Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-06-20
2003-01-14
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
Reexamination Certificate
active
06506479
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ink jet recording paper which is advantageously used when fine liquid droplets, e.g., aqueous ink are jetted from a nozzle to print a monochrome or full-color image nobly thereby making a poster or a signboard.
2. Description of the Related Art
Conventionally, current recording systems include, for example, a heat melting type thermal transfer system, sublimation type thermal transfer system, electrophotographic system and ink jet system. In recent years, an ink jet recording system have been dominantly used in view of calm sound during recording, high speediness, suitability to the recording of a large-sized image and running costs. While, there have been increased needs of making full-color and large-sized posters, signboards or the like in small lots and delivering in a short time and hence an ink jet printer using aqueous ink has attracted remarkable attention.
In the aforementioned situation, it is demanded of large-sized ink jet recording paper to be used outdoors that when an appropriate film is laminated on an ink-receiving layer and the paper is posted outdoors after a printing is made on the ink-receiving layer, the laminated film and the ink-receiving layer are not peeled when the paper is fluttered in the wind or submersed under rain water.
However, when hydrophilic components are contained in the ink-receiving layer in a large amount even if the ink-receiving layer is coated with a laminate film, water such as rain water enters toward the center of the paper through the ink-receiving layer from the non-laminated end surface of the recording paper, rendering the peeling easy.
Generally, interfacial peeling or cohesive failure arises in the most weakened interface or layer. In the case as aforementioned, it is inferred that water reaches the interface between the ink-receiving layer and an anchor coating layer which applies the receiving layer to a substrate to weaken the adhesive strength of the interface, causing peeling. Here, the interfacial peeling means the case where peeling takes place at the boundary with which each layer is in contact and the cohesive failure means the case where a layer itself is broken and peeled.
It is to be noted that the adhesive strength between the ink-receiving layer and the laminate film adhesive layer is needed to stand against the fluttering in the wind and the adhesive strength obtained after a laminate film is applied and soaked in water is needed to stand against the submersion under water.
Various improved techniques have been developed to solve the peeling problem as aforementioned.
If the amount of hydrophilic cationic components to be added to the ink-receiving layer is decreased to deal with the problem as aforementioned, the reduction in adhesive strength when the paper is submerged under rain water is restrained but the fixing ability of ink is decreased due to the reduction in the amount of cationic components and there is a possibility of bleeding of ink.
There is a method of improving adhesive strength by increasing the content of a resin in the ink-receiving layer. However, in this method, the ink-absorbing power is hindered and there is a fear that the bleeding of ink and drying inferior are caused.
SUMMARY OF THE INVENTION
Accordingly it is an object of the present invention to provide a new ink jet recording paper having high peeling strength so as to provide high laminate peeling strength in a dry condition, of course, and when the paper is submerged under water even if a cationic ink-fixing agent and filler are added in a considerable amount in an ink-receiving layer.
The structure of the present invention which has been made for the purpose of solving the above problems is characterized in that, in an ink jet recording paper provided with an ink-receiving layer, containing at least a resin and a pigment, on a substrate, major components forming an anchor coating layer of the receiving layer are a styrene/acryl copolymer resin having a glass transition point of 0° C. or more and 20°C. or less and calcium carbonate.
Specifically, the ink jet recording paper of the present invention comprises a substrate, an anchor coating layer formed on at least one surface of the substrate and an ink-receiving layer disposed on the anchor coating layer. Major components forming the anchor coating layer are a styrene/acryl copolymer resin having a glass transition point of 0° C. or more and 20°C. or less and calcium carbonate. Therefore, even if a cationic ink-fixing agent and filler are added to the ink-receiving layer in a considerable amount, no interfacial peeling takes place at the interface between the ink-receiving layer and the anchor coating layer. Also, laminate peeling strength can be improved by mixing the styrene/acryl copolymer resin and calcium carbonate in the anchor coating layer in a specific solid weight ratio. Specifically, ink jet recording paper having a dry laminate peeling strength of 7000 N or more and wet laminate peeling strength of 800 N or more can be obtained. As the aforementioned calcium carbonate, an aragonite type may be used.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the present invention will be hereinafter explained in detail.
In the basic layer structure of the ink jet recording paper of the present invention, an anchor coating layer is formed on at least one surface of a substrate and an ink-receiving layer is disposed on the coating layer. As required, a foam plastic film for improving the carriage ability and an adhesive layer provided with peelable paper applied to the outer surface thereof may be formed on the other surface of the substrate.
Given as examples of the substrate used for the recording paper of the present invention are plastic films and synthetic papers. They may be provided with voids in the inside thereof and made opaque by adding a filler. They may also be provided with corona treatment or adhesion-easing treatment to improve the adhesive property and the wettability. The thickness of the substrate is 10 to 400 &mgr;m and preferably 50 to 200 &mgr;m.
Next, the anchor coating layer formed on the substrate comprises a resin used primarily as an adhesive and a pigment used as an adhesion-improver.
As the resin for the anchor coating layer, a styrene/acryl copolymer resin having a glass transition point Tg of 0° C. or more and 20° C. or less. As the pigment, calcium carbonate is used.
The action mechanism by which the anchor coating layer produced by mixing the styrene/acryl copolymer resin having a glass transition point Tg falling in the above range and calcium carbonate and applying the mixture improves the water resistance is not clear. However, it is thought that when water, e.g., rain water, penetrates to the ink-receiving layer as the top coating layer and reaches the interface between the top coating layer and the anchor coating layer, the anchor coating layer scarcely absorbs water. Then, the hydrophilic resin of the top coating layer is swollen by water and is reduced in the adhesion to the anchor coating layer. At this time, when calcium carbonate exists in the anchor coating layer, cracks are formed in the surface layer of the anchor coating layer and the top coating layer penetrates into the cracks thereby improving the bonding strength.
Also, it is inferred that the presence of calcium carbonate in the anchor coating layer lowers the smoothness of the surface of the coating layer and improves the wettability when the top coating layer is applied, thereby improving the adhesion.
In the case where the blocking of the anchor coating layer takes place when calcium carbonate is independently used as a pigment, an organic or inorganic filler such as a plastic pigment or silica may be optionally added.
Among calcium carbonates, aragonite types are particularly preferred. The crystal forms of calcium carbonate are divided into hexagonal calcite types, vaterite types and prismatic aragonite types. There is a tendency that the aragonite type has stronger wet laminat
Duane Morris LLP
Grendzynski Michael E.
Hess Bruce H.
Nisshinbo Industries Inc.
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