JPH06339659A - Applicator - Google Patents

Abstract

PURPOSE:To provide an applicator which applies magnetic coating, metallic coating, a resin solution, and others on a sheet such as a polyester base film and a thin metal plate uniformly. CONSTITUTION:In an applicator having at least two bars and an opening for discharging liquid to be applied located between two bars, the back bar B as either one of the two, which is positioned downstream in the running direction of a support, has an edge R surface. The mean roughness (Ra) of the center line in the downstream corner of the back bar B is 0.5mum or less, and the maximum height (R max) is 6.0mum or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uniformly coats a sheet material such as a polyester base or a thin metal plate with a magnetic coating material, a metallic coating material, a resin solution or the like without any streak-like failure or coating failure such as coating unevenness. It relates to a device for applying,
In particular, the present invention relates to a coating device that is preferably used when manufacturing a magnetic magnetic medium.

[0002]

BACKGROUND OF THE INVENTION A magnetic recording medium can be obtained by coating and drying a magnetic coating liquid on a support. As a device for coating the magnetic coating liquid on the support, a roll coater, a gravure coater and an extrusion coater are generally used. Target. Among these, the extrusion coater has a coating speed of 200 m /
High-speed coating such as min or more, and undried film thickness at coating is 1
A good coating film thickness can be obtained even when a thin film having a thickness of 0 μm or less is obtained, but there is a problem that the coating film is white or streaky defects are likely to occur.

One of the causes of these failures is that foreign matter, dust or agglomerates in the magnetic coating adhere to the edge surface located on the most downstream side of the extrusion coater (hereinafter referred to as the back edge surface) during coating. Is. Therefore,
As disclosed in JP-A-2-20786 and JP-A-2-207866, the back edge surface of the extrusion coater is reduced by reducing the value of the center line average roughness (Ra) of the back edge surface of the extrusion coater. There has been proposed a method for preventing adhesion of deposits to the skin.

[0004]

With the increasing density of magnetic recording media, it is necessary to reduce the coating thickness of the magnetic layer coated on the support in the manufacturing process thereof. Also, from the viewpoint of improving productivity, the coating speed is on the increase, and there is not enough time for the coating liquid to level,
It is not sufficient to prevent coating failures such as coating unevenness and streak-like failures by merely reducing the centerline average roughness of the back edge surface of the extrusion coater as proposed in the above publication. Has become.

The inventors of the present invention have found that when coating an extrusion coater, the surface state of the liquid separating position on a bar (hereinafter referred to as a back bar) located on the most downstream side of the extrusion coater is uneven coating, coating film. The present invention has been completed by finding out experimentally that it is largely related to the coating failure such as white stripes, and paying particular attention to the fact that the liquid separation is near the cad on the downstream side of the back bar. is there. That is, the present invention is suitable for manufacturing an improved coating apparatus, particularly a magnetic recording medium, which does not cause coating unevenness and streak-like failure even under high-speed thin film coating conditions during general coating. It is an object of the present invention to provide a coating device.

[0006]

The above-mentioned object has at least two bars and a coating solution discharge port located between the two bars, and the most of the two bars with respect to the running direction of the support. In the coating apparatus in which the back bar located on the downstream side has an edge surface, the center line average roughness (Ra) of the downstream side cad of the back bar is 0.5 μm or less, and the maximum height (Rmax) is 6. It is achieved by a coating device characterized by being 0 μm or less. Further, in recent years, as the coating film thickness has become thinner, better surface properties of the coating film have been required, and the center line average roughness (R
a) is preferably 0.35 μm or less, and more preferably 0.1 μm or less. The maximum height (Rmax) is preferably 4.0 μm or less, and more preferably 1.2 μm or less.
The value of the center line average roughness (Ra) of the cad on the downstream side of the back bar largely depends on the coating unevenness, and the maximum height (Rm
It was found that the value of ax) was largely caused by the streak-like failure, and it was found that a good coating film can be obtained by combining the optimum values of both. Further, on the surface following the cad on the downstream side of the back bar, the center line average roughness (Ra) within a distance of 2.0 μm from the cad on the downstream side of the back bar is 0.5 μm or less, and the maximum height. Sa (Rm
The above object is achieved by a coating apparatus characterized in that ax) is 6.0 μm or less.

Here, the edge surface is a surface which is located in front of or behind the coating liquid discharge port and faces the support to be coated via the coating liquid during coating. Further, the downstream cad of the back bar is the edge surface R of the back bar B and the downstream cad of the back bar B in FIG. 2 which is an enlarged cross-sectional view of the Y-Z plane of the back bar B in FIG. It is a vertex formed by the surfaces R and L at a position located at the boundary of the following surfaces L. In fact, since the vertex is conceptually only present, in the present invention, the intersection point between the approximate curve T of the cross section of the surface R and the approximate straight line of the cross section of the surface L (the approximate curve when the surface L is a curve) U An area A on the back bar B located within 100 μm from K is defined as a quad. Further, the distance from the cad on the downstream side of the back bar is the distance from the intersection point K.

The center line average roughness (Ra) and the maximum height (Rmax) of the cad on the downstream side of the back bar are the grinding processing of the edge surface R of the back bar and the grinding of the surface L following the cad on the downstream side of the back bar. It is formed by processing. For example, when the grinding of the surface R is performed by the front grinding method and the surface L is performed by the side grinding method, the center line average roughness (Ra) and the maximum height (Rma) of the cut edge are calculated.
x) is different from the measured values of both the surface R and the surface L, and is a value synthesized by grinding the surface R and the surface L. As an extrusion coater used at the time of coating, JP-A-1
No. 184072, page 4, FIG. 1, JP-A-2-251
No. 265, page 6, FIG. 1 or JP-A-2-26886.
Examples thereof include those disclosed in FIG. 3, page 6, FIG. 2, but are not limited thereto.

The present invention also relates to a coating apparatus suitably used for manufacturing a magnetic recording medium, and the composition of the coating solution used is as a magnetic powder as disclosed in JP-A-4-31381.
No. 1, gazette, page 3, paragraph number [0029] to page 4, paragraph number [0052], the binder or the binder is disclosed in JP-A-3-62311, page 3, lower right column. From line 10 to page 4, upper left column, line 15, the dispersant is disclosed in JP-A-3-16015, No. 6
It is preferable to use those disclosed in lines 12 to 20 in the upper right column of the page.

In actual coating, as shown in FIGS. 3, 4 and 5, the tangent line T'on the intersection point K of the approximate curve T.
The angle θ between the tangent line T ′ and the support S is about −1, where the direction from the coating to the support S to be coated is a positive direction.
Although the coating can be performed in the range of 0 to +30 degrees, the range in which a uniform coating film can be obtained is limited, and the upper limit angle value of the range decreases as the coating speed increases.

Further, the center line average roughness (Ra) and the maximum height (Rma) of the surface L following the edge on the downstream side of the back edge surface R are measured.
x) gradually affects the coating unevenness and the streak failure as the value of the angle θ becomes smaller. Increasing the coating speed is in the direction of decreasing the angle θ, and is in the direction of increasing the influence of the surface condition of the surface L on the coating film. Here, the center line average roughness (Ra) means JIS B 0601 (19).
82), "a portion of the measurement length l is extracted from the roughness curve in the direction of its center line, the center line of this extraction is taken as the X axis, and the direction of longitudinal magnification is taken as the Y axis. When y is expressed by y = f (x), it means that the value of Ra given by the following formula is expressed in micrometers (μm).

[0012]

[Equation 1] Also, the maximum height (Rmax) is JIS B0601.
As defined in (1986), "when the extracted portion is sandwiched by two straight lines parallel to the average line of the portion extracted by the reference length from the sectional curve (hereinafter referred to as the extracted portion), the distance between these two straight lines The value obtained by measuring in the direction of the longitudinal magnification of the cross-section curve is expressed in micrometers (μm). ”As a measuring device, a contact-type surface roughness meter is used. Details will be described in Examples.

[0013]

EXAMPLES The effects of the present invention will be illustrated by the following examples. The present invention is not limited to the following examples, and it is needless to say that the present invention can be applied to other than the magnetic recording medium in view of the object of the present invention. The magnetic paint used had the following composition. Magnetic paint Fe-Al-based ferromagnetic metal powder [Hc: 16000 Oe, 120 emu / g average axis length: 220 nm X-ray particle size (average, crystallite size): 20 μm] 100 parts Vinyl chloride resin (Zeon Corporation, MR110) ) 10 parts Polyurethane resin containing sulfonic acid metal salt 5 parts (Toyobo Co., Ltd., UR8700) α-alumina 5 parts Carbon black (average particle size 40 μm) 1 part Myristic acid 1 part Stearic acid 1 part Butyl stearate 1 part Methyl ethyl ketone 100 Part Toluene 100 parts Cyclohexanone 100 parts

A part of the solvent having the above composition is added so that the solid concentration is about 80%, and the actual load electric power per 1 kg of magnetic powder is 0.2 kw or more and kneading is performed for 10 minutes or more. It is diluted to the above prescribed value using a zirconia bead having an average particle size of 1.0 mm and dispersed in a sand mill. Finally, a polyisocyanate compound (5 parts of Coronate L) is added. Prepared.

Next, a non-magnetic coating material having the composition shown below was used. Non-magnetic paint TiO ₂ 100 parts (average particle size 15 nm, BET 15 m ² / g) Vinyl chloride resin (Zeon Corporation, MR110) 1 part Sulfonate metal salt-containing polyurethane resin 5 parts (Toyobo Co., Ltd., UR8700) Myristin Acid 1 part Stearic acid 1 part Butyl stearate 1 part Methyl ethyl ketone 35 parts Toluene 35 parts Cyclohexanone 35 parts

A part of the solvent having the above composition was added so that the actual load electric power was 0.2 kW or more per kg of the non-magnetic powder, and the mixture was kneaded for 10 minutes or longer. It was diluted so as to be, and was dispersed in a sand mill using zirconia beads having an average particle diameter of 1.0 mm, and finally, a polyisocyanate compound (5 parts of Coronate L) was added to prepare. The prepared coating dispersion is a 450 mm wide single-layer extrusion coater whose cross-sectional view is shown in FIG. 4 and 450 shown in FIG.
Using a multi-layered extrusion coater with a width of mm,
The coating was applied to a polyethylene phthalate base having a thickness of 8 μm. At that time, the coating liquid discharge port of the extrusion coater is set at a position approximately in the middle between the two support rolls having a span W of 500 mm as shown in FIG. I went. At this time, the tension during conveyance was set to 15 kg width.

The evaluation of this video tape was carried out by the following method. Coating unevenness: 10 m from an arbitrary place was taken as a sample from a video tape having a coating length of 100 m cut into a width of 8 mm. The sample was taken at 200 points at intervals of 5 cm in the longitudinal direction, and the film thickness distribution in the width direction was measured by an X-ray film thickness meter.
The sample was judged as defective if the film thickness was deviated by ± 1% or more even at one of the 200 measured points for the set dry film thickness, and the defective rate was expressed.

Streak failure: coating length 1000 m, coating width 40
The number of failures was counted with transmitted light at 0 mm (excluding unnecessary portions on both sides).

C / N ratio 8mm video recorder (SONY EV09500)
Was used to record a single sine wave of 7 MHz, this signal was reproduced, and the reproduction outputs of 6 MHz and 7 MHz were measured using an output level measuring instrument, and the difference was expressed in dB.

Centerline average roughness (Ra), maximum height (Rm)
ax): Measured with a three-dimensional surface roughness meter (form tracer CS-411) manufactured by Mitutoyo. When measuring the caddy on the downstream side of the back bar, a flat stylus having a width of 2 mm as shown in FIG. 6A is used, and as shown in FIGS. 7 and 8, the stylus axis and the tangent line T are used. The angle with'is 80 degrees,
Further, the surface roughness meter was set so that the bottom of the stylus was horizontal, and the region A was measured in the width direction of the support. Also,
When measuring the surface L following the cad on the downstream side of the back bar,
An object having a cone bottom surface of 2 mm in diameter as shown in FIG. 6B is used for the stylus, and the surface roughness meter is set so that the surface L is horizontal as shown in FIGS. The total width of the coater was measured by dividing the locations of 1.0 mm, 1.5 mm, and 2.0 mm from each other by 75 mm in the width direction of the support 6 times. At this time, the cutoff is 0.25 mm
Then, the average value for Ra and the maximum value for Rmax were obtained.

Tables 1 and 2 show the results of experiments carried out using a single-layer extrusion coater and a multi-layer extrusion coater, respectively. At this time, the coating speed is 3
00 m / min, when a single layer extrusion coater is used, the undried film thickness is 3 μm, and when a multilayer extrusion coater is used, the undried film thickness of the upper layer is 3 μm.
m, the wet film thickness of the lower layer was 7 μm, and the angle θ between the tangent line T ′ and the support S was + 5 ° and −5 °.

From Tables 1 and 2, it can be seen that coating unevenness affects the decrease in C / N ratio. Therefore, it can be seen that Ra of the cad on the downstream side of the back bar is 0.5 μm or less and Rmax is 6.0 μm or less is more effective in improving the C / N ratio and preventing streak failure. In particular, Example 1
As shown in -1 to 1-8, Ra is 0.35 μm or less and Rm
It is shown that when ax is 4.0 μm or less, no streak failure is found and the C / N ratio is improved. Furthermore, Ra is 0.10 μm as in Examples 1-1 to 1-3.
It can be seen that when Rmax is 1.2 μm or less, coating unevenness is not observed, the C / N ratio is not reduced, and very good coating can be performed. Next, paying attention to the experimental result under the condition that θ is −5 degrees, Ra of the cad on the downstream side of the back bar is 0.5 μm or less and Rma as well as under the condition that θ is 5 degrees.
It can be seen that there is a clear difference in the coating unevenness, the number of streak failures, and the C / N ratio when x is 6.0 μm or less, which is effective for improvement, but when compared with the case where θ is 5 degrees, Both unevenness and streak failure show a slightly bad value. So Ra of surface L
It can be seen that when Rmax is 0.5 μm or less and Rmax is 6.0 μm or less, coating unevenness and streak failure are improved.

[0023]

EFFECT OF THE INVENTION By using the coating apparatus according to the present invention, the smoothing effect of the back edge surface can be effectively brought out, and uneven coating and streak-shaped coating failure occurring in the coating layer on the support can be prevented. It is possible to solve the above-mentioned problems.

[0024]

[Table 1]

[0025]

[Table 2]

[Brief description of drawings]

FIG. 1 is a perspective view of an exclusion coater of the present invention.

FIG. 2 is a sectional view of a cad on the downstream side of the back bar of the present invention.

[Fig.3] Layout of the exclusion coater and support roll during coating

FIG. 4 is a sectional view of a single-layer extrusion coater of the present invention.

FIG. 5 is a sectional view of a multilayer extrusion coater of the present invention.

FIG. 6 is a perspective view of a stylus of a roughness measuring instrument.

FIG. 7 is a perspective view showing an operation of a stylus of a roughness measuring instrument.

FIG. 8 is a sectional view showing an operation of a stylus of a roughness measuring instrument.

FIG. 9 is a perspective view showing an operation of a stylus of a roughness measuring instrument.

FIG. 10 is a sectional view showing an operation of a stylus of a roughness measuring instrument.

[Explanation of Codes] A-Kud A'-Area to be considered as K-B-Back bar C-Center bar F-Front bar L-Edge of the back bar Surface in contact with the downstream end of the back bar O-Coating liquid discharge port R-Back bar Edge surface S − Support T − Approximate curve of surface R T ′ − Tangent of approximate curve T at intersection K U − Approximate curve of surface L V − Support roll W − Distance of support roll opening θ − Support S and back edge Angle with surface R

Claims (1)

[Claims] 1. A back bar having at least two bars and a coating solution discharge port located between the two bars, and a back bar located on the most downstream side with respect to a traveling direction of a support of the two bars is an edge. In the coating device having a surface, the center line average roughness (Ra) of the downstream side cad of the back bar is 0.5 μm or less, and the maximum height (Rmax) is 6.0 μm or less. Coating device.