DE2307743C3 - A method of polishing the surface of a photoconductive layer of an electrophotographic recording material - Google Patents

Description

15th

In electrophotographic processes, amorphous selenium is preferably used as the photoconductive layer for electrophotographic recording material used, for which the amorphous selenium layer, on a conductive substrate, e.g. B. deposited a copper or aluminum plate by means of vacuum evaporation will. One electrophotographic process consists of:

(1) Charges the surface of the photoconductive layer by means of a corona discharge,

(2) an electrostatic latent image is created on the photoconductive layer by imagewise exposure,

(3) a visible one by electrodeposition of toners in powder form on the latent image Image generated,

(4) the visible toner image on a transfer medium, e.g. B. a sheet of paper, transfers and

(5) The transferred toner image is fused to the paper sheet.

The toners are powdery and are generally made from a mixture of carbon black and synthetic Resin, ζ. B. styrene-butadiene copolymers produced. By melting the synthetic Resin fixes the toners on the paper sheet. The xerographic process described above is known to those skilled in the art. A direct current voltage of 5 or 6 kV is used for corona discharge generally a pick-up potential of about 700 or 750 volts is obtained. This absorption potential is caused by the repeated use of the photoconductive layer, for example, ten thousand times Use, reduced to around 600 to 660 V. This decrease is caused by

(1) Toner or airborne dust is trapped on the surface of the photoconductor,

(2) this makes the surface of the layer rough and

(3) a change in surface quality due to aging entry.

It is therefore, in order to bring the deteriorated photoconductor to the original recording potential, necessary to clean or polish the surface of the photoconductor. There are several for this purpose Polishing or cleaning agents or processes are known. For example, in US Pat. No. 2,484,782 cubic crystalline salt, ζ. B. NaCl or HH4Cl, and in US-PS 31 00 726 kieselguhr and etherified cellulose suggested. From US-PS 27 72 991 are cleaning agents made of barium sulfate and a dietaphosphate known for removing toner residues, this cleaning after each copy repeated . must become. The cleaning agents used for this purpose must not be abrasive or Have a polishing effect, otherwise the photoconductive layer will be destroyed after just a few copying processes would be.

Also a solvent that removes a toner film formed on the surface of the photoconductor can, are known, but a solvent, e.g. B. Isopropyl alcohol is insufficient to the To polish or even clean the surface of the photoconductor effectively and completely.

It is therefore an object of the present invention to provide a improved polishing material and method of its use to polish a surface of a to provide amorphous selenium photoconductor.

This object is achieved in the present case by a method in which a polishing agent mixture is used which contains strontium and barium sulfate. When carrying out the method according to the invention, the surface is preferably polished with cotton or cotton wool, on which a suspension of a mixture of SrSO ₄ and BaSO ₄ in an organic solvent, e.g. B. propyl alcohol, methyl alcohol, ethyl alcohol or isopropyl alcohol, according to a further preferred embodiment <-form is a mixture of strontium and barium sulfate (15: 1 to 1: 15 parts by weight and a particle size of 0.1 to 30 μίτι) as a polishing material used.

The photoconductive layer used in this invention was prepared as follows:

The photoconductive, amorphous selenium layer was produced on an aluminum roller with a diameter of 17 cm by depositing a 50 μm thin selenium layer by vacuum evaporation. The dark resistance of the selenium layer thus formed was 10 ¹⁴ Ω cm.

The toners were made as follows:

A mixture of one part by weight carbon black and 10 parts by weight of butadiene-styrene copolymer was heated to a temperature of about 200 ⁰ C. After cooling, the powdery mixture was finely divided with particle sizes from 1 to 20 μm.

If you use the photoconductive layer and the toners, as their production was described above, the xerographic copying process (1) comprises charging by means of a corona discharge of +6 or +5 kV, (2) imagewise exposure, (3) developing, and (4) transferring repeated about ten to twenty thousand times of the picture.

The resulting, in ih ..; Efficiency Reduced photoconductive layer, was coated with absorbent cotton on each of the following Polishing materials with particle sizes from 0.1 to 30 μm were applied, polished. In this way, the usefulness of each of these polymer materials was compared and evaluated, it was surprisingly found that strontium sulfate and barium sulfate am are most effective.

The following polishing materials were used:

Calcium carbonate (CaCOs),
Cerium oxide (Ce ₂ O ₃ ),
Zirconium oxide (ZrO ₂ ),
Magnesium oxide (MgO),
Titanium oxide (TiO ₂ ),
Silicon oxide (SiO ₂ ),
Chromium oxide (Cr ₂ Os),

Aluminum silicate (abSiOs),

Magnesium silicate (Mg ₂ SiO ₄ ),
Calcium silicate (Ca ₂ SiO ₄ ),
Aluminum sulfate (Al ₂ (SO ₄ ) J),
Calcium sulfate (CaSO ₄ ),
Strontium sulfate (SrSO ₄ ),
Barium sulfate (BaSO ₄ ),
Magnesium sulfate (MgSO ₄ ),
Zinc sulfide (ZnS),
Zinc chloride (ZnCl ₂ ) and kieselguhr.

The properties of SrSO ₄ and BaSO ₄ are to be presented as follows:

SrSO4

fSaSOi

Gewit'hlMci'c

No. I.

No. 2

No. 3

No. 4

No. No. 6

SrSO ₄ (alone)
BaSO-i (alone)

Polishing suitability high> low

Recovery of the uptake low <: high uptake potential

20th

The polishing material of the present invention is used in the following manner:

After the toner adhering to the photoconductive layer has been removed by lightly rubbing the layer with soft cotton, the surface is polished by rubbing several times with absorbent cotton, onto which a dispersion of SrSO ₄ or BaSO ₄ in isopropyl alcohol! is applied. After polishing, the surface is allowed to stand for 20 to 30 seconds, which causes the isopropyl alcohol to evaporate and brownish powder to remain on the surface. The toner powders can be easily removed by rubbing the surface with soft cotton (wadding), and then the surface can be rubbed with absorbent cotton with isopropyl alcohol applied, if desired.

The following examples illustrate the invention.

example 1

Polishing materials # 1 - # 6 were made from the _4C's following ingredients:

BaS04

SrS04

BaSO4

Isopropyl alcohol

SrS04

BaS04

SrSO4

BaSO ₄

Ethyl alcohol

IO
I.

10

10
i

10

The particle sizes of SrSO ₄ and BaSO ₄ were 0.1 μm 5 30 μm.

Studies of the polishing materials No. 1 to No. 6 in the following manner for evaluation its effects carried out:

(1) A photoconductive layer was made of amorphous selenium, the photoconductive layer a pick-up potential of 750-760 V or 700-710 V with a corona discharge of + 6 kV or + 5 kV.

(2) After copying 15,000-20,000 times with toners made from carbon black and butadiene-styrene copolymer was repeated, a lower absorption potential obtained by a corona discharge of +6 kV or +5 kV was measured.

(3) After the photoconductive layer was polished with the polishing materials No. 1 - No. 6 the obtained improved absorption potential measured with the same corona discharge and that Surface appearance observed.

The values and results are given in the following table:

Polishing material No. 2 No. 3 No. 4 No. 5 No. 6 number 1 6th 6th 6th 5 5 Corona discharge (KV) 6th 760 750 750 700 710 Initial absorption potential (V) 750 20,000 20,000 20,000 15,000 15,000 Number of copies 20,000 640 660 660 600 600 Reduced absorption potential (V) 650 750 730 750 670 650 Recovered recording 720 potential (after polishing) (V) smooth pretty sleek pretty sleek smooth smooth Appearance of the surface of the photo slightly impaired head and scratched

From the above results, it can be seen that the polishing materials No. 3-No. 6 from a mixture of SrSO ₄ and BaSO _{4 have} the best polishing effect.

Example 2

An amorphous selenium photoconductor was left in the air for 6 months.

An initial uptake potential and a reduced uptake potential (after 6 months) of 750 V or 650 V by means of 6 kV corona discharge.

After the deteriorated surface of the photoconductor with the polishing materials No. 3, No. 4 and No. 5 of Example 1 were polished, a restored absorption potential was measured.

Polishing materials # 3, # 4, and # 5 provided restored pickup potentials of 740, 750, and 720 V.
The polishing material of this invention can therefore be used for polishing a photoconductor so long as it is composed of amorphous selenium, small amounts of other elements such as tellurium, arsenic, sulfur or thallium.

Claims (1)

installment entitlement: Method of polishing the surface of a photoconductive layer of an electrophotographic Recording material consisting essentially of amorphous selenium has a fine-grained one Powder-containing polishing agents, characterized in that a mixture of polishing agents is used used, which contains strontium and barium sulfate.