JPH03214422A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a good magnetic layer by smoothening a nonmagnetic supporting body, forming a dummy layer thereon, smoothening its surface and then forming a magnetic layer thereon. CONSTITUTION:A dummy layer 11 is formed on a nonmagnetic supporting body 2. This dummy layer essentially comprises a polymer resin which can be easily treated for smoothening compared to the supporting body 2 or this polymer resin and nonmagnetic particles. The dummy layer 11 is subjected to calendering after smoothening treatment is performed on the surface of the layer 11, on which a magnetic layer 12 is formed. Since the magnetic layer 12 is applied on the dummy layer 11 having good surface property, the magnetic layer 12 can be also made to have good surface property even if the surface property of the supporting body 2 is bad. Thereby, the magnetic layer having high reproduction output, low tape noise and good surface smoothness can be formed as a thin layer on a cheap supporting body 2 having rather bad surface smoothness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a magnetic recording medium, and particularly to a method for manufacturing a magnetic recording medium in which a magnetic layer is formed on a nonmagnetic support.

[Conventional technology]

Conventionally, the general manufacturing method for magnetic recording media, such as magnetic tapes such as audio tapes and video tapes, and magnetic disks such as Fronopy disks, has been to apply magnetic coating onto a non-magnetic support that is wider than normal products. After applying a liquid to form a magnetic layer, performing an orientation treatment and drying the magnetic layer, the surface of the magnetic layer is smoothed to produce a tape material, and then, in a cutting process, the tape material is It is manufactured by cutting the tape into a predetermined tape width or shape. The surface smoothing treatment is performed to polish or smooth the surface of the magnetic layer, improve the packing density, or make the coating thickness uniform. This is effective for improving playback output and reducing tape noise.

Furthermore, in recent years, there has been a strong demand for increasing the storage capacity of magnetic recording media, and it is necessary to increase the information recording density per unit area of magnetic recording media.

Therefore, in order to increase the information recording density, it is necessary to concentrate the write magnetic flux generated from the magnetic head that records and reproduces information in a minute area. Magnetic flux crabs will become extinct. Therefore, in order to reverse the direction of magnetization of the magnetic layer with the extinguished magnetic flux as shown in (1)--, the volume of the magnetic layer must be reduced, that is, the thickness of the n-type layer must be decreased. Since it is not possible to perform complete magnetization reversal, it has become necessary to reduce the thickness of the magnetic layer of the magnetic recording medium.

In addition, for coated magnetic recording media in which a magnetic coating solution in which the above-described powdery d-material is dispersed in an organic binder is coated on a non-magnetic support and dried, the coercive force and residual magnetic flux density B , is large, and the thickness of the magnetic layer can be made extremely thin. A ferromagnetic metal thin film type magnetic recording medium in which a metal thin film made of a ferromagnetic metal material is directly deposited on a nonmagnetic support by vacuum evaporation or the like. is starting to be used.

[Problem to be solved by the invention]

However, the smoothness of the surface of the magnetic layer is effective for improving the reproduction output of magnetic recording media and reducing tape noise.
Since the magnetic layer is closely related to the smoothness of the surface of the non-magnetic support on which the magnetic layer is formed, it is necessary to use a non-magnetic support with good surface smoothness in order to obtain a smooth magnetic layer surface. As mentioned above, the thinner the surface of the magnetic layer is, the more easily it is affected by the smoothness of the surface of the nonmagnetic support. Therefore, in order to obtain a magnetic recording medium with good magnetic properties, it is necessary to use a nonmagnetic support with good surface smoothness, but such nonmagnetic support materials are expensive and the manufacturing cost is high. The problem is that it gets expensive. Therefore, an object of the present invention is to solve the above problems, and to provide a magnetic layer with good surface smoothness, high playback output, low tape noise, even on the surface of an inexpensive non-magnetic support with poor surface smoothness. An object of the present invention is to provide a method for manufacturing a magnetic recording medium that can form a thin layer of magnetic recording media at low manufacturing cost.

[Failure to solve the problem]

The above object of the present invention is to form on a non-magnetic support a polymer resin whose surface is easier to smoothen than the non-magnetic support, or a dummy layer mainly composed of the polymer resin and non-magnetic particles. This is achieved by a method of manufacturing a magnetic recording medium, which comprises forming a magnetic layer on the dummy layer after smoothing the surface of the dummy layer. In addition, the polymer resin whose surface can be easily smoothed as described above is a polymer resin with a low softening temperature (l50
℃ or less), or a polymer resin with a low pressure applied by a pressure roll, and whose surface is easier to smoothen than polyethylene terephthalate (PET), which is generally used as the non-magnetic support. Molecular resins are preferred;
The polymer resin used in the dummy layer of the present invention includes:
For example, thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof can be used. As a thermoplastic resin, the softening temperature is 150°C or less and the average molecular weight is 1000.
0 to 300,000, and the degree of polymerization is about 50 to 2,000, such as vinyl chloride vinyl acetate copolymer, vinyl chloride polymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer Polymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, nylon Silicone resin, nitrocellulose-bolyamide resin, polyfukkavinyl, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose) brobiofluorite, nitrocellulose, ethylcellulose, methylcellulose, probilcellulose, methylethylcellulose, carboxymethylcellulose, acetylcellulose, etc.), styrene-butadiene copolymer,
Polyester resins, chlorovinyl ether acrylate copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof can be used.

Thermosetting resins or reactive resins have a molecular weight of 200,000 or less in the form of a coating solution, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Among these resins, those that do not melt before the resin is thermally decomposed are preferred. Specifically, for example, phenol resin, phenokine resin, evoquine resin, polyurethane curable resin, urea resin, melamine resin, alkynod resin, silicone resin, acrylic reaction resin, epoxy-bolyamide resin, nitrocellulose melamine resin, high molecular weight polyester resin. and isocyanate 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, These include polyamine resins, polyimine resins, and mixtures thereof. These thermoplastic resins, thermosetting resins, and reactive resins are
In addition to the main functional groups, functional groups include acidic groups such as carbonic acid, sulfinic acid, sulfenic acid, sulfonic acid, phosphoric acid, sulfuric acid, phosphonic acid, phosphine, boric acid, sulfuric acid ester groups, phosphoric ester groups, and alkyl ester groups thereof, and amino acids. Classes: Aminosulfonic acids, sulfuric or phosphoric acid esters of amino alcohols, amphoteric groups such as alkylhetaine types, amino groups, imino groups, imido groups, amide groups, eboxy groups, etc. Also, hydroxyl groups, alkosyl groups, thiol groups , a halogen group, a silyl group, and a siloxane group, usually containing one to six types, and each functional group contains 1 XIO-' per 1 g of resin.
It is preferable to include eq-I XIO-"eq.

Further, examples of the non-magnetic particles include carpon blank, α-alumina, T-alumina, αr-alumina,
Fused alumina, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond, α-iron oxide, garnet, emery (main components: corundum and magnetite), garnite, silica, silicon nitride, boron nitride, tungsten carbide, titanium Carbide, quartz, tripoli, diatomaceous earth, Vlomite, etc. can be used singly or in combination. Furthermore, if the size of these particles is too large, the surface properties of the surface to which the magnetic layer is coated will deteriorate, while if they are too small, the reinforcing effect of the dummy layer cannot be expected to be so great. Particles of 1 to 2 μm are desirable. Further, the mixing ratio of the particles is desirably 70% or less by weight of the resin constituting the dummy layer.

Furthermore, the dummy layer can be formed by various coating methods such as roll coating, gravure coating, extrusion hend, and doctor blade method.

[Embodiment]

Hereinafter, one embodiment of the method for manufacturing a magnetic recording medium according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing the manufacturing process of a magnetic recording medium based on the manufacturing method of the present invention. The support body 2 fed out from the feed-out port l is shown in FIG.
As shown in a), it is a non-magnetic support with relatively poor surface properties. Therefore, after coating the surface of the support 2 with a dummy layer 11 made of a polymer resin whose surface can be easily smoothed to a thickness of about 1 to 4 μm, the dummy layer 11 is coated in a drying zone 5. Dry and solidify layer 11. A liquid supply system 4 that feeds the polymer resin continuously and at a constant flow rate is connected to the first coating nozzle 3, and the polymer resin is coated on the support body with a uniform coating thickness. Apply. At this time,
The surface of the dummy layer 11 remains relatively poor in surface properties, as shown by (+) in FIG. Next, the surface of the support 2 coated with the dummy layer 11 is calendered using a pair of calender rolls 6a and 6b. At this time, the calender rolls 6a and 6b are heated to about 80°C and heated to about 150 to 400°C.
The support 2 is pressed with a pressure of kgw/cm. In other words, the polymer resin constituting the dummy rill is mainly composed of a polymer resin with a softening temperature of 150°C or less, which is relatively easy to smooth the surface of, and therefore As shown in Cl, the surface 6 of the support 2
The surface of the applied dummy layer 11 is smoothed to have good surface properties.

Then, a second coating layer 1'7 is applied to the surface of the support 2 described in iii.
A magnetic coating liquid is applied thereto and dried and solidified in a drying zone 9 to form a magnetic layer 12. To the second application of I, G7
A liquid supply system 8 for feeding the magnetic coating liquid continuously and at a constant flow rate communicates with the magnetic coating liquid, and the magnetic coating liquid is coated onto the support body with a uniform coating thickness.

Here, since the magnetic layer l2 is coated on the surface of the dummy layer 11 having good surface properties, the magnetic layer l2
Even if it is a non-magnetic support with relatively poor surface properties, the surface of the magnetic layer l2 can have good surface properties as shown in (dl) in FIG. The dried support 2 is wound up on a take-up roll 10 and sent to the next process such as a calendering process for the magnetic layer.

Therefore, it is possible to form a thin magnetic layer with high reproduction output, low tape noise, and good surface smoothness even on an inexpensive nonmagnetic support with relatively poor surface properties.

In addition, by adding non-magnetic particles such as α-A1.03 to the polymer resin constituting the dummy layer 11 whose surface is relatively easy to smooth, it is possible to It is possible to improve the film strength against defects such as resin missing and to prevent the dummy layer resin from adhering to the calender roll. Furthermore, since conventionally a non-magnetic support with a smooth surface was used, a banok coat layer was provided to roughen the surface of the diamagnetic layer of the support in order to improve the running properties of the magnetic tape in recording and reproducing devices. Therefore, frictional resistance had to be lowered. However, according to the coating method of the present invention, it is possible to form a magnetic layer on a non-magnetic support whose surface properties are relatively poor. The surface of the diamagnetic layer is rough from the beginning, and there is no need for roughening treatment.

In the above-mentioned Example B, the dummy layer It is applied by extrusion, but the present invention is not limited to this, and other application methods such as roll coating and gravure coating may be used. be able to.

Further, although the magnetic layer I2 is also applied using an extrusion head, it is of course possible to use other application means. It can also be applied to ferromagnetic metal thin film type magnetic recording media. Furthermore, it goes without saying that the magnetic layer can have a multilayer structure. Furthermore, the manufacturing process of the magnetic recording medium is not limited to the manufacturing process of the above embodiment. For example, the orientation (
(magnetic field orientation treatment) may also be performed. [Effects of the Invention] The method for manufacturing a magnetic recording medium of the present invention comprises coating a polymer resin whose surface is easier to smoothen than the non-magnetic support, or a polymer resin and non-magnetic particles on a non-magnetic support. After forming a dummy layer containing the main component and smoothing the surface of the dummy layer, a magnetic layer is formed on the dummy layer, so that the non-magnetic support is a support with relatively poor surface properties. However, the surface of the magnetic layer formed on the nonmagnetic support can have good surface properties.

Therefore, this is an inexpensive magnetic recording medium that can produce a thin magnetic layer with high playback output, low tape noise, and good surface smoothness even on the surface of an inexpensive non-magnetic support with poor surface smoothness. We can provide a manufacturing method for [Example] Hereinafter, the novel effects of the present invention will be made clearer by way of an example of the present invention. Magnetic Coating Liquids A and B were prepared by placing magnetic coating l& having the composition shown in Tables 1 and 2 below in a ball mill and mixing and dispersing for 10.5 hours. Magnetic coating liquid A thus obtained,
When the equilibrium viscosity of H was measured, the shear rate was l
0.25 pois for each O'sec-'
e and 0.30 poise.

Table 1 Composition r −Fe20,, tj〕10
0 parts by weight (S.Et value: 35rrr/g)・
2L・Locellulose lo heavy M part・
Polyisocyanate carbon black (average particle size = 20 mμm) 8 parts by weight 2 parts by weight Methyl ethyl ketone 300 parts by weight Second Table Composition Nitrocellulose 10 parts by weight Polyisocyanate 8 parts by weight Cr. 03 2 parts by weight Stearic acid 1 part by weight Butyl stearate 1 part by weight Methyl ethyl ketone 300 parts by weight Put it in IO. After mixing and dispersing for 5 hours, dummy layer coating solution A. B was prepared. When the equilibrium viscosities of the thus obtained dummy N coating solutions A and B were measured, they were 0.24 poise and 0.32 poise, respectively, at a shear rate of l x 10'sec-', as shown in Table 3 Composition Nitrocellulose 50 Weight Parts by weight Polyisocyanate 8 parts by weight Methyl ethyl ketone 300 parts by weight Table 4 Composition α1A N z O x 10 parts by weight Nitrocellulose 40 parts by weight Polyisocyanate 8 parts by weight Methyl ethyl ketone 300 parts by weight (Example 1
) Conveyance efficiency: Thickness when traveling at 200 m/min: 11.7
μm1 width = 300 theory, surface roughness: O. The above-mentioned dummy layer coating solution A was applied onto a polyethylene terephthalate support having a thickness of tS μm based on the manufacturing process of the magnetic recording medium described in the embodiment above, and dried to form a dummy layer with a dry thickness of 3.3 μm. Dry thickness of coating solution A is 4.2μ
A magnetic layer was formed by coating the material in an amount of m. However, the coating head used for coating the dummy layer is the same as the extrusion type coating head disclosed in Japanese Patent Application Laid-Open No. 60-238179, and the general configuration of the coating head 7r section is the slot width 2. 〇． 6m, diameter of pocket part:
The birch has a radius of curvature of 20 mm, a radius of curvature of the doctor edge surface: 15 mm, an effective length of the doctor edge surface of 261 mm, an effective length of the pack edge surface: 7.5 m, and a coating width of 250 cm. The dummy layer was dried and solidified by vertical air flow drying at 80°C, and the dummy layer was calendered using two hard chrome plated rolls with a diameter of 250 mm and a surface texture of 0.01 μm. Calendar linear pressure:
The test was carried out at 200 kgw/cm and a calendar temperature of 80°C. Furthermore, the coating head used for coating the magnetic layer was also manufactured by Japanese Patent Application Laid-open No. 6
It is the same as the extrusion-type coating tool disclosed in Publication No. 0-238179, and the approximate configuration of the coating end part is width of width = 0.6mm, diameter of blurring part: 20mm.
mm, Radius of curvature of Doctor Enoji surface: IO+μm,
Effective length of Tokuta Enoji surface: 5. Effective length of back Enoji surface: 7. 5 IIlm, coating width: 25
I made it so that it was 0 strokes. Further, the drying and solidification of the magnetic layer was performed in the same manner as the drying and solidification of the dummy layer, and the calendering treatment of the magnetic layer was performed in the same manner as the calendering treatment of the dummy layer after it was once wound up on a take-up roll.

The surface roughness of the magnetic layer in the magnetic recording medium thus obtained was measured. The results are shown in Table 5.

(Example 2) Instead of the dummy layer coating liquid 8 in Example 1,
A magnetic recording medium was prepared under the same conditions as in Example 1, except that dummy layer coating liquid B containing non-magnetic particles was used, and the surface roughness of the magnetic layer in this magnetic recording medium was measured. The results are shown in Table 5. (Example 3) Conveyance speed: Traveled at 200 m/min Thickness: 11.7
μm, convergence: 300 ms, surface roughness: 0.15 μm On a polyethylene terephthalate support, the above dummy layer coating solution A is applied based on the manufacturing process of the magnetic recording medium described in the above embodiment, and dried to obtain a dry thickness. After forming a dummy layer of 3.3 μm, the above magnetic coating liquid 8 was applied in layers so that the lower layer had a dry thickness of 3.5 μrn, and the above magnetic coating liquid B was applied as an upper layer with a dry thickness of 0.7 μrn. A magnetic layer with a two-layer structure was formed.

However, the coating nozzle used for coating the dummy layer was the same as that used in Example 1 above, and the calendering was performed in the same manner. Further, the coating helix used for the multilayer coating of the magnetic layer is the same as the EX] Lujon type coating hept disclosed in JP-A No. 63-88080, and the general configuration of the coating helix portion is the width of the slot for the lower layer. : 0.6mm, upper layer slot width + 0.5m, lower layer pocket diameter: 20-, upper layer pocket diameter: 15m, radius of curvature of first doctor edge surface: 15■, curvature of second doctor edge surface Radius: 20m, effective length of first doctor surface: 5
The effective length of the surface was set to 6 μm, and the coating radius was set to 250 m. Further, the drying and solidification of the magnetic layer was performed in the same manner as the drying and solidification of the dummy layer, and the calendering treatment of the magnetic layer was performed in the same manner as the calendering treatment of the dummy layer after it was once wound up on a take-up roll.

The surface roughness of the magnetic layer in the magnetic recording medium thus obtained was measured. The results are shown in Table 5. (Comparative Example 1) Thickness when traveling at conveyance speed: 200 m/min: 11.7
On a polyethylene terephthalate support having gm, width: 300 wa, and surface thickness: 0.15 μm, the magnetic coating solution A was applied to a dry thickness of 4.2 μm to form a magnetic layer.

However, the coating nozzle used for coating the magnetic layer is the same as the extrusion type coating nozzle used to coat the magnetic layer in Example 1 above, and the drying and solidification of the magnetic layer is also the same as that used for drying the magnetic layer in Example 1. The solidification was carried out in the same manner as the calendering of the magnetic layer, and the calendering of the magnetic layer was carried out in the same manner as that of the magnetic layer in Example 1 above. The surface roughness of the magnetic layer in the magnetic recording medium thus obtained was measured. The results are shown in Table 5. (Comparative Example 2) Conveyance speed: Traveled at 200 m/min Thickness: I1.7p
The above magnetic coating liquid A was applied onto a polyethylene terephthalate support having a width of 300 m and a surface roughness of 0.15 μm.
A two-layer magnetic layer was formed by applying the magnetic coating solution B as a lower layer with a dry thickness of 3.5 μm and an upper layer with a dry thickness of 0.7 μm. However, the coating method used for the multilayer coating of the magnetic layer was the same as that used in Example 3 above, and the drying and solidification of the magnetic layer was also performed in the same manner as the drying and solidification of the magnetic layer in Example 3. The calender treatment of the magnetic layer was also carried out on the same calender treatment of the magnetic layer as in Example 3 above. The surface roughness of the magnetic layer in the magnetic recording medium thus obtained was measured. The results are shown in Table 5.

Table 5 As is clear from Table 5 above, the magnetic recording medium obtained by the coating method based on the present invention has a smoother magnetic layer surface than the magnetic recording medium of the comparative example obtained under the same conditions. You can see that

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the manufacturing process of a magnetic recording medium based on the manufacturing method of the present invention, and FIG. 2 is an enlarged sectional view showing the state in the manufacturing process of a magnetic recording medium based on the manufacturing method of the present invention. It is. (Symbols in the figure) 1 - Feeding outlet - 2 - Support 3 - 1st coating head 4 - Liquid supply system 5 Drying zones 6a, 6b Calendar roll 7 2nd coating nozzle 8 - Liquid supply system

Claims (1)

[Claims] 1) Forming on a non-magnetic support a polymer resin whose surface is easier to smoothen than the non-magnetic support, or a dummy layer mainly composed of the polymer resin and non-magnetic particles. A method for manufacturing a magnetic recording medium, comprising: forming a magnetic layer on the dummy layer after smoothing the surface of the dummy layer. 2) The method for manufacturing a magnetic recording medium according to claim 1, wherein the dummy layer is made of at least one type of resin selected from thermoplastic resin, thermosetting resin, and reactive resin. 3) The non-magnetic particles in the dummy layer have an average particle size of 0.01
2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the magnetic recording medium comprises particles of ~2 μm. 4) The dummy layer is made of at least one type of resin selected from thermoplastic resin, thermosetting resin, and reactive resin, and the nonmagnetic particles in the dummy layer have an average particle size of 0.01 to 2 μm.
2. The method for manufacturing a magnetic recording medium according to claim 1, comprising particles of.