Stock material or miscellaneous articles – Ink jet stock for printing – Particles present in ink receptive layer
Reexamination Certificate
1999-04-27
2004-01-27
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Ink jet stock for printing
Particles present in ink receptive layer
C428S032310
Reexamination Certificate
active
06682788
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an aqueous coating composition containing inorganic fine particles and polyvinyl alcohol, espciaaly suitable for high speed drying, coating method thereof, coated product and an ink-jet recording sheet (hereinafter, occasionally referred to as recording sheet). The present invention also relates to an ink-jet recording sheet specifically having a void-type ink absorbing layer which specifically exhibits excellent water resistance, ink absorbability, and glossiness, and minimizes cracking.
BACKGROUND OF THE INVENTION
In recent years, the image quality of ink-jet recording has improved rapidly and is approaching that of photography. In order to achieve such photographic image quality employing ink-jet recording, improvement has been carried out with respect to the recording sheets. A recording sheet prepared by providing a fine void layer as an ink absorbing layer on an extremely smooth support is becoming one of sheets forming images most similar to photographic image quality, due to its high ink absorbability and excellent drying properties.
Generally employed as the extremely smooth support are supports which do not absorb ink, such as polyester film, polyolefin film, or paper supports covered with polyolefin. When an ink absorbing void layer is provided onto such a support that does not absorb ink, it is necessary to provide a coated layer having an adequate thickness in order to absorb sufficient ink. Generally, when a void layer is coated onto such a support that does not absorb ink, it is necessary to coat a layer having a dry thickness of at least 30 &mgr;m and preferably at least 35 &mgr;m.
When a layer is applied so as to obtain a dry layer thickness of at least 30 &mgr;m, it is necessary to apply a layer having a large wet thickness of at least 100 &mgr;m, and generally of at least 130 &mgr;m.
When an aqueous coating composition is coated onto a support so as to obtain such a large wet thickness, problems occur such that drying takes long time and non-uniformity tends to result due to the unevenness of the coated composition during drying.
Water, which is a major solvent in an aqueous solution, has a relatively high boiling point. Therefore, when drying is carried out employing only a thermal process, a remarkably long drying time as well as a huge drying zone is required.
On the other hand, while drying is carried out over such a long time, the coated composition moves locally due to various causes, so that a non-uniform coated surface is formed due to the formation of the so-called unevenness of the coated composition. When the unevenness of the coated composition occurs, the coated surface becomes non-uniform, and consequently, because a thick area is wound prior to complete drying, serious manufacturing problems may occur.
As an example in which a thick wet layer is formed by coating an aqueous coating composition, is listed the coating of a silver halide photographic emulsion comprising gelatin as a hydrophilic binder. An aqueous gelatin solution is generally in an aqueous solution state at at least 30° C., but exhibits gelled characteristic below 20 to 25° C. Utilizing this characteristic, after an aqueous solution comprising gelatin is applied onto a support, the resulting coating is chilled, and gells. Thereafter, the coating can be dried with strong blasts of air heated to a relatively low temperature (of about 20 to about 60° C.). Accordingly, gelatin can be dried within a relatively short period of time, irrespective of the wet layer thickness.
In the case of a coating layer in which gelatin can be employed, it is possible to carry out rapid drying, utilizing the characteristic of gelatin. However, in the case of the coating composition which forms a void layer, gelatin is not applicable as a major hydrophilic binder.
Namely, when gelatin is employed as a major binder in the void layer, during ink-jet recording, ink swells the gelatin to immediately clog the voids. As a result, the advantages of the voids cannot be utilized.
A technique has not been discovered, which can uniformly and highly productively coat a void layer having a large thickness, without employing gelatin in a substantial portion.
Ink-jet recording is carried out in such a manner that fine droplets of ink are allowed to fly employing various working principles and are adhered onto a recording sheet such as a sheet of paper to record images and characters. Ink-jet recording exhibits advantages such as relatively high speed, low noise, ease of multicolor production, and the like.
Conventional problems of this system regarding clogging of nozzles and maintenance have been solved by improving both aspects of ink and the device, and at present, ink-jet recording has been rapidly applied to a variety of fields such as various printers, facsimile machines, computer terminals, and the like.
Requirements for a recording sheet employed in such ink-jet recording system is that the density of printing dots is high; color tone is bright and clear; ink is rapidly absorbed and when printing dots are superimposed, ink should neither run out nor blot; the diffusion of a printing dot in the lateral direction should not be greater than that needed and the circumference should be smooth and result in no blurring; and the like.
Particularly, at low rates of ink absorption, when recording is carried out by superimposing at least two color inks, on a recording sheet, droplets result in repellence to cause unevenness and in the boundary area of different colors, mutual colors result in blurring. As a result, image quality tends to be markedly degraded. Therefore, it is required that the recording sheet exhibit high ink absorbability.
In order to solve these problems, conventionally, a great number of techniques have been proposed.
For example, Japanese Patent Publication Open to Public Inspection No. 52-53012 describes a recording sheet in which minimally sized base paper is damped with paint employed for surface treatment; Japanese Patent Publication Open to Public Inspection No. 55-5830 describes a recording sheet comprising a support in which an ink absorbing coating layer is provided on the surface of the support; Japanese Patent Publication Open to Public Inspection No. 56-157 describes a recording sheet comprising a covering layer containing non-colloidal silica powder as a pigment; Japanese Patent Publication Open to Public Inspection No. 57-107873 describes a recording sheet comprising an inorganic pigment and an organic pigment in combination; Japanese Patent Publication Open to Public Inspection No. 58-110287 describes a recording sheet which exhibits a void distribution with two peaks; Japanese Patent Publication Open to Public Inspection No. 62-111782 describes a recording sheet composed of an upper porous layer and a lower porous layer; Japanese Patent Publication Open to Public Inspection Nos. 59-68292, 59-123696, 60-18383, etc. describe a recording sheet having amorphous cracking; Japanese Patent Publication Open to Public Inspection Nos. 61-135786, 61-148092, 62-149475, etc. describe a recording sheet having a fine powder layer; Japanese Patent Publication Open to Public Inspection Nos. 63-252779, 1-108083, 2-136279, 3-65376, 3-27976, etc. describe a recording sheet comprising pigments and fine silica particles having specified physical parameters; Japanese Patent Publication Open to Public Inspection Nos. 57-14091, 60-219083, 60-210984, 61-20797, 61-188183, 5-278324, 6-92011, 6-183134, 7-137431, 7-276789, etc. describe a recording sheet containing fine silica particles such as colloidal silica; Japanese Patent Publication Open to Public Inspection Nos. 2-276671, 3-67684, 3-215082, 3-251488, 4-67986, 4-263983, 5-16517, etc. describe a recording sheet containing fine hydrated alumina particles, and the like.
Most of them are ink-jet recording sheets in which an ink absorbing layer has a void structure.
On the other hand, in ink-jet recording, in order to improve the water resistance of the obtained images, various methods are employed in whic
Mochizuki Yoshihiro
Ohbayashi Keiji
Saito Yoichi
Tsuchiya Masaru
Grendzynski Michael E.
Kelly Cynthia H.
Konica Corporation
Muserlian Lucas and Mercanti
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