JPH01206331A - Coating method - Google Patents

Abstract

PURPOSE:To eliminate a thick film at the top of a web by blowing steam to the surface at the top of the web for which coating is restarted, then blowing cold wind to the surface of the web to accelerate dew condensation and adhesion of the sprayed steam, thereby increasing the degree of pressure reduction for stabilizing a bead at the top of coating to the degree higher than at the stationary time. CONSTITUTION:A coating machine 2 is retreated by the signal from a detector installed in the proper position before the coating machine when the joint part of the web 10 approaches the coating machine 2. In addition, a timer is operated and the coating machine 2 advances upon lapse of the prescribed time when the joined tape is passed. The coating is thus restarted. A 3-way valve 34 is opened by the signal of the detector and the steam is sprayed from a nozzle 29 onto the web. A stop valve 37 is simultaneously opened and the cold wind is blown from a cold wind injection nozzle 36 onto the web, by which the dew condensation and the leakage of the coating liquid are improved. A method for increasing the degree of the pressure reduction to the degree higher than the stationary degree of the pressure reduction during coating by using a pressure reducing device 3 for the proper time at the top of the coating is used in combination. The thick film at the top is thereby eliminated, the yield is improved and the drying load is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a coating method using a slide hopper device, and more particularly to a thick film formed at the beginning of coating.

[Prior Art 1] An example of coating a continuously running flexible elongated support (hereinafter referred to as a web) with a coating liquid using a slide hopper device is the coating of a photographic light-sensitive material. In the coating method using a slide hopper device, one or more layers flow simultaneously on the slide surface, singly or in a superimposed manner, forming a bead at the point where it meets the moving web at the end of the slide, and through this bead, the layer or layers are coated. Coating layers are simultaneously applied onto the web. In this coating method, bead stability is very important, and for example, bead stability is achieved by creating an air pressure difference between the top and bottom of the bead and creating a negative pressure on the bottom side (hereinafter simply referred to as reduced pressure). techniques are often used.

In such a coating method, at the beginning of coating when the coating machine is placed close to the web at the start of coating, the thickness of the coating film becomes thick, and the bead is not stabilized, causing failures such as coating streaks. It is common practice to join webs together to form a long support, and such joints are usually pasted together with tape. After passing through the area, the coating machine is moved forward again to control the coating.

In such a case, the same problem as at the beginning of coating occurs. Hereinafter, problems at the beginning of coating refer to both the beginning of coating and the advance of the coating machine after passing the web joint. If there is a sufficient gap between the applicator and the web, the applicator may not be retracted, but even in this case, line failure may occur due to bead disturbance due to wetting of the web or joining tape. This is often the case. Particularly, the problem that the coating film becomes thick at the beginning of coating (hereinafter referred to as thick film) not only prevents this portion from becoming a product, but also puts an unnecessary burden on the drying process following coating. In other words, although the majority of the drying process is normal, a small portion of the film is thick, so a drying capacity that can handle this thick film is required. This forces excessive capacity in the drying process, and if this area is left undried, it will adhere to other areas and reduce product yield. Such local thickening of the coating layer is caused by wetting of the web by the coating liquid at the boundary between the coating area and the non-coating area, and it also affects the occurrence of streak failure due to the bead disturbance. It seems that it is.

To solve the above problems, the reduced pressure at the beginning of coating can be increased, or, in JP-A-55-119470, a low viscosity treatment liquid consisting of water or a solvent can be applied as a pretreatment to the web near the start of coating. The method of
No. 121865 discloses a method that combines the above-mentioned pressure reduction and the above-mentioned pretreatment. These require pretreatment equipment and the equipment becomes complicated.

Furthermore, Japanese Patent Application Laid-Open No. 58-81547 stipulates a certain range of the approaching speed of the coating machine to the web, and Japanese Patent Application Laid-Open No. 50-923
No. 28 proposes roughening the surface of the web, but only a web whose leading edge has been roughened in advance can be used, and it is inconvenient to deal with joints and the like during winding. Japanese Patent Publication No. 57-36025 discloses a method of improving wetting by causing dew to form on the web using steam spray and cold air at the beginning of coating. Although each of the above methods is effective to some extent, they are still not sufficient.

[Problems to be Solved by the Invention] In order to solve the above-mentioned problems, an object of the present invention is to eliminate the thick film at the top, thereby improving the yield and reducing the drying load.

[Means for Solving the Problems] The above-mentioned object of the present invention is to provide a method of applying a coating liquid to a continuously running web using a slide hopper device. This is achieved by a coating method characterized by blowing cold air onto the surface of the web after spraying the steam to promote dew and adhesion of the sprayed steam, and increasing the degree of vacuum for bead stabilization at the beginning of the coating compared to the steady state. be done.

The present invention will be specifically explained below. FIG. 1 shows a schematic cross-sectional view of an example of a slide hopper device that can be used in the present invention.

The web IO travels while being held by the coating backup roll 1, and comes into contact with the coating liquid flowing from the slot 4 of the slide hopper coating machine 2 onto the slide surface 5 at the coating machine lip 6, and forms a ribbon-shaped liquid pool at the lip. A bead 12 is formed through which the coating liquid is applied onto the web. At this time, a method is generally adopted in which the bead is stabilized by pulling the bead downward with the decompression device 3. The above mechanism is the same whether it is a single layer or two or more layers, and simultaneous multilayer coating can be performed by flowing a plurality of coating liquids onto the slide surface through a plurality of slots. The case shown in FIG. 1 is an example of two-layer coating, in which, for example, the emulsion liquid 14 is poured into the lower layer and the protective film liquid 13 is poured into the upper layer, thereby performing simultaneous overlaying.

FIG. 2 is an explanatory view showing a steam spraying device and a cold air device for forming dew on the web and improving wetting of the coating liquid.

In FIG. 2, the web lO is fed in the direction of the arrow, and after a coating liquid such as photographic emulsion is applied to the surface by a coating machine 2,
It is transferred to the setting device 22. Cold air cooled by a heat exchanger 25 coupled to a refrigerant such as a brine pipe 24 is taken into the cent device 22 via a cold air intake pipe 23. In front of the coating machine, there is a spray box 26 facing the surface of the web, and the air in the chamber 27 of this box 26 is constantly exhausted to the outside by a blower 28 to prevent accidents due to steam leakage. Ru.

According to the invention, a spray nozzle 29 is located in the chamber 27, the spray nozzle being directed towards the surface of the web 10. This nozzle 29 is connected to a steam pipe line 30, in which steam generated by a steam source 31 is reduced in pressure by a pressure reducing valve 32, and then purified by an air filter 33.
It is supplied through a direction valve 34. Further, the steam pipe line 30 is kept warm by a heat insulating coil 35 surrounding it, and maintained in a superheated state.

Meanwhile, according to the present invention, an air injection nozzle 36 is located in the spray box 26 immediately after the spray nozzle 29 . The air nozzle 36, which has a blowhole (not shown) directed toward the surface of the web 10, is branched from the cold air pipe 23 and connected to a cold air supply pipe 38 in which an on-off valve 37 is incorporated.

When the joint of the web IO approaches the applicator, a signal from a detector placed at an appropriate position in front of the applicator causes the applicator to retreat and activate a timer. After a predetermined period of time for passing the bonding tape, the coater advances and coating resumes. Further, in response to the signal from the detector, the 30,000 valve 34 is opened and steam is sprayed onto the web from the nozzle 29, and the on-off valve 37 is simultaneously opened and cold air is blown onto the web from the cold air injection nozzle 36. This causes water vapor to condense on the web, improving wetting of the coating liquid onto the web.

Furthermore, according to the method of the present invention, the coating liquid is diluted simply by spraying only steam, and the phenomenon called ``drip'', in which the sprayed steam flows to an area outside the area, does not occur.

In order to improve the wetting of the coating liquid to the web at the beginning of coating, as well as to speed up bead recovery and increase stability, the present invention uses the timer signal to adjust the degree of pressure reduction at an appropriate time at the beginning of coating, and at regular intervals during coating. The effect of the present invention is enhanced by using a method of increasing the degree of vacuum more than the normal one.

[Example 1] Hereinafter, the effects of the present invention will be explained in more detail with reference to Examples.

Example-1 A coating solution consisting of the following four layers was simultaneously coated on a triacetyl cellulose film base having a thickness of 100 μm. The first and third layers from the base side are gelatin coating liquids containing silver halide emulsions with different color sensitivities.

The second layer is an intermediate layer containing no silver halide emulsion, and the fourth layer is a protective layer containing an anionic surfactant.

The total amount of coating above is 120g/m2, and the coating speed is 1
At 50m/min, the degree of pressure reduction during steady state is -30mmaqs
The approach speed of the coating machine to the web is 0.5 cm/see
During coating, the conditions of the thick film were examined by changing the conditions as shown below and moving the coating machine backwards and forwards.

A, no treatment The degree of vacuum at the beginning and end was 160 mmaq.

C. Decompression degree at the beginning - 5 layer mmaq. Apply 10 cc/m2 of an aqueous solution containing a surfactant to the web as a pre-treatment.I;
.

2. Set the applicator speed to the web at 5 am/sec.

E. Make a knurl at a length of 2111 points from the area where the application of the triacetyl cellulose film base is scheduled to start. This depth should be approximately 50 μm.

After spraying superheated steam at 120°C on the top, 5°
Blow cold air from C.

(g), the top vacuum degree of -60 mmaqs, and the conditions described in (f) above were used in combination.

The ratio of thick film under the above conditions was evaluated using numerical values according to the following formula.

The above results are shown below.

Jin 215 mouth, 101 ha, 101 two, 80 ho, 100 to, 61 to, 11
(The present invention) The above results show that the method of the present invention is extremely superior.

Example 2 The following coating solution consisting of five layers was simultaneously coated on a triacetyl cellulose film base with a thickness of 120 μm.
.

The first layer is an antihalation layer, the third layer is an intermediate layer, the second and fourth layers are silver halide emulsion layers having different color sensitivities, and the fifth layer is a protective layer containing an anionic surfactant.

Total weight is 150g/m2, steady pressure reduction -35mmaq,
The coating speed was 180 m/the approach speed of the old n1 coating machine to the web was 0.5 cm/see, and the effects on thick films were compared under the following conditions as in Example 1.

H, No treatment, degree of reduced pressure at the beginning -70 mmaq N, Same as (c) in Example-1, Same as (d) in Example-1, Same as (e) in Example-1, Implementation The same force as in (f) of Example-1, the top vacuum degree of -70 mmaq, and the conditions in (wa) were used in combination.

Results Ch, 250 Su, 131 Nu, 92 Lu, 175 Oh, 161 Wa, 80 Power, 15 (present invention) From the above results, the method of the present invention is effective for thick films as in Example-1. is clear.

[Effects of the Invention] According to the present invention, it was possible to eliminate the thick film at the top that occurs when coating is performed using a slide hopper device, and to provide a stable coating method that improves the yield and reduces the drying load. .

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a slide hopper coating machine. 1: Coating backup roll, 2 Ni slide hopper coating machine, 3: Decompression device, 4 Ni slot, 5 Sliding surface, 6: Lip portion, 10: Web, 11: Coating film,
12: bead 13: protective film liquid; 14: emulsion liquid; FIG. 2 is an explanatory diagram of an apparatus for generating water vapor dew droplets on a web. 22: Set device 29: Steam spray nozzle 34: Three-way valve for steam supply 36: Cold air injection nozzle 37: Open/close valve for cold air supply

Claims (1)

[Claims] A method in which a coating solution is applied to a continuously running support using a slide hopper device, in which steam is blown onto the surface of the support at the beginning of coating or where coating is resumed after interruption of coating, and then cold air is blown onto the surface of the support. condensation of sprayed steam,
A coating method characterized by promoting adhesion and increasing the degree of vacuum for stabilizing the bead at the beginning of coating compared to the steady state.