Electrophotography – Image formation – Transfer
Reexamination Certificate
2001-11-20
2004-08-10
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Transfer
C399S314000, C399S390000
Reexamination Certificate
active
06775507
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a non-fixing type image receiving sheet which is formed into an uneven surface and to which a toner adheres in a removable manner, an image forming method, and an image forming apparatus.
2. Description of Prior Art
(Fixing Type Image Receiving Sheet)
In a printer which is used as an outputting means for personal computer, at present, a generally typical printing method is an electro-photography method in which toner particles are thermally fixed on an image receiving sheet comprising such as a paper or a plastic material, or an ink jet method in which an ink is dryly fixed on the image receiving sheet.
In each fixing method described above, a time is required for printing, an electricity bill and consumables such as the ink become necessary, so that a running cost is required. In addition, measures for decreasing an energy of the printer and decreasing consumption of paper are required in view of recent tendency in reduction of environmental load.
On the other hand, a paper outputted from the printer is necessary temporarily. However, it is usual that the paper becomes unnecessary and disused immediately after the paper is glanced once.
(Non-fixing Type Image Receiving Sheet)
In contrast with the above-mentioned methods, a method is generally known in which a transferred paper is reused. As a method for separating the toner from the transferred paper, for instance, there are known a method in which the transferred paper is passed through between a pair of heated rollers so as to melt and exfoliate the solidified toner, and a method in which the ink is removed by utilizing water solution such as surface active agent.
However, a large volume of energy is required for heating and for removing penetrating water content. In addition, the removed toner can not be reused because it is molten and solidified.
In order to solve such a problem, Published Patent Application (KOKAI) No. 43,682 is proposing a method in which fine projections are dispersedly formed on a surface of the image receiving sheet, a toner image is transferred on the surface of the image receiving sheet having the many fine projections and then fixed by being pressed to form an image, and the toner is separated from the image receiving sheet by means of a mechanical method, thus the image receiving sheet and the toner become reusable.
A mechanical means such as brushing etc. becomes popular as a means for removing the toner from the image receiving sheet. However, it is difficult to completely remove the toner so as not to leave contamination on the non-fixing type image receiving sheet having the many fine projections as describe above, by using the mechanical means only. In other words, toner particles remain around roots of the projections even when mechanically cleaning them by brushing, and the toner particles falling in concave portions become impossible to be removed when these fine concave portions exist.
Independently from the mechanical toner removing means, there is a measure for absorbing and removing the toner electrostatically by utilizing a magnetic brush. Namely, this method is one in which a toner collecting magnetic brush is charged to a polarity opposite to that of charged polarity of the toner, the toner is absorbed to the magnetic brush by electrostatic absorption, thus the toner is removed from the surface of the image receiving sheet.
(Image Forming Apparatus)
FIG. 10
shows an example of a transferring apparatus (image forming apparatus) used for forming the toner image of the non-fixing type image receiving sheet, the apparatus is composed of a drum-type photoreceptor
127
and a transferring roller
128
facing on it. Around the photoreceptor
127
, there are disposed a toner wiping-off (scratching-off) portion
131
, an image charging portion
132
, an exposing portion
133
, and a developing portion
134
; in an order from a transferring portion
130
contacting with the transferring roller
128
to a drum rotation direction side R.
The transferring roller
128
is applied with a bias to draw the toner particles. In order to carry out the transferring operation using such a transferring apparatus, the transferring roller
128
is applied with a bias to be charged to a positive polarity as shown by
FIG. 11
, when the toner particles are charged to a negative polarity. The toner particles charged to the negative polarity are drawn by the transferring roller
128
charged to the positive polarity and made adhere onto the surface of the image receiving sheet S.
3. Problems to be Solved by the Invention
According to the image receiving sheet as cited in Published Patent Application (KOKAI) No. 6-43682, the fine projection serves as a spacer at an upper part of the sheet so as to prevent the toner particles from adhering to a backside of an upper sheet which is placed upon the sheet surface. However, the projection does hardly fulfil its function to mechanically and securely retain the toner particles adhering to the sheet surface.
In addition, since the fine projections are formed only in the dispersed manner, there may be a case where the image receiving sheet on which the image has been formed is handled while the toner adheres to the fine projections of the image receiving sheet as it is. Although the toner is fixed to the projection by means of pressure treatment, the toner can be removed easily and mechanically from the image receiving sheet, so that fingers or sheet backsides may be contaminated when the sheet is touched with fingers or rubbed each other under piled condition.
Since the fine projections formed on the image receiving sheet are scattered independently as like a dotted pattern, they are apt to be deflected or deformed when an external force is applied. Therefore, foreign matters are apt to get in between the projections, the image is subjected to disturbance effect, and the toner image can not be protected enough.
A conventional image receiving sheet generally has a center line average roughness of sheet surface smaller than Ra=0.1 &mgr;m, so as to provide a smooth flat surface. For this reason, Funderworth Force of the toner particle becomes too large so that an adhering force of the toner particle to the sheet surface becomes large. Therefore, a good cleanability (toner removability) can not be obtained and recycling of the sheet may be prohibited. Further, since the center line average roughness Ra is small, a regular reflection light quantity (brilliance) will become too large and the image may not be seen well.
Even when the cleaning is done utilizing the electrostatic absorption by the magnetic brush, a carrier of the magnetic brush and the sheet surface layer (media) slide contacting each other, during the cleaning operation, to produce a friction charge on the sheet surface layer (or toner) so that a charge quantity on the sheet surface layer will increase.
When a conductive carrier is equipped for the carrier of the magnetic brush, an increased charge can be relieved from the conductive carrier to some extent. However, when an insulated resin carrier is equipped therefor, there is no path to let the above charge leak so that the charge quantity on the sheet surface layer will increase suddenly to cause an increase in a force to absorb the toner. For this reason, the removal ability of toner particles will decrease.
As illustrated in FIG.
10
and
FIG. 11
, in a method or an apparatus for carrying out the transferring operation by utilizing only the drawing effect of toner particles through means of the charge of the transferring roller
128
, the transferring roller is located apart from the toner particles on the surface of photoreceptor with a distance longer than a thickness of the image receiving sheet. Thereby, its electric field is weakened so that there is a limit in improving its transferability and retentivity by controlling the applied voltage only.
SUMMARY OF THE INVENTION
1. Objects of the Invention
Objects of inventions are to provide an image receiving sheet whi
Kurita Takaji
Matsuura Masahiko
Mizuno Hiroshi
Yamamoto Masashi
Chen Sophia S.
Minolta Co. , Ltd.
Morrison & Foerster / LLP
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