Liquid crystal display timepiece with variable contrast
350-337 1 W 1 l M. Z &#34;-2, 8197A KR 355141163 1 1 l a l iUlIiiiQQl Mates Pat, 1 3 -9 &#39;illreno 14 1 A r. 1, 1975 LlQUlD CRYSTAL DlSiLAY TTMElPllECE [56] References Cited 1 d WlTH VARIABLE (IONTRAST UNITED STATES PATENTS [75] Inventor; ()samju Hkeno, Suwa&#39; Japan 3,l99,285 8/l965 Caruso 61: al 58/9l X r I 3,321,905 5/1967 Krebs 58/50 R Asslgneer ,Kabushllfl Kamila guwa sellwslw, 3,722,206 3 1973 Bergey .4 58/50 R 1 Tokyo, Japan 3,732,793 5/1973 Tague 350 159 [22] Flled: Oct 1973 Primary Examiner-Edith Simmons Jackmon [2 1] Appl. No.1 402,664 Attorney, Agent, or Firm-Blum Moscovitz Friedman I &amp; Kaplan [30] 0 F203??? Aprjrlrcatron Priority Data 47 H4261 ABSTRACT CL Variable contrast in a watch using a liquid crystal dis- [52] U 5 Cl 58/50 R 350/159 play panel for showing the time is achieved by the use [5]] 5/30 6 27/28 of polarizer sheets proximate both surfaces of said [58] Fie&#39;ld 58/50 R C 127 panel. The outer of said sheets is mounted for rotation at the discretion of the wearer.  
 6 Claims, 6 Drawing Figures QILIQIUID CRYSTAL DISILAY TIMEFIECE WETH VARIABLE CONTRAST BACKGROUND OF THE INVENTION the eye of a possible purchaser or if it can give an appearance of superiority with respect to some characteristic. With such considerations in view, watch cases in general and dials in particular were metamorphosed through a myriad of variations.  
  Recently, a number of types ofilluminated digital displays have been incorporated into watches to take the place of the usual dials. Of particular interest are those displays using light-emitting diodes and liquid crystals. In general, the latter type of display is preferred because of the fact that it uses less energy. This problem is sufficiently serious so that most, but not all, electronic timepieces featuring illuminated digital displays actually show the time only when deliberately switched into actuation.  
  A type of liquid crystal display which has already become part of the art features a pair of polarizing sheets such as those sold under the tradename of Polaroid. The amount of light transmitted by such sheets depends on the angle between the axes of polarization of the two polarizing sheets incorporated in a watch. However, in the prior art constructions the angle between the planes of polarization of the two sheets has been fixed so that it is not possible to vary the degree of contrast obtainable by means of such a device in accordance with the desire or whim of the wearer. Particularly, it is not possible to adapt the combination of the two sheets to the level and angle of illumination where the watch is being used.  
 SUMMARY OF THE INVENTION In a timepiece featuring a&#39;liquid crystal display panel, polarizing plates of the plane-polarizing type are placed proximate the inner and outer surfaces of the liquid crystal display panel. The polarizing sheet proximate the outer face of the panel is mounted for rotation, making it possible to vary the contrast with which the display is shown.  
  Accordingly, an object of the present invention is a timepiece in which the time is displayed by a liquid crystal display panel wherein plane-polarizing sheets are disposed at the inner and outer faces of the display panel and the outermost sheet is mounted for rotation.  
 Another object of the present invention is a timepiece in which a liquid crystal display panel is used for the display of time wherein plane-polarizing sheets are mounted proximate the inner and outer faces of said display panel and the outer sheet can be rotated for the purpose of varying the degree of contrast ofthe display.  
  A further object of the present invention is a timepiece in which the time is displayed by a liquid crystal display panel wherein a pair of plane-polarizing sheets are mounted at the inner and Outer faces of said display panel, the outer most sheet of said pair being mounted for rotation in its own plane and at the interior face of a watch crystal, means being provided for rotating said outermost sheet from the exterior of said watch.  
 The invention accordingly comprises the features fv construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.  
 BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:  
  FIG. I is a sectional view of a timepiece in accordance with the prior art wherein a pair of planepolarizing sheets are mounted at the interior and exterior faces of a liquid crystal panel, the angle between the axes of said sheets being fixed;  
  FIG. 2 is a sectional view of a timepiece in accordance with the present invention wherein the outermost of the two polarizing sheets is internal to the timepiece and is rotatable by means operable from the exterior of said timepiece;  
  FIG. 3 represents the appearance of the display panel when the planes of polarization of said polarization sheets make an angle of with each other;  
  FIG. 4 represents the appearance of the display panel when the planes of polarization of the polarization sheets coincide;  
  FIG. 5 is a sectional view of a timepiece wherein the outermost of a pair of polarizing sheets is mounted exterior to the crystal of said timepiece; and  
  FIG. 6 is an embodiment of a timepiece in accordance with the present invention wherein the outermost of the pair of polarizing sheets is mounted at the interior surface of the crystal of said timepiece.  
 DESCRIPTION OF THE PREFERRED EMBODIMENTS In a conventional field effect liquid crystal display timepiece as shown in FIG. ll, plane-polarizing sheets 2 are secured to the inner and outer faces of display panel 1 by adhesive or the like. In such a construction, once the angle between the planes of polarization of the two polarizing sheets is established as is done during construction, it becomes difficult if not impossible to vary the contrast of the display by varying the angle between the planes of polarization of the two sheets. Consequently, design interest obtainable from such an arrangement is minimal.  
  To increase the design interest of such an array, it is desirable that at least one of the polarizing sheets be mounted in such a way as to be rotatable in its own plane. An example of such an embodiment is shown in FIG. 2 wherein polarizing sheets. 4a and 4b are mounted on either side of a liquid crystal display panel 3. The outermost sheet 4a is joined to a rotatable memher 6 within watchcase 5. The join can be made by adhesive or by a snap fit or similar means. Rotatable member 6 is in the form of a crown gear which can be rotated around its axis by rotating crown 7 exterior to the watch and thereby rotating spur gear 8. By this means, the angle between the planes of polarization of the outer polarizing sheet 4a and the inner polarizing sheet 4b can be altered. When the planes of polarization of the two sheets differ by 90 the appearance of the display is as shown in FIG. 3. When the planes coin- X I 3 cide, the level of illumination of the background and the digits is reversed so that the appearance of the display is as represented in FIG. 4. Moreover, variation of the angle between the planes of polarization, especially when near and 90 makes it possible to vary the degree of contrast between the background and the digits.  
  In the embodiment of FIG. 5, the outermost polarizing sheet 4a is affixed to a rotatable member 9, such as a bezel, which is on the outside of case 5. In such an arrangement, the sheet 4a is exterior to crystal 10. The method of attachment of rotatable member 9 to watchcase 5 may vary; a snap fit (not shown) is desirable in that member 9 and sheet 4a may readily be removed from the watch if desired.  
  A further embodiment of the invention is shown in FIG. 6 wherein a polarizing sheet 4a is joined to the interior of the timepiece crystal &#39;10 as by adhesive. As a general rule, crystal 10 cannot readily be rotated so that when a particularly desirable orientation is found by the wearer, it can be maintained. However, crystal it) is generally made to be removable with relative ease so that it is possible without serious difficulty to alter the plane of polarization of polarizing sheet 4a when the glass is circular, and even when it is square.  
  In the embodiments of FlGS. 2, 5 and 6 a projection may beaffixed to one or the other of the rotatable members so that a desirable location may be restablished if an accidental displacement occurs. Alternatively, detents may be used to assure exact location and to prevent accidental displacement.  
  In summary, the combination of the pair of polarizing sheets with a field effect liquid crystal display panel where one of the polarizing sheets is rotatable makes it possible to vary the appearance of the display and to provide novel effects, thereby making timepieces incorporating such a construction relatively attractive.  
  It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.  
  It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.  
 What is claimed is:  
  1. In an electronic timepiece including a field effect liquid crystal panel for display of the time, the improvement comprising a liquid crystal display panel having inner and outer faces, an inner fixed plane-polarizer sheet proximate the inner face of said panel and an outer plane-polarizer sheet proximate the outer face of said panel, said outer sheet being mounted for manual rotation within its plane whereby the contrast of said liquid crystal display may be altered.  
  2. An electronic timepiece including a field effect liquid crystal panel for display of the time, as defined in claim 1, wherein said timepiece has an outer transparent crystal, said rotatable outer sheet is mounted between said crystal and said outer face and further comprising means for manually rotating said outer sheet from the exterior of said timepiece.  
  3. An electronic timepiece including a field effect liquid crystal panel for display of the time, as defined in claim 1, wherein said timepiece has an outer transparent-crystal and a manually rotatable bezel and said outer sheet is mounted in said rotatable bezel for rotation therewith cxteriorly of saidcrystal.  
  4. An electronic timepiece including a field effect liquid crystal panel for display of the time, as defined in claim 1, wherein said timepiece has a manually displaceable transparent outer crystal and said outer sheet is affixed to said displaceable crystal for displacement therewith.  
  5. An electronic timepiece including a field effect liquid crystal panel for display of the time, as defined in claim 4, wherein said outer sheet is affixed to the inner face of said crystal.  
  6. An electronic timepiece including a field effect liquid crystal panel for display of the time, as defined in claim 2, wherein said timepiece has a crystal and said outer sheet is mounted for manual rotation on said timepiece exteriorly&#39; of said crystal.