JPH09141166A - Coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately set the shape of the heel part of a free falling curtain to prevent the mixing of air bubbles with a coating material in a coating apparatus allowing the coating material formed into a free falling curtain to fall on an object to be coated moving in a horizontal direction. SOLUTION: In a coating apparatus allowing a coating material to be formed into a free falling curtain 11 to fall on a strip like object 12 to be coated moving in an almost parallel direction crossing the liquid surface of the free falling curtain 11 to coat the object to be coated, a suction means having a suction port 20 opened toward a falling point on the upstream side of the falling point of the coating material is provide din the vicinity of the upper surface of the object 12 to be coated and air streams are formed in the vicinity of the falling point to form a heal part 21A protruding upstream to the coating material in the vicinity of the falling point to appropriately set the protruding quantity thereof.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating apparatus,
In particular, in order to manufacture photographic light-sensitive materials such as photographic film and photographic paper, and thermal recording materials, the paint with a free-fall curtain is dropped onto a horizontally moving object to be coated. The present invention relates to a coating device.

[0002]

2. Description of the Related Art A coating device is described in Japanese Examined Patent Publication No. 49-24133, in which a coating material having a free-fall curtain is dropped onto a horizontally moving object to be coated. ing. FIG. 6 is a front view schematically showing the appearance of such a conventional coating apparatus.

In FIG. 6, reference numeral 10 denotes a coating head, which has an oblong slit (not shown), through which the coating material is poured. 11 is the paint that has been poured from the coating head 10, and is a free-fall curtain (denoted by 11)
Is formed. Reference numeral 12 is a belt-shaped object to be coated, which is generally called a web, and is horizontal to the liquid surface of the free-fall curtain 11 (a direction orthogonal to the paper surface, in this case, the back surface side direction of the paper surface).
The paint of the free-fall curtain 11 is dropped onto it and applied. 13A and 13B are free-fall curtains
It is an edge guide that sets the width of 11 and stabilizes the falling state. In this coating method, high precision and high speed coating are required.

Although the moving speed of the object to be coated 12 affects the coating efficiency, if the moving speed of the object to be coated is increased in order to improve the coating efficiency, the paint on the free-fall curtain 11 will not be able to move at the falling point. There is a problem that the coating becomes stable, and thereby air bubbles penetrate into the coating material near the dropping point and the coating quality deteriorates. In order to stabilize the free-fall curtain 11, Japanese Patent Publication No. 49-24133 uses an air shield that blocks the flow of the surrounding air. Further, in the vicinity of the edge guides 13A and 13B, an action called Marangoni effect works and causes a thin film portion to cause the free fall curtain 11 to be unstable. To reduce the influence of the Marangoni effect. In Japanese Patent Laid-Open No. 54-68847, the edge guides on both sides of the free fall curtain are made of stainless steel wire that moves from above in the vicinity of the drop point in the free fall direction. Further, in Japanese Laid-Open Patent Publication No. 1-199668, a means for jetting the paint in a jet form is provided on the surface of the edge guide. In Japanese Patent Publication No. Sho 63-22192, a small amount of a member that forms a part of the components of the coating material is previously applied to the object to be coated.

FIG. 7 is a schematic diagram showing the shape of the coating material formed by the conventional coating apparatus according to FIG. 6 at a low speed, and FIG. FIG. 7 is a schematic view of a shape state showing a paint formed at a high speed, and each is shown in a side sectional view with respect to the front view of FIG. 6.
In this case, the workpiece 12 has a horizontal movement speed of about 200, for example.
˜600 cm / s, and the film thickness of the coating film 14 formed on the object to be coated 12 is set to be about 30 μm to 100 μm. The horizontal moving speed and the film thickness are appropriately set at any time depending on the product type of the target product. The paint that forms the free-fall curtain 11 drops on the object to be coated 12 that moves in the direction of the arrows in each figure, and the frictional resistance generated between the object to be coated 12 and the surface layer of the object to be coated 12 occurs. The paint is stretched by the resistance of the air boundary layer to form the coating film 14. When the object 12 to be coated is at a low speed, as shown in FIG. 7, a heel portion 11A having a shape similar to the heel of the foot occurs near the upstream side of the drop point. The shape of the heel portion 11A changes with a certain tendency depending on the moving speed and material of the object to be coated 12, the viscosity of the paint, the falling speed, and the like.
At a high speed, the drop point of the coating material on the article to be coated 12 moves to the downstream side, and the heel portion 11A disappears, as shown in FIG.
As shown in, a flat inflection portion 11B is produced. It is said that the shape of the heel portion 11A is closely related to the inclusion of air bubbles in the paint, and if a certain shape is achieved, the inclusion of air bubbles will occur. The diameter of this bubble is estimated to be about several μm. Further, it has been found that bubbles are not generated if the heel portion 11A is present under the coating conditions using a paint having a sufficiently large viscosity.

[0006]

In each of the coating apparatuses cited above, the local structure of the free-fall curtain at the paint drop point is not taken into consideration.
It is not always possible to adequately suppress the inclusion of bubbles due to the instability of the free-fall curtain itself. SUMMARY OF THE INVENTION It is an object of the present invention to provide a coating apparatus capable of appropriately setting the shape of the heel portion of a free-fall curtain to prevent air bubbles from being mixed into the coating material.

[0007]

In order to achieve the above object, the invention according to claim 1 moves the paint, which forms a free fall curtain, in a substantially horizontal direction so as to intersect the liquid surface of the free fall curtain. In a coating device for dropping onto a strip-shaped object to be coated, an intake air that is close to the upper surface of the object to be coated and opens toward the drop point near the upstream side of the paint drop point An intake means having a mouth was provided.

According to a second aspect of the present invention, the intake port of the air intake means according to the first aspect is provided with an inlet port 50 upstream of the paint drop point.
The invention is characterized in that the intake means is installed by opening at a position of μm to 2000 μm, and the invention according to claim 3 is such that the velocity of the air flow by the intake of the intake means according to claim 1 is The moving speed of the object to be coated is set to 80% to 120% in the vicinity of the drop point of the coating material, and the invention according to claim 4 is the coating material according to claim 1. The invention is characterized in that the work body has a curved top in the vicinity of the drop point of the paint and is inclined downward toward the upstream side and the downstream side, and the invention according to claim 5 is characterized in that the paint falls. A curved top portion of the article to be coated according to claim 4 is formed by providing a cylindrical roller that supports the article to be coated from below in a vicinity of the point and is rotatable. And invention of Claim 6 is Claim 4 The bending angle at the top of the article to be coated is 165 ° to 180 °.

According to a seventh aspect of the present invention, instead of the air intake means according to the first aspect, the liquid surface of the free-fall curtain is brought close to the upper surface of the object to be coated in the vicinity of the upstream side of the paint drop point. A thin thread was stretched in parallel. The invention according to claim 8 is characterized in that the thin yarn according to claim 7 is stretched at a position distant from 50 μm to 1000 μm from the upper surface of the article to be coated, and claim 9 The invention is characterized in that the thin yarn according to claim 7 is stretched on an extended surface of a coating surface on the upper surface of the article to be coated, and
The invention according to claim 7 is characterized in that the diameter of the fine yarn according to claim 7 is 10 μm to 50 μm, and the invention according to claim 11 is the fine yarn according to claim 7, which is a metal wire. What is characterized is, and Claim 1 is characterized by the above-mentioned.
The invention described in 2 is characterized in that the thin yarn described in claim 7 is a synthetic resin wire.

According to the first to sixth aspects of the present invention, an air flow is generated from the drop point of the paint toward the upstream side by the intake action of the intake means, and the paint near the drop point is projected to the upstream side. The overhang amount is set based on the setting condition of the intake means. In the invention according to claims 7 to 12, the capillary phenomenon is caused by the thin yarn in the vicinity of the upstream side of the paint dropping point, and the paint near the dropping point is projected to the upstream side to set the thin yarn. The overhang amount is set based on the condition.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a conceptual view of a coating apparatus showing a first embodiment of the present invention, which is a sectional side view similar to FIG. 7 and corresponds to the inventions of claims 1 to 3. . In FIG. 1, the same parts as those in FIG. 7 are designated by the same reference numerals and the description thereof is omitted. Reference numeral 20 is an air intake duct, which is close to the upper surface of the object to be coated 12 and has a free-fall curtain 11 that is the object to be coated with paint.
12 has an intake port 20A that is open toward the drop point in the vicinity of the upstream side of the drop point, and is moved by an intake pump (not shown) in the arrow direction (the direction opposite to the moving direction of the workpiece 12). Inhale. 21A is a heel portion generated in this intake state.

When the coating material forming the free-fall curtain 11 is dropped on the object 12 to be moved in the horizontal direction, it is stretched in the moving direction of the object 12 to form a coating film 14. At this time, when the moving speed of the article to be coated 12 is relatively slow at the drop point, as shown in FIG.
A heel portion 11A protruding to the upstream side of the article to be coated 12 is generated. Then, when the moving speed of the article to be coated 12 is increased in order to improve the coating efficiency, the drop point of the coating material moves to the downstream side and the heel portion 11A is not overhanged as shown in FIG. The curved portion 11B is generated. Then, in such a state, mixing of bubbles occurs at the drop point. The intake duct 20 is installed in order to prevent the mixture of the air bubbles, and by adjusting the intake appropriately, the negative pressure due to the intake changes and the amount of protrusion is adjusted.

The intake duct 20 is preferably installed with the intake port 20A opened at a position of 50 μm to 2000 μm upstream from the free fall point of the paint. This is because the air flow affects only the heel and the free fall curtain at the top.
This is because 11 is not affected as much as possible. Then, the velocity of the air flow due to the intake air of the intake duct 20 needs to be set to 80% to 120% of the moving velocity of the object to be coated 12 in the vicinity of the drop point of the paint. Object to be coated 12
When the moving speed of the coating becomes faster, the protrusion of the heel portion is reduced because the frictional resistance generated between the coating object 12 and the air boundary layer generated in the surface layer of the coating object 12 near the drop point of the paint. Due to the resistance, in order to cancel these influences, less than 80% is not sufficient, and above 120%, the coating of the free-fall curtain 11 becomes unstable.

In the configuration of FIG. 1, these intake ports 20A
By properly setting the installation condition and the intake condition, etc. as described above, the amount of protrusion of the heel portion 21A becomes appropriate, and air bubbles are not mixed into the paint. FIG. 2 shows a second embodiment of the present invention.
FIG. 8 is a conceptual diagram of the coating apparatus showing the embodiment of FIG. 7, which is shown in a sectional view of a side face similar to FIG. 7, and corresponds to the inventions of claims 4 to 6.

In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Reference numeral 32 denotes a body to be coated, which forms a bent top portion 32A in the vicinity of the drop point of the coating material, and the upstream side coating body 32B and the downstream side coating body 32C are inclined downward from the top portion 32A. The intake duct 20 is shown in Figure 1.
It is installed in the same manner as in, and sucks air in the direction of the arrow in the figure (the direction opposite to the moving direction of the article 12 to be coated). 31A is a heel portion generated in this intake state.

When the paint that has formed the free-fall curtain 11 falls on the top 32A of the object 32 to be coated, it is stretched in the moving direction on the downstream side object 32C that moves downwardly from the top 32A. A coating film 14 is formed. This coating apparatus is different from the configuration of FIG. 1 in that the heel portion 21A generated by the intake duct 20 is efficiently changed.

The object 32 to be coated is supported by a pulley (not shown) on the upstream side and the downstream side. In order to form the curved top 32A, the object 32 to be coated is made to correspond to the vicinity of the drop point of the paint. A cylindrical roller 33 that supports the coated body 32 from below at a position higher than the supporting position of these pulleys and allows it to rotate.
It has. As a result, the upstream coating object 32B and the downstream coating object 32C are formed so as to be inclined downward from the top portion 32A.

The bending angle at the top 32A of the article 32 to be coated must be 165 ° to 180 °. When the bending angle is smaller than 165 °, the coating film of the free-fall curtain 11 becomes unstable and, on the contrary, bubbles are easily mixed. In the configuration of FIG. 2, the article 32 to be coated forms the top 32A in the vicinity of the drop point of the paint, and the article 32B to be coated on the upstream side and the article 32B to be coated on the downstream side.
By inclining 32C and 32C downwardly from the top 32A and inhaling air in the same manner as in FIG. 1, it becomes possible to more appropriately set the intake condition by the intake port 20A, and the protrusion amount of the heel portion 31A becomes appropriate. As a result, air bubbles are not mixed in the paint.

FIG. 3 is a conceptual view of a coating apparatus showing a third embodiment of the present invention, which is a sectional side view similar to FIG. 7, and corresponds to the inventions of claims 7 to 12. I am letting you. 3, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Reference numeral 40 is a thin thread made of a metal wire, which instead of the intake duct 20 in FIG. It is stretched in parallel with the liquid surface of the curtain 11. 41A is a heel portion formed in the paint at the drop point.

When the coating material forming the free-fall curtain 11 in FIG. 3 falls on the object 12 to be moved in the horizontal direction, it is stretched in the moving direction of the object 12 to form a coating film 14. . At this time, at the drop point, the paint is
And the heel portion 41A is formed by the capillary phenomenon. The amount of protrusion of the heel portion 41A is adjusted by the fine yarn 40 to prevent air bubbles from entering.

The thin yarn 40 is stretched at a position 50 μm to 1000 μm away from the upper surface of the article to be coated 12 in order to properly adjust the amount of protrusion of the heel portion 41A. is necessary. And for the same reason 40 threads
Needs to be stretched on the extended surface of the coating surface of the coating film 14 on the upper surface of the article to be coated 12.

For the same reason, the fine yarn 40 has a diameter of 10
It is desirable that the thickness is from μm to 50 μm. This is 10μ
If it is less than m, proper capillarity cannot be generated, and if it exceeds 50 μm, the shape of the heel portion 41A becomes unstable. As the thin thread 40, a material having a large limit tension is required, and it is preferable to use a metal wire such as a pier wire.

As the above-mentioned thin yarn 40, in order to avoid deterioration caused by rust, it is preferable to use a synthetic resin wire, especially in the case of using an aqueous solution paint. In this case, for example, nylon wire is used as the material having a large limit tension. In the configuration of FIG.
By properly installing 40 as described above, the amount of protrusion of the heel portion 41A becomes appropriate, and bubbles are not mixed into the paint.

[0024]

Next, an operation example according to a concrete embodiment of the present invention will be described. FIG. 4 is a characteristic diagram of the critical speed (cm / s) of the object to be coated with respect to the flow rate (cc / min) of the coating material, which shows an example of the operation of the coating apparatus having the configurations of FIGS. 1 and 2. Each characteristic is based on actual measurement. In the figure, the characteristic A is the characteristic according to the configuration of FIG. 1 provided with the intake duct 20, and the characteristic B is the top 32A, the upstream coating object 32B, and the downstream coating object 32C. 2 and a characteristic C having the intake duct 20 and the intake duct 20 are characteristics according to the conventional configuration of FIG.

The paint used was a polyvinyl alcohol liquid, the viscosity was 300 cP, and the fall distance of the free fall curtain 11 was 30 cm. Generally, in a region where the viscosity of the coating is sufficiently small, the critical velocity of the article to be coated 12 or 32 increases as the flow rate of the coating increases, and when the flow rate exceeds a certain level, the critical velocity tends not to increase. Characteristic A and characteristic B
Has a critical speed of 20% or more higher than that of the conventional characteristic C, clearly showing that the coating speed can be increased. Further, the critical velocity of the characteristic B is the highest in the region where the flow rate is small, and it can be seen that the coating apparatus having the configuration of FIG. 2 is particularly effective.

FIG. 5 is a diagram showing the critical velocity characteristic of the object to be coated with respect to the flow rate of the coating material, which shows an example of the operation of the coating apparatus having the configuration of FIG. In the figure, a characteristic D is a characteristic according to the configuration of FIG. 3 including the thin yarn 40, and a characteristic C ′ is a characteristic according to the conventional configuration of FIG. 7.
The paint used was polyvinyl alcohol liquid, and the viscosity was 5
The fall distance of 0 cP and the free fall curtain 11 is 30 cm. It can be seen that when a coating material having a low viscosity is used, the coating device having the configuration shown in FIG. 3 is particularly effective in a region where the flow rate is large.

Thus, by taking appropriate measures depending on the quality of the coated product and the coating conditions, the coating efficiency can be increased at low cost.

[0028]

According to the inventions of claims 1 to 6, in a coating apparatus for coating a coating material having a free-fall curtain by dropping it onto a horizontally moving object to be coated, Since the intake means having the intake port opened toward the drop point near the upstream side of the paint drop point is provided, air is drawn from the paint drop point toward the upstream side by the intake action of the intake means. When a flow occurs, the paint near the drop point is projected to the upstream side, and by appropriately setting the installation condition of the intake means and the intake condition, this projection amount becomes appropriate and the mixture of air bubbles into the paint. Is prevented.

According to the inventions of claims 7 to 12, instead of the intake means of claims 1 to 6, the upper surface of the article to be coated is located in the vicinity of the upstream side from the drop point of the paint. Since the thin yarn is stretched in parallel with the liquid surface of the free-fall curtain, the thin yarn causes a capillary phenomenon in the vicinity of the upstream side of the paint drop point, causing the paint near the drop point to reach the upstream side. By properly installing the thin thread,
This overhang amount becomes appropriate and the mixture of air bubbles in the paint is prevented.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a coating apparatus showing a first embodiment of the present invention.

FIG. 2 is a conceptual diagram of a coating apparatus showing a second embodiment of the present invention.

FIG. 3 is a conceptual diagram of a coating apparatus showing a third embodiment of the present invention.

FIG. 4 is a critical velocity characteristic diagram of the object to be coated with respect to the flow rate of the coating material, showing an operation example of the coating device having the configurations of FIGS. 1 and 2.

5 is a critical velocity characteristic diagram of the object to be coated with respect to the flow rate of the coating material, showing an example of the operation of the coating device having the configuration of FIG.

FIG. 6 is a front view schematically showing the appearance of a conventional coating apparatus.

FIG. 7 is a schematic diagram showing a state of a paint which is formed by a conventional coating apparatus when the object to be coated is low speed.

FIG. 8 is a schematic view showing a shape state of a coating material formed by a conventional coating device at a high speed on an object to be coated.

[Explanation of symbols]

 10 Coating head 11 Paint (free fall curtain) 11A, 21A, 31A, 41A Heel part 11B Inflection part 12, 32 Coating object 13A, 13B Edge guide 14 Coating film 20 Intake duct 20A Inlet port 32A Top part 32B Upstream side Coated object 32C Downstream side coated object 33 Cylindrical roller 40 Fine thread

Claims (12)

[Claims] Claim: What is claimed is: 1. A coating apparatus for applying a coating material, which forms a free-falling curtain, onto a belt-shaped object to be coated which moves in a substantially horizontal direction so as to intersect the liquid surface of the free-falling curtain. In addition, the coating means is provided with an intake means which has an intake port which is close to the upper surface of the object to be coated and which is opened in the vicinity of the upstream side of the drop point of the coating material toward the drop point. apparatus. 2. The coating apparatus according to claim 1, wherein the air intake means has an air intake opening at a position of 50 μm to 2000 μm upstream of the point where the paint falls. 3. The air intake means has an air flow speed of 80% of the moving speed of the object to be coated in the vicinity of the paint drop point.
The coating apparatus according to claim 1, wherein the coating rate is set to 120% to 120%. 4. The coating apparatus according to claim 1, wherein the article to be coated has a curved top in the vicinity of the drop point of the coating material and is inclined downward toward the upstream side and the downstream side. 5. A bent top portion of the article to be coated is formed by providing a cylindrical roller that supports the article to be coated from below in the vicinity of a drop point of the coating material so as to be rotatable. 4. The coating apparatus according to 4. 6. The bending angle at the top of the article to be coated is 165 °.
The coating apparatus according to claim 4, wherein the coating apparatus has an angle of 180 ° to 180 °. 7. A coating apparatus for coating a coating material, which forms a free-fall curtain, by dropping it onto a belt-shaped object to be crossed with a liquid surface of the free-fall curtain and moving in a substantially horizontal direction. 2. A coating apparatus, wherein a thin thread is stretched in parallel with the liquid surface of the free-fall curtain in the vicinity of the upstream side of the dropping point of the coating material so as to be close to the upper surface of the object to be coated. 8. The coating apparatus according to claim 7, wherein the thin yarn is stretched at a position distant from the upper surface of the object to be coated by 50 μm to 1000 μm. 9. The coating apparatus according to claim 7, wherein the thin yarn is stretched on an extension surface of the coating surface on the upper surface of the object to be coated. 10. The coating apparatus according to claim 7, wherein the thin yarn has a diameter of 10 μm to 50 μm. 11. The coating apparatus according to claim 7, wherein the thin yarn is made of a metal wire. 12. The coating apparatus according to claim 7, wherein the thin yarn is made of a synthetic resin wire.