The invention relates to a catalytically active powder, its preparation, as well as a method using said powder to make insulating substrates activating for receiving electroless- ly deposited metal in a coherent metal layer.

Catalytically active powders directly suitable for activat¬ ing electroless metallizing were not known previously.

In deposition of metal on insulating substrates such as for instance plastics, the following steps may be employed: evaporation of metal under vacuum, application of conduct¬ ive paints followed by electrol tical metal deposition as well as electroless metallizing, the latter in addition possibly being followed by an electrolytical metallizing.

Electroless metallizing has gained a widespread use within electrotechnics as well as for metallizing finished: plast¬ ics. A disadvantage of the known methods for electroless metallizing is the series of wet process steps used within the commercial utilization in order to achieve a sufficient adhesion of the metal layer to the surface of the substrate. The process steps are frequently carried out in the follow¬ ing sequence: Etching, neutralizing, sensibilization, acti¬ vation, acceleration, and electroless metal deposition. In a great number of processes, sensibilization and acti¬ vation constitute one process step since the purpose there¬ of is to situate the catalyzing seeds on the surface of the substrate, said seeds catalyzing the metal deposition from the bath in a metallizing bath. Such a catalyst sensitizes and activates an insulating surface for electroless metal¬ lizing in one step and consists for instance of a mixture of SnCl_ and PdCl„, the so-called palladium-tin system. This system usually includes an aqueous solution of a col¬ loidal nature since it is important to stabilize the system

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as precipitation reactions otherwise occur involving aging and destruction of the catalyzing effect.

The patent literature refers to both organic and aqueous solutions, which by influencing an insulating substrate may make said substrate receptive to electroless metal deposi¬ tion. Danish printed accepted specification No. 132,801 de¬ scribes how a compound of an ^' element from group 8 or 1B of the periodic system or mixtures thereof in an organic-. _^ sol¬ vent, which in addition may contain an adhesive, may wet a substrate and make it catalytically active. German Offen- legungsschrift No. 26 36 457 also states an aqueous cata¬ lytic lacquer for the production of printed circuits and comprising a binder, a metal compound, a complex builder, and a reducing agent. Upon the application and drying, said metal compound is present as metal seeds which may be addi¬ tionally reinforced through, electroless metallizing. Aqueous solutions have previously been encumbered with the draw-back that hydrophobic plastic substrates can only be wetted with ^" ' difficulty. This feature was especially recog¬ nized by the so-called two-step process with separated sensibilization and activation steps, cf. e.g. US patent specification No. 4,042,730, or more detailed "Metallic Coating of Plastics" by William Golde, Vol. I, especially Chapter V. The Danish patent applications Nos. 1507/79, 4277/80, and 3300/81 state -method and powders for a dry sensibilization of the surface of an insulating substrate possessing several advantages compared to the state of the art, inter alia concerning the distribution of the adhesion of the metal and concerning reduced expenses by the metal deposition. It should in this connection be stated that the sensibilization means one process step applying a chemical compound to the surface of a substrate. This chemical compound adheres an activator/catalyst to the sub¬ strate through a galvanic process by contact with an aqueous solution containing said activator/catalyst .

Another manner of making substrates catalytical for elec¬ troless metal deposition includes adhering solid particles to the surface of the substrate, said solid particles being catalytical towards electroless metal deposition. Most suit¬ able are the systems including particles of a colloidal na¬ ture, and systems are known including precious metals, as well as other systems having an effect with non-precious metals. The aqueous SnCl ₂ /PdCl_ catalyst is the most fre¬ quently used since a reasonable stability of the aque _: ous solution is obtainable. US patent specification No.- 3,011, 920 describes a process for preparing such a colloidal catalyst, which before the use is accelerated through addi¬ tion of acid or base. Solid catalyst mixtures - used for ' the preparation of an. optically transparent liquid - .have "been described in US patent specification No. 3,672,923. Such systems are generally encumbered with the problem of a lacking long—term stability, and the literature within the field describes aging effects and the importance of the use of an accelerator solution. Within electroless metal¬ lizing, an accelerator solution means a solution of chemi¬ cals with an acid or alkaline reaction, the influence of which on the activated substrate promotes the initiation of an electroless metal deposition. In the present connection, the catalyst solution may in addition have an activating effect on the catalytic powder melted down, which corres¬ ponds to the fact that the catalyst solution in the hither¬ to known commercial utilization is activated before use through addition of a chemical. There is still doubt about the actual functioning of these systems, and a discussion thereof appears inter alia from "An Electon Diffraction Study on Mixed PdCl ₂ /SnCl ₂ Catalysts for Electroless Plat¬ ing" by T. Osaka et al. in Jour. Electrochem. Soc', Nov. 1980, p 2443ff and "A Study on Activation and Accele¬ ration by Mixed PdCl ₂ /SnCl ₂ Catalysts for Electroless Metal Deposition" by R. Zeblenski in the same journal, December 1980, p 2652ff.

It has long been desired to obtain an improved stability of the PdCl _? /SnCl„ catalysts which have gained a widespread use for processes within electrotechnics , cf. inter alia US patent specification No. 4,187,198 and US patent specifi¬ cation No. 4,212,768. Regarding the effect of these cata¬ lysts it is considered probable that the precious metal (e. g. Pd) in the elemental form is stabilized by tin compounds in the solution.

As described in US patent specification No. 3,993,799 it has turned out that systems including colloidal particles of non-precious metals are also catalytic for electroless metal deposition when appropriate baths are employed. It has in connection with such systems been difficult to ob¬ tain a high catalytic activity simultaneously with a good stability. US patent specification No. 3,958,048 describes how the colloidal nature could disappear in less than "24 hours. US patent specification No. 4,167,596 describes the use of hydro—oxides understood as a mixture of oxides and hydroxides of cobalt, nickel, iron, copper, and mixtures thereof while adding stabilizers, surfactants, and reac¬ tivity-modifying compounds. Upon immersion of the substrate into such a colloidal system, following rinsing a further immersion is carried out in a solution with a reducing com¬ pound. Apart from the wetting of the substrate such a pro¬ cess has the drawback that it cannot be carried out selec¬ tively. It has been described in the patent literature how an improved adhesion can be obtained, cf . inter alia US patent specification No. 4,233,344, wherein hydrazine hydrate is used as an adhesion—improving agent. A change of the pH in the colloidal system, cf. US patent specification No. 4,220,678, changes the charge on the colloidal par¬ ticles, which has an influence on the adhesion of said par¬ ticles to the substrate.

It has thus been highly desired to improve the adhesion be¬ tween colloidal, catalyzing systems and a insulating sub¬ strate and, if desired, to position the compounds catalytic for electroless metallizing in a prescribed pattern. In addition it is of great commercial and practical importance to produce durable chemicals for use in electroless metal¬ lizing. This is obtained by a powder according to the in¬ vention which is characterised by containing fine-grained particles of a plastic material and one or more chemical compounds catalytic for electroless metallizing, as' well as a surfactant, whereby said chemical compound and said sur¬ factant are present in an. amount of 0.2 - 20% by weight and 0.1 - 100% by weight, respectively, both parts being cal-' culated on the plastic material, and whereby upon melting down onto a substrate and acceleration followed by electro¬ less metallizing said powder results in a metal layer ad¬ hering to the plastic powder melted down- and having a limit defined by the distribution of the plastic powder melted down.

Claim 2 deals with catalytically active compounds which have proved particularly suitable as ingredients of a powder active for electroless metallizing.

Claim 3 deals with hydro-oxides of metals capable of acti¬ vating for electroless metallizing when unstable metal¬ lizing baths may be used.

Claim 4 deals with a commercial catalyst of the PdCl„/ SnCl„ type which may be used as an ingredient in a powder according to the invention.

Claim 5 deals with a powder where the active chemical com¬ pounds for electroless metallizing have been dispersed in the plastic material as colloidal particles.

-Claim 6 deals with a composition of a surfactant which as an ingredient in the powder melted down ensures a good con¬ tact with the metallizing bath, whereby a coherent metal layer is obtained.

Claim 7 indicates that a magnetic material may be incorpo¬ rated into the powder in such a manner that the powder may be transferred magnetostatically or charged electrostatic¬ ally in a controlled manner by means of a magnetic brush arrangement.

Claim 8 deals with a method for the preparation of the pow¬ der according to the invention, said method ensuring a homogenous distribution of the catalytically active com¬ pounds on each powder particle.

Claim 9 indicates that the plastic suspension is spray dried, whereby a powder having a uniform particle size is obtained.

Claim 10 states that prior to the drying of the plastic suspension, a reducing compound is added, the reaction of said reducing compounds with the catalytically active com¬ pounds improving the deposition of metal.

Claim 11 states that the powder melted down onto a sub¬ strate is treated in a salt-acid or alkaline medium with the purpose of improving the deposition of metal and ob¬ taining an improved adhesion of the metal to the plastic powder melted down.

Claim 12 states that the powder is suitable for obtaining metallizing of an insulating substrate.

Claim 13 indicates that the powder is electrostatically transferable to a substrate.

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Claim 14 states that magnetic compounds built in may ensure a magnetostatic transfer.

The powder, stated according to the invention, where a plastic powder contains the well-known PdCl ₂ /SnCl„ cata¬ lysts or other precious metal catalysts of colloidal nature or hydro-oxides of non-precious metals as well as surfact¬ ants, is characterised in that after melting down the powder onto a substrate and suitable acceleration, a.-metal- lizing with a good adhesion and a sharp metallizing limit are achievable. Such a powder provides an essential im¬ provement compared to the prior art. Thus the durability of the catalyzing compounds has been considerably increased, not the least due to the acceleration not being carried out until the powder has been .melted down onto the substrate, and not as by the conventional wet process where accelera¬ tion of the catalyst is carried out prior to immersion -of the substrate into the solution or suspension of the cata¬ lyst. It has not previously been recognized that by using catalysts in the form of catalyzing plastic powder, whether said powder contains precious metal systems or non-precious metal compounds, considerable advantages can be obtained. For instance etching of the substrate is avoided in order to form cavities in which the catalyzing compound may be sucked up so as to ensure a good adhesion. Furthermore, the colloidal nature of the catalyzing compounds of a powder according to the invention has been stabilized in a parti¬ cular manner by the used fine-grained plastic powder.

The catalytic compounds in a powder according to the inven¬ tion may include any desired compound of the metals from group 8 of the periodic system, iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium in addition to a tin compound, where tin to as large an extent as possible being present in the oxidation step +2 or another, the catalyti¬ cally active compound may be from group 1B of the periodic

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system, copper, silver, gold.

When the catalyzing compounds are complex compounds, it may be necessary to use an accelerator, which may be acid or alkaline, for the metallizing process. When commercial catalysts of the P Cl ₂ SnCl ₂ type are used, an aqueous salt acid solution (cone. HC1 to H„0 e.g. 1:2) is ^' a suitable accelerator. In this manner the stabilizing alkaline hali¬ des are removed from the catalyzing powder melted down, whereby a more water permeable surface is achieved. in addi¬ tion. At the following metallizing process, this increased surface porosity causes an extremely good adhesion of metal to plastic powder melted down.

For the preparation of a powder according to the invention including an Sn-Pd catalyst it may under certain circum¬ stances be undesired that alkaline halides are used to form a complex compound with PdCl ₂ , since this can result in a very fatty powder. However, U.S. patent specification No. 4,212,768-- states that other halides are applicable, e.g. CaCl„, 6H ₂ 0, and LaCl_, 7H„0. It was found particularly advantageous for a powder according to the invention to utilize a double salt of CaC12, 6H-0 and PdCl^, since a very electrostatic powder is thereby obtained. Another manner of avoiding unfortunate properties by a powder in¬ cluding a. conventional Sn-Pd catalyst, such as e.g. 9F from Shipley Corp., is to use a plastic emulsion instead of a jet-ground powder. In this manner the concentration of the double salt is reduced, said double salt containing the catalytically active metal.

In the field of conventional electroless metallizing, sur¬ factants have usually been added to the baths used. It was not previously recognized that an improved effect was ob¬ tainable by means of a powder capable of activating the surface of a substrate for electroless metallizing and in¬ cluding a sufactant. The hydrophobic part of this surfact-

•ant adheres to a hydrophobic plastic material being the most essential ingredient of said powder, at the same time as the hydro-philic properties of said plastic material en¬ sure a good contact between the powder melted down and an aqueous medium.

Especially regarding commercial catalysts of the PdCl ₂ / SnCla type the great advantage is obtained in connection with the invention in that said catalyst is not activated for electroless metal deposition until the powder according to the invention has been melted down, the substrate with the powder melted down being immersed into an acid or alka¬ line medium. As a result, both the powder and a plastic film formed of said powder demonstrate a durability not previously known.

A method for the preparation of a powder according to the invention includes the steps of the plastic material in the fine-grained form or prepared by an emulsion polymerisation in aqueous medium being mixed with an aqueous dispersion of a surfactant, whereafter the catalyzing- compounds are added and dried upon adjustment of the desired acidity, e.g. through spray drying. A method according to the inven¬ tion is characterised in that it is carried out in an aqeuous medium, and that colloidal particles present there¬ in or precursors for such particles, inter alia as a con¬ sequence of the influence of the surfactant, adhere strong¬ ly to each plastic part acting as stabilizer as well as a cement during the melting -down of the dry powder, said ce¬ ment binding the compounds activating/catal zing for the electroless matallizing to the surface of the substrate. The aqueous medium furthermore has the advantage that part¬ ly h ^' ydrolysed and oxide-containing compounds are present, which can be melted down through for instance the spray drying process in the surface of the powder particles and thereby improve the wetting of the powder melted down.

The preparation of a powder according to the invention in¬ cluding non-precious catalyst compounds may be carried out on the basis of commercially available solutions with stabilizers present therein and which may be accelerated in a suitable manner, or the colloidal particles may be preci¬ pitated prior to the drying process through the addition of reducing surface-active and precipitating reagents. At the subsequent drying process, the colloidal nature is in a particular manner stabilized on the surface of each powder grain as islands of catalytically active compounds.

A powder according to the invention may be applied to an insulating substrate through sprinkling, electrostatic or magnetostatic transfer directly to the substrate or via a light-sensitive master, cf. the prior art. The powder is melted down in order to obtain a suitable adhesion to the substrate. If the catalyzing compounds are so stable that they cannot directly initiate an electroless metallizing, an acceleration can be carried out. Such an acceleration may include the steps of the powder melted down on the substrate being subjected to influence in an acid or alka¬ line medium. As a result the catalyzing compounds are made active for electroless metallizing. In addition, a more porous structure is obtained, which improves additionally the adhesion of the electrolessly deposited metal. At a later galvanic process it is possible to increase the thick ness of the metal layer.

Within the neighboring field, photocopying, the magnetic one-component toners have gained increasing use. For use in equipment using this principle, it is possible to prepare a powder which in accordance with claim 7 includes a magnetic material in each powder particle, e.g. oxides of iron, the particle size of which is usually less than 2.5 μ. In addi¬ tion it is possible to precipitate a thin layer of palla¬ dium on these grains of magnetic material, e.g. by reducing a palladium salt dissolved in a slurry of said grains onto

'their suface, e.g. by addition of formaldehyde. Whether these grains of magnetic material have a thin layer of pal¬ ladium on the surface or not or are commercial powders such as for instance Bayferrox 8600 (Bayer Chemie) , a powder according to the invention can be prepared, which in each powder grain includes grains of magnetic material. It is most advantegeous that these are slurried in a plastic emul¬ sion, to which one or more of the catal tically active com¬ pounds as well as a surfactant are added, said surfactant improving the hydrophilic properties of the powder- prepared when said powder is melted down onto an insulating sub¬ strate.

The invention thus provides a cataly ically active powder which can be used directly to initiate electroless metal¬ lizing, and which possesses a novel .capacity, of achieving a good adhesion of the substrate as well as a pore-free merging. The stability of the powder prepared has proved to be surprisingly good, and it is of great environmental im¬ portance that transport of a catal st . f ^" pr electroless metal¬ lizing by using the powder according to the invention may ' be carried out as- a transport of a stable powder instead of being a transport of liquids detrimental to environment.

For further explanation of the powder stated according to the invention, its preparation and use, the following ex¬ amples are given:

Example 1.

A powder including the following ingredients

Styrene plastics (Piccolastic D 125 Hercules Corp.) 100 g

PdCl ₂ 0.1 g

SnCl„, 2H„0 (all Sn-compounds have been converted into equivalent SnCl ₂ , 2H„0) 5 g

Surfactant (Span 60 ICI-Atlas) 0.4 g

■ Example 2...

A powder as stated in Example 1 is prepared by 100 g of plastic material (Piccolastic D 125) upon crushing being ground on a Trost jet mill. The finely ground powder is slurried in an aqueous dispersion containing the surfactant in an amount corresponding to 4% by weight of the plastic material. 5 g of SnCl _? , 2H _? 0 are weighed out and heated to 95°C, whereafter 0.1 g of PdCl„ is added. Upon cooling this mixture is crushed and dissolved in water, whereafter this solution is added to the plastic suspension. Upon adjust¬ ment of the pH to 8 by means of ammonia water, the plastic suspension is dried on a spray drier (NIRO Atomizer model Minor) with a rate of rotation on the atomizer wheel of 35,000 r.p.m. and with a feeding velocity and supply of hot air adapted in such a manner that the input temperature and the output temperature were 180 C and 80 C, respectively.

Example 3.

A powder including the following ingredients:

Piccotoner 1200 (Hercules Inc.) 100 g Catalyst 9F (Shipley Inc.) 5 g Atmer 122 (ICI-Atlas) 0.3 g

Example 4.

A powder as stated in Example 3 is prepared by 100 g of Piccotoner 1200 upon crushing being added to an aqueous dispersion containing 0.3 g of Atmer 122, which is a sur¬ factant, in 1 liter of liquid. An amount corresponding to 5 g of solid matter of Catalyst 9F, which is a commercial catalyst of the PdCl ₂ /SnCl ₂ type produced by Shipley Inc.. is diluted into a volume of 1 liter and pH is adjusted by means of a 6 N NaOH solution to about 6. Under heavy stirring the diluted catalyst solution is added to the

plastic suspension. By 6N NaOH pH is adjusted to 7, and the mixture is dried on a spray drier (NIRO Atomizer model Minor) with a rate of rotation on the atomizer wheel of 35,000 r.p.m. and a feeding velocity and supply of hot air adapted in such a manner that the input temperature and the output temperature were 180 C and 80 C, respectively.

Example 5.

The use of powder as stated in Example 3 is performed by applying it to an insulating substrate completely or part¬ ly, the powder being sprinkled through seriographic mask, transferred electrophotographically or in another manner, whereafter it is melted down at a temperature of 140 C. The substrate with the powder melted down is immersed into a solution of concentrated hydrochloric acid and water in the ratio 1:3 for a period of 8 minutes. Subsequently it is treated in an accelerator solution (Shipley 19H) for 3 minutes in order upon rinsing to be metallized in a Shipley 238 electroless copper bath at room temperature. A

Exam le 6.

A powder including, the ingredients

Org-D-21 (Hercules Inc.) 1 00 g

AgN0 ₃ 7 . 5 g

Atmer 114 (Surfactant, ICI-Atlas) 0 . 3 g

Example 7

A powder including the ingredients

Org-D-21 (Hercules Inc.) 00 g

CuCl ₂ ,6H ₂ 0 8 . 0 g

Atmer 114 (Surfactant, ICI-Atlas) 0 . 3 g

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.Examp le 8 ■_

A powder as stated in Example 6 is prepared by 100 g of plastic material upon crushing being ground on a Trost jet mill. The finely ground powder is slurried in an aqueous dispersion - containing the surfactant (Atmer 114) in an amount corresponding to 3% by weight of the plastic mate¬ rial. An aqueous solution of the metal salt is added in the desired amount, whereafter pH is adjusted to 8 by 6N .NaOH. Subsequently, the plastic suspension is dried on a -spray drier (NIRO Atomizer model Minor) with a rate of rotation on the atomizer wheel- of 35,000 r.p.m. and a feeding velo¬ city and supply of hot air adapted in such a manner that the input temperature and the output temperature were 170 C and 70 C, respectively.

Example 9.

Analogous with Example 8, a powder as stated in Example 7 was prepared.

Example 10.

A powder of a plastic material containing hydro-oxides of a metal present in one or more oxidation steps was prepared by 100 g of plastic material (Piccotoner 1200) being slur¬ ried in a dispersion of a surfactant (Atmer 122 from ICI- Atlas) , the amount of which corresponds to 3% by weight of the plastic powder. An aqueous solution was admixed which contained 8 g of CuCl_, and during heavy stirring an aqueous solution of 2 g of KBH, was additionally added, whereafter a 6N NaOH solution was added until a pH of about 9 was reached. The resulting plastic suspension was dried on a spray drier (NIRO Atomizer model Minor) with a rate of rotation on the atomizer wheel of 35,000 r.p.m. and a feeding velocity and supply of hot air adapted in such a manner that the input temperature and the output tempera—

ture ere .200 C and 80 C , re sp ec t ive ly

Example 1 1 .

An aqueous plastic emulsion (Dresinol from Hercules Inc.) corresponding to 100 g of solid matter was added to an aqueous dispersion of 0.3 g of surfactant (Span 60 from ICI- Atlas) . During heavy stirring 30 g of Fe_0, of a particle size of less than 0.5 y were added to the above. Furthermore an aqueous solution of Catalyst 9F (Shipley Inc.) was added in an amount corresponding to 4% of solid matter, and the ' pH was adjusted to 8 by 6N NaOH, whereafter a spray drying was carried out on a NIRO Atomizer model Minor with a rate of rotation on the atomizer wheel of 35,000 r.p.m. and a feeding velocity and supply of hot air adapted in such a manner that the input temperature and the output tempera¬ ture were 160 C and 65 C, respectively.

Example 12.

A powder including the following ingredients

Piccotoner 1200 (Hercules Inc.) 100 g

PdCl ₂ 0.4 g

CaCl ₂ , 6H ₂ 0 2.8 g

SnCl ₂ , 2H ₂ 0 2.8 g

Atmer 121 (ICI-Atlas) 0.3 g

Example 13.

A method for the preparation of a powder as stated in Example 12 included the following steps: 0.4 g of PdCl„ were dissolved in 2.8 g of CaCl„, 6H„0, which we ^' re kept melted at 95°C. After 15 minutes 2.8 g of SnCl ₂ , 2H ₂ 0 were added. This solution was now added to a plastic suspension, where 100 g of Piccotoner 1200, which in- advance had been jet-ground, were slurried into 500 ml of distilled water,

-wherein 300 mg of surfactant Atmer 121 (ICI-Atlas) were dis ^¬ persed. The alkalinity was adjusted to pH = 8 by 6N _^ NaOH, and a NIRO Atomizer model Minor was used for the spray dry ^¬ ing. The atomizer wheel was adjusted to 35,000 r.p.m., and the feeding velocity and supply of hot air were adjusted in such a manner that the input temperature and the output temperature were 180 C and 80 C, respectively.

Example 14. _r .

A powder as prepared by the method described in Example 11 was transferred in a device for photocopying, whereby pow¬ ders containing magnetic matter are electrostatically trans¬ ferred to a light-sensitive master, said master optionally being a polyester film coated with a light-sensitive ma¬ terial. A picture obtained electrostatically by illumina¬ tion on the light-sensitive surface charged to a positive high voltage of 2.8 kV was produced by said powder by means of a conventional magnet brush arrangement kept at ground potential. Transfer of the resulting electros atic picture to an insulating substrate was carried out by charging said substrate.

Example 15.

A powder as prepared by the method described in Example 11 was used for developing a magnetically structured CrO„- coated polyester film, on which a magnetostatic picture was produced by illumination with a Xenon flash lamp. During this procedure, said CrO —coated magnetized film was il¬ luminated through a photographic film where the light pen¬ etrated the bright areas of the film and heated the magnet¬ ized film to more than its Curie point. The developing was carried out by a "powder cloud" technique (powder cloud in flow of air) . The powder grains adhering to the magnetized film were subsequently transferred to an insulating sub¬ strate being brought to a positive potential of about 20 kV.

Exampl e 1 6 _

Powders as stated in Examples 1, 3, 6, 7, and 11 were in turn transferred electrostatically as follows: The powder was charged electrostatically to a voltage of 2.2 kV in a conventional device for electrostatic powder transfer. By means of a flow of air the powder was transferred to a sub¬ strate whereafter it was melted down by heating to the melting temperature. - _v

Example 17.

A powder with a composition as stated in Example 12 and pre¬ pared as stated in Example 13 was mixed in the weight ratio 2 to 100 with iron powder of a particle size of 50 to 100 μ (a conventional carrier for use in magnet brushes) . B such a developing mixture in a conventional magnet brush arrange¬ ment, latent electrostatic pictures were developed on a photo-sensitive master, which through conventional corona discharge had been charged to a negative high voltage of 3.2 kV and subsequently illuminated selectively by means of a pattern. Transfer from said photo-sensitive master was carried out by charging an insulating substrate so that the particles were transferred by attraction. In a conventional manner the particles were fixed to the insulating substrate and electroless metallizing was carried out.