JPS61261819A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To reduce the time for a calender treatment and to improve the productivity of a magnetic tape by coating a magnetic paint on a base and starting the calender treatment at the point of the time when the solvent content of the coating layer attains a specific range thereby calendering the coated film while said film maintains adequate softness. CONSTITUTION:The magnetic paint 2 is coated with a roll coater 11 on the base 1 consisting of a polyester film, etc. and is predried at 60-80 deg.C by the hot wind fed from nozzles 13 until the solvent content in the magnetic coated film 20 decrease to 20-150mul/m<2>. The coated film is then calendered at a high speed of 150-300m/min at 60-110 deg.C in a 200-500kg/cm range in a calender roll part 18 consisting of a combination of calender rolls 15. The base is then fed to the 2nd dryer 26 where the base is subjected to normal drying at 80-95 deg.C until the remaining solvent decreases to 5-10mul/m<2>. The magnetic tape which is improved in the surface characteristic of the film 20 in the above-mentioned manner is produced with good productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a method for manufacturing magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks.

Conventional technology Magnetic recording media are generally manufactured through a process in which a magnetic paint containing magnetic powder is applied onto a base film, and after drying, the surface of the magnetic layer is smoothed by calendering under pressure and heat. . To explain this with reference to FIG. 3, first, the film-like support 1 fed out from the supply roll IO is
After applying the magnetic paint 2 using a known roll coater 11,
It is introduced into a dryer 12, where it is dried by blowing hot air 14 from nozzles 13 arranged above and below. The dried support 1 with the magnetic layer is then led to a calender part 18 consisting of a combination of calender rolls 15, where it is calendered and then wound onto a winding roll.

However, in the known device shown in FIG.
Since the magnetic coating film is completely dried (i.e., dried until the amount of residual solvent in the coating film becomes 05 to 1 μt/rr?, μ) and then calendered, the coating film is One thing we have found is that the improvement of surface properties cannot be achieved very efficiently; that is, in order to obtain sufficient surface properties, it is necessary to increase the temperature and pressure of the calender rolls 15, thereby increasing the calendering speed (i.e.
Productivity) will decrease and costs will increase.

C. OBJECTS OF THE INVENTION An object of the present invention is to provide a method and apparatus for improving the surface properties of coating films while increasing the speed of calendering and increasing productivity.

D. Structure of the invention, that is, in the present invention, the solvent content of the coating layer coated on the support is 20 to 150 μt/pr? This relates to a method for manufacturing a magnetic recording medium in which calendering is started at the time when .

E, Example Hereinafter, the present invention will be described in detail with reference to examples.

In this embodiment, parts common to those shown in FIG. 3 are given common reference numerals, and their explanations may be omitted.

According to this embodiment, the coater 1 serves as a magnetic paint coating section.
After step 1, when drying with hot air 14 in the first dryer B in the same manner as described above, the drying is not done completely but only to a certain extent. That is, in the dryer n, the magnetic coating (
The solvent content (see Figure 2) or residual solvent amount is 20 to 15.
0μt/rr? Perform preliminary drying so that
If this pre-drying is excessive, as mentioned above, the temperature and pressure of the next calender roll 15 must be increased, and if the pre-drying is insufficient, the coating film may become sticky, making it difficult to carry out the next treatment. I can't do it.

After preliminary drying in the dryer 22, calendering is performed in the calender part 18. At this time, since the magnetic coating film maintains appropriate softness due to the above pre-drying (that is, the amount of residual solvent is large), it is sufficiently calendered.
As a result, without increasing the temperature and pressure of the calender roll 15, the surface properties of the coating film after calendering can be improved, and the speed of calendering can be improved, so the coating speed can also be increased (for example, by 50%). High compaction can be obtained.

In this way, the processing speed during calendering is increased, and the productivity of the magnetic tape is improved.

After the calender treatment, the support 1 is sent to a second dryer, where main drying is performed using a hot air path from a nozzle n. That is, the magnetic coating film is dried to its original degree of dryness (until the amount of residual solvent becomes 5 to 10 μt/rl). Thereafter, it is wound up onto a take-up roll and prepared for the next slitting process (not shown).

Here, it is essential to select the drying conditions in the first dryer 22 to a residual solvent amount of 20 to 150 μt/-, and further 50 to 80 μt/? It is desirable to do so. The drying temperature at this time is 60 to 80℃, and
In a dryer with a lid, residual solvent is dried to 5 to 10 .mu.t/-, and preferably 2 to 4 .mu.t/-. The drying temperature at this time may be 80 to 95°C.

Further, the conditions for the calendering may be as long as the temperature is 60 to 110° C., the pressing force is 200 to 500, and 9/cm. The support conveyance speed or roll rotation speed at that time is 150 to 300.
It is possible to increase the speed to m/min.

In the magnetic recording medium according to the present invention, at least polyurethane can be used as the binder resin of the magnetic layer, but
It can be synthesized by reacting a polyol with a polyinsyanate. Usable polyols include organic dibasic acids such as phthalic acid, adipic acid, trimerized lyluic acid, and maleic acid; glycols such as ethylene glycol, propylene glycol, butylene glycol, and diethylene f-linear; and trimethylolpropane. , hexanetriol, glycerin, trimethylolethane, pentaerythritol natonopolyhydric alcohols, or a polyester polyol synthesized by reaction with any two or more polyols selected from these glycols and polyhydric alcohols; Or, a lactone polyester polyol synthesized from lactams such as S-caglolactam, α-methyl-1-caglolactam, 8-methyl-B-caglolactam, and γ-butyrolactam; or synthesized from ethylene oxide, propylene oxide, butylene oxide, etc. Examples include polyether polyols.

These polyols are reacted with incyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, metaxylylene diisocyanate, etc., resulting in urethanized polyester polyurethane, polyether polyurethane, and carbonate with phosgene or diphenyl carbonate. Polycarbonate polyurethane is synthesized.

These polyurethanes are usually produced primarily by the reaction of polyisocyanates with polyols and are also in the form of urethane resins or urethane prepolymers containing free isocyanate groups and/or hydroxyl groups, or containing reactive end groups of these. (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 contained as a binder resin in addition to the above-mentioned polyurethane, the dispersibility of the magnetic powder will be improved when applied to the magnetic layer, and its mechanical strength will be increased. . However, if the phenoxy resin and/or vinyl chloride copolymer is used alone, the layer will not break, but this can be prevented by containing polyurethane, and the adhesion to the support or base layer will be 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, n=82-13) For example, PKHC manufactured by Union Carbide.

There are PKHH, PKHT, etc.

In addition, as for the above-mentioned vinyl chloride copolymer that can be used, the molar ratio derived from t and m is 95 to 50 mol υ for the former unit, and 5 to 50 mol υ for the latter unit. be.

Further, X represents at least one monomer residue selected from the group consisting of monomer residues copolymerizable with vinyl chloride, vinyl acetate, vinyl alcohol, maleic anhydride, and the like. (
The degree of polymerization expressed as L+m) is preferably 100
-600, and if the degree of polymerization is less than 100, the magnetic layer etc. tend to become sticky, and if it exceeds 600, the dispersibility becomes poor. The vinyl chloride copolymer described above may be partially hydrolyzed. As a vinyl chloride copolymer,
Preferably a vinyl chloride-vinyl acetate copolymer (
Hereinafter, it will be 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 orVAGHJ and rVY manufactured by Union Carbide Co., Ltd.
HJ, “vMCH”, “Suresoku A” manufactured by Tanemizu Kagaku ■
, "Eslenoku A-5", "Eslenoku C", "Eslec M", [Denkabinir 1000 manufactured by Denki Kagaku Kogyo ■]
G J, ``Denkabinir 100OW J etc. can be used.

In addition to the above, cellulose resins can also be used as binder resins, including cellulose ether,
Cellulose inorganic acid esters, cellulose organic acid esters, etc. can be used. Cellulose ether, methyl cellulose, ethyl cellulose, etc. can be used. As cellulose inorganic acid ester, nitrocellulose,
Cellulose sulfate, cellulose phosphate, etc. can be used. Further, as the cellulose organic acid ester, acetyl cellulose, glopionyl cellulose, phthyryl 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 amount of phenoxy resin, vinyl chloride copolymer, etc.) is 90/1 by weight.
Desirably 0 to 40/60, 85/15 to 45
It has been confirmed that 155 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, surface properties are likely to be poor, especially if (a) weight i:ch is exceeded, the overall physical properties of the coating film are poor. It doesn't look very good when you look at it. In the case of vinyl chloride-vinyl acetate, it can be mixed with the urethane resin with a certain degree of freedom, and the urethane resin is preferably 15 to 75% by weight.

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, acrylic ester-styrene copolymer, etc. 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. Moreover, among these resins, those which do not soften or melt before the resin is thermally decomposed are preferable. 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.

In the magnetic recording medium, a carbon blank may be further added to the magnetic layer. It is desirable that this carbon black has electrical conductivity, but carbon black with light-shielding properties may also be added. As such conductive carbon black,
For example, Conductenox (C) manufactured by Columbia Carbon
onductex) 975 (specific surface area 250i/g,
particle size 24 mμ), conductenox 900 (specific surface area 1
25 n? / g z particle size 27 mμ), Cabot Vulcan XC-7 manufactured by Kaponodo
2 (specific surface area 254 m”/g% particle size 30 mμ)
, Raven 1040.420, #44 manufactured by Mitsubishi Kasei ■, etc. Examples of light-shielding carbon blacks include Raven 2000 (specific surface area 190 m''/g% particle size 18 mμ) manufactured by Columbia Carbon Co., Ltd., and 2100 manufactured by Columbia Carbon Co., Ltd.
．． 1170.1000, #100, #7 made by Mitsubishi Kasei ■
5, #40, #35, #addition, etc. can be used. The carbon blank has an oil absorption of 90d(DBP)/1
A weight of 00 g or more is desirable because it facilitates formation of a strutter structure and exhibits higher conductivity.

The magnetic recording medium according to the present invention has magnetic layer holes on a support 1, as shown in FIG. 1, for example.

Further, a BC layer may be provided on the surface opposite to the magnetic layer holes. Although this BC layer may be provided, it is not necessary to provide it. Magnetic powders, especially ferromagnetic powders used for magnetic layer holes include γ-Fe2O3, Co-containing γF'e20
3. Fe3O4, Co-containing iron oxide magnetic powder such as 1i'e304: FeXNi, Co, fi"e-Ni-C.

Alloy, Fe-Mn-Zn alloy, Fe-Ni-Z
n alloy, Fe-Co-Ni-Cr alloy, F
e-Co-N1-P alloy, Co-Ni alloy, etc. Fe,
Examples include various ferromagnetic powders such as metal magnetic powders containing Ni, Co, etc. as main components.

Among these, co-containing iron oxide and metal magnetic powder are preferable. Also, is the BET value of magnetic powder 25tr? /g or more,
Furthermore, 30 m''/g or more is preferable.

The magnetic layer pores may also be filled with a lubricant (e.g. silicone oil,
graphite, molybdenum disulfide, tungsten disulfide, fatty acid esters consisting of a monobasic fatty acid with 12 to 20 carbon atoms (e.g. stearic acid) and a monohydric alcohol with 13 to 26 carbon atoms, etc.), abrasives ( For example, fused alumina), antistatic agents (for example, graphite), etc. may be added.

The non-magnetic powder contained in the BC layer includes carbon blank, silicon oxide, titanium oxide, aluminum oxide,
Chromium oxide, silicon carbide, calcium carbide, zinc oxide, α
-Those consisting of Fe203, talc, kaolin, calcium sulfate, boron nitride, zinc heptaoxide, molybdenum dioxide, calcium carbonate, etc., preferably those consisting of carbon black (especially conductive carbon black) and/or titanium oxide. .

Further, as the non-magnetic powder, organic powder such as benzoguanamine resin, melamine resin, phthalocyanine pigment, etc. may be added.

Incidentally, in the magnetic recording medium shown in FIG. 1, an undercoat layer (not shown) may be provided between the magnetic layer and the support 1.

In addition, when coating and forming the above-mentioned magnetic layer, etc., it is desirable to add a predetermined amount of polyfunctional incyanate 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 preferable.

Next, the present invention will be explained with reference to specific examples.

The components, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention.

In addition, in the following examples, all "parts" are "parts by weight".
represents.

A magnetic paint having the following composition was prepared.

Co-containing - Fe203 100 parts Polyurethane (Nistan 5701 manufactured by Gutdrich)
40 parts nitrocellulose (Daicel Cell Line R8I/2
) 20 parts vinyl chloride-vinyl acetate copolymer (VA manufactured by U, C, C)
GH) 10 parts lecithin
2-part myristic acid
1 part lauric acid 1 part methyl ethyl ketone 72 parts toluene
50 parts cyclohexanone
80 parts Carbon blank (Conductenox 975) 2 parts This composition was thoroughly stirred and mixed in a ball mill, and further 10 parts of polyfunctional isocyanate (Coronet L manufactured by Nippon Polyurethane Co., Ltd.) was added, and the average pore size was 1 μm.
filtered with a filter. Next, using the apparatus shown in FIG. 1, a magnetic paint was applied to the surface of the polyethylene terephthalate base having a thickness of 12 μm to a dry thickness of 5 μm. That is, after preliminary drying in the first dryer, calender treatment was performed, and then main drying was performed.

In this case, the following conditions were applied in each step.

Coating speed: 150 m/min Pre-drying temperature: 70 °C Residence time in pre-dryer: 10 seconds Calendar temperature: 70 °C Calendar pressure 200 kg/crn Main drying temperature: 410 °C Residence time in main dryer : After 5 seconds, it was wound onto a take-up roll and further cut into a predetermined width (for example, 12.7 mrn width) by a known slitting method to obtain a magnetic tape.

On the other hand, for comparison, a magnetic tape was prepared in the same manner as above except that the apparatus shown in FIG. 3 was used.

This comparative example was carried out under the following conditions.

Application speed: 150 m/min Drying temperature near 0°C (first drying zone in a single dryer) 90'C (same year - second drying zone in the dryer) Residence time in the dryer: 10 seconds (as above) 1st drying zone in a single dryer) 5 seconds (same year - 2nd drying zone in a dryer) Calendar temperature near 0°C Calendar pressure crab 200 to 97 cm This resulted in the data shown in the table below for each tape. Obtained.

Medium chroma S/N: Color signal AM noise was measured using a VHS deck.

**Audio S/N, Audio Sensitivity: Sensitivity is I
The output is measured against a reference input level of KHz.

The S/N is the audio S/N when a JIS hearing correction filter is used.

From this result, it is clear that each characteristic is improved or improved by using the device according to the present invention. This means that the surface properties of the magnetic layer are good and that there is little deterioration in performance even when the coating speed is increased.

The examples described above can be further modified based on the technical idea of the present invention.

For example, the method of applying and drying the magnetic paint may be varied, and the arrangement and number of drying sections may also be varied.

F. Effects of the Invention As described above, the present invention has the advantage that the solvent content of the coating layer is increased by -15
0μt/rr? Since the calender treatment is started at the time when , the coating film exhibits appropriate softness during the calender treatment and can be calendered well. Therefore, a coating film with good surface properties can be obtained at high speed (that is, without increasing the calender temperature or pressure) with good productivity.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, in which FIG. 1 is a schematic diagram of a magnetic recording medium manufacturing apparatus, and FIG. 2 is a sectional view of the magnetic recording medium. FIG. 3 is a schematic diagram of a conventional magnetic recording medium manufacturing apparatus. In addition, in the symbols shown in the drawings, 1......Support 2...Magnetic paint 11...・ Roll coater (m fabric part) 13.27... Nozzle 14,
Ah...Hot wind 15...
... Calendar roll 18 ... Calendar part 22 ...... First dryer...
.....This is the second dryer.

Claims (1)

[Claims] 1. The solvent content of the coating layer coated on the support is 20~
A method for manufacturing a magnetic recording medium in which calendering is started when the concentration reaches 150 μl/m^2.