Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-12-08
2002-05-21
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S328000, C428S331000
Reexamination Certificate
active
06391428
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a recording material that can be print on with ink containing water-soluble dye. In particular, the present invention relates to an ink jet recording sheet which provides a superior combination of ink absorbency, ink coloration, resistance of the recorded image to light, resistance of the recorded image to water and surface gloss.
PRIOR ART
Ink jet recording is a method by which fine ink drops are jetted out using any kind of jetting method to form an image on a recording material. Since this method enables a recording apparatus to be operated at a high speed and the apparatus is generally inexpensive, the use of ink jet recording systems has been spreading rapidly. Moreover, the use of multicolor ink jet recording methods enables the formation of color images comparable to silver-salt films with high resolution and high quality. Digital images, for example those obtained by a digital camera, are increasingly printed with an ink jet printer. The recorded materials are more often being displayed or stored for considerably long period because of the high image quality. Therefore, it is desirable that the ink jet recording materials have good preservation characteristics, especially good light resistance, as well as high image quality.
Ordinary ink jet recording sheets, printed by an ink jet printer, are discolored by the UV light in the sunlight or fluorescent lamps. Therefore some countermeasures for this problem have been attempted to improve the long-term preservation properties of the sheet. Although some attempts utilized a pigment ink system with a pigment resistant to discoloration, in most instances it is attempted to improve the light resistance by using a dye ink system because dye ink system provide sharper images.
As examples of means to improve the light resistance, for example, a process to add UV absorber such as benzophenones and benzotriazoles (Japanese Tokkai Sho 57-87988 and Japanese Tokkai Sho 63-222885, “Tokkai” means an “unexamined published patent application”), a process to add antioxidant such as hindered amines (Japanese Tokkai Sho 61-146591), a process to add zinc oxide and cationic resins concurrently (Japanese Tokkai Hei 7-32725) and the like have been disclosed. However, since these additives are difficult to disperse evenly in the materials, these attempts did not provide a satisfactory improvement.
As a method to attain the high image quality by increasing the gloss of the recording sheet, for example, a process to use cationic colloidal silica (Japanese Tokkai Hei 6-92011) has been proposed, but this process can not provide a sufficient balance between the image quality and the image preservation.
Moreover, a process to improve the water resistance of the recording layer by setting up a coating layer comprising a colloidal silica that couples like beads and a water-soluble polymer (Japanese Tokkai Hei 5-51469) have been proposed, but this process can not achieve sufficient water resistance and its light resistance is still insufficient.
PROBLEMS ENCOUNTERED
The objective of this invention is to provide a recording material that can be recorded by ink with water-soluble dye, particularly to provide an ink jet recording sheet, which is superior in ink absorbency, ink coloration, light resistance, water resistance and surface gloss.
SUMMARY OF THE INVENTION
One subject of the present invention is an ink jet recording sheet having on an ink-receiving support an image preserving layer comprising anionic colloidal silica and zinc oxide particulates with an average particle size of about 15 to 380 nm and having a 75 degree specular glossiness of at least about 25% at the surface. Another subject of the present invention is an ink jet recording sheet having on an ink-receiving support, in succession, an image preserving layer comprising an anionic colloidal silica and zinc oxide particulates with an average particle size of about 15 to 380 nm and a fixing layer comprising a cationic colloidal silica and a cationic polymer electrolyte.
DETAILED DESCRIPTION OF THE INVENTION
The support used in the present invention may be any of known supports capable of absorbing an ink containing a water-soluble dye, is preferably a support having an ink-receiving layer comprising a pigment and a binder on a base paper.
The image preserving layer formed on the ink-receiving layer mentioned before comprises zinc oxide particulates with an average particle size of about 15 to 380 nm, preferably about 20 to 300 nm, which absorbs UV light, and anionic colloidal silica, which is compatible with said particulates and can provide a glossy surface property in order to obtain compatibility between the light resistance and the high quality of recorded image.
Colloidal silica of this invention is the stabilized colloidal solution of silica to make its utilization easy, as described in Kagaku Binran (Chemical Reference Guide) published by Maruzen, Oct.15, 1986.
When the average particle size of zinc oxide particulates is less than 15 nm, the image-preserving layer is very closely packed and therefore has a poor ink absorbency, which not only makes it difficult to obtain images of high quality but also causes problems in cost and operability. On the other hand, when the average particle size is larger than 380 nm, the transparency of the image-preserving layer becomes worse due to light scattering thereby reducing the recorded density. The average particle size of zinc oxide particulates is measured by using a scanning electron microscope.
Since the surfaces of the zinc oxide particulates, which are necessary to impart light resistance, are negatively charged, the colloidal silica, which is necessary for glossy surface, needs to be anionic colloidal silica. Since the isoelectric point of anionic silica is usually around pH 2, the silica is negatively charged in the almost all range above pH 2, which is suitable for this invention. On the contrary, the colloidal silica that is reversely charged by having cations, for example, obtained by hydrolysis of metal salts, absorbed on the surface, has problems in operability due to poor compatibility with the zinc oxide particulates.
The configuration of the anionic colloidal silica is preferably non-spherical shape, in which several particulates interlink as in a shape of beads or a ring.
It is desirable that the coverage of the image-preserving layer be about 1 to 6 g/m
2
, preferably about 1.5 to 5 g/m
2
, on a dry solids basis. When the coverage of the image-preserving layer is less than 1 g/m
2
, sufficient light resistance and surface gloss cannot be attained. On the other hand, when the coverage is larger than 6 g/m
2
, the ink absorbency of the layer becomes poor and high quality images cannot be obtained.
The content of the zinc oxide particulates in the image-preserving layer is desired to be about 2 to 25 parts by weight, preferably about 3 to 20 parts by weight based on the 100 parts by weight of the anionic colloidal silica. When the content of the zinc oxide particulates is less than 2 parts by weight, sufficient light resistance cannot be attained. On the other hand, when the content is larger than 25 parts by weight, the recorded density and the surface gloss become poor and high quality images cannot be obtained.
Further, the 75 degree specular glossiness of the image preserving layer needs to be at least about 25%, preferably at least about 30% at the surface, measured in accordance with JIS(Japanese Industrial Standards) P8142, in order to obtain sufficient reproducibility of image similar to a silver salt film.
The base paper used for an ink-receiving support of the present invention can be made from various types of paper pulps. Examples of the pulp for paper include chemical pulp such as LBKP (hardwood bleached pulp) and NBKP (softwood bleached pulp), mechanical pulp such as GP(groundwood pulp) and TMP(thermo mechanical pulp), waste paper pulp and mixture thereof, but the pulp is not limited to those.
Various additives, such as fillers, sizing agents and paper reinf
Chatani Akinobu
Kondo Noboru
Kuroyama Yoshihiro
Ueno Takashi
Cohn PLLC Gary C.
Hess Bruce H.
Nippon Paper Industries Co. Ltd.
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