JP2670834B2 - Method and apparatus for manufacturing magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a method and an apparatus for manufacturing a magnetic recording medium.

B. 2. Description of the Related Art A magnetic recording medium is obtained by applying a magnetic coating solution on a support, and the coating method is generally a roll coating, a gravure coating, or an extrusion coating. Among these, the extrusion (extrusion) coating is excellent because a uniform coating film thickness can be obtained.

By the way, as a conventional technique in an extrusion coating method mainly for the purpose of manufacturing a magnetic recording medium,
JP-A-57-84771, JP-A-58-104666 and JP-A-60-238179 are known.

The above extrusion coating method can surely obtain a uniform coating film thickness, but good coating conditions can be obtained only in a narrow range. Cannot be applied.

In particular, when applying a thin film, foreign matter adhering to the base film, dust or agglomerates in the magnetic paint adhere to or get caught on the back edge surface of the extruder, and the coating film comes out white, There were streak-shaped coating defects. In addition, a large amount of coating ram was generated, resulting in deterioration of electromagnetic conversion characteristics such as RF output.

C. OBJECT OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium with a high RF output.

D. Configuration of the Invention The present invention uses a coating method in which a magnetic coating liquid is discharged from a coating liquid discharge port to apply the magnetic coating liquid to an object to be coated, and the already-coated object is transferred along the back edge surface. In the method for manufacturing a magnetic recording medium, the back edge surface has a center line average roughness (Ra) of 3 μm or less.

Further, the present invention provides a coating liquid discharge port for discharging a magnetic coating liquid to apply the magnetic coating liquid to an object to be coated, and a side to which an uncoated object is transferred to the coating liquid discharge port. An apparatus for manufacturing a magnetic recording medium, comprising a coating device having a formed front edge surface and a back edge surface formed on a side where an already-coated object is transferred to the coating liquid discharge port. The present invention relates to an apparatus for manufacturing a magnetic recording medium, wherein the back edge surface has a center line average roughness (Ra) of 3 μm or less.

E. Examples Hereinafter, examples of the present invention will be described.

FIG. 1 is a perspective view showing an extrusion coater (extrusion coater) 1, and FIG. 2 is II-II of FIG.
FIG.

The extrusion coater 1 has a substantially rectangular parallelepiped shape in which the tip (application surface) is wedge-shaped, and a cylindrical liquid pool 3 is formed in the coater body 2 in the longitudinal direction. There is. The coating liquid is introduced into the liquid reservoir 3 from the liquid inlet 10 as shown by an arrow A. Slit from the reservoir to the tip of the coater from 3 (Liquid feeding)
4 is provided, and the coating liquid discharge port 7 is provided at the end of the slit 4. The coating liquid introduced into the liquid pool 3 is pushed out of the slit 4 as shown by an arrow B, and is pushed out of the coating liquid discharge port 7 as shown by an arrow C. A front edge surface 5 is formed on the upper side of the coating liquid discharge port 7 in FIG. 2, and a back edge surface 6 is formed on the lower side in FIG. The flexible non-magnetic base film 8 is fed along the front edge surface 5 and the back edge surface 6 as shown by the arrow D, and the surface of the base film 8 is coated with the magnetic paint discharged from the coating liquid discharge port 7. Thus, the magnetic paint coating layer 9 is formed.

What should be noted here is that the center line average roughness (Ra) of the back edge surface 6 is 3 μm or less.

That is, the present inventor, when forming the magnetic layer by the extrusion coater, as described above, has conducted research to prevent the occurrence of fine streak-like unevenness or streak-like failures in the magnetic coating film. In the course of that research, I paid particular attention to the surface condition of the edge surface of the coater head. Then, it was discovered that the above problem can be solved by setting the center line average roughness (Ra) of the back edge surface to 3 μm or less (preferably 1 μm or less). In other words, in order to prevent coating film defects, the surface state of the back edge surface that the base film should follow immediately after coating was fatally important, and by limiting Ra as described above, fine stripes The coating ram is prevented, and foreign matter that may cause streaky failure is not caught on the back edge surface.

The centerline average roughness (Ra) of the back edge surface is preferably as small as possible, but it is difficult to set it to 0.1 μm or less in terms of processing accuracy.

Here, the center line average roughness (Ra) refers to JISB 0601 (19
76) As defined on page 4, "Extract a portion of the measurement length l from the roughness curve in the direction of its center line, and use the center line of this extraction as the X-axis and the longitudinal magnification direction as the Y-axis. When the roughness curve is represented by y = f (x), it means that the value of Ra given by the following equation is represented in units of micrometers (μ).

To reduce the centerline average roughness (Ra) of the back edge surface to 5.0 μm or less, the back edge surface is surface-treated with, for example, a surface grinder (a horizontal surface grinder that uses the circumference of the tooth). do it.

FIG. 3 is an enlarged sectional view of a main part showing a periphery of an edge portion of another coater head.

This extrusion coater 21 has a front edge surface 25 on the upstream side surface, a back edge surface 26 on the downstream side surface, and a slit 4 for communicating a coating liquid reservoir (not shown) between them.

From the tangent line l ₁ at the downstream end E of the front edge surface 25,
A part of the back edge surface 26 protrudes (substantially projects upward in FIG. 3).

The support has a front edge surface 25 as indicated by the arrow D.
From the rising edge along the downstream end E, the slit 4
And, passing through the coating liquid discharge port 7, it goes to the right while going around the upper portion of the back edge surface 26 by the thickness of the coating liquid tank.

The radius of curvature r of the back edge surface 26 is preferably 3 to 10 mm.

Also in the coater head of this example, the center line average roughness (Ra) of the back edge surface 26 is set to 5.0 μm or less according to the configuration of the present invention. Further, with respect to the tangent line l ₁ at the downstream end E of the front edge surface 25, part of the back edge surface 26 (mostly in the example of FIG. 3) projects almost upward in FIG. It is considered that the force of the non-magnetic base film sent along the surface 25 to hit the downstream end E is dispersed to the back edge surface 26 and toward the back edge surface 26 through the coating liquid. Therefore, it is considered that the non-magnetic base film is less likely to be scraped by the steeply angled downstream end E, and so-called base scrap caused by this can be suppressed.

FIG. 4 is a schematic view showing an apparatus for manufacturing a magnetic recording medium such as a magnetic tape.

In general, a magnetic recording medium is manufactured through a process of applying a magnetic paint containing a magnetic powder on a base film, drying and calendering the surface of the magnetic layer by calendering under pressure and heat.

In the manufacturing apparatus shown in FIG. 4, first, the film-like support 8 unwound from the supply roll 12 is extruded by the extrusion coater 1.
After applying the magnetic paint by (21), it is oriented by the orientation magnet 13 and introduced into the dryer 14, where hot air is blown from the nozzles arranged above and below to dry it. Next, the dried support 8 with the magnetic layer is guided to a calender portion 17 composed of a combination of calender rolls 18, where it is calendered and then wound on a winding roll 19. The extrusion coater is shown schematically and may be any of those shown in FIGS. 1 to 3. The magnetic paint may be supplied to an extrusion coater through an inline mixer (not shown). In the drawings, D indicates the transport direction of the non-magnetic base film.

The magnetic recording medium to be manufactured by the coating method and the apparatus according to the present invention has a magnetic layer on a non-magnetic support 31 such as polyethylene terephthalate as shown in FIG.
33 and, if necessary, BC on the side opposite to the magnetic layer 33.
The layer 32 is provided. Further, as shown in FIG. 6, an overcoat layer (OC layer) 34 may be provided on the magnetic layer 33 of the magnetic recording medium of FIG.

The magnetic recording medium of FIGS. 5 and 6 may have an undercoat layer (not shown) provided between the magnetic layer 33 and the support 31, or may have no undercoat layer. May be. The support may be subjected to corona discharge treatment.

 Next, the material of the magnetic paint will be described.

At least polyurethane can be used as the binder resin in the magnetic coating, which can be synthesized by reacting a polyol with a polyisocyanate. When a phenoxy resin and / or a vinyl chloride type copolymer is contained together with polyurethane, the dispersibility of the magnetic powder when applied to the magnetic layer is improved and its mechanical strength is increased. Further, magnetic powders used, particularly ferromagnetic powders, include γ-Fe ₂ O
₃ , Co-containing γ-Fe ₂ O ₃ , Fe ₃ O ₄ , iron oxide magnetic powder such as Co-containing Fe ₃ O ₄ ; Fe, Ni, Co, Fe-Ni-Co alloy, Fe-Ni alloy, Fe-Al Alloy, Fe-Al-Ni alloy, Fe-Al-Co alloy, Fe-Mn-Zn alloy, Fe-Ni-Zn alloy, Fe-Al-Ni-Co alloy, Fe-Al-Ni
-Cr alloy, Fe-Al-Co-Cr alloy, Fe-Co-Ni-Cr alloy,
Fe-Co-Ni-P alloys, Co-Ni alloys, and various types of ferromagnetic powders such as metal magnetic powders containing Fe, Ni, Co, and the like as main components can be used.

Also in magnetic paints are lubricants (eg silicone oil, graphite, molybdenum disulfide, tungsten disulfide, monobasic fatty acids with 12 to 20 carbon atoms (eg stearic acid) and 13 to 14 carbon atoms in total. Fatty acid esters, etc.), abrasives (eg, fused alumina), antistatic agents (eg, carbon black, graphite), and the like.

As the material for the support, plastics such as polyethylene terephthalate and polypropylene, metals such as Al and Zn, glass, BN, Si carbide, porcelain, ceramics such as pottery and the like are used.

When forming the magnetic layer, a predetermined amount of a polyfunctional isocyanate as a crosslinking agent may be added to the coating.

The product name of the negative functional group-containing resin is "400
× 110A ”(manufactured by Zeon Corporation),“ MR-110 ”(manufactured by Zeon Corporation),“ TIM-3005 ”(manufactured by Sanyo Chemical),“ UR-830 ”
0 "," UR-8600 "," Byron 530 "(manufactured by Toyobo Co., Ltd.) and the like.

〔Example〕

Hereinafter, specific experimental examples will be described, but embodiments of the present invention are not limited thereto. In addition, "part" shall mean a "weight part."

 First, a magnetic layer was formed on a support according to the following procedure.

γ-Fe ₂ O ₃ (Hc.700Oe, BET value 25m ² / g) 100 parts Urethane resin (N3132 made by Nippon Polyurethane Co.) 7 parts Vinyl chloride-vinyl acetate copolymer (VAGH made by Union Carbide) 20 parts Alumina powder (α-Al ₂ O ₃ ) 7 parts Myristic acid 0.65 parts Stearic acid 0.35 parts Oleic acid 0.65 parts Butyl stearate 1 part Polyisocyanate 10 parts Toluene 150 parts Methyl ethyl ketone 150 parts Carbon black 5 parts The mixture was dispersed in a sand mill without addition of isocyanate, and then polyisocyanate was added and blended. Then, each magnetic paint was extrusion coated on the polyethylene terephthalate base film by an extrusion coater as shown in FIG. After that, drying and calendering (80 ° C, 70kg / cm ² )
After that, it was wound up and cured at 70 ° C. for 20 hours.

The back edge portion of the extrusion coater was ground by a horizontal axis surface grinder to have center line average roughness (Ra) as shown in the following table.

The wide film obtained as described above was cut into 1/2 inch width to obtain a video tape. The characteristics of this tape were measured as follows. The measurement results are shown in the table below.

Uneven coating: The coating was visually observed with transmitted light and reflected light over a coating length of 5 m and a coating width of 450 mm.

◎ ……… None ○ ……… Slightly △ △ …… Somewhat × ……… High Number of streak failures: Count the number of streak failures in the coating layer by transmitted light for a coating length of 10,000 m and a coating width of 450 mm. did.

RF output: The RF output at 4 MHz was measured using a VTR deck for measuring RF output, and the value after 100 times of reproduction was shown (however, in the case of the example, the reference value (0 dB) was used.) Center line average Roughness (Ra): Measured with a three-dimensional surface roughness meter (3FK) manufactured by Kosaka Laboratory (cutoff is 0.25 mm). Ra measured the back edge surface at a total of five points in the width direction of the support, and displayed the average value.

From the results shown in the above table, the following can be understood.

Coating unevenness: When Ra exceeds 3 μm, fine stripe-shaped coating unevenness becomes extremely large.

Streak failure: When Ra increases, foreign matter is easily caught on the back edge surface, and streak failure occurs from this foreign matter.

RF output: The RF output deteriorates in the manufacturing method of the comparative example due to the influence of coating unevenness.

 The above embodiments can be variously modified.

For example, the shape, dimensions, etc. of the head, front edge surface, back edge surface of the extrusion coater can be changed in various ways, and the dimensions, shape, structure, liquid pool, slits, coating solution discharge port, etc. of the entire extrusion coater can be changed. Can be variously changed.

As the coating liquid, not only magnetic coating material but also coating material for back coat layer of magnetic recording medium, coating material for undercoat layer, coating material for overcoat layer, etc., over coating of magnetic recording medium having metal thin film by vapor deposition etc. It can also be applied to layer coatings, back coat layer coatings, and the like. As a magnetic recording medium,
Not only a magnetic tape, but also a sheet-like thing, a disk-like thing, a card-like thing, etc. can be illustrated. During the manufacture of the magnetic recording medium, the order of orientation, drying, calendering, and the like can be changed.

The present invention can be applied to an extrusion coater having two or three or more application liquid discharge ports as the extrusion coater. Further, as a coating device, in addition to a device that continuously extrudes the coating liquid and coats it on the surface of the support as described above, for example, an inclined surface is slid (flowed down) onto the coating liquid, and the coating liquid is discharged through the coating liquid discharge port. It also includes those which are discharged more and applied on the support.

 The present invention can be applied to various coating methods and apparatuses.

F. EFFECTS OF THE INVENTION According to the method for manufacturing a magnetic recording medium and the apparatus therefor of the present invention, the surface roughness of the back edge surface is 3 μm or less in terms of the center line average roughness (Ra). Therefore, the magnetic recording medium having a high RF output. Is obtained.

[Brief description of the drawings]

1 is a perspective view showing an extrusion coater (extrusion coater head), FIG. 2 is a sectional view taken along the line II-II in FIG. 1, and FIG. FIG. 4 is a schematic view showing an example of an apparatus for manufacturing a magnetic recording medium, FIG. 5 and FIG. 6 are partial views showing an example of the magnetic recording medium, respectively. It is a sectional view. In the reference numerals shown in the drawings, 1, 21 ... Extrusion coater (coater head) 2 ... Coater head body 3 ... Liquid pool 4 ... Slit 5, 25 ... Front edge surface 6, 26 ... Back edge surface 7 ... Coating liquid discharge port 8 ... Magnetic support 9 ... Magnetic coating layer A, B, C ... Flow of magnetic coating D ... Transfer direction of non-magnetic support.

Claims (2)

(57) [Claims] 1. A magnetic method using a coating method in which a magnetic coating liquid is discharged from a coating liquid discharge port to apply the magnetic coating liquid to an object to be coated and the already-coated object is transferred along a back edge surface. In the method for manufacturing a recording medium, the surface roughness of the back edge surface is a center line average roughness (Ra).
Is 3 μm or less, a method of manufacturing a magnetic recording medium. 2. A coating liquid discharge port for discharging a magnetic coating liquid to apply the magnetic coating liquid to an object to be coated, and an uncoated member to be transferred to the coating liquid discharge port. In a manufacturing apparatus of a magnetic recording medium, which comprises a coating device having a front edge surface and a back edge surface formed on a side where an already-coated object is transferred to the coating liquid discharge port, The surface roughness of the back edge surface is the center line average roughness (Ra).
Is 3 μm or less, a manufacturing apparatus for a magnetic recording medium.