Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-03-03
2002-12-10
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
06492005
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ink jet recording sheet (hereinafter occasionally referred to as a recording sheet) and its production method, and specifically to an ink jet recording sheet which exhibits improved water resistance as well as improved light fastness, and its production method.
BACKGROUND OF THE INVENTION
In recent years, the image quality of ink jet recording has rapidly improved and has approached that of conventional photography. In order to realize such conventional photographic quality employing ink jet recording, improvements have been carried out in the area of the recording sheet. As a result, a recording sheet, which is comprised of a highly smoothened surface support having thereon a layer comprising minute voids, has been developed, and due to its excellent ink absorbability as well as ink drying properties, has become one of the recording sheets which are capable of producing images closest to that of conventional photography.
Accompanying such achievement of high quality image, still higher quality has been demanded for recording sheets. Specifically, an ink jet recording sheet, which is comprised of a water non-absorptive support having thereon an ink absorptive layer, is preferably employed, since it is capable of producing high quality prints due to its ability to maintain high smoothness during ink jet recording.
Further, in the ink jet recording, water-soluble dyes are commonly employed as colorants, and such water-soluble dyes are highly hydrophilic. Therefore, when recorded images are stored at high humidity for an extended period of time after recording, or a drop of water comes into contact with the recorded surface, the dyes tend to bleed.
In order to solve these problems, it is a general practice that dye-fixing materials are incorporated into the image receptive layer. Listed as such dye fixing-agent is a cationic fixing-agent such as inorganic pigment (fine alumina particles and the like) having a cationic surface, cationic polymer having quaternary ammonium bases in their molecules, and the like.
On the other hand, in ink jet recording, water-soluble dyes are commonly employed as colorants, and such water-soluble dyes are highly hydrophilic. Therefore, when recorded images are stored at high humidity for an extended period of time after recording, or a drop of water comes into contact with the recorded surface, the dyes tend to bleed. In order to solve these problems, it is a general practice that dye-fixing materials are incorporated into the image receptive layer. Listed as such dye-fixing agents are inorganic pigments (fine alumina particles and the like) having a cationic surface, cationic polymers having quaternary ammonium bases in their molecules, and the like.
The fine alumina particles themselves exhibit high dye fixability and are capable of converting an ink absorptive layer to a void layer, by using a small amount of binders (polyvinyl alcohol and the like). However, since the material cost is relatively high, it is not advantageously used in production of less expensive recording sheets.
On the other hand, cationic copolymers having the quarternary ammonium bases in their molecules, when used with various types of fine particles, are capable of providing water resistance to a void layer type ink absorptive layer.
When said cationic materials are incorporated into the porous layer, said disadvantage tends to be more marked. In addition, results of investigation performed by the present inventors have revealed that such a problem tends to occur in the areas where air is easily circulated.
Conventionally, it has been well known that antioxidants effectively minimize photofading in which oxygen is involved. However, according to the investigation results of the present inventors, photofading of images, which are recorded using a water-soluble phthalocyanine based dye on an ink jet recording sheet comprising a water non-absorptive support having thereon a void layer, has not been effectively minimized.
When added to an ink jet recording sheet, almost all compounds, which have been found to be effective, exhibit relatively sufficient minimization of photofading during the initial period of time. However, the effects tend to gradually decrease, over time, and photofading over a relatively long period of time, in which oxygen is involved, has not been satisfactorily minimized.
In order to improve the degradation of such light fastness, a number of proposals have been made regarding the addition of UV absorbers as well as various types of antioxidants.
However, the addition of such compounds to an ink jet recording sheet, comprising a void layer having high oxygen permeability, has resulted in unsatisfactory effects. When a large amount of various types of such fading resistant additives is added in order to obtain sufficient minimization of photofading, the ink absorbability of the void layer is markedly decreased.
In addition, conventional fading resistant additives surely exhibit effects during the initial period of time, when exposed to light. However, a problem occurs in which the effects are gradually lost when continually exposed to light.
Specifically, when a cationic polymer having quaternary ammonium bases in its molecule is employed, such problems are increased. Accordingly, it is sought that water resistance as well as light fastness be improved while the ink absorption rate is not adversely affected.
When the cationic polymer is employed, the degradation of light fastness is accelerated due to the void layer, and this cause has not been yet clarified. However, it is assumed that dyes tends to be fixed in a more upper layer, that is, a surface and to suffer the effects of oxygen.
Japanese Patent Publication No. 2-35675 describes an ink jet recording sheet in which light fastness is improved employing polyalkylenepolyamine-dicyandiamide ammonium salt condensation products as the cationic resin. Further, Japanese Patent Publication Open to Public Inspection No. 9-254529 describes an ink jet recording sheet which employs polyalkylenepolyamine-dicyandiamide condensation products comprising no quaternary ammonium salt structure, resulting in minimized yellow staining on the white background as well as minimized fading is minimized and improved water resistance.
When an ink absorptive layer is comprised of a void layer, during ink jet recording, uniform images without unevenness are obtained due to excellent ink absorbability. On the contrary, however, oxygen permeability is large due to the porous layer, and after image recording, images tend to fade due to light.
Specifically, when recording is carried out employing an ink jet recording sheet comprising a water non-absorptive support having thereon a porous ink absorptive layer, while employing a water based ink comprising water-soluble copper phthalocyanine as the ink colorant, it has been discovered that problems occur in which photofading tends to be accelerated depending on the ambient conditions.
The present inventors have diligently investigated this aspect and have discovered the following. Ink comprises low volatile, high boiling point organic solvents (diethylene glycol, glycerin, and the like) in an amount of about 30 percent by weight. Further, in said ink, the concentration of phthalocyanine based dye is relatively low (specifically, no more than about one percent by weight). When recording is carried out employing an ink jet recording sheet comprising a water non-absorptive support having thereon an ink absorptive layer, while employing the aforementioned ink, noticeable photofading of the copper phthalocyanine based dyes tends to occur.
Furthermore, it has been discovered that said photofading is dependent on the ambient conditions, especially humidity, and the higher the temperature, the more fading occurs. Investigation results indicated that oxygen also adversely affects said fading.
In the ink jet recording sheets described in said patent publications, only those employing water absorptive supports are described. The investigati
Hatano Osamu
Kasahara Kenzo
Ohbayashi Keiji
Bierman, Muserlian and Lucas
Hess Bruce H.
Konica Corporation
Nguyen Kimberly T.
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