JPH08131923A - Method and device for coating - Google Patents

Abstract

PURPOSE: To prevent the generation of uneven coating and liquid splash by providing a vacuum chamber on the upstream side of carrying direction of a coated liquid contact section to a substrate in a device for applying an emulsion coating liquid or the like for a photosensitive material on the substrate and setting an interstructure between an upper section close to the liquid contact section and a lower section where coating liquid is flowed down. CONSTITUTION: A given amount of respective emulsion coating liquids for a photosensitive material to be multi-layer coated is passed through a slit 5 and transferred to a slide 4, and flowed down on the slide surface 4 to form a bead 18 on a lip section 6, and then brought into liquid-contact with the surface of a continuous substrate 2 wall on a backup roller 1 and carried. In that case, a vacuum chamber 11 is provided below the lip section 6. The vacuum chamber 11 is divided into an upper chamber 15 and a lower chamber 16 by an interstructure 12, and a clearance 13 is formed between the vacuum chamber 11 and the interstructure 12, and upper and lower chambers 15 and 16 are communicated together. A suction port 14 to which a suction pump is connected is provided in the lower chamber 16. The generation of cloud-shaped unevenness and the rib-shaped unevenness are eliminated by the above arrangment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method and a coating apparatus for coating an emulsion coating solution for a photographic light-sensitive material on its support.

[0002]

2. Description of the Related Art A coating method using a slide bead coater as one of conventional flow rate control type coating machines is described in (A) US Pat. Nos. 2,681,294, 2,761,419, 2,761,791.
JP-B No. 62-50195, JP-A No. 62-121451, and (C) JP-A No. 2-222748.

In the above, the coating solution of the photographic light-sensitive material is stably coated by pulling downward the bead (liquid pool portion) which is the cross-linking portion which transfers from the coating machine to the support, that is, by depressurizing the lower portion of the bead. It is the one.

As an example thereof, as shown in the front sectional view of FIG. 7 and the side sectional view of FIG. 6, a slit 5 and a slide surface 4 for supplying a coating liquid are provided on a support 2 wound around a backup roller 1. A slide bead coater 3 including the same and a decompression chamber 11 therefor are arranged. On the other hand, an undercoat layer for adhering the emulsion layer and the support is previously coated on the support of the light-sensitive material. The subbing layer is recently being replaced from a solvent-based one using an organic solvent to an aqueous one using gelatin as a binder for reasons such as environmental friendliness. On the other hand, the photosensitive material side is also diversifying, and when various coating liquids are applied to a support having a surface different from the conventional one, uneven coating peculiar to the undercoat layer is caused when the wettability of the coating liquid is poor. May appear. Specific application unevenness includes cloud-like unevenness shown in the schematic diagram of FIG. 9 and uneven unevenness shown in FIG.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a coating method and a high-performance coating apparatus that catches the causes of the above-mentioned coating unevenness and does not cause them.

[0006]

This object is achieved by any of the following technical means (a), (b), (c) and (d).

(A) In a coating method in which one or more layers of emulsion coating solution for photographic light-sensitive material are coated on a continuous support which is conveyed at a constant speed by a flow control type coating machine, the coating on the support is carried out. A decompression chamber is provided on the upstream side of the liquid contact part in the transport direction, and a partition plate is provided between the upper part near the liquid contact part in the decompression chamber and the lower part where the coating liquid flows down when the coating is not performed. A coating method characterized by being applied.

In (b) and (a), when the absolute value of the differential pressure with the atmosphere outside the decompression chamber is defined as the degree of pressure reduction, the degree of pressure reduction in the upper portion is set to be equal to or lower than the degree of pressure reduction in the lower portion. Method.

(C) In a coating apparatus for coating one or more layers of emulsion coating solution for a photographic light-sensitive material on a continuous support which is conveyed at a constant speed by a flow control type coating machine, coating on the support A decompression chamber is provided on the upstream side of the liquid contact portion in the transport direction, and the decompression chamber is divided into an upper chamber and a lower chamber through a partition plate.
A coating device having a structure communicating with a chamber.

In the items (d) and (c), when the absolute value of the differential pressure with the atmosphere outside the decompression chamber is defined as the decompression degree, the decompression degree of the upper chamber is equal to or less than the decompression degree of the lower chamber. A coating device characterized by the above.

[0011]

The present inventors have paid attention to the air flow state and water vapor in the decompression chamber based on the occurrence of coating unevenness, and have investigated the behavior thereof, and have found the following.

(1) As shown in the side sectional view of FIG. 6 and the perspective view of FIG. 10, the air flowing in from the gap S between the outer edge portion 19 including the lateral and width directions of the decompression chamber and the backup roller 1 due to the differential pressure. And a part of the entrained air 17 due to the transfer of the support body becomes a vortex in the decompression chamber 11 and reaches the lip 6 as well.
Makes 18 unstable.

(2) Especially when the wettability of the coating liquid with respect to the support (web) 2 is poor, the vortex flow occurs when the pressure reducing chamber has a high humidity due to the coating liquid flowing down and staying before the start of coating or at the time of interruption. Rolls up water vapor and adheres to the web surface, making the web surface wettability non-uniform.

The above phenomenon is divided into two chambers, an upper chamber and a lower chamber, in which a partition plate is provided in the decompression chamber so that the decompression chamber can communicate with each other, as will be described in detail later in Examples, and the degree of decompression in the upper chamber | -Pa |
Could be eliminated by setting the pressure reduction degree of the lower chamber to not more than | -Pb |. Then, the occurrence of the above-mentioned cloud-like irregularities and streaky irregularities disappeared.

Further, as an additional effect, the coating liquid that collects at the bottom of the decompression chamber 11 below the lip portion 6 at the start of coating or the coating liquid that adheres to the middle of the lower surface is rolled up by the air stream and is a support (web). The liquid adhering to the surface sometimes caused a so-called failure, which could be prevented.

[0016]

The present invention will be described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto.

A first embodiment of the coating apparatus of the present invention will be described with reference to the side sectional view of FIG.

Each emulsion coating solution of the photographic light-sensitive material to be multi-layer coated is fed to the slide surface 4 by a predetermined amount through the slit 5 of the slide bead coater 3 as an example of a flow rate control type coating machine, and on the slide surface. The beads 18 flow down and form at the lip portion 6, and the beads 18 are applied by being in contact with the continuous support 2 wound around the backup roller 1 and conveyed.

A decompression chamber 11 is provided below the lip portion 6. The decompression chamber 11 is divided into an upper chamber 15 and a lower chamber 16 by a partition plate 12, and a gap 13 is provided between the decompression chamber 11 and the partition plate 12 to form an upper chamber 15 and a lower chamber 16. Is in communication with. The lower chamber 16 is provided with a suction port 14 to which a suction pump as a suction power source is connected. However, the suction port 14 is not limited to being provided only in the lower chamber as in this embodiment. The partition plate
12 is provided in the entire width direction.

As shown in the perspective view of FIG. 10, there is a gap S between the backup roller 1 or the support 2 wound around it and the outer edge portions 19 formed on both sides and the back surface of the upper chamber 15.

Here, as shown in the side sectional view of FIG.
By suctioning pressure -P from 14, the pressure reduction degree | -Pa | of the upper chamber 15 becomes equal to or lower than the pressure reduction degree | -Pb | of the lower chamber 16, and the air flow becomes like the streamline shown in FIG. Upper chamber 15
There is no eddy current in the area.

Furthermore, the air flow directly from the outside of the decompression chamber to the lower part of the bead is also greatly reduced.

At this time, the pressure reduction degree in the upper chamber | -Pa | is 35 mm.
Aq, and the lower chamber decompression degree | -Pb | was 40 mmAq, but the invention is not limited to this. | -Pa | ≤ |-
The relationship of Pb | is required, and | -Pa | and | -P
The b | differential pressure is preferably 0 to 10 mmAq.

Decompression degree upstream of the contact portion of the bead 18 with the support 2 in the lip portion 6 of the slide bead coater 3
-Pa |, that is, the degree of pressure reduction of the upper chamber 15 | -Pa | is 5
~ 70mmAq is desirable. Further, it is preferable that the above-mentioned gap S into which air flows between the outer edge portion 19 of the decompression chamber 11 close to the backup roller 1 and the outer peripheral surface including the width direction and the outer peripheral surface of the backup roller 1 is narrow, Especially, it is desirable that the thickness is 2 mm or less. Further, it is preferable that the gap 13 between the decompression chamber 11 and the partition plate 12 is also narrow, and particularly preferably 5 mm or less.

The partition plate 12 is set so that it can be set just before coating for adjustment around the coater before coating and cleaning of the decompression chamber 11 after coating, and can be released at other times. Is desirable.

FIG. 4 and FIG. 5 are side sectional views of a third embodiment having such a slide bead coater 3 and a decompression chamber 11 as shown in FIG. 5 from the state of the steady set shown in FIG. The slide bead coater 3 to the backup roller 1
By evacuating from the back, the decompression chamber 11 is fixed to the body on the backup roller 1 side (fixed portion) 11B and fixed to the slide bead coater 3 (moving portion) 11A.
Is divided into and

The partition plate 12A in that case is attached to the fixed portion 11B. In this state, the clearance S between the backup roller 1 and the fixed portion 11B of the decompression chamber can be easily cleaned. on the other hand,
The portion 11A fixed to the slide bead coater 3 can be easily cleaned in this state.

Although the side wall 15A of the upper chamber 15 is provided on the fixed side and the side wall 16A of the lower chamber 16 is provided on the movable side here, the way of providing each side wall is not limited.

Here, four-layer coating with a slide bead coater is shown, but the present invention is not limited to this. In addition, any coating method can be applied as long as a decompression chamber is provided on the upstream side of the coating position of the flow rate control type coating machine. A second embodiment using an extruder die 3A as an example of another coating method is shown in the side sectional view of FIG.

(Embodiment 1) Using the slide bead coater of the above embodiment and a conventional slide bead coater (without a partition plate in the decompression chamber), the gap 13 of the partition plate and the degree of decompression of the decompression chamber are changed to support. body using polyethylene terephthalate, photographic light-sensitive silver halide emulsion layer to the lower layer as a coating liquid as shown in Table 1, using an aqueous gelatin solution (protective layer) containing a surface active agent in the upper layer, the total biasing amount 60 g / m ² The coating test was conducted at a coating speed of 100 m / min and a bead gap of 150 to 200 μm. The results are shown in Table 2.

[0031]

[Table 1]

[0032]

[Table 2]

In the coating of a certain kind of photosensitive material for printing, unevenness of coating was observed on the entire surface in the conventional method and apparatus, but in the method and apparatus of the present invention, the gap 13 of the partition plate and the degree of reduced pressure are shown in Table 1. Even when the pressure was changed to a considerably wide range and the degree of pressure reduction was higher, there was no uneven coating. Further, there was no occurrence of liquid splash due to the coating liquid accumulated at the bottom of the decompression chamber and the liquid adhering to the middle of the lower surface of the flow.

[0034]

EFFECTS OF THE INVENTION According to the present invention, the occurrence of coating unevenness such as unevenness and cloud-like unevenness is eliminated, liquid splash failure is eliminated, and high-quality high-speed coating is stably performed.

[Brief description of drawings]

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

FIG. 2 is a side sectional view showing the state of the air flow in the decompression chamber.

FIG. 3 is a side sectional view of a second embodiment of the present invention.

FIG. 4 is a side sectional view when the coater according to the third embodiment of the present invention is set steadily.

FIG. 5 is a side sectional view when the coater of the third embodiment of the present invention is retracted.

FIG. 6 is a side sectional view of a conventional slide bead coater.

FIG. 7 is a front sectional view of a decompression chamber portion of a conventional slide bead coater.

FIG. 8 is a schematic diagram showing unevenness.

FIG. 9 is a schematic diagram showing cloud-like unevenness.

FIG. 10 is a perspective view showing a gap between the support on the backup roller and the outer edge of the decompression upper chamber.

[Explanation of symbols]

1 Backup Roller 2 Support 3 Slide Bead Coater 3A Extruder Die 4 Slide Surface 5 Slit 6 Lip Part 11 Decompression Chamber 11A Slide Bead Coater Fixed part (moving part) 11B Backup Roller Fixed part on machine side (fixed part) ) 12, 12A Partition plate 13 Gap 14 Suction port 14A Suction port 15 Upper chamber 16 Lower chamber 17 Entrained air 18 Bead 19 Outer edge S Gap

Claims (4)

[Claims] 1. A coating method in which one or two or more emulsion coating solutions for photographic light-sensitive materials are coated on a continuous support which is transported at a constant speed by a flow control type coating machine. A decompression chamber is provided on the upstream side of the liquid portion in the transport direction, and a partition plate is provided between the upper portion near the liquid contact portion in the decompression chamber and the lower portion where the coating liquid flows down when the coating is not performed. A coating method characterized in that 2. The coating method according to claim 1, wherein when the absolute value of the pressure difference with the atmosphere outside the decompression chamber is defined as the degree of pressure reduction, the degree of pressure reduction in the upper portion is set to be equal to or lower than the degree of pressure reduction in the lower portion. 3. A coating device for coating one or more layers of emulsion coating solution for a photographic light-sensitive material on a continuous support which is transported at a constant speed by a flow control type coating machine. A coating apparatus, wherein a decompression chamber is provided on the upstream side of the liquid section in the carrying direction, and the decompression chamber is connected to two chambers, an upper chamber and a lower chamber, via a partition plate. 4. When the absolute value of the differential pressure between the atmosphere outside the decompression chamber and the atmosphere outside the decompression chamber is defined as the decompression degree, the decompression degree of the upper chamber is equal to or less than the decompression degree of the lower chamber. Characteristic coating device.