Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2001-04-24
2003-01-07
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C399S276000
Reexamination Certificate
active
06503674
ABSTRACT:
PRIOR ART
It has already been suggested to provide members of copier, facsimile machine, printer, such as magnetic drum, doctor blade, scrappers, scraping blade, rollers, photoconductive imaging member, with specific top layer or intermediate layers.
For example U.S. Pat. No. 6,074,791 disclose a photoconductive imaging member comprised of a supporting substrate, a hole blocking layer thereover, a photo generating layer and a charge transport layer.
Tests have shown that the top layer of the members of printer in contact with toner particles has to be accurately selected in order to have the best life time, i.e. the longer working of the printer.
It has now been discovered that by using members provided with a top layer containing spherical particles with a particle size lower than 100 &mgr;m, it was possible to improve the quality of the copies of a copier and the life time of said members. For example, it has been discovered that by using a magnetic drum provided with such a top layer, it was possible to ensure good copies after more than 40,000 copies and even more. It has also been observed that the efficiency of the toner transfer was improved when using member of the invention, especially a magnetic drum of the invention.
BRIEF DESCRIPTION OF THE INVENTION
The invention relates to a member for a printer, a fax machine, a copier or a toner cartridge, in which said member has a face in contact with toner particles, said face being provided with a top layer in contact with toner particles, said cop layer comprising substantially spherical particles with a Mohs hardness of more than 3 or equal to 3, advantageously more than 4, preferably more than 4.5, most preferably comprised however between 3 and 7 and an average particle size lower than 100 &mgr;m, advantageously lower than 50 &mgr;m, preferably lower than 40 &mgr;m.
Substantially spherical particles means in the present specification particles having a spherical shape, a substantially spherical body provided with one or more (for example two) recesses, such a form similar to an apple, particles having an ovoid shape, shape having a ratio volume/surface comprised 1:4.2 and 1:2, etc.
Substantially spherical particles with a Mohs hardness of more than 3 or equal to 3 means substantially spherical particles having as such a Mohs hardness of more than 3 or equal to 3, spherical particles having a core with a Mohs hardness of more than 3 or equal to 3, as well as particles provided with an outer coating having a Mohs hardness of more than 3 or equal to 3. Preferably, the particle as such or its core has a Mohs hardness of more than 3 or equal to 3.
According to an embodiment, at least 50% of the substantially spherical particles with a Mohs hardness of more than 3 or equal to 3 have advantageously a particle size distribution factor at 80% of less than 1. Most preferably the substantially spherical particles with a Mohs hardness of more than 3 or equal to 3 and having a particle size greater than 25 &mgr;m have a distribution factor at 80% lower than 1, preferably lower than 0.8. The distribution factor at 80% is equal to:
(&phgr;
80%
−&phgr;
20%
)/[(&phgr;
80%
+&phgr;
20%
)/2]
in which
&phgr;
20%
is the maximum diameter of the particles fraction corresponding to 20% by weight of the particles, the particles of said fraction having a diameter or particle size lower than &phgr;
20%
&phgr;
80%
is the maximum diameter of the particles fraction corresponding to 80% by weight of the particles, the particles of said fraction having a diameter or particle size lower than &phgr;
80%
Preferably, at least 50% of the substantially spherical particles with a Mohs hardness of more than 3 or equal to 3 have a particle size distribution factor at 90% of less than 1, advantageously of less than 0.8, preferably of less than 0.5, most preferably of less than 0.3. A small particle size distribution factor means that substantially all the particles have a diameter corresponding substantially to the average diameter. This is advantageous in order to obtain a layer having a substantially constant thickness. Most preferably the substantially spherical particles with a Mohs hardness of more than 3 or equal to 3 and having a particle size greater than 25 &mgr;m have a distribution factor at 90% lower than 1, preferably lower than 0.8, most preferably lower than 0.5, such lower than 0.3.
The distribution factor at 90% is equal to:
(&phgr;
90%
−&phgr;
10%
)/[(&phgr;
90%
+&phgr;
10%
)/2]
in which
&phgr;
10%
is the maximum diameter of the particles fraction corresponding to 10% by weight of the particles, the particles of said fraction having a diameter or particle size lower than &phgr;
10%
&phgr;
90%
is the maximum diameter of the particles fraction corresponding to 90% by weight of the particles, the particles of said fraction having a diameter or particle size lower than &phgr;
90%
.
According to an embodiment, the top layer comprises various different fractions of substantially spherical particles with a Mohs hardness of more than 3 or equal to 3. For example, the top layer comprises substantially spherical particles with a bi-modal distribution. The top layer comprises for example a mixture of substantially spherical particles, a first fraction of which having an average diameter greater than 30 &mgr;m, and a second fraction of which having an average diameter lower than 20 &mgr;m, the weight ratio first fraction/second fraction being comprised between 1:20 and 20:1, advantageously between 1:10 and 10:1, preferably between 1:4 and 4:1. The presence of the two fractions can be seen for example when plotting a particle size curve, due to the presence of two visible peaks corresponding substantially to the average particle size of the second fraction and the average particle size of the first fraction.
When using a mixture of larger particles (such as particles with a particle size greater than 20 &mgr;m, preferably with an average particle size greater than about 30 &mgr;m), it is advantageous to add to the mixture some smaller particles (such as particles with a particle size lower than about 10 &mgr;m) so as to fill the inter space formed between the larger particles. This is particularly advantageous when the support or substrate to be provided with a top layer is not plane (is curved, for example cylindrical).
Possibly, the top layer can contain particles with a Mohs hardness of less than 3, for example substantially spherical particles with a Mohs hardness of less than 3, fibres, filaments, fabrics, metallic powders (copper, zinc, tin, iron, aluminium, etc.), metallic fibres, carbon particles, carbon black, carbon fibres, etc. Preferably, the top layer is however free or substantially free of particles with a Mohs hardness of less than 2.
According to a detail of an embodiment, the top layer comprising substantially spherical particles with a Mohs hardness of more than 3 or equal to 3 is a layer comprising a binder for binding the spherical particles in the layer, said layer having a top face at which a portion of substantially spherical particles with a Mohs hardness of more than 3 or equal to 3 is provided with a binder coating with a thickness of less than 50 &mgr;m, advantageously lower than 30 &mgr;m, preferably lower than 20 &mgr;m, most preferably of less than 10 &mgr;m.
Preferably, the top layer comprising substantially spherical particles with a Mohs hardness of more than 3 or equal to 3 is a layer comprising a binder for binding the substantially spherical particles in the layer, said layer having a top face at which a portion of spherical particles with a Mohs hardness of more than 3 or equal to 3 is substantially free of binder.
The binder is advantageously a synthetic binder, advantageously a binder being substantially stable at temperature above 50° C., advantageously above 800° C. preferably above 100° C., for example stable at temperature comprised between 130° C. and 300° C., or even more. Such binder is for example polyurethane, thermoplastic polyurethane, a polyester, a p
CF Technologies
Darby & Darby
Goodrow John
LandOfFree
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