JPH0154717B2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a liquid crystal display device.

BACKGROUND ART Recently, two-layer type liquid crystal display devices have been commercialized, which include two upper and lower liquid crystal display layers and which display two types of display by switching between the two display layers.

However, this two-layer liquid crystal display device has only one
Although one display device can display the same amount of information as two display devices, it has the disadvantage that it is quite thick because its structure is essentially a stack of two liquid crystal display cells. There is.

In order to solve these drawbacks, two layers of electrodes are formed on each of the inner surfaces of a pair of opposing substrates via an insulating film, and different patterns are displayed by switching the signals applied to each electrode. A liquid crystal display device with two-layer electrodes has been proposed.
This liquid crystal display device includes a lower layer electrode and an insulating film covering the lower layer electrode formed on at least one of the opposing surfaces of a pair of substrates facing each other with a liquid crystal interposed therebetween, and an upper layer formed on the insulating film. Electrodes are formed.

However, in this case, an insulating layer is formed on the lower electrode, and since this insulating layer is a dielectric, the actual voltage applied to the liquid crystal is lower than the voltage applied to the lower electrode. The voltage decreases by the amount of voltage between the insulating films that depends on the dielectric constant of the film and its thickness. In comparison, since there is no insulating film on the upper surface of the upper layer electrode, the voltage applied to the upper layer electrode is directly applied to the liquid crystal. Therefore, the voltage applied to the liquid crystal by the lower electrode is different from the voltage applied to the liquid crystal by the upper electrode, resulting in a disadvantage that the displayed pattern becomes uneven.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a liquid crystal display device having a two-layer electrode structure without display unevenness.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 and 2 are a pair of upper and lower transparent substrates (for example, glass plates);
The substrates 2 are adhesively polymerized via a frame-shaped sealing material 3, and the gap between the two substrates 1 and 2 is filled with liquid crystal (not shown). 4, 4 are both the substrates 1,
2, for example, the inner surface (lower surface) of the upper substrate 1
The static driving segment electrodes 4, 4 are formed in a pattern as shown in FIG. 2, for example. 5 is the static driving segment electrode 4 formed on the inner surface of the upper substrate 1;
4 and a transparent insulating layer covering the leads 4a and 4a, 6 and 7 a plurality of common electrodes for dynamic driving formed in multiple layers on the insulating layer 5, and 8 a common electrode between the common electrodes 6 and 7 of each layer. The dynamic drive common electrodes 6 and 7 have a pattern as shown in FIG. 2, for example. 6a and 7a are these common electrodes 6 and 7
is the lead. Note that this embodiment shows one driven at 1/2 duty. Further, the dynamic drive common electrodes 6, 7 are formed excluding the portions that overlap with the effective areas of the respective static drive segment electrodes 4, 4. In this embodiment, the dynamic drive common electrodes 6, 7 are are formed to be slightly larger than the actual display pattern, and the dynamic driving common electrodes 6, 7 have a missing portion 16 in a shape that matches the outline of the actual display pattern in the portion overlapping with the static driving segment electrodes 4, 4. 17. In other words, the dynamic drive common electrodes 6 and 7 also serve as shielding electrodes that define the effective areas of the static drive segment electrodes 4 and 4, and the static segment signals to the static drive segment electrodes 4 and 4 are used as shielding electrodes. If a shielding signal having a potential difference lower than the threshold voltage of the liquid crystal with respect to the potential of the static common signal is applied to the dynamic drive common electrodes 6 and 7 when , the static drive segment electrodes 4 and 4 are actually Even if the display pattern is larger than the display pattern, a voltage higher than the threshold voltage acts on the liquid crystal only in the portion corresponding to the actual display pattern (the portion corresponding to the missing portions 16 and 17 of the dynamic drive common electrodes 6 and 7). I will do it. That is, the effective area of the static driving segment electrodes 4 corresponds to the actual pattern. In this embodiment, the static driving segment electrodes 4, 4 are formed larger than the actual display pattern because the missing parts 16, 17 formed in the dynamic driving common electrodes 6, 7 are formed in the static driving common electrodes 6, 7. This is to facilitate positioning with respect to the driving segment electrodes 4, 4. Furthermore, in this embodiment, the plurality of dynamic drive common electrodes 6 and 7 are formed in a multilayer structure with an insulating layer interposed between them when the respective dynamic drive common electrodes 6 and 7 are formed on the same surface. Since it is necessary to provide an insulating gap between the edges of the adjacent common electrodes 6, 6, unnecessary parts (other than the effective area) of the static drive segment electrodes 4, 4 and the leads 4a must be left in this gap. , 4a, which are located opposite to each other, cannot be shielded.If the dynamic drive common electrodes 6, 7 are formed in multiple layers with the insulating layer 8 in between as described above, each common electrode 6 ，
7 can be formed by wrapping their edges together as shown in FIGS. 1 and 2, so that the unnecessary parts of the static drive segment electrodes 4, 4 and the leads 4a, 4a can be completely shielded. can do. In this case, the upper layer common electrode 7
It also serves as a shielding electrode that defines the effective area of the common electrode 6 in the lower layer.

On the other hand, 9, 9 is the other substrate, that is, the lower substrate 2
A plurality of groups of dynamic drive segment electrodes are formed on the inner surface (upper surface) of the dynamic drive segment electrodes 9, 9, which have a pattern as shown in FIG. 3, for example. In addition,
The segment electrodes 9, 9 for dynamic driving are connected in common for each group, with two pieces being set as one group, and the common electrodes 6, 7 for dynamic driving formed on the upper substrate 1 are connected to one of the common electrodes. 6 is formed to face one segment electrode 9 of each group, and the other common electrode 7 is formed to face the other segment electrode 9 of each group. 10 is a transparent insulating layer that covers the dynamic drive segment electrodes 9, 9 formed on the inner surface of the lower electrode substrate 2 and their leads 9a, 9a; 11 is a static drive segment electrode formed on the surface of the insulating layer 10; This static drive common electrode 11 is formed except for the portion that overlaps with the effective area (portion corresponding to the actual display pattern) of each of the dynamic drive segment electrodes 9, 9, as shown in FIG. has been done. 1
1a is a lead of the common electrode 11. 2
1 and 21 are the static drive common electrode 1
This is a missing portion having a shape that matches the outline of the actual pattern (display pattern by dynamic driving) formed in 1. In this embodiment, the dynamic drive segment electrodes 9, 9 are also formed to be slightly larger than the actual display pattern, and the missing portions 11a, 11a formed in the static drive common electrode 11 are replaced by the dynamic drive segments. It can be easily aligned with the electrodes 9, 9, and therefore the static drive common electrode 11 also serves as a shielding electrode that defines the effective area of the dynamic drive segment electrodes 9, 9. Note that each of the electrodes 4, 6, 7,
8 and 11 are made of transparent electrode material such as indium oxide. Further, in this embodiment, the static drive segment electrodes 4, 4 and the dynamic drive segment electrodes 9, 9 are connected to the substrates 1, 2.
Although these segment electrodes 4 and 9 are formed directly on the surfaces of the substrates 1 and 2, they may be formed on transparent insulating layers formed on the surfaces of the substrates 1 and 2, and if it is necessary to further form a liquid crystal alignment film. This alignment film may be formed on the dynamic drive common electrode 7 and the static drive common electrode 11 on the surface layer.

Further, of the static drive segment electrodes 4, 4, those located at positions facing the dynamic drive segment electrodes 9, 9 are the missing portions 1 of the dynamic drive common electrodes 6, 7.
The dynamic driving common electrodes 6, 7 and the static driving segment electrodes 4, 4 serve as a common electrode to supplement the dynamic driving segment electrodes 9, 9.
A complete common electrode is now formed for each. This also applies to the common electrodes for the static drive segment electrodes 4, 4, and the dynamic drive segment electrodes 9, 9 are connected to the static drive common electrode 1.
By using the common electrode to supplement the missing portion 21 of the static drive segment electrode 4, a complete common electrode for the static drive segment electrodes 4, 4 is formed.

In addition, in FIGS. 1 and 2, 1a, 1a
are terminal arrangement parts formed on both sides of the upper substrate 1, and these terminal arrangement parts 1a, 1a have respective static drive segment electrodes 4, formed on the upper substrate 1 as shown in FIG. 4 lead terminal 4
Lead terminals 6b, 7b of the dynamic drive common electrodes 6, 7 are formed, and the dynamic drive segment electrodes 9, 9 of each group on the lower substrate 2 side are lined up with these terminals 4b, 6b, 7b. Lead terminals 9b, 9b, and 11b corresponding to the static drive common electrode 10 are formed, and among these lead terminals, the lead terminal 6 of each common electrode 6, 7, and 11 is formed.
The upper surfaces of b, 7b and 11b are covered with resistors 12 and 12 having a predetermined resistance value. Further, in FIG. 3, reference numerals 9c, 9c and 11c are transfer terminals of the dynamic drive segment electrodes 9, 9 and the static drive common electrode 11 of each group formed on the lower substrate 2, and these transfer terminals 9c, 9c and 1
1c is connected to each of the lead terminals 9b, 9b, and 11b on the upper substrate 1 side via a transfer member (not shown) that penetrates the sealing material 3.

Next, the display operation of the liquid crystal display device of this example will be explained.

This liquid crystal display device performs two types of evaluation: display by static drive and display by dynamic drive. First, the display operation by static drive will be explained. In this case, the lead terminal 11b of the static drive common electrode 11 formed on the lower substrate 2 and all the static drive segment electrodes 4, The same static common signal is commonly applied to the lead terminals 9b, 9b of the dynamic drive segment electrodes 9, 9, respectively, and the lead terminals 4b, 4 of the static drive segment electrodes 4, 4 formed on the upper substrate 1 are applied in common.
A static segment signal is applied to b, and all common electrodes 6 and 7 for dynamic drive are
A shielding signal having a potential difference smaller than the threshold voltage of the liquid crystal with respect to the static common signal is applied to the lead terminals 6b and 7b. Note that this shielding signal may be at the same potential as the static common signal, but if the potential difference between the static segment signal and the shielding signal is large, the difference between the static drive segment electrodes 4, 4 and the dynamic drive common electrodes 6, 7 Since a large-capacity capacitor is formed in the signal line, power loss increases, so it is desirable that the shielding signal has a potential difference of about 1/2 of the threshold voltage with respect to the static common signal. Therefore, when a static common signal is applied to the static drive common electrode 11 and the dynamic drive segment electrodes 9, 9 that compensate for the missing portions 21, 21, all of these static drive segment electrodes 4, 4
As a result, a display pattern corresponding to the shape of the static drive segment electrodes 4, 4 to which the static segment signal is applied is displayed. Further, in this case, the dynamic drive common electrode 6,
Since the above-mentioned shielding signal is applied to 7, the unnecessary parts of the static drive segment electrodes 4, 4 (the parts overlapping with the dynamic drive common electrodes 6, 7) and their leads 4
The electric field between a, 4a and the lower substrate 2 is canceled by the dynamic driving common electrodes 6, 7, and therefore the pattern actually displayed is the effective one of the static driving segment electrodes 4, 4. The pattern corresponds to the shape of the display area.

In addition, when displaying by dynamic driving, the lead terminals 6b of the common electrodes 6 and 7 for dynamic driving formed on the upper substrate 1,
Dynamic common signals whose phases are shifted by 180 degrees from each other are applied to the terminals 7b, and the missing portions 16 and 1 of one of the dynamic drive common electrodes 6 are applied.
The same common signal as that applied to one of the dynamic drive common electrodes 6 is applied to the lead terminals 4b, 4b of the static drive segment electrodes 4, 4 that complement the static drive segment electrodes 6, and the other dynamic drive common electrode 7 The same common signal as that applied to the other dynamic drive common electrode 7 is applied to the lead terminals 4b, 4b of the static drive segment electrodes 4, 4, which compensate for the missing parts 17, 17. Note that the dynamic common signal is applied to the static drive segment electrodes 4, 4 by the dynamic drive segment electrodes 8, 4.
It is only necessary to perform this on the electrodes 4, 4 located opposite to the electrode 8. On the other hand, a dynamic segment signal is applied to the lead terminals 9b, 9b of the segment electrodes 9, 9 for dynamic driving formed on the lower substrate 2, and the lead terminal 11b of the common electrode 11 for static driving is applied to the lead terminal 11b of the static driving common electrode 11. A shielding signal having a potential difference smaller than the threshold voltage of the liquid crystal (preferably a potential difference of about 1/2 of the threshold voltage) is applied to the common signal. Therefore, in the case of dynamic drive, the common electrodes 6, 7 for dynamic drive and the segment electrodes 4, 4 for static drive that compensate for the missing parts 16, 17 act as common electrodes for the segment electrodes 9, 9 for dynamic drive. As a result, a display pattern corresponding to the shape of the dynamic driving segment electrodes 9, 9 to which the dynamic segment signal is applied is displayed. Also in this case, since the potential shielding signal as described above is applied to the static drive common electrode 11, the dynamic drive segment electrodes 9,
9 and the electric field between the leads 9a, 9a and the upper substrate 1 are canceled by the static drive common electrode 11, so that the pattern actually displayed is the dynamic drive segment electrode. The pattern corresponds to the shape of the effective area 9, 9.

That is, in principle, the liquid crystal display device of this embodiment has a plurality of static drive segment electrodes 4, 4 on the inner surface of one substrate 1 of a pair of substrates 1, 2 which are arranged opposite to each other with a liquid crystal interposed therebetween. A plurality of common electrodes 6, 7 for dynamic driving are formed, and a plurality of groups of segment electrodes 9, 9 for dynamic driving and a common electrode 11 for static driving are formed on the inner surface of the other substrate 2, so that static driving can be performed in one display layer. Two types of display are performed: display by drive and display by dynamic drive. In the liquid crystal display device of this embodiment, the dynamic drive common electrodes 6 and 7 and the static drive common electrode 11 are replaced by the static drive segment electrodes 4 and 7, respectively.
4 and dynamic drive segment electrodes 9,9
These common electrodes 6, 7 and 11 are formed except for the effective areas of the respective segment electrodes 4, 4 and 9, 9, and the common electrodes 6, 7 and 11 are Since the missing parts 16, 17 and 21 are compensated for by using the segment electrodes 4, 4 and 9, 9 as common electrodes, both static drive and dynamic drive display can be performed. , there is no unnecessary display of lead shapes, etc., and the pattern is displayed in a perfect form without any chipping. In this embodiment, the static drive segment electrodes 4, 4 and the dynamic drive segment electrodes 9, 9 are formed slightly larger than the actual display pattern; The same shape as the actual display pattern may be used, and the entire area may be used as an effective area, in which case each segment electrode 4, 4 and 9,
The edges of the missing portions 16, 17 and 21 of the respective common electrodes 6, 7 and 11 may be aligned with the periphery of the common electrodes 9. This also applies to the mutual relationship between the dynamic drive common electrodes 6 and 7.

By the way, in this liquid crystal display device, the missing portions 16, 17 of the respective common electrodes 6, 7, and 11 are
Each segment electrode 4, 4 and 9, 9 used as a common electrode to supplement the insulating layers 5, 8
and 10, the voltage applied to each of the segment electrodes 4, 4 and 9, 9 causes a voltage drop of an amount corresponding to the layer thickness of the insulating layers 5, 8, and 10, and the liquid crystal is It will work. Therefore,
For example, if we consider the case where the same common signal is applied to the static drive common electrode 11 and the dynamic drive segment electrodes 9, 9 that compensate for the missing portion 21, the potential on the surface of the common electrode 11 and the segment electrode 9 , 9 are at the same potential, the areas corresponding to the segment electrodes 9 and the common electrode 1 not covered with the insulating layer
There will be a difference in the voltage applied to the liquid crystal in the area corresponding to No. 1, and this will cause unevenness within the same display pattern. This is the dynamic drive common electrodes 6 and 7 and their missing part 1.
The same holds true when a common signal is applied to the static drive segment electrodes 4, 4 which complement the electrodes 6, 17. Note that since one dynamic drive common electrode 6 is covered with an insulating layer 8, the voltage applied to this common electrode 6 causes a voltage drop that acts on the liquid crystal, but the amount of voltage drop is greater than this voltage drop. Since the amount of voltage drop in the area corresponding to the static drive segment electrodes 4, 4 is large, the display pattern will be uneven in the same way as described above.

Therefore, in this embodiment, resistors 12 and 1 having a predetermined resistance value are disposed on the lead terminals 6b, 7b and 11b of the respective common electrodes 6, 7 and 11.
2, and the voltage applied to each of the common electrodes 6, 7, and 11 is lowered by the resistors 12, 12, and is thus connected to the drive circuit via an interconnector or the like. By forming resistors 12, 12 on the lead terminals, the respective dynamic drive common electrodes 6, 7 and their missing portions 1 can be removed.
Even if the same common signal is applied to the lead terminals 6b, 7b, 4b of the static drive segment electrodes 4, 4 which complement the electrodes 6, 17,
It is possible to equalize all the voltages applied to the liquid crystal in the areas corresponding to 7 and 4 to prevent unevenness in the display pattern, and also to compensate for the static drive common electrode 11 and its missing portion 21. Lead terminal 1 with segment electrodes 9, 9 for
Even if the same common signal is applied to electrodes 1b and 9b, it is possible to equalize the voltages applied to the liquid crystal in the area facing each electrode 11 and 9, thereby preventing unevenness in the display pattern. That is, each lead terminal 6b, 7b of each common electrode 6, 7, and 11
The resistance value of the resistors 12, 12 formed on the lead terminal 11b of the static drive common electrode 11 is determined according to the amount of voltage drop in the insulating layers 5, 8, and 10. The resistor 12 to be formed may have a resistance value that produces a voltage drop commensurate with the voltage drop in the insulating layer 10 on the dynamic drive segment electrodes 9, 9, and one of the dynamic drive common electrodes 6. The resistor 12 formed on the lead terminal 6b calculates the amount of voltage drop in the insulating layer 8 on the common electrode 6 from the amount of voltage drop in the two insulating layers 5 and 8 on the static drive segment electrodes 4 and 4. The resistor 12 formed on the lead terminal 7b of the other dynamic drive common electrode 7 has a resistance value that causes a voltage drop commensurate with the subtracted value. It is sufficient if the resistance value causes a voltage drop commensurate with the amount. Further, the resistor 1
2 and 12 may be formed of a dielectric material such as SiO ₂ , and since the resistance value thereof is determined by the layer thickness of the dielectric material, the resistance value can be set arbitrarily. Note that the resistors 12, 12 may be formed of a resistor paste.

Furthermore, in the above embodiment, the resistors 12, 12 are formed on the lead terminals 6b, 7b, and 11b of the respective common electrodes 6, 7, and 11;
2 and 12 are each common electrode 6, as shown in FIG.
7 and 11 and their lead terminals 6b, 7b and 11
Leads 6a, 7a and 1 which are electrically connected to
1a (in this case, the resistors 12, 12 may be formed of resistive paste),
Furthermore, the resistor 12 that lowers the voltage applied to the common electrode 11 on the lower substrate 2 side may also be a transfer member.

In the above embodiment, the dynamic drive common electrodes 6 and 7 are formed in multiple layers, but the dynamic drive common electrodes 6 and 7 may be formed adjacent to each other on the same surface. It is not limited to /2 duty. Further, in the above embodiment, the display is performed by static drive and dynamic drive, but this liquid crystal display device has a plurality of segment electrodes for static drive formed on both substrates 1 and 2, respectively. It is also possible to perform two types of display by static drive, in which a static drive segment electrode and a static drive common electrode facing each other are formed. Two types of display may be performed by dynamic driving, in which a plurality of common electrodes for dynamic driving are formed opposite to segment electrodes for dynamic driving on the other substrate.

Note that this liquid crystal display device may be of a twisted nematic type, a guest-host type, or any other type.

Since the liquid crystal display device of the present invention is as described above, one display layer can switch between two types of display, and therefore one display device can display two types of display. However, its thickness can be reduced, and since a resistor with a predetermined resistance value is interposed in the path that supplies drive signals to each common electrode, it is possible to insulate the segment electrodes that are also used as common electrodes. Although the common electrode is formed on the common electrode, the voltages applied to the liquid crystal in the area corresponding to the common electrode and the area corresponding to the segment electrode are made approximately equal, so that there is no unevenness. A good display can be obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view showing one embodiment of the present invention, FIGS. 2 and 3 are a plan view of an upper substrate and a plan view of a lower substrate, and FIG. 4 is a plan view of another embodiment of the invention. FIG. 1, 2...Substrate, 4,9...Segment electrode, 5,
8, 10... Insulating layer, 6, 7, 11... Common electrode,
6a, 7a, 11a...Lead, 6b, 7b, 11
b...Lead terminal, 12...Resistor.

Claims (1)

[Claims] 1. A plurality of segment electrodes, an insulating layer covering the plurality of segment electrodes, and an opposing substrate on each of opposing surfaces of a pair of substrates that are arranged opposite to each other with a liquid crystal interposed therebetween. Common electrodes facing the plurality of upper segment electrodes and stacked on the insulating layer are sequentially formed, and the common electrode corresponds to a display pattern of the segment electrodes on the substrate on which the common electrodes are formed. In the path for supplying the drive signal to the common electrode, the voltage applied to the liquid crystal is transmitted through the insulating film covering the segment electrodes formed below the common electrode. A liquid crystal display device characterized in that a resistor is interposed to cause a voltage drop corresponding to the voltage to be lowered. 2. The liquid crystal display device according to claim 1, wherein the resistor is formed on a lead terminal of the common electrode. 3. The liquid crystal display device according to claim 1, wherein the resistor is provided in a lead that electrically connects the common electrode and its lead terminal.