DE1571913C3 - Electrophotographic process for the production of a lithographic printing form - Google Patents

Description

The invention relates to an electrophotographic process for making a lithographic one Printing form, in which on the image surface of a charged photographic plate by exposure latent electrostatic image is generated.

Lithographic processes are well known. They are made using a planographic printing plate a lithographic print is produced, whereby for the production of the print the various Properties of the surface parts generating the image are essential. With the usual lithographic In methods, the non-image areas are hydrophilic while the image areas are hydrophobic. In which In the lithographic printing process, a conversion solution is applied to the printing plate, which wets the areas free of the hydrophobic image. This solution keeps the plate moist and prevents one Foaming (sludge formation). An oil-based printing ink is applied to the image surface, which is only deposited on the image areas, while the remaining hydrophilic areas repel the printing ink. The dye image created in this way can then be directly applied to a sheet of paper or another Recording surface are transferred. In general, however, it is transferred to a rubber offset pad, from which the image will be transferred to the final sheet of paper. For this reason, the lithographic plate. to carry out each printing process first with an aqueous conversion solution moistened, then colored with a lithographic printing ink and then to Printing used.

There are already known lithographic plates in which use is made of photoconductivity using a conventional developed xerographic plate as the lithographic printing plate will. Such a method is described in US Pat. Nos. 31 07 169 and 30 01 872. In this process, a zinc oxide plate is charged in a known manner with the one to be reproduced Image exposed and with a xerographic

Toner developed. The toner used is generally hydrophobic, as is the base of the xerographic plate, which consists of an inorganic binder. To the developed xerographic To be able to use plate usefully as a lithographic printing plate has to be between the toned Image and the base of the plate a differential can be generated. Since both components are hydrophobic have previously had to treat the base of the xerographic plate with a conversion solution to make them hydrophilic. Subsequently, the plate is then then with a non-aqueous Oil-based printing ink colored so that the toner takes on the color and which is now hydrophilic Underlay that repels paint.

Although this method has proven suitable for use in lithography, it shows various disadvantages. One is, for example, that to convert the initial A conversion solution is required so that the hydrophobic pad into a hydrophilic pad Underlay does not take on the oily color when coloring. Another disadvantage is that the xerographic plate contains toner powder baked onto its surface and therefore does not return is usable. Another disadvantage is the polarity sensitivity of the toner powder and the fact that that only those photoconductive plates can be used which are compatible with the toner powder Pick up charge.

The object of the invention is now to provide an improved electrophotographic process for production indicate a lithographic printing form that has the disadvantages of the above-mentioned known methods does not have.

According to the invention, this object is achieved by an electrophotographic process for production a lithographic printing form of the type described above, which is characterized in that an aqueous, polarity-insensitive developer is applied to the image area, which is accordingly the latent image is distributed pictorially, creating hydrophilic and hydrophobic surface areas, and that the developed image is transferred to a receiving surface, which is used as a lithographic printing form serves.

The invention is explained in more detail below with reference to the drawings. It shows

F i g. 1 is a perspective view of a xerographic image containing an electrostatic latent image Plate,

F i g. 2 shows the front view of such a xerographic plate, which is coated with a water-soluble polarity-insensitiveff Developer is partially developed,

F i g. Figure 3 is a front view of a developed xerographic plate fitted with an image receiving surface is in contact

Fig. 4 is a perspective view of a xerographic Plate from which the image-bearing receiving surface is partially removed, and

F i g. 5 is a perspective view of a lithographic printing plate made up of the receiving surface with partially colored image.

The in F i g. 1 shown xerographic plate 1, consisting of a base plate 2 and a photoconductive insulating layer 3, is used according to the invention for the production of a lithographic printing form used. It is charged evenly.

This charge is selectively compensated for by exposure to an image, creating one on the plate An electrostatic charge image 4 corresponding to this image is created.

F i g. 2 illustrates the development process. A polarity-insensitive aqueous developer 5 is applied to the image surface of the xerographic plate 1 with a roller 6. The developer 5 is loaded in pictorial configuration 5a on the

ίο Part 4 of the plate held. The image area is then brought into planar contact with a support surface 7 as shown in Fig. 3, wherein a pressure is exerted on the back of the plate 1, which causes a transfer of the developed image Sa from the xerographic Plattet on the receiving surface 7. If a hydrophilic surface is used as the receiving surface, then the rear side of the receiving surface is coated with a hydrophobic substance 8 after the xerographic plate has been placed on it.

This material penetrates the fibers of the contact surface and makes them water-repellent (hydrophobic). Same The coating process can be used to make existing oil-resistant surfaces more hydrophobic close.

F i g. 4 shows the process step of the detachment, in which the image receiving surface 7 is removed from the xerographic plate 1. The developed image 5a adheres to the receiving surface 7 and represents a mirror image of the original image.

F i g. 5 shows the finished printing forme 9, which consists of the receiving surface 7 and a developed image 5a wearing. The printing form is colored for printing with an aqueous printing ink 10, which by means of a Spreading device 11 is applied. The color is captured by the image area 12 while it is repelled from the background area 13. due to its hydrophobic property.

A xerographic plate is preferably used, the photoconductive layer of which forms a large contact angle with the aqueous developer, to achieve image adhesion. However, another suitable photoconductive insulating material can also be used Fabric to be used.

Typical inorganic photoconductive substances are

z. B. sulfur, selenium (glass-shaped, amorphous, Λ-monoclinic), Zinc sulfide, zinc oxide, zinc cadmium sulfide, zinc magnesium oxide, cadmium selenide, zinc silicate, calcium strontium sulfide, Cadmium sulfide, mercury iodide, mercury oxide, mercury sulfide, indium trisulfide, Gallium triselenide, arsenic disulfide, arsenic trisulfide, arsenic triselenide, antimony trisulfide, cadmium sulfoselenide, doped chalcogenides of zinc and cadmium, aluminum oxide, bismuth oxide, molybdenum oxide, lead oxide, Molybdenum iodide, molybdenum iselenide, molybdenum sulfide, molybdenum telluride, aluminum iodide, aluminum selenide, Aluminum sulfide, aluminum telluride, bismuth iodide, bismuth selenide, bismuth sulfide, bismuth telluride, Cadmium telluride, mercury selenide, mercury telluride, Lead oxide, lead selenide, lead sulfide, lead telluride, cadmium arsenide, lead chromate, gallium sulfide, Gallium telluride, indium sulfide, indium selenide, indium telluride, red lead, and mixtures thereof.

Typical organic photoconductors that can be used according to the invention are

Triphenylamine;

2,4-bis- (4,4'-diethyl-aminophenyI) -l, 3,4-oxa-

diazole;

N-isopropylcarbazole triphenylpyrrole; 4,5-diphenylimidazoIidinone; 4,5-diphenylimidazolidine ethione; 4,5-bis- (4'-aminophenyl) -imidazoIidinone; 1,5-cyanonaphthalene;
1,4-dicyanonaphth ali η,
Aminophthalonitrile;
Nitrophthalidinitrile;

! ^, S.o-Tetraazacyclooctatetraen- ^ Ao ^); 3,4-di (4'-methoxyphenyl) -7,8-diphenyl, 2,5,6-tetraaza-cyclooctotetraene (2,4,6,8); 3,4-di- (4'-phenoxyphenyl) -7,8-diphenyl (^ S.o-tetraaza-cyclooctatetraen ^ Ao ^);

octatetraene (2,4,6,8);

2-mercapto-benzothiazole;

2-phenyl-4 - «- naphthylidene-oxazolone; 2-phenyl-4-diphenylid-oxazolone; 2-phenyl-4-p-methoxybenzylidene oxazolone; 6-hydroxy-2-phenyl-3- (p-dimethylaminophenyl) benzofuran;

6-hydroxy-2,3-di (p-methoxyphenyl) benzofuran; 2,3,5,6-tetra (p-methoxyphenyl) furan (3,2 ') benzofuran;

4-dimethylaminobenzylidene benzhydrazide; 4-dimethylaminobenzylidene isonicotinic acid hydrazide;

Furfurylidene- (2) -4'-dimethylaminobenzhydrazide; 5-benzylidene-aminoacenaphthene; 3-benzylidene-aminocarbazole; (4-N, N-dimethylamino-benzylidene) -p-N, N-dimethylamino-aniline; (2-nitrobenzylidene) -p-bromo-aniline; N, N-dimethyl-N '- (2-nitro-4-cyano-benzylidene) -p-phenylenediamine;

2,3-diphenyl-quinazoline;

2- (4'-aminophenyl) -4-phenyl-quinazoline; 2-phenyl-4- (4'-dimethyl-amine o-phenyl) -7-methoxy-quinazoline;

1,3-diphenyl-tetrahydroimidazole; 1,3-di (4'-chlorophenyl) tetrahydroimidazole; 1,3-diphenyl-2- (4'-dimethyl-aminophenyl) -tetrahydroimidazole;

1,3-di (p-tolyl) -2-quinalyl- (2 ') - tetrahydroimidazole;

3- (4'-Dimethylaminophenyl) -5- (4 "-methoxyphenyl) -6-phenyl-1,2,4-triazine; 2-pyridyl- (4 ') - 5- (4 "-dimethyl-aminophenyl) -6-phenyl-1,2,4-triazine;

3- (4'-Aminophenyl) -5,6-diphenyl-1,2,4-triazine; 2,5-bis [4'-aminophenyl- (l ')] - 1,3,4-triazole; 1,2,5-bis [4'rN-ethyl-N-acetylamino-phenyl- (l ')] - 1,3,4-triazole;

1,5-diphenyl-3-methyl-pyrazoline; 1,3,4,5-tetraphenylpyrazoline; 1-phenyl-3- (p-methoxystyryl) -5- (p-methoxyphenyl) pyrazoline;

1-methyl-2- (3 ', 4'-dihydroxymethylene-phenyl) -benzimidazole;

2- (4'-dimethylaminophenyl) benzoxazole; 2- (4'-methoxyphenyl) benzothiazole; 2,5-bis- [o-aminophenyl- (l)] - 1,3,4-oxadiazole; 4,5-diphenyl-imidazolone; 3-aminocarbazole and mixtures thereof.

In the present method, the organic photoconductive layer generally takes a positive one Charge on. As already mentioned, a photoconductive insulating material layer is preferably used which forms a large contact angle with the aqueous developing solution. The best results will be achieved when this angle is greater than 90 °. It is defined as the angle within the liquid between the horizontal solid surface and the tangent to a developer drop at the point where the drop surface intersects the horizontal plane. The tangent runs in one to the horizontal Area of the vertical plane that is also in the center of the drop. Photoconductive insulating materials with these properties are z. B. zinc oxide, zinc sulfide, zinc cadmium sulfide, cadmium selenide, cadmium sulfide, Cadmium sulfoselenide, mercury oxide, mercury sulfide, gallium triselenide, arsenic disulfide, arsenic trisulfide, Arsenic triselenide, antimony trisulfide, triphenylamine, polyvinylcarbazole, 4,5-diphenyl-imidazolidinone, 1,4-dicyanonaphthalene and nitrophthalidinitrile.

In the photoconductive layer of the xerographic plate as used according to the invention, can a binding agent can be incorporated. Such binders and photoconductive layers are similar to those in FIGS U.S. Patents 3,121,006 and 3,121,007. According to the invention, preferred binders are Polystyrene, styrene-modified alkyd resins, phthalalkyd resins, polyvinyl ester resins and melamine-formaldehyde resins used. With these substances, the most favorable contact angle is easily achieved.

Any suitable material can be used as the support for the xerographic plate. It should have an electrical resistance which is less than that of the photoconductive layer, so that it acts as "ground" when the electrostatically charged coating is exposed. Such materials are aluminum, brass, glass, aluminum-coated glass, corrosion-resistant steel, nickel, steel, bronze, copper, engraving copper, granular lithographic zinc and electrically conductive and non-conductive paper. Other materials with similar electrical resistance can also be used as a base for receiving the photoconductive layer. In addition, other non-conductive materials, such as thermoplastics, can be used as the base for the xerographic plate. However, this requires charging both sides of the xerographic platen as described in US Pat. No. 2,922,883.
The aqueous polarity-insensitive developer should have a viscosity of 1000 to 100,000, preferably 5000 to 20,000 cP, since the best results are achieved in this range. Typical components of the developer are vinyl resins, such as carboxyvinyl polymers, polyvinylpyrrolidones, methyl vinyl ether-maleic anhydride interpolymers, polyvinyl alcohols, celluloses, such as sodium carboxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxyethyl cellulose and methyl cellulose, cellulose derivatives, such as starch, acrylics, ethers, and alkaline derivatives, such as esters and proteins such as ammonium polyacrylate and sodium polyacrylate, polyacrylic acid, polymethacrylic acid and their copolymers and the alkali and ammonium salts of alginic acid and mixtures thereof. The best results are achieved with the vinyl resins, since the favorable viscosity range is easily reached at low concentrations. The term "aqueous developer" is to be understood here as a developer who is used for

larger part water, to a lesser extent another solvent, e.g. B. alcohol contains.

Any conventional and / or suitable printing ink can be used for the method according to the invention be used. These are colors that contain water-soluble dyes, or pigmented colors. Typical suitable dyes are Methylene Blue (C. I. 52 015), Brillant Yellow (C. I. 24 890), potassium permanganate, Iron (III) chloride, cobalt (II) chloride and methyl violet (C. I. 42 535), Rose Bengal (C. I. 45 440) and Quinolin Yellow (C.I. 47 005).

It is also possible to use simple compounds or colored water-soluble complexes, e.g. B. such as those of a number of transitional elements that occurred primarily in the first period of the Periodic Table of the Elements are formed. Such complexes are e.g. B. the known Copper tetramine complexes, chromium salts such as chromium sulfate, chromium and potassium alum, potassium chromate, the aquo and acido complexes of trivalent chromium, certain ferric compounds, such as Iron (III) thiocyanate and the thiocyanate ferrate, the hydrogen cyanide compounds of iron, the acetate iron (III) salts, Iron ammonium citrate, the thiocyanate and the thiocyanate cobaltate of divalent cobalt, Cobalt sulfate and chloride, the large number of cobalt (III) complexes, e.g. B. the amine, the aquo and Acido complexes which are present in the same abundance as the chromium complexes, the chlorides and sulphates of divalent nickel, the copper tartrate complex, copper glycine, the soluble compounds of iron with gallic acid or tannin, the complexes of iron (II) salts with «-picolinic acid or analogous compounds, which contain an atom of nitrogen cyclically combined in the α-position with a carboxyl group, Iron or divalent cobalt complexes with the Ä-dioximes, e.g. B. Dimethyl glyoxime, the iron (III) complexes with salicylic acid, compounds between titanium or iron salts and catechol or Chromotropic acid.

Typical pigments which can be used according to the invention are, for. B. soot, titanium dioxide, white lead, zinc oxide, Zinc sulfide, iron oxide, chromium oxide, lead chromate, zinc chromate, cadmium yellow, cadmium red, red lead, antimony dioxide, Magnesium silicate, calcium carbonate, calcium silicate, phthalocyanines, benzidines, dinitranilines, Naphthols and toluidines. The pigmented dyes are preferably used as the final Prints are more permanent and have optimal density. Carbon black is particularly preferred because it is is better to use for most printing operations.

As a receiving surface for receiving the developed image and for forming the lithographic printing form any suitable material can be used. Typical materials are e.g. B. zinc, aluminum, Polyethylene, polypropylene and normal fine paper. If the receiving surface is hydrophilic, it can penetrate Covering their back with a hydrophobic substance, e.g. B. an aliphatic isoparaffin hydrocarbon, can be made water-repellent if this penetrates the receiving surface. According to the invention Polyethylene, polypropylene and normal fine papers are preferred because they are good Have flexibility.

The following examples illustrate various embodiments of the method according to the invention are described are intended to explain the invention in more detail. The proportions and percentages stated therein refer unless otherwise specified, based on weight.

example 1

A sheet of commercially available zinc oxide paper is charged to 350 to 400 volts using a corotron laboratory device that is fed from a high voltage source. The charging current is 0.1 mA at 7500 volts. A clear USAF positive test sheet is placed on the charged zinc oxide paper, which is then exposed to a 75 watt photo lamp. An exposure of 215 Luxsec is required for the zinc oxide paper. The electrostatic latent image thus formed is then developed with a l ° / _o aqueous solution of an ammonium salt of a carboxyvinyl polymer using a gravure roll skimmer. A sheet of normal fine paper is then brought into direct contact with the image surface of the zinc oxide paper. Then the

ao back of the fine paper by fine spraying with a hydrocarbon that is immiscible with water, z. B. an aliphatic isoparaffin hydrocarbon coated. On the back of the zinc oxide paper pressure is applied to transfer the developed image to the fine paper. the Sheets are then separated, and the fine paper with the clear transferred image constitutes the lithographic The image is then washed with a rubber sheet with the blue washable aqueous Dye Sheaffer Skrip (commercial color mixture) colored and the final print through Contact of the printing plate made with a copy sheet. The results are good optical images Density and resolution.

Example 2

The procedure of Example 1 is repeated, but this time instead of the zinc oxide paper. xerographic plate with a layer of amorphous selenium on an aluminum base is used. The printed images are of better quality because they have a higher resolution.

Example 3

The procedure of Example 1 is repeated, this time using a xerographic paper instead of the zinc oxide paper Plate with a binder layer with photoconductive zinc sulfide on an aluminum base is used. The resolution of the images obtained is not as good as in Example 1.

Example 4

The procedure of Example 1 is repeated, this time using a xerographic paper instead of the zinc oxide paper Plate with a photoconductive zinc cadmium sulfide layer with binder on an aluminum base is used. The resolution of the images is comparable to that of Example 3.

Example 5

The procedure of Example 1 is repeated, this time using a xerographic paper instead of the zinc oxide paper Plate with a photoconductive cadmium selenide layer with binder on an aluminum

έΟ9 608/33

9 ίο

nium pad is used. The results are as low as 1 11
with those of example 2 comparable.

. . The procedure of Example 1 is repeated, where B-e ι s ρ ι _e eb £ i [j _ESMA i _in place of a xero-Zinkoxydpapiers The procedure of Example 1 is repeated, WO-5 photographic plate with a layer of amorphous this time a forex selenium is used on an aluminum base instead of the zinc oxide paper, a graphic plate with a photoconductive cad- The developed latent image is transferred to a polypromium sulfide layer with binding agent on an aluminum sheet instead of on fine paper. While nium pad is used. The results obtained from this process are the coating of the printing plate nits are comparable with those of Example 3. Do not use a water-repellent hydrocarbon (example 1). As in Example 10, a B e ι s ρ ι e 1 7 receives _image Q _{good inter alia} ü _t ät to that of Example 2 ent-The procedure of Example 1 is repeated, talking WO. However, this time, instead of zinc oxide paper, the stability of the image on a forex polypropylene is not as good as on fine paper,
graphic plate with a photoconductive layer 15 R ^-1 Ii?
made of polyvinyl carbazole on an aluminum base ■ B e 1 s ρ 1 e 1 12
is used. The quality of the images obtained is. The procedure of Example 1 is repeated, which is comparable to that of Example 4. this time, instead of the zinc oxide paper, a forex. -ίο photographic plate having a photoconductive poly-example _"20 vinylcarbazolschicht on aluminum base-USAGE The procedure of Example 1 is repeated, WO det. The developed latent image is placed on a polyethylene sheet this time the developed latent image is held on. Transfer fine paper, ethylene sheet is transferred instead of fine paper. During this process, the coating of the printing plate with a water-repellent carbon printing plate with a water-repellent hydrocarbon (Example 1) is omitted. Refrain from using hydrogen (Example 1). When used are similar to those of Example 10.
of polyethylene, the quality of the pictures is

those from Example 1 are comparable. The service life example 13

however, of the image on a paper surface is longer. The procedure of Example 1 is repeated with

30 the difference that instead of zinc oxide paper

B is ρ ie 1 9 ^eme xerographic plate with a photoconductive

Polyvinyl carbazole layer on an aluminum base

The procedure of Example 1 is repeated, wherever is used. The developed latent image is transferred to a polypropylene sheet instead of fine paper instead of fine paper. During 35 wear. During this process, coating of the pressure drawing of the printing plate with a water-repellent plate with a water-repellent hydrocarbon (example 1) is omitted. Refrain from the results (example 1). As with the previous nits are similar to those of Example 11.
Example, it turns out that the images on an In addition, other substances in the de-paper surface are more permanent. 40 winders, the printing ink, in the paper or the forex. . graphic plate can be used, which the ■ B e 1 s ρ 1 e 1 lü properties of these substances for use in the The method of Example 1 is repeated, where- improve the invention, intensify its effect or this time instead of the zinc oxide paper a forex otherwise influence. For example, it can be a functional graphic plate with a layer of amorphous 45 moderate, the image a larger mechanical strength selenium is used on an aluminum base. ability to give. The developed latent image is applied to a polyethylene thickener or an adhesive, e.g. B. Transfer rubber sheet instead of fine paper. During this arabic, gum tragacanth, karaya gum, guar gum process, the printing plate is coated with agar-agar and dextrins without neglecting a water-repellent hydrocarbon (with disadvantages in the quality of the developed image 1). It turns out to be good pictures. The properties of the aqueous developer are of the same quality as in Example 2, but the resistance can be improved by adding alcohols, such as glycols, to the image on the printing plate if paper and glycerols or polyethylene oxides are used. will.

1 sheet of drawings

Claims (9)

Patent claims: 1. Electrophotographic process for the production of a lithographic printing form, in which on the image surface of a charged electrophotographic Plate, a latent electrostatic image is formed by exposure, thereby characterized in that an aqueous, polarity insensitive to the image area Developer is applied, which is distributed image-like according to the latent image, making hydrophilic and hydrophobic surface parts arise, and that the developed image on a receiving surface is transferred, which serves as a lithographic printing form. 2. The method according to claim 1, characterized in that the electrophotographic plate contains a photoconductive layer made of selenium. 3. The method according to claim 1, characterized in that the electrophotographic plate a photoconductive layer carries one of the inorganic photoconductors zinc oxide, zinc sulfide, Contains zinc cadmium sulfide, cadmium selenide, cadmium sulfide or mixtures thereof. 4. The method according to claim 1, characterized in that that the electrophotographic plate has a photoconductive layer which has an organic Contains photoconductor. 5. The method according to claim 4, characterized in that the organic photoconductor is polyvinyl carbazole is used. 6. The method according to any one of claims 1 to 5, characterized in that for image transmission the image surface of the electrophotographic plate in surface contact with the receiving surface is caused to apply pressure to the back of the electrophotographic plate, that is, the transfer of the developed image from the electrophotographic plate to the receiving surface allows, and that then the receiving surface is separated from the electrophotographic plate. 7. The method according to any one of claims 1 to 6, characterized in that the developer in Gel form is used. 8. The method according to claim 1 for producing a lithographic printing form using a xerographic plate with a zinc oxide layer, characterized in that the xerographic zinc oxide plate is charged that on its layer side by exposure latent electrostatic image is generated that on the layer an aqueous solution of a polarity-insensitive Developer, which consists of an ammonium salt of a carboxyvinyl polymer, is applied that the image area of the Xerographic plate brought into extensive contact with a hydrophilic paper support surface the back of which is coated with a water-immiscible, aliphatic isopaiaffin hydrocarbon is coated until it penetrates between the paper fibers and makes them water-repellent makes that a pressure is applied to the back of the xerographic plate, which the Transfer of the developed image from the xerographic plate to the receiving surface causes and that the receiving surface is separated from the xerographic plate. 9. The method according to claim 1 for producing a lithographic printing form using a xerographic plate with a zinc oxide layer, characterized in that the xerographic zinc oxide plate is charged that on its layer side by exposure latent electrostatic image is generated that on the layer an aqueous solution of a polarity-insensitive Developer, which consists of an ammonium salt of a carboxyvinyl polymer, is applied that the image area of the xerographic Plate brought into extensive contact with a hydrophobic paper support surface is that a pressure is exerted on the back of the xerographic plate that the Causes transfer of the developed image from the xerographic plate to the receiving surface, and that the receiving surface is separated from the xerographic plate.