Electrophotography – Image formation – Development
Patent
1997-06-26
1999-07-13
Grimley, Arthur T.
Electrophotography
Image formation
Development
430115, 430117, G03G 1508
Patent
active
059239298
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a liquid toner and imaging method and apparatus using the liquid toner.
BACKGROUND OF THE INVENTION
Liquid toners have been in use for a great many years. In U.S. Pat. No. 4,794,651, and in a number of other patents and publications based on this patent, liquid toner having fibrous or tentacular toner particles made of various material was described.
There has been a need to provide a liquid toner, which when used to form an image on a substrate, forms a more abrasion resistant image than those formed by prior art liquid toners.
It is known in the printing art to add particles, for example polyethylene particles, to ink or to the surface of the substrate in order to improve the abrasion resistance of the ink. Such particles project from the surface of the printed image and the image is more resistant to abrasion from paper. However, abrasion resistance to a conforming eraser is increase by a much smaller amount, if at all.
It is also known in the art to coat an already printed image with an abrasion resistant coating.
SUMMARY OF THE INVENTION
The present invention seeks to provide, in one aspect thereof, an improved toner having greater abrasion resistance than prior art toners.
The present invention seeks to provide in a related aspect a method for producing images using the new liquid toner.
It has been found that the scuff resistance, abrasion resistance and peel resistance of a wide class of liquid toners may be improved by the addition of a minor amount of an additional material which, at the fusing temperature used for the toner, has a much lower viscosity, preferably several orders of magnitude lower, than the viscosity of the toner particles at the fusing temperature and which forms a separate phase from the toner particles when solidified.
It is believed that such material, during the fusing process, migrates to the outer surface of the image. During cooling of the image after it is fused, the additional material forms a substantially separate phase resulting in a hard slippery coating of the additional material which protects the image from abrasion.
It has been found that the additional material may be added at almost any point during the toner manufacturing process, but that the effect of the material is most pronounced when the material is added during the final stage of the grinding of tire toner or when it is separately ground and added as finely ground material to the toner.
There is thus provided, in accordance with a preferred embodiment of the invention an image forming method comprising:
providing an image on a substrate, the image comprising toner particles including a polymer material, preferably comprising one or more of an ethylene copolymer, an ethylene terpolymer or an ionomer; an additional material, preferably comprising one or more of polyethylene, a polyethylene wax, a homopolymer and a low molecular weight ionomer, which additional material is solid at room temperature; and carrier liquid;
fusing the image to the substrate by heating the image to a fusing temperature at which the toner particles soften to a first viscosity,
wherein the additional material has a second viscosity at the fusing temperature which is at least ten times lower and preferably at least two or three orders of magnitude lower than the first viscosity.
Preferably the toner particles are solvated by the carrier liquid at the fusing temperature whereby their viscosity is reduced to the first viscosity. Preferably the additional material is solvated by the carrier liquid at the fusing temperature whereby its viscosity is reduced to the second viscosity.
Preferably, during fusing or subsequent cooling, the additional material migrates to the surface of the image away from the substrate. In a preferred embodiment of the invention, during cooling, at least a portion of the additional material forms a separate phase from the toner material at said surface, whereby the additional material forms a abrasion resistant layer covering the toner material.
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Almog Yaacov
Ben Avraham Peretz
Bossidon Becky
Landa Benzion
Grainger Quana
Grimley Arthur T.
Indigo N.V.
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