JPS6248550B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of coating a liquid coating composition onto a support. More specifically, the present invention relates to a multilayer simultaneous coating method for simultaneously applying a fluid coating composition in a plurality of layers onto a moving strip-shaped support (herein referred to as a "web"). BACKGROUND ART Conventionally, techniques relating to multilayer simultaneous coating methods comprising a plurality of layers have been highly developed in connection with the production of silver halide photographic materials that require many thin layers. That is, U.S. Pat. No. 2,761,791 proposes a bead coating method in which a coating liquid is continuously supplied onto a slide hopper and is layered on a moving web while maintaining an individual layer relationship. There is. However, in this method,
The disadvantages are that mutual mixing occurs between stacked layers, or that it is difficult to change the coating thickness of a specific layer. As a method to improve these drawbacks, for example, Japanese Patent Application Laid-open No. 52-115214, No. 54-1350, and No. 56-
The methods described in various publications such as No. 108566 are proposed. All of these methods are techniques for improving the above-mentioned drawbacks by changing the physical properties of only the bottom layer coating composition that comes into direct contact with the web surface. However, with this technique, even if the lower layer of the multilayer constituent layers near the support is improved, the upper layer far from the support, especially the top layer, is not improved at all, and there is no need to improve the top layer. There is no suggestion of that. The outermost surface of a silver halide photographic material contains extremely important elements. For example, the outermost surface has functions such as a protective layer that protects against physical impact and contact, resistance to static electricity, or prevention of mutual sticking of coated sheets. In offset printing plates that apply the silver salt diffusion transfer method, the outermost layer (containing physical development nuclei made of heavy metals or their sulfides) that forms the printing image is made to have ink receptivity. The top layer is a very important element. In general, the outermost layer of a silver halide photographic light-sensitive material often requires a relatively thin layer compared to the underlying layer, such as a silver halide emulsion layer or an antihalation layer. In the case of the antistatic layer or silver salt diffusion transfer printing plate element mentioned above, it is considered advantageous in terms of characteristics to have as little binder component as possible in the coating composition and to contain the target component at a high concentration. There is. Therefore, for example, in the case of offset printing plate elements, it is necessary to apply multiple layers of the lower layer fabric in advance, let it dry, and then apply a thin layer of the top layer again.
Alternatively, the current situation is that simultaneous multilayer coating is carried out using an appropriate amount of a hydrophilic binder. As a result of intensive study on the hydrodynamic behavior between the top layer and the next layer immediately below, the inventors found that
It has been found that coating defects are more likely to occur when there is a large difference in velocity gradient with respect to shear force at the portion where both the uppermost layer and the next layer contact each other on the web surface. In addition, the present inventors believe that in order to solve this problem, the top layer and the next layer should not behave hydrodynamically as separate layers, but the top layer should be able to withstand the shear force at the part where they are in contact with each other on the web surface. The present invention was completed based on the discovery that coating defects caused by conventional methods can be solved at once by making the coating behave as if it were part of the next layer. A first object of the present invention is to provide a multilayer simultaneous coating method that enables simultaneous multilayer coating of a thin layer of the coating composition of the uppermost layer when performing simultaneous multilayer coating using a slide hopper type coating device or the like. There is a particular thing. The second object of the present invention is to reduce the amount of binder,
It is an object of the present invention to provide a multilayer simultaneous coating method capable of simultaneously coating a thin layer of a coating composition containing a target component at a high density on the uppermost layer. Other objects of the invention will become apparent from the following description. The above-mentioned object of the present invention is to provide a multilayer simultaneous coating method in which a plurality of coating solutions are simultaneously applied to a moving web to form layers, in which the coating solution forming the uppermost layer is applied in an amount of 1 to 15 cm ³ per 1 m ² of the web surface. With a wet coverage of
and a hydrophilic coating composition having a viscosity of 0.5 to 2 centipoise at 40°C, and a wet coverage of ¹⁰ per square meter of the web surface of the hydrophilic coating composition forming the layer immediately below the uppermost layer. ~ ^100cm3 and 40℃
This is achieved by a multilayer simultaneous coating method characterized by a hydrophilic coating composition having a viscosity of 3 to 100 centipoise. According to a preferred embodiment of the present invention, a top layer is formed in a multilayer simultaneous coating method in which multiple layers of a coating solution are simultaneously applied onto a moving web using a slide hopper type bead coating device. The wet coverage of the coating composition on the web is 1 to 15 cm ³ /m ² , preferably 3 to 10 cm ³ /m ² , and 0.5 to 2 centipoise (hereinafter referred to as
It's called "Cp". ) (In this specification, "viscosity" means "relative viscosity" unless otherwise specified.)
The wet coating amount of the coating solution for the top layer prepared in advance so as to have a coating composition solution for forming the next layer in contact with this layer on the web is 10 to 100 cm ³ /m ² ,
Preferably 20 to 70 cm ³ /m ² and 3 at 40°C
A hydrophilic coating solution for the next layer prepared in advance to have a viscosity of ~100 Cp is supplied to the coating device. According to the present invention, when multiple layers are simultaneously coated on the same web, the uppermost layer is coated as a thin layer with "non-setting" properties under the above-mentioned specific conditions, so that shearing forces at the contact points on the web surface are reduced. On the other hand, the top layer coating liquid behaves as if it were part of the next layer, making it possible to obtain a good coated top layer.
Furthermore, by reducing the amount of coating on the top layer, it is possible to reduce the amount of moisture brought in, reducing the drying load and increasing the coating speed.
This has the effect of making it possible to significantly reduce coating and drying process costs. In this specification, the term "non-setting property" of the coating solution forming the top layer refers to the setting (equipment) conditions used to stop the flow of conventional gelatin solution coated on the web. This means that the flow as a solution does not stop even when the coating liquid forming the uppermost layer reaches the web surface 1.
0.5 at a wet coverage of 1 to 15 cm ³ per m ² and at 40 °C
a hydrophilic coating composition having a viscosity of ~2 centipoise and a wet coverage of 10 to 100 cm ³ per m ² of web surface of the hydrophilic coating forming the layer immediately below in contact with the top layer; In addition, the coating composition must be hydrophilic and have a viscosity of 3 to 100 centipoise at 40°C. The simultaneous multilayer coating method according to the present invention will be explained below using simultaneous multilayer coating of silver halide photographic materials as an example. First, the binder for the coating solution of the silver halide photographic light-sensitive material used in the present invention will be explained. Hydrophilic polymer compounds are advantageously used as such binders, such as gelatin, gelatin derivatives such as phthalated gelatin, polyvinyl alcohol, polyvinyl formal, polyvinyl acetal, hydroxyethylcellulose, hydroxymethylcellulose, ethylcellulose,
Methyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl pyrrolidone, sodium alginate, gum arabic, polyacrylamide, maleic anhydride-vinyl acetate copolymer, maleic anhydride-ethylene copolymer, maleic anhydride-methyl vinyl ether Copolymers, maleic anhydride-styrene copolymers, half esters thereof, and methacrylic acid copolymers are used, and these can be used alone or in combination. Next, the layer-forming coating composition used in the present invention will be explained. First, useful coating compositions for forming the top layer may include compositions containing a wide variety of additives conventionally used in the photographic industry, such as surfactants. agents, antistatic agents, hardeners, sensitizers, dispersants, antifoaming agents, antifoggants, stabilizers, antioxidants, fluorescent brighteners, ultraviolet absorbers, image fading inhibitors, latent image stabilization Examples include a curing agent, a matting agent, a photosensitive dye, a dye, a pigment, a mordant, a hydrophilic solvent thereof, or a physical development nucleus for silver salt diffusion transfer. These coating compositions may also contain water or a hydrophilic solvent such as methanol, ethanol, ethylene glycol, etc., and may further contain substantially no hydrophilic polymer compound such as gelatin or the synthetic polymers mentioned above. It may be contained in an amount within a range that does not set the value. In addition, the coating liquid composition of the next layer that is continuously applied immediately below the top layer may be of the usual composition used in the conventional bead coating method, and the coating liquid composition of the next layer that is continuously applied immediately below the top layer may be of the usual composition used in the conventional bead coating method. The same goes for the bottom layer that is in direct contact with the layer or web surface. As mentioned above, the next layer applied immediately below the top layer has a wet coverage of 10 to 100 cm ³ /m ² , preferably 20 to 70 cm ³ /m ² on the web surface. , and a viscosity of 3 to 100 Cp at 40° C. This is presumed to promote the transfer and penetration of the uppermost layer solvent into the next layer, thereby enabling coating. That is, by providing the above-mentioned physical properties, the top layer and the next layer come into contact with each other on the sliding surface, and then gradually penetrate into the next layer element, so that the top layer behaves as if it were part of the next layer, and the present invention It is presumed that the objectives of the project have been achieved. Regarding the above-mentioned coating constituent layers, if necessary, only the bottom layer may be coated with the above-mentioned JP-A-52-115214 and JP-A-54-1.
It is also possible to apply using a material with low viscosity properties by the methods described in Publications No. 1350 and No. 56-108566. Next, a preferred embodiment in which the coating method according to the present invention is carried out using a slide hopper type coating device for simultaneous three-layer coating will be described with reference to the accompanying drawings. FIG. 1 is a schematic side view showing a part of a slide hopper type coating device for simultaneous three-layer coating used as an example of the coating method according to the present invention. In the figure, 1 is a roll rotating in the direction of the arrow;
2 is a web which is a belt-shaped support; 3 is a bead portion;
Reference numerals 4, 5 and 6 indicate slots which are elongated passages for supplying the coating solution; 7 indicates a sliding surface through which the coating solution flows; 8 indicates a coating composition solution forming the lowermost layer in contact with the web 2; and 9 indicates the lowermost layer. A coating composition liquid forming an intermediate layer (second layer) located above the lower layer, and 10 a coating composition liquid forming an uppermost layer (third layer) used in the present invention. The web 2 is conveyed by a motor (not shown), and by the rotation of the roll 1,
Continuously transported in the direction of the arrow. The coating liquid 8, 9
and 10, each of the bottom layer, middle layer and top layer passes through the slots 4, 5 and 6, and is fed along the slide surface 7, flows down by gravity, and, as is well known, flows into the bead portion. 3, it undergoes a radial change and is pulled up to the surface of the web 2. As a result, it gradually becomes layered and a thin layer is formed. A multilayer structure formed in this manner is shown in FIG. 2, and a multilayer structure formed by a conventional coating method is shown in FIG. 3 as a comparative example. In the figure, 11 and 11' represent the support, 12 and 12' the lowermost layer, 13 and 13' the intermediate layer, and 14 and 14' the uppermost layer. As shown in the figure, whereas the top layer 14' formed by the conventional method has a high coverage,
It can be seen that the top layer 14 of the present invention is a thin layer. The coating composition 10 used in the present invention and forming the uppermost layer is an aqueous solution or a hydrophilic colloid solution, prepared in advance to have a viscosity of 2 Cp or less at 40° C., and supplied from the slot 6. Next, the coating composition liquid 9 serving as the intermediate layer and the coating composition liquid 8 serving as the bottom layer are similarly hydrophilic solutions, and are preliminarily prepared by containing an appropriate amount of a polymer compound or a thickener. The viscosity is adjusted to be in the range of 3 Cp to 100 Cp, preferably 5 to 50 Cp at 40 DEG C., and is supplied from slot 5 and slot 4, respectively. In this way, coating composition liquid 1 forming the uppermost layer
0 and the layer properties of the coating compositions 9 and 8 of the intermediate layer and the bottom layer, the top layer and the next layer do not exhibit separate hydrodynamic behavior, but, for example, when shear is applied. In some cases, the top layer behaves as if it were part of the next layer, thereby achieving the object of the present invention. The above is an example of one embodiment of the present invention; however, the present invention is not limited thereto, and various embodiments can be adopted. For example, in FIG. 1, separate layers with different layer characteristics may be inserted between the bottom layer 8 and the middle layer 9, or after simultaneous multilayer coating and drying by the method according to the present invention, It is also possible to apply further layers. Next, the present invention will be specifically explained by giving preferred examples of the coating method according to the present invention. Example 1 Simultaneous multilayer coating was carried out using a slide hopper type coating device similar to that shown in FIG. 1 using coating compositions having the following conditions. The web used was
It was triacetate cellulose based and the application speed was 200 cm per second. [Layer structure of conventional method] First layer (lower layer) A highly sensitive silver iodobromide gelatin emulsion having a viscosity of 35.0 Cp at 40°C was coated at a wet coverage ^of 30.0 cm ³ per 1 m 2 of the web surface. Second Layer (Upper Layer) A coating composition liquid containing a surfactant and an antistatic agent in an aqueous gelatin solution was prepared as a protective layer. This aqueous gelatin solution had a viscosity of 5 Cp at 40° C. and was applied at a wet coverage of 30 cm ³ per m ² of web. [Layer structure according to the method according to the present invention] First layer (bottom layer) A highly sensitive silver iodobromide gelatin emulsion having a viscosity of 35.0 Cp at 40°C was coated at a wet coverage of 30 cm ³ per 1 m ² of the web surface (as described above). Same composition liquid as the first layer of the conventional method). Second Layer (Intermediate Layer) A coating composition liquid containing only a surfactant in an aqueous gelatin solution was prepared as a protective layer. This aqueous gelatin solution has 5 Cp at 40°C and 30 Cp per m ² of web.
A wet coverage of cm ³ was applied (same composition as the conventional upper layer). Third layer (top layer) A 0.1% gelatin aqueous solution containing an antistatic agent and a surfactant was prepared. The viscosity of this aqueous gelatin solution is 0.7 Cp at 40°C, and the viscosity is 10 cm ³ per 1 m ² of web.
It was applied at a wet coverage of . As a result of examining the antistatic performance of the film thus obtained, it was found that the film produced by the method of the present invention was less susceptible to static marks due to static electricity than the film produced by the conventional method. Example 2 Simultaneous multilayer coating was carried out in the same manner as in Example 1 using coating compositions having the following conditions. The web used was photographic polyolefin coated paper.
Application was performed at a speed of 200 cm/s. [Layer structure of conventional method] First layer (lowest layer) A coating liquid for preventing halation was prepared by dispersing 4.0 g of carbon black in gelatin aqueous solution 1 to which a surfactant was added. The viscosity of this coating liquid is 15Cp at 40℃, and
A wet coverage of 60 cm ³ per m ² was applied. 2nd layer (silver halide emulsion layer) A high contrast silver chlorobromide gelatin emulsion containing a surfactant with a viscosity of 15 Cp at 40°C is coated on the web surface 1.
A wet coverage of 30 cm ³ per m ² was applied. Uppermost Layer (Physical Development Nucleus Layer) A colloidal gold aqueous solution containing a surfactant prepared by reducing chloroauric acid was used as a coating solution for the physical development nucleus layer. This coating solution had a viscosity of 5 Cp at 40° C. and was applied to the web surface at a wet coverage of 20 cm ³ /m ² .
In addition, this application amount is 5 mg/gold chloride.
m ² and the binder component was a copolymer of maleic anhydride and methyl vinyl ether in a coating amount of 6 g/m ² . [Layer structure according to the method according to the present invention] Except for the uppermost layer, this example was coated under exactly the same conditions as the conventional method described above. Uppermost Layer (Physical Development Nucleus Layer) A gold colloid solution containing a surfactant prepared by reducing chloroauric acid was used as a physical development nucleus layer coating solution. However, this coating liquid was a low viscosity liquid of 0.8 Cp at 40° C. and was applied onto the web surface at a wet coverage of 7.5 cm ³ per 1 m ² . The coating amount was 5 mg/m ² in terms of gold chloride, and the binder component, a copolymer of maleic anhydride and methyl vinyl ether, was 2.0 g/m ² . Images of the two types of sheets thus obtained were photographed using a plate-making camera, and then developed with a developer for silver salt diffusion transfer to create printing plates. Next, a lipophilizing liquid and a wetting liquid, which are generally used for offset printing by this method, were applied all over the plate surface, and then printing was carried out using a conventional offset ink. As a result, the sheet produced by the method of the present invention had good ink adhesion and clear printing, whereas the conventional method showed weak ink adhesion and caused ink stains. Example 3 A high-contrast silver chlorobromide emulsion and a gold physical development nucleus solution as in Example 2 were simultaneously coated in multiple layers on a photographic polyolefin-coated paper at a coating speed of 150 cm/sec. The conditions of the coating liquid are shown in Table 1 below.

[Table] As a result of examining the coating conditions of the three samples obtained after coating and drying, it was found that sample No. 3 of the present invention, in which the upper layer coating liquid did not set with respect to the lower layer coating liquid, had streaks and unevenness.
While there were no coating defects such as comets, uneven streaks occurred over the entire surface in Samples No. 1 and No. 2, in which the upper layer coating liquid did not show a setting property with respect to the lower layer coating liquid.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing a part of a slide hopper type coating device for simultaneous three-layer coating used as an example in the coating method according to the present invention, and FIG. FIG. 3 is a partially enlarged sectional view showing a multilayer structure formed by a conventional method. In the figure, 1 is a roll, 2 is a web, 4, 5, and 6 are slots, 7 is a slide surface, and 8, 9, and 10 are coating composition liquids.

Claims (1)

[Claims] 1. In a multilayer simultaneous coating method in which a plurality of coating solutions are applied simultaneously to form layers on a moving web, the coating solution forming the top layer has a wet coverage of 1 to 15 cm ³ per 1 m ² of the web surface, And 0.5 to 2 at 40℃
a hydrophilic coating composition having a viscosity of centipoise, and having a wet coverage of 10 to 100 cm ³ per 1 m ² of the web surface of the hydrophilic coating composition forming the layer immediately below in contact with the uppermost layer; A method for simultaneous multilayer coating, characterized in that the coating composition is a hydrophilic coating composition having a viscosity of 3 to 100 centipoise at °C.