DE1496156B1 - Etching bath for printing plates - Google Patents

Description

The invention relates to aqueous etching bath mixtures suitable for etching printing plates.

Using aqueous etching bath compositions containing a mineral acid, a film-forming Media and a water-immiscible organic liquid can be used for printing plates Their surfaces can be etched by hand using a powderless etching process. Such an etching bath contains, for example Nitric acid, optionally with the addition of small amounts of sulfuric acid, hydrochloric acid or Acetic acid; a water-immiscible organic solvent that dilutes in the presence of Acids is stable, and as a film-forming agent a halogenated diaryloxydsulfonate with a hydrophobic Group that usually contains up to 30 carbon atoms. The remainder is essentially water, e.g. B. may contain various by-products obtained from the bath components.

Substances can also be added to improve the effect of these bath compositions, that regulate film formation. Such substances are, for example, simple organic dicarboxylic acids, preferably Adipic acid, or a mixture of such substances, each consisting of only hydrogen and carbon and oxygen and usually have 4 to 10 carbon atoms with up to 3 carbons Have carbon double bonds. It can be aromatic compounds as well as act aliphatic carbon chains. The additives can be aromatic, cycloaliphatic or have aliphatic character or, like alkylaromatic substances, represent a combination thereof. By using them in the etching baths, in narrow penetration areas such as halftone areas which a clean and sufficient etching depth, without at the same time the protective effect in the open Surfaces of the line sections of the plate to be etched

is reduced, cannot be achieved by changing the bath composition, the etching depths are increased will. In addition, the substances regulating film formation can have a beneficial, stabilizing effect Effect on the protective film in the open areas

exercise areas of the plates by etching the image flanks and the formation of crumbling and reduce rough image edges.

_ The bath mixes described result in

Etching of flat plates gives satisfactory results.

However, if they are used to etch curved plates, especially those whose curvature diameter exceeds about 12.7 cm, a Severe unevenness of the image edges can occur and the peeling of the corners of the image can result in parts of the image get lost. In addition, they are often excessively wide and elongated in the direction of the curvature Image edges on. (This formation of etched flanks is called "tailing"). The image edges can thereby

The bath compositions and the other conditions of the experiments are given in the following table.

Bath composition

plate
No.

Components

lot

Volume percentage

g / l

temperature
⁰ C

Stirring speed rpm

Comparative experiments

according to example 13 of the USA patent specification 3,023,138 *)

42 ° Be ENT ₃

Solvent, 84 ° / _Q aromatics, flash point 6O ⁰ C, initial boiling point 171 ⁰ C (KB 100)

Diisodecyl phthalate (KB 68)

Dodecylbenzene (KB 44.4)

Sodium chloro-dodecyl-diphenyloxydsulfonate

water

*) The bath is with that of Example 13 of the USA patent identical except for the amount of film former. Baths with a lower film former content resulted in a virtually complete disappearance of the image on curved panels.

according to Austrian patent specification 204

42 ° Be ENT ₃

Diethylbenzene (KB 96)

Calcium dodecylbenzenesulfonate

water

12th

0.5

0.25

0.33

rest

168

2.5

2.5

21 to 22

260

11.6

7.0

0.263
rest

162.7
60.7
2.63

21 to 22

260

often very narrow, e.g. B. be formed substantially vertically, and it can in unfavorable cases a Undercutting the image area done. In addition, the curved etched plates are generally unclean, d. that is, they have pimple-like protrusions in the non-image areas. This requires too their removal and to maintain a clear plate a further process step. These undesirable effects, occurring alone or side by side of the etching bath lead to poor quality of the reproduced image or, if they are very significant the disk may be unusable.

These difficulties that occur with the etching baths described are overcome according to the invention, in that the water-immiscible, organic liquids through a three-component system organic liquid can be replaced. This system includes three groups of organic Liquids, each group in its Kauri-Butanol values in a certain range lies.

The etching bath according to the invention is characterized in that the organic, water-immiscible Liquid as the first component an organic liquid with a Kauri-Butanol value between 25 and 75, as the second component an organic liquid with a Kauri-Butanol value between 75 and 100 and as a third component an organic liquid with a Kauri-Butanol value over 100 and that it contains adipic acid.

The etching bath according to the invention leads to excellent etching results and is known herein, Baths with a similar composition, as found in German Auslegeschrift 1 031 808, German Auslegeschrift 1 003 350, Austrian patent specification 204 570 and USA.-Patentsehrift 3 023138 known are, as the comparative tests described below show, superior.

To carry out the experiments, an etching device with a device for curved Plates used for all experiments. The agitation speed and temperature were in some Changed something to get the best possible results. A magnesium printing plate was made photomechanically provided with a polyvinyl etch reserve. Identical specimens were placed on 225 · 280 · 1.6mm cut and placed on a three roll bender

ao bent to a diameter of about 200 mm. The surface of each test plate was rubbed off cleaned and then with a weak solution of nitric acid in water before etching brushed off. The image on the test plate was produced in line grid style (65-line autotype grid). The machine was thoroughly cleaned after each bath to remove any contamination from the previous one Avoid bath.

Bathroom composition

plate

Components

lot

Volume percentage

g / l

temperature
° C

Rute

speed rpm

according to German interpretation 1103 350

42 ° Be ENT ₃

Kerosene (KB 30.5)

Sodium 7-ethyl-2-methylundecane-4-sulfate

Mixture of mainly 13,16-dimethyl-14-octacosyn-13,16-diol and 15,18-dimethyl-16-dotriacontyn-15 _i 1.8-diol (added as a 50 weight percent solution in ethylene glycol)

Monoethanolamine dodecylbenzenesulfonate (88% active) (diluted 1: 1 with water to 44 ° / ₀ active, Sp. G. 1,045)

water

according to German interpretation document 1 031

42 ⁰ Be ENT ₃

Diethylbenzene (KB 96)

Sodium dioctyl sulfosuccinate

water

corresponding to plate no. 4 plus

Gelatin (added as a 0.1% aqueous solution) 11.2
3.9
0.21

0.24

0.168
rest

10.4
8th

0.30
rest

154.7

32.4

2.1

2.4
1.68

145
69.4
30.0

21 to 22

260

32 to 33

260

l, 45-10- * weight | 32 to 33
percent

250

Bathroom composition

plate
No.

Components

lot

Volume percentage

gfl

Temperature ⁰ C

Stirring speed rpm

according to the invention
42 ° Be ENT ₃

Mixture of about 90% alkylbenzenes, 2% naphthalene, 8% naphthenes (KB 83)

Dodecylbenzene (KB 44.4)

Aromatic naphthas, boiling point 200 to 260 ^° C.
(KB 108)

Adipic acid

Sodium chlorododecyldiphenyloxydsulfonate

9.0

1.0 1.0

0.5 0.2 0.3

139

8.9 8.7

9.5 2.0 3.0

21 to 22

370

The following table shows the results of the comparative tests.

Etching results

plate
No. Etching depth
on the
open
area
μ Etching depth on
the bright one
Grid point
areas of the
65 line
Autotype
rasters
μ Etching depth in
Inside the
"O" (8th Go
table
Letter)
V- cleanliness
the etching Image retention Remarks 1 · 814 101.6 101.6 satisfactory consistent gritty on the picture side wall;
elongated shoulders near
the upper end of the Kan
the semitones 2 _; 558 63.5 101.6 Well satisfactory strong undercut
the pixels; flat toe
nings 3 508 63.5 101.6 Well satisfactory to good moderate undercuts
the pixels; stronger
Loss on 70% of the daughters
area 4th 558 63.5 101.6 Well consistent no gelatin; flat between
the guy; flat semitones 5 508 76.2 165 Well bad Gelatin added; many half
etched away tone points 6th
Apply
services
for one
typical
quality
Plate.. 686
500+ 139.8
125+ 203
180+ Well
Well ■ consistent
consistent no undercuts
the pixels; very good
Etching quality

The kauri-butanol value is determined by a known kauri resin solution in butanol until it has to be added

th standard test for determining the solution a certain degree of turbidity is compared

like an organic liquid than the amount of benzene pure with the amount in such a titration

organic liquid is determined which leads to a standardization, the standard value of which is set at 100.

As indicated, the solvent has a small amount of the total amount of loamy used KB value (Kauri-butanol value), a KB value medium high KB value can be used. Her between about 25 and about 75. The main task in the present etching bath is also the clean bath temperatures essentially stable in the presence of etching. There are supposed to be pimples be dilute mineral acid, a certain amount of solvent etched plates can be avoided without becoming like for the applied film-forming agent on- shows tailing in the halftone dots. The exhibiting and essentially with water not represented by tailing in the light sections can also be considered be mixable. The stability in the presence of the "bleeding" can be referred to as it is in particular the thin mineral acid should be etched for a reasonable time. last, since a decomposition of the organic liquid affects io. In amounts from about 0.25 to about 1.5 volumes Effect of the water-immiscible bath percentage, preferably about 0.4 to about 0.6 volume component adversely affected. Likewise, the percentage of solvents with a high KB value is it is essential that this additive normally give good results at bath temperatures. Particularly ratures is liquid. Suitable organic substances that turned out to be an amount of 0.5 percent by volume as alone or in a mixture with other solvents 15 is suitable. High KB solvents are used can be used are aromatics, aliphatics, for example hexyl acetate, dibutyl phthalate and tri-naphthenes, Ethers and esters with a KB value chloroethylene are suitable. Preferably also a between 25 and 75. Such solvents from the low-boiling group of high-boiling aromatic naphtharems KB values are e.g. B. Dodecylbenzenes (an alkyl solvent used that has a boiling range of benzene, the average of the alkyl chains so 200 to 260 ° C, a KB value of about 108 and a Contains 12 carbon atoms), mineral seal oils (raffinates with a content of 99% of high-boiling aromatics in one Settlement between light and gas oil; Z e r b e, wise.

"Mineralöle", 1952, p. 298, no. 103), other alkyl For the preparation of the etching bath according to the invention

benzenes and naphthenes with about 8 to 10 alkyl are not the three components of having water carbon atoms. In general, 25 water-miscible organic solvents can be destroyed with the Miscible esters, ketones, terpenes, ethers, dilute acids, a film-forming agent and Aliphatics, naphthenes and aromatic carbo-adipic acid as a film-forming regulating agent hydrocarbons mixes with a KB value between 25 and 75 and essentially uses water as the remainder will. given. The etching liquid is sprayed on,

Quantities of about 0.5 to 2, preferably about 30 syringes or dipping into the bubbling agitated 0.75 to 1.25 percent by volume of solvents with an etching bath in contact with the surface to be etched low KB are effective. In particular, are brought. The etching continues until the Amounts of about 1.0% are desirable. desired etch depth was obtained, e.g. B. a depth

The medium KB solvent is used in from 0.635 to 1.016 mm in the wide, open nipples Image of the novel bath composition 35 of the present invention.

among other things, therefore added to the etching at The average bath temperature is between

to keep the image edges under control and by 4 to 50 ° C. You can advantageously 15 to 32 ° C and am in particular the narrowing and undercutting should be between 18 and 29 ° C.

of the image flanks in the transverse direction to the curve The metals that are etched according to the invention

to prevent the plate from degenerating. In contrast to 4 °, magnesium and magnesium are preferred other organic solvents in the etching bath which are essentially homogeneous. the if this organic liquid has a medium magnesium parent alloy, it contains 70% of the parent KB value between 75 and 100. Such suitable component. An organic acid forms selectively in the etching bath Liquids are e.g. B. a mixture of resistant film on the plate to be etched. This made of about 90% alkylbenzenes, 2% naphthalene and 45 protects the relief image flanks from lateral etching and 8% naphthenes, diethylbenzenes and other aromas prevent tailing. Curved high tables can be used and alkyl aromatic hydrocarbons with printing forms of previously unknown quality a KB value between 75 and 100. The effective can be obtained.

The amount of such an organic liquid is a preferred bath composition according to FIG

between about 0.8 to about 2.8 percent by volume of the bath 50 invention, particularly for use in a mixed. Preferably about 1.0 to about etching device is suitable for curved plates, 1.8 percent by volume used, the above-mentioned containing about 88 to about 107 g / l nitric acid, 1.0 to Mixture of about 90% alkylbenzenes, 2% naphtha- about 1.8 percent by volume of the mixture of about 90% lin and 8% naphthenes as preferred organic alkylbenzenes, 2% naphthalene and 8% naphthenes Solvent is used. 55 as a medium KB solvent, about 3.0 to

The solvents of high KB and low 3.6 g / L of a film-forming agent based on the riger viscosity are due to their immiscibility with volume percent of the bath and from a mixture Water and its relatively high KB value of over 100 is mainly characterized by the sodium salts of mono- and dige, preferably between about 100 sulfonated monochlorododecyl- mostly C-12-diphenylbis is about 130, but can also be above 130, such as 60 oxide, in which the monosulfonated oxide z. B. in the hexyl acetate, which predominates a KB value of about, about 1.2 to 1.8 g / l of adipic acid than the 203 has. In addition, these solvents are essentially film formation controlling agents, from about 0.75 to about borrowed non-reactive with the mineral acid compound 1.25 percent by volume dodecylbenzene as a solvent Component that is used in diluted form in the bath of a low KB value, as well as about 0.4 to 0.6 volume. You should therefore not use terminal functional 65 percent of an aromatic naphthalene solvent len groups have and rather carbon and with a boiling range of 200 to 260 ° C and one Hydrogen atoms in it predominate. This KB value of about 108 as a solvent of high Solvents can be used alone or in a mixture with KB value.

The following examples serve to further illustrate the invention.

Example I.

To etch curved printing plates in an etching machine, 771 powderless etching baths were used. For this purpose, 9.93 g nitric acid, 0.335 g / l diphenyloxide mixture, as described above, 1.34 volume percent of a mixture of about 90% alkylbenzenes, 2% naphthalene and 8% ία naphthenes, 1 volume percent dodecylbenzene, 0.5 vol * were added per liter. added lumprozent an aromatic Naphthalösungsmittels having a boiling range of 200 to 260 ⁰ C and a KB value of about 108, and 1.5 g / l adipic acid and the residual water was added. The bath temperature was set to 26 ° C. A longitudinally curved plate 28 cm in diameter, 45.5 cm in length and 1.63 mm in thickness made of an etchable magnesium-based alloy, which was coated as an image layer with an etch-resistant coating of a polyvinyl alcohol and bare metal at the non-image areas to be etched was attached to the retaining mandrel in the etching machine. The speed of rotation was 40 revolutions per minute, the etching liquid splashed onto the rotating plate to be etched, and the direction of rotation was changed every 20 seconds. It was etched to an etch depth of approximately 0.76 mm for 10 minutes. The etching depth in the light grid dot areas (grid width: 26 lines / cm) was about 0.127 mm.

When the etched area was examined, no tailing was found and no "bleeding" was evident. As was clearly shown, the edges of the image were very even. They had a caustic angle of everywhere 45 ° to the horizontal. The plate was immediately suitable for printing.

Example Π

For comparison purposes, a curved plate with a diameter of 200 mm was etched in a powderless etching bath in the same machine. The conditions were the same only was extended 21 to 22 ⁰ C and the etching time, the bath temperature, mm to the same etch depth of 0.76 to achieve as in Example I, into the open space. This standard bath contained 94 g / l HNO ₃ , 3.3 g / l diphenyloxide as a film-forming agent, 1.5 g / l adipic acid and 4.5% by volume of a mixture of about 90% alkylbenzenes, 2% naphthalene and 8% naphthenes. The examination of the etched plate showed strong tailing and "bleeding" of the image flanks in the direction of curvature. The transversal image flanks, ie those at an angle of 90 ° to the direction of curvature, were extremely steep, essentially vertical and in some cases undercutting of the image surface was noticeable.

In order to be able to objectively assess the strength of the tailing on the image shoulders, the etching angles of the image edges determined. For this purpose, the distance from the top edge of the image edge to the Measured point where the image flank meets the relief surface. The value thus obtained was through dividing the total etching depth of the plate. The quotient obtained is the tangent of the etching angle. The etching angle can then be taken from trigonometric tables. This operation was transversal The direction of the etching flanks is repeated and the etching angle determined in this way differs from that previously measured Etching angle subtracted. The angular difference obtained in this way gives a quality measure for the general Image flank profile. The angular difference of 59 ° obtained in this way indicated that in the direction of curvature of the Plates the edges of the picture were greatly elongated. There were also various pimples on the non-image areas available.

The foregoing etching was repeated with the same size bent plate, in the same apparatus and the same etching conditions, only a bath temperature of about 26 ⁰ C was used. The angular difference obtained was 34 °, which showed that the image flanks were more uniform and thus a plate of significantly better quality had been achieved. The plate was much cleaner and free of pimples in the non-image areas and could be printed on immediately.

Claims (8)

Patent claims: 1. Etching bath for printing plates, containing water, a mineral acid, a film-forming agent and an organic, water-immiscible liquid, characterized by geke η η, that the organic, water-immiscible liquid as the first component is an organic one Liquid with a Kauri-Butanol value between 25 and 75, as the second component an organic one Liquid with a Kauri-Butanol value between 75 and 100 and a third component contains organic liquid with a kauri-butanol value above 100 and that it contains adipic acid. 2. Bath according to claim 1, characterized in that the Kauri-butanol value of the third Component is between 100 and 130. 3. Bath according to claim 1 or 2, characterized in that the first component is an alkylbenzene is. 4. Bath according to claim 3, characterized marked. net that the first component is dodecylbenzene. 51 bath according to one of claims 1 to 4, characterized characterized in that the second component is a mixture of about 90% alkylbenzene, about 2% Is naphthalene and about 8% naphthene. 6. Bath according to one of claims 1 to 5, characterized in that the third component is an aromatic naphthalene solvent with a boiling point between 200 and 260 ⁰ C and a Kauri-butanol value of about 108. 7. Bath according to one of claims 1 to 6, characterized in that the etching bath at first Component 0.2 to 2 percent by volume, on the second component 0.8 to 2.8 percent by volume and on the third component contains 0.25 to 1.5 percent by volume, based on the total bath volume. 8. Bath according to one of claims 1 to 7, characterized in that the etching bath is used as an acid 88 to 107 g / l nitric acid, as a film-forming agent 3.0 to 3.6 g / l of a mixture of the sodium salts of mono- and disulfonated monochlorododecyldiphenyloxide and as the film formation regulating agent contains 1.2 to 1.8 g / l adipic acid.