Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Persistent internal polarization imaging
Reexamination Certificate
2001-03-16
2002-08-27
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Persistent internal polarization imaging
C347S114000, C427S466000
Reexamination Certificate
active
06440624
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming method that employs ferroelectrics, and more particularly to a method of forming an image by forming a polarization reversion pattern in ferroelectrics in accordance with image information.
The invention also relates to an apparatus for carrying out the image forming method which employs ferroelectrics, and an image formation medium that is employed in the image forming method.
2. Description of the Related Art
Electrophotography (Carlson method) is widely known as one of the image recording methods. The electrophotography is the process of recording an image, by forming an electrostatic latent image in a photosensitive substance, then developing this electrostatic latent image with toner, and transferring the toner image to recording paper.
The photosensitive substance that is employed in this electrophotography has the disadvantage that the time during which electric potential is held since the surface was charged is short and that electric potential will attenuate (dark attenuation). Because of this, it is necessary to quickly perform the write process of forming an electrostatic latent image in the photosensitive substance uniformly charged. It is also necessary to perform the development and transfer of the formed electrostatic latent image quickly.
In view of the aforementioned circumstances, various investigations and experiments have been made with respect to a memory type photosensitive substance. However, there has not yet been reported any practical memory-type photosensitive substance meeting all the following requirements: (1) memory service life is long; (2) memory formation sensitivity is high; (3) a substance that functions as memory does not degrade the sensitivity of the photosensitive substance; and (4) formation and erasion of memory are reversible.
Hence, there have been proposed a wide variety of image forming methods for forming an electrostatic latent image by use of a medium, having a memory function, which is entirely different from the conventional photosensitive substance employed in the Carlson method.
Such an image forming method has been proposed, for example, in SHINGAKU Technical Report EID 98-180, issued by the Academic Society for Electronic Information Communication. A distribution of heat corresponding to image information is applied to ferroelectrics simultaneously with application of an electric field, in order to form a polarization reversion pattern in the ferroelectrics in accordance with the image information. Then, a change in temperature is applied to the ferroelectrics so that surface charges corresponding to the polarization reversion pattern are generated by a pyroelectric effect. With the surface charges, an electrostatic latent image is obtained.
The image forming method described in the aforementioned Report EID 98-180, however, has the problem that reliability in image formation is low, because an organic polymer material being employed as ferroelectrics, more particularly a vinylidene fluoride polymer, is low in thermal durability.
SUMMARY OF THE INVENTION
The present invention has been made in view of the problem found in the prior art. Accordingly, it is an important object of the present invention to provide an image forming method, employing ferroelectrics, which is capable of enhancing reliability in image formation.
Another important object of the invention is to provide an image forming apparatus in which reliability in image formation has been enhanced.
Still another important object of the invention is to provide an image formation medium, formed from ferroelectrics whose thermal durability are high, which is capable of making a contribution to a reliability enhancement in image formation.
To achieve the aforementioned objects of the present invention and in accordance with an important aspect of the present invention, there is provided a first image forming method comprising the steps of: forming a polarization reversion pattern in ferroelectrics in accordance with image information; and obtaining an electrostatic latent image by surface charges corresponding to the polarization reversion pattern; wherein an inorganic ferroelectric oxide is employed as the ferroelectrics.
In accordance with another important aspect of the present invention, there is provided a second image forming method comprising the steps of: subjecting ferroelectrics to a distribution of heat corresponding to image information simultaneously with application of an electric field, in order to form a polarization reversion pattern in the ferroelectrics in accordance with the image information; applying a change in temperature to the ferroelectrics so that surface charges corresponding to the polarization reversion pattern are generated by a pyroelectric effect; and obtaining an electrostatic latent image by the surface charges; wherein an inorganic ferroelectric oxide is employed as the ferroelectrics.
It is preferable that the inorganic ferroelectric oxide be a thin film with metal alkoxides as raw materials and also preferable that the inorganic ferroelectric oxide be LiNb
x
Ta
1-x
O
3
(0≦x≦1).
To subject the inorganic ferroelectric oxide to the distribution of heat corresponding to image information, as described above, it is preferable to adopt an exposure method of irradiating infrared light carrying image information to the inorganic ferroelectric oxide. In such a case, it is desirable that the inorganic ferroelectric oxide contain a dopant that absorbs the infrared light carrying image information and also desirable that the dopant be composed of at least any one of elements Mg, Ti, Cr, Ni, Cu, Zn, Zr, Nb, Mo, Rh, Ag, In, Sn, Au, and Pb.
In the second image forming method, it is desirable that a photothermal conversion body in the form of a layer be disposed in close proximity or intimate contact with an image formation layer that consists of an inorganic ferroelectric oxide. The photothermal conversion body is used for absorbing the infrared light carrying image information, converting it into heat, and applying the heat to the image formation layer.
A conductive film may be disposed on one surface of the inorganic ferroelectric oxide, and an electric field may be applied across the inorganic ferroelectric oxide through the conductive film. The conductive film may be constructed of a conducting portion formed over the entire surface, or micro conducting portions and non-conducting portions. The micro conducting portions and non-conducting portions may be alternated in predetermined cycles. In the case of employing the inorganic ferroelectric oxide containing a dopant that absorbs infrared light, it is desirable that the conductive film be transparent to infrared light. In the case where the photothermal conversion body is employed, the conductive film may be an opaque conductive film such as metal.
In the image forming method of the present invention, it is desirable to perform application of an electric field by a corona charging method.
In the image forming method of the present invention, as described above, it is desirable to form a polarization reversion pattern in an inorganic ferroelectric oxide in accordance with image information, obtain an electrostatic latent image by surface charges corresponding to the polarization reversion pattern, develop the electrostatic latent image as a toner image, and transfer this toner image to recording paper.
An image forming apparatus according to the present invention performs image formation by the image forming methods of the present invention described above.
An image formation medium according to the present invention is employed in the image forming methods of the present invention described above and has an image formation layer composed of an inorganic ferroelectric oxide.
In a preferred form of the image formation medium, the image formation layer is constructed of an inorganic ferroelectric oxide containing a dopant that absorbs infrared light carrying image information. The
Fuji Photo Film Co. , Ltd.
Goodrow John
Sughrue & Mion, PLLC
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