CA1128802A - Photopolymerizable mixture containing as plasticizer, a hydroxy substituted benzoate ester or oxyethylene derivative thereof - Google Patents

Abstract

Abstract of the Disclosure This invention relates to an improvement in a photopolymer-izable mixture, comprising a polymeric binder which is soluble or at least swellable in aqueous-alkaline solutions, a compound with at least two acrylic or methacrylic acid ester groups and a boiling point above 100°C which is capable of addition polymerization, a photoinitiator, and a plasticizer, the improvement being that the plasti-cizer is a compound corresponding to Formula I

Description

~lZ88~Z Hoe 7~/K 02~

The present invention relates to a photopolymerizable mix-ture comprising polymeric binders, polymerizable compounds, and photoinitiators .
Mixtures of thls type are used in the reproduction field for the manufacture of printing plates, photoresists, i . e . etching and electroplating resists, and relief images which may be colored.
A particular group of such mixtures adapted for the produc-tion of photoresists is used in the form of a dry, photopolymeriz-able layer on a temporary support consisting of a transparent flex-ible plastic film. Under the influence of pressure and heat, the layer is laminated to a metal support which is to be imagewise modified, e.g. a copper plate, and is then exposed and developed to form the photoresist. Preferably, the layers are capable of being developed with aqueous, usually aqueous alkaline developer solu-tions. Materials of this type and methods of processing them are disclosed, e.g., in German Auslegeschrift No. 1,522,515, and German Offenlegungsschriften Nos. 2,064,079, and 2,361,041.
If they are developed with a~ueous alkaline solu~ions, the layers disclosed in the above mentioned Offenlegungsschriften have a specially good adhesion to the supportt in particular copper sup-ports, and a good resistance to etching solutions and electroplat-ing baths.
The binders required for these materials, which must be soluble or at least swellable in aqueous alkaline solutions, fre-quently have the drawback that they impart a certain brittleness to the exposed layer. This is particularly true in the case of binders containing monomer unlts which lmpart to the polymer a hlgher - 1 - ~

l~Z88~ Hoe 78/K 026 glass transition temperature and which are thus preferred because they prevent cold flow of the unexposed layer. Binders of this type aredisclosed, e.g., inU. S. PatentNo. 3,930,865.
Monomers containing more than two polymerizable groups in the molecule, which otherwise are particularly advantageous be-cause their exposure products have a high cross-linking density, normally also yield relatively brittle exposure products, especially if exposure is prolonged beyond the optimum exposure time.
Generally, it can be stated that photopolymerizable layers which have a satisfactorily law degree of cold flow in the unex-posed state and which, after exposure, show good adhesion to the metal support, good resistance to the developer, and good resis-tance to etching solutions and electroplating baths, form relatively brittle exposure products. Because this applies particularly to over-exposures, usually there is only a very narrow exposure lati-tude in the processing of such layers, if optimum combinations of properties are to be achievedO A further embrittlement may occur during storage or handling of the products under daylight.
This increased brittleness of the exposed and even of the unexposed photoresist layers may cause considerable difficulties in the further processing of these layers, e.g. in the production of printed circuits. One of these difficulties is that the brittle resist layer tends to form flakes when the copper circuit boards Iaminated to the dry resist are cut, thus leading to considerable contamina~ion and interference with the further processing of the material. As another drawback, the brlttle resist overhangs tend to break off during etching in conventional spray etching apparatuses, ~ILZ88~: Hoe 78/K 026 or fine details of photomasks crack off in aggressive electroplat- -ing baths, especially in gold baths in which the current yield is relatively low (e . g . from 45 per cent down to 25 per cent) . In this case, hydrogen is formed which may easily cause cracking of brlttle resist masks.
Although the described problems have not been clearly out-lined before for this combination of layer components and process-ing conditions, the question of the brittleness of photopolymeriz-able layers has been studied in principle, and it was recommend-ed to solve the problem by adding plasticizers to the layers.
Thus, in column 14 of German Auslegeschrift No. 2,327,513, di-butyl phthalate and other esters of aromatic and aliphatic dicarboxy-lic acids, further glycol esters, polyglycols, alkyl and aryl phos-phates, certain sulfonamides, and other compounds are mentioned as suitable plasticizers for certain types of photopolymerizable layers. These, and other similar plasticizers are also mentioned in U. S. Patent No. 3,192,194, column 4, and in German Auslege-schrift No. 2,337,645, column 12.
All the plasticizers disclosed in these publications have certain disadvantages when used in photopolymerizable layers of the above type adapted for alkaline development. Many of them are not compatible with the alkali-soluble binders requlred and ooze out from the exposed or unexposed layer durin~ storage.
; Others may have a good plasticizing effect and be compatible, but produce layers with excessive cold-flow in the unexposed state.
Still others cause an undesirable reduction of the developer resis-tance of the exposed areas of the layer, of their resistance to electroplatlng baths, or thelr adhesion to the metallic support.

~Z~38~2 Ho~ 78/K 02 6 It is the object of the present invention to provide new plasticizers for photopolymerizable mlxtures and new layer combi-nations which do not have the above-mentioned drawbacks. Above all, the unexposed layer should have only an lnsignificant cold flow and its homogeneity should undergo no changes during stor-age. After exposure, the layer should have a high cross-linking density and thus a high resistance to developer solutions and elec-troplating baths, further a good adhesion to metal supports, especi-ally copper supports, but should retain its flexibility even if considerably overexposed.
The invention is based on a photopolymerizable mixture which comprlses: a polymeric binder which is soluble or at least swellable in aqueous-alkaline solutlons; a compound with at least two acrylic or methacrylic acid ester groups in the molecule and a boiling point above 100 C whlch is capable of addition polymeri-zation; a photoinitiator; and a plasticizer.
In the mixture according to the present invention the plas-ticizer is a compound which corresponds to Formula I

2 ~
Rl~--C - o-tc - I - o _ )nR4 (I) wherein R1 is a hydrogen or halogen atom or an alkyl group with 1 to 4 carbon atoms, ~.~2~8~;~ H oe 7 8/K 02 6 R2 is a hydrogen atom, an OH group, or an alkyl group with 1 to 4 carbon atoms, R3 is a hydrogen atom or a methyl group, R4 ls an alkyl or alkenyl group with 1 to 2 0 carbon atoms, and n is zero or a whole number from 1 to 2 0, and wherein R4 has at least 4 carbon atoms if n is zero or 1.
The mixture according to the present invention normally con-tains between 1 and 3 0 per cent by weight of the new plasticizers, calculated on the weight of the non-volatile components. Prefer-ably, 10 to 25 per cent by weight of plasticizer is added. If more than 30 per cent by weight is added, the exposed areas of the layer still possess an excellent flexibility and other advantage-ous properties, but in this case the cold flow of the unexposed layer is already noticeable and may be annoying when the material is used as a dry resist film. If it is not intended to store the mixture over a relatively long time in the form of a rolled-up unex-posed dry layer, i.e. if the mixture is to be stored in dissolved form, as a liquid resist, and is to be applied to the support only immediately prior to its use, this drawback is of no consequence, so that even higher proportions of plasticizer, up to 40 per cent by : ;
weight, may be used.
If the plasticizers contain oxyalkylene units, i . e . if n is not zero, these units preferably are oxyethylene units (R3 = H).
The number n of oxyalkylene units preferably 1s between 1 and 6.
Compounds in which n = 3 and R3 = H show a particularly high resistance to electroplating haths.

~L12~ Hoe 78/K 026 The group R4 is derived from an unsaturated, or preferably, from a saturated, straight-chained or branched aliphatic alcohol with 1 to 20 carbon atoms. Even if n is more than 1, the group R4 preferably has from 4 to 20 carbon atoms. On the other hand, of the compounds in which R4 contains 4 or more carbon atoms, those are preferred in which n ls at least 1. If n is zero, the group R4 preferably contains at least 6 carbon atoms. Examples of alcohols in which R4 is OH, and which may be used for the preparation of suitable plasticizers are methanol, isopropanol, isoamyl alcohol, n-hexanol, 2, 4-dimethyl-hexanol, isooctanol, decanol, octadecyl alcohol and geraniol.
Suitable hydroxybenzene carboxylic acids which may be used for the preparation of compounds corresponding to Formula I
are, e.g., salicylic acid~ 4-hydroxy-3-chloro-benzoic acid, 2,5-dihydroxy-4-ethyl-benzoic acid, 2 ,4-dihydroxy-benzoic acid, 4-bromo-3-hydroxy-benzoic acid and 2-hydroxy-4-chloro-6-methyl-benzoic acid. If Rl isa halogen atom, it preferably is chlorine or bromine. Compounds in which Rl stands for hydrogen or alkyl are generally preferred.
The new plasticizers are readily compatible with the other components of the layer, in particular with the preferred binders and monomers referred to below. Even if they are stored for a relatively long time at relatively high temperatures, e.g. at 50 C or even 100 C, they have no tendency to migrate from the layer. Also, no migration takes place in the conventionally used acid electroplating baths. By means of the inventive plasticizers, photopolymerizable layers are obtained whlch are excellently ~2~8~Z Hoe 78fK 026 flexible before and especially after exposure. In combination with sultable blnders and monomers, they yield layers which have only a very slight eold flow or no cold flow at all. Furthermore, lt was found that when plasticizers aceording to the invention are used the re-sistance of exposed layers to electroplating baths, especially to acid gold baths, is surprisingly improved, as compared with layers con-taining no plasticizers, although other known plasticizers frequently decrease the resistance to electroplating baths. The desired combina-tion of properties which normally are hard to reconcile with each other, is even maintained if the layer is substantially over-exposed, so that the consumer is spared the expensive and troublesome task of exactly determinin~ the optimum exposure time for each original and each light source used.
Compounds according to Formula I wherein n = 1 or more have not yet been disclosed in the literature. Some of the compounds in which n = 0 are known; thu s, the 2 -ethyl -hexyl e ster of 4 -hydroxy benzoie acid, e.g., is known as a plasticizer for polyamides and poly-vlnyl chloride. It is frequently mentioned in connection with N-alkyl-phenyl sulfonamide or N-alkyl toluene sulfonamide (e.g. in German Auslegeschrift No. 1,283,796 and in U. S. Patent No. 3,395,0603.
These publications do not indicate, however, that the plasticizer is also suitable for photopolymerizable mlxtures of the above described type. N-alkyl-toluene sulfonamide, e.g. which is described as being equivalent, is completely unsuitable for this purpose and crystallizes or exudes from the solid mixture.
The plastlcizers according to the present invention may be easily prepared from alcohols, by azeotropic esterification with aro-matic carboxylic acids. The following alcohols may be us0d:

' ~
~2~8~2 ~Ioe 78/K 0Z6 (a) aliphatic monohydric alcohols with 4 to 20 carbon atoms, (b) polyglycol monoalkyl ethers obtained by reacting ali-phatlc monohydric alcohols having from 1 to 20 carbon atoms with ethylene oxlde or propylene oxlde.
The preparation of polyglycol monoalkyl ethers from alco-hols and alkylene oxides is known. Compounds of this type are commercially available.
The photopolymerizable mixtures according to the present 1 0 invention further contain polymeric, preferably thermoplastic binders whlch are soluble or at least swellable in aqueous-alkaline solu-tions. Polymers of this type contain groups which form salts in an alkaline medium, e . g . COOH, PO3H2, SO3NH2, SO2NHCO, or OH groups. Polymers containing carboxyl groups are preferred.
Maleic acid resins, polymers of N-(p-toluenesulfonyl)-carbamic acid-(,B-methacryloyloxy)~ethyl ester, and copolymers of such mono-mers, further styrene-maleic acid anhydride copolymers and in par-ticular, acrylic and methacrylic acid copolymers may be used as binders. The latter compounds may contain alkyl acrylates and alkyl methacrylates as comonomers, of which at least some have alkyl groups with 4 to 15 carbon atoms, and, additionally, styrene, substituted styrene, acrylonitrile, benzyl acrylate, or a similar monomer forming a homopolymer with a glass transition temperature Tg of at least 80 C. Such preferred binders are disclosed in U .
S. Patents Nos, 3,804,631, and 3,930,865. The binder should have an average molecular weight of at least 10, 000, preferably of about 2Q,000 to 200,000. Normally, the acld number ls between -~L~2~8~Z Hoe 78/K 02~

50 and 250, preferably between 100 and 200. Terpolymers of methacryllc acid, an alkyl-methacrylate with 4 to 12 carbon atoms ln the alkyl group, and styrene or substltuted styrene are preferred.
As a rule, the binder content is in the range from 20 to 80 per cent by welght, preferably between 35 and 65 per cent by welght of the non-volatile components of the mixture.
Furthermore, the mixtures according to the invention com-prise polymerizable compounds with at least 2 acrylic or methacrylic acid ester groups in the molecule. Compounds of this type are known in large numbers and are conventionally used for the prepa-ration of photopolymerizable compositions. Examples of suitable compounds are, e . g .: ethylene glycol diacrylate, di-, tri- and polyethyleneglycol-diacrylates, hexanediol-(l, 6)-diacrylate, tri-methylol-propane-triacrylate, trimethylol-ethane-diacrylate, penta-erythritol-triacrylate, neopentylglycol diacrylate, diglycerol diacryl-ate, and the corresponding methacrylates. Acrylic and methacrylic acid amides, e . g . methylene-bis-acrylamide, hexamethylene-bis-acrylamide, or xylylene-bis-methacrylamide, also may be used in combination with the esters. Acrylic and methacrylic acid esters containing at least two urethane groups in, their molecules are preferred, because these monomers form exposure products which are distinguished by their good flexibility and adhesion to metals.
The compounds also may include biuret groups and, if desired, carboxylic acid amide groups. Compounds of this type are dis-closed in German Offenlegungs schriften No . 2, 064, 079 and No .
2,361,041, and in U.S. Patent No. 3,850,770. Reaction products of 2 moles of hydroxyalkyl acrylate or -methacrylate and 1 mole ~Z~8132 Hoe 7~/. 0~

of a diisocyanate, e .g. hexamethylene-diisocyanate, 2, 2, 4-trimethyl-hexamethylene-diisocyanate, isophoron-diisocyanate, di-cyclohexyl-methane-diisocyanate, or tolylene-diisocyanate, are mentioned as examples. Aliphatic and cycloaliphatic diisocyanates with 2 to 12 carbon atoms are generally preferred, and among these those which contain at least one lateral methyl group. Further-more, those monomers are used with advantage which contain at least one oxyalkylene unit, preferably oxyethylene units, in the molecule. The reaction products of hydroxyl group containing acrylates and methacrylates with diisocyanates produced by the partial reaction of the above-mentioned simple diisocyanates, with diols, e.g. hexane diol, diethyleneglycol, triethylene glycol, pentaethylene glycol, trlpropylene glycol and the like, are men-tioned as examples. These compounds -with terminal isocyanate groups may contain one or more diol or polyether groups.
Polymerizable compounds obtained by reaction of the above mentioned preferred diisocyanates with di-, tri-, or tetra-ethylene-glycol, in a molar ratio from 2 : 1 to 1.1 : 1, followed by reac-tion of the resulting reaction product with 1 mole of 2-hydroxy-ethyl methacrylate per equivalent of isocyanate groups, are par-ticularly preferred.
For the preferred application of the mixtures according to the invention in the preparation of dry resist films, the methacryl-ates are generally preferred. Polymerizable compounds containing two terminal polymerizable double bonds are particularly preferred.
As a rule, the monomers are used in quantities ranging from 10 to 70 per cent by weight, preferably from 20 to 50 per cent by liZ8~ Hoe 7~/~ OZ~

weight, calculated on the weight of the non-volatile components of the mixture.
A yreat number of substances may be used as photo-inltia-tors . Benzoin, benzoin ether , multi-nuclear quinones, e . g . 2 -ethyl-anthraquinone, acrldine derivatives, e . g . 9-phenyl-acridine, 9-p-methoxyphenyl-acridlne, 9-acetyl-amino-acridine or benz(a)-acridine, phenazine derivatives, e.g. 9,10-dimethyl-benz(a)-phenazine, 9-methyl-benz(a)phenazine, 10-methoxy-benz(a)phena-zine, quinoxaline derivatives, e.g. 6,4' ,4"-trimethoxy-2 ,3-di-phenyl-quinoxaline or 4' ,4"-dimethoxy-2 ,3-diphenyl-5-aza-quin-oxaline, quinazoline derivatives, and others are mentioned as ex-amples. As a rule, their quantity is in the range from 0.1 to 10 per cent of the weight of the non-volatile components of the mix-ture .
In addition to monomers, plasticizers, photoinitiators and binders, the mixture according to the present invention may in-clude a number of further conventional additives, such as inhibi-tors to prevent thermal polymerization of the monomers, adhesion-promoting agents, hydrogen donors, sensitometric regulators, dyes, colored or uncolored pigments, color couplers and indicators.
Advantageously, these additives should be selected in a manner such that they do not excessively absorb within the actinic wave length range essential for the initiating process.
The photopolymerizable mixture according to the present invention may be marketed in known manner as a solution or dis-persion, which the consumer uses in particular for the preparation of etch resLsts. Preferably, however, the mixtures according to '11 L~8~Z Hoe 78/~ 02~

the invention are used for the preparation of dry resist films which consist of a ready-made photoresist layer on a temporary support, e . g . a transparent plastic film . Such dry resist films are lami-nated by the consumer to the support on which an image is to be formed by etching or electroplating and are then exposed and de-veloped in situ, the temporary support being removed before development .
The mixture according to the present invention is particu-larty suitable for this type of use. Alternatively, it may be manu-factured as a presensitized copying material on a suitable support, e . g . aluminum or zinc, for the photomechanical production of off-set or letterpress printing forms. ~oreover, it is suitable for the production of relief images, screen printing stencils, color proof-ing films and the like. The advantages of the present material are effective in all cases where good and lasting flexibility of the exposed layer, low cold flow of the unexposed layer, and high resistance of the exposed layer to aggressive chemicals are of importance .
The light-sensltive materials containing the mixture accord-ing to the present inventlon are prepared in known manner. Thus, a solvent may be added to the mixture and the resulting solution or dispersion may be applied to the support by casting, spraying, immersion, roller appllcation, or some other method, and the re-sulting film dried. Thicker layers (e.g. of 250~m or more) may be prepared, as a self-supporting film, by extrusion or molding and the film is then laminated to the support.

~Z88~2 Hoe 78/K 02~

- Suitable supports for the copying Iayers containing the mix-tures according to the invention are metal s, e . g . aluminum, zinc, copper, steel, chromium, brass, and other metal alloys, further supports for screen prlnting stencils, e.g. nickel or perlon gauze, and, plastic films, e.g. polyester films, especially surface-treated plastic films.
The copying layers according to the invention are expos ed and developed in the conventional manner. Suitable developers are aqueous, preferably aqueous-alkaline solutions, e.g. alkali phos-phate or alkali silicate solutions, to which, if desired, small quantities, e.g. up to 10 per cent by weight, but preferably less than 5 per cent by welght, of water-miscible organic solvents or wetting agents may be added. Development may be effected by manual treatment, or by treatment in commercial spray development or brush development apparatuses.
As already mentloned, the mixtures accordlng to the pres-ent invention may be used for very different purposes. As a par-ticularly advantageous application, they are used for the production of photoresist or etch resist layers on metal supports. They are particularly suitable for use on copper supports. In this preferred application, the excellent adhesion and flexibility of the exposed areas of the layer are of advantage not only during development, but also during the follawing etching of the support wherein the layers display good flexibility and etch resistance.
The mixtures may be used and handled with particular ad-vantage in the form of the so-called dry resist materials mention-ed abave, because even dry layers are capable of being transferred ~L~288~Z Hoe 78/K 026 onto metal supports and forming firmly adhering layers thereon.
In this case, polyester fllms may be used with particular advan-tage as temporary supporting films.
In the following examples, some embodiments of the inven-tive mixture are described. Unless stated otherwise, percentages and proportions are by weight.
Example 1 a A solution of:
6 . 5 g of a terpolymer of n-hexylmethacrylate, methacrylic acid, and styrene (60: 30: 10) with an average molecular weight of about 35,000, 2 . 8 g of a polymerizable diurethane obtained by reacting 1 mole of 2 ,2 ,4-trimethyl-hexamethylene-diisocyanate with 2 moles of hydroxyethyl methacrylate, 2 . 8 g of a polymerizable polyurethane, obtained by react-ing 11 moles of 2 ,2 ,4 trimethyl-hexamethylene-diisocyanate with 10 moles of anhydrous triethylene glycol and further reacting the resulting reaction product with 2 moles of hydroxyethyl-methacryl-ate, 0 . 2 g of 9-phenyl-acridine, 0 .1 g of 3 -mercapto-propionic acid-2, 4-dichloro-anilide 1 0.035 g of a blue azo dye, obtained by coupling 2,4-di-nitro-6-chlorobenzene-diazonium salt with 2-methoxy-5-acetylamino-N-cyanoethyl-N-hydroxy-ethyl-anillne, and 2 .8 g of the ester of 2 ,6-dihydroxy-benzoic acid with di-ethyleneglycolmono-2-ethylhexyl ether, ln 35 . 0 g of methylethyl ketone, and 2 . 0 g of ethanol, .Z~8~Z Hoe 78~. 026 is whirler-coated onto a 25 ~m thick, biaxially stretched and heat set polyethylene terephthalate film in a manner such that, after drying at 100 C, the layer weighs 28 g/m The resulting dry resist film is laminated by means of a commercial laminating apparatus, at 120 C, to a laminated pheno-plast panel provided with a 35~m thick copper foil and is then exposed for 8 seconds in a commercial exposure device. The master used is a line original, in which the lines and the dis-tances between lines have widths down to 80~m.
After exposure, the polyester film ls stripped off and the layer is developed within 50 seconds with a 0 . 8 per cent Na2CO3 solution in a spray developing apparatus.
The plate is then rinsed for 30 seconds with tap water, superficially etched for 1 minute with a 25 per cent ammonium peroxy disulfate solution and then consecutively electroplated in the following electrolyte baths:
I . ) For 40 minutes in a copper electrolyte bath marketed by Messrs, Blasberg, Solingen, under the designatlon "Feinkornkupfer-plastic-Bad", Current density: 2 A/dm2; Thickness of the metal layer produced: about 20~m, 2.~ For 10 minutes in a nickel bath of type "Norma"~marketed by Messrs, Blasberg, Solingen: Current density: 4 A/dm2; Thick~
ness of the metal layer produced: 6~,m,

3.) For 15 minutes in a gold bath of type "Autronex N", market-ed by Messrs. Blasberg, Solingen: Current density: 0.6 A/dm2;
Thickness of the metal layer produced: 2 . 5 ~m .

The plate shows no undercutting or damage.
n~ r ~c ~28~2 Hoe 78/K 026 The plate may then be decoated in a 5 per cent KOH solu-tion at 50C and the bared copper areas may be etched away by conventional etching means.
Even after 10-times overexposure, i.e. after an exposure time of 80 seconds in the above-described exposure apparatus, the above-described dry resist film is entirely flexible. This can be proved by manually stretchlng an about 2 cm wide and 2 0 cm long strip of the exposed material consisting of the support and the layer. At room temperature, the 10-times overexposed strip of dry resist film may be stretched to at least twice its original length without cracking or tearing of the layer.
This flexibility is of decisive importance for many process-ing steps, such as cutting of the laminated material, etching, gold-plating and others. The above described dry resist film has a very lc~w cold flow in the unexposed state, so that rolls can be stored for long periods of time without the resist layer squeezing out at the edges.
Examples lb to lg:
Instead of the plasticizer used in Example la, either of the following plasticizers may be used:
lb) 2 . 8 g of the ester of 2, 4-dihydroxy-benzoic acid and di-ethyleneglycolmono-2-ethylhexyl ether. Layer weight: 29 g/m2;
Exposure time: 6 seconds; Processing: as described above, the same good resistance to electroplating baths being obtained;
Flexibility: even after 10-times overexposure the materlal can be stretched without tearing or embrittlement of the layer.

~1213~2 Hoe 78/~C 026 1c) 2.8 g of the ester of 2,6-dihydroxy-benzoic acid and triethyl-eneglycolmono-2-ethylhexyl ether. Results: as above. Layer weight:
27 g/m .
ld) 2 . 8 g of the ester of 2 ,6-dihydroxy-benzoic acid and tripropyl-eneglycolmono-2-ethylhexyl-ether. Results: as above. Layer weight: 27 g/m2.
le) 2.8 g of the ester of 2,6-dihydroxy-benzoic acid and hexa-ethyleneglycol-mono-2-ethylhexyl-ether. Results: as above. Layer weight: 27 g/m2.
lf) 2.8 g of the ester of 4-hydroxy-toluene-2-carboxylic acid and diethyleneglycol-monohexyl ether. Results: as above. Layer weight: 3 2 g/m2 .
lg) 2 . 8 g of 4-hydroxy-toluene-2-carboxylic acid-n-hexylester.
Results: as above. Layer weight: 32 g/m2.
Com~arative Example lh If a solution is prepared from 6 . 5 g of the terpolymer used in Example la, 2 . 3 g of the diurethane used in Example la, 2 . 8 g of the polyurethane used in Example la, 0 . 2 g of 9-phenyl-acridine, 0.1 g of 3-mercapto-propionic acid-2,4-dichloro-anilide, 0 . 035 g of the dye used in Example la, 35 . 0 g of methylethyl ketone, and 2 . 0 g of ethanol (i.e, without the addition of a plasticizer), a dry resist film re-sults which is relatively brittle after normal exposure time and which cracks and splinters when the material is manually stretched after increasing the exposure time by 50%.

-8~ H oe 7 8/K U 2 Comparative Exa mpl e 1 i A solution is prepared from 6 . 5 g of the terpolymer used in Example la, 5 . 6 g of the diurethane used in Example la, 2 . 8 g of the polyurethane used in Example la, 0 . 2 g of 9-phenyl-acridine, 0 .1 g of 3-mercapto-propionic acid-2, 4-dichloro-anilide, 0 . 035 g of the dye used in Example la, 35 . 0 g of methylethyl ketone and 2 . 0 g of ethanol and is applied, in the manner described in Example la, to a sup-port, a layer weighing 3 0 g/m2 being the result . After an expo-sure time of only 10 seconds, this layer becomes brittle and splinters .
Example 2a A solution of 6.5 g of the terpolymer used in Example la, 2 . 8 g of the diurethane used in Example la, 2 . 8 g of the polyurethane used in Example la, 0.2 g of 9-phenyl-acridine, 0.1 g of 3-mercapto-propionic acid-2 ,4-dichloro-anilide, 0 . 035 g of the dye used in Example la, and 2.8 g of a plasticizer obtained by azeotropic esterifica-tion of 4-hydroxy-benzoic acid with triethylene-glycol-mono-tridecyl ether (commercial product), 3 5 . 0 g of methyl ethyl ketone and 2 . 0 g of ethanol, -- 1~ -~L~2~38~2 Hoe 78/K 025 is processed as described in Example la to yield a dry resist film weighing 28 g/m .
After an exposure of only 8 seconds ln the exposure appa-ratus used in Example la, an optimally exposed circuit board is obtained which yields a true copy of the line original after devel-opment in a 0 . 8 per cent Na2CO3 solution .
The resist remains flexible and does not crack or break even if it is 1 0-times overexposed .
Example 2b The plasticizer used in Example 2a is replaced by 2 . 8 g of the salicylic acid ester of triethylene-glycol-mono-ethyl ether.
Layer weight of the dry resist film: 29.4 g/m2; Exposure time: 10 seconds; Development: 70 seconds in 0 . 8 per cent Na2CO3 solu-tion. Resistance to electroplating baths: very good, even to gold baths (see Example la). Flexibility- even after an exposure time of 80 seconds, the resist layer is completely flexible and does not break or splinter if it is stretched.
ExamPles 2c to 2g-Similar results are obtained if the plasticizer used in Ex-ample 2a is replaced by 2 . 8 g of one of the following compounds:
2c) ester of 4-hydroxy-benzolc acid and triethyleneglycol-monobutyl -ether 2d) ester of 4-hydroxy-benzoic acid and 2-ethyl-hexanol 2e) ester of 4-hydroxy-benzoic acid and isotridecyl alcohol 2f) ester of 3-hydroxy-benzoic acid and 2-ethyl-hexanol 2g) ester of 4-hydroxy-benzoic acid and hexaethyleneglycol-mono-2 -ethylhexyl -ether .

,~

8~2 Hoe 78/K 026 In all cases layers weighing around 30 g/m2 are obtained which remain flexible, even if the dry resist films are grossly overexposed (e. g . 160 seconds exposure time ln the exposure apparatus used in Example la). The resistance of these layers to electroplating baths is excellent.
Example 3a A solution of 6.5 g of the terpolymer used in Example la, 5 . 0 g of a polymeriæable polyurethane obtained by reacting 2 moles of 2, 2, 4-trimethyl-hexamethylene-diisocya-nate with 1 mole of triethyleneglycol and further reactlng the reaction product with 2 moles of hydroxyethylmethacrylate, 2 . 8 g Gf 4-hydroxy-benzoic acid-2-ethylhexyl ester, 0 . 2 g of 9-phenyl-acridine, and 0.025 g of the dye "Disperse Red" ~Color Index No. 179), in 25 . 0 g of methyl ethyl ketone and 2 . 0 g of ethanol, is whirler-coated onto a polyester film as described in Example la and then dried in a manner such that the resulting layer weighs 52 g/m2. The coated film is exposed for 20 seconds through a film original comprising groups of lines of different widths, using the exposure apparatus mentioned in Example la.
After 120 seconds development in a spray developing appa-ratus, using a 0 . 8 per cent sodium carbonate solution, even lines of a width of 5014m are resolved. A test of the resistance to electroplating baths, carried through wlth the electroplating baths ~Z1~8~2 Hoe 78/K 02&

used in Example la, yields good results; no undercutting or crack-ing of the resist lines is observed ln the critical gold bath.
The flexibility is very good, even after an exposure time of 160 seconds .
The developer resistance is at least 6 minutes, even in lines only 50~m wide.
Example 3b (ComParative Example) If the plasticizer is omitted from the composition used in Example 3a, relatively brittle layers, which break when bent and cannot be stretched, are obtained after normal exposure. The re-sistance to the gold bath described in Example la is not sufficient.
Example 3c (ComParative ExamPle) If the plasticizer used in Example 3a is replaced by the same quantity (2.8 g) of the monomer used in this example, i.e.
if 7 . 8 g of the monomer is used without the addition of a plasti-cizer, the same poor results are obtained as in Example 3b.
Example 4a A solution of 6 . 5 g of the terpolymer used in Example la, 5.0 g of the polymerizable polyurethane used in Example 3a, 2 . 8 g of the 4-hydroxy-benzoic acid ester of triethylene-glycol-mono-2-ethylhexyl ether, 0 . 2 g of 9-phenyl-acridine, and 0.025 g of "Disperse Red" as a dye (C.I. 179), in 25 . 0 g of methylethyl ketone and 2 . 9 g of ethanol, 88~2 ~oe 78/K ~2 6 is whirler-coated onto a polyester film as described in Example la and dried in a manner such that a layer weighing 51 g/m2 is pro-duced. If the materlal is processed as described in Example 3a, substantially the same results are obtalned as in Example 3a.
Example 4b (Comparative Example) Example 4a is repeated, except that the plasticizer men-tioned in the example is replaced by the same quantity of diiso-decyl-adipate, a compound which is commercially used as a plas-ticizer for polymers. After an exposure of only 15 seconds the layer becomes brittle. In addition, its adhesion to copper is poor.
Example 4c (ComParative Exam~le) Example 4a is repeated, except that the plasticizer men-tioned in the example is replaced by the same quantity of 1 ) the polye ster of adipic acid and 1, 2-propane-diol, or 2) the polyester of adipic acld and butane-diol.
Both compounds are commercially available pLasticizers. Even after normal exposure (20 seconds~, brittle resist layers are ob-tained. Moreover, the adhesion of the layers to copper is poor.
-Example 5a 2 0 A s olution of 6.5 g of the terpolymer used in Example la, 5 . O g of the polymerizable diurethane used in Example la, 2 . 8 g of 4~hydroxy-benzoic acid-nerolidyl ester, 0 . 2 g of 9-phenyl-acridine, and 0.025 g of "Disperse Red" as a dye (C.I. 179) in 25 . 0 g of methyl-ethyl ketone, and 2 . 0 g of ethanol, l~Z8l~2 Hoe 78~ 026 is whirler-coated onto a polyester film as described in Example la and is dried in a manner such that a layer weLghing 50 g/m2 re-sults. The layer is processed as described in Example 3a. Even if the normal exposure time is exceeded by 200 per cent, the ex-posed resist layer is sufficiently flexible.
Example 5b (ComParative Example) Example 5a is repeated, except that the plasticizer used in Example 5a is replaced by the same quantity of N-ethyl-p-toluene-sulfonamide (a commercially available plasticizer). Immediately after preparation of the resist layer, the flexibility of the layer after normal and prolonged exposure is good, but after storing the unexposed layer for 2 or 3 days, signs of embrittlement are appar-ent after exposure. After ~ weeks storage, substantial portions of the plasticizer are lost by migration and the resist film has become useless .
Example 5c (Comparative Example) Example 5a is repeated, except that the plasticizer used in Example 5a is replaced by the same quantity of (1) diisooctyl phthalate, or (2) tricresyl phosphate. Brittle layers are produced by normal exposure (20 seconds).
If the same quantity of (3) polyethyleneglycol with an aver~
age molecular weight of 1,000 is used as the plasticizer, a layer is obtained whose adhesion to copper is no longer sufficient.
; It will be obvious to those skilled in the art that many modifications may be made within ~he scope of the pre sent inven-tion without departing from the spirit thereof, and the invention includes all such modifications.

Claims (11)

Hoe 78/K 02 WHAT IS CLAIMED IS:

1. In a photopolymerizable mixture, comprising a polymeric binder which is soluble or at least swellable in aqueous-alkaline solutions, a compound with at least two acrylic or methacrylic acid ester groups and a boiling point above 100 C which is cap-able of addition polymerization, a photoinitiator, and a plasticizer, the improvement that the plasticizer is a compound corre-sponding to Formula I

(I) wherein R1 is a hydrogen or halogen atom or an alkyl group with 1 to 4 carbon atoms, R2 is a hydrogen atom, an OH group, or an alkyl group with 1 to 4 carbon atoms, R3 is a hydrogen atom or a methyl group, R4 is an alkyl or alkenyl group with 1 to 20 carbon atoms, and n is zero or a whole number from 1 to 20, and wherein R4 has at least 4 carbon atoms if n is zero or 1.

2. A photopolymerizable mixture according to claim 1 in which the plasticizer is a compound corresponding to Formula I wherein R3 is a hydrogen atom.

Hoe 78/K 026

3. A photopolymerizable mixture according to claim 1 in which the plasticizer is a compound corresponding to Formula I wherein R4 is an alkyl group with 4 to 20 carbon atoms.

4. A photopolymerizable mixture according to claim 2 in which the plasticizer is a compound corresponding to Formula I wherein n = 3.

5. A photopolymerizable mixture according to claim 1 which contains between about 1 and 30 per cent by weight of plasticizer, calculated on the weight of the non-volatile components.

6. A photopolymerizable mixture according to claim 1 which contains a polymerizable compound containing at least two urethane groups.

7. A photopolymerizable mixture according to claim 1 in which the polymerizable compound contains two acrylic or methacrylic acid ester groups in the molecule.

8. A photopolymerizable mixture according to claim 1 in which the binder is an acrylic acid or methacrylic acid copolymer with an acid number between 50 and 250.

9. A photopolymerizable mixture according to claim 8 in which the copolymer is a terpolymer of methacrylic acid, an alkylmeth-acrylate with 4 to 15 carbon atoms in the alkyl group, and a further monomer which can be copolymerized with the first two components and the homopolymer of which has a glass transition temperature of at least 80 ° C .

Hoe 78/K 026

10. In a light-sensitive transfer material, comprising a flexible temporary support and a thermoplastic photopolymerizable layer comprising a polymeric, thermoplastic binder which is soluble or at least swellable in aqueous-alkaline solutions, a compound with at least two acrylic or methacrylic acid ester groups and a boiling point above 100° C which is capable of addition polymerization, a photoinitiator, and a plasticizer, the improvement that the plasticizer is a compound corre-sponding to Formula I

(I ) wherein R1 is a hydrogen or halogen atom or an alkyl group with 1 to 4 carbon atoms, R2 is a hydrogen atom, an OH group, or an alkyl group with 1 to 4 carbon atoms, R3 is a hydrogen atom or a methyl group, R4 is an alkyl or alkenyl group with 1 to 20 carbon atoms, and n is zero or a whole number from 1 to 20, and wherein R4 has at least 4 carbon atoms, if n is zero or 1.

11. A light-sensitive transfer material according to claim 10 in-cluding a peelable cover film on the surface of the layer remote from the support.