Abstract: Storage-stable photoimageable leuco dye/photooxidant compositions and imaging processes utilizing these compositions are disclosed. These compositions comprise deuterated leuco compounds, e.g., deuterated aminotriarylmethanes, wherein the extent of deuteration is preferably at least 60%. These new compositions and the processes utilizing these new compositions afford improved monochrome images having enhanced film stabilities and image contrast characteristics, wherein desirable higher optical densities in imaged areas (D.sub.imaged) and desirable lower optical densities in unimaged areas (D.sub.unimaged, D.sub.fixed, and D.sub.forccd) are simultaneously both achieved in accordance with the compositions and processes of the instant invention.

Abstract: The present invention relates a photopolymerizable composition which comprises:A) one or more ethylenically unsaturated, free-radical polymerizable monomers;B) one or more organic binders; andC) one or more photoinitiators, wherein the photoinitiator is an acyl or diacyl phosphine oxide, in combination with a fluorescent optical brightener;and a process for producing such a photopolymerizable composition.

Abstract: A photo-curing composition including an image forming material, an ethylenically unsaturated monomer which is curable by polymerization thereof, a polymerization initiator which initiates the polymerization of the monomer, and two or more photosensitizers each of which absorbs a light and thereby causes the polymerization initiator to initiate the polymerization of the monomer, the photosensitizers having different maximum absorption wavelengths, respectively. A photosensitive capsule including a core material including the photo-curing composition, and a shell material within which the core material is encapsulated.

Abstract: In the present invention, one produces a negative-acting color proofing element comprising, sequentially: a strippable cover sheet which is transparent to actinic radiation; a crosslinked layer containing a polymer having phenolic groups; a color layer, containing a colorant, a polymeric binder, a polymerizable monomer and, optionally, a photoinitiator; a photoadhering layer, containing a linear photosensitive polymer containing ethylenically unsaturated, free-radical polymerizable groups and having a weight average molecular weight greater than 3,000, a polymerizable monomer, and, optionally, a free radical photoinitiator, a thermoplastic adhesive layer; and a receiver sheet, at least one of the color layer and the photoadhering layer containing a photoinitiator, which is brightener.

Abstract: The sensitivity of a photoresist to actinic light is improved by the addition of certain dyes. The photoresist includes a polymer matrix, a photosensitive acid generator and at least one compound selected from the group consisting of dyes containing at least one heterosulphur atom such as 2,2.sup.1,5.sup.1,2"-terthiophene and its derivatives; thianthrene and its derivatives, and 4,6-diphenylthieno(3,4-d)-1,3-dioxol-2-one-5,5-dioxide; phenylsulfone and its derivatives; and 4,5-diphenyl-1,3-dioxol-2-one; 3,4-bis(acetoxymethyl)furan; chelidonic acid and its derivatives; and 5,7,12,14-pentacenetetrone. Resist images on a substrate are formed from the compositions.

Abstract: Photocurable addition-polymerizable compositions containing a free-radically-polymerizable monomer and a photoinitiator system containing i) an arylidonium salt, ii) a sensitizing compound, and iii) an electron donor having an oxidation potential that is greater than zero and less than or equal to that of p-dimethyoxybenzene (1.32 volts vs. S.C.E.). The compositions cure rapidly and deeply under ultraviolet or visible light.

Abstract: A reaction resin mixture, which is able to be hardened thermally and by means of UV radiation, contains the following constituents:a cationically polymerizable epoxide resin;a latent hardening initiator in the form of an aralkyl-thiolanium salt; anda sensitizer of the structure ##STR1## A being --CO--, --NR-- and --CO--CO--, and D being --O--, --S--, --CO-- and --CH.sub.2).sub.x (where x= 1 or 2) or rather a single bond or two hydrogen atoms.

Abstract: Positive-acting photothermographic elements suitable for use at contact speeds comprising a base layer having at least two layers thereon, which layers define a photosensitive medium comprising a photocurable composition, a reducible silver source, and a reducing system for silver ion comprising one or more components including a compound capable of reducing silver ion to silver metal, such that the reducible silver source and at least one component of the reducing system for silver ion are present in separate layers, wherein exposure of the element to actinic radiation causes curing of the photocurable composition in the exposed area(s), said curing preventing the reducing system from interacting with the reducible silver source during thermal processing and in which the photocurable composition comprises a free radical curable resin and a photoinitiator therefor having an absorbance to radiation in the wavelength range of 340 to 440 nm, which photoinitiator upon exposure to said actinic radiation or during

Abstract: A lithographic coating and method of framing a lithographic image are disclosed. The method comprises coating at least a portion of a surface of an article with a radiation-crosslinkable polymer, and exposing the coated surface to a pattern of radiation to crosslink the polymer in a lithographic image. The functionalized polymer is a copolymer of an isoolefin of 4 to 7 carbon atoms and para-alkylstyrene, wherein the para-alkylstyrene is functionalized with a radiation reactive group at the para-alkyl group of the para-alkylstyrene.

Abstract: A photosensitive sheet comprising a sheet-shaped substrate, one surface of which is coated with a light-reflective substance or which is made of a light-reflective substance, and pressure-rupturable capsules that coat the light-reflective surface of the substrate or the other surface of the substrate, the pressure-rupturable capsules containing chromogenic materials and photosensitive materials that are hardened when illustrated with light, and a method for the formation of images using the said photosensitive sheet.

Abstract: An image forming process of an image forming material comprising a support and provided thereon, a photosensitive layer and a covering layer in that order comprises imagewise exposing the material by laser beam scanning, and peeling the covering film from the exposed material to form an image on the support or on the covering film, wherein said photosensitive layer contains a colorant, an addition-polymerizable or cross-linkable compound and a salt of a cationic dye with a borate anion represented by the following Formula (1):Formula (1) ##STR1##

Abstract: A photosensitive composition comprising: an acid-decomposable compound having at least one substituent which is decomposed by an acid, forming a product which reacts with alkali solution and forms --COO.sup.- or --SO.sub.3.sup.- ; and a compound which generates an acid when exposed to a chemical radiation. If necessary, the composition further comprises an alkali-soluble polymer. The acid-decomposable compound is one which is represented by the following formula (1), and the alkali-soluble polymer has a softening point of 150.degree. C. or more and an average molecular weight of 3000 to 8000. When used as photoresist, the composition can form a fine resist pattern. ##STR1## where R.sub.1 and R.sub.2 are either the same or different, each of which represents at least one selected from the group consisting of hydrogen, halogen atom, cyano group, nitro group, silyl group, and monovalent organic group; X represents >C.dbd.O or --SO.sub.2 --; Y represents a divalent organic group; R.sub.1 and R.sub.

Abstract: A highly stable photopolymerizable composition which is highly photosensitive to visible light, which can be hardened using a visible light laser, such as an argon laser, which provides excellent contrast between non-irradiated portions and the substrate under red light, and, moreover, which provides excellent contrast between the portions irradiated by the laser and the portions not irradiated. The photopolymerizable composition consists of 100 parts by weight of a resin which is hardenable under visible light having an irradiation energy mainly consisting of light rays in the 400 nm to 700 nm visible light region; 0.02 to 0.5 parts by weight of at least one dye selected from the group consisting of Victoria Pure Blue, anthraquinone dyes, monoazo dyes, and merocyanine dyes, these dyes having maximum absorption wavelengths from 550 to 700 nm; 0.1 to 5 parts by weight of the leuco dye 4,4'-(phenylmethylene bis[N,N-diethylbenzene amine]; and 0.1 to 5 parts by weight of tribromomethylphenyl sulphone.

Abstract: A light-sensitive composition which comprises at least one compound represented by the following general formula (I) as light-free radical generator:S-L-A (I)in formula (I), S represents a light absorbing moiety which absorbs light having a wave length of not less than 300 nm with an absorptivity coefficient of not less than 1000, A represents an active moiety which interacts with the light absorbing moiety S in an excited state to generate free radicals and L represents a group for coupling the moieties S and A; and a photopolymerizable composition which comprises at least one radical polymerizable compound having ethylenically unsaturated group, at least one compound represented by the foregoing general formula (I) as a light-free radical generator and optionally at least one linear organic high molecular weight polymer.

Abstract: A photopolymerizable composition includes a water-insoluble olefinic compound that is polymerizable with free-radical initiators, an oil-soluble phenothiazine dye that is soluble in water-immiscible organic solvents, and a reducing agent operable to react with the dye to form reactive free radicals only when the dye is in an excited state induced by exposure to light. The reducing agent and the dye are reacted together under the influence of light, and particularly red light. The resulting reactive free radicals cause the olefinic compound to polymerize to a polymer that is substantially unaffected by the presence of moisture.

Abstract: Photopolymerizable compositions containing photoinitiator systems that absorb in the visible are disclosed. The photoinitiator system comprises a sensitizer which is a compound of the structure I: ##STR1## wherein R.sub.2 and R.sub.

Abstract: A photopolymerizable mixture is disclosed that contains a polymer binder, a polymerizable compound having at least one terminal ethylene double bond and a boiling point above 100.degree. C. at normal pressure, a hexaarylbisimidazole and a 1,3-diarylpyrazoline or a 1-aryl-3-aralkenyl-pyrazoline. The mixture is suitable for the preparation of printing plates and photoresists and is distinguished by high photosensitivity and low sensitivity towards acid solutions.

Abstract: A photopolymerizable mixture is described which contains a polymeric binder, a polymerizable compound and an acridine compound of the general formula I ##STR1## as photoinitiator, in which R.sup.1 denotes an optionally substituted alkyl or acyl group,R.sup.2, R.sup.3 are identical or different and denoteand R.sup.4 hydrogen or halogen atoms or optionally substituted alkyl or acyl groups,R.sup.5, R.sup.6 are identical or different and denoteand R.sup.7 hydrogen or halogen atoms or optionally substituted alkyl, aryl or acyl groups, or groups of the formula II ##STR2## The photoinitiators yield a mixture having high photosensitivity and have a lower tendency to diffusion than the known 9-phenylacridine.

Abstract: Compounds having a utility as photosensitive dyes in photocurable polymer based imaging systems having a nucleus of general formula (I): ##STR1## wherein: n is 1 or 2,Y is selected from the group consisting of 0 and ##STR2## Z is selected from the group consisting of 0.sup..crclbar. and ##STR3## M.sup..sym. is a cation.

Abstract: A resist composition comprising an alkali-soluble resin, a 1,2-quinone diazide compound and a compound of the general formula (I): ##STR1## wherein Z is an oxygen or sulfur atom or a group of the formula: >N--R.sub.4 in which R.sub.4 is a hydrogen atom or an alkyl group; R.sub.1, R.sub.2 and R.sub.3 are the same or different and independently a hydrogen atom, a substituted or unsubstituted alkyl group, a halogen atom, a hydroxyl group, a cyano group or a group of the formula: --OCOR" in which R" is a substituted or unsubstituted alkyl group; and X and Y are independently a cyano group or a group of the formula: ##STR2## --COOR or --CONHR' in R is an alkyl group and R' is a hydrogen atom or an aryl group, which is suitable for the formation of very fine patterns on a substrate having a high reflectance.

Abstract: Radiation-polymerizable composition which comprisesa) a constituent that can be polymerized by free radicals and has a boiling point above 100.degree. C.,b) a photoinitiator, andc) a copolymer comprising units ofc1) an .alpha., .beta.-unsaturated aliphatic carboxylic acid,c2) an alkyl, cycloalkyl or cycloalkenyl methacrylate, andc3) an alkyl, cycloalkyl or cycloalkenyl acrylateand has an acid number of 78 to 176 and a glass transition temperature of 290 to 340 K. The composition is characterized by its ready developability at a low acid number and its good resistance to alkaline etching solutions.

Abstract: A light- and heat-sensitive composition which contains a photo-hardenable composition and at least one dye, a light- and heat-sensitive recording material which contains a support having the composition provided on at least one side thereof, and an image-forming process using the recording material are disclosed.

Abstract: A photohardenable composition comprising a free radical addition polymerizable or crosslinkable compound, a cationic dye-borate anion complex, and a borate salt, said complex being capable of absorbing actinic radiation and producing free radicals which initiate free radical polymerization or crosslinking of said compound.

Abstract: Photopolymerizable compositions in which the photoinitiator system contains a hexaarylbisimidazole and/or a p-dialkyaminophenyl carbonyl compound in combination with a borate anion coinitiator are disclosed.

Abstract: This invention relates to initiator systems for photopolymerizable compositions. More particularly, this invention pertains to photopolymerizable compositions in which the initiator system comprises an anionic dye in combination with a borate anion coinitiator.

Abstract: Described herein are photopolymerizable compositions comprising at least one polymerizable ethylenically unsaturated compound, and an initiating combination of an organic soluble xanthene dye compound and an organic activator compound. These compositions are useful as radiation-curable coatings, photocurable films, and photoactive films.

Abstract: A photopolymerizable mixture is disclosed which comprisesa) a polymeric binder,b) an acrylate or alkacrylate of a polyhydric alcohol containing one or more groups which are photooxidizable on exposure in the presence of the photoreducible dye, and one or more urethane groups,c) a photoreducible dye as photoinitiator.The mixture is suitable for the production of printing plates and photoresists and is distinguished by increased photosensitivity, which can be even further increased by the addition of a photolytically cleavable compound which contains at least one trihalomethyl group. A recording material comprising the photopolymerizable mixture is also disclosed.

Abstract: A photopolymerizable mixture is disclosed that comprises,a) a polymeric binder,b) an acrylate or alkacrylate of a polyhydric alcohol containing one or more urea groups and one or more urethane groups,c) a photoreducible dye as photoinitiator,d) a trihalomethyl compound which can be cleaved by irradiation, ande) an acridine or phenazine compound which is active as a photoinitiator.The mixture is suitable for the production of printing plates and photoresists and is distinguished by an increased shelf life.

Abstract: A light-sensitive composition comprises a photo-crosslinkable polymer having a photo-dimerizable unsaturated bond and a sensitizer represented by the following general formula (I): ##STR1## wherein R.sub.1 and R.sub.2 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group or a substituted or unsubstituted allyl group, provided that R.sub.1 and R.sub.2 may form a ring together with the carbon atoms to which they are attached; n represents 0, 1 or 2; and G.sub.1 and G.sub.2 each independently represents a hydrogen atom, a cyano group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted aryloxycarbonyl group, a substituted or unsubstituted acyl group, a substituted or unsubstituted arylcarbonyl group, an alkylthio group, an arylthio group, an alkylsulfonyl group, an arylsulfonyl group or a fluoroalkylsulfonyl group, provided that G.sub.1 and G.sub.

Abstract: The present invention is directed to a compound of the formula (I): ##STR1## where D+ is a cationic dye moiety; R.sup.1 is a branched chain alkyl group, and R.sup.2, R.sup.3 and R.sup.4 are independently selected from the group consisting of alkyl, aryl, aralkyl, alkaryl, alkenyl, alkynyl, alicyclic, heterocyclic, and allyl groups.

Abstract: A photopolymerizable mixture is described which comprises a polymeric binder, a free-radically polymerizable compound having at least one polymerizable group, a photoreducible dye, a trihalomethyl compound which can be cleaved by radiation and a metallocene compound as photoinitiators. The mixture is suitable for use in the production of printing plates and photoresists and is characterized by a particularly high photosensitivity, especially in the visible spectral region. The mixture can therefore be used for the production of images, in particular by means of laser radiation in the visible region.

Abstract: A photopolymerizable composition comprising (i) a polymerizable compound having an addition polymerizable unsaturated bond, (ii) a compound represented by formula (Ia): ##STR1## a compound represented by formula (Ib): ##STR2## or a compound represented by formula (Ic): ##STR3## wherein A represents an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom, an alkyl- or aryl-substituted nitrogen atom, or a dialkyl-substituted carbon atom; Y.sup.1 represents a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group, an aralkyl group, an acyl group, an alkoxycarbonyl group, or a substituted alkoxycarbonyl group; R.sup.1 and R.sup.2 each represents a hydrogen atom, an alkyl group having from 1 to 18 carbon atoms, or an alkyl group having from 1 to 18 carbon atoms which is substituted with R.sup.3 O--, ##STR4## or a halogen atom (i.e., F, Cl, Br, and I), wherein R.sup.

Abstract: A visible radiation sensitive composition comprising:(A) a photosetting resin containing a photosensitive group capable of crosslinking or polymerizing by photoirradiation,(B) a sensitizer represented by the formula (i): ##STR1## wherein R.sub.1 and R.sub.2 are the same or different lower alkyl, and R.sub.3 is a hydrogen atom, lower alkyl group, alkoxyalkyl group, hydroxyalkoxyalkyl group or alkoxycarbonylalkyl group, and(C) a polymerization initiator.

Abstract: A photopolymerizable mixture is described comprising (a) a polymeric binder, (b) an acrylate or alkacrylate of a polyhydric alcohol, said compound being free of urethane groups and further comprising at least one group which is photooxidizable on exposure to actinic radiation in the presence of a photoreducible dye, (c) a photoinitiator comprising a photoreducible dye, (d) a second photoinitiator comprising a trihalomethyl compound capable of being cleaved by irradiation, and (e) a third photoinitiator comprising an acridine, phenazine or quinoxaline compound. The mixture is suitable for the production of printing plates and photoresists and displays increased photosensitivity.

Abstract: A photopolymerizable composition which comprises (a) a polymerizable compound having at least one ethylenic unsaturated bond, and (b) a salt formed by an organic cationic dye compound and an organic boron compound anion, wherein the salt is represented by the following formula (I), in which an organic cationic dye compound is employed as D.sup..sym. to impart high spectral sensitivities to the composition ##STR1## wherein D.sup..sym. represents a cationic dye, and R.sup.1, R.sup.2, R.sup.3 and R.sup.4, which may be the same or different, each represents an alkyl group, an aryl group, an aralkyl group, an alkaryl group, an alkenyl group, an alkynyl group, or a group derived therefrom; and two or more of the substituent groups R.sup.1 and R.sup.4 can be combined to form a cyclic structure. The cationic dye D.sup..sym. is represented by formula (II).phi..sup..sym. -L=.PSI. (II)wherein .phi. and .PSI.

Abstract: A photosensitive composition comprising a trihalomethyl-s-triazine compound and a photosensitizer, wherein the photosensitizer being a dye having a reduction potential not more than 0.10 volt higher than the reduction potential of the trihalomethyl-s-triazine compound, and a photopolymerizable composition employing the photosensitive composition.

Abstract: A photopolymerizable mixture is described comprising (a) a polymeric binder, (b) an acrylate or alkacrylate of a polyhydric alcohol, said compound comprising at least one group which is photooxidizable on exposure to actinic radiation in the presence of a photoreduciable dye, (c) a photoinitiator comprising a photoreducible benzoxanthene or benzothioxanthene dye, and (d) a second photoinitiator comprising a trihalomethyl compound capable of being cleaved by irradiation. The mixture is suitable for the production of printing plates and photoresists and displays increased photosensitivity.

Abstract: A photopolymeric composition having improved sensitivity to a visible light ray which comprises:(a) at least one ethylenic unsaturated compound which is non-gaseous at a normal temperature;(b) at least one metallic arene compound;(c) a compound selected from the group consisting of p-aminophenyl unsaturated detone compounds, pyridine derivatives or salts thereof, xanthene or thioxanthene compounds and mixtures thereof; and optionally(d) a compound selected from the group consisting of phenylglycine derivatives, cyclic diketone compounds and mixtures thereof.

Abstract: A photopolymerizable composition which comprises an addition-polymerizable compound having at least one ethylenically unsaturated double bond and a photopolymerization initiator system, characterized in that said photopolymerization initiator system essentially consists of:(a) a p-dialkylaminostyrene derivative or p-dialkylaminophenylbutadiene derivative represented by the general formula ##STR1## wherein R.sup.1 and R.sup.2 independently represent an alkyl group; Y represents a divalent atom or atomic group selected from the group consisting of --O--, --S-- and --CH.dbd.

Abstract: A photopolymerizable mixture is disclosed comprising:(a) a polymeric binder,(b) an acrylate or alkacrylate of a polyhydric alcohol containing one or more groups which are photooxidizable on exposure in the presence of the photoreducible dye, and one or more urethane groups,(c) a photoreducible dye as photoinitiator,(d) a trihalomethyl compound which can be cleaved by irradiation, and(e) an acridine or phenazine compound which is active as a photoinitiator.The mixture is suitable for the production of printing plates and photoresists and is distinguished by increased photosensitivity.

Abstract: Disclosed is a photopolymerizable composition comprising (i) a monomer having at least one ethylenic unsaturated group which is polymerizable by means of active light, (ii) an organoboron compound, and (iii) a pyrylium or thiopyrylium dye. The composition is useful, for example, as photosensitive layers for photosensitive printing plates which are sensitive and respond to an argon laser light source.

Abstract: A negative-working imaging composition suitable for use as a dry film resist, comprises, in admixture, (a) a polymeric binder, (b) a Co (III) compound capable of partial reduction to Co (II) upon exposure to activating radiation, and (c) a redox transfer ligand capable of reacting with Co (II) to form a Co (II) chelate which reduces adjacent remaining Co (III) compound and forms a Co (III) chelate effective to provide imagewise differential solubility to the composition. The composition can be imagewise exposed to activating radiation, such as a laser, heated, and developed with a developer to form a resist image in the exposed areas. An element comprising a support and a layer of the above-described composition is particularly useful in the manufacture of printed circuit boards by laser direct imaging.

Abstract: Disclosed is a photopolymerizable composition which is very sensitive to visible light. The composition comprises a polymerizable compound and a photopolymerization initiator wherein the photopolymerization initiator comprises (A) a particular xanthene, coumarin or merocianine dyestuff, (B) a diaryliodonium salt and (C) a compound having the formula; R(n)--D--CH.sub.

Abstract: Holographic photopolymer compositions having fluorinated binders are provided that produce excellent reflection holograms when holographically imaged.

Abstract: A photoinitiator composition comprising a compound which absorbs actinic radiation and directly or indirectly generates free radicals, and an O-acylthiohydroxamate compound or an N-alkoxypyridine thione; photohardenable compositions containing that photoinitiator composition; and photosensitive materials employing same.

Abstract: Photopolymerization initiator compositions having high photosensitivity to light sources giving visible rays and the other rays in the longer wavelengths. The compositions containing polymerizable compounds having at least one ethylenic unsaturated bond and organic boron compound anionic salts of indolenine dye compounds having at least one electron-attracting group in the nuclei can be used for the production of planographic plates, resin letterpress printing plates and photoresists or photomasks for printed circuit substrates. The polymerizable compounds having at least one ethylenic unsaturated bond can be encapsulated to obtain microcapsules to be used for the formation of black and white or color images.

Abstract: A photopolymerizable composition is provided containing a polymerizable compound having an ethylenically unsaturated bond, a photopolymerization initiator, and if necessary, a linear organic high molecular weight polymer. The photopolymerization initiator comprises a combination of (a) an organic compound represented by formula (I): ##STR1## wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4, which may be the same or different, each represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group a substituted or unsubstituted alkynyl group, or a substituted or unsubstituted heterocyclic group, and at least two of said R.sup.1, R.sup.2, R.sup.3, and R.sup.4 may combine to form a cyclic structure, with the proviso that at least one of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is an alkyl group, and wherein Z.sym. represents an alkali metal cation or a quaternary ammonium cation, and (b) an organic dye having no counter anion.

Abstract: A photopolymerization initiator composition is disclosed. The composition is comprised of 1,4 or 9,10 dimethoxyanthracene and 2-tri(chloro or bromo)methyl-4(1H)-quinazolinone. The initiator composition is useful in preparing photopolymerizable compositions having increased effective photospeed.

Abstract: The invention comprises a photopolymerizable mixture comprising as the essential constituents a polymeric binder, a compound capable of forming a polymer by free-radical initiated polymerization, a photoinitiator, a leuco dye and a leuco dye stabilizer having at least one epoxy group. The mixture has a better shelf life in the dark than known compositions and is preferably used in the preparation of dry photoresists.

Abstract: Disclosed is a photopolymerizable composition which is very sensitive to light, especially visible light having a wave length of 600 to 700 nm. The photopolymerizable composition comprising a polymerizable compound having an ethylenically unsaturated double bond and a photopolymerization initiator wherein the photopolymerization initiator comprises (a) a specific sensitizer and (b) a radical forming agent.