IL33511A

IL33511A - Light-sensitive material for the preparation of a multi-metal offset printing plate,and process for the preparation therefor

Info

Publication number: IL33511A
Application number: IL33511A
Authority: IL
Original assignee: Kalle Ag
Priority date: 1968-12-27
Filing date: 1969-12-09
Publication date: 1973-07-30
Also published as: CH530656A; CA931806A; DE1817107B2; FR2027168A1; DK133207B; DK133207C; NL6918151A; IL33511A0; CS151538B2; GB1286879A; SU403207A3; SE355088B; DE1817107A1; BE741743A; BR6914931D0; DE1817107C3; ES373504A1; AT292034B

Description

LIGHT-SENSITIVE MATERIAL FOR THE PREPARATION OF A MULTI-METAL OFFSET PRINTING PLATE, AND PROCESS FOR THE PREPARATION THEREOF mztaa ^mano-ai pos- ns>T»a Bzsff? TIB annam LIGHT-SENSITIVE MATERIAL FOR THE PREPARATION OF A MULTI-METAL OFFSET PRINTING PLATE , AND PROCESS FOR THE PREPARATION THEREOF Abstract of the Disclosure This invention relates to a light-sensitive material for use in the preparation of a multi-metal offset printing plate in which a chromium layer on a copper-containing layer has a reproduction lgyer thereon of a thickness of 2 to 6 microns and containing (1) a light-sensitive imino quinone diazide of the formula wherein R is an aryl group , R' is selected from the group consisting of hydrogen or an alkyl group , R" is selected from the group consisting of an a lkyl , carbocyc lie or heterocyclic aryl group , or R' and R" together form a heterocyclic group with the N-atom to which they are attached , and R' " is selected from the group consisting of hydrogen, halogen , or an alkyl or alkoxy group, and (2) 33 to 100 per cent by weight of resin, calculated on the quantity of imino quinone diazide present , at least 30 per cent by weight of the resin being an alkali-soluble resin and at least 20 per cent by weight being a film-forming polymer. . . / i This Invention is concerned with Improvements in and relating to light-sensitive materials for the preparation of multi-metal offset printing plates.

In the present specification* a "multi-metal offset printing plate" is a plate or forme in which the non-printing, hydrophllic areas of the printing plate consist of a chromium layer, and the oleophilic printing areas consist of a layer of copper or copper alloy* A multi-metal support for use according to the present invention is a support in which a copper layer is covered by a chromium layer. The thickness of the copper layer may be sudh that it Is self-supporting, or the copper layer may be very thin and may be supported by a third, self-supporting layer* Such a third> self- supporting layer may eonsistftoijlnetal, plasblets materialt or water-resistant paper* Light-sensitive materials suitable for the preparation of offset printing plates are known in numerous modifications. Their essential components are a support and a light-sensitive layer disposed thereon. Quinone dla&lde compounds have already been used, among other compounds, for the preparation of light-sensitive reproduction layers of materials which can be stored for a relatively long period of time without deterioration. The support consists normally of metal or of paper whose surface has been made water- resistant* Light-sensitive material in which a reproduction layer formed from an immno-quinone dlazlde compound of the type as specif!** below, is disposed on a multi- However* nateriai sensitised with such an imino-qulnone dlazide compound can be prepared only; wlth£ difficulty, because for processing the printing plate, the material has to be sutteeted to a treatment in which parts of the chromium layer are removed from the copper layer by etching* Since multl-raetal material is normally used or the purpose Af preparing a printing plate from which long ttuns of high quality prints can be obtained, the reproduction layer of light-sensitive material intended for the preparation of multi-metal printing plates must fulfill high demands as regards efficiency* In spite of the fafcjr that the plate is etched, it is in particular required that the resulting printing Image reproduces all details of the original under which the material was exposed for transferring the image* The above-mentioned known multi-metal material sensitized with an imlno-quinone dlazide compound can be stored for a relatively long time. However* although its light-sensitive layer contains novolak, Its resistance against the etching agent applied for removal of the chromium in the araageareas is not as stroigas desirable* Te present invention provides an improved light-sensitive immaterial for the preparation of a multi-metal offset printing plate, said material having a multi-metal support including an outer chromiun layer disposed on a layer of copper or a copper alloy and upon said support a reproduction layer wlibch contains at least one light-sensitive imlno-quinone dlazide of the general formulas wherein R is an aryl group which may be substituted at the nucleus , R' is hydrogen or an alkyl group, R" is an alkyl , carbocyclic or heterocyclic aryl group , or aryl which is substituted at the nucleus , or R' and R" together form a heterocyclic group with the N-a om to which they are attached , and R' " is hydrogen , halogen , or an alkyl or alkoxy group , and 33 to 100 per cent by weight of resin, calculated on the quantity of imino quinone diazide present . At least 30 per cent by weight of the resin consists of a novolak , or a novolak modified by condensation with mono chloro acetic acid , or an epoxy resin , or a copolymer of a vinyl compound which contains carboxyl groups , while the remainder, if any , consists of a film-forming polymer which contains no carboxyl groups , and at least 20 per cent by weight is either a film-forming polymer which contains no carboxyl groups , or a copolymer of a vinyl compound which contains carboxyl groups , the resins being present in the following quantities: 0 to 50 per cent by weight of novolak modified by condensation with monochloro acetic acid , χ 0 to 80 per cent by weight of novolak or epoxy resin , and 0 to 100 per cent by weight of a copolymer of vinyl compounds containing carboxyl groups .

The reproduction layer has a thickness of 2 to 6 microns .

The imino quinone diazides of the above formula are disclosed in U . S . Patents Nos . 3 , 175 , 906 , and 3 , 180 , 732 . Reference is expressly made to these patents , because all of the imino quinone diazide compounds mentioned in these patents may be used within the scope of the present invention.

The imino quinone diazides and the entire quantity of resins contained in the reproduction layer constitute 90 to 100 per cent by weight of the reproduction layer. Other components of the reproduction layer, which may be present in a quantity of up to 10 per cent by weight, are termed "additives " in this application. Suitable additives are , e. g . : pigments , dyestuffs , fillers , such as finely powdered silica , plasticiz-ers and anchoring agents . The use of such additives in the reproduction layers of light-sensitive materials is known and is no part of the present invention .

The combination of resins contained in the light-sensitive reproduction material is one of the essential features of the present invention. The resin component must contain at least 30 per cent by weight of alkali-soluble resin , and at least 20 per cent by weight of a film-forming polymer.

Exemplary of alkali-soluble resins are novolaks , novolaks modified by condensation with monochloro acetic acid , epoxy resins , and copolymers of vinyl compounds which contain carboxyl groups .

X Film-forming polymers are copolymers of vinyl compounds which contain carboxyl groups , polyvinyl acetate , polyvinyl acetal , and cellulose acetate.

Thus , copolymers containing carboxyl groups which may be present in the reproduction layer as a resin, are not only alkali-soluble , but they are also polymers capable of forming films which are penetrated only slowly by the etching solutions . Therefore, such polymers may constitute up to 100 per cent by weight of the entire quantity of resin. Novolak and epoxy resins also are alkali-soluble resins , but their capacity to form an etch-resistant film is low. Therefore , they may be present in the reproduction layer up to only 80 per cent by weight. Novolak modified by condensa tion with monochloro acetic acid is also alkali-soluble , but it has a very low capacity for forming a film which is resistant to etching solutions . Therefore , it should not constitute more than 50 per cent by weight of the resin contained in the reproduction layer.

Due to their content of carboxyl groups , the vinyl copolymers containing carboxyl groups , which may be present in the reproduction layer of the material of the invention, are alkali-soluble polymers . They are copolymers in which groups of at least one vinyl compound and at least one ethylenically unsaturated carboxylic acid are present.

The expression "vinyl compounds" is meant in a broad sense and comprises , e . g . , vinyl alcohol , vinyl acetate , vinyl chloride, vinylidene chloride and styrene . Acrylic acid , methacrylic acid , maleic acid , crotonic acid and itaconic acid may be used as ethylenically unsaturated carboxylic acids in the copolymerization.

The above-mentioned modification of novolak with chloro acetic acid is a known process which is described in U . S . Patent No. 3 050 387 .

According to the present invention , the reproduction layer of I the material should have a thickness of 2 to 6 microns (0.002 to 0.006 mm) . Thus , In the preparation of the light-sensitive material, solutions of the light-sensitive imlno quinone diazide preferably are used, for coating the multi-metal support, which contain about 3 to 10 per cent by weight of solids . When the solubility of the components in the solution is sufficiently high , the solutions also may contain a higher proportion of solids , but it is seldom advisable to use solutions which have a solids content of more than 20 per cent by weight, because at too high a solids content the coating solution applied to the support may form undesirable efflorescences caused by variations in temperature or atmospheric humidity during the coating process . On the other hand, solutions containing less than 3 per cent by weight of solids also may be used for coating , but it Is preferable , for economic reasons , to use solutions containing at least 1 per cent by weight of solids . The reproduction layer may be produced by two or more applications of the solution , if necessary to produce a reproduction layer of the desired thickness . The coated layer is then dried at a temperature up to 120°C The light-sensitive material according to the invention is of excellent storability . It may be used, without an appreciable loss in quality, after several years ' storage in the dark at temperatures not exceeding 20°C .

When the material is used, it is exposed and then developed with weakly alkaline solutions , I .e . the parts of the reproduction layer protected from light during exposure are removed . It is sufficient for development to gently wipe the material with a pad soaked in the developer solution . The compositions of suitable developer solutions are - When a printing plate is prepared from the material according to ' the invention, development is followed by an etching process, for which known concentrated aqueous acid solutions may be used, which are capable of dissolving the chromium layer of the multi-metal support from the copper layer beneath without attacking the areas of the reproduction layer hardened during exposure. Mixtures of chlorides and nitrates of the metals magnesium, calcium, strontium, barium, zinc, iron, cobalt or manganese, or of ammonium, in aqueous solutions may be used, e.g. , the total concentration of salts in the solution ranging advantageously from 40 to 60 per cent b weight. In order to increase the etching speed, such chromium etches normally contain, in addition, 0.1 to 8 per cent by weight of free acids, e.g. hydrochloric acid, nitric acid, citric acid or tartaric acid .

Decoating, i.e. removal of the light-hardened areas of the reproduction layer, is effected by means of alkaline or acid aqueous solutions to which organic solvents, such as ethyleneglycol alkyl ethers, alcohols or esters, may be added. One to 10 per cent by weight solutions of ethanolamines , morpholines, aliphatic amines and diamines, ammonia, sodium phosphates, sodium silicates, sodium peroxide, sodium hydroxide, or potassium hydroxide may be used, for example. If desired, decoating may be accelerated by mechanical brushing, by wiping, or by rubbing with whiting, pumice powder, or very fine sand.

As stated above, the light-sensitive material of the invention may be used with transparent positive originals instead of the negatives heretofore employed. Further advantages are its excellent storability and its relatively high light-sensitivity. Further, it is of advantage that the material can be developed and decoated with aqueous solutions.

From British Patent No. 1,078,100 and the corresponding U.S. Patent No. 3* 02,044 it is known to have a mixture of alkali-soluble resin and film-forming polymer In a light-sensitive compositon which contains a diazo compound as the light-sensitive substance. However, it the known compositions the light sensitrifce diazo compound is an o-naphthoquinonediazlde-sulfonic acid ester and, consequently, the material is a so-called positive working one, which means that by development, after image-wise exposure to actinic light, the exposed areas of its light-sensitive coaeing are removed from Its support, The light-sensitive material fcf the present application is, in contrast therfrto, a negative working one, which means that by development, after image-¾∑1fee exposure to actinic light, the unexposed areas of its light-sensitive coating are removed f om its support, the light-sensitive diazo compound being a p-imlno-qulnone diazide. Moveover, the object of the present application is a light-sensitive material which carries its light-sensitive reproduction layer on a chromium surface and must be etched with a chromium etch in the course Af its normal use. According to the teaching of the above mentioned British sad U.S. patents the compositions described therein, if they have to be highly etoh-reslstent, shall contain alkali-soluble resins in an amount which is one to six times the weight of the light-sensitive compound. According to the teaching of the present application the total amount of resins, i.e. the sum of alkali-soluble resons and film-flormlng polymers, is not more than 100 per cent ofi the w4iht of the p-iminoquinone-diazlde. Further, the cited patents neither suggest the distinct quantitive com Example 1 While rotating on a whirl-coater, a trimetal plate consisting of layers of aluminum, copper and chromium is coated, on the chromium surface thereof , with a solution of the following composition: 4.5 parts by weight of l-[(4' -methylbenzene-l'- sulfonyl)-imino]-2-(2" 5"-dimethyl-phenyl- amino-sulfonyl)-benzoquinone-(l ,4)-diazide-(4) (prepared as described in US Patent No. 3 ,175,906) , 2.0 parts by weight of a copolymer of styrene and maleic acid which contains carboxyl groups and has a specific gravity of 1. 15 and a decomposition temperature around 200°C ("Lytron 820" a product of Monsanto Chemical Co . ) , 80.0 parts by weight of methyl glycol, and .0 parts by weight of butyl acetate The material is then dried with warm air.

The reproduction layer of the presensitized material thus produced has a thickness of 3.7 microns . The material can be stored for years in the dark without substantial loss of efficiency .

When the material is used, it may be developed by wiping the entire surface of the plate with a 1 per cent solution of sodium silicate . In order to remove the chromium layer in the bared image areas , the material is wiped for about 5 to 10 minutes with a chromium etch of the following composition: 12 per cent by weight of calcium chloride, 12 per cent by weight of magnesium chloride, per cent by weight of zinc chloride, 0 . 9 per cent by weight of nitric acid , 0 . 1 per cent by weight of iron chloride , and 45 per cent by weight of water.

Decoating may be effected by wiping the surface of the plate with an aqueous solution containing 2.4 per cent by weight of sodium meta silicate, 1 .55 per cent by weight of sodium triphospha e , and 0.33 per cent by weight of monosodium phosphate .

In order to improve the hydrophilic properties of the chromium areas and the oleophilic properties of the copper areas , the plate is advantageously wiped over with a 2 per cent by weight solution of sulfuric acid before it is inked up with greasy ink.

The resulting printing plate could be immersed for 10 minutes at o a temperature of 23 C . in dilute hydrochloric acid solution without the printing image being attacked . Only when it was placed in a 20 per cent solution of hydrochloric acid , very fine etched holes of the size of needle holes became visible .

When light-sensitive material is produced by coating the tri-metal plate with a solution containing 1 .3 per cent by weight of the imino quinone diazide compound and 1 per cent by weight of monochloro acetic acid-modified novolak , printing images are obtained , under identical conditions , which are vigorously attacked by a 3 per cent hydrochloric acid solution and are completely dissolved from the plate by a 5 per cent hydrochloric acid solution.

Example 2 A chromium plated brass plate is coated on the chromium surface with a solution of the following composition: A 4.0 parts by weight of 1- ( (4'-methylbenzene-r- sulfony 1) -imino) -2- (2 " -ethy 1-phenyl-amino- sulfonyl)-benzoquinone-(l ,4)-diazide-(4) , 1.0 part by weight of the styrene copolymer described in detail in Example 1 , 1.8 parts by weight of a novolak prepared from o- o cresol and formaldehyde (melting range 75-83 C), 0.2 part by weight of polyvinyl acetal ("Formvar" 1285, a product of Shawinigan Products Co.), 0.3 part by weight of Zapon Fast Red BB (Color Index Parti, second Edition, 1956, page 2864), 70.0 parts by weight of tetrahydrofuran, and .0 parts by weight of methyl glycol.

After drying the coated layer, a light-sensitive material of good storage capacity is obtained the reproduction layer of which has a thick¬ ness of 3.6 microns.

The material may be developed, for example, with a 5 per cent solution of trisodium phosphate. A solution of the following composition may be used as a chromium etch: per cent by weight of calcium chloride, 19 per cent by weight of zinc chloride, 1 per cent by weight of hydrochloric acid, 3 per cent by weight of tartaric acid, and 47 per cent by weight of water.

For decoating, a solution of the following composition may be used: 150 parts by volume of ethyleneglycol monoethylether, arts b volume of water, and V Example 3 A trimetal plate consisting of a steel foil with a copper layer thereon and a chromium layer on top of the copper layer, is coated , on the chromium surface, with a solution of the following composition: 3. 5 parts by weight of l -( (4'-methylbenzene-l sulfonyl)-imino)-2-(4" -isopropyl-phenyl- aminosulfonyl)-benzoquinone-(l , 4)-diazide-(4) , 0 .4 part by weight of a copolymer of 85% of vinyl chloride, 14% of vinyl acetate, and 1 % of maleic acid , 1 . 8 parts by weight of the novolak referred to in Example 2 , 0. 2 part by weight of cellulose acetate, 60.0 parts by weight of tetrahydrofuran , and 40.0 parts by weight of methyl glycol .

After drying the coated layer, a light-sensitive material of good storage quality is obtained the reproduction layer of which has a thickness of 2 .8 microns .

The material may be developed , with a 1 . 5 per cent solution of sodium silicate . A mixture consisting of parts by weight of calcium chloride , parts by weight of magnesium chloride, 2 parts by weight of hydrochloric acid , 8 parts by weight of glycol, and 45 parts by weight of water may be used as an etching solution for the chromium layer. Decoating may be effected with a solution containing parts by weight of glycol, parts by weight of methanol, parts by weight of sodium metasilicate and 55 parts by weight of water.

Example 4 The chromium layer of a trimetal plate consisting of an aluminum foil with a chromium-plated copper layer thereon, is coated on the chromium surface with a solution of the following composition: .0 parts by weight of l-( (21 ,4' , 6'-trimethyl-benzene 1 '-sulfony l)-imino)-2-(4"-methoxy-phenyl-amino- sulfonyl)-benzoquinone-(l ,4)-diazide-(4) , 1.0 part by weight of a novolak prepared from o-cresol and formaldehyde (melting range 108 to 118 ° C), 0.8 part by weight of a polyvinyl acetate having a (R) specific gravity of 1.16 ("Mowilith" 40, a product of Farbwerke Hoechst A.G. , Frankfurt/M . - Hochst, Germany), 0.2 part by weight of Crystal Violet, 80.0 parts by weight of methyl glycol, and .0 parts by weight of butyl aceta e.

After drying, the coated layer has a thickness of 3.5 microns.

Example 5 The chromium surface of a multi-metal support is coated with a solution of the following composition: 2.25 parts by weight of the imino quinone diazide referred to in Example 1 , 2.25 parts by weight of the imino quinone diazide 1 5 parts by weight of a styrene/maleic acid copolymer containing carboxyl groups , 0 .9 part by weight of a chloroacetic acid modified novolak (as in Example 1) , 70.0 parts by weight of tetrahydrofuran , and .0 parts by weight of methyl glycol .

A printing form is prepared as described in Example 2.

After drying of the layer, a light-sensitive material is obtained having a reproduction layer of a thickness of 3 .2 microns .

Example 6 The chromium surface of a trimetal plate is coated with a solution of the following composition; 3.0 parts by weight of the diazo compound referred to in Example 2 , 1 . 0 part by weight of an epoxy resin having an epoxide equivalent weight of 400 to 500 and a hydroxy 1 value of 0.32 , 0 . 5 part by weight of a copolymer of vinyl acetate and crotonic acid , 60.0 parts by weight of tetrahydrofuran, and 40.0 parts by weight of methyl glyc61.

A printing form is prepared as described in Example 1 .

Example 7 The chromium surface of a trimetal plate is coated with a solution of the following composition; 3 . 5 parts by weight of the diazo compound referred to in Example 2 , 1 . 5 arts b wei ht of a co ol mer re ared by polymerization of 85% of methacrylic acid methyl ester and 15% of methacrylic acid , 40.0 parts by weight of tetrahydrofuran, and 60. 0 parts by weight of methyl glycol .

The procedure described in Example 1 is used for the preparation of the printing form .

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications .

Claims

WHAT IS CLAIMED IS:

1. Light-sensitive material for use in the preparation of a . multi-metal offset printing plate in which a chromium layer on a copper-containing layer has a reproduction layer thereon of a thickness of 2 to 6 microns and containing (1) a light-sensitive imino quinone diazide of the formula R Is an aryl group, R' Is selected from the group consisting of hydrogen or an alkyl group, R" Is selected from the group consisting of an alkyl, carbocyclic or heterocyclic aryl group, or R' and R" together form a heterocyclic group with the N -atom to which they are attached , and R'" is selected from the group consisting of hydrogen, halogen, or an alkyl or alkoxy group, and (2) 33 to 100 per cent by weight of resin , calculated on the quantity of imino quinone diazide present, the resin consisting of (a) alkali-soluble resin selected from the group consisting of novolak, novolak modified by condensation with monochloroacetic acid, epoxy resin and mer of a vinyl compound and containing carboxyl groups , polyvinyl acetate , polyvinyl acetal, and cellulose acetate , at least 30 per cent by weight of the resin being alkali-soluble resin , at least 20 per cent by weight of the resin being film-forming polymer, and not more than 50 per cent by weight of the resin being novolak modified by condensation with monochloroacetic acid .

2. . A process for the preparation of a light-sensitive material for use in the preparation of a multi-metal offset printing plate which comprises coating a chromium layer, on a copper-containing layer, with a solution and drying the solution to form a reproduction layer of a thickness of 2 to 6 microns , the solution containing (1) a light-sensitive imino quinone diazide of the formula N2 wherein R is an aryl group, R' is selected from the group consisting of hydrogen or an alkyl group, R" is selected from the group consisting of an alkyl, carbocyclic or heterocyclic aryl group, or R' and R" together form a heterocyclic group with the N -atom to which they are attached .. and R"* is selected from the group consisting of hydrogen , K 1879 and (2) 33 to 100 per cent by weight of resin , calculated on the quantity of imino quinone diazide present, the resin consisting of (a) alkali-soluble resin selected from the group consisting of novolak, novolak modified by condensation with monochloroacetic acid, epoxy resin and copolymer of a vinyl compound and containing carboxyl groups , and (b) film-forming polymer selected from the group consisting of copolymer of a vinyl compound and containing carboxyl groups , polyvinyl acetate, polyvinyl acetal, and cellulose acetate, at least 30 per cent by weight of the resin being alkali-soluble resin, at least 20 per cent by weight of the resin being film-forming polymer, and not more than 50 per cent by weight of the resin being novolak modified by condensation with monochloroacetic acid .

3. . A process according to claim 2 in which the solution has a solids content of 3 to 10 per cent by weight.

4. A process for making a printing plate which comprises exposing a reproduction layer on a support comprising chromium and copper-containing layers to light under a master, developing the resulting image, etching the bared chromium areas, and decoating the reproduction layer in the non-image areas, the reproduction layer containing (1) a light-sensitive imino quinone diazide of the formula 1879 R is an aryl group, R' is selected from the group consisting of hydrogen or an alkyl group, R" is selected from the group consisting of an alkyl, carbocyclic or heterocyclic aryl group, or R' and R" together form a heterocyclic group with the N-atom to which they are attached, and R'" is selected from the group consisting of hydrogen, halogen, or an alkyl or alkoxy group, and (2) 33 to 100 per cent by weight of resin, calculated on the quantity of imino quinone diazide present, the resin consisting of (a) alkali-soluble resin selected from the group consisting of novolak, novolak modified by condensation with monochloroacetic acid, epoxy resin and copolymer of a vinyl compound and containing carboxyl groups, and (b) film-forming polymer selected from the group consisting of copolymer of a vinyl compound and containing carboxyl groups, polyvinyl acetate, polyvinyl acetal, and cellulose acetate, at least 30 per cent by weight of the resin being alkali-soluble resin, at least 20 per cent by weight of the resin being film-forming polymer, and not more than 50 per cent by weight of the resin being novolak modified by condensation with monochloroacetic acid. P. O. Box 1169, Tel-Avi Attorneys for Applicant