DE1243700B - Presensitized planographic printing plate with a hydrophilic intermediate layer and method for making the same - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

B41n

German class: 151-2 / 02

Number: 1243 700

File number: P 32802 VI b / 151

Filing date: October 18, 1963

Opened on: July 6, 1967

The invention relates to a planographic printing plate and to a method for its manufacture. In particular, the invention relates to a method of making a sealed hydrophilic Layer or more such layers on a planographic printing plate and the one obtained thereby Planographic printing plate.

In the following description and in the claims, all percentages and proportions are given always percentages or parts by weight, unless expressly stated otherwise.

The planographic printing process is based on the immiscibility of oil and water and on the fact that an oily, image-forming substance, preferably at the image areas, and accordingly an aqueous moistening liquid is captured by the non-image areas. Will an oily picture on a suitable one Surface printed and the entire surface then moistened with an aqueous solution, so the image areas will repel the water, but the image-free areas will accept and hold onto it. When an oily printing ink is subsequently applied, the image areas take on the color while the moist, non-image areas repel them. The image is then applied to paper or fabric by means of a so-called offset cylinder applied, which is necessary to prevent mirror image printing.

To produce a planographic printing plate, a suitable support is coated with a photosensitive one Emulsion, which can be done either by the manufacturer or by the printer; then exposed the plate sensitized in this way through a photographic image with actinic Light. The exposed plate is then further treated, whereby oleophilic, ink-accepting Image or printing points and hydrophilic, ink-repellent non-image or non-printing areas are generated will; the plate treated in this way can be used to make many prints.

Depending on the type of photosensitive emulsion used, the treated plate can either serve to directly reproduce the image with which it was exposed; in this case it is a so-called positive-acting plate; vice versa can be done in the manner mentioned treated plate also to produce an image complementary to the image with which the plate was exposed Serve image; in this case it is called a negative-acting plate. In both In some cases, the image areas of the light-sensitive emulsion become oleophilic (oil-accepting) by suitable treatment made and the rest of the emulsion through

Presensitized planographic printing plate with a
hydrophilic intermediate layer and method too
their manufacture

Applicant:

Polychrome Corporation,

Yonkers, N. Y. (V. St. A.)

Representative:

Dipl.-Ing. C. Wallach, patent attorney,

Munich 2, Kaufingerstr. 8th

Named as inventor:

Gerald F. O'Connor,

Simon L. Chu, Yonkers, N.Y. (V. St. A.)

Claimed priority:
V. St. v. America October 19, 1962
(231 826)

removes a desensitization treatment, whereby the hydrophilic, non-image (non-printing) Places are formed.

It is known that the carrier material for such light printing plates is either made waterproof Use paper or a flexible metal foil. Aluminum, steel, zinc, magnesium, and chrome Copper are typical metals suitable for this purpose.

Since paper is relatively coarse-grained and tends to stretch, one achieves up with a plate metallic base layer, better reproduction and longer durability than a plate with a paper base layer. But should a metal plate with a If light-sensitive material is to be coated, the metal must first be coated with a hydrophilic surface to which the photosensitive emulsion adheres and which after removal of parts of the exposed photosensitive material the color-repellent, non-image (non-printing) places. For the production of such hydrophilic surfaces on metal plates Various methods are known for planographic printing purposes. In one such known method is a treatment of the metal surface with

709 609/300

a titanium hexahalide is provided to create a hydrophilic layer on the metal surface, whereupon this layer is sealed in a hot water bath. This procedure as well other known methods are not entirely satisfactory in that they work in this way produced printing plates often only have a limited shelf life and a limited water absorption capacity own. Furthermore, such plates tend to absorb moisture and are unsuitable in a humid, warm atmosphere, what for packaging and storage under such Conditions raises various problems.

It is therefore an object of the present invention to provide a method of making a a planographic printing plate having a hydrophilic layer, which under conditions relatively is stable and resistant to high humidity and temperature.

The invention is also intended to provide such a method and one obtained by this method Printing plate can be created that is simple and cheap to manufacture and relatively many Prints supplies.

Further advantages and details of the invention emerge from the following description Hand of working examples.

According to the invention, a planographic printing plate is produced by a method which under other steps: A metal surface is treated with a transition metal fluoride, namely with an acid, an alkali metal or alkaline earth metal salt of the transition metal tetrafluorides, -pentafluoride or -hexafluoride, treated, creating a hydrophilic surface on the metal surface Layer is generated; this layer is then sealed with chromic acid, and then the so The resulting sealed hydrophilic layer applied a photosensitive emulsion. The one in this Way sensitized printing plate is exposed to actinic light according to a photographic image; the exposed plate is used to produce an oleophilic (oil-accepting) Image further processed, which can be used to make many copies.

Surprisingly, it was found that those produced in this way sealed with chromic acid hydrophilic layers show remarkable resistance under conditions of high humidity and temperature have, so that printing plates prepared in this way under such conditions can be stored for long periods of time. Printing plates with hydrophilic layers, which by treatments sealed with hot water, on the other hand, absorb moisture and become unusable if exposed to 90% relative humidity for 1 to 2 days; in contrast, printing plates with hydrophilic layers sealed by means of chromic acid remain in accordance with of the present invention also when stored in a humid, warm atmosphere for periods of resistant for more than 6 months.

The hydrophilic surface obtained by treatment according to the invention can be applied to metal surfaces be applied in various ways. Aluminum plates are preferably used, The aluminum base layer is chemically etched, mechanically grained or degreased as required will. Although the treatment of aluminum plates is described as specific exemplary embodiments in the following, it should be particularly emphasized that of course, the invention in connection with any desired metal substrates known for printing plates is applicable.

The hydrophilic layer on the metal support is produced in such a way that this support plate is immersed in an aqueous solution of a suitable transition metal tetra-, penta- or hexafluoride. Any salt of the Group IVB metals (zirconium, titanium or hafnium) can be used for this purpose. As examples of transition metal fluorides which have been found to be satisfactory in the practice of the method according to the invention, zirconium tetrafluoride (ZrF ₄ ), hydrogen fluorozirconic acid _{(H 2 ZrF 6} ), potassium zirconium hexafluoride (K ₂ ZrF ₆ ), sodium zirconium hexafluoride _{(Na 2 ZrF 6} ) , Potassium zirconium penta-

, Natriumzirkoniumpentafluorid (NaZrF _5), titanium tetrafluoride (TiF _4), potassium titanium hexafluoride (K ₂ TiF _{6) (6} NaHfF) serve fluoride ₍₅ KZrF), hafnium tetrafluoride (HfF _4), Kaliumhafniumhexafluorid (K ₂ HfF ₆₎ and Natriumhafniumhexafruorid. In addition to the acids and alkali metal salts mentioned above, the alkaline earth metal salts and the ammonium salts of the transition metal fluorides, for example CaZrF ₆ and (NHJ ₂ ZrF ₆ , can also be used to form the hydrophilic layer; however, treatment with these last-mentioned salts leads to plates with a lower shelf life .

Preferably, the metal base layer is immersed in an aqueous solution which is about 0.01 to contains about 1% of the transition metal form. The temperature of the fluoride bath is in the range maintained from about 20 to about 80 ° C and the pH of the solution within the range of set about 3.5 to 5. The immersion time is not critical and can preferably be from about 5 seconds vary up to about 5 minutes. Of course, the temperature, the time and the transition metal fluoride concentration can be varied within the specified ranges in order to achieve optimal results. If desired, the A soluble zinc salt can also be added to the transition metal fluoride solution.

The hydrophilic layer produced in this way is sealed by treatment with chromic acid; this can, if desired, be included in the transition metal fluoride solution in an amount of about 0.001 to 2.5%; however, as explained below, it is preferable to apply the chromic acid in a separate treatment solution subsequent to the formation of the hydrophilic layer. This separate aqueous chromic acid treatment solution contains about 0.001 to about 2.5%, preferably about 0.02%, CrO ₃ and is maintained at a temperature in the range of about 20 to 80 ° C, preferably at about 70 ° C.

The metal base plate with the hydrophilic layer on it is used for a period of time which can take from about 1 minute to about 9 minutes, and preferably about 3 minutes, into the Immersed chromic acid sealing bath.

Treatment with chromic acid seals the hydrophilic layer, thereby increasing moisture absorption largely reduced and the aforementioned increased resistance to

Temperature and humidity is achieved. The exact mechanism by which the transition metal fluoride and the chromic acid to form a sealed hydrophilic layer on the aluminum or other metal carriers react with one another is not known. It is possible that the Chromic acid a chromium layer on a hydrophilic layer produced on the metallic carrier layer Forms fluoride layer and thus seals the pores in the fluoride coating. Another possibility is also that the transition metal fluoride is bound directly to the metal plate and through the Dehydration effect of the chromic acid is crosslinked or crosslinked, according to the in the drawing Equations (1) to (3) shown, which one possibility for this reaction mechanism when using hydrofluorozirconic acid to create the hydrophilic layer.

It should be emphasized that the reaction mechanisms mentioned above are possible explanations for the Mode of operation of the method according to the invention, but not restrictive in any way Should be important.

The photosensitive emulsion coated on the printing plate can be any of the known photosensitive substances commonly used for printing purposes exist, for example can use the light-sensitive diazo resins, albumin, gum, casein dichromate, furfur-acetone condensation products or cinnamyl resins are used alone or in combination. Preferably, however, a photosensitive coating is used Diazo resin for the hydrophilic layer applied to the chromic acid sealed layer photosensitive emulsion used. It has surprisingly been found that such a coating adheres or is bound more firmly to such a layer than to the previously known hydrophilic ones Layers. Printing plates sensitized with diazo according to the invention therefore show an excellent one high printability such that more than 10,000 prints can be made without difficulty can.

Any of the known diazo light-sensitive substances can be used here for example those in column 5 of U.S. Patent 2,937,085, in column 2 of U.S. Patent 2,649,373 or in column 10 of U.S. Patent 2,714,066. These or other conventional diazo sensitizers, which are inherently negative, may optionally are pretreated so that they result in a positive-acting plate.

A typical photosensitive suitable for use for the purposes of the present invention Diazo resin is the condensation product of paraformaldehyde and paradiazodiphenylamine. Using this resin, the diazo coating, for example, 1% of the resin as a dispersion in a Contain saponin solution.

The plate sensitized in this way is then used to produce a permanent oleophilic (Oil-accepting) image exposed imagewise to actinic light. The resulting from the exposure latent image is developed with the help of a suitable varnish or other developer, with a oleophilic (oil-accepting) image arises and is exposed on the underlying hydrophilic layer hydrophilic non-image (non-printing) areas remain. The plate can then on a The printing press is cocked and a large number of prints are made from it.

The surface of the metal base layer, for example the aluminum layer, is preferably degreased and chemically activated prior to treatment with the transition metal fluoride to ensure a more firmly adherent Image. The aluminum is therefore preferably pretreated with a Alkali degreaser, an acidic caustic agent, a desmutting agent and another acidic agent subjected to an acid such as phosphoric acid, chromic acid, nitric acid, It contains sulfuric acid, or oxalic acid, which activates the aluminum surface and increases its absorption capacity for the subsequent generation of the hydrophilic layer is increased.

For this purpose, typical known acidic etching treatments such as those described in US Pat U.S. Patent 2,882,153 apply. If a grainy plate is desired is, the aluminum base layer is not etched, but with suitable mechanical means, for example by rubbing with an emery, sandblasting or by brushing with a wire, Nylon or hair brush, granulated. Details of such mechanical graining processes are known see, for example, USA patent specification

2 882155).

Either phosphoric or oxalic acid are preferably used for the acidic activation solution a concentration ranging from about 0.01% to about 5% by weight is used; optimal results when using these acids with a concentration in the range of about 0.2 to about 1% achieved. The duration of immersion in the acid bath, which is at a temperature between about 10 and about 40 ° C, preferably at about 18 ° C, depending on the concentration of the bath solution between Vary about 1 second and 3 minutes, with good results with immersion times of 5 to 10 seconds were achieved. The duration, temperature and concentration of this bath treatment can be within the specified limits can be selected appropriately in order to achieve optimal results.

Further advantages and details of the invention emerge more specifically from the following description Examples which, however, are not intended to be of restrictive importance.

example 1

A piece of 3 S aluminum sheet (degree of purity 99%) was degreased in a 10% trisodium phosphate solution at about 70 ° C. for 3 minutes and etched. The plate was then placed in tap water

Rinsed for 3 minutes at room temperature and then in a desmutting solution for 10 to 15 seconds immersed, which contained 15% sulfuric acid and 2.6% chromic acid. After this The plate was taken out in running tap water for 3 minutes at room temperature flushed.

The plate pretreated in this way was immersed in a 0.18% strength solution of potassium zirconium hexafluoride for 3 minutes (pH = 4) immersed. the

Solution was maintained at a temperature in the range of about 65 to about 70 ° C during the immersion. Immediately after removing it from the hexafluoride solution, the plate was immersed in a chromic acid bath which contained 0.03% CrO ₃ and was kept at a temperature of about 65 to about 70 ° C. After staying in this bath for 3 minutes, the plate was removed, rinsed with water, dried and sensitized by applying a solution of a diazo resin to both sides of the aluminum foil. The condensation product of paraformaldehyde and paradiazodiphenylamine (containing 4 parts of formaldehyde to 30 parts of paradiazodiphenylamine) was used as the diazo resin. after drying, the plate was ready for use.

When exposed to UV radiation through a negative, the surface of the plate produced a solid, water-insoluble image. After developing the image five times, the plate became clamped on a printing press and made over 10,000 sharp, clear prints.

Example 2

The same procedure as described in Example 1 was followed, with only to produce the hydrophilic layer on the aluminum surface titanium tetrafluoride instead of Potassium zirconium hexafluoride was used; the results obtained were similar to Example 1; with the planographic printing plate obtained in this way, clear, sharp copies could be produced during printing,

Example 3

An aluminum plate was degreased, etched and prepared according to the method described in Example 1 flushed. The plate was then immersed in a desmutting solution which contained 6% sulfuric acid and 1% vol chromic acid.

After further rinsing, the plate pretreated in this way was for 3 minutes at about 20 to 30 ° C immersed in a 0.06 ° / qige solution of hydrofluorozirconic acid. The one made in this way hydrophilic layer was then sealed by immersing the plate in a bath solution containing a Mixture of 0.03% chromic acid and 0.07% hydrofluorozirconic acid contained.

The thus sealed hydrophilic layer was provided with the photosensitive diazo resin coating, it was then exposed and further processed in the same manner as in Example 1. The thus obtained Printing plate gave clear, sharp prints.

The present invention describes a process for the production of planographic printing plates, the panels produced by this method under conditions of relatively higher Are resistant to humidity and temperature and allow a large number of prints. Of course are the exemplary embodiments described with regard to details of the method and the structure of the printing plate thus obtained can be modified in many ways without this the scope of the invention is left.

Claims (5)

* 5 claims: 1. Presensitized planographic printing plate with a hydrophilic intermediate layer which has a metallic Carrier, especially made of aluminum, ao and a photosensitive emulsion applied to this metallic support, characterized in that the hydrophilic layer is the reaction product of a transition metal fluoride from the group: acids, Alkali metal, alkaline earth metal and ammonium salts of transition metal tetrafluorides and pentafluorides and hexafluorides, with chromic acid. 2. Planographic printing plate according to claim 1, characterized in that the transition metal fluoride is a zirconium hexafluoride. 3. Printing plate according to claim 1, characterized in that the transition metal fluoride Is zirconium tetrafluoride. 4. Method of making a hydrophilic intermediate layer in presensitized planographic printing plates based on aluminum according to one or more of the preceding claims, characterized in that the aluminum surface treated with a 0.01 to 1% aqueous solution of the transition metal fluoride and that the seal is made with a 0.001 to 2.5% chromic acid solution. 5. The method according to claim 4, characterized in that the treatment of the defatted Metal surface with the transition metal · fluoride solution for a period of 5 seconds to 5 minutes and at a temperature ranging between about 20 and about 80 ° C takes place and that the treatment with the chromic acid solution for sealing during a time from 1 minute to 9 minutes and at a temperature between about 20 and about 80 ° C. 1 sheet of drawings