Electrophotography – Image formation – Transfer
Reexamination Certificate
1999-06-28
2002-12-24
Braun, Fred L. (Department: 2852)
Electrophotography
Image formation
Transfer
C399S174000, C399S320000, C399S328000
Reexamination Certificate
active
06498918
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to thiophene filled material coatings for xerographic components useful in xerographic applications including digital, image on image, and contact electrostatic applications. In particular, the present invention relates to thiophene filled material coatings for transfer/transfuse, intermediate transfer, bias charging, bias transfer, fusing, and like xerographic components. In embodiments, the thiophene filled material coatings can be useful as outermost coatings, intermediate coatings, or as adhesives between other polymer layers. Also, the thiophene filled material coatings can be useful in both dry and liquid toner applications and in color toner applications. The thiophene filled material coatings, in embodiments, allow for adjusting and controlling desired resistivity, and also allow for increased temperature, hydrolytic, and good light stability. The thiophene filled material coatings are easily fabricated and have increased stability.
The electrical property of many xerographic components such as transfer members, biasable members, fusing members, transfuse members and other like xerographic components, is a very important characteristic of the xerographic component. If desired electrical properties of a xerographic component are not obtained, a multitude of copy or print failures can occur. Examples of these adverse results include decrease in copy quality, copy quality defects, print failure, and decrease in the life of the xerographic component. Most of these adverse results are due to ineffective toner release caused by the xerographic component not possessing the desired resistivity. The adverse results often also occur when the xerographic component does not retain its desired resistivity over time.
One type of xerographic component is a transfer member including intermediate transfer and transfix components. Transfer/transfix members allow for positive attributes such as enabling high throughput at modest process speeds, improving registration of the final color toner image in color systems using synchronous development of one or more component colors using one or more transfer stations, and increasing the range of final substrates that can be used. However, a disadvantage of using a transfer/transfix member is that a plurality of transfer steps is required allowing for the possibility of charge exchange occurring between toner particles and the transfer member which ultimately can lead to less than complete toner transfer. The result is low resolution images on the image receiving substrate and image deterioration. When the image is in color, the image can additionally suffer from color shifting and color deterioration. In addition, the incorporation of charging agents in liquid developers, although providing acceptable quality images and acceptable resolution due to improved charging of the toner, can exacerbate the problem of charge exchange between the toner and the intermediate transfer member.
Preferably, the resistivity of the transfer/transfix member is within a preferred range to allow for sufficient transfer. It is also important that the intermediate transfer or transfix member have a controlled resistivity, wherein the resistivity is virtually unaffected by changes in humidity, temperature, bias field, and operating time. In addition, a controlled resistivity is important so that a bias field can be established for electrostatic transfer. It is important that the transfer/transfix member not be too conductive as air breakdown can possibly occur.
Other xerographic components include charging devices. Contact charging or bias charging members function by applying a voltage to the charge-receiving member (photoconductive member). Such bias charging members require a resistivity of the entire charging member within a desired range. Specifically, materials with too low resistivities will cause shorting and/or unacceptably high current flow to the photoconductor. Materials with too high resistivities will require unacceptably high voltages. Other problems which can result if the resistivity is not within the required range include low charging potential and non-uniform charging, which can result in poor image quality.
Therefore, it is desired in biasable members, that the resistivity be tailored to a desired range and that the resistivity remain within this desired range. Accordingly, it is desirable that the resistivity be unaffected or virtually unaffected to changes in temperature, relative humidity, running time, and leaching out of contamination to photoconductors.
Fusing the toner to a copy substrate is an important step in the xerographic process and fuser members are another type of xerographic component. It is important in the fusing process that minimal or no offset of the toner particles from the support to the fuser member take place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the background or interfering with the material being copied there. The referred to “hot offset” occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser, and accordingly it is desired to provide a fusing surface which has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils to prevent toner offset.
It is desirable that upon fusing, virtually no toner is left on the fuser member, and if so, subsequent copies will be contaminated. Therefore, it is desired to increase release properties of the fuser member.
Efforts have been made to tailor resistivity of xerographic components, and to obtain controlled resistivity of these components once the desired resistivity is attained. These methods have included adding conductive fillers or carbon black to the outer layer. While addition of ionic additives to elastomers may partially control the resistivity of the elastomers to some extent, there are problems associated with the use of ionic additives. In particular, undissolved particles frequently appear in the elastomer which causes an imperfection in the elastomer. This leads to a nonuniform resistivity, which in turn, leads to poor transfer properties and poor mechanical strength. Furthermore, bubbles appear in the conductive elastomer. These bubbles provide the same kind of difficulty as the undissolved particles in the elastomer namely, poor or nonuniform electrical properties, poor mechanical properties such as durometer, tensile strength, elongation, a decrease in the modulus and a decrease in the toughness of the material. In addition, the ionic additives themselves are sensitive to changes in temperature, humidity, operating time and applied field. These sensitivities often limit the resistivity range. For example, the resistivity usually decreases by up to two orders of magnitude or more as the humidity increases from 20% to 80% relative humidity. This effect limits the operational or process latitude. Moreover, ion transfer can also occur in these systems. The transfer of ions will lead to contamination problems, which in turn, can reduce the life of the machine. Ion transfer also increases the resistivity of the member after repetitive use. This can limit the process and operational latitude and eventually, the ion-filled component will be unusable.
Conductive particulate fillers, such as carbons, have also been used in an attempt to control the resistivity. Generally, carbon additives control the resistivities and provide stable resistivities upon c
Schlueter Jr. Edward L.
Sharf Lucille M.
Smith James F.
Bade Annette L.
Braun Fred L.
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