Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-08-22
2002-01-01
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S097000
Reexamination Certificate
active
06335139
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner for electrostatic image development which is employed in electrophotographic methods, electrostatic recording methods, and electrostatic printing methods.
2. Description of Related Art
Various electrophotographic methods have been disclosed in, for example, U.S. Pat. No. 2,297,691, Japanese Patent Application, Second Publication No. Sho 42-23910, and Japanese Patent Application, Second Publication No. Sho 43-24748; commonly, an electrostatic latent image is formed on an electrostatic latent image bearing medium such as a photoconductive photosensitive medium or the like by means of charge or light exposure, and then this electrostatic latent image is developed employing a toner composition containing a colorant in a binder resin, and the resulting toner image is transferred to a support medium such as transfer paper or the like and fixed, and a visible image is thus formed.
Apparatuses employing such an electrostatic image development method include copying machines, printers and the like. The processing speed varies depending on the manufacturer and type, but apparatuses having processing speeds corresponding to 30 sheets per minute in the case of office printers or about 60-100 sheets per minute in the case of office copying machines, when converted to printing speed on A4 size paper, are common. Due to increases in the speed of the developing apparatuses, conventional developing apparatuses have recently been replaced by high-speed apparatuses which have a processing speed corresponding to 100 sheets per minute when converted to a printing speed on A4 size paper in a longitudinal direction and 140 sheets per minute when converted to a printing speed on A4 size paper in a lateral direction, and which have fixing speeds of 30 m/min.
Due to power saving measure, the heat applied to the fixation of the toner has been reduced steadily, thereby reducing the heat applied from the heat roll during the fixation and shortening the pressing time due to the heat roll, thus making good sharp melting properties and low temperature fixing properties indispensable.
Also in high-speed apparatuses, there is a high possibility that the developed image makes contact with the heat roll for a long period of time if a problem occurs and that it will be exposed to excess calories, thus requiring sufficient anti-offset properties at high temperatures.
Accordingly, the toner for electrostatic image development employed therein requires a proper level according to the service conditions in electrical properties such as frictional charging properties and electric resistance related to the development and transfer properties, thermal properties related to fixation and anti-offset properties, and mechanical properties as powders such as fluidity, hardness and the like.
As the resin material for the powdered toner, for example, there have hitherto been investigated polyester, polystyrene, styrene-(meth)acrylic ester copolymer, styrene-butadiene copolymer, epoxy resin and the like, and various proposals have been made for the design of such resins depending on the use thereof.
With respect to resins for toners for fixing employing a heat roller, a lot of design examples have been proposed for the purpose of improving the fixation and anti-offset properties. To improve viscoelastic behavior during the melting by heating or to suppress changes in melt viscosity due to changes in temperature, various techniques such as enlargement of the molecular weight distribution, provision of a crosslinked structure, application of a rubbery elastic material and the like have been studied.
Due to energy reductions during the heat roll fixation or the enhancement of requirements for fixation properties at low temperatures accompanying the speeding up the apparatus, polyester resin has attracted special interest recently.
In research to date, it has been widely known that polyester resin may be employed as a resin for heat roller fixation. This is the case in, for example, Japanese Patent Application, Second Publication No. Sho 52-25420, Japanese Patent Application, Second Publication, No. Sho 53-17496, Japanese Patent Application, Second Publication No. Sho 55-49305 , Japanese Patent Application, First Publication No. Sho 55-38524, Japanese Patent Application, First Publication No. Sho 57-37353, Japanese Patent Application, First Publication No. Sho 58-11952, and the like.
However, in conventionally proposed inventions, when anti-offset properties are improved, it is not possible to avoid increases in the softening point or molecular weight of the resin, thereby degrading the anti-offset properties at low temperatures and fixation properties at low temperatures. On the other hand, when the anti-offset properties at low temperatures and fixation properties at low temperatures are improved, the softening point or molecular weight of the resin is lowered, thereby degrading the anti-offset properties at high temperatures and resistance to blocking.
A toner which reconciles these properties, which are in conflict with each other, with good balance is required. However, since properties such as anti-offset properties, fixation strength and charge characteristics vary drastically depending on the electrostatic image developing apparatus employing the toner and service conditions, design of the properties suited for these purposes is required.
Means for simply measuring the properties such as thermal characteristics and viscosity characteristics of the resin includes, for example, a constant load extrusion type capillary rheometer.
The constant load extrusion type capillary rheometer is employed for measuring the viscosity resistance in situations in which melt passes through a capillary tube, and specific examples thereof include Flow Tester “CFT-500” manufactured by Shimadzu Corporation.
The structure of the cylinder portion of this measuring apparatus is shown in FIG.
1
.
In the drawing, the reference symbols
1
denotes a piston,
2
denotes a cylinder,
3
denotes a heater,
4
denotes a die,
5
denotes a die press, and
6
denotes a sample, respectively.
With regard to measurement by the temperature elevating method using this apparatus, measurement can be carried out continuously through out processes in which the sample
6
passes through a solid range, a transition range, a rubber elasticity range, and a fluidized range when testing while elevating the temperature at a fixed speed with the passage of the testing time. By employing this apparatus, the shear rate and viscosity at each temperature in the fluidized range can be simply measured.
The flowing curve by the temperature elevating method is shown in FIG.
2
.
The range AB (softening curve) indicates a stage where the sample
6
is deformed by compression and inner pores are slowly reduced.
The point B is a temperature at which the inner pores disappear to form a transparent medium or phase having uniform appearance while maintaining a non-uniform stress distribution, and indicates an inflection point. This temperature is defined as a softening temperature Ts.
The range BC (terminating curve) indicates a range where the position of a piston
1
does not clearly change within a limited time and the sample
6
begins to flow through a die
4
, and includes the rubber elasticity range of the sample
6
. For a crystalline polymer, this range is short and the softening temperature shows a value close to a flow beginning temperature described hereinafter.
The point C indicates a temperature at which the sample
6
begins to flow through the die
4
as a result of a reduction in viscosity, and this temperature is defined as a flow beginning temperature Tfb.
The range CDE (flowing curve) indicates a range where the sample
6
flows through the die
4
. In this range, in general, an irreversible viscous flow occurs.
The melting temperature T½ by the ½-process indicates a temperature at the half point of a piston stroke between Tfb and a flow ending temperature Ten
Amaya Shinji
Gambayashi Hideki
Kogawara Toshiro
Nakamura Masanobu
Armstrong Westerman Hattori McLeland & Naughton LLP
Dainippon Ink and Chemicals Inc.
Goodrow John
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