US3785143A - Transparent instrument cover having anti-reflection coating on selected portions thereof - Google Patents

Transparent instrument cover having anti-reflection coating on selected portions thereof Download PDF

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Publication number
US3785143A
US3785143A US00208867A US20886771A US3785143A US 3785143 A US3785143 A US 3785143A US 00208867 A US00208867 A US 00208867A US 20886771 A US20886771 A US 20886771A US 3785143 A US3785143 A US 3785143A
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US
United States
Prior art keywords
indicia
watch glass
coating
reflection
reflection coating
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US00208867A
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English (en)
Inventor
Y Fujimori
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Suwa Seikosha KK
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Suwa Seikosha KK
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Publication date
Application filed by Suwa Seikosha KK filed Critical Suwa Seikosha KK
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    • G—PHYSICS
    • G04—HOROLOGY
    • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
    • G04B39/00—Watch crystals; Fastening or sealing of crystals; Clock glasses

Definitions

  • a conventional transparent instrument cover to be referred to hereinafter as a watch glass
  • part of the surface may be cut at an angle to the remainder, the objective being to give rise to reflection of incident light thereon and to cause sparkle, generally considered to be attractive.
  • a variety of designs are used in which different portions of the glass are cut at different angles.
  • An anti-reflection coating is applied only to selected portions of the surface of the watch glass, the portions being so selected as to avoid unwanted reflection from those areas through which the indicia on the dial beneath are read.
  • Light is reflected normally from those portions of the watch glass not covered by an antireflection coating; the differences in reflection from the coated and uncoated portions of the glass give an effect which is quite similar to that of a watch glass cut at a variety of angles.
  • the effect is achieved without refraction normally present in a conventional watch glass, so that the indicia are readily read.
  • the anti-reflection coating preferably is of MgF which is well known and which is deposited by vacuum deposition.
  • an object of the present invention is to provide an improved watch glass through which the indicia can be readily read while providing the appearance of a watch glass having faces cut at an angle to each other.
  • Another object of the present invention is to provide an improved watch glass through which the indicia can be read without refraction.
  • a further object of the invention is to provide an improved watchglass which gives the effect of having faces cut at an angle to each other, said effect being procured at lower cost than is the case with angle-cut watch glasses.
  • the invention accordingly comprises an article of manufacture possessing the features, properties, and the relation of elements which will be exemplified in the article hereinafter described, and the scope of the invention will be indicated in the claims.
  • FIG. 1 is a vertical section through a conventional watch glass
  • FIG. 2 is a vertical section through a watch glass coated in accordance with the present invention.
  • FIG. 3 is a plan view of the watch glass of FIG. 2;
  • FIG. 4 is a plan view of another embodiment of the present invention.
  • FIG. 5 is a plan view of a further embodiment of the invention.
  • a conventional watch glass generally indicated by the reference numeral 11 generally has two parallel faces 12 and 13 as well as a face 14 cut at an angle to face 12.
  • One effect of this arrangement is that the reflections of light incident on the watch glass to the viewer differ for different parts of the watch glass. Consequently, parts of the watch glass seem to sparkle, this generally being considered an attractive phenomenon.
  • this type of watch glass suffers from the fact that indicia including the hands of the watch appear to be bent when viewed in part through face 12 and in part through face 14 so that reading of the dial beneath the glass is difficult.
  • cutting of the face 14 is expensive, involving as it does time-consuming polishing and grinding as well as special machinery to carry out these processes.
  • FIG. 2 The attractive effect consisting of different reflections from different parts of the watch glass can be obtained by the arrangement shown in FIG. 2 where watch glass 15 has parallel faces 16 and 17, one of which, in this case 16, has thereon an anti-reflection coating 18.
  • coating 18 covers only a portion of surface 16 so that uncoated portions of surface 16 reflect light normally, the difference between the reflections from the coated and uncoated portions of surface 16 providing the effect obtained from the angle-cut surface 14 of the prior art.
  • the undesirable refraction which renders reading of the indicia difficult is absent.
  • the watch glass of FIG. 2 is shown in plan in FIG. 3, where as before, the coated portion is indicated by the reference numeral 18 and the uncoated portion is indicated by the numeral 19.
  • FIG. 3 also shows the appearance of indicia 21 beneath the coating 18.
  • the arrangement of the indicia in this case is such that none of the indicia lie below the uncoated portion IS.
  • coated portion 23 is in the form of an annulus
  • uncoated portion 24 is in the form of a circle within the annulus 23.
  • the difference in reflectivity between the coated and uncoated sections can be enhanced by coating the opposite face of the glass, in this case, the inner face.
  • the purpose is to eliminate the essentially uniform reflectance from the second surface, which is usually about 4 percent of the total incident light falling thereon.
  • the preferred coating is a magnesium fluoride coating applied by vacuum deposition.
  • the technique of using suitable masks in order to control the regions coated and uncoated is too well known to need comment.
  • FIG. 5 shows a watch glass 25 which is coated with an antireflection coating 26 immediately over indicia on the dial ofa watch.
  • the shape and size of each island of coating should be such that the indicium immediately beneath can be conveniently read from a position approximately that immediately above the watch glass. With such an island of coating over each of the indicia, the visibility of the indicia is unaffected by the angle at which light strikes the watch glass.
  • a flat transparent instrument watch glass for use over a dial having spaced indicia thereon and providing improved visibility of said indicia thereunder and enhanced appearance, comprising an adherent antireflection coating on one surface of said watch glass, said coating being divided into separate and distinct portions with a portion immediately over each of said indicia, each portion of said coating being substantially the same size as the indicium directly below said portion, thereby making said indicia visible regardless of the angle of light incident thereon while permitting reflection of incident light from uncoated portions of said watch glass.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electric Clocks (AREA)
  • Surface Treatment Of Optical Elements (AREA)
  • Surface Treatment Of Glass (AREA)
US00208867A 1970-12-21 1971-12-16 Transparent instrument cover having anti-reflection coating on selected portions thereof Expired - Lifetime US3785143A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1970128083U JPS5044126Y1 (enrdf_load_stackoverflow) 1970-12-21 1970-12-21

Publications (1)

Publication Number Publication Date
US3785143A true US3785143A (en) 1974-01-15

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Application Number Title Priority Date Filing Date
US00208867A Expired - Lifetime US3785143A (en) 1970-12-21 1971-12-16 Transparent instrument cover having anti-reflection coating on selected portions thereof

Country Status (3)

Country Link
US (1) US3785143A (enrdf_load_stackoverflow)
JP (1) JPS5044126Y1 (enrdf_load_stackoverflow)
GB (1) GB1338629A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4122663A (en) * 1976-03-18 1978-10-31 Kock Bruce A Stop watch and timing device
EP0114566A1 (de) * 1983-01-25 1984-08-01 W. Bloesch Ag Glas mit einem Dekor für ein Messinstrument, insbesondere Armbanduhr und Verfahren zur Herstellung desselben
EP0699980A1 (de) * 1994-08-29 1996-03-06 W. Blösch AG Verfahren zur Herstellung eines Zifferblattes
US20060256666A1 (en) * 2005-05-14 2006-11-16 Jong-Chan Lee Watch assembly having a dial integrally formed in the watch-glass

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH650375GA3 (enrdf_load_stackoverflow) * 1982-07-07 1985-07-31
JPH0397691U (enrdf_load_stackoverflow) * 1990-01-26 1991-10-08

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2220861A (en) * 1938-06-16 1940-11-05 Gen Electric Reduction of surface reflection
US2256200A (en) * 1939-07-28 1941-09-16 Donovan J Heilman Watchcase

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2220861A (en) * 1938-06-16 1940-11-05 Gen Electric Reduction of surface reflection
US2256200A (en) * 1939-07-28 1941-09-16 Donovan J Heilman Watchcase

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4122663A (en) * 1976-03-18 1978-10-31 Kock Bruce A Stop watch and timing device
EP0114566A1 (de) * 1983-01-25 1984-08-01 W. Bloesch Ag Glas mit einem Dekor für ein Messinstrument, insbesondere Armbanduhr und Verfahren zur Herstellung desselben
EP0699980A1 (de) * 1994-08-29 1996-03-06 W. Blösch AG Verfahren zur Herstellung eines Zifferblattes
US20060256666A1 (en) * 2005-05-14 2006-11-16 Jong-Chan Lee Watch assembly having a dial integrally formed in the watch-glass
US7347619B2 (en) * 2005-05-14 2008-03-25 Jong-Chan Lee Watch assembly having a dial integrally formed in the watch-glass

Also Published As

Publication number Publication date
GB1338629A (en) 1973-11-28
JPS5044126Y1 (enrdf_load_stackoverflow) 1975-12-16

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