JP2691602B2 - Coating method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method and its apparatus (for example, a coating method for magnetic layer coating material and its apparatus).

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 coating a thin film relatively, unevenness of the coating film thickness was often generated, and streak-shaped coating failure (coating defect) occurred at a place where the coating film thickness was small. Furthermore, unevenness of the film thickness occurs in the width direction of an object to be coated such as a non-magnetic base film. For example, when 10,000 m is applied and wound up on a winding roll, unevenness is generated on the winding roll to form a winding shape. Became worse, and sometimes the winding was broken and winding wrinkles occurred.

C. Object of the invention The object of the present invention is that the coating film thickness does not become uneven and can be made uniform, and when the coated product is wound up, the winding shape is clean and there is no winding collapse or winding wrinkle. It is to provide a coating technology that becomes

D. According to the present invention, the object to be coated is transferred along the front edge surface, the coating solution is discharged from the coating solution discharge port to apply the coating liquid to the object to be coated, and the already-coated object is back edged. In the coating method of transferring along a surface, the straightness of the waviness component of the front edge surface and the back edge surface (in the width direction of the object to be coated) is 20 μm / m or less. It is related.

Further, according to the present invention, a coating liquid ejection port for ejecting a coating liquid to apply the coating liquid to an object to be coated, and an uncoated substrate to be transferred to the coating liquid ejection port are formed. In a coating apparatus 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 waviness of the front edge surface and the back edge surface The present invention relates to a coating apparatus, wherein the straightness of the components (in the width direction of the coated object) is 20 μm / m 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. A slit (liquid feed hole) 4 is provided from the liquid reservoir 3 toward the tip of the coater, and a 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. Second of the coating liquid discharge port 7
A front edge surface 5 is formed on the upper side in the figure, and a back edge surface 6 is formed on the lower side in the figure. 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.

It should be noted here that the back edge surface 6 and the front edge surface 5 are in the x-axis direction (the non-magnetic base film 8).
The straightness of the waviness component in the width direction is 20 μm / m or less (preferably 5 μm / m or less).

First, the straightness will be described. The cross-sectional curve of the back edge surface 6 (or the front edge surface 5) in the x-axis direction is schematically shown in FIG. This cross-section curve YI consists of a swell component (low frequency component) and a finer roughness component (high frequency component). If only the swell component is extracted and the roughness component is cut, the swell shown in Fig. 4 is obtained. The curve YII is obtained. The straightness referred to here is the degree of "deflection" from the ideal straight line of the waviness curve YII. Specifically, the back edge surface 6 and the front edge surface 5 have a waviness curve of length l (that is, 1 m) in the x-axis direction.
YII is taken and ideal straight lines L ₁ and L ₂ that are in contact with the wavy curve YII and are parallel to each other are drawn, and the distance between L ₁ and L ₂ is K. This K is the straightness per length l. In the present invention, l = 1 m and the unit of K is μm, so the straightness is K μm / 1 m. The straightness per 1 m of edge length is set because the larger the measured edge length is, the larger the bending amount becomes.

The present inventor has conducted research to prevent the occurrence of film thickness unevenness and streak-like failures of the magnetic coating film as described above when forming the magnetic layer by the extrusion coater. During this process, we 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 straightness of the waviness component of the front edge surface and the back edge surface (in the width direction of the non-magnetic base film) to 20 μm / m or less.
In other words, in order to prevent coating film defects, it was fatally important that the badge surface (front edge surface, back edge surface) to be followed by the base film being conveyed was not deflected as a whole. Specifically, by specifying the straightness of the waviness component of the edge surface in the width direction of the non-magnetic base film as described above, the film thickness of the magnetic coating film on the base film conveyed along the edge surface. Was uniform and the unevenness of the film thickness in the width direction could be prevented. As a result of suppressing the film thickness unevenness, the streak-shaped coating failure that has conventionally occurred in the thin film portion does not occur. With this, even if the already applied base film is wound into a roll,
The unevenness in the width direction and the winding shape did not deteriorate.

The straightness (in the width direction of the object to be coated) of the waviness component of the back edge surface and the front edge surface is preferably as small as possible, but the processing accuracy is limited to about 1 μm / m.

In order to set the straightness to 20 μm / m or less, the back edge surface may be surface-processed by, for example, a surface grinding machine (a horizontal axis surface grinding machine that performs work using the circumference of a tooth).

FIG. 5 is an enlarged sectional view of an essential part showing the periphery of the edge part of another coater head.

The extrusion coater 21 has a front edge surface 25 on the upstream surface, a back edge surface 26 on the downstream surface, and a slit 4 communicating with 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 is made to project (almost upward in FIG. 5).

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.

In the coater head of this example, the back edge surface 26 and / or
Alternatively, the straightness of the waviness component of the front edge surface 25 (in the width direction of the base film) is set to 20 μm in accordance with the constitution of the present invention.
m / m or less. Further, with respect to the tangent line l ₁ at the downstream end E of the front edge surface 25, a part of the back edge surface 26 (mostly in the example of FIG. 5) 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 via 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. 6 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. 6, first, the film-shaped support 8 fed from the supply roll 12 is 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 schematically shown and may be any of those shown in FIGS. 1 to 5. 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. 8, 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 shown in FIGS. 7 and 8 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-based 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-A
l 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 alloy, Co-Ni alloy, etc. Metal magnetism containing Fe, Ni, Co, etc. as main components Various ferromagnetic powders such as powder 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 40 carbon atoms in total. Abrasives (eg fused alumina), antistatic agents (eg carbon black, graphite), etc. may be added, such as fatty acid esters.

Further, as the material of the support, plastics such as polyethylene terephthalate and polypropylene, metals such as Al and Zn, glass, BN, Si carbide, ceramics such as porcelain and pottery 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.

(Experimental 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 ₃ 100 parts (Hc.700Oe, BET value 25 m ² / g) Urethane resin 7 parts (N3132 made by Nippon Polyurethane Co.) Vinyl chloride-vinyl acetate copolymer 20 parts (VAGH made by Union Carbide) 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 Dispersion was carried out by a sand mill without addition of isocyanate, and then polyisocyanate was added to prepare a mixture. Then, each magnetic paint was extrusion coated onto 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 part and the front edge part of the extrusion coater were ground by a horizontal axis surface grinder, and had the straightness of the waviness component (the width direction of the polyethylene terephthalate base film) 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.

Straightness: Measured with a straightness measuring machine. It should be noted that the measurement may be performed with a straight edge or the like.

Roll shape: 10000m on polyethylene terephthalate base film
The magnetic paint was applied, and this was wound on a winding roll and the winding shape was observed.

From the results shown in the above table, it can be seen that when the straightness exceeds 50 μm / m, coating unevenness and streak failures increase, failures occur when wound in a roll shape, and cutting cannot be performed.

 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-shaped one, a disk-shaped one, a card-shaped one and the like can be exemplified. 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 coating method and the apparatus thereof according to the present invention, since the straightness of the waviness component of the front edge surface and the back edge surface (in the width direction of the object to be coated) is set to 20 μm / m or less, coating is performed. Uniformity can be achieved without unevenness of the film thickness, and the winding shape when winding the coated one is beautiful,
There will be no collapse or wrinkles.

[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 of FIG. 1, and FIG. 3 is a back view. FIG. 4 is a schematic diagram showing the cross-sectional shapes of the edge and the front edge, FIG. 4 is a schematic diagram showing the waviness of the back edge and the front edge, and FIG. 5 is an enlarged cross-sectional view of the main part showing the edge surface periphery of another coater head. FIG. 6 is a schematic view showing an example of a magnetic recording medium manufacturing apparatus, and FIGS. 7 and 8 are partial cross-sectional views showing an example of the magnetic recording medium. 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 ... Non-magnetic support 9 ... Magnetic coating layer A, B, C ... Flow of magnetic coating D ... Transfer direction of non-magnetic support YI ... Back edge / Front edge Cross-section curve YII …… Waviness curve of back and front edges K …… Straightness x …… Width direction of non-magnetic base film.

Claims (2)

(57) [Claims] 1. An object to be coated is transferred along a front edge surface, the coating solution is discharged from a coating solution discharge port to apply the coating solution to the object to be coated, and the already-coated object is applied to the back edge surface. In the coating method of transferring along, the straightness of the waviness component of the front edge surface and the back edge surface (in the width direction of the object to be coated) is 20 μm / m or less. 2. A coating liquid discharge port for discharging a coating liquid to apply the coating liquid to an object to be coated, and an uncoated member to be transferred to the coating liquid discharge port. In a coating apparatus 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, a waviness component of the front edge surface and the back edge surface The straightness (in the width direction of the object to be coated) is 20 μm / m or less.