JPH11138079A - Method and apparatus for curtain coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a film thickness uniform over the whole width by a method in which concerning a distribution in the width direction of the thickness of a land part at the end of a die lip connected to a slide surface having a prescribed inclination to a horizontal surface, and the thickness of both end parts is set up to be thinner than that of a central part. SOLUTION: The coater die 1 of an applicator used in the production of X-ray films by applying an emulsifier chiefly for photographic photosensitive materials on various supports applies a coating liquid from a slide surface 2 having a prescribed inclination to a horizontal surface on a support by dropping the liquid in the shape of a curtain. The end of the slide surface 2 is made to be a die grip 20, and the liquid flows down from a land part 21, which is the end face of the die grip 20, in the shape of a curtain. As regards a distribution in the width direction of the thickness of the land part 21 at the end of the die grip 20, the thickness Y of both end parts is set up to be thinner than the thickness X of a central part. In this way, the film thickness formed on the support can be made uniform over the whole width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method generally referred to as curtain coating, and more particularly, to a shape of a tip land portion of a die lip of a coater die.

[0002]

2. Description of the Related Art Techniques for forming various layers by coating an emulsion or the like on a continuously transported support (paper, metal, synthetic resin, etc.) include slide bead coating,
There are methods such as rod coating, extrusion coating, and curtain coating. Among them, the curtain coating method is one in which the coating liquid flows out from a slit provided on the slide surface and flows down uniformly on the slide surface. do it,
The coating layer is transmitted in the form of a curtain film between the edge guides provided on both sides of the die lip connected to the lower end of the slide surface, and collides with the continuously transported support to form a coating layer. This curtain coating method enables high-speed and thin-film coating as compared with conventional slide hopper coating, for example, and is superior to slide bead coating in terms of mass production and energy saving.

On the other hand, however, a "process of forming a coating liquid into a curtain film" is newly generated, so that, for example, the end portions tend to be non-uniform. This tends to occur because the thickness of the end portion in the width direction perpendicular to the transport direction of the layer formed by application becomes large, and the layer thickness of the entire application layer becomes inconsistent. . In this regard, it has been known from various studies that the unevenness of the curtain thickness in the width direction increases as the curtain film flows down between the edge guides.

Furthermore, the flow rate of the curtain film (coating solution) is particularly low near the edge guide, which may cause the curtain film to break at the end.

[0005] That is, in performing suitable curtain coating, there is a need for a technique for stably forming the curtain film itself and keeping the film thickness uniform in the width direction.

In response to these demands, for example, (1) Japanese Patent Application Laid-Open No. 51-57734 and (2) Japanese Patent Application Laid-Open No. 4-35456.
The technique disclosed in Japanese Patent Publication No. 3 has been proposed. These are all devised shapes of the edge guide. However, (1) has a problem that the curtain film itself is stable, but the unevenness in the width direction increases. This problem is particularly remarkable when a coating liquid having a low surface tension is used. (2)
The effect is insufficient as a whole, and in particular, as the flow rate of the coating liquid decreases, the instability and unevenness of the curtain film increase.

Therefore, as an approach different from these techniques, (3) JP-A-59-132966,
(4) Japanese Unexamined Patent Publication No. Hei 3-50085, (5) Japanese Unexamined Patent Publication No.
As described in Japanese Patent Application Laid-Open No. 1996-668 and (6) Japanese Patent Application Laid-Open No. 5-293429, a so-called "side" in which a liquid different from the coating liquid flows down to the edge guide and the curtain film is supported through the liquid. A technique relating to “liquid” has been proposed.

However, even with these techniques, although effective in terms of "forming a curtain film stably", the problem of "unevenness in the width direction" has not yet been sufficiently solved. It is. In particular, when the flow rate of the side liquid is large, there is a problem that the side liquid and the coating liquid are mixed near the edge guide, and the “unevenness in the width direction” increases.

The unevenness of the film thickness near the end is as shown in FIG. 5, and the side liquid as described above is caused to flow down, or after the application, the coating liquid at the end is sucked or coated. Although techniques such as devising physical properties of liquids have been proposed, none of them are effective solutions, and at present, they cannot cope with further high-speed coating.

[0010]

On the other hand, as shown in FIG. 2, if the thickness (W) of the flat portion (end surface) of the tip of the die lip connected to the slide surface of the coater die is large, the lowermost layer is partially missing. (Repelling failure) is less likely to occur, but uniformity of the film thickness at both ends in the width direction cannot be obtained. Conversely, when the thickness W is small, a failure in which the lowermost layer is partially missing (repelling failure) occurs. The present inventor has experimentally found that it is easy to obtain the uniformity of the film thickness at both ends. The boundary between the case where the thickness W is small and the case where the thickness W is large is about 0.4 mm. The flat portion (end surface) of the tip portion is referred to as a land portion, and the thickness W is referred to as a land length.

According to the present invention, a curtain film is stably formed, the above-mentioned problem of unevenness of the film thickness in the width direction is eliminated, and furthermore, the lowermost layer is prevented from being interrupted. An object of the present invention is to realize a curtain coating which can be realized, lower the manufacturing cost, and has a product effective width as large as possible and a high yield and high productivity.

[0012]

As a result of various studies, the inventors of the present invention have found that the land is formed in a shape in which the length of the land is changed in the width direction so that the film thickness is uniform at both ends and the center at the time of coating. In addition, it was confirmed that coating could be performed without causing the lowermost layer to be lost.

Further, it has been found that a more preferable result can be obtained by injecting the auxiliary liquid from the liquid inlets provided on both side ends of the slide surface.

The present invention has been made based on these findings, and is constituted by the following technical means.

(1) A coating liquid supply slit, a slide surface having a predetermined inclination with respect to the horizontal, a die lip connected to the slide surface, and a pair of side plates provided at both ends of the slide surface and the die lip. In a curtain coating apparatus, the coating liquid flows down between the pair of edge guides from a coater die having a pair of edge guides connected to the side plate, and is applied onto a conveyed support. A curtain coating apparatus, wherein the thickness of the land portion at the tip of the die lip has a distribution in the width direction, and the thickness of both end portions is smaller than the thickness of the central portion.

(2) There is provided a liquid injection means provided on each of the pair of side plates and for supplying an auxiliary liquid from a liquid injection port in contact with the slide surface. Curtain coating equipment.

(3) A curtain coating method, wherein the coating is performed using the curtain coating apparatus according to the above mode (1) or (2).

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific examples. In the following examples, an emulsion for photographic light-sensitive material is mainly applied to various supports, for example, polyethylene terephthalate (PET) or triacetate (TAC) to produce an X-ray film, and to a paper support. Although the case where photographic paper is manufactured will be described, the present invention is not limited to this example.When curtain coating is performed on a continuously transported support, for example, a photographic film, a magnetic recording material such as a magnetic tape, The present invention can be applied to the manufacture of information recording paper such as pressure-sensitive paper and thermal paper.

FIG. 1 shows a coater die 1 of a coating apparatus according to the present invention, which applies a curtain coating to a support B in a process of reversing the transport direction by a backup roller R.

The support B is transported by transport means (not shown). As the support to be conveyed, a metal thin plate or the like is used in addition to the paper, coated paper, plastic film, and resin film as described above, and can be appropriately selected in order to obtain a target object to be coated. The backup roller R is
It may or may not contact the support. In the case of a backup roller that does not contact the support, a so-called airbag roller that blows fluid such as air from a number of small holes provided on the roller surface can be used.

The coater die 1 constituting the main part of the coating apparatus has at least a slide surface 2 and, as shown in an enlarged side view of FIG. 2, a die lip 20 at its tip and a land 21 as its tip surface. It has a liquid supply slit 3, edge guides 4, 4 'and side plates 5, 5'.

The coating liquid is uniformly supplied in the width direction from the coating liquid supply slit 3 and flows down the slide surface 2 to form a thin film of the coating liquid. The thin film flowing down the slide surface 2 further propagates as a curtain film between a pair of edge guides 4 and 4 'provided at both ends of the lower end portion of the slide surface, and collides with the transported support B. To form a coating layer.

Further, a slit 3 for uniformly supplying the coating liquid.
It is possible to provide a predetermined number of as required, and a coating liquid in the form of a thin film can be simultaneously laminated by flowing the coating liquid from a plurality of slits 3.

As shown in FIG. 1, side plates 5 and 5 'are provided at both ends of a slide surface 2 of a coater die 1 of a coating device, and a coating liquid supplied from a slit 3 is supplied to the slide surface. They are regulated so that they do not run off the side edges.

In the present invention, the shape of the land portion 21 which is the tip surface of the die lip 20 formed at the tip portion of the slide surface 2 of the coater die 1 is a plane figure as shown in the plan view of FIG. ing. That is, the land has a portion of the dimension X where the thickness W of the land is thick at the center, and a portion of the dimension Y where the thickness W of the land is thin at both ends in the width direction. The length in the width direction of the thin land portion at both ends with respect to the coating solution flowing width is A, the length in the width direction of the thick land portion at the center is C, and B is the length in the width direction of the inclined portion. This is significantly different from the conventional rectangular shape of the land portion shown in the plan view of FIG.

Although the configuration of the first invention of the present invention is as described above, the configuration of the second invention is obtained by adding the following configuration to the configuration of the first invention.

That is, as shown in the perspective view of FIG. 4, a liquid inlet 6 can be provided in the side plates 5, 5 '.

The injection port 6 is rectangular in shape, and one side thereof is in contact with the slide surface. The injection port 6 is connected to an injection mechanism (not shown), and supplies an auxiliary liquid (side liquid) such as a gelatin solution. By supplying the auxiliary liquid from the injection port 6, the coating liquid flowing down on the slide surface flows down along with the auxiliary liquid to the boundary portion between the side plate and the gap between the edge guides via the auxiliary liquid. Propagates and is applied to the support. Also, from the injection means on both sides,
An equal amount of the auxiliary liquid is allowed to flow down, and the amount is set in the range of 0.3 to 3 cc / min on one side. By applying the shape of the land portion and using the liquid injection means together, the curtain film can be formed stably, and the film thickness non-uniformity near the edge guide can be further reduced and the effective product width can be increased. it can.

In this case, there is no possibility that the side liquid is mixed with the coating liquid. Further, the size and height of the cross-sectional area of the liquid injection port 6 can be appropriately designed and adjusted to a height in contact with all layers of the coating liquid flowing down the slide surface.

It is preferable that the injection port is located at the same height as the coating liquid supply slit or at a position higher than the same, so that the auxiliary liquid can be surely made to follow the end of the coating liquid. In particular, when there are a plurality of application liquid supply slits, it is preferable that the slits be located at the same height as the highest slit on the slide surface or at a higher position.

An embodiment of product application by a coating apparatus according to the present invention will be described below. The coating for the X-ray film was performed as in Example 1, and the coating for color photographic paper was performed as in Example 2 by four tests of test numbers 1 to 4. Of the tests, test numbers 1, 2, and 3 use a coater die of the type shown in the perspective view of FIG. 4, and test numbers 4, 5, and 6 are of the type shown in the perspective view of FIG. A coater dice having the same was used.

The test conditions and results of Examples 1 and 2 are as shown in Tables 1 and 2 below.

Example 1 Support PET PET coating speed 200 m / min Downward width of coating solution 1800 mm Number of layers at coating 3 layers Structure and thickness of each layer at coating Lower layer X-ray emulsion 20 μm Middle layer gelatin solution 30 μm Upper layer gelatin solution 30 μm Under the conditions of a coating solution viscosity of 40 cp or more, the shape test of the land portion of the die lip was changed as described below, and a production test of a film for X-ray was performed with and without using the side solution. That is, six types of tests of test numbers 1 to 6 were performed for each 400 m, and the results in Table 1 were obtained.

[0034]

[Table 1]

By adopting the shape of the land portion of the present invention, a good coating state as shown in Test Nos. 3 and 4 could be obtained. And it was confirmed that the test sample No. 4 can obtain a good coating state without the help of the side solution. However, it was found that the result of the test No. 3 using the side liquid was that the effective product width was further increased as compared with the test No. 4 and the yield was improved.

[0036] Under the above conditions, the shape conditions of the land portion of the die lip were changed as described below, and a production test of a color photographic paper was performed in the case where the side liquid was used and the case where the side liquid was not used. That is, six types of tests of test numbers 1 to 6 were performed for each 400 m, and the results in Table 2 were obtained.

[0037]

[Table 2]

By adopting the shape of the land portion of the present invention, a good coating state as shown in Test Nos. 3 and 4 could be obtained. And it was confirmed that the test sample No. 4 can obtain a good coating state without the help of the side solution. However, the result of the test No. 3 using the side liquid was that the effective product width was further increased as compared with the test No. 4 and the yield was improved.

In Test Nos. 3 and 4 of each of the above embodiments, the appropriate values of Y, X, A, B,... Of the land portion of the die lip are changed by changing the coating speed and the coating film thickness. It was confirmed that a preferable suitability value was obtained within the range shown in FIG.

[0040]

[Table 3]

[0041]

According to the first and third aspects of the present invention, the curtain film can be formed stably, the trouble that the lowermost coating film is partially interrupted and dropped is eliminated, and the effective width of the product is reduced. As a result, it is possible to perform coating with high yield and productivity.

According to the second aspect of the present invention, the effective width of the product is further increased, and the yield and productivity are further improved.

According to the present invention, since a coating layer with less edge nonuniformity can be formed, the load of the step of drying after coating is reduced, and there is an advantage that the cost is reduced from the viewpoint of manufacturing equipment. .

[Brief description of the drawings]

FIG. 1 is a perspective view of one embodiment of a coating apparatus according to the present invention.

FIG. 2 is a side view showing a die lip and a land portion of a coater die of a coating apparatus according to the present invention.

FIG. 3A is a plan view of a land portion according to an embodiment of the present invention, and FIG. 3B is a plan view of a conventional land portion.

FIG. 4 is a perspective view of another embodiment of the coating apparatus according to the present invention.

FIG. 5 is a cross-sectional view showing a conventional state in which the film thickness at the end portion in the width direction is uneven.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coater die 2 Slide surface 3 Coating liquid supply slit 4, 4 'Edge guide 5, 5' Side plate 6 Injection port 20 Die lip 21 Land part B Support R Backup roller W Land thickness

Claims (3)

[Claims] 1. A coating liquid supply slit, a slide surface having a predetermined inclination with respect to the horizontal, a die lip connected to the slide surface, and a pair of side plates provided at both end portions of the slide surface and the die lip. In a curtain coating apparatus for applying a coating solution from a coater die having a pair of edge guides connected to the side plate to the space between the pair of edge guides and applying the coating solution onto a conveyed support, A curtain coating apparatus, wherein the thickness of the land portion at the tip has a distribution in the width direction, and the thickness at both ends is smaller than the thickness at the center. 2. A curtain according to claim 1, further comprising a liquid injection means provided on each of said pair of side plates and supplying an auxiliary liquid from a liquid injection port in contact with said slide surface. Coating device. 3. A curtain coating method, wherein coating is performed using the curtain coating apparatus according to claim 1.