JP3048631B2 - Organic photoconductor - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates generally to photoconductors, and more particularly to organic photoconductors.

BACKGROUND OF THE INVENTION Various types of organic photoconductors are known. Most organic photoconductors are susceptible to attack by organic solvents of the type used in liquid toner electrophotography and are therefore unsuitable for such applications. Some of these photoconductors are soluble in these and other solvents that, when under stress, especially under tension, cause cracking as a result of solvent exposure.

It is known in the art to provide a protective coating on organic photoconductors. Examples of these coatings are shown in U.S. Patent Nos. 4,891,290 and 4,894,304.

SUMMARY OF THE INVENTION The present invention seeks to provide an improved organic photoconductor that is resistant to cracking in a stressed environment in the presence of organic solvents of the type used in liquid toner electrophotography. is there.

Thus, according to one preferred aspect of the present invention, an organic photoconductor comprising a base layer formed from a first substance and a photoconductive layer formed from a second substance, wherein the photoconductor is The organic photoconductor is provided, wherein the photoconductive layer is subjected to a smaller stress than the base layer when the photoconductive layer is held in a curved arrangement facing outward.
According to another preferred aspect of the present invention, the first substance is relatively more flexible than the second substance. Another one of the present invention
According to one preferred embodiment, the first substance is relatively flexible and extensible, and the second substance is chemically treated to increase its extensibility and flexibility, initially It is a material with low flexibility and extensibility.

According to another preferred embodiment of the present invention, an organic photoconductor including a base layer formed from a first substance and a photoconductive layer formed from a second substance is provided. There is also provided the organic photoconductor, wherein the layers are pre-stressed in the opposite direction.

According to another preferred embodiment of the present invention, an organic photoconductor including a base layer formed from a first substance and a photoconductive layer formed from a second substance, wherein the second substance has a stress therein. There is further provided the organic photoconductor, which has been chemically treated to mitigate phenomena. In one preferred embodiment of the invention, the chemical treatment renders the photoconductive layer more flexible and extensible. This photoconductive layer is preferably more elastic or plastic.

Further, according to another preferred embodiment of the present invention, a step of providing an organic conductor having a base layer and a photoconductive layer, and reducing the stress of the photoconductive layer by at least one of the base layer and the photoconductive layer. A method of manufacturing an organic photoconductor is provided that includes a step of treating to mitigate.

In addition, according to the above aspect of the present invention, the organic photoconductor base layer has greater flexibility and extensibility than the photoconductive layer.

Further, according to the above aspect of the invention, the base layer has a higher stress relaxation temperature than the photoconductive layer.

In addition, according to a preceding aspect of the present invention, the processing includes stressing the base layer and the photoconductive layer, and applying stress to the base layer and the conductive layer while controlling the stress relaxation temperature and light intensity of the base layer. Heating to a temperature between the stress relaxation temperature of the conductive layer.

According to another aspect of the invention, the treating step includes the step of chemically treating the photoconductive layer to soften and render the layer more elastic or plastic than its previous state.

Furthermore, according to another preferred embodiment of the present invention, a drum, a photoconductive surface provided on the drum,
A device for forming a latent image on the photoconductive surface, a device for developing the latent image on the photoconductive surface with a liquid toner, and a device for transferring an image to a final substrate after the development. A liquid toner electrophotographic system is provided, the surface of which comprises an organic photoconductor sheet mounted on the drum.

According to another preferred embodiment of the present invention, the photoconductor sheet is constructed and operated according to any of the above embodiments alone or in a suitable combination.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood and appreciated from the following detailed description taken in conjunction with the drawings.

In the drawings, FIG. 1 is a simplified cross-sectional illustration of a liquid toner electrophotographic apparatus constructed and operated in accordance with one preferred embodiment of the present invention; FIG. 2 is a schematic illustration of an organic photoconductor useful in the embodiment of FIG. And FIG. 3 is a detailed prestressing illustration of a photoconductor in accordance with another aspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, FIG. 1 illustrates an electrophotographic image forming apparatus using liquid toner constructed and operated in accordance with one preferred embodiment of the present invention. The present invention will be described for a liquid developer system having negatively charged toner particles and a negatively charged photoconductor, ie, a system that operates in a reversal mode. For other combinations of toner particles and photoconductor polarity, the voltage value and polarity are varied according to the principles of the present invention.

Although the present invention can be practiced with a variety of liquid developer types, it is particularly useful for liquid developers comprising a carrier liquid and pigmented polymeric toner particles. In one preferred embodiment of the invention, the carrier liquid is Isopar (Exxo [Exxo]
n]). Examples of such developers are shown in U.S. Pat. No. 4,794,651. The disclosure of this US patent is hereby incorporated by reference.

As in a conventional electrophotographic system, the apparatus of FIG. 1 typically comprises a drum 10 arranged to rotate about a mandrel 12 in a direction generally indicated by arrow 14.
The organic photoconductor 100 is placed on the drum 10, stretched by the stretcher 99, and stretched.

The corona discharge device 18 acts on a substantially uniformly charged negatively charged organic photoconductor. Continuous rotation of drum 10 causes charged organic photoconductor 100 to be brought into image-receiving relationship by an exposure device including lens 20. Lens 20 focuses the image on charged organic photoconductor 100 and selectively discharges the photoconductor, thus creating an electrostatic latent image on the photoconductor. The latent image consists of an image area at a predetermined potential range and a background area at a different potential. The image may be laser generated, as in the case of printing from a computer, or may be an original image, as in a copier.

Continuous rotation of the drum 10 guides the charged photoconductor 100 having an electrostatic latent image to a developing device 22 including a charged developing plate 24. Developing device 22 acts to apply a liquid developer. Liquid developers consist of a solid portion containing pigmented toner particles and a liquid portion containing a carrier liquid, preferably an organic liquid, for developing an electrostatic latent image. The developed image includes an image area having on its surface pigmented toner particles and a background area.

Although developer unit 22 is shown as a conventional type single color developer, it may be replaced with multiple single color developers for full color image generation as is known in the art. Alternatively, a full-color image can be generated by changing the liquid toner of the developing device when changing the color to be printed. Alternatively, highlight color development may be employed as is known in the art.

According to one preferred embodiment of the present invention, following application of the toner to photoconductor 100, the photoconductor is rotated, typically in the direction indicated by arrow 28, and typically becomes charged. Through the rotating roller 26. Typically, the spatial separation between rollers 26 from photoconductor 100 is about 50 microns. Roller 26 thus acts as a metering roller, as is known in the art, to reduce the amount of carrier liquid on the background area and to reduce the amount of liquid covering the image.

The potential on roller 26 is preferably intermediate between the potential of the latent image area and the potential of the background area on the photoconductor. Typical approximate voltage is roller 26: -200 to -800V,
Background area: -1000V and latent image area: -150V
It is.

It should be relatively free of pigmented particles except in the area of the latent image of the liquid toner image passing through the roller 26.

Downstream of roller 26 is a rigidizing roller
Preferably, 30 are provided. The stiffening roller 30 preferably has only native conductivity or is formed from an elastic polymeric material such as polyurethane filled with carbon black to increase conductivity.

According to one aspect of the invention, roller 30 is pressed against photoconductor 100, such as by a spring mount (not shown). The surface of the roller 30 typically moves at the same speed and in the same direction as the photoconductor surface to remove liquid from the image.

Preferably, roller 30 is a biased squeegee as described in U.S. Pat. No. 4,286,039. The disclosure of the above U.S. Patent is incorporated herein by reference. Roller 30 is biased to a potential of at least a few hundred volts and less than a few thousand volts relative to the potential of the developed image on photoconductor 100, so that roller 30 repels the charged pigmented particles and causes them to shine. It is brought closer to the image area of the conductor 100, thus compressing and stiffening the image.

In one preferred embodiment of the present invention, the stiffening roller 30 has a Shore A hardness of about 30 to 35 and a volume resistance of about 30 to 35.
10 is a ⁸ ohm -cm, made of aluminum core thickness has been coated with carbon-filled polyurethane coating of 4mm diameter 20 mm. Roller 30 is preferably pressed against photoconductor 100 at a pressure of about 40-70 grams per cm of contact line extending along the length of the drum. A voltage of -1800 to -2800 volts is applied to the aluminum core of the stiffening roller 30 to provide a voltage difference between the core and the photoconductor in the image area, preferably of about 1600 to 2700 volts.

Under these conditions and for the preferred toner, the solids in the image portion is considered to be as high as 35% or more. After stiffening, the solids percentage should be at least 25
It is preferred to have an image that is 3030%.

Downstream of the stiffening roller 30, the image is printed with an organic photoconductor 100.
There is provided an apparatus for directly transferring the paper from the paper to a base material 130 such as paper. Direct transfer is achieved by providing guide rollers 132, 134 for guiding the continuous web of substrate 130 and drive rollers 138 which cooperate with the support web 140. In order to electrophoretically transfer the image from the photoconductor 100 to the base material 130, the base material is charged at a transfer position by a suitable charging device, for example, a corona discharge device 142.

After transferring the toner image to the substrate 130, the photoconductor 100 is engaged by the cleaning roller 50. The cleaning roller 50 typically rotates in the direction indicated by arrow 52 in which the roller surface 50 moves in a direction opposite to the movement of the adjacent surface of the photoconductor 100 with which the surface 50 effectively engages. . The cleaning roller 50 acts to rub and clean the photoconductor 100. Cleaning roller
50 can supply a cleaning material, such as toner or another cleaning solvent, via conduit 54. A wiper blade 56 completes the cleaning of the photoconductor surface. Any residual charge remaining on photoconductor 100 is removed by shining light from lamp 58 over the entire photoconductor surface.

In a multicolor system, after a cycle is completed for one color, the cycle is repeated for the other colors that are sequentially transferred from photoconductor 100 to substrate 130.

Alternatively, the direct transfer device can be used to transfer an image to a photoconductor 10
It may be replaced by an intermediate transfer member that receives the images from 0 and transfers those images to the final substrate.

FIG. 2 illustrates a preferred organic photoconductor sheet 100 useful in the embodiment of FIG. This sheet is base layer 1
02. The base layer 102 is typically formed from aluminized polyethylene terephthalate, commercially available under the trade name Mylar. The base layer is about 80 thick
Preferably it is micron and has a melting point of 250 ° C.

Disposed over the base layer 102 is a secondary layer 104 having a thickness of about 0.2 microns, typically formed from polyester, toluenesulfonamide-formaldehyde resin and polyamide. Disposed over the secondary layer 104 is a charge generation layer 106, typically formed from a hydroxysquarylium dye and a toluenesulfonamide resin, having a thickness of about 0.3 microns.

On top of layer 106 is a charge transport layer, typically about 18 microns thick, formed from polyester, polycarbonate, yellow dye, 4- [N, N-diethylamino] benzaldehyde phenylhydrazone and a small proportion of polysiloxane. 108 are located. Charge transport layer 108 and charge generation layer 10
6 together define the photoconductor layer described above.

The organic photoconductors described thus far are commercially available from IBM under the trade name Emerald.

According to one embodiment of the present invention, and as illustrated in FIG. 3, an organic photoconductor obtained from IBM is subjected to an annealing operation. This annealing operation will now be described in detail.

According to one embodiment of the present invention, the organic photoconductor 100 is mounted on a stretcher 120 and has a per cm width of the photoconductor 100.
Tension is applied up to 3 kg strain. The photoconductor 100 is subjected to the above-described strain, preferably in an oven (not shown) at 60 ° C.
Heat to a temperature of about 30 minutes. Thereafter, the photoconductor 100 is cooled to room temperature, and then external stress is removed therefrom.

It can be seen that the temperature of 60 ° C. is intermediate between the stress relaxation temperature of the base layer 102 of about 150 ° C. and the glass transition temperature of the charge transport layer 108 of about 45 ° C.

Even after processing as described above, i.e., after removing external stresses from the sheet photoconductor 100, the charge transport layer 108 of the photoconductor 100 remains stressed under compression,
On the other hand, the base layer 102 remains stressed under tension.
When the photoconductor 100 is mounted on the drum 10 and subjected to external tension as described in FIG. 1, the charge transport layer 108 is in a compressed state or relatively free of stress; It is therefore less susceptible to cracking or other defects as a result of exposure to organic solvents such as isopearl, which are common in liquid toner electrophotographic environments.

For example, the organic photoconductor 100 that was not annealed as described above cracked after about 500 copying cycles in a liquid toner copier. On the other hand, the organic photoconductor treated as described above did not crack even after several tens of thousands of copy cycles. It should be noted that annealing the sheet photoconductor without simultaneously applying tension does not substantially improve the isopearl resistance of the photoconductor.

According to another aspect of the present invention, an organic photoconductor 10
Zero can also be chemically treated to reduce the occurrence of stress cracking in a liquid toner environment. According to this aspect, the charge transport layer 108 is treated with a solvent or other reagent to soften it and make it more extensible, ie, more plastic or elastic than its previous state.

The chemical treatment is selected so as to keep the electrical and optical properties of the photoconductor essentially unchanged. When the photoconductor sheet subjected to such chemical treatment is stretched around the drum 10, no stress is generated in the charge transport layer. Thus, when the stretched photoconductor 100 is exposed to an organic solvent, the photoconductor does not tend to crack.

One particular chemical treatment that has been found to be effective is to soak the photoconductor 100 in cyclohexanone diluted 1: 5 with isopropyl alcohol for 2 minutes. This treatment does not significantly alter the electrical and optical properties of the photoconductor and eliminates the occurrence of the cracking described above.

Another chemical treatment uses cyclohexanone alone or the Columbia Chase Corporatio, Woodside, NY, USA.
n) HumiSeal Division
Using a modified vinyl epoxy 1A24, diluted 1:20 with cyclohexanone, commercially available from Sigma-Aldrich, Inc. These materials can be applied to the upper surface of photoconductor 100 by wire-rod techniques. In such cases, the United Kingdom, Merts, Royston, Littington
Bar # 2 from RK Print-Coat Instrument Ltd.
A model KCC303 coater using a rod diameter of 13 mm and wire diameter of 0.15 mm can be operated at a bar linear speed of 70 mm / sec.

Using pure cyclohexanone, the results are similar to those for immersion, with the solvent evaporating within about 20-30 seconds.

When a mixture of cyclohexanone and epoxy is used, in addition to the effects described above for cyclohexanone, the residual vinyl modified epoxy forms a mechanically protective overcoat that is substantially adherent to toner particles after evaporation of the solvent. .

Those skilled in the art will appreciate that the present invention is not limited by what has been particularly shown and described above. The scope of the present invention is defined only by the claims that follow.

──────────────────────────────────────────────────の Continuation of the front page (72) Inventor Shatou, Ehuit 49 49 Petak Tikuba, Haavib Street, 15 (56) References JP-A-52-76928 (JP, A) JP, B1) JP 49-15500 (JP, B1) U.S. Pat. No. 4,497,566 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 5/00 101 G03G 5/05 102 G03G 5/10 G03G 5/147 502

Claims (18)

(57) [Claims] A step of providing an organic photoconductor having a base layer and a photoconductive layer; a step of applying a stress to the organic photoconductor; and a step of applying the stressed organic photoconductor to a stress relaxation temperature of the base layer. Heat-treating by heating to a temperature between the stress relaxation temperatures of the photoconductive layer to relieve the stress in the photoconductive layer, without removing the stress from the organic photoconductor; Cooling the photoconductor and removing external stresses from the photoconductor prior to using the photoconductor for imaging, wherein the base layer has higher strain relaxation than the photoconductive layer. A method for producing a photoconductor having a temperature. 2. The method of claim 1, wherein applying the stress comprises applying tension to the organic photoconductor in a planar configuration. 3. The method according to claim 1, wherein the photoconductor is in a compressed state after the step of removing external stress. 4. The method according to claim 1, further comprising the step of, after the step of removing external stress, providing the photoconductor on a curved drum in an image forming apparatus. 5. The method of claim 4, wherein said photoconductive layer is in a compressed state after the step of relieving external stress and remains in a compressed state during use in said imaging device. 6. The process of providing an organic photoconductor having a base layer and a photoconductive layer, and chemically reducing the photoconductive layer of the organic photoconductor to relieve stress in the photoconductive layer. A method for producing a photoconductor, comprising a step of treating. 7. The organic photoconductor base layer has greater flexibility and extensibility than the photoconductive layer.
The method described in. 8. The method of claim 6, wherein said chemically treating comprises softening said photoconductive layer to make it more elastic than before. 9. The method of claim 6, wherein said chemically treating comprises softening said photoconductive layer to make it more plastic than before. 10. The method of claim 8, wherein said chemically treating comprises forming a protective layer on said photoconductive layer. 11. The method according to claim 10, wherein said protective layer comprises a vinyl-modified epoxy. 12. The method according to claim 6, wherein said step of chemically treating comprises applying an organic solvent to said photoconductive layer. 13. The step of chemically treating comprises applying an organic solvent containing a protective material to the photoconductive layer, whereby the solvent softens the photoconductive layer to make it more elastic. A method according to any of claims 6 to 11, comprising the step of evaporating said solvent to leave a protective coating on said photoconductive layer. 14. The method according to claim 12, wherein the solvent is cyclohexanone. 15. An organic photoconductor produced by the method according to claim 1. 16. A photoconductive layer comprising a base layer comprising a first substance and a photoconductive layer comprising a second substance, wherein the first and second substances are in opposite directions to the photoconductive layer in a compressed state. Organic photoconductor pre-stressed. 17. An organic material comprising: a base layer of a first substance; and a photoconductive layer of a second substance, wherein the photoconductive layer is in a compressed state when exposed to externally applied tension. Photoconductor. 18. A drum, an organic photoconductor produced by the method of any of claims 15 to 17, or produced by the method of any of claims 1 to 14, the photoconductive surface A liquid toner electrophotographic system comprising: means for forming a latent image on the photoconductive surface; means for developing the latent image on the photoconductive surface with liquid toner; and means for transferring the developed image to a final substrate.