JPH0235959A - Coating apparatus - Google Patents

Abstract

PURPOSE:To contrive the coating in an acceptably thin film preventing uneven streaks by providing the slot side of a doctor edge surface with a small flat area and forming a clearance between the doctor edge surface and a supporting body at the outlet end of a slot with the accompanying arrangement of the cross section of the edge surface. CONSTITUTION:A doctor edge surface 5 is provided with a curved surface 5a capable of being swollen toward a supporting body W and a slot 4 with a flat surface 5b having a width of 0.01-1mm. There are also provided a downstream end A of the edge surface 5, an intersecting line B of the curved surface 5a and the flat surface 5b, an inward end C of the slot 4 joining the flat surface 5b and an outlet D of the slot 4 joining a back edge surface 6. Given that an angle formed by a tangent touching the curved surface 5a at the intersecting line B and BC is theta1 and that an angle formed by the aforesaid tangent at the line B and BD is theta2, the outlet end D is positioned as to satisfy theta1<theta2<180 deg. and make an angle formed by a tangent touching the curved surface of an edge surface 6 at D and BD larger than an angle formed by the tangent touching the curved surface of the edge surface 6 at D and a tangent touching the curved surface 5a at A.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coating device, and more specifically, the present invention relates to a coating device, and more specifically, a part of the coating device near its tip is made into a doctor edge, and the coating device continuously coats the surface of a moving support. The present invention relates to an extrusion type coating device that applies a uniformly extruded coating liquid to the surface of the support via the doctor edge.

The flexible support in the present invention refers to a flexible sheet or web such as a plastic film, paper, polyolefin coated paper, or metal sheet such as aluminum copper, even if an undercoat layer or the like is provided. good. Magnetic coating liquids, photosensitive coating liquids, and other various coating liquids are coated on such supports to produce magnetic recording media, various photographic films, photographic papers, and the like.

[Conventional technology]

As mentioned above, various coating methods are used for coating, and one of them is an extrusion type coating device with a doctor edge. 54-7306, JP 57-84771, JP 58-10
Publication No. 4666).

However, a common drawback of these extrusion type coating devices is that the coatable area is very small. In particular, at speeds of 100 to 150 m/min or more, it is extremely difficult to stably apply a liquid coating of 20 μm or less using any method.

As a result of research conducted by the present inventors, it has been found that this phenomenon is due to the reasons described below. That is, 100 to 1
At speeds above 50 rn/min, the running support (
The entrainment of air drawn into the extruder section by the web) suddenly becomes noticeable, but in order to uniformly apply a thin film in this area, it is important to be able to appropriately control the liquid pressure at the slot outlet. Therefore, if only a small liquid pressure can be obtained, air bubbles may be mixed into the coating film, or the coating liquid may be scraped off, that is, the coating liquid may flow back upstream, resulting in non-uniform film thickness.

On the other hand, a coating device that can only obtain a large liquid pressure tends to cause thickness differences in the width direction when applying a small amount (thin layer coating).

In an attempt to eliminate these drawbacks of the conventional techniques and enable high-speed coating, Japanese Patent Laid-Open No. 10466/1983 (Fig. 6),
JP-A-58-109162 (FIG. 7) discloses this. As shown in FIGS. 6 and 7, when these coating devices 1 are used, extremely high pressure is applied to the coating liquid F at the slot-side apex B of the doctor edge surface of the doctor edge portion 5, so that the bank edge surface This prevents air from entering from the sides, making it possible to apply ultra-high speed and uniform thin layers.

[Problem to be solved by the invention]

However, if continuous coating is performed for a long period of time using a coating device that has been improved to prevent air from entering from the backing surface side and can coat a uniform thin layer at ultra-high speed, as mentioned above, streaks may appear on the coated surface. Nonuniformity occurs, and for example, in the case of a magnetic recording medium, it may adversely affect characteristics such as S/N and C/N.

As a result of investigating the cause of such uneven streaks, the present inventors found that undispersed particles and aggregates of fine and relatively hard foreign particles such as ferromagnetic iron oxide powder and abrasive particles in the coating solution. It was found that the doctor edge could not get over the top of the slot side, causing trapping and uneven streaks.

SUMMARY OF THE INVENTION Therefore, an object of the present invention has been made in view of the shortcomings of the prior art. There is a particular thing.

[Means to solve the problem]

As a result of extensive studies, the inventors of the present invention created a minute plane on the throw/ ) side of the doctor edge surface, created a gap between the doctor edge surface and the support at the slot exit end, and It has been found that by adjusting the cross section of the surface, it is possible to prevent uneven streaks without losing the above characteristics.

That is, the above object of the present invention is to continuously extrude the coating liquid from the tip of the slot onto the surface of a flexible support that runs continuously along the back edge surface and the doctor edge surface, thereby applying the coating liquid onto the surface of the support. In an extrusion type coating device for coating, the doctor edge surface has a curved surface that bulges toward the support, and the slot side of the doctor edge surface is provided with a flat surface having a width in the range of 001 to 1 mm; When the downstream end of the surface is A, the intersection line of the curved surface of the doctor edge surface and the plane is B, the slot inner end of the plane is C1, and the slot exit end of the back edge surface is D, at the above distance. An angle θI between a tangent drawn to the curved surface of the doctor edge surface and BC;
The angle θ2 formed by the tangent drawn to the curved surface of the doctor edge surface and BD at the above point is θ1<θ2<180
The slot exit end of the backwage surface is positioned at a position that satisfies the curved surface of the backwage surface, and the angle formed by the tangent line drawn to the curved surface of the backwage surface in the above step and BD is It is characterized in that the angle formed by the tangent line and the tangent line drawn to the curved surface of the doctor edge surface at the point A is larger than that, and the back edge surface does not protrude toward the support body from the tangent line drawn to the doctor edge surface at the point A. This is accomplished by a coating device.

Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a schematic sectional view showing an example of an extrusion type coating device 1 with a doctor edge according to the present invention.
This shows the coating state where the is set against the support. FIG. 2 shows the geometrical relationship of the coating device 1 (hereinafter simply referred to as extruder 1).

The main parts of the extruder 1 according to the present invention are divided into a liquid supply system 2, a pocket part 3, a slot part 4, a doctor edge part 5, and a back edge part 6, each of which will be described in detail below.

(1) Liquid supply system 2: The liquid supply system 2 is provided outside the body of the extruder 1 and includes a metering liquid pump means (not shown) capable of continuously feeding the coating liquid F at a constant flow rate. (b), and a piping member for communicating the pump means with the pocket portion 3 which is transparent in the inside of the frame of the extruder 1 in the width direction of the support W.

(2) Pocket portion 3: The pocket portion 3 has a substantially circular cross section and a third
As shown in the figure, it is a type of liquid reservoir extending in the width direction of the support W with a cross-sectional shape of a groove.

Further, its effective length is usually set to be equal to or slightly longer than the coating width.

Note that the openings at both ends through which the pocket portion 3 passes are the third
As shown in the figure, it is closed by shields 7.8 attached to both ends of the extruder 1.

By connecting the liquid supply system 2 to a short pipe 9 protruding from one of the shield plates 7, the coating liquid F is injected into the pocket portion 3 and filled, and the slot portion 4, which will be described later, is filled with the coating liquid F.
The coating liquid F is pressed to the outside with a uniform liquid pressure distribution.

(3) Slot portion 4: The slot portion 4 is connected from the pocket portion 3 to the support W.
A relatively narrow flow path that penetrates the inside of the frame of the extruder 1 with an opening width of usually 0.03 to 2 mm and extends in the width direction of the support W in the same way as the pocket portion 3. The opening length in the width direction of the support W is set to the coating width and the path gap.

Note that the length of the flow path toward the support W in the slot portion 4 can be appropriately set in consideration of various conditions such as the liquid composition, physical properties, supply flow rate, supply liquid pressure, etc. of the coating liquid F. The point is that the coating liquid F flows in the pocket portion 3 in a laminar flow with a uniform flow rate and liquid pressure distribution in the width direction of the support W.
It is good if it can flow out from the source.

In addition, in FIG. 1, the outlet tip of the slot portion 4 is
One end C (upstream side in the running direction of the support) is in contact with the doctor edge part 5, and the other end D (downstream side in the running direction of the support) is in contact with the back edge part 6.

(4) Doctor edge B5 and back edge part 6: The doctor edge part 5 is located on the downstream side of the support W from the outlet of the slot part 4, and the back edge part 6 is located on the same upstream side, downstream of the doctor edge surface. When the end is A, the intersection line of the curved surface 5a of the doctor edge surface and the plane 5b is 81, and the slot exit end of the doctor edge surface is C, the edge surface of the doctor edge portion 5 facing the support W is formed according to the present invention to have a curved surface 5a from B to A (AS) and a minute flat surface 5b from C to B (BC) on the slot side, and furthermore, the slot exit end of the backing portion 6 is designated as D. When this happens, the larger angle θ1 between the tangent drawn to the curved surface 5a of the doctor edge surface and BC at the other end, and the larger angle θ2 between the tangent drawn to the curved surface 5a of the doctor edge surface and BD at the other end. is θ1<θ
The slot exit edge of the back edge surface is located at a position satisfying 2<180°, and the length 11 of the plane BC of the doctor edge surface is 0.01 to 1 city, preferably 0.03 to 0.3
The range is set. Curved surface 5 of the doctor edge surface
The degree of a is approximately 1 to 20 mm as the radius of curvature R, particularly 2 to 20 mm.
10 proof is preferred.

In addition, the effective length of the doctor edge surface (distance between A and 0, 1.-z22 in Figure 2) is approximately 0.5 as a straight line.
~ about 17 mm, the effective length of the surface of the backing portion 6 (distance between D and E, the surface in contact with the support) is about 0.1 to about 5
0, the surface shape of the backing portion 6 may be flat or slightly rounded.

As described above, the present invention has a structure in which the support W is mounted in such a manner that it can be bent slightly in the thickness direction with a substantially constant tension between each traveling guide means such as a guide roller. As shown in FIG. 1, the doctor edge part 5 and the back edge part 6 are curved approximately parallel to each other and are brought close to each other via an extruder support mechanism (not shown), while the liquid supply system 2 When feeding the liquid F at a desired flow rate, the coating liquid F passes through the pocket portion 3 and the slot portion 4, and then the flat surface 5b acts to press the coating liquid F onto the support W. It is extruded to the outlet tip of the slot portion 4 with uniform flow rate and pressure distribution in the width direction.

The application liquid F pushed out to the outlet tip of the slot portion 4 generates a liquid pressure that is appropriately controlled by defining the shape of the edge portion as described above, and removes the entrained air of the support W. The doctor edge part 5 is moved along the surface of the support body continuously moving in the direction of arrow R while preventing contamination and creating a small gap between the surface of the support body W and the edge part. It passes through the gap between the edge surface and the support W so as to be spread out.

If the movement of the coating liquid F as described above is maintained continuously,
The entire edge surface of the doctor edge portion 5 and the support W
The surface of the substrate is completely separated with a predetermined gap by the coating liquid F, which passes in a thin layer over the entire width direction. Furthermore, since the doctor edge portion 5 does not protrude more than necessary toward the support as described above, trapping of dust and foreign matter is suppressed at the edge.

Further, the separation interval between the doctor edge part 5 and the support W is determined by the tension of the support W, the supply amount of the coating liquid F,
In particular, by changing only the setting of the supply amount of the coating liquid F, the desired separation interval, that is, the thickness of the coating film can be obtained very easily and accurately.

In addition, by employing a cemented carbide material or a ceramic material as the constituent material of the doctor edge portion 5 and the back edge portion 6, and further increasing the straightness and flatness of both the edge portions, the above-mentioned spacing can be increased in the width direction. As a result, the uniformity of the coating film thickness in the width direction was further improved, and the suitability for high speed and thin layer coating was further improved.

FIGS. 4 and 5 show a modification of the method of supplying the coating liquid F to the pocket portion 3. FIG.

The supply method shown in FIG. 4 is one in which the coating liquid F is supplied to the pocket portion 3 on one side in the same way as the method shown in FIG.
0, and a part of the coating liquid F injected into the pocket part 3 through the short tube 9 of the one shield plate 7 is discharged to the outside through the other short tube 10. It is possible to prevent F from remaining significantly in the pocket portion 3, and it is an extremely effective means especially for magnetic coating liquids that have thixotropy and tend to aggregate.

In addition, FIG. 5 shows another short tube 1 communicating with the substantially central portion of the pocket portion 3 in addition to the short tubes 9 and 10 on both sides as shown in FIG.
1 is installed and the coating liquid F is supplied from the short tube 11.

A part of the coating liquid F injected into the pocket part 3 is discharged to the outside from the short pipes 9 and 10 on both sides, and the remaining coating liquid F does not stagnate in the pocket part 3 and is kept under pressure. It is extruded from the slot portion 4 with a more uniform distribution.

Note that the method of supplying the coating liquid in the apparatus of the present invention is not limited to the methods shown in FIGS. 3 to 5 described above, and may be performed in an appropriate combination. Furthermore, the pocket portion 3 is not limited to the cylindrical shape described above, but can be changed to a rectangular shape, a boat bottom shape, etc. In short, any shape may be used as long as it can uniformly distribute the hydraulic pressure in the width direction.

〔Effect of the invention〕

As described above, the coating apparatus of the present invention has the following effects.

(1) Since the degree of protrusion of the doctor edge surface toward the support is suppressed to a certain level or less, foreign matter in the coating liquid or foreign matter drawn in as the support runs is not trapped on the doctor edge surface, and streaks due to foreign matter are prevented. It is possible to maintain good suitability for high-speed coating over a long period of time without causing unevenness.

(2) The flat surface formed on the upstream side of the doctor edge surface allows the liquid pressure of the coating liquid toward the support to be maintained at an appropriate level, improving the suitability for thin layer coating, even in liquid form with a film thickness of about 10 μm. Can be applied to a uniform thickness.

(3) The liquid pressure at the outlet tip of the slot portion 4 can be arbitrarily controlled to avoid a situation in which foreign matter is likely to be trapped on the doctor edge surface, so contact between the support and the edge portion and accompanying This can prevent both from being scratched.

(4) Furthermore, since the liquid pressure can be controlled arbitrarily as described above, it is possible to provide a coating device that can respond to a wider range of viscosities of various coating liquids than ever before, and has a wide range of applicability. Ta. Further, by using cemented carbide or ceramic for the edge portion, the above-mentioned effects can be further enhanced, and deterioration in current performance due to abrasion of the edge portion that occurs particularly during application of the magnetic tape coating liquid can be prevented.

Next, the effects of the present invention will be made clearer by way of examples.

〔Example〕

An embodiment of the present invention will be described. However, the present invention is not limited to this example.

After putting each component of the composition shown in Table 1 into a ball mill and thoroughly mixing and dispersing it, epoxy resin (epoxy equivalent: 50
0) was added thereto and uniformly mixed and dispersed to prepare a magnetic coating liquid.

Table 1 The equilibrium viscosity of the magnetic coating liquid thus obtained was measured using a Shimadzu rheometer RM-1 manufactured by Shimabara Manufacturing Co., Ltd., and found to be 8 ρoise at a shear rate of 1 Qsec -'.

Also, 5QQsec-' showed l poise.

Next, the coating liquid was applied using the coating apparatus described below under the following conditions.

1. Support: Material: Polyethylene terephthalate film Thickness:
・20μm Width: 300m Tension: 2kg/full width and 4kg/full width Travel speed: 1
00m/min, 200m/min, 300m/m
in.

400m/m1n 2, extruder No. 1...Extruder N of the present invention shown in FIG.
o, 2...Extruder 3 described in JP-A-58-104666 shown in FIG. 6, coating thickness (liquid) 10μ, 20μ, 50μ coating results are shown in Table 2. In addition, the ○ mark in the table indicates good coating,
Δ marks may give good results, but the reproducibility is poor, X
The mark indicates that the coating could not be applied uniformly.

Table 2 As shown in Table 2 above, the conventional extruder N
Although extruder No. 2 was not able to perform high-speed coating at 400 m/min, extruder N011 of the present invention has improved high-speed suitability.

Next, various shapes of the extruder of the present invention were used and coating was carried out under the following conditions, and the occurrence of streak unevenness was investigated.

1. Support: Material: Polyethylene terephthalate film Width: 3
00 mm Tension: 4 kg/full width Coating length: 4000 m Coating thickness: 50 μm in liquid form 2. Extruder The extruder according to the present invention shown in FIG. 1 was used.

Note that the display in Table 3 is as follows.

β1: Length of doctor edge plane BC 12: Length of doctor edge curved surface AC R: Radius of doctor edge curved surface θl: Larger angle θ2 between BC and the tangent drawn to the curved surface of doctor edge at This is the larger angle between BD and the tangent drawn to the curved surface of the doctor edge at B.

The coating results are shown in Table 3.

Table 3 As shown above, in the extratrader of the present invention, β
It can be seen that when the length of 1 is in the range of 0.01 to 1.00 mm, the suitability for high-speed coating is good and good coating without uneven coating can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the coating device of the present invention set on a support. 2 is a cross-sectional view showing the edge surface shape of the coating device shown in FIG. 1, FIG. 3 is a perspective view showing a part of the coating device in FIG. 1, and FIGS. A perspective view showing a modified example of the method of supplying a coating liquid to a coating device according to the present invention, and FIGS. 6 and 7 are cross-sectional views of a conventional coating device. 1... Extruder, 2... Liquid supply system, 3...
Pocket part, 4... Slot part, 5... Doctor edge part, 5a... Curved surface, 5b... Plane, 6... Back edge part, 7.8... Shield plate, 9.10 ...Short tube, W...Support F...Coating liquid. Sit map chart

Claims (1)

[Claims] In an extrusion type coating device that applies a coating liquid to the surface of a flexible support by continuously extruding it from the tip of a slot onto the surface of a flexible support that continuously runs along a back edge surface and a doctor edge surface. , the doctor edge surface has a curved surface that bulges toward the support side, and the slot side of the doctor edge surface is provided with a flat surface having a width in the range of 0.01 to 1 mm, and further, the downstream end of the doctor edge surface is provided with A, When the intersection line of the curved surface of the doctor edge surface and the plane is B, the slot inner end of the plane is C, and the slot exit end of the back edge surface is D, at B, the doctor edge surface Tangent line drawn to curved surface and BC
The slot exit end D of the back edge surface is located at a position where the angle θ_1 formed by BD and the angle θ_2 formed between BD and the tangent drawn to the curved surface of the doctor edge surface at B satisfy θ_1 < θ_2 < 180°. The angle between the tangent drawn to the curved surface of the back edge surface at D and BD is the angle between the tangent drawn to the curved surface of the back edge surface at D and the curved surface of the doctor edge surface at A. A coating device characterized in that the angle is larger than the angle formed by the tangent line drawn to the doctor edge surface, and the back edge surface does not protrude toward the support side from the tangent line drawn to the doctor edge surface at B.