FR2607820A1 - PHOTOSENSITIVE COATING COMPOSITION AND PROCESS FOR THE PREPARATION OF AN ULTRAVIOLET-SENSITIVE POLYMER - Google Patents

Abstract

THE ULTRAVIOLET-SENSITIVE COATING COMPOSITION OF THE INVENTION, WHICH IS PARTICULARLY USEFUL FOR FORMING MASKS FOR WELDING, CONTAINS A POLYMER PREPARED BY CONDENSATION REACTION OF A DIISOCYANATE, A DI- OR TRI (METH) ACRYLATE OF HYDROXYCO AND OF A CARBOXYLIC ACID-POLYOL, OPTIONALLY WITH ALSO A POLYOL AND OR A DICARBOXYLIC ACID-POLYOL. THE COATING POLYMER SO PREPARED MAY ALSO BE COMBINED WITH BINDERS AND CROSSLINKERS.

Description

PHOTOSENSITIVE COATING COMPOSITION AND PREPARATION METHOD

  OF AN ULTRAVIOLET-SENSITIVE POLYMER

  The present invention relates to a photosensitive coating composition and a process for preparing an ultraviolet sensitive polymer. More particularly, it relates to a photosensitive resin composition for forming a protective coating film having excellent characteristics, which can either be used alone to form a tacky photosensitive coating, or be combined with various other types of ingredients, such as a crosslinker to increase the crosslinking density, a resin to suppress tackiness or another photosensitive ingredient to increase sensitivity to light. The uses of the present photosensitive coating composition therefore include applications as a photoresist, such as a plating reserve, a chemical attack reserve and a mask for soldering. Solder masks are used to produce printed circuit connection boards. The welding masks act basically by avoiding the welding bridges, in 2O maintaining the electrical insulation between the conductors to avoid conduction between the welding zones and by avoiding the corrosion of a bare copper conductor. It is also desirable to have photosensitive welding masks which can preserve an image which can be used as a plane on which the welding is placed. Since it is desirable to increase the wiring density, it is also desirable to use a solder mask having precise resolution and extremely good electrical insulation properties. The present photosensitive composition

provides these benefits.

  Known welding masks are described in US Pat. No. 4,499,163 which describes a photosensitive resin composition which contains a urethane-diacrylate or -dimethacrylate, a linear polymeric compound having a glass transition temperature between about 40 ° C and 150 ° C. and a sensitizer which produces actinic radicals. The linear polymeric compound described free in actinic light. The linear polymeric compound described includes linear vinyl polymers or copolymers, such as, for example, polymers made of vinyl monomers, including methyl methacrylate, butyl methacrylate, methylstyrene, vinyltoluene and the like. The free radical-producing sensitizer includes, for example, quinones

  substituted or unsubstituted polymorphonuclear cells.

  We will also find the description of another composition

  of photocurable urethane acrylate resin indicated as useful for permanent storage in US Patent 4,587,201. The composition described therein uses a urethane acrylate resin which is composed of a polybutadiene polymer. This resin is combined with a photopolymerization initiator to form a

permanent reserve material.

  However, for the most part, photosensitive welding masks cannot be developed in an aqueous solution. They require the use of development solutions consisting of an organic solvent. The use of such organic solvents has become undesirable as a result of regulations

  relating to the environment which limit solvent emissions.

  Another drawback of welding masks using development solutions based on organic solvent is the maintenance of the sensitivity of the final product to organic solvent, such as methylene chloride. In some products, this

sensitivity is undesirable.

  It is therefore desired to develop coating compositions for masks for photosensitive welding which can be developed in aqueous solutions and which are resistant to organic solvents, such as methylene chloride. An object of the invention is to provide such a coating composition. Another object of the invention is to provide a coating composition for welding masks which can be removed with commercial alkaline strippers. The photosensitive resin compositions described herein have excellent properties of resolution, flexibility, adhesion to metals, resistance to solvents,

  resistance to high temperatures and electrical insulation.

  Specific embodiments of the present composition provide a highly viscous photosensitive material which is useful as an additive for compositions requiring both thickening and the addition of photosensitive coating material. The present photosensitive materials therefore play a dual role, both as a thickener and as a photocurable photosensitive additive. These embodiments of the present compositions are therefore photosensitive and photocurable thickening agents useful for materials such as paints, inks, etc. A photocurable coating composition according to the invention comprises an ultraviolet-sensitive compound chosen from: a carboxylated urethane-diacrylate, a urethane-triacrylate

  carboxylated, a carboxylated urethane dimethacrylate and a urethane-

  carboxylated trimethacrylate. This group of compounds is hereinafter called urethane-di- (and / or) tri (meth) acrylates carboxylated. It should be noted that the term (meth) acrylate here designates an acrylate and / or a methacrylate. These urethane-di- (and / or) tri (meth) acrylates are prepared carboxylated from acidified fragments providing the carboxyl group. These compositions are prepared by condensation of a diisocyanate, a carboxylic acid polyol and a hydroxyalkyl (meth) acrylate. The polyol carboxylic acid must be present in

  an amount necessary to provide at least about 0.3 milli-

  equivalent of acid per gram of the total combined amount of the reactants which are referred to hereinafter as meq / g of RT (the total reactants are generally diisocyanate,

  carboxylic acid polyol and hydroxyalkyl (meth) acrylate).

  To obtain an appropriate photosensitivity rate in this product, hydroxyalkyl (meth) acrylate should be used in a minimum amount of about 0.5 milliequivalents per gram of the combined amount of diisocyanate, carboxylic acid-di- or triol and

hydroxyalkyl (meth) acrylate.

  The present invention includes various embodiments obtained by combining the above coating composition with other specifically selected ingredients. These ingredients chosen to ensure or enhance a specific quality or characteristic include: a binder, a crosslinking agent, dyes, pigments, thermopolymerization inhibitors and additives designed to improve

coating properties.

  The present invention will now be described in detail. The present photocurable coating composition contains the carboxyl moiety which modifies the organophilic nature of the urethane- (meth) acrylate polymer. As a result, the present coating compositions become more organophobic and therefore resistant to organic solvents, such as methylene chloride. In addition, these carboxylated photosensitive polymers can be mixed in large quantities with other hydrophilic binders and crosslinkers. In addition, the introduction of the carboxyl moiety allows the present coating compositions to dissolve or swell in aqueous alkaline solutions (pH greater than 7.5) before exposure to ultraviolet light. Advantageously, when the present compositions are used to form a photocurable coating or a mask for soldering, the development stage can be carried out in aqueous alkaline solutions. It should therefore be noted that, although the incorporation of the carboxyl moiety modifies the nature of the urethane- (meth) acrylate by making it soluble in aqueous alkalis, the sensitivity of the compound to ultraviolet light is retained. In addition, carboxylation improves adhesion to metals. Therefore, the combination of a binder, a crosslinker and a urethane-di (and / or) tri (meth) acrylate carboxylate provides an improved welding mask. A preferred combination uses a styrene / maleic anhydride copolymer as a binder (also providing carboxyl groups). The preferred crosslinkers are monomers of

  (meth) acrylate and polyfontional (meth) acrylate.

  The preferred carboxylated urethane-di- (and / or) tri (meth) acrylate of the invention can be represented by the following formula (I): Formula 1

R! H H H H H H R1

  CH = C-COR OCNRNC (O [ROCNRNC O] R5OCNR3NC) nOR2OCC = CH

0 0 0 O O O

  where n is an integer from 1 to 4; k can be 0 or 1; and R1, which is derived from the acrylate reaction component (c), may be either hydrogen or a methyl group; R2, which also derives from the reaction component. (meth) acrylate (c), can be a linear or branched saturated hydrocarbon fragment having from 2 to 28 carbon atoms; R3 is derived from the diisocyanate portion of the reaction mixture. R3 can be a branched, linear or cyclic, saturated, unsaturated or aromatic hydrocarbon moiety. R3 can have from 4 to 20 carbon atoms and it preferably has from 6 to 18 carbon atoms. In other preferred embodiments, R3 is derived from the reacting diisocyanate chosen from trimethylhexamethylene-,

  hexamethylene-, isophorone-, tolylene-, 4,4-methylene-bis-cyclo-

  hexyl-, methylenediphenyl- and tetramethylxylene-diisocyanates. R4 is a linear, cyclic or branched hydrocarbon fragment,

  aromatic, saturated or unsaturated, having 2 to 28 carbon atoms.

  R4 may optionally also contain a hydroxyl moiety (constituting a residue of the polyol used in the preparation of the composition). R5 is derived from a reaction mixture comprising (a) the carboxylic acid-polyol illustrated by formula (2) and described below; or (b) the carboxylic polyol acid of formula (2) and the hydroxydicarboxylic acid illustrated by formula (3) and described below. Therefore, R5 always has at least one COOH fragment and has at least 3 carbon atoms. When R5 is derived from (a) (only from compounds corresponding to formula (2)), it has only one COOH group with a branched, linear or cyclic, saturated, unsaturated or aromatic hydrocarbon moiety having in total from 3 to 30 carbon atoms, including the carboxylic carbon atom. When R5 is derived from (b), the overall composition comprises R5 fragments derived from the carboxylic acid-polyol of formula (2) and also R5 fragments derived from hydroxydicarboxylic acids of formula (3). The R5 fragments derived from hydroxydicarboxylic acids of formula (3) obviously have two COOH groups and can also have from 3 to 30 carbon atoms, including the two carbons

  carboxylic. The descriptions of the compounds of formula (2) and

  formula (3) provide additional relative information

  at the concentrations and the preferred structures of these R5 fragments.

  It should be noted that the exact location of each R5 fragment in the polymer molecule depends on the number of reactive hydroxyl groups originating from the compounds of formula (2) or of formula (3) and the condensation reaction which is somewhat statistical. For example, when R5 is derived from (b) and y of the formula (3) is 1, R5 is a terminal group having two COOH moieties; Simultaneously, the other R5 fragments of the same reaction mixture (derivatives of the polyol carboxylic acid of formula (2)) are located randomly in the main chain of the polymer molecular structure, as indicated

above in formula (1).

  In formula (1), the R2 fragment preferably has 2 to 16 carbon atoms, and better still is a fragment chosen from the group consisting of ethyl, propyl, butyl and:

O O

1 11

(CH2 * 5c [O (CH2) 5-C

where m is 1 or 2.

  R4 is derived from the polyol which can optionally be added to the reaction mixture. R4 therefore has from 2 to 28 carbon atoms and 2 to oxygen atoms. The oxygen atoms can optionally be in an unreacted hydroxyl moiety. When R4 is present, it can have from 2 to 28 carbon atoms or preferably from 2 to 16 carbon atoms; it can also optionally have a hydroxyl moiety. Other preferred embodiments allow R4 to be a saturated or unsaturated hydrocarbon fragment having from 2 to 10 carbon atoms and from 2 to 5 oxygen atoms,

  optionally in the form of an unreacted hydroxyl group.

  In specific examples of such preferred embodiments, R4 is a moiety selected from ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl and having 2 to 5 oxygen atoms from the foregoing hydroxyl moieties. R4 can also

  derive from glycerol or 2-ethyl-2- (hydroxymethyl) -1,3-propylene.

  The carboxylated urethane-di- (and / or) tri (meth) acrylates of the invention can be obtained by condensation of a diisocyanate with a carboxylic acid-polyol (see formula (2)) and a (meth) acrylate d hydroxyalkyl in a single stage reaction. The carboxylated polyol can be any carboxylic acid containing 2 or more hydroxyl moieties. Suitably, there are 2 to 5 hydroxyl groups. Preferably, it is either an acid

  carboxylic-diol or a carboxylic acid-triol.

  Thus, suitably, the carboxylic acid-polyol can correspond to the following illustrated formula (2) Formula 2 [0o] x-R6-COOR in which x is an integer from 2 to 5 and R6 is a branched hydrocarbon fragment, cyclic or linear, saturated, unsaturated or aromatic having from 2 to 29 carbon atoms. Preferably, R6 has from 2 to 24 carbon atoms while x is 2 or 3 (as is the case in a diol or a triol). More preferably, x is 2 and R6 is a branched, cyclic or linear, saturated, unsaturated or aromatic hydrocarbon structure of 2 to 20 carbon atoms. A preferred embodiment uses an o, & .- dimethylolalkanoic acid as the carboxylated diol more preferably having an alkyl group of 1 to 8 carbon atoms. Other preferred carboxylic acid-diols are chosen from: &, & e-dimethylolacetic acid, a, t-dimethylolpropionic acid, ox, cx-dimethylolbutyric acid, &, &, - diethylolacetic acid, l a, cc-diethylolpropionic acid, 3,0 o-dipropylolpropionic acid, acid,% -dipropylolbutyric acid and

2,3-dihydroxypropanoic acid.

  Optionally, a polyol can also be added to the reaction mixture. This increases the molecular weight of the present product. The presence of the polyol provides materials as illustrated

  by the formula 1 in which k = 1.

  An embodiment of the invention has the advantage of ensuring an increased concentration of hydroxyl groups (for example by addition of a polyol or by use of an acid

  carboxylic as illustrated by formula (2) where x is 3, 4 or 5).

  In this embodiment, a hydroxydicarboxylic acid is added to the reaction mixture. Formula 3 below presents the formula of certain suitable hydroxycarboxylic acids: Formula 3 [HO] y-R7- (COOH) 2 in which y may have a value of 1 to 5 (preferably 1 to 3) and R7 is a linear, cyclic or branched, saturated, unsaturated or aromatic hydrocarbon fragment which may have from 1 to 28 carbon atoms, preferably having from 1 to 18 carbon atoms and more preferably from 1 to 12 carbon atoms. If there is a value from 2 to, R7 preferably has from 2 to 18 carbon atoms. Preferably, these diacids should be used when the concentration of

  hydroxyl content of the total reaction mixture is at least 0.3 milli-

  equivalent of OH per gram of the combined amount of the reactants (diisocyanate, carboxylic acid polyol, hydroxyalkyl (meth) acrylate, hydroxydicarboxylic acid and polyol when present). These diacids can suitably be used in an amount of from about 0.3 to about 0.7 milliequivalents of acid per gram of the combined amount of the reactants. Suitable hydroxydicarboxylic acids can be chosen from the group consisting of malic acid,

  tartaric acid, dihydroxytartric acid, hydroxyadi- acid

  pike, dihydroxyadipic acid and trihydroxyadipic acid.

  These dicarboxylic acids can be used to provide lateral or terminal thermosetting moieties. Advantageously, these fragments can also provide reactive sites for further reaction with other materials. Melanin and an epoxy are, for example, two compounds or fragments which can be reacted with the terminal carboxyl groups. These reactions make it possible to further modify or increase the characteristics of the material. The specific characteristics or qualities desired depend on the use to which one

destines the material.

  To prepare the coating composition based on urethane-di- (and / or) tri (meth) acrylate carboxylate, the reaction is carried out in a solution of an anhydrous solvent which itself does not react with the isocyanate. Examples of such suitable solvents are esters, such as ethyl acetate and propylene glycol monomethyl ether acetate, ketones, such as

  than methyl ethyl ketone, methyl isobutyl ketone and N-methyl-

  pyrrolidone, aromatic hydrocarbons, such as toluene and

  xylene, and mixtures thereof.

  Suitably, the preparation reaction of the present coating composition is carried out with a solids content of the solution in the range of about 20 to about 100%, preferably in the range of about 35 to about 95% and better from about 65 to about 85% by weight. The reaction temperature is generally from about 50 to about 95 ° C and preferably from about to about 85 ° C. Preferably, the homopolymerization is inhibited by adding a radical polymerization inhibitor, such as

  hydroquinone, m-dinitrobenzene, phenothiazine and the like.

  More preferably, they are used in an amount of from about 0.005% to about 1% by weight relative to the weight of the dry materials. It is also preferred to use a condensation catalyst such as tin or amine catalysts. These catalysts can be chosen from the group consisting of dilaurate

  dibutyltin, dimethyltin dineodecanoate, bis-octylthio-

  dibutyltin glycolate, triethylamine and triethylene-

  diamine. To obtain the best results, the reaction is carried out

tion under dry air protection.

  The diisocyanate can comprise a branched, linear or cyclic, saturated, unsaturated or aromatic hydrocarbon fragment. It can have from 4 to 20 carbon atoms and preferably it has from 6 to

18 carbon atoms.

  The diisocyanates can be chosen from the group made up

  by xylylene diisocyanate, the: 1-isocyanato-3-isocyanatomethyl-

  3,5,5-trimethylcyclohexane, 3,3'-dimethyldiphenylmethane-4,4'-

  diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene-diiso-

  cyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-tri-

  methylhexamethylene diisocyanate, methylene-bis (4-cyclohexyliso-

  cyanate), hexamethylene diisocyanate, meta-tetramethylxylene-

  diisocyanate, para-tetramethylxylene-diisocyanate, methylene-

  bis-phenyldiisocyanate, 1,5-naphthylene diisocyanate, meta-

  phenylene diisocyanate and mixtures thereof. The most preferred diisocyanates are 2,6-tolylene diisocyanate,

  2,4-tolylene diisocyanate, 1-isocyanato-3-isocyanatomethyl-

  3,5,5-trimethylcyclohexane, 2,2,4-trimethylhexamethylene-diiso-

  cyanate and 2,4,4-trimethylhexamethylene diisocyanate.

  When a polyol is included, the molecular weight,

  cure speed and crosslinking density are increased.

  The polyol can have from 2 to 28 carbon atoms. The hydrocarbon portion can be branched, linear or cyclic, saturated, unsaturated or aromatic and has from 2 to 5 hydroxyl fragments. Preferably, the polyol is a diol or a triol having from 2 to 16 carbon atoms. The preferred diols are chosen from ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, octanediol, neopentylglycol, 2-methylpropane-1,3-diol, cyclohexanedimethanol and diethylene glycol. Other preferred polyols which can also be used include glycerol,

  trimethylolpropane or hexanetriol.

  The hydroxyalkyl (meth) acrylate (component c) may have an alkyl group having from about 2 to 28 carbon atoms. The alkyl fragment can also be linear, branched or cyclic, saturated or unsaturated. Preferably, the alkyl group of

  (meth) hydroxyalkyl acrylate has from 2 to 12 carbon atoms.

  Certain preferred hydroxyalkyl (meth) acrylates can be chosen from hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and the compounds corresponding to the general formula:

0 0 0

  Il p Il CH2 = CH-C-O [C (CH2) 50] mC (CH2) 5OH

where m is 1 or 2.

  When preparing the present coating composition, the concentrations of the reactants should be such that the total concentration of the hydroxyl groups is at least approximately equal to the amount of diisocyanate present. Generally speaking, this means that the concentration of polyols, plus the diols of dialkoylolcarboxylic acid, plus the hydroxyalkyl (meth) acrylate is sufficient to bring the ratio of hydroxyl to diisocyanate to at least about 0.95 / 1 and preferably at least 1/1. Particularly preferably, the equivalents of hydroxyl moieties are in excess. Preferably, the excess of hydroxyl equivalents over the diisocyanate should correspond to the range of about 1.05 / 1 to about 0.95 / 1, more

  preferably in the range of about 1.02 / 1 to about 1/1.

  Carboxylic acid polyol is an important ingredient in the present coating composition and it is preferred that it be present in an amount sufficient for the uncured copolymer to be soluble or swell in aqueous alkaline solutions. Suitably, the carboxylic acid polyol is present in a minimum proportion of about 0.3 milliequivalents of acid / gram of the total amount of the reactants; preferably in a proportion equal to or greater than 0.5 milliequivalents of acid / gram of the total amount of the reactants. The polar solubility is further increased when the carboxylic acid-polyol is used in the reaction mixture in a proportion greater than 0.8 milliequivalents of acid per gram of the total amount of

  reacting compounds (meq / g of RT).

  A preferred range of meq of acid / g of RT is from about 0.8 to about 1.6 meq of acid / g of RT. If a highly viscous product is desired which is extremely suitable for combination with other materials, it is particularly preferred that the reaction mixture contain at least about 1 meq of acid / g of RT; a very particularly preferred range is from about 1 to about 1.6 meq of acid / g of RT. The use of the diacid of formula (3) can also make it possible to increase the amount of milliequivalents of acid. Another advantage of the carboxylation of urethane-di- and tri (meth) acrylates is that the ultraviolet-sensitive compound can be combined with hydrophilic resins. In addition, by modifying the proportion of carboxylation of urethane-di- and tri (meth) acrylates, it is possible, to a certain extent, to adjust the hydrophilicity of this compound sensitive to ultraviolet rays. This makes it possible to adapt the hydrophilic nature to a particular resin. Therefore, when it is desired to use a more hydrophobic or less hydrophilic resin, a lower proportion of carboxylation in the urethanedi- and tri (meth) acrylate can be used to increase compatibility with the resin chosen. Conversely, if it is desired to use a hydrophilic resin, the concentration of the carboxyl groups will be increased so that the resin and the urethane-di- and tri (meth) acrylate can be mixed at higher concentrations. The carboxylic acid-polyol can be used in the reaction mixture at concentrations such that the carboxylated polyol constitutes from approximately 5 to approximately 45% by weight of the total amount of the reactants (weight of RT), preferably approximately 5 to about 25% of the weight of RT, and more

  preferably from about 12 to about 25% of the weight of RT.

  When it is also desired to incorporate a specific polyol, it can be used in the reaction mixture in a proportion of approximately 2 to approximately 18% of the weight of RT; preferably around

2 to about 15% of the weight of RT.

  For the diisocyanate, a suitable range of concentrations is from about 30 to about 80% by weight of RT. Of

  preferably, the range is from about 50 to about 75% of the weight of RT.

  The hydroxyalkyl (meth) acrylate must be present in the reaction mixture in a minimum proportion of approximately 0.50 meq of acrylate / g of RT to ensure appropriate sensitivity to ultraviolet light. A suitable range is from about 0.5 to about 1.6 meq of acrylate / g of RT. An acceptable range of weight percentages is between about 5 and about 50% of the weight of RT, and preferably a range varying from about 10 to about 50 is used.

% of the weight of RT.

  The present coating composition based on a urethane-di (and / or) tri (meth) acrylate carboxylated copolymer may have a weight average molecular weight of from about 500 to about 6,500, preferably from about 800 to about 3,000 and more preferably from about 1,000 to about 2,500 (determined with a gel filtration chromatography apparatus and relatively to

  a calibration curve with standard polystyrene).

  In a preferred embodiment, the present coating composition is combined with a binder. The resin used for this purpose should preferably have a glass transition temperature (Tg) of about 155 ° C or more and most preferably is hydrophilic. The high Tg improves the temperature resistance. Various commercial resins can be used. We can get

  mixtures compatible with the present urethane-di- (and / or) tri (meth) -

  carboxylated acrylates by varying the concentration of carboxyl groups. Suitable resins which can be used for this purpose are styrene / maleic anhydride copolymers, especially those which have been partially esterified with

low molecular weight alcohols.

  Styrene / anhydridemaleic copolymers which have been esterified with mixtures of alcohols ranging from methyl to butyl are commercially available. These copolymers are marketed in a wide range of molecular weights. Suitably, the molecular weight of this resinous binder should be in the range of from about 25,000 to about 300,000 and more, preferably from about 60,000 to about 250,000. Preferably, the copolymer used has a ratio of styrene to maleic anhydride in the range of about 1/1 to about 2/1. A range

  The preferred Tg of the binder is from about 150 ° C to about 200 ° C.

  The binder can be used in an amount of from about 85 to about 25% of the weight of the total composition, and preferably from about 17 to about 60% of the weight of the total composition. Preferably, the urethane-di- (and / or) tri (meth) acrylate carboxylated coating composition is mixed with the binder, so that the glass transition temperature (Tg) of the final product is d 'around 70 to around 190C. Preferably, the acid number of the binder is from about 120 to about 280 mg of KOH / g of binder. Other polymers having the molecular weight, the Tg and the acid number described above can be used as binders with the present coating composition based on urethane-di- (and / or) tri (meth). carboxylated acrylate. Copolynerics suitable for use as binders include a methyl methacrylate / methacrylic acid copolymer and a polymer of

  methyl methacrylate / methyl acrylate / methacrylic acid.

  When using the present urethane-di- (and / or) tri (meth) -

  acrylate carboxylated with other materials, such as the binders described above, or other additives which can be added, such as crosslinkers, dyes, solvents, pigments, photoinitiators and thermal inhibitors, the concentration of the ultraviolet sensitive carboxylated coating ingredient should be in the range of about 10 to about 85% of the weight of the total combined composition. Preferably it is in the range of about 15 to about 75% and most preferably it is in the range of about 17 to about 60% of the weight of the composition

total combined.

  The preferred crosslinkers are the (meth) acrylates monomers.

  Crosslinkers are used when it is desirable to obtain a composition having an increased crosslinking density, which improves resistance to solvents, such as methylene chloride. Polyfunctional monomer (meth) acrylates are particularly preferred. These polyfunctional monomers can be

  chosen from trimethylolpropane-tri (meth) acrylate, trimethyl-

  ethoxylated olpropane-tri (meth) acrylate, hydroxy-dipentaerythritol

  pentaacrylate and dimethylolpropane-tetraacrylate.

  Other useful crosslinkers can be chosen from the group consisting of divinyl ethers, acrylated epoxides, epoxy resins and aminoplast resins. Acrylic epoxides are preferred because they improve the overall resistance to

  heat, resistance to solvents and overall adhesion.

  When the present carboxylated coating composition is used as a solder mask, an appropriate substrate is coated with the composition and dried in a non-tacky form. The coated substrate is then subjected to photo-printing with about 75 to about 105 mJ / cm2 of ultraviolet radiation and can then be developed with an aqueous alkaline solution. Preferably, the aqueous alkaline solution is based on potassium or sodium carbonate. Generally, the coated substrate bearing

the photographic image.

  An advantage of using the present coating composition is that, if desired, a coating can easily be removed with an aqueous alkaline stripper and a new coating applied. The amount of alkali that the pickling or developing solution must contain is very small. A solution containing 1% by weight of a base can be used. When the desired image quality is obtained, the present coating can be subjected to an ultraviolet post-hardening of 3 to J / cm 2. Thereafter, thermal curing is carried out, preferably at 150 ° C., for a sufficient time. The present compositions have excellent properties of resolution, flexibility and

adhesion to metals.

  The invention is illustrated by the following nonlimiting examples in which all the parts and all the percentages

  are by weight, unless otherwise noted.

Example 1

  This example illustrates a preparation of the composition of

photosensitive coating.

  The following ingredients are introduced into a 5-liter round bottom flask fitted with a mechanical stirrer, a thermometer,

  a refrigerant, a gas inlet and a heating jacket

  leaf: 236.0 grams (g) (about 4 equivalents) of 1,6-hexanediol, 268.0 g (about 4 equivalents) dimethylolpropionic acid, 951.2 g (about 8.2 equivalents). of 2-hydroxyethyl, 0.23514 g of phenothiazine as radical inhibitor, 783.8 g of N-methyl-2-pyrrolidone as solvent and 31.35 g of dibutyltin dilaurate (T-12) as catalyst. Under a dry air protection with stirring, 1,680.0 g (about 16 equivalents) of trimethylhexamethylene diisocyanate are introduced into the mixture in two equal portions at an interval of 30 minutes. Each addition is accompanied by an exothermic surge. The reaction temperature is kept below 85 ° C. by cooling with a bath

  of ice water and, after the second addition of trimethylhexa-

  methylene diisocyanate, the reaction temperature is maintained at a constant value of 85 ° C. for 10 to 12 hours until the infrared absorption peak of the isocyanate has disappeared, which

  indicates that the reaction is complete.

  Example 2 The photosensitive coating composition prepared in Example 1 is used to prepare a photosensitive mask for soldering. To prepare the mask for welding, the following ingredients are introduced into a 500 ml round bottom flask fitted with a stirrer, a gas inlet, a thermometer and a coolant: 6.5 g of a low molecular weight copolymer anti-foaming agent, 91.25 g of N-methyl-2-pyrrolidone as solvent and 82.0 g of an esterified copolymer of styrene / maleic anhydride as binder. (The resin used is the Scripset 550 from MONSANTO). The mixture is stirred and heated to 95 ° C for 30 minutes to obtain a cloudy solution. Then, the temperature is lowered to 'C, then the following ingredients are added to the mixture: 0.004 g of phenothiazine as an inhibitor of radical polymerization, 77.5 g of the coating composition sensitive to ultraviolet prepared in examples 1 and 9 .0 g of a green pigment. By protecting the mixture with a stream of dry air, a premixed solution containing the following constituents is added: 47.8 g of trimethylolpropane triacrylate (SR 351) as crosslinking agent, 6.5 g of isopropylthioxanthone (designated by the abbreviation ITX) as photoinitiator and 8.4 g of ethyl pdimethylaminobenzoate (designated

  by the abbreviation EPD) as a sensitizer.

  The above ingredients are left to mix under a dry air protection for 30 minutes at 70 ° C. then they are introduced into an amber-colored pot. The welding mask thus prepared is used as described in Example 3.

Example 3

  The composition prepared in Example 2 is applied in the form of a coating with two bare tables of copper-plated epoxy resin 15 cm x 20 cm (6 "x 8") over a thickness of approximately 0.051 mm (2 mils ) using a polyester monofilament fabric with mesh sizes of approximately 0.2 mm (75 mesh) using a rubber doctor blade having a durometer hardness of 70. This wet coating is dried in a forced air oven at 100C for a period of 12 minutes to form a 0.036 mm (1.4 mil) thick non-sticky film. After these dried films have cooled to room temperature, they are exposed to mJ / cm2 through a negative IPC (Institute for Interconnecting Packaging electronic Circuits) n 'B-25 model with a 400 watt mercury vapor lamp. The exposed films are then developed manually in a 1% K2CO3 solution for 45 seconds and rinsed with fresh water. Excellent resolution of the IPC B-25 is obtained. After this development, the tables are hardened to 3 J / cm 2 and subjected to thermal cooking at 150 ° C. for 1 hour as post-hardening treatment. One of the tables is then immersed in methylene chloride (designated by the abbreviation MeCl2) for 15 minutes and no degradation of the mask is observed (solvent resistance test). The other panel is subjected to an adhesion test after cross-hatching according to ASTM-D3359-78 method B and no decrease in adhesion is observed. The panels are then coated with a resinous flux and floated with the face carrying the mask for welding below on a crucible of molten solder at 260-275 ° C. for 10 seconds. After the solder crucible test, the table is immediately rinsed with 1,1,1-trichloroethane while the table is still hot. One hour later, the table is subjected to the same adhesion test after cross-checking and no

drop in membership.

Example 4

  Using the device and the general operating mode

  described in Example 1, urethane oligomers are prepared

  diacrylate with varying importance of carboxylation.

  Sample 4 is not carboxylated and sample 9 has the maximum carboxylation. All samples are prepared with 80% dry matter. The composition used for each sample

  individual is shown in Table 1 below.

Table 1

  The following abbreviations are used: DMPA = dimethylolpropionic acid 2HEA = 2-hydroxyethyl acrylate TMDI = trimethylhexamethylenediisocyanate DTN = dimethyltin dineodecanoate M-Pyrol = Nmethylpyrrolidone eq = equivalent Sample 4 Sample 5 s weight (g) e_ weight (g) 1.6 hexanediol 8,472 7.0 413.0

DMPA - - 1.0 67.0

2HEA 8.1 939.6 8.2 951.2

TMDI 16 1,680.0 16.0 i 680.0

DTN - 15.46 - 15.56

  M-Pyrol - 772.9 - 777.8 Phenothiazine - 0.309 - 0.311 Sample 6 Sample 7 eq weight (g) e_ weight (g) 1.6 hexanediol 3.0 177.0 2.0 118.0

DMPA 5.0 335.0 6.0 402.0

2HEA 8.2 951.2 8.2 951.2

TMDI 16.0 1,680.0 16.0 1,680.0

DTN - 15.72 - 15.76

  M-Pyrol - 785.8 - 762.8 Phenothiazine - 0.314 - 0.315 Sample 8 Sample 9 aq weight (g) e_ weight (g) 1.6 hexanediol 1.0 59.0 0 0

DMPA 7.0 469.0 8.0 536.0

2HEA 8.2 951.2 8.2 951.8

TMDI 16.0 1,680.0 16.0 1,680.0

DTN - 15.8 - 31.67

  M-Pyrol - 789.8 - 791.8 Phenothiazine - 0.316 - 0.317 We measure the viscosities of samples 4 to 9 (in cP) at 23.9'C (75'F) using a Brookfield RVT viscometer rod n6 at

rpm

  Sample 4 5 6 7 8 9 Viscosity 20,400 22,400 41,600 44,800 68,800 86,400

Example 5

  Samples 5 to 9 of carboxylated urethane acrylates are used to prepare masks for welding. These masks for welding are then subjected to tests to compare their properties. This example and the following examples 6 and 7 make it possible to compare the properties of masks containing carboxylated urethane acrylates with those of masks containing

  non-carboxylated urethane-acrylates.

  The welding masks called here samples D to H are prepared with the apparatus and the general procedure described in

Example 2.

  The quantity of each ingredient is shown in Table 2 below:

Table 2

  Solder mask composition common to samples D to H Modalflow (a low molecular weight copolymer) 6.5 Nmethylpyrrolidone 91.25 Styrene / maleic anhydride (Scripset 550) 82.0 Phenothiazine 0.004 Urethane-carboxylated acrylate 77.5 Green pigment ( 9G5) 9, 0 Isopropylthioxanthone 6.5 ethyl p-dimethylaminobenzoate 8.4 trimethylolpropane-triacrylate (SR 351) 47.8 Summary of properties of masks for carboxylated welding Mask for welding (sample :) DEFGH Carretylated urethane 5 6 7 8 9 According to the general method described in Example 3, masks for welding are formed with samples D to H on bare tables of copper-plated epoxy resin. We submit

  then the tables to tests and evaluations.

  Photographic speed: excellent at 75 mJ / cm2 for samples D to H. Development: excellent for samples D to H in a

1% aqueous solution of K2CO3.

  In 1,1,1-trichloroethane, the development is poor for samples D to H. Adhesion test: ASTM-D3359-78 method B (5 = no decrease in adhesion) (O = complete loss of adhesion) DEFGH sample Adhesion before the molten weld 5 4-5 4-5 5 4-5 Adhesion after application of the melted 5 5 5 5 5

Example 6

  The following samples of a mask composition for welding are prepared as described in Example 2 using the

  non-carboxylated material constituting the sample 4.

  The ingredients and their quantities are shown in the following table 3:

Table.3

  Sample A Sample B Composition of mask for solder mask for soldering Defoamer 1.10 1.30 N-methylpyrrolidone 41.8 50.35 Scripset 550 30.68 36.50 Phenothiazine 0.0024 0.003 Green pigment (9G5) 3.1 3.1 Sample 4 29.0 75.0

SR 351 16.2 -

Isopropylthioxanthone 2.25 3.0

EPD 3.1 4.0

  To establish a comparison according to the procedures described in Example 3 between each of these compositions (A and B), they are subjected to tests and they are used to coat a bare table of copper-plated epoxy resin than the subject to further testing. The results are shown below: Sample A of Sample B of mask for solder mask for solder Limited compatibility Total separation of phases

  Stability at 23.9'C (75'F) 1 month ---

Development

1% aqueous K2CO3 excellent ---

  Poor 1,1,1-trichloroethane ---

  Properties Resistance to methylene chloride is poor, the effect

  solvent appearing after only 2 minutes of exposure.

  Adhesion before molten weld * 5 after molten weld * 5 SR 351 = trimethylolpropane-triacrylate EPD = ethyl p-dimethylaminobenzoate * adhesion after cross-hatching - ASTM-D3359-78 method B = no decrease in adhesion 0 = loss full membership

Example 7

  Also for comparison purposes, the material constituting the sample 4 is used to prepare a photosensitive element.

  the development of which is evaluated in different types of solvents.

  To prepare the photosensitive element (sample C), the ingredients in table 3 are mixed at 50 ° C. in a 500 ml round bottom flask fitted with a stirrer, a gas inlet, a thermometer and d 'a refrigerant. Table 4 below shows the amount of

each ingredient.

  Table 4 Composition of welding mask (sample C) containing a non-carboxylated urethane diacrylate (sample 4) Composition (tg) Urethane diacrylate (sample 4) 122.5 Elvacite 2008 94.0

PMA 131.0

  Phenothiazine 0.0044 Irgacure 651 6.2 Leucoderivative of crystallized violet (dye) 0.2 Development in 1,1,1-trichloroethane excellent in 1% aqueous K2C03 no development Note: Elvacite 2008 = polymethyl methacrylate (PM = 79,000) PMA = propylene glycol monomethyl ether acetate Irgacure 651 = 2,2-dimethoxy-2phenylacetophenone Non-carboxylated urethane diacrylate (sample 4) has very limited compatibility with styrene resin / anhydride

  maleic (Scripset 550). Homogeneous mixtures of urethane-

  non-carboxylated diacrylate and styrene / anhydride resin

  maleic could only be obtained during relati-

  briefly (less than a month) and only when the ratio of urethane diacrylate to resin is less than 1. When the ratio increases, phase separation occurs

(sample B).

  On the other hand, the urethane-di- or tri (meth) acrylate carboxylated can have a carboxylation of variable importance allowing it to be miscible and compatible in all proportions with

  styrene resin / maleic anhydride and other resinous binders.

  The products obtained have excellent properties of duration of

  storage conservation, uniformity and performance.

Example 8

  Carboxylated urethane triacrylate samples are prepared using the apparatus and general procedure described in Example 1. The specific ingredients of each sample

  triacrylate are shown in Table 5 below.

Table 5

  Sample 10 Sample 11 (eq) (weight in g) (eq) (weight in g)

1,6-hexanediol 2.0 118.0 - -

Tone 0301 - - 4.0 400.0

Glycerol-DMPA 2.0 61.4 - -

DMPA 4.0 268.0 4.0 268.0

2HEA 8.1 939.6 - -

Tone M-100 - - 8.2 2,820.8

* TMDI 16.0 1,680.0 - -

IPDI - - 16.0 1,777.6

DTN - - - 52.66

T-12 - 30.67 - -

  M-Pyrol - 766.8 - 1,316.6 Phenothiazine - 0.23 - 0.395 Note: Tone 0301 = polycaprolactonetriol having a molecular weight of 300 Tone M-100 = caprolactone-reactive acrylate IPDI = isophorone-diisocyanate = 1isocyanato-3- isocyanatomethyl-3,5,5-trimethylcyclohexane Then samples 10 and 11 are used to prepare the mask samples for welding I and J respectively

  illustrated in Table 6 below.

  Masks are prepared for welding using the device

  and the general procedure described in Example 2.

Table 6

  Compositions of masks for welding based on urethane-carboxylated triacrylates Composition Sample I Sample J Modaflow 1.10 1.10 Nmethylpyrrolidone 41.8 41.8 Scripset 550 30.68 30.68 Phenothiazine 0.0024 0.0024

Sample 10 29.0 -

  Sample 11 - 29.0 Green pigment (9G5) 3.1 3.1

ITX 2.25 2.25

EPD 3.10 3.10

SR 351 16.2 16.2

  Development properties: In aqueous K2CO3 Excellent Excellent at 1% by weight Resistance to MeCl2 6 min (good) 8 min (good) (Test by immersion in solvent for the period indicated and evaluation of the results as good in the absence of 'effect and

poor if the solvent acts).

  Adhesion after cross-hatching - ASTM-D3359-78 method B 5 = no decrease in adhesion O = complete loss of adhesion Adhesion before molten welding 5 4 after molten welding 5 3

Note: ITX = isopropylthioxanthone.

  The tables used in the above tests are prepared using samples I and J according to the procedure described

in example 3.

Claims (13)

  1. A photosensitive coating composition characterized in that it comprises: an ultraviolet-sensitive polymer chosen from the group consisting of: a carboxylated urethane-dimethacrylate, a carboxylated urethanediacrylate, a carboxylated urethane-triacrylate and a carboxylated urethanetrimethacrylate, this sensitive polymer with ultraviolet light being prepared by condensation of a reaction mixture comprising as component (a) a diisocyanate having from 6 to   18 carbon atoms, as component (b) a carboxylic acid-   polyol having the formula [OH] x-R6-COOH in which x can be an integer from 2 to 5 and R6 is a linear, branched or cyclic, saturated, unsaturated or aromatic hydrocarbon moiety having from 2 to 29 atoms   carbon, and as component (c) a hydroxy- (meth) acrylate   alkyl, of which the alkyl has from 2 to 28 carbon atoms; with the proviso that component (a) is present in a proportion of approximately 30 to approximately 80% of the weight of the total amount of the reaction mixture,   component (b) is present in a proportion of about 5 to about   45% by weight of the total amount of the reaction mixture with a minimum of about 0.3 milliequivalents of acid per gram of the total amount of the reaction mixture, and that component (c) is present in a proportion of about 5 to about 50% of the weight of the total amount of the reaction mixture, with a minimum of 0.5 milliequivalent of acrylate per gram of the total amount of reaction mixture.   2. Composition according to claim 1, characterized in that   that it also contains a binder.   3. Composition according to claim 1, characterized in that the reaction mixture also comprises a polyol having from 2 to   28 carbon atoms and 2 to 5 hydroxyl fragments.   4. Composition according to any one of claims 1 to   3, characterized in that the reaction mixture also comprises a dicarboxylic acid corresponding to the formula: [OH] y-R7- (COOH) 2   in which y is an integer from 1 to 5 and R7 is a hydro-   carbon having i to 28 carbon atoms.   5. Composition according to any one of claims 1 to   4, characterized in that component (b) is further selected from the group consisting of: ", t-dimethylolacetic acid, &," dimethylolpropionic acid, ", o-dimethylolbutyric acid, acid adiethanolacetic acid x, & - diethylolpropionic acid & &, adiethylolbutyric acid.   6. Composition according to claim 3, 4 or 5, character-   in that it also comprises a binder which is a copolymer of styrene / maleic anhydride having a transition temperature glassy of around 155 ° C or more.   7. Composition according to any one of claims 1 to   6, characterized in that the reaction mixture contains from about 0.8 to about 1.6 milliequivalents of acid per gram of the amount total of the reaction mixture.   8. Composition according to any one of claims 1 to   7, characterized in that the diisocyanate is chosen from the group   consisting of: 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-   cyclohexane; xylene diisocyanate; 3,3'-dimethyldiphenyl-   methane-4,4'-diisocyanate; 2,4-tolylene diisocyanate; the   2,6-tolylene diisocyanate; 2,2,4-trimethylhexamethylene-diiso-   cyanate; 2,4,4-trimethylhexamethylene diisocyanate; the   methylene-bis- (4-cyclohexyldiisocyanate); hexamethylene-diiso-   cyanate; 1,5-naphthylene diisocyanate; meta-phenylene-diiso-   cyanate; meta-tetramethylxylene diisocyanate; the paratetra-   methylxylne-diisocyanate and methylene-bisphenyldiisocyanate.   9. Composition according to claim 8, characterized in that   that it also contains a crosslinker.   10. Process for the preparation of a polymer sensitive to ultraviolet rays, characterized in that it comprises carrying out a condensation reaction with a reaction mixture comprising as component (a) a diisocyanate having from 6 to 18 carbon atoms, as component (b) a carboxylic acid-polyol having the formula [OH] x-R6-COOH in which x can be an integer from 2 to 5 and R6 is a linear, branched or cyclic, saturated, unsaturated or aromatic hydrocarbon fragment, having from 2 to 29 carbon atoms, and as component (c) a hydroxyalkyl (meth) acrylate, of which   the alkyl has from 2 to 28 carbon atoms, provided that the compound   sant (a) is present in a proportion of about 30 to about 80% of the weight of the total amount of the reaction mixture, component (b) is present in a proportion of about 5 to about 45% of the weight of the amount total of the reaction mixture, with a minimum of about 0.3 milliequivalents of acid per gram of the total amount of the reaction mixture, and that component (c) is present 0 in a proportion of about 5 to about 50% of the quantity weight   total reaction mixture, with a minimum of 0.5 milliequiva-   slow acrylate per gram of the total amount of the reaction mixture. 11. The method of claim 10, characterized in that the temperature of the reaction mixture is in the range of about 50 at around 95'C.   12. Method according to claim 10 or 11, characterized in that the reaction mixture also contains an inhibitor of   radical polymerization and a condensation catalyst.   13. Method according to any one of claims 10 to   12, characterized in that the reaction mixture is in dry air during the reaction.