CA1247446A - Multiple registration and imaging process to form a set of registered imaged elements - Google Patents

Abstract

TITLE
MULTIPLE REGISTRATION AND IMAGING PROCESS
TO FORM A SET OF REGISTERED IMAGED ELEMENTS
AESTRACT Of THE DISCLOSURE
Method for registering and imagewise exposing to actinic radiation a sequence of sheet substrates which are registerable to one another to produce a composite image.

Description

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TITLE
__ MULTIPLE REGISTRATION ANO IMAGING PROGESS
"TO FORM A SET OF REGISTERED IMAGED ELEMENTS
BACKGR ~
There is a continuing need in the graphic arts and related industries to transfcr images photographically ~rom original (positive or negative~
photomasks to light sensitive sh~et elements to form a set of imaged elements which can be combined in reglster to produce a composite image. The set o~
imaged elements may be combined directly as ~or instance in the ~crmation of an overlay plcture from registered superposition of individual transparencies, or the use of the set o~ imaged elements may requlre further process steps as ~or instance the formation of a multicolored printed image using a set o~ individual photopolymer printing plates. In either case, each imaged eLement o~ a set must he provided with a common means o~ registration by which a ~inal composite image can be prepared by aligning or registerin~ precisely the locations previously established on each imaged element of the set. In all cases, the photographic operation is carried out in a manner which maintains, to the greatest preoision possible, both the definition and the relative lacations o~ the ~eatures o~ the images.
Composite images formed by simple assembly o~ the lmaged elements ~n register are typified by the preparation o~ multicolor overLays and particularly four-color overlay pro~fs. Such processes are disclosed in U.S. Patents 3,060,024;
4,282,308-; and 4,229,520. In the processes described, each of four photopolymerizable elements comprising a photopolymer layer and a transparent PD-1985 35 suppart is image~ise exposed to a photomask ...'~....

~presenting each of the ~our colors to be used, e.g., black, yellow, magenta and cyan. Either the lmaging expasure produces registra~ion marks on the photopolymer elemPnt or both the photomask and the photohardenable element contain at least two contact points, usually precisely punched holes. After imaging exposure the elements are then processed to produce a set ~f imaged elements each having a different uniform color but all having the same regi~ratîon marks or points. By superposing the ~our elements and aligning the marks or points, a ~u~l color rendition of the origlnal picture is ~ormed.
Compos~te images formed by sequenti~l trans~er in reg~ster of images from a set o~ imaged photosensitive elements to a receptor sheet is .~ typi~ied by full color printing using relief printing, planographic printing, and intaglio printing, or by formatlon of ~our color proofs by a trans~er process simllar to that des^ribed in U.S.
Patents 3,06~,~24 and ~,582,327. The fundamentals of full color printing are described in "The Printing Industry" by Victor Strau~s; Printing Industries o~
America Inc~ 1967, and photopolymer elements for preparing printing plates are described in U.S.
Pat~nts 2,~60,a63; 2,791,504; 2,964,401; 3,458,311;
4,072,527, 4,072,5Z8; 3,829~204; 4,32~,637 and 4,177,074.
Contact printing is virtually the universal method of exposure used today in the previously described photoduplication processes despite certain known shortcomings. Although low in equipment costs, sLmple to use, and capable of excellent line and halftone definition, contact printing is labor 3S intensive and slow (because of long conditioning

2~ 6 and~or vacuum draw-down times). It also is subject to losses due to damaqed or dirty photomasks resulting from repeated use. This, in turn, requires ~requent and expensive touch up and replace~ent of photomasks to avoid yield penalties. Much time is also lost in the constant and tedious process of inspecting photomasks for dsfects between exposure.
In addition, variations in frame temperature and ambient hu~idlty a~fect corner-to-cornec reglstration, especially ~or large elements such as printing plate/
Alternative exposure methods such as gap printing, projection printing and laser scanning each offer some significant advantages over contact printing. However in the current state o~
d.evelopment, all have serious limitations for high productivity applications and are i~trinsically much higher in equipment C05t.
SUMMA~Y OF THE INVENTI~N
The present ~nvention is directed to a - -- process o~ registering and imagewise exposlng to actinic radiation a set of sheet substrat~s ; registratable to one another to produce a composite image, each substrate containing a photosensitive layer comprising the steps of:
~1) advancing a substrate to a position in a device to undertake in either order or concurrently (a) aligning the substrate and a photomask in a predetermined relationship to one another;
(b) applyins a liquid between the photosensitive layer and the photomask;

(2~ c~ntacting through the liquid the substrate containing the photosensitive layer and the photomask whereby during said contacting substan,tially no m~vement o~ the photosensitlve layer relative to the photamask occurs ~n the liquid layer other than a more inti~ate c~ntact due to ~isplacem~nt of the liquid ~r~m a liquid layer during sald contact and whereby at least one of interfacial or viscous force due to the liquid }ayer aids to maintain the photosensitive layer and photomask in a fixed position relative to one another;

(3) exposlng the photosensitive layer to actin~c radiation through the photomask;

(4) removing the photomask from the exposed photosensitive layer and removing the - exposed substrate from the device;

(5) repeating steps 1 to 4 for each sheet substrate of said set employing at least one additional photomask whereby the exposed substrates are resistratable to one anotner to produce a composite image.
3RIEF DESCRIPTION Of THE DRAWING
Figure 1 is a side elevation of an apparatus use~ul in carrying out the process o~ the invention in a horizontal plane.
figure 2 is a side elevation of an apparatus useful in carrying out tha process of the invention - - in a vertical plane.
OETAILED DESCRIPTION OF THE INVENTON
In the process o~ the invention it is pre~erred that similar substrates containing a '7~

photosensitive layer with or without a top support or cover sheet are introduced into a registration and exposure device so that ~he imaged elements formed can be combined or used to produce a composite image having excellent registration. Conventionally a different photomask will be employed with each substrate of a set to produce a composite image since the substrates are registerable to one another. The photosensitive layer composition which is not present as a liquid preferably comprises a photosensitive polymer which can be negative or positive working.
Conventionally, the substrate is rectangular although this is not a limitation to this process. The registration portion of the apparatus comprises a rectangular film element, preferably flexible, and which is a photomask or phototool. The leading edge of the element can be joined in parallel, hinged relationship on one side of a thin rectangular carrier. The hinged relationship maintains the registration between the photomask and carrier. The apparatus disclosed in concurrently filed application Serial No. 387,534 now U.S. Patent Nos. 4,518,667 and 4,527,890 can be employed in the present invention except it is ordinarily necessary to employ a different photomask for each substrate of the set.
Also typically only one side of the substrate is exposed.
A substrate containing a photosen~itive layer is positioned or aligned adjacent to the photomask so that one substrate edge is in registration contact and approximately parallel to the length of the carrier.
In some instances, registration contact can be simple edge to edge contact of the substrate with the carrier wherein the only added criterion is tha~ the image pattern of the photomask is completely contained within the area of ~z~

the sheet to be imaged. However, registration cantact more generally requires the precise alignment o~ the'photosensitive sheet substrate with details of the photomask image or images. In this instance at S least two contact points on or in the sheet are brought into a ~ixed relationship with twa corresponding contact points fixed to the carrier.
Such points may be notches and tabs suitably spaced on the sheet and carrier edges. Alternatively the points may cons$st of registration pin and hole ' ccmbinations wherein the sheet contains precisely located registration holes which are posltioned ln the desired orientation by registration pins. Since the registration is identical ~rom substrate to substrate in a set, the imagad photosensitive layers can be combined in register and used to produce a composite image.
Once a substrate containing a photosensitive layer is in registration relatlonship to the carrier, the flexibl~ film photomask is applied to the side of the suhstrate bearing the ph~tosensitive layer in the presence of a llquid interface by applying normai pressure in a line roughly parallel to the carrier on the outer surface of the photomask at or near the hinged edge and advancing (relatively) the pressure line in the direction perpendicular to the hinge line and parallel to the sensitized substrate surface and, concurrent with the advance9 applying the liquid, e.g., by spraying, to the nlp between the substrate and the inner surface o~ the photomask forned by the -- a~vancing pressure line. In effect the photomask is - temporarily ~et-laminated to one side of the' substrate in register wherein the substrate is separated from-the photomask sur~ace by a Liquid interface. This laminatian process is pr~erably 7~

carried out by passing the hing~d photGmask-registered sheet assembly through a pair of pr~ssure rollers~ In this mode of operation, pressure is applied at or near the leading edge of th~ sensitized substrate and tne flexible photomask.
L~uid, pre~erahly water, is then sprayed into the nip ~ormed between the photomask and the substrate.
Preferahly, the registration apparatus is oriented so that the general directlon o~ the wet lamination is upward, i.e., the substrate travels in an upward direction relative to the pressure rolls and liquid applicators. When so oriented, a cleaning action of the liquid on both the photomask and the photosensitive layer or support or cover sheet can be achieved, which is enhanced by the use o~ excess liquid directed at both surfaces and which will simply drain into a catching basin carrying ~ny exkraneous matter with it. In addition, the area above the pressure rolls where actlnic expqsure , pre~erably occurs can more ~as11y be kept free o~
unwanted liquid. This process~of obtaining alignment of a substrate and photomask is obtained without ths use of vacuum. However,~ a vacuum could be used to remove excess liqu~d.
It is understood that in the present speci~ication that "substantially no movement" means that surface of the photosensitive layer and the photomask do not move relative to one another in directions parallel to their surfaces9 i.e., the 3~ sur~ac~s do not slide relative to one another to change the alignment o~ the photo~as~ to the substrate. However, it is understood that "substantially no movement" allows relative movement of the photomask and the photosensitive layer in the direction perpendicular to their surfaces to form a 2~:7~

more inti~ate contact, e.g., as liquid is squeezed ~rom the interface between the photosensitive layer and the photomask. However, the photosensitive layer and photamask, already contactect by the advancin~
5 pressure line~ will remaîn in a fixed relationshlp in directions parallel to their sur~ace.
Also it is understood in the present speci~ica~ion that '~contacting" through the liquid layer a substrate containing 2 photosensitive layer 10 and a photomask does not exclude intermedi~te layers. For example, the photosensitive layer may have a support or cover sheet which allows actinic radiation to pass or the photomask may contain a release coating. Such support or cover sheet or 15 release coating could contact the liquid layer.
In the present speci~ication, a photosenstive laye~ is employed to mean a pre~ormed layer and excludes a photosensitive layer present as . . a llquld.
2a Once the photomask has been fixed in : register over the photosensitive layer, the subst~ate with its photosensitlv~ material may be exposed to:
any sau~ce of actinic radiation. The radiation may emanate ~rom point sources or be in the ~orm of parallel rays or divergent beams. By usin~ a broad radiation source relatively close ta the i~age-~earing transparency, actinic radiation ent2rs as divergent beams and thus irradiates a continually diverging area in the photosensitive layer un~erneath the clear portians a~ the transparency~ With thick photosensitive layers such as on let~erpress or fle~ographic printin~ ~lates, this results in a polymeric relief havins its greatest width at the bottom of the photosensitive layer, i.2., a frustum, the top sur~ac o~ the relie~ ~eing the dimensions of the clear area (for negative working systems).

Inasmuch as the free-radical generating systems activatable by actinic radiation generally exhiblt their max~mum sensitivity in the ultraviQlet rang~, the radiation source should furnish an 5 ef~ective amount of this radiation, pre~erably having a w~velength range of ~000 A to 4000 A or above.
Suitable sources of such radiation, in addition to sunlLght, include earbon arcs, mercury vapor arcs, ~luorescent lamps with ultraviolet radiation-emitting 10 phosphors, argon glow lamps, electronic ~lash units and photographic flood lamps, ~tc~ Of these9 the mercury vapor lamps and the ~luorescent sun lamps are most suitable.
It i5 also possible to completely remove the 15 substrate containlng the photosensitive layer fram the registration device and expose it on any suitable exposure unit. In this instance the photomask and carrier remain fixed in registration with the photasensit~ve layer by the action of su~face or visca~s ~orces induced by the inter~ace liquid. It is understood that both surface and viscous ~orces may be pr~sent.
When imaging exposu-re is complete, the photomask ls peeled from the sur~ace of the exposed 2S photosensitive element thus releasing the imaged element ~rom registration. The imaged element is then transferred from the registration-exposure apparatus and the hinged photomask is replaced by one o~ the remaining phatomasks in the set. The hinged photomask-carrier assembly is then returned to its initial position to recelve the next substrate containing the photosensitive layer in the set to be imaged. In a preferred mode of operation, a~ter exposure, the pre-exposu~e proc~ss steps, for the most part, are reversed. Thus the exposed substrate 7~

passes back through the p~essure means such as rollers and the photomask is pulled back until the hinged area on tne carrier is reached. The rollers are moved apa~t, the photomask carrier ls lifted and the photomask is replaced by a another one in the ~ set. Other means than rollers may be used to apply pressure, e.g., a squee~ee.
The sheet substrate during the registration and imagewise exposure process may be in any orientation including a horizontal plane or vertical plane. Prefera~ly the substrate will be in a substantially vertical plane. In the process of this invention any means can be used to convey the sensitized substrate to and ~rom the registration position in the apparatus.
The liquid which is applied to the photosensitive layer ar suppart or cover sheet and ; photomask serves several vital functi~ns in the process o~ this invention. The liquid serves to uni~ormly ~ix the photomask in intimate re~istered contact t~ the photosensitiYe surface or support or cover sheet during actinic exposure and after exposure allaws the photomask to be easily removed from the exposed sensitlzed substxate without damage or transfer o~ either. The excess liquid serves to - clean the surface of the photamask and individually each photosensitive surface or support layer thus preventing deterioration o~ the photomask Lmage and/or the resulting exposed image, particularl~ by ~a element born dirt. 3y spraying liquid on the phat~mask the environment and temperaturs of the photomask is maintained constant and less susceptibla to changes in amhient temperature or humidity. In this respect, it is also desirabla to spray liquid on 3S the exterior sur~ace o~ the photomask, provided the 4~

liquid does not interfere with exposure or is removed there~rom before actinic exposure. The liquid interface should be substantially transparent to actinlc radiation and should n~t: damage the phctomasks or the photosensitive sheet surface or cover sheet unless surface modif~ication is desired.
Neither should it interfsre Wit~l ~he exposure of the photosensitive layer. The liquid should preferably wet both surfaces of the photomask and the surface of the photosensitive layer or support or cover sheet, have low volatility at ambient temperatures, and have sufficient viscosity to ~ul~ill the vital functions o~ the liquid. The pre~erred liquid is water or aqueous solutions containing adjuvants which improve liqu~d characteristics, e.g., sur~ace actiYe agents, viscosity ad~usting agents~ etc. Other liqu~ds, o~
course, can be used depending on-the conditions required, ~., alcohols, glycols, glycol ethers, halogenated hydrocarbons, para~ins, etc., provide~
2~ they full~il the above criteria. In the instance when long exposure ti~es are requir0d with actinic sources which induce bu~ldup of heat, a high boiling point liquid like ethylene glycol is preferred.
Since the li~uid remains a~ter the expasure step, a photosensitive liquid is not used for this component ^ o~ the process.
The process of this invention is useful for imaging any substrate containing a photosensitive layer which is compatible with the llquid treatment.
3~ I~ the photosensitive composition îs not compatibls with the liquid~ preferably a support or cover sheet than will be used to protect this composition. The process is particularly useful ~or exposing elaments typlcally used for producing lithographic printing platas or any other thin stencil mask image.

.

The registration and imagewise exposur~
p~ocess of th0 present invention is applicable to a w~de variPty of sheet substrates provided at least one sur~ase contains a photosensitive layer which may S have an optional support or cover sheet.
Some elements use~ul in preparing printing plates are provided with auxilia;ry cover layers to protect the photomask and prevent it from adhering to the tacky photopolymer layer, or particle-containing, oxygen-barrier overcoat mat layers which are usPd to achieve ~aster vacuum drawdown during the conventional exposure step. Using the process of the lnvention, slip and overcoat layers can be present or with cover sheets provided with a release coa~ing, such as, sil~ . one treated polyethylene te~ephthalate, wh$ch can be peeled o~ prior to expGsure can be used. The elim~natlon of these layers can reduce manufacturing costs ~or these photopolymerizable elements... .
2~ ln practicing the inYention, a sheet substrate ~earing photosensitlve c~mpositions o~
various types, e.g., negati~e or positive working, may be used. Photopolyme~izable elements useful in making lithographic printing plates are disclosed in U.S. 3,458,311, U.S. 4,293,635, u.S. 4,072,528 and U.S~ 4,072,527. Elements useful in preparing litho ~ilms are disclosed in U.S. 4,229,~17.
PhotosensltiYe compositions useful in making ~lexographlc printing plates are disclosed in U.S.
4,323,fi~7, U.5. 4 177,074, and U.S. 4,229,520.
Photosensitive elements useful in preparing an o~erlay print are disclosed in U.S. 4,229,520 and u.S~ 4,282,308.

~5 figure 1 is a pictorial representation of an apparatus useful in carrying out the process o~ the invention. This process will now be described with re~erence to this appa~atus. In this processS a set of similar substrates with a photosensitive layer and th~ir corresponding set o~ photomasks are aligned and punched along one ed~e using a commercially available punch. One prepunched sensitized substrate desl~nated as (1) is taken, and the holes in its leading edge are fitted over the corresponding pins in pin registration set (2). The punched phatomask (6~ is then affixed in a parallel, hinged relationship to photomask carrler (5) the prepunched holas in the photomask (6) corresponding to the - 15 registration pin receiving hole (~) in carrier (5).
The photomask carrier (5~ is then lowered and regi~tered to substrate (1) using piQ registration set ~2). (Alternatively a photomask with holes can ~it on the same pins as the substrate.) Stop pins ~4) are retracted and nip ralls (3) and (~1) are then activated bringing upper roll (31) in contact with lower roll (3) thus ~orming a nip between the substrate (1) and photomask (6). Since Figure 1 is only a side view, only one pin in the registration pin set and one hole is shown. In reality, two or more holes are present in the photomask carrler and a like number o~ pins in the registration pin set are provided. Liquid spray (7) is turned on so llquid is sprayed at the nip farmed oetween the photomask (6) and the substrate (1). rhe suastrate (1~ in register with photomask (6) is then moved to the expasure position t5'). and exposed using exposure unit (8~.
Intimate contact is achieved prior to exposure by squeezing out the excess liquid between substrate (1) and photomask (6) with the aid o~ nip rolls (3) and ~7~16 (31). A~ter expasure the mechanis~ is reversed.
Substrate ~1~ in register with photamask (6) is moved back, nip rolls (3) and (31) are moved apart, photomask carriex (5) is lifted so it ls out of contact with the pins in registration pin set (2) and the exposed substrate (1~ and photomask (6) are released. Similar prepunched she~t substrates can th~n be registered and exposed using a remaining photomask of the set, and the steps described above, whereby a set o~ imaged elements are formed which can be combined in rsgister or used to produce a composite image.
In Fig. 2, is shown a reg~stration and ima~ewise exposure process in a vertical mode. The apparatus is particularly adapted to ~xpose both sides o~ a substrate but in the present case only one side is exposed. The substrate (11) contains at least two pin register holes along its leading edge.
8e~are a substrate ~tI) is introduced, the following conditions are establlshed:
Nip ralls t12 and 12') are open;
Clamp (13) is open;
Photcmask assembly (15) which c~ntains a photomask (16) and a flexible sheet 2S material (16') and its carrier is registered to clamp (13) by carrier register pins (19) with the photomask and fleixhle she~t kept taut around nip rolls t12 and 12');
3~ Pin register bar (14) is not engaged;
- Liquid spray (17 and 17~) is on; and Exposure sources (18 and 18') is on standby.
Substrate (11) with the sensitized side facing Exposure source (18) is then lifted up to register pqsition inside clamps (13) through nip rolls (12 and 12'). Pln register bar (14) closes; ~irst engaging carrler r@gister pins (19) on clamp (13) and then picking up preformed register holes (10) on substrate ~11) with its own pins. Registration of substrate ~11) to photomasks assembly tl5) is achieved when the pins are engaged. Next clamp (13) is closed to maintain registrati~n and pin regist~r bar (14) is subsequently retracted. Clamp ~:L3) is.moved down, carrying photomask assembly (15) and substrate (11) to n~p ralls (12 and 12'). Then nip rolls are closed and clamp (13) is moved up to exposure position (18). Intimate contact of photomasks (16) and flexible sheet (16') and substrat~ (11) is achieved by squeezing out excess liquid with nip rolls (12 and 12'). Exposure on one side is made. A~ter the exposure, the mechanism is reversed, clamp (13) moves down to its initia1 registered position and then both it and n~p rolls ~12 and 12') are opened. The exp~sed substrate (11) is releassd to allow 2~ repetitlon o~ the process excep~ a new substrate and new photomask is used.
In a particular instance where both the substrate support and the ~lexible sheet (16'~ are transparent to actinic radiation, e.g., transparent polymeric ~ilms, the photosensitive layer of the substrate can be uniformly exposed through the support to exposure source (18') either prior to, concurrent with, or after the imaging exposure with exposure source (L8) so as to modify the imaged substrate.
Such modification may be conditionin~ :
exposure as disclosed in U.S. 37144,331; an exposure to form a uniformly polymerized stratum as described in E~ample 4; a uniform exposure which is an integral 3S step of a two exposure imaging process such as fl~

disclosed in U.S. 4,269,933 and 4,162,162.
The invention is illustrated but is not intended to be llmited to the following examples.
All parts are by weight unless otherwise indicated.
Example 1 Eight coated photopolymeri~able elements comprising a 0.012 inch ~0.~05 mm) aluminum support, - a 0.00015 inch (0.004 mm) photapolymerizable layer and a 0.00005 inch (C.OOL3 mm) p~lyvinyl alcohol (PVA) containing overcoat are p:repared. The photopolymerizable layer has the ~ollowing composition:

Methylmethacrylate/methacryliC 58.5 acid (90~10) mol. wt. o~ 20,000 Trinethylol propane triacrylate 2n.4 Trlethylene ~lycoL dicaprate and 8.
tr~ethy~ene glycol dicapryiate 20 ~enzophenone 8.0 2,2'-~is(2-~hlorophenyl)-4,4',5,5'- 3,4 : tetraphenyl biimidazole 4,4'-~is(dimethylamino)benzophenone 0.8 (Michler's ketone) 4,4',4" methylidynetrls ~NjN-dimethyl 0.8 aniline) Vi~tar Green Pig~ent ~C.I. Pigment 0.1 G~een 18) 30The PVA containing laye~ has the following .~omposition:

~f~

In2redient ~ y_~
Poly(vinyl alcohol) 13% solution 88.2 Poly(vinyl pyrrolidone (70~/vinyl 10.8 acetate (30)) copolymer 5 10% Solution of octyl phenoxy 1.0 polyethoxy ethanol, dispersing agent Four of the elements are punched in register with the set of photomasks to be used during exposure using a commercially available punch. Each punched element is registered to and exposed through one photomask in the set using the process of the inven-tion described earlier. The liquid sprayed into the nip formea between the photomask and the photopolymerizable element is Nujol~ (mineral oil) manufactured by Plough Sales Corp., Memphis, TN. The elements are exposed for approximately 15 seconds using a 4KW Xenon lamp at a distance of 24 inches (60.96 cms).
Each of the remaining four photopolymerizable elements are aligned to one of ~he photomasks in the set, drawn down for 2 minutes in an exposure vacuum frame, and exposed for 15 seconds using the light source described above. These four elements serve as a control.
The exposed elements are then developed in an Enco* Processor Model No. N-322 manufactured by Azo~late Corp., Morristown, NJ using the following developer:
Sodium carbonate1.92 30 Butyl carbitol 11.74 Water 86.34 ph 11.5 + 0.2 -k denotes trade mark b 7~

The developed elements are finished in a sodium pyrophosphate finisher and are dried in hot air to give eight lithographic printing plates. One set of four lithographic printing plates are prepared using the registration and exposure process of the invention, and the other set of four serves as the control. Each of the four plates in the set corre~
sponds to one of the four colors to be printed, The plates are mounted on a 4 color Miehle*
49 FC Printing Press, Series 42~, manufactured by the Miehle Company, a division of Miehle-Goss-Dexter, Chicago, IL. The registration pins on the plate cylinder are 30 inches (76.2 cms) apart (15 inches (38.1) from the center). The plate~ are dampened using the Miehle Matic dampening system which comprises a 2 roll metering system using a 20%
alcohol/water ratio, 1~ oz. of red etch which is a solution of magnesium nitrate, ammonium dichromate, phosphoric acid diluted with water to a pH on press of 3.8 and 4 oz~. of gun/gallon.
The inks for use in the printing operation are Crowe Inks manufactured by Crowe Corp., Philadelphia, PA having an Inkometer reading of uni-form #14 tack, and are listed below in the sequence in which they are printed:
Yellow Ink: Series I l/D PC Yellow Blank Ink: Series II 2/D PC Black Magenta Ink: Series II PC Magenta Cyan Ink: Series I PC Cyan The pla~es corresponding to each color îdentified above are pin registered and mounted on the plate cylinder~ and the four-color image is printed on paperO Using the process of the invention excellent registration of the four-color image on the print is obtained.
* denotes trade mark ., ~2~7~

~e~
Example 1 is repeated with the following exceptions:
o The polyvinyl alcohol containing overcoat S is replaced by a 0.0005 inch ~.00127 cm) thlck polyethylene terephthalate cover sheet which is peeled off prior to exposure.
o Liquid sprayed into the nip ~ormed between the photomasl< and laminated photopolymerizable e:Lement is water.
Using the process of the invention, the overcoat layer can be eli~inated b~cause th~ vacuum - drawdown requirsd during convention~l exposure is not needed.
Example 3 four laminated elements are prepared by Steps X, II and III in Example 1 of U.S. 4,282,308.
These laminated elements ~nd four hal~tone color separation negatives tone ~or each color? are aligned and holes pun~hed along one edge using a commercially ava~lable Kndak~ Register punch. . The punched elements are then registered and exposed an the apparatus shown in Figure 1 using the process a~ the inventian described earlier. The liquid sprayed into the nip ~armed between the laminated element and the hal~tone color separation negative is water. The exposure device is a carban arc (E - lC oonstank arc - 140 amp, Na. 111~ - Ld 612 MacBeth Arc Lamp Ca., Philadelphia, PA. Each element is exposed in register with the halftone color separation ne~ative ~or 15 seconds at 56 inches (142.24 cms) ~rom the . .
lamp. Five minutes after exposure, the elements are delaminated and toned as described in Example 1 o~
U.S. 4,282,308. The toned elements are then assembled in register to give an excellent quality negative color proof of the overlay typeO
Exam~le 4 Eight laminated photosensitive elements are 5 prepared as described in Example 8 of Canadian Patent Application Serial ~o. 396,870 of Munger et al filed February 23, 1982. These elemen1:s comprise in order, a support, an adhesive layer, a photosensitive layer, a polyamide layer and a cover sheet.
lQ These elements are th~n placed support side up in a Cyrel~ 3040 Exposure Unit (registered trade mark of E. I. du Pont de Nemours and Company, Wilmington, DE) fitted with Sylvania BL-VH0* fluores-cent lamps, and are given an overall exposure in air at atrnospheric pressure about 3 minutes through the support to polymerize a predetermined thickness of the photopolymerizable layer adjacent the adhered support. The elements are then aligned to the photo-masks to be used in the next exposure step, and punched along one edge using a commercially available punch. The holes are punched relative to the loca-tion o~ ~he pins, in the registration pin set shown in Figure l.
The cover sheets on four of the punched elements are removed leaving the polyamide layer adhered to the photopolymerizable layer, and these elements are registered to and exposed through the photomasks (negatives~ using the process of ~e in-vention described earlier. The elements are exposed for 5 minutes to Sylvania BL-VH0 fluorescent lamps at a distance of 2 inches. The liquid sprayed into the nip formed by the element and photomask is water.
The exposed elements are then developed, dried, and post exposed as described in Example 8 of Canadian Application Serial No. 396,870 filed * denotes trade mark ~ `r''b February 23t 1982 to give four printing plates corresponding to the four colors to be printed.
Prior to the post-exposure step, each dry printing plate is immersed for 2 minutes in an aqueous solution of potassium bromate~potassium bromide having a solution pH of 1.2. The bromide solution is pre-pared as follows: to 1800 mls of tap water is added 20 ml of conc. hydrochloric acid with mixing. To this solution is added with mixing a mixture of 200 ml tap water, 10 g potassium bromide and 2.8 g potassium bromate (90.56% H20/8.81% HCl/0.49% Ksr and 0.14-KsrO3). The free bromine concentration is 0.4%.
The cover sheets on the remaining four punched elements are removed and the elements are exposed/ developed, dried and post exposed as described in Example 1 of Canadian Application Serial No. 396,870 filed February 23/ 1982 to give four additional printing plates which serve as a control.
Prior to the post-exposure step these plates (control) are bromine treated as described above.
The printing plates are mounted in color register on plate cylinders with commercially avail-able double sided adhesive tape using the apparatus described in Canadian Application Serial No. 346/423 filed February 26, 1980/ and printed with standard flexographic inks.
A four-color print is made using the plates which are registered and exposed according to the process of the invention to show the four colors in register. The printing plates using the conventional exposure process have to be manually registered while they are being mounted, and the mounting step takes much longer than that for the plates which are prepared using the process of the invention. Further, using the process of the invention no vacuum draw down is required.

~2 Using the two sided exposure apparatus depicted in figure 2, the initial 3 minute uniform preexp~sure through thP support can be accomplished with exposure source (18'), e.g., with Sylvania S ~L-VH0 ~luorescent lamps, just prior to i~aging exposure with exposure source (18).
E~ample S
Eight flexographic printing plates are prepared as in Example 4 with on~ exception: the polyamide layer present between the photosensitive : layer and the cover sheet in the laminated photosensitive elements prepared is eliminated, and a sil~cone.treated cover sheet is used.
The results can show that after registration and exposure using the process of the invention the photomask does not adhere to the tacky photopolymer layer because of the prbsence of a layer of water between them. However, using the conventional exposure step where the photomask is placed Ln contact with the phot~polymerizable layer, on separation a~ter exposure, the photomask can stick to the tacky photopolymer layer and is ruined~ Thls example shows the polyamide layer ~slip layer) can be eliminated when using the registration and exposure process af the in~ention thereby reducing the costs for manufacturing the laminated photosensitive elements. ~.
Example 6 Four coating solutions are prepared, sach ~o containing tne following ingredients:

. .
. . ..

~5 .~ ~2~7~4~

Methylene chloride solvent 81 M~thanol solvent 4 5 2,~ is(~chlorophenyl)-4,4',5,5'- , 1.0 tetraphenyl biimidazole 4,4'-~is(dimethylamino)benzophenone 0.1 (Michler's ketone) T~rpolymer ~ormed from 56% ethyl 4.1 acrylate, 37X methyl methacrylate and 7% acrylic acid, mol. wt. ca.
260,00~, acid number 76-85 1:1 copolymer oF styrene and maleio 6.6 anhydride, partially esterified with isopropyl alcohol, ~ol. wt.
ca. 1700, acid number ca~ 27 Triethylene glycol dimethacrylate 3.2 Nonionic ~luorocarbon sur~actant 0.04 FC-430, Minnesota Mining and M~g. Corp., 10% solution in CH2Clz 20 Ultraviolet Absorber (2,2'-~ihydroxy- 1.0 4-methoxybenzophenone) To each individual solution is also added one o~ the following dyes:
25 ~9E~g~9~ .
.rasol~ Fast 0rill. Red RI l.û
(C.I. Solvent Red 96) Irgacet~ Yellow 2RL 1.0 (C.I. Solvent Yellow 91) 30 Irgacet~ arill~ alue 2SLN 1.3 (C.I. Solvent 81ue 4a) Luxol~ Fast alack L 1.0 (C.I. Solvent alack 17) ~7~

Each of the above four solutions is coated via a "doctor" knife on a 0.004 inch (0.101 mm) thick polyethylene terephthalate film support having a 0.000~ inch (0.0051 mm) thick soluble .substratum whioh is a mod~fication o~ that disclosed in Rawlins, U.S. Patent 3,443,9501~
This modification adds two acid terpolymers in a weight ratio o~ approximately.l2:8.01:1, (Rawlins sub~first polymer:second polymer) wherein the ~irst polymer is formed ~rom ethyl acrylate t56%~, methylmethacrylate (37%) and acrylic acid (7%), and the second polymer is ~ormed from 66%
methylmethac~ylate, 29% ethyl acrylate, and 5~
methacryllc acid, to the substratum described in the above cited patent. ~fter hot air drying, the dried coating weights are approximately 0.0004 ~nch ~0.01 mm)..... Each photopolymerizable layer is then .
ave~coated with a thln oxygen barrier polymer~ . :
. substantially as described below.
5~0 g of polyvinyl alcohol (98-98.8%
saponi~ied, low vlscosity) are added to 5000 g.of distilled water and heated at 85C for 2 hours.
100 9 0~ the solution are mixed with 262 S distilled, water, 18 9 polyoxyethylene surfactant (10~ aqueous ~5 solution), 10 9 ethyl cellosolve, and 10 9 ethyl alcohol. To 100 9 o~ the above mixture are added 2.7 g of a 30X colloidal silica dispersion containing pa~tlcle sizes in the range of 12 to 15 millimicrons and 30 9 of distilled ~Nater. This res~lts in an o~ercoat formulation in grams as follows:
polyvinyl alcohol 2.25 distilled water 122.50 polyoxyethylene surfactant 0.45 ethyl cellosolve ~.50 ethyl alcohol 2.50 colloidal silica 2.70 ": ~2~4~o~

Uslng a 2-mil (O.OS mm) doctor kni~e, the above overcoat solution is coated directly on the - .photopolymerizable sur~ace and allowed to dry. The coating welght of the overcoat is 10.0 mg/dm2.
Eaoh o~ the colored elements is then registered to and exposed through a hal~tone separation negative (one for each color~ using the process Q~ the invention described earlier The liquid sprayed into the nip ~ormed between the hal~tone s@paration negative (photomask) and the colo~ed element is Nujol~ which is a mineral oil manu~actured by Pl~ugh Sales Corp., Memphis, TN.
Each element is exposed to a 4KW Xenon arc lamp for 90 seconds. Each exposed element is then developed ~cr 15 seconds with an aqueous solution (pH 10.4) of . potassium carbonate (1.5%) and potassium bicarbonate (1~5%) at 29C, ~ollowed by rinsing in warm water (38C), and drying, to give a faithful image o~ the hal~tone targets, one ln magenta, one in yellow, one in cyan, and one in black.
The ~our elements are then assembled in register to give an excellent quality color proo~ of ..
the overlay type. -Example 6 is repeated with two exceptions:
(1) the elements us~d do not have an overcoat, and (2) ~he liquid is sprayed into the nip ~ormed between the hal~tone separation negative (photomas~) and element during the registration and exposure proc~ss 3~ is water.
The exposed, developed, rinsed and dried - elements are placed in register to give an excelient quality color pro~ sf th~ overlay type. This example is to show that using the process ~f the 35 invention the overcoat layer, which is required to '7~

aohieve draw down in the conventional exposure proc~ss, can be elminated.

Four photopolymerizable elements are 5 pr~pared as in Example 1 o~ U.S. 3,582,327 with one exc ption: coating wt. o~ photopolymerizable composition is 80 mg~dm2. Each ele~ent is registered to and exposed through one process transparency in the set o~ ~our (one ~or each colo-r) 10 using the process of the invention described earlier. The liquid used in the process is water, and the expasure source, a 4KW Xenan lamp. Each element is exposed ~or 2~ seconds at a distance of 24 inch@s (60.96 cm). The polyethylene terephthalate 15 cover sheet on each element is then stripped o~f and the imagewise exposed photopolymeri2able layers are resp`ectively toned with yellow, magenta, cyan and black toners. The yellow toned element is placed in contact with glossy paper laminated between a hot 2~ roll and hnt platen at 115C at a pressure of 1.5 lbs per linear inch and stripped while hot at a rate of 0.2" per second. The next toned image.trans~arred is magenta, ~ollowed by cyan and then black using the ; same transfer process described earlier with regard to the yellow image. The paper support is provided with registration holes corresponding to those on the photopolymerized elements and a registration pin set slmilar to that disclosed Ln Flgure 1 is used to assure reyistration o~ the transferred toned images.
Toners used are those disclosed in ExampLe 1 af U.S.
3,64~,268.
~ The four-color print so formed is to show the ~our colors in excellent register.

Claims (15)

27

1. A process of registering and imagewise exposing to actinic radiation a set of sheet substrates registratable to one another to produce a composite image, each substrate containing a photosensitive layer comprising the steps of:
(1) advancing a substrate to a position in a device to undertake in either order or concurrently (a) aligning the substrate and a photomask in a predetermined relationship to one another;
(b) applying a liquid between the photosensitive layer and the photomask;
(2) contacting through the liquid the substrate containing the photosensitive layer and the photomask whereby during said contacting substantially no movement of the photosensitive layer relative to the photomask occurs other than a more intimate contact due to displacement of the liquid from a liquid layer and whereby at least one of interfacial or viscous force due to the liquid layer aids to maintain the photasensitive layer and photomask in a fixed position relative to one another;
(3) exposing the photosensitive layer to actinic radiation through the photomask;
(4) removing the photomask from the exposed photosensitive layer and removing the exposed substrate from the device;
(5) repeating steps 1 to 4 for each sheet substrate of said set employing at least one additional photomask whereby the exposed substrates are registratable to one another to produce a composite image.

2. The process of Claim 1 whereby liquid between the photosensitive layer and a photomask is displaced when the substrate and photomask are brought into more intimate contact by an advancing pressure line.

3. The process of claim 2 wherein said advancing pressure line employs a nip.

4. The process of Claim 1 wherein the application of liquid is to a substrate surface held in a substantially vertical plane.

5. The process of Claim 1 wherein steps 1 to 4 are with the substrate surface held in a substantially vertical plane.

6. The process of Claim 2 with the substrate held in a substantially vertical plane.

7. The process of Claim 1 wherein the photosensitive layer is positive working.

8. The process of Claim 1 wherein the photosensitive layer is negative working.

9. The process of Claim 1 wherein the photosensitive layer contains a photohardenable component.

10. The process of Claim 1 wherein the photosensitive layer contains a photohardenable addition polymerizable component.

11. The process of Claim 9 wherein the photohardenable-component is photocrosslinkable or photodimerizable.

12. The process of Claim 1 wherein the photomask is flexible.

13. Ths process of Claim 1 wherein the surface of the photosensitive layer directly contacts the photomask through the liquid.

14. The process of Claim 1 wherein the photosensitive layer is separated trom the liquid layer by a cover sheet or layer which allows actinic radiation to pass.

15. The process of Claim 1 wherein the liquid comprises water.