Incremental printing of symbolic information – Thermal marking apparatus or processes – Record receiver and transfer medium feeding or driving means
Reexamination Certificate
1999-11-10
2001-07-17
Le, N. (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Record receiver and transfer medium feeding or driving means
C347S248000
Reexamination Certificate
active
06262756
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a thermal development apparatus as well as a thermal development method in which an image is formed by feeding a thermally developable material on the outer circumferential surface of a drum and heating it.
A thermal development apparatus is developed in which by successively feeding a sheet of thermally developable material onto the outer circumferential surface of a heated drum, the thermally developable material undergoing a thermal reaction so that an image formed as a latent image will be visible (refer to Japanese Patent Publication Open to Public Inspection under PCT Application No. 10-500497). Such a thermal development apparatus is constituted in such a manner that sheets of thermally developable material are fed onto the outer circumferential surface of a drum which rotates at a constant speed; after the drum rotates a specified angle, while the material is held on the surface, the thermally developable material, which has been heated, is peeled from the outer circumferential surface of the drum; at the same time, another sheet of thermally developable material is fed onto the outer circumferential surface of the drum; and thus, sheets of thermally developable material can be efficiently heated.
Such a thermal development apparatus has been supposed to be preferable based on the fact that when time TR required for one rotation of the drum is the same as the interval between the time when the leading edge of the sheet of thermally developable material is fed to the drum and the time when the following sheet is fed to the same, the sheets of thermally developable material which are seccessively heated by the drum can be developed under the same conditions, and further, a sheet of thermally developable material catching mechanism can be provided onto the drum.
However, when an apparatus is constructed in the manner as described above, it has been found that after many sheets of thermal developable materials are thermally developed, uneven density results at the leading edge portion as well as the rear edge portion, in the drum rotation direction. In particular, it has also been found that in an apparatus which can thermally develop sheets of thermally developable materials of a plurality of sizes in the drum rotational direction, small-sized sheets of thermally developable material are thermally developed, and thereafter, when a larger-sized sheet of thermally developable material is thermally developed, uneven density results in the center of the image, markedly degrading the image quality of the larger size.
In view of such problems, an object of the present invention is to minimize such uneven density and to make it possible to carry out thermal development to yield high image quality at high speed.
Furthermore, a drum in a thermal development apparatus based on conventional techniques is constructed on the assumption that single-sized sheets of thermally developable material will be employed. It is supposed that the drum is not constructed so as to heat different-sized sheets of thermally developable material. Accordingly, when a drum based on conventional techniques is employed to heat sheets of thermally developable material of different sizes without any adjustment, mismatching between the circumference of the drum and the length of the sheet of thermally developable material in the drum rotation direction occurs. For example, due to the excessively small diameter of the drum, curl and the like tend to result on the sheets.
Furthermore, in view of such problems of conventional techniques, an object of the present invention is to provide a thermal development apparatus as well as a thermal development method which can correspond to different-sized sheets of thermally developable material and can also ensure high image quality, while forming images in a short period of time.
SUMMARY OF THE INVENTION
The inventors of the present invention have diligently investigated causes of the formation of the aforementioned uneven density. As a result, the following has been discovered to create the present invention. Means to overcome the above-mentioned problems are described below.
(1) In a thermal development apparatus which comprises a drum to heat a thermally developable material on its outer circumferential surface while rotating at a predetermined rotation speed and a feeding means which feeds a sheet-like thermally developable material onto the outer circumferential surface of the drum, and thermally develop the thermally developable material fed by the feeding means by heating it while holding it on the outer circumferential surface of the drum, the feeding means feeds each of thermally developable materials to the drum with a timing to shift a position of the leading end of each of thermally developable materials held on the drum into a rotation direction of the drum among the thermally developable materials fed onto the drum with the shortest time interval Tmin so as to be continuously heated by the drum.
The position of each of thermally developable materials among the thermally developable materials fed onto the drum with the shortest time interval Tmin is shifted in the rotation direction of the drum to a different position from others, it is possible to maintain the entire outer circumferential surface of the drum at the same temperature by varying the position at which the leading edge of the sheet of the thermally developable material is held without resulting in a decrease in temperature at only one portion of the outer circumferential surface of the drum. As a result, it is possible to minimize the formation of uneven density and to improve image quality obtained by thermal development.
With this structure, the shortest time interval Tmin and a time period TR during which the drum rotates a single rotation satisfy the following formula in terms of arbitrary natural number N.
Tmin≠N×TR
(2) In the thermal development apparatus described in (1), formula 1 described below is satisfied in terms of arbitrary natural number N;
formula 1:
(
N−
{fraction (1/20)})×
TR≧Tmin
or
(
N+
{fraction (1/20)})×
TR≦Tmin
wherein Tmin denotes the shortest time interval between the time when the leading edge of the sheet of thermally developable material is fed to the drum and the time when the following sheet is fed to the drum, TR denotes the time required for one rotation of the drum.
Since the position of each of thermally developable materials fed on the drum is different by at least {fraction (1/20)} of the circumference of the drum from others among the thermally developable materials continuously heated by the drum, uneven temperature on the drum in the rotational direction is less likely to result, and owing to that, it is possible to effectively minimize the formation of uneven density.
(3) In the thermal development apparatus described in (2), formula 2 described below is satisfied in terms of arbitrary natural number N;
formula 2:
(
N−
{fraction (1/20)})×
TR≧
2
×Tmin
or
(
N+
{fraction (1/20)})×
TR≦
2
×Tmin
wherein Tmin denotes the shortest time interval between the time when the leading edge of the sheet of thermally developable material is fed to the drum and the time when the following sheet is fed to the drum, TR denotes the time required for one rotation of the drum.
Since the position of each of thermally developable materials fed on the drum is different by at least {fraction (1/20)} of the circumference of the drum from others among the thermally developable materials continuously heated by the drum on the basis of every other sheet, uneven temperature on the drum in the rotational direction is less likely to result, and owing to that, it is possible to effectively minimize the formation of uneven density.
(4) In the thermal development apparatus described in (3), an existing ratio of natural number N which satisfy all formulas 3 to 5 described below is 50 percent or more in terms of an arbitrary natural number.
formula 3:
(
Kashino Teruo
Taguchi Akira
Tamakoshi Yasuaki
Tateishi Yosuke
Feggins K.
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Konica Corporation
Le N.
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