US2450340A - Silver base alloy for metal evaporation - Google Patents

Description

Sept. 28, 1948.

F. R. HENsEL ETAL SILVER BAS ALLOY FORI METAL EVAPORATON Filed Feb. 3, 1944 x x 574974762 il.

@zag N 7'0 Vid/UM PUMP SY/ver o r Cop/ur Hilo] can Za 'ny Plus/Aunis INVENToRs 'dnz Ji. Hensel By Earl j.' anni #TTOFNEYS Patented Sept. 28, 1948 SILVER BASE ALLOY FOR METAL EVAPORATION Franz R. Hensel and Earl l. Larsen, Indianapolis,

Ind., assignors to P. R. Mallory & Co., Inc., Indianapolis, Ind., a corporation of Delaware Application February 3, 1944, Serial No. 520,97 4

(Cl. i5-173) 1 Claim. l

This invention relates to improvements in metal evaporation.

An object of the invention is to improve the evaporation of silver and copper and their alloys.

Other objects of the invention Will be apparent from the description and claim.

Figure 1 is a sectional elevation of a metal evaporation apparatus, and

Figure 2 is a fragmentary cross-section of the tungsten lament coated with the metal to be evaporated.

The vaporization process for depositing silver, copper and other metals has been known for some time and used commercially to some extent. The processing as applied to silver is described in considerable detail in the book Silver in Industry edited by Lawrence Addicks (Reinhold 1940) pages 291 to 296.

In carrying out the process the metal to be evaporated is usually hung on a tungsten filament as small loops of wire. then passed through the filament toV heat it and the wire loops are melted and the fused metal Electric current isv clings to the lament and evaporates as the heating is continued. One diiculty which has been encountered with silver and copper has been the failure of these metals to wet the tungsten suiciently to cling to it during the vaporization process. The metal tends to ball up and drop on' the filament before it can be evaporated. It also sometimes tends to spatter during evaporation, probably due to the accumulation of the liquid metal in large globules.

, We have now discovered that this diiculty can be overcome and satisfactory wetting of the tungsten filament obtained by adding a small percentage of phosphorus to the silver or copper or their alloys. For example, an alloy of Per cent Phosphorus .04 Platinum 4.97 Silver Balance was found to wet the tungsten extremely well and to give no spattering during evaporation while a similar alloy without the phosphorus content was found to operate erratically.

In general the amount of phosphorus which should be alloyed with the silver may fall within the range of .001 to 1%. Other alloying ingredients may be present in the silver. Platinum and palladium in proportions ranging from .25 to 20% are sometimes desirable for improving the wettability still further. In some cases nickel, cobalt or iron may be present in percentages ranging from .001 to .5%.

For copper and copper alloys similar percentages of phosphorus may be used and similar addition metals if desired.

Referring to the drawing, Figure 1 shows a metal vaporization app-aratus comprising a bell jar l0 resting on a pump plate ll with a rubber gasket I2 between them to aiiord a gas seal. The bell jar is connected to a vacuum pump through pipe I3 and a Pirani g-auge i4 may be provided to measure the degree of vacuum obtained.

The articles to be coated with a thin lm of silver or copper such as glass plates or mirror blanks I5 are mounted on the inside wall of a cylindrical container I6 supported Within the bell jar. The tungsten lament I1 is mounted axially Within the container and connected to insulated terminals I8 and I9.

The silver or copper alloy to be evaporated is hung on the spiral tungsten filament as little Wire loops 20 so that when the filament heats up the loops will melt and cling to the lament.

. Figure 2 is a fragment-ary cross-section of the tungsten lament I1 coated with the fused alloy 2l of silver or copper preparatory to evaporation.

While specific embodiments of the invention have been described, it is intended to cover the invention broadly within the spirit and scope of the appended claim.

What is claimed is:

An alloy wire for metal evaporation composed of about .04% phosphorus, 5% platinum and the balance of silver.

FRANZ R. EENS-EL. EARL I. LARSEN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,652,107 Escholtz Dec. 6, 1927 2,019,984 Leach Nov. 5, 1935 2,160,714 Briggs May 30, 1939 2,162,627 MacGregor June 13, 1939 2,166,248 Hensel et al. July 18, 1939 2,196,306 Hensel et al. Apr. 9, 1940 2,259,668 Spanner Oct. 21, 1941 FOREIGN PATENTS Number Country Date 755,701 France Sept. 11, 1933 452,401 Great Britain Aug. 21, 1936

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