GB2198735A - Photopolymerisable material containing photoinitiator system - Google Patents

Abstract

A photopolymerisable material comprising a light-sensitive layer that contains monomers, binders and a photoinitiator system, and optionally other auxiliary layers, contains as photoinitiator system a water-soluble photo-initiator system comprising (i) a betaine structure-forming component of the formula I, (ii) a compound of the formula II and (iii) an onium compound, e.g. of the formula III, On<+> Y<->.

Description

Photopolymerisable material The invention relates to photopolymerisable materials suitable for recording information, especially in the form of reproduction materials for the manufacture of printed circuits and relief images for printing plates or for the manufacture of imagewise exposed surface coatings.

It is known that many ethylenically unsaturated compounds may be polymerised using a photo-initiator which forms radicals under the influence of light, these radicals initiating polymerisation. A number of compounds are known that form radicals under the influence of light according to a wide variety of mechanisms, the radicals then initiating photopolymerisation. Typical examples of the initiators used in photopolymerisation are benzoin. and benzoin ether (DE-OS 1 769 168 , 2 232 365, GB-PS i 429 053), halogenated carbonyl compounds (US-PS 4 001 098), peroxides (S.. Cohem, B.E Ostberg, D.B. Sparrow, E.R. Blout; J. Polym. Sci, 3, (1948) 264; E.R. Bell, F.F. Rust, W.E. Vaugham; J. Amer. Chem.Soc. 72 (1950) 337, benzil ketals (R. Kirchmayr, . Berner, G. Rist ; Farbe-Lacke 86 (1980) 6), benzophenone derivatives (DE-OS 1 949 010), anthraquinones (US-PS 2 951 758, 3 046 127), mixtures of benzophenone and michler's ketone (DE-OS 2 216 154). dycstoff redox systems (US-PS 3 092 096) and arenediazonium salts in combination eith donors (US-PS 3 615 452; T. amass, T. Ikawa, H. Koao, E. Inoue; Phot. Sci. Eng., 17 (1973) 23, 268).In DD WP 158 281, attempts are made to increase the efficiency of the actinically active light in order to improve the light-sensitivity of the photopolymeric material by the use of a co-initiator and the triggering of a cationic polymerisation or crosslinking, which occurs in addition to the radical polymerisation.

Using these photoinitiators it is possible to build up photopolymerisable layers that in additionoto the photo initiator contain polymerisable or crosslinkable compounds, a binder and, if desired, one or more additives such as inhibitors, plasticisers, pigments or dyes.

The photopolymerisable layers are best applied to the support by applying a solution of all the individual components.

Depending on the intended use, a wide variety of natural or synthetic materials are used as support materials, and these may be produced in the form of flexible or rigid sheets or plates. Sheets or plates of copper, oriented polyester film, laminated papers, gl3ss, aluminium with a coating of aluminium oxide, and silicon have been used as support materials in tze prior art. Nood is also suitable as a material, as shown by its extensive use when surface covering layers are being made using image-wise exposure.

To produce an image the photopolymerisable layers are cross-linked on exposure to light, that is to say are image-wise cured. The image-wise exposure of photopolymeric systems does not generally lead to visible images but to an image-wise modification of the physical properties of the exposed areas as a result of polymerisation or cross-linking. These property modifications can then be used in a subsequent developing step to make the information imprint visible. In one known developing process, the unexposed parts of the layer are removed by washing out with an appropriate solvent or solvent mixture. After development, relief images are obtained on the support material, which can be used as printing formes, or which after colouring produce a transparencies or prints.

In principle, solutions using a wide variety of solvents can be used for applying the photo polymer i- sable layers to the support material. In the manufacture of composite photopolymerisable materials there are a number of technological and economic requirements and conditions that have arisen from the necessity to protect against risks to the environment and to the health of workers, and against the risk of combustion.

For example, the solvent used is required to be non combustible and to have 4 values 100 mg/rn3.

These requirements are best met by the solvent water.

According to the present invention there is provided a photopolymerisable material with a highly sensitive photoinitiator system that is spectrally suitable for use with high-pressure mercury lamps. It is, moreover, possible for the material to be applied and developed using water and aqueous solutions. The present inventors have found that, in accordance with the present invention, by the use of a novel watersoluble photoinitiator system there is obtained a photopolymerisable material that can be developed ith water or aqueous solutions.

The present invention provides a potoolynrisable material, comprising z lightsensitive layer that contains a water-soluble photoinitiator system, the photoinitiator system comprising: (t) a betaine structure-forming component A of the general formula I

in which R1 and R3 each represents NR52 R2 represents H, -C02X or -SO3X, R4 represents -CO2X or -S03X, each R5 independently represents H or C1-C4 alkyl, and x represents H, Li, Na or Kt (B) a component B of the general formula II

in which R6 and R8 may be the same or different and each represents H or alkyl in the o or P-position, R7 represents H, -CO2X or -SO3X, in the m- or position, R9 represents -C02X or -SO3X, in the m- or position, X represents H, Li, Na or K; and (C) â compound containing an 'onium cation.

The light-sensitive layer is preferably in the form of a layer on a Dort. Advantageously, the water-soluble photo-initiator system contains as component (C) an 'onium compound selected from the group consisting of trono-, di and tri-substituted arenediazonium salts, bisdiazonium compounds, and 'onium salts containing one or more elements of main groups V, VI and VII of the Periodic Table.

The present invention further provides an image bearing material, especially a printed circuit or a printing plate that has been obtained by image-wise exposure of a photopolymerisable material according to the invention and subseauent development in an aaueous medium.

The 'onium compound used in accordance with the invention may for example be a compound having the general formula III On+Y- III in which On+ represents an 'onium cation, and represents an anion.

The 'onium compound On+ Y', may be, for example: - mono, di- or tri-substituted arenediazonium salts having alkoxy, halogen, sulphonylamido, aryl, aryloxy, alkoxy and acylamido radicals as the substltuents, - bisdiazonium compounds of the general structure AN 10-Z-R 11 in which P10 and R11 represent substituted benzene radicals and Z represents a single bond or groups such as, for example -O-, -CH2- and -OCH2-; - 'onium salts of elements of main group V, such as, for example, phosphonium salts with organic radicals, such as substituted phenyl, naphthyl, anthranyl, benzyl and alkyl, with anionic radicals such as, for example, halogen and CN;; - 'onium salts of elements of main group VI, such as, for example, sulphonium salts and selenium salts with organic radicals, such as substituted phenyl, anthranyl, benzyl, alkyl and acyl; - 'onium salts of elements of main group VII, preferably organic iodonium compounds with organic radicals, such as phenyl, substituted phenyl, naphthyl, anthranyl, benzyl and phnacyl; there being used as y anions that on the one hand stabilise the 'onium compounds and on the other hand also give an adequately high solubility of the 'onium compounds in water. Anions which may be used as Y are, for example, Cl ,Br , HSO4 or also the complex anions BF4-, PtF6-,AsF6-, SbF6-, SbCl6-, SnCl5-, CaCl4 BiCl52-, AlF6-, InF4', TiF6- or ZrF6-.

Advantaqeously the water-soluble initiator system is used in a ratio of t:B:C = a:b:c' the numbers a, b and c ranging from 0.1 to 10.

Especially suitable is a water-soluble initiator system that contains as component A disu.'phonated 4,4'- bis-p-diethylaminobenzophenone or 4,4'-bis-pdimethylaminobenzophenone, as component B the sodium salt of p-benzoylbenzoic acid or m,m'-benzo- phenonesulphonic acid or its sodium salt, and as component C -chlorobenzenediazonium fluoroborate or diphenyliodonium hydrogen sulphate.

The photopolymerisable layers furthermore may desirably contain water-soluble or water-dispersible organic compounds that have at least one group that can be polymerised by radicals. Since component C forms species that in addition to a radical polymerisation can also initiate a cation polymerisation, there are therefore also suitable monomers that polytrerise with cationic initiation and thus have an additional crosslinking effect.

Furthermore, the photopolymerisable layers may contain a water-soluble natural or synthetic polymeric binder. The addition of binder is especially advantageous when the compounds that are to be polymerised are liquid substances. There are suitable as binders those polymers or polymer mixtures that after exposure to light exhibit adequate solubility in the aoueous developer, such as, for example, gelatine, polyvinyl alcohol, polyvinylpyrrolidone, and copolymers of maleic acid anhydride with styrene, propylene and ethyi methacryLote in the form of their sodium or potassium salts. Depending on the intended use, the photopolymerisable layers may also contain stabilisers, inhibitors, plasticisers, pigments or dyes.

The photopolymerisable layers are best prepared by applying a solution of all the individual components to the support. There are suitable as support a wide variety of natural or synthetic materials such as, for example, flexible or rigid sheets or plates of copper, oriented polyester film, laminated papers, glass, aluminium with a coating of aluminium oxide, silicon and wood. The layer thickness depends on the intended use and generally ranges from 0.5 to 100 pm. For protection against mechanical damage and the inhibiting action of oxygen, one or more protective layers may be applied to the light-sensitive layer.

The exposure of the layers produced according to the invention is advantageously effected with highpressure mercury lamps customarily used in reproduction technology. Other light sources, such as high-pressurv xenon lamps, carbon arc lamps, halogen lamps and sunlight are, however, also suitable for the exposure of the material according to the invention.

After the image-wise exposure, development is advantageously carried out with water or with a 1-2% strength aqueous solution of Na2CO3 or ;laRCO3 or KzCO3 or KHCO3. Other developers that inlay be used are aaueo ws solution of silicates (water lass!, phosphates or borax.

The following examples illustrate the inventin.

In each of the examples exposure of the photopolymerisable layers is effected with a 500 watt ultra-high pressure mercury lamp at a distance of 1 in.

The exposure time required to produce a relief image is determined by exposure in stages in an exposure box.

Developing is then carried out with water having a temperature of 30 to 400C with gentle movement of the layer or by spraying the layer. The supports used for the photopolymerisable layers were electrochemically grained, anodised aluminium plates or hydrophilized polyester film. The layer thicknesses of the photopolymerisable layers are from 5-8 urn.

Example 1 The support was coated using a coating solution containing the following constituents: 1 part of a compound of the formula I in which R1 and R3 each represents -dimethylamino and B2 and R4 each represents m-SO3E, 5 parts of a compound of the formula II in which R6 and r8 each represents H, and R7 and R9 each represents m-SO3Na, parts of diphenyliodonium hydrogen sulphate, 20 parts of a rylamide, 0 parts of N,N'-methylene bisacrylamide, 20 parts of N,N1-dimethylpropyl acrylamide, 24 parts of gelatine, 26 parts of polyvinyl alcohol, and 900 parts of water.

After exposure for an exposure time of 2 seconds and development, a polymeric relief image is obtained.

Example 2 The support was coated using a coating solution containing the following constituents: 1 part of a compound of the formula I in which P1 and R3 each represents p-diethylamino and R2 and 24 each represents -m-SO3H, 6 parts of a compound of the formula II in which R6, R7 and R8 each represents H and R9 represents m-SO3Na, 6 parts of diphenyliodonium hydrogen sulphate, 10 parts of acrylamide, 20 parts of N,N'-rnethylene bisacrylamide, 20 parts of N,N-diethylaminoethyl acrylamide 5 parts of methyl glycidyl ether, 30 parts of gelatine, 20 parts of polyvinyl alcohol, and 870 parts of water.

After exposure for an exposure time of 3 seconds and development, a Dolymeric relief image is owta-red.

Exainpie 3 The support is coated with a coating solution composed of the following constituents: 1 part of a compound of the formula I in which R1 and R3 each represents -dimethylamino and R2 and R4 each represents m-SO3H 5 parts of a compound of the formula II in which R6, and R8 each represents H and R9 represents m-SO3Na 5 parts of -chlorobenzenediazonium tetrafluoroborate, 10 parts of acrylamide, 10 parts of N,N'-methylene bisacrylamide, 30 parts of N,N-dimetbylaminopropyl acrylamide, 30 parts of gelatine, 2C parts of polyvinyl alcohol, and 900 parts of water.

After exposure for an exposure time of 2 seconds and development, a polymeric relief image is obtained.

Example 4 The support is coated using a coating solution composed of the following constituents: 1 part of a compound of the formula I in which p 1 and P3 each represents -diinethylamino and P2 and B4 each represents m-SO3H 10 parts of a compound of the formula II in which 6 and S each represents E and R7 and Eq each repre- sents rn-SO3Na, 10 parts of diphenyliodonium hydrogen sulphate, 10 parts of acrylamide, 10 parts of N,N'-methylene bisacrylamide, 20 parts of N,N-dimethylaminopropyl acrylamide 25 parts of gelatine, 5 parts of polyvinylpyrrolidone, 20 parts of polyvinyl alcohol and 890 parts of water.

After exposure for an exposure time of 2 seconds and development, a polymeric relief image is obtained.

Example ; The support is coated with â coating solution containing the same constituents as in Example 2.

After exposure and the warm water development the material is treated in a colouring bath, for example with methylene blue, Solamin light fast blue, Walk brilliant red or Wofalan black. After intermediate washing coloured polymeric relief images are obtained.

Claims (13)

laims:

1. A photopolymerisable material, comprising a lightsensitive layer that contains a water-soluble photoinitiator system, the photoinitiator system comprising: (A) a betaine structure-forming component A of the general formula I

in which R1 and R3 each represents NR52 2 represents H, -02X or -SO3X, R4 represents -CO2X or -SO3X, each R5 independently represents H or C1-C4 alkyl, and X represents H, Li, Na or K;; (B) a component B of the general formula II

in which R6 and R8 may be the same or different an9 each represents H or alkyl in the o or position, R7 represents H, -CO2X or -SO3X, in the m- or -position, R9 represents -C02X or -SO3X, in the m- or pposition, X represents H, Li, Na or R; and (C) a compound containing an 'onium cation.

2. A photopolymerisable material as claimed in claim 1, wherein the light-sensitive layer is in the form of a layer on a support.

3. t photopolymerisable material as claimed in claim 1 or claim 2, wherein the light-sensitive layer comprises at least one polymerisable monomer.

4. A photopolymerisable material as claimed in any one of claims 1 to 3, wherein the water-soluble photoinitiator system contains as component (C) an 'onium compound selected from the group consisting of mono-, di- and tri-substituted arenediazonium salts, bisdiazonium compounds, and 'onium salts containing one or more elements of main groups V, VI and VII of the Periodic Table.

5. A photopolymerisable material as claimed in any one of claims , to 4, wherein the ratio A:B:C of the components of the wter-soluble photo-initiator system is a:b:c, the values for a, b, c each ranging from 0.1 to 10.

6. A photopolymerisable material as claimed in any one of claims 1 to 5, wherein the water-soluble photo- initiator system comprises disulphonated 4,4'-bis-p- diethylaminobenzophenone or 4,4'-bis-- dimethylaminobenzophenone as component A, the sodium salt of P-benzoylbenzoic acid or m,m'-benzo phenonesulphonic acid or its sodium salt as component B, and p-chlorobenzenediazonium fluoroborate or diphenyllodonium hydrogen sulphate as component C.

7. 4 photopolymerisable material as claimed in any one of claims 1 to 6, wherein the light-sensitive layer comprises additional components selected from binders, stabilisers, inhibitors, plasticisers, pigments and dyes.

8. A Photopolymeriseble material as claimed in any one of claims 1 to 7, which also comprises at least one layer other than that specified.

9. A photopolymerisabie malarial as claimed in any one of claim 1 to R, wherein the components of the light-sensitive layer are so selected. that after exposure the material may be developed in an aqueous medium.

10. A photopolymerisable material substantially as described in any one of Examples 1 to 5 herein.

11. An image bearing material which has been obtained by the image-wise exposure of a photopolymerisable material as claimed in any one of claims 1 to 10 followed by development in an aqueous medium.

12. A printed circuit or a printing plate that has been manufactured by the image-wise exposure to actinic radiation Or a polymerisasle material as claimed in any one of claims 1 to 10 and subsequent development in an aqueous medium.

13. Any novel feature herein disclosed or any novel combination of herein disclosed features.