Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/06—Silver salts

Definitions

• G03f 7/06 ABSTRACT OF THE DISCLOSURE In a process for producing a lithographic printing plate comprising exposing an imaging medium comprising a developer layer containing a developing agent capable of oxidation in the presence of a hydrophilic organic colloid to form an image receptive to greasy printing ink, and over the developer layer a hydrophilic organic colloid photosensitive emulsion capable of reacting with the developer to produce a visible metal image, and the emulsion containing a hardener, in which the colloid has a hardness equivalent to that of a gelatin layer containing from about 2 grams to about grams of dry formaldehyde per gram of gelatin, which exposed imaging medium is contacted with an activator solution for the developer to produce a lithographic plate, the improvement comprising redueing the water absorption characteristics of printing plate by contacting the imaging medium with an antiswelling agent which is preferably a solution of an alkali metal halide, sulfate or nitrate.
• This invention relates to photographic reproduction processes. More precisely, the invention disclosed herein relates to processes involving photolithographic printing plates and especially to methods for improving photolithographic printing plates which comprise silver halide photographic emulsions.
• Photolithographic printing plates are well known to the art.
• photolithographic plates useful in the practice of the present invention and manners of producing same are disclosed in more detail in U.S. Patent 3,146,104 which is incorporated herein by reference.
• the essential elements of photolithographic printing plates are a suitable substrate and generally a plurality of layers, at least one of which comprises a radiation sensitive, e.g., light sensitive, system which in most cases comprises a silver halide and an organic binder material, generally gelatin.
• a radiation sensitive e.g., light sensitive
• an organic binder material generally gelatin.
• one of the additional layers of said plates comprises a developing agent and more often than not, the developing agent is disposed in a layer adjacent the radiation sensitive layer.
• the uppermost layer of said plates comprises gelatin which is generally prehardened to a particular degree.
• the production of photolithographic plates involves the exposure of said plates to a pattern of activating radiation modified by an image pattern and development thereof.
• the character of the organic binder material of the uppermost layer undergoes changes.
• the binder in the developed portions is rendered oleophilic, e.g., ink receptive, whereas the binder in the non-developed portion maintains its oleophobic, e.g., Water receptive character.
• ink is applied to the plate and adheres preferentially to the oleophilic portions thereof. Accordingly, a plurality of copies can be printed from the plates in accordance with known techniques.
• blinding An outstanding problem in the production of suitable photolithographic printing plates involves a phenomenon known to the art as blinding. Essentially, the problem of blinding is caused by the absence of adequate or definitive difierentiation between the ink receptive and water too receptive portions of the developed photolithographic plate. Accordingly, blinding indicates that the ink receptivity of the oleophilic portion of the developed lithographic plate is adversely impaired and poor quality reproductions are obtained therefrom. Oftentimes blinding can occur immediately after the printing step is begun. For example, in some instances, as many as 50 or more copies must be printed before the photolithographic plate develops suflicient ink receptivity to produce quality copies.
• blinding can also manifest itself during the printing run, for example, after about 100 or more copies are produced.
• the only way to adequately correct the problem of blinding is to produce another photolithographic plate. Accordingly, such a problem is time consuming and uneconomical and any process whereby blinding can be eliminated or effectively minimized would be indeed a notable contribution to the art.
• a principal object of the present invention is to provide improved photolithographic plates.
• Another object of the present invention is to provide an improved process for producing photolithographic plates.
• Still another object of the present invention is to provide a process for improving the ink receptivity of photolithographic plates.
• Still another object of the present invention is to provide a process for correcting the problem of blinding which may arise at any time during the production of copies from photolithographic plates.
• Another more specific object of the present invention is to provide an improved acid stop bath for processing photolithographic plates.
• the above objects and advantages are realized in accordance with the practice of the present invention by adjusting the water absorption characteristics of the binder in that layer of the photolithographic plate which is ultimately rendered oleophilic and oleophobic.
• the water absorption characteristics of the binder employed in said layers is an important factor in maintaining difierentiations between the oleophilic and the oleophobic portions of the layer.
• the overall ink receptivity of the photolithographic plate is advantageously improved.
• improved photolithographic plates are produced by employing as the binder in the uppermost layer of said plates, gelatins which inherently have low water absorption characteristics.
• gelatins which inherently have low water absorption characteristics.
• Many manners of producing gelatins having low moisture absorption characteristics are known to the art. For example, on pages 69 and 70 of The Theory of the Photographic Process by Mees, Revised Edition, published by the MacMillan Company in 1954, two such methods are disclosed.
• gelatins of reduced water absorption characteristics can be produced by lowering the pH of the sol from which the gelatin is produced before drying same.
• gelatins of suitable reduced water absorption characteristics are produced by adjusting the pH of the sol to less than about 5.
• gelatins of reduced water absorption characteristics suitable in the practice of the present invention can be produced by increasing the concentrations of the original sol to amounts above about percent.
• -I prefer to reduce the water absorption characteristics of the gelatin layers by applying solutions comprising specific materials to photolithographic plates during the development processing thereof.
• photolithographic plates of improved initial in-k receptivity can be produced. Plates produced in accordance with this aspect can be used to produce printed copies with a high degree of assurance that the phenomenon of blinding will not be encountered there-with.
• Another aspect of this embodiment of my invention involves the application of the solutions to photolithographic plates which have been processed according to development techniques presently known to the art and which manifest blinding during the copy printing step. In accordance with this aspect, said blinding can be eliminated without the need of producing a new photolithographic plate.
• anti-swelling agents for the binder materials employed in photolithographic plates.
• anti-swelling agents for gelatin are disclosed in pages 64 and 65 of The Theory of the Photographic Process by Mees, Revised Edition, published by the MacMillan Company.
• the organic and inorganic salts of the alkali metals are definitely preferred.
• especially preferred antiswelling agents are the sulfates, tartrates, citrates, acetates, halides, nitrates and the like of the alkali metals and especially the above mentioned salts of sodium and potassium.
• aqueous solutions of the above mentioned salts are preferably employed but partially aqueous solutions can be used if desired.
• concentration of said salts in the solutions can vary depending primarily on the solubility of the particular salt employed but normally solutions of less than about percent by weight of the salts are suitable.
• the benefits which flow from the practice of the present invention are realized by applying the aforesaid solutions to the lithographic plates preferably after the development of the image pattern therein.
• An especially suitable and preferred method of applying said solutions involves employing same in combination with acids as stop baths since such stop baths are normally employed in the processing of photolithographic plates.
• the developed plate is contacted with a solution comprising an alkali metal salt and an amount of acid suflicient to reduce the pH of the solution to preferably less than about 2.0.
• the acids such as citric, glycolic and phosphoric acid or others with similar dissociation constant.
• the plate is immersed in the stop bath for about 20 seconds but somewhat longer times can be employed.
• the alkali metal salts need not be added directly to such stop baths.
• the developed lithographic plate can be contacted with solutions of said salts either before, but preferably after, the plate is immersed in said stop baths.
• solutions of the alkali metal salts can be applied to the developed lithographic plate while the plate is employed to produce printed copies.
• dilute solutions of said salts can be employed as fountain solutions during the copy printing step.
• plates processed in accordance with this technique do not manifest blinding during the copy printing step.
• plates processed in this fashion immediately manifest a high degree of ink receptivity. Accordingly, the initial copies reproduced therefrom are of high quality and need not be discarded as is oftentimes the situation presently in the art.
• my solutions can also be advantageously employed to correct any blinding which occurs during the printing step with plates processed in accordance with development techniques presently known to the art. For example, I have found that such plates need not be discarded since the blinding can be eliminated by contacting said plates with the solutions of the present invention.
• the photolithographic plate material involved is similar to that described in FIGURE 2 of US. Patent 3,146,104.
• Said patent describes photolithographic plates which are representative of the type used in the practice of the present invention.
• the plate material employed essentially comprises a support and a plurality of layers thereon.
• the layer adjacent the support comprises gelatin and a polyhydroxybenzene silver halide developing agent which, upon reaction with silver halide, can produce an oxidation product which renders the binder, e.g., gelatin oleophilic.
• Over said developer containing layer is an unfogged gelatino-silver halide emulsion layer while over said emulsion layer is a fogged gelatino-silver halide emulsion layer uniformly hardened with a hardener.
• EXAMPLE 1 A lithographic plate material, as described above, was exposed to a line positive, processed for about 20 seconds in a 4 percent aqueous sodium carbonate monohydrate solution and treated for about one minute in an aqueous stop bath of the following formulation:
• the plate of the example was immersed in an aqueous solution of sodium sulfate.
• the solution comprised about 10 percent by weight sodium sulfate.
• the plate was then run on a lfithographic press and high quality copies produced thererom.
• EXAMPLE 3 A lithographic plate material was exposed to an image pattern and developed in accordance with the procedure of Example 1. After development, a portion of the plate was immersed in the stop bath of Example 2 whereas another portion thereof was immersed in an aqueous stop bath of the following formulation:
• the plate was then run on a lithographic printing press. After one printing, the copy produced from the portion of the plate immersed in the stop bath of the above described formulation was of high quality indicating an improved ink receptivity of the portion of the plate processed in accordance with the practice of my invention. In contrast thereto, the copy produced from the portion of the plate immersed in the stop bath of Example 1 did not manifest such quality until after about 50 prints were produced.
• a lithographic printing plate from an imaging medium comprising a developer layer containing a developing agent capable of oxidation in the presence of a hydrophilic organic colloid to form an image receptive to greasy printing ink, and over the developer layer a hydrophilic organic colloid photosensitive emulsion capable of reacting with the developer to produce a visible metal image, and the emulsion containing a hardener, in which the colloid has a hardness equivalent to that of a gelatin layer containing from about 2 grams to about 15 grams of dry formaldehyde per gram of dry gelatin, which imaging medium is exposed and contacted with an activator solution for the developer to produce an element useful as a lithographic plate by reasons of differences in ink receptivity between the exposed and non-exposed areas of the medium, the improvement comprising reducing the water absorption characteristics of the printing plate by contacting the imaging medium with an antiswelling agent.
• hydrophilic colloid photosensitive emulsion comprises a gelatin-silver halide emulsion.
• a first layer comprising a silver halide developing agent capable of oxidation in the presence of a hydrophilic organic colloid to form an image receptive to greasy printing inks
• a second layer comprising an exposed hydrophilic organic colloid silver halide emulsion
• a third layer comprising a fogged hydrophilic organic colloid silver halide emulsion containing a hardener, in which the colloid has a hardness equivalent to that of a gelatin layer containing from about 2 grams to about 15 grams of formaldehyde per pound of gelatin, which imaging medium is contacted with an activator solution for the silver halide developing agent thereby producing an element useful as a lithographic plate
• the improvement comprising contacting the plate with a solution comprising contacting an antiswelling agent for the hydrophilic organic colloid.
• a photographic stop bath for use in processing photolitographic printing plates which comprises a solution comprising phosphoric acid and a salt chosen from the group consisting of the halides, sulfates and nitrates of an alkali metal.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Photosensitive Polymer And Photoresist Processing (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=24054303

Family Applications (1)

Country Status (7)

Cited By (1)

Citations (8)

• 1965
  • 1965-12-23 US US516141A patent/US3429703A/en not_active Expired - Lifetime
• 1966
  • 1966-12-20 NL NL6617911A patent/NL6617911A/xx unknown
  • 1966-12-21 DE DE19661522491 patent/DE1522491A1/de active Pending
  • 1966-12-21 BE BE691556D patent/BE691556A/xx unknown
  • 1966-12-22 FR FR88487A patent/FR1514202A/fr not_active Expired
  • 1966-12-22 GB GB57488/66A patent/GB1174788A/en not_active Expired
  • 1966-12-23 CH CH1842466A patent/CH491412A/fr not_active IP Right Cessation

Patent Citations (8)

Also Published As

Similar Documents

Legal Events