Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-08-30
2003-11-04
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S109300, C430S111400
Reexamination Certificate
active
06641966
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner composition used, for example, as dry toner for developing an electrostatic latent image.
2. Description of Related Art
A toner using a binder resin as the major component and containing a pigment, a charge controlling agent, an external additive or the like has conventionally been used as a toner for a printer employing an electrostatic latent image developing system.
For example, in a printer employing an electrostatic latent image developing system as shown in
FIG. 7
, this type of toner T may be fed off from a tank
1
by a supply roller
2
. After a toner layer formed on a developing roller
3
is made uniform by a blade
7
, the toner T is applied to the surface of a photoconductor
4
.
The surface of the photoconductor
4
is charged so as to correspond to a certain image pattern by a laser scanner unit
5
and a corona unit
6
, while the toner T is charged to a polarity opposite to that on the surface of the photoconductor
4
. The toner T is therefore attracted onto a portion charged on the photoconductor
4
, but not to portions which are not charged. Namely, the toner T is dispersed so as to correspond to the certain image pattern (charge pattern) on the surface of the photoconductor
4
.
A medium
9
such as paper or the like is then pressed against the photoconductor
4
via an image transfer roller
8
so that the toner image may be transferred onto the medium
9
. Heat is then applied to the toner T by a fusing roller
10
so that it is melted and fused on the surface of the medium, thus accomplishing printing of the image.
Because of such applications involved, toner is required of a strength (mechanical strength) and durability of a level sufficient to ensure that it is not crushed, or softened to stick to a roller or the photoconductor of the printer during a printing process.
It is often the case with toner, for the purpose of controlling the amount of charge of toner, that a charge controlling agent is treated and a substance such as hydrophobic silica or the like is externally added to the surface of toner. If the toner lacks in adequate strength, however, the charge controlling agent or the external additive could be embedded in toner, causing the toner to be charged insufficiently. As a result, the toner distribution pattern on the surface of the photoconductor does not accurately correspond to the charged pattern of the photoconductor, resulting in print quality being degraded.
As a solution to this problem, the degree of crosslinking of the binder resin that makes up toner has been enhanced and a gel percentage increased, thereby enhancing strength of toner.
When printing is done on a transparent medium such as OHP transparencies using toner having a color other than black (color toner), a layer made up of toner fused onto the surface of the transparent medium (a toner layer) is required to have a high light transmission.
The type of toner having a high gel percentage is, however, not melted sufficiently even when heat is applied thereto during a fusing process. As a result, the surface of the toner layer after the fusing process is irregularly shaped because an original shape of powder is left unchanged.
If such a type of toner is used to print on a transparent medium, the toner layer scatters rays of light because of its irregular surface shape, thus presenting a-problem of poor light transmission.
SUMMARY OF THE INVENTION
In view of the foregoing, it is therefore an object of the invention to provide a toner composition that offers a high light transmission when printing is done on a transparent medium, in addition to a superb strength and durability.
To achieve the foregoing object, a toner composition according to one aspect of the invention comprises at least one kind of binder resin and has a gel percentage of 2 to 15% and a flow-out starting temperature of 80 to 120° C.
Since the toner composition according to the invention has a gel percentage of 2% or more, it offers a sufficiently high strength and durability and is never crushed or softened to stick to a roller or a photoconductor of a printer during a print process.
Further, since the toner composition according to the invention has a gel percentage of 15% or less, it is difficult to become brittle and is less likely to crack during a print process.
In terms of preventing the toner composition from becoming brittle, it is even more preferable that the gel percentage be 8% or less.
In the case where the toner composition according to the invention is, for example, transferred to a medium and fused by applying heat thereto, the toner composition according to the invention is melted sufficiently thanks to a low flow-out starting temperature of 120° C. or lower thereof and a layer made up of the toner composition (a toner layer) formed on the surface of the medium after the fusing process has a smooth surface shape.
If printing is done on, for example, a transparent medium such as OHP transparencies or the like, using the toner composition according to the invention, therefore, the toner layer, because of smoothness of the flat surface involved therein, allows a large part of an incidence light to pass therethrough without allowing it to disperse, thus offering a high light transmission. The toner composition according to the invention is therefore superior as a color toner used with a transparent medium.
Since the flow-out starting temperature of the toner composition according to the invention is 80° C. or higher, toner melted during fusing can be prevented from sticking to a fusing roller. During any time other than fusing, the toner composition is not softened, making it easy to handle.
A gel percentage refers to a percentage of a portion that remains solid to that melted away of, for example, a solid substance (sample) which has been immersed in a certain solvent. Suppose, for example, A g of a sample is placed in a certain solvent (e.g., tetrahydrofuran) and we have B g left as solid without being dissolved. Then, B/A is the gel percentage.
The flow-out starting temperature refers to a temperature at which a solid substance is softened to start exhibiting fluidity.
For example, a solid substance-(sample) is placed in an apparatus (e.g., the flow tester recommended by the Society of Polymer Chemistry manufactured by Shimadzu Corporation) having a restricted outlet (e.g., a nozzle with an orifice diameter of 1 mm and a length of 10 mm) and capable of applying a predetermined load (e.g., 10 kg/cm
2
) to the sample by means of a plunger; when the sample is heated at a constant rate (e.g., 6° C./min.) with the load kept applied thereto, the sample is eventually fluidized to start flowing out through the outlet, which, in turn, causes the plunger to start lowering. The temperature at which the plunger starts lowering may be considered as the flow-out starting temperature.
The toner composition according to the invention may contain components, for example, a dye, pigment, organic finely divided powder, charge controlling agents hydrophobic silica, conductive titanium oxide, and the like, in addition to the binder resin. It should be noted that more than two kinds of dye, pigment, organic finely divided powder, charge controlling agent, hydrophobic silica, conductive titanium oxide, and the likes may be used.
The hydrophobic silica and the conductive titanium oxide have the effect of, for example, improving fluidity of the toner composition or uniformity in charging, respectively.
Typical types of hydrophobic silica include silica subjected to surface treatment using dimethyldichlorosilane, dimethyl polysiloxane, hexamethyldisilazine, amino-silane, and amine. Commercially available silica products include, for example, H2000, H3004, HVK2150, and the like manufactured by Nippon Wacker Co., Ltd. and R974, RY200, RX200, RX300, RA200H, REA200, and the like manufactured by Nippon Aerosil Co., Ltd.
As the conductive titanium oxide, it is preferable that titanium oxide having undergone surface treatment u
Endo Akira
Ohira Hideo
Ohta Mitsuru
Brother Kogyo Kabushiki Kaisha
Goodrow John
Oliff & Berridg,e PLC
LandOfFree
Toner composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Toner composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Toner composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3117069