JPH0531428A - Coating device - Google Patents

Abstract

PURPOSE:To obtain the coating device which can form a coating film having a smooth surface and high quality by positioning the front end of a smoothing blade on a tangent at the downstream side end of a front blade surface. CONSTITUTION:The front end in the direction where a coating material is extruded from a slit 4 is the downstream side end A at the front blade surface 8a and is the terminal B of a plane part 9b of the smoothing blade surface 9a. The magnetic coating material 3 supplied into a pocket 2 of a die 1 uniformized by the accumulator effect due to the coating material pressure and is uniformly extruded to the slit 4. A base film 7 travels continuously in the state of being embraced along the front blade 8 and smoothing blade 9 provided at the outlet end of the slit 4, and the magnetic coating material 3 extruded from the slit 4 is made into the coating film having the uniform coating thickness and smooth surface by the smoothing blade 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion type coating apparatus called a die coater.

[0002]

2. Description of the Related Art Conventionally, as a coating method of a magnetic coating material for manufacturing a coating type magnetic recording medium, a roll coating method using a roll is mainly used as represented by a gravure roll method and a reverse roll method. Is becoming However, in these roll coating methods, output fluctuations due to uneven coating thickness due to poor transfer of paint from the roll to the base film, drop-out due to paint scattering, and paint quality due to excessive supply of paint being returned to the mixing process There are problems such as deterioration, and these problems tend to become more prominent as the coating speed increases.

In recent years, an extrusion (die) method has attracted attention as a new coating method capable of solving these problems, and it has already been partially put into practical use in the manufacturing process of a coating type magnetic recording medium. The extrusion method has a narrow slit with a predetermined width at the tip and uses a die with a doctor edge in the vicinity of the tip, and the paint continuously extruded toward the surface of the moving support is used as the doctor. The edged surface is applied on a support with a uniform thickness, which has been used in the fields of photographic film, photographic paper, and the like.

[0004]

By the way, in the extrusion type coating apparatus, it is known that the shape of the tip end surface of the die that abuts against the flexible support greatly affects the coating quality. , So far, improvements have been made in various fields. For example, JP-A-57-84771
JP-A-58-104666, JP-A-60-
No. 238179, Japanese Patent Application Laid-Open No. 1-288364, Japanese Patent Application Laid-Open No. 2-35959 and the like disclose coating apparatuses in which various shapes of the die tip portion (so-called lip portion) are defined.

However, even with these techniques, it is not possible to sufficiently suppress the occurrence of coating unevenness and streaks.
Further improvements are desired. Therefore, the present invention has been proposed in view of such conventional circumstances, a stable coating state is obtained, the coating thickness is uniform, to form a high-quality coating film having a smooth surface without streaks etc. It is an object of the present invention to provide a coating device to be obtained.

[0006]

In order to achieve the above object, the coating apparatus of the present invention is provided on a flexible support which continuously runs along the front blade surface and the smoothing blade surface of the die tip. In an extrusion type coating apparatus for coating the coating material while extruding the coating material from a slit provided at the tip of the die, the tip of the smoothing blade surface is located on the tangent line at the downstream end of the front blade surface. Is. In the present invention, the die tip portion (lip portion) located on the upstream side (the entry side of the flexible support) is set to the front blade and the downstream side with respect to the continuously running flexible support. The lip portion located at is referred to as a smoothing blade.

[0007]

[Operation] At the lip of the die, the front blade is ahead of the smoothing blade (paint extrusion direction)
When the protrusion is projected to, the excessive contact pressure is applied to the support body at the downstream end portion of the front blade, and the support body is bent, so that scratches and shavings are generated. On the contrary, when the smoothing blade protrudes from the front blade, the clearance between the smoothing blade and the support body becomes too large at the downstream end portion of the front blade, and air entrainment and air pressure uneven streaks occur. Also, if the front blade surface retracts too much,
The paint pressurized on the smoothing blade surface and the support surface overflows to the front blade side and cannot be applied.

In the present invention, the tip of the smoothing blade surface is located on the tangent line at the downstream end of the front blade surface, and the problems of scratches and shavings on the support caused by the projection of the front blade are solved. At the same time, the problems of uneven streaks and overflow caused by the protrusion of the smoothing blade are eliminated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings.

Embodiment 1 The coating apparatus of this embodiment is used for coating a magnetic coating material in a manufacturing process of a coating type magnetic recording medium, and as shown in FIG. 1, a pocket of a die (extruder) 1 ( Magnetic paint 3 is supplied into paint reservoir 2 and slit 4
Is supplied to the base film 7 and extruded, and is applied onto the base film 7 which is run through the guide rolls 5, 6 and the like.

As shown in FIG. 2, the die 1 is made of a metal block having a substantially rectangular parallelepiped shape having a predetermined width, and the tip end thereof is shaved obliquely to form a so-called wedge shape, and its tip end is formed. A front blade 8 and a smoothing blade 9 formed of cemented carbide or the like are integrally provided on the portion 1a. Further, although slits 4 are formed in the die 1 so as to face the tip surface 1a of the die 1 in accordance with the coating width, the slits 4 serve as gaps through which the paint is extruded, 0.01
It is a very narrow gap of about 2 mm.

On the back side of the slit 4, a pocket 2 communicating with the slit 4 is formed as a cylindrical space having a length substantially equal to the width of the slit 4. The paint supply ports 10 and 11 having an inner diameter smaller than the inner diameter of the pocket 2 are provided at both ends of the pocket 2.
It is provided so as to open on both side surfaces 1b, 1c of the magnetic tape 3 and the magnetic paint 3 is supplied from there into the pocket 2. Therefore, the pocket 2 becomes a space for receiving the paint pressure-fed from the paint supply device and has a function of an accumulator.

In the coating device having such a structure, the magnetic paint 3 supplied from the precision paint supply device to the pocket 2 of the die 1 has its paint pressure uniformized by its accumulator effect, and is extruded uniformly into the slit 4. Be done. The base film 7 includes a front blade 8 and a smoothing blade 9 provided at the exit end of the slit 4.
The magnetic paint 3 extruded from the slit 4 is continuously run in a state of being held along with the smoothing blade 9 to form a coating film having a uniform coating thickness and a smooth surface.

The above is the schematic configuration of the coating apparatus of the present embodiment. In such a coating apparatus, the front blade 8 is used.
The shape of the tip surface (front blade surface) 8a of the No. 2 and the tip surface (smoothing blade surface) 9a of the smoothing blade 9 greatly affects the quality of the coating film formed. Therefore, the shapes of the front blade surface 8a and the smoothing blade surface 9a will be described below in detail with reference to FIG.

First, the smoothing blade surface 9a needs to have a curved surface shape in order to obtain a smooth paint flow. The front blade surface 8a is also preferably a curved surface shape in consideration of the traveling property of the base film 7 and the like. Therefore, in this embodiment, the smoothing blade surface 9a is a curved surface having a curvature radius R ₂ = 60 mm, and the front blade surface 8a is a curvature radius R ₁ = 10 mm or 60
It was a curved surface of mm.

Further, in order to float the base film 7 with the paint on the smoothing blade surface 9a, it is necessary to increase the pressure by forming a wedge-shaped space between the upstream end of the smoothing blade surface 9a and the base film 7. Therefore, a flat surface portion 9b having an appropriate angle with respect to the base film 7 is provided at the upstream end of the smoothing blade 9. In this embodiment, the plane portion 9b
Has a length L of 1 mm <L ≦ 1.5 mm. this is,
If the length of the flat surface portion 9b is short, that is, if L is 1 mm or less, the paint pressure in the space surrounded by the flat surface portion 9b and the base film 7 rises sharply, and the applied state becomes unstable. If the length is more than 1.5 mm and is too long, the meaning of providing the flat surface portion 9b is diminished. In the space surrounded by the flat surface portion 9b and the base film 7, it is preferable that the paint pressure rises gently, and the range is determined from this viewpoint.

In the front blade surface 8a and the smoothing blade surface 9a, the tip end in the extrusion direction of the paint from the slit 4 (the arrow X direction in FIG. 2) is the downstream end portion (point A in FIG. 2). ), Which is the end portion (point B) of the flat portion 9b on the smoothing blade surface 9a. In the present embodiment, when the tangent line t ₁ is drawn at the tip portion (point A in the figure) of the front blade surface 8a, the tip portion (point B in the figure) of the smoothing blade surface 9a is an extension of this tangent line t ₁ . Set to be on the line. Here, it is ideal that the point B completely coincides with the tangent line t ₁ , but it is assumed that a slight deviation due to processing accuracy or the like is allowed.

When the point B is at a position retracted from the tangent line t ₁ , that is, the front blade surface 8a is in front of the smoothing blade surface 9a (paint extrusion direction).
If it is projected, the excessive contact pressure is applied to the base film 7 at the downstream side end portion (point A) of the front blade surface 8a, and the base film 7 may be bent to cause scratches or shavings. There is. On the other hand, when the point B is in a position advanced from the tangent line t ₁ , that is, when the smoothing blade surface 9a projects from the front blade surface 8a, the gap between the front film 8a and the base film 7 at the downstream end thereof. Becomes too large, causing streak unevenness due to air entrapment and air pressure. Further, when the front blade surface 8a moves back too much, the smoothing blade surface 9a and the paint 3 pressed by the base film 7
Flows back onto the front blade surface 8a
However, it becomes impossible to apply.

Further, the tangent line t ₁ and the point B at the above point A
Tangent t ₂ drawn on the smoothing blade surface 9a at
The angle α formed by is preferably 0 ° ≦ α ≦ 15 °. This is because when the angle α is too large, the base film 7 is strongly bent at the point B, causing an excessive increase in pressure, and dust on the base film 7 or agglomerates in the paint, foreign matter, etc. are easily caught and stable coating is performed. Due to the inability to do so. Also, making the entrance angle of the base film 7 shallow means that the angle α is on the minus side (less than 0 °).
Setting the value to A causes the point A to be set back, and the above requirement cannot be satisfied.

On the other hand, it is preferable that the angle of the flat surface portion 9b provided at the upstream end of the smoothing blade 9 be shallow, and the angle θ with the tangent line t _{1 at the} point A is ₁ to 45.
It is preferable to set it to °. As a result of the paint flow analysis, a large vortex is generated in the paint near the plane portion 9b, and if the angle θ is made too large, dust on the base film 7, aggregates in the paint, foreign matters, etc. are accumulated. Streaks are likely to occur.

In the die having the above-mentioned shape, if the base film 7 contacts the front blade 8 during coating, scratches and shavings may occur and serious defects may occur. If the entrance angle of the base film 7 is set so as to coincide with the line connecting the points B, the front blade 8 and the base film 7 are not brought into contact with each other by being pushed up by the paint 3 as shown in FIG. 4 during application.

Next, the shape of the tip of the die was variously changed and the magnetic paint was actually applied to confirm the effect of the present invention. The structure of the die used in the experiment is as follows. <Structure of die> Die: Extrusion die with a total width of 340 mm and coating width of 290 mm Pocket: Cylindrical hole with a diameter of 40 mm penetrates in the width direction of the die Slit: 0.2 mm gap Front blade: Carbide with a thickness of 5 mm Alloy smoothing blade: cemented carbide with a wall thickness of 5 mm

The coating conditions and the composition of the coating used are as follows. <Coating conditions> Base film: polyethylene terephthalate film having a width of 305 mm and a thickness of 15 μm Tension: 5 kg of the entire width of the base film Coating speed: 50 to 150 m / min Coating thickness: 3 to 6 μm after drying

<Coating composition> Magnetic powder (Co-adhered γ-Fe ₂ O ₃ ): 100 parts by weight Vinyl chloride binder: 10 parts by weight Polyurethane binder: 10 parts by weight Alumina・ 3 parts by weight carbon ・ ・ ・ 2 parts by weight myristic acid ・ ・ ・ 1 part by weight n-butyl stearate ・ ・ ・ 1 part by weight methyl ethyl ketone ・ ・ ・ 100 parts by weight toluene ・ ・ ・ 60 parts by weight cyclohexanone ・ ・ ・ 60 parts by weight Department

In Table 1, when the tip B of the smoothing blade surface 9a coincides with the tangent t ₁ , the tip B is tangent t _1.
The phenomenon at the time of application will be described in each of the case where the tip portion B projects further than the tangent line t ₁ and the tip portion B recedes from the tangent line t ₁ .

[0026]

[Table 1]

As is apparent from this table, in order to eliminate both scratches and overflow of the base film, it is necessary to align the tip B of the smoothing blade surface 9a with the tangent line t ₁ .

Embodiment 2 This embodiment is an embodiment in which the shape of the smoothing blade surface is changed. Other configurations of the apparatus are the same as those in the first embodiment, and therefore, the same members are designated by the same reference numerals and detailed description thereof will be omitted.

FIG. 5 is an enlarged view showing the shapes of the front blade surface 8a and the smoothing blade surface 9a in this embodiment. That is, in this embodiment,
Unlike the first embodiment, the smoothing blade 9 is not provided with the flat surface portion 9b at the upstream end thereof, and the smoothing blade surface 9a is composed of only a continuous curved surface. The space between the film 7 and the film 7 is wedge shaped to generate wedge pressure.

Therefore, the point B is the front blade surface 8
It is located on the tangent t ₁ at the point A at the downstream end of a, and the angle ψ between the tangent t _{3 at the} point C and the tangent t ₁ is set to 1 ° to 45 °. Here, the reason why the point B is located on the extension of the tangent line t ₁ is as described in the first embodiment. Also, the tangent line t ₃ and the tangent line t
_The angle ψ with ₁ is limited to the above range because it is required to be 1 ° or more in order to generate wedge pressure. If it exceeds 45 °, a large vortex is generated in the wedge shape and foreign matter is accumulated and streaks occur. Is more likely to occur.

The angle formed by the tangent line t ₄ drawn to the smoothing blade surface 9a at the downstream end (point D) of the smoothing blade surface 9a and the tangent line t _{1 at} point A at the downstream end of the front blade surface 8a. β is 0 ° to 45
Let be °. As described above, the smoothing blade surface 9a
With a simple R shape, it is possible to obtain a smooth flow of the coating material, and at the same time, it is possible to prevent dust on the base film 7 that causes streaks, aggregates in the coating material, and foreign matter from getting caught easily.

Although the embodiments to which the present invention is applied have been described above, the present invention is not limited to these embodiments, and the dimensions, materials, shapes, etc. are appropriately changed without departing from the gist of the present invention. It goes without saying that it can be changed.

[0033]

As is apparent from the above description, in the present invention, since the shape of the float blade or the smoothing blade at the tip of the die is proper, problems such as scratches on the base film and entrapment of air may occur. It is possible to obtain a stable coating state. Therefore, when it is used for manufacturing a magnetic recording medium, for example, it is possible to form a coating film with less uneven coating thickness, and it is possible to manufacture a magnetic recording medium with less output fluctuation.

[Brief description of drawings]

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

FIG. 2 is a schematic perspective view showing a die partially cut away.

FIG. 3 is a schematic view showing the shapes of a front blade and a smoothing blade in one embodiment to which the present invention is applied.

FIG. 4 is a schematic diagram showing a coating state in an example to which the present invention is applied.

FIG. 5 is a schematic view showing the shapes of a front blade and a smoothing blade in another embodiment to which the present invention is applied.

[Explanation of symbols]

 1 ... Die 4 ... Slit 7 ... Base film (support) 8a ... Front blade surface 9a ... Smoothing blade surface

Claims (1)

Claim: What is claimed is: 1. A coating is extruded onto a flexible support that continuously runs along the front blade surface and the smoothing blade surface at the tip of the die while extruding the paint through a slit provided at the tip of the die. In the extrusion type coating apparatus, the tip of the smoothing blade surface is located on the tangent line at the downstream end of the front blade surface.