EP0341167A1 - Process for manufacturing a perforated nickel frame by electroforming - Google Patents

Abstract

Production, by electroforming, of perforated frames used especially for making up flat or cylindrical printing frames. According to the invention, the procedure is in two stages, with two separate electrochemical baths, the second bath containing a pyridinium compound of general formula: <IMAGE> in which: - R is an optionally substituted alkyl chain - R' is a hydrocarbon atom or a substituent group in any position relative to the nitrogen atom of the pyridinium nucleus.

Description

The present invention relates to a method of manufacturing a perforated nickel frame, by electroforming.

Such perforated frames are in particular used as printing frames, whether they are called "flat frame" prints, or so-called "rotary frame" prints.

More specifically, the invention relates to a manufacturing process, as described and proposed by patent US-A-2,226,384, the content of which is incorporated into the present description.

According to this process, we start from a support mandrel made of solid copper, stainless steel, or copper-plated steel. Alveoli, the shape and dimensions of which correspond to the meshes of the perforated frame to be obtained, are formed on the surface of the mandrel by different etching processes, such as chemical attack, seam etching, or electronic etching.

The hollow opening of the cells is filled with a non-conductive resin leaving uncovered the edge or edge of the same cells, remaining conductive.

Then, according to a first step, and in a first electrolysis bath, a first deposit of nickel is carried out on the support mandrel, for a limited time, so as to obtain a nickel skeleton whose perforations correspond substantially to the original cells. of the mandrel. The duration of this first stage is therefore chosen to limit the growth of the nickel deposit from the edges of the cells, preferably upwards. At the end of this first step, the skeleton is separated from the mandrel, for example by simple cooling causing differential expansion and therefore detachment of the skeleton relative to the mandrel.

According to a second step, and in a second electrolysis bath, a second deposit of nickel is carried out on the skeleton. This additional contribution of metal envelops and reinforces all the nickel cords of the skeleton, to obtain the final perforated frame.

One of the problems posed by this manufacturing process, in particular when it is used to obtain perforated frames with unitary meshes of very small dimensions, relates to the obturation with nickel of the perforations of the skeleton, during the second stage d 'electrolysis. In addition to the alteration or modification of the original shape and dimensions of the skeleton perforations, this additional nickel deposit reduces the passage section of each unit cell of the final perforated frame. Such a reduction in the free cross section of each unitary mesh subsequently decreases the quantity of printing fluid which can pass through the perforated frame, when the latter is used as a printing frame.

The user of the usual and traditional additives in electrochemistry, namely the use of products described and designated in the literature as "primary brighteners" and "secondary brighteners" allows to a large extent to respect the shape and the starting dimensions. skeletal perforations, as established on pages 52-53 of the Nickel Electroforming Guide published in 1975 by International Nickel (INCO). This is explained by the fact that the expected leveling effect cannot be exerted in the hollow or empty parts corresponding to the perforations of the skeleton, and therefore refers accordingly in height, on either side of the nickel beads. of the same skeleton.

Nevertheless this being so, this respect for the original perforations of the skeleton leads to a relatively significant reduction in the passage section, by "homothetic" progression towards the interior of the nickel deposit, starting from the edge of each perforation of the skeleton.

The subject of the present invention is a method as described above, making it possible to strengthen the skeleton resulting from the first step, both by respecting essentially the dimensions of the perforations of said skeleton, and by limiting the reduction in the free cross section of the meshes. of the perforated frame obtained.

The present invention also relates to an electronic method, which remains simple in its implementation, and in particular does not resort to sophisticated technological solutions such as a pulsed supply current.

dans laquelle :
- R est une chaine saturée alkyle comportant au moins un atome de carbone, éventuellement substituée
- R′ est un atome d'hydrogène ou un groupement substituant, en position quelconque par rapport à l'atome d'azote du noyau pyridinium.According to the present invention, it has been discovered that this effect can be obtained by using at least in the second bath a pyridinium compound corresponding to the general formula:

in which :
- R is a saturated alkyl chain containing at least one carbon atom, optionally substituted
- R ′ is a hydrogen atom or a substituent group, in any position with respect to the nitrogen atom of the pyridinium nucleus.

Preferably, but not exclusively:
- R is an alkyl chain substituted by at least one group having no double or triple bond with a carbon atom
- And / or R ′ is a substituent group having no bond with a carbon atom.

By double or triple bond with a carbon atom, one understands bonds of the type:
C = C, C≡C, C = O, C = N, C≡N

By way of example of the pyridinium compounds which can be used according to the invention, mention may be made of the following sulfopropylated compounds, identified according to the CAS nomenclature:
- 4-methyl-1- (3-sulfopropyl) -pyridinium
- 4-benzyl-1- (3-sulfopropyl) -pyridinium
- 1- (2-hydroxy-3-sulfopropyl) -pyridinium
- 3-methyl-1- (3-sulfopropyl) -pyridinium
- 1- (3-sulfopropyl) -pyridinium
- 2-methyl-1- (3 sulfopropyl) -pyridinium

According to a preferred embodiment of the invention, the pyridinium compound is used in the second electrolysis bath, together with a compound listed in the relevant literature by way of tension reducer. Such a compound can be a sulfonimide, such as saccharin, a sulfonamide, paratoluene-sulfonamide, sodium metabenzenedisulfonate, sodium naphthalene trisulfonate 1,3,6, arylsulfonic acid, etc.

The pyridinium compound is used at a rate of 60 to 250 g for 10,000 A / h, preferably at the same time as a voltage reducer, as described above, in the proportions of 10 to 500 g for 10,000 A / h.

• - la figure 1 représente en coupe transversale le squelette de nickel obtenu à l'issue de la première etape d'électrolyse, en position sur le mandrin-support
• - la figure 2 représente une vue de dessus de la cuve d'électrolyse assurant pendant la deuxième étape le dépot de nickel sur le squelette obtenu à l'issue de la première étape
• - la figure 3 est une vue de détail fortement agrandie, en coupe selon la ligne AA de la figure 5, de la maille d'un cadre perforé obtenu avec un deuxième bain électrochimique traditionnel, pendant la deuxième étape, c'est à dire avec un bain comprenant des composés répertoriés dans la littérature traditionnelle comme brillanteurs primaires et secondaires
• - la figure 4 est une vue de détail similaire à la figure 3, de la maille obtenue avec un deuxième bain électrochimique selon l'invention
• - la figure 5 est une vue de dessus, du côté intérieur au cylindre perforé, à échelle agrandie, de la maille obtenue à partir d'un même squelet­te, avec un deuxième bain électrochimique traditionnel (représentation en traits pointillés), et avec un deuxième bain électrochimique selon l'inven­tion (représentation en traits pleins)

The present invention is now described with reference to the accompanying drawings, in which:

• - Figure 1 shows in cross section the nickel skeleton obtained at the end of the first electrolysis step, in position on the support mandrel
• - Figure 2 shows a top view of the electrolysis tank ensuring during the second step the deposit of nickel on the skeleton obtained at the end of the first step
• - Figure 3 is a greatly enlarged detail view, in section along line AA of Figure 5, of the mesh of a perforated frame obtained with a second traditional electrochemical bath, during the second step, that is to say with a bath comprising compounds listed in traditional literature as primary and secondary brighteners
• - Figure 4 is a detail view similar to Figure 3, of the mesh obtained with a second electrochemical bath according to the invention
• - Figure 5 is a top view, on the inside of the perforated cylinder, on an enlarged scale, of the mesh obtained from the same skeleton, with a second traditional electrochemical bath (representation in dotted lines), and with a second electrochemical bath according to the invention (representation in solid lines)

The electrochemical process according to the invention is generally in accordance with the process described in patent US-A-2,226,384, so that it does not appear useful to describe this process with precision.

According to the first step of the process, in accordance with FIG. 1, a matrix or mandrel-support 1 is used, comprising cells 2, the opening of which has been closed with a non-conductive material, such as a resin 3. In correspondence, the edge or edge 4 of the same cells remains electrically conductive. At the end of the first step of the method, and with a first traditional electrolysis bath, a nickel skeleton 5 is obtained, comprising perforations 7 corresponding substantially to the openings of the original alvoles 2. This approximate correspondence is obtained by an appropriate limitation of the duration of the first electrochemical step. At the end of the latter, the skeleton 5 is detached from the support mandrel 1.

According to the second step of the process, and in accordance with FIG. 2, the skeleton 5 is immersed in a second bath 8 for nickel electrolysis, added with a pyridinium compound according to the invention. The bath is preferably made to circulate in the direction of the arrows B, that is to say parallel to the anode 6, and therefore to a generator of the skeleton 5 in the form of a cylinder in the present case. The speed of circulation of the bath is between 5 and 10 cm / second; in correspondence, the arrows A indicate the direction of the current lines from the anode 6 to the cathode 5. These lines are perpendicular to the cathode skeleton, as well as to the direction of movement of the electrolysis bath. The circulation mode of the second electrochemical bath selected according to the invention provides various advantages. On the one hand, the ion exchange between the anode (s) (6) and the cathode constituted by the nickel skeleton (5) can increase significantly, increasing the intensity of the current. On the other hand, all the impurities liable to detach from the anodes or from the skeleton-cathode are entrained outside the latter.

During the second step, the nickel is gradually deposited around the cords 4a of the skeleton 5, passing inside the perforations 7, and circulating along the internal and external walls of the skeleton 5.

Thanks to the action of the pyridinium compound according to the invention, introduced into the second electrolysis bath, the perforated frame obtained has a very characteristic mesh profile, represented in FIG. 4 as regards a cross section of the nickel beads. according to the line AA of FIG. 5, and in FIG. 5, in solid line, as regards the flat shape of the mesh, on the inside of the perforated cylindrical frame.

In accordance with FIG. 4, there is surprisingly a rounding of the nickel deposit, not only outside the cylinder, but also inside, unlike the burst observed on the inside, according to FIG. 3 , for a deposit with a bath added with a traditional primary and secondary gloss. According to the invention, therefore, nickel beads are obtained having both their upper part and their lower part of the bulges 12 and 13, directed in the direction of the height, these bulges being connected together by rounded parts 11 and 14.

With reference to FIG. 5, and assuming that the support matrix 1 comprises cells having a flat hexagonal shape, in order to obtain a perforated frame with a hexagonal mesh, it can be seen that the perforations obtained according to the invention actually have this flat shape generally hexagonal in shape, but with a rounded profile at all points, sort of inscribing the hexagonal profile. This is shown by the solid line 15, delimiting each perforation of the frame, relative to the dotted line 16, corresponding to the flat shape finally obtained with a second electrochemical bath added in the traditional way with a primary and secondary glosser. , all the other electrochemical parameters remaining equal elsewhere. In FIG. 5, the broken line 17 shows the flat shape of the skeleton openings resulting from the first electrolysis step, before electrochemical treatment according to the second step of the process.

In total, by comparison of Figures 3 and 4 on the one hand, and dashed lines 16 and solid lines 15 according to FIG. 5, it can be seen that for a substantially equal height of nickel h according to the invention and according to the prior art, the addition of the pyridinium compound makes it possible to obtain an opening (x) of perforation substantially greater than the perforation opening (y) obtained according to the prior art, that is to say with an electrolysis bath completed in the traditional way. For the same perforation size of the final frame, expressed for example in mesh, the result of this for the benefit of the invention is a non-negligible advantage as regards the value of the passage section of each unitary mesh.

Two examples of the application of the second electrochemical bath according to the invention are described below.

The first example of a nickel bath used is of the nickel salt type and contains:
- 300 g per liter of nickel sulfate
- 50 g per liter of nickel chloride
- 50 g per liter of boric acid
- 100 g of 1- (3-sulfopropyl) -pyridinium, for 10,000 A / h
- 250 g of sodium naphthalene-trisulfonate, for 10,000 A / h

Electrolysis of the second bath is carried out in a conventional manner, the bath circulating, moreover, parallel to the anode and to the cathode cylinder.

A second example of a bath in accordance with the invention comprises:
- 250 g per liter of nickel sulfate
- 40 g per liter of nickel chloride
- 45 g per liter of boric acid
- 150 g per liter of 1- (2-hydroxy-3-sulfopropyl) -pyridinium, for 10,000 A / h
- 100 g of sodium saccharinate for 10,000 A / h
- 40 cc of wetting agent for 10,000 A / h

A microscopic examination of the perforated frames obtained with these two baths reveals that the deposit of nickel made on the basic skeleton has the original appearance described above, from a support mandrel comprising cells of hexagonal flat shape. .

The process according to the invention is very suitable for depositing nickel from a nickel anode containing sulfur (nickel S). However, it seems preferable to use sulfur-free nickel to limit internal tensions.

As already said, the method according to the invention also applies good at making flat perforated frames than cylindrical frames.

Claims (9)

1) Method of manufacturing by electroforming a perforated nickel frame, according to which one operates in at least two steps:
a) according to a first step, and in a first electrolysis bath, a first nickel deposit is made on an engraved support mandrel, comprising cells whose opening is closed by a non-conductive material, and whose border or edge is conductive, and a nickel skeleton is separated from the mandrel, the perforations of which correspond substantially to the cells of said mandrel
b) according to a second step, and in a second electrolysis bath, a second deposit of nickel is carried out on the skeleton, characterized in that at least the second bath is added with a pyridinium compound of formula:

in which :
- R is a saturated alkyl chain comprising at least one carbon atom, optionally substituted,
- R ′ is a hydrogen atom or a sustituant group, in any position relative to the nitrogen atom of the pyridinium nucleus 2) Method according to claim 1, characterized in that R is an alkyl chain substituted by at least one group having no double or triple bond with a carbon atom 3) Process according to claim 1, characterized in that R ′ is a substituent group comprising no double or triple bond with a carbon atom. 4) Process according to claim 1, characterized in that the pyridinium compound is sulfopropylated and R is an alkyl chain comprising three carbon atoms 5) Method according to claim 2, characterized in that the alkyl chain is substituted, in position 2 relative to the pyridinium nucleus, by a hydroxy group 6) Process according to claim 3, characterized in that the pyridinium ring is substituted by at least one group chosen from the following groups, namely methyl and benzyl 7) Method according to claim 1, characterized in that the composition se pyridinium is used in the second bath, at a rate of 60 to 250 g for 10,000 A / h 8) Method according to claim 1, characterized in that the second bath is circulated parallel to the anode, with a speed between 5 and 20 cm / second 9) Method according to claim 1, characterized in that the pyridinium compound is used in the second bath with a tension reducing compound

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