JPH0822410B2 - Coating method and coating device - Google Patents

Description

TECHNICAL FIELD The present invention relates to slide bead coating, and more particularly to coating using a pressure reducing means for bead stabilization.

(Prior Art) A photographic material generally supports a silver halide grain and a hydrophilic colloid (eg gelatin) solution containing an additive for adjusting photographic characteristics and productivity, a flexible long-length support such as polyethylene terephthalate or baryta paper. It is manufactured by continuously applying it to a body (hereinafter referred to as a web) and drying it.

Initially, the dip method, the double roll method, the air doctor method, etc. were used as the method for coating the photographic layers constituting the photographic material on the web. The law was developed,
Currently, the slide bead coating method has become the mainstream. For the slide bead coating method, US Pat.
1,294, 2,761,419, 2,761,179 and British Patent 8
No. 37,095.

As described in the above patent, the slide bead coating method extrudes one or more coating liquids as a continuous wide ribbon from a slit provided in a coating liquid casting feeder (slide hopper) to form a coating liquid casting surface (sliding surface). ), A single layer or laminated ribbon of the coating liquid is stretched over the surface of the web running near the end (lip portion) to form a bead, and the casting speed of the coating liquid and the web that holds the ribbon away from the bead. A single-layer or laminated coating film is applied on the web in conformity with the running speed. In general, the traveling web is stretched around a coating backup roller provided close to the lip portion.

Therefore, in the slide bead coating method configured as described above, it is an essential condition that the coating liquid supply amount and the running speed (coating speed) of the web are perfectly matched. The shape stability of the bead formed by the applied coating liquid ribbon has a great influence on the uniformity and dry finish of the coating film.

For example, if the bead follows or delays with respect to the running direction of the web, that is, if vibration of the bead occurs in the longitudinal direction of the web, horizontal stripes (uneven ribs), coating breakage occur, and further the vibration causes gas-liquid at the bead position. -If the solid phase part is not disturbed, vertical streaks will occur.

These disadvantages cannot be avoided unless the bead itself has a positive self-restoring force for stabilizing the bead shape.

In U.S. Pat. No. 2,681,294, a decompression chamber is attached and the beads are sucked by decompression in the direction opposite to the running direction of the web to stabilize the beads. This will be specifically described below with reference to the drawings.

FIG. 4 is a side sectional view of a conventional slide bead coating machine having a decompression chamber.
The coating liquid layer 3 flowing on the sliding surface of 20 forms a ribbon-shaped liquid reservoir, that is, a bead 4, between the lip portion 23 and the web 2 that runs while holding the coating backup roller 1. A decompression chamber 30 in which this bead is decompressed by a decompression pump 33.
The beads are stabilized by sucking the beads downward.

However, in this case, air flows into the decompression chamber 30 through the gap between the web before coating and the wall of the decompression chamber, and this air causes a vortex in the decompression chamber to destabilize the bead.

In contrast, US Pat. No. 4,335,672 has two decompression chambers.
A method of making a chamber is disclosed. FIG. 5 (a) is a schematic side sectional view of the coating machine shown in the US patent. In the figure, the decompression chamber is divided into an inner decompression chamber 32 on the applicator side and an outer decompression chamber 31 on the outer side.
Is sucked under reduced pressure. The inner decompression chamber 32 is sucked and decompressed toward the outer decompression chamber through the gap between the web 2 that runs while holding the coating backup roller 1 and the partition walls of both decompression chambers. This is a method of stabilizing the degree of pressure reduction of the inner pressure reducing chamber 3 including the bead portion.

However, even this method has not been a sufficient countermeasure against coating unevenness. Possible causes are, for example, in the coating machine, when a bead is formed, the inflow of air into the internal decompression chamber 32 becomes minimal, so that the flow of air from the internal decompression chamber 32 toward the outer decompression chamber 31. Disappears, and A and B shown in FIG. 5 (b) have the same degree of reduced pressure. FIG. 5 (b) is an enlarged sectional view of the decompression chamber of the method of the US patent. Therefore, it is considered that the influence of the vortex generated in the outer decompression chamber 31 is still transmitted to the inner decompression chamber 32 as a compressional wave, which affects the stability of the beat.

(Problems to be Solved by the Invention) With respect to the problems as described above, the object of the present invention is to improve the depressurizing method in a slide bead coating machine to stabilize the coating bead and to prevent coating unevenness and the like. Resistant coating method and coating apparatus having coating properties.

(Means for Solving Problems) The above-mentioned object of the present invention is to provide a method of applying a coating solution to at least one layer on a continuously traveling support using a slide bead application device. A slide bead characterized in that a bead decompression chamber for directly decompressing the bead to maintain the bead is provided with a communication means directly connected to the atmosphere, and further a suction decompression chamber for suction decompression is connected to the outside of the bead decompression chamber. It is achieved by a coating method and a coating apparatus according to the method.

Further, as an aspect of the present invention, it is preferable that the communication means directly connected to the atmosphere has an adjusting means for adjusting an inflow amount of air.

Hereinafter, the method of the present invention will be described in detail with reference to the drawings. FIG. 1 (a) is a schematic side sectional view showing one embodiment according to the present invention. Slide bead applicator 20 in the figure
In the above, one or a plurality of coating liquids 5 sent from the coating liquid pump 21 flow through the coating slits 22 on the slide surface in a single layer or a plurality of layers, and run while holding the coating backup roller 1. Between the web and the coating machine lip
At 23, a ribbon-shaped liquid pool called a bead is formed. This bead is stabilized by pulling it down by decompression. The decompression chamber of the present invention is shown in FIG.
As shown in, the coating machine is composed of two chambers, a bead decompression chamber 32 and a suction decompression chamber 31 from the coating machine side.
It is suction-decompressed by 33. FIG. 1 (b) is a perspective sectional view showing the structure of the decompression chamber. In the figure, the bead decompression chamber 32
Has a structure of being put in the suction decompression chamber 31, and both chambers are circulated through a gap between the web holding the coating backup roller 1 and the decompression chamber. Sunahachi Bead Decompression Room
32 is also decompressed via the decompression of the suction decompression chamber.

Further, the bead decompression chamber 32 has an atmospheric control valve 35.
It has a structure in which one or a plurality of air communication pipes 34 are directly connected to and communicate with the atmosphere. FIG. 2 is an enlarged side sectional view of a decompression chamber according to the present invention, showing various embodiments. The bead decompression chamber 32, which is decompressed via the suction decompression chamber 31, maintains an appropriate decompression state. Moreover, by creating a uniform air flow with a slight air inflow, it is possible to prevent the bead from having an unstable effect. FIG. 2 shows a method for achieving a stable flow without creating vortices due to the flow of the atmosphere, and FIG. 2 (a) shows a case where the atmosphere is introduced into the bead decompression chamber 32 through the atmosphere communication pipe 34. This is an example of using the plate 36. In the same figure (b), the filter 37 is used and the filter is provided across the width, so that the width is uniform and the flow velocity of the atmosphere is slower, which has the effect of suppressing the generation of vortices. FIG. 7C shows an example in which a vortex prevention plate 38, for example, a semicircular shape having a large cross section is installed. In FIG. 7D, the partition walls 39 of both decompression chambers have a shape with a small resistance. Here is an example. The above examples may be used alone or in combination, and are not limited to this embodiment.

Further, the present invention uses the above-mentioned bead coating method, that is, the rotating back-up roller is directly held on the back side of the web and tightly stretched to reverse the direction of conveyance, and the emulsion is bead-coated on the smooth coating surface formed by the back-up roller. In addition to the shape, a tensioning mechanism member that reverses the direction of web traveling without contacting the web is provided, and a smooth coating surface for reverse traveling is created on the web and bead coating of emulsion while receiving the web Floating coating It also applies to the method.

The non-contact tension mechanism member in the floating coating method is the third
As shown in the figure, a static pressure support surface 10 'having a large number of fine gas ejection openings 11' for ejecting gas (generally air) toward the back surface of the web is provided at the portion where the web is reversed and the tension of the web is adjusted. A sufficient amount of gas is jetted out, and preferably 20 to 500 μm between the back surface of the web and the static pressure supporting surface 10 '.
The static pressure gas layer 12 'is provided.

The bead coating is performed by making a coating machine 20 'and a bead 4'on the surface of the hydrostatically supported smooth web, which is similar to the case of the above-mentioned close contact tension.

In FIG. 3, the above-mentioned symbols and the same symbols have the same meanings.
Is a cooling / drying chamber, 1'is a non-contact tension mechanism member, and 3'is a newly coated emulsion layer. Illustration of the double decompression chamber according to the present invention is omitted.

This floating coating method is a very useful method in terms of production technology, because the emulsion can be simultaneously coated on the side opposite to the bead-coated web side by the above-mentioned adhesion stretching.

Even in this floating coating mode, fluctuations in the gap between the lip part of the coater and the web for forming beads, that is, fluctuations in the thickness of the static pressure gas layer during floating coating, fatally lowers the coating quality.
In particular, the thickness of the static pressure gas layer in the floating coating method is completely dependent on the given static pressure level, and also counteracts with the pressure reduction level of the decompression chamber via the web. The pressure pulsation or instability is most contraindicated, and the floating coating method is the most suitable application object of the present invention.

(Example) Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Example 1. Coating was performed under the following conditions.

Lower layer coating liquid: A silver halide emulsion containing the specified additive and gelatin, having a viscosity of 10 cp at 35 ° C and a wet thickness of about
It is 0.05 mm.

Upper layer coating liquid: A solution containing predetermined additives, gelatin and a surfactant, having a viscosity of 11 cp at 35 ° C and a wet thickness of about 0.02 mm.

Web: Polyethylene terephthalate film with subbing.

Decompression degree: suction decompression chamber −34 mmAq bead decompression chamber −17 mmAq The above two layers were simultaneously coated using the apparatus shown in FIG. The air communication pipes were installed in two places on the left and right.

 As a result, the coating property was good with no coating unevenness.

Example 2. Same as Example 1 except the degree of vacuum.

Decompression degree: Suction pressure chamber −33 mmAq Bead decompression chamber −24 mmAq was applied.

This result showed good coatability and was superior to Example 1.

Example 3 Same as Example 1 except for the degree of reduced pressure Decompression degree: suction decompression chamber −40 mmAq bead decompression chamber −30 mmAq This result was also good as in Example 2.

Comparative Example As a comparative example, the conventional apparatus shown in FIG. 4 was used, and the conditions were the same as in Example 1 except that the pressure reduction degree was −21 mmAq and −34 mmAq. The results were all inferior in coatability to Examples 1, 2, and 3.

Further, the result of applying the present invention to the floating coating method was as good as the result of applying the conventional bead coating method.

(Effects of the Invention) According to the present invention, it is possible to provide a coating method and a device having excellent coating properties such as stable coating bead and uneven coating by improving the depressurizing method in the slide bead coating.

[Brief description of drawings]

FIG. 1 (a) is a schematic side sectional view showing an embodiment of a slide bead coating machine according to the present invention, and FIG. 1 (b) is a schematic perspective view of a decompression chamber according to the present invention. FIG. 2 is a side sectional view showing various embodiments of the decompression chamber according to the present invention. FIG. 3 is a schematic side view of an apparatus used for the floating coating method. FIG. 4 is a schematic side sectional view of a slide bead coating apparatus having a conventional pressure reducing method. FIG. 5 (a) is a side sectional view of a bead coating machine having internal and external decompression chambers, and FIG. 5 (b) is an enlarged sectional view of the decompression chamber at the same time (a). 1: coating backup roller, 2: web 3: coating liquid layer, 4: bead 20: slide bead coating machine 21: coating liquid pump 22: coating slit, 23: lip part 30: decompression chamber, 31: suction decompression chamber 32 : Bead decompression chamber, 33: Decompression pump 34: Air communication pipe, 35: Atmosphere control valve

Continuation of the front page (56) References Japanese Patent Publication Sho 46-16271 (JP, B1)

Claims (3)

[Claims] 1. A method for applying a coating solution to at least one layer on a continuously running support using a slide bead application device, wherein beads are directly depressurized to maintain the beads. A slide bead coating method characterized in that a decompression chamber is provided with a communicating means directly connected to the atmosphere, and a suction decompression chamber for decompressing by suction is connected to the outside of the bead decompression chamber. 2. A method for applying a coating solution to at least one layer on a continuously running support using a slide bead application device, wherein the bead is directly depressurized to maintain the bead. A slide bead coating apparatus, characterized in that a communication means that is directly connected to the atmosphere is provided in the decompression chamber, and a suction decompression chamber for suction decompression is connected to the outside of the bead decompression chamber. 3. The slide bead coating apparatus according to claim 2, wherein the communicating means directly connected to the atmosphere has adjusting means for adjusting an inflow amount of air.