FI57429C - FOTOPOLYMERISERBAR KOMPOSITION INNEFATTANDE ETT ADDITIONSPOLYMERISERBART MATERIAL ETT INITIATORSYSTEM FOER ADDITIONSPOLYMERISATIONEN EN INHIBITOR FOER TERMISK ADDITIONSPOLYMERISATION OCH ETT POLYMERT BINDEMEDEL - Google Patents

Description

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Patent »och regitterttyrelsan Amekan utlagd och utUkriften publlcond 30.04.80 (32) (33) (31) Pyydetty atuoikaua — Boglrd priorltat 01 *. 02.71 USA (US) 112797 (71) Dynachem Corporation, 13000 East Firestone Boulevard, Santa Fe Springs, California 90670, USA (72) Richard Edmund Beaupre, West Barrington, Rhode.Island, Michael Nicholas Gilano, Fullerton, California, Melvin Alan Lipson,

Fullerton, California, USA (US) (7M Berggren Oy Ab (5M Photopolymerizable blend comprising an addition polymerizable agent, an addition polymerization initiation system, a thermal addition polymerization inhibitor and a polymeric binder) The present invention relates to a new and improved photopolymerizable composition, and more particularly to a photosensitive composition which can be easily developed by means of an aqueous alkaline solution to give a product useful in printing plates and light protection. in the manufacture of printed circuits because the resistors made from them do not pass through conventional electroplating solutions.

The desire to produce photosensitive mixtures that can be developed without the need for conventional organic solvents has long been recognized. Organic solvents are expensive, dangerous because of their toxicity and sensitive flammability, and pollute the air and water.

However, the benefits of such aqueous mixtures were observed as long ago as 1952 U.S. Patent No. 2,760,863i did not disclose any particular preparations, and it can be assumed that the applicant was unable to find a satisfactory preparation. Further references to such water-soluble preparations are given in U.S. Patent Nos. 2,927,022 and 2,893,868. Whatever the merits of the preparations disclosed in these patents, it appears that such preparations, in so far as they can be developed with alkaline aqueous solutions, were either insufficiently insoluble. exposed parts or were damaged by conventional electroplating and etching solutions when light shielding was applied to the printed circuit board.

It is an object of the present invention to provide photopolymerizable compositions which can be developed with aqueous alkaline solutions and whose exposed areas have excellent resistance to alkaline solutions, including alkaline etchants and alkaline electroplating solutions often found in the manufacture of printed circuits and chemically treated parts.

The invention is thus directed to a photopolymerizable mixture comprising (A) an addition polymerizable agent, (B) a photoinitiated initiation polymerization initiation system operating to generate free radicals, (C) a thermal addition polymerization inhibitor and (D) a polymeric binder, and is characterized in that the addition polymerizable substance (A) consists essentially of 10 to 60 parts by weight of one or more esters of a polyhydric alcohol and an acrylic acid having a boiling point above 100 ° C at atmospheric pressure and containing at least two terminal ethylene groups, and a photoinitiated initiation system (B); that the amount of the thermal addition polymerization inhibitor (C) is 0.001 to 5 parts by weight, and that the polymeric binder (D) comprises 00 to 90 parts by weight of a preformed styrene or vinyl acetate and alpha-beta a copolymer of an unsaturated monomer having 3 to 15 carbon atoms containing carboxyl groups, whereby styrene or vin the ratio of the amounts of yl acetate to the carboxyl group-containing monomer is such that the binder is soluble in a 2% aqueous solution of trisodium phosphate.

Ethylene unsaturated compounds suitable for use in the composition of the invention are disclosed in U.S. Patent No. 2,760,863. The compounds are preferably non-gaseous at 20 ° C and normal pressure, preferably contain 2 or more ethylene end groups, and act as a plasticizer for the thermoplastic polymeric binder. Suitable compounds which may be used alone or in combination are alkylene or polyalkylene glycol acrylate prepared from alkylene glycols having 2 to 15 carbon atoms, or polyalkylene ether glycols having 1 to 10 ether bonds.

The following typical compounds further illustrate these compounds: ethylene diacrylate, diethylene glycol diacrylate, glycerol diacrylate, glycerol triacrylate, ethylene dimethacrylate; 1,3-propylene dimethacrylate, 1,2,4-butanetriol trimethyl-3,5429 acrylate, 1,4-benzenediol dimethacrylate, pentaerythritol tetramethacrylate, 1-3-propanediol diacrylate, 1,5-pentane diol diiretacrylate and polyethylene of molecular weight 200-500 bis-acrylates or methacrylates.

Preferred monomeric compounds are divalent or polyvalent monomers, but monovalent monomers can also be used. The amount of monomer added varies depending on the thermoplastic polymer used.

The second comonomer may be a monomer containing one or more unsaturated carboxyl groups having 3 to 15, but preferably 3 to 6 carbon atoms. The most preferred compounds are acrylic acid and methacrylic acid. Other acids which may be used are cinnamic acid, crotonic acid, sorbic acid, itaconic acid, propionic acid, maleic acid and fumaric acid or the corresponding half-esters or, if possible, the corresponding anhydrides.

The ratio of styrene or vinyl component to acidic comonomer is selected so that the copolymer is soluble in alkaline aqueous solution. If the amount of styrene or vinyl monomer is too large, the unexposed portion is not sufficiently soluble; on the other hand if styrene! the amount of vinyl monomer is too low, the exposed portion is sticky, swollen, or soluble in an alkaline aqueous solution. As a practical criterion, it can be said that the binder copolymer enters ditches such that the viscosity of its 40 solution in ketones and alcohols is 100 to 50,000 cP.

Typical comonomer ratios are 70:30 to 35:15 for styrene-acrylic acid or netacrylic acid; 35: 65-70: 30 for styrene-nonobu-style maleate and 70: 33-95: 5 for vinyl acetate-crotonic acid. the degree of polymerization of the fide copolymer is such that the binder forms a non-sticky, continuous film after exposure and development. Broadly speaking, the molecular weight is in the range from 1000 to 500,000. This applies to a molecular weight of about 1000-500,000.

As shown, the protection within the scope of this invention is resistant to common electroplating and etching solutions. Most amazingly, it is resistant to copper pyrophosphate, which is used in pattern galvanizing and is extremely alkaline. Other solutions that leave the protection unchanged are ferric chloride, ammonium persulfate and chromium sulfuric acid.

The photoinitiators used in the preparations are preferably those which can be activated by photochemical light and are thermally inactive at 185 ° C or below. These include substituted or unsubstituted polynuclear quinones, 9,10-anthraquinone, 1-chloroanthraquinone, 2-chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, octamethylanthraquinone, 1,4-naphthoquinone; 9,10-phenanthrenequinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2-methyl-1,4-naphthoquinone, 2,3-dichloronaphthoquinone, 1,4-dimethylanthraquinone, 2,3-dimethylanthraquinone, 2- phenylanthraquinone, 2,3-diphenylanthraquinone, anthraquinone-alpha-sulfonic acid sodium salt, 3-chloro-2-methylanthraquinone, retenequinone, 7,8,9,10-tetrahydronaphthalenequinone and 1,2,3,4-uetranedrobenzanthracene-7,12 dione.

The following photoinitiators described in U.S. Patent No. 2,700,363, some of which may be thermally active at temperatures as low as 85 ° C, are also useful: ketaldonyl proxies such as diacetyl and benzyl compounds, alpha-ketaldonyl alcohols; such as benzoin and pivaloin, acyloline ethers, e.g., benzoin methyl and ethyl ethers, and alpha-hydrocarbon substituted aromatic acylins such as alpha-methylbenzoin, alpha-allylbenzoin and alpha-phenylbenzoin.

Silver persulfate is also useful as a free radical generating initiator that can be activated by photochemical radiation. Certain aromatic ketones, e.g., benzophenone and 4,4'-bis-dialkylaminobenzophenones, are also useful.

Thermal polymerization inhibitors are also present in the preferred formulations. These include p-methoxyphenol, hydroquinone and alkyl- and aryl-substituted hydroquinones and quinones, tert-butyl catechol, pyrogallol, copper resinate, naphthylamines, beta-naphthol, cuprous chloride, 2,6-di-tert-butyl-p-cresol , 2,2-methylenebis- (4-ethyl-6-t-butylphenol), phenothiazine, pyridine, nitrobenzene, dinitrobenzene, p-toluquinone, chloranil, aryl phosphites and arylalkyl phosphites.

If desired, the preparations may contain colorants and pigments. Suitable dyes are miscible with photosensitive preparations and do not significantly interfere with the photosensitivity of the preparation. The following typical compounds are illustrative: Fuchsine (C.I. 42510), Auramine Base (C.I. 4100B), Calcocid Green S (C.I. 44090), Para Magenta (C.I. 42500), Tryparosan (C.I. 42505), New Magenta (C.I.

42520), Acid Violet RRH (C.I. 42425), Red Violet 5 RS (C.I. 42690),

Nile Blue 2 3 (C.I. 51135), New Methylene Blue GO (C.I. 51195), C.I. Basic Blue 20 (C.I. 42585), Iodone Green (C.I. 4255b), Night Green B (C.I. 42115), C.I. Direct Yellow 9 (C.I. 19540), C.I. Acid Yellow 17 (C.I. 18965), C.I. Acid Yellow 29 (CI 18900), Tartrazine (CI 19140), Supramine Yellow G (CI 19300), Buffalo Black 10B (CI 27790), Naphthalene Black 12R (CI 20350), Fast Black L (CI 51215), Ethyl Violet (CI 42600), Pontacyl Wool Blue BL (CI 50315), Pontacyl Wood Blue GL (CI 52320), (Figures obtained from the second edition of the Color Index).

The photopolymerizable parts are exposed by means of a photochemical radiation source. This can be done by means of a halftone image or a translucent image method, e.g. a negative or positive method, a diagram or a cover plate. Exposure also took place through a continuous negative or positive image. Exposure can occur by touch! by a projection method, either using a cover plate with or without a photopolymerizable layer or using a cover plate in the projector. These procedures are very familiar to those skilled in the art.

Because free radical-generating addition polymerization initiators that are activatable by photochemical radiation 6,572,49 generally have their maximum sensitivity in the ultraviolet range, the radiation source must emit an effective amount of this radiation. Both point and diffuse radiation sources are efficient. Such sources include carbon arcs, mercury vapor arcs, fluorescent lamps with ultraviolet light emitting luminaires, argon filament lamps, electronic flash units, and photographic floodlights. Of these, mercury vapor lamps, especially sunlight lamps, are the most suitable. Under certain conditions, it may be advantageous to illuminate with visible light using a photoinitiator which is sensitive to the visible part of the spectrum, e.g. 9,10-phenanthrene quinone. In such cases, the radiation source should emit an effective amount of visible radiation. Many of the radiation sources listed above produce the required amount of visible light.

Photopolymerizable preparations can be developed after exposure, e.g. by bombarding them with spray nozzles, brushing them immersed in a mixed liquid or washing them to the desired dryness with aqueous solutions of bases, e.g. aqueous solutions of water-soluble bases, generally in concentrations ranging from 0.01 to 10% by weight.

Suitable bases for development include alkali metal hydroxides, e.g. lithium, sodium and potassium hydroxide, alkali metal salts of weakly reactive weak acids, e.g. lithium, sodium and potassium carbonates and bicarbonates, amines having a 66 base ionization constant greater than. x 10 e.g. primary amines such as benzyl, butyl and allylamines, secondary amines such as dimethylamine and benzylmethylamine, tertiary amines, e.g. trimethylamine and triethylamine, primary, secondary and tertiary hydroxyamines, e.g. propanol and ethanol, e.g. 2-amino-2-hydroxymethyl-1,3-propanediol, cyclic amines e.g. ammonium hydroxides, e.g. tetramethyl, tetr acetyl, trimethylbenzyl and trimethylphenylammonium hydroxides, sulfonium hydroxides e.g. and potassium pyrophosphates, tetrasubstituted (preferably entirely with alkyl groups) phosphonium, arsonium, and stibonium hydroxide, 7 57429 e.g. tetramethylphosphonium hydroxide.

Photopolymerized preparations can generally be removed by immersion in heated solutions of strong alkalis or, if desired, in patented washing compositions well known in the art.

To further illustrate the invention, attention is drawn to the following examples.

Example I

The following solution was coated with a 0.025 mm (1/1000 '') thick polyester film and air dried. The thickness of the photosensitive layer when dry was also about 0.025 mm. The dried layer was again covered with a 0.025 mm thick polyethylene film.

Copolymer with 57% styrene and 63% monobutyl maleate, average molecular weight 20,000, viscosity of 10% aqueous ammonium salt solution = 150 cP 67.0 g

Trimethylolpropane triacrylate 22.0 g

Tetraethylene glycol diacrylate 11.0 g

Benzophenone 2.3 g 4,4'-bis- (dimethylamino) benzophenone 0.3 g 2,2'-methylene-bis-β-ethyl-δ-tert-butylphenol) 0.1 g

Ethyl violet 0.07 g

Benzotriazole 0.20 g

Methyl ethyl ketone 1 * 10.0 g

A piece of copper-coated epoxy fiberglass board was cleaned by rubbing it with an abrasive cleaner, wiping and rinsing thoroughly in water. It was then immersed in a dilute hydrochloric acid solution (2 volumes of water and 1 volume of concentrated hydrochloric acid) for 20 seconds, then rinsed with water and then dried with compressed air.

The uppermost polyethylene film was removed from a portion of the layered photopolymerizable preparation. The exposed protective layer with its polyester backing films was laminated to pure copper so that the surface of the photopolymerizable layer came into contact with the copper surface. Lamination was performed with rubber coated rollers using a temperature of 120 ° C and a pressure of 210 g / cnr at the contact point at a speed of 2 ft / min. The resulting photosensitive copper-coated sheet, which was protected as such by the polyester film, could be stored for later use if necessary. In fact, it was illuminated with light passing through a heavily tinted translucent image, with the conductive pattern appearing as translucent areas on a dim background. Exposure was performed by placing a photosensitive copper-coated plate (with the polyester film still attached) and a translucent image in the photocopy frame. Exposure lasted 45 seconds with a 400 W, 50 A mercury vapor lamp at a distance of 30 cm. The polyethylene terephthalate backing film was peeled off and the exposed protective layer was developed by stirring the plate for 3 1/2 minutes in a tray containing 2% sodium carbonate in water and then rinsing with water.

The resulting plate contained a discolored protective pattern caused by bright areas of the exposure translucent image.

The plate was now etched with a 45 ° solution of ferric chloride in Baume, after which it was rinsed and dried. Residual copper was removed from the shield by immersing it in 3% aqueous sodium hydroxide solution at 70 ° C for 2 minutes. The result was a high quality printed circuit board.

Example II

The following solution was coated with a 0.025 mm thick polyester film and allowed to dry at ambient conditions for 30 minutes.

Copolymer of 75% styrene and 25% methacrylic acid with a viscosity of 10360 cP of a 40% methyl ethyl ketone solution 11.0 g

4.66 g of trimethylolpropane triacrylate

Tetraethylene glycol diacrylate 2.33 g

B benzophenone 0.75 S

4,4'-bis- (dimethylamino) benzophenone 0.10 g 2,2'-methylene-bis- (4-ethyl-6-tert-butylphenone) 0.3 g

Methyl violet 0.2 g

Benzotriazole 0.07 E

Methyl ethyl ketone 30.0 g

The thickness of the photosensitive layer when dry was about 0.035 mm. The coated material was then laminated to the surface of the cleaned copper-coated plate as in Example 1. Exposure was performed through a hearing plate containing a matte pattern of known size with the exposure unit described in Example I and lasted for 1 1/2 min. The polyester backing film was torn off and the exposed protective layer was developed by stirring the plate for 2 min in a tray containing a $ 2 aqueous solution of trisodium phosphate, after which it was rinsed with water.

After development, the exposed copper surface was further purified by immersing the plate in a 20% ammonium persulfate bath for 30 seconds, washing with copious amounts of water, dipping for 30 seconds in a 20 L aqueous solution of hydrochloric acid, rinsing with water, and then drying the plate with compressed air. This cleaned plate

O

was then boiled for 45 minutes at a current density in a 3.2 A / dm 2 copper pyrophosphate electroplating bath at 55 ° C.

Example III

A piece of epoxy glass fiber coated with copper was cleaned as described in Example I. The cleaned, dried plate was made photosensitive by allowing the following solution to flow over the surface of the plate: Copolymer of 37 l of styrene and 63% mono-butyl maleate, average molecular weight 20,000, viscosity of 10% aqueous ammonium salt solution = 150 cP 40.0 g

Pentaerythritol tetraacrylate 23.0 g

Beathonone 1.5 g 4,4'-bis- (dimethylamino) benzophenone 0.2 g 2,2'-methylene-bis- (4-ethyl-6-tert-butylphenol) 0.6 g

Methyl violet 0.4 g 1'ethyl ethyl ketone 100.0 g

Benzotriazole 0.15 g

Excess solution is drained from the plate at room temperature for 2 minutes. The coating was further dried by heating in a convection oven at 60 ° C for 5 minutes.

After cooling, the coated plate was exposed as described in Example I. Protection was developed by stirring the plate in a $ 2 aqueous solution of trisodium phosphate for 1 minute and then rinsing with water. The plate was now etched in ferric chloride as shown in Example I. After etching, the exposed shield was washed from the copper covering it by immersing the plate in a $ 3 aqueous solution of sodium hydroxide at 50 ° C for 2 minutes. The result is a high quality printed circuit board.

Example IV

The next solution was coated with a 0.025 mm thick polyester film and air dried.

Copolymer with 95% vinyl acetate and 5% crotonic acid, average molecular weight 90,000, viscosity of 8.6% ethyl alcohol solution between 13-18 cP 70.0 g

Pentaerythritol tetraacrylate 30.0 g

Benphenophenone 2.3 g 10 57429 4,4'-Bis- (dimethylamino) -b'-cophenone 0.3 g 2,2'-methylene-bis- (4-ethyl-6-tert-butylphenol) 0, ]. g .lethyl violet 0.07 5

Benzotria solia 0.20 g

Methyl ethyl ketone 150.0 g

The thickness of the photosensitive layer when dry was about 0.025 mm. A copper-coated plate was prepared, the protective layer was laminated on it, and the resulting preparation was exposed exactly as in Example I. The backing film was torn off, and the exposed protective layer was developed by stirring the plate for 2 minutes in a tray containing 2 of trisodium phosphate and then rinsing with water.

The plate was now etched as in Example I to obtain a high quality printed circuit board.

Example V

Zinc, magnesium and copper printing plates were coated with the photosensitive solution described in Example I. After drying in hot air to a dry thickness of about 0.025 mm, the photosensitive layer is coated with a dilute aqueous solution of polyvinyl alcohol and re-dried with hot air. The water-soluble polymer forms a thin protective barrier against oxygen. These pre-photosensitized metal sheets can be stored for long periods of time.

When exposed to photochemical light through a suitable photographic imaging negative, an unexposed photosensitive layer and a water-soluble surface layer can be developed simultaneously, with the metal sheet ready for etching. The light-polymerized image area then acts as an excellent protection in the deep etching processes normally used in the manufacture of metal printing plates. These resulting sheets are resistant to common etchings, e.g., ferric chloride and nitric acid, film-forming agents, and trimming agents, which are commonly added to the etching mixture to adjust the etching geometry. Example VI

The procedure of Example V is followed except that a 0.025 mm thick polyester film is used as the protective layer instead of a water-soluble polymer. After exposure to photochemical light, the protective layer is torn off before development in an alkaline aqueous solution. As in Example V, the photopolymerized image area serves as an excellent protection in the deep etching of printing plates.

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Example VII

The photosensitive solution described in Example I is coated with a 0.025 mm thick polyester film, air dried and covered with a 0.025 mm thick polyethylene film. This three-layer film combination can be stored as sheets or rolls in light-protected locations for unlimited lengths of time. Prior to use, the polyethylene cover is torn off and the photosensitive layer is brought into contact with a metal sheet of the type described in Example V and backed by lamination. After the plate is exposed to photochemical light, the protective polyester layer is torn off and developed in an alkaline aqueous solution. As in Example V, the photopolymerized image area is an excellent protection in the deep etching of printing plates.

Example VIII

The photosensitive solution described in Example I is coated on thin aluminum sheets commonly used in offset lithographic printing by the methods set forth in Examples V, VI and VII.

When the plates are exposed to photochemical light and developed in an initial aqueous solution, the photopolymerized image area acts as an excellent ink-absorbing substrate. It also has excellent abrasion resistance. The resulting plates can be used with excellent results in offset lithography.

Example IX

The photosensitive solution described in Example I is coated on a woven reticulated substrate by the methods described in Examples V, VI and VII. When the network is exposed to photochemical light and developed with an alkaline aqueous solution, the photopolymerized image area acts as excellent protection. This application has proven to be useful in silk screen printing.

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Claims (9)

12 57429 A photopolymerizable composition suitable for coating printing plates comprising (A) an addition polymerizable agent, (B) a photoinitiated initiation polymerization initiation system operating to generate free radicals, (C) a thermal addition polymerization inhibitor, and (D) a polymeric binder known therefrom; (A) consists essentially of 10 to 60 parts by weight of one or more polyhydric alcohols and acrylic acid esters having a boiling point above 100 ° C and containing at least two terminal ethylene groups, the amount of the photoinitiated initiation system (B) being 0.001- 10 parts by weight that the amount of the thermal addition polymerization inhibitor (C) is 0.001 to 5 parts by weight, and that the polymeric binder (D) comprises 40 to 90 parts by weight of the previously prepared styrene or vinyl acetate and alpha-beta unsaturated, 3 “Copolymer of a monomer containing 15 carbon atoms with carboxyl groups, whereby styrene or vinyl the ratio of the amounts of acetate to monomer containing carboxyl groups is such that the binder is soluble in a 2% aqueous solution of trisodium phosphate. Mixture according to Claim 1, characterized in that the unsaturated carboxyl-containing monomer is methacrylic acid. Mixture according to Claim 1, characterized in that the unsaturated monomer containing carboxyl groups is acrylic acid. Mixture according to Claim 1, characterized in that the unsaturated carboxyl-containing monomer is maleic anhydride, maleic acid, maleic acid half-ester or a mixture thereof. Mixture according to one of the preceding claims, characterized in that the addition-polymerizable compound is a mixture of trimethylolpropane triacrylate and tetraethylene glycol diacrylate. Mixture according to one of Claims 1 to 4, characterized in that the addition-polymerizable compound is a mixture of acrylate esters of pentaerythritol. Mixture according to one of Claims 1 to 4, characterized in that the addition-polymerizable compound is a mixture of pentaerythritol acrylate esters and tetraethylene glycol diacrylate. δ. Mixture according to one of the preceding claims, characterized in that the addition polymerization initiation system contains benzophenone, 4, N-bis- (dimethylamino) benzophenone or mixtures thereof. Mixture according to one of the preceding claims, characterized in that it additionally contains at most 1% of triazole, for example benzotriazole, tolutriazole or naphthotriazole, in order to improve the adhesion to metal substrates.