Liquid crystal display with central interconnections

A liquid crystal display adapted for a solid state analog timepiece has front and rear transparent substrates with radial transparent electrodes to represent hour, minute and second hands. The contact terminals connected to the electrodes are grouped in an array at the center of the front substrate. An elastomeric connector containing multiple discrete conductors extends through a center hole in the rear substrate to connect the array of contact terminals on the front substrate with a similar array of contact terminals on a printed circuit board behind the display. Liquid crystal material is sealed between the substrates both at the periphery of the display and around the central hole.

BACKGROUND OF THE INVENTION 
This invention relates to liquid crystal displays adapted for timepieces, 
especially solid state analog timepieces having radial "hands" to display 
the time. 
Conventional liquid crystal displays have front and rear transparent 
substrates with transparent electrodes or segments arranged to display 
information when actuated by signals from an electrical circuit. Liquid 
crystal displays of various types are well known in the art and, for 
example, may include liquid crystal material sealed between the 
substrates, and associated with one or more polarizers to provide the 
well-known twisted nematic, field effect, liquid crystal display. 
Conventional liquid crystal displays are arranged with the contact 
terminals on the periphery of the display, usually on the underside an 
over-hanging edge of the top substrate as seen in U.S. Pat. No. 
3,863,436--Schwarzschild, et al issued Feb. 4, 1975. Contact terminals 
have also been provided at the edges of the display as shown in U.S. Pat. 
No. 4,391,531--Yokota et al issued July 5, 1983. Both of these patents are 
assigned to the present assignee. 
Liquid crystal displays with radial "hands" representing mechanical hour, 
minute and second hands have been proposed as seen in U.S. Pat. No. 
3,540,209 to Zatsky, et al issued Nov. 17, 1970; and in British Patent 
Specification No. 1,472,260, these being merely exemplary. Timepieces 
using radial hand liquid crystal displays are sometimes called solid state 
analog or liquid crystal analog timepieces. 
When constructing a liquid crystal display for a timepiece with radial 
members, it is desirable to use as much of the outer part of the display 
surface as possible, so that the "hands" can extend as far as possible 
from the center for ease of readability. The conventional placement of 
contact terminals on the outside edges of the display, especially when 
using the technique requiring an overlapping edge on the top substrate, 
reduces the effective display area which is available for visible 
segments. It would also be desirable to have more flexibility at the outer 
periphery of the display to use round, octagonal, oval or other shapes of 
display than rectangular. 
Liquid crystal displays for solid state analog timepieces have been 
proposed in which the integrated circuit and quartz crystal were disposed 
on the underside of the upper display substrate. The proposed construction 
is described in Inter Electronique, dated Dec. 11, 1972, pages 33-36. Such 
an arrangement naturally leads to a very large central opening and 
difficult construction. 
It has also been suggested to provide a liquid crystal display for a 
digital timepiece combined with mechanical analog hands carried on a stem 
extending through a central hole in the display. Such an arrangement is 
shown in British Published Patent Application No. GB 2 084 764A--Maliska, 
published Apr. 15, 1982, assigned to the present assignee. 
Accordingly, one object of the present invention is to provide an improved 
liquid crystal display for a solid state analog timepiece which increases 
the availability of display area at the outer part of the display. 
Another object of the invention is to provide an improved liquid crystal 
display with improved means to connect the display to an external circuit 
which permits greater flexibility to choose the shape of the display.

SUMMARY OF THE INVENTION 
Briefly stated, the invention is practiced by providing a liquid crystal 
display having transparent radial segments on an upper substrate connected 
to an array of contact terminals in a central portion of the upper 
substrate. The array of terminals is accessible through a central hole in 
a second substrate also having transparent electrodes. Liquid crystal 
material is sealed between the substrates at the periphery and around the 
hole. An elastomeric connector having a plurality of discrete conductors 
embedded therein is adapted to provide contact between the array of 
contact terminals on the upper substrate and an array of aligned contact 
terminals on the printed circuit board. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1 of the drawing, a liquid crystal display shown 
generally as 1 is mounted on a printed circuit board, shown generally as 
2. The overall shape of the printed circuit board 2 is not material to the 
present invention, and it can be larger than, smaller than or the same 
size as display 1 in order to suit a particular application. Printed 
circuit board 2 serves to mount an integrated circuit 3 for timekeeping 
and to actuate the display. The integrated circuit 3 has output pins for 
connecting its LCD driving circuit to display 1 over conductive tracks 4 
on the printed circuit board. Display 1 displays the time, in accordance 
with signals received from integrated circuit 3 in analog timekeeping 
fashion by means of an hour "hand" 5, a minute "hand" 6 and a seconds 
marker 7, in a manner well known in the art. 
Display 2, as more clearly seen in FIG. 2 comprises an upper glass 
substrate 8, and a lower glass substrate 9 with a liquid crystal material 
sealed between the substrates. An upper polarizer sheet 10 and a lower 
polarizer sheet 11 are disposed above and below substrate 8 and 9 
respectively. A reflector 12 is disposed below the polarizer 11. In 
accordance with the present invention, the lower members, substrate 9, 
polarizer 11 and reflector 12 are pierced at the center with a hole 13, so 
as to expose an array 14 of contact terminals on the underside of upper 
substrate 8. 
Referring to FIG. 3 of the drawing, substrate 8 is shown to have an 
octagonal outer perimeter with radial transparent electrodes 15. Each 
electrode 15 is connected at its inner end to a contact terminal 15A, 
which is part of array 14. 
In order to make crossover connections from the other substrate, crossover 
connection terminals such as 16 located between electrodes 15 are each 
connected to a contact terminal 16a in the central array 14 of terminals. 
Reference to FIG. 4 shows that the lower substrate 9 is provided with a 
pair of circular concentric transparent electrodes 17, 18 around the 
center hole 13. Crossover connections 18a, 17a are arranged to match up 
with the crossover connections 16 on the upper substrate when the two 
plates are aligned. In this way, in a manner known in the art, the 
electrodes 17 and 18 on substrate 9 are connected to the central array 14 
of terminals on substrate 8. 
Referring to FIG. 5, the printed circuit board 2 has an array 19 of 
conductive dots 19a serve as contact terminals, which are individually 
connected by leads or conductive tracks 4 on the printed circuit board to 
the integrated circuit 3. The array 19 of contact terminals on the printed 
circuit board is precisely arranged to match the array 14 on the under 
side of upper substrate 8. 
FIG. 6 shows a connector 20 which comprises an elastomeric insulating 
substance 20a having a plurality of embedded discrete conductors 20b. Such 
an elastomeric material with parallel discrete conductors is commercially 
available in sheets, one source being Shin-etsu Polymer America, Inc. The 
connector 20 is cut from the sheet in a circular shape so that it will fit 
hole 13 and, when the display is aligned so that the array 14 is precisely 
matched with array 19 on the board, each of the contact terminals on the 
upper substrate of the display will be connected with a corresponding 
contact terminal on the printed circuit board. The elastomer 20a is 
compressible to permit good terminal contact. Suitable means (not shown) 
for positioning and locating the display with respect to the printed 
circuit board will be apparent to those skilled in the art. It should be 
apparent that the array of terminals 19 should be precisely a mirror image 
of the array 14. The number and arrangement of discrete conductors 20b in 
the connector 20 must be selected to interconnect the individual contact 
terminals, which are spaced from and aligned with one another in 
respective pairs, ie. a terminal in one array with its respective 
counterpart in the other array. For some applications, one discrete 
conductor per terminal will suffice. However the density of discrete 
conductors may be much greater, for example 3 conductors per contact 
terminal. 
Application of an electrical potential between appropriate radial segments 
on one substrate and the concentric segments on the other substrate 
permits showing hours, minutes and seconds, as described more fully in the 
aforementioned Zatsky patent or British Patent Specification No. 
1,472,260, which are incorporated herein by reference. While there has 
been disclosed what is considered to be the preferred embodiment of the 
invention, other modifictions will occur with those skilled in the art, 
and it is desired to include in the appended claims all such modifications 
as fall within the true spirit and scope of the invention.