DE1182524B - Electrophotographic recording material - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: G 03 c

Pat. Bl.

German class: 57 b - 1O ₁ ,

New act,

Number: 1182 524

File number: E 21202 LX a / 57 b

Filing date: June 8, 1961

Opening day: November 26, 1964

The invention relates to an electrophotographic which is particularly suitable for xerographic purposes Recording material which can be handled in subdued light.

It is known to electrostatically charge a photoconductive layer, then pass the charged layer through to expose a master copy and to develop the resulting charge image by adding a powdery or liquid electrophotographic developer is applied to the charge image, the toner is attracted to the parts of the image that have remained charged.

The photoconductive layer can be charged in various ways. One of the most functional known method is that it is passed under a corona discharge. If zinc oxide is used as a photoconductor, the charge has negative polarity. The zinc oxide has that Property that it can store negative charges in the dark for a certain period of time. Usually apply a high intensity corona discharge long enough to reach the saturation potential and to ensure that the maximum amount of toner is attracted to the unexposed parts of the image will.

Once the electrophotographic recording material is charged, it is necessary to operate under dark room conditions, i.e. H. with color lamps too work, because otherwise the electrical charges are deleted in an undesirable manner. Since that Surface potential of the photoconductive layer decreases proportionally with exposure and at a certain exposure becomes zero, so that in the subsequent development practically none If toner sticks more, even a very short exposure to dim light can reduce the surface potential a charged photographic material to an ineffective one Reduce the amount.

The object of the invention is to provide an electrophotographic Specify recording material that is handled in a charged state in subdued light can be.

The subject of the invention is based on an electrophotographic recording material which consists of an electrically conductive layer support and a photoconductive ZnO binder layer with an inorganic additive, and is characterized in that the photoconductive layer contains titanium dioxide, magnesium oxide, zirconium oxide, aluminum silicate or strontium sulfate as the inorganic additive contains.
It has proven to be particularly advantageous if electrophotographic recording material

Applicant:

Eastman Kodak Company, Rochester, N.Y.

(V. St. A.)

Representative:

Dr.-Ing. W. Wolff and H. Bartels, patent attorneys, Stuttgart 1, Lange Str. 51

Named as inventor:

Dale Leroy Smith, Rochester, N.Y. (V. St. A.)

Claimed priority:

V. St. v. America June 27, 1960 (39154) -

the electrophotographic recording material according to the invention as an inorganic additive Contains a mixture of titanium dioxide and magnesium oxide or zirconium oxide. The material appropriately contains based on the total weight of the photoconductive zinc oxide and the inorganic additive, 3 to 90 percent by weight, preferably 3 to 80 percent by weight of titanium dioxide, magnesium oxide, zirconium oxide, Aluminum silicate or strontium sulfate.

Paper can advantageously be used as the substrate and a styrene-butadiene copolymer, optionally mixed with a silicone resin, can be used.

The knowledge on which the invention is based is surprising for the following reasons:

With a poorly or non-photoconductive material dispersed in a common binder a lower surface potential is obtained than with a good photoconductive material, such as Zinc oxide. Accordingly, it had to be expected that by mixing a weak or non-photoconductive material to photoconductive zinc oxide the surface potential is lowered. In Not to be expected, however, it has now been found that a weakly photoconductive material, such as, for example Titanium dioxide mixed with zinc oxide in a suitable ratio to a higher surface potential can be charged as zinc oxide alone.

The saturation potential is important in xerographic processes to the extent that it is important for exposure

409 729/333

3 4

the saturation potential is proportional to the exposure generated. At the parts of the image where the light is reduced to an amount at which the photoconductive layer strikes, charges 12 'in the original charge can be completely erased. If there is a shift in the direction of the layer carrier 11 and there is no longer any charge, they reject a charge image. In Fig. 2c is that on speaking image parts of the final copy a 5 developed in a known manner, ie with a so-called minimum density D _n H _n on. The image is shown where the toner is dusted, with the toner lightening, which has the saturation potential at the. unexposed parts of the image 24 depressed value, which just gives Dmax , is the Beiich- has. These image parts 24 indicate in the final copy processing threshold of the method. The greater exposure, D _max , while the exposed, discharged image is just sufficient to remove all charge, io parts 23 D _m , _n . It is thus obtained with a positive so that Dmin is obtained, the largest in which the original 21 is directly obtained a positive copy. Effective exposure method. The area As shown in FIG. As can be seen in Figure 3, the light takes between the exposure threshold and this greatest sensitivity of photoconductive mixtures of effective exposure is referred to as the exposure scale zinc oxide and titanium dioxide in a suitable binder. 15 medium (logarithmic) proportionally with increasing Will, therefore, a common electrophotographic titanium dioxide content. Accordingly, it becomes more difficult in recording material after charging to a degree, as the ratio of exposure used before it is exposed imagewise, titanium dioxide to zinc oxide grows, a photographic recording material that has already been charged so far is then reduced. that so that D _max cannot be achieved. 20 to discharge with subdued light. If the recording material is used anyway, the proportion of titanium dioxide in the zinc oxide is obtained, so a copy with insufficient contrast. Almost any titanium dioxide mixture is obtained. between the sensitivity of 100% zinc-The saturation potential is defined as the amount of charge oxide and 100% titanium dioxide that a particular photoconductive layer can obtain. A photoconductive layer can accommodate. 100% zinc oxide requires an exposure of 15 foot candle seconds (about 150 lux seconds) with the help of the drawings. It shows a tungsten lamp, whereas a faint F i g. 1 shows a section through an electrophotographic photoconductive layer made of titanium dioxide an exposure recording material requires after a period of 5000 foot candlestick seconds. The preferred embodiment of the invention, the exposure required in each case (in Fußkerzensekun-F i g. 2 a schematic flow diagram of a xerograph) is a yardstick for the exposure stability, the phic process, which has a certain photoconductive mixture in subdued light. The works, length of time during which a charged electrophoto-fi g. 3 shows a diagram from which the effect of a graphic recording material with attenuated addition of TiO ₂ to ZnO on the exposure stability to light can be manipulated, depends on the photoconductive layers, the stability to light and the rest of the figure used. 4 is a diagram showing the synergistic light source. For example, because of the higher effect of _{adding TiO 2} to ZnO on the saturation ultraviolet content, exposure using fluorescence generation potential of a photoconductive layer reduces the surface potential more strongly than it does, for example exposure using tungsten lamps. F i g. Fig. 5 is a graph showing the time during which, therefore, a charged electrophotographic one of the recording materials can be handled in dim light, recording material under fluorescent lighting. only a correspondingly shorter time without damage

The in Fig. The electrophotographic load shown in FIG. 1 can be handled.

Drawing material 10 consists of a layer carrier in FIG. 4 is the saturation potential of 0 to 11 of paper on which a zinc oxide of 13,100 ° / ₀ of titanium dioxide containing zinc oxide-titanium-titanium dioxide 14 and an insulating binder 15 shown dioxide mixtures. The synergistic effect existing photoconductive layer 12 is applied. the combination in question can be seen from the saturation in FIG. It is important that a sufficient charge remains in the photoconductive layer by means of a glow discharge 17 in the photoconductive layer so that a charge which is obtained from parts of the copy which are at a high negative potential with respect to an under-maximum optical density in the unexposed image layer 19 is retained will. This can best be assumed by electrode 18, the potential of a 55 being explained by means of an example. Power source 16 is generated. The electrode 18, which, assuming a recording material is used in the form of a recording material parallel to the photoconductive layer 12, which is present after treatment with a glowing fine wire, is discharged across the surface to a saturation potential of 350 volts and moved back to achieve a uniform charge ensure a 1.0 unit exposure scale on the log. 60 Ε scale. The photoconductive layer 12 used for this recording takes a, as can be seen from FIG. Always paint a surface potential after the exposure; office light remains at least 300 volts for several seconds, the optical density is retained. In order to make a copy, a maximum of 65 is (D _max ) . All image parts on which a transparent positive template 21, the surface potentials between 300 and 350 volts vervon a lamp is illuminated 20 by means of a remained are, are thus developed on D _ma x, currency lens 22 on the photoconductive layer 12, a light - rend all parts of the image with a surface potential of

5 6

less than 300 volts to an optical density of dioxyde in the form of rutile or anatase in connection

which, with zinc oxide, gave better results than any of the remaining charge

speaks, with those parts of the picture on which practically other addition. Both naturally occurring crystal

no charge remains, tetragonal male optical density can be developed on Dmtn, that is, on minimal forms of titanium dioxide. However, there is 5 crystal symmetry or a tetragonal lattice.

an electrophotographic recording material The spectral sensitivity of the recording

of the type in question after charging, the material and the contrast of the images may change

its saturation potential inevitably depends on the selection of zinc oxide, the inorganic additive

know is subject to a decrease in the charge, it is possible that and of the binding agent and the quantitative ratio Dmax are not achieved, that is to say that each constituent is regulated in the present case.

Example, the potential drops below 300 volts. The ratio of the photoconductor to the binder

Recording materials according to the invention can vary over a very wide range,

to a considerably higher saturation potential than A preferred range is between 50 and 90%

To achieve D _{max it is} necessary to have a charged content of photoconductor + additive and 50 to 10% and thus provide a safety factor, so 15 binders.

that with the recording material D _ma .x is still used to produce a recording material

can be enough after a certain charge a binder in a suitable organic

waste has occurred. The meaning of the in F i g. 4 Solvents dissolved and the powdery zinc oxide

The synergistic effect shown is evident, and the powdery additive is added. Around Since the mixture of zinc oxide and titanium dioxide produces the best results, the powdery

charges to a saturation potential that considerably zinc oxide and the powdery additive before the

is greater than the saturation potential of the individual addition to the binder solution mixed with one another

Components alone. Without this being synergistic. In another way of working, the

The electrophotophotoconductive mixture according to the invention could have an effect without using one Graphic recording material not on a saturation solvent by kneading the powdery

supply potential, the Dmax in the end-constituents with a softened thermoplastic

results in a valid copy if a certain amount of binder is produced.

attenuated, light-induced charge drop allows. The inventive recording material fact, the charge decay in subdued done ensures that the handling of xero light so slowly that the surface potential of only 30 light-sensitive materials considerably ernach some time under the most minimal for D _ma x facilitated is because without the necessary is that particular amount of volts required goes down. Dark rooms, screens, light traps and the like in FIG. Figure 5 shows the length of time during which simple electrophotographic office charged electrophotographic copiers in accordance with the invention can be used. Recording materials in subdued light can be handled without the contrast in a completely sufficient sensitivity and the final copy can be reduced. For attenuated light in a reasonable time to the saturation potential, 30 to 50 foot candles (about 300 to 500 lux) are to be charged. The recording material of the invention with a cold, white fluorescent light illumination is particularly suitable for processing in copies. The curve 29 in FIG. Figure 5 shows the 40 in hand-operated copiers. The time during which the inventive recording The materials to be handled under subdued light can be handled under fluorescent light illumination electrophotographic recording materials of 30 foot candles, and measured according to the invention are in the following with reference to the curve 30 the time during which they are described under an example. Fluorescent light illumination of 50 foot candles 45

can be handled. When a tungsten glow Example 1 lamp lighting with a color temperature of

3450 ° K is used, at least 100 foot candles are required (This example relates to the production of one required to obtain a comparable curve. Comparative sample not according to the invention) Typical office lighting using tungsten incandescent 50 A dispersion was made by mixing in a lamp has a color temperature of about 2850 ° K, electrically driven, rotating mixer while so that more than 100 foot candles are still required to obtain a comparable curve around 10 minutes from the following components. It is therefore posed:
the in F i g. 5 should only be regarded as a minimum time, since curves 55 copolymer were obtained from 45 percent by weight under more stringent conditions than butadiene and 55 percent by weight

for example, with an illumination by means of tungsten-styrene 37.3 g

lightbulbs. Silicone resin made from hydrolyzed, mixed

For the production of photoconductive layers th methyl-phenyl-chlorosilanes 4.7 g

suitable zinc oxide can be obtained by known methods 60 zinc oxide 56.0 g

getting produced. A useful procedure is given in γ 1 1 100 0 ff

U.S. Patents 2,727,807 and 2,727,808 f ^{y °, WYV '}

described. Methyl alcohol 2.0 g

Among the additives used in the manufacture of the

photoconductive layers mixed with zinc oxide 65 The dispersion was made into one layer on paper can include titanium dioxide, magnesium thickness of 0.025 mm (measured dry) applied, oxide, zirconium oxide, aluminum silicate, calcium silicate After charging, this layer reached a saturation point Strontium sulfate. Titanium has been found to have a potential of 340 volts, which is less than one

Second completely lost in dim light-

Example 2

In this example, an electrophotographic recording material with 70% zinc oxide and 30% Titanium dioxide described in the photoconductive layer.

A dispersion was prepared as in Example 1 by mixing the following ingredients:

Copolymer of 45 percent by weight butadiene and 55 percent by weight Styrene 37.3 g

Silicone resin from hydrolyzed, mixed methyl-phenyl-chlorosilanes 4.7 g

Zinc oxide 39.2 g

Titanium dioxide (anatase) 16.8 g

Xylene 100.0 g

A dispersion was made by mixing in an electrically powered mixer for 10 minutes made from the following components:

Copolymer of 45 percent by weight butadiene and 55 percent by weight Styrene 37.3 g

Silicone resin made from hydrolyzed, mixed

Methyl phenyl chlorosilanes 4.7 g

Titanium dioxide (rutile) 56.0 g

Xylene 100.0 g

The dispersion was applied to paper in a layer thickness of 0.025 mm (measured dry).

After being charged, the electrophotographic recording material reached a saturation potential of 120 volts. It was exposed and developed as in Example 2. The quality of line or raster copies, obtained according to this example was hardly acceptable in terms of contrast, although the recording material would otherwise be quite useful for copying documents.

The charged recording material could be exposed to 5000 foot candle seconds at 3450 ° K

The dispersion was applied to paper in a layer thickness of 0.025 mm, which (measured dry) corresponded to ^{about 27 g / m 2.} The layer reached a saturation potential of 510 volts. That

charged recording material could at 25 den without the contrast decreasing. Fluorescent light illumination of 40 foot candles can be handled for 3 to 5 seconds without adverse effects on contrast have been found. It was taking a negative or a positive Line art or screened copy original exposed 30 recording material written on, which except for 60% and according to the in RCA Review, 15, p. 469 zinc oxide and 40% titanium dioxide in the photoleitbis 484 (1954), specified specification developed. Under a tungsten lamp lighting of a color temperature of 3450 ° K, the charged

Example 5 In this example, an electrophotographic

capable layer contains a sensitizing dye.
A dispersion was carried out as in Example 1

Drawing material up to 200 foot candlesticks 35 Mixing the following components made:

can be exposed without the contrast decreasing.

Example 3

In this example, an electrophotographic recording material with 50% zinc oxide and 50% Titanium dioxide described in the photoconductive layer:

A dispersion was prepared as in Example 2 from the following ingredients:

Copolymer of 45 percent by weight butadiene and 55 percent by weight

Styrene 37.3 g

Silicone resin from hydrolyzed, mixed methyl-phenyl-chlorosilanes 4.7 g

Zinc oxide 28.0 g

Titanium dioxide (anatase) 28.0 g

Xylene 100.0 g

The dispersion was applied to paper as in Example 2. The charged layer reached a Saturation potential of 550 volts. She could under a fluorescent light illumination of 40 foot candles Copolymer of 45 percent by weight butadiene and 55 percent by weight styrene 37.3 g

Silicone resin from hydrolyzed, mixed methyl-phenyl-chlorosilanes 4.7 g

Zinc oxide 33.6 g

Titanium dioxide (anatase) 22.4 g

Xylene 100.0 g

Rose Bengal (C.I. No. 779) 0.00113 g

Methyl alcohol 2.0 g

The dispersion was applied to paper in a layer thickness of 0.025 mm (measured dry). After charging, the electrophotographic recording material reached a saturation potential of 530 volts. As indicated in Example 2, it was exposed and developed. Copies made with it with a line art were of high quality. The charged recording material was under fluorescent lamp illumination of 40 foot candles for 5 to 7 seconds without noticeable damage to the contrast in the final copy. The loaded recording material could with

300 foot candle seconds are exposed at 3450 ° K,

For 15 to 18 seconds without a decrease in contrast without decreasing the contrast in the final image, trastes to be handled in the final copy. It was also sensitive in terms of its optical sensitivity Exposure and development of the element against one without the use of a color were made as carried out in example 2. Fabric made a little better.

Example 4

In this example, an electrophotographic recording material with 100% titanium dioxide in the described photoconductive layer.

Example 6

In this example, an electrophotographic recording material containing zinc oxide and magnesium oxide is used described in the photoconductive layer.

Claims (1)

9 ίο A dispersion was prepared as in Example 1 from an electrically conductive layer support and the following components: a photoconductive layer with an electrical copolymer of 45 percent by weight insulating binder, a photoconductive butadiene and 55 percent by weight ZnO and an emern inorganic additive, thereby gt j 37 3 g 5 characterized that the photoconductive SiUkonharZäushydrölysierten, 'gemiscl ·' layer contains as inorganic additive titanium dioxide, th methyl-phenyl-chlorosilanes 4.7 g magnesium oxide, zirconium oxide, aluminum silicate zinc oxide 39 2 ε ° strontium sulfate. Magnesium oxide ". '.'. '.'. '.'. '.'. '.'. '.'. '.'. '.'. '.'. '.'. 16.8 g 2 :, Electrophotographic recording material according to claim 1, characterized in that the inorganic additive used is a mixture. The dispersion was applied to paper in a layer of titanium dioxide and magnesium oxide or zirconium thickness of 0.013 mm (measured dry) When charged, the electrophotographic 3rd electrophotographic recording material reached a saturation potential of 230 volts Effect of conductive ZnO and the inorganic additive, on the contrast in the final copy handled 3 to 90 percent by weight of titanium dioxide, magnesium at contains. The charged recording material could be exposed with 4. Electrophotographic recording time 1000 foot candle seconds at 3450 ° K material according to claim 3, characterized in that without the contrast in the final image decreasing, based on the total weight of the photo. In order to produce a satisfactory copy of the conductive ZnO and the inorganic additive, however, it was necessary to develop in an as 30 to 80 percent by weight titanium dioxide or electric field containing magnesium oxide of suitable orientation and size. in order to suppress the haze in the background. 5. Electrophotographic recording method. material according to one of claims 1 to 4, characterized in that it is a styrene-butadiene copolymer as the layer support and as the binder, 1. Electrophotographic recording material - optionally mixed with a silicone resin, material, especially for xerography, contains. 1 sheet of drawings 409 729/333 11.64 © Bundesdruckerei Berlin