JPS6028851A - Method and device for coating - Google Patents

Abstract

PURPOSE:To stabilize the shape of a bead with a slide bead coating method by increasing the down flow speed of the coating liquid flowing down on a sliding surface within the limited time just before and after the passage of the joint of a web through the bead. CONSTITUTION:A liquid film accelerator 14 which can inject air along the coating liquid films 6, 6' flowing down on a sliding surface 2 within the limited time just before and after the passage of the joint 12 of a web 9 through a bead 7 is disposed above the surface 2 with a slide bead coating device. More specifically, said accelerator increases the down flow speed of the coating liquid flowing down on the surface 2 of a sliding hopper 1 during the limited time just before and after the passage of the joint 12 between the rear end of the web 9 under coating and the front end of the web to be freshly supplied through the bead 7 and therefore the dynamic pressure under which the coating liquid flows into the bead increases and the bead can overcome substantially the force disturbed by the passage of the joint. The shape of the bead is stabilized and the cause for making a thick film part, etc. on the coated surface is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for applying a coating liquid to a continuous web.

One of the methods for applying a coating liquid to a continuous web, such as in the production of photographic film, is the slide bead coating method.

In this coating method, the coating liquid is caused to flow down by its own weight along the sliding surface of a slide hopper, and is deposited on a web running close to the lower edge of the sliding surface. In this method, in order to stabilize the coating, it is important to prevent the bead of coating liquid formed between the lower edge of the slide surface and the web from being carried away by the running web. Therefore, the bead always maintains its shape by applying a negative pressure on the front side in the running direction of the web.

However, in order to continuously feed a finite web into a coating device, it is unavoidable that a seam is formed in the middle of the web, and the seam disturbs the shape of the bead and causes thick film parts and "streak failure" on the coating surface. ” was the cause of the occurrence. That is.

This is because the joining tape is usually attached to the application side at the seam of the web, so that a step is created by the thick bone of the tape, and this step causes the bead to be carried away in the running direction of the web. Although the time it takes for the seam to pass through the bead is almost instantaneous, the resulting disturbance of the bead has an extremely large effect, and various countermeasures have been studied to date.

As a conventional measure.

(2) Method disclosed in Japanese Patent Publication No. 57-14912 In this method, the differential pressure of air applied to stabilize the shape of the bead is increased when the seam passes through the bead. This increase in air pressure difference can be said to be effective in preventing the collapse of the bead that occurs when the seam passes through the bead, and also in quickly recovering the unstable state of the bead when the seam passes through it. Coating speed is 50m/m
At high speeds higher than 1.5 in., vertical streaks with regular pitches appeared over the entire width of the coating in the coating film area when the differential pressure increased, and even when the pressure was returned to normal differential pressure, these lines remained and caused a significant loss of product. .

■The method disclosed in Japanese Patent Publication No. 47-42725 This method involves applying an oily-hydrophobic substance to the discontinuous portions before applying the coating liquid to the webs spliced together using a splicing tape, or This slopes the rear edge and is effective in eliminating the space that entrains air behind the discontinuous part, but if an oil-based/hydrophobic substance is applied, the adhesion of the dried paint film in that area is poor. Therefore, the dried coating film easily separates, leading to process contamination. Also, the slope of the trailing edge of the tape is substantially superior considering the thickness of the tape.

■The method disclosed in Japanese Patent Application Laid-Open No. 54-34343 This method fixes the leading edge of a joining tape that connects the ends of the web to the rear edge of the front side of the old web, and the trailing edge of the tape to the front edge of the back side of the new web. .

By forming a stepped break on the front side of the web joint, it is possible to eliminate bead disorder, but when a web support roll is used.

There is a risk that the canting part of the web following the seam flat part may come into contact with the lip end of the slide hopper, causing the problem that the seam part may come off or vertical streaks may easily occur on the subsequent coating film.

■The method disclosed in Japanese Patent Application Laid-Open No. 50-49338. This method uses a splicing tape to increase the height of the downstream surface of the spliced web, thereby increasing the air entrainment space behind the discontinuous part. Although this process is effective in eliminating the problem, there is a problem in that the processing needs to be performed prior to coating, which increases the number of processes required to achieve the purpose.

■The method disclosed in JP-A No. 50-43140 This method roughens the surface of the downstream side of the web spliced using splicing tape in advance to make it easier for the coating liquid to adhere to the rear of the discontinuous portion. However, as in the case (2) above, a pretreatment for roughening the surface is required, and there is a problem in that the number of processes required to achieve the purpose increases.

This invention is intended to solve the above-mentioned various problems, and in the slide bead coating method, the flow rate of the coating liquid flowing down the slide surface is controlled for a limited period of time from just before the web joint passes through the joint. It is an object of the present invention to provide a coating method and an apparatus therefor, in which the dynamic pressure at which the coating liquid flows into the bead is increased, and the bead can be coated without being disturbed by passing through the seam.

Next, the present invention will be explained based on the accompanying drawings.

In the figure, l is a slide hopper, and the slide hopper 1 has an inclined slide surface 2.

The slide surface 2 is provided with liquid reservoirs 4, 4' communicating with each other via slits 3, 3'. The two types of coating liquids 5.5' are supplied to the liquid reservoir 4.4 at a constant flow rate by a pump (not shown).
', passes through the slits 3, 3', protrudes like a film onto the slide surface 2, and descends along the slope thereof. Liquid film 6 descending down the slide surface 2.
6', the liquid film 6 on the upstream side is deposited on the upper surface of the liquid film 6' on the downstream side and forms a bead 7.

8 is a support roll for the web 9, and the support roll 8 is disposed close to the lip end 10 of the slide hopper 1;
It is designed to rotate in the direction of the arrow. The liquid 151i6.6' that has flowed down the slide surface 2 of the slide hopper 1 during the run is attached to the web 9 supported by the support roll 8 by the bead 7, and two layers of coating film are simultaneously applied. ]
Reference numeral 1 denotes a decompression chamber surrounding the space between the front surface of the slide hopper 1 and the lower surface of the support roll 8. The inside of the decompression chamber 11 is made negative pressure by a vacuum pump (not shown), and the pressure is reduced between the lip end 10 and the web 9. The bead 7 formed on the web 9 is suctioned so as not to be carried away by the running web 9, and its state is maintained stably.

Reference numeral 12 denotes a seam between the webs 9. The seam 12 is formed by butting the tip of a newly supplied web 9 against the end of the web 9 being coated, and pasting a splicing tape 13 in the width direction between both ends of the web. Since this splicing tape 13 is attached to the coated surface side of the web to avoid scratching the peripheral surface of the support roll 8, etc., a step of the seam 12 inevitably appears on the coated surface side, and when passing through the bead 7, This disturbs the shape of the bead 7 and causes vertical streaks on the coating surface. This cause can be eliminated by providing such stability that the stepped portion of the seam 12 does not disturb the bead when it passes through the bead 7.

Reference numeral 14 denotes an accelerator that increases the velocity of the liquid films 6, 6' flowing down on the slide surface 2 of the slide hopper 1, and the acceleration bag W14 has a box 15 surrounding the space above the slide surface 2. .

It consists of an air jet pipe 16 disposed on the rear wall side of the box 15 and a slit 17 formed on the lower surface of the front wall of the box 15. This device blows high-pressure air into the box 15 from an air jet pipe 16, and sends the high-pressure air through the slit 1 on the lower surface of the front wall.
7 along the slide surface 2, and accelerates (presses) the liquid film 6.6' flowing down on the slide surface 2 in the direction of flow to a speed higher than the normal flow velocity. It has been experimentally confirmed that it is possible to provide such morphological stability that the bead is not disturbed when the 12 step portions pass through the bead 7. During a short period of time from just before the seam 12 passes through the bead 7 to immediately after it passes through the slit 1
6, and functions to immediately return to normal speed after the seam 12 has completely passed. The operation timing of this accelerator 14 is determined by the air ejection pipe 16.
A position detection device (not shown) may be used to detect the proximity of the pulp (not shown) provided between the pulp (not shown) and an air pump (not shown) to the seam 12, and this detection signal may be used.
Furthermore, since these controls can be achieved using a known microcomputer, a detailed description of its configuration will be omitted. It goes without saying that the accelerating device 14 need not be limited to the configuration shown in the two figures as long as it has the above-described effect.

Example Lower layer: geladine, an aqueous solution of silver halide, having a viscosity of 9.0 centipore size at 35°C, and a non-dry coating thickness of about 0.055 m. Upper layer: gelatin, an aqueous surfactant solution, at 35°C. The above layers were simultaneously coated onto a subbed polyethylene terephthalate web running at 50 rn/1 Ilin, having a viscosity of 7.8 centipore size and a dry coating thickness of about 0.020 M. At this time, the negative pressure for coating was 18.5 am of water column, and the amount of air introduced into the box of the accelerator was 0-3 n? /ll1in.

As a result, compared to the case where air is not introduced into the box, when the above method is adopted, good results are obtained without the occurrence of thick film parts or streak failures due to bead disturbance on the downstream side of the discontinuous part. Ta.

In addition, although the above-mentioned example showed the case where two layers were applied to the web at the same time, there is no need to limit it to this, and it goes without saying that the application can be applied to application of one layer or 3M or more.

As described above, according to the present invention, during a limited period of time from just before the joint between the end of the web being coated and the leading edge of the newly supplied web passes the bead, the flow flows down the slide surface of the slide hopper. By increasing the flow rate of the coating liquid, the dynamic pressure that causes the coating liquid to flow into the bead increases.

The bead can sufficiently resist the force disturbed by passing through the seam, and the bead shape is stabilized, so it has the excellent effect of not causing thick film areas or vertical streaks on the coated surface. It is something that plays.

Note that although the above embodiments are described assuming that a photosensitive material is applied to a web of photographic film, the present invention is not limited to this, and the present invention is not limited to this, and the present invention is not limited to applying a liquid material to a substantially continuous web using a slide hopper device. If so, it can be widely applied to other products.

[Brief explanation of drawings]

The figure is a sectional view showing an embodiment of the invention. 1-Slide hopper, 2-Slide. 5.5'-coating liquid, 6.6'-liquid film. 7-bead, 9-web, 12-seam. 14-accelerator, 15-.-box. 16-Air ejection pipe, 17-Front wall lower surface slit.

Claims (1)

[Claims] +11 A slide bead coating method, characterized in that the velocity of the coating liquid flowing down the slide surface is increased during a limited period of time from immediately before to immediately after the web seam passes through the bead. . (2) In a slide bead coating device, a liquid that can spray air above the slide surface along the coating liquid film flowing down the slide surface during a limited period of time from just before to after the web seam passes the bead. A coating device characterized in that a film accelerator is arranged.