GB2106522A - Radiation-sensitive crosslinking composition - Google Patents

Abstract

A radiation-sensitive composition and method of crosslinking, suitable for use as a resist or litho plate composition comprises a polymer comprising a recurring unit having a moiety having an epoxy, carboxyl, hydroxy, tertiary amino, morpholino, unsaturated nitrogen-containing heterocycle or mercapto group, and as the sole effective crosslinking agent for the polymer, a radiation-sensitive transition metal carbonyl. The composition is substantially free of any compound which reacts in response to activating radiation, to form a free radical. The carbonyl may be a low M.W. compound, or a polymer whose recurring units include transition metal carbonyl groups. Alternatively the polymer to be crosslinked may itself contain such recurring units.

Description

SPECIFICATION Radiation-sensitive crosslinking composition This invention relates to a composition that provides crosslinking in response to activating radiation suitable for, e.g., negative-working litho plates and resists.

A major segment of the resist and litho plate industry features the use of negative-working compositions that photocrosslink where exposed. The crosslinking serves to render the exposed areas relatively insoluble to a developer that is effective to dissolve the unexposed portions.

The photochemistry of transition metal complexes has received much attention. In this context the metal carbonyl derivatives have been particularly widely studied and reviewed. (See G. L. Geoffroy, M. S. Wrighton; "Organometallic Photochemistry", Academic Press, New York (1979) and M. S.

Wrighton; Chem. Rev., 74, 401(1974)).

A process involving photoinitiation of polymerization through the interaction of a metal carbonyl complex with active halogen compounds is described in U.K. Patent Specification No. 1,463,816. The halogen compounds react with the metal carbonyl complexes upon exposure to activating radiation, to form a free radical. Although that process has proven to be highly useful, it has required the protection of the active components from the presence of oxygen which inhibits the polymerization, for example, by the use of an oxygen-impermeable overcoat.

There has been a need, therefore, prior to this invention, for a crosslinkable composition using transition metal carbonyls, that is insensitive to the presence of oxygen.

We have found that a composition containing nucleophilic compounds and metal carbonyls is crosslinked after exposure to actinic radiation, without requiring the formation of a free radical intermediate, and without requiring the use of a photocatalyst or other crosslinking agents.

Thus, according to the present invention there is provided a radiation-sensitive composition comprising a polymer comprising a recurring unit having an epoxy, carboxyl, hydroxy, tertiary amino, morpholino, unsaturated nitrogen-containing heterocycle or mercapto group (as nucleophilic groups), and as the sole crosslinking agent for the polymer, a radiation-sensitive transition metal carbonyl, the composition being substantially free of any compound which reacts in response to activating radiation, to form a free radical.

In accord with another aspect of the invention, the aforesaid composition permits a method of crosslinking, comprising the steps of exposing such composition to activating radiation, and optionally developing the exposed composition by removing any non-exposed portions of the compositions with a solvent.

As a result, the present invention provides a radiation-sensitive composition and crosslinking method involving a transition metal carbonyl as crosslinking agent, that needs no protection from oxygen and has excellent thermal stability. Separate crosslinking agents are not needed in addition to the transition metal carbonyl, resulting in an economy of materials and manufacturing procedure.

In one embodiment of the present invention the transition metal carbonyls are employed to photocrosslink polymers containing a nucleophilic group. In this embodiment crosslinking may be effected imagewise using a polymer suitable for making a photoresist or a lithographic plate. In addition, the composition and method of the invention are useful in any product in which exposure to activating radiation of any kind is effective to generate crosslinking, whether it be imagewise exposure or a blanket exposure.

The composition of this invention features a polymer that is to be crosslinked, and as the sole crosslinking agent, a transition metal carbonyl. As will be readily understood a crosslinking agent is a compound which is present in an amount and is of a nature such that crosslinking is effected by the agent. The metal carbonyl is present as discrete molecules, that is, as monomers or simple compounds, or as a moiety pendent from a polymer backbone.

Transition metal carbonyls which are useful in the present invention include those described in U.K. Specification 1,463,816. These include toluene-, aniline- and mesitylene-chromium tricarbonyl, dimanganese decacarbonyl and molybdenum hexacarbonyl. Preferred carbonyls are described in the Examples below. The preferred transition metal is chromium. Benzene chromium tricarbonyl is the preferred monomeric form because of superior photographic speed and availability.Also useful are benzyl alcohol chromium tricarbonyl and di(benzyl chromium tricarbonyl)ether having the respective structural formulae

Of the polymeric form of the transition metal carbonyl, preferred are those polymers comprising recurring units having the structural formula:

wherein R is hydrogen or methyl; R1 and R2 are individually arylene of from 6 to 1 0 carbon atoms, for example, phenylene or naphthalene; M is a transition metal; R3 is aryl of from 6 to 10 carbon atoms, e.g., phenyl or naphthyl; m is 0 or 1; and n is an integer of from 1 to 3.

Formulas a) and b) are vinyl-addition polymers, whereas formula c) is a condensation polymer.

Such metal carbonyl-containing polymers are either known or are prepared using conventional syntheses. The following preparations are illustrative. All temperatures are in degrees Celsius.

Preparation No. 1

was prepared as follows: 118-(2-phenylethanol)tricarbonylchromium (PEMT) was reacted with methacryloyl chloride. Poly ,i6- [ (2-phenylethylmethacrylate)tricarbonylchromium ] was then prepared by heating PEMT under a nitrogen blanket with 2,2'-azobis [ 2-methylpropionitrile ] (ABIN) in refluxing 1,2-dichloroethane for 24 hours as shown in Reaction i):

Preparation No. 2 Poly-n6-[(2-phenylethyl-4'-methacryloyloxybenzoate)tricarbonylchromium] was prepared in a manner similar to that of Preparation No. 1 as follows::

Preparation No. 3 To prepare poly [ (sWrene)-co-#6(sWrene)tricarbonylchrnmiu m ] , polystyrene was treated with chromium hexacarbonyl to give poly [ (styrene)-co#6(swrene)tricarbonylchrnmium ] shown in Reaction iii).

a. x=.88 y=.12 b. x=.57 y=.43

where x and y are mole fractions The degree of substitution depends upon the heating time and amount of Cr(C0)6 used.

Preparation No. 4 Poly(methyl methacrylate-co-#6- [ 2-phenylethyl methacrylate ] tricarbonylchromium) was prepared using PEMT of Preparation No. 1, as follows: Recipe 6(2-phenylethyl methacrylate)tdcarb6nyl chromium 1.53 g Methyl methacrylate 1 ml Azobisisobutyronitrile 0.027 g 1 4-dioxane 50 ml The molar ratio of methyl methacrylate to rls(2-phenylethyl methacrylate)tricarbonylchromium in the above recipe is 2:1.

Procedure The above mixture was stirred and heated at 600C under a nitrogen atmosphere for 20 hours.

The polymer was recovered by precipitation into methanol. Exposure of the reactants or the product to light was minimized throughout.

Analysis Cr, 5.53% (by atomic absorption spectrophotometry).

Based on this, the molar ratio of monomer units in the polymer, methyl methacrylate:#(2-phenyl- ethyl methacrylate)tricarbonylchromium, equaled 6.14:1.

This monomer ratio requires: C, 58.34; H, 6.71% Found: C, 55.96; H, 5.83% Alternatively, useful examples of a polymeric form of the transition metal carbonyl include the crosslinkable polymer bearing a nucleophilic group as hereinafter described, copolymerized with a recurring unit having structural formula a), b), or c) described above, to form a novel copolymer.

Particularly preferred are vinyl-addition ter- and copolymers of methacrylic acid and any of < [ 2- phenylethyl methacrylate]trica rbonylchromium, #6 [ 2-phenylethyl-4'-methacryloyloxybenzoate ] td- carbonyl chromium, and 116 [ (styrene)tricarbonylchromium ] .

Preferably, the polymer to be crosslinked, containing one of the moieties noted in the Summary, is soluble in an organic solvent and on crosslinking becomes insoluble. The crosslinked polymer should also be ink-accepting when intended for use as a lithographic plate.

Examples of polymers containing nucleophilic groups which are useful in the present invention include:

wherein m and n are mole ratios of the starting materials and are between 1:1 and 5:1.

The nucleophilic groups in the above polymers are

Other useful nucleophilic groups include:

wherein R4 is H or alkyl such as methyl, ethyl, propyl, isopropyl and the like.

Additional examples of nucleophilic groups are the following unsaturated nitrogen-containing heterocycles: pyrazolyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, and benzo derivatives of each of these, e.g., benzothiazolyl and the like.

In preferred embodiments, polymers such as are obtained from monomers containing the above groups copolymerized with acrylate or methacrylate esters or with styrene or vinyl acetate, are used.

Preferably, at least 10 mole % of the starting monomers of the polymer comprises the recurring unit bearing the nucleophilic group.

Optionally, monomeric or simple crosslinkable compounds also containing one or more of the nucleophilic groups described above, are useful when included in the composition with the polymer containing the nucleophilic groups. An example is glycerol triglycidyl ether.

The proportion of weight of metal carbonyl in the polymer layer ranges from 1 to 30% by weight, preferably from 2 to 5% by weight.

The following polymers were prepared for use in the Examples of the invention described herein.

All the polymers were prepared in solution, such as dioxane. The temperature was held at 600C and a nitrogen atmosphere was maintained throughout the polymerization. Azodiisobutyronitrile (A.l.B.N.) (0.5% of total monomer weight) was the initiator. The reaction was allowed to proceed for twenty hours and the polymers were then isolated by precipitation into a non-solvent, usually ether.

The polymers were washed with precipitating solvent and dried under vacuum.

In the case of copolymers, the molar ratio of the monomers used is given, and where the monomer ratio in the resulting copolymers is different this is indicated in the description of the polymers below. L.V.N. is the log viscosity number. (ml/g).

Preparations 5-13 appear in Table I.

Table I Preparation Polymer Monomer Atomic Atomic % no. name ratio L. V.N. formula calculated found 5 Poly(styrene-co- 1:1 **34 ml/g C15H,8Ot C, 73.17% C, 72.42% glycidyl meth- H, 7.32 H, 7.10 acrylate) 6 Poly(vinyl ace- 1:1 **25 ml/g C"H,605 C, 57.89 C, 58.13 tate-co-glycidyl H, 7.01 H, 6.97 methacrylate) 7 Poly(methyl meth- 4:1 ***31 ml/g C24H38O10 C, 59.26 C, 57.96 acrylate-co-meth- H, 7.82 H, 7.56 acrylic acid) 8 Poly(methyl meth- 8:1 ***23 ml/g C44H0O,8* C, 59.59 C, 59.61 acrylate-co-meth- H, 7.90 H, 7.73 acrylic acid) 9 Poly(methyl meth- 3::1 ***23 ml/g C22H37NO8 N, 3.16 N, 2.4 acrylate-co-N- [ 2- hydroxypropyl] methacrylamide) *Titrating against 0.1 MNaOfi, polymer had an equivalent wt. of 898, compared to theoretical of 886.

**1% in dioxan at 250C ***1% in ethanoi/acetone (3:1 v/v) at 250C Table I (continued) Preparation Polymer Monomer Atomic Atomic % no. name ratio L. VN. formula Calculated Found 10 Poly(methyl meth- 8:1 +36 ml/g C47H77NO,8 N, 1.48% N, 1.18% acrylate-co-N-[2 hydroxypropyl methacrylamide) 11 Poly(methyl meth- 3:2 ***16 ml/g C3,H54N2O,0 N, 4.56 N, 4.15 acrylate-co-N,N dimethylaminoethyl methacrylate) 12 Poly(methyl meth- 2:1 ***32 ml/g C,8H3,NO6 N, 3.92 N, 3.82 acrylate-co-N,N dimethylamino ethylmethacrylate) 13 Poly(methyl meth- 4:1 +16 ml/g C27H3gNO8++ N, 2.77 N, 3.3 acrylate-co-4 vinylpyridine 14 Poly(styrene)-co- 2::1 **32 ml/g C23H26O3 C, 78.85 C, 76.09 (glycidyl meth- H, 7.43 H, 7.31 acrylate) ++NMR showed a monomer ratio in the polymer of 3.4 to 1.

+1% in acetone at 250C In Preparations 15~17, the following procedure was carried out: Methyl methacrylate, glycidyl methacrylate and dioxane were placed in a 500 ml three-necked flask, fitted with a magnetic stirrer, condenser and a nitrogen inlet tube reaching below the surface of the liquid. Nitrogen was bubbled continuously through the solution. Azodiisobutyronitrile (A.l.B.N.) initiator was added and the apparatus was placed in a thermostated oil bath set at 700C. Heating and stirring were continued for 20 hours. The polymer was then isolated from the viscous solution by the slow addition of the latter from a dropping funnel into stirred methanol (2.5 1) or by precipitation into ether. The polymer was washed with fresh methanol, filtered and dried under vacuum.

Table II Preparation Polymer Monomer Atomic Atomic % no. name ratio L. V.N. formula Calculated Found 15 Poly(methyl meth- 1:1 18 ml/g C12H180s C, 59.509/0 C, 59.63% acrylate)-co- H, 7.44 H, 7.36 (glycidyl meth acrylate) 16 Poly(methyl meth- 2:1 44 ml/g C17H26O7 C, 59.64 C, 59.41 acrylate)-co- H, 7.89 H, 7.52 (glycidyl meth acrylate) 17 Poly(styrene- 3::1 43 ml/g C22H3409 C, 59.72 C, 58.87 co-(glycidyl H, 7.69 H, 7.45 methacrylate) Preparation No. 18 Poly( methyl methacrylate-co-#6 [ 2-phenylethyl methacrylate ] tricarbonylchrom U m-co- methacrylic acid) Recipe #6 [ 2-phenylethyl methacrylate]tricarbonyl chromium 3.06 g Solution of methacrylic acid (1.0 g) in methyl methacrylate (10 ml) 2 ml Azobisisobutyronitrile 0.052 9 1,4-dioxane 50 ml The molar ratio of methyl methacrylate:#6(2-phenylethyl methacrylate:methacrylic acid in the above recipe is 8.06; 4.45:1.

Procedure The above mixture was stirred and heated at 600C under a nitrogen atmosphere for 20 hours.

The polymer was recovered by precipitation into methanol. Exposure of the reactants or the product to light was minimized throughout.

Analysis Cr, 8.65% (by atomic absorption spectrophotometry). Based on this, and the assumption that the ratio of monomer units methyl methacrylate:methacrylic acid in the polymer is 8.06:1, as it is in the feed, the ratio of the three monomer units in the polymer, methyl methacrylate:#(2-phenylethyl methacrylate)tricarbonylchromium:methylacrylic acid=8.06: 3.24:1.

The composition of the invention is useful as a resist or litho plate composition, when applied as a coating to a suitable support. Depending upon whether the coating is a resist or a litho plate composition, suitable supports include metal plates, sheets and foils of metals such as aluminum, copper, magnesium, zinc, etc.; glass and glass coated with such metals as chromium, chromium alloys, steel, silver, gold, platinum, etc.; synthetic polymeric materials such as poly(alkyl methacrylates), e.g., poly(methyl methacrylate); polyester film base, e.g., poly(ethylene terephthalate); poly(vinyl acetals); polyamides, e.g., nylon; cellulose ester film base, e.g., cellulose nitrate, cellulose acetate, cellulose acetate propionate and cellulose acetate butyrate.For the manufacture of integrated circuit devices, silicon or silicon dioxide wafers, as well as silicon nitride and chromium-coated glass plate supports, are particularly useful. Depending upon the support selected, adhesion aids are optionally applied first as a sub-coating.

Any conventional method can be used to apply the composition to the support. The preferred method is as a coating using an appropriate solvent. Useful coating techniques include whirler coating, spray coating, curtain coating, and roll coating. Useful solvents include alcohols, esters, ethers, and ketones and particularly ethanol, 2-ethoxyethyl acetate, n-butyl acetate, 4-butyrolactone, and mixtures thereof.

Preferred final thicknesses of the coatings vary, depending upon the final use and the etchants that are to be used, if any.

The equipment used to expose the resist is conventional. The exposure times vary depending on the desired results and equipment used.

Following exposure, the latent image so formed is developed by treating the exposed composition with an appropriate developer.

Any activating radiation is useful to promote crosslinking. Most preferably the radiation is ultraviolet light, e.g., that is available from medium pressure mercury lamps.

Examples The following procedures were adopted in the Examples 1-1 5 of the invention described below.

Composition The composition of each example is given in Table Ill. "BCT" refers to benzene chromium tricarbonyl, "BACT" refers to benzyl alcohol chromium tricarbonyl, and "DBCTE" refers to di(benzyl chromium tricarbonyl ether.

Coating An AK Control Coater (RK Print-Coat Instruments Ltd., Royston, Herts), set at a wet film thickness of 24so, was used. The base was polyacrylamide subbed, grained, anodized aluminum. Coatings were dried at ambient laboratory temperature.

Exposure Plates were exposed in a vacuum frame, through a 0.15 density step tablet, to four 125 w high pressure mercury vapor lamps at a distance of 18 inches. The plates described here were given 30 seconds, except for Examples 1 and 2 which had two minutes exposure. Speed data are listed as the last solid step at the exposure given.

Development and inking Plates were developed by spraying with acetone and/or swabbing with acetone for periods of up to 30 seconds. The developed samples were inked with "Simplink" (Rotaprint Ltd.) applied with a cotton wool pad saturated with water.

The following Examples, Table Ill, give details of coating solution composition, and speed following the methods described above.

Table Ill Metal carbonyl Polymer Solvent Example (amount) (amount) (amount) Speed 1 BCT (0.035 g) Prep. 5 (0.5 g) acetone Step 9 (10 ml) 2 BCT (0.035 g) Prep. 6 (0.5 g) acetone Step 10 (10 ml) 3 BCT (0.018 g) Prep. 7 (0.5 g) acetone* Step 8 (5 ml) 4 BCT (0.018 g) Prep. 8 (0.5 g) acetone Step 11 (5 ml) 5 BCT (0.018 g) Prep. (0.5 g) acetone* Step 12 (5 ml) 6 BCT (0.035 g) Prep. 9 (1.0 g) acetone Step 3 (10 ml) 7 BCT (0.035 g) Prep. 10 (1.0 g) acetone Step 8 (10 ml) 8 BCT (0.035 g) Prep. 11(1.0 g) acetone Step 4 (10 ml) 9 BCT(0.035g) Prep. 12 (lOg) acetone Step6 (10 ml) 10 BCT (0.035 g) Prep. 13 (1.0 g) ethanol/ Step 7 acetone (3:1) (10 ml) 11 BCT (0.035 g) Poly-styrene-co- acetone Step 6 N-vinylimidazole (10 ml) (1::1) (1.0 9) 12 BACT (0.02 g) Prep. 7 (0.5 g) acetone Step 6 (5 ml) 13 BACT (0.02 g) Prep. 8 (0.5 g) acetone Step 12 (5 ml) 14 DBCTE (0.039 g) Prep. 7 (0.5 g) acetone* Step 9 (5 ml) 15 DBCTE (0.039 g) Prep. (0.5 g) acetone* Step 12 (5 ml) *These examples also included 0.2 g of glycerol triglycidyl ether as a material to be crosslinked.

Only 1 speed step improvement was noted in Example 5, compared to Example 4.

Examples 16-38 The coating solution used in the practice of this invention as illustrated by the following Examples 16-38 comprises simply the metal carbonyl compound (abbreviated as in Examples 1-15) plus either an epoxy resin, a prepolymer (binder) with pendent crosslinkable epoxide groups, or a mixture thereof, in a suitable solvent. Such a coating solution is applied to an appropriate support to produce a lithographic printing plate or photoresist materials. Curing was by exposure to high pressure mercury vapor lamps and photographic speed was comparable to conventional plates.

Also in the following examples, the following epoxy resins were used in place of or in conjunction with the polymers described in Preparations 5 and 14-1 6 in some of the Examples described.

"Epikote 1001" (Epoxy resin obtained from Shell)

"CY 179" (obtained from Ciba-Geigy, Plastics Division)

"CY-1 83" (obtained from Ciba-Geigy, Plastics Division)

Composition amounts are given in Table IV.

The following procedures were used in the Examples of the invention described below.

Coating An AK Control Coater (RK Print-Coat Instruments Ltd., Royston, Herts), set at a wet film thickness of 24u, was used. Coatings were dried at ambient laboratory temperature.

Exposure Plates were exposed in a vacuum frame, through a 0.15 density step tablet, to four 125 w high pressure mercury vapor lamps at a distance of 18 inches. All plates were given two minutes exposure and speed data for the Examples (listed as last solid step) refer to this exposure.

Etching (Photoresist applications only, Examples 27, 28 and 38):0.5--1.5 hours in ferric chloride solution.

Development and inking Lithographic samples were developed by swabbing with acetone (Examples 1 9-26, 29-32) and water-acetone (7:3) mixtures (Examples 16-1 8, 33-37), for periods of 10 to 30 seconds.

Photoresist materials (Examples 27, 28 and 38) were developed by spraying with acetone.

Lithographic samples were inked with "Simplink" (Rotaprint Ltd.) applied with a cotton wool pad saturated with water.

Supports Photoresist applications (Examples 27, 28 and 38) These examples used Schjel-Clad L~5575 copper/polyester laminate (G. T. Schjeldahl Ltd.) as the support.

Lithographic plate applications (Examples 1 6-26, 29-37) Grained, anodized aluminum foil, subbed with polyacrylamide, was used as the support.

Table IV Metal Other carbonyl Polymer polymer Solvent Example (amount) (amount) (amount) (amount) Speed 16 BCT (0.13 9) - Epikote 1001 acetone Step 7 (0.5 9) (10 ml) 17 BCT (0.14 g) - CY 179 acetone Step 15 (0.5 9) (10 ml) 18 BCT (0.14 9) - CY 183 acetone Step 13 (0.5 9) (10 ml) 19 BCT (0.14 g) - CY 179 acetone Step 12 (0.25 9) plus (10 ml) Epikote 1001 (0.25 9) 20 BCT (0.14 9) - CY 183 acetone Step 10 (0.25 9) plus (10 ml) Epikote 1001 (0.25 9) 21 BCT(0.14g) Prep. 14 CY179 acetone Step 7 (0.05 9) (0.5 g) (10 ml) 22 BCT (0.14 g) Prep. 14 CY 183 acetone Step 10 (0.5g) (0.5 9) (10 ml) 23 BCT (0.14 9) Prep.15 - acetone Step 6 (0.5g) (10 ml) 24 BCT(0.14g) Prep. 16 - acetone Step 6 (0.5g) (10 ml) 25 BCT (0.14 9) Prep. 15 CY 179 acetone Step 14 (0.25 9) (0.25 9) (10 ml) 26 BCT (0.14 9) Prep. 16 CY 179 acetone Step 11 (0.25 g) (0.25 9) (10 ml) 27 BCT(0.14g) Prep. 15 CY 179 acetone Step 4 (0.25 9) (0.25 g) (10 ml) after etching 28 BCT (0.14 9) Prep. 16 CY 179 acetone Step 2 (0.25 9) (0.25 9) (10 ml) after etching 29 BCT (0.14 9) Prep. 5 - acetone Step 6 (0.5 9) (10 ml) 30 BCT(0.14g) Prep. 17 - acetone Step 6 (0.5 g) (10 ml) 31 BCT(0.14g) Prep.5 CY183 acetone Step 13 (0.25 9) (0.25 9) (10 ml) 32 BCT(0.14g) Prep. 17 CY 183 acetone Step 13 (0.25 9) (10 ml) 33 Toluene - CY 179 acetone Step 11 chromium tri- (0.5 9) (10 ml) carbonyl (0.15 9) 34 Aniline - CY 179 acetone Step 8 chromium tri- (0.5 9) (10 ml) carbonyl (0.15g) 35 Mesitylene - CY 179 acetone Step 9 chromium tri- (0.5 9) (10 ml) carbonyl (0.16 9) 36 Dimanganese - Epikote 1001 ethyl acetate Step 2 decacarbonyl (0.5 9) (10 ml) (0.15 9) 37 Molybdenum - Epikote 1001 ethyl acetate Step 4 hexacarbonyl (0.5 9) (10 ml) (0.17 g) 38 BCT(0.14g) Prep. 17 - acetone Step 2 (0.5 9) (10 ml) after etching Example 39 (Polymeric form of the transition metal carbonyl) photoresist application 0.5 g of poly(#6- [ 2-phenylethyl methacrylatejtricarbonylchromium-co-methyl methacrylate and 1.0 g of poly(methyl methacrylate-co-methacrylic acid) (1 8:1) were added to 10 ml of acetone. The composition was applied to a support comprising Schjel-Clad L~5575 copper/polyester laminate using an AK Control Coater (RK Print-Coat Instruments Ltd., Royston, Herts), set at a wet film thickness of 60y. Coatings were dried at ambient laboratory temperature.The samples so prepared were exposed in a vacuum frame, through a suitable printed circuit test negative, to four 125 w high pressure mercury vapor lamps at a distance of 1 8 inches for a period of five minutes. After samples were developed by wafting in acetone and warmed in a drying oven (about 800C for 1 hour) the resist was found to give acceptable protection during etching in ferric chloride solution.

Example 40 (Copolymer of nucleophilic group and transition metal carbonyl) The procedure of Example 39 was followed to coat and expose the following composition: Coating solution formulation Poly(methyl methacrylate-co-#6 [ 2-phenyl ethyl methacrylate ] tricarbonylchromium co-methacrylic acid) 1.0 g Acetone 10 ml.

After development following the procedure of Example 39, the resist was found to give acceptable protection during etching with ferric chloride solution.

Claims (13)

Claims

1. A radiation-sensitive composition comprising a polymer comprising a recurring unit having an epoxy, carboxyl, hydroxy, tertiary amino, morpholino, unsaturated nitrogen-containing heterocycle or mercapto group, and as the sole crosslinking agent for said polymer, a radiation-sensitive transition metal carbonyl, the composition being substantially free of any compound which reacts in response to activating radiation, to form a free radical.

2. A composition according to Claim 1 in which said carbonyl is benzene chromium tricarbonyl.

3. A composition as claimed in Claim 1, wherein said transition metal carbonyl is attached to a polymer.

4. A composition as claimed in Claim 3, wherein said transition metal carbonyl polymer comprises recurring units having the structural formula:

wherein R is hydrogen or methyl; R' and R2 are individually arylene of from 6 to 10 carbon atoms; R3 is aryl of from 6 to 10 carbon atoms; M is a transition metal; m is O or 1; and n is an integer of from 1 to 3.

5. A composition as claimed in Claim 3, wherein said transition metal is chromium.

6. A composition as claimed in Claim 1 or 2, wherein said transition metal carbonyl is attached to said polymer.

7. A radiation-sensitive composition according to Claim 1 substantially as described herein and with reference to the Examples.

8. An element comprising a support having thereon a composition as claimed in any of Claims 1~7.

9. An element as claimed in Claim 8, wherein said support is a lithographic plate support.

10. An element according to Claim 8 substantially as described herein and with reference to the Examples.

11. A radiation-sensitive polymer comprising a recurring unit having an epoxy, carboxyl, hydroxy, tertiary amino, morpholino, unsaturated nitrogen-containing heterocycle or mercapto group, and an additional recurring unit having a moiety attached thereto that is a radiation-sensitive transition metal carbonyl.

12. Poly(methyl methacrylate-co-t;8 [ 2-phenylethyl methacrylate]tricarbonylchromium-comethacrylic acid).

13. A method of crosslinking a composition to render it insoluble in a solvent that is effective to dissolve the non-crosslinked portions of the composition, the method comprising the steps of a) exposing to activating radiation a composition according to any of Claims 1-7; b) optionally developing the exposed com-position by removing any non-exposed portions of the composition with said solvent.