JPH10411A - Applicator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an applicator which discharges coating without retention in a slit and forms a high quality coating film by checking the generation of uneven application and stripes. SOLUTION: An extrusion type applicator is equipped with a die 2 having a coating bank 5 to which coating 4 is supplied and applies the coating 4 on a support 1 traveling continuously while extruding the coating 4 from a slit 3 formed at the end of the die 2. Surface treatment by a composite plating coat in which fine particles of polytetrafluoroethylene are dispersed uniformly in an electroless nickel coat is applied on the inner wall surface of the slit 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus, and more particularly to a coating apparatus used for applying a magnetic paint or the like when manufacturing a magnetic recording medium.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a coating type magnetic recording medium, as a coating device for a magnetic paint or a non-magnetic paint, a coating device using a roll such as a gravure roll or a reverse roll has been mainly used. Particularly wide structural viscosity (thixotropic)
The direct gravure method which can apply the thing of high gravure is common.

However, in the gravure roll described above, depending on the structural viscosity of the magnetic paint, the transferability of the dye onto the base film, which is a nonmagnetic support, is impaired, and the coating thickness becomes uneven and the paint tends to diffuse. . When such thickness unevenness occurs in the magnetic coating film, it induces output fluctuation. Also, paint diffusion causes dropout.
Such poor transfer of paint is remarkable when a magnetic paint having a high structural viscosity, for example, a metal-based magnetic paint is used, and also between a cell groove of a gravure roll and a support even in high-speed coating. Because it is easier to create an air layer,
There is a problem that poor transfer is likely to occur.

On the other hand, as a coating apparatus capable of solving these problems, an extrusion (die) type coating apparatus has attracted attention and has already been put to practical use. This extrusion-type coating apparatus has a wide slit facing the front end surface, a die having a doctor edge near the front end portion, and the slit is directed from the slit toward the surface of the running support. The magnetic paint is continuously extruded, and the magnetic paint is slid by the doctor edge so as to be applied on the support with a uniform thickness.

[0005] Such an extrusion type coating apparatus can easily form a coating film having a uniform thickness, and can reduce the cost and size of the apparatus because a roll having a large diameter is not used. This is advantageous in that it has been used in fields such as photographic film and photographic paper.

[0006] In this extrusion type coating apparatus, the tip end surface of the die is constituted by a pair of upper and lower lips, and a slit is formed between the lips.
An orifice-shaped pocket having a length substantially equal to the width of the slit is provided on the back side of the slit. The paint is stored in the pocket and is pushed out of the pocket into the slit with a predetermined pressure, and is supplied stably to the surface of the support from the tip of the slit. The support runs from the upper lip side to the lower lip side of the coating apparatus.

However, when the speed of the extrusion type coating apparatus is increased, an air film invades the upper lip side and beads are formed to be large, so that the formation of the coating film becomes unstable.

Therefore, in this extrusion type coating apparatus, various structures such as lip protrusion and chamfering have been studied so that a stable coating film can be formed. For example, the extruded paint wraps around the back side of the support and contaminates the running roll, and after drying of the coating film, both ends in the width direction of the magnetic recording medium are swollen and a shape defect occurs. In order to eliminate inconveniences such as fraying, spacers are interposed at both ends in the width direction of the slit to substantially narrow the width of the slit so that a stable coating film can be formed. Various improvements are underway.

[0009]

By the way, the improvement of the structure of the coating apparatus as described above alone cannot provide a sufficient effect, and the quality characteristics of the obtained magnetic recording medium cannot be said to be sufficient.

In particular, in the step of applying the back coating of the non-magnetic layer, since the particles contained in the magnetic coating are coarser, clogging tends to occur during discharge from the slit, and the coating tends to stay on the inner wall of the slit. In particular, 1.0 μm
It was very difficult to form the following thin film layers.

The present invention has been proposed in view of such a conventional situation, and a paint is discharged without remaining in a slit, and a coating film of high quality can be formed by suppressing uneven coating and streaks. It is an object of the present invention to provide a coating apparatus for forming a coating.

[0012]

The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, have found that in the step of applying a magnetic paint or a non-magnetic paint, large unevenness or streaking may occur. It was found that there was uneven discharge in the slit as a factor.

The coating apparatus according to the present invention has been completed on the basis of such knowledge, and is provided with a die having a paint reservoir to which paint is supplied, and is provided on a continuously running support. In an extrusion-type coating apparatus for applying a coating while extruding paint from a slit provided at the tip of a die, fine particles of ethylene tetrafluoride were uniformly dispersed and co-deposited in the electroless nickel coating on the inner wall surface of the slit. It is characterized by being subjected to a surface treatment with a composite plating film.

In the coating apparatus according to the present invention, since the surface treatment with the composite plating film having an appropriate contact angle is performed on the inner wall surface of the slit, the coating material does not stay in the slit and has a full width. Is discharged uniformly and smoothly over the entire surface. Therefore, a high-quality coating film can be formed without causing uneven coating or streaks on the support.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an extrusion type coating apparatus to which the present invention is applied will be described below in detail with reference to the drawings.

In this coating apparatus, as shown in FIG. 1, a support 1 is formed of a substantially rectangular parallelepiped metal block having a predetermined width in a middle portion of the support 1 which is sequentially moved from the unwinding side to the winding side. A die (extruder) 2 is provided. The die 2 is disposed on the side of the support 1 running downward from above in FIG. 1, and a pair of upper and lower lips 2 a and 2 b constituting the tip end surface of the die 2 are provided on the surface of the support 1. They are arranged to face each other.

As shown in FIG. 2, this die 2 has a so-called wedge shape in which the vicinity of the tip surface is cut off obliquely in a straight line, and its lips 2a and 2b are formed of a cemented carbide or the like. Has been Further, a slit 3 corresponding to the application width is formed between the upper lip 2a and the lower lip 2b. The slit 3 serves as a gap through which the paint 4 is extruded, and is usually 0.0
It is a very narrow gap of about 1 to 2.0 mm.

On the back side of the slit 3, a slit 3
(A paint pool) 5 communicating with the slit 3 is formed as an orifice-shaped space having a length substantially equal to the width of the slit 3. A paint supply port (not shown) is provided at both ends of the pocket 5, and a paint supply pipe 6 for introducing the paint 4 is connected thereto. A pump 7 is mounted in the middle of the paint supply pipe 6.
As a result, the paint 4 is fed from the paint supply pipe 6 into the pocket 5 at a predetermined pressure. The pocket 5 becomes a space for receiving the paint 4 to be pumped, and has a function of an accumulator. Paint 4 pumped into this pocket 5
Is supplied into the slit 3, and a pair of upper and lower lips 2a, 2a
b and is extruded on the surface of a support running opposite to the surface of the support and is displayed as a coating film 8.

The support 1 moving and running from the unwinding side to the winding side is supported by guide rolls 9a and 9b, and is appropriately tensioned so that smooth running can be performed. ing. Therefore, in this coating apparatus, as shown in FIG. 3, the support 1 which is fed from the unwinding side and travels in the direction A in FIGS.
A pair of upper and lower lips 2 at the tip of the die 2 with respect to the surface of
a and 2b are brought into contact with each other, and the paint 4 is extruded from the slit 3 into the contact surface to form a coating film 8.

[0020] At this time, by regulating the width of the slit 3, the coating width W ₂ of the coating film 8 formed on the support 1 having a width W ₁ is restricted. Here, the uncoated portion 10 is formed to have a width of about 3 to 10 mm at both ends in the width direction of the support 1. As a result, the extruded paint 4 does not go around the back side of the support, and a good coating film can be formed.

The above is the basic configuration of this device.
In this coating device, the slit inner wall surfaces 3a, 3a
b is subjected to a surface treatment with a composite plating film.
The composite plating film is obtained by uniformly dispersing and co-depositing fine particles of fluororesin (ethylene tetrafluoride) in an electroless nickel film having a chemical composition of nickel (Ni) and phosphorus (P).

Since the composite plating film has an appropriate contact angle, the coating 4 does not stay in the slit 3 over the entire width of the slit inner wall surfaces 3 a and 3 b on which the composite plating treatment has been performed. The coating is discharged uniformly and smoothly over the entire surface of the support 1, and a stable coating film is formed without causing uneven coating or streaks on the support 1.

The composite plating film has a thickness of 7 to 20 μm.
m. When the thickness is 6 μm or less, the adhesion to the slit inner wall surface 3a is poor, and when the thickness is 21 μm or more, there are many problems in uniformity.

Further, it is preferable that the composite plating film has a slight releasability, and is formed with an appropriate wetting property with a contact angle to water of about 45 °. The contact angle is 45
When the angle is smaller than 0 ° (when the wetting property is too good), the flow of the paint 4 discharged along the inner wall surface 3a of the slit is deteriorated, and the effect of preventing the above-described retention is small. When the contact angle is 4
If the angle is larger than 5 ° (the wettability is poor), a water-repellent phenomenon occurs in which the paint 4 pops, and the paint 4 is disturbed on the inner wall surface 3a of the slit, making it impossible to discharge smoothly.

As shown in FIG. 4, the entire upper and lower lips 2a and 2b in the width direction (shaded portions in FIG. 4).
Also, a surface treatment with the composite plating film may be performed. By subjecting this portion to a surface treatment with a composite plating film, the coefficient of friction on the surface of the support 1 is reduced, and good slidability is obtained. As a result, the support 1 due to the contact between the lips 2a and 2b and the surface of the support 1
, And the lips 2a, 2b are prevented from being damaged, and a more stable coating film can be formed.

The above-described coating apparatus is suitable for application of a magnetic paint or a non-magnetic paint on a coating type magnetic recording medium. In this case, a non-magnetic support, a magnetic coating, a non-magnetic coating Any of conventionally known magnetic powders, binders, and the like can be used, and there is no particular limitation.

For example, as the nonmagnetic support,
Examples include polyester resin films such as polyethylene terephthalate and polyethylene-2, aromatic polyamide resin films, and polyimide resin films.

As the magnetic powder of the magnetic coating film, Fe-C
o, Fe-Ni, Co-Ni, Fe-Co-Ni, Fe
-Co-B, Fe-Co-Cr-B, Fe-Mn-Z
Metal particles containing Fe, Co, and Ni as main components, such as n and Fe-Co-Ni-P, are preferable. In the above magnetic powder, Al, Si,
Metal components such as Ti, Cr, Mn, Cu, and Zn may be added.

Further, in addition to the binder and the magnetic powder, a dispersant, an internal additive, an abrasive, an antistatic agent, a rust inhibitor and the like may be added to the magnetic layer.

As the non-magnetic powder of the non-magnetic coating film, those having an antistatic effect and a friction reducing effect such as carbon black can be used. These nonmagnetic layers are formed as a back layer on the side of the nonmagnetic support opposite to the side on which the magnetic layer is formed.

As binders for dispersing and binding these magnetic and non-magnetic powders, vinyl chloride, vinyl acetate, vinyl alcohol, vinylidene chloride, acrylonitrile, acrylate, methacrylate, styrene, butadiene And the like, or a copolymer of two or more of these, a polyurethane resin, a polyester resin, an epoxy resin, and the like.

Organic solvents for preparing these paints include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, and esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate and glycol monoethyl ether such as glycol acetate. Solvents include glycol ether solvents such as glycol dimethyl ether, glycol monoethyl ether, and dioxane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; and aliphatic hydrocarbon solvents such as hexane.

[0033]

EXAMPLES Hereinafter, a magnetic tape was manufactured using the coating apparatus having the above-described configuration, and the effect thereof was examined.

Examination of Surface Treatment of Inner Wall By changing the type of surface treatment of the slit inner walls 3a and 3b and the material of the die 2 of the above-described coating apparatus, a magnetic layer which becomes a magnetic layer on one surface of the non-magnetic support is obtained. The coating was applied to the other surface of the non-magnetic support with a non-magnetic coating to be a backing layer to produce a magnetic tape. (Hereinafter, these are shown as Example 1, Example 2, and Comparative Examples 1 to 3.) The types of surface treatment of the slit inner wall surfaces 3a and 3b include a composite plating film, a chrome plating film, and a tetrafluoroethylene resin film. (Hereinafter, referred to as a Teflon film), and no treatment is selected.
It was selected from one of stainless steel, cemented carbide, and carbon tool steel. The contact angles of the composite plating film, the chrome plating film, the Teflon film, and the cemented carbide with water are about 45 °, about 35 °, about 65 °, and about 40 °, respectively.

As the non-magnetic support, a 7.5 μm polyester film was used, and the running speed was 500 m / m.
Minutes.

As the magnetic paint, Co powder is applied to the magnetic powder.
γFe ₂ O ₃ , a vinyl chloride copolymer, a polyurethane resin as a binder, methyl ethyl ketone, cyclohexanone, toluene as a solvent, and lecithin as an additive were used, each having a solid content of 38% and a viscosity of 3,200 cps.

As the non-magnetic coating material, a coating material containing carbon black as a main component and having a solid content of 15% and a viscosity of 80 cps using the same binder, solvent and additives as those of the above magnetic coating material was used.

Then, the obtained magnetic tape (Example 1,
Example 2 and Comparative Examples 1 to 3) were examined for coating conditions. Table 1 shows the results. In Table 1, in each of the evaluation items, a circle indicates a stable coating state without streaks or coating unevenness, and a cross indicates a coating state in which streaks or coating unevenness is conspicuous and greatly affects the quality of the magnetic tape. The mark “△” indicates a coating state that slightly affects the quality of the magnetic tape.

[0039]

[Table 1]

As can be seen from Table 1, in Examples 1 and 2 in which a composite plating film having a contact angle of 45 ° was formed on the inner wall surfaces 3a and 3b of the slit made of stainless steel or cemented carbide, Both the magnetic paint and the non-magnetic paint are uniformly and smoothly discharged over the entire width without stagnating in the slit 3, and do not generate uneven coating or streaks on the support 1, and provide a high-quality coating film. (Magnetic layer, back layer) were obtained.

On the other hand, the inner wall surfaces 3a, 3b of the slit
In Comparative Example 1 in which no friction reduction treatment was applied to the steel (the contact angle of the cemented carbide was about 40 °), in the case where a non-magnetic paint having more coarse particles than the magnetic paint was applied, the non- Clogging and stagnation of the magnetic paint were apt to occur, and streaks and coating unevenness occurred in the coating film (back layer).

Further, in Comparative Example 2 in which the inner wall surfaces 3a and 3b of the slits were subjected to a chrome plating coating treatment with a small contact angle of about 35 ° (high wettability), as in Comparative Example 1, As a result, coating retention and discharge unevenness tended to occur, and streaks and coating unevenness occurred in the coating film (magnetic layer and back layer).

Comparative Example 3 in which the inner wall surface of the slit was treated with a Teflon film having a large contact of about 60 ° (small wetting).
In the case, the water repellent phenomenon in which the paint 4
Did not discharge smoothly, and streaks occurred in the coating film.

Therefore, in order to obtain a high quality coating film (magnetic layer, back layer), a low friction surface treatment with a composite plating film having a contact angle of about 45 ° is applied to the inner wall surfaces 3a and 3b of the slit. Has been found to be effective.

Examination of Surface Treatment of Die Tip Surface The lip 2 on the tip surface of the die 2 of the above-mentioned coating apparatus
a, 2b, the type of the surface treatment, the surface treatment width, and the material of the die 2 were changed.
A magnetic coating material to be a magnetic layer is applied to one surface of the non-magnetic support 1
Apply a non-magnetic paint to be the back layer on the other side of the
A magnetic tape was produced. (Hereinafter, these are shown as Experimental Examples 1 to 7.) The coating status of the obtained magnetic tapes (Experimental Examples 1 to 7) was examined. Table 2 shows the results. In Table 2, in each of the evaluation items, the mark “○” indicates that no dust was generated from the non-magnetic support 1 or that the lip 2
a, 2b shows no scratches, and also shows a situation where the applied state is very stable. The x mark indicates that some dust is generated from the non-magnetic support 1, and the lips 2a, 2b are slightly scratched. Indicates a situation where the application situation was slightly affected by the situation, and a triangle indicates a coating situation slightly inferior to a circle.

[0046]

[Table 2]

From the results shown in Table 2, a pair of upper and lower lips 2a,
In Experimental Examples 1 and 2 in which the surface treatment with the composite plating film was performed on the entire surface in the width direction of 2b, extremely high quality coating films (magnetic layer and back layer) were obtained. This is because, by performing a surface treatment with a composite plating film on the entire surface of the lips 2a and 2b in the width direction, excellent lubricity is obtained, the coefficient of friction with the nonmagnetic support 1 is reduced, and the effect is maintained for a long time. Because it was done.

On the other hand, Experimental Example 3 in which a chrome plating film treatment was performed, Experimental Example 4 in which a Teflon film treatment was performed, and
In Experimental Example 5 in which no surface treatment was performed, the results were slightly inferior to Experimental Examples 1 and 2.

Experimental examples 6 and 7 in which only the widthwise ends of the pair of upper and lower lips 2a and 2b which are in direct contact with the uncoated portion 10 of the nonmagnetic support 1 are subjected to surface treatment.
In the above, the coating condition at both ends was good, but the coating condition at the center was not satisfactory. This became remarkable as the coating speed increased.

Therefore, a better coating film (magnetic layer,
In order to obtain the back layer), the lip 2a on the tip surface of the die 2
It is effective to apply a low friction surface treatment to the composite lip 2b with a composite plating film having a contact angle of about 45 °. More preferably, the surface treatment is applied to the entire surface of the lips 2a and 2b in the width direction. . Also, by applying the surface treatment to the lips 2a and 2b, the coating, the lips 2a and 2b
The deterioration of the accuracy of the slit 3 provided between them is reduced, and a more stable coating film can be formed.
The durability of itself is also improved.

[0051]

As is clear from the above description, in the coating apparatus according to the present invention, since the inner wall surface of the slit is subjected to the surface treatment with the composite plating film having an appropriate contact angle, the coating material is not coated. The ink is discharged uniformly and smoothly over the entire width without stagnation in the slit, and a high-quality coating film can be formed without causing coating unevenness or streaks on the support.

Further, in this coating apparatus, by performing a surface treatment with the composite plating film on the tip end surface of the die, a more stable coating film can be formed, and the durability of the coating apparatus can be improved.

Therefore, the coating apparatus according to the present invention can form a high-quality coating film, and can provide a magnetic recording medium having excellent quality characteristics.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of a coating apparatus to which the present invention is applied.

FIG. 2 is an enlarged sectional view of a main part showing a configuration near a tip end surface of a die.

FIG. 3 is an enlarged plan view of a main part showing a state in which a running support and a tip end surface of a die are in contact with each other.

FIG. 4 is an enlarged plan view of a main part showing a state in which a composite plating film treatment has been performed on the entire width direction of the tip end surface of the die.

[Explanation of symbols]

1 support, 2 dies, 2a upper lip, 2b lower lip, 3 slits, 4 paints, 5 pockets,

Claims (2)

[Claims] An extrusion-type die, comprising a die having a paint reservoir to which paint is supplied, and applying the paint while extruding the paint from a slit provided at the tip of the die onto a continuously running support. In the coating apparatus, the inner wall surface of the slit is subjected to a surface treatment with a composite plating film in which fine particles of ethylene tetrafluoride are uniformly dispersed and eutectoid in an electroless nickel film. 2. The tip surface of the die is subjected to a surface treatment with a composite plating film in which fine particles of ethylene tetrafluoride are uniformly dispersed and eutectoid in an electroless nickel film. 2. The coating device according to 1.