DE2332799A1 - Light-sensitive copying material for making stencils - for screen printing sensitised with diazonium salt condensate - Google Patents

Abstract

The material consists of a flexible (temporary) substrate and a light-sensitive film, contg. a hydrophilic macromol. binder and a sensitiser (I), opt. covered with a flexible sheet, which can be peeled off easily, (I) being a high-mol. condensate of an aromatic diazonium salt (esp. of a diphenylamine-4-diazonium salt and HCHO). The material gives accurate copies, can be developed with water alone and can be kept for long periods in the pre-sensitised form.

Description

K 2233 FP-Dr.N.-ur June 25, 1973

description
to register the

KALLE AKTIENGESELLSCHAFT
Wiesbaden-Biebrich

for a patent

Photosensitive copying material
and process for the production of screen printing stencils

The invention relates to a light-sensitive copying material for the production of screen printing stencils, which consists of a flexible temporary support sheet, a light-sensitive layer which contains a hydrophilic macromolecular binder and a sensitizer, and optionally a flexible, lightweight
peelable cover sheet on the free surface of the

light-sensitive layer. It also concerns

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a process for the production of screen printing stencils by transferring a photosensitive layer of a copy material of the type mentioned on a screen printing stencil carrier (see terms for screen printing, DIN 16610).

A distinction is made between two basic processes for the production of screen printing stencils, direct and the indirect. With the direct method, the fabric or the screen printing stencil carrier is immediately more sensitive to light Emulsion coated and dried. Then it is exposed and developed under an original. at the indirect method is on an intermediate carrier, e.g. B. a glass plate or a film, a photosensitive Layer produced, exposed and developed, and the still moist hardened relief image transferred to the fabric and dried there. Both methods have advantages and disadvantages. B. in the German patent 1 123 204 are described.

Attempts have also been made to use the advantages of both methods by combined methods, in which in the Usually a pre-made, non-sensitized film

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while moistening with the sensitizing agent transferred to the fabric and then the dried layer exposed (USA patents 3,532,052 and 2,131,225 as well as DOS 1 597 760).

In the German patent application P 20 58 178 has also been proposed with a light-sensitive Layer of pre-coated film to be used. In this case, the in itself not sufficiently light-curable Layer moistened with a solution of a crosslinking agent and then applied to the fabric, after which in Usually the stencil is made.

Finally, the German Offenlegungsschrift 1 9 ^ 7 351 describes a similar method in which a an intermediate support thermoplastic photopolymerizable layer under pressure and heating is transferred to the tissue when dry.

All of these methods still have certain disadvantages

afflicted. So there is where the sensitization or the tannable only together with the transfer of the Layer takes place, a precisely controlled and dosed diffusion of the sensitizer is always required, to get accurate and reproducible results.

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In the last-mentioned process, in which the photopolymerizable Layer already contains all of the components required for light curing, is the case with screen printing very desirable developability cannot be achieved with pure water. In general, the the nature described therein requires development with organic solvents, the obvious disadvantages compared to the purely aqueous development. Photopolymerizable layers also give due to their sensitivity compared to atmospheric oxygen in this application, certain problems, since the atmospheric oxygen during the exposure through the mesh of the screen has access to the layer and affects its hardening at these points.

The object of the invention was therefore to propose a material and a method for producing screen printing stencils, which avoid the noted disadvantages of the prior art and in particular an accurate reproduction the template while maintaining reciprocity, an environmentally friendly purely aqueous development and a long Allow storage of the presensitized material.

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The invention is based on a light-sensitive copying material for the production of screen printing stencils, consisting of a flexible support sheet, a photosensitive layer that is a hydrophilic Contains macromolecular binder and a sensitizer, and optionally a flexible easily peelable Cover sheet on the free surface of the photosensitive layer.

The material according to the invention is characterized in that the photosensitive layer acts as a sensitizer Contains higher molecular weight condensation product of an aromatic diazonium salt.

The condensation product preferably consists of recurring units of the general types A-NpX and B, linked by double-bonded intermediate links derived from a condensable carbonyl compound are, where the units A-NpX are formed from compounds of the general formula (FL -R * -) Rp-NpX and whereby

X is the anion of the diazonium compound, ρ is an integer from 1 to 3 _S

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a carbocyclic or heterocyclic aromatic radical with at least one condensable Position, an arylene group of the benzene or naphthalene series, a single bond or one of the groups:

- (CH ₂ ) _q -NR ₄ -

-O- (CH ₂ ) _r -NR ₄ -

-S- (CH ₂ ) _r -NR ₄ -

-0-R ₆ -O-

-S-

-CO-NRjl- or

-SO ₂ -NR ₄ -,

wherein

q is a number from 0 to 5, r is a number from 2 to 5,

R _{4 is} hydrogen, an alkyl group with 1-5 carbon atoms, an aralkyl group with 7-12 carbon atoms or an aryl group with 6-12 carbon atoms,

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R ^ hydrogen or an alkyl group with

■ 1-5 carbon atoms and Rg is an arylene group with 6-12 carbon atoms,

B the radical of an aromatic which is free of diazonium groups Amine, phenol, thiophenol, phenol ether, aromatic thioether, aromatic hydrocarbon, one aromatic heterocyclic compound or an organic acid amide.

X is preferably the anion of an aliphatic monosulfonic acid with 1-6 carbon atoms.

The mixed condensation products from AN ₃ X and B are known. Their production and use in photosensitive materials is described in German Offenlegungsschriften 2,024,244 and 2,024,242. The use of the preferred alkyl sulfonic acid salts in screen printing materials is described in German Offenlegungsschrift 2,041,395. Reference is made here in particular to the information in this application.

In addition to the mixed condensation products mentioned, in the case of lower demands on the screen printing materials also the condensation products from diazonium salts, especially

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special diphenylamine-4-diazonium salts, and formaldehyde , are used, the z. B. in German Auslegeschrift 1 289 741 in connection with screen printing materials are described.

According to the invention a method for producing a screen printing stencil is also proposed in which one prefabricated photosensitive layer, which is located on a temporary support, in the unexposed state transfers to the stencil carrier and which is characterized in that the on the temporary carrier located photosensitive layer, which a hydrophilic macromolecular binder and a higher molecular Contains condensation product of an aromatic diazonium salt with water or an aqueous one Solution of a crosslinking agent for the hydrophilic binder moistened, pressed together with the stencil carrier and allowed to dry, the dried layer is imagewise exposed and developed, and the temporary support peeled off before developing.

Aldehydes, in particular, are particularly suitable as crosslinking agents

Formaldehyde and N-methylol acid amides, preferably N ₉ N ¹ -dimethylol urea, are suitable. These crosslinking agents

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are in combination with screen printing films, the light-sensitive monomeric diazonium salts, z. B. Diphenylamine-4-diazonium salts contained, described in the German Offenlegungsschrift 2,058,178. With the one described there Processes, these crosslinking agents are necessary for layer hardening; H. at the points of the layer in If no crosslinking agent has diffused in during the transfer, there is insufficient light curing. In the present process, on the other hand, the photosensitive layer is already fully light-curable itself, so that the use of crosslinking medium solutions in the transfer of the layer is merely an advantageous one Represents measure.

An aqueous solution of the layer components can also be used for moistening d. H. So use the same screen printing varnish as used to make the screen printing film became. The meshes of the fabric are also filled in. This method is generally not preferred because it does usually does not result in any further improvement. However, it can be used in cases where an even better anchoring of the layer required or desired, be an advantage.

The method according to the invention is very simple. The factory-made prefabricated one with a constant layer thickness storable, photosensitive screen printing film is treated with water, aqueous crosslinking agent or screen printing lacquer solution moisturizes. This softens the photosensitive layer so that it can be used during transfer penetrates into the mesh on the fabric and is firmly anchored there. After drying, exposure and development the layer adheres much more firmly than a corresponding non-presensitized layer that is obtained with aqueous bichromate solution moistened and then transferred. One special

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Good adhesion is achieved with layers which have been produced from copying compounds in accordance with DOS 2,041,395 are. For these layers, transfer with pure water is preferred because the use of the said crosslinking agent practically no longer gives any improvement. Against this is the use of Crosslinking agents in connection with screen printing layers according to DAS 1 289 7 ^ 1 are advantageous because they are a causes a significant improvement in the adhesion to the stencil carrier. In general, 0.5 - 10 #igen is used here Networking solutions worked. However, the shelf life of the dried, crosslinking agent is limited containing materials limited to a few days.

The method according to the invention can be carried out as follows. Either a) the on a The light-sensitive layer applied to the carrier film is briefly drawn through water or an aqueous solution, moistened and slightly swollen and then transferred to the stencil fabric and lightly pressed or b) the film is laid out flat and the tissue freshly moistened by wiping or squeegeeing in the stretched frame pressed onto it or c) as a combined method, dry the film and the stencil

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carrier pressed together and then from the stencil side, z. B. wiped over with a sponge or squeegee. the the latter variant is preferred, since the moistening can be better dosed and z. B. by something more intense Swelling relatively thick layers of screen printing penetrate deeper into the mesh of coarse fabrics.

The exposure is preferably carried out after the temporary support has been peeled off. If this is transparent and is sufficiently thin, can also be exposed through it. Then in a known manner with aqueous Solutions, preferably with pure water, developed.

The photosensitive layers of the copying materials according to the invention have a thickness of about 10-20, u, thicknesses of 15-35 / rev are preferred. Your composition can be different depending on the intended use. The screen printing layers are preferred for printing with Solvent-based screen printing inks. Such screen printing materials contain in a known manner in addition to non-water-soluble resins a relatively larger amount of water-soluble or water-swellable resins or Colloids, preferably polyvinyl alcohol. Next to the

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The screen printing layers can contain diazonium salt polycondensate, wetting agents, anti-foaming agents and, above all, dyes contain. Preference is given to pigment dyes that are used in Do not bleed when printing with solvent inks. When applying or using certain soluble Dyes, e.g. B. triphenylmethane dyes, one has the advantage that the exposed before development Places can already be seen.

Plastic foils can be used as temporary supports, PVC and polyolefin foils are the cheapest. especially polypropylene films. Those for coating, drying, packaging and processing as a whole The best and preferred supports are polyester films. For technical and dust reasons, the use of a Cover film for the free surface of the photosensitive layer be advantageous; this is what polyethylene foils are for Most appropriate. The material according to the invention is used in rolls of up to 1.20 m wide and above. Another advantage of this material is that it can be used to produce stencils of any (smaller) size and type of fabric can be and that the squeegee application of screen printing varnish can be omitted. The following examples are provided for

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further explanation of the invention. Unless otherwise stated, percentages are percentages by weight; Parts by weight and parts by volume are related to each other from g to ecm.

example 1

An approx. 30 % ± ge polyvinyl alcohol solution obtained by stirring polyvinyl alcohol with a K value of 50 and a residual acetyl group content of approx. 12 % (Mowiol N 50-88) in water at approx. 85 ° C in an open for 8 hours Kettle had been prepared, with 1 % polyglycol P 1200 (Dow Corning Corp.) was added as an antifoam agent, was mixed in a weight ratio of 3: 1 with the 55 # dispersion of a vinyl acetate-maleate copolymer (Mowilith DM 1). 10 g of the water-soluble diazo compound described in Example 2 of DOS 2 04l were stirred into 1000 g of the mixture. A 50 .mu.m thick polyester film 30 .mu.m thick was coated with this screen printing lacquer (dry thickness).

A piece of this screen printing film was attached to the layer

placed on top of a flat plate and a screen printing frame covered with fabric with the print side

laid on it. Now wiped over twice

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of the fabric with a damp sponge Foil and the fabric brought into moist contact so that all air bubbles disappeared from the mesh and the film penetrated somewhat into the fabric. By drying overnight or Blowing air with a hair dryer, the film was dried onto the fabric.

The carrier film was then peeled off with a gentle pull, the smooth side of the layer under a positive one The template is exposed and the stencil is developed with cold water by spraying, the layer being applied to the unexposed areas was removed with a sharp edge. After drying, the stencil could be used with the commercially available, Solvent-containing screen printing inks are used for printing on paper and plastics.

The screen printing film and stencils coated with it have at least unchanged light sensitivity Can be stored for 1/2 year at room temperature.

Example 2

To 1000 g of a screen printing emulsion, which is composed of 3 parts by weight of a 53 # vinyl acetate copolymer Dispersion (Mowilith DM 2 HB from Farbwerke Hoechst) and 2 parts by weight of one produced by dissolving and concentrating

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A 24% solution of polyvinyl alcohol with a K value of 75 and a residual acetyl group content of about 12 % (Mowiol N 75-88) consisted of a solution of 15 g of the diazo compound described in Example 1 of DOS 2 04l 395 in 120 ml of water and 5 g of Imperon blue KB (Farbwerke Hoechst) were added. A 25 u thick polypropylene film with a thickness of 35 u was coated with this screen printing varnish.

A piece of this screen printing film was briefly pulled through water in a tub and spread out while moistened and press the stencil holder onto it with a damp cloth. After drying it was marked with a positive Original exposed, developed with a sharp jet of water and dried. The screen printing stencil is excellent suitable for printing textiles with the usual aqueous textile printing inks.

A screen printing stencil was produced parallel to this, but in which the same screen printing film was transferred in this way was that the same screen printing varnish was applied to the inside that was used to produce this Screen printing film had been used. Despite that

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reached almost complete mesh filling behaved the stencil produced in this way in the comparative rub test on a Buser film printing machine is no better than the stencil made with water transfer of the screen printing film. After a printing performance that has already been 8000 running Meters of printed fabric, the experiment was terminated.

Example 3

A solution was added to 1000 g of a screen printing emulsion made from 100 parts by weight of an approximately 30% strength aqueous solution of polyvinyl alcohol with a K value of 70 and a residual acetyl group content of about 12 % (Mowiol N 70-88), 5 parts by volume of dibutyl phthalate and 10 parts by weight of finely divided silica of 15 g of an oily crude condensate, which had been prepared by condensation of diphenylamine-4-diazonium sulfate with formaldehyde in phosphoric acid according to DT-PS 1 214 086, in 50 ml of water. This screen printing varnish was colored blue with 2 g of crystal violet. A 20 u thick screen printing layer produced from this on 25 u thick polyester film as a carrier and with 40 u thick polyethylene as a cover film was processed as follows for the production of screen printing stencils for printing on PVC plastics. With the carrier film facing down, the laminate was placed on a flat glass plate of the appropriate size, the polyethylene

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Deek foil peeled off and the screen printing frame with the stretched fabric placed on it. A stencil was prepared by moistening with water, a second with an aqueous 0.55% solution of Dimethylolurea moistened, and at the third the fabric was coated with 8% N-methylol-chloroacetamide solution when the screen printing film was pressed on, until the film was tight.

After exposure, development and drying, the three identical-looking stencils were thinned into one Solution of sodium hypochlorite, which is used in higher concentrations for stripping. at In this test, the stencil from the transfer with dimethylolurea showed the best adhesion; with N-methylolchloroacetamide was only slightly stronger than that layer transferred with water.

Example 4

In 1000 g of a screen printing emulsion, which consisted of equal parts by weight of a 25 # solution of the polyvinyl alcohol used in Example 2 and a 55 % ± gen dispersion of the polyvinyl acetate used in Example 2, a solution of 18 g of that in Example 4

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the DOS 2 O4l 395 described diazo compound in Stir in 150 ml of water and 4 g of Imperon blue K-B. This screen printing varnish was used to create a 60 u thick PVC polie coated and carefully dried, a layer thickness of 40 µ being obtained.

This screen printing film was used to create a fine screen printing steel mesh coated by pressing it onto the screen printing film and moistening it for so long until the film swelled evenly and adhered to the tissue without bubbles. After exposure, drying and developing, this screen printing stencil could be used for printing with ceramic pastes.

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Claims (7)

Patent claims 1.) Photosensitive copying material for the production of screen printing stencils, consisting of a flexible carrier sheet, a photosensitive layer which contains a hydrophilic macromolecular binder and a sensitizer, and optionally a flexible, easily removable cover sheet on the free surface of the photosensitive layer, characterized in that the photosensitive layer contains a higher molecular weight condensation product of an aromatic diazonium salt as a sensitizer. 2. copying material according to claim 1, characterized in that the condensation product consists of recurring units of the general types A-NpX and B, which are connected by divalent intermediate members derived from a condensable carbonyl compound, the units A-NpX consisting of compounds of the general formula (R ₁ -R ^ -) pR2 ~ N2X and where X is the anion of the diazonium compound, ρ is an integer from 1 to 3> 4Q9883 / U686 a carbocyclic or heterocyclic aromatic radical with at least one condensable Position, an arylene group of the benzene or naphthalene series, a single bond or one of the groups: - (CH ₂ ) _q - ₄ - (CH ₂ ) _q -NR ₄ - (CH ₂ ) _r -NR ₅ - -0- (CH ₂ ) _r -NR ₄ - -OR _fi -O- - S -CO-NRi, - or -SO ₂ - where q is a number from 0 to 5, r is a number from 2 to 5, R _{14 is} hydrogen, an alkyl group with 1-5 carbon atoms, an aralkyl group with 7 carbon atoms or an aryl group with 6-12 carbon atoms, 409883/0686 FL · hydrogen or an alkyl group with 5 1-5 carbon atoms and Rg is an arylene group with 6-12 carbon atoms, B the radical of an aromatic amine, phenol, thiophenol, phenol ether, aromatic, free of diazonium groups Thioether, aromatic hydrocarbon, aromatic heterocyclic compound or one mean organic acid amide. 3. copying material according to claim 2, characterized in that it contains a condensation product, wherein X is the anion of an aliphatic monosulfonic acid with 1-6 carbon atoms. 4. copying material according to claim 1, characterized characterized in that the sensitizer is a condensation product of a diphenylamine-4-diazonium salt and is formaldehyde. 5. copying material according to claim 1, characterized in that the carrier sheet is a plastic film 409883/0686 6. Process for the production of a screen printing stencil, in which a prefabricated light-sensitive Layer, which is located on a temporary carrier, in the unexposed state on the Stencil carrier transfers, characterized in that one is located on the temporary carrier photosensitive and photohardenable layer containing a hydrophilic macromolecular binder and contains a higher molecular weight condensation product of an aromatic diazonium salt with water or an aqueous solution of a crosslinking agent for the hydrophilic binder moistened with the Stencil carrier is pressed together and allowed to dry, the dried layer is exposed imagewise and developed and peeled off the temporary carrier prior to developing. 7. The method according to claim 6, characterized in that the crosslinking agent is formaldehyde or an N-methylol acid amide is used. 409883/0686