JPH10187102A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device suppressing a delay of a signal waveform when a drive signal supplied to a common electrode rises and falls, and enhancing display quality in an active matrix type LCD panel. SOLUTION: In the LCD panel 2 in the liquid crystal display device, a frame like conductive pattern 17 connected to conductive material 16 is formed on the outside of an area where a liquid crystal is sealed of an opposite surface of a lower glass substrate 11a, and the common electrode 15b arranged on the opposite surface of an upper glass substrate 11b is provided extending to a position opposite to this conductive pattern 17, and a capacity forming part 18 is formed by the conductive pattern 17 and the common electrode 15b making air lying between them a dielectric. The capacity C of this capacity forming part 18 is connected parallel to the resistance R of the conductive material 16, and suppresses the delay of the signal waveform when a common electrode drive signal VCOM rises and falls.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having an active matrix type LCD panel.

[0002]

2. Description of the Related Art Conventionally, a thin film transistor (TFT) has been disclosed.
A liquid crystal display device that includes an active matrix type LCD panel using a switching element such as a film transistor, writes a display signal for each pixel at a scanning timing according to a video input signal, and drives and displays the LCD panel is known. Have been.

FIG. 6 shows a sectional structure of this active matrix type LCD panel. As shown in the figure, the LCD panel 52 has a sealant 54 applied to a peripheral portion between a lower glass substrate 53a and an upper glass substrate 53b which are opposed to each other, and seals the liquid crystal 55 therein. A large number of TFTs 56 are arranged in a matrix on the opposing surface inside the sealant 54.

On the opposite surface of the lower glass substrate 53a, the TFT 56 is selectively driven, and a display signal is written to each pixel electrode (not shown) connected to the subsequent stage of the TFT 56. A gate line for supplying various drive signals for driving the display of the panel 52, a signal line, a CS line (not shown), a common electrode line 5
7a and the like are laminated with an insulating layer interposed therebetween, and further provided with an insulating protective film 53c.

On the other hand, a transparent electrode 57b in the form of a thin film serving as a common electrode is adhered to the opposing surface of the upper glass substrate 53b. A conductive material 58 is provided outside (partly) of the sealant 54 between the upper and lower glass substrates 53a and 53b. The conductive material 58 is made of silver paste or the like, and is provided with a common electrode line 57 formed on the opposite surface of the lower glass substrate 53a.
a, and a driving signal (common electrode driving signal VCOM) supplied from a driving circuit (not shown) provided outside the LCD panel 52 to the common electrode line.
Common electrode 57b (transparent electrode) attached to the opposing surface of 3b
Is applied.

Next, FIG.
FIG. 3 is a diagram illustrating an equivalent circuit for a pixel. In the figure, a scanning line (gate line) X extended in the row direction is provided.
n, a gate drive signal VG is supplied, and a signal line (drain line) Y extending in the column direction is provided.
A display signal (drain drive signal VD) is supplied to m.

A TFT 56 as a switching element is disposed at the intersection of the scanning line Xn and the signal line Ym.
However, the signal line Ym is connected to the drain electrode D. A liquid crystal capacitance CL and a resistance R of the conductive material 58 and a storage capacitance CS connected in series are connected to the source electrode S in parallel, and the common electrode 57b is connected to the common electrode line 57a via the resistance R. And the storage capacitor CS
Are connected to the CS line.

The liquid crystal capacitance CL is a capacitance formed by the pixel electrode 56a connected to the source electrode S of the TFT 56 and the common electrode 57b, and using the liquid crystal 55 interposed between the two electrodes as a dielectric. CS is an auxiliary capacitance that prevents the influence of the parasitic capacitance generated in the TFT 56 and supplements the holding operation of the liquid crystal capacitance CL.

FIG. 8 is a diagram showing signal waveforms of various drive signals in the frame inversion method. The gate drive signal VG (dotted line) and the drain drive signal V shown in FIG.
D (solid line) is generated in a drive circuit (not shown) provided outside the LCD panel 52, and includes gate lines,
The signal is supplied to the gate electrode G and the drain electrode D of each TFT 56 via a signal line. A common electrode drive signal VCOM (thick line) shown in FIG. 4B is generated in the drive circuit, and is connected to the common electrode line 57a and the conductive material 58 formed on the opposite surface of the lower glass substrate 53a. 57b.

The TFT 56 shown in FIG. 7 is in the selected state during the period when the voltage level of the gate drive signal VG applied to the gate electrode G via the scanning line Xn becomes VGH (see FIG. 8A). The conduction between the drain electrode D and the source electrode S is conducted, and during this period, the signal line Ym
a, a drain drive signal VD (display signal) supplied to
The common electrode drive signal VCO applied to the common electrode 57b
The potential difference from M is written to the liquid crystal capacitance CL and the storage capacitance CS as electric charges.

The liquid crystal 55 is driven for each pixel for a predetermined period until the TFT 56 is next selected based on the amount of charge written in the liquid crystal capacitance CL and the storage capacitance CS.

In FIG. 8, the liquid crystal 55 is AC-driven by inverting the voltage polarity of the drain drive signal VD and the common electrode drive signal VCOM every frame (frame inversion method). This is because if the LCDs are continuously driven with the same voltage polarity, the liquid crystal element is deteriorated.

[0013]

However, the conventional liquid crystal display device 51 having such an active matrix type LCD panel 52 has the following problems.

That is, a large number of pixels are arranged in a matrix on the LCD panel 52, and the dielectric constant of the liquid crystal 55 sealed between the upper and lower glass substrates 53a and 53b is a relatively large value. For this reason, the capacitance value of the liquid crystal capacitance CL becomes large.

For this reason, a drive circuit provided outside the LCD panel 52 generates a rectangular common electrode drive signal VCOM as shown by the bold line in FIG. The signal is supplied to the common electrode 57b via the common electrode 57b. The waveform of the common electrode drive signal VCOM actually applied to the common electrode 57b is changed when the signal waveform rises and falls as shown by a thin line in FIG. Delay (dull)
Will occur.

As a result, the amount of charges written in the liquid crystal capacitance CL and the storage capacitance CS is reduced based on the potential difference between the drain drive signal VD and the common electrode drive signal VCOM due to the dulling of the signal waveform, and the liquid crystal 55 is correctly driven for display. Not LC
There is a problem that the display quality of the D panel 52 is deteriorated.

According to the present invention, there is provided an active matrix type LCD panel in which a display signal quality is improved by suppressing a delay of a signal waveform at a rise and a fall of a drive signal supplied to a common electrode in an active matrix type LCD panel. It is to provide a display device.

[0018]

According to a first aspect of the present invention, there is provided a liquid crystal display device, wherein a liquid crystal is sealed between first and second substrates arranged opposite to each other, and a plurality of signals are provided on an opposite surface of the first substrate. Lines and a plurality of scanning lines are arranged in a matrix, pixel electrodes are connected to respective intersections of the signal lines and the scanning lines via switching elements, and the second electrodes are opposed to these pixel electrode groups.
A liquid crystal display panel having a common electrode disposed on the opposite surface of the substrate, and sequentially scanning each of the scanning lines disposed on the first substrate at a scanning timing according to a video input signal; To the second substrate through the conductive material from the first substrate through a conductive material, and supplies a display signal that is positively inverted every predetermined period to the first substrate.
A liquid crystal display device for driving the liquid crystal display panel by alternating current driving the liquid crystal for each pixel by supplying the common signal to a common electrode provided on the substrate, and supplying the common signal to the liquid crystal display panel. In the path, a capacitance element is connected in parallel to the resistance component of the conductive material, and a delay of a signal waveform at the time of rising and falling of the common signal is suppressed.

According to the first aspect of the invention, in the liquid crystal display panel, a series of common steps from the first substrate to the common electrode disposed on the facing surface of the second substrate via the conductive material. In the signal supply path, since a capacitance element is connected in parallel to the resistance component of the conductive material, the signal waveform at the time of rising and falling of the common signal is suppressed, and supplied to the pixel electrode. The amount of charge written to the liquid crystal capacitor and the storage capacitor based on the potential difference between the display signal supplied to the common electrode and the common signal supplied to the common electrode is reduced in the signal waveform at the rise and fall of the common signal as in the related art. Due to this, it is possible to suppress the decrease in the charge amount and to drive the liquid crystal between the two electrodes for display with a more appropriate charge amount. as a result,
The display quality on the LCD panel can be improved.

According to a second aspect of the present invention, in the liquid crystal display device according to the first aspect, a conductive pattern connected to the conductive material is formed on an opposite surface of the first substrate in a region where the liquid crystal is sealed. A material formed outside and extending a common electrode disposed on the facing surface of the second substrate to a position facing the conductive pattern, and a material interposed therebetween by the conductive pattern and the common electrode. Is characterized in that the capacitor is formed using a dielectric as a dielectric.

According to the second aspect of the present invention, the conductive pattern connected to the conductive material is formed on the facing surface of the first substrate outside the region where the liquid crystal is sealed, and the conductive pattern faces the conductive pattern. A common electrode disposed on the opposing surface of the second substrate is provided to extend to a position where the capacitor is connected in parallel with the resistance component of the conductive material. Is formed as a dielectric, so that the same effect as described in the above-described claim 1 can be obtained, and further, by replacing the substance interposed as the dielectric,
It is possible to change the capacitance value of the capacitive element according to the dielectric constant of the substance, and it is possible to adjust the degree of suppression of the signal waveform delay when the common signal rises and falls.

Further, in the liquid crystal display device according to the second aspect, the conductive pattern may have a frame shape.

According to the third aspect of the present invention, since the conductive pattern has a frame shape, the capacitance of the capacitive element can be increased with a simple structure, and the display quality of the LCD panel can be further improved. .

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to FIGS. FIG. 1 is a diagram showing a lower glass substrate 11a in an active matrix LCD panel 2 of a liquid crystal display device 1 to which the present invention is applied. A gate line, a signal line, a CS line, and a common electrode line 15 are provided on the opposite surface of the lower glass substrate 11a.
a and the like are formed with an insulating layer interposed therebetween, and after the insulating protective film 11c is provided, a frame-shaped conductive pattern 17 shown in FIG. Are formed in the region indicated by.

In FIG. 1 (b), a rectangular area surrounded by a dashed line is an upper glass substrate arrangement area 11a1 where the upper glass substrate 11b is arranged to face, and a frame-shaped area enclosed by a dotted line is upper and lower. Of the liquid crystal 13 between the glass substrates 11a and 11b.
The sealant application region 11a2 to which the sealant 12 for sealing the sealant is applied, a rectangular region surrounded by a two-dot chain line is
This is a conductive material placement area 11a3 where the conductive material 16 is placed.

The conductive pattern 17 is formed on the lower glass substrate 11a.
Is formed in a frame-shaped area 11a4 (hatched in the figure) occupying the outer part of the sealant application area 11a2 in the upper glass substrate arrangement area 11a1 and connected to a common electrode line formed in the lower layer. I have. The conductive pattern 17 is formed of, for example, Al, Cr, ITO, or the like.

The location of the conductive material 16 is shown in FIG.
It is not limited to one place as shown in (b),
In order to reduce the value of the resistance R of the conductive material 16, for example, a total of four places, such as four sides of the sealant application area 11a2, are used.
There may be more than one.

Next, FIG. 2 is a sectional view of the active matrix type LCD panel 2 of the liquid crystal display device 1 to which the present invention is applied. In FIG. 2, a description of a portion having the same structure as the cross-sectional structure (see FIG. 6) of the active matrix type LCD panel 52 in the conventional example described above is omitted, and only a portion unique to the present invention will be described. It shall be.

In FIG. 2, a conductive pattern 17 is formed on the outer peripheral portion of the sealant 12 on the surface facing the lower glass substrate 11a.
Are formed. On the other hand, a transparent electrode 15b in the form of a thin film serving as a common electrode is attached to the opposing surface of the upper glass substrate 11b so as to cover the entire surface.

A conductive material 16 is provided outside (partly) of the sealant 12 between the upper and lower glass substrates 11a and 11b. The conductive material 16 is made of silver paste or the like, and is supplied from a drive circuit (not shown) provided outside the LCD panel 2 via a common electrode line 15 a formed on the opposite surface of the lower glass substrate 11 a and a conductive pattern 17. The common electrode drive signal VCOM is applied to the common electrode 15b (transparent electrode) attached to the opposite surface of the upper glass substrate 11b.

With such a cross-sectional structure of the LCD panel 2, air interposed between the upper and lower glass substrates 11a and 11b is provided between the upper and lower glass substrates 11a and 11b by the conductive pattern 17 and the common electrode 15b. A frame-shaped capacitance forming portion 18 serving as a dielectric is formed.

FIG. 3 is a diagram showing an equivalent circuit for one pixel in the LCD panel 2. As shown in FIG. 3, the capacitance C of the capacitance forming portion 18 is in parallel with the resistance R of the conductive material 16. Connected. Note that the circuit configuration other than the capacitance C in FIG. 3 is the same as the equivalent circuit for one pixel in the above-described conventional example (see FIG. 7), and a description thereof will be omitted.

Next, FIG. 4 shows the common electrode drive signal VCOM in the conventional LCD panel 52 and the L to which the present invention is applied.
FIG. 9 is a diagram (part 1) illustrating a comparison of a signal waveform with a common electrode drive signal VCOM in the CD panel 2.

As shown in FIG. 3A, the waveform of the common electrode drive signal VCOM finally applied to the common electrode 57 in the conventional LCD panel 52 is based on the supply path of the common electrode drive signal VCOM (LCD panel). An exponential function curve based on a time constant R × CL determined by the resistance R of the conductive material 58 in (inside 52) and the liquid crystal capacitance CL is given by the following equation (1).

(Equation 1)

On the other hand, as shown in FIG. 3B, the waveform of the common electrode drive signal VCOM finally applied to the common electrode 15 in the LCD panel 2 of the present invention is the same as that of the common electrode drive signal VCOM. Assuming that the combined impedance of the resistance R of the conductive material 16 in the supply path (in the LCD panel 2) and the capacitance C connected in parallel to the resistance R is Z, when the combined impedance Z is determined by the liquid crystal capacitance CL. An exponential function curve based on the constant Z × CL is obtained, and is represented by the following equation (2).

(Equation 2)

Here, in the LCD panel 2 of the present invention, as shown in FIG. 3B, when a sharp change occurs in the signal waveform in the supply path of the common electrode drive signal VCOM, that is, the common electrode drive signal VCOM When the signal VCOM rises and falls, a transient current Ic flows through the capacitor C side. Compared with the conventional case shown in FIG. It is possible to suppress the components and reduce the value of the time constant Z × CL.

As a result, as shown in FIG. 5, the LCD panel 2 of the present invention finally ends up with the common electrode 15 as compared with the conventional common electrode drive signal VCOM (thin line).
b) The signal waveform at the rise and fall of the common electrode drive signal VCOM (middle line) applied to the signal b is sharpened, the delay (dullness) of the signal waveform at the rise and fall is improved, and the ideal drive is performed. It can be made closer to a rectangular waveform (thick line) at the time of generation in a circuit (not shown).

As a result, based on the potential difference between the drain drive signal VD supplied to the pixel electrode 14a and the common electrode drive signal VCOM supplied to the common electrode 15, the amount of charge written in the liquid crystal capacitance CL and the storage capacitance CS is determined. In addition, it is possible to suppress the decrease in the charge amount due to the blunted signal waveform at the time of rising and falling of the common electrode drive signal VCOM as in the related art, and drive the liquid crystal 55 between both electrodes with a more appropriate charge amount. Becomes possible.

The value of the capacitance C in the capacitance forming section 18 is, for example, in the case of a 10-inch LCD panel 2, the width L1 of the conductive pattern 17 is 1.0 [mm], and the distance between the conductive pattern 17 and the common electrode 15b is The interval, that is, the opposing interval d between the upper and lower glass substrates 11a and 11b is 5.0 [μm],
When the dielectric constant ε of air is 8.855 [pF / m] (the relative dielectric constant of air ε s = 1), the length L 2 around the display area
Is about 75 [cm], which is about 1300 [pF] from the following equation (3).

(Equation 3) This value is a value sufficient to improve the dullness of the signal waveform at the time of rising and falling of the common electrode drive signal VCOM.

In this embodiment, the case where the dielectric in the capacitance forming portion 18 is air has been described, but the dielectric is not limited to air. That is, the capacitor C may be formed by interposing a substance serving as a dielectric between the conductive pattern 17 and the common electrode 15b. At this time, if a substance having a higher dielectric constant than air is used as the dielectric, it is possible to further improve the dullness of the signal waveform at the time of rising and falling of the common electrode drive signal VCOM.

As described above, according to the liquid crystal display device 1 of the present embodiment, the active matrix type L
In the CD panel 2, the conductive pattern 1 is formed from the common electrode line 15a formed on the opposite surface of the lower glass substrate 11a.
7. In the supply path of the series of common electrode drive signals VCOM up to the common electrode 15b attached to the opposing surface of the upper glass substrate 11b via the conductive material 16, the resistance R of the conductive material 16 Since the capacitor C is connected in parallel, the delay of the signal waveform at the rise and fall of the common electrode drive signal VCOM is suppressed, and the drain drive signal VD supplied to the pixel electrode 14a and the common electrode drive signal VCOM are supplied to the common electrode 15b. The amount of charge written in the liquid crystal capacitance CL and the storage capacitance CS based on the potential difference with the common electrode drive signal VCOM
It is possible to suppress the decrease in the charge amount due to the dull signal waveform at the time of rising and falling of the common electrode drive signal VCOM as in the related art, and to drive the liquid crystal 55 between both electrodes with a more appropriate charge amount. It becomes possible.

Further, according to the liquid crystal display device 1 of the present embodiment, the liquid crystal 55 on the surface facing the lower glass substrate 11a is provided.
A conductive pattern 17 connected to the conductive material 16 is formed outside the region where the conductive pattern 1 is sealed.
7, a common electrode 15b disposed on the facing surface of the upper glass substrate 11b is provided so as to extend to a position facing the conductive material 7.
6, the capacitor C connected in parallel to the resistor R is formed by using the conductive pattern 17 and the common electrode 15b to form a dielectric material interposed between the conductive pattern 17 and the common electrode 15b. The delay of the signal waveform at the time of rising and falling of VCOM can be suppressed, and the value of the capacitance C is changed according to the dielectric constant of the substance by changing the substance interposed as the dielectric. This makes it possible to adjust the degree of suppression of signal waveform delay at the time of rising and falling of the common electrode drive signal VCOM. Further, since the conductive pattern 17 is formed in a frame shape, the capacitance C can be increased with a simple structure, and the above-described adjustment is facilitated.

Further, according to the liquid crystal display device 1 of the present embodiment, since the dielectric is air, there is no need to interpose a substance serving as a dielectric between the conductive pattern 17 and the common electrode 15b. In addition, the manufacturing process of the LCD panel can be simplified.

As described above, the present invention has been specifically described based on the embodiments. However, the present invention is not limited to the above embodiments, and can be appropriately changed without departing from the gist of the present invention. Of course.

For example, in the present embodiment, the active matrix type LCD panel 2 using the TFT 14 as the switching element has been described as an example, but the switching element is not limited to the TFT.

In the present embodiment, the frame inversion method has been described as an example of the drive method for AC driving the liquid crystal. However, the drive method is not limited to the frame inversion method. Instead, for example, a line inversion method or the like may be used.

[0047]

According to the first aspect of the present invention, in the liquid crystal display panel, a series of steps from the first substrate to the common electrode disposed on the facing surface of the second substrate via the conductive material. In the common signal supply path, since the capacitance element is connected in parallel to the resistance component of the conductive material,
Suppress the delay of the signal waveform at the time of rising and falling of the common signal, and write the liquid crystal capacitor and the storage capacitor based on the potential difference between the display signal supplied to the pixel electrode and the common signal supplied to the common electrode. With respect to the charge amount, it is possible to suppress a decrease in the charge amount due to the blunted signal waveform at the time of rising and falling of the common signal as in the related art, and to drive the liquid crystal between both electrodes with a more appropriate charge amount. Becomes possible. As a result, display quality on the LCD panel can be improved.

According to the second aspect of the present invention, the conductive pattern connected to the conductive material is formed on the opposite surface of the first substrate outside the region where the liquid crystal is sealed, and the conductive pattern is opposed to the conductive pattern. A common electrode disposed on the opposing surface of the second substrate is provided to extend to a position where the capacitor is connected in parallel with the resistance component of the conductive material. Is formed as a dielectric, so that the same effect as described in the above-described claim 1 can be obtained, and further, by replacing the substance interposed as the dielectric,
It is possible to change the capacitance value of the capacitive element according to the dielectric constant of the substance, and it is possible to adjust the degree of suppression of the signal waveform delay when the common signal rises and falls.

According to the third aspect of the present invention, since the conductive pattern has a frame shape, the capacitance of the capacitive element can be increased with a simple structure, and the display quality of the LCD panel can be improved. .

[Brief description of the drawings]

FIG. 1 is a view showing a lower glass substrate in an active matrix type LCD panel of a liquid crystal display device to which the present invention is applied.

FIG. 2 is a sectional view of an active matrix type LCD panel of a liquid crystal display device to which the present invention is applied.

3 is a diagram showing an equivalent circuit for one pixel in the LCD panel shown in FIG.

FIG. 4 is a diagram (part 1) illustrating a comparison of signal waveforms of a common electrode drive signal VCOM in a conventional LCD panel and a common electrode drive signal VCOM in an LCD panel to which the present invention is applied.

FIG. 5 is a diagram (part 2) illustrating a comparison between signal waveforms of a common electrode drive signal VCOM in a conventional LCD panel and a common electrode drive signal VCOM in an LCD panel to which the present invention is applied.

FIG. 6 is a sectional view of a conventional active matrix type LCD panel.

7 is a diagram showing an equivalent circuit for one pixel in the LCD panel shown in FIG.

FIG. 8 is a diagram showing signal waveforms of various drive signals in a frame inversion method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 LCD panel 11a Lower glass substrate 11a1 Upper glass substrate arrangement area 11a2 Sealant application area 11a3 Conductive material arrangement area 11a4 Conductive pattern formation area 11b Upper glass substrate 12 Sealant 13 Liquid crystal 14 TFT 15 Common electrode (transparent electrode) Reference Signs List 16 conductive material 17 conductive pattern 18 capacitance forming portion 51 liquid crystal display device 52 LCD panel 53a lower glass substrate 53b upper glass substrate 54 sealant 55 liquid crystal 56 TFT 57 common electrode (transparent electrode) 58 conductive material

Claims (3)

[Claims] 1. A liquid crystal is sealed between a first substrate and a second substrate which are opposed to each other, and a plurality of signal lines and a plurality of scanning lines are arranged in a matrix on an opposed surface of the first substrate. A pixel electrode is connected to each intersection of the signal line and the scanning line via a switching element, and a common electrode is provided on the facing surface of the second substrate so as to face the pixel electrode group. A panel, wherein each of the scanning lines provided on the first substrate is sequentially scanned at a scanning timing according to a video input signal, and a display signal, which is inverted at a predetermined cycle, is supplied to each of the signal lines. Further, each pixel is supplied with a common signal, which is polar-inverted in the same cycle as the display signal, from the first substrate to a common electrode provided on the second substrate via a conductive material. A liquid crystal for driving the liquid crystal display panel by driving the liquid crystal alternately every time. In the display device, a capacitance element is connected in parallel to a resistance component of the conductive material in a supply path of the common signal in the liquid crystal display panel, and a delay of a signal waveform at the time of rising and falling of the common signal is provided. A liquid crystal display device characterized by suppressing the above. 2. A conductive pattern connected to the conductive material on an opposite surface of the first substrate is formed outside a region where the liquid crystal is sealed, and the conductive pattern is formed up to a position facing the conductive pattern. A common electrode disposed on the opposing surface of the second substrate and extending, and the capacitive element is formed by using a material interposed between the conductive pattern and the common electrode as a dielectric. Item 2. The liquid crystal display device according to item 1. 3. The liquid crystal display device according to claim 2, wherein said conductive pattern has a frame shape.