US1942686A - Mirror and process of making it - Google Patents

Description

`5am. 9,1934. G. F. coLBERT Er' AL 1,942,686

MIiRROR AND PROCESS OF MAKING IT I File'd Jan'. 19, 1952 lamas l-GLAss 5- corren run 2- su. van n Guss' 6- una FILM `lcuss -slLvER FILM INVENTORS Patented Jan. 9, 1934 o 1,94z,ssc

MIRROR AND PaocEss oF MAKING n George F. Colbert, Pittsburgh. and William H. Colbert, Brackenridge, Pa., assignors to Lib-` erty Mirror Worksra corporation oi* Pennsylvania Application January 19, 1932. somo No. 531,533 s claims. (ci. i1- 43) The invention relates to an improved mirror oi the multitone type shown in our Patents Nos.

. 1,788,562 and 1,802,168, 'and to en improved method oimaking such mirror. The term f ror is used here in its broad sense to include ornamental plates whose surfaces are of a refleeting character whether such surfaces are designed to be utilized as ordinary household mirrors or for purely ornamental Purpose, such as ues, table tops, coasters, and the like. While the tal phase oi the invention is as the more important one, the invention has industrial applications, one ol which is round in the plating of reiiector bulbs to reduce the glare 4from automobile headlights as hereinafter more fully set iorth. InV manng muititone mirrors, in which the rst deposited lm'ls of sliver, part oi vwhich n removed to form a pattern which is tlg :oiled m with a metal coat or paint oi a contrasting color, curity arises in handling and storing the silvered platos,.aothat they will not be damaged by such handling or in storing'them preliminary to the nent coating. Further the plates can not be hold for length of time without deterioration due to the oxidation of the silver, and it io incont, if not impossible, to always prooecd with the :dnal steps of the operation as soon se the nlverlng is completed. Y

The prent invention is designed to obviate 'the ioregomg difficulties, and further to give a finished multitone plate which will not develop defecto in the silvering in a relatively short time, such as often occurs with mirrors made by the Briey stated this result'is accomplished by ploting or coating the silver with a metal protection as soon as ble after the silvering step. The protecting coat or film is copper, an such copper is preferably electroplated onto e ailvenbut the protecting coat or filmmay be of some other metal, such as nickel. .Alter the' application of the protecting nlm of metal, the plates may be handled without danger of injury to thesllvcring and may' be kept indenitely without deterioration due to oxidation. When plates'of this character are used in multltone work, the n nished product is free from any deterioration of Athe silver portion of the pattern work, such as is very apt to occur with multitoneplates made by the ordinary methods. including the wellknown silk'screen method of. patterning. Cer-V Ytainembodiments oi' the invention' are shown in the aoc drawing. whereinr g Figure lisafaceviewotanomamental multi-l art. -'The next step is the acation of the proprcoessee'heretofore mown and'used in the art.'

tone plate. Fig. 2 is a section on the line Il-II of Fig. 1, the iilms of material shown in this tlgure and Figs. 3 to 8 being much exaggerated'in thickness for the purpose of clear illustration. Figs. 3 to 'l are sections illustrating the steps of the operation. And Fig. 8 is a sectional view of a lamp bulb to whose construction the process has been applied.

Referringto'the drawing. 1 is a sheetof glass, 2x is a precipitated film, o r 1. silver (and the term siiver" is used here in the sense ordimanly-used in mirror work to cover' either actual silver or Quicksilver) which covers the main porv/ tion of one of the surfaces oi theglass, and 3 is a coating of a contrasting color such as black paint. The two lms'are disposed so as to give, an ornamental design which present a wide variety both 'as to demgn and colors. Y

'In y out theprocess to make theparticulor mirror shown, the ass is placed'in a horizontal position and the silver nlm 2 is de- DOSlted over thoentire back of the sheet, as indicated Vin Fis. 3, by the usual procedure of the I tecting illm or coating 5, preferably of copper, which is electroplated onto the silver. is

. -w i done by placing the plate, silver side down, in a plating bath and prcoee in a mannerwell known in the art, the production oi cop backed mirrors being a process Weil momo. in the art.

desired pattern. a number of proc complishing which are fullo explain in our Potent No. 1,802,163 heretofore referred to. one 9? of these is the cold top enamel process, which consists in coating the copper-Illini withan emul-v sion nlm 6 (Fig. 5)v sensitive to light. The desired design is then impressed on the sensitized surface by the projection of an illuminated image thereon, or by covering with a stencil sheet which is exposed to light. After the ee, the latent image is developed in such manner that the light treated portions 01 the emulsion are insoluble and .the plate is washed to remove the l other portions of the emulsion. In this case the ligure 3 at the'center of the plate is the portion of the enamel film .which is not exposed to light, so thatsuch portion is solvent and therefore removed by the washing as indicated in Fig, 6.v

The plate as thus prepared for etching is now placed in a tray containing a dilute solution (e. 8. about10%) of nitric acid. This treatment removes .the portions ofthe copper and silver 'llinlsnot protected by the enamel, namely the in central portion, in the particular design illustrated, thus bringing the plate to the condition shown in Fig. 7, so that viewed from the front the plate shows a silver background surrounding the central clear portion which constitutes the head.

'I'he ilnal step consisting in applying the paint film over the back of the plate, thus covering the enamel film 6 and the open space '7, is shown in Fig. '7. Black paint is ordinarily used, thus giving a black silhouette against a silver background, as viewed from the front of the plate, but other colors may be used, and if desired a precipitated metallic nlm may be substituted for the paint as in our patents heretofore referred to.

Fig. 8 illustrates another application of the process in silvering non-glare automobilelamps 10. As here shown, 8 is a circular spot of silver and 9 is a protecting nlm of copper. In carrying out the process, an area somewhat larger than the area 8 is covered with a precipitated silver nlm and over this is electroplated a copper film 9. A silk screen is then placed over the area covered by the two metal films, such screen having an untreated central portion corresponding to the desired area 8, and a portion surrounding such central portion treated with a material which renders it impervious to the inking resist later used. The screen is now inked with a resist which penetrates the central portion thereof, but not the outer portion. The screen is now removed and the bulb treated with a dilute etching acid which removes all of the metal films except the central portions 8, 9 which were protected by the resist. The silk screen method of applying a patterned resist preliminary to the etching may be used in a wide variety of work, including that required to produce the design of Figs. 1 and 2. Such method lends itself most readily to the simpler designs.

In addition to the advantages of the process as heretofore explained, a further utility is present when silver and lead sulphide coatings are to be used in combinationlto produce a multitone ered by the silver.

effect. With these combinations it has been impracticable heretofore to use the silver as the first or foundation coat. as the lead sulphide, when applied as the second coat will discolor the silver. The use of the copper plating obviates this difficulty as it protects the silver from discoloration.

The term solvent" is used throughout in its broad sense to designate any compound which isV effective to remove or dissolve certain unprotected portions of the nlms by chemical reaction therewith or otherwise.

What we claim is:

1. A process of partially silvering a glass surface, which consists in precipitating over the area a coat of silver, electroplating a nlm of copper over said coat, placing a pattern resistant to the action .of a solvent of said metals on said iilm so that a part thereof is covered and a part is left uncovered. and then exposing the nlm thus partially protected to the action of said solvent.

2. A process of partially coating a glass surface with metal which consists in precipitating over the area a coat of silver. electroplating a film of metal over said coat, placing a pattern resistant to the action' of a solvent of said metals on said film so that apart thereof is covered and a part is left uncovered, and then exposing the film thus partially protected to the action of said solvent.

3. A process of partially coating a glass surface with metal which consists in precipitating over the area a coat of silver, electroplating a nlm of metal over said coat, placing a pattern resistant to the action of a solvent of said metals on said nlm so that a part thereof is covered and a part left uncovered, exposing the film thus partially protected to the action of said solvent, and applying a coat of material of a color contrasting to the silver to those portions of the glass not cov- GEQRGE F. COLBERT. n. consan'r.

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