JPH0655121A - Device and method for coating slide bead - Google Patents

Abstract

PURPOSE: To make it possible to stabilize a slide bead edges by providing a coating applicator with a stripe coating material which initially applies a pair of liquid strips coalescing with the edge of the subsequent side coating bead on a moving base. CONSTITUTION: The slide bead coating applicator has a bead region where the flowing fluid layer forming a film is continuously applied on the moving base 6, a roller for transporting the base 6 in a longitudinal direction through the bead region and a driving means thereof. The applicator also has a means for continuously supplying the flowing fluid layer to the sliding surface of a coating head, a coating grip end 26 within the bead region at the terminal of the sliding surface of the coating head and a means for forming the coating bead 21 of the flowing fluid layer between the base 6 and the coating grip end 26. The applicator has the stripe coating material for initially applying the two liquid stripes 20 coalescing with the end of the fluid layer to be applied afterward on the moving base 6.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to slide bead coating, and more particularly to an apparatus and method for slide bead coating of a single or multiple liquid layers on a moving substrate.

The description of this specification is based on the description of US patent application Ser. No. 07 / 905,354, which is the basis of the priority of the present application, and the reference is made to the number of the US patent application. The contents of the description of the US patent application are hereby incorporated by reference.

[0003]

BACKGROUND OF THE INVENTION The slide bead coating method is well known in the art. It involves flowing down a liquid layer or layers on an inclined slide surface to an outflow end, or lip, located a short distance from a moving substrate. This liquid forms a bridge or bead in the gap between the lip and the moving substrate. A negative pressure chamber below the bead may control the pressure differential between the upper and lower sides of the bead so that the bead position and shape are maintained and the flow through the bead is stable and uniform. The moving substrate carries the liquid away from within the bead formed in the same layer on the slide. For example, Rusel et
al. See U.S. Pat. Nos. 2,761,8791, and 2,761,419.

Typically, the width of the bead on the applicator is controlled by end guides located on the beveled surface and at the outflow end or coating lip. As the liquid flows across the gap between the coating lip and the moving substrate, the surface tension acting on the surface of the bead destabilizes the end of the bead and pulls it away from the tip of the end guide. Thus, the coating width is sandwiched and the coating thickness at the end is increased. To compensate for this, the width of the liquid layer of the coater is slightly larger than the desired final width of the film and is removed by applying a slight negative pressure before the slightly thicker end of the coating dries. .
Under stable coating conditions, this device works well to produce films of desired final width and thickness.

If the coating bead is stable at the edges, the beads will shrink slightly, increasing the thickness of the coating edge. This slight reduction in width may not spread to the desired final width. However, the bulky end may not be removed even with suction. In the subsequent drying step, these thick edges are not completely dried. This is because the drying conditions have been optimized for the desired film thickness. The partially dried edges are unacceptably tacky, causing problems for further processing.

If the ends of the coating bead are slightly unstable, the reduction in width spreads to the desired final width, causing a significant loss in yield. Finally, if
If the coating bead is very unstable, it fluctuates wildly and is attributed to the overall disruption of the coating process.

Actuating the negative pressure chamber below the bead to create a large pressure differential helps stabilize the bead at the desired coating width.

However, this method is not effective.
This is because the negative pressure required is large enough to cause undesirable streaking in the coating, or edge turbulence due to uneven coating.

US Pat. No. 4,265,941 discloses the use of greater negative pressure at the ends than at the points along the width of the coating bead. Although this device eliminates unwanted streaks, it still has limited effectiveness. This is because large end vacuums often do not sufficiently stabilize the end and may actually cause instability in the end region. Moreover, it is difficult to achieve a beneficial spatial distribution of different negative pressure levels, since the end regions under high negative pressure must be minimized to avoid the streaks mentioned above.

Another method of stabilizing the ends of the coating utilizes an additional flow of liquid, usually of low viscosity, along the ends of the coating flow on the sliding surface. DE 1631 033 introduces a low-viscosity liquid at the end of the stream on the slide surface of the applicator via a tube outlet located at the top of the end guide of the slide.
In U.S. Pat. No. 4,297,396, a low viscosity liquid is introduced at the end of the coating bead through a slot in the end guide. Japanese Patent Laid-Open No. 63-144
No. 347, a shear thinning liquid is introduced at the end of the coating bead through an additional narrow distribution slot on the slide and an additional end guide pair for channeling the end flow. U.S. Pat. No. 4,313,980
The use of multiple layers wider than the desired coating width is disclosed.
With all of these methods introducing additional end flow on the slide, the combined flow must also cross the gap. Thus, they may reduce the problems associated with stability and shrunken and bulky edges, but do not eliminate them reliably. Furthermore, practically,
It is difficult to choose the proper end flow rate, end liquid characteristics, and means to introduce end flow on the slide without disturbing adjacent coating flow areas.

[0011]

SUMMARY OF THE INVENTION A slide beam coating apparatus of the present invention comprises a bead region continuously applied to a substrate on which a flowing liquid layer forming a film is moving, and the substrate passing through the bead region to cover the substrate. A roller for conveying in the longitudinal direction and its driving means, a means for continuously supplying the flowing liquid layer to the slide surface of the coating head, and a coating lip tip in the bead region at the end of the slide surface of the coating head. And a means for forming a bead of the flowing liquid layer between the substrate and the tip of the coating lip, the coating device further comprising: A stripe coating material which first coats two liquid stripes which merge with an end of the liquid layer to be applied later. That.

The method of the present invention is also a method of forming a photographic element comprising a substrate and a film comprising at least one hydrophilic colloid layer, at least one of which is a photosensitive layer, the coating of a slide bead coating apparatus. Supplying a film-forming liquid layer to the slide surface of the head, flowing the liquid layer into the gap between the substrate and the tip of the coating lip at the end of the slide surface to form a bead region, and Transporting the substrate longitudinally through the bead region such that a polar colloid is continuously removed from the bead region in the form of a liquid film coating on the substrate, and
The substrate is initially provided with two liquid stripes which are positioned so that the liquid in the stripes can merge with the liquid forming the film and the stripes are merged with the ends of the film-forming liquid layer to be subsequently applied. It is characterized by being applied to remove the edge stripes on the substrate and the volatile components of the liquid film coating to form a substantially rigid hydrophilic colloid coating on the substrate.

The liquid stripe is 0.05 from the substrate.
It may be supplied by a nozzle having outlet orifices separated by mm to 0.50 mm.

More preferably, the outlet orifice is located 0.05 mm to 0.25 mm from the substrate.

The stripe has a thickness of 0.1 to 10.0 mm.
Is more preferably 1.0 mm to 5.0 mm, and the thickness is 20 μm to 250 μm, further preferably 50 to 100 μm.

Further, the stripe liquid may be water.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENT Throughout the following detailed description, the same reference numerals denote the same elements throughout the drawings.

In a conventional slide beam coating apparatus as shown in FIG. 1, the liquids 1 and 2 to be coated flow down the inclined slide surfaces of the plates 3 and 4 and between the nearest plate 3 and substrate 6. It passes through the gap 5, which coats the substrate. The substrate 6 is conveyed by the coating roll 7. The coating liquid is supplied by an appropriate number of supply pumps 8 and 9, which pumps into the cavities 10 and 11 and the slots 12 and 13 in the plates 3 and 4. Other plates and a suitable number of pumps, cavities and slots are required to coat the additional layers. The chamber 14 and associated pump 15 control the gas pressure at the lower surface of the liquid in the gap 5 such that the lower surface of the liquid is lower than the upper surface of the liquid.

Focusing on the gap, that is, the bead region shown in FIG. 2, the coating liquids 1 and 2 flow down the slide surface to cover the lip tip 16 of the coating machine, and a continuous liquid between the lip surface 17 and the substrate 6. Form a bridge. Lip tip 16 and substrate 6 referred to as coating gap 5.
The shortest distance on the surface is generally 0.1 mm to 0.5 mm. The pressure difference between the gas above the liquid upper surface, which is usually atmospheric pressure, and the gas below the liquid lower surface exerted by the chamber 14 draws the liquid bead into the gap between the lip surface 17 and the substrate 6. . Typically 40
A pressure difference of 0-4000 dynes / cm ² is exerted. The pressure difference exerted is the spatially stationary liquid wetting line,
That is, to produce a stable bead having a static contact line 18 on the lip surface 17 of the applicator and a spatially constant liquid wetting line, ie a dynamic contact line 19 on the moving substrate 6. Is useful to. Typical substrate speed is 25 ~
It is 300 cm / sec.

The stripe coater in the embodiment of FIG. 3 is a nozzle 22 having a small outlet orifice 23 and provided with a liquid supply means 24. The nozzle 22 has the orifice 23, the bead 21 and the liquid stripe 20 at the end.
It is positioned so as to approach the base 6 at a lateral position that allows it to merge with.

FIG. 3 shows an example of one coated end of the liquid layer of the present invention. The other coating ends would be stabilized as well, but are not shown here. A single coating layer 1 is shown for clarity. A narrow liquid stripe 20 is first applied to the substrate 6 by a stripe coater. Base 6 with stripes
Then contacts the coating beads 21 and carries away the layered liquid film formed on the slide.

The stripe coater in the embodiment of FIG. 3 is a nozzle 22 with a small outlet orifice 23 and is provided with a liquid supply means 24. The nozzle 22 has the orifice 23, the bead 21 and the liquid stripe 20 at the end.
Substrate 6 in a lateral position that allows it to contact and merge
It is located so as to approach.

Other than the particular nozzle orifice shown in FIG. 3, other methods of providing the advantageous stripes of the present invention are well known and can be practiced by those skilled in the art. Examples of these methods include, but are not limited to, spray coating in which a sponge or other porous and wicking material applicator is contacted with a substrate via a spray nozzle as shown in FIG. And gravure wheel coating are included.

Of the various methods, stripe coating via an orifice located in close proximity to the substrate is preferred. The stripes applied by this method are stable, easy to control and easily and accurately positioned.

The clearance between the nozzle orifice and the substrate is preferably 0.05 mm to 0.50 mm, more preferably 0.05 mm to 0.25 mm. These narrow clearances allow the use of thin and narrower liquid stripes. Preferably, this liquid stripe has the same thickness (within 25%) as the subsequent nominal (display) coating.
Is preferred. For this reason, the coating thickness of pre-coated stripes is usually 0.020 mm to 0.250 mm, more typically 0.05 mm to 0.100 mm thick. In some cases, it may be desirable to apply thicker stripes than later coatings. Similarly, in some cases, the stripes are pre-applied due to the intentional thick coating of the end areas by substantially overlapping the pre-applied channels with the end areas of the coating bead. Is desirable. like this,
The array can be effectively used to stabilize the edges of the coating. However, the later thick ends usually have to be removed or dried before or during drying.

The width of the stripe is usually 0.1 mm to 10 mm.
0 mm, more typically 1.0 mm to 5.0 mm
Width. Wide stripes are beneficial, but undesirable because excess liquid must eventually be removed.
Further, when the stripe is widened, stability of the end portion of the stripe and contraction of the stripe itself become problems, which makes it difficult to effectively position the stripe.

In the preferred embodiment, the striped applicators are located closer to, rather than away from, the coating lip and located at a point along the path of the substrate.
The stripes must be present in liquid form and contact the edges of the coating bead to stabilize the edges of the coating bead during the coating process. if,
If a striped applicator is attached to the coating head structure, as shown in FIG. 3, for example,
The coating of the stripes can start during the beginning of movement, with the coating head and the substrate almost in the coating position. In many cases, it is easier to start coating the substrate with stripes than with the coating bead liquid. The applicator closer to the lip will result in stripes at the lip end of the applicator that will contact the liquid later, faster than would otherwise be the case. This has the benefit of starting the bead coating at the edges sooner than it would normally occur without stripes, thus reducing the loss of film at the beginning of the coating process. To do. In other cases where the bead liquid rapidly coats the substrate, a closer striped applicator provides stability at the coating bead edge at the beginning of coating before the bead edge becomes susceptible to shrinkage. To ensure. An example of a striped applicator of the type shown in Figure 3 is 100 mm from the coating lip.
It is preferably located within. More preferably 25 m
Located within m. Of course, a stripe application method that allows stripes to be applied regardless of the proximity of the stripe applicator to the substrate, and / or FIG.
Proximity insensitive methods such as those with spray nozzles do not have to accept this preference, as will be apparent to those skilled in the art. However, the stripes applied by one of the alternatives prior to the negative pressure chamber structure may be subject to potentially detrimental interference by the negative pressure chamber structure.

FIG. 5 is a cross-sectional view of the most preferred embodiment of applying stripes. Nozzle 32 is striped liquid 2
The stream 9 is directed towards the moving substrate 6. A liquid inlet 33 is attached to the nozzle for the introduction of striped liquid 29. The liquid is the nozzle surface 31 and the substrate 6.
Flows into the open cavity 30 formed between the two and is carried away by the moving substrate 6. In this embodiment, the nozzle is conveniently integrated with the applicator structure 3 to facilitate accurate alignment with the applicator edge and accurate clearance with the substrate. In addition, stripes are applied very close to the edges of the coating bead, after starting the coating process by bringing the coating head and substrate into a functional coating clearance, but before the edges of the coating bead are susceptible to shrinkage. , Stabilize this end almost.

The location of the striped liquid inlet 33 for the preferred embodiment of FIG. 5 with respect to the entire apparatus is shown in FIG. This inlet is preferably adapted to allow a removable coupler from the supply means.

Coupling means known in the art such as threaded holes, compression fittings, snap fittings and the like can be used. Standard supply means such as direct hookups with standard water supply lines, reservoirs and pumps etc. are suitable. Preferably, a flow meter is included in the supply means as is known in the art. The nozzles can be fed and controlled individually or in series.

The liquid used for the stripes may be any liquid that wets the substrate and coalesces with the coating beads. The fact that the bead ends merge with the liquid stripe requires that they be in contact. The contact or slight overlap of the two ends is usually sufficient contact. Preferably, this coalescence is achieved by choosing a striped liquid in which the coating bead liquid tends to spread over the striped liquid. More preferably,
The striped liquid is also miscible with the coating bead liquid. Furthermore, the stripe liquid may be achieved by mechanical removal such as by subsequent drying and / or suction or scraping, which may occur simultaneously with the drying of the coating in a film drying oven, or by, for example, microwave or jet impingement drying. It should be suitable for selective removal by impregnated drying confined to a large stripe area. In particular, for use with aqueous coatings, the liquid may be water or a main aqueous solution such as a dilute gelatin solution. Viscosity modifiers such as surfactants and / or shear thinning agents may also be included.

The invention described herein is useful with a myriad of flowing liquids, including, but not limited to, photosensitive and / or radiation sensitive layers. These light sensitive and / or radiation sensitive layers may be those well known for imaging and reproduction in areas such as graphic arts, printing, medical and information systems. Silver halide photosensitive layers and their associated layers are preferred. Photopolymer, diazo, vesicle (r
esicular) imaging compositions and other systems may also be used in addition to silver halide. Typically,
The desired composition is formulated in an emulsion with a hydrophilic colloid. The hydrophilic colloid or gelatin functions as a binder for the composition.

The emulsion layer film support used in this novel process may be any suitable transparent plastic or paper. Examples of suitable plastics include, but are not limited to, cellulose supports such as cellulose acetate, cellulose triacetate, cellulose mixed esters, polyethylene terephthalate / isophthalate, and the like. The polyester films are particularly suitable because of their dimensional stability.

During the production of the film, for example Rawlin
vinylidene chloride-itaconic acid, mixed polymer basecoat compositions taught in US Pat. No. 3,567,452, or Miller US Pat. No. 4,916,011.
It is preferred to apply a resin subbing layer such as the antistatic composition taught in US Pat. No. 4,701,403 and Cho US Pat. No. 4,891,308.

The coating element of the photographic film is dried by liquid substrate evaporation. Evaporation is preferably accelerated by conduction, convection and / or radiant heating. Heat transfer occurs through a support, such as by physical contact with a heated drum or roller, or by direct contact with a gaseous medium such as warm air. Jet impingement with the gaseous medium of the coating results in both heat and mass transfer. Radiation of relatively insensitive photographic elements can be used to facilitate liquid substrate evaporation, as well as microwave heating.

The invention described herein is further illustrated by the following experimental examples, which are not intended to limit the scope of the invention.

(Experimental Example) Two liquid layers were simultaneously coated by slide beads on a substrate moving at a speed of 150 cm / sec. In each case, the upper layer is 9.2%
Gelatin-water solution (viscosity = 21 cp), and the lower layer was an 8.8% gelatin solution (viscosity = 18 cp) with a 7% AgBr colloidal suspension. The slide applicator is
The width between the end guides is about 14 cm, inclined about 23 degrees from the horizontal, and the coating lip and the substrate surface are spaced apart from each other.
It was equipped with a sliding surface that was positioned with a 25 mm gap.

As reported in Table 1, the total flow rate varied from experiment to experiment, from 8.4 cc / sec to 16.4 c.
It was in the range of c / sec. In each case, 75% of the total flow was lower flow and 25% was upper flow. At each flow rate, with a pressure differential that gives a stable coating that is continuous and slightly narrower than the width between the end guides,
The coating has started. The pressure difference was then reduced to a critical value below which the coating became unstable. As mentioned previously, the increased pressure differential helps stabilize the ends of the coating bead. Conversely, the reduced pressure differential destabilizes the ends of the coating bead. The critical pressure difference is thus an indicator of relative coating bead edge stability. Table 1 shows the critical pressure difference corresponding to coatings at different coating flow rates without the benefit of the edge stripes, ie without the edge stripes applied.

[0039]

[Table 1] Reference example Coating flow rate (cc / sec) Pressure difference (dynes / cm ² ) 1 16.4 1120 2 14.4 1370 3 10.4 1650 4 8.4 2050 Examples 1 to 4 Reference examples are repeated. It was However, the edge stripes were applied about 20 mm prior to the coating lip and were positioned so that the edges of the stripe were approximately aligned with the edges of the edge guides. The stripe is a tap (t with a flow rate of 0.19 cc / sec from a 1.6 mm diameter exit hole of a small block).
ap) Coated with water. The clearance between the block and the substrate was about 0.25 mm. The water channels on the substrate were consequently 2-3 mm wide.

Table 2 shows the critical pressure difference. In each case, the mode of instability was excessive elongation and subsequent turbulence that first started in the central region of the bead width and spread rapidly towards each end. The turbulence gave the impression of a draw-under and did not appear to be directly related to the edges.

It should be noted that the critical pressure difference in Table 2 is greatly reduced with respect to the corresponding values in the reference example of Table 1 and that the perceived instability mode is not edge-related. . This means that the ends are highly stabilized by the presence of converging water stripes.

[0042]

[Table 2] Example Coating flow rate (cc / sec) Critical pressure difference (dynes / cm ² ) 1 16.4 170 2 14.4 250 3 10.4 370 4 8.4 250

[Brief description of drawings]

FIG. 1 is a sectional view of a conventional slide bead coating device.

FIG. 2 is a sectional view of a bead region of a conventional slide bead coating device.

FIG. 3 is a cross-sectional view of one embodiment of the present invention showing the orientation of the liquid stripe with respect to the coating solution and device.

FIG. 4 is a cross-sectional view of an embodiment of the present invention showing a nozzle that applies a liquid stripe to a substrate.

FIG. 5 is a sectional view of a stripe coating region according to an embodiment of the present invention.

FIG. 6 is a perspective view of an embodiment of the present invention showing the relationship between stripes and a coating device.

[Explanation of symbols]

 1 coating liquid 2 coating liquid 3 plate 4 plate 5 gap 6 substrate 7 coating roll 8 supply pump 9 supply pump 10 cavity 11 cavity 12 slot 13 slot 14 chamber 15 pump 16 lip tip 17 lip surface 18 static contact line 19 dynamic contact Line 20 Liquid stripe 21 Coating bead 22 Nozzle 23 Exit orifice 24 Liquid supply device 29 Stripe liquid 30 Open cavity 31 Nozzle surface 32 Nozzle 33 Stripe liquid inlet

Claims (2)

[Claims] 1. A bead region continuously applied to a substrate on which a fluidized liquid layer forming a film is moving, a roller for longitudinally transporting the substrate through the bead region, and a driving means for the roller, and a coating. A means for continuously supplying the flowing liquid layer to the sliding surface of the head; a coating lip tip in the bead region at the end of the sliding surface of the coating head; between the substrate and the coating lip tip. And a means for forming beads of the flowing liquid layer on the slide bead coating device, wherein the coating device further comprises: an end portion of the liquid layer to be applied later to the moving substrate. A slide bead coating device comprising a stripe coating material that first coats two merging liquid stripes. 2. A method of forming a photographic element comprising a substrate and a film comprising at least one hydrophilic colloid layer, at least one of which is a photosensitive layer, the film being formed on a sliding surface of a coating head of a slide bead applicator. Forming a bead region by flowing a liquid layer into the gap between the substrate and the tip of the coating lip at the end of the sliding surface to form a bead region. Transporting the substrate longitudinally through the bead area so as to be continuously removed from the substrate in the form of a liquid film coating on the substrate. Is capable of merging with the forming liquid and merging with the edge of the film-forming liquid layer on which the stripes are subsequently applied Applying two liquid stripes positioned to remove the volatile components of the end stripes on the substrate and the liquid film coating to form a substantially rigid hydrophilic colloid coating on the substrate. how to.