Coating processes – Foraminous product produced – Microporous coating
Reexamination Certificate
1997-06-11
2003-03-18
Yamnitzky, Marie (Department: 1774)
Coating processes
Foraminous product produced
Microporous coating
C427S246000, C427S336000, C427S373000
Reexamination Certificate
active
06534123
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a recording material, and in particular to a recording material suitable for use in ink jet printing applications.
2. Description of the Related Art
Ink jet printing techniques typically involve the application of droplets of a recording fluid (for example, ink) to the surface of the recording material. The ink usually includes at least a colorant and an ink fluid.
There are fundamentally two variant methods for droplet generation and application. The first method is a continuous process in which an ink jet is expelled from a discharge nozzle and, due to surface tension, breaks apart into microscopically small droplets. The droplets are electrically charged and placed on the underlay or diverted to a reservoir by downstream diversion plates that are controlled by the digital signals. In the second method, or the so-called “drop-on-demand” method, the image signal trips a mechanical pulse that expels the droplet. The earliest “drop-on-demand” printers employed the piezoelectric effect to bring about the expulsion of the droplets. Today, this “drop-on-demand” method has been largely replaced by the thermal ink jet, also known as the bubble jet. In accordance with the thermal ink jet method, the image signal activates a heating element, which creates a vapor bubble in the aqueous ink. The resultant vapor pressure expels the droplet.
Commercial demands and expectations have placed stringent performance requirements on the ink jet image-receiving (i.e., recording) materials. For example, the recording materials are expected to be capable of producing an ink-jet-printed image having high resolution, high color density, good resistance to smearing (smearfastness), good waterproofness, and good rub resistance (i.e., resistance to being rubbed off when wetted).
To achieve these and other expectations, the following fundamental conditions should be met by the recording material:
quick absorption of the ink by the recording material (short drying times);
accurate spreading of the sprayed-on ink droplets (e.g., in circles) to ensure precise demarcations;
controlled ink diffusion in the recording material, such that the diameter of the dots of ink is not enlarged more than absolutely necessary;
excellent ability to overlap an ink dot on a previously-applied ink dot without impairing or wiping away the previously-applied ink drop;
high visual reflection density and high brilliance of the colors exhibited by the surface of the recording material; and
high dimensional stability of the recording material, without stretching after printing.
The provision of a recording material that satisfies each of these demands is difficult, especially since these demands conflict with one another to some extent. For instance, overly rapid attainment of a smearproof state means that an ink droplet will spread only a little, if at all, which impairs the clarity of the resultant image.
The difficulties involved with satisfying the above-mentioned demands are compounded by recent improvements in the performance—such as higher recording speeds—of ink jet recording equipment.
Conventional ink jet recording materials contain a support and ink absorbing layers. The support can be made of polyester resin or diacetate film or paper or other substrates, such as woven or non-woven layers.
The ink absorbing layers are porous and comprise hydrophilic pigments and water soluble polymeric binders, such as gelatin, starch, pectin, casein, carboxymethyl cellulose, or polyvinyl alcohol. Pigments and binders serve to increase the whiteness of the material and to retain dye from the ink at the surface of the sheet. A high image resolution may be achieved with said absorbing layers; however, the difficulty in achieving a high gloss is a significant problem with these papers.
To achieve a high gloss (>70% at 60°) in recording papers, it has been proposed to first extrusion-coat the base paper with water-insoluble polymers, such as polyethylene, and then provide the base paper with a receiving layer. However, this proposed method makes for poor drying times.
In order to achieve faster drying times, it has been proposed to modify the ink absorbing layer of conventional recording materials to allow ink fluid to pass therethrough by capillary flow and hence quickly. Such a flow is faster by orders of magnitude than a flow by diffusion only and therefore causes rapid drying out of the ink fluid on the dye-receiving layer. In this regard, according to Hagen-Poisuelle's Law, the quantity of liquid per unit of time that passes through an arrangement of pores is proportional to the fourth power of the mean diameter of the pores. Therefore, most of the flow of liquid passes through pores having large radii. The achievement of sufficiently fast drying times in conventional recording materials generally requires layers having a pore diameter distribution in which the mean value is shifted to relatively large pores, e.g., 10 &mgr;m to 30 &mgr;m. However, such large pore diameter distributions result in a lessening in the desired gloss of the recording material. Not until a mean pore size on the order of magnitude of 0.1 to 1 &mgr;m is attained is a high gloss for the dye-receiving layer achieved.
A long-felt need therefore has existed to provide a recording material that simultaneously exhibits high gloss and has a high drying speed with respect to the ink fluid, as well as exhibits good color density and resolution.
SUMMARY OF THE INVENTION
It is, therefore, an objective of the present invention to solve the aforementioned problems associated with the related art as well as to address the need expressed above.
It is another objective of the present invention to provide a recording paper having high gloss and high drying speed.
In accordance with the principles of the present invention, these objectives are obtained by providing a recording material comprising: (a) at least one dye-receiving layer having opposing first and second surfaces; (b) at least one support layer having opposing first and second surfaces, the first surface of the support layer facing the second surface (backside) of the dye-receiving layer; and (c) at least one member selected from the group consisting of (i) at least one microporous membrane layer interposed between the dye-receiving layer and the support layer and/or (ii) at least one microporous membrane layer having an inner surface facing the first surface of the dye-receiving layer.
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Patent Abstracts of Japan, M-495, Jul. 4, 1986, Vo. 10, No. 191, 61-35275, Okura, Feb. 1986.
Kaufman Clifford M.
Mukherjee Debabrata
Pillsbury & Winthrop LLP
Schoeller Technical Papers, Inc.
Yamnitzky Marie
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