COMPOSITE ALUMINUM ALLOY SUPPORT FOR LITHOGRAPHIC PRINTING PLATE

Abstract: A composite aluminum alloy support for a lithographic printing plate, comprising: a sheet of core material comprised of aluminum alloy and having a stress resistance of 15 kg/mm² or more; and an outer layer of sheet material fused to at least one surface of the core material, the outer layer having a thickness of 10 microns or more and being comprised of 99.5% or more Al, 0.3% or less Fe and other impurities in respective portions of 0.15% or less.

Description: COMPOSITE ALUMINUM ALLOY SUPPORT FOR LITHOGRAPHIC PRINTING PLATE The present .invention relates to a support f a printing plate comprised of aluminum alloxys having an excellent mechanical strength, printability and which can b produced at low cost. Lithographic printing plates which are now prevail- ingly employed are obtained by submitting so-called presensitized printing plates (hereinafter referred to as "9S @ ates'). The PS plates are prepared by coat-ing light-sensitive terials on aluminum plates having surfaces which have been sub cted to surface treatments such as a graining treatment, an xidizing treatment, and so on. After these treatment, they re dried and subjected to a plate-making processing. The process ing includes an imagewise exposing step, a developing ep, a water washing step, a step of treating with lacquer and so on. It is well-known that non-image areas are formed from portions where a light-sensitive layer remains undissolved after completing a developing step as described above. They are also formed from portions where the light-sensitive layer is not exposed in order' to make the'underlaying alumi surface water-acceptable. Aluminum plates are generally used as the su orts of such lithographic printing plates. Conventional materials used for this purpose are prepared from aluminum alloy 8 ates produced by casting aluminum alloys, such as SIS A3003, IS A1100, JIS A1050, etc., into ingots using the usual continuous casting process, The ingots are submitted to a h t rolling proces, a cold rolling process and optionally, a heat treatment at an intermediate, stage during the rolling processes. The thus produced aluminum. alloy plates are also subjected to a surface roughening treatment using a mec ani- cal, a chemical organ electrochemical technique and,subse- quently, to an anodic oxidization. More specifically, there have been known aluminum plates subjected to la mechanical roughening treatment, chemical etching treatment:as well as an anodic oxidization process. Such platens. are described in U.S. Patent 3.8 ,998. Aluminum plates subjected to a chemical etching treatmeat and subsequently, to anodic oxidization processing are desoribed in Japanese Patent Application (OPI) No. 61304/76. Aluminum plates subjected to an electrochemical treatment and to anodic oxidization processing are described in Japanese Patent Application (OPI) No. 146234/79. Aluminum plates subjected 0 an electrochemical treatment, a chemical etching treatmen and anodic oxidization processing are described in Japanes Patent Publication No. 28123/73. Aluminum plates subj ted to a mechanical noughening.treatment and subsequently, o the other treatments are described in Japanese Patent @@@ cation No. 28123/73. Hoever, these conventional aluminum alloy p tes sometimes generate dot-form@defects upon both theh chemical etching and the electrochemical etching treatments. This causes stains in prints obtained. Accordingly, they have turned out to be undesirable with respect to print qua ty. Recently, printing speed has increased with th progress of printing techniques in general. This -caus an @ increase in the stress applied to the printing plate fired mechanically to both ends of a rotating cylinder insta ed in a printing machine, .Therefore,, when 'aluminum alloy lates have insufficient mechanical strengths, this. frequents causes deformations or breaks in'the printing plate at he above-described fixed parts. This results in problems such as a shear in printing or a breakdown of the printing ate which takes it impossible to continue printing In addition, rather thick aluminum alloy pia s must be employed to ensure sufficient mechanical stren h, e.g., dimentional stability or so on. This is the main cause'.for'itheiincrease in manufacturing costs of sithog aphic printing plates. Therefore, a primary object of the present in en tion is to provide an aluminum alloy support for;a printing plate which ftlrnishes a simultaneous solution of the ab ; @e- described three problems, that is, the problem of print ility, the problem of insufficiency of mechanical strength land he economic problem. Therefore, the primary object of the inven- tion is to provide an aluminum alloy support for a printing plate which is inexpensive and has both printability:an mechanical strength high enough to be suitable for high speed printing. The inventors have found that dot-form stains tend to be observed in printed matter when the aluminum allo plates are prepared using 'conventional .a'luminum alloys, JIS. A1100 (the purity of aluminum: 99.0%), JIS A1200 (the purity of aluminum: 99.0%) and JIS A3003 (the purity of alumi um: 98.0 - 98.5%) and subjecting them to a chemical or an e ectrochemical etching treatment and are then used.as support for printing plates. By carefully analyzing this phenome on the inventors have confirmed that the dot-form,stains are caused by dot-form defects present at the surface ofrth support. The dot-form defects result from coarse grain of certain intermetallic compounds distributed in the aluminum alloy plates before these plates receive the surface tr at- mints. More specifically, the Al6Mn compound and the Al-Fe Si compound are necessarily crystallized into grains se eral tens of microns in size out of the aluminum alloy JIS' 003 and the pure aluminum series alloys,like A1100 or A1200 respectively; upon solidification in the casting process The thus formed grains are crushed to some degree in sul sequenti?;carried out hot rolling and cold rolling proce ses. However grains which remain about 5 to 10 microns in siz are still distributed even in the final rolled plates. These grains are dissolved and dropped away in the form of a lump during roughening-due to the surface.treatments and hot measuring 10 microns or larger.in size are left.. Durin actual printing, ink is captured in these holes which C ates stains on the prints In view.of their limited workability which is determined.by the thickness of the ingot and the thickn 5 of the final plate, as well as the fact that these compounds are quite.stable to heat and decomposed by, heat with difficulty, it is almost impossible to finely divide or eliminate grains of the intermetallic compounds by only.rolling p - cesses and heat treatment given.at an;intermediate stag during the rolling processes. The inventors carried out examinations of various aluminum alloy plates which contain intermetallic compounds to be crystallized out in very reduced amounts. The characteristics of the plates as supports for lithographic printing plates were studied with the intention of excluding the harmful effects of the intermetallic compounds as described above. As a result of these studies it has now been fo nd that a remarkable decrease in the abo.ve-described stair can be attained by using a cold rolled plate of high.purit aluminum containing 99.5% or more of aluminum, 0,3% or ess of iron and other impurities in their respective propo ions of 0.15% or less. However, a printing plate obtained by the single use of-a rolled plate made up of such high puri aluminum is not as strong as one prepared from aluminums alloys. Consequently, cracks are frequently generated in the vitinity of mechanically fixed parts during printing. This can cause the plate to break making the continuance of printing @@ - possible. Accordingly methods for eliminating the lack f. mechanical' strength have been examined. As a result o: such examinations it.has now been found that it is possible ;o produce supports having stress resistance of 15 Kg/mm2 or above and that, such supports are adequate for industri purposes. The inventors have produced a high purity al@@minum rolled plate having excellent surface processability for a printing plate which is :empioyed as an outer layer mate @ial and provided on either side or both-sides of an albumin alloy rolled plate.. The aluminum alloy rolled plate i produced specifically as a core material and therefore has excellent mechanical strength.,.By fusing their surfacas together the three problems regarding printability, me hanical strength and cost:can be overcome at the same time. The composite aluminum alloy plates of the present invention and aluminum alloys employed as core materia will be:described in detail below. The strength of the composite plate, a, is gi en by the following equation: # = #f#f+ #c#(1-f) wherein #f is the:strength of an outer layer material, is a fraction representing: the thickness of the outer layed with respect ot the total thickness of the composite plate and a, is the strength of a corie.material. Accordingly the thickness sharing in ,the composite plate is designed de ending upon the strength a necessitated by the printing plates the strength #c of an aluminum material to be used as i s core material, and the strength #f of an aluminum materi 1 to be used as its outer-layer. By considering these fa tors the thickness of the outer layer material fitted to receive roughening treatments is determined. However, since the composite plate is etched in its thickness direction, i is necessary for the'outer layer to have thickness of at least 10 microns or more, preferably 10 to 100 microns. The thickness of the core material ranges fro -80 to 500 microns, preferably 80 to 300 microns. Aluminum alloys which can be used as :the core material include various ones capable of exhibiting stress resistance of 1S Kg/mn or more when it received a cold rolling process. ata roll g rate of 40% or more. Specific examples of such materials include JIS A1100 (which has a stress resistance of 15 to 16.5 Kg/mmê), JIS A1200 (which has a stress resistance of 15.0 to 16.5 Kg/mmê), JIS A3003 (which has a stress resistance of 15.O to 22.0 Kg/mm2), JIS A3004 (which has a stress resistance. of 20.0 to 27.0 Kg/mm2), JIS A5052 (which h a stress resistance of 22.0 to 29.0 Kg/mm2),and so on. The use of these aluminum alloys inevitably increases manufacturing cost. The increased costs are brought about because these aluminum alloys generally F ve chemical constituents which must be .closely controlled during the manufacturing process. The present inventi is characterized by the use of@such aluminum alloys which ave purities of 99 to 95% but which do not receive particu r controls with respect to their chemical constituents. Specifically; it is possible to use not only secondary lumi- num ingots belonging to the second clas (those having aluminum purities of 98; or higher) and the third class (th e having aluminum purities of 97% or higher) enacted in S H2103, but also aluminum alloys containing impurities relatively high contents which are obtained by regener ing scrap aluminum once used for printing and other purpos Therefore, materials of the present invention are superior to conventional material from an economical point of vi Core materials having stress resistances.not higher than 15 Kg/mmê do not increase the strengths of the resulting composite plates because their stress resistances are below those of the outer layer materials. Furthermore, they tend to cause kinks during handling of the plate in the plate- making process. Therefore, these materials make workin' difficult. In addition these materials' do not have me hanical strengths high enough to be.supported by both end of a rotating cylinder installed in a high speed off-set rotary press. .Therefore, a cut in-the printing is caused by d forma- tion at the fixed parts, or printing becomes impossible due, to a breakdown of the plate. Consequently, these mater als are ineligible as the core material of the present invention. The stress resistance of 15 Kg/mm2 corresponds to that which ean be acquired by the aluminum alloy having a purity of 99.0% when it recieved a cold rolling process at a rolling rate of 75%. Obtaining stress resistances not lower than 15 Kg/mm2 can be easily acquired by heightening rolling rates or using aluminum alloys having purities f 99 to 95%. When core materials having stress resistances not lower than 20- Kg/mmê are used, the resulting composite plates.have markedly increased mechanical strengths. en when the total thickness of the composite plate is red ed it can possess a mechanical strength higher than those f conventional ones. Therefore, .the amount of aluminum a of used as the core material can be reduced. The reductio. of the amount used and the'use of a low price ingot are combined to contribute greatly to the reduction of manufacturing costs. Processes for surface treating the aluminum plates of the present invention which are used as supports of itho- graphic printing plates are described in detail below. Suitable examples of the graining process which can be applied to the pre,sent invention include an elec rochemical graining process. In this process graining is carried out in an electrolytic solution comprising hydr chaotic acid or nitric acid by passing an electric cur nut Other useful processes include mechanical graining processes such as a wire brush graining process where.in aluminum @ ur faces are scratched.with metal wire, a ball graining per cress wherein aluminum surfaces are rubbed with abrasive ball and abrasives, a nylon brush graining.process wherein alum um surfaces are rubbed-with a nylon brush and abrasives, d so These graining processes may be employed independently or in combination. After the graining-process the aluminum plate is subjected to chemical etching processing using an acid or an alkali. If an acids used as the etching agent, it takes a very long time to destroy the fine structure. Accor ngly, the use of acids as etching agents are disadvantageous hen applying the present invention industrially, IIowev.er, his disadvantage can be remedied by using an alkali as the' tching agent. Examples of the alkali agent which can be advantageously employed ill the present invention include sodium hydroxide, sodium carbonate, sodium aluminate, sodium metasilicate, sodium phosphate, potassium hydr'o'xide, lithi hydroxide and the like. Of those;agents, : :sodium alumi te is particularly preferred. A preferred concentration such an alkali in the etching solution and a pre,ferre temperature for the etching processing range from 1 to 0 wt% and from 20 to 100 C, respectively,so as to dissolve the aluminum in an amount of S to 20 g/m2 After the , etching process, the aluminum plat is pickled with an acid in order to remove smut. remaining n its surface. Acids which can be used for this purpose include nitric acid, sulfuric acid, phosphoric acid, chromic acid, hydrofluoric acid, borofluoric acid,and the like. Upon the removal of smut particularly after the electrochemical roughening treatment; a method as desc bed in Japanese Patent Application (OPI) No. 12739/78, wherein the smut.is removed by coming into.contact with 15 to wt% sulfuric acid at a temperature of 50-90 C, of the method of etching with alkali, ;which is described;in Japanese atent Publication No. 28123/73,' can be advantageously employ The thus processed aluminum plates can be use as the supports for lithographic printing 'plates. Also;.t ey can be furhter submitted to an anodic oxidization proce sing, a chemical processing, or the like. The anodic oxidation processing can be carrie out using techniques which have so far been employed in the art. Por example, an anodically:oxidized film can be formed. n the surface of an aluminum support by passing:33C or AC current through the aluminum support in an aqueous or a non aqueous solution containing sulfuric acid, phosphoric a id, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, or a mixture of two or more of these acids. Processing conditions of anodic oxidation are changed depending on what kind of electrolytic solution is used and,therefore, can not be determined indiscriminat ly. However, as a general guide, it can be said that an el tro lytic solution having a concentration of'.l t,o 80 'wt%, solution temperature of 5 to 70 C, a current density of 0.5 to 60 ampere/dm2, a voltage applied of 1 to 100 V, and an electrolyzing time 0± 10 to 100 seconds can produce a desired result. Particularly effective anodic' oxidization pr esses are the processes used in British Patent 1,412,768,wherein anodic oxidation is carried out in sulfuric acid by passing a high density electric current, and the process described in U.S. Patent 3,511,661, wherein anodic oxidation is c ried out using phosphoric acid as an electrolytic bath. The aluminum plate which has been anodically @ idized may be further treated with an aqueous solution of an a ali metal silicate such as sodium silicate or the like usin a conventional technique, e.g., a dipping technique, as described in U.S. Patents 2,7-14,066 and 3,181,461. .Alter tively, a subbing layer made up of hydrophilic cellulose (e.g., carboxymethylcellulose, etc.) containing.a water solubi metal salt (e.g., zinc acetate, etc.) may be additionally provided on the anodically oxidized aluminum plate as described '1 U.S. Patent 3,860,426. On the support for a lithographic printing plate which is prepared in accordance with an embodiment of e present invention, a light-sensitive layer which is kn to have be used for*PS plates is provided to produce a re- sensitized lithographic printing plate. The lithograp c printing plate obtained by subjecting this PS plate to p'late-making process has. excellent properties. Suitable examples of the composition of the ovedescribed light-sensitive layer are.described below. (1) Light-sensitive layer comprised of a diazo resin and a binder Preferred examples of the diazo resin includ those described in U.S. Patents 2,063,631 and 2,667,415 (inc rpo-a reted herein by reference), Japanese Patent Publication Nos. 48001/74, 45322/74.and 45323/74 and British Patent 1,3 ,9.25. Preferred examples of the binder include those describ in British Patents 1,350,521 and 1,460,978 and U..S. Paten 4,123,276, 3,751,257 and 3,660,097 (incorporated herein by reference).. (2) Light-sensitive layer comprised of an o-quin e- diazide:compound i Particul,arly'preferable examples - include o-n phtho- quinonediazide compounds a's described in U.S. Patents 2,766,118, 2,767,092, 2,772,972, 2,859,112, 2,907,665, 3,046,110, 3,046,111, 3,046,115, 3,046,118, 3,046,119, 3,046,120, 3,046,121, 3,046,122, 3,046,123, 3,061,430, 3,102,809, 3,106,465, 3,635,709 and 3,647,443 '(incorpo ated herein by reference) and many other publications. (3) Light-sensitive layer comprised of a composition containing an azide compound and a biiider (macromolecu ar: compound) Specific examples of the composition include com positions comprised of azide compounds and water soluble or alkali soluble macromolecular compounds which are described in British Patents 1,235,281 and 1,495,861, Japanese Patent Application (OPI) Nos. 32331/76 and 36128/76, and so on and compositions comprdsed of azido group-containing polymers and macromolecular compounds acting as binders as described in Japanese Patent Application (OPI) Nos. 5102/75, 843 /75, 84303/75 and 12984/78; and so on. (4) ' Light-sensitive layers comprised of other .li t,- sensitive.res'inous compositions Specific examples include.the polyester comp@ nds disclosed in Japanese Patent Application (OPI) No. 96696/77; polyvinylcinnamate series resins described in British tents 1,112,277, :1,313,390, 1,341,004 and 1,377,747 and so on; and p-hotopolymerizable photopolymer compositio.ns 'descr @ed in U.S'. Patents 4,072,528 and 4,072,52,7 (incorporated erein by reference)' and so on. The amount of-the light-sensitive layer prov ded on the support is controlled to between about 0.1 to a out. 7 g/m2, preferably 0.5 to 4 g/m2. PS plates are .subjected to processings inclu ing a developing step in a conventional manner after image ise exposure. to form resin images. For instance,.a PS pl e having the;light-sensitive layer (1) comprising a dia resin and a binder has unexposed portions of the light. sensitive layer removed by development after imagewise exposure to produce a lithographic printing plate. Howev @ a PS plate having a light,sensitive layer (2) has expos portions of the light-sensitive layer which are remov by development with an alkaline aqueous solution after imagewise exposure:to produce a lithographic printing plat The present invention will now.be described i greater detail by reference t.o the following examples. EXAMPLE 1 Material (1) of the present invention i-s comprised of chemical constituents as shown in Table 1.. A comparative material (1) also has its chemical constituents as show@ in Table 1. The alloy B employed as the core material of the invention material (1) was obtained by regenerating scraps of aluminum alloy plates of the kind which have been widely used for making screw caps. The alloys A, B and C were each cast into ingots for rolling by means of a conventional continuous casting technique. The ingot of the alloy A was cut so that its surface segregation layer.was removed | erefrom and then heated to a temperature of 525 C. Thereafter it was submitted to a hot rolling process in order to @ oduce a plate having a thickness of 17 mm. The ingot of the alloy B was then cut along its @: rolled planes till its thickness was reduced to 480 mm and one of the thus cut planes was provisionally bonded the 17 mm thick plate of the above-described alloy A for the outer layer. This compounded ingot was heated to a tempers re.of 480 C and subjected to the hot rolling process. Thus, the outer layer material and the core material were fused ogether at their contact plane. The plate was.hot-rolled so as to have a thi kness of S mm and was subsequently subjected to a cold roll in process to be turned into the 2 mm thick plate. The pl e was then submitted to one hour's intermediate annealing at a temperature of'3500C and thereafter.to a final cold r 11ing process to be turned into a 0.30 mm thick plate. T us, the material (1) of the present invention was prepared. The comparative material (1) was prepared as follows. 5 5 mm thick plate was prepared by cutting;a ingot of alloy C for rolling so that its surface segregation layer was removed therefrom and its thi.ckness might become 460 mm. This as done by subjecting it to a hot rolling process at 525 C The thus obtain.ed 5 mm thick plate was then turned into a 0.30 mm thick plate according to the same processes as n the invention material (1). In both the invention material (1) and the comparative material (I), the final cold r ling rate was 85%. Table I Constituents (% by weight) Alloy Fe Si Cu Mn Mg Cr Zn Ti Al Invention Material (1) Outer Layer A 0.20 '0.10 0.01 0.005'. 0.003 :0.01 0.01. . .02 99.61 Material Core B 0,79 0.56 0.03 0.02 0.02 0.01 0.01 0.18 98.38 Material Comparative C 0.38 0.14 0.02 0.007 0.002 0.01 0.01 .02 99.41 Material (1) Each of these aluminum alloy rolled plates w @ then submitted toia graining treatment in a suspension of pu ice stone.in water using a rotated nylon brush. The plate as then etched with a 20% aqueous solution of sodium'hydro ide at 50 C for 60 seconds. As a result, 8 g/m2 of aluminum dis solved. After being washed thoroughly with running water, the plate was pickled with a 25% aqueous solution of ni@ric acid and subsequently washed with water to prepare a ba e plate. The thus prepared base plate was electrolyzed i 'an electrolytic bath containing 0.5 to 2.5% nitric acid by pass ing AC current therethrough with a current density of 2 A/ dm2 or higher as described in Japanese Patent Applicati n COPI) 'No. 146234/79. Next, the surface fo the base plate was cleaned by dipping it in a 50 C aqueous solution of 15% sulfuric acid for 3 minutes. The plate was then proces ed to provide an oxidized film at a thickness of 3 g/dm2 i Åa 300C electrolytic bath containing 20% sulfuric-acid as major component. On the thus prepared support, was coated a Ii ht- sensitive layer having the following composition at a dry thickness of 2.5 g/m2. Ester compounds of naphthoquinone-1,2-diazido-5- 0 75 g sulfonyl chloride with pyrogallol and acetone resin (described in Example 1 of U.S. Patent 3,635,709) Cresol.novolak resin 2 OO g Oil Blue @603 (product of Orient Chemical Co., Ltd.) 0 04 g Ethylene dichloride 16 2-Methoxyethylacetate 12 The thus obtained presensitized printing plat was imagewise exposed for 60 seconds by means of a metal halide lamp of 3 KW placed at a distance of 1 meter. After ex @sure it was developed with a sodium silicate aqueous solution having a SiO2/Na2O molar ratio of 1.2:I and SiO2 content of 1.5%. After development it was washed with water and d ied. and then subjected to a comparative printing test using an offset rotary press SYSTEM-C18 (made by Komori Printing Machine Co., Ltd.). As a result of the printing test comparative ,te- rial (I) showed printed stains due to the dot-form defe S. The stains were present on the average of 17 per 25.cm2 However, the invention material (1) had an outer layer high purity aluminum with a reduced Fe -content. The pr t- ing test showed that the dot-form stain was not observe at all. Accordingly, the invention material (1) exhibited excel Ient printing characteristics. In addition, the invention material (1) had strength characteristics superior to the comparative material (1 as shown in Table 2. This is because the comparative example had an aluminum alloy containing impurities in consider ble: amounts for its core material Accordingly, when fitte to- the rotating cylinder of.the rotary press and impressed on continuous sheets of paper, the comparative material (1 was cracked at its fixed parts when 180,000 sheets of print d paper had been passed. On .the other hand, the inventio material (1) was not cracked even when 250,000 sheets o prints were obtained. T a b l e 2 Number of Printed Stress Tensional Dot-form Stain Sheets at the Time Resistance Strength Elongation Occurrence of Plate Cracking (Kg/mm2 (Kg/mm2) (%) (Number/25 cm2) Invention 17.8 19.9 3 zero 250,000 or more Material (1) Comparative 14.7 16.4 2 17 180,000 Material (1) EXAMPLE 2 Ingots for rolling having their respective ch nical constituents as shown in Table 3 were prepared. The in ot of alloy D was used as the outer layer materiaL of an inven- tion material (2) dnd the ingot of the:alloy F was used as the outer layer material of an invention material (3). he' ingots were cut so that their individual surface segreg tion layers was removed therefrom. They were then 'heated 'to a, temperature of 580 C and maintained at that temperature for 8 hours in order to homogenize the temperature throughout the ingots. After waiting for the temperature drop to 30 C, they.were each subjected to a hot rolling process and rolled into plates having a thickness of 35 mm. Ingots of alloys ,E and.G which were used as core materials were cut at their individual surfaces till their thicknesses were reduced to 400 mm. One side of the t s cut plate. of the alloy E and one side of the thus.cut p ate of the alloy G were provisionally united with a 35 mm t@ ick plate of the above-described alloy S D and that of the a ve-, described alloy F, respectively. These compounded ingots were heated to a temperature of 500 C and subjected to a hot rolling process in order to fuse them together at their individual contact planes. Thus, the plates having a thickness of 5 mm were obtained. S sequently, these plates were subjected toga cold roll process in order to produce plates 1.5 mm thick. The p ates were then submitted to one hour's intermediate annealin at a temperature of 350 C and, thereafter, to a final cold oll- ing process in order to produce plates 0.30 mm.thick. With respect to both invention materials (2) nd (3), the final cold'rolling rate was 80%, the thickness of the outer layer material in the composite plate was 24 ic-. rons, and the thickness of the core material was 276 mi rons. Comparative matenials (2) and (3) were prepar d as follows-: The 500 mm thick ingots for rolling which were made up of the alloys H and I, respectively, were submitted to the homogenization processing at 580 C for 8 hours. Th reafter, they were cut so as to remove their individual surface segregation layers. These ingots were heated again to 000C and then subjected to a hot rolling process to be rolle into the 5 mm thick plates. Further., these plates were thinned to 2 mm by cold rolling The plates were then ub-' mitted to one hour's intermediate annealing at a temperature of 350 C and thereafter to .a final' cold rolling process in order to produce th'e 0.'30 mm thick plates. In both the comparative materials (2) and (3), -the'final cold rolli g rate was 85%. T a b l e 3 Constituents (% by weight) Alloy Fe Si Cu Mn Mg Cr Zn Ti Al Remark Invention Material (2) Outer layer Material D 0.15 0.07 0,01 0.005 0.002 0.01 0.01 0.01 99.73 Core Material E 0.60 0.28 0.15 1.15 0.01 0.007 0.01 0.01 97.78 JIS A3003 Invention Material (3) Outer Layer Material F 0.29 0.11 0.01 0.004 0.003 0.005 0.01 0.02 99.55 Core Material G 0,31 0.09 0.02 0.03 2.43 0.22 0.01 0.01 96.88 JIS A5O52 Comparative Material (2) H 0.55 0,16 0.11 0.01 0.01 0.007 0.01 0.01 99.13 JIS A1100 Comparative Material (3) I 0.59 0.26 0.13 1.17 0.01 0.006 0.01 0.01 97.18 JIS A3003 These aiuminum alloy rolled plates together @ th the invention material .(1) and the comparative materia (1) obtained in Example 1 were submitted to graining treat nt in the same manner as in Example <RTI ID=25.4> 1. This treatment in lved the use of rotated nylon brushes in a suspension of p ce stone and water. Thereafter, these plates were etched ith a 20% aquepus solution of sodium hydroxide at 509C for 0 seconds. As a result, 3 g/m2 of aluminum dissolved. After etching, ,the plates were washed throughly with running ater, pickled with a 25% nitric acid aqueous solution, and w hed with water to prepare base plates. The thus prepared base plates.were procesed im order to provide oxidized fil at their individual surfaces at the same thickness of 3 g 2 in a 30 C electrolytic bath containing 20% sulfuric acid as a major component. On each of.the thus prepared supports was coated the same light-sensitive layer for the lithographic printing plate used in Example;1 at a dry thickness of 2.5 g/mê The thus obtained printing plates were subjected to the same plate-making procesings as in Example 1 and then to the comparative printing test using the offset rotary press SYSTEM C-18. As a result of such.printing,tests, a number of : dot-form stains occurred in comparative materials (1), (2) and (3). .IIowever, the;occurrence of dot-form stain wa hardly observed in any.of'the!materials.of the present invent on. The materials of the present invention all exhibited ex' Ilent printing characteristics. I In addition, the comparative materials (1) an (2) were cracked at their individual fixeed parts when 170,000 and 210,000 sheets of paper respectively had been printed. However, the materials of the present invention were no cracked even when 250,000 sheets- of. prints were obtaine The strength characteristics and t,he results of the pri ing tests of both the invention materials .and the comparative materials are shown: in Table 4. i T a b l e 4 Number of Printed Stress Tensional Dot-form Stain Sheets at the Time Resistance Strength Elongation Occurrence of Plate Cracking (Kg/mm2) (Kg/mm2) (%) (Number/25 cm2) Invention 17.8 19.9 3 1 250,000 or more Material (1) Invention 18.4 20.3 3 zero 250,000 or more Material (2) Invention 28.7 30.5 3 2 250,000 or more Material (3) Comparative 14.7 16.4 2 25 170,000 Material (1) Comparative 15.6 17.2 2 45 210,000 Material (2) Comparative 20.5 22.8 2 50 or more 250,000 or more Material (3) Wile the invention has been described in detail and with reference to specific embodiment thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

Claims: Claims: 1. A composite aluminum alloy support for a lith graphic printing plate., comprising: a sheet, of core material comprised of alumina alloy and having a stress resistance of 15 kg/mm2 or more; an an outer layer of sheet.material fused -to at east one surface of. the core material, the outer layer having a thickness of 10 microns or more and being comprised of 99.5% or more Al, 0.3% or less Fe and other impurities in respec tive portions of 0.158 -or less. A A composite aluminum alloy support for a lit graphic printing plate as claimed in Claim 1, wherein the outer layer surface of said support is roughened ahd then, anodica y oxidized. 3. ¯5' A composite aluminum alloy support for a lit graphic printing plate as claimed in Claim 1, said outer layer aving a thickness of from 10 to 100 microns. 4. A composite aluminum alloy support for a lithographic printing plate as claimed in any of Claims 1, 2 or 3, wherein the core material as a thickness of 80 to 500 microns. 5. A composite aluminum alloy support for a lithographic printing plate as claimed :in Claim 4, -wherein the core aterial has a thickness of from.80 to 300 microns. 6. A lithographic printing plate having a compos te aluminium alloy support as claimed in any preceding Clain. 7. The features herein described, or their equivalents, in any novel selection.

Inventors: HAYASHI, YOSHIKATSI, OHASHI, AZUSA, SHIRAI, AKIRA, TAKIZAWA, KAZUSHIGE, TERAI, SHIRO, TSUCHIDA, SHIN
Applicants: FUJI PHOTO FILM CO., LTD., SUMITOMO LIGHT METAL INDUSTRIES LIMITED
Application year: 1982
Main classification: B41N1
IPC codes: B32B15, B41N1