JPH0824873B2 - Coating device and coating method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus and a coating method for forming a liquid coating film on a thin web or the like.

Conventional technology Coating methods for thin film webs such as various photographic films and magnetic tapes include gravure method, kiss method,
There is a groove groove type reverse method, etc., and they have been used properly according to their purpose. For example, with respect to the entire width of the web, this is divided substantially evenly and provided at intervals to continuously apply in a striped pattern,
The so-called stripe-type reverse method has been mainly adopted for so-called stripe coating. Here, the stripe coating method will be described by taking the grooved groove reverse method as an example.

FIG. 6 is a schematic view of a striped coating method by the groove-reverse type. Reference numeral 71 is a web, and 72 is a backup roll, which is in close contact with the web 71 and rotates at a substantially constant peripheral speed.
73 is a grooved roll for transferring the striped coating film to the web 71, 74 is an application roll, 75 is a metering roll, 76 is a pool of paint, and 77 is a blade for scraping paint.

The operation of the coating apparatus configured as described above will be described below. First, the application role
While rotating 74 at a substantially constant peripheral speed, it invades the paint pool 76.
The coating material adhered to the application roll 74 is formed in an appropriate amount by the metering roll 75 and then transferred to the grooved roll 73. Next, the paint adhered to the grooved roll 73 is applied to the web 71.
And a striped coating film is obtained.

However, it is said that the maximum coating speed of the above-described groove-groove reverse method is about 200 m / min because of the limit that the coating liquid on the rotating roll is scattered by centrifugal force.

Further, since the coating liquid comes into contact with the atmosphere, the coating material diluted with the solvent and applied changes with time due to evaporation of the solvent, resulting in a defective coating film. Due to the recent needs for rationalization of mass production in the coating field, the above-mentioned development is becoming a big issue.

On the other hand, when a paint diluted with a solvent is used, a large volume shrinkage occurs due to the solidification of the coating film during the drying process.
Usually, volume shrinkage is reduced to about 1/5 to 1/20 in terms of film thickness change amount, although it depends on the type of paint or solvent. The contraction / solidification phenomenon at this time will be briefly described. The paint on the joint surface with the web satisfies the NO-Slip condition in fluid dynamics and does not move, so there is no apparent change, and in a form that compensates for this,
The free fluid above the bonding surface flows with contraction, and determines the final coating film distribution shape. The movement of the paint at this time is schematically shown in FIG. Drip occurs at the edge (A portion) of the coating film. However, 1 is a part of the web, 2 is the paint shape immediately after coating, and 3 is the paint shape after drying.

By the way, with respect to the entire width of the web, this is divided substantially evenly and provided with intervals to continuously apply in a striped pattern, that is, in the case of so-called striped coating, since one set of coating film width is narrow, Deterioration of film thickness uniformity due to sagging is fatal in quality.

In view of the above problems, the present invention provides an apparatus and a coating method for applying a striped coating film at high speed without causing defective coating or edge sagging due to natural drying of the coating.

Means for Solving the Problems In order to solve the above problems, the coating apparatus of the present invention is
The die has a structure having grooves of substantially constant depth, which are provided at the tip of the nozzle of the die in a substantially even manner. It also provides a coating method in which tension is applied to the web to bake it.

Effect The present invention can prevent the paint from scattering due to centrifugal force and the natural drying phenomenon of the paint by the above-mentioned constitution, and can apply a striped coating film without coating film defects at high speed.
Further, the edge sag can be eliminated by applying tension to the web to cause the web to enter the inside of the groove.

Example Hereinafter, a first example of the present invention will be described with reference to the drawings.

It is an object of the present invention to provide an apparatus for applying a stripe-shaped coating film at high speed by providing a groove at the tip of a nozzle without causing coating film defects due to natural drying of the coating material.

FIG. 1 is a perspective view of a coating apparatus according to an embodiment of the present invention. 11a and 11b are die bodies, 12 is a paint reservoir provided near the center of the die bodies 11a and 11b, 13 is a flow groove provided in connection with the paint reservoir 12, and 14 is a stripe of paint from the flow groove 13. 15 is a nozzle and 16 is a nozzle tip.

Reference numeral 17 is a web that is in soft contact with the nozzle tip 16 and slides at a constant relative velocity U with respect to the nozzle tip 16, and 18 is a stripe-shaped coating film forming groove provided on the surface of the nozzle tip 16 and having a constant depth. .

2 is an enlarged view of the area A in FIG. 1, FIG. 3 is a sectional view taken along the line BB in FIG. 2, and 35 in FIG. 3 is a free surface portion where the paint comes into contact with the atmosphere.

The operation of the coating device configured as described above will be described below. The paint sent from another supply means (not shown) is stored in the paint reservoir 12 for one day. When the paint is further supplied, the fluid pressure in the paint reservoir 12 rises, and when the fluid resistance of the flow groove 13 and the paint supply groove 14 is exceeded, the paint is ejected to the stripe-shaped coating film forming groove 18. Also web
17 has a constant tension applied to the traveling direction, and the nozzle tip 16 has a curved surface with a substantially constant radius of curvature, so if the web 17 is contacted along the curved surface,
The web 17 closely contacts the nozzle tip 16.

Therefore, the paint other than the free surface portion 35 is sealed inside the groove 18, and the degree of change over time of the paint due to spontaneous evaporation of the solvent is significantly reduced. Moreover, since the sealing paint has no fear of being scattered by centrifugal force, high-speed coating of about 200 m / min or more is possible.

As described above, it is possible to obtain a coating film free from defects due to natural drying of the coating in high-speed striped coating, which has been a problem in the past, at a high coating speed of about 200 m / min.

In the present invention, the nozzle tip portion is a curved surface having a constant radius of curvature, but striped coating is possible even if it is a flat surface.

Needless to say, a striped coating film can also be obtained by winding the film around a backup roll.

An embodiment of the second invention will be described below with reference to the drawings. When a paint diluted with a solvent is used, an edge sag phenomenon occurs as shown in FIG. 7 during the drying process. The sagging phenomenon at the edge of the coating film, which attaches importance to the uniformity of the formed film, not only lowers the quality stability of the coating film but also leads to a lower yield rate. Furthermore, since a set of coating film widths is narrow during striped coating, deterioration of the film pressure uniformity due to sagging from both edges becomes fatal. An object of the present invention is to provide a coating method that solves the above problems.

FIG. 4 is a perspective view of the embodiment of the present invention. 41 is a nozzle, 42 is a stripe-shaped coating film forming groove provided at the tip of the nozzle, 43 is a paint supply groove for supplying paint in a stripe shape from a flow groove (not shown), and 44 is a web.

FIG. 5 is a sectional view taken along the plane AA in FIG.

The operation of the coating device configured as described above will be described in detail. As shown in FIG. 4, the web 44 is wound around the surface of the nozzle tip 45 by applying tension in the traveling direction.

Depending on the degree of tension, the wound web 44 can be grooved.
It will come inside 42. Moreover, the proportion is groove
It becomes maximum near the center of 42. This is shown in FIG. It is also known that the coating thickness immediately after coating is proportional to the groove depth, assuming Couette flow. for that reason,
The phenomenon shown in FIG. 5 is equivalent to that the groove depth in the central portion is apparently shallower than the groove depth in the peripheral portion, and the thickness of the formed coating film immediately after coating is the minimum in the central portion, Maximum in the peripheral area.

By the way, as shown in FIG. 7, even if the coating film is uniformly flattened and coated, the peripheral portion shrinks in volume under the assumption of drying, and the edge is always sagged. In order to compensate for this defect, the phenomenon of the web 44 entering the grooves 42 when tension is applied to the web 44 is effectively utilized, and immediately after coating, the thickness of the peripheral portion is compared with the thickness of the central portion, Leave as a thick film.

With the above configuration, the coating film obtained as a product after drying due to the volume contraction phenomenon in the peripheral portion in the drying step following the coating is rather a uniformly flattened film without edge sagging in the peripheral portion.

When applied with a tension of about 20 g / mm, the distance from the beginning of wetting of the coating to the flat area (called the rising distance) is about 30μ.
It was m. On the other hand, considering that the edge rising distance after drying when applied uniformly is several hundred μm,
It can be seen that the sagging of the edge part has been greatly improved.

In the present invention, the case of striped coating has been described as an example, but even in the coating method for coating the entire coating region, this coating method is effective when the unevenness of the film thickness due to edge sag poses a problem.

EFFECTS OF THE INVENTION As described above, according to the present invention, by providing a substantially constant depth groove provided at the tip of the nozzle substantially evenly,
It is possible to apply a high-quality product with a uniform film thickness and free from coating film defects due to the change with time of the coating material.

In addition, edge tension can be eliminated by applying tension to the web to cause the web to enter the inside of the groove.

[Brief description of drawings]

FIG. 1 is a perspective view of a coating apparatus according to an embodiment of the present invention,
2 is an enlarged view of a main part of FIG. 1, and FIG. 3 is BB of FIG.
Sectional view, FIG. 4 is a perspective view of a nozzle tip in another embodiment of the present invention, FIG. 5 is a sectional view taken along line AA of FIG. 4, and FIG. 6 is a perspective view of a stripe coating method in a conventional example. FIG. 7 is an explanatory diagram of changes due to drying of the paint on the web. 11a, 11b …… Die body, 12 …… Paint reservoir, 13 …… Flow groove, 14,43 …… Paint supply groove, 15,41 …… Nozzle, 16 …… Nozzle tip, 17,44 …… Web, 18 , 42 …… Stripe coating film forming groove.

Claims (2)

[Claims] 1. A block-shaped die body, and a block-shaped nozzle provided so as to project from one side surface of the die body.
A curved surface having a substantially constant curvature provided at the tip of the nozzle, an opening having a substantially rectangular cross section that is substantially evenly divided and provided at a substantially central portion of the tip of the nozzle, and a tip of the nozzle. A groove having a substantially constant depth provided by being divided substantially evenly,
A coating apparatus comprising: a paint reservoir provided on the die body; and a flow groove of a substantially thin plate-like void that is fluidly connected to the opening and the paint reservoir and is substantially evenly divided. 2. A coating method using a coating apparatus according to claim 1, wherein the web is wound around the curved surface of the tip of the nozzle, and tension is applied to the web so that the web penetrates into the groove.