JPS63239442A - Method and device for coating - Google Patents

Abstract

PURPOSE:To stabilize a bead of coating liquids and to decrease generation of uneven coating by adjusting a difference in gaseous pressure between the front and rear sides of the bead so as to maintain said difference. CONSTITUTION:A web 1 is moved without contact by the flow of the gas from a gas injector 2 and the bead 8 of two layers of the coating liquids through slits 6a, 6b is formed on the surface of the web. The gaseous pressure by a pump P, a filter 13, a pressure regulating box 10, etc., is exerted to the front side of such bead 8. On the other hand, a regulating valve 12 is controlled by the flow of the gas from the injector 2, by which the difference in the gaseous pressure between the front and rear sides of the bead 8 is maintained at a prescribed value. The fluctuation of the bead and the floating of the web are thereby prevented and the generation of the uneven coating is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a slide bead coating method and an apparatus therefor, and more specifically, the present invention relates to a slide bead coating method and an apparatus thereof, and more specifically, to a slide bead coating method and an apparatus therefor. The present invention also relates to a coating method and apparatus for applying a coating liquid to this web via coating liquid crosslinking (hereinafter referred to as beads).

(Technical background) Regarding such slide bead coating, as described in U.S. Pat. No. 2,681,294 or U.S. Pat. It is necessary to stabilize the bead, and for this purpose it is effective to provide an air pressure difference between the upper and lower surfaces of the bead. This method includes the aforementioned U.S. Patent No. 2,681,
As exemplified in No. 294, it has been common practice to reduce the pressure on the underside of the bead. In addition, especially in the case of coating with a low viscosity, for example, an organic solvent, there is a method, as described in JP-A-58-180262, in which pressure is applied on the underside of the bead to prevent the bead from falling. However, in all of these conventional methods, one side, for example, only the lower surface of the bead, is depressurized or pressurized, and the other side, that is, the upper surface of the bead, is left open to the atmosphere. Therefore, pressure fluctuations in the decompression chamber or the pressurization chamber become the pressure difference between the upper and lower sides of the bead, which becomes a factor in the instability of coating.

Furthermore, in order to support the web in a slide bead coating device, rotatable rolls are provided on both sides of the gas jet, and both ends of the web are brought into contact with the rotatable rolls, as described in Japanese Patent Laid-Open No. 51-38737. There is a method of supporting the web by blowing gas from a gas ejector to float the web and supporting it in a non-contact manner, and applying the coating liquid to the opposite side of the web. In this case, although there is naturally no change in the thickness direction at both ends of the web that are in contact with each other, negative pressure is caused by changes in the gap (referred to as floating amount) between the gas jet and the web due to changes in tension while the web is running. The gap between the side wall of the chamber and the web changes, which affects the pressure in the negative pressure chamber and changes the air pressure difference between the upper and lower sides of the bead. In either case, it is necessary to stabilize the air pressure difference between the top and bottom sides of the bead in order to stabilize the bead, but especially in the case of non-contact support, there is also a change in the floating surface, so it is necessary to stabilize this air pressure difference. was difficult to maintain.

(Problems to be Solved by the Invention) As mentioned above, it is necessary to stabilize the bead of the coating liquid in order to make the coating smooth. It is effective to apply an air pressure difference to However, in the past, negative pressure was mainly applied to the lower surface of the bead, or in rare cases, positive pressure was applied, but in either case, one side was open to the atmosphere. Therefore, pressure fluctuations on the negative pressure or positive pressure side directly result in air pressure differences, which is a cause of bead instability. This problem becomes even more unstable, especially when the web is supported in a non-contact manner by a gas jet, since there are more factors that cause the amount of floating of the web to vary than in the case of a contact-type support roll.

The present invention has been made in view of the above circumstances, and is a coating method and apparatus for maintaining a stable air pressure difference between the upper surface side and the lower surface side of the bead, eliminating instability of the bead, and enabling good coating. is intended to provide.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a coating method of the first invention in which the coating liquid is caused to flow down on the sliding surface of the coating liquid supply device. In a coating method in which a bead of the coating liquid is formed between the coating liquid and the support and the coating liquid is applied to the support surface, a pressure difference is applied to the gas between the upper surface side and the lower surface side of the bead of the coating liquid, and this pressure difference is further applied. The coating device of the second invention is characterized in that the coating is performed by adjusting the coating liquid to maintain the coating liquid, and the coating liquid is caused to flow down on the sliding surface of the coating liquid supply device,
In a coating device that forms a bead of coating solution between the coating solution supply device and a support that moves continuously,
The present invention is characterized by comprising means for creating a pressure difference between the gas applied to the upper surface side and the lower surface side of the bead of the coating liquid, and a pressure crab J4 regulating means for maintaining this gas pressure difference.

This invention creates a gas pressure difference between the lower surface side and the lower surface side of the coating liquid bead formed between the coating liquid supply device and the web, and maintains this pressure difference constant to increase the bead itself. stabilize.

In this case, a pressure difference can be applied to both the upper and lower sides of the bead by negative pressure, but it is also possible to apply a pressure difference by positive pressure.
When the web lifts up due to speed fluctuations, etc., this lifting is suppressed, and when the web sinks, it lifts up and is allowed to float to the north, thereby suppressing web fluctuations. In this way, by suppressing fluctuations in the floating amount of the web, the bead can be stabilized.

In this invention, the adjustment to maintain the gas pressure difference is achieved by providing pressure adjustment boxes on the upper and lower sides of the bead, respectively.
These two boxes are communicated with each other to maintain a stable gas pressure difference against pressure fluctuations in one or both of the upper side pressure adjustment box and the lower side pressure adjustment box.

The coating liquid used in the coating method of the present invention may be a variety of solutions, but in particular a hydrophilic colloid solution for photographic light-sensitive materials, such as a hydrophilic binder such as gelatin or polyvinyl alcohol, and a low viscosity of 4 to 40 ep. Suitable for viscous coating compositions. In addition, evaporation of the coating liquid containing a volatile solvent on the slide surface can be suppressed by applying positive pressure.

Further, as the web on which the hydrophilic colloid solution as described above is applied, a support for a photographic material such as a plastic film such as polyethylene terephthalate, triacetyl cellulose, or polypropylene or paper or the like is used.

The coating method and coating apparatus of the present invention will be further explained based on specific examples shown in the drawings.

FIG. 1 is a schematic diagram of a coating apparatus of the present invention, in which a web 1, which is a support to which a coating liquid is applied, is conveyed at high speed via a gas ejector 2. In this embodiment, the injection hole 2a is formed on the entire circumference or part of the gas ejector 2, and the gas ejector 2
Although air is blown onto the web 1 to support it in a non-contact state, it is also possible to use a contact type support roll to run the web in contact with it.

A coating liquid supply device 3 is located close to this gas jetter 2, and its liquid supply paths 4a, 4b include a flow pump 5a,
Different types of coating liquids are supplied by driving 5b. In this embodiment, two types of coating liquids are supplied, but one or more types may be used. Vertical narrow slits 6a, 6b are formed above the liquid supply paths 4a, 4b, and the coating liquid flows out to the sliding surface 7F of the coating liquid supply device 3 through these slits 6a, 6b. This sliding surface 7 is inclined toward the direction of the gas jetter 2, and the coating liquid that flows out flows down the layer,
The coating liquid is applied to the web 1 from the lower end of the slide surface 7, and there is a rack m (
bead) 8 is formed.

There is a lower pressure adjustment box 9 on the lower surface side of this bead 8,
An upper pressure adjustment box 10 is provided on the 11 side, and the meat pressure adjustment boxes 9 and 10 are communicated with each other through a continuous filter tube 11. This communication pipe 11 is provided with a control valve 12, and the cross-sectional area of the communication pipe 11 is adjusted to adjust the gas pressure difference between the lower pressure adjustment box 9 and the upper pressure adjustment box 10.

The L-side pressure adjustment box 10 is equipped with a filter 13, and positive pressure is applied to the upper surface of the bead so that a pressure difference is generated between the gas pressure applied to the upper surface and the lower surface of the bead via the air filter I3. Due to the stiffness, the air pressure on the top side of the bead is high and the air pressure on the bottom side is small, pressing the bead from top to bottom. That is, through the air filter 13,
Air is taken in and pushes the bead downward, creating a positive pressure inside the pressure adjustment box 10, and the pressurized air is introduced into the lower pressure adjustment box 9 through the pressure adjustment valve 12.

In addition, when increasing the pressure on the lower surface side of the bead, if the inside of the lower pressure adjustment box 9 is made to have a positive pressure, the result is opposite to that described in 1. In this way, even if the pressure on the upper and lower sides of the bead fluctuates, by connecting the upper and lower pressure adjustment boxes 9 and 10 with the communication pipe 11, fluctuations in the air pressure difference can be suppressed. .

This invention is particularly effective when traveling while supporting the web 1 in a non-contact manner. That is, when the distance between the gas jet 2 and the web 1, that is, the amount of floating of the web 1 changes due to tension fluctuations and speed fluctuations of the web 1, or other factors, the air pressure difference between the upper and lower surfaces of the bead is stabilized. It is necessary to aim for In this case, if a clearance S is set between the 5-pressure adjustment box 10 and the web 1 and a positive pressure is created in the pressure adjustment box 10 to create an air pressure difference, tension fluctuations and speed fluctuations occur when the web 1 runs. Even if a fluctuation occurs, for example, the web 1 floats and narrows the clearance S, the amount of air flowing out from the pressure adjustment box 10 through the clearance S decreases, so the pressure inside the pressure adjustment box 10 increases. to suppress lifting of web 1.

On the other hand, for example, if the floating amount of the web 1 decreases and the clearance S increases, the pressure inside the pressure adjustment box 10 decreases, causing the web 1 to float, narrowing the clearance S and maintaining it at a predetermined set amount. As a result, fluctuations in the floating amount of the web 1 are prevented, and stable coating is performed.

FIG. 2 shows a modified example of the coating device shown in FIG. Furthermore, the air pressure difference between the two can be set using pressure regulating valves 14 and 15 provided exclusively for each.

Furthermore, the pressure regulating valves 14.15 are measured by installing a pressure sensor (not shown) in each pressure regulating box 9.10, and inputting the pressure information to a control device, for example, by using a stepping motor or the like to control the pressure regulating valves 14.15. may be controlled so that the pressure difference between the two is always at a set value.

(Operation) In the present invention, a gas pressure difference is applied between the upper surface and the lower surface of the bead, and the pressure difference is always maintained constant by a control means to stabilize the bead itself and the web, and the coating liquid is applied.

Then, by providing an upper pressure adjustment box and a lower pressure adjustment box, and communicating the boxes so that a pressure change in one also affects the other, it is possible to stably maintain the air pressure difference between the two.

Furthermore, by creating a pressure difference between the upper and lower sides of the bead by applying positive pressure, when the web lifts up due to speed fluctuations, it is suppressed, and when the web sinks, it is allowed to lift up. to reduce web fluctuations. In this way, the bead is stabilized by applying positive pressure from the upper surface of the coating liquid bead to suppress fluctuations in the floating amount of the web.

(Effect of the invention) In this invention, a pressure difference is created between the gas pressure applied to the upper surface side and the lower surface side of the bead of coating liquid formed between the coating liquid supply device and the web, and this pressure difference is always kept constant. By maintaining this, it is possible to suppress fluctuations in the bead itself, and it is also possible to suppress changes in the lifting amount of the web, which stabilizes the bead and reduces the occurrence of coating unevenness.

(Example) Example (1) Lower layer of photographic light-sensitive material by simultaneous coating of two layers on one side Gelatin silver halide aqueous solution containing various additives Application temperature: 35°C Viscosity: 9. Ocp non-dry coating thickness approx. 0.055 mm Upper layer Gelatin surfactant solution containing various additives Coating temperature 35°C Viscosity 7.8 cp non-dry coating thickness approx. 0.020 mm Support Subbed polyethylene terephthalate support roll Contact support Coating speed 50 m/rnin Bead top side + 35 m1'nAg Differential pressure 25 rnmAg Bead bottom side +, 10 rnmAg Example (2) Same as Example (1) except for the positive pressure conditions applied to the bead Bead top side + 25 wa m A g difference Pressure 15mmAg
Bead lower surface side +10 mmAg Example (3) The support was supported in a non-contact manner using a gas blower, and the coating was carried out under all other conditions as in Example (1).

Example (4) The coating was carried out under the same conditions as Example (2), except that the support was supported in a non-contact manner using a gas blower.

Comparative Example (1) A conventional coating apparatus is used, that is, in FIG. 3, the top side of the door is open to the atmosphere, and the bottom side of the box 16 is under negative pressure. All the coating equipment and pressure conditions were the same as in Example (1).

Bead bottom side -25rnmAg Comparative example (2) Same as Example (2) except coating device and pressure conditions Bead bottom side -15mmAg Comparative example (3) Same as Example (3) except coating device and pressure conditions Same bead bottom side -25mmAg Comparative example (4) Same as Example (4) except coating device and pressure conditions Bead bottom side -15mmAg In all of the above examples, the bead is more stable than Comparative Examples (1) to (4). It showed a good coating condition. That is, in terms of coating properties, the horizontal step-like unevenness was improved, and the pressure difference fluctuation was reduced to 1/2 or less of that of Comparative Examples (1) to (2).

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a coating apparatus used in the coating method of the present invention, FIG. 2 is a cross-sectional view of another embodiment, and FIG. 3 is a cross-sectional view of a coating apparatus used in a conventional coating method. In the figure, the symbol is a web, 2 is a gas jetter, 3 is a coating liquid supply device, 8 is a bead, 9 and 10 are pressure adjustment boxes, 11
is a communication pipe, and 12, 14, and 15 are pressure regulating valves. Figure 1 Figure 2 Figure 3 Procedural amendment May 1, 1988 1 Indication of the case 1988 Patent Application No. 015853 2 Title of the invention Coating method and device 3 Person making the amendment Relationship with the case Patent Applicant Address: 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name (1)
27) Roku Konishi Photo Industry Co., Ltd. 4 Agent 151 Address 2-23-1 Yoyogi, Shibuya-ku, Tokyo Karasu (1) "Bead bottom side" on page 6, line 17 of the specification is referred to as "bead top side" correct. (2) In the third line of page 10 of the same book, "to apply positive pressure" is corrected to "to apply positive pressure." (3) "r(2)" on page 16, line 11 of the same book as "r(4)"
I am corrected. that's all

Claims (6)

[Claims] (1) In a coating method in which the coating liquid is caused to flow down onto the sliding surface of a coating liquid supply device, a bead of the coating liquid is formed between the coating liquid supply device and the support, and the coating liquid is applied to the support surface, A coating method characterized in that a pressure difference is applied between the gas on the upper surface side and the lower surface side of the bead of the coating liquid, and the coating is performed while adjusting to maintain this pressure difference. (2) The coating method according to claim 1, characterized in that a positive pressure is applied to both the upper and lower surfaces of the bead of the coating liquid in the difference in gas pressure applied thereto. (3) The coating method according to claim 1 or 2, wherein the support is supported in a non-contact state by blowing gas and travels continuously. (4) In a coating device that causes a coating solution to flow down onto a sliding surface of a coating solution supply device, and forms a bead of the coating solution between this coating solution supply device and a continuously running support, the coating device A coating device comprising means for creating a pressure difference between gas applied to the upper and lower surfaces of a bead of liquid, and pressure adjusting means for maintaining this gas pressure difference. (5) Pressure adjustment boxes are provided on the upper surface side and the lower surface side of the bead of the coating liquid, and the pressure adjustment boxes are communicated with each other to maintain the pressure difference in both pressure adjustment boxes. The coating device according to scope 3. (6) The coating device according to claim 4 or 5, further comprising a gas ejector that sprays gas onto the support and supports the support in a non-contact state.