JPH0191315A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a medium having superior surface properties, durability, satisfactory magnetic characteristics and electromagnetic transducing characteristics by introducing tert. amine into the molecule of polyurethane resin as the binder of a magnetic layer. CONSTITUTION: Tert. amine is introduced into polyurethane resin as the binder of a magnetic layer by using diol contg. a tert. amino group as part of a chain extender. The resulting binder has great affinity for magnetic powder and maintains satisfactory dispersibility even in case of hyperfine magnetic powder or magnetic powder having a large extent of magnetization. When a magnetic layer contg. the binder is formed, the properties as a film are improved and a medium having superior durability, surface properties, magnetic characteristics and electromagnetic transducing characteristics is obtd. The binder has low viscosity, is easily handled and improves work efficiency.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium such as a magnetic tape, and more particularly to a binder contained in a magnetic layer formed on a non-magnetic support. This is related to the improvement of

[Summary of the invention]

The present invention improves the dispersibility of magnetic powder and the properties of the coating film when formed as a magnetic layer by introducing a tertiary amine into the molecules of polyurethane resin used as a binder for coated magnetic recording media. .

The purpose is to provide a binder with excellent properties in terms of workability during coating film formation, and to provide a magnetic recording medium with excellent surface properties and durability, and good magnetic properties and electromagnetic conversion properties. .

[Conventional technology]

In recent years, magnetic recording media, especially magnetic recording media for VTRs (video tape recorders), have improved their magnetic properties and electromagnetic conversion properties so that high playback output can be obtained even when recording at short wavelengths. It is requested. As a countermeasure, efforts have been made to make the magnetic powder particles finer and to increase the magnetic force, and there is a strong tendency to increase the packing density of the magnetic powder in the magnetic layer, the so-called backing density.

On the other hand, conventionally used binders for magnetic recording media include vinyl chloride-vinyl acetate copolymer, vinyl chloride-propionic acid copolymer, and vinyl chloride-vinyl acetate copolymer.
Vinyl chloride-based binders such as vinyl alcohol copolymers have been used, and binders based mainly on polyurethane resins have come to be used. However, with the above-mentioned increase in backing density and the demand for rings with improved durability, various problems have arisen with these binders, and it is currently difficult to adequately address them. .

For example, as the specific surface area increases due to finer particles of magnetic powder and the cohesive force increases due to high magnetizing force, satisfactory dispersibility and surface area cannot be obtained with the above-mentioned binders, and the buffing density of the magnetic powder increases. This has also become difficult. Therefore, the durability, feelability, and electromagnetic conversion characteristics were also insufficient. In particular, performance has been insufficient for magnetic powders made into ultrafine particles or magnetic powders with a high amount of magnetization in order to meet higher recording densities.

In this case, for example, a method such as using a surfactant as a dispersant may be considered, but since the surfactant is a low molecular weight, powder falling off and blooming due to changes over time may occur.
Problems arise in mechanical strength, durability, etc.

Therefore, for example, in Japanese Patent Publication No. 58-41565, etc.,
A binder in which a sulfonic acid metal base is introduced into a polyurethane resin has been proposed, and attempts have been made to improve the dispersibility of magnetic powder, but it is still far from satisfactory. For example, when used as a magnetic recording medium. However, there was still a need for improvement in terms of durability.

[Problem that the invention seeks to solve]

In this way, conventionally widely used vinyl chloride copolymers, polyurethane resins, and binders containing sulfonic acid metal bases have problems with dispersibility for magnetic powder, physical properties of coatings, handling during manufacturing, etc. There were many points that needed to be resolved, and it was difficult to ensure the desired durability, magnetic properties, and electromagnetic conversion properties.

Therefore, the present invention has been proposed to solve the above-mentioned drawbacks in the technical field, and is aimed at improving the dispersibility of magnetic powder, the properties of the coating film when formed as a magnetic layer, and the workability when forming the coating film. We provide a binder with excellent properties such as
The object of the present invention is to provide a magnetic recording medium with excellent surface properties and durability, and good magnetic properties and electromagnetic conversion properties.

Means for Solving Problem C] The present inventors have discovered that by introducing a tertiary amine into the side chain as a polar group, it exhibits high affinity for magnetic powder, improves dispersibility, and further improves workability. The present invention was completed by paying attention to the fact that it is effective in improving The magnetic recording medium is characterized in that the binder contains a polyurethane resin containing a tertiary amine.

The polyurethane resin used in the present invention has excellent coating strength and is obtained by the reaction of a polyhydroxy compound and a polyisocyanate. It is preferable to use a long chain diol with a molecular weight of 500 to 5000, a short chain diol with a molecular weight of 50 to 500, and an organic diisocyanate.

The above-mentioned long-chain diols are broadly classified into polyester diols, polyether diols, polyether ester glycols, etc., as well as polycarbonate polyols,
Also included are acrylic polyols and the like. Examples of polyester diols include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid;
Aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid or their lower alcohol esters, and ethylene glycol, 1.3-propylene glycol, 1.4-butylene glycol, 1.6-hexane glycol, diethylene glycol, neopentyl glycol, or Examples include polyester diols obtained by reacting an ethylene oxide adduct of bisphenol A or a mixture thereof, and lactone-based polyester diols obtained by ring-opening polymerization of a lactone such as ε-cabrolactone. Examples of polyether diols include polyethylene glycol, polypropylene ether glycol,
Examples include polytetramethylene ether glycols and copolymerized polyether glycols thereof. Also,
Examples of polyether ester glycols include polyester glycols obtained by reacting the above polyalkylene ether glycol as a polyol component with an aliphatic or aromatic dicarboxylic acid. If the molecular weight of this long-chain diol is too small, the urethane group concentration of the resulting polyurethane resin will be too high, resulting in poor flexibility of the resin and poor solubility in solvents, making it difficult to use as a binder for magnetic recording media. I don't like it very much. Additionally, if the molecular weight of the long-chain diol is too large, the content of the long-chain diol in the resin will be too large and the urethane group concentration will be relatively very low, resulting in a decrease in the abrasion resistance and heat resistance of the resin. do.

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

Furthermore, glycerin, ethylene oxide adduct of glycerin, 2-methylpropane-1,2,3-triol, 4-(bis(2-hydroxyethyl))-2-hydroxypentane, 3-methylpentane-1,3, 5-
It is also possible to use a triol such as a propion oxide adduct of triol, 1.2.6-hexane glycol, 1-bis(2-hydroxyethyl)amino-2-propatol, and jetanolamine.

Examples of the organic diisocyanate include aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2.6-tolylene diisocyanate, diphenylmethane diisocyanate, 3.3-dimethoxy-4,4′-biphenylene diisocyanate,
313'-dimethyl-414'-biphenylene diisocyanate, 4,4'-diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate, 2,4-
Aromatic diisocyanates such as naphthalene diisocyanate, 1,3-diisocyanatomethylcyclohexane,
1,4-diisocyanatomethylcyclohexane, 4,
Examples include alicyclic diisocyanates such as 4'-diisocyanate dicyclohexylmethane and isophorone diisocyanate.

Reaction methods employed in the production of polyurethane resins include melt polymerization in which the reaction is carried out in a molten state, and inert solvents such as ethyl acetate, methyl ethyl ketone, acetone, I-luene, etc. alone or in combination with the above-mentioned holes 5. Solution polymerization is carried out by dissolving the raw materials of It is more preferable to carry out solution polymerization by adding the above-mentioned inert solvent before carrying out melt polymerization and carrying out chain extension reaction.

In the reaction, an organometallic compound, for example, an organotin compound such as dibutyltin dilaurate, or tertiary amine, such as N-methylmorpholine or triethylamine, may be added as a catalyst. Further, in order to increase the stability of the product, antioxidants, ultraviolet absorbers, hydrolysis inhibitors, etc. may be added in an amount of about 5% or less based on the solid content.

Furthermore, a tertiary amine is introduced into the polyurethane resin as a hydrophilic polar group. Here, tertiary amines are very effective in improving the dispersibility of magnetic powder, and when used as a magnetic recording medium, have a particularly large effect on reducing powder falling off, and when used as a paint, the particle size is also excellent for practical use. Become something.

According to the experiments conducted by the present inventors, by using a polyurethane resin having a tertiary amine in the molecule, it is possible to obtain a paint with good particle size characteristics without impairing the powder drop reduction effect, and the dispersibility is improved. It has been found that an excellent magnetic recording medium can be obtained.

By the way, the following method may be used to introduce these tertiary amines into the polyurethane resin.

That is, by using the following 37th mino group-containing diol as part of the chain extender, it is introduced into the main chain of the polyurethane resin.

Examples of the tertiary amine group-containing diol include the following.

Further, by utilizing the side chains or terminal hydroxyl groups of the polyurethane resin, this may be modified with a compound having a group capable of reacting with active hydrogen and a tertiary amine in the molecule.

The compound having a group capable of reacting with active hydrogen and a tertiary amine in the molecule is expressed by the following formula (however, in any of the above polar groups, R has 1 carbon number
m represents 2 or 3, respectively. ) and the like.

These compounds are synthesized as follows.

Specific examples of these compounds include the following.

When a compound having a group capable of reacting with active hydrogen and a tertiary amine in its molecule is reacted with a polyurethane resin, the 1NGO group remaining in the former reacts with the 10H group in the polyurethane resin, A polyurethane resin into which a tertiary amine, which is a hydrophilic polar group, is introduced is obtained.

It can also be synthesized by the following method.

That is, a compound containing a tertiary amine and chlorine in the molecule,
A polyurethane resin having a polyfunctional OH group is dissolved in a solvent such as dimethylformamide or dimethyl sulfoxide in which both components are soluble, and amines such as pyridine, picoline, triethylamine, epoxy compounds such as ethylene oxide, propylene oxide, etc. There is a method of introducing a tertiary amine by a dechlorination reaction between an 10H group and chlorine in the presence of a dehydrochlorination agent.

The tertiary amine can be introduced into the polyurethane resin in the manner described above.

The amount of tertiary amine introduced into the polyurethane resin used as a binder is 0.001 to 1.0 a
preferably nol/g. If the amount of the tertiary amine introduced is less than 0.001 +w+wol/g, a sufficient effect on the dispersibility of the ferromagnetic powder will not be observed, and the amount of the hydrophilic polar group introduced is less than 1, Q mnol.
If it exceeds /g, intermolecular or intramolecular aggregation is likely to occur, resulting in deterioration of solubility in solvents and at the same time, there is a risk that moisture resistance of the coating film will be deteriorated.

Further, the number average molecular weight of the polyurethane resin according to the present invention is preferably 10,000 to 100,000. If the number average molecular weight is less than 10,000, the coating film forming ability of the resin will be insufficient, resulting in powder removal and lack of durability. Moreover, if the number average molecular weight exceeds 100,000, the solubility in solvents deteriorates, making it difficult to mix, transport, and
There is a possibility that problems may occur during processes such as coating.

The polyurethane resins according to the invention can be used in combination with other thermoplastics, thermosets or reactive resins.

The thermoplastic resin has a softening temperature of 150°C or less,
Average molecular weight is toooo~200000 and degree of polymerization is about 2
00 to about 20,000, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer.

Vinyl chloride-vinyl acetate-maleic acid copolymer.

Vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester- styrene copolymer,
Thermoplastic polyurethane resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyamide resin.

Polyvinyl butyral, cellulose derivatives, styrene
Synthetic rubber resins such as butadiene copolymers and polyester resins include polybutadiene.

Examples of thermosetting resins or reactive resins include phenolic resins, epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea-formaldehyde resins, silicone resins, acrylic reactive resins, and epoxy-polyamide resins. resin, nitrocellulose
Melamine resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanate.

Examples include polyamine resins and mixtures thereof. Among these, it is desirable to use in combination with those that have good dispersibility in ferromagnetic powder.

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

Here, as the ferromagnetic powder used in the present invention, any ordinary magnetic powder can be used. Therefore, usable ferromagnetic powders include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powders, hexagonal barium ferrite particles, iron nitride, and the like.

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

X=1.50), magnetite (Fe304.
= 1.33) and their solid solutions (FeOx, 1.3
3 < There are two types.

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

A material to which at least one of Sn, Te, Sb, Fe, Ti, V, Mn, etc. is added can be used.

Examples of the ferromagnetic alloy powder include Fe, Co, and l'Ji.

Fe-Co, Fe-Nt, Fe-Co-Ni, C.

-Ni, Fe-Go-B, Fe-Go-Cr-B.

Mn-B1. Mn-Al, Fe-Co-V, etc. can be used, and AI+S can be used to improve various properties of these materials.
Metal components such as i, Ti, Cr, Mn, Cu, and Zn may be added.

In addition to the binder and ferromagnetic powder, the magnetic layer also contains additives such as a dispersant, a lubricant, an abrasive, an antistatic agent,
Rust inhibitors and the like may also be added.

The above-mentioned dispersant (111 wetting agent) includes caprylic acid,
Fatty acids with 12 to 18 carbon atoms (R?C0OH, R.

is an alkyl or alkenyl group having 11 to 17 carbon atoms)
, 1 t of alkali gold (Li, Nrr,
K, etc.) or alkaline earth metals (Mg, Ca, Ba, etc.)
), amides of the aforementioned fatty acids, polyalkylene oxide alkyl phosphate esters, trialkyl polyolefin oxy quaternary ammonium salts (alkyl has 1 to 5 carbon atoms, olefin is ethylene, propylene, etc.), etc. . In addition, higher alcohols having 12 or more carbon atoms, sulfuric esters, etc. can also be used. These dispersants are added in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder.

Examples of the lubricant include dialkyl polysiloxane (alkyl has 1 to 5 carbon atoms) and dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms).

Silicone oil such as monoalkylmonoalkoxypolysiloxane (alkyl has 1 to 5 carbon atoms, alkoxy has 1 to 4 carbon atoms), phenylpolysiloxane, fluoroalkyl polysiloxane (alkyl has 1 to 5 carbon atoms), graphite Conductive fine powder such as molybdenum disulfide, tungsten disulfide, etc., inorganic fine powder such as polyethylene, polypropylene.

Polyethylene vinyl chloride copolymers, fine plastic powders such as polytetrafluoroethylene, α-olefin polymers, unsaturated aliphatic hydrocarbons that are liquid at room temperature (compounds in which an n-olefin double bond is bonded to the terminal carbon, carbon number about 2
0), fatty acid ester (monoester, diester) consisting of a fatty acid having 12 to 22 carbon atoms and an alcohol having 3 to 22 carbon atoms.

It may be any triester, or even a higher polyfunctional polyester. ), fatty acids or their metal salts, fatty acid amides, fatty acid alcohols or their alkoxides, fatty acid amines, polyhydric alcohols, sorbitan esters, manniratan esters, sulfurized fatty acids, aliphatic mercaptans, perfluoroalkyl ethylene oxides, perfluoropolyethers, Higher alkyl sulfonic acid or its metal salt, perfluoroalkyl sulfonic acid or its ammonium salt or its metal salt, perfluoroalkyl carboxylic acid or its metal salt,
Fluorocarbon etc. can be used.

These lubricants contain 0°2 to 100 parts by weight of binder.
It is added in an amount of 20 parts by weight.

The above-mentioned abrasives are commonly used materials such as fused alumina, silicon carbide, chromium oxide (C1Os), corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main ingredients: corundum and magnetite).
etc. are used. These abrasives have a Mohs hardness of 5 or more and an average particle diameter of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm. These abrasives are added in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the binder.

The antistatic agent mentioned above is carbon black.

Conductive fine powder such as carbon blank graft polymer,
Natural surfactants such as saponin, nonionic surfactants such as alkylene oxide, glycerin, and glycidol, and higher alkylamines.

Quaternary ammonium salts, pyridine and other heterocycles,
Cationic surfactants such as phosphoniums, carboxylic acids,
Anionic surfactants containing acidic groups such as sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric ester groups, amino acids,
Aminosulfonic acids.

Ampholytic activators such as sulfuric acid or phosphoric acid esters of amino alcohols are used. The above conductive fine powder is added in an amount of 0.2 to 20 parts by weight, and the surfactant is added in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the binder. These surfactants may be added alone or in combination.
Although these are used as antistatic agents, they are sometimes used for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

As the rust preventive agent, phosphoric acid, sulfamide, guanidine, pyridine, amine, urea, zinc chromate, calcium chromate, strontium chromate, etc. can be used, but in particular, dicyclohexylamine nitrite,
Volatile rust inhibitors (amine , an inorganic acid salt or an organic acid salt such as an amide or an imide), the rust prevention effect is improved. These rust inhibitors are used in amounts of 0.01 to 20 parts by weight per 100 parts by weight of ferromagnetic fine powder.
Used in parts by weight range.

The constituent materials of the magnetic layer described above are prepared as a magnetic paint by dissolving it in an organic solvent, and are applied onto a non-magnetic support.
Solvents for the magnetic paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl acetate, glycol dimethyl ether, and glycol monoethyl ether. Glycol ethers such as ether and dioxane, aromatic hydrocarbons such as benzene, toluene, and xylene,
Aliphatic hydrocarbons such as hexane and heptane, methylene chloride, and ethylene chloride.

Carbon tetrachloride, chloroform, ethylene chlorohydrin,
Examples include chlorinated hydrocarbons such as dichlorobenzene.

The material of the non-magnetic support to which these constituent materials are coated may be any material that is normally used in this type of magnetic recording medium, such as polyethylene terephthalate, polyethylene-2,6-naphthalate, etc. polyesters such as polyethylene, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate-1-, cellulose acetate butyrate, cellulose acetate propionate, vinyl resins such as polyvinyl chloride, polyvinylidene chloride, etc. , polycarbonate polyimide.

Plastics such as polyamide and polyamide-imide, non-magnetic metals such as aluminum, copper, tin, zinc or non-magnetic alloys containing these, light alloys such as aluminum alloys and titanium alloys, ceramics, and pottery.

Ceramics such as porcelain, single crystal silicon, and paper.

Baryta or polyethylene, polypropylene.

Paper such as paper coated with or laminated with an α-polyolefin having 2 to 10 carbon atoms such as an ethylene-butene copolymer can be used. The forms of these non-magnetic supports are as follows:
Film, tape, sheet.

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

[Effect]

As mentioned above, by using a polyurethane resin with a tertiary amine introduced into the molecule as a binder, the affinity for magnetic powder is greatly improved, resulting in ultrafine magnetic powder and magnetic powder with a large amount of magnetization. Even if it is, it is well dispersed.

In particular, by introducing a tertiary amine, the viscosity characteristics of the binder can be improved.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

First, a polyurethane resin into which a tertiary amine was introduced was synthesized by the method described herein. Table 1 shows the properties of the synthesized polyurethane resin.

Table 1 The following examples were carried out using the tertiary amine-containing polyurethane resins shown in Table 1.

Implementation M Upper magnetic coating composition Ferromagnetic metal iron powder 670 parts by weight (specific surface area 45r+(/g, axial ratio 11-13) Binder 1
100 parts by weight of abrasive (CrzO
= particles) 60 parts by weight Antistatic agent (carbon black) 35ffif
lubricant (olive oil) 7 parts by weight Toluene 350 parts by weight Methyl ethyl ketone 350 parts by weight Cyclohexanone 350 parts by weight After kneading and dispersing the above composition in a ball mill for 20 hours, an isocyanate compound (desmodulant: manufactured by Bayer AG) ) was added and dispersed under high speed shearing to obtain a magnetic paint.

This magnetic paint was applied to one side of polyethylene terephthalate with a thickness of 14 μm and a surface roughness of 0.03 μm to a dry thickness of 4.0 μm.
The sample tape was coated so as to have a width of m, then subjected to orientation treatment in a DC magnetic field of 2500 Gauss, and further cut into 1/2 inch width to prepare a sample tape.

2 to 4 Sample tapes were prepared in the same manner as in Example 1 except that Binder 2 to Binder 4 were used in place of Binder 1 in the composition of Example 1.

This ILL A sample tape was prepared in the same manner as in Example 1 except that Binder 5 was used in place of Binder 1 in the composition of Example 1.

Surface gloss, powder removal, paint viscosity, and still characteristics were measured for each sample tape obtained.

The above surface gloss was measured using a gloss meter (GLO5S METE).
I+) under the conditions of an incident angle of 60° and a reflection angle of 60''.In addition, the amount of powder falling on the head drum, guide, etc. was visually observed after running the shuttle 100 times for 60 minutes. The paint viscosity was evaluated using the subtraction method (-5 to 0).
The values shown are those measured with a B-type rotational viscometer using a No. 4 rotor at 30 rotations. Still characteristics are 4.2 MHz on tape
The video signal was recorded, and the time required for the playback output to attenuate to 50% is shown.

The measurement results are shown in Table 2.

As is clear from the results in Table 2, each sample tape according to the present invention not only has excellent surface gloss, powder removal, and still characteristics, but also has low paint viscosity and excellent workability. I can see that it is something.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Because a tertiary amine is introduced into the polyurethane resin molecule and used as a binder, it has a high affinity for magnetic powder, even if it is an ultra-fine magnetic powder or a magnetic powder with a large amount of magnetization. The dispersibility becomes good.

Therefore, the properties of the coating film when formed as a magnetic layer are improved, resulting in a magnetic recording medium with extremely excellent durability, surface properties, and electromagnetic conversion characteristics.

Moreover, since the paint containing the binder has a low viscosity and is easy to handle, it has excellent properties in terms of workability when forming a paint film.

Patent applicant: Sony Corporation Agent Patent Attorney Akira Kobe Same column Sakae Same as Masaru Sato

Claims (1)

[Claims] A magnetic recording medium in which a magnetic layer mainly composed of magnetic powder and a binder is formed on a non-magnetic support, wherein the binder contains a polyurethane resin having a tertiary amine. Features of magnetic recording media.