Coating processes – Applying superposed diverse coating or coating a coated base – Synthetic resin coating
Reexamination Certificate
2002-10-08
2004-06-08
Bareford, Katherine A. (Department: 1762)
Coating processes
Applying superposed diverse coating or coating a coated base
Synthetic resin coating
C427S420000
Reexamination Certificate
active
06746718
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for producing an information recording material and a coating solution for use therein. More specifically, the present invention relates to a process for well productively producing an information recording material such as a thermal recording material or an inkjet recording material excellent particularly in the quality of coating layers and excellent in various properties, and a coating solution for use in this process.
TECHNICAL BACKGROUND
Information recording materials having an information-recording layer formed on a substrate are used in broad fields. A variety of recording materials such as a pressure-sensitive recording material, a heat-sensitive recording material, a photo-sensitive heat-sensitive recording material, a photo-sensitive pressure-sensitive recording material, a thermal transfer recording material, an inkjet recording material, etc., are practically used as such information recording materials. In recent years, information recording materials having two or more layers formed on a substrate are also used to comply with demands for higher functions and higher performances.
A thermal recording material is generally a material in which a heat-sensitive recording layer containing a thermally color-formable material is formed on a substrate. The thermal recording material is heated with a thermal head (hot head), a thermal pen, laser light, or the like, to form an image.
The above thermal recording material is advantageous in that a recording can be obtained with a relatively simple unit, that maintenance is easy and that no noise is made, so that it is widely used in the fields of measuring recorders, facsimile machines, printing machines, computer terminals, labels, automatic vending machines of tickets, etc. In recent years, further, for attaining superior color density and sensitivity, image stability and tones of a plurality of colors, there are practically used thermal recording materials having at least one protective layer or undercoat layer or both and two or more heat-sensitive recording layers, in addition to a thermal recording material having a single heat-sensitive recording layer alone.
An inkjet recording method is a method in which fine globules of an ink are ejected from an inkjet recording device and allowed to adhere to an inkjet recording material to form an image or letters. As the above inkjet recording material, a material such as a non-coated paper having no ink receptor layer is sometimes used. However, an ink receptor layer is formed on a substrate for use when printing is made on a synthetic resin film having no ink-reception properties or when it is intended to obtain a finer image. With diversification in use, color imaging or higher performances such as faster printing in recent years, a larger amount of an ink is ejected, and a higher-capacity ink absorption and a higher print density come to be required. Since no sufficient performances for the above requirements can be obtained with any conventional single ink receptor layer, an inkjet recording material having two or more ink receptor layers are practically used as well.
In a conventional information recording material having two or more layers laminated on a substrate, each layer is independently formed by application and drying to form the laminated layers, and the application is carried out by a method such as an air knife coating method, a blade coating method, a rod coating method or a reverse roll coating method. However, an information recording material prepared by any one of the above methods has problems that the quality of coating layers is poor, that an upper layer has pin holes caused by infiltration of an upper layer coating solution into a lower layer and repellency during application to form the upper layer and that the quality varies due to continuous coating for a long period of time. Moreover, there are problems in a limit to application at a high rate and a decrease in productivity due to application procedures to be carried out a plurality of times.
As compared with these methods, the curtain coating method disclosed in Japanese Patent Publication No. 49-24133, etc., is a method in which a free-fall curtain of a coating solution is formed and allowed to collide with a substrate to apply the coating solution to the substrate, and it is known that the curtain coating method achieves a good quality of coating layers and has suitability to application at a high rate. Further, since a plurality of layers can be simultaneously formed by curtain-coating of a coating composition film formed of a plurality of coating solution layers, the productivity in multi-layer application can be improved to a great extent. In the simultaneous multi-layer application using a curtain coating method, the coating composition film made of a plurality of coating solution layers is formed, and thereafter, it is required to dry the coating composition film to solidness without disturbing the layer structure thereof. When the layer structure is disturbed to cause an intermingling of layers, the layers comes to exhibit no sufficient functions thereof, so that an information recording material is degraded in various properties. In the field of conventional photographic photosensitive materials prepared by simultaneous multi-layer application using a curtain coating method, generally, each coating solution contains gelatin as a binder, and coating composition layers are cooled immediately after coating composition solutions are transferred onto a substrate, so that the coating solutions are immobilized by gelling of the gelatin therein, whereby no intermingling of the layers takes place.
In the information recording material, for example, in a heat-sensitive recording material, there is a problem that addition of gelatin sufficient for immobilizing coating solutions by cooling degrades various properties such as color-formability, image stability, etc., to a great extent. An inkjet recording material involves problems that no sufficient ink absorption capacity or absorption rate can be obtained. Further, there has been found no method of immobilizing coating solutions with any other substance than gelatin without impairing the above properties, and it is not yet possible to prevent the intermingling of layers by a method similar to the method employed for a photographic photosensitive material.
Meanwhile, unlike a photographic photosensitive material, most of information recording materials use a substrate having a very high water absorbing property such as paper, and a layer having a high water absorbing property is pre-coated on a substrate in many cases. When a coating composition film made of a plurality of layers of coating solutions is curtain-coated on such a substrate, water in the coating solution of the lowermost layer constituting the above coating composition film migrates into the substrate or a layer pre-coated on the substrate, and water in the coating solution of one upper layer accordingly migrates into another lower layer. The problem is that non-water components contained in layers also migrate from one upper layer to another lower layer due to the migration of water and cause the intermingling of layers.
DISCLOSURE OF THE INVENTION
It is a first object of the present invention to overcome the above drawbacks of prior art and provide a process for efficiently producing an information recording material such as a heat-sensitive recording material, an inkjet recording material, or the like, which is particularly excellent in the quality of coating layers and excellent in various properties.
It is a second object of the present invention to provide coating solutions suitable for use in the above process.
The present inventors have made diligent studies for achieving the above objects, and as a result, in the process for the production of an information recording material having an information recording layer formed on a substrate, it has been found that the first object can be achieved by
(1) curtain-coati
Bareford Katherine A.
Mitsubishi Paper Mills Ltd.
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