JPH0358322A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a medium having excellent electromagnetic conversion characteristics and to realize significant improvement in still durability, head abrasion and odor of residual solvents by mixing a solvent having a high solubility parameter with another solvent having a low solubility parameter at a specified mixing ratio, kneading the mixture solvent with ferromagnetic powder and a binder. CONSTITUTION:The first solvent having the solubility parameter of >=9.5 (Cal.cm<-3>)<1/2> and the second solvent having the solubility parameter of <8.7 (Cal.cm<-3>)<1/2> are mixed at the mixing ratio of 70/30 - 30/70 by weight, and this mixture is used in a process of kneading the ferromagnetic powder and binder in solvent. By this method, packing density Bm can be increased and the obtd. medium has excellent squareness ratio Br/Bm and high output. Packing density of the powder can be increased and kneading can be done with high shear, which results in strong bonding of ferromagnetic powder and improvement in still durability of the medium. Namely, the first solvent gives good kneading property and solubility for the binder, while the second solvent gives an effective increases in shear and enables fast and simple method of removing the solvent.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a magnetic recording medium, and in particular to a method for manufacturing a magnetic recording medium that has excellent electromagnetic conversion characteristics, improved still durability, head wear, and residual solvent odor. Regarding the method.

(Prior Art) Magnetic recording media having a magnetic layer on a non-magnetic support are used as magnetic recording media for computers, video, audio, and the like.

Such magnetic recording media are manufactured by coating a magnetic coating material, in which a magnetic layer-forming material such as ferromagnetic powder and resin material is dissolved or dispersed in an organic solvent, on a non-magnetic support, and then coating the layer in this coating layer. It is manufactured by a process that involves removing the organic solvent of

In recent years, there has been an increasing demand for high-density recording in magnetic recording media, and in response to these demands, finely powdered ferromagnetic powder is being used.

Generally, electromagnetic conversion characteristics can be improved by using finely divided ferromagnetic powder, but as the ferromagnetic powder becomes finer, the dispersibility of the ferromagnetic powder in the magnetic paint decreases.

Therefore, the squareness ratio of the magnetic layer of the obtained magnetic recording medium may not be sufficiently improved, and the surface of the magnetic layer may not be sufficiently smooth. That is, electric Tj5! Even though finely divided ferromagnetic powder is used for the purpose of improving the conversion characteristics, a problem arises in that the electromagnetic conversion characteristics of the obtained magnetic recording medium do not improve to the expected level.

Magnetic paints are generally prepared by adding a small amount of an organic solvent to a magnetic layer forming component such as a ferromagnetic powder or a resin component, kneading the mixture, and dispersing the resulting kneaded product in a large amount of the organic solvent.

Conventionally, it has been thought that organic solvents used in preparing magnetic paints have little effect on the characteristics of magnetic recording media. Therefore, organic solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, which are inexpensive and whose boiling points are within an appropriate range, are usually used throughout the kneading and dispersion steps.

However, as a result of study, it was found that when kneading ferromagnetic powder and resin ingredients, the amount of resin component supplied to the surface of each particle of ferromagnetic rice powder and It was found that the condition was different. It has also been found that such a difference affects the electric {R conversion characteristics of the obtained magnetic recording medium. That is, in the manufacturing method of a magnetic recording medium, there is still room for improvement regarding the organic solvent used when preparing the conventional magnetic paint.

As a method to solve these drawbacks, Japanese Patent Application Laid-Open No. 62-246
No. 142 discloses a magnetic coating comprising applying a magnetic coating comprising a magnetic layer containing ferromagnetic powder and a resin component dispersed in an organic solvent onto a non-magnetic support, and then drying the applied layer. In manufacturing a recording medium, the magnetic paint has a magnetic layer shape and a solubility parameter determined by Small's method of 9. 5 CCaA -cm-'
) After kneading the above first} container, the solubility parameter of the organic solvent in the magnetic coating material is 9. 5 C
A second solvent is added to the kneaded material so that the concentration is less than Cal . A method for producing a magnetic recording medium characterized in that it is obtained by dispersing it in agent B has been proposed. However, this method has the following drawbacks.

Solubility parameters9. 5 CCal -cm-'
) When kneading was carried out using only the above first solvent, the kneading was too strong and the solvent was strongly adsorbed, resulting in more solvent than necessary remaining when forming a coating film. Furthermore, since the binder is compressed and adheres to the powder, canoping becomes strong and a sufficient waveform cannot be obtained during recording and reproduction. Also, the paint film is harder than necessary,
It had drawbacks such as becoming brittle and having poor scratch resistance.

(Objective of the Invention) An object of the present invention is to provide a method for manufacturing a magnetic recording medium that has excellent electromagnetic characteristics and improved still durability, head wear, and residual solvent odor.

(Construction of the Invention) That is, the above-mentioned object of the present invention includes a step of kneading ferromagnetic powder with a binder in a solvent, a step of adding the remaining binder to the obtained kneading solution and dispersing it, and a step of dispersing the obtained dispersion. In a method for manufacturing a magnetic recording medium comprising a step of coating on a non-magnetic support, the solvent used in the kneading step has a solubility parameter of 9. 5 (CaA-cm-3)
8. 7
This can be achieved by a method for manufacturing a magnetic recording medium characterized in that the solvent is a mixture of less than (Caff -cm-) '' in a weight ratio of 70/30 to 30/70. can.

More preferably, the method for manufacturing a magnetic recording medium is characterized in that the binder used in the kneading step is a vinyl chloride resin and a polyurethane resin.

Various methods are known for determining the solubility parameter of a solvent, but in the present invention, the solubility parameter of the solvent is determined by the Small method.

The solubility parameter (δ) by Small's method can be determined by the following equation.

δ - ρ (ΣG/M) However, in the above 2, ρ represents the density of the organic solvent, G represents the molecular bond constant, and M represents the molecular weight.

The above molecular binding constant (G) is P. ^． Sma
ll: J. Appl. Chem. 3. 7 1
(1953). The details of the solubility parameters based on the Small's method can be found in T. C. P
"Paint Fluidity and Pigment Dispersion" by John Atton (1973)
Published by Kyoritsu Shuppan 01), pages 274-275.

That is, in the present invention, when the ferromagnetic powder and the binder are kneaded using a solvent that is a mixture of a solvent with a high solubility parameter and a solvent with a low solubility parameter at a certain ratio, it is possible to knead the ferromagnetic powder and the binder by applying extremely high shear. As a result, it has excellent electromagnetic characteristics, and can significantly improve still durability, hemlock wear, and residual solvent odor.

Preferred embodiments of the present invention are as follows.

(11 The solubility parameter 9.5 (Ca
b'-cm-3]l/2 or more solvent and solubility parameter 8.7 CCal am-3) wt
The solubility parameter of a solvent prepared by mixing less than 70/30 to 30/70 solvents in a weight ratio of 8. 9 2-9
．． A method for manufacturing a magnetic recording medium, characterized in that the magnetic recording medium is 4 8 CCal .cm-"J1-2.

(2) In the kneading step, the kneading process? 10~ for a liquid
A method for producing a magnetic recording medium, comprising carbon black having an average particle size of Loomμ.

(3) A method for manufacturing a magnetic recording medium, characterized in that the kneading step includes an inorganic powder having an average particle size of 0.05 to 0.5 μ and a Mohs hardness of 6 or more.

(4) A method for manufacturing a magnetic recording medium, characterized in that the remaining thickening agent added in the dispersing step is a vinyl chloride resin and/or a polyurethane resin and a polyisocyanate.

(5) The binder is an Epoquine group, -SO3M, OS○S
At least one polar type selected from M, P 03 M2, O P○3M2 (where M represents hydrogen, alkali metal, and ammonium) per 1 g of polymer.
A magnetic recording medium comprising a vinyl chloride resin and/or a crystalline polyurethane resin having an equivalent amount of IO-' to IXIO-'.

(6) The binder used in the kneading step is 2 of the total binder.
A method for manufacturing a magnetic recording medium, characterized in that the content is 0 to 60% by weight.

(7) The solubility parameter is 9. 5 CCal
-cm-3) I/2 or higher solvent is cyclohexanone, acetone, cyclohexanol, tetrahydrofuran, ethylene glycol monomethyl ester,
At least one solvent selected from acetonitrile, ethylene glycol monoethyl ester dioxane, and DMF, and the solubility parameter is 8.7 (Ca
Production of a magnetic recording medium, characterized in that the solvent less than 1 -am-J "" is at least one solvent selected from carbon tetrachloride, cellosolp acetate, butyl acetate, isobutyl acetate, cyclohexane, and MIBK. Method.

The method for manufacturing a magnetic recording medium of the present invention includes a step of kneading ferromagnetic powder with a binder in a solvent, a step of adding the remaining binder to the obtained kneading solution and dispersing it, and a step of dispersing the obtained dispersion using a non-magnetic support. It consists of a process of applying it on the body.

The binder can be selected from conventional binders.

Examples of binders include vinyl chloride-based copolymers (e.g., vinyl chloride copolymers, vinyl chloride-vinyl acetate copolymers, and vinyl chloride-vinyl acetate containing a tertiary repeating unit such as maleic anhydride). cellulose derivatives (e.g. nitrocellulose), acrylic resins, polyvinyl acecool resins, polyvinyl butyral resins, evoquin resins, phenoxy resins, polyurethane resins (e.g. polyester polyurethane resins, Examples include polyether-based polyurethane resins and polycarbonate-based polyurethane resins.

In the present invention, it is particularly preferable to use the above-mentioned vinyl chloride copolymer and polyurethane resin in combination. In addition, the vinyl chloride copolymer and the polyurethane resin have an epoxy group, -O}{, -Soco M1-03
03 M, COOM, P 03 M2, 10PO
Those containing a polar group such as 3M2 (where M represents hydrogen, alkali metal, or ammonium) are preferred.

The content of the binder in the magnetic paint is usually 10-100 parts by weight (preferably 20-40 parts by weight) per 100 parts by weight of the ferromagnetic powder.

IA! Commonly used magnetic powders can also be used.

Examples of ferromagnetic powders include metal oxide-based ferromagnetic powders such as gamma iron oxide, dissimilar metal/iron oxide-based ferromagnetic powders such as cobalt-containing T iron oxide, and ferromagnetic powders containing iron, cobalt, or nickel. Mention may be made of ferromagnetic metal powders.

In the present invention, when using a dissimilar metal/iron oxide based ferromagnetic powder as the above-mentioned ferromagnetic powder, one having a specific surface area of usually 3 og/g or more is used. In addition, when using ferromagnetic metal fine powder, the specific surface area is usually 4
Use one with a concentration of 2 ffl/g or more (preferably 45 mlg or more).

As the dissimilar metal/iron oxide type ferromagnetic powder, known types such as cobalt doped type, cobalt deposited type, cobalt adsorption type, and surface layer type can be used.

Further, as an example of a ferromagnetic metal fine powder, the metal content in the ferromagnetic metal fine powder is 75% by weight or more, and 80% by weight or more of the metal content is at least one type of ferromagnetic metal or alloy (e.g., Fe..co, Ni..Fe-Co, Fe
-Ni, Co-Ni, Co-Ni-Fe), and other precepts (e.g. A1
, Si, pb. ．． ScSTi, V, Cr. ．． Mn1Cu
．． ．． B, Y, MoSRh. ．． Pd, AgSSn, SbS
P, Ba, Ta, W. ．． Re, Au. ．． Hgs S%
B i, La, Ce, Pr, Nd, Zn, T
Mention may be made of alloys which may contain eSZn). Further, the ferromagnetic metal may contain a small amount of water, hydroxide, or oxide. The methods for manufacturing these ferromagnetic metal fine powders are already known, and the ferromagnetic metal fine powders used in the method for manufacturing the magnetic recording medium of the present invention can also be manufactured according to these known methods.

There are no particular restrictions on the shape of the ferromagnetic powder, but needle-like, granular, dice-like, rice-grain-like, and plate-like shapes are usually used.

A magnetic layer containing such a ferromagnetic powder and a binder is mixed with two kinds of solvents (organic solvents) having different solubility parameters.
Knead with.

This first solvent has a solubility parameter of 9,5 (Ca
(1・(m-3) "" or more. Especially as the first organic solvent, the solubility parameter is 9.5 to 1 1
．． It is preferred to use a neutral organic solvent within the range of 5 CCafl -cm-'')''.

That is, the first solvent has high polarity, is a good solvent for fat fractions, and has a high affinity for ferromagnetic rice powder. Therefore, by using a JlaWj medium having a solubility parameter within the above range, the dissolved state or dispersion state of the resin precipitate at the time of crosstalk becomes good.

Since the above-mentioned organic solvent has a good affinity for the ferromagnetic powder, the organic solvent penetrates into the gaps between the individual particles of the ferromagnetic powder and into the recesses formed on the surface of the ferromagnetic powder. The resin content can be supplied throughout the ferromagnetic powder particles. Therefore, since the ferromagnetic powder particles become coated with resin particles, the particles can be deagglomerated, effectively preventing the particles from agglomerating again during kneading and dispersion as described below. can do.

Therefore, the solubility parameter is 9. 5 (Cab
・c,,-1) If less than 1/2 of an organic solvent is used for kneading, the supply of resin components to the ferromagnetic powder will be insufficient, resulting in a high squareness ratio and a good result. This makes it difficult to manufacture a magnetic recording medium with suitable electromagnetic conversion characteristics.

An example of a solvent exhibiting such a solubility parameter is cyclohexanone (δ-value 9.9 (Ca 7!・■-
3) l/2), cyclohexanol (δ= 1 1
．． 4 (Caj! -am-') "", dioxane (δ=9.9 (Caj! -cm-')
”, Tetrahi Fl:! 7' run (δ=9.9
(Cab -cm-') ""), ethylene glycol monomethyl ester (δ-10.8CCa 12
-(A)1jl)I/2) and ethylene glycol monoethyl ester (δ-9.9.(Caj!)
-cm-')1'2), and in the present invention, at least one of these Ja-containing solvents is used.

The second organic solvent used in the kneading step has a solubility parameter of less than 8.7. In particular, the second organic solvent has a solubility parameter of 7. 5-8.
It is preferable to use an organic solvent within the range of 7 (Cab·cm-3).

The second solvent has a lower solubility in the binder than the first solvent, so by adding it, the shear during kneading can be used effectively.

An example of the organic solvent used as the second solvent is carbon tetrachloride (δ = 8, 6 CCal cm-3).
), MIBK (methyl isobutyl ketone) (δ=
8.4 (Caf-am-3) ”” ), isofuti acetate JLz (.6 = 8.3 CCal ・c
m-3) ""), vinegar M phthyl (δ=8.5 (C
aj! - am-33 +/2 ), cellosulfur acetate (δ = 8.7 (Ca6 -cm-")"
”), cyclohexane (δ-8.3 (Cal
-cm-')""), and it is necessary to use at least one of these.

The weight ratio of these first solvent and second solvent is 70/30~
A 30/70 mixture of solvents is required. If the weight ratio of the solvent is more than 70/30, the amount of solvent remaining in the coating film will increase, and there will be disadvantages such as increased cambering of the tape.

On the other hand, if the weight ratio of the solvent is less than 30/70, sufficient shear during kneading will not be provided, resulting in a soft film and the binder filling rate will not increase. This is the coating form or later,
This is thought to be because the paint film tends to become mirror-like due to repeated running, etc.

In addition, the solubility parameters of these mixed solvents are 892~
9. 4 8 (Caf·cm-') "" is preferable. If it is smaller than this range, the solubility of the binder will be extremely poor and effective kneading properties cannot be imparted.

On the other hand, if it is larger than this range, the kneading properties with the binder will improve, but the solvent will be strongly adsorbed to the binder and filler, making it difficult to remove it.

The reason why at least two kinds of solvents having different solubility parameters are used for the kneading is as follows.

That is, the first solvent provides more effective kneading properties and provides sufficient binder dissolving power. It also improves the wetting speed of ferromagnetic powder and aids in kneading. The second solvent also provides an effective shear increase, making removal of the solvent quick and easy.

When kneading the above solvent and the magnetic layer, the weight ratio of the solvent and the magnetic layer is usually within the range of 1:1 to 1:5 (preferably zi.s to 1:3). Set it to .

In addition, kneading is carried out using ordinary kneading equipment (e.g., roll mill, paddle mill, screw extruder, auger kneader, pressurized 21 goo, open 21 goo, continuous kneader, helical rotor), etc. This can be done according to conventional methods.

The kneading time can be appropriately set in consideration of various conditions such as the type of kneading device used and the type of binder. Usually, it is 10 minutes to 20 hours.

The remaining binder in the dispersing step is the remainder of the binder added in the kneading step. All of the binder may be added during the kneading process. The binder added in the kneading step and the remaining binder added in the dispersion step may be the same or different. The remaining binder is vinyl chloride resin and/or
Alternatively, polyurethane resin or epoxy resin is preferable.

The type of binder that can be used is the same as the binder used in the kneading step.

In the dispersion step, the amount of organic solvent in the magnetic paint is usually within the range of 100 to 500 parts by weight (preferably within the range of 150 to 350 parts by weight) per 100 parts by weight of the ferromagnetic powder.
Dispersion is carried out by adding a solvent so as to achieve the following.

Dispersion can be carried out using conventional dispersion equipment (eg, sand mill, pole mill) according to conventional methods.

The dispersion time can be appropriately set in consideration of various conditions such as the type of minute tik device used and the type of resin precipitate. Usually, it is 10 minutes to 60 hours.

In addition to the binder and ferromagnetic powder described above, the magnetic layer usually contains other magnetic layers such as abrasives, lubricants (e.g., fatty acids, fatty acid esters), antistatic agents (e.g., carpon blanks), etc. Contains formative power. Such other 6Ii layer forms can be added at any stage during kneading or dispersion. However, it is preferable to add the abrasive at the time of mixing. By doing so, the abrasive material is sufficiently dispersed in the binder, and uniform polishing performance can be obtained.

When an abrasive material is used, an abrasive material commonly used for magnetic recording media can be used as the abrasive material.

Examples of abrasive materials include α-Al20*. ．． Crzo
3Sn○2, Sl02, TtQ2, CtFe2
03 and Fe304, which can be used alone or in mixtures.

Among these, α-Ai! Zo* has high hardness and is suitable as an abrasive material in the present invention.

The content of the abrasive in the magnetic paint is usually 1 to 2 parts by weight per 100 parts by weight of the ferromagnetic powder contained in the magnetic layer.
It is set within the range of 0 parts by weight (preferably 5 to 15 parts by weight).

Further, it is preferable to use a hardening agent in addition to the above-mentioned resin as a binder. As the curing agent, polyisocyanate compounds are usually used. In the present invention, it is particularly preferable to add this polyisocyanate compound just before the end of minute +1+ or just before the start of coating. By doing so, the curing reaction by the polyisocyanate compound proceeds effectively after the magnetic paint is applied, so that a magnetic layer with high strength can be obtained.

In addition, when using a polyisocyanate compound, the polyisocyanate compound and the resin component are mixed in a ratio of 5:95 to so.
:so (weight ratio).

The magnetic paint thus prepared is applied onto a non-magnetic support. Coating can be carried out using conventional coating methods such as using a reverse roll or a doctor blade.

The coating layer of the magnetic paint is applied so that the thickness of the magnetic layer of the obtained magnetic recording medium is usually within the range of 0.5 to 10 μm.

As the non-magnetic support, commonly used supports such as Plastinok supports can be used.

In addition, as a non-magnetic support, -C has a thickness of 3 to 50 μm.
m (preferably 5 to 30 μm) is used.

A back layer (basoking layer) may be provided on the surface of the nonmagnetic support used in the present invention that is not coated with the magnetic paint. Further, an adhesive layer may be attached to the surface of the nonmagnetic support on which the magnetic paint is applied.

Usually, the applied amount of the magnetic paint is dried after being subjected to a process for orienting the ferromagnetic powder contained in the applied layer of the magnetic paint, that is, a magnetic field orientation process.

After being dried in this manner, the coated layer is usually subjected to a surface smoothing treatment and then cut into a desired shape. For example, a super force render roll is used for the surface smoothing process. By performing the surface smoothing treatment, the pores generated due to the removal of the solvent during drying disappear and the filling rate of the ferromagnetic powder in the magnetic layer is improved, thereby obtaining a magnetic recording medium with high electromagnetic conversion characteristics. be able to.

The cutting can be carried out under normal conditions using a normal cutting machine such as a Surinotar.

(Effect of the invention) The present invention has a solubility parameter of 9.
5 CCaI! -cm") "" or higher solvent, agent (first solvent) and solubility parameter 8.7 CCa
(!・Cffl-') Solvent less than "" (second solvent)
By using a solvent mixed in a weight ratio of 70/30 to 30/70, the filling degree Bm can be increased and the output can be improved.

It also has an excellent squareness ratio B r /13 m and improves output. In addition, by increasing the filling degree and kneading firmly, the binder and IA! The magnetic powder is strongly bonded and the still durability is improved. That is, the first solvent provides effective kneadability and sufficient binder dissolving power. It also improves the wetting speed of ferromagnetic powder and aids in kneading. The second solvent also provides a useful shear increase and makes solvent removal quick and easy.

In this way, the present invention shows that by kneading the ferromagnetic powder and the binder using a solvent that is a mixture of a solvent with a high solubility parameter and a solvent with a low solubility parameter at a certain ratio, the solubility increases and at the same time extremely strong high shear As a result, the electromagnetic properties are excellent, and still durability, head wear, and residual solvent odor can be significantly improved.

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

In addition, in the following examples, "parts" indicate "parts by weight" unless otherwise specified.

Example 1 Next, the binder listed in Table 1 of the ferromagnetic powder of the composition was placed in a kneader and thoroughly kneaded, and the remaining portion was mixed, placed in a sand mill, and thoroughly dispersed. Product name> Add 24 copies,
A magnetic paint was created by uniformly mixing and dispersing it.

Go-containing r-FetOs powder 300 parts (Fe/
Fe=2. 8wt%, Co=3. 5ut%, SBE1 35m/g, Powder Hc = 6800e) Carbon powder (Condac 13 parts Tex S average particle size 20mμ, Columbian (L) Abrasive (α-alumina, Hit50 15
Part 0.2 μ Sumitomo Chemical 0 grade! ! ) Oleic acid 1 part Octyl laurate 3 parts Lauric acid
3 part solvent
It is listed in Table 1.

After adjusting the viscosity of this magnetic paint, a 19μm undercoat layer was applied.
A sample was prepared by coating the surface of a polyethylene terephthalate substrate to a thickness of 4.5 μm, orienting it, drying it, calendering it, and subsequently connecting it to perform the following coating process.

After kneading and adjusting the back liquid of the following composition using a ball mill, 5 parts of polyisocyanate (Coronate 2061 manufactured by Nippon Polyurethane) was added and mixed and dispersed uniformly.The viscosity was adjusted to RNN, and 1. .8
It was applied to a μ thickness and dried.

Carbon Brasok 100 parts (Leben MTP, average particle size 250 mμ, manufactured by Cabo Soto ■) Polyurethane resin (Esten 570 l, manufactured by Gusodo Sochi ■) 40 parts Phenoxy resin (PKHH, 10 parts manufactured by Union Carbide ■) Copper oleate 0.1 part Stearic acid 0.3 parts Methyl ethyl ketone 700 parts Cyclohexanone
30'O parts of this tape was polished to a mirror finish using a calender, and then slit in 1 inch to produce samples ml to 9 in Table 1.

Example 2 Ferromagnetic powder of the following composition, the binder used in the kneading step shown in Table 1, abrasives, carbon blanks, etc., if necessary, were mixed with a solvent and thoroughly kneaded using a 21-goo machine. The remaining binder used in the dispersion process, the remaining solvent, an abrasive if necessary, carbon blank, etc. are added to the sand mill and thoroughly dispersed.
-75, manufactured by Bayer) were added and uniformly mixed and dispersed to prepare a magnetic paint.

300 parts of CO-containing 1-FezOs powder (Fe=
8wt%, Co=4wt%, Smit=55 m/g, powder Hc=
9000e) 8600, manufactured by Toyobo ■) 7 Carbon fiber rank 13 parts (H
S-100, 50mμ, made by Denka Iliki) Abrasive 15 parts (SiC0
．． 2um manufactured by Ibiden ■) Oleic acid 1 part octyl laurate 3 parts lauric acid
3 part solvent
After adjusting the viscosity of this magnetic paint in the amount listed in Table 1, 1
4.5 on the surface of a 9 μm polyethylene terephthalate substrate.
A sample was prepared by coating to a μ thickness, orienting, drying, and calendering. Next, a bank layer was provided in the same manner as in Example 1, and the resulting tape was polished to a mirror finish using a calender, and then slit into 1 inch width to form sample No. 1 in Table 1. 10-18
The sample was disciplined.

(Glossiness of magnetic layer surface) According to JIS Z8741, the refractive index is 1.0 at an incident angle of 45°. -Measurements were made with the specular gloss of the glass surface of 567 as 100%.

(Br/Bm, SQ value) VSM-II (Toei Kogyo!!) Measured at 25°C (
External magnetic field (5KOe) expressed in Br/Bm.

(Still durability) When playing stills with Sony BVH 1000 and increasing the load by 200g, the output signal is -3d.
The time required for B was measured.

(Head Wear) The head wear amount of Sony ■BVHIOOO is shown in terms of the value per 100 hours of running.

(Amount of residual solvent) 5 cffl of the tape was cut out, and the amount of solvent was examined using a gas chromatograph. In addition, a sensory test was conducted, and those with a solvent odor were rated x, and those with no solvent odor were rated O.

As is clear from the results in Table 1, solubility parameter 9.
5 (Caffi-cm-') "" or more and 8.7
[Cal-ca+-"]"" The mixture of solvents with a weight ratio of 70/30 to 30/70 has a gloss level of B.
Excellent r/Bm and improved output. It also has an effect on still durability and reduces wear on the heel. Conventionally, still durability has been compensated for by increasing the amount of abrasive, but this has the drawback of increasing head wear, and this point has been significantly improved.

Also, within the scope of the present invention, the residual solvent odor is particularly excellent.

Claims (2)

[Claims] (1) A step of kneading the ferromagnetic powder with a binder in a solvent, a step of adding the remaining binder to the obtained kneading liquid and dispersing it, and a step of coating the obtained dispersion liquid on a non-magnetic support. In the method for manufacturing a magnetic recording medium, the solvent used in the kneading step has a solubility parameter of 9.5.
Cal・cm^-^3]^1^/^2 or more solvent and solubility parameter 8.7 [Cal・cm^-^3]^1^
A method for manufacturing a magnetic recording medium, characterized in that the solvent is a mixture of less than /^2 solvents at a weight ratio of 70/30 to 30/70. (2) The method for manufacturing a magnetic recording medium according to claim (1), wherein the binder used in the kneading step is a vinyl chloride resin and a polyurethane resin.