JPS6070532A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having a magnetic layer characterized by high rectangular property of a magnetic hysteresis curve by forming a coating means and a magnetic field orientation means inside a drying means, and while setting up the composition of a coating film within a specific range under control by the drying means, orientating the magnetic field immediately after coating the magnetic coating solution. CONSTITUTION:The magnetic coating solution 5 is applied to the surface of a continuously transferred non-magnetic supporting body 3 by a coating head 4 and the coated film 5' is dried and hardened by drying means 17, 27 to form a magnetic layer. The magnetic coating solution 5 is obtained by dispersing ferromagnetic fine powder into a bonding agent resolved by a solvent. While controlling the evaporating concentration of the solvent by controlling a control valve 26 for controlling dry air temperature so that the solvent in the coating film 5' immediately before the entry into an orientation magnet 6 occupies the ferromagnetic fine powder at a rate of 210-500 to 100, the ferromagnetic fine powder in the coating film is orientated in a prescribed direction by the orientation magnet 6 and the coating film is dried and hardened. Consequently, the magnetic field orientation processing is performed always stably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a tape-shaped magnetic recording medium, and more particularly, to a method for manufacturing a magnetic recording medium in which magnetic field alignment treatment is performed reliably and stably.

Recently, high-density recording is required in magnetic recording. High-density recording can be achieved by improving magnetic recording/reproducing devices and recording methods, but it can also be achieved by improving magnetic recording media.

Improving electromagnetic conversion characteristics is known as an example of improving magnetic recording media to achieve high-density recording, and in particular, increasing the residual magnetic flux density (Br) and coercive force (Hc) of the magnetic layer, and making the magnetic hysteresis curve more square. It is known that it is effective to improve the overall shape (squareness). As a general magnetic recording medium, so-called magnetic tape is known as a magnetic coating liquid gold, which is made by dispersing ferromagnetic fine powder in a binder dissolved in a solvent, and coated on a long, strip-shaped non-magnetic support. Is there any squareness in this type of magnetic recording medium? As a method for improving this, a method is known in which a total external magnetic field is applied to the magnetic recording medium to orient all the easy magnetization axes of the ferromagnetic fine powder in a desired direction. For example, as shown in FIG. 1, as a specific technique for applying magnetic field orientation treatment to such a tape-shaped magnetic recording medium, it is possible to continuously transport the tape-shaped magnetic recording medium after it has been completely fed out from a delivery roll 1, and then wind it onto a take-up roll 2. The magnetic coating liquid 5 is completely coated on the long strip-shaped non-magnetic support 3 to be taken using the coating head 4 to form a coating film 5. (The coating film 5 is subjected to full magnetic field orientation treatment by the disposed orientation magnet 6, and then the coating film is smelted by the drying means 7 disposed downstream of the orientation magnet 6.
A technique is known in which the entire magnetic layer is formed by drying and solidifying the orientation magnet 6. Also, as shown in FIG.
It is also known to arrange the device inside the device. Details of such techniques are described in, for example, Japanese Patent Publications No. 4.5-21547, No. 52-2602, No. 58-84706, etc. However, by the conventional method as described above,
It has been extremely difficult to obtain profitable magnetic recording media with sufficient squareness. In other words, in the method shown in FIG. 1, the easy magnetization axis of the ferromagnetic fine powder is oriented by the orienting magnet 6 because the coating film tends to dry while being transferred from the coating head 4 to the orienting magnet 6. On the other hand, after passing through the orientation magnet 6 and before entering the drying means 7, the once oriented easy magnetization 11+ tends to return to the non-oriented state. In the method shown in Fig. 2, since the drying process is performed immediately after the orientation process, it is difficult for the easily magnetized axis once oriented to return to its original non-oriented state, but it is still difficult for the easily magnetized 11Qi to become oriented. This problem occurs in the same manner as in the method shown in FIG. 1 above.

The present invention has been made in view of the above circumstances, and provides a complete method for manufacturing a magnetic recording medium in which magnetic field orientation is performed reliably and stably, and a magnetic layer r with high squareness can be formed. The present invention has been made based on the knowledge that the success or failure of the magnetic field orientation is largely controlled by the viscosity of the magnetic coating liquid immediately before the magnetic field orientation treatment. A method for producing a magnetic recording medium includes a coating means for coating a magnetic coating liquid as described above on a continuously transported strip-shaped non-magnetic support, and a coating means is provided in a total drying means, and the magnetic coating liquid is coated in the drying means. The solvent contained in the coating film layered on the support was 210 to 50 parts by weight per 100 parts by weight of the ferromagnetic fine powder.
The ferromagnetic fine powder in the coating film was all oriented in a predetermined direction by a magnetic field orienting means disposed within the drying means while controlling the total evaporated concentration of the solvent so as to account for 0 parts by weight by the drying means. After that, the coating film is dried and solidified.

Through the research of the present inventors, it was found that the composition of the magnetic coating film was maintained as above and subjected to magnetic field orientation treatment? It was confirmed that magnetic field alignment was achieved reliably when applied. The coating means and the magnetic field orientation means in the drying means are configured to completely set the composition of the coating film under the control of the drying means, and to perform magnetic field orientation immediately after applying the magnetic coating liquid. The composition will not change due to drying of the coating film between the time and the magnetic field orientation treatment, and the magnetic field orientation treatment will always be stably performed on the coating film having the above composition. Furthermore, since the magnetic field orientation is carried out within the drying means, the coating film subjected to the magnetic field orientation treatment immediately dries and solidifies, making it difficult for the ferromagnetic fine powder once oriented to return to the non-oriented state. drawing? Examples of the present invention will be described in detail with reference to the drawings.

FIG. 3 shows an example of an apparatus for carrying out the method of manufacturing a magnetic recording medium of the present invention. In the apparatus shown in FIG. 3, a non-magnetic support is 3 is sent out from the delivery roll 1, continuously transported, and wound up on the winding roll 2. The continuously transported non-metallic support 3 passes through two adjacent drying means 17.27.These drying means 17.27
are drying air introduction ports 17a through which drying air is introduced.

27a and exhaust ports 17b, 27b.
c, has 27ci, each dry air introduction '017a and 27a
For example, a steam heater 1'8,
28 heating sections are provided, and these heaters 18, 28 send drying air into the chambers 17c, 27c. A coating head 4 and an orientation/magnet 6 disposed downstream of the head 4 are provided in the drying means 27 on the upstream side in the transport direction of the long, strip-shaped nonmagnetic support 3.

A control valve 26 is interposed in a steam pipe 29 that supplies heating steam to a steam heater 28 for the drying means 27.

The magnetic coating liquid 5 is applied by the coating head 4 to the surface (the upper surface in the figure) of the non-magnetic support 3 that is continuously transferred, and the coating film 5' is dried and solidified by the drying means 17, 27. A magnetic layer is formed. The magnetic coating liquid 5 is made by dispersing ferromagnetic fine powder in a binder dissolved in a solvent, and examples of the ferromagnetic fine powder used in the present invention include r-Fez03, Co-containing powder, and Co-containing powder. Fe203, Fe5r4, co gold-containing D Fe5r4.
CrO2, Co-N1-P alloy, Co-Ni-Pe
Known ferromagnetic fine powders such as alloys can be used, specifically, those disclosed in Japanese Patent Publication No. 14090/1983 and Japanese Patent Publication No. 18372/1983.
Publication No. 47-22062, Special Publication No. 47-22062, Publication No. 47-22062
Publication No. 22513, Japanese Patent Publication No. 46-, Publication No. 28466,
Special Publication No. 4.6-38755, Special Publication No. 47-428
Publication No. 6, Special Publication No. 47-1.2422, Special Publication No. 4
7-1.7284, Japanese Patent Publication No. 47-18509, Japanese Patent Publication No. 18573-1987, etc. The binder used in the present invention is a conventionally known thermoplastic resin. , thermosetting resins, reactive resins, ultraviolet curable resins, IIi electron beam curable resins, and mixtures thereof.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10,000 to 200,000, and a polymerization degree of about 20.
0 to 500, such as vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic Acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylitine chloride copolymer, methacrylic acid ester styrene copolymer, urethane distomer, nylon-silicon based resin, nitrocellulose Polyamide resin, polyvinyl fluoride, bichloride I) denacrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral,
Cellulose derivatives (cellulose acetate butyrate,
cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.),
Styrene-butadiene copolymers, polyester resins, chlorovinyl ether acrylate copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof may be used.

Examples of these resins are listed in Japanese Patent Publication No. 37 6877M39-1
No. 2528, No. 39-19282, No. 40-5349,
No. 40-20907, old No. 9463, old No. 14059
No. 41-16985, No. 42-6428, /I2-
No. 11621, 43-. No. 4.623, 4.3-152
No. 06, 4.4. -2889, 44-1794.7, 4.4-18232, 45-14020, 4.5
-]/No. 1500, No. 47-18573, 4.7-2
No. 2063, No. 4.7-22064, No. 4.7-2206
No. 8, No. 47-22069, No. 4.7-22070, 4
This is disclosed in publications such as No. 7-27886.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating solution, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Also, among these resins, those that do not soften or melt during the process of thermal decomposition are preferred. Specifically, for example, phenol resin, nipoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, /recon resin, acrylic reaction resin, nipoxy-bolyamide resin, nitrocellulose melamine resin, high molecular weight Mixtures of polyester resins and inocyanate polymers, mixtures of methacrylate copolymers and diinocyanate polymers, mixtures of polyester polyols and polyisocyanates, mixtures of urea formaldehyde diol/trienylmethane triisocyanate, These include polyamine resins and mixtures thereof.

Examples of these resins are given in Japanese Patent Publication No. 39-8] No. 03, 4.
, 0-977! '1, old-7192, 4.1-80
No. 16, No. 44-14275, No. 42-18179. 4.3-], 2Q8] issue, 4.4-28023
No. 45-14501, No. 45-24902, 4
．． 6-1.3103, 4.7-22065, 4
No. 7-22066, /17-22067, 4
No. 7-22072, No. 47-22073, 47
- No. 2804.5, 47-2804, No. 8, 71.
This is published in publications such as No. 7-28922.

These binders may be used alone or in combination;
Other additives may be added. The mixing ratio of the ferromagnetic fine powder and the binder is 1 part by weight of the binder to 100 parts by weight of the ferromagnetic fine powder.
It is set in a range of 0 to 200 parts by weight.

Additives include dispersants, lubricants, abrasives, and the like.

Organic solvents used during dispersion, kneading, and coating include acetone, methyl ethyl ketone, methyl isobutyl keto/, and ketone systems such as cyclohexanone; alcohol systems such as methanol, ethanol, propatool, and butanol; and methyl acetate and acetic acid. Ethyl, butyl acetate, ethyl lactate, vinegar [esters such as glycol, monoethyl ether, glycol dimethyl ether, glycol monoethyl ether, dioxane q (
7) y IJ Co-. ix-chill system. benzene,
Cool type (aromatic hydrocarbons) such as toluene and quinoa:
Chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chloride, dichlorobenzene, etc. can be used in equal amounts.

The thickness of the non-magnetic support 3 is 25~]. About O O tt,
Preferably, one with a diameter of about 3 to 40 tt is used for a 75 degree angle. The materials include polyesters such as polyethylene naphthalate, polyolefins such as polypropylene, mono(
・Cellulose derivatives such as Roast 1 noacetate and cellulose diacetate, vinyl-based products such as polyvinyl chloride@
In addition to plastics such as polycarbonate and polycarbonate,
Metals such as aluminum and copper, ceramics such as glass, etc. may also be used.

Methods for applying the above magnetic coating liquid 5 to the support 3 include air doctor coating, braid coating, air knife coating, squeeze coating, and impregnating coating.
, Rinoku Slow Nol/21-1・,
Transfer roll coat, rib coat, kiss coat, cast coat, spray coat, etc. can be used, and other methods are also possible.Specific explanations of these methods can be found in "Coach Ink Engineering J25"
3M ~ 27 7Fj (published on March 20, 1972) for details.

As the orientation magnet 6, a solenoid ゛koino+- (i = used electric magnet or permanent magnet) can be used, and in order to effectively orient the ferromagnetic fine powder easily Various self ii'i powers; possible.

Next, select and use a specific monthly fee from each of the monthly fees explained above,
A detailed example of how the material was manufactured completely using the apparatus shown in Figure 3. i-en'J-1 [Example 1] The following composition was put into a ball mill and thoroughly kneaded, and then 2 parts by weight of Desmodur L-75 (Bayer tJ [trade name of polyisocyanate compound)] was added as a binder. (hereinafter referred to as the section)? In addition, the magnetic coating liquid 5 was prepared by uniformly mixing and dispersing the mixture.

Co-containing -1-Fe2O3 powder (ferromagnetic fine powder) 100
parts (nitrogen adsorption specific surface area 30rrt/g) Nitrocellulose (binder) 10 parts Polyurethane bimolecular weight approx. 30,000 (binder) 10 parts Vinyl chloride-vinyl acetate vinyl main alcohol copolymer (binder) 10 parts myristic acid (Lubricant) 2 parts Nontin (Lubricant) 1 part n-butyl acetate (solvent) 220 parts A polyester film was used as the non-magnetic support 3,
The magnetic coating liquid 5 was coated on the surface of the non-magnetic support 3, which was continuously transported, using the coating head 4. All orientation magnets 6 having a magnetic flux density of 1000 Gauss and a length of 1 m were used, and the coating speed was set at 50 m/min (ie, the residence time of the coating film 5' in the orientation magnet 6 was 2×10'' minutes).

The coating film 51 applied to the surface of the non-magnetic support 3 is a drying means]
, 7 and 27, the control valve 26 for fully controlling the drying air temperature is controlled to control the evaporation concentration of the solvent, so that the solvent in the coating film 51 just before entering the orientation magnet 6 is ferromagnetic. So that the amount is 220 parts per 100 parts of fine powder (
In other words, the setting was made so that almost no solvent evaporated between the coating head 4 and the orientation magnet 6.

As described above, a complete magnetic tape was prepared in which a 5° coating film was solidified on the surface of the non-magnetic support 3 and a magnetic layer was layered thereon. Next, the magnetic tape was subjected to mirror polishing treatment, and then cut into 2-inch width pieces to obtain sample flat 1, and its horizontal squareness ratio (SQ) v was measured. This squareness ratio is the residual magnetic flux density (Br
) i is the value divided by the saturation magnetic flux density (Bm).

As comparative samples, magnetic tapes were prepared using the apparatuses shown in Figs. 1 and 2 (respectively from the sample shop), which had the same materials and coating solution application conditions as Sample 1, but which did not have a means for controlling the evaporation concentration of the solvent. 2) were prepared and their squareness ratios were measured in the same manner. The results of these measurements are shown in Table 1 below.

Table 1 How the magnetic tape of sample AI according to the method of the present invention is
It contains a squareness ratio of 0.90 or more, which has been extremely difficult to obtain in the past.

[Second Example] After the following composition was thoroughly kneaded in a Keball mill, 8 parts of Desmodur L-75 (trade name of a polyisocyanate compound manufactured by Bayer AG) was added as a binder, and the mixture was uniformly mixed and dispersed to make it magnetic. Coating liquid 5 was used.

Co-containing -γ-Fe203 (ferromagnetic fine powder) 100 parts (nitrogen adsorption method specific surface area 30 m'/?) Vinyl chloride-hinyl acetate-vinyl alcohol copolymer (binder) 1 () part epoxy resin (bond agent) 10 parts dimethylpolysiloxane (lubricant) 1 part (25°C
Viscosity 1000cs) Butyl palmitate (lubricant) '1 part Ae20
3 (abrasive) 6 parts n-butyl acetate (solvent) X part solvent n-butyl acetate 160 parts and 180 parts, respectively,
200 copies, 215 copies, 222 copies.

230 parts of six kinds of magnetic coating liquids 5 were prepared. The solvent evaporation concentration is controlled by the control valve 26 in the drying means 27 using the coating head 4 and the orientation magnet 6, as in the first embodiment. This was done in such a way that the solvent hardly evaporated between the steps.

The six types of magnetic tapes obtained as described above were each subjected to a mirror polishing treatment, and then cut into 2-inch width pieces to prepare sample A4-flat 9, and the squareness ratio of each tape was completely measured. The results are shown in Table 2 below.

Table 2 As is clear from Table 2 above, when the amount of solvent in the coating film 5'' during the magnetic field orientation treatment is 200 parts by weight or less based on 1.0 parts by weight of the ferromagnetic fine powder, the squareness ratio becomes 0.90. below,
A very significant effect of improving the squareness ratio cannot be obtained. Therefore, it is necessary to set the amount of the above solvent to 210 parts by weight or more, but if it exceeds 500 parts by weight, the coating surface will become rough during drying, which is undesirable, so 500 parts by weight is the upper limit. [Third Example] After putting the following composition into a ball mill and thoroughly kneading it, 5 parts of Desmodur L-75 (trade name of a polyiso/anate compound manufactured by Bayer AG) was added as a binder, and the mixture was uniformly mixed and dispersed. A magnetic coating liquid 5 was obtained.

Co-containing -γ-F'e203 powder (ferromagnetic fine powder) 10
0 parts (nitrogen adsorption specific surface area 35 m'/g) Nitrocellulose (binder) I, 0 parts polyurethane bimolecular weight approximately 30,000 (binder) 10 parts copolymer of vinyl chloride/hinyl acetate/vinyl alcohol (binder) 1
0 parts stearic acid (lubricant) 2 parts dimethylpolysiloxane (lubricant) 0.5 parts (]0
0 cp) 200 parts of n-butyl acetate (solvent) 30 parts of sochlorohexanone (solvent) This magnetic coating liquid 5 was coated on a polyester film using the apparatus shown in FIG. A magnetic tape was obtained by coating it on a non-magnetic support 3 consisting of:

The solvent evaporation concentration was controlled by the control valve 26 in the drying means 27, as in the first embodiment, so that almost no solvent evaporated between the coating head 4 and the orientation magnet 6.

Then, an S-N facing permanent magnet with an average magnetic flux density of 1500 Gauss and a length of 1 m was used as the orientation magnet 6, and the non-magnetic support 3
By changing the transfer speed, that is, the coating speed of the coating liquid 5, the residence time of the coating film 5 in the orientation magnet 6 can be changed as shown below.
All five types of samples were prepared using the following settings, and the squareness ratio of each sample was completely measured. The residence time of the coating film 5' in the orientation magnet 6 was determined by dividing the length of the orientation magnet 6 by the support transport speed. Measurement result of squareness ratio? It is shown in Table 3 below.

Table 3 As is clear from Table 3, the amount of solvent in the coating film 51 during magnetic easy orientation treatment is 2 parts by weight per 100 parts by weight of the total ferromagnetic fine powder.
Even if the amount is set to 10 parts by weight or more, if the magnetic field residence time of the coating film 5' is set to a small value, the squareness ratio may decrease by 0.9 i, so the magnetic field residence time of the coating film 5' is 9 x 10-
``It is desirable to set the magnetic field to a level that is easy to understand.The magnetic residence time of this coating film 5゜ can be increased by setting the coating speed to a low value, but In media production, if the total coating speed is set too low, productivity will decrease completely, so the coating speed should be set at least 5.
It is preferable to set the speed to about 0 m/min.

In the first to third embodiments described above, the drying means 27 is controlled so that almost no solvent evaporates between the coating head 4 and the orientation magnet 6. The solvent evaporates to some extent during this time and as a result enters the orientation magnet 6. The drying means 27 may be controlled just before drying so that the amount of solvent in the coating film 5' is set within the range described above.

Further, in the apparatus shown in FIG. 3, the coating head 4 is arranged close to the orientation magnet 6, and as shown in FIG. 4, the drying air inlet 27a.

Exhaust port 27b, chamber 27C, heater 28° steam pipe 2
9. Dry air inlet 37a and air outlet 3 similar to control valve 26
A drying means 37 having a heater 38, a steam pipe 39 and a control valve 36 is installed away from the drying means 27 in which the orientation magnet 6 is disposed, and a coating head is installed within this drying means 37. Arrange 4.

By controlling both the drying means 37 and the drying means 27,
The total amount of solvent in the coating film 5' immediately before entering the orientation magnet 6 may be set to a desired value.

As explained in detail above, according to the method of the present invention, a magnetic recording medium having an extremely high squareness ratio and meeting the demand for high-density recording can be provided.

[Brief explanation of drawings]

1st. Fig. 2 is a schematic diagram of an apparatus for carrying out the conventional method for manufacturing magnetic recording media, Fig. 3 is a schematic diagram showing an example of an apparatus for carrying out the entire method of the present invention, and Fig. 4 is a schematic diagram of an apparatus for carrying out the entire method of the present invention. It is a schematic diagram showing another example. １・・・・・・・・・Feeding roll ２・・・・・・・・・
... Winding roll 3 ...... Non-magnetic support
4......Coating head 5...Magnetic coating liquid 5''...Coating film 6...
... Orienting magnet 7.17, 27.37 ... Drying means 1B, 28.38 ... Heater 26.36.
・・・・・・・・・・・・Continued from page 1 of control valve 0 Inventor: Toshimitsu Okutsu Ogimachi, Odawara City ≦0 Inventor: Masaaki Fujiyama 2:1 Ogimachi, Odawara City, No. 1 Fuji Photo Film Co., Ltd.: Chome 1, 1, No. 1
Fuji Photo Film Co., Ltd. (Voluntary) Procedural Amendment December 12, 1982 2 Name of the invention Method for manufacturing magnetic recording media 3 Relationship with the person making the amendment Patent applicant Location 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Address Name: Fuji Photo Film Co., Ltd. 4, Agent: 6, Number of inventions to be increased by the amendment: None 7, Subject of the amendment: Column 8, “Detailed explanation of the F invention of Ichima Akitama”, Contents of the amendment: 1) Details On page 11 of the book, line 4, ``Nipoxy resin'' is corrected to ``■Poxy resin.'' 2) Lines 6-7 of the same page

Claims (2)

[Claims] (1) A magnetic coating liquid consisting of fine ferromagnetic powder dispersed in a binder dissolved in a solvent is placed in a drying means on a continuously transported strip-shaped non-magnetic support. The evaporation concentration of the solvent is adjusted so that the solvent contained in the coating layered on the support by the coating means accounts for 210 to 500 parts by weight based on 100 parts by weight of the ferromagnetic fine powder. The fine ferromagnetic powder in the coating film is controlled by the magnetic field orienting means disposed within the drying means. After orientation treatment in a predetermined direction, the coating film is completely dried and solidified? Features: Manufacturing method of magnetic recording media (2) the coating speed of the coating liquid is 50 m/min or more;
and the residence time of the coating film in the magnetic field orientation means is 9 X ],
2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the time is 0'-3 minutes or more. -1-