U.S. patent number 3,640,712 [Application Number 04/882,951] was granted by the patent office on 1972-02-08 for hydrophilic-hydrophobic photon-sensitive medium.
This patent grant is currently assigned to Hughes Aircraft Company. Invention is credited to Lester M. Field, William E. McKee, Richard A. Walker.
United States Patent |
3,640,712 |
Field , et al. |
February 8, 1972 |
HYDROPHILIC-HYDROPHOBIC PHOTON-SENSITIVE MEDIUM
Abstract
A medium which is hydrophobic when unexposed, and hydrophilic
when photon exposed is employed to produce discrete
photon-developed areas. The medium comprises a solid dispersion in
a film-forming binder of a photoconductive sensitive material such
as zinc oxide, a sensitization enhancing material such as a copper
salt and a hydrophobicity inducing agent such as a water repellent
silicone, fluorocarbon material or a higher molecular weight
organic acid such as stearic acid or linoleic acid. Exemplary
processes of developing the photon exposed medium include
application of aqueous liquids to form visible and/or transferable
or relief images.
Inventors: |
Field; Lester M. (Sherman Oaks,
CA), Walker; Richard A. (Woodland Hills, CA), McKee;
William E. (Woodland Hills, CA) |
Assignee: |
Hughes Aircraft Company (Culver
City, CA)
|
Family
ID: |
25381677 |
Appl.
No.: |
04/882,951 |
Filed: |
December 8, 1969 |
Current U.S.
Class: |
430/302; 430/310;
430/947 |
Current CPC
Class: |
G03F
7/0044 (20130101); Y10S 430/148 (20130101) |
Current International
Class: |
G03F
7/004 (20060101); G03c 005/09 (); G03c
001/00 () |
Field of
Search: |
;96/88,1.5,27 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Torchin; Norman G.
Assistant Examiner: Kimlin; Edward C.
Claims
What is claimed is:
1. A hydrophilic-hydrophobic, photon-sensitive medium
comprising:
a film-forming binder in which is substantially uniformly
dispersed:
a photon-sensitive material selected from the group consisting of
oxides of zinc, titanium, tantalum, indium, magnesium, germanium,
tin and bismuth, sulfides and selenides of calcium, zinc, cadmium,
iron and indium, boron nitride, calcium tungstate, beryllium
aluminide, lithium carbonate, zinc carbonate, cadmium niobate,
lithium niobate, anthracene and cesium-activated calcium-magnesium
silicate and mixtures thereof;
a sensitization enhancing material selected from the group
consisting of copper chloride, copper (II) acetylacetonate, bismuth
trioxide, a mixture of cuprous chloride and the trimethylamine salt
of tetracyanoquino-methane, cuprous chloride and copper (II)
acetylacetonate, a mixture of copper formate and cuprous chloride,
cupric sulfate, cupric chloride dihydrate, cupric bromide, cuprous
sulfite, cupric thiocyanate, cuprous sulfide, cupric molybdate,
cupric lactate, cupric formate, copper p-toluene sulfonate, cupric
salicylate, cupric lineolate, cupric acetate, glycine cupric salt,
cupric stearate, cupric oleate, cupric tartrate, cupric citrate,
d,l-malic acid copper salt, cupric oxalate, bis-(ethyl
acetoacetato) copper, bis-(1-phenyl 1, 3-butane-dione) copper,
cupric dimethyl dithiocarbamate, cuprous sulfate-.beta.-napthol,
cuprous acetoacetonate, silver benzotriazole, silver nitrate,
silver fluoride, silver oxide, and gallium (III) nitrate; and
a hydrophobicity-inducing agent selected from the group consisting
of a liquid or solid polymer formed from tetrafluoroethylene,
chlorotrifluoroethylene, fluorinated ethylene-propylene, vinylidene
fluoride or hexafluoropropylene; fluorinated organic acid salts
including the copper salts of heptafluorobutyric acid,
perfluorooctanoic acid, pentafluoropropionic acid,
p-fluorophenylacetic, 2-hydroxy-hexafluoroisobutyric acid,
trifluoroacetic, or 3-trifluoromethyl-3-hydroxybutyric acid; a
saturated or unsaturated aliphatic acid having a carbon content
from C.sub.10 to C.sub.24, a fatty acid having a carbon content
from C.sub.16 to C.sub.22 including palmitic acid, stearic acid,
oleic acid, linoleic acid and linolenic acid, napthenic acid;
polydimethyl siloxane, silane modified silica, copper salt of
fluorinated alkanoic acid; a polymer of tetrafluoroethylene,
chlorotrifluoroethylene, fluorinated ethylene-propylene, vinylidene
fluoride or hexafluoropropylene.
2. The medium according to claim 1 in which the hydrophobicity
agent is selected from the group consisting of napthenic acid,
palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic
acid, polydimethyl siloxane, a silane modified silica, copper salt
of fluorinated alhanoic acid and a polymer of tetrafluorethylene,
chlorotrifluoroethylene, fluorinated ethylene-propylene, vinylidene
fluoride or hexafluoropropylene.
3. The process of preparing an image corresponding to a photon
exposure comprising the steps of:
photon-exposing a selective area of the photon-sensitive,
hydrophobic medium of claim 1 to render the medium hydrophilic in
the exposed areas; and
treating the sensitive medium with a material to produce a physical
representation of the photon-exposed area.
4. The process of preparing an image corresponding to a photon
exposure comprising the steps of:
photon-exposing a selective area of a photon-sensitive, hydrophobic
medium to render the medium hydrophilic in the exposed areas, the
sensitive medium comprising a substantially uniform solid
dispersion in an organic film-forming binder of a photon-sensitive
material, a sensitization-enhancing material and a
hydrophobicity-inducing agent selected from the group consisting of
a liquid or solid polymer formed from tetrafluoroethylene,
chlorotrifluoroethylene, fluorinated ethylene-propylene, vinylidene
fluoride or hexafluoropropylene; fluorinated organic acid salts
including the copper salts of heptafluorobutyric acid,
perfluorooctanoic acid, pentafluoropropionic acid,
p-fluorphenylacetic, 2-hydroxy-hexafluoroisobutyric acid,
trifluoroacetic, or 3-trifluoromethyl-3-hydroxybutyric acid; a
saturated or unsaturated aliphatic acid having a carbon content
from C.sub.10 to C.sub.24, a fatty acid having a carbon content
from C.sub.16 to C.sub.22 including palmitic acid, stearic acid,
oleic acid, linoleic acid and linolenic acid, napthenic acid;
polydimethyl siloxane, silane modified silica, copper salt of
fluorinated alkanoic acid; a polymer of tetrafluoroethylene,
chlorotrifluoroethylene, fluorinated ethylene-propylene, vinylidene
fluoride or hexafluoropropylene; and
treating the sensitive medium with a source of vaporous metal to
the photon exposed medium and depositing said metal selectively on
aid exposed hydrophilic area.
5. The process of preparing an image in accordance with claim 4
wherein the sensitization-enhancing material is selected from the
group consisting of copper chloride, copper (II) acetylacetonate,
bismuth trioxide, a mixture of cuprous chloride and the
trimethylamine salt of tetracyanoquinomethane, cuprous chloride and
copper (II) acetylacetonate, a mixture of copper formate and
cuprous chloride, cupric sulfate, cupric chloride dihydrate, cupric
bromide, cuprous sulfite, cupric thiocyanate, cuprous sulfide,
cupric molybdate, cupric lactate, cupric formate, copper p-toluene
sulfonate, cupric salicylate, cupric lineolate, cupric acetate,
glycine cupric salt, cupric stearate, cupric oleate, cupric
tartrate, cupric citrate, d,l-malic acid copper salt, cupric
oxalate, bis-(ethyl acetoacetato) copper, bis-(1phenyl 1,
3-butane-dione) copper, cupric dimethyl dithiocarbamate, cuprous
sulphate-.beta.-naphthol, cuprous acetoacetonate, silver
benzotriazole, silver nitrate, silver fluoride, silver oxide, and
gallium (III) nitrate.
6. The process of preparing an image in accordance with claim 3
wherein the preparing step includes coating the sensitive material
on an etchable metal; and
the treating step comprises treating the sensitive material with an
aqueous metal etchant.
7. The process of preparing an image in accordance with claim 6
wherein the treating step of treating the sensitive material with
an aqueous metal etchant is followed by a solvent step wherein the
etched metal is treated with a solvent which dissolves the
sensitive medium from the metal backing.
8. The process of preparing an image in accordance with claim 3
wherein the treating of the sensitive material to form a water film
on the hydrophilic, exposed areas is followed by the steps of:
treating the sensitive medium with an oil base ink so that the oil
base ink is positioned on the hydrophobic areas of the sensitive
medium and is rejected by the adsorbed water covered exposed
hydrophilic areas of the sensitive medium; and
imprinting the ink upon a base by pressing the sensitive medium
having oil base ink on the hydrophobic areas thereof against the
base.
9. The process of preparing an image in accordance with claim 3
wherein the treating step comprises:
placing ink upon the sensitive medium in accordance with the
pattern determined by the hydrophilic and hydrophobic areas of the
sensitive medium.
10. The process of preparing an image in accordance with claim 9
wherein the selective placement of ink comprises the steps of:
forming a water film on the hydrophilic areas of the sensitive
medium;
forming a built-up wax layer on the hydrophobic areas of the
sensitive medium;
filling the hydrophilic areas between the built-up wax with gravure
ink; and
printing a base by pressing the medium against the base to be
printed.
Description
BACKGROUND OF THE INVENTION
This invention is directed to employment of a medium to produce an
image. The image is such that it is hydrophobic when unexposed and
hydrophilic when exposed. The hydrophobicity-hydrophilicity
difference is employed to produce a useful or visible image.
The prior art abounds in silver halide media and other actinically
sensitive media whereby a visible image is obtained by photon
exposing the media and suitably developing and fixing the media to
produce a visible image. The silver halide media and the processes
employing the silver halide media are not the only other processes
beyond the present process wherein physicochemical amplification
occurs in the media to permit rapid image development from a fairly
weak photon source. However, most of these processes require a
fairly long development time, or involve other complex
processing.
Other types of photon sensitive media are fairly "slow" in that
they do not employ physical or chemical multiplication and require
a much larger photon exposure before a usable image can result
therefrom. For instance, processes used in diazo printing, and the
media used in photoresists, are not of the nature which incorporate
amplification of exposure, and thus they require very long
exposures to be useful. Thus, the silver halide process requires
considerable development time, while the remaining processes
require a considerable exposure time, so that none of the prior art
processes are capable of quickly producing a usable image from a
normal photon source.
Additionally, in regards to use of photosensitive materials as a
master lithographic and other printing processes, most of the
conventional photosensitive materials are negative-working in that
they produce a reversal of tones whereby photon exposed areas print
dark and the nonexposed areas print light. This requires the
additional step in processing of preparing an intermediate negative
in order to produce a final positive print. Also the conventional
presensitized printing plates do not have any ability to print grey
scale, but print black and white. This requires the additional
complication of utilizing a halftone screen to reproduce grey
scale.
Copending applications, Ser. No. 717,503, filed Apr. 1, 1968, and
Ser. No. 721,773, filed Apr. 16, 1968, disclose a
hydrophilic-hydrophobic, photon-sensitive medium containing a
photosensitive compound, a sensitization enhancing agent and a
hydrophobicity-inducing agent dispersed in film-forming binder. The
particular hydrophobicity agents disclosed are water or water
bearing materials such as aqueous formaldehyde solutions.
OBJECTS AND SUMMARY OF THE INVENTION
This invention is directed to the discovery of new classes of
hydrophobicity-inducing agents useful in preparing a
hydrophilic-hydrophobic photon-sensitive medium and particularly to
water-repelling agents such as silicones, fluorocarbons or organic
acids containing two to 24 carbon atoms. The invention is also
directed to various processes utilizing aqueous liquids to form
images on the photon-developed medium.
On selective exposure of the medium a hydrophilic image is formed
supported and surrounded by hydrophobic nonimage or background
areas. The materials may be dispersed in a film-forming binder to
form a film which may be either self-supporting or may be supported
upon a suitable substrate. A dispersion of the materials in the
binder may be formulated by forming a liquid dispersion of the
agents, materials and binder in a liquid, suitably a solvent for
the film-forming binder. After thorough mixing, the film is formed
as a self-supporting film or as a coated film and is permitted to
dry. In such a state the medium is photosensitive and hydrophobic
and is ready for further processing in accordance with the
invention.
The invention will now become better understood by reference to the
following detailed portion of the specification when considered in
conjunction with the claims and the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic elevational view with a front housing cover
removed of a photon exposure aqueous development imaging system
employing the medium in a first process of this invention.
FIG. 2 is a schematic illustration of a lithographic printing
process in accordance with the invention.
FIG. 3 is a schematic illustration of a deposition process in
accordance with the invention; and
FIG. 4 is a schematic illustration of an etching process in
accordance with the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The hydrophilic, photon-sensitive medium in accordance with the
invention, consists of a material which is sensitive to the
impingement of photons, a metallic compound which is a
sensitization-enhancing agent, a material which selectively renders
the medium hydrophobic or hydrophilic in accordance with the photon
exposure and a binder for forming a solid solution or dispersion of
these ingredients in the form of a film. In some cases the strength
of the binder is sufficient to form a self-supporting film and in
other cases the film is supported on a substrate.
The substrate is a passive structure which does not enter into the
activity of the photon-sensitive medium, except to act as a
supporting structure, substrate or carrier. Therefore, the role of
the substrate is entirely physical and mechanical as far as the
practice of the invention is concerned. Suitable support substrates
may be formed of almost any material and may partake of almost any
geometry. Thus, paper, and especially paper in the form of a tape,
may serve as suitable support substrate and is particularly
desirable because of its flexibility. A number of synthetic polymer
composition materials are also suitable. For example, the substrate
may be formed of thermoplastic or thermosetting materials such as
polyethylene, polypropylene or styrene polymers such as
butadiene-styrene, polyesters such as polyethylene-terephthalate,
acrylics such as methyl methacrylate, or cellulose derivatives such
as cellulose acetate and the like.
Flexible substrates permit processing from continuous roll supplies
and conformation of the finished and developed media to
arcuate-shaped printing rolls and the like. However, rigid
substrates can just as well be used for flat planographic printing,
etching of printed circuit boards and the like. Rigid substrates
can be formed of synthetic polymer composition materials, glass,
metal, ceramic, refractory or impregnated woven sheets such as
impregnated phenolic printed circuit boards and the like.
A satisfactory binder or matrix for forming the film of
photosensitive media, according to the invention, may be any of the
well known film-forming synthetic organic resins, particularly
those formed of vinyl, diene monomers of their mixtures. The vinyl
monomers may be ethylene, propylene, vinyl chloride, vinylidene
chloride, vinyl esters such as vinyl butyrate and preferably are
vinyl aromatics such as styrene or vinyl toluene. The diene
monomers may be C.sub.4 to C.sub.10 dienes such as butadiene,
isoprene, methyl butadiene, dimethylbutadiene and the like. A
typical binder of the styrene-butadiene type of copolymer which has
been used successfully in the practice of the present invention, is
one identified as "Pliolite S-7" (30 percent solids in toluene),
manufactured by Goodyear Tire and Rubber Company, Chemical
Division, Akron, Ohio. Other satisfactory matrix materials are
polystyrene, chlorinated rubber, polyvinylidene chloride, polyvinyl
butyral and the like.
A solid dispersion or solution of the active materials may be
within the matrix or binder may be formed by any of the well-known
techniques such as by adding a solution or dispersion of the
materials to a solution or emulsion of binder particles, intimately
mixing and then drying. Suitably, the binder is dissolved in a
solvent to form a solution of reduced viscosity and the solid
materials are added to the solution and dispersed therein. Any
suitable solvent may be utilized to adjust the miscibility and
spreadability of the dispersion. For styrene-butadiene resins such
as Pliolite, the solvent may be an aromatic such as toluene or an
ether such as dioxane. Other solvents for butadiene-styrene resins
are chlorinated hydrocarbons and some ketones.
The solvent or dispersion may be cast onto a release surface to
form a self supporting film or the material may be applied to the
surface of a substrate, support or backing material by flow
coating, dipping, spraying, doctor blade or other conventional
coating operation. On removal of the solvent, the media is ready
for further processing to form images by exposure and
development.
The photosensitive material suitable for use in the practice of the
present invention, appears to include materials which are
classifiable as either photoconductive or photoemissive. The
material is sensitive to the impingement of electrons, ions or
photons. In general the photosensitive compounds are solids formed
from one element to the left of Group IV of the Periodic Chart of
the Elements compounded with another element from a group of the
Periodic Chart to the right of Group IV. Preferably the
photosensitive materials for use in recording media, according to
the invention, are selected from compounds formed by elements of
Group II such as zinc, calcium, cadmium and magnesium with elements
of Group VI such as oxygen, sulfur and selenium.
More particularly, the sensitive materials for use in the recording
media of the invention, include compounds such as the oxides of
zinc, titanium, tantalum indium, magnesium, germanium, tin and
bismuth as well as sulfides and selenides of calcium, zinc,
cadmium, iron and indium. In addition to these, it has been found
that such compounds as boron nitride, calcium tungstate, beryllium
aluminide, lithium carbonate, zinc carbonate, cadmium niobate,
lithium niobate, anthracene and certain phosphor compounds such as
cesium-activated calcium-magnesium silicate may also be employed,
as well as the mixtures of these compounds.
The sensitization-enhancing materials suitable for use in the
practice of the invention are, in general, any of the metal
compounds such as ionic salts or covalent bonded or coordination
complexes thereof. The metal is suitably a Group I or IV element
such as copper, bismuth, chromium, or silver. Typical inorganic
salts are formed with inorganic anions such as halogen, oxygen,
sulphate, sulfite, thiocyanate, sulfide, molybdate, sulfite and
nitrate and the like. Salts of organic acids may also be utilized
such as formic acid, alkanoic acids, aromatic acids, unsaturated
aliphatic acids and hydroxy-substituted derivatives thereof. The
acids may be the short chain acids containing one to nine carbon
atoms but preferably are salts of the fatty acids containing 10 to
24 carbon atoms, whether saturated or unsaturated.
Coordination or chelate complexes may be formed with ligands such
as acetylacetonate, bis-(ethyl aceto acetato), bis (1-phenyl-1,
3-butane dione), dimethyl dithiocarbamate, .beta.-naphthol sulfate
and benzotriazole.
Exemplary sensitization-enhancing materials suitable for use in the
practice of the present invention and especially with zinc oxide as
the actinically active sensitive material are copper chloride,
copper (II) acetylacetonate, bismuth trioxide, a mixture of cuprous
chloride and the trimethylamine salt of tetracyanoquinomethane,
cuprous chloride and copper (II) acetylacetonate, a mixture of
copper formate and cuprous chloride, cupric sulfate, cupric
chloride dihydrate, cupric bromide, cuprous sulfite, cupric
thiocyanate, cuprous sulfide, cupric molybdate, cupric lactate,
cupric formate, copper p-toluenesulfonate, cupric salicylate,
cupric lineolate, cupric acetate, glycine cupric salt, cupric
stearate, cupric oleate, cupric tartrate, cupric citrate, d,l-malic
acid copper salt, cupric oxalate, bis-(ethyl acetoacetato) copper,
bis-(1-phenyl 1, 3-butane-dione) copper, cupric dimethyl
dithiocarbamate, cuprous sulphate-.beta.-naphthol, cuprous
acetoacetonate, silver benzotriazole, silver nitrate, silver
fluoride, silver oxide, and gallium (III) nitrate. The amount of
sensitization-enhancing material incorporated in the film forming
may be varied over wide ranges. Ratios of sensitization-enhancing
agent to photosensitive material from 10.sup.-.sup.3 to
10.sup.-.sup.4 have given substantially equivalent results with no
discernible differences.
The material which renders the photosensitive medium hydrophobic
according to this invention is a water-proofing agent suitably a
silicone, fluorocarbon or a higher molecular weight organic
carboxylic acid.
A suitable hydrophobic silicone is an organosiloxane, typically a
polydimethylsiloxane, which may be a liquid or solid polymer. An
exemplary commercial available liquid material is G.E. "SR-82"
silicone resin. Another form of hydrophobic silicone is a
hydrophobic silicon dioxide aerosil obtained by reaction with a
chlorosilane. The chlorine reacts with surface silanol groups to
attach the silane to the silica particle. Typically, dimethyl
chlorosilane attaches to silica to provide a carbon content of 0.8
to 0.9 percent per 100 m.sup.2 of product. An exemplary commercial
product is (Degussa) "Aerosil R-972."
The water-repellent fluorocarbon material may be a liquid or solid
polymer formed from tetrafluoroethylene, chlorotrifluoroethylene,
fluorinated ethylene-propylene, vinylidene fluoride or
hexafluoropropylene. Fluorinated organic acid salts such as the
copper salt of heptafluorobutyric acid, perfluorooctanoic acid,
pentafluoro-propionic acid, p-fluorophenylacetic,
2-hydroxy-hexafluoro-isobutyric acid, trifluoroacetic, or
3-trifluoromethyl-3-hydroxybutyric acid, may also be utilized.
The organic acid may be a naphthenic acid. Commercial napthenic
acid is a mixture of saturated cycloaliphatic acids, predominating
in monocyclic, monocarboxylic acids containing a substantial
percentage of materials having a carbon content from C.sub.6 to
C.sub.8. The acids present in naphthenic acid typically have
molecular weights in the range of 180 to 350. The organic acid may
also be a saturated or unsaturated aliphatic acid having a carbon
content from C.sub.10 to C.sub.24 preferably a fatty acid having a
carbon content from C.sub.16 to C.sub.22 such as palmitic acid,
stearic acid, oleic acid, linoleic acid and linolenic acid.
The hydrophobicity agent is present in the range of 0.05 to 10
grams, preferably below 5 grams based on 100 grams of film forming
solids. If the agent is utilized in the presence of another
hydrophobicity agent such as the hydrated salts, fatty acid salts
or water containing materials disclosed in copending application
Ser. No. 883,086 filed Dec. 8, 1969, the normal amount of each
material is reduced to a level to provide satisfactory but not
excessive hydrophobicity.
The sensitive material, sensitization enhancing material are both
usually in a finely comminuted form. The dry powder materials are
mixed together with the hydrophobicity inducing material and with
the desired binder and solvent, for example, toluene, suitably in
an orbital ball mill, jar mill or vibratory mill until thorough
dispersion of the ingredients is achieved. The mixture is then
applied to a suitable substrate by conventional knife-coating
equipment so as to form a film thereon having a wet thickness of
25-100 microns. For example, in general, the dry thickness of the
film varies between 25 to 50 percent of the wet thickness. Upon
drying the film is ready for use.
The selected hydrophilicity is utilized, in accordance with the
invention, to provide aqueous developed images which are useful for
selectively attracting water or water-bearing materials to the
nucleated image or in the converse for rejecting hydrophobic
materials from the aqueous developed areas. The aqueous developer
may carry a solution or dispersion of dye or pigment so that when
water is selectively adhered to the hydrophilic areas of the
medium, the dye or pigment deposits thereon to form a visible
image. When dry, the developed print is a positive reproduction of
the original information design, indicia or the like. In the case
of colloidal pigments suspended in water, the colloid is firmly
attached to the surface in the hydrophilic exposed and developed
areas so that it properly remains in place after the aqueous
solution has evaporated. Of course, the hydrophobic areas repel the
water so that there is no dye or pigment absorption or
deposition.
Following the exposure and development in an aqueous media,
tenaciously adsorbed water images are formed on the surface of the
hydrophilic exposed areas. This water image will repel hydrophobic
materials such as oil-based ink or molten wax. With the subsequent
application of a hydrophobic lithographic ink, the ink will be
repelled by the hydrophilic water developed image areas and will be
retained by the hydrophobic background areas. A lithographic
printing process results by transferring the ink image to a sheet
of paper either directly or by means of an intermediate rubber
blanket. The process of alternately water wetting and inking can be
repeated to produce multiple prints on any conventional
lithographic press.
If the hydrophobic compound is molten wax, on cooling and
solidification of the wax, an in-depth wax image is formed which
could be used as a gravure printing plate for an intaglio printing
process, or alternatively, the wax image could be used as an
etchant-resist for making a photoresist printed circuit board or
the like.
In a variation of the development step in accordance with the
invention, the photon activated nucleated surface is also
selectively sensitive to the deposition of metallic vapor. When a
metal is delivered to the surface in vapor form, the impinging
vapor atoms will deposit selectively on the nucleation site because
of the higher adsorption energy. On the unexposed areas, the
reevaporation rate will nearly equal the incident rate and there
will be no deposition while on the nucleation sites the
reevaporation rate will be very low. The vaporous metal is
preferably selected to have increased hydrophilicity and
lyophobicity and is suitably zinc, cadmium or mercury. The vaporous
metal coated media when wet with water exhibits increased
resolution and better continuous-tone reproduction.
All of the aforementioned processes can be utilized with the water
developed exposed hydrophilic image or with the metal vapor
developed image. Vapor development in a vapor of a hydrophilic
metal such as zinc, mercury or cadmium can contribute to resolution
of the images.
In another variation of utilizing the hydrophilic properties of the
exposed image, a photoresist may be directly produced by further
developing the nucleated image with a material that forms a hard
imagewise deposit. For example, potassium dichromate when applied
to the nucleated image and "developed" by exposure to ultraviolet
radiation, forms such a deposit. The hard and impermeable image
will act as a resist when the material is dipped in a solvent that
dissolves the binder for the sensitive layer thereby exposing the
base material. The solvent etched assembly could be used directly
as a printing plate or as a photoresist preliminary to chemical
milling with an etchant suitable for the base material.
Referring now to FIG. 1, an aqueous developing imaging system
employing the hydrophobic-hydrophilic media, according to the
invention, is generally indicated as the device 10. The device 10
comprises a housing 12 which is preferably lighttight because of
the photon-sensitive character of the medium employed therein.
However, for purposes of illustration, the near side cover of the
device 10 has been removed so that the interior can be seen. The
housing 12 contains a first chamber 14 which functions as a storage
chamber for the medium, and if desired, can include coating
equipment for applying the medium to a substrate 28. The chamber 14
is connected to a second chamber 16 through light trap 18.
Similarly, chamber 16 is connected to a chamber 19 through light
trap 22. Then the medium leaves chamber 19 through a light trap 23
and enters a third chamber 20. The medium leaves the device 10
through a light trap 24.
Within chamber 14 a storage reel 26 furnishes a supply of substrate
28 which is lead under coater 30 containing a supply of media and
around guide rolls 32 and 34 so that it can pass through light trap
18 into chamber 16. The coating is permitted to dry during passage
around guide rolls 32 and 34 and if desired, a forced air dryer can
be incorporated within chamber 14 facing the top surface of
substrate 28, coated with the medium. Since the medium being
applied to the substrate is photosensitive, the coating is carried
out in chamber 14 which has a light level sufficiently low that
exposure and activation of the media does not take place. It is
again noted that the coating process need not be an integral part
of the exposing and developing system. The substrate may be coated
many months in advance of the actual use and a reel of coated
presensitized media inserted into chamber 14 and wound onto the
appropriate drive and guide rollers.
The coated and dried medium is now ready for exposure which occurs
within the second chamber 10. In chamber 16 the medium is exposed
by light source 36 which is powered by power supply 38. Light
source 36 can be a suitable projector which projects an image upon
the sensitive surface of the medium in which case the medium 38 is
held stationary for an adequate length of time, during exposure. On
the other hand, light source can be a suitable scanning light beam
which scans transversely to the direction of motion of medium 38,
in which case the advance of medium passed the transversely
scanning light source can be at an appropriate rate to provide the
necessary spacing longitudinally of the medium 38.
The light sensitivity of the media will depend on the composition
thereof, but the coating given in Example 1 below, typically has an
exposure range from unexposed to fully exposed over an exposure
range of ultraviolet light from 10 ergs/cm..sup.2 to 1,000
ergs/cm..sup.2 . The medium is completely hydrophobic before
exposure to the minimum value of light energy given above and is
hydrophilic when subjected to the full exposure. At the
intermediate levels of exposure, certain of the active sites are
exposed and render particular areas at the sites hydrophilic so
that the materials dissolved in water are carried by water to be
deposited thereon. The intermediate range of exposure thus result
in closely spaced hydrophobic and hydrophilic areas so that
irregular or discontinuous images result.
After exposure, the medium 38 passes through light trap 22 into an
optional third chamber 19. If desired, the exposed activated image
areas of the media 38 can be coated with metal within this chamber,
or, the metal coating may be accomplished simultaneously with
exposure within chamber 16. As a result of the exposure to
electrons, ions or photons, the surface of the media 38 is provided
with a latent image comprising a number of nucleating sites in a
pattern corresponding to the indicia to be reproduced. When metal
vapor is applied to the surface of the exposed media, atoms or
molecules from the vapor are selectively attracted to and retained
by the nucleated areas comprising the latent image. Each atom in a
nucleating site may capture as many as 10,000 atoms from the vapor.
The necessary vapor is supplied from a source 25 usually associated
with a controlled heater means 27. Generally the vaporous metal
developer materials are metal, such as zinc, cadmium or mercury in
bulk or powder form in a crucible or as a wire source. The metal
vapor may also be supplied in the form of a reducible or thermally
decomposible metal compound such as a metal carbonyl compound.
Metal vapor development takes place under the usual conditions
governing the depositions of metal in vacuum. Thus, chamber 19 is
placed under vacuum and the media 18 is spaced a distance from the
vapor source 25 not more than the mean free path existing in the
chamber at given conditions. Pressures in the ranges of
10.sup.-.sup.1 to 10.sup.-.sup.4 torr may be used for this purpose.
Inert gases such as helium-argon may also be employed and
introduced into the chamber to modify the velocity at which vapor
molecules reach the surface, permitting a greater degree of control
of image contrast.
After exposure and optionally after metal vapor development, the
medium 38 passes through light trap 23 into aqueous development
chamber 20 and from chamber 20 the medium 38 passes out of the
device 10 through light trap 24. Within the chamber 20 the medium
38 passes around guide rolls 40, 42 and 44; during passage around
guide roll 42 the medium is submerged within an aqueous bath 46 and
the liquid is selectively deposited on the hydrophilic image areas.
If the aqueous bath 46 carries dye or pigment, the coloring matter
will be deposited on the hydrophilic image areas. The media 38
leaves chamber 20 with an aqueous developed image formed on the
hydrophilic exposed areas, regardless of whether it has been
developed with metallic vapor in chamber 19.
It should be understood that complete immersion in liquid is shown
for purposes of illustration and that this is one of only many
suitable methods for applying the developer. Other methods are
easily as satisfactory and include surface application of the
liquid from a revolving roller, spray application and other
well-known means of solution application.
The aqueous developing time for this process is characteristically
very short. The required time will vary as a function of the
concentration of the hydrophobicity-inducing agent in the medium
(being less for smaller concentrations thereof), as a function of
the concentration of sensitization agent, being less for smaller
concentrations thereof, as a function of ball milling time used to
blend the ingredients (being less for longer ball-mill time), and
as a function of developer temperature (being less for higher
developer temperatures). Depending on the aforementioned variables,
developing time may vary from 0.1 second up to 20 seconds. Typical
developing times are from 0.5 to 5 seconds at 70.degree. F.
Following development, no further processing is required. However,
to facilitate handling of the product, it may be desirable to use
forced-air or radiant drying (or both) to dry the excess developer
solution adhering on the surface of the medium.
As the medium comes out of light trap 24, it is ready for
inspection and handling.
The following examples are intended to illustrate the preparation
of the novel recording media of the invention, its exposure and
development and not to restrict the scope thereof.
EXAMPLE I
A large number of coatings were made based on the same basic
formula as follows:
Zinc Oxide (Photox 80l) 50-75 grams; Pliolite S-7 18 grams; Toluene
50-80 cc.; Methanol 4 cc.
Various sensitizers and hydrophobicity-inducing agents were then
added to this basic formula and the ingredients combined in a 500
cc. gross-capacity aluminum oxide ball mill with 100 10 mm.
diameter agate balls, and milled on a planetary ball mill for 45
minutes. The media was then coated to a wet thickness of 25 to 100
microns on a substrate of aluminized polyester film base or other
suitable support. The resultant in coatings were tested for
hydrophobicity. The addenda and results of the test coatings are
given in Table I. (See next page).
It is seen from the Table that best results are achieved with
linoleic acid present in an amount of 1 to 2 grams or with the
silane treated silica material. The media according to the examples
can be exposed with approximately 300 ergs/cm..sup.2 of 3625 A.,
ultraviolet radiation. Development can then consist of a one second
surface application of a water suspension of colloidal graphite or
suitable dyes. A graphite developer can be prepared by dispersing
83 grams of Acheson Colloids "Aquadag
---------------------------------------------------------------------------
TABLE I
Tape Sensitization Agent Hydrophobicity Resulting Composition
Agent(s)
__________________________________________________________________________
1a Copper Stearic Acid Fair acetylacetonate (0.25g.) (0.10g.) 1b
Copper Stearic Acid Fair acetylacetonate (0.50 g.) (0.1 g.) 2a
Copper Napthenic Acid Poor acetylacetonate (0.5 g.) (0.1 g.) 2b
Copper Napthenic Acid Poor acetylacetonate (1.0 g.) (0.10 g.) 3a
Copper Linoleic Acid Fair acetylacetonate (0.25 g.) (0.10 g.) 3b
Copper Linoleic Acid Fair acetylacetonate (0.50 g.) (0.10 g.) 3c
Copper Linoleic Acid Good acetylacetonate (1.0 (0.10 g.) 3d Copper
Linoleic Acid Good acetylacetonate (2.0 g.) (0.10 g.) 4 Cuprous
Chloride Aerosil R-972 Good (0.10 g.) (0.30 g.) 5 Cuprous Chloride
Formalin (8 ml. Good (0.10 g.) and Aerosil R-972 (0.3 g.) 6 Cuprous
Chloride G.E. SR-82 Fair (0.10 g.) Silicone Resin (1.0 g.)
__________________________________________________________________________
(22 percent solids in water)" in 1 liter of deionized water. The
alkalinity of the developer can be adjusted with ammonia or acetic
acid to produce a pH between 8 and 11. The higher pH produces more
rapid but less selective development.
The exposed sheet can also be developed by immersion for 1-20
seconds in tap water or preferably in a lithographic fountain
solution. Referring now to FIG. 2, a length 60 of the medium 28
developed, in accordance with FIG. 1, is removed and cut to
printing plate size. The plate 60 is applied to a printing roller
62. Tank 64 contains fountain solution 66 such as
Addressograph-Multigraph (AM) Multilith "Repelex" fountain solution
(concentrate diluted 1:30 with deionized water). Tank 68 contains
an oil-based printing ink 70 such as Von Son Holland "Quickset
Printing Ink" or AM "MLS Series Multilith Ink." Rollers 72 and 74
apply the respective fountain solution 66 and ink 70 to the surface
of the printing plate 60.
A source of paper 75 from roll 76 passes around guide roll 78 and
is pressed against the surface of the printing plate 60 by means of
press roll 80 and then passes by guide roll 82 before being rewound
on takeup roller 84. On each revolution of the printing roller 62
the fountain solution 66 will selectively adhere to the exposed
hydrophilic areas of the plate 60 and therefore the subsequently
applied ink 70 will be rejected by these areas to provide a clear
and sharp background for the finished prints. The ink accepted by
the nonexposed areas is transferred to the paper 75 passed in
contact with the printing plate 60.
Multilith prints made from a hydrophilic-hydrophobic medium,
according to the invention, exhibit greatly improved contrast and
lack of ink pickup in the background areas. A press run is capable
of producing several hundred clear legible copies with good
resolving power. Furthermore, the Multilith-produced prints do not
show the characteristic fill-in of circular shapes such as the
center of the letter "o" and "e" which is typical of aqueous
development by dipping. This is attributable to the printing press
breaking the bubbles by pressure of the rollers.
In the case of media subjected to vacuum-development with metal
vapor such as zinc in chamber 19 of FIG. 1, the copies produced are
somewhat sharper and exhibit a degree of direct halftone
reproduction without the use of halftone screens.
A further process utilizing the aqueous developed media, prepared
in FIG. 1 is illustrated in FIG. 3. In this process a hardenable
oleophilic compound is applied to the aqueous developed exposed
medium. The oleophilic material hardens to form an impermeable
image having a relief image corresponding to the exposed portions
of the medium. Referring now to the drawings, the exposed medium 28
enters chamber 20 whereas it passes around guide roll 42; it is
aqueous developed within the water bath 46.
The developed media 28 then passes through light trap 24 into
lighttight chamber 90. The media passes around guide rolls 91, 92
and 94 within chamber 90. As the medium passes around roll 92, it
is submerged within a liquid oleophilic compound such as hot wax
96. The wax is repelled by the olephobic water-adsorbed exposed
image areas, but it builds up upon the unexposed portions of the
sensitive medium on web 28. The hard wax is cooled by any
convenient means such as by cooling immersion roller 92 so that a
solid wax image is built up upon the unexposed areas. The medium
leaves chamber 90 through a trap 98.
The medium having the built up image prepared in accordance with
the last figure can be utilized as a gravure printing plate to
produce copies. A water-base ink when applied to such a plate will
adhere to the relieved hydrophilic areas, but will be repelled by
the built-up wax areas. Furthermore, since the image areas are
depressed, the ink can be wiped off the raised nonimage areas.
After wipeoff the ink can be transferred by pressing the plate
against a transfer sheet such as paper. The gravure printing plate
can be repeatedly reinked with gravure ink and printed against
paper. In such a case a portion of the web corresponding to the
pattern to be printed in multiple copies is severed from the web
and inserted in a press as a printing plate for producing multiple
copies.
It should be noted that the wax image can be used as an etchant
resist. In such a case the substrate should be an etchable material
such as a film of metal or a film of metal laminated to an inert
support, suitably a polyester such as "Mylar." The etchant can be
any suitable solvent for the etchable substrate which does not
attack the layer and may be an acid or alkali material oxidizing
agent or reducing agent. The etching process may again be operated
on the severed sheets of media in a batch type of operation rather
than the continuous operations that have been illustrated.
A process which yields a photoresist directly from the photon
exposed media of FIG. 1 without the need for forming a relief image
is illustrated in FIG. 4. The photon exposed media 28 passes
through light trap 23 into lighttight chamber 20. The aqueous media
46, in this case, contains a compound that forms a hard impermeable
deposit upon the hydrophilic exposed areas. An aqueous solution of
potassium dichromate is suitable for this use. The
dichromate-treated media leaves chamber 20 through light trap 24
and enters chamber 102.
Within chamber 102 the treated media is exposed overall to
ultraviolet radiation from a high intensity ultraviolet lamp 103
which acts to cross-link, polymerize or otherwise harden the
dichromate coated, exposed areas. The treated media leaves the
chamber 102 through light trap 104 and enters chamber 106. Within
chamber 106 the media passes around guide rolls 108, 110 and 112.
The roll 110 is at least partially immersed within a bath 114 which
contains a solvent for the media. The solvent dissolves the
film-forming binder of the photosensitive coated film 28 so that
the web beneath the unexposed areas is removed to expose the
underlying portions of the web substrate. A suitable solvent for
the film forming binder is toluene.
As the web 28 leaves chamber 106 through light trap 115, the
originally photon unexposed areas of the web are unprotected while
the photon exposed areas are protected both by a layer of the
sensitive material and a layer of the hard impermeable deposited
material. The web 28 may then be delivered to a tank 116 containing
a bath of etchant 118. The web passes over rollers 120, 122 and
124. Roller 122 is again partially submerged within the bath 118
and as the web passes over this roller the etchant removes material
from the unprotected areas of the tape corresponding to the photon
unexposed areas. This process can be used for preparing printing
plates or in processes of chemical milling. Again the process may
be carried out in a step-by-step batch basis on separate sheets of
material prepared on rigid substrates.
This invention having been described in its preferred embodiments,
it is clear that it is susceptible to numerous modifications and
embodiments within the ability of those skilled in the art and
without the exercise of the inventive faculty. Accordingly, the
scope of this invention is defined by the scope of the following
claims.
* * * * *