Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-05-10
2003-04-15
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C156S235000, C427S146000, C427S152000
Reexamination Certificate
active
06548149
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording material and a process for producing the same. More particularly, the present invention relates to an ink jet recording material having excellent gloss, ink-receiving property, water-resistance, weather resistance and being capable of recording ink images with excellent color density and brightness and clarity, and a process for producing the same.
2. Description of the Related Art
The ink jet recording system is an ink image recording system wherein ink droplets are jetted through an ink-jetting nozzle toward a recording material and jetted ink droplets are absorbed in and fixed on the recording material, to form ink images. This ink jet recording system is advantageous in that full colored images can be easily formed and the printing noise is low.
The ink usable for the ink jet recording system contains a large amount of a solvent in which a coloring material is dissolved or dispersed and thus, to obtain a high color density of the recorded ink images, a large amount of the ink must be absorbed in the recording material. In the complete absorption of the ink droplets reached the recording material, a certain length of time is necessary. This feature of the ink jet recording system causes such a disadvantage that when the ink droplets are continuously jetted imagewise to form ink dots on the recording material surface, sometimes the ink droplets reach a target dot before an ink dot adjacent to the target dot has been completely absorbed in the recording material, and the target ink dot is connected to the adjacent ink dot so that the resultant ink image becomes unclear.
Accordingly, if the recording material for the ink jet recording system is to have such an advantage that the ink dots formed thereon have high color density and brightness and a high clarity, the ink droplets must be rapidly absorbed therein and even if the ink dots are overlapped on each other, substantially no blotting of the ink may occur.
When a coated paper sheet is used as a substrate for the ink jet recording material, at least one ink-receiving layer comprising a porous pigment is formed on the coated paper sheet to control the color brightness and sharpness of the ink images from which the image quality is established and to enhance the color-reproducibility and image-reproductivity. For example, Japanese Unexamined Patent Publication No. 62-111,782, No. 63-13,776 and No. 63-104,878 disclose an ink jet recording sheet having an ink-receiving layer containing primary or secondary pigment particles (usually, silica or alumina particles) having fine pores, and a binder. Also, Japanese Examined Patent Publication No. 63-22,977 discloses an ink jet recording sheet which has an ink-receiving layer including an uppermost layer provided with pores having a peak size of from 0.2 to 10 &mgr;m, and is capable of receiving an absorbed ink in voids having a size of 0.05 &mgr;m or less, and of forming ink images with a high quality.
Currently, due to the rapid spread of ink jet printers, various ink jet prints with a high gloss similar to that of photographic prints are demanded for publications and packing paper sheets. Particularly, in colored prints, film type or coated sheet type ink jet recording sheets which have high ink-absorbing and fixing rates and a high ink absorption are in great demand. To provide the above-mentioned ink-receiving layer having an increased porosity, it is necessary to use pigment particles having an increased particle size in the &mgr;m order or to utilize secondary particles of pigment. When the size of the pigment particles is increased, the resultant ink-receiving layer exhibits a decreased smoothness and a reduced light transmission. Namely, the resultant ink-receiving layer is opaque and has a poor gloss.
Various types of ink jet recording sheets having an ink-receiving layer containing a resin capable of dissolving therein the ink and of swelling by the ink are practically used. These types of ink jet recording sheets have an enhanced gloss. However, they are disadvantageous in that the resultant ink-receiving layer exhibits a low ink-drying rate and unsatisfactory resistance to moisture and water.
To enhance the smoothness and gloss of the ink-receiving layer, it has been attempted to form the ink-receiving layer in a two or more layered structure wherein an uppermost layer has a high gloss. This type of ink jet recording sheet is disclosed in, for example, Japanese Unexamined Patent Publications No. 3-215,080, No. 3-256,785, No. 7-89,220, 7-101,142 and 7-117,335. In this type of ink jet recording sheet, colloidal particles or a complex of colloidal particles are commonly used as a principal component of the high gloss layer. This type of high gloss layer is formed from the colloidal particles or complex thereof dispersed in a binder comprising a polymer latex, to establish a satisfactory transparency and ink-absorption. When the polymer latex is used as a binder, a plurality of small cracks are formed in the resultant coating layer. The small cracks are contributory to enhancing the ink-absorption of the ink-receiving layer. However, the small cracks cause the resultant ink dots formed on the cracked ink-receiving layer to have jagged circumferences significantly different from round circumferences, and thus the resultant ink images to exhibit reduced clarity and sharpness. Also, the small cracks cause the printed ink to spread on the ink-receiving layer and thus the ink dots to be enlarged. When the ink dots are formed in a usual density of the level of 360 dots per inch×360 dots per inch (dpi), the spread of the ink dots due to the small cracks of the ink-receiving layer does not cause any problems. However, if the ink dots are formed in a high density of the level of 720 dots per inch×720 dots per inch or more, the spread of the ink causes the spread ink dots to be connected to each other and thus the resultant ink images exhibits significantly reduced clarity and sharpness. Also, the colloidal particles in the uppermost high-gloss layer are primary particles and thus have substantially no fine pores capable of receiving the ink therein. Therefore, the ink is absorbed in the ink-fixing layer formed under the uppermost high-gloss layer. In the above-mentioned multi-layered ink-receiving layer, an ink-fixing layer is formed under the high gloss layer, and the thickness of the ink-fixing layer is larger than that of the high gloss layer. Also, the ink-fixing layer contains secondary particles of a pigment having a particle size in a &mgr;m order, the resultant multi-layered ink-receiving layer exhibits a significantly reduced transparency and thus the ink images fixed in the ink-receiving layer exhibit an unsatisfactory color density. Especially, this type of ink-receiving layer exhibits a reduced light reflection and thus an insufficient gloss.
To prevent the formation of the small cracks in the ink-receiving layer, Japanese Unexamined Patent Publication No. 7-117,334 provides an ink-receiving layer formed from a composition comprising pigment particles with a particle size of 0.1 &mgr;m or less and a polyvinyl alcohol with a degree of polymerization of 4,000 or more. The pigment particles are selected from primary pigment particles for example, colloidal silica or alumina sol. Therefore, in the resultant ink-receiving layer, the ink absorption and the transparency are unbalanced. Namely, since the pigment primary particles per se have no ink-absorption, the ink is absorbed in the gaps between the pigment primary particles. The gaps between the pigment primary particles in the ink-receiving layer are filled by a film-forming binder which is necessary to bond the pigment particles and to form an ink receiving layer. Therefore, the binder-filled gaps between the pigment particles exhibit a low ink absorption. To completely absorb a large amount of the ink, the ink-receiving layer must be formed in a large thickness. The ink-receiving layer with a large thick
Kubota Masami
Liu Bo
Mukoyoshi Shun-ichiro
Nemoto Hiroyuki
Arent Fox Kintner & Plotkin & Kahn, PLLC
Hess Bruce H.
Oji Paper Co. Ltd.
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