JPS5950971B2 - curable composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to curable compositions, particularly curable compositions whose curing can be controlled by the use of suitable curing agents.

Printing plates contain photosensitizers and are cross-linked by the action of actinic radiation. It is known that they can be produced by curing ethylenically unsaturated compounds which are dried and insolubilized.

When such a composition is formed into a printing plate under the action of actinic radiation at room temperature, addition polymerization of the polymerizable double bonds in the compound is inhibited by the air. This suppression causes a very thin liquid film to be present on the surface, making it sticky. Eventually, it is possible to replace the oxygen at the photosensitive surface with an inert gas, treat the surface with chemical additives that absorb or inert the oxygen, or use very intense light sources that literally burn off the oxygen4. , is generally considered desirable. The main object of the present invention is to provide a liquid or solid illuminable composition for producing relief printing plates that substantially satisfies the following:1. Imagewise exposure of the composition, even in the presence of air, gives a surface that is not tacky, thereby eliminating the need for continued processing of the crosslinked areas to form a relief image or exposure in the absence of oxygen. Eliminating the need for expensive equipment to perform.

2. The exposure time of the composition required is as short as possible, reducing cycle times for the production of finished printing plates as required in the newspaper industry.

The compositions, methods of forming coatings on supports and methods of forming printing plates of the present invention form essentially non-tacky surfaces.

According to the invention, (1) about 10 to about 97% by weight of the composition;
(2) a C-C unsaturated polymeric resin selected from monoalkenyl aromatic diene copolymers, butadiene polymers, acrylonitrile resins and mixtures thereof, a C-C saturated polymeric binder or mixtures thereof; at least about 1% by weight of material (1) at least one monomer having at least one crosslinkable unsaturated bond; and (3) from about 0.1 to about 35% by weight of material (1) thiol; A composition is provided, wherein the concentration of thiol is preferably chosen so as not to significantly change the oxidative properties of the composition with respect to the same composition without thiol.

This composition is such that the radiation-cured composition has a tacky surface when the thiol is omitted, i.e., a sufficient amount of thiol is present in the composition to substantially eliminate tackiness on the surface. or create a non-stick surface. Preferably the monomer contains at least two crosslinkable C-C double bonds; it is an addition polymerizable ethylenically unsaturated acrylic or methacrylic ester containing two or more acrylate or methacrylate groups per molecule. and generally at least 5% or 10% by weight of material 1, especially when the resin is a monoalkenyl aromatic diene, e.g.
Present in an amount of ˜60% by weight, and in some embodiments more preferably from 15 to 30% by weight, but not more than 10% by weight when the resin is a halogen-substituted butadiene resin.

The thiol is preferably a polythiol and preferably comprises from 0.1 to 10% by weight of material 1, such as from 0.5 to 10% by weight of material 1.
Present in an amount of 10% by weight. The C-C saturated polymeric binder or C-C unsaturated polymeric resin (Material (1)) suitably comprises 10 to 80% by weight of Material (1), generally at least 20%, preferably at least about 40% by weight. %, so preferably at least about 60% by weight, especially when the resin is a polyene, such as from 40 to 60% by weight, or especially when a halogen-substituted butadiene resin, at least 80% by weight.

Material (1) is less than 95%, preferably 50-9
Present in an amount of 0%.

The present invention also provides a method of forming a coating on a support, comprising applying onto the surface of the support a layer of the composition of the invention, in which the monomer is radiation crosslinkable.

After application, the composition is exposed to actinic radiation or high energy ionizing radiation or combinations thereof. Exposure at random. Preferably the photoinitiator is contained in an amount of about 0.01 to about 10%, most preferably 0.2 to 5% by weight of the material (1) of the composition.

This method of forming a coating can be used in the production of printing plates,
In this case, this person. The method consists of exposing the coating to actinic radiation projected through an image-bearing transparency, thereby curing selected portions thereof. The following description relates primarily to the production of printing plates. C-C unsaturated polymer resin [
Component (1)] is monoa. alkenyl aromatic diene copolymers, butadiene polymers, acrylonitrile resins and mixtures thereof.

The resin is generally a polyene having a polymeric structure and an average molecular weight of at least about 5,000. Preferred monoalkenyl aromatic-diene copolymer resins have the general formula:
A-B-A, where A can be the same or different, and have an average molecular weight of 2000 to 100,00
0 and a glass transition temperature of 25°C or higher, the total content of Block A is 10 to 50% by weight of the copolymer, and B has an average molecular weight of 25°C. ,000~1,000,000
It is an elastomerginin polymer block having a glass transition temperature of 10° C. or less. These terminal blocks (A) are typically derived from monoalkenyl aromatic compounds having the general formula: where X is hydrogen or a C1 or C2 alkyl group (methyl or ethyl); Y is hydrogen or an alkyl group having 1 to 4 carbon atoms (methyl, ethyl, n-propyl, isopropyl, n-butyl, Sec-butyl or tert-butyl); and n is an integer of 1 to 5.

Examples are styrene, α-methylstyrene, tert-butylstyrene, vinyltoluene, o- and m-methylstyrene, o- and P-methyl-α-methylstyrene,
and o- and P-ethylstyrene. The elastic block (B) is preferably a diene polymer block derived from a conjugated diene hydrocarbon compound having the general formula: where each R is individually hydrogen or an alkyl group having 1 or 2 carbon atoms (methyl or ethyl). ).

Examples are 1,3-butadiene and 2-methyl-1,3-butadiene. Useful such monoalkenyl aromatic block copolymers are described in US Pat. No. 3,265,765.

Another generally less preferred monoalkenyl aromatic diene copolymer resin has the general formula: A-B, where A and B are as defined above.

This can have a sharp or undefined or "flowing" transition between two block segments of a copolymer formed solely from diene-hydrocarbon or styrene-monomers. The two-block copolymers generally contain 5 to 70% by weight, preferably 10 to 40%, of styrenic type units, resulting in 30 to 95%, preferably 60 to 90%, of polymerized diene hydrocarbons. Contains terminal units. Such two-block copolymers are described, for example, in U.S. Pat. No. 3,149,182, LRunty
．． J. POlymerSci. Engineering (1961), 569
-586 and Y. U. Spirinetal J. P.O.
lymerSci. 58 (1962) 1181-118
It can be manufactured as described in 9.

Copolymers can be produced continuously or discontinuously. When producing copolymers with sharply separated block segments by stepwise polymerization, it is advantageous to start with the polymerization of monomers that predominate quantitatively. Advantageously 2
-Protect copolymers are prepared by solution polymerization; suitable solvents are in particular hydrocarbons or mixtures thereof, which are preferred, as well as polar solvents such as tetrahydrofuran. The type of solvent affects the microstructure of the two-block copolymer, such as the shape of the diene polymer segments. using a solution of a PROTSTA copolymer produced by solution polymerization directly or in a concentrated state;
It is then particularly advantageous to add other coating components to produce the photocrosslinkable layer by casting. Suitable 2-block copolymers of the type shown have approximately 60 to 350 ml/g, measured as a 0.5% by weight solution in toluene.
, in particular a viscosity number of 90 to 250 m1/g, which corresponds approximately to a molecular weight range Mυ of 75,000 to 200,000.

Preferred butadiene resins include butadiene, most preferably halogen-substituted butadiene of the 1,3-butadiene type, most preferably 2-chloro-1,3-butadiene,
Derived from 2-fluoro-1,8-butadiene and 2,3-dichloro-1,3-butadiene.

Most preferred is 2-taloS-rho-1,3-butadiene (chlorobrene). A preferred acrylonitrile resin is a copolymer of butadiene and acrylonitrile, where the acrylonitrile is generally 22% by weight of the copolymer.
~532%.

The C-C saturated polymeric binder of component (1) can be, for example, polyvinylpyrrolidone, cellulose acetate butyrate or cellulose acetate stannate.

These binders and/or mixtures of such binders may also be used, and preferably their polymeric structures have an average molecular weight of at least about 5,000. It is of course also possible to use mixtures of C--C unsaturated polymer resins and C--C saturated binders.

For certain special applications, component (1) can be combined with small amounts of other compatible polymers and certain elastomers. Component (2) is a non-gaseous addition-polymerizable ethylenically unsaturated compound, which generally has a boiling point of 100° C. or more at atmospheric pressure and a molecular weight of about 100 to 1,500, and can easily form a high-molecular-weight addition polymer.

Preferably the addition polymerization is a photoinitiated addition polymerization in the presence of an addition initiator. For superior printing plate products, the monomers are preferably addition photopolymerizable polyethylenically unsaturated acrylic or methacrylate esters or mixtures thereof containing two or more acrylate or methacrylate groups per molecule. Examples of such polyfunctional acrylates are ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetra-acrylate or pentaerythritol-tetramethacrylate, hexanediol-1,6 - dimethacrylate, and diethylene glycol dimethacrylate. Those that are useful in certain special cases are monoacrylates, e.g.
n-butyl-acrylate, n-butyl-methacrylate, 2-ethylhexyl-acrylate, lauryl-acrylate and 2-hydroxypropyl-acrylate.

Small amounts of amides of (meth)acrylic acid, such as N-methylol methacrylamide butyl ether, are also suitable. N-vinyl compounds, such as N-vinyl-pyrrolidone, vinyl esters of aliphatic monocarboxylic acids, such as vinyl oleate, vinyl esters of diols, such as butanediol-1,4-vinyl ether and allyl ether and allyl Esters are also suitable. Isocyanate-liberating reaction products of organic polyisocyanates, such as hexamethylene diisocyanate, isophorone diisocyanate or tolylene diisocyanate, with (meth)acrylates containing hydroxyl groups, such as glycol monoacrylate, hydroxypropyl methacrylate or 1,4-butanediol-diisocyanate. Reaction products with monoacrylates are also suitable as long as they are reasonably compatible with the resin. The same applies to the reaction products of di- or polyepoxides, such as butane-diol-1,4-diglycidyl-ether or bisphenol-A-diglycidyl-niter, with (meth)acrylic acid. The properties of the photopolymerizable layer can be varied by appropriate selection of monomers or mixtures thereof for the particular purpose. The thiol (component 3)) is preferably a polythiol, which is a simple or complex organic compound with an average of several pendant or terminal --SH functions per molecule.

They are 70
It typically has a viscosity ranging from slightly greater than o to about 20 million centiboads (Cps) at °C. As used herein, "polythiol" includes materials having viscosities in the above viscosity range at 70°C in the presence of reactive plasticizers, such as diallyl phthalate. Suitable polythiols have polythiols ranging from about 95 to about 20,000 or more, preferably about 1
00 to about 10,000. A preferred polythiol that provides a non-tacky surface has the general formula: R6
−←SH)n, where n is at least 2
and R8 is a polyvalent organic moiety that does not contain "reactive" carbon-to-carbon unsaturation. That is, R. is a cyclic group and a small amount of foreign atoms, e.g., N, S, . P or O
but primarily contain carbon-hydrogen, carbon-oxygen, or silicon-oxygen-containing chain linkages without "reactive" carbon-to-carbon unsaturation. One class of polythiols that provides cured polythiol coatings and relief images that are essentially odorless include thiol-containing acids of the general formula: HS-R9-COOH and the general structure: R,.

=(-0H)n with a polyhydroxy compound, where R, is an organic moiety free of "reactive" carbon-to-carbon unsaturation, and R,. is an organic moiety that does not contain "reactive" carbon-to-carbon unsaturation, and n is 2 or more. These components react under appropriate conditions to provide a polythiol having the general structure:

Certain thiols, such as aliphatic monomeric polythiols (e.g. ethanedithiol, hexamethylene dithiol, decamethylene dithiol and tolylene-2,4-dithiol) and some polymeric polythiols, e.g. thiol-terminated ethyl Cyclohexyl dimerkabutane polymers are conveniently and commonly synthesized on a commercial scale and can also be used, although they have an unpleasant odor.

A preferred series of polythiol compounds due to their relatively low odor and rapid curing rate is thioglycolic acid (HS
-CH2-COOH), α-mercaptopropionic acid (
HS-CH(CH3)-COOH) and β-mercaptopropionic acid (HS-CH.

CH. COOH) and polyhydroxy compounds, e.g.
Esters of glycols, triols, tetraols, pentaols and hexaols. The specific columns are: Ethylene Glycol Bis (Thioglycolate), Ethylene Glycol Bis (β-Mercaptopropionate), Trimethylol Propane Tris (Thioglycolate), Pentaerythritol Tetrakis (Thioglycolate) and the most preferred pentaerythritol tetrakis (β-menolecaptopropionate)
and trimethylolpropane tris (β-mercaptopropionate), and mixtures thereof: all of these are commercially available. Monothiols such as β-mercaptopcapionic acid can be used in some cases. Although monothiols significantly reduce tackiness, they generally do not eliminate tackiness to the extent desired for general use. The compositions of the present invention were generally cured using a curing agent, and the curing agent was controlled.

Promotes rapid and measurable or predictable curing performance. Curing agents generally act as free radical generators. Preferably, the free radical generator includes initiation by radiation, ie actinic radiation or high energy ionizing radiation. Most preferably the actinic radiation is ultraviolet radiation. The compositions are used with particular advantage in UV curing for the formation of relief images, in particular for the production of indicia. Preferably, the ultraviolet radiation is emitted from a point source or in the form of parallel beams, but diverging beams can also be used.

Practically any high-intensity UV source can be used, for example carbon arc, mercury arc, fluorescent lamps with special UV-emitting phosphors, xenon arc, sunlight, tungsten halide lamps, argon flow lamps, photographic flat wraps. and can use laser beams. When actinic radiation is used for curing, a photoinitiator or . A catalyst is typically added to the composition to increase the reaction rate and initiate photopolymerization.

Preferred catalysts or initiators are substantially stable in the photocurable composition and are effective in promoting rapid polymerization to cure the composition. A number of suitable photoinitiators or catalysts are described in 1 US Pat. No. 4,008,341, to which reference will be made. Preferred photoinitiators are
1 o Aldehyde and ketone carbonyl 1 compounds having at least one aromatic nucleus directly bonded to the 1 o group. The most preferred photoinitiators are benzophenone and 2,
2-dimethoxy-2-phenylacetophenone.
The compositions of the present invention can also be cured by high energy ionic radiation or bombardment, as described in the aforementioned US Pat. No. 4,008,341.

In another preferred form of the invention, low molecular weight liquid rubbery polymers are incorporated into the composition, for example to increase the softness of the relief plates produced.

Suitable liquid rubber polymers have a molecular weight of 750 to 43,000 and are comprised of homopolymers and copolymers of butadiene, where the copolymers contain at least 30% by weight of the copolymer, more preferably at least 60% by weight of butadiene and the balance. of styrene or atarylonitrile. The addition of such liquid rubber polymer is not more than 50% by weight of the total composition, preferably 0.1 to 50% by weight, more preferably 5% by weight.
It should constitute ~30% by weight. A "liquid" rubber polymer means that it is liquid at temperatures below 23°C. The compositions of the invention include additives such as antioxidants, inhibitors,
Activators, fillers, pigments, dyes, antistatic agents, viscosity modifiers and plasticizers are generally present up to 500 parts by weight, preferably from 0.0005 to 30 parts by weight, per 100 parts by weight of the curable composition.
It is contained in an amount of 0 parts by weight.

The type or concentration of additives must be carefully selected so that, in a preferred embodiment, the final composition is radiation curable under the exposure conditions and suitable for use. The curing period can be delayed or accelerated from, for example, 1 minute or less to, for example, 30 days or more.

Common cure inhibitors or retarders that can be used to stabilize components or curable compositions to prevent premature curing include hydroquinone; pt-butynolecatechol; 2,6-di-t- Butyl-P-methylphenol; phenothiazine; N-phenyl-2-naphthylamine; phosphorous acid and pyrogallol. Examples of common reaction accelerators which speed up the curing reaction rate and extend the range of usable light wavelengths are trimethylphosphite, triethylphosphite, triphenylphosphite, rose bengal and acetone. The method of mixing the components of the photosensitive composition of the present invention is not critical.

Solutions and dispersions of photopolymerizable compositions may be prepared in solvents such as aromatic hydrocarbons such as benzene, toluene and xylene; chlorinated hydrocarbons such as chloroform, carbon tetrachloride, trichloroethylene and chlorotoluene; ketones such as , methyl ethyl ketone, diethyl ketone and methyl isobutyl ketone and blends of such solvents. On the other hand, solid mixtures can be made by mixing the components in a mill or internal mixer, such as a pan-free mixer. The resulting polymerizable composition can be in the form of a liquid solution, liquid dispersion, or solid mixture. The liquid solution or liquid dispersion can be cast directly onto the support, or it can be first cast onto a suitable wheel or belt, peeled off and then fixed onto the support surface. The solid mixture can be extruded or calendered directly onto the support or as a self-supporting sheet and then fixed to the surface of the support.
A convenient method of forming a printing plate involves fixing an image-bearing line or halftone stencil or positive or negative transparency to a support or to a light-absorbing layer on a photocurable composition. parallel to the surface of the

The surfaces of the image-bearing transparency and the photocurable composition should preferably be in contact. To facilitate separation of the image-bearing transparency and printing plate after photopolymerization, it is desirable to coat the printing plate with a "separation" layer or slip coat. Suitable coatings include common acrylic latex coatings, silicone grease, and the like. The photocurable layer is exposed through the transparency to a source of actinic radiation until the photocurable layer is cured to the point that it is insoluble in the exposed areas. The ultimate relief thickness in such methods can be adjusted by varying the layer thickness and/or exposure time of the photocurable composition. Development can be carried out by conventional means.

Generally, after exposure of the plate, the unexposed areas are removed by suitable means. Suitable means have good solvent action on the unexposed radiation-curable composition and on the cured photopolymerized image or on the support, antihalation coating,
Another option is to use a suitable liquid that has relatively little effect on the anchor layer during the period required to remove the unpolymerized portion. Examples of suitable organic solvents for most of the unexposed radiation curable compositions are aliphatic hydrocarbons such as hexane, octane, mineral oil and naphtha, aromatic solvents such as toluene and xylene, halogenated organic solvents. , for example, methylene chloride, trichloroethane, Freon D (FreOn
D), and blends of such solvents. The best solvent to use depends on the exact composition of the radiation curable composition. In the development step to form the relief, the solvent can be applied in any convenient manner, for example by pouring, dipping or spraying. Brushing or stirring removes the unpolymerized portion of the composition. Promote leaving.
The use of ultrasonic cleaning techniques is a convenient means of removing unpolymerized areas of relief printing plates. In the case of liquid systems, air knife stripping can be used to remove unexposed areas. Preferred relief plates of the present invention preferably have a 2 to 200
mil (0.051-5.1mm) or 250 mil (6
．． 35 mm) thick layer of the photopolymerizable composition.

A layer of 3 to 60 mils (0.076 to 1.524 mm) thick can be used for letter. Used for most press printing plates.

Layers 50 to 60 mils (1.27 to 1.524 mm) thick can be used to print relatively large areas and designs in letterpress printing plates.

Generally, the layer forming the relief height of the photocurable layer must be essentially non-light scattering. It is important that the final photosensitive composition has sufficient transparency to transmit a sufficient amount of light to effect addition polymerization. In making printing plates, it is important that the exposure be sufficient to harden the photocurable composition in the exposed image areas and not significantly harden the non-image areas.

In addition to exposure time and light intensity, the degree of exposure depends on the thickness of the photocurable layer, the curing temperature, the polymer used, the monomer used, the thiol used, the photoinitiator, the diluent, and the photocurable composition. It depends on the presence of light-absorbing pigments or dyes therein and on the properties of the layer to be reproduced. Generally, the thicker the layer to be cured, the longer the exposure time. Curing generally begins at the surface of the photocurable layer closest to the light source and progresses toward the support. If the exposure is insufficient, the layer will harden hard at the surface but will lack hardening throughout and the relief will be removed upon removal of the unexposed areas. Cure rate typically increases with higher temperatures, so less exposure is required at temperatures above room temperature. Therefore, a UV source that emits heat is always more efficient than a cold UV source. However, if the temperature is too high, the photocurable composition may thermally expand and distort the image, so care must be taken not to reach such a temperature during photocuring. Therefore, photocuring is preferably carried out at a temperature in the range of about 20 to about 70<0>C. Because there are many variables that affect exposure time, optimal results are best determined experimentally, for example, by stepwise exposure using characterization after each exposure. The support material can actually be a natural or synthetic product, which is generally dimensionally stable and flexible and can be present in the form of a film or sheet.

Sheet metal, such as aluminum or steel, or plastic, such as polyester or polyamide films, are typically used as supports. A preferred support is polyester film. Such materials can be made non-reflective by coating with an antihalation layer, if desired. Suitable antihalation coatings can be made by dispersing finely divided dyes or pigments that substantially absorb actinic radiation in solutions or aqueous dispersions of resins or polymers. Antihalation layers can also be formulated to act as a binder or adhesive layer between the support and the photosensitive composition. Examples of antihalation pigments are carbon black, manganese dioxide and dyes such as acid blue black (CI2O47O) and acid blue black.
It is magenta O (CI42685). Dye-containing metal plates are also useful. If a rotary press plate is desired, the support material can be used to form a flat relief plate, which is then formed into the desired shape.

Additionally, such rotary press plates use various types of cylindrical support plates carrying a curable composition that is exposed directly to actinic radiation through a concentrically arranged image-supporting transparency. It can be operated by In the present invention, the thiol appears to act in some way to modulate and facilitate the polymerization of the other components of the composition.

When the resin is C-C unsaturated and cross-links with the monomer as a major property-giving reaction, the thiols actually act much like scavengers that scavenge oxygen and inhibit other fundamental properties of the system. do not change. C-C saturated binders have a thiol function in the same way, but it is the monomer that bridges itself to form a lattice, and the binder fills the space between the bridged chains, thereby allowing the bond to form. The binder acts as a matrices to hold the crosslinking monomers in place to form the appropriate product. The following discussion relates to many of the advantages of the present invention. (although it is believed that this does not form part of this invention).

When curing the compositions of the present invention, the terminal vinyl groups, even if present in unsaturated polymers or reactive monomers, undergo addition reactions. At the same time, thiol groups compete with molecular oxygen for free radicals, and thiol groups form free radicals faster (lower activation energy), thus forming hydroperoxide groups, which are the moieties that cause stickiness. minimize the formation of The following reaction equation involving a benzoin ether initiator hints at how the use of polythiol minimizes tackiness.

Benzoin and benzoinetherole are a pair of radicals,
Splits into benzoyl and benzyl radicals.

The benzoyl radical O is very reactive and reacts primarily by suction of hydrogen, e.g., and is therefore a very efficient initiator.

The newly formed radical M initiates polymerization by reaction with the acrylic or vinyl double bond. Polymerization proceeds step by step as more monomer is added, resulting in a growing chain.

Such.

A number of things happen to a growing chain: a.
it can attract hydrogen from other molecules,
For example, this will stop the chain.

Can the new radical A゜ start a new chain?
or fails to initiate b, the growing chain encounters other radicals and reacts with them to form covalent bonds. C. The most serious problem: the growing chain is cleaved by oxygen molecules, producing peroxyl radicals, which then do not form a new chain or continue the original chain. It can be disassembled without causing damage.

does not initiate further polymerization.

Obviously oxygen prevents polymerization, but must be excluded, otherwise the surface where most of the oxygen can be found consists of a layer of sticky low molecular weight material.

In the above reaction formula, when the thiol compound is positioned,
The following can happen: the benzyl radical attracts hydrogen from the thiol compound (activation energy considerations)
, forming a thiyl radical.

The thiyl radical then begins to grow the chain. The growing chain can then participate in the following reactions: a) abstraction of hydrogen from other polymer molecules b) the kinetics of the bonding reaction favor the formation of thiyl radicals over the formation of peroxides.

Therefore, a growth phase is obtained rather than a termination reaction. The growth step through thiylradiel prevents oxygen from entering the polymerization, thus minimizing surface stickiness. The compositions of the invention can be used for making relief plates for letterpress printing as well as flexographic printing (solid plates).
This composition is superior to other addition-polymerizable systems for making printing plates, producing high definition relief images with short exposure times. Even in the presence of air, printing plates with non-tacky surfaces can be produced. Furthermore, such plates exhibit excellent ink transfer properties and generally swell only slightly with printing inks. These properties are, of course, influenced by the basic nature of the resin or binder system used. As used herein, the term "curing" refers to the relative curing of a radiation curable composition.

This is compared to "removing unexposed radiation-curable composition," which means removing relatively uncured material. Thus the words "cured" or "hardened" do not mean that curing can no longer occur, and "unexposed" does not mean that radiation has not reached that portion of the composition. . Primarily, the term refers to the condition in which the "hardened" portion can be separated from the unexposed, or uncured, portion. The term "non-stick" means not tacky to the touch, and therefore generally not tacky. The term "tacky" means the tendency of a material to stick to the touch and thus generally be sticky and bring such a surface into contact with that surface. Limiting the thiol to an amount that does not fundamentally change the curability means that fundamental properties such as stiffness, hardness, elasticity, and brittleness are generally unchanged.

As can be seen, surface tackiness is eliminated in the case of the preferred polythiols and substantially reduced in the case of other thiols, such as monothiols. Furthermore, some increase in the rate of photopolymerization, as well as some changes in other properties,
commonly occurs. The invention will be further illustrated by the following examples.

Unless otherwise indicated, parts in the formulations are to be understood as parts by weight. Example 1 A photosensitive composition was prepared consisting of the following mixture: a) 1
00 parts of styrene-isoprene-styrene (SIS) protuta copolymer b) 15 parts of trimethylolpropane trimethacrylate C) 2 parts of pentaerythritol tetracrystalline (β-menolecaptopropionate) d)
2 parts of 2,2-dimethoxy-2-phenylacetophenone e) 2 parts of hindered phenol (IOnO
l8) (hardening inhibitor).

Granular SIS copolymer was manufactured by Shel Chemical Company (Shel Chemical Company).
KratOn8 manufactured by lChmical Company)
It was composed of approximately 14% by weight polystyrene (distributed equally on the two prong edges) and the remainder polyisoprene.

The relief plates were made by dissolving the composition in toluene in a stirred resin bottle. Component a) was added first, then b), d) and e) were dissolved in rapid succession, then c) after the others had dissolved. This solution was then spread onto a polyester support sheet for approximately 80 minutes. It was cast to a thickness of mill (203 mm). The dried photosensitive layer was then coated with a standard commercially available amide-based slip coat to less than a quarter mil (0.0064 mm).

The resulting plate is 10 inches x 12 inches (25.4 cm x 3
0.5 cm) was placed in a vacuum frame and the coated photopolymer surface was then brought into contact with the line process negative.
The element was then exposed to actinic radiation (500 μW/CIIl3) for 10
exposed for minutes. After exposure, the negative was stripped from the element and the element was treated with an etching bath containing trichloroethane to remove unexposed polymer. A relief image corresponding to the clear areas of the negative was obtained. The photopolymerized relief plates were characterized by excellent flexibility, elasticity, image sharpness and essentially non-tacky surfaces. This plate was placed on the printing cylinder of a flexo press and an excellent print of the original image was obtained on the polyester film. Visual observation showed that the relief plate also had excellent abrasion resistance, durability, and printing ink solvent resistance. The composition of Example 1 had the following properties.

82% by weight of the composition is a monoalkenyl aromatic diene copolymer resin or material (1), 15% by weight of the monomers of material (1) are substantially compatible with material 1, and at least one photolinkable It has a C-C double bond.

2% photoinitiator by weight of material (1).

Example 11 A printing plate was prepared essentially as in Example 1, but
The composition consisted of a mixture of: a) 100 parts of the same SIS copolymer b) 20 parts of trimethylolpropane trimethacrylate C) 2 parts of pentaerythritol tetrakis (β-menolecaptofropionate) d) 2 parts of 2,2-dimethoxy-2-phenylacetophenone e) 2 parts of hindered phenol.

The results were essentially the same as those described in Example 1, including the results of the print test.

Example 111 A printing plate was prepared as in Example 1, but the composition consisted of a mixture of: a) 10
0 parts of the same SIS copolymer b) 15 parts of trimethylolpropane trimethacrylate C) 2 parts of pentaerythritol tetra-scratch (
β-mercaptopropionate) d) 4 parts of benzophenone e) 2 parts of hindered phenol.

The results, including the results of the printing test, were identical to those described in Example 1.

Example 1V A printing plate was prepared essentially as described in Example 1, but the composition consisted of a mixture of: a) 100 parts of the same SIS copolymer b) 15 parts of trimethylolpropane Triacetate C) 2 parts of pentaerythritol tetra-scratch (″13-menolecaptopropionate)
d) 2 parts of 2,2-dimethoxy-2-phenylacetophenone e) 2 parts of hindered phenol.

The results, including the results of the printing test, were essentially the same as those described in Examples 1 and 2.

Example v A printing plate was prepared essentially as in Example 1, but
The composition consisted of a mixture of: a) 100 parts of styrene-butadiene-styrene, (SBS) block copolymer (KratOn8llO2, Dienole Chemicanole) b) 15 parts of trimethylolpropane trimethacrylate C) 2 parts pentaerythritol tetra-scratch (β-menolecaptopropionate) d)
The results were essentially identical to those of the 2-part 2,2-dimethoxy-2-phenyl control.

Example XIV A printing plate was prepared essentially as in Example 1, but the composition consisted of a mixture of: a) 100 parts of the same SIS copolymer b) 10 parts of trimethylolpropane Methacrylate acetophenone e) 2 parts hindered phenol.

The components were not dissolved in toluene, but instead were compounded in an internal shear mixer and subsequently rolled onto a polyester support.

The results were essentially the same as those described in Example 1, including the printing test.

Example VI A printing plate was prepared essentially as in Example 1, but
The composition consisted of a mixture of: a) 100 parts of the same SIS copolymer b) 15 parts of trimethylolpropane trimethacrylate C) 2 parts of pentaerythritol tetrakis (β-mercaptopropionate) d
) 2 parts of 2,2-dimethoxy-2-phenylacetophenone e) 2 parts of hindered phenol f) 15 parts of liquid butadiene rubber [ArcO
) of POiybdcs-15].

The results, including print test results, were essentially the same as those described in Example 1. Example I" Comparative Example The procedure of Examples 1-V was repeated, but with components c),
Pentaerythritol tetras (β-mercaptopropionate) was excluded in each example.

The plates had similar properties, but they had a sticky surface according to hand surface contact testing.

Furthermore, the plate showed slow activation, as clearly shown in Table 1 after Example XIV. EXAMPLE XIII CONTROL A printing plate was prepared essentially as in Example 1, but
The composition consisted of a mixture of: a) 100 parts of the same SIS copolymer b) 15 parts of trimethylolpropane trimethacrylate c) None d) 1 part of 2,2-dimethoxy-2-phenylaceto Phenone e) 2 parts hindered phenol.

These results are consistent with other pairs described in Examples 1 to C) 2
1 part of pentaerythritol tetrakid (β-mercaptopropionate) d) 1 part of 2,2-dimethoxy-
2-Phenylacetophenone e) 2 parts of hindered phenol.

The results were essentially the same as those described in Example 1, including the results of the print test.

The higher the number of activities, the longer the period required for proper curing.

Therefore, as a general proposition, the lower the number of "activities", the better the plate forming properties of the composition. The number of activations is the minimum number of light units required to stabilize a 5% 150 line halftone spot in the photosensitive layer to form a printing plate. The photosensitive layer is exposed through a test negative containing the data shown and the photosensitive layer is then etched as described in the Examples, but using varying light units. Read the recorded units from the light regulator. This light modulator adjusts the unit of light used. Elongation and tensile strength were determined by ASTM method D27O7-
72. Elasticity is ASTM method D2632-
74 and Shore-A were measured by ASTM method D224O-75. Example x In a resin bottle, 362 g toluene and 163 g plastic polychloroprene (155 g (7) WRT + 40 g
AD-40) was added.

Then 151.1 g of trimethylolpropane trimethacrylate, 0.8 g of 2,6-di-t-butylcresol, 1.6 g of 2,2-dimethoxy-2-phenylacetophenone and 3.3 g of pentaerythritol tetra Added scratches (β-mercaptopropionate). After mixing the solution well, an 8 inch x 10 inch XO. The molds were cast by pouring into 1 inch (20 cm x 25 cm x 0.25 cm) molds. Dry thickness is 100 mils (
4). 25cm). This polymerizable layer is adhered to a polyester support, the resulting plate is placed in a vacuum frame, the polymer surface is brought into contact with a line negative and exposed as in Example 1, but the duration of exposure is several minutes. It was hot. After exposure, the negative was peeled from the plate and the unexposed polymer was removed as in Example 1. A relief image of at least 30 mils (0.76 mm) was obtained corresponding to the clear areas of the negative. Photopolymers are extremely elastic, not brittle,
It is non-tacky and bendable, with no adverse effects observed when bent 180°. The plate was placed on the printing cylinder as in Example 1 and a satisfactory print of the original image was obtained. The plate remained non-adhesive when touched by hand. Example XVI The procedure of Example x was repeated, but instead of 15.1 g of trimethylolpropane trimethacrylate, 13.0 g
using trimethylolpropane triacrylate,
The solution was then cast directly onto the aluminum support.

The printing results were substantially the same as in Example x, and the plate was non-tacky to the touch. The present invention provides a simple and effective relief printing plate using inexpensive materials and with minimal labor requirements.

Claims (1)

[Scope of Claims] 1 (1) 10 to 97% by weight of the composition of C-C selected from monoalkenyl aromatic diene copolymers, butadiene polymers, acrylonitrile resins, and mixtures thereof.
an unsaturated polymeric resin, a C-C saturated polymeric binder or a mixture thereof; (2) one monomer with at least one crosslinkable C-C unsaturated bond in at least 1% by weight of the material (1); (3) A composition consisting of thiol in an amount of 0.1 to 35% by weight of material (1). 2. The composition of claim 1, wherein the amount of thiol is limited to an amount that does not essentially change the curability of the composition in which the thiol is omitted. 3. The monomer is an addition-polymerizable polyethylenically unsaturated acrylic or methacrylic ester containing two or more acrylate or methacrylate groups per molecule, or a mixture thereof, and in an amount of at least 5% by weight of material (1). A composition according to claim 1 or 2, as present. 4. The composition of claim 3, wherein the monomer is diethylene glycol dimethacrylate or diacrylate or trimethylolpropane trimethacrylate. 5. A composition according to any of claims 1 to 4, wherein the monomer is present in an amount of 15 to 30% by weight of material (1). 6. The composition according to any one of claims 1 to 5, wherein the material is a monoalkenyl aromatic diene copolymer, a halogen-substituted butadiene resin, an acrylonitrile resin, or a mixture thereof. 7. The material (1) is a polyene C-C unsaturated polymer resin having a polymeric structure and an average molecular weight of at least about 5,000;
A composition according to any of claims 1 to 5, wherein the composition is present in an amount of %. 8. A composition according to any of claims 1 to 5, wherein the material (1) is a C-C saturated polymeric binder and is present in an amount of at least 40% by weight of the composition. 9. The composition of claim 8, wherein said material (1) is polyvinylpyrrolidone, cellulose acetate butyrate, cellulose acetate succinate and mixtures thereof. 10 Claims in which the material (1) is a C-C saturated polymeric resin having a polymeric structure and an average molecular weight of at least about 5,000, and is present in an amount of at least about 60% of the composition. The composition according to item 8. 11 The thiol is pentaerythritol tetrakis (
(β-mercaptopropionate), trimethylolpropane tris (β-mercaptopropionate) or mixtures thereof and is present in an amount of 0.5 to 10% by weight of material (1). The composition according to any one of items 1 to 10. 12. A composition according to any of claims 1 to 11, further comprising a photoinitiator in an amount of 0.2 to 5%. 13 The composition is such that it has a tacky surface upon curing when the thiol is omitted, and the thiol is present in an amount sufficient to form a non-tacky surface when the composition is cured. The composition according to any one of claims 1 to 12, which is a polythiol.