JPH07275774A - Die head for coating - Google Patents

Abstract

PURPOSE:To prevent unnecessary heating and thermal distortion of a die head and to improve coating accuracy by heating a coating material flowing from a storage section to a discharge port, thereby lowering the viscosity and shearing restoring force of the coating material and forming a uniform coating film and, on the other hand, by cooling the circumference of a heating means. CONSTITUTION:A die unit 1 is provided with a die pocket 3 for holding the coating material 2 and a die slit 5 for discharging the coating material 2. The coating material 2 is discharged to form the coating film while the coating surface 4a of a material 4 to be coated is relatively moved at the time of coating. In such a case, a heater 8 is located as a means for heating the coating material flowing between the die pocket 3 and the die slit 5. As a result, the uniform coating film is formed by heating up the coating material 2 and degrading its viscosity and shearing restoring force. On the other hand, a heat insulating material 10 is located around the heater 8 and a piping 11 for passing a refrigerant is located as a cooling means on the outer periphery thereof. As a result, the unnecessary heating and thermal distortion of the die unit 1 by the heater 8 are prevented and the coating accuracy is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating die head used for manufacturing magnetic tapes, thermal transfer ink ribbons and the like.

[0002]

2. Description of the Related Art A magnetic tape is manufactured by applying a coating material (magnetic powder), a resin binder and a solvent on a base film to form a coating film. A die head for coating is used for the work.

As shown in FIG. 2 (FIG. 2 (a): perspective view, FIG. 2 (b): sectional view), a coating die head is usually a die pocket for holding a coating material 2 in a die unit 1. 3 and a slit-shaped ejection port (die slit) 5 for ejecting the coating material held in the die pocket 3 onto the coating surface 4a of the article 4 to be coated. Further, a filter element 6 is provided inside the die pocket 3, and the paint 2 is injected into the filter element and the hydraulic pressure is increased by a pump to make the die pocket 3
It will be pushed out and held. At the time of coating the coating material, the coating surface 4a of the object to be coated 4 such as a base film is moved at a predetermined relative speed with respect to the die slit 5, and the coating material 2 is discharged from the die slit 5 onto the coating surface 4a. To form a coating film.

In this case, since the coating material 2 to be applied usually has high viscoelasticity, the coating material 2 is simply passed through the die slit 5.
It is not possible to uniformly form a thin coating film only by discharging. Therefore, by changing the width (w) and depth of the die slit 5, the shape of the die lip 7 which is the tip member of the die slit, the size of the die pocket 3 and the like, a shearing force is applied to the coating material 2 discharged onto the coating surface 4a. In addition, it is possible to instantaneously reduce the viscosity coefficient of the paint and improve the coatability.

[0005]

However, in recent years,
Along with the demand for higher density of magnetic recording, the resin binder contained in the coating is made higher in polymer, the crosslinked structure is made denser, and the coating particles are made finer. Therefore, the viscosity and the shear recovery force of the paint become extremely high, which makes it difficult to apply the paint to the applied surface in a uniform thickness. In particular, since the shear recovery force is increased, fine streak lines in the longitudinal direction are formed in the coating film, and the resulting magnetic tape causes a problem such as setting failure for a predetermined application.

The present invention is intended to solve the problems of the prior art as described above, and when manufacturing a magnetic tape, a thermal transfer ink ribbon, or the like, a highly viscous coating material is applied to a substrate film or the like by using a die head for coating. Even when using a paint with particularly high viscosity and shear recovery when applying to the object to be coated, it is possible to prevent fine streaks in the longitudinal direction from entering the coating film and enable uniform coating. The purpose is to

[0007]

The inventor of the present invention has a limit in sufficiently reducing the viscosity of the coating material by merely applying the shearing force to the coating material discharged from the die pocket, and the shear recovery force is sufficiently reduced. It cannot be lowered, and it is not possible to obtain a uniform coating film. In contrast, the conventional shearing force is applied to the paint and the paint temperature is raised immediately before coating, which reduces the viscosity of the paint. And, it was found that the shear recovery force can be sufficiently lowered, the leveling property (self-smoothness) of the coating film surface immediately after coating can be improved, and a uniform coating film can be obtained, and the present invention was completed. Came to let.

That is, according to the present invention, there are provided a die pocket for holding a coating material containing coating particles, a resin binder and a solvent, and a slit-shaped discharge port for discharging the coating material held in the die pocket onto a coated surface of an object to be coated. A die for coating, which comprises a coating die head for forming a coating film on a coating surface of a coating object that moves at a relative speed with respect to the discharging port by discharging a coating material from the discharging port, A heating means for heating the paint flowing between the pocket and the discharge port, a heat insulating material arranged around the heating means, and a cooling means arranged outside the heat insulating material. Provide a die head for engineering.

Particularly, in such a coating die head, heating means is provided in the vicinity of the discharge port, and the heating temperature of the coating material by the heating means is not less than the glass transition point of the resin binder contained in the coating material. Provided is one having a boiling point not higher than that of the solvent contained in the paint.

[0010]

In the coating die head of the present invention, since the heating means for heating the paint flowing between the die pocket and the discharge port is provided, the temperature of the paint discharged from the die slit can be increased. . Therefore, even when injecting high-viscosity paint into the coating die head,
At the time of coating in which the paint is discharged from the die slit, it is possible to sufficiently reduce the viscosity and shear recovery force of the paint, thereby improving the leveling property (self-smoothness) of the coating surface immediately after coating. . Therefore, a uniform coating film can be obtained.

Further, in the die head of the present invention, since the heat insulating material is arranged around the heating means and the cooling means is further provided outside the heat insulating material, unnecessary heating of the die unit by the heating means is prevented. It is possible to prevent thermal distortion. Therefore, it is possible to maintain high coating accuracy.

In particular, in the present invention, when the heating means is provided in the vicinity of the discharge port, the temperature of the paint immediately before coating is sufficiently increased, but the temperature rise of the paint held in the die pocket is suppressed. Therefore, the viscosity of the paint in the die pocket can be kept high, and the pressure distribution in the width direction of the die slit of the paint in the die pocket can be made uniform.

Further, the heating temperature of the paint by the heating means is
When the glass transition temperature of the resin binder contained in the paint is higher than the boiling point of the solvent contained in the paint, the coating particles in the paint, the resin binder, and the solvent can be applied while maintaining a good dispersion state. Becomes

[0014]

EXAMPLES The present invention will be specifically described below based on examples.

FIG. 1 is a sectional view of an embodiment of the present invention.
In the figure, the same reference numerals as those of the above-described conventional example shown in FIG. 2 represent the same or equivalent constituent elements.

In the coating die head of the embodiment shown in FIG. 1, as in the conventional example shown in FIG. 2, the die unit 1 is provided with a die pocket 3 and a discharge port (die slit) 5. A filter element 6 is provided inside the die pocket 3. And when applying the paint,
Similar to the conventional example, the coating surface 4a of the article to be coated 4 is moved at a predetermined relative speed with respect to the die slit 5 while the coating material 4 is discharged from the die slit 5 to form a coating film. To do.

However, the coating die head shown in FIG. 1 is provided with a heater 8 as a heating means for heating the paint flowing between the die pocket 3 and the discharge port 5. The heater 8 heats the paint flowing between the die pocket 3 and the discharge port 5 to a temperature not lower than the glass transition point of the resin binder contained in the paint and not higher than the boiling point of the solvent contained in the paint. Is preferably provided. By heating to a temperature not lower than the glass transition point of the resin binder, the viscosity and shear recovery force of the coating material discharged from the discharge port 5 are sufficiently reduced, whereby the leveling property (self-smoothness) of the coating film surface immediately after coating is reduced. It is possible to improve the property) and obtain a uniform coating film. Further, by setting the heating temperature to the boiling point of the solvent or lower, it becomes possible to maintain good dispersibility of the coating particles, the resin binder and the solvent. Such a heater 8 can be specifically configured by a heating wire, a pipe through which a heat medium such as oil, hot water, or steam having a predetermined temperature is passed.

The heater 8 is preferably provided in the die unit 1 at a position closer to the discharge port 5 than the die pocket 3. As a result, the temperature of the paint held in the die pocket 3 can be suppressed as much as possible, and the viscosity of the paint in the die pocket can be kept high, and the pressure distribution in the width direction of the die slit of the paint in the die pocket can be maintained. It becomes possible to make it uniform.

Further, in this embodiment, since the heating temperature of the coating material by the heater 8 is controlled so as to fall within the above range, in the coating material flow path between the die pocket 3 and the discharge port 5,
Thermocouples 9a, 9b and 9c are provided at three locations near the die pocket, near the discharge port and in the middle thereof.

A heat insulating material 10 is provided around the heater 8, and a pipe 11 for passing a refrigerant is provided outside the heat insulating material 10 as a cooling means. Since the coating die head is usually assembled at room temperature and used at room temperature, when the temperature of the paint in the die unit is raised, thermal distortion occurs in each part such as the die pocket, die slit, and die lip, and the coating film Although it may be difficult to precisely control the thickness, the provision of the heat insulating material 10 and the cooling means 11 can prevent the die unit from being heated, so that the coating accuracy can be kept high. It becomes possible to do. As such a heat insulating material, a heat insulating material made of a heat resistant resin or the like can be used.

[0021]

According to the coating die head of the present invention, since the heating means for heating the coating material flowing between the die pocket and the discharge port is provided, a highly viscous coating material is injected into the coating die head. Even when coating, the temperature of the paint discharged from the die slit is increased to sufficiently reduce the viscosity and shear recovery force of the paint during coating, thereby leveling the coating surface immediately after coating ( It is possible to improve the (self-smoothness) and obtain a uniform coating film.

Further, by lowering the viscosity of the coating material in this way, the pump pressure required for discharging the coating material from the die slit can be lowered, so that the deformation of the coating die head due to the pump pressure is suppressed. be able to. Conventionally, as the die unit, a large block made of stainless steel has been used to prevent such deformation, but as described above, it is possible to reduce the pump pressure and suppress the deformation due to the pump pressure. The die unit can be downsized, and the coating accuracy can be improved. Furthermore, since the width of the die slit can be narrowed by lowering the pump pressure,
It is also possible to form a thinner coating film.

Further, according to the present invention, since the viscosity of the coating material discharged onto the coating surface can be lowered by heating the coating material, the shearing force required to be applied to the coating material during coating is conventionally reduced. Can be further reduced. Therefore, it is possible to reduce the tension of the article to be coated such as the base film required to obtain the shearing force. Further, the moving speed of the object to be coated with respect to the die slit can be widely selected from low speed to high speed.

Further, generally, after forming a coating film on an object to be coated using the coating die head, the object to be coated is usually dried in a drying oven, but the coating die head of the present invention is used. Since the paint temperature during coating is high, the coating film can be dried quickly. Furthermore, according to the present invention, since a high-viscosity coating material can be used as described above, it is possible to reduce the solvent content in the coating material, which also allows rapid drying of the coating film. It will be possible. Therefore,
Product productivity can be improved, and drying equipment can be simplified.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a perspective view (FIG. 2A) and a cross-sectional view (FIG. 2B) of a conventional coating die head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die unit 2 Paint 3 Die pocket 4 Work piece 4a Work surface 5 Discharge port (die slit) 6 Filter element 7 Die lip 8 Heater 9 Thermocouple 10 Insulating material 11 Cooling means

Claims (3)

[Claims] 1. A die pocket for holding a coating material containing coating particles, a resin binder and a solvent, and a slit-shaped discharge port for discharging the coating material held in the die pocket onto the coated surface of an object to be coated. , A die pocket and a discharge port in a coating die head that forms a coating film on a coated surface of a coating object that moves at a relative speed with respect to the discharge port by discharging a paint from the discharge port. A coating die head, comprising: heating means for heating the paint flowing between the heating means, a heat insulating material arranged around the heating means, and a cooling means arranged outside the heat insulating material. 2. The coating die head according to claim 1, wherein the heating means is provided in the vicinity of the discharge port. 3. The heating means heats the paint flowing between the die pocket and the discharge port to a temperature not lower than the glass transition point of the resin binder contained in the paint and not higher than the boiling point of the solvent contained in the paint. The coating die head according to claim 1.