, polyvinylpyrrolidone rubber, polyvinyl alcohol, and polyacrolene.

With such cross-linked polybums, the cross-linking reaction occurs even without the above-mentioned modification, so in addition to the above-mentioned modified products, these resins can be used as they are as back coat resins for radiation cross-linking. be.

Furthermore, according to this method, even a solvent-free resin that does not use a solvent can be cured in a short time, so such a resin can be used for a back coat.

Particularly preferred combinations of the radiation-curable resin compositions of the present invention include:

Vinyl chloride-vinyl acetate copolymer in which the compound (A) is partially saponified, vinyl chloride-vinyl acetate copolymer in which carboxylic acid is introduced, incyanate obtained by reacting a polyisocyanate compound with a phenoxy resin. It is a compound obtained by reacting a compound having a group with an acrylic compound or a methacrylic compound having a functional group that is reactive with an incyanate group.

The compound (B) is a compound obtained by reacting an incyanate compound with a polyol or a polyol (polyurethane elastomer) with an acrylic compound or methacrylic compound having a reactive functional group. Yes, (C) is a polyfunctional (meth)acrylate monomer.

These are oligoester acrylates or (B) low molecular weight compounds.

When manufacturing a magnetic recording medium, when forming a thermosetting backcoat surface, if the backcoat surface is formed before the magnetic surface, the thermosetting treatment of the backcoat surface will reduce the surface roughness of the base surface due to the tightness of the base. This is undesirable as it reduces the

In addition, after forming the magnetic surface, a thermosetting treatment was performed. Therefore, the coating treatment is usually carried out on the back side of the support after a magnetic coating is formed on the support, but when a radiation-curable binder is used in the present invention.

Since there is no tight winding on the back coat surface, the back coat treatment is performed using magnetic layer type rIt? It is not necessary to conduct a high-performance magnetic recording Q medium with extremely good electromagnetic conversion characteristics and reliability of physical properties.

Furthermore, in the present invention, a back coat layer, a top coat F'
Substantially the same lubricant is used so that lubricant transfer between the steps does not cause any inconvenience.

In particular, it is desirable that the lubricant used be a fatty acid-based lubricant.

This can improve running friction and running durability, and also reduces deterioration of electromagnetic conversion characteristics when head clogging is improved.

In particular, preferred combinations of dual-thermal lubricants include one compound or a molecular moiety exhibiting lubricating properties such as stearic acid-stearic acid, stearic acid-palmitic acid, and palmitic acid-stearic acid.
Palmitic acid, palmitic acid-myristic acid, etc. are preferred, and various types can be used as magnetic heads for jaw-like media.

In this case, the magnetic head is preferably one in which at least the end face of the gap portion is made of a metal magnetic material.

In this case, the entire core may be formed from a metal ferromagnetic material, and if necessary, a portion of the core including the end face of the gap portion may be formed from a metal ferromagnetic material.

In Figure 0'51, a metal ferromagnetic material 31°32 with a thickness of about 1 to 5 pm is coated by sputtering or the like on the end face of the gap part of the core half-hole 21.22 made of a ferrite or other ferromagnetic material. An example is shown in which a magnetic heald l is constructed by connecting core half-holes 21 and 22 through a gap 4 such as a gap 4.

As a result, extremely good electromagnetic conversion characteristics can be obtained, and the running performance is also good, and head adhesion and head clogging are also improved.

The shape, structure, etc. thereof may be known.

However, as mentioned above, the gap length a is usually O, L-
0.5 gm, especially 0.1-0.4 μm, and the track width is usually 10-50 m, especially 10-20 μm.

Various metal ferromagnetic materials can be used, including amorphous magnetic metal and sendust.

Hard permalloy, permalloy, etc. can all be used.

However, among these, an amorphous magnetic alloy containing Go as a main component has particularly low head clogging or adhesion and has good electromagnetic characteristics.

Such amorphous magnetic alloys include Co70-95a
t%, Zr as a vitrification element.

Nb, Ta, Hf, rare earth elements, Si, B.

P, C, Au, etc., # with Zr and/or Nb 5 to 2
One containing 0 at% is preferable.

Alternatively, one containing 65 to 85 at% of Co and 15 to 35 aL% of Si and/or B as a vitrifying element is also suitable. in this case.

Furthermore, Fe of 10at% or less, Ni of 25aL% or less,
Cr, Ti, Ru with a total IQ of 20at% or less.

One or more of W 1M o , T i , M n and the like may be contained.

These amorphous magnetic alloys are formed into core halves, gap portions, etc. using spar twotaling, high-speed quenching, or the like.

In order to perform recording and reproduction on the above-mentioned medium using such a magnetic head, it is sufficient to follow a known video recording system such as the so-called VH5 system, Beta system, 8-layer video system, U standard system, etc.

(2) Specific effects of the invention According to the invention, running friction is extremely reduced and stabilized.

In addition, the running durability is significantly improved, there is no increase in running friction even after many runs, the number of repeat recordings and playbacks is significantly improved, and the 3-still characteristics are significantly improved.

It also has high running stability, exhibiting extremely high stability under a wide range of conditions, from high temperature and humidity to low temperature and low humidity.

4. ν, since the lubricants of the top coat layer and the back coat W are substantially the same, it is possible to store it by rolling it.

In particular, even if the lubricant transfers between the back coat and top coat during storage under high temperature and high humidity conditions, the properties will not change.
Good lubrication, low coefficient of dynamic friction, and little deterioration over time.

Furthermore, the reproduction output due to spacing loss is also extremely small.

Also, noise is extremely low.

In addition, head clogging and head adhesion are extremely rare.

Such effects are even higher when a metal ferromagnetic head is used.

Moreover, such an effect becomes even higher in high-density recording at a minimum recording wavelength of less than l or m.

■Specific embodiments of the invention Examples of the present invention are shown below.

Example 1 Colloidal silica was deposited on a smooth polyester film (12 pm thick) that was substantially free of particulates. A substrate having microprotrusions was obtained.

The height of the protrusion is approximately 100 people.

The protrusion density was 4×106 (1!f/+om2).

(1) Formation of magnetic layer and stand-up” J and t above: Move the plate along the circumferential surface of the cylindrical cooling can, and apply 02+Ar (volume ratio 1:1) at 800 cc/min.
An alloy consisting of C080 and Ni2O was melted in a chamber with a vacuum level of 1.0XIO-'Torr, and was deposited obliquely only at the part of the incident f1 from 90° to 30°. 15 gm of Go-Ni-0 thin++q was formed.

A large amount of oxygen was unevenly distributed at the interface with the base and on the surface opposite to the base.

Further, the surface opposite to the base was covered with only one layer of oxide.

Hc=lOOOOe.

The average amount of oxygen in each sample was 40% in terms of atomic ratio to Go and Ni. In the chamber where 0XLO'43↑orr was set, the door was opened in the same way as in the case of Toko Nara fullH Yu.

11Q has a thickness of 0.15 gm and is substantially made of Go-Ni.

This tape was forcibly oxidized in an atmosphere of 90° C. and 20% RH, so that only oxide was formed on the surface opposite to the base.

HC=900 0e.

The average amount of oxygen in the film is 45 in atomic ratio to Go and Ni.
%Met.

The above substrate was moved along the circumferential surface of a cylindrical cooling can, and the degree of vacuum was increased to 5°C. In a chamber at 0.04 Tarr.

=r　　　t''.

The IIg thickness was 0.15 pm and was substantially made of Co--Ni.

HC=9500e, (2) Formation of top coat layer-L
Monoglycol salicylate acrylate 5 myristine 063 myristyl alcohol methacrylate 1.0 MEK/) toluene (1
/l) This was coated as it was on 100 ferromagnetic thin nQ, and 80''C124 rJI 1iii conversion was performed.

There were 20 people in one camp.

hy Sansan Nihina Kyoue LI dimethylamino methacrylate 3 fluorine (electrolytic method) 0.3 MEK/toluene (1/1) 100 Coat this on a ferromagnetic thin 11 tube, accelerate at a voltage of 150 KeV,
Irradiation was performed at an electrode current of 6a+A, 3 Mrad, and in N2 gas.

1112 thickness was 80 people.

2-2-2-year-old Unier's acrylate 3-engineered poxy modified product (contains succinic acid) 2 Molecular weight 6000 Myristic acid 0.3 Myristyl alcohol methacrylate 1.0 MEK/) Luene (1/1) 100 On the ferromagnetic thin film,
This was irradiated in N2 gas at g; AjL, acceleration voltage 150 KeV, electrode current 6 mA, 3 Mrad.

+1! J thickness was 50 people.

Topecoat - 4 modified I part and droxyethyl methacrylate 2 phosphate salt - vinyl acetate (contains maleic acid) 05 molecules! i) 20000 polyfunctional 7 acrylate molecule #i) 300 0,5 stearic acid 0,5 stearic acid modified silicone 0.5 toluene
100 was coated on the 1 ferromagnetic film and cured in the same manner as the top coat layer 3.

The film thickness was 40 people.

Taupe coat.・5 Hair volume part 2.
6-tert-butyl p-fresol epentaerythritol tetraacrylate molecule 352
1.5 Stearic acid 0.1MEK
100 ferromagnetic thin 1
Apply this directly on 1λ! D, acceleration voltage 150
Irradiation was performed in KeV, electrode current 6 mA, 3 Nrad, and N2 gas.

1g thickness was 20 people.

Taupe Coat 6 Higashikabu Seven glycol salicylate acrylate 1 Pentatritrithritol tetraacrylate Molecular weight 352
0.6N-vinylpyrrolidone molecule P&1110.
3 Myristin Ugly 0.3M
EK/) Ruen l/I) to.

This was applied onto the ferromagnetic g film, and an acceleration voltage of 1501 [e
Irradiation was carried out in N2 gas at an electrode current of 6 mA and 3 Mrad.

The film thickness was 40 people.

Top coat ・7 parts by weight Butyl (2) hydroxy methacrylate 2 phosphate (mixture of mono and di) Fluorine modified silicone stearate 0.4 MEK
100 ferromagnetic thin film, the above top coat composition was applied, and an accelerating voltage of 150K was applied.
eV, electrode current 6 mA.

It was irradiated at 3 Mrad in N2 gas and closed with Topcoal I to a film thickness of 15.

L mue yuni stop'" tun I butyl (
3) Hydroxymethacrylate 3 phosphate (
mixture of mono-, di-, and tri) stearin M
O,5 stearic acid modified silicone
0.5 toluene/ethanol (9/l)
A top coat layer was formed on the No. 100 ferromagnetic thin film in the same manner as the above top coat 1.

The number of participants in the 11th quarter was 30.

Part by weight Butyl (
2) Hydroxymethacrylate 1 phosphate (
(mixture of mono- and di-) Acrylic modified iQ bee vinegar bee vinyl alcohol (containing maleic acid) copolymer ♀ 20,000 molecules 1 Fluorine modified silicone stearate 0.4 MEK
Zo.

The above TOPCO 8 composition was applied onto the ferromagnetic thin film, and the acceleration voltage was 150 KeV, the electrode current was 6 mA, and 3 rad was applied.
It was irradiated in N2 gas to form a top coat with a thickness of 20.

Top coat 10 parts by weight Ethyl (3) Hydroxy methacrylate 2 phosphate (mixture of mono, di, tri) Epoxy modified product (contains succinic acid) 1 Molecular weight 6000 Stearinated 0.5 Stearic acid modified silicone 0.5 Toluene/ethanol (9 /l) A top coat layer was formed on the 100% ferromagnetic thin film in the same manner as in the above Top Coat 9.

The film thickness was 30 people.

(3) Formation of back coat layer 8. Cocoat, 1 Heavy part zinc oxide 80 End m 200 Hardening agent Coronate 1 20 State lubricant Stearic acid modified silicone 4 Butyl stearate
2 Ninitrified cotton 40 Vinyl chloride-vinyl acetate-vinyl alcohol copolymer (Made by Block Chemical Co., Ltd., Esleac A) 30 Polyurethane elastomer 30 (Made by F. Mix the mixture well.

After applying this paint on a 15pm polyester film and drying the solvent with an infrared lamp or hot air,
After the surface smoothing treatment, the roll was kept open for 48 hours at 80'C to promote the crosslinking reaction by incyanate.

Coat, ・2 heavy 11 parts carbon black 5゜Asahi Carbon (
Co., Ltd. 100 μm (A) Acrylic-modified group-vinyl alcohol copolymer, molecular weight 45,000 50 (B) Acrylic-modified polyurethane elastomer molecular weight, 5,000
50 Stearin 2 Butyl stearate 2 Mixed solvent (MI
BK/)Luene-1/l) 300 The above mixture was dispersed in a ball mill for 5 hours, applied to the back side of a polyester film on which a magnetic surface was formed to a dry thickness of 1 ps, and then applied using an electrocurtain type electron beam accelerator. Acceleration voltage 150KeV, IK pole current 10mA
, absorption line * 5 Mrad, the back coat layer was irradiated with an electron beam in N2 gas.

Bar coat ・3 Parts by weight Zinc sulfide Particle size variable 30 Carbon black z5 Acrylic modified vinyl chloride-vinyl acetate-vinyl alcohol copolymer (molecular weight 30,000) 40 Acrylic modified polyurethane elastomer (molecular weight 20,000) 40 Polyfunctional acrylate (molecular weight 1000) 20 oleic acid 4 stearic acid methacrylate 2 mixed solvent (MIBK
/) Luene) 250 These were treated and manufactured in the same manner as back coat layer 2.

Bar coat/4 ton 5 parts CaC
o3805m 50 acrylic modified J
fi-vinyl alcohol copolymer (molecular weight 3
0000) 30 Acrylic modified polyurethane elastomer (molecules * 50000) 30 Acrylic modified phenoxy resin (molecular weight 35000) 20 Polyfunctional acrylate (molecular % 500) 20
Myristic acid 4 Solvent (MEK/) Luene 1/1) 300 These were treated and produced in the same manner as above.

A ferromagnetic thin film, a top coat layer, and a back coat layer shown in Table 1 below were formed on the substrate to produce a magnetic tape.

Using these, initial characteristics, temperature 50℃, humidity 80%
The characteristics were measured after being left for 11 JI for 10 days under the following conditions.

The results are shown in Table 1.

Furthermore, in both cases, the lubricant contained in the back coat was detected in the top coat layer after standing.

The magnetic head used is shown in FIG. 1 and has a gap length of 0.25 pm and a track length of 201. In this case, the core half holes 21 and 22 are made of ferrite, and the gap end face is made of 3.
It was made of Co0.8NiO, lZr0.1 (atomic ratio) with a thickness of 0.0 mm, and the gap material was glass.

Note that 105/a2 is 1.6X10B-t-.

Note that the method for measuring the above characteristics will be described below.

1. Protrusion observation SEM (scanning electron microscope) and TEM (transmission electron microscope) were used. 2. Still characteristics were recorded at 5 MHz, and the still characteristics of the reproduced output were determined by δ11.

10 minutes or more is considered an OK level.

3. Measurement of friction on the magnetic side Wrap the magnetic tape so that it is on the cylinder side, apply a load of 20g to one end face, and measure the friction by reading the change in tension when the cylinder is rotated 90 degrees.

4.S/N ratio when recording and reproducing at an output center frequency of 5MHz (
In addition, its stability was evaluated.

VH5CF) Modify the VTR so that it can measure up to 5MH2.

5. Head clogged VH5 VTRTR is heavy. Clogging was measured after 100 runs.

6. Top coat scraping was measured by optical microscopic observation of the tape tested a predetermined number of times.

Example 2 The relationship between the height and density of the protrusions on the magnetic surface and the characteristics is shown in the table below.

Note that the shortest recording wavelength is 0. Experiments were conducted using signals in micrometers. The amorphous head and ferrite head of Example 1 were used as magnetic heads.

In addition, the top coat used was 8 of Example 1, the coat layer was 2 of Example 1, and the magnetic film was 1 of Example 1.

1 50 2X106 Amorphous
0.5 Small 2 50 5X107
Amorphous 0.1 None 3 100
4X105 Amorphous O-free 4t
oo 5X107 Amorphous -0,1 None 5 too 2X109 Amorphous
-0,3 less 6 200 4X105 Amorphous -0,3 less 7 200 4X10g
Amorphous -0,4 No 8 200 1X
IOIO Amorphous -0.4 9 300 4
X, 10B Amorphous -0,3 No 10
300 3X107 Amorphous -0,2 None++ 300 3X109 Amorphous
-0,5 small 12- - Amorphous
0 Large+3 1000 4X108
Amorphous -7,5 large +4 too
lX106 Amorphous 0
Medium+5 100 4X108 Ferrite
-16 out of 20 100 txtoa ferrite -1.5 large +7 1000 4X10
8 Ferrite - 10 Large Further, as a result of Auger spectroscopic analysis, it was found that the surfaces of these magnetic layers were covered with an oxide layer of 100 to 200 people.

In the above embodiments, colloidal silica was used as the inorganic fine particles, but it goes without saying that other materials such as alumina sol, titanium platy, zirconia, or various types of dorosol may also be used.

Note that similar results were obtained when a head made using Go-Fe-Ru-Cr-5i-B-based amorphous material was used.

Furthermore, when a head made using sendust was used, the effect was less than in the above case.

[Brief explanation of drawings]

FIG. 1 is a front view showing an example of a magnetic head used in the present invention. l...magnetic heh, de. 21.22... Core half-day off. 31.32...Metal ferromagnetic material. 4...Fist cap 1) 2L1

Claims (17)

[Claims] (1) A ferromagnetic metal thin film layer containing Co as a main component was provided on one surface of a flexible substrate, an organic top coat layer was provided on the surface of the ferromagnetic metal thin film layer, and a back coat layer was provided on the other surface. In the magnetic recording medium, the organic top coat layer contains a lubricant, the back coat layer contains an inorganic pigment, an organic binder, and a lubricant, the ferromagnetic metal thin film layer contains oxygen, and When the gap length is aμm,
The medium surface has an average of 10^5/a^2 or more protrusions per 1 mm^2, the protrusions have a height of 30 to 300 Å, and the organic top coat layer and back coat layer are substantially the same. A magnetic recording medium comprising a lubricant. (2) The magnetic recording medium according to claim 1, wherein the organic top coat layer contains an oxidizing agent and a lubricant. (3) The magnetic recording medium according to claim 1, wherein the organic top coat layer contains a radiation-curable compound, an antioxidant, and a lubricant. (4) The magnetic recording medium according to claim 2 or 3, wherein the antioxidant is of a radiation-curable type. (5) The magnetic recording medium according to claim 4, wherein the antioxidant is a radiation-curable phosphate ester. (6) The magnetic recording medium according to claim 1, wherein the radiation-curable compound has a molecular weight of less than 2,000. (7) The flexible substrate is made of polymer, and on this substrate,
Arranging fine particles having a diameter of 30 to 300 Å,
7. The magnetic recording medium according to claim 1, further comprising a ferromagnetic metal thin film layer and an organic top coat layer. (8) The magnetic recording medium according to any one of claims 1 to 7, wherein the ferromagnetic metal thin film has a ferromagnetic metal oxide layer on its surface. (9) The magnetic recording medium according to any one of claims 1 to 8, wherein the organic top coat layer and/or back coat layer contains a radiation-curable lubricant. (10) The thickness of the organic top coat layer is 10 to 100 Å
A magnetic recording medium according to any one of claims 1 to 9. (11) The magnetic recording medium according to any one of claims 1 to 10, wherein the organic binder of the back coat layer is a radiation-curable compound. (12) The organic binder of the back coat layer is (A) a plastic-like compound having a molecular weight of 5,000 to 100,000 and having two or more unsaturated double bonds that are curable by radiation; (B) an unsaturated compound that is curable by radiation. Molecular weight 3 having one or more double bonds or not having radiation curability
000 to 100,000 and (C) a compound having a molecular weight of 200 to 3,000 and having one or more unsaturated double bonds that are curable by radiation. 12. The magnetic recording medium according to any one of Item 11. (13) The magnetic recording medium according to any one of claims 1 to 12, wherein a is 0.1 to 0.5 μm. (14) A ferromagnetic metal thin film layer containing Co as a main component was provided on one surface of the flexible substrate, an organic top coat layer was provided on the surface of the ferromagnetic metal thin film layer, and a back coat layer was provided on the other surface. In a magnetic recording method for recording and reproducing information on a magnetic recording medium using a magnetic head, an organic top coat layer contains a lubricant, a back coat layer contains an inorganic pigment, an organic binder, and a lubricant, and a strong When the magnetic metal thin film layer contains oxygen and the gap length of the magnetic head is aμm,
The medium surface has an average of 10^5/a^2 or more protrusions per 1 mm^2, the protrusions have a height of 30 to 300 Å, and the organic top coat layer and back coat layer are substantially the same. A magnetic recording method comprising: a lubricant. (15) The magnetic recording method according to claim 14, wherein at least the end face of the gap portion of the magnetic head is made of a metal ferromagnetic material. (16) The magnetic recording method according to claim 14 or 15, wherein the metal ferromagnetic material is an amorphous magnetic alloy containing Co as a main component. (17) The magnetic recording method according to any one of claims 14 to 16, wherein a is 0.1 to 0.5 μm.