Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2000-09-11
2001-07-03
Schilling, Richard L. (Department: 1752)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S407000, C428S447000, C428S511000, C428S513000, C430S510000, C430S523000, C430S536000, C430S538000, C106S443000
Reexamination Certificate
active
06254992
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a support for recording sheet. More specifically, the present invention relates to a support for recording sheet which is provided with a substrate having disposed on both sides thereof a coating layer of a water-resistant resin, which support for recording sheet has excellent image sharpness (resolution) and excellent image light-fading resistance.
2. Description of the Related Art
Conventionally, support for recording sheets coated with a resin on both sides, such as photographic printing paper, thermographic paper, full color thermographic paper, and the like have been known. In particular, titanium dioxide, pigments, blueing agents (including blue pigments), fluorescent brighteners, and the like have been included in the coating layer of the paper used for photographic printing paper (U.S. Pat. No. 3,501,298).
The titanium dioxide used in this case has an effect of heightening the efficiency of light reflectance, and it is known that the more the content of the titanium dioxide is increased, the more image resolution is improved.
At the time a coating layer of a water-resistant resin is formed, the water-resistant resin which contains titanium dioxide is melted and extruded in the form of film from a slit die for a short period of time. However, when the titanium dioxide is incorporated in the resin coating in an amount of 20 wt % or more and the molten extrusion is conducted at a discharge temperature of 290° C. to 350° C., as has conventionally been the case, cracks (hereinafter referred to as “film cracking”) are caused in the coating layer of the water-resistant resin, and stripes (hereinafter referred to as “die-lip stripes”) are easily generated at the die-lip portion of the extruder.
When such film cracking occurs, the external appearance of the product not only deteriorates, but also, the product is deprived of its commercial value due to the loss of its water-resistant capability. Further, when die-lip stripes are generated, consecutive stripes are formed in the longitudinal direction on the surface of the manufactured film or laminate. Therefore, not only does the external appearance of the product deteriorate remarkably, but even during secondary processing such as drawing, the transparency of the film is non-uniform, and thus the commercial value of the product is lowered considerably.
In order to overcome such drawbacks, as the applicants of Japanese Patent Application Laid-Open (JP-A) No. 10-307367 have already noted and disclosed, by using a titanium dioxide pigment in which the particle surface of the titanium dioxide to be used has been subjected to a wet-process silane coupling agent coating treatment, the titanium dioxide pigment can easily be incorporated in an amount of 20 wt % or more in a polyolefine resin layer. Therefore, even when the water-resistant resin is extrusion molded at a melting temperature of around 325° C., there are no occurrences of film cracking, die-lip stripes and the like.
The present inventors examined in detail the aforementioned high-resolution support for recording sheet. It was found that with the silane coupling agent coating treatment, although the titanium dioxide can be melted and extruded at a high temperature, the generation of die-lip stripes cannot be controlled completely since the activity of the titanium dioxide is not inhibited. It was also noted that there is a tendency for the light fading resistance of the print surface of the support for recording sheet to deteriorate.
Further, JP-A No. 10-307367 discloses that by surface treating the titanium dioxide with Al
2
O
3
, aggregation of the titanium dioxide pigment at the time of lamination is prevented. However, when the Al
2
O
3
treatment is used, effects with regard to high filling capability and fading resistance remain insufficient.
SUMMARY OF THE INVENTION
As a result of their extensive studies to produce a high-resolution support for recording sheet in which light fading resistance is not harmed and the occurrence of die-lip stripes is inhibited, the present inventors devised the present invention. Although the mechanism resulting in the working of the present invention is not altogether clear, it was found that by using a titanium dioxide pigment whose particle surface has been subjected to a wet-process coating treatment with a silane coupling agent and aluminum phosphate in an amount of 0.05 to 1.2 wt %, the titanium dioxide pigment can easily be incorporated in an amount of 20% by weight or more in a polyolefine resin layer without hindering the production of the titanium dioxide pigment. Therefore, even when the titanium dioxide is extrusion molded at a melting temperature of around 325° C., there is no film cracking, the generation of die-lip stripes is inhibited, and excellent light-fading resistance is preserved.
In accordance with an aspect of the present invention, a support for recording sheet comprising: (a) a substrate having an image printing side and another side opposite the image printing side; (b) a water resistant resin coating layer provided on each side of the substrate, at least the resin coating layer provided on the image printing side containing a titanium dioxide pigment, the titanium dioxide pigment including a titanium dioxide having a particulate surface treated by a silane coupling agent and aluminum phosphate in an aqueous slurry state, with a treatment amount of the aluminum phosphate with respect to the titanium dioxide being from 0.05 wt % to 1.2 wt %.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A detailed description of a support for recording sheet and a manufacturing method thereof will be given hereinafter. In the present invention, a layer for coating the surface of a substrate can be a single layer structure, or a multilayer structure formed by two or three layers.
A water-resistant resin for forming a coating layer in the present invention can be appropriately selected from resins which can be molten and extruded at a temperature of 170° C. to 345 ° C. However, ordinarily, a polyolefine resin such as polyethylene or polypropylene is used.
The polyethylene may be high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (L-LDPE), or the like. However, when the rigidity of a support for a photographic printing paper is considered to be important, polypropylene, high density polyethylene (HDPE), linear low density polyethylene (L-LDPE), or the like is preferably used.
These resins can be used solely, or two or more thereof can be used in combination. In the present invention, from the standpoint of improving image quality, titanium dioxide is contained in at least one layer of a water-resistant resin coating layer at the side at which an image is formed, and a blueing agent, a fluorescent brightener, or the like is preferably contained therein. The amount of titanium dioxide which is contained in at least one layer of a water-resistant resin coating layer can also be 13 wt % or more, or 20 wt % or more. From the standpoint of improving adhesiveness between the water-resistant resin coating layer and substrate, a tackifier resin, an adhesive resin, or the like can be included in the lowermost layer of the water-resistant resin coating layer which comes into contact with the substrate. Further, in accordance with the intended use of the support for recording sheet, an antioxidant, a release agent, a hollow polymer, or the like can be appropriately contained.
The form of the titanium dioxide pigment used in the present invention can be either anatase-type or rutile-type. However, when the degree of whiteness is considered to be important, an anatase-type titanium dioxide pigment is preferably used. When sharpness is considered to be important, a rutile-type titanium dioxide pigment is preferably used. Further, in consideration of both the degree of whiteness and sharpness, an anatase-type titanium dioxide pigment and the rutile-type titanium dioxide pigment can be used in combination. Alternately,
Fuji Photo Film Co. , Ltd.
Schilling Richard L.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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