JPS621120A - Method and apparatus for producing magnetic recording medium - Google Patents

Abstract

PURPOSE:To effectively make magnetic particles non-oriented by a simple device by forming a layer contg. the magnetic particles on a base and passing the base through plural orienting magnetic fields having substantially the same magnetic field intensity so that the magnetic particles are made non-oriented. CONSTITUTION:The magnetic particles in a coated film receive the effect by which the magnetic particles are oriented in a conveying direction 7 from magnetic lines of forces 11 (in parallel with the conveying direction 7) of bar magnets 4a-1, 4a-2, ..., 4a-n and 4b-1, 4b-2, ..., 4b-n when the base 1 enters the plural orienting magnetic fields 4. However, the drying of the coated film is started by hot wind 5b before the magnetic particles are oriented in the direction 7 and the movement of the magnetic particles is hindered by the drying of the coated film in the stage of being oriented in the direction 7, by which the directions thereof are made random and the magnetic particles are made non-oriented. Each magnetic field intensity is made smaller than the coercive force of the magnetic particles and is preferably made about 10-50% thereof. The number (n) of the magnets for forming the plural orienting magnetic fields is preferably >=3 pieces, more preferably >=10 pieces. The magnetic field intensities of these magnets are made substantially the same in terms of the operability of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a method and apparatus for manufacturing a magnetic recording medium.

BACKGROUND OF THE INVENTION Magnetic recording media are widely used as magnetic tapes for audio and other recording purposes, magnetic recording tapes for VTRs, magnetic disks for computers, word processors, and the like. Since a magnetic tape for a VTR comes into sliding contact obliquely with a magnetic head at a predetermined angle, it is inconvenient for the magnetic particles in the magnetic layer to be oriented only in the longitudinal direction of the tape. The presence of magnetic particles is required. Moreover, the magnetic disk is oriented in the circumferential direction.
l requires the presence of magnetic particles.

In recent years, it has become possible to increase the density of magnetic particles in a magnetic layer, making it possible to randomly orient the magnetic particles to make them non-oriented and increase the number of magnetic particles oriented in a predetermined direction as described above. ing. Therefore, attempts have been made to improve productivity by cutting magnetic tapes and magnetic disks from long non-oriented magnetic recording media. Such an attempt is
In particular, this leads to a significant improvement in the productivity of magnetic disk manufacturing.

For example, the following method has been proposed as a method for making a magnetic recording medium non-oriented.

(i) A method in which magnetic particles are oriented in the direction of application of magnetic paint by a first oriented magnetic field, and then non-oriented by a weak second oriented magnetic field in the opposite direction to the first oriented magnetic field ( (Japanese Unexamined Patent Publication No. 104206/1983).

(ii) A method in which magnetic particles are oriented in the direction of application of magnetic paint by a first oriented magnetic field, and then non-oriented by a plurality of oriented magnetic fields weaker than the first oriented magnetic field (JP-A-54-1
49607).

(iii) Five or more magnets are arranged on the surface to which the magnetic paint is applied or the surface opposite to the magnetic paint with alternately different polarities and gradually decrease in the transport direction of the support, and the magnetic field lines adjacent to each other are substantially A method of continuous non-orientation (JP-A-59-124039).

(iv) alternating directions (preferably +45°, −
at an angle of 45°), and a method of non-orientation using a gradually decreasing magnetic field with the direction reversed (Japanese Patent Laid-Open Publication No. 159204/1983).

(v) A method in which bar magnets are divided and arranged in the width direction at an angle of 5 to 45 degrees with respect to the direction in which the magnetic paint is applied to achieve non-orientation (Japanese Patent Application Laid-Open No. 59-42644).

(vi) A method of achieving non-orientation using an orientation roller such that the magnetic field is along the axial direction (Japanese Patent Application Laid-open No. 189344/1983)
.

(vi) A non-oriented method by arranging a large number of magnets with alternating N and S poles so as to form a magnetic field perpendicular to the conveying direction of the coated web (Japanese Unexamined Patent Publication No. 148140/1982) .

(vii) A method in which magnets are arranged alternately with N and S poles so as to form a magnetic field perpendicular to the direction in which the magnetic paint is applied (Japanese Unexamined Patent Publication No. 148140/1982).

However, the above conventional method has the following problems.

In the methods (i) to (iii), it is necessary to set the magnetic field strength in a predetermined pattern, which results in poor reproducibility in measurements and settings, and is unstable in terms of operational and production stability.

Methods (iv) and (V) lack versatility for different magnetic particles, and method (iv) in particular produces a non-oriented assembly in which the directions alternate and the directions gradually decrease in the opposite direction. It is difficult to

Methods (vi), (vi), and (vii) require the use of special rollers or a large number of magnets and solenoids, and are difficult to employ as practical devices.

It is an object of the present invention to provide a method and apparatus for manufacturing a magnetic recording medium that effectively renders magnetic particles non-oriented using a simple apparatus.

2. Structure of the Invention The first aspect of the present invention is to form a layer containing magnetic particles on a support, and to pass the support through a plurality of orienting magnetic fields having substantially the same magnetic field strength to The present invention relates to a method of manufacturing a magnetic recording medium in which particles are made non-oriented.

A second invention of the present invention comprises means for forming a layer containing magnetic particles on a support, a plurality of orienting magnetic fields having substantially the same magnetic field strength, and a drying means, and the plurality of orienting magnetic fields The present invention relates to an apparatus for manufacturing a magnetic recording medium, in which a later orientation magnetic field is located in the drying means.

E, Example Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 shows an outline of the apparatus, in which a support 1 wound around a supply roll 2 is conveyed to a magnetic paint application means 3, where a coating film containing magnetic particles is formed, and a plurality of orienting magnetic fields 4 ( ), the magnetic particles in the coating film are made non-oriented, and then the coating film is dried by passing through a drying means 5 to form a magnetic layer, and then a calender roll The fibers are guided to a calender section 6 consisting of a combination of 6a and calendered, and then wound onto a winding roll 22. The thus manufactured magnetic recording medium is subjected to the next slitting process or punching process (not shown) into a disk shape. In the same figure,
3a is an opposing roll for coating, 3b is a blade for scraping off excess paint, and 3c is a magnetic paint.

In magnetic recording media, at least polyurethane can be used as a binder resin for the magnetic layer, which can be synthesized by reacting a polyol with a polyisocyanate. Usable polyols include organic dibasic acids such as phthalic acid, adipic acid, trimerized lyluic acid, and maleic acid, and glycols such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol, or trimethylolpropane, hexanetriol, Polyester polyol synthesized by reaction with polyhydric alcohols such as glycerin, trimethylolethane, pentaerythritol, or any two or more polyols selected from these glycols and polyhydric alcohols; or S - caprolactam,
Lactone polyester polyols synthesized from lactams such as α-methyl-1-caprolactam, S-methyl-8-caprolactam, and T-butyrolactam; or polyether polyols synthesized from ethylene oxide, propylene oxide, butylene oxide, etc. can be mentioned.

These polyols are reacted with isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, metaxylylene diisocyanate, etc., resulting in urethanized polyester polyurethane, polyether polyurethane, and polycarbonate carbonated with phosgene or diphenyl carbonate. Polyurethane is synthesized. These polyurethanes are usually produced primarily by the reaction of polyisocyanates and polyols and are also in the form of urethane resins or urethane prepolymers containing free isocyanate groups and/or hydroxyl groups, or in the form of reactive end groups thereof. (for example, in the form of a urethane elastomer).

Since the methods for producing polyurethane, urethane prepolymers, urethane elastomers, curing and crosslinking methods, etc. are well known, detailed explanation thereof will be omitted.

In addition, if a phenoxy resin and/or a vinyl chloride copolymer is also included as a binder resin in addition to the above-mentioned polyurethane, the dispersibility of the magnetic powder will be improved when it is used in a magnetic layer, and its mechanical strength will be increased. . However, if only the phenoxy resin and/or the vinyl chloride copolymer is used, the layer becomes too hard, but this can be prevented by containing polyurethane, and the adhesion to the support or base layer is improved.

The phenoxy resin that can be used is a polymer obtained by polymerizing bisphenol A and epichlorohydrin, and is represented by the following general formula.

(However, n82-13) For example, PKHC manufactured by Union Carbide.

There are PKHH, PKHT, etc.

In addition, as for the vinyl chloride copolymer that can be used, the molar ratio derived from l and m in the former unit is 95 to 50 mol%, and the latter unit is 5 to 50 mol%. It is. In addition, X represents a monomer residue that can be copolymerized with vinyl chloride, vinyl acetate,
The degree of polymerization expressed as (j2+m) is preferably 100 to 600, and if the degree of polymerization is less than 100, the magnetic layer etc. tends to become sticky, 6
If it exceeds 00, the dispersibility will deteriorate. The vinyl chloride copolymer described above may be partially hydrolyzed. The vinyl chloride copolymer is preferably a copolymer containing vinyl chloride-vinyl acetate (hereinafter referred to as "vinyl chloride-vinyl acetate copolymer"). Examples of vinyl chloride-vinyl acetate copolymers include vinyl chloride-vinyl acetate-vinyl alcohol, vinyl chloride-vinyl acetate-maleic anhydride copolymers, and vinyl chloride-vinyl acetate copolymers. Among these, partially hydrolyzed copolymers are preferred. Specific examples of the above-mentioned vinyl chloride-vinyl acetate copolymers include rVAGHJ, "V Y HHJ, rVMCHJ" manufactured by Union Carbide, and "S-LEC A" and "S-RESOC A-5" manufactured by Suzui Kagaku Co., Ltd.
, "S-Resoku C", "S-Lec M", "Denkabinir 1000GJ", "Denkabinir 1" manufactured by Denki Kagaku Kogyo Co., Ltd.
00OWJ etc. can be used.

In addition to the above, cellulose resins can be used as the binder resin, such as cellulose ethers, cellulose inorganic acid esters, cellulose organic acid esters, and the like. As the cellulose ether, methyl cellulose, ethyl cellulose, etc. can be used. As the cellulose inorganic acid ester, nitrocellulose, cellulose sulfate, cellulose phosphate, etc. can be used. Also,
As the cellulose organic acid ester, acetyl cellulose, propionyl cellulose, butyryl cellulose, etc. can be used. Among these cellulose resins, nitrocellulose is preferred.

In addition, regarding the entire binder composition, the ratio of the above-mentioned urethane resin to other resins (total N of phenoxy + l JJM and vinyl chloride copolymer, etc.) is 90/10 to 40/60 by weight. Preferably, 85/1
It has been confirmed that 5 to 45155 is more desirable.

Outside this range, if the amount of urethane resin is large, dispersion tends to be poor, and if the amount of other resins is large, the surface properties tend to be poor, and especially if it exceeds 60% by weight, the physical properties of the coating film become unfavorable overall. . In the case of vinyl chloride-vinyl acetate, it can be mixed with urethane resin with a considerable degree of freedom.
Preferably the urethane resin is 15 to 75ii%.

As the binder resin for the layer constituting the magnetic recording medium,
In addition to those mentioned above, thermoplastic resins, thermosetting resins, reactive resins, and electron beam curable resins may be used.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10.000 to 200.000, and a degree of polymerization of about 2.
For example, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, and acrylic ester-styrene copolymer are used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Furthermore, among these resins, those that do not soften or melt until the resin is thermally decomposed are preferred. Specifically, for example, phenol resin, epoxy resin, urea resin, melamine resin, alkyd resin, etc. are used.

Examples of electron beam irradiation-curable resins include unsaturated prepolymers,
Examples include maleic anhydride type, urethane acrylic type, and polyester acrylic type.

Carbon black may further be added to the magnetic layer.

This carbon black is preferably electrically conductive, but light-shielding carbon black may also be added. Examples of such conductive carbon black include Conductex 97 manufactured by Columbia Carbon Co., Ltd.
5 (specific surface area 250 m/g - particle size 24 mμ), Conductenx 900 (specific surface area 125 m/g, particle size 27
mμ), Cabot Vul
can) As a carbon blank for light shielding,
For example, Raben 2000 manufactured by Columbia Carbon (
Specific surface area 190g/g, particle size 18mμ), 2100.1
170.1000, #100, #75 manufactured by Mitsubishi Chemical Corporation
, #40, #35, #30, etc. can be used. Carbon black has an oil absorption of 90ml (D B P
) /100g or more is desirable because it facilitates formation of a struttered structure and exhibits higher conductivity.

In the present invention, the magnetic recording medium has magnetic layers 20 on both sides of the support 1, as shown in FIG. 6, for example. The magnetic powder, particularly the ferromagnetic powder, used in the magnetic layer 20 is γ-Fe 203,C.

Contains 7 Fe2O3, Fe3O4, Co-containing Fe3O
Iron oxide magnetic powder such as 4; Fe, Ni, C01Fe-Ni-
Co alloy, Fe-Mn-Zn alloy, Fe-Ni
-Z n alloy, Fe-Co-Ni-Cr alloy, Fe-C
o-N1-P alloy, Co-Ni alloy, etc. Fes Nib
Examples include various ferromagnetic powders such as metal magnetic powders containing Co or the like as a main component. Among these, Co-containing iron oxide and metal magnetic powder are preferable.

Further, the BET value of the magnetic powder is preferably 25 rrr/g or more, more preferably 30 rd/g or more, the magnetic powder exhibits an acicular shape, and the viscosity of the magnetic paint is usually 1000 to 5000 CPS. The magnetic layer 20 also contains a lubricant (e.g. silicone oil,
graphite, molybdenum disulfide, tungsten disulfide, fatty acid ester consisting of a monobasic fatty acid with 12 to 20 carbon atoms (e.g. stearic acid) and monovalent alconoC with 13 to 26 carbon atoms, etc.), abrasives (for example, fused alumina), antistatic agents (for example, graphite), etc. may be added.

The magnetic recording medium shown in FIG. 6 includes a magnetic layer 20 and a support 1.
It is not necessarily necessary to provide an undercoat layer (not shown) between the two.

In addition, when coating and forming the above-mentioned magnetic layer, etc., it is desirable to add a predetermined amount of polyfunctional isocyanate as a crosslinking agent to the coating material. Examples of such crosslinking agents include, in addition to the polyfunctional polyisocyanates mentioned above, triphenylmethane triisocyanate, tris-(P-isocyanate phenyl) thiophosphite, polymethylene polyphenylisocyanate, methylene diisocyanate, tolylene diisocyanate, etc. Isocyanate type is better.

In addition, materials for the support 1 mentioned above include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, plastics such as polycarbonate, etc. Metals such as L, Zn, etc. are used. The thickness of these supports is approximately 3 to 100 μm in the case of a film or sheet, preferably 20 to 75 μm.
In the case of disks and cards, the diameter is 30 μm to 10 μm.
If it is drum-shaped, it is cylindrical, and its shape is determined depending on the recorder used.

Coating methods for coating the magnetic paint onto the support to form a magnetic layer include air knife coating, blade coating, doctor blade coating, air knife coating,
squeeze coat, impregnation coat, reverse roll coat,
Transfer roll coat, gravure coat, kiss coat, cast coat, spray coat, etc. are available.
Other methods are also possible.

In FIG. 1, a support 1 is conveyed to a magnetic paint application means 3 to form a coating film containing magnetic particles, and while passing through a plurality of orienting magnetic fields 4, the support 1 is conveyed to a magnetic paint application means 3 in a conveying direction 7. The magnetic particles mechanically oriented in the transport direction 7
and/or in the coating film to be oriented in the opposite direction,
exercise with. However, before the magnetic particles are fully oriented in the above-mentioned direction, the support 1 enters the drying means 5 and the drying of the coating begins, and the movement of the magnetic particles is blocked and their orientation becomes random. , it becomes unoriented. In order to increase the degree of non-orientation, among the plurality of orienting magnetic fields 4,
It is effective to adopt a structure in which a part of the orientation magnetic field on the latter stage enters the drying means 5, so that drying of the coating film starts while the magnetic particles are moving in the plurality of orientation magnetic fields 4. .

The magnetic particles become non-oriented and the coating dries to form the magnetic layer 20 (
The support body 1 on which the structure (see FIG. 6) is formed is wound up on a winding roll 22 via a calender section 6.

The above operation is performed twice to obtain a magnetic recording medium having magnetic layers 20 on both sides of the support 1 shown in FIG. 6.

Next, an example of the orientation magnetic field 4 will be explained.

FIG. 2 is an internal front view showing the interior of the plurality of orienting magnetic fields 4 and the drying means 5. FIG.

The plurality of alignment magnetic fields 4 are generated by n bar magnets 4a-1, 4a-2-, which are arranged such that the same poles face each other with the support 1 in between and adjacent poles alternate in the transport direction 7. 1・
......, 4a-n and 4b-1, 4b-2,
. . . is formed by arranging 4b-n. These bar magnets are all arranged in a direction perpendicular to the conveyance direction 7.

Warm air 5b is blown from a nozzle 5a at a stage subsequent to the bar magnets 4a-3 and 4b-3 to dry the coating film.

When the support body 1 enters a plurality of alignment magnetic fields 4, the magnetic particles in the coating film become bar magnets 4a-1, 4a-2,...
, 4a-n and 4b-1, 4b-2, ...
. , 4b-n (parallel to the conveying direction 7). However, before the magnetic particles are completely oriented in the transport direction 7, the hot air 5b
The drying of the coating film is started, and the magnetic particles move in the transport direction 7.
During the process of orientation, the movement is blocked by the drying of the coating film, and the orientation becomes random. As a result, the magnetic particles become non-oriented.

In the example shown in Figure 2, the lines of magnetic force of each magnet are independent, but the lines of force in the third
As shown in the figure, lines of magnetic force may be formed across adjacent poles.

In addition, as shown in FIG. 4, they may be placed either on the coating film side or on the opposite side of the coating film (in FIG. 4, the coating film side) with respect to the support 1, or they may be placed adjacent to each other. The magnets may be arranged so that the poles of the magnets are the same.

In addition, a DC solenoid coil can be used instead of the bar magnet, and as shown in Figure 5, the electromagnet 4C
-1,4C-2, 4cmn and 4
d-1, 4d-2, ......, 4d-n are used to form magnetic lines of force 12 in only one direction, thereby making the magnetic particles non-oriented. The magnetic field strength is
It is preferable that the coercive force is smaller than the coercive force of the magnetic particles, and is about 10 to 50% of the coercive force.

The number of magnets (n above) for forming a plurality of orientation magnetic fields is preferably 3 or more, more preferably 10 or more. Furthermore, the magnetic field strengths of these magnets are substantially the same from the viewpoint of operability of the peeling device.

In the above example, the support is made to pass through a plurality of orienting magnetic fields following the application of the magnetic paint, but both steps are performed in duplicate, that is, at least in the first stage of the plurality of orienting magnetic fields. It is also possible to apply magnetic paint.

By doing so, it is possible to downsize the device.

The orientation magnetic field and the drying start time are described below.

Preferably, the support is passed through the magnetic field of at least one or one set of magnets, preferably two or more or more sets, after the support has substantially begun to dry. Since drying is not completed immediately after the actual drying starts, the magnetic particles continue to move during the drying process (if this is done, f!)! Particle flVt! WMlnl! 1l-1'yX-
The motion of the magnetic particles becomes slower as the drying progresses, and eventually the magnetic particles become fixed. As described above, when a part of the latter side of the plurality of orienting magnetic fields overlaps with the drying means, the orientation of the magnetic particles becomes partially random, and the magnetic particles 21 (first (see Figure 6) becomes highly non-oriented. Particularly in the production of magnetic disks that require a high degree of non-orientation, it is desirable to do as described above.

For drying, in addition to forced drying with wind as in the above example, natural drying (in this case, use a quick-drying binder resin), drying with a halogen heater lamp or infrared lamp, or drying as appropriate for the embodiment. It can depend on the method.

In the above example, the orientation magnetic field is provided in a direction parallel to the conveying direction of the support, but the direction of the orientation magnetic field is not limited to this, and may be provided in any direction.

Next, the present invention will be explained by giving specific examples.

On one side of a support made of polyethylene terephthalate having a thickness of 75 μm on a sample plate, by the method shown in FIGS.
A magnetic paint having the composition shown in Table 1 below was dried by the doctor blade method at a conveying speed of 2 Cm/min to a thickness of 2.
Non-orientation treatment was performed while coating to a thickness of 5 μm. In the non-orientation process, 10 stages of opposed bar magnets were provided, the strength of each magnetic field was 100 Gauss, and drying was started from the third magnetic field from the rear stage.

(The following margins are continued on the next page.) Table 1 After the non-orientation treatment was completed, drying was started, and the material was carried out in the same manner as in Example 1 to obtain a magnetic recording medium.

For the magnetic recording medium thus obtained, the squareness in the transport direction of the support and the squareness ratio in the direction perpendicular to the transport direction were measured, and the ratio of these, that is, the orientation degree ratio (〃/upper) was determined. Ta. Here, the squareness ratio refers to (residual magnetic flux density/maximum magnetic flux density).

For comparison, similar measurements were performed on a magnetic recording medium obtained under the same conditions as in the above example without undergoing any alignment treatment.

The results are shown in Table 2 below.

Table 2 In particular, magnetic disks are required to have a high degree of non-orientation, and the orientation degree ratio is required to be 1.05 or less. The comparative example does not meet this requirement, whereas the examples do meet the requirement, especially in Example 1 where drying was started before the end of the orientation process, the degree of orientation ratio was 1.
It shows complete non-orientation called OO.

As described in the detailed description of the invention, the first aspect of the present invention is to pass a plurality of orienting magnetic fields having substantially the same magnetic field strength through a support on which a layer containing magnetic particles is formed. Since this method does not require complicated control of magnetic field strength, the device has a simple structure and is easy to operate. As a result, the magnetic recording medium obtained has high reliability in non-orientation.

Further, in the second aspect of the present invention, the latter alignment magnetic field of the plurality of alignment magnetic fields is located in the drying means, so that in addition to the above effects, the following effects can be obtained. is played. That is, the magnetic particles are fixed during the progress of orientation, and as a result, a magnetic recording medium with an extremely high degree of non-orientation can be obtained.

[Brief explanation of drawings]

The drawings all show embodiments of the present invention, in which Fig. 1 is a schematic diagram showing an overview of the manufacturing process of a magnetic recording medium, Fig. 2 is a schematic internal front view of the orienting magnetic field and drying means, and Fig. 3 4 and 5 are schematic front views of other orientation magnetic fields, and FIG. 6 is an enlarged sectional view of the magnetic recording medium. In addition, in the reference numerals shown in the drawings, 1......Support 3...Magnetic paint application means 3C...
. . . Magnetic paint 4 . . . Plural orienting magnetic fields 4a-1, 4a-2, 4a-3, 4a-n. 4b-1, 4b-2, 4b-3, 4b-n. ......Bar magnet 4C-1, 4C-2, 4C-3, 4cmn. 4d-1, 4d-2, 4d-3, 4d-n. ...... Electromagnet 5 ... Drying means 5 a ... Nozzle 5 b ... Warm air 7 ... . . . Support transport direction 11.12 . . . Lines of magnetic force 20 . . . Magnetic layer 21 . . . Magnetic particles.

Claims (1)

[Scope of Claims] 1. A layer containing magnetic particles is formed on a support, and the support is passed through a plurality of orienting magnetic fields having substantially the same magnetic field strength to render the magnetic particles non-oriented. A method for manufacturing a magnetic recording medium. 2. A method comprising means for forming a layer containing magnetic particles on a support, a plurality of orienting magnetic fields having substantially the same magnetic field strength, and a drying means, the orienting magnetic field on the latter side of the plurality of orienting magnetic fields. is located in the drying means, an apparatus for manufacturing a magnetic recording medium.