JPH06290458A - Magnetic field treatment of magnetic coating film - Google Patents

Abstract

PURPOSE:To uniformize a magnetic field distribution between the part near the web center and end of a solenoid coil for applying magnetic fields to a nonmagnetic base having a magnetic coating film by providing the coil with various densities in winding density so as to satisfy specific conditions. CONSTITUTION:The band-shaped nonmagnetic base 11 is coated with a magnetic coating material and is then passed through the inside of the solenoid coil 10 in the coating direction prior to drying of the magnetic coating film, the by the magnetic field is impressed to the magnetic coating film and the magnetic field treatment of the magnetic coating film is executed. The coil 10 is wound more coarsely in a winding part 16 existing on the outer side of the end of the base 11, i.e., the side part, than in a winding part 14 existing above the web center 18 of the coating surface 13 coated with the magnetic coating film and a winding part 15 existing below the web center. The winding density expressed by the number of windings per unit length of the solenoid coil is 0.77 times the winding density of the winding parts 14 and 15, in such a case.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic coating film for magnetic field orientation or non-orientation after coating a non-magnetic support with a magnetic coating used for magnetic recording media such as floppy disks and magnetic tapes. It is related to the magnetic field processing method.

[0002]

2. Description of the Related Art A magnetic recording medium such as a floppy disk is usually provided with a magnetic coating material mainly composed of magnetic powder and a binder on a long non-magnetic support made of polyester or the like. It is manufactured by coating and drying and solidifying the coated magnetic coating film. At this time, since the magnetic powder in the magnetic coating film is subjected to orientation or non-orientation treatment, before the magnetic coating film is dried after coating, for example, a non-magnetic support in which a magnetic coating material is coated in a rectangular solenoid coil. The magnetic field (DC magnetic field in the case of orientation, alternating magnetic field in the case of non-orientation) is applied while the non-magnetic support passes through the solenoid coil to control the direction of the magnetic powder in the desired direction. A method has been proposed.

FIG. 3 is a schematic diagram showing an example of such a magnetic field treatment method. The magnetic paint is sent from a stock container 35 to a coater head 33 through a liquid sending pipe 36 after a dispersion process. A long non-magnetic support 32 made of polyethylene terephthalate or the like is coated with magnetic paint while advancing in the direction shown by the arrow in the figure, and further passes through a normal rectangular solenoid coil 31 that generates a magnetic field, and then dried. The magnetic coating film is dried in the container 37.

FIG. 4 is an enlarged perspective view showing the vicinity of the solenoid coil 31. The undried magnetic coating film on the non-magnetic support 32 gives an appropriate magnetic field when passing through the coil 31. Received, oriented or non-oriented. FIG. 5 is a graph showing a magnetic field intensity distribution obtained from such a rectangular solenoid coil (width 50 cm, length 30 cm). Note that, hereinafter, the coating direction, the width direction, and the vertical direction are the directions shown in FIG. 4, respectively. In FIG. 5, the horizontal axis represents the distance in the coating direction, with the center in the length direction of the coil (hereinafter referred to as the coil center) being 0, and the vertical axis represents the strength at the maximum magnetic field strength. 1
Is the magnetic field strength. In addition, in FIG.
1a and 51b are the center of the non-magnetic support in the width direction (shown by the dotted line 33 in FIG. 4, hereinafter referred to as the web center) and the distribution of the application direction component of the magnetic field at a position 15 cm away from the web center in the width direction. Is. Moreover, 52 is the distribution of the width direction component of the magnetic field at a location 15 cm away from the center of the web in the width direction. Although not shown in FIG. 5, the widthwise component of the magnetic field at the center of the web is substantially zero. As is clear from Fig. 5, the web center and 1 from there
It can be seen that there is a difference in the strength of the magnetic field at the point 5 cm away.

Therefore, when the above-mentioned magnetic field treatment is carried out using such an ordinary rectangular solenoid coil, the portion of the magnetic coating on the non-magnetic support which has passed near the center of the web and the web. There is a drawback that the characteristics are different from those of a portion that passes through a portion (hereinafter, referred to as a web end portion) that is largely displaced from the center in the width direction. It is considered that such non-uniformity of the magnetic field distribution near the center of the web of the coil and at the end of the web is due to the magnetic field generated by the current flowing in the vertical direction at the side of the coil, which is indicated by 34 in FIG. That is, such nonuniformity occurs because the application direction component and the width direction component of the magnetic field are different between the central portion of the web and the end portion of the web.

In order to eliminate such non-uniformity, there is also a method of using a coil having a sufficiently wide frontage with respect to the width of the non-magnetic support (base film) used. In this case, however, the power source becomes larger as the coil becomes larger. There is a drawback that the capacity is inevitably large and the power consumption is large.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of these problems and has been made in order to solve the problems. The purpose of the present invention is to provide a magnetic material having uniform properties at each point of a non-magnetic support. It is to provide a magnetic field treatment method for a coating film. As a result of earnest studies to achieve the above object, the present inventor has found that when a coil having a specific winding configuration is used for magnetic field treatment, the magnetic field distribution is substantially uniform near the center of the web of the coil and the end of the web. Therefore, they have found that it is possible to provide a magnetic recording medium having an extremely small difference in characteristics when a magnetic coating film on a non-magnetic support is oriented or non-oriented.

That is, the gist of the present invention is to apply a magnetic coating material to a running belt-shaped non-magnetic support to form a magnetic coating film, and before the magnetic coating film dries, the non-magnetic support is solenoid-operated. A magnetic field is applied by passing it through a coil, and in the magnetic field treatment method for a magnetic coating film, which comprises orienting or non-orienting the magnetic coating film, as the solenoid coil,
The winding density, which is represented by the number of windings per unit length, is smaller at the end of the non-magnetic support than at the widthwise center of the non-magnetic support. A magnetic field treatment method for a magnetic coating film, characterized in that a solenoid coil provided with is used.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below in more detail with reference to the drawings. FIG. 1 is a perspective view showing an example of a solenoid coil for carrying out the method of the present invention. Note that, hereinafter, the application direction, the width direction, and the vertical direction are the directions shown in FIG.

The strip-shaped non-magnetic support 11 passes through the inside of the solenoid coil 10 in the coating direction after the magnetic coating is applied and before the formed magnetic coating is dried, and a magnetic field is applied to the magnetic coating. The magnetic field treatment of the membrane is performed. The coil 10 is located outside or on the side of the end of the non-magnetic support 11 than the winding portion 14 above the web center 18 and the winding portion 15 below the web center 18 of the coating surface 13 coated with the magnetic coating film. Winding part 16
Is wound more sparsely. For example, in this case, the winding density (hereinafter, also referred to as pitch) represented by the number of windings per unit length of the solenoid coil is about 0 in the winding portions 14 and 15. ．
It is 77 times. Winding portion 14 with pitch of winding portion 16
The ratio of the pitches at 15 and 15 is not particularly limited and depends on the overall shape of the solenoid coil, but the magnetic field distribution in the width direction may be made as uniform as possible. Also, the current flowing in the coil is
The direct current is used for the orientation treatment, and the alternating current is used for the non-orientation treatment, but the conditions such as the strength thereof may be appropriately optimized according to the type of the magnetic paint.

FIG. 2 is a graph showing the intensity distribution of the magnetic field obtained from the same solenoid coil (width 50 cm, length 30 cm) as in FIG. Both the horizontal axis and the vertical axis are the same as the horizontal axis and the vertical axis in FIG. 2 in FIG.
1a, 21b and 22 are 51a in FIG. 5, respectively.
51b and 52, in order, the distribution of the application direction component of the magnetic field at the center of the web, and the distribution of the application direction component of the magnetic field at a location 15 cm away from the center of the web in the width direction, and its width direction component. Is the distribution of. In addition,
As in FIG. 5, the widthwise component of the magnetic field at the center of the web is substantially zero. As is apparent from FIG. 2, there is substantially no difference in the distribution of the magnetic field between the center of the web and the place 15 cm away from it. This means that the distribution of the magnetic field in the width direction is substantially uniform.

In the present invention, the magnetic field treatment is carried out by passing the inside of the solenoid coil through a non-magnetic support having an undried magnetic coating film. The magnetic paint is mainly composed of magnetic powder and a binder, and may also contain various additives such as a lubricant, an abrasive, an antistatic agent and a dispersant. Examples of the magnetic powder include Fe, Ni, Co, Fe-Co alloy, Fe-Ni alloy, Fe-Co-Ni alloy, and Fe-N.
i-Zn alloy, Fe-Co-Ni-Cr alloy, Co-N
Powders of ferromagnetic metals such as i alloys such as Fe, Ni and Co, or magnetic alloys containing these as the main components, γ-Fe ₂ O ₃ , F
e ₃ O ₄ , Co-containing γ-Fe ₂ O ₃ , Co-containing Fe ₃ O
Iron oxide magnetic powder such as ₄ , CrO ₂ , barium ferrite,
Examples thereof include various ferromagnetic powders such as metal oxide magnetic powders such as strontium ferrite.

The amount of the magnetic powder used is such that the content of the ferromagnetic powder in the magnetic layer formed after drying the magnetic coating film is 50 to 90% by weight, particularly 55 to 85% by weight. Is preferred. As the binder, one having excellent adhesion to the non-magnetic support and abrasion resistance is appropriately used. For example, polyurethane resins, polyester resins, cellulose acetate butyrate, cellulose diacetate, cellulose derivatives such as nitrocellulose, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylic copolymers. Examples thereof include vinyl chloride resins such as polymers, various synthetic rubbers such as styrene-butadiene copolymers, epoxy resins, phenoxy resins, etc. These may be used alone or in combination of two or more.

The binder is preferably used so that its content in the magnetic layer is 2 to 50% by weight, particularly 5 to 35% by weight. By further incorporating a low molecular weight polyisocyanate compound having a plurality of isocyanate groups into the magnetic paint, it is possible to form a three-dimensional network structure in the magnetic layer and improve its mechanical strength. Examples of such a low molecular weight polyisocyanate compound include a trimethylolpropane adduct of tolylene diisocyanate. Such a low molecular weight polyisocyanate compound is preferably used in a proportion of 5 to 100% by weight with respect to the binder.

As the lubricant, various kinds of lubricants such as aliphatic type, fluorine type, silicone type and hydrocarbon type can be used. Examples of the aliphatic lubricant include fatty acids, fatty acid metal salts, fatty acid esters, fatty acid amides, and aliphatic alcohols. Examples of the fatty acid include oleic acid, lauric acid, myristic acid, palmitic acid, stearic acid and behenic acid. Examples of the fatty acid metal salt include magnesium salts, aluminum salts, sodium salts and calcium salts of these fatty acids.
Examples of the fatty acid ester include butyl ester, octyl ester and glyceride of the above fatty acids, and examples of the fatty acid amide include amides of the above acids, linoleic acid amide and caproic acid amide. Examples of the aliphatic alcohol include lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, oleyl alcohol and the like.

Examples of fluorine-based lubricants include perfluoroalkyl polyethers and perfluoroalkyl carboxylic acids. As a silicone lubricant,
Examples thereof include silicone oil and modified silicone oil. Further, solid lubricants such as molybdenum disulfide and tungsten disulfide, and phosphoric acid esters can also be used. Hydrocarbon lubricants include, for example, paraffin, squalane,
Wax etc. are mentioned. The content of the lubricant in the magnetic layer is usually 0.1 to 20% by weight, preferably 1 to 1
The range is 0% by weight. When two magnetic layers are laminated, the content of the lubricant may be different between the upper layer and the lower layer.

Examples of the abrasive include alumina, fused alumina, corundum, silicon carbide, chromium oxide, silicon nitride and the like, and among these, those having relatively high hardness are preferably used. The number average particle diameter is preferably 2 μm or less. The content of the abrasive in the magnetic layer is preferably in the range of 1 to 20% by weight. Examples of the antistatic agent include natural surfactants such as carbon black, graphite and saponin, nonionic surfactants such as alkylene oxide and glycerin, higher alkylamines, quaternary ammonium salts, pyridine and other heterocycles. Cationic surfactants, anionic surfactants containing acidic groups such as carboxylic acid groups, sulfonic acid groups, phosphoric acid groups, sulfuric acid ester groups, phosphoric acid ester groups, amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of aminoalcohols And amphoteric surfactants and the like are used. In addition,
These surfactants may be used alone or in combination. The amount of the antistatic agent used is usually in the range of 1 to 15% by weight in the magnetic layer. These are used as antistatic agents, but sometimes their purpose is to improve dispersibility and lubricity.

Examples of the dispersant include fatty acids having 12 to 18 carbon atoms such as capric acid, lauric acid, myristic acid, oleic acid and linoleic acid, metal soaps composed of alkali metal or alkaline earth metal salts of these fatty acids, lecithin and the like. Is used. The amount of the dispersant used is usually in the range of 0 to 20% by weight in the magnetic layer. The magnetic paint can be usually obtained by kneading and dispersing the above-mentioned components together with a solvent. Examples of the solvent include ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, alcohols such as methanol, ethanol, propanol and isopropyl alcohol, esters such as methyl acetate, ethyl acetate and butyl acetate, ethers such as diethyl ether and tetrahydrofuran. And aromatic hydrocarbons such as benzene, toluene and xylene, and aliphatic hydrocarbons such as hexane.

The kneading and dispersing methods, the addition order of each component, and the like may be the usual methods applied to the kneading and dispersing of magnetic coating materials. As the non-magnetic support, polyesters such as polyethylene terephthalate and polyethylene naphthalate,
Polyolefins such as polypropylene and polyethylene,
Cellulose derivatives such as cellulose acetate, various plastics such as polycarbonate, polyamide, and polyimide, and glass can also be used.

As a method for applying the magnetic coating material on such a support, various methods which are usually applied, such as air doctor coating, blade coating, reverse roll coating and gravure coating, are adopted. When a plurality of magnetic coating materials are applied, the lower layer coating solution and the upper layer coating solution may be applied simultaneously in a wet state, or each layer may be applied sequentially. Of the components of the magnetic paint mentioned above,
A magnetic paint was prepared with the composition shown below.

[0021]

[Table 1] Co-γ-Fe ₂ O ₃ (Hc = 700 Oe, SSA = 20 m ² / g) 100 parts by weight Polyurethane (manufactured by Nippon Polyurethane Company; N2304, MDI-based polyester polyurethane) 18 parts by weight Vinyl chloride / vinyl acetate / Vinyl alcohol copolymer (US Union Carbide Co .; VAGH) 18 parts by weight α-alumina (particle size: 0.5 μm) 3 parts by weight Carbon black (Mitsubishi Kasei; # 3250B) 8 parts by weight Lecithin 5 parts by weight Butyl stearate 5 parts by weight Methyl ethyl ketone 170 parts by weight Cyclohexanone 170 parts by weight

The above magnetic coating material was applied onto a non-magnetic support made of polyester by using a coating machine, and the solenoid coil shown in FIG. 1 (width 50 cm, length 30 cm, Example 1) or the solenoid shown in FIG. Coil (width of frontage 50c
m, length 30 cm, comparative example 1) was used for non-orientation treatment. The applied magnetic field is an alternating magnetic field with a peak intensity of 300 Oe. After the treatment, a floppy disk was produced by a conventional method, and the modulation of the floppy disk obtained from each of the central portion and the end portion of the web was measured. The modulation is data indicating the variation in the output of one round of the disk, and the variation in the output with respect to the average value of the outputs is expressed in%. In this case, it is an average value of 27 pieces of sampling data. The results are shown in Table-1.

[0023]

[Table 2]

As can be seen from Table 1, when the method of the present invention is used (Example 1), the difference in modulation between the center of the web and the end of the web is small, and the difference in characteristics is small.

[0025]

According to the method of the present invention, the difference in the characteristics of the magnetic coating film between the center of the web and the end of the web can be made extremely small. Moreover, the size of the coil used in the present invention only needs to be such that the width of the base film can be passed, and it can be made small, so that the coil and the power supply are inexpensive, and therefore the power consumption is extremely low, which is extremely economical. Is.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a coil for carrying out the method of the present invention.

FIG. 2 is a graph showing an example of a magnetic field intensity distribution obtained from the coil of FIG.

FIG. 3 is a schematic diagram showing an example of a normal magnetic field processing method.

FIG. 4 is a perspective view showing an example of a coil used for normal magnetic field processing.

5 is a graph showing an example of a magnetic field intensity distribution obtained from the coil of FIG.

[Explanation of symbols]

 10 coil 11 non-magnetic support

Claims (1)

[Claims] 1. A magnetic coating is applied on a running belt-shaped non-magnetic support to form a magnetic coating, and the non-magnetic support is passed through a solenoid coil before the magnetic coating is dried. In the magnetic field treatment method for a magnetic coating film, which comprises orienting or non-orienting the magnetic coating film, the solenoid coil has a winding density represented by the number of windings per unit length as described above. A magnetic coating film is characterized in that a solenoid coil having a winding density is used so that the end portion of the nonmagnetic support is smaller than the widthwise center of the nonmagnetic support. Magnetic field processing method.