DE1571913B2 - A photographic 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. With them, a lithographic print is produced using a planographic printing plate, wherein for the production of the print the various properties of the surface parts that create the image are essential. In the usual lithographic processes, the non-image areas are hydrophilic, while the image areas are hydrophobic. In the lithographic printing process, a conversion solution is used applied to the printing plate, which wets the areas free of the hydrophobic image. This solution keeps the plate moist and prevents foam formation (sludge formation). On the picture surface an oil-based printing ink is applied, which only deposits on the image areas while the remaining hydrophilic areas repel the printing ink. The resulting dye image can then be transferred directly to a sheet of paper or other recording surface. In general however, it is transferred to a rubber offset pad from which the image is transferred to the final sheet Paper is transferred. For this reason, the lithographic plate is used for every The printing process is first moistened with an aqueous conversion solution, then with a lithographic one Ink colored and then used for printing.

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

3 4

Toner developed. The toner used is in the This charge is produced by exposure to an image generally hydrophobic as well as the backing of the selectively balanced, creating a on the plate xerographic plate made from an inorganic electrostatic charge binder corresponding to this image consists. Around the developed xerographic image 4 is created.

see plate usefully as lithographic printing. 2 illustrates the development process,

To be able to use the plate, you have to move between the

toned image and the base of the plate a differential plate 1 a polarity-insensitive

rential be generated. Since both components hydro-aqueous developer 5 is applied. The developer 5

are phob, so far the document of the forex has to be loaded in pictorial configuration Sa on the

graphic plate with a conversion solution held ίο part 4 of the plate. The image area will then be in

act to make them hydrophilic. Surface contact with a receiving surface 7

finally, the plate is then brought to a non-aqueous solution, as shown in FIG. 3, with the

Rigen printing ink dyed on an oil basis, so that the back of the plate 1 a pressure is exerted, the

Toner takes on the color and the now hydrophilic a transfer of the developed image 5a from the

Underlay that repels paint. 15 xerographic plate 1 on the receiving surface 7

Although this procedure works well for the application. Used as a receiving surface a hydrophilic one Has proven to be suitable in lithography, it has to be used after laying on the area various disadvantages. One example is the xerographic plate that is made up of the back of the recording mode in that for the conversion of the initial surface coated with a hydrophobic substance 8, hydrophobic pad in a hydrophilic pad ao This substance penetrates through the fibers of the support surface a conversion solution is needed to make them water repellent (hydrophobic). The underlay when coloring the oily paint, the same coating process can be used, takes. Another disadvantage is that the oil-resistant surfaces that are already present are hydroxerographic To make the plate solidified on its surface.

Contains baked toner powder and thus not again 25 F i g. 4 shows the process step of the detachment,

is usable. Another disadvantage is the polarity in which the image recording surface 7 of the forex

sensitivity of the toner powder and the fact that graphic plate 1 is removed. That developed

that only such photoconductive plates are used. Image Sa adheres to the receiving surface 7 and sets

which is a grain-mirror image of the original image with the toner powder.

Acceptable charge. 30 Fig. 5 shows the finished printing forme 9, which is from the

The object of the invention is now to have an improved receiving surface 7 and a developed image 5a

electrophotographic process contributes to the production. The printing form is used for printing with a

indicate a lithographic printing form that the aqueous printing ink 10 colored by means of a

Disadvantages of the above known methods on spreading device 11 is applied. The color

does not have. 35 is captured by the image area 12 while it

This object is achieved according to the invention by an electrophotographic process for producing phobic property being repelled from the background area 13 as a result of its hydrostatic properties,
A lithographic printing form of the type described at the outset is preferably used, which is characterized in that the photoconductive layer of which forms a large, aqueous, polarity-insensitive contact angle with the aqueous developer, is applied to the image area in order to achieve an image adhesion. It can, however, also be distributed imagewise in a manner corresponding to the latent image, whereby another suitable photoconductive, insulating hydrophilic and hydrophobic surface area is produced, substance can be used.

and that the developed image on a receiving surface are typical inorganic photoconductive substances

is transferred, which is used as a lithographic printing form 45 z. B. sulfur, selenium (glass-shaped, amorphous, a-mono-

serves. clin), zinc sulfide, zinc oxide, zinc cadmium sulfide, zinc

The invention is described below with reference to magnesium oxide, cadmium selenide, zinc silicate, CaI-

explained in more detail on the drawings. It shows ciumstrontium sulfide, cadmium sulfide, mercury jo-

F i g. 1 is a perspective view of a lat- did, mercury oxide, mercury sulfide, indium tri-

tes electrostatic image containing xerographic 50 sulfide, gallium triselenide, arsenic disulfide, arsenic trisulfide,

Plate, arsenic triselenide, antimony trisulfide, cadmium sulfosele-

F i g. 2 the front view of such a xerographinide, doped chalcogenides of zinc and cadmium, see plate which is partially developed with a water-soluble polarity- aluminum oxide, bismuth oxide, molybdenum oxide, lead-insensitive developer, oxide, molybdenum iodide, molybdenum selenide, molybdenum-

F i g. 3 the front view of a developed forex sulfide, molybdenum telluride, aluminum iodide, aluminum

graphic plate containing nium selenide, aluminum sulfide, aluminum telluride,

is in contact, bismuth iodide, bismuth selenide, bismuth sulfide, bismuth

F i g. 4 the perspective view of a forex telluride, cadmium telluride, mercury selenide, mercury Plate from which the image-bearing silver telluride, lead oxide, lead selenide, lead sulphide, lead receiving surface is partially removed, and 60 telluride, cadmium arsenide, lead chromate, gallium sulfide,

F i g. 5 the perspective view of a lithographic printing telluride consisting of gallium telluride, indium sulfide, indium selenide, indium receiving surface, red lead and mixtures thereof.
plate with partially colored image. Typical organic compounds that can be used according to the invention

The xerographic plate 1 shown in Fig. 1 are photoconductors

consisting of a base plate 2 and a photo 65

conductive insulating layer 3, is triphenylamine according to the invention;

measure for the production of a lithographic print- 2,4-bis- (4,4'-diethyl-aminophenyl) -l, 3,4-oxa-

shape used. It is charged evenly. diazole;

N-isopropylcarbazole triphenylpyrrole; 4,5-diphenylimidazolidinone; 4,5-diphenylimidazolidine ethione; 4,5-bis (4'-aminophenyl) imidazolidinone; 1,5-cyanonaphthalene;
1,4-dicyanonaphthalene,
Aminophthalonitrile;
Nitrophthalidinitrile;

1,2, S.ö-Tetraazacyclooctatetraen- ^ Aö, 8); 3,4-di- (4'-methoxyphenyl) -7,8-diphenyl l ^ o)

3,4-di (4'-phenoxyphenyl) -7,8-diphenyl, 2,5,6-tetraaza-cyclooctatetraene (2,4,6,8);

octatetraene (2,4,6,8);

2-mercapto-benzothiazole;

2-phenyl-4-a-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-aminoacenaphtheii; 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'-dimethylamino-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-t4'-N-ethyl-N-acetylamino-phenyl- (l ')] - 1,3,4-triazole;

!, S-diphenyl-S-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.

so in the photoconductive layer of the xerographic A binder can be incorporated into the plate as used in accordance with the invention. Such binders and photoconductive layers are similar to those described in U.S. Patents 3,121,006 and 3,121,007. According to the invention, preferably 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 a 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, alkali-soluble proteins, casein salts, water, etc. 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 φ hydrogen cyanide compounds of iron, the acetatoj iron (III) salts, iron ammonium citrate, the thiocyanate

! and the thiocyanate cobaltates of divalent cobalt, cobalt sulfate and chloride, the large number of cobalt (III) complexes, z. B. the amine, the aquo and

Acido complexes, which are present in equal abundance

j like the chromium complexes, the chlorides and sulfates of

j 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 α-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 α-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 Any suitable material can be used to form the image and to form the lithographic printing form. Typical materials are e.g. B. zinc, aluminum, polyethylene, polypropylene and normal fine paper. If the receiving surface is hydrophilic, it can be coated with a hydrophobic coating on its rear side Fabric, e.g. B. an aliphatic isoparaffin hydrocarbon, can be made water repellent if this penetrates the receiving surface. According to the invention are polyethylene, polypropylene and normal Fine papers are preferably used because they have good 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.!.

A sheet of commercially available zinc oxide paper is used with a corotron laboratory device consisting of a High voltage source is fed, charged to 350 to 400VoIt. The charging current is at 7500 volts 0.1 mA. A clear USAF positive test sheet is placed on the loaded zinc oxide paper, which is then exposed to a 75 watt photo lamp. For the zinc oxide paper there is an exposure with 215 Luxsec required. The electrostatic latent image thus formed is then treated with a 1% aqueous Solution of an ammonium salt of a carboxyvinyl polymer using a gravure doctor roller developed. A sheet of normal fine paper is then aligned with the image surface of the zinc oxide paper brought into direct contact. Then the back of the fine paper is finely sprayed with a water immiscible hydrocarbon, e.g. B. an aliphatic isoparaffin hydrocarbon, overdrawn. Pressure is applied to the back of the zinc oxide paper to prevent the developed Transfer the image to the fine paper. The sheets are then separated, and the fine paper with The lithographic printing plate represents the clear transferred image. The image is then combined with a Rubber sheet with the blue washable aqueous dye Sheaffer Skrip (commercial color mixture) inked and the final print by touching the printing plate with a copy sheet manufactured. The result is images with good optical density and resolution.

Example 2

The procedure of Example 1 is repeated, wherein this time, however, instead of the zinc oxide paper, a xerographic plate with a layer of amorphous material Selenium is used on an aluminum base. The printed images have better quality since 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

509 528/12

Niurri pad is used. The results are with those of example 2 comparable.

B e i s ρ i el 6

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

Example7

The procedure of Example 1 is repeated, wherein this time a xerographic plate with a photoconductive layer instead of the zinc oxide paper made of polyvinyl carbazole on an aluminum base. The quality of the images received is with that of Example 4 comparable.

Examples

The procedure of Example 1 is repeated, this time the developed latent image on a polyethylene sheet instead of being transferred to fine paper. During this process, the coating of the Refrain from printing plates with a water-repellent hydrocarbon (example 1). Using of polyethylene, the quality of the images is comparable to that from Example 1. The lifespan however, the image on a sheet of paper is longer.

Example 9

The procedure of Example 1 is repeated, this time the developed image on a polypropylene sheet instead of being transferred to fine paper. During this process, the pressure plate is coated refrain from using a water-repellent hydrocarbon (Example 1). As with the previous one Example, it turns out that the images are more permanent on a paper surface.

For ρ iel 10

The procedure of Example 1 is repeated, this time using a xerographic plate with a layer of amorphous selenium on an aluminum base instead of the zinc oxide paper. The developed latent image is transferred to a sheet of polyethylene instead of fine paper. During this process, the printing plate is not coated with a water-repellent hydrocarbon (Example 1). The images are of good quality as in Example 2, but the durability of the image on the printing plate is better when paper is used.

10

Example 11

The procedure of Example 1 is repeated, where-. this time a xerographic one instead of the zinc oxide paper Plate with a layer of amorphous selenium on an aluminum base is used. The developed latent image is transferred to a polypropylene sheet rather than fine paper. While This process involves coating the pressure plate ίο with a water-repellent hydrocarbon (example 1) refrain. As in Example 10, an image of good quality which corresponds to that of Example 2 is obtained. However, the image persistence on polypropylene is not as good as on fine paper.

Example 12

The procedure of Example 1 is repeated, this time using a xerographic paper instead of the zinc oxide paper Plate with a photoconductive poly

ao vinyl carbazole layer used on an aluminum base will. The developed latent image is transferred to a sheet of polyethylene instead of fine paper. During this process, the printing plate is coated with a water-repellent hydrocarbon (Example 1) omit. The results are similar to those of Example 10.

B e i s ρ i e 1 13

The procedure of Example 1 is repeated with the difference that instead of the zinc oxide paper a xerographic plate with a photoconductive polyvinyl carbazole layer on an aluminum base is used. The developed latent image is transferred to a sheet of polypropylene instead of fine paper.

wear. During this process, the printing plate is not coated with a water-repellent hydrocarbon (Example 1). The results are similar to those of Example 11.
In addition, other substances can be used in the developer, the printing ink, the paper or the xerographic plate which improve the properties of these substances for use in the invention, intensify their effect or otherwise influence them. For example, it can be useful to give the image greater mechanical strength. For this purpose, the developing solution can be a thickener or an adhesive, e.g. B. gum arabic, gum tragacanth, karaya gum, guar gum, agar-agar and dextrins, without any disadvantages in the quality of the developed image. The properties of the aqueous developer can be changed by adding alcohols such as glycols and glycerols or polyethylene oxides.

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 by exposure latent electrostatic image is generated, characterized by that on the Image area an aqueous, polarity-insensitive developer is applied, which is accordingly distributed imagewise to the latent image, whereby hydrophilic and hydrophobic surface parts arise, and that the developed image is transferred to a receiving surface, which is used as a lithographic printing form serves. 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 the electrophotographic plate carries a photoconductive layer which contains an organic 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 isoparaffin 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.