CN1818752A - Electrooptical apparatus, driving device and method for electrooptical apparatus, and electronic equipment - Google Patents

Abstract

The substrate includes a plurality of pixel electrodes, TFTs for switching the pixel electrodes, scanning lines for supplying scanning signals to the gates of the TFTs, data lines for supplying image signals to the pixel electrodes via the TFTs when the TFTs are turned on, and A scan signal supply circuit that supplies scan signals line-sequentially. The scanning signal supply circuit fixes the scanning signal at an intermediate potential for a predetermined time while turning the TFT to a high potential in an on state and a low potential in an off state.

Description

Electro-optical device, driving device, driving method and electronic device thereof

technical field

The present invention belongs to the technical field of electro-optic devices such as liquid crystal devices, in particular, belongs to the method of providing a transistor for switching and controlling pixel electrodes arranged in a matrix and supplying scanning signals in line order to the scanning lines arranged in each pixel row so as to perform effective operation. The technical field of electro-optical devices in the form of source matrix driving, driving devices suitable for use in such electro-optical devices, and electronic devices equipped with such electro-optical devices.

Background technique

In such an electro-optical device, a pixel electrode, a thin film transistor (hereinafter appropriately referred to as TFT) for switching the pixel electrode, a scanning line for supplying a scanning signal to the gate of the TFT, and a gate of the TFT are arranged on a substrate. A data line for supplying an image signal, a storage capacitor connected to a pixel electrode, and the like are provided in the image display area. Further, driving circuits such as a scanning line driving circuit for supplying scanning signals to the scanning lines, a data line driving circuit for supplying image signals to the data lines, and a sampling circuit are provided in a peripheral area located around the image display area.

More specifically, the scanning line driver circuit supplies a scanning signal having a pulse-like waveform to each scanning line or row sequentially. That is, a scanning signal is supplied to turn off the TFTs connected to the scanning line in the mth (here, m is a natural number) row, and simultaneously turn on the TFTs connected to the scanning line in the (m+1)th row. In parallel with this, the data line drive circuit supplies an image signal to each data line in each horizontal scanning period, so that the image signal is written from the source of the TFT turned on by the scanning signal to the pixel electrode through the drain. Then, by supplying such a scanning signal and an image signal, an image of one row is written in one horizontal scanning period. Furthermore, this writing operation is performed sequentially for all the rows in the vertical scanning period, and constitutes writing of one image.

However, since TFTs, scan lines, capacitor lines, data lines, etc. are made in the gaps of the pixel electrodes arranged in a matrix on the plane, the pixel electrodes of the m+1th row and the drains of the TFTs of the mth row, scan lines, There is parasitic capacitance between the capacitor lines and the like. Therefore, if the TFTs in the m+1th row are turned on at the instant when the TFTs in the mth row are turned off using a scanning signal having a pulse-like waveform, the image signal written to the pixel electrodes in the mth row In , the scanning signal etc. in the m+1th row are added as noise. As a result, the pixel potential that should be held in each pixel electrode changes. In particular, unevenness occurs on a pixel-by-pixel basis in the parasitic capacitance, so there is a problem that pixel color unevenness eventually occurs on a displayed image.

Moreover, following the general requirements in the technical field of high-definition display images, along with the miniaturization of the pixel pitch, the pixel electrodes in the m+1th row and the drains, scanning lines, and capacitors of the TFTs in the mth row The parasitic capacitance between lines and the like relatively increases, so that the above-mentioned problem becomes more serious.

In addition, the waveform of the scan signal becomes dull due to this wiring capacitance. Therefore, the degree of dulling of the scanning signal is greater in the peripheral portion of the image display area close to the scanning line driving circuit and in the central portion of the image display area farther from the scanning line driving circuit, whichever is the latter. Therefore, the timing of turning on and off of the TFT differs between the peripheral portion and the central portion according to the extent to which the waveform of the scanning signal becomes dull. As a result, as described above, the influence of noise caused by the scanning signal of the next line, etc., which is mixed into the image signal when the TFT is turned off is also different between the peripheral portion and the central portion. Therefore, in particular, in order to prevent deterioration of the liquid crystal and the like and prevent flickering, when an AC inversion driving in which the driving potential of each pixel electrode is reversed is used in a field period, etc., in the center of the image display area, if the counter electrode is adjusted Potential, so that no DC component is generated in the potential applied to the liquid crystal, and such a DC component is generated in the peripheral portion. Conversely, in the peripheral portion of the image display area, if the potential of the scanning signal etc. is adjusted so that no DC component is generated in the potential applied to the liquid crystal, such a DC component is generated in the central portion. Therefore, there is a problem of flicker occurring in both the peripheral portion and the central portion.

On the other hand, considering the scanning line of the m-th row and the TFT of the m-th row driven by it, since there is a parasitic capacitance between the scanning line and the drain of the TFT, the pulse-like waveform of the scanning signal has an effect on the pixel potential in the drain. Influence. Specifically, at the moment when the corresponding gate is turned off, the pulse-like potential corresponding to the pulse-like waveform of the scanning line is attached as noise to the potential of the image signal and held as the pixel potential. Therefore, at this time, since the degree of bluntness of the scanning signal differs between the peripheral portion and the central portion, the influence of noise mixed into the image signal also differs between the peripheral portion and the central portion. Therefore, the potentials applied to the liquid crystals are different, resulting in different luminance levels, and there is also a problem that flickering occurs in either the peripheral portion or the central portion when the alternating current is reversed. Furthermore, in order to prevent such flicker from occurring, Japanese Unexamined Patent Application Laid-Open No. 6-110035 discloses a technique in which the falling waveform of the scanning signal is not a rectangular waveform but a ramp waveform or a stepped waveform. However, this method cannot prevent the occurrence of pixel color unevenness and flicker due to parasitic capacitance between the pixel electrode of the m+1th row and the drain of the TFT of the mth row, the scanning line, the capacitor line, and the like.

Contents of the invention

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an electro-optical device capable of high-quality image display in order to enable reduction of brightness unevenness and flicker in both the central portion and the peripheral portion of an image display area. , a driving device suitable for such an electro-optical device, and an electronic device equipped with such an electro-optical device.

In order to solve the above-mentioned problems, the electro-optic device of the present invention includes a plurality of pixel electrodes arranged in a matrix on a substrate, a thin film transistor for switching and controlling the pixel electrodes, and a gate of the thin film transistor should be supplied so that the thin film transistor A scanning line provided for a scanning signal to be in an on state or an off state, a data line provided for supplying an image signal to the pixel electrode via its source and drain when the thin film transistor is in the on state, and the scanning line sequentially A scanning signal supply circuit for supplying the above-mentioned scanning signal by line. The scan signal supply circuit changes the potential of the scan signal from the high potential that turns the thin film transistor on to the low potential that turns the thin film transistor on, and when the potential of the scan signal changes from the low potential to the off state. While changing to the high potential, the potential of the scan signal is fixed at an intermediate potential between the high potential and the low potential for a predetermined time.

According to the electro-optic device of the present invention, when it is in operation, scan signals are supplied to the thin film transistors line-sequentially from the scan signal supply circuit via the scan lines provided on the substrate. In parallel with this, an image signal is supplied to the source of the thin film transistor via the data line. Then, an image signal is written into each pixel electrode via the thin film transistor turned on by the scanning signal. Thus, electro-optical operation using an active matrix driving method becomes possible.

Here, in particular, the scanning signal supply circuit fixes the potential of the scanning signal at an intermediate potential for a predetermined time while changing the potential of the scanning signal from a high potential to a low potential for each scanning line. In addition, while changing the potential of the scanning signal from a low potential to a high potential for each scanning line, the potential of the scanning signal is fixed at an intermediate potential for a predetermined time. Therefore, if the scanning lines of the mth row and the m+1th row are considered, the period in which the potential of the mth row of the scanning line drops from a high potential to an intermediate potential and the period in which the potential of the m+1th row of the scanning line changes from a low potential to Periods during which the potential rises to an intermediate potential can be overlapped. Alternatively, the period in which the potential of the scan line in the mth row falls from the high potential to the middle potential and the period in which the potential of the scan line in the m+1th row rises from the low potential to the middle potential may be overlapped. These results are that when the TFTs in the mth row are turned off, according to the parasitic capacitance between the pixel electrodes of the m+1th row and the drains of the thin film transistors in the mth row, scanning lines, etc., even the TFTs in the m+1th row Scanning signals and the like are mixed as noise into the image signal written to the pixel electrodes in the mth row, and the transistors in the mth row are not completely turned off, so the change in the pixel potential that should be held in each pixel electrode is reduced. quantity. That is, changing the scanning signal directly from a high potential to a low potential reduces the amount of potential change of the temporary scanning signal compared with the case of directly changing the scanning signal from a low potential to a high potential, thereby reducing the size of the relevant parasitic capacitance. amount of noise. Thus, although there is unevenness in units of pixels in the parasitic capacitance concerned, it is possible to reduce pixel color unevenness generated on a finally displayed image. Therefore, even if the related parasitic capacitance relatively increases due to the miniaturization of the pixel pitch, the adverse effect on the image quality can be reduced.

In addition, in the case of using AC inversion driving, in both the central part and the peripheral part of the image display area, since the waveform shape of the scanning signal can be adjusted so that there is no difference in the DC component in the pixel potential, so in both Both reduce flicker. Similarly, even if the scanning signal or the like exerts a bad influence on the pixel potential due to the parasitic capacitance existing between the scanning line in the m-th row and the drain of the TFT in the m-th row driven by it, assuming the degree of influence in the peripheral part and the central part are the same, flickering in both the peripheral and central portions at the time of alternating current reversal can still be reduced.

The above results enable the reduction of pixel color unevenness and flicker in both the central portion and the peripheral portion of the pixel display area, enabling high-quality image display.

In one aspect of the electro-optic device of the present invention, the scanning signal supply circuit supplies the scanning signal such that the preceding scanning signal of the two scanning signals supplied to adjacent scanning lines changes from the high potential to the intermediate potential. The period overlaps with the period during which the subsequent scanning signal changes from the low potential to the intermediate potential.

According to this aspect, the period in which the preceding scanning signal changes from high potential to intermediate potential in the scanning line on the mth row overlaps with the period in which the subsequent scanning signal changes from low potential to intermediate potential in the scanning line on the (m+1)th row. stand up. Therefore, even if the scanning signal in the m+1th row etc. is mixed as noise into the image signal written to the pixel electrode in the mth row, compared with the case where the scanning signal is directly changed between a high potential and a low potential, , which also reduces the amount of noise.

In another aspect of the electro-optical device of the present invention, the intermediate potential is set to a potential at which the thin film transistor is incompletely turned on.

According to this aspect, when the thin film transistors in the mth row are changed from the fully on state to the incompletely off state, the thin film transistors in the m+1th row are changed from the completely off state to the incompletely on state. Therefore, even if the scanning signal in the m+1th row is mixed into the image signal written into the pixel electrode in the mth row as noise, it is not the same as directly changing the thin film transistor between a completely on state and a completely off state. Compared with the case, the amount of noise can also be reduced.

In another aspect of the electro-optical device according to the present invention, the scanning signal supply circuit fixes the potential of the scanning signal at a range including the intermediate potential for a predetermined period while changing the potential of the scanning signal from the high potential to the low potential. In the process of changing the potential of the scanning signal from the low potential to the high potential, each of them is fixed at a plurality of different potentials including the intermediate potential within a predetermined period. .

According to this aspect, when the scanning signal changes between a high potential and a low potential, its potential changes stepwise. Therefore, compared with the case where the scanning signal is directly changed between a high potential and a low potential, the amount of potential change of the temporary scanning signal can be reduced, or high-frequency components in the scanning signal can be reduced. According to this, the relative noise amount to the size of the parasitic capacitance as described above can be reduced.

In another aspect of the electro-optic device of the present invention, the scanning signal supply circuit includes a shift register circuit that sequentially outputs a transmission signal for each of the scanning lines, and simultaneously transmits the scanning signal line-sequentially while inputting the transmission signal. An output circuit for outputting to the above-mentioned scanning lines, and a power variation circuit for changing an external power supply that defines a high potential on the output side of the output circuit in binary.

According to this aspect, when the scanning signal supply circuit operates, the shift register circuit sequentially outputs the transfer signal to each scanning line. And, the scanning signal is output to the scanning lines line-sequentially by the output circuit according to the transfer signal. Here, in particular, the high potential external power supply that defines the output side of the output circuit is changed by a binary value by the power supply varying circuit. Therefore, the potential of the scanning signal in the mth row can be changed from a high potential to an intermediate potential, and then changed from an intermediate potential to a low potential after a predetermined time, and at the same time, the potential of the scanning signal in the m+1th row can be changed from a low potential to a low potential. The potential changes to an intermediate potential, and then changes from the intermediate potential to a high potential over a predetermined period of time.

In an aspect of the shift register circuit or the like, the output circuit may be constituted by an inverter circuit or a buffer circuit including a complementary transistor circuit connecting the external power supply to a high potential side.

With such a configuration, the external power supply that specifies the high potential on the output side can be changed in binary by the inverter circuit or buffer circuit in the power supply variable circuit, and the scanning signal can be changed to an intermediate potential relatively easily. Furthermore, the inverter circuit or buffer circuit may have an amplification function.

In an aspect of the shift register circuit or the like, the power supply varying circuit may include a switch for switching and outputting two power supplies.

With such a configuration, the high potential on the output side of the output circuit can be reliably changed in binary, and the scanning signal can be changed to an intermediate potential relatively easily.

In an aspect of the shift register circuit or the like, the power supply varying circuit may include a programmable DA (digital-to-analog) converter that converts and outputs two power supplies.

According to this configuration, the high potential on the output side of the output circuit can be reliably changed in binary, and the scanning signal can be changed to an intermediate potential relatively easily.

In an aspect of the shift register circuit, etc., the output circuit includes a first system unit that sequentially outputs the scanning signal to odd-numbered scanning lines among the plurality of scanning lines and a first system unit that sequentially outputs the scanning signal to even-numbered lines among the plurality of scanning lines. The scanning line sequentially outputs the second system part of the scanning signal, and the power supply variation circuit can be configured to change the external power supply in binary values other than the first system part and the second system part.

With such a configuration, since the potential of the scanning signal is changed to an intermediate potential in the first system part and the second system part, when the 1H inversion driving method in which the driving potential of the pixel electrode is alternately inverted for each scanning line is adopted , Even if scanning signals and the like are doped as noise due to the effect of parasitic capacitance as described above, occurrence of flicker can be effectively prevented.

In another aspect of the electro-optic device of the present invention, it further includes a counter substrate facing the above-mentioned substrate, and an electro-optic material layer sandwiched between the above-mentioned substrate and the above-mentioned counter substrate.

With such a configuration, an electro-optical device such as a liquid crystal device in which the electro-optic material layer is sandwiched between the pair of substrates and the counter substrate can be realized.

In order to solve the above-mentioned problems, the electro-optic device of the present invention includes a plurality of pixel electrodes arranged in a matrix on a substrate, a thin film transistor for switching and controlling the pixel electrodes, and a gate of the thin film transistor should be supplied so that the thin film transistor A scanning line provided for a scanning signal to be in an on state or an off state, and a data line provided for supplying an image signal to the pixel electrode via a source and a drain of the thin film transistor when the thin film transistor is in the on state. It also includes changing the potential of the scan signal from the high potential that turns the thin film transistor into the on state to the low potential that turns the thin film transistor into the off state, and changing the potential of the scan signal from the low potential to the high potential. A scan signal supply circuit that fixes the potential of the scan signal at an intermediate potential between the high potential and the low potential for a predetermined time while the potential is changing.

According to the driving device of the electro-optical device of the present invention, by the same effect as in the case of the above-mentioned electro-optical device of the present invention, it becomes possible to reduce pixel color unevenness and flicker in both the central part and the peripheral part of the image display area, and the high High-quality image display is possible.

In one aspect of the electro-optic device driving device of the present invention, the scanning signal supply circuit includes a shift register circuit that sequentially outputs a transfer signal for each of the scanning lines, and sequentially shifts the transfer signal line by line while inputting the transfer signal. The scan signal is output to an output circuit in the scan line, and a power variation circuit that changes an external power supply that specifies a high potential on an output side of the output circuit in binary.

According to this aspect, when the scanning signal supply circuit operates, the shift register circuit sequentially outputs the transfer signal to each scanning line. And, the scanning signal is output to the scanning lines line-sequentially by the output circuit according to the transfer signal. Here, in particular, the high potential external power supply that defines the output side of the output circuit is changed by a binary value by the power supply varying circuit. Therefore, the potential of the scanning signal in the mth row can be changed from a high potential to an intermediate potential, and then changed from an intermediate potential to a low potential after a predetermined time, and at the same time, the potential of the scanning signal in the m+1th row can be changed from a low potential to a low potential. The potential changes to an intermediate potential, and then changes from the intermediate potential to a high potential over a predetermined period of time.

In another aspect of the driving device of the electro-optical device according to the present invention, it further includes an image signal supply circuit for supplying the image signal to the data line.

According to this aspect, the scan signal can be supplied from the scan signal supply circuit, and the image signal can be supplied from the image signal supply circuit at the same time. A driving device including such a scanning signal supply circuit and an image signal supply circuit can be fabricated on the substrate of the electro-optic device, and can be constructed as an external IC (integrated circuit) connected to the electro-optic device.

In order to solve the above-mentioned problems, an electronic device of the present invention includes the above-mentioned electro-optical device of the present invention (here, various forms thereof are also included).

According to the electronic device of the present invention, since it is constituted with the above-mentioned electro-optic device of the present invention, pixel color unevenness and flickering are reduced, and projectors, liquid crystal televisions, mobile phones, electronic notebooks, etc. with excellent display quality can be realized. Various electronic devices such as word processors, viewfinder or direct-view video recorders, workstations, video phones, POS terminals, and touch screens.

Such effects and other advantages of the present invention can be understood from the examples described below.

Description of drawings

1 is a circuit diagram showing equivalent circuits of various elements, wiring, and the like provided on a plurality of pixels in a matrix forming an image display area in an embodiment of the electro-optical device of the present invention, together with peripheral driving circuits.

2 is a plan view of a TFT array substrate on which data lines, scan lines, pixel electrodes, etc. in the electro-optic device of the embodiment are formed.

FIG. 3 is a timing chart of data signals, scan signals, and the like in a comparative example.

Fig. 4 is a block diagram of the middle wave circuit and the scanning signal supply circuit in this embodiment.

FIG. 5 is a timing chart of data signals, scan signals, and the like in this embodiment.

6 is a timing chart showing the timing of data line drive signals, scan signals, and the like in the second embodiment of the present invention.

Fig. 7 is a block diagram of a midband circuit and a scanning signal supply circuit in the second embodiment.

8 is a plan view of the TFT array substrate in the electro-optical device of the embodiment as viewed from the opposite substrate side, and each component formed thereon.

Fig. 9 is a H-H' sectional view of Fig. 8 .

10 is a diagrammatic sectional view showing a color liquid crystal projector as an example of a projection type color display device which is an embodiment of the electronic device of the present invention.

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following examples, the electro-optical device of the present invention is applied to a liquid crystal device.

(first embodiment)

A first embodiment of the electro-optical device of the present invention will be described with reference to FIGS. 1 to 5. FIG.

First, the basic structure of the electro-optical device in the first embodiment will be described with reference to FIGS. 1 to 3 . Here, FIG. 1 is a circuit diagram showing equivalent circuits of various elements, wiring, and the like on a plurality of pixels formed in a matrix forming an image display region of an electro-optic device together with peripheral driving circuits. 2 is a plan view of a plurality of adjacent pixel groups of a TFT array substrate on which data lines, scanning lines, pixel electrodes, etc. are formed. FIG. 3 is a timing chart of data signals, scan signals, and the like in a comparative example.

In FIG. 1, a pixel electrode 9a and a TFT 30 for switching and controlling the pixel electrode 9a are respectively formed on a plurality of pixels formed in a matrix constituting the image display area of the electro-optic device of this embodiment, and an image signal is supplied. The data line 6a is electrically connected to the source of the TFT30. The scanning line 3a for supplying a scanning signal is electrically connected to the gate of the TFT 30 . The pixel electrode 9 a and the storage capacitor 70 are electrically connected to the drain of the TFT 30 .

The electro-optical device is provided with a data signal supply circuit 101 and a scanning signal supply circuit 104 in a peripheral area located around the image display area.

The data signal supply circuit 101 includes a data line driving circuit, a sampling circuit, etc., and is configured to sample image signals on the image signal lines at a predetermined timing, and sequentially write them as image signals S1, S2, ..., Sn to each on the data line 6a.

On the other hand, the scanning signal supply circuit 104 is configured to supply the scanning signals G1 , G2 , .

Furthermore, in this embodiment, in particular, scanning signals G1, G2, ..., Gm not only obtain the high level that makes TFT30 turn on and the low level that makes TFT30 turn off, but also take TFT30 to turn off. The mid-level potential of the incompletely on or incompletely off state. Details of such scan signals will be described later.

In the image display area, scanning signals G1, G2, . . . , Gm are applied to the gates of the TFTs in line order from the scanning signal supply circuit 104 via the scanning line 3a. The image signals S1, S2, . . . , Sn supplied from the data line 6a are written to the pixel electrode 9a at a predetermined timing by turning off the switch of the TFT 30 as a pixel switching element for a predetermined period. Image signals S1, S2, . Keep a constant period. According to the applied voltage level, the orientation and order of the molecular assembly of the liquid crystal change, thereby modulating the light and making grayscale display possible. In normally white mode, the transmittance of incident light decreases with the applied voltage for each pixel, and in normally black mode, the transmittance of incident light decreases with the applied voltage for each pixel Added, as a whole, light having a contrast corresponding to the image signal is emitted from the electro-optical device. Here, in order to prevent the retained image signal from leaking, a storage capacitor 70 is added in parallel with the liquid crystal capacitor formed between the pixel electrode 9a and the counter electrode. As will be described later in detail, the storage capacitor 70 includes a pixel potential side capacitor electrode connected to the pixel electrode 9 a and a fixed potential side capacitor electrode oppositely disposed with a dielectric film interposed therebetween. A part of the fixed potential capacitive line 300 arranged in parallel with the scanning line 3 a is formed as such a fixed potential side capacitive electrode.

Next, as shown in FIG. 2, on the TFT array substrate of the electro-optic device, a plurality of transparent pixel electrodes 9a (the outline of which is shown by the dotted line part 9a') are arranged in a matrix, along the vertical and horizontal boundaries of the pixel electrodes 9a respectively. The data line 6a and the scanning line 3a are provided.

In addition, the scanning line 3a is arranged so as to face the channel region 1a' shown by the oblique area sloping upward and rightward in FIG. 2 in the semiconductor layer 1a, and the scanning line 3a includes a gate electrode. The scanning line 3a is formed so that the portion of the gate electrode facing the channel region 1a' has a wider width.

In this way, pixel switching TFTs 30 are provided at the intersections of the scanning lines 3a and the main body portions 61a of the data lines 6a, respectively, in the channel region 1a' where a part of the scanning lines 3a is used as a gate electrode and opposed to each other.

The relay layer 71 is provided as a pixel potential side capacitive electrode connected to the high-concentration drain region of the TFT 30 and the pixel electrode 9 a. On the upper side of the relay layer 71, a part of the capacitor line 300 serving as the fixed potential side capacitor electrode is provided along the scanning line 3a, and both the pixel potential side capacitor electrode and the fixed potential side capacitor electrode face each other with a dielectric film in between. configuration, thereby forming a storage capacitor connected to the pixel electrode 9a. Viewed on a plan view, the capacitance line 300 extends in strips along the scanning line 3a, and the portion overlapping with the TFT 30 protrudes upwards and downwards in FIG. 2 . On the lower side of the TFTs 30 on the TFT array substrate 10 , the lower light-shielding film 11 a is provided in a grid pattern. On the scan line 3a, an interlayer insulating film is formed to respectively open a contact hole 81 leading from the data line 6a to the high-concentration source region and a contact hole 83 leading to the high-concentration drain region from the relay layer 71 .

On the data line 6a, an interlayer insulating film forming a contact hole 85 leading from the pixel electrode 9a to the relay layer 71 is formed, and the pixel electrode 9a is provided on the interlayer insulating film.

Next, the scanning signal supply circuit described above will be described in detail with reference to FIGS. 1 to 5 . Here, FIG. 3 is a timing chart of data signals, scan signals, and the like in the comparative example. FIG. 4 is a block diagram of the middle wave circuit and the scanning signal supply circuit in this embodiment, and FIG. 5 is a timing diagram of data signals, scanning signals, etc. in this embodiment.

In addition, in this embodiment, all the pixel electrodes 9a are driven with potentials of the same polarity in the same field, and field inversion driving for inverting these potentials in a field period is performed simultaneously. That is, the image signal supplied from the data signal supply circuit 101 is an image signal in which alternating current is inverted in units of fields.

In FIG. 2 , the gate of the TFT 30 connected to the pixel electrode B located in the m-th row of the pixel electrodes 9 a is assumed to be the gate 402 , and the scanning signal supplied to the gate 402 is assumed to be the scanning signal Gm. On the other hand, assume that the gate of the TFT 30 connected to the pixel electrode C located in the m+1th row in the pixel electrode 9a is the gate 404, and the scanning signal supplied to the gate 404 is the scanning signal Gm+1.

In the configuration shown in FIG. 2 , on the scanning line 3 a to which the scanning signal Gm is supplied, a portion E of the pixel electrodes C in the next row overlapped by hatching. Furthermore, since the interlayer insulating film laminated between the two stacked ones is relatively thin, a parasitic capacitance is generated between the two. In addition, the drain of the TFT 30 , the data line 6 a and the capacitance line 300 also have large or small parasitic capacitances with the pixel electrode C of the next row.

Therefore, assuming that in such a structure, when the TFT 30 of the m-th row is turned off, assuming that the scan signal Gm, Gm+1, . . . When the TFT 30 in the m+1 row is turned on, due to the effect of the parasitic capacitance, the scanning signal and image signal in the m+1 row are mixed into the pixel potential of the pixel electrode B in the m row as noise.

A more specific situation is shown in Figure 3. The shift register circuit generates the basic waveform P1 of the scanning signals G1 to Gm from the clock. The basic waveform P1 is a transmission output waveform shifted in the order of the scanning signals G1 to Gm. If at the falling edge 452 of the scan signal Gm, at the moment when the gate 402 of the pixel electrode B is to be closed, the gate 404 of the pixel electrode C is opened at the rising edge 454 of the scan signal Gm+1, then the pixel electrode C passing through the gate 404 The voltage change in , for example, changes the potential of the scanning signal Gm due to the effect of the above-mentioned parasitic capacitance. Thus, for example, the falling edge 452 of the scanning signal Gm is skewed like the curve 456, and the gate 402 of the pixel electrode B cannot be turned off. Then, the image signal 464 to be written to the pixel electrode C is also mixed into the image signal 462 to be written to the pixel electrode B as noise. Furthermore, since the above-mentioned parasitic capacitance has non-uniformity on a pixel-by-pixel basis, such a write potential variation causes color non-uniformity of the pixel. Furthermore, in order to perform field inversion driving, the image signal Sn shown in FIG. 3 is based on the reference voltage 458 of, for example, 0V, and the image signal 462 and the image signal 464 have the same polarity.

Furthermore, in the case of the comparative example shown in FIG. 3, the waveforms of the scanning signals Gm, Gm+1, . . . are actually blunted by the wiring capacitance of the scanning line 3a. Therefore, the on-off timing of the TFT 30 differs between the peripheral portion and the central portion in the left-right direction in FIG. 1 and FIG. 2 according to the degree of dullness of the waveform of the scanning signal. As a result, at the moment when the TFT 30 is turned off as described above, the influence of noise due to the scanning signal of the next line mixed in the image signal differs between the peripheral portion and the central portion. Therefore, in particular, in the case of employing AC inversion driving in which the driving potential of each pixel electrode is reversed in the field period or the like, if the potential of the scanning signal etc. is adjusted in the center of the image display area so that there is no When a DC component due to such noise is generated, a DC component due to such noise is generated in the peripheral portion. Conversely, if the potential of the scanning signal is adjusted so that no DC component due to such noise is generated in the driving potential at the peripheral portion of the image display area, such a DC component due to noise is generated in the central portion.

As a result of the above, according to the comparative example shown in FIG. 3 , flickering occurred in the peripheral portion or the central portion while pixel color unevenness was generated.

In this regard, especially in this embodiment, as shown in FIG. 4 and FIG. 5 , the scanning signal supply circuit 104 is configured such that the power supply voltage Vdd2 supplied to the buffer circuit 508 at the final stage thereof is converted into a binary value by means of a midband wave circuit 550 . Changes to voltage Vm and voltage Vc1. Furthermore, for each scanning line, while changing the potential of the scanning signals G1 to Gm from the high potential Vc1 to the low potential 0, the potential of the scanning signals G1 to Gm is fixed at the intermediate potential Vm for a fixed time. The scanning lines keep the potentials of the scanning signals G1 to Gm fixed at the intermediate potential Vm for a fixed period of time while changing the potentials of the scanning signals G1 to Gm from the low potential 0 to the high potential Vc1.

Hereinafter, with reference to FIG. 4 and FIG. 5 , the detailed structure and operation of the scanning signal supply circuit 104 and midband circuit 550 configured in this way will be further described.

In FIG. 4 , the scanning signal supply circuit 104 includes a shift register circuit 504 , an inverter circuit 506 and a buffer circuit 508 . The shift register circuit 504 establishes the basic waveform P1 of each scanning signal G1-Gm from the clock Vdd1. The basic waveform P1 is a transmission output waveform shifted in the order of the scanning signals G1 to Gm. The basic waveform P1 is formed by the inverter circuit 506 and the buffer circuit 508 into the scanning signals G1 to Gm having a two-step waveform as shown in FIG. 5 .

The midband circuit 550 includes a DAC 520 , variable resistors 522 , 528 , and 530 , an amplifier 524 , transistors 532 , 534 , and 536 , and a pulse generating circuit 526 .

In order to determine the intermediate potential Vm, the output of the DA converter 520 is input to a variable resistor 522 . This is because the analog potential amount (A) can be determined from the digital signal (D) by the DA converter 520 , and the potential can also be determined in the variable resistor 522 . The output of the variable resistor 522 is impedance-converted by the amplifier 524 . The output of this amplifier 524 is set to the intermediate potential Vm.

On the other hand, the pulse generation circuit 526 generates a pulse that rises after the rise of the basic waveform P1 by the time ta and falls before the fall of the basic waveform P1 by the time tb from the clock Vdd1. Here, the ta time and tb time can be changed using variable resistors 528 and 530 . The output of the pulse generating circuit 526 generates a pulse whose peak voltage is the middle potential Vm via the transistor 532 . The voltage level of this pulse is shifted by the transistor 534 , and the pulse whose peak voltage is the power supply voltage Vc1 and whose lower potential is the intermediate potential Vm is formed by the transistor 536 .

In this way, with the middle wave circuit 550, as shown in FIG. 5 , the lower potential of the pulse becomes the middle potential Vm, and the power supply voltage Vc1 that reaches the peak voltage rises with a lag time ta from the rise of the basic waveform P1 and generates a ratio The fall of the basic waveform P1 falls ahead of time tb and reaches the power supply voltage Vdd2 of the intermediate potential Vm. In addition, the image signal Sn includes a pulse drop of the power supply voltage Vdd2.

Then, such a power supply voltage Vdd2 is input as a high power supply to the source of the complementary TFT of the buffer circuit 508 . Then, since the inverted waveform of the basic waveform P1 is input to the gate of the complementary TFT of the buffer circuit 508, the output of the buffer circuit 508 becomes its synthesized waveform. That is, the output of the buffer circuit 508 becomes the scanning signals G1, G2, . . . having the two-step waveform 604 shown in FIG. 5 . More specifically, scanning signals G1 , G2 , . Here, the scan signal is held at the intermediate potential Vm for the time ta. After the time ta, the potential of the power supply voltage Vc1 is further reached and held at this potential. As a result, the gate of the pixel switching TFT is opened, and writing of the image signal Sn is started. Thereafter, the scanning signals G1 , G2 , . It falls to the reference potential (0V) of the ground substantially simultaneously with the falling timing of the basic waveform P1. Then, since the data signal Sn includes a fall of the scan time, the gate of the pixel switching TFT is turned off, and the writing of the image signal Sn is completed.

The intermediate potential Vm of the scanning signals G1 , G2 , . Therefore, as shown in FIG. 3, compared with the case of the comparative example in which the full ON state and the full OFF state are directly switched, even if the scanning signal, the image signal, etc. of the m+1th row are affected by the above parasitic capacitance, The component is incorporated as a noise component into the scan signal, image signal, etc. of the m-th row, and the potential change caused by the noise component can also be reduced.

As described above, according to this embodiment, in FIGS. 1 and 2, when the TFT 30 in the mth row is turned off, even if the scanning signal in the m+1th row is mixed as noise due to the effect of the above-mentioned parasitic capacitance Alternatively, the amount of change in the pixel potential that should be held in each pixel electrode 9 a can be reduced by the scanning signals G1 to Gm having a two-step waveform. Consequently, pixel color unevenness generated on a displayed image can be finally reduced. In particular, even if the above-mentioned parasitic capacitance increases after the pixel pitch is miniaturized, the adverse effect on the image quality caused by this can be reduced. Furthermore, when AC inversion driving is employed, flicker can be reduced in both the central portion and the peripheral portion of the image display area. As a result, high-quality image display with reduced pixel color unevenness and flicker can finally be realized.

In addition, in the embodiment described above, the TFT 30 for pixel switching is defined as a top-gate type, but it may be a bottom-gate type TFT. In addition, the TFT 30 may also be configured to include a single crystal semiconductor layer introduced by bonded SOI. In addition, the switching TFT 30 preferably has an LDD structure, but it may have an offset structure in which impurity ions are not implanted into the low-concentration source region 1b and the low-concentration drain region 1c, or may be a gate electrode composed of a part of the scanning line 3a. A self-aligned TFT that implants impurity ions at a high concentration as a mask and forms a high-concentration source region and drain region in a self-aligned manner. In addition, in this embodiment, a single gate structure may be formed in which only one gate electrode of the pixel switching TFT 30 is arranged between the high-concentration source region 1d and the high-concentration drain region 1e, but it may also be arranged between them. 2 or more gate electrodes. In addition, the application of the present invention is not limited to projection-type or transmissive-type liquid crystal devices, and can also be applied to reflective-type liquid crystal devices, and the effect of reducing uneven color and flickering of pixels in this embodiment can also be obtained.

(second embodiment)

Next, a second embodiment of the electro-optical device will be described with reference to FIGS. 6 and 7. FIG. Here, FIG. 6 is a timing chart showing the timing of the data line drive signal and the scanning signal in the second embodiment, and FIG. 7 is a mid-range wave circuit and a scanning signal in this embodiment configured to generate two systems of scanning signals. Block diagram of the scan signal supply circuit.

In the second embodiment, the pixel electrodes 9a in the same row are driven with potentials of the same polarity, and 1H inversion driving is performed in which the polarity of the related potential is reversed for each row in a field period. That is, the image signal supplied from the data signal supply circuit 101 is a signal in which the polarity is inverted for each line in units of fields. Thus, deterioration due to application of a DC voltage to the liquid crystal can be effectively avoided. The basic configuration of the electro-optical device of the second embodiment is the same as that of the first embodiment described with reference to FIGS. 1 and 2 .

That is, as shown in FIG. 6, in the second embodiment, the potential polarity of the image signal Sn is inverted with respect to the fixed potential Vb every horizontal scanning period. More specifically, in FIG. 6, during the first horizontal scanning period, the writing potential 722 of the image signal Sn is higher than the fixed potential Vb by Vs1, and during the next horizontal scanning period, the writing potential 724 of the image signal Sn is higher than the fixed potential Vb. Vb is lower than Vs2. In the next horizontal scanning period, the write potential 726 of the image signal Sn is higher than the fixed potential Vb by Vs1.

In the second embodiment, since such image signal Sn is used for display, it is divided into odd-numbered lines and even-numbered lines that are always driven with the same potential polarity, and the doping of inter-line noise caused by the above-mentioned parasitic capacitance is dealt with. And this aspect of blunting of the scanning signal can reduce the adverse effects caused by it. Therefore, in the second embodiment, the middle wave circuit of the first embodiment shown in FIG. 4 is classified into another system for odd-numbered and even-numbered scanning lines.

That is, as shown in FIG. 7, the buffer circuits 854, 858, . Buffer circuits 856, 860, . . . connected to the scan lines of the row.

The first mid-wave circuit 862 has a configuration similar to that of the mid-wave circuit 550 described in the first embodiment, and generates a peak voltage Vc12 and an intermediate potential Vm2 from a power supply voltage Vc1 and a clock Vdd1. The specific value of the intermediate potential Vm2 can be determined by experiment or experience as long as the condition of flickering is observed.

As shown in FIG. 6, in the first middle wave Vp1 corresponding to the scanning signal G1, its peak voltage Vc12, middle potential Vm2, ta time and tb time for maintaining the middle potential can be set to reduce flicker. Then, scan signals G1 , G3 , G5 , . . . having two-step waveforms 704 , 706 , 712 , . On the other hand, corresponding to the scanning lines of the even-numbered rows, scans having two-step waveforms 706, 710, . Signals G2, G4, . . . The specific value of the intermediate potential Vm3 can be determined by experiment or experience as long as the condition of flickering is observed. In this way, the intermediate potentials of the first middle wave and the second middle wave, and the high potentials of the first middle wave and the second middle wave can be set to be different.

As described above, according to this embodiment, in the 1H inversion driving mode, when the TFT 30 in the mth row is turned off, even if the scanning signal in the m+1th row is mixed as noise due to the effect of the above-mentioned parasitic capacitance, The amount of change in the pixel potential that should be held in each pixel electrode 9 a can be reduced by the scan signals G1 , G, . . . having a two-step waveform. Consequently, pixel color unevenness generated on a displayed image can be finally reduced. In particular, flicker can be reduced in both the central portion and the peripheral portion of the image display area. As a result, high-quality image display with reduced pixel color unevenness and flicker can finally be realized.

Furthermore, in the 1H inversion driving mode in this embodiment, the polarity of the driving voltage can be reversed for each row, and the polarity of the driving voltage can be reversed for every two adjacent rows or every row. .

(variation)

In each of the above-mentioned embodiments, the intermediate potential is set by the DA converter and the variable resistor, but it can also be automatically generated according to the degree by detecting pixel color unevenness and flicker before shipment or during normal operation. The digital signal is used as the digital input signal of the DA converter 520 to set the intermediate potential.

In addition, in the above-mentioned embodiments, the holding time of the intermediate potential of the scanning signal having a two-step waveform, that is, the setting of the ta time or tb time is changed by the variable resistors 528 and 530, but this can also be changed by the detection pixel Color unevenness and flickering are automatically generated as digital signals according to their degree, and are set as digital input signals of the DA converter 520, and the output analog voltage is input to the pulse generating circuit 526 for setting.

In this way, as long as the pixel color unevenness and flicker are detected and the second-step waveform in the scanning signal is controlled, the discreteness of each product and the pixel color unevenness and flicker caused by time-varying can be advantageously dealt with.

In addition, in each of the above-mentioned embodiments, one intermediate potential is formed each at the time of rising and falling, but it is also possible to set a plurality of intermediate potentials instead to generate a scanning signal having a plurality of staircase waveforms in a staircase shape to obtain a similar Effect.

(The overall structure of the electro-optic device)

The overall structure of the electro-optical device in each embodiment configured as above will be described with reference to FIGS. 8 and 9 . Furthermore, FIG. 8 is a plan view of the TFT array substrate viewed from the side of the opposing substrate and each component formed thereon, and FIG. 9 is a cross-sectional view taken along line H-H' of FIG. 8 .

In FIG. 8 , on the TFT array substrate 10 , a sealing material 52 is provided along the edge of the substrate 10 , and a light-shielding film 53 as a frame defining the periphery of the image display area 10 a is provided parallel to the inner side of the sealing material 52 . In the outer region of the sealing material 52, the data signal supply circuit 101 and the external circuit connection terminal 102 are provided along one side of the TFT array substrate 10, and the scanning signal supply circuit 104 is provided along two sides adjacent to this side. As long as the delay of the scanning signal supplied to the scanning line 3a is not a problem, it goes without saying that the scanning signal supplying circuit 104 is also possible on only one side. Alternatively, the data signal supply circuits 101 may be arranged on both sides of the image display area 10a along the side thereof. In addition, on the remaining side of the TFT array substrate 10, a plurality of wirings 105 for connecting the scanning signal supply circuits 104 provided on both sides of the image display area 10a are provided. In addition, at least one corner portion of the counter substrate 20 is provided with a conduction material 106 for establishing electrical conduction between the TFT array substrate 10 and the counter substrate 20 . Then, as shown in FIG. 9 , the counter substrate 20 having substantially the same profile as the sealing material 52 shown in FIG. 8 is adhered on the TFT array substrate 10 by the sealing material 52 .

In addition, on the TFT array substrate 10, in addition to the data signal supply circuit 101, the scanning signal supply circuit 104, etc., it is also possible to form a precharge circuit that supplies a predetermined voltage level to each of the plurality of data lines 6a before supplying image signals. Signal pre-charging circuit, inspection circuit for checking the quality and defects of the electro-optical device during the manufacturing process and when it leaves the factory, etc.

In the embodiments described above with reference to FIGS. The anisotropic conductive film on the part is electrically and mechanically connected to a driving LSI mounted on, for example, a TAB (tape automated bonding) substrate. In addition, on the incident side of the projected light of the opposite substrate 20 and the outgoing side of the emitted light of the TFT array substrate 10, respectively, according to such as TN (twisted nematic) mode, STN (super twisted nematic) mode, VA (vertical Orientation) mode, PDLC (Polymer Dispersed Liquid Crystal) mode, etc., and the difference between normally white mode/normal black mode, arrange polarizing film, retardation film, polarizing plate, etc. in a predetermined direction.

In order to apply the electro-optic device in the embodiment described above to a projector, three electro-optic devices are used as light valves for RGB, and the decomposed color lights are used as projection light through dichroic mirrors for RGB color decomposition. incident on each light valve. Therefore, in each embodiment, no color filter layer is provided on the counter substrate 20 . However, an RGB color filter layer may be formed on the counter substrate 20 together with its protective film in a predetermined region facing the pixel electrode 9a. If this is done, the electro-optic devices in the respective embodiments can be applied to direct-view and reflection-type color electro-optic devices other than projectors. In addition, microlenses are formed on the counter substrate 20 in a one-to-one correspondence with pixels. Alternatively, a color filter layer may be formed with a color resist or the like under the pixel electrodes 9 a facing RGB on the TFT array substrate 10 . If this is done, a bright electro-optical device can be realized by increasing the condensing efficiency of incident light. In addition, by depositing several interference layers with different refractive indices on the opposite substrate 20, a dichroic color filter layer for creating RGB colors can also be formed by utilizing light interference. A brighter color electro-optical device can be realized by utilizing the counter substrate with a dichroic color filter layer.

(Embodiment of Electronic Device)

Next, an overall structure, especially an optical structure, of an embodiment of a projection type color display device as an example of an electronic device using the electro-optical device described in detail above as a light valve will be described. Here, FIG. 10 is a schematic sectional view of a projection type color display device.

In FIG. 10, a liquid crystal projector 1100 as an example of a projection-type color display device in this embodiment can be configured as follows: prepare three liquid crystal modules including a liquid crystal device 100 in which a driving circuit is mounted on a TFT array substrate, as A projector used as the light valves 100R, 100G, and 100B for RGB. In the liquid crystal projector 1100, when projected light is emitted from a lamp unit 1102 of a white light source such as a metal halide lamp, three mirrors 1106 and two dichroic mirrors 1108 are used to split light into light components corresponding to the three primary colors of RGB, R, G, B, are respectively introduced into the light valves 100R, 100G, and 100B corresponding to the respective colors. At this time, in order to prevent light loss caused in a long optical path, the B light should be introduced after passing through the relay lens system 1121 composed of the incident lens 1122 , the relay lens 1123 and the exit lens 1124 . Then, the light components corresponding to the three primary colors modulated by the light valves 100R, 100G, and 100B are recombined by the dichroic prism 1112 , and projected on the screen 1120 as a color image through the projection lens 1114 .

The present invention is not limited to the above-described embodiments, and appropriate changes can be made within the scope of not departing from the gist or idea of the invention read from the scope of the claims and the entire specification, and the electro-optical device and its driving circuit accompanying such changes And electronic devices are also included in the technical scope of the present invention.

Claims (6)

1. An electro-optic device, characterized in that, comprising on the substrate: a plurality of pixel electrodes arranged in a matrix; a pixel switching element for switching and controlling the pixel electrode; A scanning line provided to supply the gate of the pixel switching element with a scanning signal for turning the pixel switching element into an on state or an off state; a data line provided for supplying an image signal to the pixel electrode via its source and drain when the pixel switching element is in the ON state; and a scanning signal supply circuit for supplying the scanning signal to the scanning line in line order; The scanning signal supply circuit changes the potential of the scanning signal Only fixed at the intermediate potential between the above-mentioned high potential and the above-mentioned low potential for a specified time; The setting of the high potential of the scanning signal supplied to the scanning lines adjacent to each other is different. 2. A driving device for an electro-optical device, comprising on a substrate: A plurality of pixel electrodes arranged in a matrix, a pixel switch element for switching the pixel electrodes, and a scan signal provided to turn the pixel switch element on or off by supplying a scan signal to the gate of the pixel switch element. line, the electro-optic device of the data line provided for supplying the image signal to the pixel electrode via its source and drain when the pixel switching element is in the open state, supplies the scanning signal, It is characterized by: having In the process of changing the potential of the scanning signal from a high potential to a low potential, and in the process of changing the potential of the scanning signal from the low potential to the high potential, the potential of the scanning signal is fixed only for a predetermined time. A scanning signal supply circuit that is at an intermediate potential between the high potential and the low potential and that sets the high potential of the scanning signal supplied to the adjacent scanning lines differently. 3. A driving method of an electro-optic device, the electro-optic device has a plurality of scanning lines driven in line order, the driving method is characterized in that: including supplying a scan signal to a gate of a pixel switching element to turn the pixel switching element into an on state or an off state, have: a step of changing the scanning signal from a low potential to an intermediate potential and maintaining the intermediate potential for a specified time, and changing from the intermediate potential to a high potential; and The step of changing from the above-mentioned intermediate potential to a high potential and maintaining it for a specified time; Steps of changing from the above-mentioned high potential to an intermediate potential and maintaining the intermediate potential for a specified time, and changing from the above-mentioned intermediate potential to a low potential; The setting of the high potential of the scanning signal is different for the scanning lines adjacent to each other. 4. An electronic device, characterized in that: Among other things, it has an electro-optic device that includes on a substrate: a plurality of pixel electrodes arranged in a matrix; a pixel switching element for switching and controlling the pixel electrode; A scanning line provided to supply the gate of the pixel switching element with a scanning signal for turning the pixel switching element into an on state or an off state; a data line provided for supplying an image signal to the pixel electrode via its source and drain when the pixel switching element is in the ON state; and a scanning signal supply circuit for supplying the scanning signal to the scanning line in line order; The scanning signal supply circuit changes the potential of the scanning signal Only fixed at the intermediate potential between the above-mentioned high potential and the above-mentioned low potential for a specified time; The setting of the high potential of the scanning signal supplied to the scanning lines adjacent to each other is different. 5. An electro-optical device, characterized in that, comprising on the substrate: a plurality of pixel electrodes arranged in a matrix; a pixel switching element for switching and controlling the pixel electrode; A scanning line provided to supply the gate of the pixel switching element with a scanning signal for turning the pixel switching element into an on state or an off state; a data line provided for supplying an image signal to the pixel electrode via its source and drain when the pixel switching element is in the ON state; and a scanning signal supply circuit for supplying the scanning signal to the scanning line in line order; The scan signal supply circuit changes the potential of the scan signal from a high potential that turns the pixel switching element into the on state to a low potential that turns the pixel switching element into the off state, and when changing the potential of the scan signal from the off state to the off state. In the process of changing from the low potential of the on state to the high potential of the on state, the potential of the scanning signal is fixed at an intermediate potential between the potential of the on state and the potential of the off state for a predetermined time only; changing the potential of the scanning signal from the potential of the off state to the potential of the on state the intermediate potential, and changing the potential of the scanning signal from the potential of the on state to the potential of the off state The above-mentioned intermediate potentials during the process are equal to each other. 6. An electro-optic device, characterized in that, comprising on the substrate: a plurality of pixel electrodes arranged in a matrix; a pixel switching element for switching and controlling the pixel electrode; A scanning line provided to supply the gate of the pixel switching element with a scanning signal for turning the pixel switching element into an on state or an off state; a data line provided for supplying an image signal to the pixel electrode via its source and drain when the pixel switching element is in the ON state; and a scanning signal supply circuit for supplying the scanning signal to the scanning line in line order; The scanning signal supply circuit changes the potential of the scanning signal from the potential of the pixel switching element to the potential of the off state to the potential of the on state, and changes the potential of the scanning signal to the potential of the off state. The above-mentioned pixel switching elements between the potentials in the on-state and the potential in the on-state are fixed at the potential in the incomplete on-state only for a predetermined period of time.

Images