JP3218798B2 - Application method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a method of applying a magnetic paint when manufacturing a coating type magnetic recording medium, a roll coating method using a roll, such as a gravure roll method or a reverse roll method, is mainly used. Has become.

However, in these roll coating methods, output fluctuation due to coating thickness unevenness due to poor transfer of the paint from the roll to the base film, drop-out due to paint scattering, and excessive supply paint are returned to the mixing step. There are problems such as deterioration of paint quality, and these problems tend to become more remarkable particularly as the coating speed is increased.

In recent years, as a new coating method capable of solving these problems, an extrusion (die) method has been attracting attention and has already been partially put into practical use.

In the extrusion method, a die having a wide slit for extruding paint at the tip end and having a doctor edge near the tip end is used. The die is continuously passed through the slit toward the surface of the moving support. In this method, the extruded paint is applied to the support with a uniform thickness by the doctor edge, and has been used in the fields of photographic film and photographic paper.

[0006]

In the extrusion coating method, the paint is supplied by a pump to a paint reservoir of a die called a pocket, from which the paint is extruded into a slit with a predetermined pressure.

At this time, the relationship between the supply flow rate of the paint by the pump and the coating thickness of the coating on the support after the coating is dried is not clear. Determining is extremely complicated. That is, as a condition for obtaining a predetermined coating thickness, for example, the rotation speed of the pump is 100 (r / min).
Or the supply flow rate of the paint is 5.0 (liter / mi)
n), and when the target coating thickness is to be changed, the change of these conditions is determined by repeated trial and error.

Further, when the running speed of the support is changed, it is necessary to change the supply flow rate of the paint in order to maintain the coating thickness on the support at a target value. . Also in this case, the change of the supply flow rate of the paint is performed by repeating trial and error, which is a complicated operation.

Conventionally, as described in Japanese Patent Application Laid-Open No. 3-248330, the flow rate of paint supplied by the pump is always measured by a flow meter or the like, and the measurement result is fed back to the pump. There has been proposed an application method in which a pump is controlled. However, when the supply flow rate of the paint is fed back to the control of the pump in this way, the supply flow rate of the paint tends to pulsate, and it is extremely difficult to maintain a constant coating thickness of the paint on the support.

Therefore, the present invention has been proposed in view of the above-mentioned circumstances, and it is possible to easily determine a supply flow rate of a paint for realizing a target coating thickness on a support.
It is another object of the present invention to provide a coating method capable of preventing the pulsation of the supply flow rate of the coating material and maintaining the coating thickness of the coating material on the support at a constant value.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve the above-mentioned object, the present invention provides a method in which a paint is supplied to a die by a pump and the paint can be run continuously through a slit provided at the tip of the die. In an extrusion-type coating method of applying a paint while extruding a paint on a flexible support,
The supply flow rate of the paint supplied to the die is Q, the ratio of the coating thickness before and after drying of the paint applied to the flexible support is α, and the paint of the paint on the flexible support is α. When the coating thickness after drying is T _D , the running speed of the flexible support is V, and the width of the flexible support is W, α, Q, T _D , V and W relationship, Q = with control means for controlling the pump based on _{α · T D · V · W} , input the control target coating thickness T _D after drying of the running speed V and the paint to the control unit The supply flow rate Q is determined by means.

[0012]

In the coating method according to the present invention, the control means controls the coating thickness T _D of the coating on the flexible support after drying.
And the traveling speed V of the flexible support are input, and the supply flow rate of the paint supplied to the die is Q, and the coating thickness before and after drying of the paint applied to the flexible support is When the ratio is α and the width of the flexible support is W,
These Q, alpha, T _D, a relational expression V and W, and controls the pump based on the _{Q = α · T D · V} · W, directly enter the target value of the coating thickness T _D after drying it is possible to perform the control of the coating thickness T _D with.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. The coating method according to the present invention is performed when a magnetic paint is applied to a film base in a manufacturing process of a coating type magnetic recording medium. As shown in FIG. 1, this coating method includes a die 7 and a die 7.
Pump (precision gear pump) that supplies the above magnetic paint to the machine 6
It can be carried out by a coating apparatus configured to have

In this coating apparatus, the magnetic paint 19 in the paint tank 9 is supplied to the pocket (paint pool) 3 of the die (extruder) 7 by the pump 6 through the supply pipe 14.
And feed it to the slit 4 and push it out.
It is applied on a base film 8 which is a flexible support to be run. The pump 6 and the die 7
The filter 10 is interposed between and. The magnetic paint 19 sent out by the pump 6 passes through the filter 10 and reaches the die 7.

In this coating apparatus for carrying out the coating method according to the present invention, the pump 6 has a coating thickness control device 18 having the controller 1 as a control means.
Controls the delivery flow rate.

As shown in FIGS. 1 and 2, the die 7 is formed of a metal block having a substantially rectangular parallelepiped shape having a predetermined width. The surface 17 is formed of a cemented carbide or the like to form a doctor edge portion. A slit 4 is formed in the die 7 according to the application width so as to face the tip end surface 17 of the die 7. This slit 4
Is a gap through which the paint is extruded, and is formed as an extremely narrow gap of, for example, about 0.01 mm to 0.02 mm. The slit 4 is formed such that the longitudinal direction is the width direction of the die 7.

In the die 7, the pocket 3 is located behind the slit 4 and communicates with the slit 4.
Is formed as a columnar space having a length substantially equal to the length of the slit 4. At both ends of the pocket 3, paint supply ports having an inner diameter smaller than the inner diameter of the pocket 3 are provided, for example, so as to open on both side surfaces of the die 7. From this paint supply port,
The magnetic paint 19 is supplied into the pocket 3. Therefore, the pocket 3 serves as a space for receiving the magnetic paint 19 pumped by the pump 6 and has a function of an accumulator.

The filter 10 eliminates pulsation caused by the pump 6 with a certain pressure loss, and has a pulsation removing function. Examples of the filter 10 include a metal sintered filter (for example, a stainless steel sintered filter) and a ceramics filter, as well as a filter made of a fibrous material and a filter incorporating various foams. In addition, a general accumulator corresponding to an organic solvent can be used as the filter 10.

The base film 8 is unwound from a supply reel (not shown), is guided and driven by guide rollers 11 and drive rollers 12, and is wound on a take-up reel (not shown). The drive roller 12 is rotated by a motor (not shown) controlled by the traveling controller 13 to keep the rotation speed constant. That is, the traveling controller 13 keeps the traveling speed of the film base 8 constant.

In this coating apparatus, an arrow V in FIG.
As shown by, the film base 8 is fed at a constant speed, and the magnetic paint 19 is pushed out through the slit 4 to the tip end side of the die 7 as shown by an arrow Q in FIG. Thereby, on the film base 8,
The magnetic paint 19 is applied, and the coating film 15 is formed. After the coating film 15 is formed on the film base 8, the coating film 15 is heated by a dryer 16 arranged in parallel with the die 7 and opposed to the film base 8 to evaporate the solvent. dry.

The coating thickness control device 18 includes the controller 1, a coating thickness setting unit 2 for inputting a numerical value indicating the coating thickness to the controller 1, and the pump 6 based on the output of the controller 1. And an inverter 5 for controlling the number of rotations. In addition, the controller 1 provides the travel controller 13 with:
Numerical information indicating the target value of the running speed of the film base 8 is sent.

The controller 1 has a sequencer in which an arithmetic expression for the applied thickness of the magnetic paint is programmed in advance. This arithmetic expression means that the supply flow rate of the paint supplied to the die 7 is Q (liter / min), and the coating thickness (before and after drying) of the coating film 15 formed by applying the magnetic coating material 19 to the film base 8 ( Α)
The coating thickness of the coating film 15 after drying on the film base 8 is defined as T _D (μm).
When the running speed of the film base 8 is V (m / min) and the width of the film base 8 is W (mm),
It is a relational expression of T _D , V and W, and is expressed by the following equation: Q = k · α · T _D · V · W (Equation 1) In this equation 1, k is a constant for performing unit conversion, and in this example, k = 1 ×
10 ^-6 .

As shown in FIG. 2, the ratio α in the above formula 1 is defined as T _{W where} the coating thickness before the coating film 15 is dried by the dryer 16 is T _W. the coating thickness after being dried when the T _D, a T _W / T _D. That is, the supply flow rate of the magnetic paint 19 to the die 7 needs to be controlled by the coating thickness T _W of the coating film 15 before drying, while the quality control of the magnetic recording medium is controlled by the coating thickness T _W. The ratio α is introduced into the above-mentioned arithmetic expression because it is necessary to perform the coating thickness T _D after drying. This ratio α is 5, for audio tape,
The value is 6 for an oxide (iron oxide) tape for video, and 7 for a so-called metal tape for video.

In the coating method according to the present invention, the controller 1 controls the pump 6 based on the above equation (1). That is, the controller 1, the dry coating thickness T _D through the coating thickness setting unit 2 is input, and the running speed V of the film base 8 which is supplied from the travel controller 13, is set in advance Based on the width W of the film base 8 and the ratio α,
As shown in FIG. 3, and calculates the supply flow rate Q corresponding to a dry coating thickness T _D input. And this controller 1
Via the inverter 5 so that the flow rate of the magnetic paint in the pump 6 becomes the calculated supply flow rate Q.
The rotation speed of the pump 6 is controlled. In FIG. 3, a solid line indicates a calculated value based on the above equation 1, and a portion indicated by a dot with a circle indicates an actually measured value.

For example, when an audio tape is manufactured using a film base having a width of 610 (mm), the supply flow rate Q (liter / min) can be calculated by the following equation (1): Q = 5 × 610 × the _{^{10 -6 (T D · V)}} ≒ 3 × 10 -3 (T D · V) ···· ( equation 2). Here, when the running speed V and 100 (m / min), Q ≒ 3 × 10 -1 T D ············ ( Equation 3), and the dry coating thickness T _D is 3 (Μm), about 0.9
Liter / min and the dry coating thickness T _D is 5 (μm)
Then, it becomes about 1.5 liter / min.

The controller 1 includes the inverter 5
, The rotation speed of the pump 6 is controlled to be constant, and the flow rate of the magnetic paint 19 and the film base 8 are controlled.
Since the feedback due to the running speed of the magnetic paint is not received, the supply flow rate of the magnetic paint is controlled without causing pulsation. Therefore, according to this coating method, it is possible to form a coating film of a magnetic coating material having a stable coating thickness on the film base 8, and to manufacture a magnetic recording medium constituted by laminating two or more coating films. Is also facilitated.

[0027]

As described above, according to the present invention, in the coating method according to the present invention, the control means, flexible coating thickness after drying of the coating in a support on T _D and the traveling speed V of the flexible support Is input, the supply flow rate of the paint supplied to the die is Q, the ratio of the coating thickness before and after drying of the paint applied to the flexible support is α, and the flexible support is when the width is W, these Q, alpha, T _D, a relational expression V and W, and controls the pump based on the _{Q = α · T D · V} · W.

[0028] Thus, in this coating method, the target value of the coating thickness T _D after drying in direct input, it is possible to control the coating thickness T _D.

That is, the present invention can provide a coating method capable of easily determining a supply flow rate of a coating material for realizing a target coating thickness on a support.

In the coating method according to the present invention,
Since the control means controls the pump without receiving feedback from the supply flow rate of the paint, pulsation of the supply flow rate of the paint is prevented, and the coating thickness of the paint on the support is maintained constant.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a coating apparatus for performing a coating method according to the present invention.

FIG. 2 is an enlarged sectional view showing a state of a coating film formed by the coating device.

FIG. 3 is a graph showing the relationship between the coating flow rate and the coating thickness in the above-described coating method for each traveling speed of a support.

[Explanation of symbols]

 1. Controller 2. Application thickness setting section 6. Pump 7. ······ Die head 8 ··· Base film

────────────────────────────────────────────────── (5) References JP-A-2-165150 (JP, A) JP-A-62-117669 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B05D 1/00-7/26 G11B 5/842

Claims (1)

(57) [Claims] 1. An extrusion-type coating method in which a paint is supplied to a die by a pump, and the paint is applied while extruding the paint onto a flexible support continuously running through a slit provided at the tip of the die. The supply flow rate of the paint supplied to the die is Q, the ratio of the coating thickness before and after drying of the paint applied to the flexible support is α, and the paint of the paint on the flexible support is α. When the coating thickness after drying is T _D , the running speed of the flexible support is V, and the width of the flexible support is W, α, Q, T _D , V and W relationship, based on the _{Q = α · T D · V} · W, with a control means for controlling the pump, enter the target coating thickness T _D after drying of the running speed V and the paint to the control means, The control means determines the supply flow rate Q. Coating method that.