JPH01102736A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the generation and splashing of debris of the raw sheet of a nonmagnetic base, etc., to be generated by using a smoother and to prevent the degradation in electromagnetic conversion characteristics or traveling durability by coating an org. solvent on the noncoating part of the raw sheet of the nonmagnetic material prior to smoothing by the smoother. CONSTITUTION:The org. solvent is dropped or coated onto the noncoating parts 5a, 5b just before the smoother 1 and a coating layer 4 come into contact. The amt. of the org. solvent to be coated is sufficient with about the amt. at which the noncoating parts 5a, 5b are wet at the time when said parts come into contact with the smoother. The amt. of said solvent to be coated is usually set within the range of the coating thickness of 0.3-2.0 times the wet film thickness in the coating part. The generation and splashing of the debris generated by the contact of the parts at the edges 5a, 5b of the raw sheet 3 of the nonmagnetic base where the magnetic coating compd. is not coated and the smoother 1 are thereby obviated and, therefore, the instantaneous drop or drop- out of the reproduction signal such as the drop-out by the debris sticking to the surface of the magnetic layer 4 is effectively prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a magnetic recording medium that can effectively prevent instantaneous drop or dropout of a reproduced signal.

[Prior art and its problems] Magnetic recording media are generally produced by applying magnetic paint to a long non-magnetic support material, leaving uncoated areas at the edges in the width direction.
After performing necessary treatments such as magnetic field orientation treatment, the coated layer of magnetic paint is dried, followed by surface smoothing treatment such as calender treatment, and is manufactured by cutting into the desired shape.

Furthermore, in order to prevent a drop in the reproduced signal due to spacing loss between the magnetic layer and the magnetic head, after applying the magnetic paint, the surface of the applied layer is brought into contact with a smoother while the applied layer is not dry. A method is used to smooth the surface of the layer.

However, it has been found that when a smoother is used, instantaneous drop or dropout of the reproduced signal of the magnetic recording medium may increase. This phenomenon occurs when the magnetic material obtained by cutting a non-magnetic support material (material material for magnetic recording media) coated with an m-based paint within a range of several tens of am from the edge in the width direction. Often seen in recording media.

As a result of investigating the cause of such a phenomenon, the present inventor found that when smoothing a coated layer of magnetic paint, the uncoated portion of the widthwise edge of a long non-magnetic support material and the smoother When the non-magnetic support comes into contact with In addition, when shavings adhere to the surface of the calender roll used in the subsequent surface smoothing process, they form four parts on the magnetic layer, which is an indirect cause of instantaneous drop or loss of the reproduced signal. It turned out to be.

The present invention effectively prevents the generation and scattering of shavings from the non-magnetic support material generated by using a smoother. It is an object of the present invention to provide a method for manufacturing a magnetic recording medium that can effectively prevent deterioration in conversion characteristics or running durability.

[Means for solving the above-mentioned problems] The structure of the present invention is such that a non-coated portion is left on the widthwise edge of the elongated non-magnetic support material and the surface of the non-magnetic support material is coated. In a method for producing a magnetic recording medium comprising the steps of applying a magnetic paint and smoothing the surface of the applied magnetic paint with a smoother, the uncoated surface of the original non-magnetic material support is removed before smoothing with the smoother. This is a method of manufacturing a magnetic recording medium characterized by coating a portion with an organic solvent.

Basically, the method for producing a magnetic recording medium of the present invention involves the presence of an organic solvent at the edge in the width direction of an elongated non-magnetic support material, thereby allowing the non-magnetic support material to be removed from the smoother. This prevents the generation and scattering of cutting powder caused by contact with the magnetic layer, and effectively prevents the reproduction signal from being lost or degraded due to adhesion of the cutting powder to the magnetic layer.

In the method for manufacturing a magnetic recording medium of the present invention, first, a magnetic paint is applied to the widthwise edges of a long non-magnetic support material, leaving uncoated areas.

-Non-magnetic support material- In the method for producing a magnetic recording medium of the present invention, a normal long non-magnetic support material can be used.9Non-magnetic support used in the present invention Examples of materials forming the original fabric include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate;
Mention may be made of polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polycarbonate.

The thickness of the nonmagnetic support fabric formed using these materials is usually within the range of 3 to 100 JLITI.

A back coat layer can also be provided on the back surface of the original nonmagnetic support for the purpose of improving running performance.

Additionally, an intermediate layer (e.g., adhesive layer, undercoat layer) is provided between the non-magnetic support material and the magnetic layer for the purpose of improving the adhesion between the magnetic layer and the non-magnetic support material. You can also do that.

The raw non-magnetic support used in the production method of the present invention is a long one, and usually such a long raw non-magnetic support is run continuously to form the support. A magnetic recording medium material is manufactured by applying magnetic paint to the surface of the material, bringing it into contact with a smoother, and then undergoing steps such as magnetic field orientation treatment and surface smoothing treatment. A magnetic recording medium can be obtained by cutting into a shape.

1. Magnetic Paint 1. A magnetic paint to be coated on a non-magnetic support material is basically one in which magnetic layer-forming components including magnetic powder and a resin binder component are dispersed in an organic solvent.

11 Magnetic Powder 11 There is no particular restriction on the magnetic powder used in the method for producing a magnetic recording medium of the present invention, and any magnetic powder that can be used in ordinary magnetic recording media can be used.

Examples of magnetic powders that can be used in the present invention include iron oxide magnetic powders (e.g., γ-Fe2O3, Fe-04),
Oxide-based magnetic powder containing other components such as Co (e.g. Co-containing iron oxide), Ba ferrite, Fe, Ni
, Ferromagnetic alloy powder containing ferromagnetic metal such as Go and other components (e.g., Fe-Al1 alloy powder, Fe-Al1-Ni
Alloy powder, Fe-Ni-Co alloy powder, Fe-Mn
-Zn alloy powder, Fe-Ni-Zn alloy powder, Fe-G
o-Ni-Cr alloy powder, Fe-Go-Ni-P alloy powder, Go-Ni alloy powder, Fe-, Al-Co alloy powder, Fe-Ni-Go-A1 alloy powder and Go-P
alloy powders) and ferromagnetic metals (e.g. Fe.

Examples include fine ferromagnetic metal powders consisting of Ni and Go.

There is no particular restriction on the shape of the magnetic powder that can be used in the present invention, and for example, needle-like, spherical, ellipsoidal, or plate-like shapes can be used.

11 Resin Component 1 - The resin binder component that forms the magnetic paint together with the above magnetic powder includes resin components such as thermoplastic resins, thermosetting resins, reactive resins, and electron beam curable resins. Furthermore, these resins and a curing agent can also be used in combination.

As the thermoplastic resin, those having a softening temperature of 150° C. or less, an average molecular weight of 10,000 to 200,000, and a polymerization degree of 100 to 2,000 can be used. Examples of such thermoplastic resins include:
Vinyl chloride copolymers, acrylic acid copolymers, cellulose derivatives, urethane elastomers, polyvinyl fluoride resins, vinylidene chloride-acrylonitrile copolymers, acrylonitrile-butadiene copolymers, polyamide resins, polyvinyl butyral Examples include copolymers, styrene-butadiene copolymers, polyester resins, chlorovinyl ether-acrylic acid ester copolymers, amino resins, and synthetic rubber thermoplastic resins.

The thermosetting resin or reactive resin has a molecular weight within the range of 10,000 to 200,000 in the magnetic paint, and after coating and drying, it becomes a cured resin with an infinite molecular weight through condensation reaction, addition reaction, etc. Preferably.

These resin cured products include, for example, combinations of polyurethane resins, phenoxy resins, and curing agents, combinations of high molecular weight polyester resins and cured products, combinations of methacrylate copolymers and cured products, and combinations of polyester polyols and cured products. Combinations with low molecular weight glycols, high molecular weight diols, and cured substances, phenolic resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, silicone resins, and acrylic reactive resins, etc. hardening resin,
It can be obtained by curing a cured urea formaldehyde resin and a polyamine resin.

Examples of electron beam irradiation-curable resins include unsaturated prepolymers and polyfunctional polymers.

These resins can be used alone or in combination. Furthermore, in addition to the resin component, a curing agent such as a polyisocyanate compound can also be used in combination.

The mixing ratio of the magnetic powder and the resin binder component (including the curing agent if a curing agent is used) in the magnetic paint is determined by considering both electromagnetic conversion characteristics and running durability.
The amount is usually set within a range of 5 to 400 parts by weight per 100 parts by weight of magnetic powder.

- Solvent constituting the monomagnetic paint - The solvent used in preparing the monomagnetic paint can be selected appropriately, taking into account solubility in the resin, dispersibility in magnetic powder, etc., removability, economic efficiency, etc. Ru. Examples of such solvents include ketone solvents such as methyl ethyl ketone (MEK), methyl isobutyl ketone (11118K) and cyclohexanone: methanol, ethanol,
Alcohol solvents such as propatool and butanol:
Ester solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, and ethylene glycol 1,000 acetate Ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; Aromatic solvents such as benzene, toluene, and xylene Solvents: and halogenated hydrocarbon solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene may be mentioned. In the present invention,
Solvents can be used alone or in combination.

m - Other components - In addition to the magnetic powder and resin binder components described above, the magnetic paint contains components contained in the magnetic layer of ordinary magnetic recording media, such as abrasives, antistatic agents, and lubricants. can be blended.

Examples of abrasives that can be used in the present invention include organic powders with a Mohs hardness of 5 or more (e.g., benzoguanamine resin powder, melamine resin powder, and phthalocyanine compound powder) or inorganic powders (e.g., α-alumina, titanium oxide, etc.). , silicon oxide, silicon nitride, chromium oxide and boron carbide). These can be used alone or in combination. The average particle size of these abrasives is usually in the range of 0.05 to 2.0 lm.

Further, the blending amount of these abrasives is usually within the range of 0.5 to 20 parts by weight per 100 parts by weight of the magnetic powder.

Examples of antistatic agents that can be used in the present invention include conductive powders (e.g., graphite, carbon black,
tin oxide - (titanium oxide) - antimony oxide compound, carbon black graft polymer), natural surfactant (
Mention may be made, for example, of saponins), nonionic surfactants, higher alkylamines, cationic surfactants, anionic surfactants and amphoteric surfactants. These antistatic agents can be used alone or in combination.

The blending amount of the antistatic agent is based on 100 parts by weight of magnetic powder.
It is usually in the range of 0.5 to 20 parts by weight.

As the lubricant blended into the magnetic paint, those used as lubricants for ordinary magnetic recording media can be used. Examples of such lubricants include fatty acid esters, fatty acids, silicon compounds, modified lubricants, etc. Silicon compounds (e.g.
ester-modified silicon compounds, fluorine-modified silicon compounds), liquid paraffins, mineral oils and solid lubricants (e.g. carbon black, graphite, carbon black graft polymers, molybdenum disulfide and tungsten disulfide), which alone Or they can be used in combination.

The amount of lubricant to be blended is usually in the range of 1 to 15% by weight based on 100 parts by weight of the magnetic powder. Note that lubricants other than the solid lubricant may be dissolved in an organic solvent and applied onto the magnetic layer without being blended into the magnetic paint.

In addition, in the present invention, abrasives, lubricants, antistatic agents, dispersants, etc. described below do not have only independent effects, and for example, - components may act as lubricants and antistatic agents. . Therefore, the above-mentioned classifications in the present invention indicate the main effects, and are not limited by the effects of the classified compounds or the effects shown in the classification.

1. Kneading and dispersion method - Mixing and dispersion of the magnetic layer forming components including the above-mentioned components can be carried out by a conventional method.

When mixing and dispersing the magnetic paint components, there is no particular restriction on the order in which the magnetic paint components are added, and the mixing and dispersion can be carried out by adding each component according to a conventional method. However, when using a curing agent, it is preferable to add the curing agent immediately before applying the magnetic paint in order to prevent the curing reaction from proceeding due to the curing agent during kneading and dispersion.

A known cross-dispersion device can be used for cross-mixing and dispersion, and examples of such kneading and dispersion devices include Miki roll mill, Miki roll mill, ball mill, pebble mill, Sundklinder, and Sqeg.
Mention may be made of the vari attritor, high speed impeller disperser, high speed stone mill, high speed impact mill, Disper Kneader-1 high speed mixer, homogenizer and ultrasonic disperser.

When kneading and dispersing, use a dispersant (e.g. fatty acids, lecithin,
Phosphate ester, amine compound, alkyl sulfate,
Fatty acid amide, higher alcohol, polyethylene oxide, sulfosuccinic acid, sulfosuccinic acid ester, surfactant exhibiting a dispersing action, and polymer-based dispersant containing a negative organic group can also be used.Dispersants include magnetic powder 100.
It is usually added within the range of 1 to 20 parts by weight.

1. Coating method 1. Apply the thus prepared magnetic paint onto a long non-magnetic support material by a known method, leaving an uncoated portion at the edge in the width direction of the long non-magnetic support material. . The width of the non-coated portion at this time is usually within the range of 1 to 20 mm.

Examples of coating methods that may be utilized in the present invention include clavier roll coating, wire bar coating, doctor blade coating, reverse roll coating, tip coating, air knife coating, calendar coating, squeegee coating, kiss coating and fan coating. One can mention tin coating.

The wet film thickness of the magnetic paint applied in this manner is usually within the range of 5 to 1'00 JLm.

-Smoother- After applying the magnetic paint onto the original non-magnetic support,
While the coated layer of magnetic paint is not dry, the surface of the coated layer is smoothed by passing it through a smoother.

There are no restrictions on the shape of the smoother as long as it can contact and smooth the surface of the coating layer, and usually the cross section of the contact surface in the length direction of the smoother is arcuate or linear. Alternatively, the shape is a combination of these shapes, and a rod-like shape and a film-like shape with a corner end of the contact surface are used.

FIG. 1 shows an example of smoother processing using a non-flexible rod-shaped smoother with a fan-shaped cross section.

In FIG. 1, the smoother is designated l. The smoother 1 is usually made of a long non-flexible body such as metal, hard plastic, or ceramic. The fan-shaped arc portion 2 of the smoother 1 smoothes the surface of the coated layer 4 by coming into surface contact with the coated layer 4 of magnetic paint coated on the elongated non-magnetic support material 3. do. Smoother-1
Since it essentially smoothes the surface of the coating layer 4, it is sufficient that the length corresponds to the coating width of the coating layer 4.
If it is shorter than the width of the non-magnetic support material 3, the non-magnetic support material 3 will be damaged due to contact between the edge of the smoother and the non-magnetic support material 3, so in order to prevent this, Usually, the width is longer than the width of the non-magnetic support material 3.

Therefore, the widthwise edge of the elongated non-magnetic support material is not l! The smoother 1 contacts the i&cloth portions 5a and 5b,
The non-applied portions 5a and 5b are scraped off by the smoother 1 to generate powder.

The method for manufacturing a magnetic recording medium of the present invention includes non-coated portions 5a, 5.
The presence of an organic solvent in b prevents the generation and scattering of cutting powder generated by contact with the smoother 1.

As a method for making the organic solvent exist in the non-coated parts 5a and 5b, the non-coated part 5a of the smoother-1 is used.

There are various methods such as a method in which the organic solvent is made to exist in the non-coated parts 5a and 5b by providing a fine hole in the part that contacts with the smoother-1 and allowing the organic solvent to seep out from there. Particularly effective is a method in which an organic solvent is dropped or applied to the non-coated portions 5a, 5b immediately before the coating layer 4 comes into contact with the organic solvent.

The amount of the organic solvent to be applied is sufficient as long as the non-applied areas 5a and 5b are moist when they come into contact with the smoother, and the amount to be applied is determined as appropriate, taking into account the amount of evaporation of the organic solvent, etc. Although it can be set.

Usually, the coating thickness is set within the range of 0.3 to 2.0 times the wet coating thickness of the coated area. If the coating thickness of the organic solvent is greater than 2.0 times the wet film thickness of the coated area, the resin components of the coating layer of the magnetic paint may be eluted, reducing the running durability of the magnetic layer in this area. If it is thinner than 0.3 times, it may not be possible to effectively prevent the generation and scattering of cutting powder.

As the organic solvent used in the production method of the present invention, those generally used in coating resins can be used.In particular, in the present invention, those used in the preparation of ordinary magnetic paints can be used. It is preferable to use an appropriately selected one from among those obtained, and it is further preferable that it contains at least one type of organic solvent from among the organic solvents used in preparing the magnetic paint of the present invention.

Therefore, 1. For example, if cyclohexanone and methyl ethyl ketone are used as the ketone solvent and toluene is used as the aromatic solvent when preparing a magnetic paint,
It is preferable to select at least one organic solvent from cyclohexanone, methyl ethyl ketone, and toluene, and to use it by blending other solvents if necessary. By doing so, the properties of the resin will not change even if the coated layer of magnetic paint comes into contact with an organic solvent.

Furthermore, it is preferable to select and use organic solvents with a relatively high boiling point among the organic solvents used in preparing the magnetic paint. This is because a substance with a low boiling point, such as methyl ethyl ketone, evaporates in a short time after application, so that a sufficient amount of organic solvent may not remain when it comes into contact with the smoother.

In addition, as a rod-shaped smoother made of a non-flexible material,
You can use a regular one.

Furthermore, an improved smoother is used in which the part that contacts the edge of the non-magnetic support material is curved upward into an arc or other shape to avoid contact with the non-magnetic support material as much as possible. I have something to do.

-Other processes- After smoothing the surface of the coating layer using a smoother in this way, when manufacturing tape-shaped magnetic recording media such as video tapes and audio tapes, the magnetic paint is left undried. A magnetic layer is formed by performing a magnetic field orientation treatment in the state of .

This drying also removes the organic solvent present in the non-coated areas 5a and 5b.

Next, a surface smoothing treatment is usually performed using a calender roll or the like.

The magnetic recording medium material obtained in this manner is cut into a desired shape such as a tape shape or a disk shape.

[Example] In the Examples and Comparative Examples described below, the expression "parts" represents "parts by weight."

(Example 1) The magnetic paint component [1] shown below was mixed with cyclohexanone,
Using a mixed solvent of toluene and methyl ethyl ketone (mixing volume ratio = 4:3:3) as a solvent, the mixture was sufficiently kneaded and dispersed using a disper kneader and a ball mill.
Then, immediately before coating, 5 parts of a polyisocyanate compound (Coronate, manufactured by Nippon Polyurethane) was added and mixed to prepare a magnetic paint.

・ ■ Iron oxide magnetic powder・・・・・・・・・・・・・・・・・・
......100 parts (Main component: cobalt-coated iron oxide, Go content 3.2% by weight, specific surface area = 44ba/g, coercive force (He): 6800e) Polyurethane resin...・・・・・・・・・・・・・・・
・・・・・・・・・5 parts: Tuboran 2304, made by Nippon Polyurethane) Phenoxy resin・・・・・・・・・・・・
・・・・・・・・・・・・・・・8 parts (manufactured by P to II former US company U, C, C) α-Alumina・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・7 parts carbon black・・・・
・・・・・・・・・・・・・・・・・・・・・1 part particle size +
50muL.

Specific surface area: 30nf/g, butyl stearate・・・・・・・・・・・・・・・
...3 parts of the obtained magnetic paint was filtered, and a polyethylene terephthalate film support original (thickness: 14
gm) was continuously coated using a reverse roll coater so that the wet film thickness was 35 μLm, leaving a 5 mm uncoated area on both sides.

Next, toluene was added dropwise to the non-coated portion of the support, and the coated layer was immediately smoothed through a smoother. The amount of toluene dropped is based on a wet a film thickness of 30#Lm (30m/m2
) was set.

After smoothing, it was dried by passing through a dryer zone, and then calendered to obtain a magnetic recording medium original fabric.

This original magnetic recording medium was slit into 1/2 inch width to produce a VH5 type videotape.

Of the obtained videotape, the videotape obtained by slitting the original magnetic recording medium within 5 cm from the non-coated part was loaded into a video deck for dropout measurement that was modified from a commercially available VH5 type videotape recorder, and the videotape was dropped. The number of occurrences of outs was measured.

The number of dropouts occurring per minute of videotape running was 11.

Note that the recorded image signal was 100% white, the measured dropout was 3 seconds or more in length, and the reproduction output was reduced by 114 dB or more.

(Comparative Example 1) A VH3 type videotape was manufactured in the same manner as in Example 1 except that toluene was not dropped into the non-coated area, and dropout was performed in the same manner.

The number of occurrences was measured.

The number of dropouts occurring per minute of videotape running was 34.

[Effects of the Invention] According to the method for producing a magnetic recording medium of the present invention, there is no generation or scattering of cutting powder due to contact between the smoother and the non-applied portion of the magnetic paint on the edge of the non-magnetic support material. Therefore, it is possible to effectively prevent the instantaneous drop or dropout of the reproduced signal, such as dropout caused by flying powder that is scattered and attached to the surface of the magnetic layer, which occurs in the conventional method.

Furthermore, since the calender rolls are not contaminated by cutting powder, no recesses are formed on the magnetic layer surface during surface smoothing treatment, which prevents momentary drops or omissions of the reproduced signal such as dropouts. It can be effectively prevented.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of surface smoothing of a coated layer of magnetic paint using a smoother.

Claims (3)

[Claims] (1) Apply magnetic paint to the surface of the long non-magnetic support material, leaving an unpainted part at the edge in the width direction of the non-magnetic support material, and then apply the magnetic paint to the surface of the applied magnetic paint. A method for manufacturing a magnetic recording medium comprising a step of smoothing with a smoother, characterized in that an organic solvent is applied to a non-painted portion of the original non-magnetic material support before smoothing with the smoother. Manufacturing method. (2) The method for manufacturing a magnetic recording medium according to claim 1, wherein the composition of the organic solvent includes at least one solvent among the solvents used for preparing the magnetic coating material. (3) The method for manufacturing a magnetic recording medium according to claim 1, wherein an organic solvent is applied to the non-applied portion immediately before the coated layer of the magnetic paint comes into contact with a smoother.