US3607484A

US3607484A - Etching of aluminum

Info

Publication number: US3607484A
Application number: US783717A
Authority: US
Inventors: Gohein Marukawa; Takashi Oikawa; Ryotatsu Otsuka; Naomi Kagaya
Original assignee: Showa Denko KK
Current assignee: Resonac Holdings Corp
Priority date: 1967-12-13
Filing date: 1968-12-13
Publication date: 1971-09-21
Anticipated expiration: 1988-09-21
Also published as: JPS4811459B1

Abstract

An etchant liquid for metals (which consist mainly of aluminum) comprising an aqueous sulfuric acid solution containing halogen ions and the ions of a metal having an ionization tendency less than that of aluminum. An etching bath containing the above liquid also comprising a water-immiscible organic liquid, and a surface active agent prepared by the phosphoric esterification of a polyalkylene glycol having alkylene oxide linked with the hydrocarbon residual group thereof. A process for forming a photographic image of an acid-resistant coating applied to the surface of a metallic plate (which consists mainly of aluminum) which comprises etching the plate using the described etchant liquid or etching bath.

Description

United States Patent Gohein Marukawa Takashi Oikawa, Tokyo; Ryotatsu Otsuka, Tokyo; Naomi Kagaya, Kawasaki-shi, all of [72] Inventors 32 Priority Dec. 13, 1967, Sept. 7, 1968, Sept. 27, 1968,

Nov. 6, 1968 [33] Japan [31] 42/79542, 43/64051, 43/69420, and 43/80626 [54] ETCHING OF ALUMINUM 8 Claims, No Drawings [52] US. Cl 156/22, 156/14, 252/794 [51] Int. Cl C23i 1/00, B44c l/22,C23g H22 [50] Field of Search l56/22, 23,

[ 56] References Cited OTHER REFERENCES Chemical Abstracts" Vol. 67, 1967 Article 24659f on Chemical Polishing of Aluminum.

Primary Examiner-Jacob H. Steinberg Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak ABSTRACT: An etchant liquid for metals (which consist mainly of aluminum) comprising an aqueous sulfuric acid solution containing halogen ions and] the ions of a metal having an ionization tendency less than that of aluminum.

An etching bath containing the above liquid also comprising a water-immiscible organic liquid, and a surface active agent prepared by the phosphoric esterification of a polyalkylene glycol having alkylene oxide linked with the hydrocarbon residual group thereof.

A prdcess for forming a photographic image of an acidresistant coating applied to the surface of a metallic plate (which consists mainly of aluminum) which comprises etching the plate using the described etchant liquid or etching bath.

ETCIIING F ALUMINUM BACKGROUND OF THE INVENTION I. Field of the Invention The present invention relates to the etching of metallic plates consisting primarily of aluminum.

2. Description of the Prior Art There have hitherto been developed various etching methods for processing magnesium, zinc, copper, or alloys thereof, but there has never been proposed a practical corroding or etching method for metallic plates mainly consisting of aluminum which is inexpensive in comparison to processes for etching plates made of magnesium, zinc or alloys thereof. This is surprising since aluminum is light in weight when compared with a zinc plate or copper plate of the same thickness. Thus, the handling of an aluminum plate is easier.

In addition, the etching of metallic plates mainly consisting of aluminum in accordance with this invention is rapid, about -20 percent faster, in comparison to processes for etching plates made of magnesium, zinc or alloys thereof.

As materials for rapidly etchant metals mainly consisting of aluminum, there are the acids, such as hydrochloric acid, hydrofluoric acid, phosphoric acid and the like; and alkalis, such as sodium hydroxide. However, the surface of metals mainly consisting of aluminum which have been etched by such materials are very rough. Thus, such materials are unsuitable for use as an etching bath. An etching bath is required to have the following properties: it must etch the metal rapidly; the resist must not be damaged at the etching site; the relief which is formed must not be side-etched; and the cor roded or etched surface must be smooth. Moreover, it is desirable, if possible, that the concentration of the etchant liquid be low and that the etchant liquid not generate harmful gases during etching. The present invention amply meets all of the requirements of the art.

The present invention provides a photoengraving process, a method of manufacturing name plates and metallic patterns or the like, by using as the printing plate a metal mainly consisting of aluminum.

SUMMARY OF THE INVENTION An etchant liquid for metals which consist mainly of aluminum is provided comprising an aqueous sulfuric acid solution containing halogen ions and the ions of a metal having an ionization tendency less than that of aluminum.

An etching bath for metals which consist mainly of aluminum is provided basically comprising the above liquid and also containing a water-immiscible organic liquid, and a surface active agent prepared by the phosphoric-esterification of a polyalkylene glycol having alkylene oxide linked with the hydrocarbon residual group thereof.

A process for corroding or etching a photographic image of an acid resistant coating which has been applied to the surface of a metallic plate which consists mainly of aluminum is also provided comprising etching utilizing either the above described etchant liquid or etching bath.

As an optional embodiment, nitrate ion (N0 may be present in the etching bath or the corroding liquid.

An object of the present invention is to provide a etchant liquid for rapidly and uniformly etching a photographic image of an acid resistant coating on the surface of a metal which mainly consists of aluminum.

Still another object of the present invention is to provide metals which mainly consist of aluminum and which can suitably be used in the etching process of this invention.

A still further object of this invention is to provide articles of a metal mainly consisting of aluminum prepared by the etching process of this invention.

These and further additional objects of this invention can be attained by the present invention, which will be explained in further detail by the material which follows:

DESCRIPTION OF THE PREFERRED EMBODIMENTS The most preferred metal used in the present invention is a metal consisting essentially of Al, i.e., A1 metal per se, consisting of more than 97 percent by weight Al and unavoidable impurities, or an Al-base alloy containing Zn or Zn and Sn.

When these metals are etched with a etchant liquid, the metals have a smooth and beautiful surface. In addition, the metals have the properties set out in the following paragraphs.

The smoothness of the surface of the Al-base metal or alloy consisting of more than 97 percent by weight Al when etched by a etchant liquid of the present invention, shows increased smoothness. In addition, the etching speed of the etchant liquid of the present invention is increased as the purity of the metal (proportion of Al) is increased. Accordingly, AI base metal having a purity of greater than 99 percent by weight is preferable in the present invention. On the other hand, if the purity of the Al used becomes less than 97 percent by weight, problems occur, such as that the Al-plate will crack during working, which makes the etched surface unacceptable.

An Al-base alloy having incorporated therein from about 0.5 to about 10 percent by weight Zn, or an Al-base alloy having incorporated therein from about 0 .5 to about 10 percent by weight Zn and from about 0.04 to about 2 percent by weight Sn will be more rapidly etched than the aforesaid Albase metal or alloy. In addition, the etched surface of the alloy will be smooth and uniform, and the fabricability of the alloy into shaped articles, such as plates, will not be harmed by etching.

To further define the aluminum purity which is required in the metals and alloys processed in the present invention, when an aluminum alloy is utilized, the amount of aluminum contained therein should be more than percent. However, in the case of an aluminum metal" (not an alloy), the amount of aluminum contained therein should be greater than 97 percent. The amount of materials which remain are, essentially, unavoidable impurities.

One embodiment of this invention is an etchant liquid for consisting essentially of aluminum and comprising an aqueous sulfuric acid solution containing the ions of at least one halogen and the ions of at least one metal having an ionization tendency which is less than that of aluminum. In another embodiment of this invention, the etchant liquid is an aqueous sulfuric acid solution containing the ions of at least one halogen and N0 together with the ions of at least one metal having an ionization tendency less than that of aluminum. Unless otherwise indicated in this description, parts means parts by weight."

The ions of any metal having an ionization tendency less than that of aluminum (hereinafter often referred to as an LI. metal, which is to represent low ionization"), may be incorporated in the aforesaid etchant liquid of this invention but Cu, Fe, Ni, Co, Sn and Zn are preferred, with Cu, Fe, and Ni being most preferred.

To incorporate the ions of the metal with a reduced ionization tendency in an aqueous sulfuric acid solution, there is added thereto a compound of the metal which is capable of being dissolved, in the aqueous solution to dissociate the metallic ions therein, such as a halogen compound, such as chloride, a nitrate, a sulfate, a phosphate, a hydroxide, or an oxide of the metal. In addition, the Li. metallic ions may be formed in an aqueous sulfuric acid solution by dissolving the metal directly in the aqueous solution, instead of adding the aforesaid metallic compound.

The halogen ions, namely, Cl, F, Br and I, may all be incorporated into the aforesaid etchant liquid of this invention, but C1 and F are preferred.

To provide the halogen ions in the aqueous sulfuric acid solution, the Li. metal may be added to the aqueous sulfuric acid solution as a salt of halogen, preferably the chloride or fluoride salt; or a hydrogen halide, preferably hydrochloric acid or hydrofluoric acid may be added to the system separately from the addition of the aforesaid L.l. metallic ions.

To provide the No in the aqueous sulfuric acid solution, the aforesaid L.l. metal may be added to the aqueous sulfuric acid solution as a nitrate of the metal, or nitric acid may be added to the system.

The concentration of the sulfuric acid in the etchant liquid of this invention generally is about 3 to about 20 percent by weight, preferably about to about percent by weight. If the sulfuric acid concentration is lower than about 3 percent by weight, the etching power of the liquid is weak, while if the concentration thereof is greater than about percent by weight, the etching action is too violent, and the relief which is made by etching a photographic image of an acid-resistant coating on the surface of the metallic plate will be side-etched during the etching operation.

The concentration of the L.[. metallic ions in the etchant liquid is usually about 0.004 to about 2.0 gram-ions/liter, preferably about 0.01 to about 1.0 gram-ions/liter. If the concentration of the LL metallic ions is lower than about 0.004 gram-ions/liter, there is no acceleration of the etching rate by the ions of the L1. metal, while if the concentration thereof is greater than about 2.0 gram-ions/liter, the relief will be violently side-etched.

The concentration of the halogen ions is usually about 0.1 to about 7.0 gram-ions/liter, preferably about 0.15 to about 5.0 gram-ions/liter. If the concentration of the halogen ions is lower than about 0.1 gram-ions/liter, the rate of etching will not be increased too greatly, and will not become violent, while if the halogen concentration is greater than about 7.0 gram-ions/liter, the surface of the etched areas become very rough.

The concentration of the NO is usually lower than about 2 gram-ions/liter but preferably less than about 1 gramions/liter. 1f the concentration of the ion is higher than about 2 gram-ions/liter, the etched surface of a metal mainly consisting of aluminum will become passive, which reduces the etching speed.

When a metal mainly consisting of aluminum (hereinafter referred to by the abbreviated phrase Al metal") is etched in an aqueous solution about 3-20 percent by weight sulfuric acid solution at room temperature, the etching rate is very low. ln contrast to this, when the Al metal is etched in the etchant liquid of this invention, that is, an aqueous sulfuric acid solution of about 3-20 percent by weight, containing halogen ions and the ions of a metal having an ionization tendency less than that of aluminum at room temperature, the etching speed is greatly increased, without any roughening of the etched surface of the metal. Moreover, when NO is further added to the etchant liquid containing the aforesaid halogen ions and the L.l." metal ions, the etching rate is even further increased.

The following nonlimiting theory is offered to explain the unexpected results obtained upon the practice of the present invention.

It is believed that when the surface of a metallic plate mainly consisting of aluminum is treated with the etchant liquid of this invention, the ions of the metal having an ionization tendency less than that of aluminum which are etching in the liquid are replaced with aluminum to cause the reaction:

A] A1 +3 e whereby the replaced metal is deposited on the etched surface of the metal. A similar viewpoint is that the etching reaction occurs when the metal ion is reduced as, for example, in the following formula:

Fe +e Fe Thus, in any reaction, the metal ions in the etchant liquid promote the etching of the metal mainly consisting of aluminum. Also, when the halogen ion or the halogen ions and the NO 'are added to an aqueous sulfuric acid solution containing the, ions of the metal having an ionization tendency less than that of aluminum, the etching rate of the metal mainly consisting of aluminum is further increased by the interaction between 13*, S0,, the metal ions, the halogen ions and the NO 'ions. This interaction is a specific one that does not occur in the case where a metal mainly consisting of aluminum is treated only with an aqueous sulfuric acid solution or an aqueous sulfuric acid solution containing only the ions of the aforesaid L.l." metal. 1

In the following table, the results of etching tests are shown wherein various etchant liquids consisting of aqueous sulfuric acid solutions containing various ions are utilized to treat metals mainly consisting of aluminum.

1n the test, ml. of the etchant liquid is charged in a 200 ml. beaker, and while maintaining the temperature of the beaker at 24 C. i 1 C., various test pieces (20X40Xl mm.') are immersed in the etchant liquid for 15 minutes, the etched depth of the metal then being measured.

In the following table, percent means percent by weight. For instance, in experiment No. 11, the iron recited therein will be dissolved in a mixed solution of sulfuric acid and hydrochloric acid to form FeCl and Fe,(SO,) in the liquid. It is believed that the moieties formed in the ionized solutions under consideration will be self-apparent to one skilled in the art.

TABLE I Tabulation of Etching Data on Metals Mainly Consisting of Al No, Composition of Depth of etchant Composition of Corrosion liquid (by weight) Metal (by weight) (mm.)

1. H 80, 10% Zn 1%, slight 0 'impulily level Bal. water balance AI 2, H 50, 10%, "CI 1.0% Zn 1%, slight O impurity level Hal. Water balance Al 3.11, so, 10%,HF1.0% Zn 1%, slight 0 impurity level Bal. water balance A1 4.11,,so,10%,c11so,

1.0% Zn 1%, slight 0 impurity level lial. water balance A1 5111,80, 10%,CuCl

1.0% Zn 1%, slight 0.12

impurity level Bal. water balance Al 011,50, 10%,cuc1,

l.0% Zn 1%, slight 0.30

impurity level HCl 3.0%, bal. water balance A1 7. 11,so, 10%, 0150,

1.0% Zn 1%, slight 0.33

impurity level HF 3.0%, Hal. water balance Al s.11,so,10%,cuc1,

1.0%, Zn 1%, slight 0.67

impurity level HCl 3.0%, HNO 1.0% balance Al Bal. water 911,50, 10%, 011040,

1.3% Zn 1%, slight 0.55

impurity level NaF 3.0%, Bal. water balance A1 10.H,S0, 10%, FeCl 2.0% Zn 1%, slight 0.31

impurity level HCl 5.0%, Bal. water balance Al 11.11,so,11.2%,11c1

6.4% Zn 1%, slight 0.25

impurity level Fe powder 08%, Bal. water balance Al 12. H,SO,10%, NiCl,

0.5% Zn 1%, slight 0.48

impurity level (30040, 1.0%,13111. water balance Al 13.11,so,10%,1-11c1,

0.5% Zn 1%, slight 0.48

impurity level 011010, 0.9%, net 0.6% balance Al Bal. water 14.14 50, l0%, NiCl,

1.0% Zn 1%, slight 0.37

Table l Continued impurity level CuSO, HCl 0.6%, balance Al Bal. water 15. 11,80, 10%, Cu(N0 1.0% Zn 1%, slight 0.42

impurity level HCl 3.0%, Bel. water balance Al 16. 11,80, 10%, CoCl 1.0% Zn 1%, slight 0.52

impurity level CuCl, 0.5%, HCl 2.0%, balance A1 Bal, water 17. n,so, 10%, 21101,

2.0% Zn 1%, slight 0.30

im urity levcl CuCl, 0.5%, HCl 2.0%, balance A1 Bal, water lll. H,so, 10%, sncl,

2.0%, Zn 1%,slight 0.25

impurity level NiCl 1.0%, CI 2.0%, balance Al Bal. water 19. H,SO 10%, NiCl,

045%, A1. 99.2% of 0.20 Cu(NO 0.9%, "CI 0.6% rest impurity 2011,80, 10%,N1C1,

0.5%, Zn 2%, rest 0.55 Cu(NO 03%, HCl 0.6% impurity and Al 21. H,S0 10%, MC],

0.5%, Zn 1%, Sn 0.2%, 0.80 Cu(NO,), 0.9%, HCl 0.6% rest impurity and Al 22. H,SO 10%, HBr 3.5% Zn 1%, unavoidable 0.l4

Cu(NO,,) 1.0%, Bal. water impurity, bal Al 23. H,S0, 11%, Hl3.5% 0.11

Cu(N0 1.0%, bal. water According to another embodiment of the present invention, there is provided an etching bath for a metal mainly consisting of aluminum which comprises an aqueous sulfuric acid solution containing the ions of at least one metal having an ionization tendency less than that of aluminum, the ions of at least one halogen, a water-immiscible organic liquid, and a surface active agent prepared by the phosphoric-esterification of a condensed alkylene oxide-type nonionic surface active agent.

Further, according to still another embodiment of the present invention, there is proposed an etching bath for a metal mainly consisting of aluminum which comprises an aqueous sulfuric acid solution containing the ions of at least one metal having an ionization tendency less than that of aluminum, the ions of at least one halogen, N0 a water-immiscible organic liquid, and a surface active agent prepared by the phosphoric-esterification of a condensed alkylene oxidetype nonionic surface active agent.

In the above two embodiments, the types, the amounts added to the etching bath, the metal mainly consisting of aluminum, sulfuric acid, the ions of at least one metal having an ionization tendency less than that of aluminum, and the ions of at least one halogen" have the same meanings as explained in the aforesaid portion of the application relating to the etchant liquid of the present invention.

The water-immiscible organic liquid employed in the present invention may be illustrated by compounds such as aromatic, aliphatic, and naphthenic hydrocarbons having a boiling point higher than 80 C., such as ligroin, kerosene, gas oils, hydrocarbon type lubricating oils, aromatic solvents (for example, Solvesso No. 100 and No. 150, trade name of the Esso Standard Oil Co.), terpene, liquid paraffin, etc.; chlorinated hydrocarbons such as liquid chlorinated paraffin, chlorodiphenyl, etc.; unsaturated higher aliphatic acids; natural fats and the like. In other words, all the solvents conventionally used for etching magnesium, zinc and alloys thereof in making printing plates can be used in the present invention. As representative of the commercially available aromatic liquids which can also be utilized, there are Penola H.A.N. (trade nan1e) and hellSol 71 (trade name of The Shell International Petroleum Co., Ltd.). When the metal plate mainly consisting of aluminum is treated with the etching bath having the desired composition containing the aforesaid organic liquid, a large amount of heat is generated, and thus a liquid having a low boiling point tends to be evaporated during the operation. This will change the composition of the etching bath. However, when one of the preferred organic liquids of this invention, having a boiling point higher than C., is employed, the life of the etching bath is prolonged. Also, it is a necessary condition that the organic liquid be in a liquid state at the etching temperature and that the organic liquid be chemically stable. The organic liquids described above can be used alone or as mixtures thereof. The amount of the organic liquid which is added is usually about l-l0 percent by volume, preferably about 2-5 percent based on the volume of the etching bath.

From the above description, it is clear that any water-immiscible organic solvents can be employed in this invention ifthey will form a film on the surface of an aluminum base metal or an aluminum base alloy to thereby provide acid resistance to the surface.

For use in the invention, the organic solvents must satisfy a few conditions. First, they must be liquid in the etching process, and they must not be dissolved in the etching bath, this being implied by the expression water-immiscible. It should be noted that the term water-immiscible is not, strictly speaking, entirely correct, since some organic solvents which are utilized can be immiscible with water but may be dissolved in an aqueous solution of the sulfuric acid as utilized in the present invention. However, the basic requirements are that the organic solvents retain their liquid state, do not lead to decomposition, have an acid protective power" and maintain the acid protective power" during processing. In general, it is to be understood that water-immiscible solvents satisfy the aforesaid requirements.

The reason for adding the water-immiscible organic liquid to the etching bath will be described below, together with an explanation of the action of the surface active agent during etching.

First, the surface active agent to be incorporated into the etching path and the etchant liquid of this invention will be explained in greater detail.

The surface active agent employed in this invention is one prepared by the phosphoric-esteriflcation of an alkylene oxide condensed type nonionic surface active agent, which may be in the form of a free acid, a neutralized salt, or an additive, such as a salt of Na, K, Li or the like, or an amine salt. The surface active agent of the present invention may be used in combination with other surface active agents.

As the alkylene oxide employed in the surface active agent used in this invention, there is preferably employed a lower alkylene oxide, such as ethylene oxide or propylene oxide. The alkylene oxide may be used as a form ofa single condensate or a mixed condensate.

Typical examples of the aforesaid surface active agent are shown by the following general formulas:

(ill) (CHKEHO) and (CH CH O) may occupy any desired posltlon.

position.

Some types of surface active agents represented by the aforesaid general formulas cannot be prepared as a pure form of compound but are usually obtained as a mixture, and this mixture may be effectively added to the etchant liquid as a mixture, with comparable results to the case of adding the surface active agent in pure fon'n. in addition, the number of ethylene oxide or propylene oxide units (the number shown by a, b,---, l in the above formula) added during the preparation of the surface active agents depends on the kind and concentration of the water-immiscible organic liquid, and the type of oleophilic group in the phosphoric acid ester. In general, it is preferable that the groups be added so as to provide a suitable HLB value to emulsify the organic solvent, e.g., a HLB value of 8-18.

To further amplify upon the above paragraph, when producing an ethylene oxide addition product or a propylene oxide addition product, the average addition number to the groups is shown by the general formula R O (the aliphatic alcohol group). This number may be known, but the composition of the polyoxyethylene alkyl ethers obtained show a distribution with respect to the number of ethylene oxide groups present when they are esterified with phosphoric acid. Accordingly, it is very difficult to obtain the pure monoester, diester, or triester. In the present invention, mixtures of these esterscan be effectively employed, and, as indicated, a highly purified form thereof is not always required.

Further, as recited, the number of the ethylene oxide or propylene oxide units (a, b, c, l) are selected so that the resultant phosphoric ester has the required HLB value. The ethylene oxide-HLB relationship is fairly significant, but the propylene oxide-HLB relationship is somewhat lessened. The number of units utilized can be easily selected according to the type and the amount (concentration) of the water-immiscible organic liquid utilized, the general theories involved being well known in the field of surface active agents.

Further, note that the number of oleophilic groups is one in general formula (1), two in general formula (2) and three in general formula (3). This illustrates that mixtures of the above may be utilized, since HLB illustrates an additive effect. Of course, it is always necessary to consider the emulsifying action of the organic liquid involved.

The carbon number of R in the formula must be greater than 4, preferably from -20, and the number of propylene oxide and ethylene oxide groups is usually 1-40, preferably 3-20. The hydrophilic property of the surface active agent will be increased as the number of these groups increases. The phosphoric acid ester is stable in the etchant liquid of this invention and has the property of absorbing on the surface of the aforesaid metals having a high hydrophilic property more in preferentially than the corrosive components in the etching bath.

The amount of the aforesaid surface active agent which is added is about 0.05-about 8 percent by weight, preferably about 0.1-about 1 percent by weight, based on the total weight of the etching bath. If the amount of the surface active agent is less than about'0.05 percent by weight, the anticorrosion film becomes weak, which causes side etching (undercutting) of the relief. if the amount of the surface active agent is larger than about 8 percent by weight the anticorrosion film becomes too strong to allow the etching to proceed effectively, and hence the relief does not obtain a vertical configuration but develops an inclined etching pattern, which is generally unacceptable.

it is believed that the actions of the water-immiscible organic liquid and the surface active agent in the etching bath of this invention are as follows:

The surface active agent will emulsify the aforesaid waterimmiscible organic liquid in the etching bath by stirring the bath, and when the etching bath containing the surface active agent splashes or flows along the surface of the plate of a metal mainly consisting of aluminum, the emulsion will be destroyed and the hydrophilic group of the surface active agent will be absorbed on the surface of the aforesaid metal plate while the oleophilic group thereof will be combined with the organic liquid, thereby forming a corrosion-resistant film oforganic liquid on the surface of the aforesaid metal. In other words, when the etching bath of this invention is splashed onto the surface of the metallic plate having the photographic image of an acid-resistant coating which is subjected to an acid-resistant coating treatment, the etching proceeds, leaving the acid-resistant coating portions intact. Further, the etched portions will always be covered by the aforesaid anticorrosion film. The film is broken" by the mechanical action, such as the splashing action of etching bath which is further splashed onto the plate, thereby causing etching by means of the etching components therein. However, since the action of the etching components which reach the relief by breaking" the anticorrosion film of the relief, will be weak in comparison to the action thereof on the portions excluding the relief, which is covered by the anticorrosion film, side etching of the relief will be prevented, thereby achieving etching in accordance with the present invention.

To further amplify on the above, the emulsion of the etching liquid is destroyed on the surface of the metal to form an anticorrosion film of the surface active agent and the organic liquid. This film is fairly weak, and hence when the etching bath splashes upon the film, the film will be removed and fresh etching component will reach the metal surface to etch the metal. in this case, since the impact force of the etching bath which is splashed up to the film on the relief side is weaker than the impact force thereof splashed onto a flat surface of the plate, the proportion of the film removed at the side of the relief will be lessened, and hence the relief area will be etched to a lesser extent than other portions of the plate. See Example 1.

in addition, according to the third and fourth embodiments of the present invention, there is provided a process wherein the surface of a metal mainly consisting of aluminum having thereon a photographic image (which has been subjected to an acid resistant coating treatment) is etched with either the aforesaid etchant liquid or the etching bath of the present invention. That is, the metal is etched by splashing thereon the etchant liquid consisting of an aqueous sulfuric acid solution containing the ions of at least one halogen and the ions of at least one metal having an ionization tendency less than that of aluminum; the etchant liquid may also further contain No therein.

To conduct the etching process of this invention more effectively, the etchant liquid is charged into the tank of an etching machine and the etchant liquid is splashed upon a flat or cylindrical plate of the metal mainly consisting of aluminum having thereon, for instance, a halftone photographic image which has been subjected to an acid resistant coating treatment, or a light sensitive coating on the surface of the metal can be exposed to light through a negative having an image therein, developed to form an image and (usually) further hardened so that the unexposed areas of the composite image will be etched while the acid resistant coating produces the image areas of the metal plate. The process can comprise rotating the splash paddle of the etching machine flow etchant over the plate. The apparatus described is well known to those skilled in the art.

In still another embodiment of the process of this invention there is provided an etching process wherein the etching of the metallic plate made of metal mainly consisting of aluminum is conducted by using the etching bath of this invention. ln this embodiment of the process of this invention, the surface of a metallic plate made of metal mainly consisting of aluminum having thereon a photographic image which has been subjected to an acid resistant coating treatment is etched by the etching bath consisting of an aqueous sulfuric acid solution containing the ions of at least one halogen, the ions of at least one metal having an ionization tendency less than that of aluminum, a watebimmiscible organic liquid and a surface active agent prepared by the phosphoric-esterification of a condensed type nonionic surface active agent of alkylene oxide, or (another embodiment) the etching bath may further contain N To perform the etching process of this invention more effec tively, the etching bath composition of this invention is emulsified by stirring it in a tank of an etching machine. Thereafter, the emulsified etching bath is applied to the surface of a flat or cylindrical metallic plate made of metal mainly consisting of aluminum having thereon a line, a character, or halftone photographic image which has been subjected to an acid resistant coating treatment by rotating the splash paddle of the etching machine. This etching process can be conducted in almost the same manner as the well-known powderless" etching process.

The extent of the side etch" can be shown by the etch factor, which is the numerical value obtained by dividing the depth of etching by one-half of the reduced width of the acid resistant coating. Etching is better as this value is larger. In this specification, the etch factor is employed as a means for determining the extent of etching.

The practical application of the present invention will now be explained with reference to the following examples.

EXAMPLE 1 Into an etching tank equipped with a stirrer and a splashing paddle for splashing an etchant liquid onto the surface of a metallic plate having thereon a photographic image of an acidresistant coating, there was charged a mixture of the following components to provide an etchant liquid:

A flat plate of an alloy consisting of 1.1 percent by weight Zn, unavoidable impurities, balance A1, x20 sq. cm. in area, having thereon a halftone image of 6.5 line/sq. inch consisting of an acid-resistant coating, was mounted on an etching machine, the resist face of the plate facing the etching tank containing the etchant liquid prepared above. The etchant liquid was then splashed onto the surface of the metallic plate for about 2 minutes by rotating the splashing paddle while also rotating the metallic plate and moving it back and forth and from side-to-side in the tank. A temperature of 30-32 C. was used to provide an etched plate. The etched plate was then soaked in water, soaked in aqueous 3 percent by weight NaOH solution, washed with water and dried.

The depth of the deepest portions of the halftone was 0.22 mm., that of the shallowest portions thereof was 0.08 mm., and the etched plate could be used as a halftone engraving.

When the same procedure as above was repeated employing hydrofluoric acid H percent nickel fluoride 0.41 percent, almost identical results were obtained.

EXAMPLE 2 Into the tank of the etching machine employed in example 1, there was charged a mixture of the folllowing components to provide an etchant liquid:

Parts by weight Water Commercial sulfuric acid (98% by weight H 50, s.g., I84) Commercial hydrochloric acid (36% by weight HCl s.g. LIX) Aqueous FcCl solution [42% by weight FeCl s.g. L45) 7.8 liters (85.2%)

0530 litcr 13.2%)

0.210111mo4'se 0.480 li1er 1.2%

A flat plate of alloy consisting of l.4% Zn, 0.4% Sn, unavoidable impurities, balance Al having thereon the same halftone image as in example 1 was etched under the same conditions as in example 1 to provide the etched metallic plate.

The depth of the deepest portions of the halftone was 0.16 mm., that of the shallowest portions thereof was 0.08 mm., and the etched metallic plate could be used as a halftone engraving.

EXAMPLE 3 Into an etching tank equipped with a stirrer and a splashing paddle for splashing an etching bath onto the surface of a plate having thereon a photographic image which had been subjected to an acid-resistant coating treatment, there was charged a mixture of the following components to provide an etchant liquid:

To the etchant liquid prepared above were added the following components to provide an etching bath:

6. Solvesso lSO 7. Na-salt of the phosphoric acid ester of polyoxyethylenc lauryl ether (mainly monocstcr) 0.35 liter (4.0% by vol.)

Before starting etching, the etching bath thus prepared was stirred for several minutes. A flat plate (l0X20 sq. cm.) of an alloy consisting of 3.5 Zn, unavoidable impurities, balance A1, having thereon a photographic image which had been subjected to an acid resistant coating treatment was mounted in the etching machine, the resist face of the plate facing the bottom of the tank. The etching bath was then splashed onto the resist face of the plate for l5 minutes at 303 2 C. by rotating the etching paddle of the etching machine while rotating the metallic plate back and forth and form side-to-side. The side of the characters of the photographic image formed on the metallic plate was 7-8 point type, and they illustrated both a thick rule and a fine rule. The etched plate was washed with water and dried. The etch factor of the etched specimen was 40-60.

In addition, when the same procedure as above was repeated employing hydrofluoric acid 0.3 percent and nickel fluoride about 0.4 percent almost identical results were obtained.

EXAMPLE 4 Parts by weight Water Commercial sulfuric acid (98% by weight H,SO s.g., L84) Commercial hydrochloric acid (36% by weight of HCl s.g., L18) CuCl,.2H,0

8 liters (871%) 0.52s liter 10.0%

0.240 liter l 1%)- To the etchant liquid prepared above were added the following components to provide an etching bath:

5. Diethylbenzcne 6. Phosphoric acid ester of polyoxyethylene nonylphenyl ether (mixture of monoester and diester) 0.35 liter (4.0% by vol.)

A flat plate of an aluminum alloy consisting of l.l% Zn, unavoidable impurities, balance Al (lX20 sq. cm.) having thereon a photographic image of an acid-resistant coating was mounted on the etching machine with the resist facing the bottom. After emulsifying the etching bath, the etching bath was splashed onto the resist face for IS minutes at 3032 C., by rotating the splashing paddle of the etching machine. The etched plate was soaked in an aqueous 3 percent by weight NaOH solution, washed with water and dried. The average depth of the etch was 0.35 mm. andthe etch factor was about 30.

EXAMPLE 5 Parts by weight Water Commercial sulfuric acid (98% by weight ",SO,

. Commercial hydrochloric acid Commercial nitric acid (63% by weight HNO s.g., L38) 8 liters (86.7%)

0.528 liter (100%) 0.240 nmume 0.056 liter (0.5%)

To the etchant liquid prepared above, the following compositions were added to provide an etching bath:

6. Solvesso I50 0.353 liter (4.0% by vol.) 7. Phosphoric acid ester of polyoxyethylene nonylphenyl) ether (mixture of monoestcr and diester) 28.7 g. (030%) A flat plate of an aluminum alloy consisting of l.l% Zn, unavoidable impurities, balance Al (area 10x20 sq. cm.) having thereon a photographic image as, in example 4 was mounted on the etching machine with the resist face facing the bottom of the tank. After emulsifying the etching bath, the etching bath was splashed onto the resist face for l0 minutes at 3033 C. by rotating the splashing paddle to conduct etching. The etched plate was soaked in a caustic soda aqueous solution of 3 percent by weight NaOH washed with water and dried. The depth of the deepest portion of the etched portions was about 0. l 45 mm. and the etch factor was about 30.

EXAMPLE 6 Parts by weight 7.5 liters (847%) Water Commercial sulfuric acid (98% by weight l"l,SO s.g., L84 .Cnmmercial hydrochloric acid (36% by weight HCl sg, l.ltl) .Commcrcial nitric acid (63% by weight HNO s.gr, L38) Aqueous FcCl solution (45% by weight FcCL s.g., L45) 0.528 liter (9.8%)

0.480 liter (2.2%),

0.ll2 liter L011) 0.432 liter (2.l'b)

6. Penola H.A.N.

7. Phosphoric acid ester of polyoxyethylcnc nonylphcnyl ether (monoester and diester) 0.302 liter (3.4% by vol.

A flat metallic plate as in example 4 was mounted on'the etching machine, facing the resist face thereof to the bottom, and after emulsifying the etching bath prepared above, the etching bath was splashed onto the resist face of the plate for 10 minutes at 2933 C. The etched plate was soaked in an aqueous 3 percent by weight NaOH solution, washed with water and dried. The depth of the deepest portion of etch was about 40 mm. and the etch factor was about l5.

3. Commercial hydro- EXAM P LE 7 Continued Table- Continued chloric acid 0144 liter 0.7% (36% by weight HCl (36% by weight ac] 5. ms s.g., l.l8) 4. Commercial nitric acid 0.056 liter (0.5%) 4. ciici,.6it,o 140 g. 0.8% 5 03% by weight HNO, 5. CuCl, so 0.7% 5 ms s.cuc|,.2|i,o 232 2.0%

To the etchant liquid were added the following components to provide an etching bath; To the etchant liquid prepared above were added the following components to provide an etching bath:

6. Solvesso I50 302 g. (3.5% by vol.) 7. Phosphoric acid ester 6. Diisopropyl benzene 0.350 liter (4.0% by vol.)

of polyoxyethylcne 7. Phosphoric acid ester 7 nonylphenyl) ether of polyoxycthylene (mainly diester) 23.2 g. (0.25%) nonylphcnyl ether 28.4 (0.30%)

A flat plate of an aluminum alloy consisting of 2.0% Zn, A g 8 3. 2" g 9 a unavoidable impurities, balance Al, having thereon a photounfvm e 'f f a g i 8 graphic image of an acid-resistant coating as in example 4 was if? as i i s a t 'P etched for 10 minutes at 26-30 C. The metallic plate thus i t mg "2 etched was soaked in a diluted caustic soda aqueous solution E e F as 522 6 8 (4 percent by weight NaOH), washed with water and dried. t i f E i or ggz g g f The average depth of the etch was 0.40 mm. and the etch fac- SP g pd e at a rage o 6 etc 8 p ale tor was about 40 soaked in an aqueous 3 percent by welght NaOH solution,

washed with water and dried. The depth of the deepest etch EXAMPLE 8 portion was about 0.45 mm. and the etch factor was 30-45.

30 EXAMPLE 10 P' rt. b w-i ht d g y L g Into the tank of the etchmg machmc employed in example 3 there was charged a mixture of the following component to l. Water 8 liters (86.2%) i h .d 2. Commercial sulfuric p 6 etc ant q acid 0.630 liter 12.0%) (98% by weight H1804 5. L84) NiCl,.6H,0 180 g. |.0% 1. Water 1.5 liters ssssa 4. Cu(NO ),.3H O 90 g. (0.8%). 2. Commercial sulfuric acid 0.590 liter [0.0%]

(98% by Weight mm. $.g. 1.84) 3. Commercial hydrochloric To the etchant llquld thus prepared were added the followacid 0.495 liter 2.0% ing composition to provide an etching bath: Weigh s.g. l. 4. Commercial nitric acid (H25 liter l.0%)

(63% by weight HNO; 5 Sh -|1'r 1| -01 L e uh l I 5. Aqueous FeCl sulution 0.473 liter (2.7%)

(trade name of Shell c International Petrol- (42 b by Weigh FLC I sag. L45) cum Co.) 0.396 liter (4.6% by vol.) 6. Na-salt ol'the phosphoric ('U(NO)"'H*O (05%) acid ester of polynxy- 5 ethylene lauryl ether (mm'y (032%) To the etchant liquid prepared above were added the following components to provide an etching bath:

A flat plate of an aluminum alloy consisting of 1.0% Zn, 0.5% Sn, unavoidable impurities, balance Al, having thereon t a photographic image of an acid resistant coating as in exam- 18mm" by o o 8. Phosphorlc acid ester pie 4 was etched by the etching bath for 15 minutes at 25 -27 of pmymymhymc C. The metallic plate thus etched was soaked in an aqueous (3 nonylphenyl ether 43.0 g. 0.25% percent by weight) NaOH solution, washed with water and dried. The average depth of the etch was 0.55 mm. and the etch fa r w a u 4 A flat plate of an aluminum alloy consisting of 1.3% Zn and unavoidable impurities (having an area of 12X22 sq. cm.) hav' EXAMPLE 9 ing thereon a photographic image of an acid-resistant coating, lnto the tank of the etching machine employed in example 3 the Images of whlch were characiefs of 6 P l YP was there was charged a mixture of the following components to mounted the t g machlhe facing the f"? the provide an etcham liquid; bottom. After emulsifying the etching bath with stirring. the plate was etched for 10 minutes at 3335 by rotating the splashing paddle at a rate of 390 rpm. The etched plate was soaked in an aqueous 3 percent by weight NaOH solution, Pam by washed with water, and dried. The depth of the deepest etch portion was about 0.40 mm. and the etch factor was 35. 1. Water 8 liters (86.9%) 2. Commercial sulfuric EXAMPLE 1 1 acid 0.52s liter (98%] a 75 lnto the tank of the etching machine employed in example 3 s. 3 Commercial hydro there was charged a m xture of the following components to chloric acid 0.13s liter 0.3% provide an etchant liquid:

Parts by weight 0.680 liter (13.9%)

0.07 liter 0.3% 170 g. 1.0% 105 g. 0.9%

6. Solvesso 150 0.305 liter (3.4%

by volume) 7. Compound prepared by phosphoric esterilication of an equimolar mixture of polyoxycthylene nonylphenyl ether and lauryl alcohol A flat plate (12x20 sq. cm. in area) of an aluminum alloy consisting of 1.0% Zn, 0.1% Sn, unavoidable impurities, balance Al, having thereon a photographic image of a resist as in example 10, was mounted on the etching machine facing the resist face towards the etching tank. After emulsifying the etching bath by stirring, the plate was etched with the etching bath at 30-32 C. for 10 minutes by splashing it onto the surface of the plate by rotating the splashing paddle of the etching machine. The etched plate was soaked in an aqueous 3 percent by weight NaOH solution, washed with water and dried. The depth of the deepest etch was 0.60 mm. and the average etch factor was 30.

EXAMPLE l2 Parts by weight 1. Water 2. Commercial sulfuric acid (98% by weight l'l,SO s.g. 1.84)

3. Commercial hydrochloric acid (36% by weight HCI, 8.5.

7.8 liters (85.3%)

0.530 liter (10.0%)

Ollfllhcr (0.9%) 4. Aqueous FcCl, solution 0.480 liter (3.0%)

5. Cu(NO,),3H,0 100 g. 0.5%

0.275 liter (3.0% by volume) 6. Solvesso 100 7. Compound prepared by the phosphoric esteril'ication of a mixture of a synthetic alcohol having 12- carbon and polyoxyethylene alltyl ether of the alcohol added with ethylene oxide A flat plate (10X20 sq. cm. in area) consisting of 99.4 percent and unavoidable impurities, having thereon a photographic image of a resist consisting of 5 point style characters, was mounted on the etching machine facing the resist face towards the etching tank. After emulsifying the etching bath in the tank with stirring, the plate was etched by splashing the etching bath onto the resist face of the plate for 10 minutes. The etched plate was soaked in an aqueous 3 percent by weight NaOH solution, washed with water and dried. The depth of the deepest etch was 0.3 mm. and the average etch factor was 35.

EXAMPLE l3 Into the tank of the etching machine employed in example 3 there was charged a mixture of the following components:

Parts by weight acid (36% by weight HCl, s.g.

0.530 liter l0.0%

1.18) 0.067 liter 0.3% 4. NiCl,-6H,0 360 g. 2.0% 5.CuC1,2H,0 97 g. (0.8%)

To the etchant liquid thus prepared were added the following components to provide an etching bath:

0345 litcr (4.0% by volume) 28.5 g. 0.30%

6. Kerosene 7. Phosphoric acid ester of polyoxyethylenc alkyl ether prepared by adding 3 moles of propylene oxide and 5 moles of ethylene oxide to 1 mole of lauryl alcohol A flat plate (10x22 sq. cm. in area) of an aluminum alloy consisting of 1.1% Zn, unavoidable impurities, balance Al, having thereon a photographic image of resist (the images being 6 point style characters with a fine rule and a fine wave rule) was mounted on the etching machine facing the resist face to the bottom. After emulsifying the etching bath by stirring, the plate was etched by the etching bath by splashing the etching bath onto the resist face for 10 minutes. The etched plate was soaked in an aqueous 3 percent by weight NaOH solution, washed with water and dried. The depth of the deepest etch was 0.50 mm. and the average etch factor was In addition, an etching bath having the same composition as above with the exception that Shell Vitrea Oil 13 was used instead of kerosene was used to perform an etch in the same manner. The results were almost identical to those above, and the average etch factor was 30.

EXAMPLE 14 lnto the tank of the etching machine employed in example 3 there was charged a mixture of the following components to provide an etchant liquid:

Parts by weight 1. Water 8 liters (86.5%) 2. Commercial sulfuric acid (98% by weight H,S0,, s.g.

1.84) 0.585 liter (11.0%) 3. NiCl,-6H,0 260 g. (1.5%) 4. CuCl,'2H,0 128 g. (1.0%)

EXAMPLE l6 Into the tank of the etching machine employed in example 3, there was charged a mixture of the following components to 5 provide an etchant liquid:

5. Solvesso I50 0.3 liter 2.5% by volume) Parts by weight 6. Compounds prepared by the phosphoric esterification of an equimolar mixmm of 1. Water 8 liters (88.2%) l o h l alky] Ether 2. Commercial sulfuric acid obtained by adding 3 moles of (98% y Weight "1504- 4;- propylene oxide and 8 moles of 0.48 liter (9.2%] ethylene id to 1 mole f 3. Commercial hydrochloric acid lauryl alcohol and polyoxyethylene y wflighl lauryl ether obtained by adding -8- 014 NIH-1%) 8 moles of ethylene oxide to l z' '80 B- (L195) mole of lauryl alcohol 33 g. 0.35% I QM Q 36 g A flat plate (10x22 sq. cm. in area) of an aluminum alloy T0 the etchant liquid prepared above were added the folconsisting of 3.2 percent Cu, 0.25% Mg, unavoidable impurilowing p n nts t Provide n t hing balhl ties, balance Al, having thereon a photographic image of a resist as in example l3, was mounted on the etching machine facing the resist face to the bottom. After emulsifying the rsolvcsfl, m0 0 32mcr(3 6% by etching bath prepared above with stirring, the plate was volume) etched with splashing the etching bath onto the resist fact of P acid the plate for 10 minutes. The etched plate was soaked in an polymycmylcnc ether 21.6 g. (polyoxyethylcne aqueous 3 percent by weight NaOH solution, washed with waterand dried. The depth of the deepest etch was 0.35 mm. and the avera e etch factor was 40.

g A flat plate (10x20 sq. cm. In area) of an aluminum alloy EXAMPLE 5 consisting of 1.3% Zn, 0.2% Sn, unavoidable impurities, i balance Al, having thereon a halftone photographic image or [mo a of an etching machme f' a Surfer resist, said image being 7-8 point style characters with a fine i Splashmg paddle was charged flmlxture of the rule, was mounted on the etching machine facing the resist owing components to provide an etchant liquid. face to the bottom. The plate was then etched by splashing the etching bath onto the resist face by rotating the splashing paddle at 440 rpm. for 10 minutes at 26-27 C. The etched plate Parts by weight 40 was soaked in a caustic soda aqueous solution of 3 percent by weight NaOH, washed with water and dried. The depth of the 1. Water 40 m (310%) etch was 0.40 mm. in average. 2. Commercial sulfuric acid When the same procedure as above was repeated employing :32 by 2 64 mm) 8%) Xylene instead of Solvesso 100, substantially identical results 3. Commercial hydrochloric acid were obtamed'.

(36% by weight HCI, As a final point, with respect to the use of the expression uismm (13%) 13%) navoidable in describing the aluminum of the present inven- 382 (043%) tion, this term is utilized because it is impossible, in practice, 5. cuci zmo 286 g. 0.47%

to easily produce an alumina having a purity of 100 percent. 50 Accordingly, commercially available high purity aluminum To the etchant liquid prepared above were added the foL conta ns, as a matter of course a very small amount ofimpuril ties. Since the removal of such impurities IS very difficult from owing components to provide an etching bath: u

a commercial viewpoint, the term unavoidable has been utilized to define such aluminum. We claim: Suit/c550 150 L13 liters y 1. An etching process which comprises splashing an etchant Phosphoric acid ester of mum) liquid upon the surface of a metallic plate, said plate comprispolyoxyelhylenemdccyl 135 (018%) ing a metal consisting essentially of aluminum, and having ether thereon a photographic image formed of an acid resistant coating, said etchant liquid comprising an aqueous sulfuric acid solution containing the ions of at least one halogen and the ions of at least one metal having an ionization tendency A flat plate (27x42 sq. cm. in area) of an aluminum alloy less than that of aluminum, said etchant liquid containing the consisting of 1.5% Zn, unavoidable impurities, balance Al, sulfuric acid in an amount of from about 3 to about 20 percent having a photographic image of a resist, the image of which by weight, said metal ions in an amount of from about 0.004 to was 68 point style characters with a thick rule and a fine rule, about 2.0 gram-ions/liter, and said halogen ions in an amount was mounted on the etching machine. After emulsifying the of from about 0.1 to about 7.0 grams-ions/liter. etching bath by rotating the stirrer, the plate was etched by 2. The etching process of claim 1 wherein the etchant liquid splashing the etching bath onto the resist face at 3 l-35 C. for further comprises N0 1 in an amount less than about 2 gram- 7 minutes by rotating the splashing paddle at a rate of 580 ions/liter. rpm. The etched plate was then soaked in an aqueous 3 per- 3. The etching process of claim 1 wherein said metal is an cent by weight NaOH solution, washed with water and dried. aluminum alloy consisting essentially of about 0.5 to about 10 The average depth of etch was 0.55 mm. and the average etch percent by weight Zn and a small amount of impurities, the factor was 50. balance being aluminum.

4. The etching process of claim 1 wherein said metal is an aluminum alloy consisting essentially of about 0.5 to about percent by weight Zn, about 0.04 to about 2.0 percent by weight Sn and a small amount of impurities, the balance being aluminum.

5. An etching process which comprises splashing an'etching bath upon the surface of a metallic plate, said plate comprising a metal consisting essentially of aluminum and having thereon a photographic image of an acid-resistant coating, said etching bath comprising at least one halogen ion present in a concentration of from about 0.1 to about 7.0 grams-ions/liter, from about 0.004 to about 2.0 gram-ions/liter of the ions of a metal having an ionization tendency less than that of aluminum, from about 1 percent to about 10 percent by volume of a water-immiscible organic liquid, from about 0.05 percent to about 8 percent by weight of a surface active agent prepared by the phosphoric-esterification of a condensation-type 7. The etching process of claim 5 wherein said metal is an aluminum alloy consisting essentially of about 0.5 to about l0 percent by weight Zn, about 0.04 to about 2.0 percent by weight Sn and a small amount ofimpurities, the balance being aluminum.

8. The etching process of claim 5 wherein said metal is an aluminum alloy consisting essentially of about 0.5 to about 10 percent by weight Zn and a small amount of impurities, the balance being aluminum.

Claims

2. The etching process of claim 1 wherein the etchant liquid further comprises NO3 in an amount less than about 2 gram-ions/liter.
3. The etching process of claim 1 wherein said metal is an aluminum alloy consisting essentially of about 0.5 to about 10 percent by weight Zn and a small amount of impurities, the balance being aluminum.
4. The etching process of claim 1 wherein said metal is an aluminum alloy consisting essentially of about 0.5 to about 10 percent by weight Zn, about 0.04 to about 2.0 percent by weight Sn and a small amount of impurities, the balance being aluminum.
5. An etching process which comprises splashing an etching bath upon the surface of a metallic plate, said plate comprising a metal consisting essentially of aluminum and having thereon a photographic image of an acid-resistant coating, said etching bath comprising at least one halogen ion present in a concentration of from about 0.1 to about 7.0 grams-ions/liter, from about 0.004 to about 2.0 gram-ions/liter of the ions of a metal having an ionization tendency less than that of aluminum, from about 1 percent to about 10 percent by volume of a water-immiscible organic liquid, from about 0.05 percent to about 8 percent by weight of a surface active agent prepared by the phosphoric-esterification of a condensation-type nonionic surface active agent of an alkylene oxide and from about 3 percent to about 20 percent by weight sulfuric acid, the materials recited being present in an aqueous solution.
6. The etching process of claim 5 wherein said etching bath further comprises NO3 in an amount less than about 2 gram-ions/liter.
7. The etching process of claim 5 wherein said metal is an aluminum alloy consisting essentially of about 0.5 to about 10 percent by weight Zn, about 0.04 to about 2.0 percent by weight Sn and a small amount of impurities, the balance being aluminum.
8. The etching process of claim 5 wherein said metal is an aluminum alloy consisting essentially of about 0.5 to about 10 percent by weight Zn and a small amount of impurities, the balance being aluminum.