DE2224504A1 - Improved Electrophotographic Process - Google Patents

Description

AGFA-GEVA ERT AKTIENGESELLSCHAFT LEVERKUSEN

May 18, 1972

Improved Electrophotographic Process

Priority: Great Britain, May 21, 1971, note no. 16 346/71

The present invention relates to electrophotography and particularly the improvements in the production of images by electrophotographic processes.

Known electrophotographic processes for producing visible images comprise the following steps: The electrostatic Charging of a photoconductive surface of an inorganic photoconductor in the dark, e.g. zinc oxide and selenium, or an organic photoconductor, the imagewise exposure of the surface to generate a latent, electrostatic Image and the development of the material to produce a visible image by applying a finely divided, electroscopic material, usually a resin that can be colored and known as a "toner" is. Depending on the sign of the electrostatic charge, the particles of the toner are attracted and on the charged Areas of the latent image are deposited, or they are repelled by the charged areas and in the uncharged areas deposited. The "Toner ^" image will then be fixed either by heating, by overlaying or by the action of solvents. Before fixing can the toner image can be transferred to the surface of a carrier such as paper and permanently bonded to it. Instead of that To form latent electrostatic images through the steps described above, it is also possible to use the photoconductive layer to charge directly in image form.

For better control of the development of the latent image

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the toner is used in combination with solid carrier particles, or the toner particles can be in an insulating liquid be dispersed.

If a dry developer is used, it is made up of two components: A finely ground pigmented one or colored, resinous toner and a relatively coarse-grained carrier material. To develop the latent image the developer mixture can simply be poured over the exposed plate. The carrier material, e.g. glass or steel beads, which is coated with a resin-like, film-forming product can be enveloped, · carries the toner when it is over the plate trickles; as a result, the toner particles also become triboelectric charged in the desired polarity. When the toner / carrier mix flows over the surface that bears the latent, electrostatic image, the toner particles are charged by the Areas of the image rather than being attracted by the discharged or background areas of the image. Most of the toner particles which are accidentally deposited on the background areas of the image are removed by the rolling carrier particles- ' taken, which is the greater electrostatic attraction between the toner and the carrier as opposed to that of the toner and the is to be ascribed to discharged background .. The powder image formed is then, as described above, on the photoconductive obab * surface or can be transferred to a receiving surface, e.g. a sheet of paper. The transfer can take place, ^ ■ by bringing the powder image into contact with the receiving surface, if necessary, in the presence of an electrostatic one Field. If the surface of the receiver, e.g. the sheet of paper, then it is owned by the photo. Surface is peeled off, j there is a substantial amount of toner particles thereon in the form of the desired image. Subsequently, this image can consistently, ',

made, i.e. fixed, after each desired | Method such as heating or solvent fixation. ι

Apart from the so-called "cascade development" mentioned above as described in U.S. Patent 2,618,552

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other developer techniques-suitable, wherein dry developer mixes can be used, e.g. the well-known technique of magnetic Brush as described in U.S. Patent 2,874,063. . '

It is known in electrophotographic processes to be photoconductive * to use capable elements in the form of drums rotating continuously through a cycle of successive operations, | which include charging, exposure, development, transfer and cleaning. During the development of the electrostatic! ^ latent image becomes a powder image on the photoconductive member formed which "then electrostatically onto a receiving surface is transmitted. Usually a residue of the powder image remains on the photoconductive surface after transfer. It is therefore necessary before the surface is reused to produce a subsequent, latent, electrostatic image will remove the remaining powder to stain the subsequent Avoid transmission image. The remaining powder image is removed by touching the surface with the remaining powder image with a cleaning device, the cleaning agent for use with a brush, which is described, for example, in U.S. Patent 2,832,977, and web cleaning agents as discussed in US Pat. No. 3,186,838 « The removal of the remaining powder on the plate by means of the brush cleaning is usually carried out in such a way that the Brushing off powder with one or more rotating brushes in a stream of air that is sucked off by a filter system. That Web cleaning agent contains a web of fibrous material that is in pressing and rubbing contact on the surface of the Recording material is moved.

The cleaning of reusable, photoconductive plates and drumming is not always satisfactory as the cleaning of depends on a number of factors, e.g. the type of toner / carrier mixture used and the relative humidity. When the relative humidity is high, the electrical and transmission properties of the photoconductive Element generally opposed to A-G 990

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affected, making it difficult to clean properly. Some toners and carriers are by nature abrasives, so that when they come into contact with the registration surfaces, mutual impairment is accelerated. The cleaning, Devices, when brought into contact with them, also have a grinding effect on the recording surfaces * The erosion of the recording surfaces makes cleaning even more difficult.

The subject of the present invention is an electrophotographic A recording process which includes the following steps: Formation of a latent, electrostatic image a recording surface; Creation of a powder image that corresponds to the electrostatic image by touching the surface applies a developing material; Transfer of the Powder image from the recording surface to a receiving surface and cleaning the recording surface. The procedure the invention is characterized in that at least one hydrophobic, divalent or trivalent metal salt Half-ester of a branched-chain or straight-chain, aliphatic Dicarboxylic acid and / or at least one divalent or trivalent Metal salt of a monoester or D.ester of a phosphoroxy acid on the recording surface before and / or during can be applied to cleaning.

The application of one or more metal salts to the recording surface not only facilitates general cleaning between use and re-use of the recording surface is carried out by promoting the removal of the residual toner particles from the registration surface but it also reduces the abrasion of the photoconductive surfaces, it also reduces pollution of the electrophotographic images obtained on receiving materials and gives images with improved contrast. GV 549

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If one or more of the metal salts are used on the recording surface before the electrostatic latent image is formed or before it is developed, it is advisable to use one To leave a layer of such a salt (or several salts) on this surface in order to facilitate its subsequent cleaning. Such a layer can be effective for any desired length of time, and the invention includes any electrophotographic recording process one that involves the formation of an electrostatic image on a recording surface, its development by means of powder and then the image-wise transfer of the powder from the recording surface to a receiving material, wherein the recording surface is a surface on which there is a thin layer of one or more metal salts, as listed above. The recording surface used in such a process can be cleaned very quickly, without it being sanded off.

One or more of these metal salts can be applied to the recording surface in any manner before the latent, electrostatic image is generated or after moving the powder image from the recording surface to the receiving surface has transferred. The salts can be applied to the recording surface as a loose powder, as a melt, as a solution or as an emulsion or dispersion, etc. can be applied. Loose powder can be applied to the Record whether the surface is sprinkled and liquids that are spread which contain metal salts in dissolved or dispersed form can be applied to the surface according to any conventional coating method can be applied, e.g., by spraying, dipping, etc. The metal salts are preferably dissolved in a suitable solvent dissolved or * dispersed; the solution is then applied to the recording surface, followed by the solvent removed by evaporation. Analogous to the cascade development, the metal salts can also be applied in the form of powder over the surfaces let trickle.

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According to a preferred embodiment of the invention the metal salts on the recording surface after the transfer of the powder image applied to the receiving surface, to promote cleaning of the recording surface at this stage. In either case, the salt (or salts) can be applied by rubbing or wiping the surface for a certain period of time using an applicator contains such salt (or several salts) on-at least the side, that is in contact with such a surface. The applicator can be used alone to apply the photoconductive The plate, the drum and another part that supplies the recording surface with the metal salt (or salts) treat, but is preferably also used to clean the reusable photoconductive plate, as mentioned above was executed. Therefore, the application of the metal salt (or salts) to the recording surface and its Cleaning can be combined into a single operation between use and reuse. In some cases it can Salt (or the salts) applied to the recording surface will be wiped away completely. According to a particularly important embodiment, the cleaning of the recording surface carried out in such a way that a deposit of the salt (or salts), possibly in a very thin layer, on the surface remains behind. This applies primarily with regard to the reuse of the surface in the creation of another, electrophotographic image. P-ur in the event that this The process is carried out cyclically using, for example, a rotatable drum having a photoconductive surface the cleaning by means of the salt (or salts) take place periodically, e.g. in each cycle or at intervals of two or more several cycles.

The metal salts for use in accordance with the present invention should be hydrophobic, i.e. essentially insoluble in water, otherwise they will be affected by the relative humidity of the surrounding Air are adversely affected. For this purpose, the metal salts should generally have a straight-chain or branched

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chain, aliphatic ^ hydrocarbon group of at least 5
Carbon atoms, preferably at least 10 carbon atoms,
contain, -wherein the groups are substituted with hydrophobic groups *
can be, for example halogen, preferably fluorine and / or by '·. Heteroatoms can be interrupted, for example oxygen, sulfur. · -; ., and nitrogen "The group may be a Estergruppe the metal salts * ¹ or a substituent on the chain be, that binds the two carboxyl groups of the dicarboxylic acid to phosphorus oxychloride;!. ' acids are preferably all replaced by a metal atom replaceable hydrogen atoms by metal atoms.

J Typical dicarboxylic acids from which the metal salts hydrophobic ^l> '\ can be derived are: succinic acid, glutaric acid,' 1 maleic acid and glutaconic acid, "and mixtures thereof. The phosphofcoxy acids include ortho, pyro and hypophosphorous acids, phosphorus, and phosphinic acids. Excellent results are obtained when; ..; - the metal salts are zinc salts. However, also other salts can be used i, for example magnesium salts, C alciumsalze, 4 strontium salts, barium salts, iron salts, nickel salts, cobalt salts Kupfersalzej, cadmium salts, aluminum salts and lead salts. f; |

■ • ■ pi?

The manufacture of the metal salts of the esters of phosphorus oxy acids ^f | is, as will be described, very simple. According to a particularly ^'Λ suitable method, a stoichiometric amount of oxy- || acid ester dissolved in an aliphatic alcohol and converted into a; I solution or suspension of a metal acetate in an aliphatic; ¹ alcohol given. The metal salt of the phosphoroxy acid ester
is usually caused by precipitation in alcohol or ~ 7.

obtained by evaporation of the solvent. . _c : '

The following preparations illustrate how metal salts are made. Phosphorus oxy acids can be obtained. ■ O

•!

Manufacture 1``. ·

£ ΒΕ £ ® £ ίϊϊ2ΐ§ΗίΣΐΕ ^ 2 ^ Ε ^ 22§ *

4 g of copper (II) acetate monohydrate are dissolved in 250 ml of methanol at '

5O * <3 solved. If 6 laurylphosphonic acid is added to the warm solution, copper (II) laurylphosphonate precipitates. The precipitate is then washed with methanol of 50 ⁰ C.
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Manufacture; 2:

a) Mono (2-butyloctyl) phosphoric acid

A solution of 2 moles of 2-butyl octanol in 500 ml of dichloroethane is added dropwise with stirring to a solution of 2 moles of phosphorus oxychloride and 2.05 mol of pyridine in .500 ml of dichloroethane while · the temperature to about 22 ¹ GJmIt. · The pyridine hydrochloride formed is filtered off with suction and the filtrate is concentrated. The remaining oil is mixed with 1 liter of water and heated for 2 hours with stirring on a boiling water bath. The mixture is then extracted with benzene and the latter is evaporated under reduced pressure. The residue obtained is completely degassed using an oil pump.
Yield: 70 %.

b) zinc mono (2-butyl octyl) phosphate

A solution of 1 mole of zinc acetate dihydrate in 750 ml of methanol at 55 ° becomes a solution of 0.7 mol of mono (2-butylοctyl) phosphoric acid given in 500 ml of methanol. The zinc salt settles; after JO minutes the liquid floating on top is removed. The precipitate is dissolved three times for 15 minutes in 55 ° ml of methanol, heated in a water bath and the methanol decanted each time.

After the last decantation, the residue is dissolved by heating it in 1.7 liters of acetone on a reflux condenser. After cooling, the zinc salt crystallizes out of the solution. Yield: ^%.

Manufacturing $

Zinc monoisohexadecyl ehosghat

a) In a 2 liter reaction vessel with a stirrer, a Thermometer and a dropping funnel are 459 g (3 mol) phosphorus oxychloride brought. The phosphorus oxychloride is cooled to 0 ° and then 726 g (3 mol) of isohexadecanol (im Commercially available from Esso Belgium N.V., Antwerp) so added dropwise * that the hydrogen chloride formed gradually escapes. As soon as all of the Isohexadeαanol has been added, the '

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Temperature rose to about 25 ° q. The mixture is allowed to stand overnight and then stirred for a few hours while introducing nitrogen to remove residual hydrogen chloride. Yield: 1055 S (98 %),

b) 2.8 * liters of water, 300 ml of hydrochloric acid and 1260 ml of dioxane are placed in a 10 liter reaction vessel equipped with a stirrer, a thermometer and a dropping funnel. ^{The mixture is heated to 80 °} C. on a boiling water bath, whereupon a solution of 1010 g of the product obtained under a) in 1250 ml of dioxane is added dropwise over the course of 90 minutes. The temperature rises to 92 * 0, and the mixture is stirred for 5 hours at this temperature, cooled and the oil is separated off and stirred up with benzene. After concentration in a water bath at 75 ° C., 890 g (98 %) isohexadecyl phosphate are formed.

c) 1 mol of isohexadecyl phosphate is dissolved in methanol, whereupon a solution of 1 mol of zinc acetate dihydrate in 750 ml of methanol is added will. The precipitate formed is separated off and then stirred several times with warm methanol, the product up heated in a water bath to remove all methanol and then recrystallized from ethylene glycol monomethyl ether.

The metal salts of the half esters of aliphatic dicarboxylic acids can be prepared in a similar manner. A stoichiometric one Amount of the half ester is dissolved in acetone and the resulting solution to a solution of a metal acetate in an aliphatic Given alcohol. The metal salt of the half-ester separates itself through Precipitation from. The half esters used can be prepared, for example, by combining the cyclic dicarboxylic acid anhydride and the Heat alcohol in toluene on the reflux condenser and then the solvent evaporates.

The following preparation illustrates how the metal salts of the half esters of the dicarboxylic acids are prepared .

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Manufacturing 4

0.05 moles of succinic anhydride and 0.05 moles of dodecanol will be used Hours in 100 ml of toluene heated on the reflux condenser. The solution is concentrated and the residue solidifies at room temperature calmly. The monolaurylsuccinic acid is recrystallized from 100 ml of hexane.

A solution of 0.02 mol of monolaurylsuccinic acid in 100 ml Acetone is mixed with a solution of 0.01 mol of zinc acetate in 20 ml of ethanol. The mixture is left to stand over a compartment, whereupon the precipitate formed is filtered off with suction, washed with ethanol, acetone and Ither and dried in vacuo. Melting point: 124t !.

In a similar manner are prepared: Zinkdecylsuccinat (melting point: 123 ° C), Zinkundecylsuccinat (melting point: 121 ° C), Zinktetradecylsuccinat (melting point: 123 ⁰ C), Zinkhexadecylsuccinat (melting point; 124 ° C), Zinkoctadecylsuccinat (melting point: 123 ⁰ O) , Zinc docosyl succinate (melting point: 123 ⁰ G),

(H ₅ COOC-CH ₂ -CH-COO) ₂ Zn (melting point: 68 ° C) and

(CH ₂ ) ₁₇ CH ₅
(H ₃ C- (CH ₂ ) _{Λ 7} -00C-CH ₂ -CH-C00) ₂ Zn (melting point: 56 ⁰ C)

The amount of metal salt is applied directly to the registration surface can vary widely, however, depends on the electrical properties of the photoconductive layer from which the metal salt certain limits is the maximum acceptable thickness of the layer _f '. If the metal salt is first brought into the treatment device, which is then brought into contact with the registration surface, the amount of metal salt can also vary widely and depends on the way in which it is brought to the device, further on the type of special device used by the

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~ 11 -

Duration of contact between the treatment device and the photoconductive surface, etc. In general, satisfactory ones are obtained Results when from 0.005 g to 5 g, preferably from 0.05 g to 2 g of metal salt per m2 of surface area is present.

If you bring the salt (or salts) to an applicator, which also cleans the registration surface can be used, this device preferably contains a fibrous, woven or non-woven material, since this promotes uniformity of treatment; such ; fibrous treatment device can be of any suitable type Be in shape, such as in the form of a continuous web or a continuous cylinder or band * s. Suitable fibrous Materials include paper tissue, fur, natural fibers such as cotton, flannel, wool and hair, and synthetic fiber such as nylon or cellulose derivatives.

The following examples illustrate the present invention.

Example 1 '. .

An electrophotographic, dry mixture consisting of approximately 99 parts by weight of glass carrier particles with one particle size between 0.6 and 0.8 mm and about 1 part by weight of toner particles with a particle size between 2 and 30 microns poured over a selenium surface that bears an electrostatic image. The toner was made up of 8 parts by weight Polystyrene with a molecular weight of 30,000, one part by weight of polyvinyl butyral, which is in addition to vinyl butyral groups 20% by weight of vinyl alcohol groups and 2.5% by weight of vinyl acetate » groups, and 1st part by weight soot. The developed image! is transferred to a sheet of paper by electrostatic means, whereupon it is fused with heat.

A common, continuous cleaning of fabric, as used in a xerographic copying apparatus is, with ■ a 1% solution of Zinkoctadecylsuccinat in dimethyl ^formamide impregnated and dried. The treated cleaning

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~ ¹² ~ .22245CH

■ au - ■::; it uses the developed image of the photoconductive selenium surface after the transfer of the remaining ^r Pul will supply fabric ground for removal ve: .-.

After repeating the copying procedure several times, each time using the cleaning fabric as described above, the copies and the photoconductive one become The registration surface is examined for its quality and its wear and tear. Compared to the copies you get if the cleaning fabric has not been treated with the metal salt of the invention, the copies show according to the invention better image contrast and no background deposition.

Furthermore, the registration surface shows less wear than if the cleaning fabric is not treated.

Example 2

A dispersion of 0.5 g of the compound having the formula

in 100 ml IBOPAR G (trade name of an isoparaffinic hydrocarbon mixture having a boiling range of 160-177 ⁰ C, marketed by Esso Belgium NV, Antwerp, ¹ Belgium) as used in a xerographic copying apparatus is sprayed onto an ordinary cleaning fabric. 100 ml are needed to get O ₁ ^ τη? Cover 7-U, After the solvent has evaporated, the fabric is placed in the copier to cover the selenium surface after developing an electrostatic image and transferring the developed image to JiIaLL paper as described in Example 1 clean.

When examining the copies and the photoconductive selenoburic surface on quality or wear and tear can be found in comparison to Use of a non-treated cleaning fabric that the copies show an excellent quality (higher density for same haze value) and the selenium drum has fewer scratches.

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This gives the same favorable results when the above-mentioned zinc salt of a dispersion in η-hexane, isododecane and Isopar H (trade name of an isoparaffinic hydrocarbon mixture having, a boiling range of 177-188 ⁰ C, available from Esso Belgium NV, Antwerp, Belgium) is applied.

Example 5

Example 1 is repeated, with the difference that the cleaning fabric has not been pretreated with a zinc salt, as described in Example 1.

For the purpose of treating the cleaning fabric with a zinc salt in accordance with the present invention, there is zinc dodecyl succinate pressed in the shape of a rod that can be seen in the xerograph Copier is attached so that the cleaning fabric comes into contact with the rod of zinc salt before it hits the Selenium drum rubs.

By treating the cleaning fabric with zinc dodecyl succinate The copies are of higher quality than cleaning fabrics that did not come into contact with the zinc salt before rub them against the selenium drum. The registration surface also shows less wear.

Example 4-

Zinc docosyl succinate is pressed in the shape of a stick. The rod is against a selenium drum of a xerographic copier rubbed, so that there is a deposit of zinc docosyl succinate each time before the electrostatic charging of the Drum emerges.

If the copying process with the steps treating the selenium drum with a stick of zinc docosyl succinate, electrostatic charging of the drum, image-wise exposure of the selenium surface, Develop the electrostatic image formed as described in Example 1 and transfer the developed Image on a sheet of paper, repeated several times, one finds that the copies produced are of higher quality and the registration surface shows less wear than with untreated selenium drum.

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Claims (16)

Pat ent claims / Iy Electrophotographic recording process which comprises the steps of forming a latent, electrostatic image on the surface of a recording material, generating a powder image corresponding to the electrostatic image by applying a developing material to the surface, transferring the powder image from the surface to a receiving material and the Cleaning the surface, characterized in that at least one hydrophobic, divalent or trivalent metal salt of a half-ester of a branched, fatty or straight-chain, aliphatic dicarboxylic acid and / or at least one divalent or trivalent metal salt of a monoester or diester of a phosphoroxy acid is applied to the surface of the recording material in front of and / or applied during their cleaning. 2. The method according to claim 1, characterized in that a Metal salt is deposited on the surface of the recording material prior to the formation of the electrostatic latent image and on that surface remains during the formation and development of such a latent image. 3.Verfahren according to claim 1, characterized in that a Metal salt is applied to the surface after the transfer of the powder image onto a receiving material. 4. The method according to claim 3? characterized by »\ that the Application of the metal salt to the surface of the recording material and the cleaning of this surface take place at the same time, 5. The method according to any one of claims 1 to 4, characterized in that that a metal salt on the surface of the records materials is applied by rubbing or wiping the surface with an applicator for a certain period of time, the such a SaIs (or such salts) at least on one side contains and touches the surface. A-G 990 ^GV 549 209849/1098 6. The method according to claim 5 »characterized in that the application device contains a fibrous web of fabric which comes into contact with the surface. 7. The method according to claim 5 or 6, characterized in that before the contact of the surface of the application device with the Surface of the recording material the surface of the applicator a metal salt or metal salt in an amount 2
carries between 0.005 g and 5 g per m. 8. The method according to any one of the preceding claims, characterized in that the metal salt used is a zinc salt 9. The method according to any one of the preceding claims, characterized characterized in that a salt is used which has a branched-chain or straight-chain, aliphatic hydrocarbon group of at least 5 carbon atoms. 10. The method according to claim 9 »characterized in that the hydrocarbon group in the ester part of the compound or as Substituent is present on the chain connecting the two carboxyl groups of the dicarboxylic acid. 11. The method according to any one of the preceding claims, characterized in that a salt is used, which is a salt of a half ester of succinic acid. 12. Electrophotographic recording method that enables generation an electrostatic image on a recording surface, its powder development, and then the imagewise transfer of the powder from the recording surface includes a receiving material, characterized in that, that the recording surface is a layer of at least one hydrophobic, divalent or trivalent metal salt a half-ester of a branched-chain or straight-chain, aliphatic Dicarboxylic acid and / or at least one divalent, valent or trivalent metal salt of a monoester or di- eisters «in phosphorus oxy acid. ^; '" ^{G 39C} 209 849/1098 -ig- 222A504 13. Electrophotographic recording process according to Claim 12, characterized in that the metal salt is a zinc salt. 14. Electrophotographic recording process according to Claim 12 or 13, characterized in that a salt which is a branched or straight chain aliphatic hydrocarbon group of at least 5 carbon atoms is used contains. 15. Electrophotographic recording method according to claim 14, characterized in that the hydrocarbon group is in the ester part of the compound or as a substituent on the chain is present, the two carboxyl groups of the dicarboxylic acid connects. 16. Slectrophotographic recording method according to each of the Claims 12 to 15, characterized in that a salt is used which is a salt of a half ester of succinic acid is. AG 990
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