Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-11-04
2003-01-07
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S195100, C428S206000, C428S325000, C428S411100
Reexamination Certificate
active
06503604
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ink jet recording sheet, and specifically to an ink jet recording sheet in which image blur, after printing, is reduced.
BACKGROUND OF THE INVENTION
Ink jet recording is carried out by ejecting micro-droplets employing various working principles and attaching them onto a recording sheet of paper and the like to record images, letters etc., and exhibits advantages such as relatively high speed, low noise, easy application for multicolor, etc. Conventional problems of this system regarding clogging of nozzles and maintenance have been solved by improving both aspects of ink and 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 printed dots is high, color tone is bright and clear, ink is rapidly absorbed and when printed dots are superimposed, ink should neither run nor blot, the diffusion of a printed dot in the lateral direction should not be greater than needed, and the circumference should be smooth and result in no blurring; and the like.
Specifically, at low rates of ink absorption, when recording is carried out by superimposing at least two color ink droplets, on a recording sheet, droplets result in repellence to cause unevenness, and in the boundary area of different colors, different color inks blot with each other. As a result, image quality tends to be markedly degraded. Therefore, it is required that the recording sheet exhibits high ink absorbability.
In order to solve these problems, conventionally, a great number of techniques have been proposed.
For example, a recording sheet comprising pigments and fine silica particles having specified physical parameters described in Japanese Patent Publication Open to Public Inspection No. 3-27976, etc.; a recording sheet containing fine silica particles such as colloidal silica described in Japanese Patent Publication Open to Public Inspection No. 7-276789, etc.; a recording sheet containing fine hydrated alumina particles described in Japanese Patent Publication Open to Public Inspection No. 5-16517, etc., and the like.
These void type recording sheets are preferred in which fine voids are formed in the ink receptive layer employing fine inorganic particles and a hydrophilic binder because relatively high gloss is obtained, as high quality glossy sheets.
As such fine inorganic particles, fine silica particles having anionic surfaces are preferably employed, because excellent gloss is obtained. Of these, specifically preferred are composite particles having an average particle diameter of no more than 100 nm, which are prepared by combining fine silica particles with an average primary particle diameter of no more than 30 nm, synthesized employing a gas phase method, with a cationic polymer in terms of the possible coexistence of high gloss and void ratio.
Further, after ink jet recording, a problem occurs in which when recorded images are stored under high humidity, or water droplets adhere to images, images tend to blot.
In order to overcome this problem, a number of techniques have been proposed.
Japanese Patent Publication Open to Public Inspection No. 57-36692 describes the use of basic mordant latex; Japanese Patent Publication Open to Public Inspection No. 59-198188 describes a method of impregnating polyethyleneimine; and Japanese Patent Publication Open to Public Inspection No. 62-174184 describes the use of polyarylamine as a mordant.
Further, in Japanese Patent Publication Open to Public Inspection Nos. 6-234268, 7-125411, etc., many techniques are disclosed in which the dying affinity of an ink dye is improved by the addition of cationic mordants.
However, almost all of them disclosed in the prior art result in problems in which when mixed with fine inorganic particles with anionic surfaces, such as silica, coagula tend to be formed and good coating composition cannot be prepared, or the glossiness of a coated layer surface markedly decreases, and the like.
In order to improve this point, in the previous application (Japanese Patent Publication Open to Public Inspection No. 10-217601), the present applicants applied for a patent in which a water-soluble cationic polymer having an average molecular weight of no more than 500,000 was employed. Employing this, excellent water resistance and gloss have been obtained.
However, as a result of inspections since then, it was found that when within a relatively short period after printing with an ink jet printer, ink jet printed sheets were piled or stored in a clear file, etc., images tended to blot during aging. Thus, further improvement has been desired.
This blur during aging depends on the types of dyes in the employed ink, or the content of water-soluble high boiling point organic solvents. In addition, it has been found that the blur also depended on the dye fixability of recording sheets.
The present inventors are presenting the present invention having discovered that image blur after printing is improved by employing the specified structure of cationic polymers as well as the specified pH of the coated layer.
An object of the present invention is to provide an ink jet recording sheet in which in an ink jet recording sheet having a void layer comprised of fine inorganic particles as well as a hydrophilic binder, image blur after printing is reduced while maintaining high glossiness as well as a high void ratio.
DESCRIPTION OF THE INVENTION
The ink jet recording sheet of the invention is described.
1. An ink jet recording sheet comprising a support having thereon an ink-absorptive layer comprising a hydrophilic binder, fine inorganic particles having an average particle diameter of no more than 200 nm and a water-soluble cationic polymer represented by formula (1) described below, wherein pH of a surface of the ink-absorptive layer is 3 to 6.5.
Formula (1)
In the formula R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R
1
, R
2
, and R
3
each independently represents an alkyl group, and J represents a divalent bonding group. X
−
represents an anion. Q represents a repeat unit, derived from a monomer having an ethylenic unsaturated group. Q includes the case in which at least two types of monomers are polymerized. x represents 40 to 100 mole percent and y represents 0 to 60 mole percent.
2. An ink jet recording sheet comprising a support having thereon an ink-absorptive layer comprising a hydrophilic binder, fine particles having an average particle diameter of no more than 200 nm which are formed by composing inorganic particles having an average primary particle diameter of no more than 30 nm, and a water-soluble cationic polymer represented by formula (1) described below, wherein pH of a surface of the ink-absorptive layer is 3 to 6.5.
Formula (1)
In the formula R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R
1
, R
2
, and R
3
each independently represents an alkyl group, and J represents a divalent bonding group. X
−
represents an anion. Q represents a repeat unit, derived from a monomer having an ethylenic unsaturated group. Q includes the case in which at least two types of monomers are polymerized. x represents 40 to 100 mole percent and y represents 0 to 60 mole percent.
3. An ink jet recording sheet comprising a support having thereon an ink-absorptive layer comprising a hydrophilic binder, fine particles having an average particle diameter of no more than 200 nm which are formed by composing inorganic particles having an average primary particle diameter of no more than 30 nm, and a water-soluble cationic polymer represented by formula (1) described below, having an average molecular weight of no more than 100,000, wherein pH of a surface of the ink-absorptive layer is 3 to 6.
Formula (1)
In the formula R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R
1
, R
2
, and R
3
each inde
Kasahara Kenzo
Mochizuki Yoshihiro
Saito Yoichi
Hess Bruce H.
Konica Corporation
Shewareged B.
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