Compatible, aqueous developable photopolymerizable composition consisting essentially of (a) 22 to 32% by wt. of a monomeric compound having at least two terminal ethylenic groups, (b) 0.1 to 5.0% by wt of a photoinitiator or initiator system, (c) 40 to 80% by wt of a binder system which is the reaction product of (1) 65 to 87 parts by wt of a terpolymer of methylmethacrylate, butylmethacrylate and methacrylic acid as defined, (2) 5 to 20 parts by wt of a polyamide resin and (3) 5 to 20 parts by wt of a copolymer of vinyl pyrrolidone and vinyl acetate, (d) 0.03 to 0.10% by wt of a thermal polymerization inhibitor, and optionally up to 18% by wt of a plasticizer and up to 2.0% by wt of a tertiary amine capable of salt formation with a carboxylic acid. Aqueous developable photopolymerizable elements comprise a support bearing a layer of the composition. Relief printing plates can be prepared by imagewise exposing and developing the elements.

BACKGROUND OF THE INVENTION 
Description 
Technical Field 
This invention relates to photopolymerizable compositions. More 
particularly, this invention relates to photopolymerizable compositions 
which are developable under aqueous conditions. This invention also 
relates to photopolymerizable elements prepared from the 
photopolymerizable compositions and to an extrusion process for preparing 
the elements. 
Background Art 
Photopolymerizable compositions are known to those skilled in the art. 
These compositions have many uses, e.g., in the preparation of printing 
plates for various printing uses such as letterpress, flexographic, dry 
offset, etc., photoresists, etc. Of particular interest are the 
photopolymerizable compositions which are soluble in aqueous solutions. 
One such aqueous soluble photopolymerizable composition which contains an 
acidic cellulose derivative as the polymeric binder is disclosed in U.S. 
Pat. No. 2,927,022. The compositions containing the acidic cellulose 
derivatives are processable to film or layer form from solution or by 
conventional mechanical means, e.g., extruding, calendering, etc., with or 
without added plasticizers. Cellulose hydroacetate, one monomer from which 
the acidic cellulose derivatives are obtained, is difficult to prepare and 
use. U.S. Pat. Nos. 2,923,673 and 3,012,952 describe procedures which 
enable the preparation of good quality photopolymerizable compositions 
containing cellulose derivatives. Photopolymerizable elements prepared 
from compositions containing cellulose derivatives have the disadvantage 
that they are rather slow photographically, i.e., they require 
correspondingly long imagewise exposures to actinic radiation. The 
radiation sources used for the exposure generate heat sufficient to cause 
the art work used during an imagewise exposure to adhere to the 
photopolymerizable layer. To prevent heat buildup the exposure generally 
is conducted in short increments of time with cooling occurring between 
successive exposure increments. It is desirable to prepare 
photopolymerizable compositions which not only have good quality but have 
environmental advantages at reduced mill costs over prior art 
compositions. It is also desirable to prepare photopolymerizable elements 
which possess improved photographic speed which can be exposed imagewise 
by a single exposure. 
DISCLOSURE OF INVENTION 
In accordance with this invention, there is provided a compatible, aqueous 
developable photopolymerizable composition consisting essentially of 
(a) 22 to 32% by weight of an ethylenically unsaturated monomeric compound 
having at least two terminal ethylenic groups capable of forming a high 
polymer by free-radical initiated chain-propagated addition 
polymerization; 
(b) 0.1 to 5.0% by weight of a free radical generating, addition 
polymerization initiator or initiator system activatable by actinic 
radiation; 
(c) 40 to 80% by weight of a binder system which is the reaction product of 
(1) 65 to 87 parts by weight of a terpolymer of methylmethacrylate, 
butylmethacrylate, and methacrylic acid, the terpolymer having an acid 
number of 175 to 200 and an inherent viscosity of about 0.4 to 0.5, 
(2) 5 to 20 parts by weight of amine-terminated polyamide resin, and 
(3) 5 to 20 parts by weight of a copolymer of vinyl pyrrolidone and vinyl 
acetate; 
(d) 0.03 to 0.10% by weight of a thermal polymerization inhibitor; 
(e) 0 to 18% by weight of a plasticizer for the composition; and 
(f) 0 to 2% by weight of a tertiary amine capable of salt formation with a 
carboxylic acid, the percentages of the composition components being based 
on the total weight of the composition. 
In accordance with an embodiment of this invention, there is provided an 
aqueous developable photopolymerizable element which comprises a support 
bearing a layer, 0.0005 to 0.250 inch (0.00127 to 0.635 cm) of the 
above-described photopolymerizable composition. 
The compatible, aqueous developable photopolymerizable compositions of the 
invention contain as required ingredients: addition polymerizable 
ethylenically unsaturated monomeric compounds having at least two terminal 
ethylenic groups (a), free radical generating addition polymerization 
initiator or initiator system (b), polymeric binder system (c), and 
thermal polymerization inhibitor (d). Preferably a plasticizer (e) for the 
composition and optionally a tertiary amine capable of salt formation with 
a carboxylic acid (f) are present in the composition. By "compatible" is 
meant the ability of two or more constituents to remain dispersed in one 
another without causing any significant amount of scattering of actinic 
radiation. Compatibility is often limited by the relative proportions of 
the constituents, and incompatibility is evidenced by formation of haze 
and "bleeding" or "blooming" of components in the photosensitive 
composition. Some slight haze can be tolerated from such compositions 
before or during exposure in the preparation of printing reliefs, but when 
fine detail is desired, haze should be completely avoided, and bleeding or 
blooming should not occur at any time. The amount of ethylenically 
unsaturated compound, or any other constituent, used is therefore limited 
to those concentrations which do not produce these undesired effects. 
The addition polymerizable ethylenically unsaturated monomeric compounds 
(a) having at least two terminal ethylenic groups useful in this invention 
include: tetraethylene glycol diacrylate (preferred), triethylene glycol 
diacrylate, triethylene glycol dimethacrylate, hexamethylene glycol 
diacrylate, trimethylolpropane triacrylate, ethylene glycol diacrylate, 
diethylene glycol diacrylate, tetramethylene glycol diacrylate, 
polyethylene glycol diacrylate, with an average molecular weight of the 
glycol ranging from 200 to 600, ethylene glycol dimethacrylate, diethylene 
glycol dimethacrylate, tetramethylene glycol dimethacrylate, 
1,3-propanediol dimethacrylate, 1,2,4-butanetriol trimethacrylate, 
1,4-cyclohexanediol diacrylate, 1,4-benzenediol dimethacrylate, 
1,2-benzenedimethanol diacrylate, glycerol triacrylate, trimethololpropane 
triacrylate, pentaerythritol triacrylate, pentaerythritol 
tetramethacrylate, 1,3-propanediol diacrylate, 1,3-pentanediol 
dimethacrylate, 1,4-butanediol diacrylate, 2,2-dimethylolpropane 
diacrylate, tripropylene glycol diacrylate, 2,2-di(p-hydroxyphenyl)propane 
diacrylate, 2,2-di(p-hydroxyphenyl)propane dimethacrylate, 
polyoxyethyl-2,2-di(p-hydroxyphenyl)propane dimethacrylate, 
polyoxyethyl-2,2-di(p-hydroxyphenyl) propane triacrylate, 1,4-butanediol 
dimethacrylate, hexamethylene glycol dimethacrylate, 
2,2,4-trimethyl-1,3-pentanediol dimethacrylate, 
1-phenylethylene-1,2-dimethacrylate, trimethylolpropane trimethacrylate, 
polyoxyethyltrimethylolpropane triacrylate, diacrylate and dimethacrylate 
esters of diepoxy polyethers derived from aromatic polyhydroxy compounds 
such as bisphenols, novolaks and similar compounds such as those described 
by Crary in U.S. Pat. No. 3,661,576, which is incorporated by reference, 
the bis-acrylates and methacrylates of polyethylene glycols of molecular 
weight 200-500, etc. The monomers are present in an amount of 22 to 32% by 
weight based on the total weight of the composition, preferably 26 to 28% 
by weight. 
The required addition polymerization initiator or initiator system (b) 
includes: benzil type compounds, e.g., benzil, benzil monodimethyl ketal, 
benzil monomethyl ethyl ketal, benzil monomethyl benzyl ketal, benzil 
mononeopentyl ketal, etc.; acetophenones, e.g., 2,2-dimethoxy-2-phenyl 
acetophenone, etc.; biimidazolyl dimers; quinone type compounds such as 
are disclosed in U.S. Pat. No. 2,951,758, e.g., 9,10-anthraquinone, 
1-chloroanthraquinone, 2-chloroanthraquinone, 2-methylanthraquinone, 
2-tert-butylanthraquinone, octamethylanthraquinone, 1,4-naphthoquinone, 
9,10-phenanthrenequinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 
2-methyl-1,4-naphthoquinone, 2,3-dichloronaphthoquinone, 
1,4-dimethylanthraquinone, 2,3-dimethylanthraquinone, 
2-phenylanthraquinone, 2,3-diphenylanthraquinone, sodium salt of 
anthraquinone alpha-sulfonic acid, 3-chloro-2-methylanthraquinone, 
retenequinone, 7,8,9,10-tetrahydronaphthacenequinone, and 
1,2,3,4-tetrahydrobenz[a]anthracene-7,12-dione, ethyl anthraquinone, etc. 
The initiator is present in an amount of 0.1 to 5.0% by weight based on 
the total weight of the composition, preferably 1.0 to 1.4% by weight. 
The useful binder system (c) of this invention is a reaction product of 
three polymer components. Polymer component (1) is a terpolymer of methyl 
methacrylate (27 to 31%, preferably 29%)/n-butylmethacrylate (40 to 45%, 
preferably 42 or 43%)/methacrylic acid (26 to 32%, preferably 28% to 30%). 
The terpolymer has an acid number in the range of about 175 to 200 and an 
inherent viscosity of about 0.4 to 0.5. Polymer component (2) is an amine 
terminated polyamide resin, e.g., of the 6 (81.3%)/66 (0.7%)/610 (18.0%) 
type having a melting point of 145.degree.-150.degree. C. (this resin is 
generally present with 3 to 18% by weight of a plasticizer, preferably 15% 
by weight; or the 6 (5 to 10%)/66 (20 to 30%)/12 (60 to 70%) type having a 
melting point of 120.degree.-130.degree. C. which is preferred. The 
polyamide codes of the resins are: 6 is polycaprolactam, 12 is poly-omega 
laurolactam, 66 is polyhexamethylenediamine adipate, and 610 is 
polydecamethylenediamine adipate. Polymer component (3) is a copolymer of 
vinyl pyrrolidone (60%) and vinyl acetate (40%). All the above values in 
this paragraph are weight percent. Component (1) is present in the binder 
in amounts of 65 to 87% by weight, preferably 70 to 75% by weight; 
component (2) is present in amounts of 5 to 20% by weight, preferably 12 
to 18% by weight, and component (3) is present in amounts of 5 to 20% by 
weight, preferably 9 to 13% by weight, all based on the total weight of 
the binder component. Based on the total weight of photopolymerizable 
composition, the binder is present in a range of 40 to 80% by weight, 
preferably 60 to 65% by weight. 
Suitable thermal polymerization inhibitors present in the 
photopolymerizable compositions include: 
1,4,4-trimethyl-2,5-diazobicyclo[3.2.2]-non-2-ene-N,N'-dioxide (preferred) 
as well as p-methoxyphenol, hydroquinone, alkyl and aryl-substituted 
hydroquinones, tert-butyl catechol, pyrogallol, naphthylamines, 
.beta.-naphthol, p-benzoquinone, 2,6-di-tert-butyl-p-cresol, 
dicyclopentadienyliron, phenothiazine, pyridine, nitrobenzene, 
dinitrobenzene, p-toluquinone, chloranil, and thiazine dyes, e.g., 
thionine, thionine blue G, methylene blue B and toluidine blue O, etc. The 
thermal polymerization inhibitor is present in the composition in 0.03 to 
0.10% by weight based on the total weight of the composition, preferably 
0.05 to 0.07% by weight. 
Optionally a plasticizer for the composition can be present in amounts of 0 
to 18% by weight, preferably 6 to 15%, most preferably 9% by weight based 
on the weight of composition. Useful plasticizers include well known solid 
types such as triphenyl phosphate, glyceroltriacetate (triacetin), 
glyceroltributyrate, triethylene glycol diproprionate, dimethyl phthalate, 
mixed o,p-toluene sulfonamides, etc. 
Another optional component is a tertiary amine capable of salt formation 
with a carboxylic acid. When present this component is present in an 
amount of 0 to 2% by weight based on the total weight of the composition, 
preferably 0.5 to 1.5% by weight, if present. Suitable tertiary amines 
include: diethylcyclohexylamine (preferred), triethylenediamine, pyridine, 
triethylamine, tributylamine, triamylamine, trimethylamine acetate, 
pyridine acetate, etc. 
Additional optional additives include: dyes, preferably window dyes, 
pigments, fillers, etc. 
The above ingredients can be mixed in a twinscrew extruder device as 
described below and the composition formed extruded into the nip of a 
calender. The extruded composition is calendered between two surfaces, 
i.e., a support and a cover sheet. The calender nip is adjustable to 
provide variations in layer thickness, e.g., 0.010 to 0.250 inch (0.254 to 
6.35 mm). Layers within this range of thickness will be used for the 
majority of the printing plates. Thinner layers, e.g., to a thickness of 
at least 0.0005 inch (0.0127 mm) can be provided by known coating 
techniques using suitable solvents and standard coating equipment. The 
laminated photopolymer element formed is cooled, e.g., by blowing with 
cool air, etc., and is cut into a desired size. Suitable supports include: 
metal and polymer film supports. Suitable metal supports are copper, 
aluminum, steel, tin-plated steel, chrome-plated steel, chromate-treated 
aluminum, copper plated aluminum, etc. The metal supports generally have a 
thickness in the range of 0.001 to 0.100 inch (0.025 to 2.5 mm). Suitable 
film supports are polyethylene terephthalate, flame-treated polyethylene 
terephthalate, electron-discharge treated polyethylene terephthalate, etc. 
which can be coated with a suitable adhesive or subbing layer. Removable 
cover sheets useful to protect the photopolymer surface of the element 
include: polyethylene terephthalate which may be sub-treated and gelatin 
coated, and other known cover sheets. 
Printing reliefs can be made in accordance with this invention by exposing 
to actinic radiation selected portions of a photopolymer layer of an 
element described above, for example, through a process transparency, 
i.e., an image-bearing transparency or stencil having areas substantially 
transparent to actinic radiation and of substantially uniform optical 
density and of areas opaque to actinic radiation and of substantially 
uniform optical density until substantial addition-polymerization takes 
place. The image areas can be comprised of halftone dots. During the 
addition-polymerization, the ethylenically unsaturated compound is 
converted to the insoluble state in the radiation-exposed portions of the 
layer, with no significant polymerization taking place in the unexposed 
portions or areas of the layer. The unexposed portions of the layer are 
removed by means of an aqueous alkaline solution, e.g., 0.01 to 0.2 N, 
preferably 0.04 N sodium hydroxide solution, as well as other alkali metal 
hydroxides, e.g., lithium and potassium hydroxide; the base-reacting 
alkali metal salts of weak acids, e.g., lithium, sodium, and potassium 
carbonates and bicarbonates; ammonium hydroxide and tetra-substituted 
ammonium hydroxides, e.g., tetramethyl-, tetraethyl-, trimethylbenzyl-, 
and trimethylphenylammonium hydroxides, sulfonium hydroxides, e.g., 
trimethyl-, diethylmethyl, dimethylbenzyl-, sulfonium hydroxides, and the 
basic soluble salts thereof, e.g., the carbonates, bicarbonates and 
sulfides; alkali metal phosphates and pyrophosphates, e.g., sodium and 
potassium triphosphates and sodium and potassium pyrophosphates; 
tetra-substituted (preferably wholly alkyl) phosphonium, arsonium, and 
stibonium hydroxide, e.g., tetramethylphosphonium hydroxide. The process 
transparency may be prepared from any suitable material including oriented 
polyester film, cellulose acetate film, etc. 
Actinic radiation from any source and of any type can be used in the 
photopolymerization process. The radiation may emanate from point sources 
or be in the form of parallel rays or divergent beams. By using a broad 
radiation source relatively close to the image-bearing transparency, the 
radiation passing through the clear areas of the transparency enters as 
divergent beams and thus irradiates a continually diverging area in the 
photosensitive layer underneath the clear portions of the transparency. 
This results in a polymeric relief having its greatest width at the bottom 
of the photosensitive layer, i.e., a frustum, the top surface of the 
relief being approximately the dimensions of the clear area. 
Inasmuch as the free-radical generating systems activatable by actinic 
radiation generally exhibit their maximum sensitivity in the ultraviolet 
range, the radiation source should furnish an effective amount of this 
radiation, preferably having a wavelength range between about 2500 A and 
5000 A. Suitable sources of such radiation, in addition to sunlight, 
include carbon arcs, mercury-vapor arcs, fluorescent lamps with 
ultraviolet radiation-emitting phosphors, argon glow lamps, electron flash 
units and photographic flood lamps. Of these, the mercury-vapor lamps, 
particularly the sun lamp or "black light" type, and the fluorescent sun 
lamps, are most suitable. Electron accelerators and electron beam sources 
through an appropriate mask may also be used. 
The radiation exposure time may vary from fractions of a second to minutes, 
depending upon the intensity and spectral energy distribution of the 
radiation source, its distance from the composition and the nature and 
amount of the composition available. Customarily, a mercury vapor arc or a 
sunlamp is used at a distance of about 1.5 to about 60 inches (3.8 to 153 
cm) from the photosensitive composition. Exposure temperatures are not 
particularly critical, but it is preferred to operate at about ambient 
temperatures or slightly higher, i.e., about 20.degree. to about 
35.degree. C. 
Solvent development may be carried out at about 25.degree. C., but best 
results are sometimes obtained when the solvent is warm, e.g., 30.degree. 
to 60.degree. C. Development time can be varied but preferably is in the 
range of 5 to 25 minutes. 
In the development step where the relief is formed, the solvent may be 
applied in any convenient manner, as by pouring, immersion, spraying, or 
roller application. Brushing aids in the removal of the unpolymerized or 
uncrosslinked portions of the composition. 
After liquid development the plate is dried, e.g., by placing in front of a 
fan, optionally in hot air, to a temperature of about 20.degree. (room 
temperature) to 25.degree. C. for 0.75 to 8 hours for maximum strength. 
BEST MODE FOR CARRYING OUT THE INVENTION 
The best mode is illustrated in Example 1. 
INDUSTRIAL APPLICABILITY 
The aqueous developable photopolymerizable compositions are useful in the 
preparation of photopolymerizable elements which upon imagewise exposure 
and aqueous development result in printing plates. The printing plates 
which are long wearing and flexible are useful in many types of printing 
but particularly for dry offset, relief or letterpress printing plates. 
The printing plates are produced by a less expensive and more ecologically 
sound method. The new printing plates also do not require 
photoconditioning prior to use. 
EXAMPLES 
The invention is illustrated by the following examples wherein the parts 
and percentages are by weight. The polymeric molecular weights are 
expressed as number average molecular weights (Mn). The Mn for the 
polymers described herein can be determined by gel permeation 
chromatography employing a polybutadiene standard or other standard known 
to those skilled in the art. 
The following screening procedure is utilized to determine whether a 
particular photopolymerizable composition is of proper quality. The 
procedure describes the preparation of photopolymerizable compositions 
(A), the preparation of photopolymerizable elements utilizing the 
compositions (B), and the preparation of exposed and developed elements 
(C) and their evaluation for specified properties as set forth below. 
SCREENING PROCEDURE 
A. Preparation of Photopolymerizable Compositions 
The three components making up the binder system are weighed together, as 
are the other ingredients of the photopolymerizable composition, e.g., 
monomer, initiator, inhibitor, plasticizer, etc. The mixtures are blended, 
e.g., on a two roll rubber mill (3 inch by 8 inch rolls, 7.62 cm by 20.32 
cm), for 5 to 7 minutes at 150.degree. to 160.degree. C. roll temperature. 
A significant melt toughening is observed as the binder components react 
with one another. After milling, the mill is cooled and the composition is 
removed from the mill as a slab. The slab is weighed to determine the 
percentage yield, e.g., generally about 95%. 
B. Preparation of Photopolymerizable Elements 
The slab prepared in A above is pressed between an adhesive-coated metal 
support and an 0.004 inch (0.102 mm) polyethylene terephthalate cover 
sheet in an 0.030 inch (0.762 mm) mold at 145.degree. C. and the ram 
pressure conditions indicated below in a Dake 25 ton (25,410 kg) 
Laboratory Press with steam heated platens, Model 44-069, or similar type 
hydraulic press. 
Cycle: 
2 minutes warm up in press 
1 minute at 10,000 lbs (4535.9 kg) 
1 minute at 20,000 lbs (9071.8 kg) 
1 minute at 30,000 lbs (13,607.7 kg) cool under pressure to room 
temperature and release pressure 
The unexposed element is tested for washout or development rate in 0.04 N 
aqueous NaOH solution at 85.degree. F. (29.degree. C.) in a washout 
machine, e.g., Du Pont.RTM. Master Flat Plate Washout apparatus or 
Dycril.RTM. Hi Speed Rotary Washout apparatus, E. I. du Pont de Nemours 
and Company, Wilmington, Del. Element thickness is determined 
micrometrically before and after one minute washout and subsequent drying, 
and the difference is taken as the washout rate. The washed out areas are 
examined visually and by touch for the presence of "grit" or roughness of 
finish which is an indication of inhomogeneity of the photopolymer matrix. 
In addition, a separate unexposed element is washed out to complete 
removal of unexposed photopolymer matrix from the support, and the time is 
recorded. 
C. Preparation of Exposed and Developed Elements 
(1) Photoconditioning 
Photoconditioning is preferred to prevent inhibition of the photoreaction 
by oxygen diffusing into the element. An unexposed element prepared as 
described in B above with the cover sheet removed is placed in a flatbed 
exposure unit, e.g., Du Pont.RTM. Flat Blacklight Exposure Unit, E. I. du 
Pont de Nemours and Company, Wilmington, Del. under a Krene.RTM. 
(polyvinyl chloride) cover sheet and a polyvinyl fluoride film filter and 
is exposed to actinic radiation from a bank of 18 Sylvania VHO tubes 2 
inches (5.08 cm) from the surface. An opaque mask covers a 2-inch (5.08 
cm) strip of the element during a 20 second initial exposure and is 
advanced 1 to 1.5 inches (2.54 to 3.81 cm) for each succeeding five-second 
exposure increment to a total of twelve. The exposed element is washed out 
for the time found under B above and is dried. The photoconditioning time 
is taken to be about 50% of the minimum exposure time giving complete 
polymerization through the layer in the corresponding exposure step area. 
Following the photoconditioning exposure set forth above, within 2 minutes 
the element is exposed through a sensitometric test negative, matte side 
down, and the Krene.RTM. (polyvinyl chloride) cover sheet under 15 inches 
vacuum (38.1 cm mercury). Exposures of one minute through 31/2 minutes at 
1/2 minute intervals are performed on the test element. The element is 
then removed from the exposure device, is washed out for the time noted 
above, is dried, is examined with a 10x glass, and the minimum exposure 
yielding an acceptable 0.012 inch (0.305 mm) isolated dot, i.e., minimal 
to zero undercutting, and good 5 percent (120 line screen) highlight dots 
is determined. This is the smallest acceptable exposure (SAE). 
The exposed, developed and finished elements are evaluated with respect to 
the following properties as appropriate. 
1. Knoop hardness: ASTM-D1474-69, Method A 
2. Photospeed: (SAE) 
3. Image quality: Shadow well depths and image element profiles 
4. Flexibility: under conditions of 5% relative humidity 
5. Wear resistance of printing reliefs: Taber Abraser 
Knoop hardness values, 1 above, are determined by ASTM-D1474-69, Method A. 
Photospeed, 2 above, is determined as noted above (SAE). Image quality of 
printing reliefs, 3 above, includes both qualitative and quantitative 
evaluation. The image profiles of the exposed and developed elements are 
judged subjectively with respect to correct frustum shape. Shadow well 
depths are measured microscopically using a Zeiss Opton.RTM. interference 
microscope fitted with a distance scale on the focusing dial. The 
difference in readings when interference fringes appear in the microscope 
focused on the printing surface and focused on the bottom surface of the 
shadow well is the shadow well depth. Flexibility at low relative 
humidity, 4 above, is determined as follows: a photopolymer element is 
given an overall uniform SAE exposure using an ultraviolet blacklite 
source. The exposed element is given a 5-minute washout using 0.04 N 
aqueous NaOH at 85.degree. F. (30.degree. C.), is rinsed with water and is 
dried in air at ambient temperature for 10 minutes. The element is 
transferred to a low humidity room (5 to 15% RH/70.degree. to 75.degree. 
F. (21.degree. to 24.degree. C.) for storage. Testing of the element is 
accomplished after 1 hour and 24 hours at the low humidity. The sample is 
placed in a bending jig and is bent until fracture occurs or the bending 
limit of 100 degrees deflection is reached. A suitable testing device is a 
Tabor Stiffness Tester modified to withstand the stresses imposed in 
testing metal-supported plates. The larger the angle through which bending 
without fracture occurs, the better the plate quality. 
The wear resistance of printing reliefs, 5 above, is determined as follows: 
a dried, exposed developed element prepared as described in test 4 above 
is placed in a small pan of Varntine.RTM. solvent (mineral spirits sold by 
Varn Products Co., Oakland, N.J.) on the sample holder of a Taber Abraser 
fitted with a 500 g counterweight and a H-38 wheel. The sample is abraded 
for 45 minutes at room temperature, is removed from the solvent bath, is 
blotted dry, and is measured for abrasion loss with a micrometer. 
In Example 1, the photopolymerizable composition is prepared by means of a 
Werner and Pfleiderer 83 mm co-rotating intermeshed twin screw compounding 
extruder, model ZSK 83, configured and operating as set forth below and in 
Table 1:157 to 160.degree. C. melt temperature, 150 to 190 rpm screw 
speed, and 200 to 300 pounds (90 to 136 kg)/hour delivery rate. 
TABLE 1 
______________________________________ 
Screw 
Screw Bushing.sup.2 
Running 
Barrel.sup.1 
Temp Designa- 
Length 
No. .degree.C. Lead.sup.2a 
Length.sup.2b 
tion.sup.2c 
(mm) 
______________________________________ 
1 RT &lt; T .ltoreq. 100 
120 120 SK.sub.3 -RH.sub.4 
120 
120 120 SK-RH 240 
2 95-113 120 40 SK-N 280 
120 120 RH 400 
90 30 RH 430 
3 95-113 75 150 RH 580 
75 150 RH 730 
4 95-113 75 75 RH 805 
75 25 RH 830 
75 25 RH 855 
KB.sup.6 
30 RH 885 
KB 45 N.sup.7 
930 
KB 30 LH.sup.8 
960 
KB 45 N 1005 
5 95-113 KB 45 N 1050 
KB 30 RH 1080 
KB 45 N 1125 
KB 45 N 1170 
75 25 LH 1195 
75 25 LH 1220 
6 79 120 120 RH 1340 
120 120 RH 1460 
7 94 90 90 RH 1550 
75 150 RH 1700 
8 94 75 150 RH 1850 
75 75 RH 1925 
75 75 RH 2000 
60 20 RH 2020 
60 20 RH 2040 
______________________________________ 
Input and Removal Locations: The three solids input occur between 60 and 
180 mm; the fluid input port is located between 280 and 400 mm; and vapor 
is removed under vacuum at about 1280 mm, all values are expressed in 
screw running length. 
.sup.1 Housing building block for extruder screw. 
.sup.2 Extruder screw building block. 
.sup.2a Screw length in mm for 360.degree. rotation. 
.sup.2b Actual length of the element in mm. 
.sup.2c Manufacturer's element code. 
.sup.3 SK is undercut. 
.sup.4 RH is righthanded. 
.sup.5 Transition from undercut to regular screw. 
.sup.6 KB is kneading block. 
.sup.7 Transition element from RH .rarw..fwdarw. LH. 
.sup.8 LH is left handed.

EXAMPLE 1 
A photopolymerizable composition is prepared as follows: 
The following three solid ingredients are fed by three separate feeders 
simultaneously into the solids input port of a Werner and Pfleiderer 83 mm 
co-rotating twin screw intermeshed compounding extruder. 
______________________________________ 
Ingredient Amount (%) 
______________________________________ 
Terpolymer of methylmethacrylate (29) 
45.74 
n-butylmethacrylate (43)/methacrylic 
acid (28) having an acid no. of 175- 
200 and an inherent viscosity of ca. 
0.4 to 0.5 
Amine-terminated polyamide 
10.00 
resin (6/66/12) (5-10/20-30/60- 70), 
melting point of 120 to 130 C. 
Copolymer of vinyl pyrolidone (60)/ 
7.00 
and vinyl acetate (40) 
______________________________________ 
The following substantially liquid ingredients after being mixed together, 
are added through the liquid input port of the extruder simultaneously 
with the above solids. 
______________________________________ 
Ingredient Amount (%) 
______________________________________ 
Tetraethylene glycol diacrylate 
27.00 
Triphenyl phosphate 9.00 
2,2-Dimethoxy-2-phenyl 
1.20 
acetophenone 
1,4,4-Trimethyl-2,5-diazobicyclo- 
0.06 
[3.2.2]-non-2-ene-N,N'--dioxide 
______________________________________ 
The extruder performs the functions of melting, pre-mixing, homogenizing, 
devolatilizing and filtering the composition before delivery at 
155.degree. to 175.degree. C. to the extrusion die. The extruded 
composition enters the rotating bank of a two roll calender, 16 inches by 
48 inches (40.64 by 121.92 cm), and is calendered between the coated side 
of an electrolytic tin plate support, 0.012 inch (0.305 mm) in thickness 
and the release side of a polyethylene terephthalate cover sheet having a 
subbing layer as described in U.S. Pat. No. 2,627,088 Example IV and a 
gelatin layer, 0.007 inch (0.18 mm) in thickness. The coated side of the 
tin plate support contains in succession a primer coating comprising an 
epoxy-urea formaldehyde resin and a red iron oxide pigment; an adhesive 
layer comprising an isocyanate-modified copolyester; and a barrier and 
anchor layer to improve adhesion and prevent or inhibit monomer migration 
and comprising a composition similar to the photosensitive composition but 
with benzoyl peroxide replacing the photoinitiator. The coatings are 
successively applied to the metal support and cured by commercial coil 
coating techniques known to those skilled in the art. The calender nip can 
be adjusted to produce variations in layer thickness which in this 
instance is 0.030 inch (0.762 mm) thick. The laminated element is cooled 
with blown air and is cut to the desired size. 
The element is placed in a Du Pont Flat Blacklight Exposure Unit, E. I. du 
Pont de Nemours and Company, Wilmington, Del., over which is placed a 
0.001 inch (0.254 mm) thick polyvinyl fluoride film filter and is exposed 
for 1 to 2 minutes through an image containing halftone dots and 
highlights to actinic radiation from a bank of 20 Sylvania VHO 65 watt 
tubes 2 inches (5.08 cm) from the surface. The exposed element is removed 
from the exposure device and is placed in a washout developer device 
described in the Screening Procedure above, and is developed for 5 minutes 
using a 0.04 N aqueous NaOH solution at 85.degree. F. (29.degree. C.). A 
good quality relief printing plate having the properties set forth in 
Table 2 is achieved. 
TABLE 2 
______________________________________ 
Test Result 
______________________________________ 
1. Photosensitization 
(a) Exposure time (sec.) 
25.0 
2. Photoimaging exposure 
Photosensitized (min.) 
1.0 
Nonphotosensitized (min.) 
2.0 
3. Washout time (min.) 
5.5 
4. Flatness Good; no round 
edges 
5. Adhesion 
100 to 2000 M impressions 
Good 
6. Print quality Good 
7. Devlopment rate 
inch/min. (mm/min.) 
0.005 (0.127) 
8. Reverse dot well, inch (mm) 
0.00241 (0.0612) 
9. Wear, inch (mm) 0.0043 (0.011) 
10. Flexibility No break at 100 
degrees 
deflection 
______________________________________ 
EXAMPLE 2 
Three printing plates, A, B and C, having the ingredients described in 
Table 3 below are prepared according to the Screening Procedure. 
TABLE 3 
______________________________________ 
Samples (Parts) 
Ingredient A B C 
______________________________________ 
Terpolymer of methylmeth- 
42.74 -- -- 
acrylate (28.5)/n-butylacrylate 
(42)/methacrylic acid (29.5) 
having an acid no. of 175-200 
and an inherent viscosity of 
ca. 0.4 to 0.5 
Terpolymer described in 
-- 45.74 -- 
Example 1 
Amine-terminated polyamide as 
10.0 10.0 -- 
described in Example 1 
Poly[vinyl pyrrolidone (60)/ 
7.0 7.0 -- 
vinyl acetate (40)] 
Cellulose acetate succinate 
-- -- 50.93 
Cellulose acetate -- -- 9.67 
Tetraethyleneglycol diacrylate 
23.0 27.0 -- 
Triethyleneglycol diacrylate 
-- -- 24.73 
Triphenyl phosphate 16.0 9.0 -- 
Tributoxyethyl phosphate 
-- -- 12.89 
2,2-Dimethoxy-2-phenyl 
1.2 1.2 -- 
acetophenone 
2-Ethylanthraquinone 
-- -- 0.10 
1,4,4-Trimethyl-2,5- 
0.03 0.06 -- 
diazobicyclo-[3.2.2]-non- 
2-ene-N,N'--dioxide 
Hydroquinonemonomethyl ether 
-- -- 0.20 
Diethylcyclohexylamine 
-- -- 1.48 
______________________________________ 
Elements A and C are tested according to the procedures described above 
with the results shown in Table 4 being achieved. 
TABLE 4 
______________________________________ 
Samples 
Test A C 
______________________________________ 
1. Flexibility No break No break 
2. Wear, inch 0.00043 .+-. 0.00013 
0.00053 .+-. 0.0001 
mm 0.0109 .+-. 0.0033 
0.01346 .+-. 0.00254 
3. Reverse Dot 
Depth, 0.005 
inch/ 0.00241 0.00227 
0.127 mm 0.0612 0.0577 
4. Grit None Trace 
______________________________________ 
The printing plate of the invention (A) has less wear, improved large dot 
retention, and absence of grit while it is at least equal in flexibility 
to the prior art printing plate (C). 
Printing plate B is compared to printing plate C is press tests. The 
comparative results are set forth in Table 5. 
TABLE 5 
______________________________________ 
Samples 
Characteristic B C 
______________________________________ 
1. Photsensitization 
(a) Exposure time (sec.) 
25.0 90.0 
(b) Relative speed 
3.6 1.0 
2. Photoimaging exposure 
Photosensitized (min.) 
1.0 4.0 
Nonphotosensitized (min.) 
2.0 10.0 
3. Relative imaging speed 
Photosensitized 4.0 1.0 
Nonphotosensitized 
5.0 1.0 
4. Washout 
Time (min.) 5.5 7.5 
Relative rate ca. 1.4 1.0 
5. Flatness Good Edges 
Rounded 
6. Adhesion Good Good 
172.sup.1 -250.sup.2 M impressions 
7. Print Quality Good Good 
______________________________________ 
.sup.1 General Web Dynamics, 2color Webaligner at 1500 feet/min. (457.2 
m/min.) 
.sup.2 Hamilton Web, 3color Press 
The printing plate of the invention is superior to the prior art printing 
plate in its photosensitization time, photoimaging time, washout time, 
flatness and is at least equal in adhesion to the support and print 
quality. 
EXAMPLE 3 
This example illustrates the superiority of photopolymerizable compositions 
containing the three component binder system of the invention over those 
containing two-component and single-component binders. Three printing 
plates, A, B and C, having the ingredients described in Table 6 below are 
prepared according to the Screening Procedure. 
TABLE 6 
______________________________________ 
Samples (%) 
Ingredient A B C D 
______________________________________ 
Terpolymer 45.74 52.74 55.74 
55.10 
described in 
Example 2 
Amine-terminated 
10.0 10.0 -- -- 
polyamide 
described in 
Example 1 
Poly[vinyl 7.0 -- 7.0 -- 
pyrrolidone (60)/ 
vinyl acetate (40)] 
Tetraethylene- 27.0 27.0 27.0 32.526 
glycol diacrylate 
Triphenyl 9.0 9.0 9.0 10.842 
phosphate 
2,2-Dimethoxy- 1.2 1.2 1.2 1.445 
2-phenyl 
acetophenone 
1,4,4-Trimethyl- 
0.06 0.06 0.06 0.007 
2,5-diazo-bicyclo 
[3.2.2]-non-2-ene- 
N,N'--dioxide 
______________________________________ 
The elements are tested according to the Screening Procedures and achieve 
the results shown in Table 7. No element is made from Sample D since the 
composition does not homogenize on the rubber mill and falls off. 
TABLE 7 
______________________________________ 
Samples 
Test A B C 
______________________________________ 
Development rate 
inch/min. 0.0057 0.0041 0.004 
(mm/min.) (0.145) (0.104) (0.102) 
Reverse dot 
well, inch (mm) 
0.00235 0.00033 0.00218 
(0.0597) (0.0084) (0.0554) 
Wear, inch (mm) 
0.00032 0.00037 0.00072 
(0.0081) 0.0094) (0.0183) 
Flexibility (.degree.) 
82.0 60.0 56.0 
______________________________________ 
Sample A, which illustrates the invention, is superior with respect to 
development rate, reverse dot well rendition, wear, and flexibility over 
printing plates B and C.