Coating processes – With post-treatment of coating or coating material – Solid treating member or material contacts coating
Reexamination Certificate
1999-06-28
2001-03-06
Bareford, Katherine A. (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Solid treating member or material contacts coating
C427S358000, C118S411000
Reexamination Certificate
active
06197379
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a simultaneous multilayer coating method for an organic solvent-based coating composition and a production method of a thermally developable photosensitive material using the same.
BACKGROUND OF THE INVENTION
Known as a photosensitive photographic material in which organic solvents are employed in composing layer coating compositions is a thermally developable photosensitive material called “Dry Silver”. This material commonly comprises a support having thereon two functional layers consisting of a photosensitive layer and a protective layer comprising dyes.
Cited as one method to provide a plurality of functional layers on a support is a successive multilayer coating method in which coating and drying of each layer are repeated, and employed are roll coating methods such as reverse roll coating, gravure coating, etc., or a blade coating, wire bar coating, die coating, etc.
There are simultaneous multilayer coating methods in which employing a plurality of coaters, before drying a previously coated layer, the subsequent layer is applied thereon, and a plurality of layers are simultaneously dried, or employing slide coating or curtain coating, simultaneous multilayer coating is carried out through laminating a plurality of coating compositions on the slide surface.
In the successive multilayer coating method, a plurality of passages through a coating and drying process are required. As a result, abrasion results due to contact with holding rolls in the transporting section, or the functional properties are degraded due to the relatively frequent contact with outside air. Further, coating defects are caused due to foreign matter introduced from the outside. Further, because a plurality of thermal drying processes are provided, from the viewpoint of utilization efficiency of energy, productivity is not good.
In the method in which employing a plurality of coaters, before drying a previously coated layer, the subsequent layer is coated, and a plurality of layers are simultaneously dried, coating defects caused by foreign matter introduced from the outside are markedly decreased. However, because so-called wet on wet coating is carried out, coating defects may be caused due to irregularities of the previously coated layer. The wet on wet coating as described herein denotes that a subsequent coating is carried out before the preceding coating has dried.
In the coating method in which a plurality of coating layers are laminated, coating defects caused by foreign matter introduced from the outside can be minimized. However, mixing between layer tends to result due to the flow, diffusion and density differences of each layer. Specifically in a coating composition employing organic solvents, differences in properties of solvents serves to enhance the mixing between layers, making it difficult to properly realize the function of each layer.
Specifically, in thermally developable photosensitive materials, when mixing occurs between the photosensitive layer and the protective layer, the amount and wavelength of light which passes through the photosensitive layer cannot be controlled. As a result, when the predetermined amount of exposure is given, an excessive shortage of exposure may occur and during subsequent thermal development, the photosensitive layer in a semi-melted state may move up to the surface of the protective layer to deteriorate the properties of the photographic material, and further, to stain the heating roll of the development device.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention has been accomplished. An object of the present invention is that a plurality of functional layers are coated employing a simultaneous multilayer coating method so that no mixing between layers results. Another object is that a thermally developable photosensitive material is produced employing a simultaneous multilayer coating method.
The invention and embodiment thereof are described. A multilayer coating method comprising a step to form at least two layers in such a manner that at least two coating compositions based on different solvents are coated onto a support, of at least said two layers, the layer other than the layer adjacent to said support is coated onto a layer lower than the layer, before the coating composition of the layer adjacent to the layer has been dried, of at least said two layers, the viscosity of the uppermost layer is at least 0.1 Pa.s during coating and of at least said two layers, the viscosity of the layer other than said uppermost layer is at least 0.03 Pa.s.
In a method according to the Invention, at least two types of said organic solvent-based coating compositions satisfy the formula described below:
&mgr;1/&mgr;2<2
wherein &mgr;1 represents the viscosity of the coating composition at a shear rate of A1 at 25° C., and &mgr;2 represents the viscosity of the coating composition at a shear rate of A2 at 25° C., and A1<A2.
Desirably, A1 is 100 S
−1
and A2 is at least 200 S
−1
; it is preferred that A2 is 400 S
−1
. The viscosity of the uppermost layer coating composition is advantageously between 0.1 and 1 Pa.s during coating, and the viscosity of coating compositions of layers other than said uppermost layer is between 0.03 and 0.7 Pa.s during coating. When the viscosity of the coating composition of the uppermost layer is between 0.3 and 0.7 Pa.s during coating, the viscosity of the coating compositions of layers other than said uppermost layer is usefully between 0.2 and 0.6 Pa.s.
The absolute value of the difference between the viscosity of the coating composition of said uppermost layer during coating and the viscosity of the coating composition of the layer other than said uppermost layer during coating is no more than 0.3 Pa.s. Desirably, the shear rate of at least two types of said organic solvent-based coating compositions during coating is between 200 and 500 S
−1
. The Invention also includes a multilayer coating method in which an uppermost layer coating composition having a viscosity of 0.1 to 1 Pa.s during coating, and other coating compositions having a viscosity of 0.03 to 0.7 Pa.s during coating are ejected from the slit of an extrusion-type die coater, laminated, and coated onto a support under a manifold pressure of 10 to 500 kPa during coating.
The Invention further comprises a multilayer coating method in which an upper layer coating composition having a viscosity of 0.1 to 1 Pa.s during coating and a lower layer coating composition having a viscosity of 0.03 to 0.7 Pa.s during coating are ejected from two 50 to 400 &mgr;m slits of an extrusion-type die coater, laminated, and coated onto a support under a manifold pressure of 10 to 500 kPa so as to obtain a total wet thickness of 50 to 200 &mgr;m.
The Invention further includes commencing drying of said at least two layers within 10 seconds after coating at least two different said organic solvent-based coating compositions.
It is also useful to coat said at least two organic solvent-based coating compositions by employing an extrusion-type die coater. The manifold pressure for said at least two organic solvent-based coating compositions is between 10 and 500 kPa.
The other embodiments are described.
In a multilayer coating method in which the viscosity of an uppermost layer coating composition is adjusted to at least 0.1 Pa.s during coating, while the viscosity of the other layer coating composition is adjusted to at least 0.03 Pa.s, and a plurality of organic solvent-based coating compositions are coated onto a support employing wet on wet, each coating composition is ejected from an extrusion-type die coater and laminated, the content of the organic solvent in each coating composition, which is employed in each composition in common, is more than other organic solvents, and the coated material is forwarded to a drying process within 10 seconds after coating.
A multilayer coating method wherein an uppermost layer coating composition, having a viscosity of 0.1 to 1 Pa.s during coat
Bareford Katherine A.
Bierman Jordan B.
Bierman, Muserlian and Lucas
Konica Corporation
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