US2147778A - Planogbaphic printing plate - Google Patents

Planogbaphic printing plate Download PDF

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US2147778A
US2147778A US6504636A US2147778A US 2147778 A US2147778 A US 2147778A US 6504636 A US6504636 A US 6504636A US 2147778 A US2147778 A US 2147778A
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aluminum
plates
bath
image
pits
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Priority to US22629938 priority patent/US2208703A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
    • B41N3/00—Preparing for use and conserving printing surfaces
    • B41N3/03—Chemical or electrical pretreatment
    • B41N3/038—Treatment with a chromium compound, a silicon compound, a phophorus compound or a compound of a metal of group IVB; Hydrophilic coatings obtained by hydrolysis of organometallic compounds

Definitions

  • This invention relates to a method of preparing sheet aluminum forplanographic printing and to the product of said method; and it comprises treating sheet aluminum progressively, or
  • non-image areas are customarily etched" or desensitized by treatment with an aqueous solution adapted to at least neutralize the basic condition previously produced, and preferably to render these areas lyophilic.
  • an aqueous solution adapted to at least neutralize the basic condition previously produced, and preferably to render these areas lyophilic.
  • certain salts of the metal are preferentially water-wettable in themselves, and hence if present do not require the adsorption of a lyophilic colloid.
  • Metal plates are customarily roughened or grained for the purpose of minimizing the attritional effect of the ink rollers on the image and, perhaps more importantly, for the purpose of preventing these rollers from too greatly reducing the film of moisture which must be retained in order to prevent ink contamination of the nonprinting image.
  • This graining operation is customarily performed by gyrating marbles over fine sand on the plate; and it is a costly, time-consuming operation requiring much skill.
  • Another object of this invention is to provide aluminum planographic printing plates which are highly sensitized to usual direct image-forming substances and yet are equally serviceable for the 55 delineated with a usual greasy image-forming' material without the necessity for any counteretching" or supplementary treatment to sensitize said plates to grease for image reception and retention. It is yet another object of this invention to provide planographic printing plates of sheet aluminum characterized by minute surface pits containing a deposit of microporous oxide of the metal. It is also an object to provide a iinely pitted or grained aluminum planographic printing plate with a continuous surface layer of relatively soft microporous material comprising an oxide of the metal, whereby said plates are particularly sensitive to ordinary carbon paper.
  • a further object of this invention is to provide an alternative modification of said process wherein the aluminum is first treated in a bath of high relative activity and subsequently in a bath of less activity, whereby the said aluminum is pitted in the ilrst bath and a coating deposited in the second bath with a substantial saving in time over that which would be required to yield like pitting and coating in a single bath.
  • a still further object is to provide a process of treating aluminum in which the said aluminum is both pitted and coated with a deposit of microporous oxide by means of an alkali bath, is freed from the scum, sometimes incident to such treatment, by means of an acid bath, and subsequently is rendered most highly sensitive to image-forming materials comprising fatty acids by means of a momentary dip in the same or another alkali bath, whereby the said oxide is rendered alkaline reacting.
  • the plates of this invention may be mentioned the fact that they are useful for the reception and retention of images directly delineated by usual greasy image-forming materials, and for photographic images as well.
  • Another advantage of the said plates is that the high sensitivity to usual direct imageforming materials imparted by the process of this invention is not diminished by long storage, and yet their grease-sensitive surfaces may be readily desensitized by etches comprising adsorbable lyophilic colloids or by such weakly acidic phosphate etches as are buffered at or about the isoelectric point of usual photographic imageforming materials.
  • Still another advantage of the plates of this invention is that they are particularly retentive of poorly coherent greasy image-forming materials such as the more or less pulverulent coating of ordinary carbon paper.
  • a still further advantage of the said plates is that they are adapted to print from an image, as directly delineated in crayon or the like, without the necessity of washing out the original image forming material and the replacement thereof with asphaltum or the like as is common practice, and thus their use affords much saving of time and expense. Moreover, and by reason of the firm retention of the image as originally directly delineated on the plate, much less skill is required than is requisite when the original work has to be washed out and redeveloped, as is the usual practice; and this is of material advantage.
  • Fig. 1 shows a portion of a plate I0 embodying this invention having a character Il upon the surface I2 thereof;
  • Figs. 2 and 3 are enlarged sectional views showing the plate with pits l5 therein and provided with a coating or layer Il, in Fig. 2 the pits alone being coated and in Fig. 3 both the pits and surface being coated; and
  • Fig. 4 is an emerged plan view of a portionof the Plate.
  • the process of this invention comprises treating sheet aluminum in a hot alkaline bath and sometimes subsequently further treating the aluminum by swabbing or preferably with acid to remove an undesirable scum incident to So far as I am aware.
  • planographic printing plates of aluminum and zinc have always heretofore been prepared for the reception and retention of a direct printing image by a "counteretching" step which provided a basic surface with which the fatty acids of the usual direct imageforming material could react and from which the subsequently applied acidic etches and fountain solutions could not displace the reacted image material.
  • the alkaline plates resulting from one embodiment of the process of this invention, are more 'sensitive to the usual image-forming materials than are the "acidic plates of this invention, I have further discovered, nevertheless, that there is substantially no difference in the length of printing life of a direct image impressed on an alkaline plate" from that of a like image on an acidic plate" when'all other factors affecting the length of the printing life are maintained constant; and are adjusted to give maximum printing life from the acidic plate".
  • Relatively pure aluminum is particularly suited to the purposes of this invention; and it is preferred to use aluminum in the higher grades of purity, and that alloy of aluminum and manganese for instance, designated by its manufacturers and known to the trade as 3SH", may be satisfactorily used and with particular advantage ii a heavy deposit in the pits of the plate or over the pitted surface is desired.
  • a bath suitable for the practice of this invention may be made by dissolving sodium aluminate in ordinary tap water.
  • sodium Aaluminate may be replaced either in part orin whole by other alkali aluminates, such as potassium aluminate; but sodium aluminate aloneis preferred.
  • white soluble NaAlOa the compounds may however be made as required by well-known methods, such as by the reaction of sodium hydroxide with metallic aluminum or an aluminum salt.
  • a bath which contains five grams of the 90% sodium aluminate referred to above for everycc. of water. Best results are obtained when the bath is maintained at a temperature slightly below the boiling point. A temperature of F. plus or minus 5 has been found satisfactory.
  • a substantially batch method consists of a ratio of one square foot of aluminum surface to every two and onehalf gallons of solution, and an immersion time of ll/z minutes with a pause between batches of 11A; minutes. If there were no pause between batches, the relationship would be the same as that given for the continuous operation, ior reasons which will later become apparent.
  • One of the desirable effects of treating aluminum in a bath of an alkali aluminate is an erosion or pitting of the surface of the metal. This erosion is accompanied by loss of weight and loss of thickness of the sheet aluminum.
  • the treatment is considered to be at its optimum when maximum pitting occurs with minimum loss of thickness.
  • the optimum treatment of sheet aluminum according to this invention may be yobtained over a Wide range of concentrations of sodium aluminate by adjusting the above-mentioned variables, as stated. This adjustment is not critical in so far as the production of a satisfactory pitting or grainlng is concerned, and approaches theA critical only when it is desired so as to balance all the variables that the loss of thickness is held to a consistently low value.
  • the amount of sodium hydroxide in the bath at any time, after hydrolysis has been initiated by the reactive presence therein of metallic aluminum and under otherwise constant conditions depends upon the ratio of the surface of aluminum immersed in the bath to the volume of the bath.
  • alkali is present in the bath as sodium hydroxide and as sodium aluminate, and each can be determined as such by titration. It is convenient to express the concentration of sodium hydroxide in terms of mol percent; that is to say that the ratio of the mol of sodium hydroxide to the mol of total alkali present may be expressed in percentage. While satisfactory plate surface treatment is obtainable from alkali aluminate baths over a wide range of molal concentrations of sodium hydroxide, it has been found that about 15 mol percent sodium hydroxide concentration corresponds to substantial equilibrium at an expedient rate of treatment and at a convenient ratio of bath volume to immersed aluminum surface.
  • the mol percent of sodium hydroxide drops rapidly as the aluminum reacts therewith; and then, as hydrolysis is in some way stimulated as a consequence of this reaction, the mol percent of sodium hydroxide rises again.
  • the mol percent of sodium hydroxide may be maintained within the range of that of the bath as freshly made; and, as stated, a molal concentration of 15% sodium hydroxide has been found convenient and satisfactory.
  • the individual sheets of aluminum are preferably maintained in a substantially vertical position and spaced apart by at least two inches.
  • the desired substantially vertical position of the aluminum is sufllclently obtained by feeding the ribbon of metal through the bath in one or more loops such that for the most part the ribbon is vertically pendant therein.
  • a sheet of aluminum may, after the above-described treatment, conveniently be substantially coated with a thin but discernible and firmly adherent layer of relatively soft microporous material, assumed to be aluminum oxide and comprising a trace of alkali, by a repetition of the said treatment modified only to the extent that the solution is made up with 0.75 gram of sodium aluminate to every 100 cc.
  • the molal concentration of sodium hydroxide will be approximately and the mentioned variables should preferably be so adjusted that the mol percent of sodium hydroxide does not rise above ten in order to avoid any unnecessary loss of weight.
  • the molal concentration of sodium hydroxide is about 5 percent, the loss of weight is of the order of 116 of a 'gram per square foot of surface and is therefore negligible, and the coating obtained is of the order of one one-thousandth of a millimeter.
  • thesheet aluminum may be simultaneously pitted and coated in a single bath made up of 1.5 grams of lsodium aluminate to every 100 cc. of water and adjusted to a molal concentration of sodium hydroxide between 5 and l0 percent, with an immersion time of ten minutes. Under these conditions, the loss of weight is of the order of one gram per square foot of surface and the loss in thickness is negligibly small.
  • the sheet aluminum may be variously surfaced over a range from extremely small pits and very thin coatings to large pits and heavy coatings. as desired. While baths of higher sodium aluminate content may be adjusted to yield satisfactorily coated plates, less concentrated baths are not in general desirable because they may be. and usually are, in-
  • aluminum hydroxide is precipitated as a sediment; and -it is convenient to allow this sediment to collect in the bottom of the tank and to remove it at daily intervals. Best results are obtained when the sediment is not agitated, although avoidance of agitation is not essential. It is, however, essential for uniform results and .therefore desirable that the metal being treated should be kept from contact with the concentrated sediment. 'I'he treating solution is conveniently heated by jacketing the treating tank in known manner.
  • the treated sheet aluminum should be rinsed in running water immediately after treatment in order to remove the entrained solution. If rinsing is deferred, an unsightly brown discoloration of the metal sometimes occurs; and while this discoloration seems not to adversely affect the behavior of the aluminum as a printing plate. it is unsightly; as stated, and for that reasonI its formation is preferably prevented.
  • the aluminum may be swabbed with a soft rubber sponge or with cotton wedding if the product is to become an "alkaline plate". or. and preferably, the aluminum maybe immersed for thirty seconds to one minute in a strong but not necessarily concentrated nitric acid solution and then rinsed and redipped momentarily in the alkali bath and rinsed again.
  • the effect of the described treatment is threefold; it removes not only the superficial grease but also that grease which has been ground into the metal in the process of rolling it into sheet form; it so pits the surface as to provide a fine grain"; and it deposits in the pits and on the intra-pit surface a coating of microporous oxide.
  • the complete absence of grease is of course of vital importance because any residual trace of grease would act as an ink-receptive image and would print a tone in the non-printed areas.
  • 0f vital importance also is the microporosity of the resultant surface, because upon this microporosity depends much of the "anchorage of, the image-forming material which is necessary to the retention of direct images under printing conditions and for long editions.
  • the grain constituted by the pits while not a prime essential, is nevertheless highly desirable because the dampening solution (with which the plate is wet between successive inkings during printing) is better retained by the plate when the surface continuity of its plane surface is broken up by such "grain as is provided by the pits of this invention; and also, although less importantly, because this grain" provides a tooth which is of advantage when a direct image is delineated in pencil or crayon.
  • the grain of the plates of this invention is of so fine a texture that it is not objectionable when the image is formed photographically from even the nest halftones.
  • the mean diameter of the pits varies over the range lying between something less than 0.001 and 0.015 millimeter. It is observed that in general the average of the mean diameters of the pits in a given area is roughly inversely proportional to the concentration of pits in that area. Thus when the number oi pits per square millimeter is of the order of il've thousand, the average of their mean diameters is o! the order of 0.008 millimeter; and when there are but two thousand pits per square millimeter, the average of their mean diameters is oi' the order oi 0.012 millimeter. The ratio o! pitted to non-pitted areas appears to vary much less than does the concentration oi pits from one minute area to the next.
  • the depth of the pits appears to be roughly proportional to their mean diameter.
  • the grain constituted by the pits as described and within the above limits is very iine when compared to the grain which is obtained by abrasive attrition under gyrating marbles, as is the common practice; and yet it is iully eiIective to retain, against the squeegee action oi the ink rollers, a suihciency oi dampening solution. It is one of the advantages o! the plates oi this invention that less dampening solution ⁇ is required to maintain the non-printing portions clear from tone than is required by plates with the finest grain mechanically obtainable.
  • the microporous deposit is limited to the pitted areas of the plate, its presence though not its porosity may be observed by inspection of a microtomed section under vertical incident illumination. If the deposit extends beyond the pitted areas, it may be discerned without sectioning, by microscopic inspection under vertical incident illumination. In either case. whether limited to the pitted areas or extended over the entire surface of the plate, the relative thickness of the deposit maybe estimated microscopically under incident dark eld illumination.
  • the rnicroporosity of the deposit may be demonstrated in terms ot its high adsorptive capacity for iinely divided pigment, as carbon black for instance, by the following procedure, which also serves to show the contrasting behavior of the normal oxide coating on the non-pitted areas when the latter are free from the microporous deposit oi the process of this invention.
  • Usual black lithographie ink is ilrst well rolled onto a restricted area of the plate and then washed out with an appropriate solvent,l as carbon tetrachloride ior instance. The so-treated area, when microscoplcally viewed at a magnication.
  • the above-described procedure affords a test for the continuity of the deposit as well as for its microporosity.
  • the deposit is continuous over the entire surface, the demarcation of the inked area, after aiutava washing the ink therefrom, will still be microscopically discernible; although contrast between these and the surrounding normal areas of the plate surface will be very much weaker.
  • the entire inked and washed area will appear markedly darkerin color than the surrounding normal plate surface and will comprise at least two distinct shades;' the darker of these shades will appear as isolated small patches against a continuous background of a lighter and sometimes slightly varying shade.
  • microporous deposits on the plates of this invention may be distinguished from both normal atmospheric oxide and from anodic aluminum oxide by two distinct characteristics.
  • the said deposit appears under the microscope and at a magnification oi 100 diameters or so, to consist oi whitish particles suggestive of a relatively delicate and iinely crystalline material and distinctly not comparable to the powdery product of a similarly scratched hard amorphous mass, such as the relatively dense aluminum oxide produced by anodic deposition. It is thought that the expression microporous crystalline oxide is useful in distinguishing the oxide deposited by the process of this invention both from normal atmospheric oxide and from oxide produced anodically.
  • the second distinguishing characteristic is that the microporous crystalline oxide deposited by the process oi' this invention is always accompanied by microscopically detectable pitting of the Igeneral order above described, whereas normal atmospheric and anodic oxides are not normally associated with pitting.
  • the advantages of the microporosity of the deposit is that it provides the equivalent of a presensitized surface, i. e., a surface from which acidic etches are incapable of displacing usual direct imageforming materials; and thus is avoided the necessity for sensitizing or counter-etching by the user.
  • Another advantage is manifested by the substantially greater ease with which iingermarks and like adventitious smears may be removed irom the acidic plates" oi this invention than i'rom planographic plates as usually sensitized to grease or from the alkaline plates of -the process of this invention, as stated.
  • a still further advantage of the plates of this invention is that, after the delineation of a printing image thereupon, the non-printing areas thereof are readily desensitized to grease by phosphate etches without the necessity for the inclusion therein of adsorbable gums, as gum arabic ior instance.
  • An advantage accruing from the acid step of the process oi this invention is that the resulting plates are more silvery in color and therefore aiord greater visual contrast between plate background and image than is aiorded by plates otherwise similarly treated except for swabbing instead of acid-dipping.
  • the "acidic plates" of this invention may be distinguished from the alkaline plates of the process of this invention by the difference in sensitivity-as ordinarily understood-between these plates, and the greater ease with which superiicial smears are removed from the acidic plate than from the "alkaline plate, may be demonstrated by lightly rolling an inked brayer over each and immediately flooding the inked area with an acid phosphate etch such as that abovementioned. 'I'he supercial smear of ink on the acidic plate will be observed to free itself from the surface of that plate in a few minutes,
  • Method of preparing planographic printing plates from sheet aluminum comprising the steps of treating the aluminum in a hot aqueous solution of an alkali aluminate and an alkali hydroxide for such time and in such ratio 'of aluminum surface to solution vvolume that the ratio of the aluminate to the hydroxide is maintained sub- 2.
  • Method of preparing planographic printing plates from sheet aluminum comprising the steps of treating the aluminum in a hot aqueous solution of an l alkali aluminate and an alkali hydroxide for such time and in such ratio of aluminum surface to solution volume that the ratio of the aluminate to the hydroxide is maintained substantially constant, to remove all traces of grease from the surface, to pit such surfaces and to coat the surfaces with a layer of microporous oxide, rinsing and swabbing the aluminum to remove surface contamination from the surfaces, and again treating the aluminum in a hot aqueous solution of alkali aluminate and alkali hy.V
  • aluminate has a higher ratio to the hydroxide than in the solution by which the aluminum was originally treated.
  • Method of preparing planographic printing plates from sheet aluminum comprising the steps of treating the aluminum in a hot solution of an alkali aluminate whereby traces of grease are removed from the surfaces of the aluminum, such surfaces are pitted and coated with layers of microporous aluminum oxide, and dipping said ⁇ treated aluminum in an acid bath to remove scum therefrom and to neutralize any adsorbed alkali in the layers of microporous aluminum oxide on the surfaces, such surfaces being re tentive of an impressed greasy image and freeable from superficial grease by the application of an acid phosphate etch.
  • Method of preparing planographic printing plates from sheet aluminum including the step of treating the aluminum in a bath consisting of an aqueous solution of an alkali aluminate and an alkali hydroxide, the concentration of the solution corresponding to about 11/2 to 5 g. oi 90% alkali aluminate for 100 c.c. of water and the alkali hydroxide concentration being between 5 and 15 mol percent and the ratio of aluminum surface to the volume of the bath being maintained at one square foot to five gallons.
  • Method of preparing planographic printing plates from sheet aluminum which consists in treating said aluminum in a bath of alkali aluminate maintained at a. temperature slightly below the boiling point, said bath containing in solution alkali aluminate equivalent to between 1% .plates from sheet aluminum comprising the steps of first treating the aluminum in a solution of an alkali aluminate whereby all traces of grease are removed lfrom the surfaces, the surfaces are pitted and coatings of microporous aluminum oxide are deposited in the pits, secondV removing any surface contamination from the pitted and coated aluminum present after such treatment and not removed by said alkali aluminate, and third treating the aluminum in a solution of an alkali aluminate whereby the pitted surfaces having coatings deposited in the pits are further coated with a continuous deposit of microporous aluminum oxide.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Printing Plates And Materials Therefor (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
US6504636 1936-02-21 1936-02-21 Planogbaphic printing plate Expired - Lifetime US2147778A (en)

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US6504636 US2147778A (en) 1936-02-21 1936-02-21 Planogbaphic printing plate
GB104837A GB483591A (enrdf_load_stackoverflow) 1936-02-21 1937-01-13
US22629938 US2208703A (en) 1936-02-21 1938-08-23 Aluminum planographic printing

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US6504636 US2147778A (en) 1936-02-21 1936-02-21 Planogbaphic printing plate
US22629938 US2208703A (en) 1936-02-21 1938-08-23 Aluminum planographic printing

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US22629938 Expired - Lifetime US2208703A (en) 1936-02-21 1938-08-23 Aluminum planographic printing

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2507314A (en) * 1943-03-31 1950-05-09 Aluminum Co Of America Method of treating aluminum surfaces
US3183832A (en) * 1960-02-01 1965-05-18 Azoplate Corp Lithographic printing foil
US3231376A (en) * 1960-12-09 1966-01-25 Harris Intertype Corp Lithographic printing surface

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2713822A (en) * 1948-12-20 1955-07-26 Columbia Ribbon & Carbon Planographic printing

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2507314A (en) * 1943-03-31 1950-05-09 Aluminum Co Of America Method of treating aluminum surfaces
US3183832A (en) * 1960-02-01 1965-05-18 Azoplate Corp Lithographic printing foil
US3231376A (en) * 1960-12-09 1966-01-25 Harris Intertype Corp Lithographic printing surface

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US2208703A (en) 1940-07-23
GB483591A (enrdf_load_stackoverflow) 1938-04-22

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