JP3137883B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device having a non-linear resistance two-terminal element.

[0002]

2. Description of the Related Art In a conventional general reflection type liquid crystal display device using a non-linear resistance two-terminal element, a plan view of a substrate on which a non-linear resistance two-terminal element is formed among a pair of substrates provided in a liquid crystal panel is shown. As shown in FIG. In addition, FIG.
FIG. 6 shows a cross-sectional view taken along line -C ′.

Referring to FIGS. 5 and 6, a scanning signal line 101, a semiconductor layer 102, and an insulating film layer 103 are formed on a glass substrate 100 on which a nonlinear resistance two-terminal element 106 is formed.
Then, the pixel electrode 104 is formed. Scanning signal line 101
Are arranged in parallel with each other, and each scanning signal line 101 has a connection terminal portion (not shown) with a scanning line driving driver. The semiconductor layer 102 is formed on the entire surface of the substrate except for the connection terminal portion. The insulating film layer 103
The scanning signal line 10 is formed on the semiconductor layer 102 and
Through holes 105 are respectively formed at predetermined positions on the optical disk 1. A large number of pixel electrodes 104 are arranged between the adjacent scanning signal lines 101, and each pixel electrode 104 covers a through hole 105.

The nonlinear resistance two-terminal element 106 is located at each through hole 105 and has a structure of lower metal-semiconductor-upper metal. That is, the scanning signal line 101 is a lower metal, the semiconductor layer 102 is a semiconductor, and the pixel electrode 10
4 functions as an upper metal.

[0005]

However, the above-mentioned conventional structure has the following problems.

The characteristics of each nonlinear resistance two-terminal element 106 are as follows:
It varies greatly depending on the size and shape of the formed through hole 105. On the other hand, it is difficult to form the through hole 105 having the same size and shape over the entire substrate. This is because, for example, a photosensitive resin is used for the insulating film layer 103 and the through holes 105 are formed by photolithography.
This is because the insulating film layer 103 does not have a uniform film thickness over the entire substrate, and irradiation unevenness in the exposure step and development unevenness in the development step cannot be avoided.

Therefore, the nonlinear resistance two-terminal element 106
Are not the same over the entire substrate. As a result, even when the same voltage is applied to each pixel, the voltage actually applied to the liquid crystal is different, and display unevenness occurs.

Therefore, Japanese Patent Application Laid-Open No. Sho 64-33532 discloses
JP-A-2-33191 and JP-A-3-2799
No. 26 proposes a liquid crystal display device in which a plurality of non-linear resistance two-terminal elements are arranged in each pixel electrode in order to suppress display unevenness. However, none of them is sufficient to suppress display unevenness.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device capable of suppressing display unevenness and making it less noticeable.

[0010]

According to a first aspect of the present invention, there is provided a liquid crystal display device comprising: a liquid crystal layer sealed between a pair of substrates; and one of the pair of substrates. A plurality of scanning signal lines disposed in parallel with each other on a substrate, a plurality of pixel electrodes respectively disposed between adjacent scanning signal lines, and a plurality of pixel electrodes disposed on the other of the pair of substrates. A plurality of data signal lines disposed so as to intersect with the scanning signal lines, wherein the scanning signal lines are sequentially selected when performing image display, and the selected scanning signal lines and the data signal lines are In a liquid crystal display device to which a voltage is applied, each of the pixel electrodes is connected to adjacent two adjacent scanning signal lines via a plurality of types of non-linear resistance two-terminal elements. Of the terminal elements, the elements of the first group are the above two One of the scanning signal lines is connected to one of the scanning signal lines, and a second group of the plurality of types of non-linear resistance two-terminal elements is connected to the other of the two scanning signal lines. The first group of elements is formed such that the sum of the current values flowing through the elements when the same voltage is applied is larger than that of the second group of elements, and the capacitance of the first group of elements and When the image is displayed, the sum of the capacitance of the element in the first group and the capacitance in parallel is smaller than the sum of the capacitance of the element in the second group and the capacitance in parallel with the element of the second group. The period in which the one scanning signal line is selected includes a writing period in which the elements of the first group are turned on by an applied voltage, and the other scanning signal line is selected following the one scanning signal line. Period It is characterized by comprising the compensation period in which elements of the second group is turned by the applied voltage and reverse polarity voltage applied.

According to the above configuration, the variation in the characteristics of the elements of the first group can be compensated by the elements of the second group connected to the same pixel electrode.

That is, in a pixel in which the current value of the element of the first group is relatively large, the current value of the element of the second group is also relatively large. Thereby, in this pixel, the charge applied to the liquid crystal layer during the writing period in which the first group of elements is turned on and the voltage applied to the liquid crystal layer during the compensation period in which the second group of elements are turned on are lost by the applied voltage of the opposite polarity Both the charge and the charge increase.

In a pixel in which the current value of the first group of elements is relatively small, the current value of the second group of elements is also relatively small. Thereby, in this pixel, the charge applied to the liquid crystal layer during the writing period in which the first group of elements is turned on and the voltage applied to the liquid crystal layer during the compensation period in which the second group of elements are turned on are lost by the applied voltage of the opposite polarity. Both the charge and the charge decrease.

As a result, the charge applied to the liquid crystal layer during the selection period of each pixel becomes substantially constant irrespective of the variation in the characteristics of the elements of the first group.

Therefore, the variation in the voltage applied to the liquid crystal due to the variation in the characteristics of the non-linear resistance two-terminal element can be suppressed, so that the display unevenness can be suppressed and made inconspicuous.

Further, since the sum of the capacitance of the element of the second group and the capacitance in parallel with the element is larger than the sum of the capacitance of the element of the first group and the capacitance in parallel with the element, writing of each pixel is performed. The value of the applied voltage can be set so that the elements of the first group become conductive during the period and the elements of the second group become conductive during the compensation period.

According to a second aspect of the present invention, there is provided a liquid crystal display device in addition to the configuration of the first aspect, in order to solve the above problem.
The first group of elements and the second group
It is characterized in that the elements of the group are connected one by one.

According to the above configuration, the configuration according to claim 1 can be realized with a simpler configuration and a simpler manufacturing process, and display unevenness can be suppressed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a plan view of a substrate on which a non-linear resistance two-terminal element is formed among a pair of substrates provided in a liquid crystal panel in a reflection type liquid crystal display device according to an embodiment of the present invention. FIG. 2A is a cross-sectional view taken along the line AA ′ of FIG. 1, and FIG. 2B is a cross-sectional view taken along the line BB ′ of FIG.

Referring to FIGS. 1 and 2A and 2B, on a glass substrate 1 on which a non-linear resistance two-terminal element is formed, a scanning signal line 2, a semiconductor layer 3 and an insulating layer are formed. A membrane layer 4,
The pixel electrode 5 is formed. A plurality of scanning signal lines 2 are arranged in parallel with each other, and each scanning signal line 2 has a connection terminal (not shown) for connection with a scanning line driving driver. The semiconductor layer 3 is formed on the entire surface of the substrate except for the connection terminal portions. The insulating film layer 4 is formed on the semiconductor layer 3 and two types of through holes 6 and 7 are formed at predetermined positions on the scanning signal line 2. A large number of pixel electrodes 5 are arranged between the adjacent scanning signal lines 2, and each pixel electrode 5 covers two types of through holes 6 and 7, respectively.

The first non-linear resistance two-terminal element 8 for driving the liquid crystal is located at each through hole 6 and has a structure of lower metal-semiconductor-upper metal. Further, the second non-linear resistance two-terminal element 9 for variation compensation is located at each through hole 7 and has a structure of lower metal-semiconductor-upper metal. In each of the first and second nonlinear resistance two-terminal elements 8 and 9, the scanning signal line 2 functions as a lower metal, the semiconductor layer 3 functions as a semiconductor, and the pixel electrode 5 functions as an upper metal.

The pixel electrode 5 has a region 5 a which overlaps the scanning signal line 2 in a plane via the semiconductor layer 3 and the insulating film layer 4, and is in parallel with the second nonlinear resistance two-terminal element 9. It works to increase the capacity.

Further, the size of the through hole 7 is as follows.
The through hole 6 is formed so as to be 1/20 in size.

However, when the photosensitive resin is used for the insulating film layer 4 and the through holes 6 and 7 are formed by photolithography, each of the through holes 6 and 7 is formed to have the same size and shape over the entire substrate. It is difficult. This is because, as described above, the insulating film layer 4 does not have a uniform film thickness over the entire substrate, and exposure unevenness in the exposure step and development unevenness in the development step cannot be avoided. .

However, even if the thickness of the insulating film layer 4 is not uniform over the entire substrate and exposure unevenness and development unevenness exist, the film thickness of the insulating film layer 4 is uniform within a narrow region of the substrate. It can be considered that there is no unevenness and unevenness in development. Therefore, for example, even if the sizes of the through holes 6 and 7 vary in the entire substrate, the size ratio of the two types of through holes 6 and 7 covered by the same pixel electrode 5 is the same. That is, each pixel electrode 5
In the two types of through-holes 6 and 7 connected to, even though the size of the through-holes 6 and 7 is out of the standard, whether the through-holes 6 and 7 are both larger than the standard,
Alternatively, both of the through holes 6 and 7 are smaller than the standard.

The liquid crystal panel used in the above-mentioned reflection type liquid crystal display device is manufactured as follows.

First, a Ta thin film is formed on the entire surface of the glass substrate 1 by a sputtering method. A plurality of scanning signal lines 2 are pattern-formed from the Ta thin film after film formation by photolithography. Next, a ZnS thin film is formed on the entire surface of the substrate by a sputtering method, and the film on the connection terminal portion of the scanning signal line 2 with the driver for driving the scanning line is removed from the formed ZnS thin film by photolithography. Then, the semiconductor layer 3 is formed.

Next, a photosensitive insulating film is formed on the entire surface of the substrate by a spinner, and through holes 6 and 7 are formed by photolithography, and a connection terminal portion for connecting the scanning signal line 2 to a scanning line driving driver is formed. By removing the film, an insulating film layer 4 is formed. Next, an Al thin film is formed on the entire surface of the substrate by sputtering, and the pixel electrodes 5 are patterned by photolithography.

On the other hand, on the substrate on which the non-linear resistance two-terminal element is not formed, an ITO thin film is formed on a glass substrate by a sputtering method, and a plurality of stripes as shown in FIG. Of the data signal lines 10 are patterned.

The two substrates are fixed with a sealing resin so that the scanning signal lines 2 and the data signal lines 10 intersect at right angles to each other, and a liquid crystal is filled between the two substrates to complete a liquid crystal panel. . Further, a step of connecting a scan driver to the terminal of the scanning signal line 2 to be taken out and connecting the data driver to a terminal of the data signal line 10 will be continued.

FIG. 3 is a timing chart showing driving waveforms of various signals used for driving the liquid crystal in the reflection type liquid crystal display device.

Referring to FIG. 3, (a) shows a scanning signal applied to the n-th scanning signal line 2, and (b) shows n +
This is a scanning signal applied to the first scanning signal line 2. (C) is a data signal applied to the data signal line 10.

FIG. 3D shows a first non-linear resistance two-terminal element 8 for driving liquid crystal and a liquid crystal layer in a pixel located between the n-th scanning signal line 2 and the (n + 1) -th scanning signal line 2. This signal is the sum of the signal of (a) and the signal of (c). Also,
(E) is applied to a series circuit of the second non-linear resistance two-terminal element 9 for compensating variation in the pixel located between the n-th scanning signal line 2 and the (n + 1) -th scanning signal line 2 and the liquid crystal layer. This signal is the sum of the signal of (b) and the signal of (c). (F) shows a voltage applied to the liquid crystal layer in a pixel located between the nth scanning signal line 2 and the (n + 1) th scanning signal line 2.

Each signal in FIG. 3 can be divided into a selection period A and a non-selection period B according to pixels located between the n-th scanning signal line 2 and the (n + 1) -th scanning signal line 2. Further, the selection period A is the first period in the pixel at this position.
The write period A1 in which the non-linear resistance two-terminal element 8 is in a conductive state and the compensation period A2 in which the second non-linear resistance two-terminal element 9 is in a conductive state. Further, in the non-selection period B immediately after the selection period A, the same voltage as that in the writing period A1 is applied to the (n + 1) th scanning signal line 2, and the (n + 1) th scanning signal line 2 and the (n + 2) th scanning signal line 2 There is a period B1 during which a signal is written to a pixel located therebetween.

The signal in the writing period A1 needs to be a voltage that makes the first nonlinear resistance two-terminal element 8 for driving the liquid crystal sufficiently conductive. Further, the signal in the compensation period A2 needs to be a voltage that makes the second nonlinear resistance two-terminal element 9 for variation compensation sufficiently conductive.

Further, the signal in the period B1 is n
A voltage that sufficiently turns on the first non-linear resistance two-terminal element 8 of the pixel located between the (+1) th scanning signal line 2 and the (n + 2) th scanning signal line 2; It is necessary that the voltage is such that the second non-linear resistance two-terminal element 9 of the pixel located between the line 2 and the (n + 1) th scanning signal line 2 is not turned on. Therefore, as described above, an additional capacitance in parallel with the second non-linear resistance two-terminal element 9 is formed in a portion where the scanning signal line 2 and a part of the region 5a of the pixel electrode 5 overlap (FIG. 1). And FIG. 2). At the same time, the applied voltage is set as follows.

The voltage applied to the series circuit of the non-linear resistance two-terminal element and the liquid crystal layer is Vop, the capacitance of the non-linear resistance two-terminal element is Cd, the additional capacitance in parallel with this is Cs, and the capacitance of the liquid crystal layer is Assuming Clc, the voltage Vd applied to the non-linear resistance two-terminal element is expressed by the following equation.

Vd = {Clc / (Clc + Cd + Cs)} * Vop According to the above equation, Vd can be reduced by increasing Cs.

Therefore, by forming an additional capacitor in parallel only with the second non-linear resistance two-terminal element 9 for variation compensation, the voltage Vop required to make the second non-linear resistance two-terminal element 9 conductive is formed. Is a voltage V necessary to make the first nonlinear resistance two-terminal element 8 for driving the liquid crystal conductive.
larger than op.

Therefore, the voltage applied to the (n + 1) th scanning signal line 2 in the period B1 is set as follows. That is, the second non-linear resistance two-terminal element 9 of the pixel located between the n-th scanning signal line 2 and the (n + 1) -th scanning signal line 2 does not become conductive, and the (n + 1) -th scanning signal line 2 Is set to a voltage value that causes the first non-linear resistance two-terminal element 8 of the pixel located between the pixel and the (n + 2) th scanning signal line 2 to be in a conductive state. With this setting, the signal in the period B1 is equal to the (n + 1) th scanning signal line 2 and n +
A voltage that sufficiently turns on the first nonlinear resistance two-terminal element 8 of the pixel located between the second scanning signal line 2 and the nth scanning signal line 2 and the (n + 1) th scanning signal The voltage can be set so that the second non-linear resistance two-terminal element 9 of the pixel located between the line 2 and the line 2 does not conduct.

FIG. 3 (f) shows two waveform diagrams as the voltage applied to the liquid crystal layer according to the size of the through holes 6 and 7 of the non-linear resistance two-terminal element. That is, the voltage applied to the liquid crystal layer of the pixel in which the through-holes 6 and 7 formed in the insulating film layer 4 are relatively small and the current values of the first and second nonlinear resistance two-terminal elements 8 and 9 are both small is small. Solid line 16
And the through holes 6 and 7 formed in the insulating film layer 4 are relatively large, and the current values of the first and second nonlinear resistance two-terminal elements 8 and 9 are both large. The applied voltage is shown by the broken line 15. However, the portion where the waveforms of the two applied voltages overlap is indicated by a solid line 16.

As shown in the figure, in a pixel where the current values of the first and second nonlinear resistance two-terminal elements 8 and 9 are both large, the charge applied to the liquid crystal layer during the writing period A1 and the compensation period A2 are lost. Both the charge and the charge increase. Meanwhile, the first
In a pixel in which the current values of the second non-linear resistance two-terminal elements 8 and 9 are both small, the charge applied to the liquid crystal layer during the writing period A1 and the charge lost during the compensation period A2 are both small.

As a result, the charge applied to the liquid crystal layer during the selection period A becomes substantially constant regardless of the variation in the current value of the non-linear resistance two-terminal element.

The through holes 6 formed in the insulating film layer 4
Variations in the size and shape of 7 can be ignored in a narrow area. That is, unevenness in film thickness in the step of applying the insulating film layer 4, irradiation unevenness in the exposure step by the photolithography method, or uneven development in the developing step can be ignored in a narrow region. Therefore, there is no pixel in which the current value of the first non-linear resistance two-terminal element 8 for driving the liquid crystal is relatively large and the current value of the second non-linear resistance two-terminal element 9 for dispersion compensation is relatively small. May be.
In addition, it can be said that there is no pixel in which the current value of the first nonlinear resistance two-terminal element 8 is relatively small and the current value of the second nonlinear resistance two-terminal element 9 is relatively large.

The liquid crystal display of this embodiment was driven under the following driving conditions to perform display. That is, the selection period A was 26 μs, the non-selection period B was 12.5 ms, the writing period A1 was 16 μs, and the compensation period A2 was 10 μs.
Further, the potential 17 in the writing period A1 of the scanning signal line 2 is ± 21 V, the potential 18 in the compensation period A2 of the scanning signal line 2 is ± 27 V, and the potential 19 of the data signal line 10 is ± 3 V (see FIG. 3). ).

When display was performed by the liquid crystal display device of the present embodiment under the above driving conditions, the liquid crystal applied voltage VLC in the device was displayed.
Is VL when the liquid crystal applied voltage VLC is high.
C = 4.9 to 5.0, and VLC = 1.6 to 1.8 in the case of display with a low liquid crystal applied voltage VLC. Therefore, the display unevenness fell within a range that was not conspicuous, and display unevenness was hardly observed.

On the other hand, when the conventional liquid crystal display device as shown in FIGS. 5 and 6 is driven by the voltage averaging method, when the liquid crystal applied voltage VLC is high, VLC = 4.6 to VLC.
5.1, and in the case of display with a low liquid crystal applied voltage VLC, VLC = 1.4 to 1.9, and display unevenness was observed.

As described above, in the liquid crystal display device of the present embodiment, it is possible to suppress variations in the voltage applied to the liquid crystal due to variations in the characteristics of the non-linear resistance two-terminal element. Therefore, display unevenness due to variations in the characteristics of the nonlinear resistance two-terminal element can be suppressed and made less noticeable.

[0050]

According to the first aspect of the present invention, there is provided a liquid crystal display device.
As described above, each of the pixel electrodes is connected to neighboring two adjacent scanning signal lines via a plurality of types of non-linear resistance two-terminal elements. The one group of elements is connected to one of the two scanning signal lines, and the second group of the plurality of types of non-linear resistance two-terminal elements is the two scanning signal lines.
One of the scanning signal lines is connected to the other scanning signal line, and the elements of the first group have a larger sum of current values flowing through the elements when the same voltage is applied than the elements of the second group. And the sum of the capacitance of the first group of elements and the capacitance in parallel with the first group of elements is the sum of the capacitance of the second group of elements and the capacitance in parallel with the second group of elements. The period in which the one scanning signal line is selected when the image is displayed and the one scanning signal line is selected includes a writing period in which the elements of the first group are turned on by an applied voltage. The period in which the other scanning signal line is selected following the scanning signal line includes a compensation period in which the elements of the second group are turned on by an applied voltage having a polarity opposite to the applied voltage. .

As a result, variations in the characteristics of the elements of the first group can be compensated for by the elements of the second group connected to the same pixel electrode, and as a result, the voltage applied to the liquid crystal layer during the selection period of each pixel. Charge is substantially constant irrespective of variations in the characteristics of the elements of the first group.

Therefore, the variation in the voltage applied to the liquid crystal due to the variation in the characteristics of the non-linear resistance two-terminal element can be suppressed, so that the effect of suppressing the display unevenness and making the display inconspicuous can be obtained.

Further, since the sum of the capacitance of the element of the second group and the capacitance in parallel with the element is larger than the sum of the capacitance of the element of the first group and the capacitance in parallel with the element, writing of each pixel is performed. The value of the applied voltage can be set so that the elements of the first group become conductive during the period and the elements of the second group become conductive during the compensation period.

As described above, in the liquid crystal display device according to the second aspect of the invention, in addition to the configuration of the first aspect, each of the pixel electrodes includes the first group of elements and the second group of elements. This is a configuration in which the components are connected one by one.

As a result, the configuration according to claim 1 can be realized with a simpler configuration and a simpler manufacturing process, and display unevenness can be suppressed.

[Brief description of the drawings]

FIG. 1 is a plan view of a substrate on which a non-linear resistance two-terminal element is formed among a pair of substrates provided in a liquid crystal panel in a reflection type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line AA ′ and line BB ′ in FIG.

FIG. 3 is a timing chart showing driving waveforms of various signals used for driving liquid crystal in the reflective liquid crystal display device.

FIG. 4 is a plan view of a substrate on which a non-linear resistance two-terminal element is not formed among a pair of substrates provided in a liquid crystal panel in the reflection type liquid crystal display device.

FIG. 5 is a plan view of a substrate on which a non-linear resistance two-terminal element is formed, of a pair of substrates provided in a liquid crystal panel in a conventional reflective liquid crystal display device.

FIG. 6 is a sectional view taken along line C-C ′ of FIG. 5;

[Explanation of symbols]

Reference Signs List 1 glass substrate 2 scanning signal line 3 semiconductor layer 4 insulating film layer 5 pixel electrode 6 through hole 7 through hole 8 first nonlinear resistance two-terminal element (element of first group) 9 second nonlinear resistance two-terminal element (second element) 2 groups of elements) 10 Data signal line

Claims (2)

(57) [Claims] 1. A liquid crystal layer sealed between a pair of substrates, a plurality of scanning signal lines disposed in parallel with each other on one of the pair of substrates, and an adjacent scanning signal line A plurality of pixel electrodes respectively disposed between the plurality of data signal lines, and a plurality of data signal lines disposed on the other of the pair of substrates so as to intersect with the scanning signal lines. In the liquid crystal display device in which the scanning signal lines are sequentially selected when performing the operation, and a voltage is applied to the selected scanning signal line and the data signal line, each of the pixel electrodes includes a plurality of types of nonlinear resistance two-terminal elements. Are connected to adjacent two adjacent scanning signal lines, and the first group of elements of the plurality of types of nonlinear resistance two-terminal elements is one of the two scanning signal lines. Connected to two or more types of nonlinear resistors Elements of the second group among the child elements are connected to the other of the two scanning signal lines, and the same voltage is applied to the elements of the first group as compared to the elements of the second group. In this case, the sum of the values of the currents flowing through the elements is increased, and the sum of the capacitance of the elements of the first group and the capacitance in parallel with the elements of the first group is equal to the capacitance of the elements of the second group. And the capacitance in parallel with the elements of the second group are formed so as to be smaller than the sum of the capacitances in parallel with the elements of the second group. In a period including a writing period in which the elements are in a conductive state, during a period in which the other scanning signal line is selected following the one scanning signal line, the elements of the second group are applied by an applied voltage having a polarity opposite to the applied voltage. Conduction A liquid crystal display device comprising a compensation period that is in a state. 2. The liquid crystal display device according to claim 1, wherein each of said pixel electrodes is connected to one of said first group of elements and one of said second groups of elements.