CA1091969A - Photosensitive unilayer film structure cast from a polymeric emulsion dispersion - Google Patents
Photosensitive unilayer film structure cast from a polymeric emulsion dispersionInfo
- Publication number
- CA1091969A CA1091969A CA249,489A CA249489A CA1091969A CA 1091969 A CA1091969 A CA 1091969A CA 249489 A CA249489 A CA 249489A CA 1091969 A CA1091969 A CA 1091969A
- Authority
- CA
- Canada
- Prior art keywords
- photosensitive
- film structure
- phase
- phase material
- film
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/004—Photosensitive materials
- G03F7/04—Chromates
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/004—Photosensitive materials
- G03F7/016—Diazonium salts or compounds
- G03F7/021—Macromolecular diazonium compounds; Macromolecular additives, e.g. binders
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/004—Photosensitive materials
- G03F7/038—Macromolecular compounds which are rendered insoluble or differentially wettable
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/004—Photosensitive materials
- G03F7/06—Silver salts
Abstract
ABSTRACT OF THE DISCLOSURE
A novel photosensitive film structure comprises a generally continuous first or minor phase material and a generally discontinuous second or major phase material. The first or minor phase includes a photosensitive compound whose solubility relative to a selected solvent changes upon exposure to electromagnetic radiation, while the second or major phase is not photosensitive nor soluble in the solvent. The two phases are uniformly interdispersed throughout the film structure.
Imagewise exposure to electromagnetic radiation renders the film structure selectively permeable to the selected solvent, and, after development, the film structure exhibits the chemical and physical properties of the second or major phase material. The film structure finds varied application in the manufacture of graphic arts articles such as lithographic printing plates and photoresists.
A novel photosensitive film structure comprises a generally continuous first or minor phase material and a generally discontinuous second or major phase material. The first or minor phase includes a photosensitive compound whose solubility relative to a selected solvent changes upon exposure to electromagnetic radiation, while the second or major phase is not photosensitive nor soluble in the solvent. The two phases are uniformly interdispersed throughout the film structure.
Imagewise exposure to electromagnetic radiation renders the film structure selectively permeable to the selected solvent, and, after development, the film structure exhibits the chemical and physical properties of the second or major phase material. The film structure finds varied application in the manufacture of graphic arts articles such as lithographic printing plates and photoresists.
Description
PHOTOSENSITIVE llNILAYER FILM ST~UCTtTRE C~\~T FROM ~'\ rOL~
EMULSION DISPERSION
-BACKGROUND OF THE INVENTION
The present invention relates generally to photo-sensitive structures and more particular:ly to a photosensitive, unilayer, film structure suitable for use in the manufacture of water-processable printing plates and other graphic arts elements.
Many different photosensitive systems are well-krlown in the art for the manufacture and preparation of lithoqraphi.c plates.
Diazo compounds are, of course, frequently used as the photosensitive component in such systems. The diazo compounds can be formulated to possess several assets which make them desirable for use in this field, including low-cost, long shelf-like, water solubility, and good photosensitivity. However, the ink receptivity of diazo compounds is seriously reduced when they are contacted by water and the inherent durability of diazo resins is relatively low. Accordingly, approaches to the manufacture and preparation of printing plates utilizing diazo compounds have sought to overcome this problem by using lacquer-based developers, or overcoating the diazo with an ultra-violet transmitting lacquer or other material. These approaches, while enjoying some success, result in the loss of the simple water processing of the diazo compound plates and in some instances have required increased exposure times. Moreover, cliazo compounds lack sufficient bond strengths to smoother substrates and therefore it has been necessary to provide grained substrate surfaces to increase the mechanical bonding oE these photosensitive coatings, in order to achieve useful lengths of press runs.
.~ .
Another popular photosensitive system employs photopolymers which have both high ink receptivity and durability. These systems however, generally require special solvents to develop the plate, thereby increasing system complexity compared to simple water processing and, in addition, presentlng undesirable ecological waste problems.
SUMMARY OF THE INVENTION
In an attempt to overcome the problems and ex-tend the performance features of prior art pho-tosensitive systems used in the preparation oE printing plates and other graphic arts articles, a new photosensitive film structure has beell discovered which provides a highly desirable combination oE
properties in the various articles in which it finds application.
Accordlngly, the present invention is direc-ted to a unilayer film structure which includes a generally continuous first or minor phase dispersed within a generally discontinuous second or major phase. The :Eirst or minor phase comprises a photosensitive material which changes solubility relative to a selected solvent upon exposure to light, while the second or major phase comprises a particulate material which is not photosensitive and not soluble in the solvent.
More particularly the invention comprehends a photosensitive unilayer film structure cas-t from a polymeric emulsion dispersion comprising a generally continuous first phase material dispersed with a generally discontinuous second
EMULSION DISPERSION
-BACKGROUND OF THE INVENTION
The present invention relates generally to photo-sensitive structures and more particular:ly to a photosensitive, unilayer, film structure suitable for use in the manufacture of water-processable printing plates and other graphic arts elements.
Many different photosensitive systems are well-krlown in the art for the manufacture and preparation of lithoqraphi.c plates.
Diazo compounds are, of course, frequently used as the photosensitive component in such systems. The diazo compounds can be formulated to possess several assets which make them desirable for use in this field, including low-cost, long shelf-like, water solubility, and good photosensitivity. However, the ink receptivity of diazo compounds is seriously reduced when they are contacted by water and the inherent durability of diazo resins is relatively low. Accordingly, approaches to the manufacture and preparation of printing plates utilizing diazo compounds have sought to overcome this problem by using lacquer-based developers, or overcoating the diazo with an ultra-violet transmitting lacquer or other material. These approaches, while enjoying some success, result in the loss of the simple water processing of the diazo compound plates and in some instances have required increased exposure times. Moreover, cliazo compounds lack sufficient bond strengths to smoother substrates and therefore it has been necessary to provide grained substrate surfaces to increase the mechanical bonding oE these photosensitive coatings, in order to achieve useful lengths of press runs.
.~ .
Another popular photosensitive system employs photopolymers which have both high ink receptivity and durability. These systems however, generally require special solvents to develop the plate, thereby increasing system complexity compared to simple water processing and, in addition, presentlng undesirable ecological waste problems.
SUMMARY OF THE INVENTION
In an attempt to overcome the problems and ex-tend the performance features of prior art pho-tosensitive systems used in the preparation oE printing plates and other graphic arts articles, a new photosensitive film structure has beell discovered which provides a highly desirable combination oE
properties in the various articles in which it finds application.
Accordlngly, the present invention is direc-ted to a unilayer film structure which includes a generally continuous first or minor phase dispersed within a generally discontinuous second or major phase. The :Eirst or minor phase comprises a photosensitive material which changes solubility relative to a selected solvent upon exposure to light, while the second or major phase comprises a particulate material which is not photosensitive and not soluble in the solvent.
More particularly the invention comprehends a photosensitive unilayer film structure cas-t from a polymeric emulsion dispersion comprising a generally continuous first phase material dispersed with a generally discontinuous second
-2~
9~9 phase material. The first phase is a minor constituent by weight of the structure and is composed o:E a photosensitive material whose solubility with respect to a given solvent is changed upon exposure to electromagnetic :radiation. The second : phase is a major constituent by weight of the structure and is composed oE a material which is substantially insoluble in the solvent. The first phase material is a photosensitive material of the group consisting of aromatic diazo compounds, photopolymers, light sensitive dyestuffs, azo compounds, dichromates and silver halide gelatin systems, and the second phase material is a member of the group consisting of polyacrylics, copolymers oE ace-tate and ethylene, copolymers oE
styrene and acrylates, polyvinyl aceta-tes and copolymers of vinyl acetate and acrylates. The terms "generally continuous"
and "generally discontinuous" as used herein refer to the overall character of the minor and.major phases, respectively.
Thus, while the minor phase may have random and remote discontinuities, it will, over the film structure as a whole, comprise a continuous unbroken material. Similarly, the major phase may have a few particles joined to adjacent particl.es, yet over the film structure as a whole the major phase will comprise discrete particles separated by the minor phase.
It has been found that such a film structure may be made selectively permeable through imagewise exposure to light and ~D 3 ~LQ~ 9 thereafter used in a variety of graphic arts applications wherein selective permeability to fluids is necessary or desirable.
Therefore, various objects of the present invention include providing a unique photosensitive film structure which may be made selectively permeable to fluids upon exposure to light; one wherein the photosensitive phase cons-titutes a minor fraction of the film's mass and volume, thereby offering considerable performance latitude and improvement, and cost reductions as well and one which may be developed by water subse~uent to imagewise exposure to ligl~t, withou~ tl~e use o~
the organic or inorganic solvents. The film is su:itable ~or use in the manufacture and provision of lithographic or offset printiny plates in which the ink receptivity and durability of the imaging areas are relatively independent of the exposure techni~ue and the development compositions used in making the finished plate.
Other objects of the invention are -to provide a unique photoresist material and to provide a photosensitive film structure having a high bond s-trength to a variety of surfaces.
A BRIEF DESCRIPTION OF THE DRAWINGS
The novel features which are believed to be characteristic of the present invention are set forth in the appended claims. The invention itself, however, together with L9~i9 forthcoming objects and attendant advantages will be best understood by referring to the following description taken in connection with the accompanying drawings in which FIGURES 1, 2 and 3 are enlarged cross-sectional schematic views, each illustrating an emhodiment of the film structure of the present invention. It should be noted, however, that these schematic representations only serve to illustrate the structure and mechanism of the present invention and are not intended to limit - the scope thereof.
The photosensitive unilayer film composition of the present invention comprises a first (minor) phase material dispersed within a second (major) phase material.
The first or minor phase is photosensitive, generally continuous throughout the structure and capable of changing solubility with respect to a given solvent. The second or major phase comprises discontinuous (discrete particular) material which is not photosensitive and chosen to be relatively insoluble in the solvent for the minor phase. Thus, -the "two phase" concept of the present invention relates to the physical structure of the phases, one being continuous and the other being discontinuous and the solubility of the phases, Olle heillg selectively soluble in a given solvent of the imagewise exposure to light while the other phase is insoluble in the solvent irrespective of light exposure. The photosensitive unilayer film structure of the present invention may be best dcscribed as a lattice cast from an emulsion-dispersion. Several lattices formed from these emulsion-dispersions have been identified, each of which offers various performance features.
6~
One of the lattices which embodies the concepts of the present invention is illustrated schematically in FIGURE 1.
This lattice is cast from a dispersion of substantially monodimensional coa-ted spheres and is shown as it might typically be utilized, as a coating on a suitable substrate.
Thus, in this system the generally continuous photosensitive minor phase cons~itutes a coating for the generally discontinuous major phase material.
The minor phase material chosen to wet and coat the major phase particles is soluble in the selected solvent whereas the major phase is insoluble in this solvent. After actinic exposure, however, the minor phase is, Eor example, rendered insoluble. Thus, after imagewise exposure of the photosensitive structure and upon application of the selected solvent thereto, the unexposed areas of the lattice may be wetted and permeated by the solvent due to the con-tinuing solubility of the minor phase coating in those areas. Significantly, ~liS permeatioll of the lattice permits the physical removal of bo-th the first and second phase materials from the substrate by mechanical techniques such as wiping, brushing, or the like.
The wettability and spreading characteristics oE the substrate with water and the capillary pressures at the lattice/
substrate interface are believed to assist in this "development"
process and may thereby offer additional system control.
Another lattice embodying the concepts of the present invention is illustrated schematically in FIGURE 2.
In this lattice system the interstices of the discontlnuous major phase material, or void space, is filled with the continuous minor phase pho-tosensitive material. The ~r -96~
close packing of the spherical major phase particles as shown in FIGURE 2, results in a void volume of approximately 25% when the spheres are of substantially uniform size. This theoretical void space is independent of actual sphere size so long as uniformity of sphere size is main~ained. In accordance with this la-ttice structure, the interstices between the major phase particles may be filled with a variety of photosensitive materials, such as silver-halide/gelatin, dichromated colloids, photopolymers, diazo-colloid systems and the like.
Using this lattice system, imagewise exposure produces in the exposed areas an effective bonding medium for the major phase material, whereas unexposed areas remain water soluble and, therefore, accommodate the desired solvent permeation and subsequent development.
Still another lattice useful in -the practice of the present invention is illustrated in FIGURE 3. The la-ttice again includes a generally continuous photosensitive minor phase material as disclosed for the previously mentioned systems interdispersed with a generally discontinuous major phase comprising polydimensional spheres.
As noted above, a matrix of monodimensional spheres will have a void space of approximately 25%. The use of polydimensional spheres results in a reduction of this void space, thereby enabling the use of smaller quantities of the minor phase material in the manufacture of photo-sensitive structures. This, of course, may be highly 6~
desirable in terms of lower costs and in permitting the physical and chemical characteristics of the major phase to dominate to an even greater extent the properties of the entire film structure.
The photosensitive materials useful as the minor phase in the practice of the instant invention include any photosensitive compound wherein exposure to electromagnetic radiation creates a change in solubility characteristics in a selected solvent.
Photosensitive compounds which may be used in the present invention include aromatic diazo compounds, light sensitive dyestuffs, azo compounds, dichromates, photopolymers, and silver halide gelatin systems. Further useful minor phase materials may be found in the disclosures of U.S. patents Nos.
2,063,631 and 2,679,478 and in Light Sensitive SYstems authored by J. Kosar and published by John Wiley & Sons (1965).
Particularly preferred minor phase materials include condensation products of carbonyl compounds, such as formaldehyde or paraformaldehyde, and a diazo compound such as 4-diazo-1, l'-diphenylamine. Such condensation products are available under the trade names DiazoT~ No. 4 and Diazo No.
~L from the Fairmont Chemical Co., Newark, New Jersey.
The major phase of the film structures of the present invention may be chosen to tailor F ~D
~IL43~9~9 the physical and chemical properties of the final produc-t for a given application. These properties include, among others:
durability or physical toughness, the ability to adhere to substrates, water repellency (and therefore ink receptivity), permeability, solvent resistance, particle size, viscosity, solids content, heat sealing characteristics, film forming characteristics and molecular weight.
Some of the homopolymers and copolymers, in emulsion-dispersion form, which are suitable for use as the major phase of the present invention include, amonr~] others: aclyllcs, copolymers of acetate and ethylene, copolymers of s-tyrene and acrylates, polyvinyl acetates, and copolymers of vinyl acetate and acrylates. Each of these may be used with or without protective colloids, wetting agents, plasticizers and o-ther modifying agents.
In accordance with one preferred embodiment of the present invention the photosensitive film structure may be formed by casting, either as a self-supporting film or onto a suitable substrate, an emulsion containing water, a suitable diazo compound, and a PVA-acrylate emulsion. Upon drying, the resulting film structure comprises a con-tinuous diazo compound minor phase which coats the discontinuous PVA-acrylate major phase spheres and/or fills -the interstices thereof. This major phase material is known to form a water insoluble film which is non-emulsifiable whereas the diazo compounds only become water insoluble upon exposure to light.
, .~
g_ ~a~ 69 A most important application of the present invention is in the field of lithoyraphic offset printing. Offset printing plates can be prepared usinq a hydrophylic subs-trate such as silicated aluminum and the like with the composition of the present invention molded or cast as a film on its surface. The aforementioned copolymer of vinyl acetate and a long chain acrylate provides a flexible, non re-emulsifiable film with high water repellency.
Surprisingly, the addition of the diazo resin with this major phase material results in the ability to wash th:in layers of the film structure from the substrate subsequent to imagewise exposure to light. Those areas of the film which have been exposed to light are not removed Erom the subs-trate during the water wash/scrub processl whereas those portions of the film which are not exposed to light may be removed.
Moreover/ the light exposed areas exhibit desirable ink receptive properties and efficient bonding even to non-porous surfaces such as silicated, ungrained aluminum.
It is believed that the film structures of the presen-t invention are rendered selectively permeable -to a given solvent upon imagewise exposure to light due to the unique physical arran~ement of the minor and major phases. Thus, in the case of a diazo-PV~/acrylate composition, upon exposure -to a light image the diazo will become insoluble in those portions of the film exposed to light thereby making the entire film in those portions impermeable to water. On the other hand, the h ~ ^
9~9 diazo in those portions oE the film not exposed to light will remain water soluble thereby permitting water to permeate the film structure. The permeation of water may create hiqh interllal stresses permitting a film splitting failure or it may simply provide access to the substrate promoting adhesive failure.
Thus, the photosensitive film structure of the present invention discussed herein is made selectively permeable to water through exposure to a light image.
When such a photosensitive film structure as described herein is utilized with a hydrophylic substrate in the manufacture of lithographic printing plates, those portions of the structure not exposed to light are easily removed durin~ the water development step. It is believed that the water insoluble major phase is capable of removal Erom the subs-tra-te due partly to the action oE water at the film substrate interface, as previously stated, which water has reached this interface due to the permeability of the non-exposed portions of the film. Since the PVA-acrylate copolymer major phase is hydrophobic (and oleophilic), the photosensitive film structures of the present invention are ideally suited for use in lithographic offset printing processes. Moreover, since these major phase material is not light sensitive and are not affected by the light exposure and developing processes, i~ may be selected largly for the purpose of optimizing the ink receptivity, durability, and bonding properties of the resulting plates~
It will be appreciated from the foregoing that films made in accord with the present invention, because of their two phase structure, may be compounded from a wide variety of materials to optimize both developmel)t and performallcc characteristics. The photosensitive phase, being a relatively minor constituent, does not interfere wi-th the performance characteristics of the film and may be chosen largly for desirable development properties; while the major phase may be chosen to optimize the film's physical and chemical properties 3LIQ~969 such as durability for a given application without regard to development. In addition, since the photosensitve phase is a minor constituent, the particles of the ma~or phase material will be ciosely packed in the film structure, as illustrated schematically in the drawings. Thus, the particles of the major phase are sufficiently proximate to one another to permit their coalescence by means of heat of chemical treatment after the film has been developed. Such post development coalescence has been found to significantly enhance the performance of lithographic printlng plates made in accord with the present invention.
By proper choice of the major phase material, thickness and substrate, it is possible to create both hydrophobic and hydrophilic characteristics in the film itself, which are relatively independent of those of the substrate. In such cases, after imagewise exposure, the photosensitive minor phase of the film retains its solubility in the unexposed areas such that a porous surface can be obtained by leaching with the selected solvent. sy developing the film withou-t scrubbing or brushing, the major phase material retains substantial structural continuity over the substrate. Thus, the unexposed, porous areas thereof may thereafter be mechanically wetted with water, whereas the exposed areas are non-porous and exhibi-t hydrophobic characteristics. This "wet-tability" di~ferential over the surface of the film has been found suitable for lithographic printing and thereby frees the manufacturer to choose any low cost substrate material for use therein.
The utilization of the improved photosensitive, unilayer film structures of the present invention has been illustrated above in the context of the manufacture and preparation of lithographic offset printing plates. It is to be understood, however, that the scope of the present invention is not intended to be so limited. The pho-tosensi-tive film structures of the presen-t invention may be utilized in other applications wherein selective permeability to a given fluld or solvent is desirable. For example, the photosensitive film structures of the present invention may be cast as a self-supporting film and subse~uen-t]y exposed to a light image and developed without destroying the structural integrity of the ma-trix. In this manner, a skeletal template is obtained which is selectively permeable to certain fluids. Such a template may then be used for any number of diverse purposes such as the ap-plication of designs, patterns, or images, on an underlying sur-face by means of inks or the like wllicll are cap.~le o E perlllc-ating the template.
For example, numerous photoresist applications may also be practicable with the photosensitive structures of the :Lnstant invention. Of course, the major phase material may be chosen and tailored to the appropriate environment. Thus, resistance to certain acids or bases or a necessary dielectric constant for plating resist applications wlll point those skilled ln the art to the selection of a particular major phase material. Once chosen a compatible photosensitive phase may be added and the desired performance obtained.
It will be appreciated that development ease for -the photo-sensitive structures of the present invention is proportionally related to the concentration of the minor phase material; -that is, easier development occurs at higher minor phase concentra-tion. On the other hand, it is often preEerable to minimize the concentration oE the minor phase, since the major phase material provides the improved durability, bonding properties and print-ing characteristics which form an important part of the present invention. Accordingly, the relative amounts of the first and second phase materials utilized will depend upon the properties sought to be obtained in the given photosensitve structure. By way of illustration, however, the amount of minor phase diazo material utilized in Example III set forth in detail below may range from 0.03 to 10 weight percent without signiEicantly affecting the final product. Similarly by way oE further 6~
illustra-tion of the amount of minor ph~se in the diazo/polyvinyl acetate system utilized in Example IV (which allows ~or post development coalescence of the major phase by heat of chemical treatment to provide for greater durability), the minor phase preferably constitutes less than about 10 percent, by weight of the film and most preferably between about 2 and 6 percent, by weight, of the film. Although such quantitative analyses are dependent upon the size of the particulate material comprising the major phase, it will nevertheless be appreciated by tllose skilled in the art that the quantity of minor phase material is preferably sufficiently small to allow post development coalescence of the major phase. Otherwise, the physical and chemical properties of the major phase would not dominate the film structures characteristics.
The thickness of the photosensitive Eilm compositioll also affects the developmen-t of the pho-tosensi-tive structure, since the solvent must permeate a greater distance to reach the substrate when thicker films are employed. Photosensitive films having a thickness from about 0.5 to 25 microns have been found generally suitable. However, the particle size of the major phase material and the type of lattice structure employed may influence the ap~ropriate thickness limits Eor a give application.
The pho-tosensitive film struc-tures of the present invention also exhibit improved light sensitivity as compared to many prior art systems. For example, the photosensitive printing plates described herein may be "activated" by actinic exposure about 3 - 5 times faster than conventional wipe-on diazo plates.
This improved photosensitive responsiveness oEfers further advantages. For example, since development efficacy is influenced significantly by the wettability and pe~leabili-ty of the surface of -the film, a brief actinic exposure which acts --l'i--~La5~69 only at the surface or near-surface levels has proven efEective in permittlng selective permeation and development. Such a brief exposure technique may be preferred particularly in those instances where heat is used subsequent to development since in such cases the finished structure's ink receptivity and durability bear no relationship to exposure.
The following examples, while not intended to be taken as limiting the scope of the present invention, will serve to illustrate the process and compositions for making the photosensitive structures of the present invention.
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EXAMPLE I
100 ml of Rhoplex AC-388 (an acrylic emulsion vehicle available from Rohm & Haas, Philadelphia, Pa.), 10 ml oE wa-ter, and 2 grams of Diazo 4L are hlended for about 5 minutes or until well mixed. This admixture is then used to charge a roller-coater and applied to a brush grained alwninum substrate -to form a dry film having a thickness of about 5 microns. Air drying occurs in about 2 minutes. The sensitized pla-te is then placed in vacuum contact with a film negative and exposed for 15 seconds to the output of a 2 KW Xenon source. After exposure the plate is developed with ordinary tap water and gummed. The plate is then mounted on an offset press using conventional fountain solutions and inks. Up to 80,000 high quality copies are obtained with minimal image deterioration.
EXAMPLE II
100 ml of Elvace 1875 (a water based ace-ta-te/e-thylene copolymer emulsion available from DuPon-t, Wilmington, Del.), 5 ml of water, and 1 gram of Diazo (a light sensitive material available from Graf-Com Co., Easton, Maryland) are blended until well-mixed or about 2 minutes in a conventional stir-mixer.
This admixture is then wiped onto a brush grained aluminum substrate and dried to a film -thickness of about 2 microns. Air ~3~6~
drying occurs in about 1 minute. The sensitized p:late is then - placed in vacuum contact with a film negative and exposed for about 30 seconds to the output of a 2 KW Xenon source. Af-ter exposure the plate is developed wi-th tap water and gummed conventionally. The plate is then mounted on an offset press (e.g., 1250 Addressograph/Multigraph) and printed using a conventional alkaline fountain solution and an ink. Several thousand copies were obtained.
EXAMPLE III
100 ml of GelvaT TS 100 (a water based polyvin~ cet.llo,~lo~
chain acrylate copolymer emulsion available from Monsanto Corp., Newport Beach, Cal.), lO ml of water, and 4 grams of Diazo ~L
are blended until well mixed. This admixture is applied to an ungrained silicated aluminum substrate and dried to a thickness of about 5 microns. Air drying occurs in about 2 minu-tes. The sensitized plate is then placed in vacuum contact wi-th a film negative and exposed for 5 seconds to the output oE a 3 liW
Mercury Vapor source. Af-ter exposure the plate is developed with ordinary tap water. Af-ter developmen-t -the plate is mounted onto an offset press and printed using conventional press materials. Six thousand high quality copies were obtained with no apparent image wear.
EXAMPLE IV
100 ml oE Gelva TS 30 and 100 ml of Gelva S 52 (both water based polyvinyl ace-tate emulsions available from ~lonsanto ~orp., Newport Beach, Cal.) and 2 grams of Diazo are blended for about 2 minutes. This admixture is applied to a brush grained aluminum substrate and dried to a film thickness of about 10 microns. Two sensi-tized pla-tes made as disclosed ahove are then placed in vacuum contact with a film negative and exposed for 60 seconds to the output of a 3 KW Xenon source. After exposure the plates are deveLoped with tap water and gummed. One plate is then placed in a convection oven set at 250F for 2 minutes.
Comparison testin~ reveals much greater durability and higher ink receptivity of the hea-ted sample. Both plates, however, provide high quality copies. About 50,000 copies were obtained with the unheated plate, and over 200,000 copies were obtained with the heated plate.
EXAMPLE V
100 ml of Gelva TS 100, 50 ml of wa-ter, and 1 clm cf Diazo 4L are blended until well mixed (abou-t 1 minu-te). This admix-ture is then applied to a telurium clad MYI.AR ~ substrate and dried to a film thickness of about 2 microns. Air drying occurs in about I minu-te. The sensitized plate is then placed in vacuum contac-t with a film negative and exposed for 10 seconds to the output of a 3 KW Mercury Vapor source. After exposure the pla-te is dip developed . . . ~
in an aqueous solution of NaOCL and NaOH ~ithout scrubbing or brushing. Inspection of the plate reveals that the tellurium has been etched by the solution in the unexposed areas and that the film coating of the plate is intact.
Thus, no removal occurred but rather only a selective permeation.
EXA~PLE VI
50 ml of Gelva TS 100, 50 ml of water, and 2 grams of Diazo are blended until well mixed (about 2 minutes in a stir-mixer). This admixture is then applied to a ball grained non-s~licated aluminum substrate and dried to a film thickness of about 2 microns. Air drying occurs in about 2 minutes. The sensitized plate is then placed in vacuum contact with a Eilm negative and expased for 30 seconds to the output of a 2 KW Xenon source. After exposure the plate is developed via simple tap water wetting and rinsing. No wiping is used and the coating remains intact.
The plate ls then tested for differential wetting and inking by wetting with a conventional fountain solution and inking with a cotton swab and ink. Selective imagewise inking is observed and confirms the fact that the unexposed areas are rendered water wettable due to the leached diazo and resulting porosity.
EXAMPLE VII
50 ml of TS 30 and 50 ml oE TS 98 (both polyvinyl acetate, water based emulsions from Monsanto Corp., Newport Beach, Cal.) and 2 grams Diazo 4L are blended until well mixed (about 2 minutes in a conventional stir-mixer). This admixture is then, applied to a shallow grained and a deep grained aluminum substrate. The films are dried in air in about 3 minutes to a thickness of about 8 microns. The sensitized plates are then placed in vacuum contact with a film negative and ~xposed for 90 seconds to the output of a 3 KW Xenon source. After exposure the plates are developed using tap water and gentle scrubbing and then gummed. Both plates are subjected to a heat treatment at 250F for 2 minutes and then mounted on a commercial web lithographic press. No signs of image wear are observed after printing over 150,000 impressions on either the shallow grain plate or the deeper grained plate.
'~
6~
It should be understood -that various changes and modifications of the invention as described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its attendant advantages. For example, many variatio.ns of the lattice designs described herein above are possible when viewed within the spirit and scope of this invention. In addition, passive fill materials may be used to improve shelf life to enhance color or to provide special photo, magnetic or electrical prope:rties. It is therefore intended that such changes and modifications be covered by the following claims:
~D -21-SUPPLEMENTARY DISCl:.OSUl~
It has been previously noted that the thickness oE the photosensitive film composition also affects development of the photosensitive structure, since the solvent must permeate a greater distance to reach the substrate when thicker films are employed. Moreover, the particle size of the major phase material influences the development rate, since for a given film thickness smaller major phase particles result in a more tortuous or circuitous development path as the minor phase solvent per-meates to the substrate. Accordingly, a :Eilm thickness less thanabout 10 times the average diameter of the major phase particles is preferred in the practice of the present invention since dev-elopment time otherwise becomes excessive. Preferably, the film thickness is less than about five times the average diameter of the ma~or phase particles. By way of example, many of the major phase materials listed in the principal disclosure and herein are composed of particles with average diameters in the range of 0.5 to 3.0 microns. For film structures using such major phase materials, a maximum film thickness less than about 10 microns is preferred. The verv thin photosensi-tive film structures minimize the cost of expensive compound used in the formation of these structures. Nevertheless, these thin film structures are surprisingly durable and resistant to abrasion due -to the fact that major phase materials may be employed -to optimize these properties.
As noted in the originally framed disclosure, the photo-sensitive film structure of the invention also exhibit improved light sensitivity compared to many prior art systems. Since relat-ively thin films are employed, enhanced image quali-ty and resolu-t-ion are obtained in producing lithographic printing plates.
The following additional examples of exemplary embodimentsof the invention, while not intended to limi-t the scope of the invention, will serve to illus-trate further the process for making the photoscnsitive filn~ str~lcture of the illVelltiOIl.
L96~
Example Emulsion-Dispersion Photosensitive Material VIII 100 parts by weight 0.5 parts by weight Gelva TS65 (water based Anthraquinone B-Sulfonic polyvinyl acetate available Acid Sodium Salt (AQS) from Monsanto Corp.) IX Same 0.6 parts by weight AQS + Ferric Ammonium Citrate 10 X Same 0.6 parts by weight AQS ~ P-Toluene Sulfonic Acid XI Same 0.6 parts by weight AQS + Acryl Phosphate XII Same 0.6 parts by weight AQS ~ 4, 4'-Diazide Stilbene 2, 2'-Disulfonic Acid, Sodium Salt Each of these formulations was blended until wel] mixed and then whirl coated onto a grained aluminum substrate and dried at 45C for about five minutes. The samples were then exposed from about 15 to 40 seconds at 15cm to the radiation from a 450 watt chemical lamp. After exposure, each sample was developed in tap water at 15-20C for a few seconds with light mechanical action (rubbing). The resulting lithographic plates were then inked and found to provide quality lithographic performance.
EXAMPLE XIII
150 ml of Polyco 218~ (a water based polyvinyl acetate co-polymer emulsion having a solids concentration of 50% and marketed by the Borden Chemical Co.), 35 ml of water and 8 grams of (NH4)2 Cr2 O7 are blended until well mixed and hand coated using a conventional draw bar technique onto an aluminum substrate. The cast emulsion was dried with forced air flow at room temperature for about 30 seconds, exposed to a 3KWA~I mercury vapor source for 10 seconds and then developed 96~33 with tap water at room temperature. The resulting lithographic plate provided excellent lithographic performance.
EXAMPLE XIV
50 parts by weight Gelva TS 65 (see Examples VIII-XII) and 1 part by weight of a mixture of 100 parts water and 1 part photopolymer (disclosed in United States Patent No.
9~9 phase material. The first phase is a minor constituent by weight of the structure and is composed o:E a photosensitive material whose solubility with respect to a given solvent is changed upon exposure to electromagnetic :radiation. The second : phase is a major constituent by weight of the structure and is composed oE a material which is substantially insoluble in the solvent. The first phase material is a photosensitive material of the group consisting of aromatic diazo compounds, photopolymers, light sensitive dyestuffs, azo compounds, dichromates and silver halide gelatin systems, and the second phase material is a member of the group consisting of polyacrylics, copolymers oE ace-tate and ethylene, copolymers oE
styrene and acrylates, polyvinyl aceta-tes and copolymers of vinyl acetate and acrylates. The terms "generally continuous"
and "generally discontinuous" as used herein refer to the overall character of the minor and.major phases, respectively.
Thus, while the minor phase may have random and remote discontinuities, it will, over the film structure as a whole, comprise a continuous unbroken material. Similarly, the major phase may have a few particles joined to adjacent particl.es, yet over the film structure as a whole the major phase will comprise discrete particles separated by the minor phase.
It has been found that such a film structure may be made selectively permeable through imagewise exposure to light and ~D 3 ~LQ~ 9 thereafter used in a variety of graphic arts applications wherein selective permeability to fluids is necessary or desirable.
Therefore, various objects of the present invention include providing a unique photosensitive film structure which may be made selectively permeable to fluids upon exposure to light; one wherein the photosensitive phase cons-titutes a minor fraction of the film's mass and volume, thereby offering considerable performance latitude and improvement, and cost reductions as well and one which may be developed by water subse~uent to imagewise exposure to ligl~t, withou~ tl~e use o~
the organic or inorganic solvents. The film is su:itable ~or use in the manufacture and provision of lithographic or offset printiny plates in which the ink receptivity and durability of the imaging areas are relatively independent of the exposure techni~ue and the development compositions used in making the finished plate.
Other objects of the invention are -to provide a unique photoresist material and to provide a photosensitive film structure having a high bond s-trength to a variety of surfaces.
A BRIEF DESCRIPTION OF THE DRAWINGS
The novel features which are believed to be characteristic of the present invention are set forth in the appended claims. The invention itself, however, together with L9~i9 forthcoming objects and attendant advantages will be best understood by referring to the following description taken in connection with the accompanying drawings in which FIGURES 1, 2 and 3 are enlarged cross-sectional schematic views, each illustrating an emhodiment of the film structure of the present invention. It should be noted, however, that these schematic representations only serve to illustrate the structure and mechanism of the present invention and are not intended to limit - the scope thereof.
The photosensitive unilayer film composition of the present invention comprises a first (minor) phase material dispersed within a second (major) phase material.
The first or minor phase is photosensitive, generally continuous throughout the structure and capable of changing solubility with respect to a given solvent. The second or major phase comprises discontinuous (discrete particular) material which is not photosensitive and chosen to be relatively insoluble in the solvent for the minor phase. Thus, -the "two phase" concept of the present invention relates to the physical structure of the phases, one being continuous and the other being discontinuous and the solubility of the phases, Olle heillg selectively soluble in a given solvent of the imagewise exposure to light while the other phase is insoluble in the solvent irrespective of light exposure. The photosensitive unilayer film structure of the present invention may be best dcscribed as a lattice cast from an emulsion-dispersion. Several lattices formed from these emulsion-dispersions have been identified, each of which offers various performance features.
6~
One of the lattices which embodies the concepts of the present invention is illustrated schematically in FIGURE 1.
This lattice is cast from a dispersion of substantially monodimensional coa-ted spheres and is shown as it might typically be utilized, as a coating on a suitable substrate.
Thus, in this system the generally continuous photosensitive minor phase cons~itutes a coating for the generally discontinuous major phase material.
The minor phase material chosen to wet and coat the major phase particles is soluble in the selected solvent whereas the major phase is insoluble in this solvent. After actinic exposure, however, the minor phase is, Eor example, rendered insoluble. Thus, after imagewise exposure of the photosensitive structure and upon application of the selected solvent thereto, the unexposed areas of the lattice may be wetted and permeated by the solvent due to the con-tinuing solubility of the minor phase coating in those areas. Significantly, ~liS permeatioll of the lattice permits the physical removal of bo-th the first and second phase materials from the substrate by mechanical techniques such as wiping, brushing, or the like.
The wettability and spreading characteristics oE the substrate with water and the capillary pressures at the lattice/
substrate interface are believed to assist in this "development"
process and may thereby offer additional system control.
Another lattice embodying the concepts of the present invention is illustrated schematically in FIGURE 2.
In this lattice system the interstices of the discontlnuous major phase material, or void space, is filled with the continuous minor phase pho-tosensitive material. The ~r -96~
close packing of the spherical major phase particles as shown in FIGURE 2, results in a void volume of approximately 25% when the spheres are of substantially uniform size. This theoretical void space is independent of actual sphere size so long as uniformity of sphere size is main~ained. In accordance with this la-ttice structure, the interstices between the major phase particles may be filled with a variety of photosensitive materials, such as silver-halide/gelatin, dichromated colloids, photopolymers, diazo-colloid systems and the like.
Using this lattice system, imagewise exposure produces in the exposed areas an effective bonding medium for the major phase material, whereas unexposed areas remain water soluble and, therefore, accommodate the desired solvent permeation and subsequent development.
Still another lattice useful in -the practice of the present invention is illustrated in FIGURE 3. The la-ttice again includes a generally continuous photosensitive minor phase material as disclosed for the previously mentioned systems interdispersed with a generally discontinuous major phase comprising polydimensional spheres.
As noted above, a matrix of monodimensional spheres will have a void space of approximately 25%. The use of polydimensional spheres results in a reduction of this void space, thereby enabling the use of smaller quantities of the minor phase material in the manufacture of photo-sensitive structures. This, of course, may be highly 6~
desirable in terms of lower costs and in permitting the physical and chemical characteristics of the major phase to dominate to an even greater extent the properties of the entire film structure.
The photosensitive materials useful as the minor phase in the practice of the instant invention include any photosensitive compound wherein exposure to electromagnetic radiation creates a change in solubility characteristics in a selected solvent.
Photosensitive compounds which may be used in the present invention include aromatic diazo compounds, light sensitive dyestuffs, azo compounds, dichromates, photopolymers, and silver halide gelatin systems. Further useful minor phase materials may be found in the disclosures of U.S. patents Nos.
2,063,631 and 2,679,478 and in Light Sensitive SYstems authored by J. Kosar and published by John Wiley & Sons (1965).
Particularly preferred minor phase materials include condensation products of carbonyl compounds, such as formaldehyde or paraformaldehyde, and a diazo compound such as 4-diazo-1, l'-diphenylamine. Such condensation products are available under the trade names DiazoT~ No. 4 and Diazo No.
~L from the Fairmont Chemical Co., Newark, New Jersey.
The major phase of the film structures of the present invention may be chosen to tailor F ~D
~IL43~9~9 the physical and chemical properties of the final produc-t for a given application. These properties include, among others:
durability or physical toughness, the ability to adhere to substrates, water repellency (and therefore ink receptivity), permeability, solvent resistance, particle size, viscosity, solids content, heat sealing characteristics, film forming characteristics and molecular weight.
Some of the homopolymers and copolymers, in emulsion-dispersion form, which are suitable for use as the major phase of the present invention include, amonr~] others: aclyllcs, copolymers of acetate and ethylene, copolymers of s-tyrene and acrylates, polyvinyl acetates, and copolymers of vinyl acetate and acrylates. Each of these may be used with or without protective colloids, wetting agents, plasticizers and o-ther modifying agents.
In accordance with one preferred embodiment of the present invention the photosensitive film structure may be formed by casting, either as a self-supporting film or onto a suitable substrate, an emulsion containing water, a suitable diazo compound, and a PVA-acrylate emulsion. Upon drying, the resulting film structure comprises a con-tinuous diazo compound minor phase which coats the discontinuous PVA-acrylate major phase spheres and/or fills -the interstices thereof. This major phase material is known to form a water insoluble film which is non-emulsifiable whereas the diazo compounds only become water insoluble upon exposure to light.
, .~
g_ ~a~ 69 A most important application of the present invention is in the field of lithoyraphic offset printing. Offset printing plates can be prepared usinq a hydrophylic subs-trate such as silicated aluminum and the like with the composition of the present invention molded or cast as a film on its surface. The aforementioned copolymer of vinyl acetate and a long chain acrylate provides a flexible, non re-emulsifiable film with high water repellency.
Surprisingly, the addition of the diazo resin with this major phase material results in the ability to wash th:in layers of the film structure from the substrate subsequent to imagewise exposure to light. Those areas of the film which have been exposed to light are not removed Erom the subs-trate during the water wash/scrub processl whereas those portions of the film which are not exposed to light may be removed.
Moreover/ the light exposed areas exhibit desirable ink receptive properties and efficient bonding even to non-porous surfaces such as silicated, ungrained aluminum.
It is believed that the film structures of the presen-t invention are rendered selectively permeable -to a given solvent upon imagewise exposure to light due to the unique physical arran~ement of the minor and major phases. Thus, in the case of a diazo-PV~/acrylate composition, upon exposure -to a light image the diazo will become insoluble in those portions of the film exposed to light thereby making the entire film in those portions impermeable to water. On the other hand, the h ~ ^
9~9 diazo in those portions oE the film not exposed to light will remain water soluble thereby permitting water to permeate the film structure. The permeation of water may create hiqh interllal stresses permitting a film splitting failure or it may simply provide access to the substrate promoting adhesive failure.
Thus, the photosensitive film structure of the present invention discussed herein is made selectively permeable to water through exposure to a light image.
When such a photosensitive film structure as described herein is utilized with a hydrophylic substrate in the manufacture of lithographic printing plates, those portions of the structure not exposed to light are easily removed durin~ the water development step. It is believed that the water insoluble major phase is capable of removal Erom the subs-tra-te due partly to the action oE water at the film substrate interface, as previously stated, which water has reached this interface due to the permeability of the non-exposed portions of the film. Since the PVA-acrylate copolymer major phase is hydrophobic (and oleophilic), the photosensitive film structures of the present invention are ideally suited for use in lithographic offset printing processes. Moreover, since these major phase material is not light sensitive and are not affected by the light exposure and developing processes, i~ may be selected largly for the purpose of optimizing the ink receptivity, durability, and bonding properties of the resulting plates~
It will be appreciated from the foregoing that films made in accord with the present invention, because of their two phase structure, may be compounded from a wide variety of materials to optimize both developmel)t and performallcc characteristics. The photosensitive phase, being a relatively minor constituent, does not interfere wi-th the performance characteristics of the film and may be chosen largly for desirable development properties; while the major phase may be chosen to optimize the film's physical and chemical properties 3LIQ~969 such as durability for a given application without regard to development. In addition, since the photosensitve phase is a minor constituent, the particles of the ma~or phase material will be ciosely packed in the film structure, as illustrated schematically in the drawings. Thus, the particles of the major phase are sufficiently proximate to one another to permit their coalescence by means of heat of chemical treatment after the film has been developed. Such post development coalescence has been found to significantly enhance the performance of lithographic printlng plates made in accord with the present invention.
By proper choice of the major phase material, thickness and substrate, it is possible to create both hydrophobic and hydrophilic characteristics in the film itself, which are relatively independent of those of the substrate. In such cases, after imagewise exposure, the photosensitive minor phase of the film retains its solubility in the unexposed areas such that a porous surface can be obtained by leaching with the selected solvent. sy developing the film withou-t scrubbing or brushing, the major phase material retains substantial structural continuity over the substrate. Thus, the unexposed, porous areas thereof may thereafter be mechanically wetted with water, whereas the exposed areas are non-porous and exhibi-t hydrophobic characteristics. This "wet-tability" di~ferential over the surface of the film has been found suitable for lithographic printing and thereby frees the manufacturer to choose any low cost substrate material for use therein.
The utilization of the improved photosensitive, unilayer film structures of the present invention has been illustrated above in the context of the manufacture and preparation of lithographic offset printing plates. It is to be understood, however, that the scope of the present invention is not intended to be so limited. The pho-tosensi-tive film structures of the presen-t invention may be utilized in other applications wherein selective permeability to a given fluld or solvent is desirable. For example, the photosensitive film structures of the present invention may be cast as a self-supporting film and subse~uen-t]y exposed to a light image and developed without destroying the structural integrity of the ma-trix. In this manner, a skeletal template is obtained which is selectively permeable to certain fluids. Such a template may then be used for any number of diverse purposes such as the ap-plication of designs, patterns, or images, on an underlying sur-face by means of inks or the like wllicll are cap.~le o E perlllc-ating the template.
For example, numerous photoresist applications may also be practicable with the photosensitive structures of the :Lnstant invention. Of course, the major phase material may be chosen and tailored to the appropriate environment. Thus, resistance to certain acids or bases or a necessary dielectric constant for plating resist applications wlll point those skilled ln the art to the selection of a particular major phase material. Once chosen a compatible photosensitive phase may be added and the desired performance obtained.
It will be appreciated that development ease for -the photo-sensitive structures of the present invention is proportionally related to the concentration of the minor phase material; -that is, easier development occurs at higher minor phase concentra-tion. On the other hand, it is often preEerable to minimize the concentration oE the minor phase, since the major phase material provides the improved durability, bonding properties and print-ing characteristics which form an important part of the present invention. Accordingly, the relative amounts of the first and second phase materials utilized will depend upon the properties sought to be obtained in the given photosensitve structure. By way of illustration, however, the amount of minor phase diazo material utilized in Example III set forth in detail below may range from 0.03 to 10 weight percent without signiEicantly affecting the final product. Similarly by way oE further 6~
illustra-tion of the amount of minor ph~se in the diazo/polyvinyl acetate system utilized in Example IV (which allows ~or post development coalescence of the major phase by heat of chemical treatment to provide for greater durability), the minor phase preferably constitutes less than about 10 percent, by weight of the film and most preferably between about 2 and 6 percent, by weight, of the film. Although such quantitative analyses are dependent upon the size of the particulate material comprising the major phase, it will nevertheless be appreciated by tllose skilled in the art that the quantity of minor phase material is preferably sufficiently small to allow post development coalescence of the major phase. Otherwise, the physical and chemical properties of the major phase would not dominate the film structures characteristics.
The thickness of the photosensitive Eilm compositioll also affects the developmen-t of the pho-tosensi-tive structure, since the solvent must permeate a greater distance to reach the substrate when thicker films are employed. Photosensitive films having a thickness from about 0.5 to 25 microns have been found generally suitable. However, the particle size of the major phase material and the type of lattice structure employed may influence the ap~ropriate thickness limits Eor a give application.
The pho-tosensitive film struc-tures of the present invention also exhibit improved light sensitivity as compared to many prior art systems. For example, the photosensitive printing plates described herein may be "activated" by actinic exposure about 3 - 5 times faster than conventional wipe-on diazo plates.
This improved photosensitive responsiveness oEfers further advantages. For example, since development efficacy is influenced significantly by the wettability and pe~leabili-ty of the surface of -the film, a brief actinic exposure which acts --l'i--~La5~69 only at the surface or near-surface levels has proven efEective in permittlng selective permeation and development. Such a brief exposure technique may be preferred particularly in those instances where heat is used subsequent to development since in such cases the finished structure's ink receptivity and durability bear no relationship to exposure.
The following examples, while not intended to be taken as limiting the scope of the present invention, will serve to illustrate the process and compositions for making the photosensitive structures of the present invention.
6~
EXAMPLE I
100 ml of Rhoplex AC-388 (an acrylic emulsion vehicle available from Rohm & Haas, Philadelphia, Pa.), 10 ml oE wa-ter, and 2 grams of Diazo 4L are hlended for about 5 minutes or until well mixed. This admixture is then used to charge a roller-coater and applied to a brush grained alwninum substrate -to form a dry film having a thickness of about 5 microns. Air drying occurs in about 2 minutes. The sensitized pla-te is then placed in vacuum contact with a film negative and exposed for 15 seconds to the output of a 2 KW Xenon source. After exposure the plate is developed with ordinary tap water and gummed. The plate is then mounted on an offset press using conventional fountain solutions and inks. Up to 80,000 high quality copies are obtained with minimal image deterioration.
EXAMPLE II
100 ml of Elvace 1875 (a water based ace-ta-te/e-thylene copolymer emulsion available from DuPon-t, Wilmington, Del.), 5 ml of water, and 1 gram of Diazo (a light sensitive material available from Graf-Com Co., Easton, Maryland) are blended until well-mixed or about 2 minutes in a conventional stir-mixer.
This admixture is then wiped onto a brush grained aluminum substrate and dried to a film -thickness of about 2 microns. Air ~3~6~
drying occurs in about 1 minute. The sensitized p:late is then - placed in vacuum contact with a film negative and exposed for about 30 seconds to the output of a 2 KW Xenon source. Af-ter exposure the plate is developed wi-th tap water and gummed conventionally. The plate is then mounted on an offset press (e.g., 1250 Addressograph/Multigraph) and printed using a conventional alkaline fountain solution and an ink. Several thousand copies were obtained.
EXAMPLE III
100 ml of GelvaT TS 100 (a water based polyvin~ cet.llo,~lo~
chain acrylate copolymer emulsion available from Monsanto Corp., Newport Beach, Cal.), lO ml of water, and 4 grams of Diazo ~L
are blended until well mixed. This admixture is applied to an ungrained silicated aluminum substrate and dried to a thickness of about 5 microns. Air drying occurs in about 2 minu-tes. The sensitized plate is then placed in vacuum contact wi-th a film negative and exposed for 5 seconds to the output oE a 3 liW
Mercury Vapor source. Af-ter exposure the plate is developed with ordinary tap water. Af-ter developmen-t -the plate is mounted onto an offset press and printed using conventional press materials. Six thousand high quality copies were obtained with no apparent image wear.
EXAMPLE IV
100 ml oE Gelva TS 30 and 100 ml of Gelva S 52 (both water based polyvinyl ace-tate emulsions available from ~lonsanto ~orp., Newport Beach, Cal.) and 2 grams of Diazo are blended for about 2 minutes. This admixture is applied to a brush grained aluminum substrate and dried to a film thickness of about 10 microns. Two sensi-tized pla-tes made as disclosed ahove are then placed in vacuum contact with a film negative and exposed for 60 seconds to the output of a 3 KW Xenon source. After exposure the plates are deveLoped with tap water and gummed. One plate is then placed in a convection oven set at 250F for 2 minutes.
Comparison testin~ reveals much greater durability and higher ink receptivity of the hea-ted sample. Both plates, however, provide high quality copies. About 50,000 copies were obtained with the unheated plate, and over 200,000 copies were obtained with the heated plate.
EXAMPLE V
100 ml of Gelva TS 100, 50 ml of wa-ter, and 1 clm cf Diazo 4L are blended until well mixed (abou-t 1 minu-te). This admix-ture is then applied to a telurium clad MYI.AR ~ substrate and dried to a film thickness of about 2 microns. Air drying occurs in about I minu-te. The sensitized plate is then placed in vacuum contac-t with a film negative and exposed for 10 seconds to the output of a 3 KW Mercury Vapor source. After exposure the pla-te is dip developed . . . ~
in an aqueous solution of NaOCL and NaOH ~ithout scrubbing or brushing. Inspection of the plate reveals that the tellurium has been etched by the solution in the unexposed areas and that the film coating of the plate is intact.
Thus, no removal occurred but rather only a selective permeation.
EXA~PLE VI
50 ml of Gelva TS 100, 50 ml of water, and 2 grams of Diazo are blended until well mixed (about 2 minutes in a stir-mixer). This admixture is then applied to a ball grained non-s~licated aluminum substrate and dried to a film thickness of about 2 microns. Air drying occurs in about 2 minutes. The sensitized plate is then placed in vacuum contact with a Eilm negative and expased for 30 seconds to the output of a 2 KW Xenon source. After exposure the plate is developed via simple tap water wetting and rinsing. No wiping is used and the coating remains intact.
The plate ls then tested for differential wetting and inking by wetting with a conventional fountain solution and inking with a cotton swab and ink. Selective imagewise inking is observed and confirms the fact that the unexposed areas are rendered water wettable due to the leached diazo and resulting porosity.
EXAMPLE VII
50 ml of TS 30 and 50 ml oE TS 98 (both polyvinyl acetate, water based emulsions from Monsanto Corp., Newport Beach, Cal.) and 2 grams Diazo 4L are blended until well mixed (about 2 minutes in a conventional stir-mixer). This admixture is then, applied to a shallow grained and a deep grained aluminum substrate. The films are dried in air in about 3 minutes to a thickness of about 8 microns. The sensitized plates are then placed in vacuum contact with a film negative and ~xposed for 90 seconds to the output of a 3 KW Xenon source. After exposure the plates are developed using tap water and gentle scrubbing and then gummed. Both plates are subjected to a heat treatment at 250F for 2 minutes and then mounted on a commercial web lithographic press. No signs of image wear are observed after printing over 150,000 impressions on either the shallow grain plate or the deeper grained plate.
'~
6~
It should be understood -that various changes and modifications of the invention as described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its attendant advantages. For example, many variatio.ns of the lattice designs described herein above are possible when viewed within the spirit and scope of this invention. In addition, passive fill materials may be used to improve shelf life to enhance color or to provide special photo, magnetic or electrical prope:rties. It is therefore intended that such changes and modifications be covered by the following claims:
~D -21-SUPPLEMENTARY DISCl:.OSUl~
It has been previously noted that the thickness oE the photosensitive film composition also affects development of the photosensitive structure, since the solvent must permeate a greater distance to reach the substrate when thicker films are employed. Moreover, the particle size of the major phase material influences the development rate, since for a given film thickness smaller major phase particles result in a more tortuous or circuitous development path as the minor phase solvent per-meates to the substrate. Accordingly, a :Eilm thickness less thanabout 10 times the average diameter of the major phase particles is preferred in the practice of the present invention since dev-elopment time otherwise becomes excessive. Preferably, the film thickness is less than about five times the average diameter of the ma~or phase particles. By way of example, many of the major phase materials listed in the principal disclosure and herein are composed of particles with average diameters in the range of 0.5 to 3.0 microns. For film structures using such major phase materials, a maximum film thickness less than about 10 microns is preferred. The verv thin photosensi-tive film structures minimize the cost of expensive compound used in the formation of these structures. Nevertheless, these thin film structures are surprisingly durable and resistant to abrasion due -to the fact that major phase materials may be employed -to optimize these properties.
As noted in the originally framed disclosure, the photo-sensitive film structure of the invention also exhibit improved light sensitivity compared to many prior art systems. Since relat-ively thin films are employed, enhanced image quali-ty and resolu-t-ion are obtained in producing lithographic printing plates.
The following additional examples of exemplary embodimentsof the invention, while not intended to limi-t the scope of the invention, will serve to illus-trate further the process for making the photoscnsitive filn~ str~lcture of the illVelltiOIl.
L96~
Example Emulsion-Dispersion Photosensitive Material VIII 100 parts by weight 0.5 parts by weight Gelva TS65 (water based Anthraquinone B-Sulfonic polyvinyl acetate available Acid Sodium Salt (AQS) from Monsanto Corp.) IX Same 0.6 parts by weight AQS + Ferric Ammonium Citrate 10 X Same 0.6 parts by weight AQS ~ P-Toluene Sulfonic Acid XI Same 0.6 parts by weight AQS + Acryl Phosphate XII Same 0.6 parts by weight AQS ~ 4, 4'-Diazide Stilbene 2, 2'-Disulfonic Acid, Sodium Salt Each of these formulations was blended until wel] mixed and then whirl coated onto a grained aluminum substrate and dried at 45C for about five minutes. The samples were then exposed from about 15 to 40 seconds at 15cm to the radiation from a 450 watt chemical lamp. After exposure, each sample was developed in tap water at 15-20C for a few seconds with light mechanical action (rubbing). The resulting lithographic plates were then inked and found to provide quality lithographic performance.
EXAMPLE XIII
150 ml of Polyco 218~ (a water based polyvinyl acetate co-polymer emulsion having a solids concentration of 50% and marketed by the Borden Chemical Co.), 35 ml of water and 8 grams of (NH4)2 Cr2 O7 are blended until well mixed and hand coated using a conventional draw bar technique onto an aluminum substrate. The cast emulsion was dried with forced air flow at room temperature for about 30 seconds, exposed to a 3KWA~I mercury vapor source for 10 seconds and then developed 96~33 with tap water at room temperature. The resulting lithographic plate provided excellent lithographic performance.
EXAMPLE XIV
50 parts by weight Gelva TS 65 (see Examples VIII-XII) and 1 part by weight of a mixture of 100 parts water and 1 part photopolymer (disclosed in United States Patent No.
3,801,328 issued to Takimoto) are blended until well mixed and draw bar coated onto an aluminum substrate. The cast emulsion is dried by forced air flow at room temperature, exposed to a 3KW radiation source for 60 seconds and then water developed at room temperature. The resulting imaged plate provides excellent lithographic performance.
EXAMPLE XV
~ mixture (A) of Polyco 2186, carbon black, water and a surfactant was ball milled for 8 hours. To this was added a mixture (B) of a Polyco 2186, water and diazo 4L and milled for an additional 8 hours. The following proportions were used:
50 g Polyco 2186 9 g Carbon black Mix A
35 g H2O
3 g Surfactant 300 g Polyco 2186 Mix B
60 g H2O
10 g 4L
The resulting emulsion was cast on a synthetic paper (such as a polyethelene paper marketed under the trade name Kimdura by Kimberly-Clark), dried, exposed to a 2-5KW light source for 30 seconds and water developed. The dried article exhibited - good abrasion resistance and high contrast images useful for proofing purposes.
.
11;9 EXAMPLE XVI
A mixture of 9 grams Phthalocyanine Blue pigment, 80 ml of water and a surfactant was milled for 4 hours. 300 ml of 81 B
Cascokes (a water based polyvinyl acetate and acrylic copolymer emulsion marketed by the Bordon Co.) and 10 grams of Diazo ~L
were added, and the mixture milled an additional 2 hours. The resulting emulsion was cast on mylar, dried, light exposed and developed with water. The resulting transparent article exhibits high abrasion resistance and is useful as a color proof.
EXAMPLE XV
~ mixture (A) of Polyco 2186, carbon black, water and a surfactant was ball milled for 8 hours. To this was added a mixture (B) of a Polyco 2186, water and diazo 4L and milled for an additional 8 hours. The following proportions were used:
50 g Polyco 2186 9 g Carbon black Mix A
35 g H2O
3 g Surfactant 300 g Polyco 2186 Mix B
60 g H2O
10 g 4L
The resulting emulsion was cast on a synthetic paper (such as a polyethelene paper marketed under the trade name Kimdura by Kimberly-Clark), dried, exposed to a 2-5KW light source for 30 seconds and water developed. The dried article exhibited - good abrasion resistance and high contrast images useful for proofing purposes.
.
11;9 EXAMPLE XVI
A mixture of 9 grams Phthalocyanine Blue pigment, 80 ml of water and a surfactant was milled for 4 hours. 300 ml of 81 B
Cascokes (a water based polyvinyl acetate and acrylic copolymer emulsion marketed by the Bordon Co.) and 10 grams of Diazo ~L
were added, and the mixture milled an additional 2 hours. The resulting emulsion was cast on mylar, dried, light exposed and developed with water. The resulting transparent article exhibits high abrasion resistance and is useful as a color proof.
Claims (21)
1. A photosensitive unilayer film structure cast from a polymeric emulsion dispersion comprising a generally continuous first phase material dispersed with a generally discontinuous second phase material, said first phase being a minor constituent by weight of said structure and composed of a photosensitive material whose solubility with respect to a given solvent is changed upon exposure to electromagnetic radiation, and said second phase being a major constituent by weight of said structure and composed of a material which is substantially insoluble in said solvent, said first phase material being a photosensitive material of the group consisting of aromatic diazo compounds, photopolymers, light sensitive dyestuffs, azo compounds, dichromates and silver halide gelatin systems, said second phase material being a member of the group consisting of polyacrylics, copolymers of acetate and ethylene, copolymers of styrene and acrylates, polyvinyl acetates and copolymers of vinyl acetate and acrylates.
2. The photosensitive structure of Claim 1 wherein said first phase material is a condensation product of a carbonyl compound and a diazo compound.
3. The photosensitive structure of Claim 1 wherein said first phase material is a condensation product of a carbonyl compound and 4-diazo-1, 1'-diphenylamine.
4. The photosensitive structure of Claim 1 wherein said first phase is a water-soluble diazo compound which is rendered water insoluble upon actinic exposure and said second phase is cast from a water based polymeric emulsion-dispersion.
5. The photosensitive structure of Claim 4 wherein said second phase is cast from an acrylic emulsion-dispersion.
6. The photosensitive structure of Claim 4 wherein said second phase is cast from an acetate/ethylene copolymer emulsion-dispersion.
7. The photosensitive structure of Claim 4 wherein said second phase is cast from a polyvinyl acetate/long chain acrylic copolymer emulsion-dispersion.
8. The photosensitive structure of Claim 4 wherein said second phase is cast from a polyvinyl acetate emulsion-dispersion.
9. A photosensitive printing plate comprising a substrate layer having applied on at least one side thereof the photosensi-tive, unilayer film structure of Claim 1.
10. A water-processable printing plate comprising a sub-strate layer having applied on at least one side thereof the photo-sensitive, unilayer film composition of Claim 4.
11. The printing plate of Claim 10 wherein subsequent to actinic exposure and water processing said plate is heat treated to provide a coalesced second phase material.
12. The printing plate of Claim 10 wherein said photosensi-tive structure has a thickness of from about 0.5 to 25 microns.
13. A photosensitive lithographic printing plate comprising the photosensitive film structure of Claim 1 covering a substrate layer, the second phase material maintaining substantially complete structural integrity over said substrate layer and said film structure exhibiting a selected water-wettability differential over its surface in response to imagewise actinic exposure.
14. A photoresist comprising a substrate layer having applied on at least one side thereof the photosensitive unilayer film structure of Claim 1.
15. A water processable photoresist comprising a substrate layer having applied on at least one surface thereof the photosensitive, unilayer film structure of Claim 4.
16. A photosensitive article comprising a substrate layer having applied on one side thereof the photosensitive film structure of Claim 1, and wherein said first phase material also includes a material which colors said film structure.
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
17. The photosensitive unilayer film structure of Claim 1, Claim 2 or Claim 3 wherein said film structure has a maximum thickness not greater than about ten (10) times the average diameter of the particles comprising the major phase material.
18. The photosensitive unilayer film structure of Claims 4, Claim 5 or Claim 6 wherein said film structure has a maximum thickness not greater than about ten (10) times the average diameter of the particles comprising the major phase material.
19. The photosensitive unilayer film structure of Claim 7, Claim 8 or Claim 9 wherein said film structure has a maximum thickness not greater than about ten (10) times the average diameter of the particles comprising the major phase material.
20. The photosensitive unilayer film structure of Claim 10, Claim 11 or Claim 13 wherein said film structure has a maximum thickness not greater than about ten (10) times the average diameter of the particles comprising the major phase material.
21. The photosensitive unilayer film structure of Claim 14, Claim 15 or Claim 16 wherein said film structure has a maximum thickness not greater than about ten (10) times the average diameter of the particles comprising the major phase material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US58833475A | 1975-06-19 | 1975-06-19 | |
| US588,334 | 1975-06-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1091969A true CA1091969A (en) | 1980-12-23 |
Family
ID=24353419
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA249,489A Expired CA1091969A (en) | 1975-06-19 | 1976-04-02 | Photosensitive unilayer film structure cast from a polymeric emulsion dispersion |
Country Status (12)
| Country | Link |
|---|---|
| JP (1) | JPS5936731B2 (en) |
| BE (1) | BE841797A (en) |
| CA (1) | CA1091969A (en) |
| CH (1) | CH633893A5 (en) |
| DE (1) | DE2626066A1 (en) |
| DK (1) | DK232276A (en) |
| FR (1) | FR2315110A1 (en) |
| GB (1) | GB1548764A (en) |
| IT (1) | IT1061234B (en) |
| NL (1) | NL7604774A (en) |
| NO (1) | NO762006L (en) |
| SE (1) | SE422847B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS52154626A (en) * | 1976-06-18 | 1977-12-22 | Fuji Photo Film Co Ltd | Silver halide light sensitive material |
| JPS52154627A (en) * | 1976-06-18 | 1977-12-22 | Fuji Photo Film Co Ltd | Silver halide light sensitive material |
| JPS5518621A (en) * | 1978-07-26 | 1980-02-08 | Fuji Photo Film Co Ltd | Photosensitive lithographic printing plate |
| DE2834059A1 (en) * | 1978-08-03 | 1980-02-14 | Hoechst Ag | LIGHT SENSITIVE COPY MATERIAL AND METHOD FOR THE PRODUCTION THEREOF |
| JPS5823026A (en) * | 1981-08-04 | 1983-02-10 | Nippon Paint Co Ltd | Water developable material for lithographic plate |
| JPS58174939A (en) * | 1982-03-18 | 1983-10-14 | Konishiroku Photo Ind Co Ltd | Image forming material |
| US4551415A (en) * | 1982-04-22 | 1985-11-05 | E. I. Du Pont De Nemours And Company | Photosensitive coatings containing crosslinked beads |
| US4668604A (en) * | 1982-04-22 | 1987-05-26 | E.I. Du Pont De Nemours And Company | Positive-working photosensitive elements containing crosslinked beads and process of use |
| US4601970A (en) * | 1982-04-22 | 1986-07-22 | E. I. Du Pont De Nemours And Company | Dry photosensitive film containing crosslinked beads |
| DE3328019A1 (en) * | 1982-09-21 | 1984-03-22 | Polychrome Corp., 10702 Yonkers, N.Y. | PRESSURE PLATE DEVELOPABLE WITH WATER |
| GB2273366B (en) * | 1992-11-18 | 1996-03-27 | Du Pont | Forming images on radiation-sensitive plates |
| US5688627A (en) * | 1996-07-02 | 1997-11-18 | Precision Lithograining Corp. | Light sensitive diazonium compounds having both bisulfate and zincate parts, method of making the compounds and compositions utilizing them |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3382069A (en) * | 1964-06-18 | 1968-05-07 | Azoplate Corp | Planographic printing plate |
| GB1469941A (en) * | 1973-04-10 | 1977-04-06 | Andrews Paper & Chem Co Inc | Diazotype reproduction layer |
-
1976
- 1976-04-02 CA CA249,489A patent/CA1091969A/en not_active Expired
- 1976-04-12 GB GB14886/76A patent/GB1548764A/en not_active Expired
- 1976-04-28 CH CH534076A patent/CH633893A5/en not_active IP Right Cessation
- 1976-05-03 IT IT49301/76A patent/IT1061234B/en active
- 1976-05-03 FR FR7613143A patent/FR2315110A1/en active Granted
- 1976-05-04 SE SE7605083A patent/SE422847B/en unknown
- 1976-05-05 NL NL7604774A patent/NL7604774A/en not_active Application Discontinuation
- 1976-05-13 BE BE167002A patent/BE841797A/en not_active IP Right Cessation
- 1976-05-26 DK DK232276A patent/DK232276A/en not_active Application Discontinuation
- 1976-06-08 JP JP51067029A patent/JPS5936731B2/en not_active Expired
- 1976-06-10 DE DE19762626066 patent/DE2626066A1/en not_active Withdrawn
- 1976-06-10 NO NO762006A patent/NO762006L/no unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPS522520A (en) | 1977-01-10 |
| NO762006L (en) | 1976-12-21 |
| DE2626066A1 (en) | 1977-01-20 |
| SE7605083L (en) | 1976-12-20 |
| GB1548764A (en) | 1979-07-18 |
| CH633893A5 (en) | 1982-12-31 |
| SE422847B (en) | 1982-03-29 |
| JPS5936731B2 (en) | 1984-09-05 |
| FR2315110B1 (en) | 1981-11-13 |
| FR2315110A1 (en) | 1977-01-14 |
| IT1061234B (en) | 1983-02-28 |
| NL7604774A (en) | 1976-12-21 |
| DK232276A (en) | 1976-12-20 |
| BE841797A (en) | 1976-09-01 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |