A simplified method for photoimaging a photosensitive layer produces in situ a radiation-opaque photomask on the photosensitive layer or on a cover sheet of the layer. A nonvisible latent image is toned and the toner is transferred to a layer or cover sheet to form an actinic radiation-opaque photomask.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to photosensitive imaging and, more particularly, to 
producing a radiation-opaque photomask on a photosensitive surface or 
cover sheet. 
2. Description of the Prior Art 
It is well known to use a variety of preimaged layers as photomasks for 
imaging photosensitive elements. Diazo, electrographic, silver halide, and 
photopolymer films have all been useful for the production of such 
photomasks. These prior art methods all employ a photosensitive film which 
is coated or laminated onto a support. After appropriate exposure and 
processing the photosensitive layer produces density areas comprised of 
toner, dye, silver, photopolymer, etc. When the photomask layer is placed 
over a photosensitive element and irradiated, the density areas block or 
modulate the radiation and thus control the exposure within the 
photosensitive layer of the photosensitive element. 
Both halftone and continuous tone imaging may employ such photomask films 
or layers. U.S. Pat. No. 3,060,026 teaches that a cover sheet useful for 
photopolymer films may contain useful information such as graphs or other 
detail and in this fashion also serve as a photomask layer. U.S. Pat. No. 
3,755,892 teaches that a silk-screened image or a developed photosensitive 
layer may be adhered to the protective layer over a photosensitive resist. 
U.S. Pat. No. 3,740,225 teaches the use of punched tape as a photomask for 
imaging a photosensitive material. 
Both electrostatic and magnetic toners have been described in useful 
applications for information transfer. U.S. Pat. No. 2,956,875 discloses 
toning an electrostatic latent image and transferring the dry powder image 
to a premoistened gelatine surface to produce a silk screen. U.S. Pat. No. 
3,740,205 discloses that magnetic information on a magnetic tape may be 
toned by a fluid magnetic toner which can then be transferred and fixed 
upon a surface. U.S. Pat. No. 3,804,511 and U.S. Pat. No. 3,993,484 teach 
that magnetic toner in correspondence with an electrostatic image may be 
used to produce surface images by transfer to a copy medium such as paper, 
to produce multiple or color images. U.S. Pat. No. 4,135,195 discloses 
magnetic toning which includes a heat transfer step. British patent 
applications Nos. 2000728 and 2000729 disclose a method of transferring 
powder magnetic toner via an intermediate magnetized drum to increase 
resolution of the final image. U.S. Pat. No. 4,117,498 teaches a means for 
producing colored toner particles suitable for printing on fabric. 
A wealth of techniques, devices, and processes are available by which 
information may be transferred. In the case where it is desired to provide 
a photomask for the purpose of photoimaging a photosensitive substrate it 
is necessary to interpose a layer or film between the exposing radiation 
and the photosensitive substrate. Thus in view of the difficulties 
attendant with the every increasing demands of productivity it would be 
advantageous if this process could be simplified so that no layer or film 
were required. 
SUMMARY OF THE INVENTION 
The invention is a process for photoimaging a photosensitive layer by which 
a photomask is PG,4 created in situ, thereby eliminating the requirement 
for a separate photomask. The in situ photomask may be created directly on 
the surface or indirectly by transfer to the surface. The process is 
adaptable for electronic information systems. 
The invention is directed to a process for photoimaging a photosensitive 
layer comprising the steps: 
(a) transferring an actinic radiation-opaque image onto the layer or onto a 
transparent cover sheet thereon; 
(b) exposing the image-bearing layer to actinic radiation by which the 
layer is photoimaged; 
(c) removing the cover sheet if one is used; and 
(d) developing or fixing the resultant photoimage. 
The process by which the image is transferred onto the layer or cover sheet 
preferably comprises the steps: 
(i) forming a latent image on a magnetic or electrostatic recording 
surface; 
(ii) toning the recording surface with opaque toner to form a toner image; 
and 
(iii) transferring the toned image to the photosensitive layer or cover 
sheet. 
Within the scope of the present invention the image so transferred may 
optionally be removed either with a cover sheet, if one is used, or during 
fixing or development of the photosensitive stratum. Still other 
applications may require that the transferred image remain on the 
photoimage after fixing or development. 
It is a particularly preferred application of the present invention that 
the photosensitive layer be laminated to a metal or polymeric substrate 
for the purpose of producing an end product such as a printing plate, 
printed circuit, solder mask, color print, transparency, etc. 
The process of the present invention may be used to produce either positive 
or negative images. 
A particular advantage of the present invention is that a visible photomask 
is produced from nonvisible stored information, thereby eliminating the 
contact and productivity problems which exist with conventional 
photomasks. 
High resolution images are produced with exposed and processed photopolymer 
films upon the surface or cover sheet on which was applied an image opaque 
to the actinic radiation used for the exposure. Suitable ways by which the 
opaque image can be formed on the surface or cover sheet include 
mechanical, electromagnetic, or thermal imaging methods; these include 
techniques such as printing, magnetic toning, and laser writing. The 
opaque image may be formed on one surface and contact transferred to 
another surface or cover sheet. These high resolution images are capable 
of rapid and multiple reproduction. 
While the use of a conventional photomask requires a vacuum contact 
exposure device to obtain high resolution; the present invention 
facilitates automation in that photomasking steps may be eliminated, 
simplified, or made more efficient. It is also important to note that 
images may be rapidly generated from digital or analog information, which 
is highly significant in situations where the entire automated process is 
to be under computer control and based on electronic information.

DETAILED DESCRIPTION OF THE INVENTION 
The thrust of modern technology continues to stress electronic information 
gathering, transmittal, and display. Once it is available in either 
digital or analog modes, this electronic information may switch or 
modulate a variety of circuits or devices. In this way such electronic 
information may be used with magnetic systems, pulsed radiation, high 
speed printers, cathode ray tubes, microwave, etc. It is within the scope 
of the present invention to simplify the process by which this electronic 
information may be converted into a useful end product via photomask 
creation by either directly imaging a suitably prepared photosensitive 
element by means such as laser or microwave or by forming the photomask on 
a separate surface and transferring by contacting it to the photosensitive 
element or its cover sheet. 
A wide range of transparent film supports are useful within the practice of 
the present invention, including glass, cellulose triacetate, polyethylene 
terephthalate, polystyrene, and polymerized acrylates. Films produced 
according to U.S. Pat. No. 2,779,684, U.S. Pat. No. 3,052,543, Canadian 
Pat. No. 562,672 and British Pat. No. 766,290 are particularly suitable 
because of their dimensional stability. In applications such as printing 
plates, solder masks, and printed circuits, the support may be opaque and 
contain metal or plastic. For other uses a paper or rubber composition may 
provide a suitable flexible support. 
Suitable cover sheet materials include polyethylene terephthalate, 
regenerated cellulose, cellulose triacetate, polyethylene, polypropylene, 
polyamide, polyvinyl alcohol, and polyacrylate. One particular function of 
such cover sheets is to provide an oxygen barrier to protect an underlying 
photopolymer layer. The present invention is not, however, limited to 
producing a photomask on a transparent cover sheet to a photosensitive 
element. 
The photosensitive layer which is imaged through the photomask either on 
the layer itself or on its cover sheet may be chosen from a wide variety 
of diazo, silver halide, photopolymer, or electrographic films. Both 
positive and negative working films are useful for practicing the present 
invention. 
After being exposed through the photomask, these films may be processed in 
accordance with methods known in the art which include toning, heating, 
solvent washing, ammonia vapor treatment, dry peel apart, diffusion 
transfer, color coupling, and the conventional silver halide emulsion 
processing steps of developing, fixing, and washing. A particularly 
preferred method of practicing the present invention is to use a 
photopolymer film which has been laminated onto a substrate which will 
provide a final end product such as a color proof or transparency, solder 
mask, printed circuit, printing plate, etc. 
DETAILED DESCRIPTION OF THE DRAWINGS 
FIG. 1A: The magnetic element consists of a magnetic layer 1 in which, in 
the absence of any applied magnetic field, there is no net magnetic 
attraction on the polymeric support 2. 
FIG. 1B: When the element has been magnetized in a manner which corresponds 
to electronic information, the magnetic layer contains magnetized portions 
3 and unmagnetized portions 4. 
FIG. 1C: Magnetic toner particles 5 when contacted with the support 2 are 
attracted to the magnetized portions 3. 
FIG.1D: The magnetized and toned element is placed in contact with a 
photosensitive element such that the toner particles 5 are against the 
transparent cover sheet 6 attached to the photosensitive layer 7 adhering 
to the support 8. 
FIG. 1E: Radiation 9 exposes the photosensitive element only in areas not 
blocked by the toner 5 which functions as a photomask. 
FIG. 1F: As the radiation 9 continues to expose areas 10 within the layer 
they react to produce a polymerized or crosslinked structure. In areas 11 
the original structure is preserved. 
FIG. 1G: Cover sheet 6 with the toner photomask 5 is removed from the 
photosensitive layer 7. 
FIG. 1H: By a suitable processing step, such as solvent washing, the 
unexposed areas are removed whereby only the exposed areas 10 remain on 
the support 8. The resultant image areas represent a transformation of the 
original electronic information to a final image without the use of a 
conventional photomask. 
FIG. 2A: The electrostatic imaging element consists of a layer 13 
containing regions which can store charge and a support layer 14. 
FIG. 2B: By receiving electronic information the element has charged 
regions 15 and uncharged regions 16. 
FIG. 2C: Electrostatic toner 17 is attracted to the support 14 in the 
charged areas 15. 
FIG. 2D: The element is contacted to a photosensitive element comprising a 
photosensitive layer 18 and a support 19 so that the toner 17 adheres to 
the surface. 
FIG. 2E: The exposing radiation 20 is absorbed by the opaque toner 17 and a 
new radiation frequency 21 causes these areas of the photosensitive layer 
18 to react, while the exposing radiation 20 otherwise passes through the 
element without effect. 
FIG. 2F: By suitable washing or development imaged areas are produced which 
correspond to the original electrostatic image. 
FIG. 3A: A thermal developable element contains a support 25, a 
photosensitive layer 24, an opaque thermal release layer 23, and a thermal 
absorption cover sheet 22. 
FIG. 3B: Thermal radiation 26 such as produced by a laser hits the thermal 
absorption cover sheet 22 and is transmitted through area 27 to produce 
areas 28 within the opaque thermal release layer 23. These areas 28 now 
adhere to the photosensitive layer 24 instead of the thermal absorption 
cover sheet 22. 
FIG. 3C: Due to the thermally induced change in adhesion, these opaque 
areas 28 remain on the surface of the photosensitive layer 24 when the 
thermal absorption cover sheet 22 is peeled off with the nonexposed 
thermal release layer 23 still intact. 
FIG. 3D: An exposing radiation 29 reaches only the areas of the 
photosensitive layer 24 which are not protected by the photomask produced 
by the opaque areas 28. 
FIG. 3E: By continued exposure or development process the exposed regions 
30 are reacted in relation to unexposed regions 31 which were beneath the 
opaque regions 28. 
FIG. 3F: By washing or fixing of the unexposed areas an image is produced 
which is a reversal of the original exposing radiation. 
FIG. 4A: A photosensitive element comprising a support 36, a photosensitive 
layer 37, and a cover sheet 38 passes between heaters prior to passing 
between a pressure roll 33 and a drum transfer roll 34 having on its 
surface variable density toner 35 which transfers on contact to the cover 
sheet 35 which has been heated sufficiently to accept the toner 35. 
FIG. 4B: Radiation 39 produces variable eposure of the photosensitive layer 
37 according to the density of the toner 35 on the cover sheet 38. 
FIG. 4C: After the cover sheet has been removed toner 40 is applied to the 
surface which produces variable density in accord with the amount of 
exposure permitted by the photomask and thereby produces a negative 
continuous tone image. 
FIG. 4D: The transferred tone 35 may be treated to give a finished surface 
and placed in direct contact with the photosensitive layer 37 in order to 
produce a sharper continuous tone image after exposure and toning. 
Since it is well known in the art that photosensitive elements may be 
formulated for either direct or reversal imagings, there are many other 
possibilities not shown which could encompass the basic concept of the 
present invention by providing for the production of a radiation opaque 
photomask on the surface of a photosensitive element or some cover sheet 
or protective layer over such photosensitive element. It should be clear 
that the opaque photomask produced in situ can be removed with an outer 
layer, be incoporated into the final image, or be removed by some step in 
the processing of the image-bearing photosensitive layer. 
The opaque image may be formed using, for example, magnetic toner, 
electrostatic toner, or photopolymer tack toner. Suitable photosensitive 
substrates include silver halide, photopolymer, photoplasticization, as 
well as vesicular, thermographic, and diazo systems or the like. 
These photosensitive substrates show a differential response to light 
between imaged and nonimaged areas. In some the response is immediately 
visible, while in others a latent image is formed which must be converted 
to a visible image by a development or processing step. Dry room 
temperature peel apart photopolymer films represent a useful 
photosensitive element for the present invention since the image is 
produced by simply peeling off the cover sheet with the photomask. Areas 
of the photosensitive substrates not part of the final image must in some 
cases be removed by fixing or washing to make the image visible. 
Protective cover sheets are employed with photopolymer films which provide 
a convenient layer for receiving an opaque material such as toner 
particles, ink, or carbon black. Particularly useful are such commercial 
products as Riston.RTM. photoresist film, Dycril.RTM. printing plate, 
Cyrel.RTM. flexographic printing plate, Dylux.RTM. photosensitive paper, 
Cromalin.RTM. color proofing film, etc. The above are trademarks of the E. 
I. du Pont de Nemours and Company. 
The following examples serve to illustrate the practice of the present 
invention, but are not intended to limit the concept of an in situ 
production of an imaging photomask. 
EXAMPLE 1 
Three types of artwork, continuous tone, line work, and halftone dots, were 
each transferred into magnetic images by being optically scanned and 
having the output signal from a photodetector used to modulate the 
recording field of a magnetic head in contact with a ferromagnetic coating 
of chromium dioxide. The magnetic recording element was comprised of a 
11.4 microns thick chromium dioxide magnetic recording medium coated onto 
a transparent 0.18 mm polyethylene terephthalate film support. The 
line-to-line spacing was 50.8 microns and the magnetic head was 4.3 
microns wide. For the continuous tone originals which were scanned the 
variable output from the photodetector was used to produce recording 
fields that varied as a function of the optical density of the original. 
The line work images were scanned at 430 revolutions/cm while recording 
black image information at 390 cycles/cm and recording white image 
information at 8,200 cycles/cm. 
Halftone images are of about 59 lines per cm (150 lines per inch) were made 
with the scanner operating at 670 revolutions/cm while recording with a 
square wave of 197 cycles/cm where black image information was being 
recorded and using 8,200 cycles/cm for white information. 
The 8,200 cycles/cm wavelength is too short to produce magnetic signals on 
the chromium dioxide surface that will attract the magnetic toner 
particles used in image development. 
The magnetic images were toned in magnetic toner baths, rinsed and air 
dried. High resolution images were obtained with two different toner 
baths. 
______________________________________ 
Toner Bath #1 
2 g Fluorad .RTM. FC 128.sup.(1) 
10 g Magnetic toner 8 particles 
Toner composition: Fe/Fe.sub.3 O.sub.4 Versamid 
930.sup.(4) 500 cc H.sub.2 O 
Toner Bath #2 
2 g Fluorad .RTM. FC 128.sup.(1) 
10 g Magnetic toner 7 particles 
Toner composition: Fe.sub.3 O.sub.4 Atlac 580E.sup.(3) 
500 cc H.sub.2 O 
Rinse Bath 
2 g Fluorad .RTM. FC 128.sup.(1) 
500 cc H.sub.2 O 
______________________________________ 
.sup.(1) Fluorad FC 128 Purchased from 3M Co. A fluorocarbon dispersing 
agent. 
.sup.(2) Versamid 930 Tradename of Henkel Adhesives. A polyamide aromatic 
adhesive. 
.sup.(3) Atlac 580E Tradename of ICI, Ltd. A propoxylated bisphenolA, 
fumaric acid polyester having a tack point of 70.degree. C. and a liquid 
point of 100.degree. C. 
Because the amplitude of the recording signal varied, the amount of 
magnetic toner attracted to the image varied giving a toned image which 
had image densities that approximated the continuous tone original. For 
the line and halftone only the black image areas produced a toned image. 
The toned magnetic images were mounted on the drum of a magnetic toner 
transfer machine (FIG. 4A). 
Cromalin.RTM. color proofing film manufactured according to U.S. Pat. No. 
3,854,950 was thermally laminated to seven point Kromekote.RTM.* paper, 
placed in the heater and heated to 128.degree. C. The magnetic toner image 
was transferred to the Cromalin.RTM. layer at 50 cm/sec. drum speed and a 
pressure of 7 kg per linear cm. 
FNT *Trademark of Champion International Co. 
In the same manner magnetic toner was also transferred to a polyethylene 
terephthalate film heated to 128.degree. C. in the heater. 
The Cromalin.RTM. laminates with toner images of line work, halftone, and 
continuous tone imaged on their surfaces were each placed in a Berkly 
vacuum frame which was evacuated for 30 sec. They were then exposed for 20 
seconds (FIG. 4B). 
The cover sheets were removed and the Cromalin.RTM. laminates were toned 
with a mixture of two parts by weight cyan toner with one part white 
toner. Images of good quality were produced on the Cromalin.RTM. surfaces. 
FIG. 4C is a representation of the variable toner density obtained for the 
continuous tone image reproduction. 
The heated polyethylene terephthalate film with magnetic image was also 
used as a cover sheet material for Cromalin.RTM. and used in a similar 
fashion as a photomask for imaging. 
High quality, high resolution and products were produced with all the types 
of artwork and either with or without the use of a cover sheet. 
EXAMPLE 2 
To increase the sharpness of the Cromalin.RTM. images produced in Example 
1, the cover sheet of the Cromalin.RTM. laminate containing the magnetic 
image of a continuous tone image on its surface was polished with Du Pont 
Slipspray lubricant. The polyethylene terephthalate cover sheet was 
removed from the Cromalin.RTM. laminate and the magnetic image was placed 
with the polished toner image against the Cromalin.RTM. polymer layer 
(FIG. 4D). This sample was exposed and toned as in Example 1 to produce a 
sharper image. 
EXAMPLE 3 
A photosensitive photopolymer resist layer was prepared according to U.S. 
Pat. No. 770,438 and coated on a polyethylene terephthalate cover sheet. 
This was laminated to a 0.004 cm thick copper clad sheet. An opaque image 
was printed on the cover sheet surface according to the teaching of 
copending application Ser. No. 124,605 of the Assignee filed Feb. 25, 
1980. 
The photopolymer layer was exposed by a DMVL-HP manufactured by Colight 
2000 watt ultraviolet source for 60 seconds. The cover sheet was removed 
by peeling it off with the image adhering to it. The resist layer was 
immersed in methyl chloroform to remove the unexposed areas. The copper 
was etched in a 42.degree. Baume solution of ferric chloride and 
hydrochloric acid to produce a printed circuit board. The process 
eliminated the normal phototool and vacuum contact exposure device but 
gave a high quality and high resolution end product. 
EXAMPLE 4 
A dry-developing room temperature peel apart resist film was prepared as 
described in Example 1 of Assignee's copending application Ser. No. 
6,144,300 filed April 28, 1980. When an opaque image was created on the 
cover sheet surface as in either Example 1 or Example 3 of the present 
invention a visible photomask was produced. When the cover sheet was 
removed the image was simultaneously developed as the cover sheet was 
removed. Productivity is increased since the conventional steps of 
positioning the photomask and removing it after exposure have been 
eliminated. 
EXAMPLE 5 
Du Pont positive Cromalin.RTM..sup.(1) proofing film C4/CP was laminated to 
white bond paper. This paper was substituted for the ordinary white paper 
normally used in a Kodak Ektoprint.RTM..sup.(2) 100 Copier Duplicator. An 
electrostatic toned image was thus formed on the cover sheet over the 
photosensitive photopolymer layer laminated on the white bond paper. The 
electrostatic toned image on the cover sheet served as a photomask for a 
30 unit exposure of the photopolymer film in a 2KW Berkey-Ascor vacuum 
printer. The cover sheet with the electrostatic photomask was removed and 
Cromalin.RTM. magenta toner 50PM was applied to the photopolymer layer on 
the paper. The excess toner was removed. A negative image was obtained on 
the paper support. Similar results were also obtained with cyan and black 
toners. 
FNT (1) Trademark of E. I. du Pont de Nemours and Company, Wilmington, DE for 
color display films. 
FNT (2) Tradename of Eastman Kodak Co., Rochester, NY for electrostatic copying 
apparatus. 
EXAMPLE 6 
The procedure of Example 5 was repeated except that instead of white bond 
paper, a clear transparency film made for the Kodak Ektoprint.RTM. by 
Imaging Products 12696 Rockhaven Road, Cleveland, Ohio 44026 was used. A 5 
unit exposure was given prior to removing the cover sheet with the 
electrostatic toner photomask. Toning with a cyan toner and removing the 
excess toner produced a satisfactory transparency image. Both the 
electrostatic image on the cover sheet and the toned photopolymer image on 
the transparent film provided useful transparent images.