US2582786A

US2582786A - Mirror

Info

Publication number: US2582786A
Application number: US151389A
Authority: US
Inventors: Seth G Malby
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-03-23
Filing date: 1950-03-23
Publication date: 1952-01-15
Anticipated expiration: 1969-01-15

Description

Jan. 15, 1952 s. e. MALBY 2,582,786

MIRROR Filed March 23, 1950 INVENTOR 55 n7 G. MALE Y ATTORNEYS Patented Jan. 15, 1 952 MIRROR seine. Malby, Edgewater, N. J. Application March 23, 1950, Serial No.151',389

This invention relates to mirror assemblies and is particularly directedto the-improvement which comprises providing a protective covering of aluminum foil for the back of a mirror.

The ordinary mirror, such as that seen'cn a dressing table or in-a vanity compact, is'a plate of clear glass having an opaque metal reflecting backing. Most of these metal backings are silver because this metal may be readily deposited in a smooth, continuous and very highly reflective film upon the glassplate; and a considerable industry has grown up-relating to the silvering of glass plates for mirrors.

With thedevelopment of themirrorsilvering industry, it was recognized that unless protective measures were takenthe silver filmwould tarnish, become blackened; andeventually peel ofl. due to deterioration by moistura hydrolyticaction due to combination with water vapor in the air, and chemical action with gases in the air, as

for example the'formationof silver oxides and sulfides through contamination-by oxygen and sulphur gases in the air. Theiilm also had to be protected against wear and abrasion.

Various methods have-been proposed throughout the years for protecting-the--silver coating against tarnishing and abrasion. The method most widely used today for-making these mirrors is as follows. 'First a thin butopaque layer or film of silver is precipitated onto the glass plate 'from an ammoniacal solution of silver nitrate.

The procedures 1 for doing this-are well-known and do not comprise part0! thepresent invention. Then a coatingof shellac isapplied to completelycover the deposited silverlayer. The shellac dries relatively quickly-to provide-a; clear overlayer, and its' intended purpose is to provide a hard-protective coating'ior keeping moisture and atmosphere gases away from the underlying silver film. After the shellac has'become hard.

a coating of paint, usually a dark grey: asphalt base paint whichdoes not chemically act on the shellac, is applied overlying the layer of shellac.

The shellac is chemically inert;.with respect to the silver, and 1 the major purpose of the paint is to provide an abrasiveresistant -and so-called 3 claims. (01. 88- 105) ing became deteriorated, the difference being only a matter of timebeiore. the atmospheric moisture and gases penetrated through the paint and shellac to the underlying silverfilm. Also the pain and shellac layers are readily scratched and as the pain agesit tends to crack and peel,

While these conventional-mirrors may be sat isfactory for" a shortperiodof time and in-iact all. permitting entry .of moisture .;,to.attack the silver layer.

Asa result there has been. constant research and many diiierent proposals have been made for the protective backing of the silver film. :Among these is another conventional method by which; instead of coating with paint and shellac,;a coat of copper is immediately electroedeposited directly upon the silver to serve as an opaque abrasive'resistant cover. This deposited. layer has proved more or less porous, and eventually the silver *film becomes discolored, .zdarkened, "and a the entiremirror therefore unsatisfactory.

The present invention: comprises the. backing of a mirror of this type with aluminum foil sheeting applied insuch a manner as to provide ,a tough abrasion-resistant, gas andmoisture tight coating for the entire mirror back.

The major object of my invention ispto provide a novel mirror assembly wherein-the deposited silverreflecting layer is protectedby a continuous aluminum foil covering.

' It is a further object of my invention to provide a novel mirror assembly having. an. adhesively secured water and air tightalumium foil backing. A further object ofthe invention is to provide a mirror assembly wherein the mirror backis covered with aluminum foil sheeting secured thereto by a normally-tacky; pressure sensitive water insoluble adhesive.

"Further objects of: the invention will appear as the description proceeds intconnection: with, the appended claims -'and the annexed drawings wherein:

Figure l is a rear elevation of a mirror assem- =bly according, to a preferred embodiment of. the invention, partly brokenyaway to showdits construction;

Figure 2 is an endpelevation of the mirror assembly;

Figure 3. a fragmentary enlarged section ,illustrating the structure at an zedge .ofithe mirror assembly. 50

In carrying out the invention I prefer tostart with a mirror which has been silveredshellacked. and painted accordingtoythe above prior methed. In other words, .I may start vwith-.9; mirror which is produced and sold to. the consumer today as-a" finishedarticlehaving an a1leged;mois

ture and gas-proof backing. Upon the back of this mirror I apply a layer of aluminum foil, preferably in a single sheet, but it may be made of one or more sheets overlapped at adjacent edges if the mirror is a large one. The first step in applying the foil to the back of the mirror according to my preferred procedure is to apply a border strip of adhesive material all around the periphery of the mirror back in overlying relation to the coating of paint and preferably extending slightly outwardly beyond the edges of the mirror so as to extend over and cover the edges of the paint, shellac, and silver layers along the edges of the glass. For this purpose I must use an adhesive material which is comparatively free of the relatively acidic and chemically reactive materials that characterize many adhesives, and for the purpose I have found that it is extremely satisfactory to employ one of the known pressure sensitive adhesives which are variously known as crude rubber base adhesives.

The pressure sensitive adhesive may be any of those disclosed in United States Letters Patent Nos. 2,156,380; 2,206,899; 2,236,527; 2,410,079 and 2,444,830. These pressure sensitive adhesives are normally tacky at room temperatures and do not appreciably harden with age. Their composition is relatively dense so that they provide a watertight seal, and they are insoluble in water. They are chemically neutral and inert with respect to aluminum, silver and the paint on the mirror back.

These pressure sensitive adhesives are mainly crude rubber bases treated specially or admixed with ester gum or some rosin or resin to provide a normally tacky state wherein they are adhesive without the need for solvents or heat. This absence of solvents and other elements from the adhesive materially reduces the chance of chemical attack upon the paint layer.

A prime advantage of using pressure sensitive adhesives is that no heat, chemical or mechanical action beyond merely smoothly pressing the aluminum foil onto the mirror back is required to complete the assembly wherein it is tight between the sealed portions.

These particular rubber base adhesives, besides being free of elements which might react with either the aluminum foil or the underlying paint or silver layers on the glass, are very strongly adhesive and provide a water and gas tight bond between the foil and the back of the mirror, The foil sheet, after the adhesive has been placed around the periphery of the back of the mirror, is placed directly upon the mirror back. Preferably an oversized sheet is used, and it is drawn taut and pressed tightly into smooth engagement with the adhesive, and then the edges are trimmed off and smoothed over the corners leaving a neat, smooth, clean appearance at the back of the mirror.

For purposes of the invention, I have found that aluminum foil having a thickness at least in the order of about .0015" should be used since with present day methods of manufacture, this is the minimum thickness that is surely uniformly free of pin holes or weak spots that might admit air and gas. However, a foil thickness of about .0025 or more is preferable for the invention, because Of the desirable resistance to abrasion and facility of handling ofiered by the thicker foil. Foil of about .0015" thickness, laminated with a sheet of cellulose acetate or the like, as will later be described, may be employed because the thickness of the laminated product will make it as easy to handle and as abrasive resistant as the thicker foil.

Referring to the drawings, the mirror assembly comprises a clear transparent glass plate ll having a smooth fiat front surface 12 and a smooth fiat rear surface l3 parallel to surface 12. Overlying rear surface I3 is a deposited film of silver [4 which provides the reflecting surface of the mirror. Overlying silver film 14 are a layer l5 of shellac and a layer I 6 of the usual grey paint in succession. This is the usual commercial mirror.

In the invention I apply a border strip I! of adhesive entirely around the perimeter of the mirror overlying the paint layer. This adhesive is of the rubber base pressure sensitive type above described and may be sprayed or otherwise applied to the mirror. In practicing the invention I have found it very satisfactory to make strip I I of lengths of flexible tape coated on both sides with the pressure sensitive adhesive. Such a double coated tape is available on the market under the designation of No. 400 Scotch tape, and a double coated tape of this nature is disclosed in Patents 2,206,399 and 2,444,830. Preferably I simply lay lengths of this tape along the mirror back with overlapped or abutted ends at the corners, so as to provide a complete and continuous strip of adhesive I? all around the periphery.

Then, in the case of a mirror of fairly small size, I take a single sheet I8 of aluminum foil (preferably of the .0025" thickness above pointed out) and draw it tightly and smoothly across the mirror back and press it onto adhesive strip l! which retains it in the assembly. Where the mirror is large, I use several sheets of foil, with their adjacent edges overlapped and bonded by the pressure sensitive adhesive.

As illustrated in Figure 3, the side edges of strip I! may extend slightly outwardly beyond the plane of the edge of glass II, and the aluminum foil sheeting is slightly oversize, so that it may be bent over to cover and seal the hitherto exposed side edges of the layers of silver, shellac and paint in the assembly.

The aluminum foil backing presents a smooth, clean and pleasing appearance. It is tough and abrasion resistant and is itself free of holes so as to be gas and moisture tight. The flexible, resilient sealing strip l1 around the perimeter of the mirror back is impervious to moisture and provides a cushioned seal which increases its sealing action when it is mounted in a holder or frame that may clamp the mirror edges, The adhesive material of strip 1! remains tacky for a long period thereby retaining its high adhesive quality indefinitely.

While I have above described providing adhesive only in a strip which may be about an inch wide along the mirror periphery, the strip i! need .be wide enough only to maintain the seal, and on the other hand the entire back of the mirror may be adhesive covered if desired, without departing from the spirit of the invention. Wherever I refer to a sheet of aluminum foil in the claims, this is intended to cover both single shielets and overlapped bonded multiple sheets of f0 The aluminum foil and the adhesive strip I! may be combined together before attachment to the mirror back. For example the double coated tape may be secured along the perimeter of a pre-cut sheet of the aluminum foil, and then the adhesive bearing foil sheet applied and smoothed over the back of the mirror.

Also for many applications of the invention it is possible to secure a good mirror by eliminating the shellac and paint layers and adhesively securing the aluminum foil directly upon the deposited silver backing, but this should be done immediately after the silver has been deposited and the deposited silver layer dried.

The aluminum foil may be plain or decorative. This decoration may be provided either by direct printing upon the back of the foil sheeting, or by laminating the foil sheeting, prior to assembly with the mirror, with a printed or otherwise decorated sheet of a transparent plastic like cellulose acetate of rubber hydrochloride. The cellulose acetate, printed and colored as at on the side to be secured to the foil, is secured to the foil by a suitable adhesive which may be transparent or colored for added ornamentation. Where sheet rubber hydrochloride, such as Pliofilm, is used, the laminated bond may be heat sealed. Where the printing or decorating is done on the foil itself, the printed surface may be overlaid with a transparent sheet of the above mentioned plastic fully bonded to it. The laminated foil and plastic sheet coverings may use the thinner foil as above explained.

The aluminum foil backed mirror assembly of the invention is more resistant to attack by moisture and atmospheric gas than any prior constructions. I have determined by actual test that it stands up under severe conditions such as may be encountered in hot humid seasons and countries, where the usual paint and shellac. backed mirrors have failed. For example, in tests at temperatures of 100 F. and upward, in a relative humidity range of twenty-five to one hundred percent, mirrors made according to the invention were unchanged and standard commercial mirrors with painted backs all showed signs of deterioration within a short time. Scratch tests clearly show my foil back mirrors to be of superior abrasion resistance. I have also found that in case the mirror is shattered the foil sheet is strong enough to hold pieces together and reduce splinters and glass fragments.

In the mirror assembly of the invention the metallic layers of silver and aluminum are entirely separated and electrically insulated by a barrier layer that comprises the shellac and paint coats, and it is an inherent property of this barrier' layer that it prevents any electrolytic action between the two metallic layers.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. 7

What is claimed and desired to be secured by the United States Letters Patent is:

1. In a mirror, a transparent glass plate having a rear surface coating presenting a highly reflective metal surface when viewed from the front face of the mirror, a continuous narrow band of adhesive extending around the entire periphery of the back surface of said coating and over all of the side edges of said coating to the edges of the glass plate-peripherally of the mirror, and an imperforate metal foil sheet mounted in overlying relation to said coating and extending over all of the side edges of said coating to the edges of the glass plate at least as far as the adhesive band for bonding the foil to the mirror and sealing said coating edges against entry of moisture and gases, the major part of the area of the foil peripherally within said adhesive band being substantially free of bonding with the coating, and said adhesive being chemically and electrolytically neutral with respect to both the coating and foil.

2. In the mirror defined in claim 1, said foil being a sheet of aluminum foil having a thickness of at least. about 0.0025 inch.

3. In a mirror, a transparent glass plate having a rear surface coating presenting a highly reflective metal surface when viewed from the front face of the mirror, a continuous narrow band of normally tacky pressure sensitive adhesive extending around the entire periphery of back surfaces of the coating and over all of the side edges of said coating tothe edges of the glass plate peripherally of the mirror, and an imperforate metal foil sheet mounted in overlying relation to said coating and extending over all of the side edges of said coating to the edges of the glass plate at least as far as the adhesive band for bonding the foil to the mirror and sealing said coating edges against entry of moisture and gases, the major part of the area of the foil peripherally within said adhesive band being substantially free of bonding with the coating, and said adhesive being chemically and electrolytically neutral with respect to both the coating and foil.

SETH G. MALBY.

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

UNITED STATES PATENTS Number Name Date 250,028 Wiederer Nov. 22, 1881 290,744 Conroy et al Dec. 25, 1883 893,755 Saegmuller July 21, 1908 1,285,901 Bausch et al. Nov. 26, 1918 1,488,923 Hitchcock Apr. 1, 1924 1,653,018 Colbert et al Nov. 24, 1925 2,019,951 Caprio Nov. 5, 1935 2,061,558 Brandt Nov. 24, 1936 2,091,714 Mathews Aug. 31, 1937 2,113,977 Barnes Apr. 12, 1938 2,281,027 Dennison Apr. 28, 1942 2,352,923 Turner July 4, 1944 FOREIGN PATENTS Number Country Date 605,524 Great Britain July 26, 1948

Claims

1. IN A MIRROR, A TRANSPARENT GLASS PLATE HAVING A REAR SURFACE COATING PRESENTING A HIGHLY REFLECTIVE METAL SURFACE WHEN VIEWED FROM THE FRONT FACE OF THE MIRROR, A CONTINUOUS NARROW BAND OF ADHESIVE EXTENDING AROUND THE ENTIRE PERIPHERY OF THE BAKING SURFACE OF SAID COATING AND OVER ALL OF THE SIDE EDGES OF SAID COATING TO THE EDGES OF THE GLASS PLATE PERIPHERALLY OF THE MIRROR, AND AN IMPERFORATE METAL FOIL SHEET MOUNTED IN OVERLYING RELATION TO SAID COATING AND EXTENDING OVER ALL OF THE SIDE EDGES OF SAID COATING TO THE EDGES OF THE GLASS PLATE AT LEAST AS FAR AS THE ADHESIVE BAND FOR BONDING THE FOIL TO THE MIRROR AND SEALING SAID COATING EDGES AGAINST ENTRY OF MOISTURE AND GASES, THE MAJOR PART OF THE AREA OF THE FOIL PERIPHERALLY WITHIN SAID ADHESIVE BAND BEING SUBSTANTIALLY FREE OF BONDING WITH THE COATING, AND SAID ADHESIVE BEING CHEMICALLY AND ELECTROLYTICALLY NEUTRAL WITH RESPECT TO BOTH THE COATING AND FOIL.