JP3407698B2 - Liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a horizontal electric field type liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have come into widespread use as display devices for OA equipment, personal thin-screen TVs, etc. because of their thin and lightweight characteristics.

Among them, the horizontal electric field type liquid crystal display device is
A sharp image can be observed even when viewed from a large angle with respect to the display surface, and it is noted that it has a so-called wide viewing angle.

However, the response speed of the gradation change in the display image has been a problem in a liquid crystal TV or the like which displays a moving image. Regarding this, several driving methods have been invented to accelerate the response speed of gradation change, and Japanese Patent Application Laid-Open No. 7-121143 compares the received display data with the previous display data. A method of converting display data according to the above and outputting it to a pixel is described.

In the above-mentioned known example, the received display data is compared with the previous display data and the display data is output to the pixel as a larger value if the value is larger and a smaller value if the value is smaller. . This is so-called overdrive driving in which display data (= overdrive voltage) exceeding the gradation change amount is input to the pixel to increase the voltage change amount and improve the response speed. An example of this driving method is shown in FIG.

FIG. 2 shows a case in which gradation is changed from a state in which no voltage is applied to a halftone. In the overdrive driving in this case, a voltage higher than the voltage showing the halftone is applied immediately after the gradation change, so that the time required to reach the target transmittance is shortened.

This driving method is a simple matrix driving type liquid crystal display device in which the liquid crystal operates by a cumulative response effect, or the response characteristic of the liquid crystal is that no voltage is applied or the voltage (= operating voltage) is sufficient to drive the liquid crystal. The response speed is fast, but it is effective when using a liquid crystal composition having a slow response speed to the halftone, and the response speed near the halftone is improved to be extremely slow, and the response characteristics are The tone can be almost flattened.

[0008]

However, when this overdrive drive is used, it is easy to apply a DC voltage to the liquid crystal. This is because the absolute values of the positive and negative overdrive voltages are unbalanced at a certain gradation. In other words, the absolute values of the overdrive voltage from the time when no voltage is applied to the halftone and the overdrive voltage from the operating voltage to the halftone are different, and the difference becomes a DC voltage and is applied to the liquid crystal.

On the other hand, in the current horizontal electric field type liquid crystal display device, a low viscosity for high speed response as a liquid crystal composition,
A composition using a cyano liquid crystal component is used in order to achieve both high Δε for low voltage driving. Also, chromium (C) is mainly used for various wirings, pixel electrodes, and counter electrodes.
A metal mainly composed of r) is used. These wirings and electrodes are supposed to be covered with an insulating layer so as not to come into direct contact with the above liquid crystal composition, but there are rarely portions that are in contact with the liquid crystal layer due to defects in the insulating layer.

In the current horizontal electric field type liquid crystal display device as described above, when a DC voltage is applied to the liquid crystal, the liquid crystal and the metal react with each other on the metal surface of the defective portion to easily generate ions. The generated ions reduce the voltage holding ratio of the liquid crystal portion around the defective portion, so that the voltage is not sufficiently applied, resulting in a black blotchy image defect. It should be noted that this image quality defect is more likely to occur as the DC voltage value applied to the liquid crystal is larger.

From the above, when the overdrive driving is applied to the horizontal electric field type liquid crystal display device having the electrode structure mainly containing Cr metal including the current cyano liquid crystal,
Since a DC voltage is easily applied to the liquid crystal, there is a problem that black spots and poor image quality are likely to occur.

Further, this overdrive drive does not improve the response speed in all gradations.
This is because the voltage applied to the liquid crystal layer of the liquid crystal display device is usually an AC voltage, and there is no voltage below the voltage non-applied (0 V) on the low voltage side. This is because the response speed to the gradation to be expressed cannot be increased. Also on the high voltage side, the voltage that can be applied to the pixel is limited due to the electric breakdown voltage of the signal line driver, and normally, the voltage is approximately equal to the voltage (= operating voltage) that sufficiently drives the liquid crystal. Therefore, since there is almost no voltage width that can be used to accelerate the response speed of the high-voltage side gradation, the response speed to the high-voltage side expressed gradation cannot be increased.

From the above, the overdrive drive is mainly for speeding up the response speed to the halftone and making it substantially equal to the response speed to no voltage application or operating voltage, and to flatten the response characteristics in all gradations. It can be seen that this is a driving method and not a driving method that speeds up the response speed to white display or black display (or black display or white display) that is normally expressed by no voltage application or operating voltage.

As described above, in the case of using the overdrive drive, if the response speed to no voltage is applied or the operating voltage is fast, the response speed is fast in all gradations.
The current response speed of liquid crystal to no voltage application or operating voltage is not yet high enough to display moving images.

Therefore, in order to increase the response speed of the liquid crystal display device, not only the overdrive drive is applied, but also the response speed when no voltage is applied or when the operating voltage is applied must be increased.

The present invention solves the above problems at the same time. That is, an object of the present invention is to provide a horizontal electric field liquid crystal display device in which the response speed of the liquid crystal is flat in all gradation regions, the high speed response is achieved, and the number of image quality defects is small.

[0017]

A pair of substrates, at least one of which is transparent, a liquid crystal layer sandwiched between the pair of substrates, and a pixel electrode on one of the pair of substrates facing the liquid crystal layer. A liquid crystal display section provided with a counter electrode, which generates an electric field in parallel with the substrate by applying a voltage between the pixel electrode and the counter electrode, and display data supplied from a means for supplying data to be displayed, In a liquid crystal display device including a driving unit that drives each pixel of the display unit by applying a voltage corresponding to display data, at least one of the pixel electrode and the counter electrode is made of indium-tin.
The display means is composed of an oxide (ITO) film, and the drive means compares new display data supplied from means for supplying data to be displayed with previous display data, and depending on the comparison result. Data conversion means for converting the display data into predetermined display data is provided.

As the data converting means, when the supplied display data is higher than the value of the previous display data, it is converted into data higher than the supplied display data, and the supplied display data is When the value is lower than the value of the display data, the data is converted to a value lower than the supplied display data.

Further, in the liquid crystal display unit, a thin film transistor, a scanning line connected to the thin film transistor and operating the thin film transistor, and a scanning line which is substantially orthogonal to the scanning line and is connected to the pixel electrode through the thin film transistor, the thin film transistor operates. In this case, a signal wiring for supplying a display signal voltage to the pixel electrode, a common wiring for supplying a counter voltage to the counter electrode, or a scan wiring may be provided.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to Examples.

[First Embodiment] <Single-Pixel Liquid Crystal Display Device> An embodiment in which the present invention is applied to a single-pixel liquid crystal display device will be described below.

FIG. 3 is a block diagram of a single pixel liquid crystal display device according to this embodiment. The liquid crystal display device includes a liquid crystal display unit 400 and a liquid crystal drive circuit unit 401 that receives data from an image output source 402 and converts the data into a voltage signal for driving the liquid crystal display unit 400. The liquid crystal drive circuit unit 401 is composed of a controller 300 and a power supply circuit 301. Each of these parts will be described in detail below.

First, FIG. 4 shows the structure of the wiring side substrate of the liquid crystal display section 400. The pixel electrodes 104 and the counter electrodes 105 are alternately arranged in a comb shape. Here, both the pixel electrode 104 and the counter electrode 105 are composed of an indium tin oxide (ITO) film. Although the indium tin oxide film has conductivity, it does not easily react with the liquid crystal even when a DC voltage is applied, and thus black spots of poor image quality are less likely to occur.

In this embodiment, both the pixel electrode 104 and the counter electrode 105 are designed to have an electrode width of 7 μm and an electrode interval of 10 μm.

Next, a sectional view of the liquid crystal display section 400 (A
-A 'line) is shown in FIG. Lower substrate 201 and upper substrate 2
In No. 02, the transparent glass plates 110 and 116 each having a thickness of 0.7 mm and having a polished surface are used as substrates. The lower substrate 2
01 denotes the pixel electrode 104 and the counter electrode 105 shown in FIG.
However, there is no electrode structure on the upper substrate.
The alignment films 130 and 131 are applied to the innermost outer surfaces of the two substrates and subjected to a rubbing treatment, and then the liquid crystal composition 119 is applied between the substrates.
Is enclosed. Further, the outermost surface on the outer side of the substrate is provided with two polarizing plates 11
The liquid crystal display portion is configured by sandwiching it with 7,118.

In this embodiment, polyimide is used as the alignment film. The rubbing directions on the upper and lower interfaces were substantially parallel to each other, and the angle formed with the direction of the applied electric field was 75 degrees.
The gap between the upper and lower substrates was 4.5 μm in a liquid crystal-enclosed state with spherical polymer beads dispersed and sandwiched between the substrates. The enclosed liquid crystal composition 119 is a composition containing a cyano liquid crystal component, and its refractive index anisotropy Δε is positive at 7.3 (1 kH).
z) and the birefringence Δn is 0.072 (589 nm, 20
(° C.) nematic liquid crystal composition. Therefore, Δn · d
Is 0.324 μm. Made by Nitto Denko as the polarizing plate
Using the G1220DU, make the polarization transmission axis of one of the polarizing plates almost parallel to the rubbing direction (75 degrees), and make the other orthogonal to it (-
15 degrees). As a result, when a voltage is applied between the pixel electrode 104 and the counter electrode 105, a normally closed characteristic can be obtained in which the voltage is not applied and the dark state is obtained, and the high voltage side is in the bright state. The transmitted light intensity of the liquid crystal display section generates an electric field E such that the applied voltage becomes parallel to the substrate 110 between the pixel electrode 104 and the counter electrode 105, and the liquid crystal composition 119.
It is controlled by changing the alignment state of the liquid crystal molecules 120 inside and modulating the polarization state.

Next, FIG. 6 shows a block diagram of the controller 300 in the liquid crystal drive circuit section 401.

The image data supplied from the image output source 402 is temporarily stored in the memory 311. Then, when the new image data is supplied, it is compared with the previous image data stored in the memory 311, and if the new image data is larger than the previous image data, the new image data is set to a larger value and the new image data is changed. If the data is smaller than the previous image data, the data is converted to a smaller value. This data conversion is performed by the lookup table (LU
T) is stored inside the 312 as a conversion table,
By inputting the old image data and the new image data to the LUT 312, the converted data can be obtained. The timing of the converted image data is adjusted, converted into a voltage value by digital-analog conversion, and then output to the liquid crystal display unit 400. Here, the reference voltage and the liquid crystal driving voltage at the time of digital-analog conversion are the power supply circuit 301.
Sourced from. Further, the above data conversion, timing adjustment, and the like are all controlled by the main controller 310.

In this embodiment, the image data supply frequency from the image output source 402 is set to 60 Hz.

FIG. 7 shows the voltage-transmittance characteristic and the voltage-response speed curve of the liquid crystal display section when the above single pixel liquid crystal display device is driven. In this figure, there is no data conversion mode, that is, the voltage-response speed curve when the conversion table in the LUT 312 is adjusted so that the data from the image output source 402 is output as it is, and the overdrive drive by the data conversion. The voltage-response speed curve is shown. Note that FIG. 8 shows a curve when a conventional metal film mainly composed of Cr is used for the pixel electrode and the counter electrode of the liquid crystal display portion. Here, the voltage-response speed curve indicates the time required for the transmittance to change by 90% when there is a voltage change (image data change) from the initial voltage Vi to the ultimate voltage (horizontal axis). It is a curve. 7 and 8, the initial voltage is 0 V with no voltage applied and the operating voltage of the liquid crystal is 6 V.
The voltage-response speed curves are shown respectively.

According to these figures, first, the pixel electrode 10
By using an ITO film for 4 and the counter electrode 105,
It can be seen that the transmittance of the liquid crystal display portion is improved by about 15%, and the response speed to no operating voltage or liquid crystal operating voltage is improved by about 30%. This is because the liquid crystal composition 119 has a high response speed because the electric field is concentrated on the pixel electrode 104 and the counter electrode 105, particularly at the electrode end portion.
When a light-shielding conductive film such as a metal is used for the pixel electrode 104 or the counter electrode 105, light in this portion does not pass through, but the ITO film has a light-transmitting property, so that this response speed is fast. Since the transmitted light can be used, the transmittance is improved and the response speed of the entire pixel is also improved.

Further, the voltage with data conversion shown in FIG. 7 and FIG.
Comparing the response speed curves, the fact that the response speed to no voltage application or operating voltage is faster as described above, the response speed to the halftone region is improved, and the flatness of the response speed is improved. I understand.

Finally, in order to investigate the occurrence of the black-spotted image quality defect due to the DC voltage in this single-pixel liquid crystal display device, it was operated by overdrive for 30 hours in a constant temperature bath at 100 ° C. However, even in this high-temperature accelerated continuous energization test, no black-spotted image quality defect due to application of a DC voltage to the liquid crystal occurred.

From the above, in the present embodiment, in the horizontal electric field type single pixel liquid crystal display device, the ITO film is used for the pixel electrode and the counter electrode of the liquid crystal display section, and the image output source is used for the liquid crystal drive circuit section. By having a means for comparing the data from the previous data with the data and converting the data, the response speed is flattened in the entire gradation region without causing image quality defects,
Moreover, high-speed response was realized.

[Embodiment 2] <Active matrix liquid crystal display device> An embodiment in which the present invention is applied to an active matrix liquid crystal display device will be described below.

FIG. 9 shows a block diagram of an active matrix type liquid crystal display device in this embodiment. The liquid crystal display device includes a liquid crystal display unit 400 and a liquid crystal drive circuit unit 401 that receives data from an image output source 402 and converts the data into a voltage signal for driving the liquid crystal display unit 400. Also,
The liquid crystal drive circuit unit 401 includes a controller 300, a power supply circuit 301, a vertical scanning circuit 302, and a display signal output circuit 303. Each of these parts will be described in detail below.

First, FIG. 1 shows the structure of the TFT side substrate of the liquid crystal display section 400. The scanning wirings 101 and the signal wirings 102 are arranged in a grid pattern, and a thin film transistor 106 is formed at the intersections of the wirings with the respective wirings as terminals. The other terminal of the thin film transistor 106 is connected to the pixel electrode 104 and serves as a switch for applying a voltage to the liquid crystal between the thin film transistor 106 and the counter electrode 105. The counter electrode 105 is connected to the common wiring 103 having a parallel structure with the scanning wiring 101. Here, since the thin film transistor 106 serves as a switch, the voltage applied between the pixel electrode 104 and the counter electrode 105 is not affected by the voltage of another pixel applied to the signal wiring 102, and the next pixel The data is held for a certain period (= refresh rate, usually 60 Hz) until the data is written. As a result, the voltage applied to the liquid crystal composition 119 can accurately maintain the converted voltage in order to improve the response speed by the overdrive driving described later, so that the factor that delays the response speed is reduced and the response speed is substantially reduced. improves.

Next, FIG. 10 shows a cross-sectional view of the liquid crystal display portion 400 taken along the line BB 'in FIG. The lower substrate 201 and the upper substrate 202 are made of transparent glass plates 110 and 116 each having a thickness of 0.7 mm and whose surfaces are polished. Lower substrate 2
In 01, there are the signal wiring 102, the pixel electrode 104, and the counter electrode 105 as shown in FIG. 1, and there are the insulating first layer 111 and the insulating second layer 112 separating them. Here, since the pixel electrode 104 uses the ITO film, it is possible to reduce the occurrence of the black-spotted image quality defect due to the application of the DC voltage to the electrode. Further, since the light at the end of the pixel electrode 104 is transmitted, the response speed to no voltage application or operating voltage becomes faster. Further, since the pixel electrode 104 is arranged in the uppermost layer of the lower substrate 201 and has a structure in contact with the liquid crystal composition 119 via the alignment film 130, the pixel electrode 104 is the insulating second layer 112. The liquid crystal composition 119 at the end portion of the pixel electrode 104 is different from that at the lower side.
Since the efficiency of the electric field applied to the device is high, the response speed at the operating voltage is further increased.

On the other glass plate 116, the pixel electrode 104 and the counter electrode 10 are formed in order to improve the contrast.
A low-conductivity light-shielding layer (black matrix) 115 is formed so as to prevent light from leaking from gaps other than the space 5 between, and red (R), green (G), and blue (B) for color display are formed thereon. The three color filter layers 114 are formed in stripes.
Further, an overcoat layer 113 for flattening the surface was laminated on the color filter to form the upper substrate 202. After the alignment films 130 and 131 are applied to the innermost outer surfaces of the two substrates and subjected to a rubbing treatment, the liquid crystal composition 119 is sealed between the substrates. Further, the outermost surface on the outer side of the substrate is provided with two polarizing plates 11
The liquid crystal display portion is configured by sandwiching it with 7,118.
The conditions such as the alignment film, the liquid crystal composition, and the rubbing direction in this example are the same as in Example 1, and the liquid crystal composition 119 is a composition containing a cyano liquid crystal. Therefore, the voltage-transmittance curve also has a normally closed characteristic as in the first embodiment.

Next, FIG. 11 shows a block diagram of the controller 300 in the liquid crystal drive circuit 401. Image output source 40
As for the image data supplied from No. 2, the image data for one screen is stored in the memory 311. Then, when the new image data of the next screen is supplied, it is compared with the image data of the previous screen stored in the memory 311, and if the image data of the new screen is larger than the previous image data, If the new image data is larger than the previous image data and the new image data is smaller than the previous image data, the data is converted into the overdrive type data so that the value becomes smaller. This data conversion is held as a conversion table in the look-up table (LUT) 312, and the converted data can be obtained by inputting the previous image data and the new image data to the LUT 312. . After the timing of the converted image data is adjusted, the vertical scanning circuit 302
And to the display signal output circuit 303 together with the control signal. The above data conversion and timing adjustment are all controlled by the main controller 310.
In the present embodiment, the screen rewriting frequency of the image data supplied from the image output source 402 is the normal 60 Hz.

By using the liquid crystal drive circuit unit 401 having the above-mentioned configuration, the liquid crystal display unit 400, which has a high response speed when no voltage is applied or at operating voltage, is overdriven by image data conversion, and all floors are driven. The response speed is flat in the adjustment area, and high-speed response can be achieved.

Also in the liquid crystal display device of the present embodiment, no black-spotted image quality defect occurred even when the continuous energization test of high temperature acceleration was carried out.

As described above, in this embodiment, in the horizontal electric field type active matrix type liquid crystal display device, the ITO film is used for the pixel electrode of the liquid crystal display portion, and
The liquid crystal drive circuit unit has means for comparing data from the image output source with the previous data and converting the data, so that the response speed is flat and high in all gradation regions without causing image quality defects. Response was realized.

[Embodiment 3] This embodiment is the same as Embodiment 2 except for the following points.

FIG. 12 shows the liquid crystal display unit 40 in this embodiment.
The structure of the TFT side substrate of No. 0 is shown. Scan line 101, signal line 102, thin film transistor 106, pixel electrode 10
4 and the common wiring 103 are the same as those in the second embodiment, but in this embodiment, the counter electrode 105 is made of the ITO film like the pixel electrode 104. As a result, defective images are less likely to occur, and the response speed to no voltage application or operating voltage is further increased. Here, the counter electrode 105
Is made of an ITO film, but the common wiring 103 to which the counter electrode 105 is connected is made of a metal film.
If the common wiring 103 is made of an ITO film, the wiring resistance becomes large and the waveform delay becomes large, so that the response speed of the liquid crystal becomes slow, but this is avoided in the present embodiment.

Further, FIG. 13 shows a cross-sectional view of the liquid crystal display portion 400 taken along the line CC ′ in FIG. 12, but in the present embodiment, the counter electrode 105, like the pixel electrode 104, also includes the lower substrate 201. Is disposed on the uppermost layer of the liquid crystal composition 1
Since it is in contact with 19 via the alignment film 130, the response speed to the operating voltage can be further increased.

From the above, in the present embodiment, the second embodiment
Furthermore, since the image quality is not further deteriorated and the response speed to no voltage is applied and the operating voltage is high, the response speed can be further flattened and the response speed can be further increased in the entire gradation region.

[Embodiment 4] This embodiment is the same as Embodiment 2 except for the following points.

FIG. 14 shows the structure of the TFT side substrate of the liquid crystal display section 400. The scanning wiring 101, the signal wiring 102, the thin film transistor 106, and the pixel electrode 104 are the same as those in the second embodiment, but in this embodiment, the counter electrode 105 is connected to the preceding scanning wiring 101. Even in the case of the horizontal electric field type active matrix type liquid crystal display device having such a structure, since the ITO film is used for the pixel electrode 104,
Poor image quality is less likely to occur, and no voltage is applied and the response speed to the operating voltage is increased. Further, since it has a data conversion function similar to that of the second embodiment, the response speed to no voltage application or operating voltage is increased, so that it is flat in all gradation regions and the response speed is high. Was realized.

[Embodiment 5] This embodiment is the same as Embodiment 4 except for the following points.

FIG. 15 shows the liquid crystal display unit 40 in this embodiment.
The structure of the TFT side substrate of No. 0 is shown. Scan line 101, signal line 102, thin film transistor 106, pixel electrode 10
4 and the common wiring 103 are the same as those in the fourth embodiment, but in the present embodiment, the counter electrode 105 is made of the ITO film like the pixel electrode 104. As a result, defective images are less likely to occur, and the response speed to no voltage application or operating voltage is further increased. Here, the counter electrode 105
Is made of an ITO film, but the scanning wiring 101 to which the counter electrode 105 is connected is made of a metal film.
If the scanning wiring 101 is made of an ITO film, the wiring resistance becomes large and the waveform delay becomes large, so that the response speed of the liquid crystal becomes slow, but this is avoided in the present embodiment.

The cross-sectional view of the liquid crystal display unit 400 is the same as that of the third embodiment, the counter electrode 105 is arranged on the uppermost layer of the lower substrate 201, like the pixel electrode 104, and is aligned with the liquid crystal composition 119. Since the structure is in contact with the film 130, the response speed to the operating voltage can be further increased as compared with the fourth embodiment.

From the above, in the present embodiment, the fourth embodiment
Without causing further image quality deterioration, and because the response speed when no voltage is applied and when the operating voltage is high,
It was possible to further flatten the response speed and increase the response speed in all gradation regions.

[Embodiment 6] This embodiment is the same as Embodiment 3 except for the following points.

FIG. 16 shows a liquid crystal display section 40 in this embodiment.
The structure of the TFT side substrate of No. 0 is shown. Scan line 101, signal line 102, thin film transistor 106, pixel electrode 10
The configuration of the common wiring 103 and the common wiring 103 is the same as that of the third embodiment, but the counter electrode 105 overlaps the upper portion of the signal wiring 102 in the present embodiment.

FIG. 17 is a sectional view of the liquid crystal display section 400 taken along the line DD 'in FIG. As described above, the difference from Example 3 is that the counter electrode 105 is sandwiched between the signal line 102 and the liquid crystal composition 119 with the insulating second layer 112 interposed therebetween. With this configuration, a crosstalk electric field from the signal wiring 102 to the counter electrode 105 is generated in the liquid crystal composition 1.
19 does not pass through, and the electric field is effectively applied to the liquid crystal composition 119 at the end portions of the pixel electrode 104 and the counter electrode 105. Therefore, the response speed when no voltage is applied or at the operating voltage is further increased in this portion. Speed up.

As described above, in this embodiment, the response speed can be flattened and the response speed can be made faster than in the third embodiment.

[Embodiment 7] This embodiment is the same as Embodiment 5 except for the following points.

FIG. 18 shows a liquid crystal display section 40 in this embodiment.
The structure of the TFT side substrate of No. 0 is shown. Scan line 101, signal line 102, thin film transistor 106, pixel electrode 10
4 and the common wiring 103 are the same as those in the fifth embodiment, but in this embodiment, the counter electrode 105 overlaps the signal wiring 102.

The sectional view of the liquid crystal display portion 400 in this embodiment is the same as that in the sixth embodiment. As described above, the difference from Example 5 is that the counter electrode 105 is sandwiched between the signal line 102 and the liquid crystal composition 119 with the insulating second layer 112 interposed therebetween. With this configuration, a crosstalk electric field from the signal wiring 102 to the counter electrode 105 is generated in the liquid crystal composition 1.
19 and the electric field is effectively applied to the liquid crystal composition 119 at the end portions of the pixel electrode 104 and the counter electrode 105. Therefore, the response speed to no voltage application or operating voltage is further increased in this portion. As described above, in the present embodiment, the response speed can be flattened and the response speed can be increased in the entire gradation region as compared with the fifth embodiment.

[Embodiment 8] This embodiment is the same as Embodiments 1 to 7 except for the following points.

FIG. 19 shows the controller 3 in this embodiment.
Indicates 00. In this embodiment, the controller 300 outputs the screen rewriting frequency (output scan rate) output to the vertical scanning circuit 302 and the display signal output circuit 303 to the screen rewriting frequency (input scan rate) of the image data supplied from the image output source 402. ) Has a scan rate conversion function that converts it into an integer multiple or arbitrary magnification.
For example, when converting the output scan rate to double,
The image data supplied from the image output source 402 is stored in the memory 311 for one screen, and while the data for the next one screen is being transferred, the data for the previous screen stored in the memory 311 is stored. The data is output twice to the display signal output circuit 303. Alternatively, the motion compensation circuit or the like causes the main controller 310 to generate the image data of the intermediate screen from the image data of the previous screen and the next screen, and outputs it. Of course, data conversion for overdrive driving is also executed at the same time, but when the data stored in the memory 311 is output again as in the former case, the image data does not substantially change, so data conversion is not performed. I will not be missed.

In the data conversion by the overdrive drive, in order to normally create the data conversion table in the LUT 312 so that the target transmittance is reached after one scan cycle, by increasing the frequency of the scan rate, all the gradations are further increased. It is possible to improve the response speed of.

However, for this purpose, the response speed of the liquid crystal to no voltage applied or to the operating voltage must be about the same as one scan cycle.

Conversely, if one scan cycle can be changed to an extent equivalent to the response speed of a certain liquid crystal composition to no voltage application or operating voltage, the drive circuit can maximize the characteristics of the liquid crystal composition. .

In this embodiment, like the other embodiments,
Since the pixel electrode 104 and the counter electrode 105 are made of the ITO film, the response speed to no voltage application or operating voltage is increased. By changing the one scan cycle according to the response speed and performing overdrive driving, it was possible to further flatten the response speed and achieve a faster response in the entire gradation region.

Further, in this embodiment, even when a high-speed response liquid crystal different from the other embodiments is used as the liquid crystal composition 119, the response characteristic of the liquid crystal can be maximized, and all gradations can be obtained. The response characteristics are flat and high-speed response can be realized.

As described above, according to the present invention, by using the ITO film for the pixel electrode and the counter electrode, even if a DC voltage is applied to the liquid crystal by overdrive driving, it is difficult to react with the liquid crystal and no voltage is applied. It is possible to speed up the response speed of the gradation change to the operating voltage. By performing overdrive drive on this liquid crystal display unit to compare the old and new image data from the image output source and convert the image data, the image quality is less defective, the response speed is flat in all gradation regions,
Moreover, a liquid crystal display device capable of high-speed response can be obtained. Here, since both the pixel electrode and the counter electrode are made of ITO film, the part that easily reacts with the liquid crystal is reduced, so that the image quality is less likely to occur, and the voltage is not applied and the response speed to the operating voltage is high. Therefore, a liquid crystal display device capable of higher speed response can be obtained. Further, by arranging the pixel electrode and the counter electrode in contact with the liquid crystal layer via the alignment film, a voltage is efficiently applied to the liquid crystal at the upper end of the electrode, so that a liquid crystal display device capable of higher speed response is provided. can get. Furthermore, by adjusting the screen rewriting frequency according to the response speed when no voltage is applied or operating voltage, and by adjusting the data conversion table for overdrive drive, a liquid crystal display device that can achieve even faster response is obtained. To be

[0069]

According to the present invention, it is possible to provide a liquid crystal display device which achieves both a response speed and improvement of image quality defect.

[Brief description of drawings]

FIG. 1 is a diagram showing a planar structure of a liquid crystal display unit according to a second embodiment of the present invention.

FIG. 2 is an explanatory diagram of overdrive driving.

FIG. 3 is a block diagram of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a planar structure of the liquid crystal display unit according to the first embodiment of the present invention.

5 is a diagram showing a cross-sectional structure of the liquid crystal display portion taken along the line AA ′ in FIG.

FIG. 6 illustrates a configuration of a controller according to the first exemplary embodiment.

FIG. 7 shows a voltage-transmittance curve and a voltage-response speed curve in the liquid crystal display device of Example 1.

FIG. 8 shows a voltage-transmittance curve and a voltage-response speed curve in a conventional liquid crystal display device.

FIG. 9 is a block diagram of a liquid crystal display device according to a second embodiment.

10 is a diagram showing a cross-sectional structure of the liquid crystal display portion taken along the line BB ′ of FIG.

FIG. 11 is a diagram showing a configuration of a controller according to the second embodiment.

FIG. 12 is a diagram showing a planar structure of a liquid crystal display unit of Example 3;

13 is a diagram showing a cross-sectional structure of the liquid crystal display portion taken along the line CC ′ of FIG.

FIG. 14 is a diagram showing a planar structure of a liquid crystal display unit of Example 4.

FIG. 15 is a diagram showing a planar structure of a liquid crystal display unit of Example 5.

FIG. 16 is a diagram showing a planar structure of a liquid crystal display unit of Example 6.

17 is a diagram showing a cross-sectional structure of the liquid crystal display section taken along the line DD ′ of FIG.

FIG. 18 is a diagram showing a planar structure of a liquid crystal display unit of Example 7.

FIG. 19 is a diagram showing the configuration of a controller according to the eighth embodiment.

[Explanation of symbols]

100, 101 ... Scan wiring, 102 ... Signal wiring, 103
... common wiring, 104 ... pixel electrode, 105 ... counter electrode, 1
06 ... Thin film transistor, 107, 108, 109, 1
10 ... Lower glass plate, 111 ... Insulating first layer, 112 ... Insulating second layer, 113 ... Overcoat layer, 114 ... Color filter layer, 115 ... Light-shielding layer (black matrix),
116 ... Upper glass plate 117, 118 ... Polarizing plate, 11
9 ... Liquid crystal composition, 120 ... Liquid crystal molecule, 130, 131 ...
Alignment film, 201 ... Lower glass substrate, 202 ... Upper glass substrate, 300 ... Controller, 301 ... Power supply circuit, 30
2 ... Vertical scanning circuit, 303 ... Display signal output circuit, 310
... main controller 311, memory 312, lookup table (LUT) 313 DA converter,
400 ... Liquid crystal display section, 401 ... Liquid crystal drive circuit section, 402
Image output source, 500 Graph of applied voltage and optical response,
501 ... Voltage waveform during normal drive, 502 ... Voltage waveform during overdrive, 503 ... Optical response of liquid crystal during normal drive, 504 ... Optical response during overdrive, 505
… Optical response when overdrive voltage is continuously applied.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI G09G 3/20 670 G02F 1/136 500 (72) Inventor Keikazu Araya 7-1 Omika-cho, Hitachi-shi, Ibaraki Co., Ltd. Hitachi, Ltd., Hitachi Research Laboratory (56) Reference JP-A-11-126050 (JP, A) JP-A-8-340505 (JP, A) JP-A-4-318595 (JP, A) International Publication 99/035521 (WO , A1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G09G 3/36 G02F 1/133 550 G02F 1/1368 G09G 3/20 612 G09G 3/20 621 G09G 3/20 670

Claims (8)

(57) [Claims] 1. A pair of substrates, at least one of which is transparent, a liquid crystal layer sandwiched between the pair of substrates, and a pixel electrode and a counter electrode on one of the pair of substrates facing the liquid crystal layer. Display data is supplied from a liquid crystal display unit which is provided and mainly generates an electric field in parallel with the substrate by applying a voltage between the pixel electrode and the counter electrode, and display data is supplied from the liquid crystal display unit. In a liquid crystal display device including a driving unit that drives each pixel of the unit by applying a voltage corresponding to display data, at least one of the pixel electrode and the counter electrode is IT.
The display means is composed of an O film, and the drive means compares the new display data supplied from the means for supplying the data to be displayed with the previous display data, and displays the display data according to the comparison result. A liquid crystal display device comprising data conversion means for converting display data. 2. The data conversion means according to claim 1, when the supplied display data is higher than the value of the previous display data, the data conversion means converts the supplied display data into data higher than the supplied display data, and the supplied display. A liquid crystal display device that converts data to a value lower than the supplied display data when the data is lower than the value of the previous display data. 3. The liquid crystal display unit according to claim 1, wherein the liquid crystal display section includes a thin film transistor, a scanning line connected to the thin film transistor and operating the thin film transistor, and substantially orthogonal to the scanning line, and via the pixel electrode and the thin film transistor. A liquid crystal display device comprising: a signal line that is connected and supplies a display signal voltage to a pixel electrode when a thin film transistor operates; and a common line that supplies a counter voltage to a counter electrode. 4. The liquid crystal display unit according to claim 1, wherein the liquid crystal display section includes a thin film transistor, a scanning line which is connected to the thin film transistor to operate and which supplies a counter voltage to a counter electrode, and the scan line. A liquid crystal display device, comprising a signal line connected to the pixel electrode through a thin film transistor and supplying a display signal voltage to the pixel electrode when the thin film transistor operates. 5. The conductive film according to claim 3 or 4, wherein at least a part of the counter electrode is formed of an ITO film, and the common wiring to which the counter electrode is connected or the scanning wiring is made of another conductive material different from ITO. Liquid crystal display device composed of a film. 6. The liquid crystal display according to claim 1, wherein a part of the counter electrode or the pixel electrode is in contact with the liquid crystal layer via an alignment film, and the electrode is made of an ITO film. apparatus. 7. The liquid crystal display device according to claim 3, wherein the counter electrode is sandwiched between the signal line and the liquid crystal layer with an insulating layer interposed therebetween. 8. The screen of the liquid crystal display unit according to claim 1, wherein the drive means has an integral multiple of a rewriting frequency of a screen supplied from a means for supplying display data, or an arbitrary frequency. Liquid crystal display device that has the function of converting the rewriting frequency.