Electro-optical display device

An electro-optical display device comprises electro-optical material sandwiched between a pair of substrates each having formed thereon electrodes. The electrodes on one substrate comprise a segment display electrode part comprised of a plurality of seven-segment electrodes, and a dot matrix display electrode part comprised of a plurality of parallel linear electrodes. The electrodes on the other substrate comprise a complementary counter electrode part corresponding to the segment display electrode part, and a complementary counter electrode part comprised of a plurality of parallel linear electrodes perpendicularly intersecting the linear electrodes formed on the other substrate. The electrode leads which are connected to some of the seven-segment electrodes also comprise some of the linear electrodes of the dot matrix display thereby reducing the overall number of separate electrodes and enabling construction of a more simple display device.

BACKGROUND OF THE INVENTION 
This invention relates to an electro-optical display device having both a 
segment display and a dot matrix display employing electro-optical 
material, e.g., liquid crystal, PLZT or single crystal material which 
exhibits the electro-optical effect such as gadolinium molybdate. 
Recently, a micro calculator, a watch or the like having a digital display 
have become more popular due to the development of the electro-optical 
material, e.g., liquid crystal. On the display device of the micro 
calculator or watch, an electrode structure of the 7-segment type, which 
forms the numeral letter 8, is generally used for displaying numerals and 
letters. Further a dot matrix display device using liquid crystal has been 
developed for the display part of the terminal equipment of a computer. An 
advantage according to the segment display is that it is able to display 
numeral letters or simple letters. The dot matrix display is 
disadvantageous in that it needs many electrodes for display. The dot 
matrix display, however, has an advantage in that it can provide almost 
all displays, e.g., numeral letters or letters and give fine numeral 
letter or letter displays. Furthermore, by providing a memory circuit and 
suitably selecting a decoder, it is possible to easily change the letter 
for display. 
On the liquid crystal display for a watch, the segment display of the 
7-segment type which forms the figure 8 is used for displaying the 
information of time. In a timepiece, the display of hour, minute, second, 
date, year or the like by numeral letters using the segment display of the 
7-segment type can be readily obtained. However, displaying letters, e.g., 
7 days, by the segment display has disadvantages which makes the letter 
large in part and makes the letter difficult to read. Using the display, 
it is almost impossible to change English letters, Japanese letters or the 
like to another letter. 
It is an object of the invention to overcome the foregoing disadvantages. 
It is another object of the invention to provide an electro-optical 
display device which has fine display letters and a means to change easily 
the letter, e.g., Japanese letters or English letters. It is another 
object of the invention to provide an electro-optical display device which 
has a simple structure and has merits of both the dot matrix display and 
the segment display.

DETAILED DESCRIPTION OF INVENTION 
FIG. 1 shows an embodiment of the invention in the case of using liquid 
crystal as an electro-optical material. 
On the inner surface of a first transparent substrate 1, transparent 
display electrodes, which comprise a segment display electrode part 3 and 
a dot matrix display electrode part 5, are formed, as shown in FIG. 1. A 
linear polarizer 8 is attached on the upper surface of the transparent 
substrate 1. On the inner surface of a second transparent substrate 2, 
transparent counter electrodes, which comprise a counter electrode part 4 
for the segment display electrode part 3 and a counter electrode part 6 
for the dot matrix disply electrode part 5, are formed. On the lower 
surface of the second transparent substrate 2 is provided a linear 
polarizer 9 (the polarizing axis of which is perpendicular to that of said 
linear polarizer 8). On the lower surface of the polarizer 9, a reflector 
10 is attached. Liquid crystal 7 is filled in the cell formed by the first 
transparent substrate 1, the second transparent substrate 2 and a spacer 
11 which forms a gap between those substrates and is also used as a 
bonding agent. 
In case of needing to use different kinds of liquid crystal material for 
the segment display and dot matrix display, respectively, it is necessary 
to divide the cell into two parts by a sealing member 12 (as shown in FIG. 
1) and to fill predetermined liquid crystal in each cell respectively. 
In the above embodiment, both of the electro-optical materials in the two 
cells are liquid crystals. However, in the case of at least one of those 
being a solid display element, e.g., PLZT, it is not necessary to provide 
the sealing member 12 separating the cells. 
In the case of the electro-optical material being only a solid display 
element, it is possible to attach electrodes on the electro-optical 
material directly and the first and second transparent substrates become 
useless. 
In FIG. 1, the alignment treatments on the segment display electrode part 3 
and the dot matrix display electrode part 5 are performed in the same 
direction to that of the polarizing axis of the polarizer 8. The alignment 
treatments on the opposed electrodes 4 and 6 are respectively performed in 
the right-angle direction to the treatment direction of the display 
electrode parts 3 and 5. Therefore, the liquid crystal 7 becomes twisted 
about 90 degrees from the electrode parts for displays 3 and 5 to the 
opposite electrode parts 4 and 6. 
If desired, the liquid crystal of the segment display part and that of the 
dot matrix display part may be given different orientation to each other. 
For example, if the liquid crystal of the segment display part is given a 
parallel orientation and that of the matrix display part is given a 
right-angle orientation to that of the opposite surface, i.e., a twisted 
type of orientation, and the direction of polarization of the polarizer in 
each part is selected properly, the segment display part gives a white 
display on a black ground and the matrix display part gives a black 
display on a white ground. 
It is possible to design a variety of displays by using different kinds of 
electro-optical materials, e.g., a liquid crystal and PLZT, or a nematic 
liquid crystal exhibiting homogeneous orientation and a nematic liquid 
crystal exhibiting homeotropic orientation. 
It is possible to not use a field-effect type of liquid crystal and to use 
a dynamic scattering type of liquid crystal. In this case, it is desirable 
to make the liquid crystal orient perpendicularly to the surface of the 
substrate for improvement of contrast. The polarizers 8 and 9 as shown in 
FIG. 1 are not necessary and the opposite electrodes 4 and 6 may be made 
from metal. 
FIG. 2 and FIG. 3 show an embodiment of the transparent substrate 1 and the 
second transparent substrate 2 respectively. 
In FIG. 2, on the lower half part of the first transparent substrate 1, 
segment display electrodes 201, 202, . . . , . . . 222, leads 401, 402, . 
. . , 422 connected to the segment electrodes respectively and an external 
connecting terminal 13 are provided. 
On the upper half part, many parallel linear electrodes 301, 302, . . . , 
330 for the dot matrix display are provided. On the upper right hand, 
external connecting terminals 101, 102, . . . , for the counter electrode 
6 for the dot matrix display are provided. 
On the lower half part of the second transparent substrate 2, a counter 
electrode 4 for the segment display corresponding to the segment display 
electrode is provided as shown in FIG. 3. 
On the upper half part, many parallel linear counter electrodes 501, 502, . 
. . , 512 for the dot matrix display are formed perpendicularly to the 
electrodes 301, 302, . . . , 330 for dot matrix display. These counter 
electrodes 501, 502, . . . , 512 for the dot matrix display are connected 
to the external connecting terminals 101, 102, . . . respectively through 
conductive materials, e.g., silver paste, indium or lead, which is 
provided on the side of the spacer 11. The lead terminal 4a of the counter 
electrode 4 for the segment display is similarly connected to the external 
connecting terminal 13 through a conductive material. Each electrode is 
connected to an external driving circuit through the leads 401, 402, . . . 
, 416 and 417, the terminals of the electrodes 301, 302, . . . , 330 and 
the external connecting terminal 13 and 101, 102, . . . respectively. 
The counter electrode 4 for the segment display in FIG. 3 is common to each 
digit in order to drive statically. In order to perform multiplex drive, 
it may divide the counter electrode to every digit or every two digits. If 
the dot matrix display is performed by multiplex drive, it is possible to 
obtain various kinds of display, e.g., a display of numeral letters or a 
display of letters. 
FIG. 4 and FIG. 5 show another embodiment of the transparent electrodes 
formed on the first and second transparent substrates respectively. 
On the transparent substrate 1 as shown in FIG. 4, segment display 
electrodes 701, 702, . . . , 722, dot matrix display electrodes 801, 802, 
. . . , 829, external connecting terminals 601, 602, . . . for the dot 
matrix display counter electrodes and external connecting terminals 14, 15 
. . . , 18 for the segment display counter electrodes are formed, 
similarly to the embodiment shown in FIG. 2. What differs from the 
embodiment of FIG. 2 is the fact that the leads of the segment display 
electrodes 701, 702, . . . , 722 also serve as leads for some of the dot 
matrix display electrodes 801, 802, . . . , 813, 820, . . . , 829 
respectively. By this manner, it is possible to reduce the number of lead 
terminals in comparison with the embodiment as shown in FIG. 2 and to 
obtain a display device having a very simple structure. In this case, the 
number of the dot matrix display electrodes 801, 802, . . . , 829 may be 
the same as that of the segment display electrodes 701, 702, . . . , 722. 
However, it is possible to add only dot matrix electrodes in order to 
increase the number of dots, as shown by the dot matrix display electrodes 
814, 815, . . . , 819 in FIG. 4. 
On the transparent substrate 2 as shown in FIG. 5, dot matrix display 
counter electrodes 901, 902, . . . , 908 and segment display counter 
electrodes 41, 42, . . . , 45 are formed, similarly to the embodiment as 
shown in FIG. 3. In this figure, the segment display counter electrodes 
41, 42, . . . , 45 are divided to every digit in order to perform not only 
dot matrix display but also segment display by multiplex drive. The 
segment display counter electrodes 41, 42, . . . , and 45 may be common to 
every digit similarly to that shown in FIG. 3, however, in this case, the 
display device has the disadvantage that the drive circuit or the like is 
more complicated. For that reason, in the case of serving both as the 
leads of the segment display electrodes and the dot matrix display 
electrodes, it is desirable to divide the dot matrix display counter 
electrode to every one digit as shown in FIG. 5, to every two digits or to 
every three digits. 
FIG. 6 shows an embodiment which displays hours 18 and minutes 19 by a 
segment display and day 20 and date 21 by a dot matrix display by means of 
the display device of the invention. It is easy to change the language of 
the day, e.g., from English to Japanese, French or German by changing an 
external driving circuit or a memory circuit. 
As mentioned above, according to the invention, it is possible to provide 
an electro-optical display device having the advantage of a to segment 
display in that it may display time information, e.g., hour, minute or 
second, by a small number of elements and the advantage of a dot matrix 
display in that it may display finely letters, e.g., day, and may change 
to various languages easily.