JP3093511B2 - Display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device used for an image information processing apparatus such as a television receiver, a computer terminal, and a video camera viewfinder, and more particularly to a flat type display having scanning lines and information signal lines. The present invention relates to a display device.

[0002]

2. Description of the Related Art As flat display devices, there are a device using an electron-emitting device for each pixel and a device using a liquid crystal device for each pixel. In particular, a liquid crystal display device using a liquid crystal has attracted attention as being widely spread.

A liquid crystal element used in an actual display device is:
For example, it is configured using a simple matrix substrate as shown in FIG. FIG. 2A is a cross-sectional view of the cell.
In the figure, 21a and 21b are glass substrates, 22a and 22b are stripe electrodes made of ITO and the like formed on glass substrates 21a and 21b, and 23a and 23b are made of silicon dioxide and the like formed on stripe electrodes 22a and 22b. An insulating film, 24a and 24b are alignment films made of polyimide or the like formed on the insulating films 23a and 23b, 25 is a sealing member, and 26 is a liquid crystal sealed in the cell by the sealing member 25.

FIG. 16B shows a stripe electrode 22a.
FIG. 11 is a plan view showing a substrate 21a having the same structure, and the other substrate 21b has the same configuration. These substrates 21
16A can be obtained by injecting the liquid crystal 26 by superimposing them at predetermined intervals so that a and 21b intersect. As the liquid crystal 26, a twisted nematic liquid crystal or the like is used.

FIG. 17 is a circuit configuration diagram of such a display device, which is a 6 × 4 matrix for simplification of description. One of the stripe electrode groups is connected to a scanning line selection circuit, for example, a vertical shift register 2, and a scanning line S ₁
Used as to S _6, the other stripe electrode group connected to the write circuit 1, is used as the information signal lines I ₁ ~I _4.

[0006] Such a display device is driven as follows to display an image. First, the scan pulse thereto scan lines S ₁ is selected and applied by the shift register 2. In synchronization with this scanning pulse, the information signal is divided into four information signal lines I.
At the same time it applied to ₁ ~I _4. Thus the electric field due to the combined signal of the scan pulse and the data signal is applied to the liquid crystal of the four pixels on the scanning line S _1. In this way, an image for one scanning line is displayed according to the transmittance according to the synthesized signal. Such driving method is then performed for the pixels on the scanning line S _2. Furthermore, to display a single screen image performs scanning from sequential chronological order scan lines S ₃ to S _6.

FIG. 18 is a timing chart of the driving method described above. Here, for the sake of simplicity, each scanning pulse and each information signal are shown as simple rectangular pulses. However, in practice, signals are appropriately selected from signals having various waveforms according to the characteristics of the liquid crystal material and the like. .

The time required to display an image on one screen is appropriately selected according to the characteristics of the liquid crystal material. However, if this time is long, that is, if the frame frequency is low, flickering of the entire screen appears to flicker. A phenomenon occurs.

The phenomenon of flicker is a phenomenon in which, when the speed of writing one screen in an image display element is low, human eyes recognize a change in the amount of light in a writing portion in the screen. For example, in the case of a ferroelectric liquid crystal, two processes of erasing and writing are often performed in order to effectively use the memory property.
Furthermore, since scanning lines are written line by line one by one,
The change in light amount within one writing time is large. Such flickers appear most intense when one screen is sequentially written. Even if it scans every 32 lines in an interlace, for example, it does not completely disappear. In other words, if interless scanning is employed, flicker is averaged over the entire screen, but when viewed partially, the scanning time is slow, so that slight flickering of the screen remains. Currently, the selection time for one scanning line of a ferroelectric liquid crystal panel is 100 μs.
It is the limit to shorten the degree. If the selection time is further reduced, delay due to wiring resistance in the panel cannot be ignored, and it becomes difficult to realize a large-screen and high-definition liquid crystal display element. However, in order for the flicker to be invisible even by such line sequential scanning, a frame frequency of 40 Hz or more is required. When the selection time of one scanning line is 100 μs, flicker occurs because the frame frequency for writing a panel having 1024 scanning lines is 9.8 Hz.

In other words, in order to realize a frame frequency of 40 Hz, the selection time of one scanning line must be 24.4 μs. However, depending on the liquid crystal material, the selection time of one scanning line is reduced by the response characteristics. It can be difficult.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above technical problems, and has as its object to provide a display device capable of displaying an image with reduced flicker.

Another object of the present invention is to provide a display device capable of displaying an image in which flicker is suppressed without being substantially affected by the electrical response characteristics of a functional material constituting a pixel such as a liquid crystal material. It is in.

Still another object of the present invention is to provide a display device having a versatile flicker suppression function by improving a driving method.

Another object of the present invention is to provide a display device suitable for performing gradation display.

[0015]

According to the present invention, there is provided a display apparatus comprising: a plurality of scanning lines; a plurality of signal lines intersecting the scanning lines; and an intersection between the scanning lines and the signal lines. A display element having a plurality of display states arranged in accordance with signals applied to the scanning line and the signal line and having a memory pixel made of ferroelectric liquid crystal, and applying a selection signal to the scanning line; Writing means for applying, to the plurality of signal lines, an information signal for causing the pixel to have a predetermined display state in cooperation with a selection signal; and a scanning line corresponding to at least one of the scanning lines in a non-selected state. Signal applying means for applying a dummy signal for temporarily changing the display state of the pixel,
The selection signal is applied to the scanning line by line-sequential scanning, and after a predetermined time that can suppress flicker after the selection signal is applied, the dummy signal is applied to the scanning line in a line-sequential manner, and the selection signal is applied. The amount of change in the amount of transmitted light of the liquid crystal layer forming the memory pixel on the applied scanning line is not more than twice the amount of change in the amount of transmitted light of the liquid crystal layer forming the pixel on the scanning line to which the dummy signal is applied. It is characterized by.

Further, the display device of the present invention includes a plurality of scanning lines, a plurality of signal lines intersecting the scanning lines, and a memory pixel provided at an intersection of the scanning lines and the signal lines. A display element, a selection signal application circuit for applying a selection signal to at least two adjacent ones of the plurality of scanning lines, an information signal application circuit for applying an information signal containing gradation information to the plurality of signal lines, A dummy signal application circuit for applying a dummy signal to at least one of the remaining scanning lines to which the selection signal is not applied, wherein the selection signal is applied to one of the at least two adjacent scanning lines. The selected signal includes a signal component for compensating a display state due to the signal applied to the other, and the selection signal is applied to the scanning line by line-sequential scanning, and flicker can be suppressed after the selection signal is applied. After the lapse of time, the dummy signal is applied line-sequentially to the scanning line, and the variation amount of the transmitted light amount of the liquid crystal layer made of the ferroelectric liquid crystal, which constitutes a memory pixel on the scanning line to which the selection signal is applied, is It is characterized in that the fluctuation amount of the transmitted light amount of the liquid crystal layer constituting the pixel on the scanning line to which the dummy signal is applied is twice or less.

[0017]

As described above, according to the present invention, in a display device having a plurality of scanning lines, a dummy signal for suppressing flicker is applied to an arbitrary scanning line in addition to a selection signal applied at a predetermined cycle.

That is, a dummy signal is applied to one scanning line during one period from when the selection signal is applied to one scanning line to when the next selection signal is applied, so that one scanning line is applied to one scanning line. The period of the applied signal is shortened, in other words,
The frequency of the applied signal is increased, thereby suppressing flicker.

[0019]

FIG. 1 is a circuit diagram of a display device according to an embodiment of the present invention. FIG. 1 shows a device having a 6.times.4 matrix of pixels corresponding to FIG. FIG. 2 is a drive timing chart of the apparatus of FIG.

As shown in FIG. 1, the scanning lines S ₁ -S ₆ are provided with a dummy signal application circuit 3 for applying a dummy signal in addition to the scanning line selection circuit 2. A write circuit 1 is provided for the information signal lines I ₁ -I ₄ .

The scanning line as shown in the timing of FIG. 2 S ₁
Are dummy signal SD ₁ is applied between the one period T _SS of the selection signal SS _1, it can be seen that the period of the applied signal is at a shorter T _SD than T _SS in. Here, the applied signal means both the selection signal and the dummy signal. Sequential selection signals to other scan lines S ₂ -S ₆ SS ₂ ~SS ₆ and the dummy signal SD ₂ to SD ₆ is applied in the same manner.

Such a dummy signal is applied plural times during one cycle of the selection signal, so that the frequency of the applied signal can be further increased.

FIG. 3 shows another driving method. In the example of FIG.
Dummy signals SD _{1 to} SD _{6 are set} so as to be １ ／ cycle of _SS.
Although but has been applied, the dummy signal SD ₁ to SD ₆ so that the 1/3 cycle of T _SS in the example of FIG. 3 is applied.

Although FIG. 1 shows the circuit 2 for applying the selection signal and the circuit 3 for applying the dummy signal separately, these may be formed as one circuit block.

Although FIGS. 2 and 3 illustrate the scanning line selection signal, the information signal and the dummy signal using the simplest rectangular pulse, this is to facilitate understanding of the basic technical concept of the present invention. A signal having a preferable waveform is appropriately adopted according to image information to be displayed, a material to be used, and the like.

The scanning line selection signal used in the present invention is a signal for writing image information for each scanning line when displaying an image on a display screen, and is associated with an information signal applied to the information signal line. This changes the display state of the pixel. More preferably, when the information signal line is at the reference potential and the information signal is not applied, a reset signal component that can temporarily set the display state of the pixel to a reference display state such as all black or all white Is included.

On the other hand, it is desirable that the information signal is a signal that does not substantially change the display state of the pixel when there is no scanning line selection signal.

Further, the dummy signal temporarily changes the display state of the pixel, that is, the light transmittance of the pixel, in cooperation with the information signal. A signal capable of substantially returning to the display state is preferably used.

The peak value and pulse width of such a dummy signal are appropriately selected according to the configuration of the pixel and the characteristics of the constituent material of the pixel.

When a memory-type liquid crystal pixel is used as a pixel configuration, particularly when a pixel is formed using a ferroelectric liquid crystal, liquid crystal molecules transition from one stable state to another stable state as a dummy signal. Nevertheless, a signal having a waveform sufficient to allow the liquid crystal molecules to temporarily change the direction of the molecules and cause a slight variation in light transmittance is used. That is, the dummy signal is set so that the energy of the combined signal of the dummy signal and the information signal applied to the liquid crystal does not become larger than the potential energy serving as the liquid crystal inversion threshold value. By setting the dummy signal in this manner, a pixel that changes its display state when the dummy signal is applied, but returns to the original display state when the application of the dummy signal ends can be provided. In contrast, the selection signal applied to the scanning line of the pixel using the ferroelectric liquid crystal cooperates with the information signal to display all the liquid crystal molecules in the pixel or the liquid crystal molecules in some domains in the pixel. From one stable state to the other.

The operation of the present invention will be specifically described. As mentioned above, flicker occurs when the writing speed is low. When the writing speed exceeds the frame frequency of 40 Hz, flicker disappears. This is because the same screen state is formed 40 times per second, thereby eliminating the following of the eye image change. Therefore, when the writing speed is low, for example, even when the frame frequency is 9.8 Hz, four times per second.
It is considered that flicker disappears if the same screen state is formed about 0 times. Therefore, when a certain scanning line is focused on the screen, the drive circuit is designed so that the dummy signal is applied 25 ms after the scanning line is selected, and the change in the light amount at the time of selection and the light amount at the time of applying the dummy signal. If the change is not so different, it looks the same as if the pixels on that scan line were selected every 25 ms. In other words, the same screen state is formed 40 times per second, so that flicker disappears.

This will be described with reference to FIG. FIG. 4 is a graph obtained based on the examination results of the present inventors. 4, the vertical axis represents the frame frequency of the selection signal for scanning one screen, and the horizontal axis represents the number of active scanning lines. Here, the active scanning line is a scanning line to which a selection signal or a dummy signal is input. Therefore, when selecting and writing one frame at a time,
= 1, and n = 2 when two are simultaneously selected and written
It is. When two lines are simultaneously selected and written and a dummy signal is input to one scanning line, n = 3. The intervals between active scanning lines were configured to be uniform. This means that, when focusing on a certain scanning line, the time interval (T _SD ) from the activation to the next activation is equal. Circles shown in FIG. 4 (connected by solid lines)
Is the frame frequency of the selection signal without flicker at each n. When n = 1, 40 Hz is required, but when n = 2, it is about 30 Hz, and when n = 4, it is about 19.2H.
z. The relationship between the frequency (f _th ) at which flicker is no longer perceived and the number (n) of active scanning lines is as follows.

[0033]

(Equation 1)

The fact that f _th is proportional to 1 / n ^1/2 in the equation (1) is strange in view of the above-described concept, and it seems that it must be proportional to 1 / n. It is considered that the difference between this concept and the actual measurement shown in FIG. 4 is caused by the following causes. FIG.
The dashed-dotted line frequency f _eye shown therein is a frequency below which the instant at which the movement of the eyeball follows, no matter how many active scanning lines (n) are present. Therefore, below this frequency, flicker cannot be eliminated when sequential scanning is performed. Although f _eye shown in FIG. 4 is 12 Hz, the value may slightly fluctuate in the case of commercialization because there are individual differences among humans. Also, f _eye is the moving speed of the scanning line that is more active than the frame frequency.
Is 1.8 m / s in this case), but in any case, f _th does not change linearly with the increase of n because f _eye exists. That is, it is considered that because the human eye has such characteristics, the frequency at which flicker can be tolerated cannot approach 0 but approaches f _eye . In FIG. 4, triangles (connected by dotted lines) indicate the upper limit frequencies at which flicker can be tolerated. As described above, even if the selection time of one scanning line is long and one screen cannot be driven at 40 Hz, screen scanning without flicker can be realized by increasing the number of active scanning lines on one screen by applying a dummy signal.

As the structure of the pixel used in the present invention, a structure in which a liquid crystal material is sandwiched between upper and lower sides is employed. Ferroelectric liquid crystal (FLC) is used as the liquid crystal material. Ferroelectric liquid crystals have many advantages such as a high response speed and a wide viewing angle when a display device is constructed.

Display devices using a ferroelectric liquid crystal are disclosed in NA Clark and ST Lagbar.
U.S. Pat. No. 4,367,9 to U.S. Pat.
No. 24 and US Pat.
No. 5,561, or JP-A-61-94023.
No. PR and N.I. A. Clark et al. MC
LC, 1983, Vol. 94, pp213-2
34 and the like.

That is, a display element using a ferroelectric liquid crystal is a liquid crystal cell in which two glass substrates on which transparent electrodes are formed and subjected to an alignment treatment face each other while maintaining a cell gap of about 1 to 3 microns. Is known in which ferroelectric liquid crystal is injected. The features of the above display device using ferroelectric liquid crystal are that the coupling force between the spontaneous polarization of the ferroelectric liquid crystal and an external electric field can be used for switching, and that the major axis direction of the ferroelectric liquid crystal molecule is the same as the polarization direction of the spontaneous polarization. One-to-one correspondence means that switching can be performed depending on the polarity of the external electric field. Since a chiral smectic liquid crystal (SmC *, SmH *) is generally used as the ferroelectric liquid crystal, the liquid crystal molecule has a twisted long axis in the bulk state. However, in the above-mentioned cell gap having a cell gap of about 1 to 3 microns. In this arrangement, the twist of the long axis of the liquid crystal molecules can be eliminated.

As a display method of the display device of the present invention, even if an image is displayed by binary information of black and white, a gradation display is performed by multi-value information like a color image. May be. Among them, a gradation display method using a ferroelectric liquid crystal having excellent responsiveness and a wide viewing angle is preferable in displaying a good image.

Here, a gradation display method using a ferroelectric liquid crystal will be described. The gradation display method is disclosed in U.S. Pat. No. 4,712,877 to Okada et al., U.S. Pat. No. 4,747,671 to Takahashi et al., And U.S. Pat. Patent No. 4,763,994
It is disclosed in the specification and the like.

More specifically, when the gradation display method using FLC is classified, a method of dividing and driving pixels independently (dither method), a method of generating a potential gradient in the pixel and dividing a display region ( Potential gradient method), a method of applying a unidirectional electric field to the monostable liquid crystal and controlling the displacement of the liquid crystal molecules in the long axis direction by the electric field strength, and changing the thickness of the liquid crystal layer in the pixel As a typical example, a method of performing gradation display by changing the intensity of the electric field applied to the liquid crystal layer by the above-described method is given.

However, in the gradation display method using the FLC, the characteristics of the FLC greatly vary in threshold value due to a temperature change, and it is difficult to maintain the same gradation level due to the temperature change. In order to solve this problem, the present inventors have disclosed Japanese Patent Application No. 3-320542 and December 1993.
A driving method called "pixel shift method (two-pulse method)" is proposed in U.S. Application No. 986,694, filed on May 2, 1998.
An outline of this driving method will be described. Writing is performed by line-sequential scanning from the first scanning line to the n-th scanning line.
At this time, two consecutive scanning lines (L-th and L + 1-th) are simultaneously selected and written. Here, L is an integer, and 1 ≦
L ≦ n. Then, at the next selection timing, two scanning lines (L + 1 and L + 2) are shifted at the same time, and two scanning lines are simultaneously selected. L is a scanning line for temperature compensation of (L + 1) among two scanning lines (L-th and L + 1-th) selected at the same time. This means that writing is performed only on the scanning line L + 1 when the liquid crystal cell is at the reference temperature, and writing is performed on the scanning line L when the temperature changes. That is, the gradation information originally displayed on the scanning line L + 1 moves on the scanning line L with the temperature fluctuation.

That is, in the two-pulse method, an undesired display state of a pixel on one of the at least two adjacent scanning lines is compensated by a display state of a pixel on the other scanning line. That is, the combined display state of the adjacent pixels on at least two scanning lines on the same signal line is set as one unit for gradation display. In this way, any desired one of the pixels in the one unit can be supplemented by the display state of the other pixel, and a normal display can be performed as a whole.

In order to realize such a write operation,
Specifically, the following conditions are set. The scanning signals input to the two scanning lines selected at the same time are made different. They are determined so that the threshold values of two pixels existing at the intersection of the information signal line and the two scanning lines are continuous. “The threshold value becomes continuous” is a condition for performing a smooth shift of information between two scanning lines sequentially written by line sequential scanning. It is necessary that the distribution of the threshold value for the transmittance is present in the pixel.

However, in such a driving method, the pixel information moves at the position due to the temperature fluctuation.
It is difficult to display the frame image completely. That is,
The pixels on the first scanning line have no moving scanning line, and the n-th scanning line has not been processed after the pixel information is moved due to the temperature fluctuation.

Further, in such a two-pulse method, line-sequential scanning must be performed sequentially from the first scanning line to the n-th scanning line, and interlaced scanning cannot be performed. The frame drawing speed of FLC is, for example, 1024
The frame frequency is 3 to 20 Hz in the case of one scanning line
Therefore, if interlace scanning cannot be performed, flicker will occur on the entire liquid crystal panel.

In short, the present invention can be suitably used for suppressing flicker which is likely to occur when performing the above-described gradation driving.

Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to these examples, and each component within a range in which the object of the present invention is achieved. This includes those in which replacement with equivalent substitutes or addition of another element is performed.

[0048]

Embodiment 1 As a first embodiment, a liquid crystal cell having a sectional shape as shown in FIG. 5 was prepared. In the figure, the saw shape of the lower substrate was made by forming an original shape on a mold and transferring it to a glass substrate 21a with an acrylic UV curing resin. An approximately 1500 ° ITO film is formed on the saw shape 27 by sputtering, and the ITO film is patterned along a ridge in a stripe shape so that one side of the saw shape has a width of one pixel. ) 22a was formed. Furthermore, an LQ-1802 manufactured by Hitachi Chemical Co., Ltd. was spin-coated on the upper layer to a thickness of about 300 ° to form an alignment film 24a. The electrode substrate on the opposite side is a stripe (ITO) electrode (information signal line) 2 on the planar surface of the glass substrate 21b.
2b is formed, and an alignment film 24b similar to the lower substrate is formed on the electrode 22b, and has no unevenness. The rubbing directions of the upper and lower substrates were parallel to each other, and the rubbing direction of the lower substrate was shifted by about 6 degrees in the right-hand screw direction with respect to the rubbing direction of the upper substrate to form a cell. The cell thickness (liquid crystal layer thickness) was controlled so that the thin portion was about 1.0 μm and the thick part was about 1.4 μm. The width of the stripe electrode 22a was set to 300 μm, the width of the stripe electrode 22b was set to 300 μm, and the pixel size was set to a rectangle of 300 μm × 200 μm. The panel overall structure of the scanning electrode 6 as a 1024 Y-direction electrode from S ₁ to S _1024, the information-side electrode configured as an X-direction electrodes 1000 from I ₁ to I ₁₀₀₀ I have. Then, a liquid crystal exhibiting ferroelectricity was used as a liquid crystal material. Table 1 shows the characteristics of the liquid crystal material 55 used.
Shown in

[0049]

[Table 1]

FIG. 7 shows a pulse width-voltage curve (a relation between the pulse width and the voltage at the threshold value of the switching pulse) of a panel having a cell thickness of 1 μm using this liquid crystal material. The threshold value of the liquid crystal panel (liquid crystal element) in FIG. 5 is 11.5 volt / μm (80
μs pulse, 25 ° C.), and the threshold value of each pixel is 11.
5 to 16.1 volt (80 μs pulse, 25 ° C.).

FIG. 8 shows a driving waveform. In FIG.
(A) is the waveform of the scanning signal, (b) is the waveform of the information signal,
(C) shows a waveform of a dummy signal which is an improvement of the present invention. The waveform (a) of the scanning signal compensates for the reset pulse P ₁ , the selection pulse P ₂ for writing the scanning line, and the fluctuation of the threshold value of the adjacent scanning line (the fluctuation of the threshold value of the ferroelectric liquid crystal due to temperature fluctuation or the like). and a selection pulse P ₃ and the auxiliary pulse P ₄ for. Information signal waveform (b)
Is constituted by the auxiliary pulse Q ₂ and Q ₃ to offset the DC component of the selection pulses Q _1, Q ₁ having the gradation information. In FIG. 8, 1H _B is a period during which the information signal waveform of the scanning line is applied, and 1H _A is a period during which the information signal waveform of the adjacent scanning line is applied. ΔT is a period during which the selection pulses P ₂ and Q ₁ , and P ₃ and Q ₁ ′ are synchronized. The dummy signal waveform (c) is composed of an AC waveform with no DC component remaining, and a voltage that does not change the information in the pixel even when the combined waveform of the dummy signal waveform and the information signal waveform is applied to the liquid crystal layer is applied. Have been. This is because a voltage that does not invert the liquid crystal molecules is applied to the liquid crystal layer to shake the liquid crystal molecules, thereby making the above-mentioned flickers invisible.

Next, the time series setting of the drive waveform and its operation will be described with reference to FIGS. In the figure, S _{1 to} S
₈ and S _{250 to} S ₂₅₇ are _{one of} S _{1 to} S ₁₀₂₄ , respectively.
Only 16 of the 024 scanning lines are extracted, and the period in which the selection signal is applied and the period in which the dummy signal is applied are extracted and drawn. For example, when the selection signal to the scan lines S ₁ is applied, if the scan line actually being applied dummy signal simultaneously in this embodiment, 4 _{S 251, S 501, S 751} , S 1001 There is a book. This is because the apparent scanning speed needs to be about 40 Hz in order to eliminate flicker (see FIG. 4). For this purpose, the first scanning line (S ₁ ) is selected, and at the same time, the 251st scanning line (S ₂₅₁ ), the 501st scanning line (S ₅₀₁ ), the 751st scanning line (S ₇₅₁ ), and the 1001th scanning line (S ₁₀₀₁ ). Input a dummy signal. By driving the selection signal and the dummy signal in a line-sequential manner, the apparent scanning speed can be made about 40 Hz. That is, the time interval for applying the selection signal or the dummy signal is set within 25 ms regardless of which scanning line in the panel is taken. I indicates a waveform example of an information signal applied to a certain information signal line. S ₁
-I is the first, S ₂ -I is the second scanning line,
3 shows a voltage waveform applied to a pixel to which an information signal is applied. Similarly, S ₂₅₀ -I and S ₂₅₁ -I are the 250th and 2nd, respectively.
The voltage waveform applied to the pixel on the 51st scanning line is shown.

The temperature distribution of the liquid crystal panel was suppressed to 25 ° C. to 30 ° C. by temperature adjusting means such as a temperature sensor, a heater and a fan, and the pulse width and voltage value of each pulse in FIG. 8 were set as follows.

[0054] _{dt 1 = 70μs dt 2 = 50μs} dt 3 = 31μs dt 4 = 19μs V 0 = 25volt V 1 = 18volt V 2 = 18volt V 3 = 6volt information signal voltage _{V i} is the time of gradation display of x% Is applied with a voltage determined by the following equation. When selecting white

[0055]

(Equation 2) When selecting black

[0056]

(Equation 3) And

This voltage setting is a reference pixel (25 ° C.)
When a pulse having a pulse width of 50 μs and a voltage of 18.4 volts is applied, a part of the pixel is written and the voltage is increased.
When 5.8 volt is set, all the parts in the pixel depend on the written result.

In FIG. 9, the component C of the voltage waveform S ₂ -I applied to the liquid crystal between the scanning line S ₂ and the information signal line I indicates that all the pixels on the scanning line S ₂ are erased (black or white). To the scanning line S _2).
The write component to the pixel located at the intersection with I above is shown. On the other hand, in the voltage waveform S ₁ -I applied to the liquid crystal between the scanning line S ₁ and the information signal line I, the component A is the scanning line S ₂
The information to be written to the pixels on the scanning lines S ₁ for temperature compensation of the pixel above. In FIG. 10, a voltage waveform S ₂₅₁ -I applied to the pixels on the information signal line I and the scanning line S ₂₅₁ is shown.
And a voltage waveform S ₂₅₂ -I applied to the pixels on the information signal line I and the scanning line S ₂₅₂ are also shown. Performing gradation display with such a cell drive waveform configuration achieves stable gradation display free from flicker despite temperature unevenness of the liquid crystal panel (temperature distribution within the panel of 25 ° C. to 30 ° C.). Was completed.

FIG. 11 is a block diagram of a drive system of the display device of this embodiment. A scanning line of the liquid crystal panel 41 serving as a display screen is a common-side driving IC 4 as means for selecting a scanning line, applying a selection signal, and also applying a dummy signal.
6 and the information signal line is connected to a segment side driving IC 43 as a means for applying an information signal. Image information from an image information generator 48 such as an image sensor or a wireless receiver is controlled by a controller 49 to be divided into a common side signal and a segment side signal and displayed. On the common side, the shift register 47 and the driving IC 46 form a scanning signal based on a reference voltage distributed by an analog switch of the driving power supply 42, and also form a dummy signal. On the other hand, on the segment side, the digital gradation signal supplied via the shift register 45 and the latch circuit 44 is converted into an analog signal by a D / A converter in the drive IC 43 and supplied to the information signal line. For example, for a 4-bit digital signal, 2 ^4, ie, 16
Are converted to analog signals.

Here, the digital signal before conversion into an analog signal is latched, but a method in which a capacitor is provided in parallel with the drive IC 43 and the analog signal is directly latched may be adopted.

With such a drive system, FIGS.
By applying the signals as shown in (1) to the liquid crystal panel 41, an analog gray scale display without flicker can be performed.

[0062]

[Embodiment 2] When gradation display is performed by the two-pulse method, the stability of gradation display is expanded by increasing the selection interval between adjacent scanning lines. In Example 1, the selection was made every 100 μs, but it was confirmed that the gradation display was further stabilized when an interval of 200 μs or more was provided. This is presumably because the switching of the ferroelectric liquid crystal molecules was not completely completed within the voltage application time in the liquid crystal material employed in Example 1. Therefore, a method of adopting an interlace as the driving method and increasing the selection interval was studied.

In the present embodiment, an example in which the driving method of the present invention is combined with the interlace method so that a good image is displayed even when scanning lines are sequentially selected at such long intervals. Show.

That is, in the present embodiment, the scanning lines of the matrix panel shown in FIG.
Divide into two blocks and perform interlacing. FIG.
Block A Block B made up of a scanning line of S ₁ to S ₅₁₂ is composed of a scanning line to S ₅₁₃ to S ₁₀₂₄ in. The scanning line selection order is S ₁ , S ₅₁₃ ,
.., S ₂ , S ₅₁₄ , S ₃ , S ₅₁₅ . In this case, when a total of four dummy signals were input every 150 scanning lines for each block, the apparent frame frequency exceeded 40 Hz, so that good gradation display without flicker could be realized. This embodiment is the same as the first embodiment except for the scanning method.

[0065]

Third Embodiment In the third embodiment, the variation in the amount of transmitted light when selecting a scanning line to which a selection signal is applied is substantially equal to the amount of variation in the amount of transmitted light when applying a dummy signal to a scanning line to which a dummy signal is applied. A dummy signal is applied so as to be equal.

In order to eliminate flicker by the method described above, the variation (I) of the amount of transmitted light when a scanning line is selected and the amount of variation of the amount of transmitted light when a dummy signal is applied to a scanning line to which a dummy signal is applied (I). If (II) is (I) / (II) ≦ 2.0, there is a certain effect. However, it is desirable that (I) and (II) are equal to obtain the most effect. If the variation in the amount of transmitted light due to the dummy signal is too large, the pixel information will not be destroyed by one application, but the pixel information will be gradually destroyed if the dummy signal is continuously applied for many frames. In order to avoid this, it is desirable that the fluctuation of the amount of transmitted light of one scanning line be kept small to some extent. Therefore, in this embodiment, the number of scanning lines to which the dummy signal is applied is set to two, and the voltage value of the dummy signal is reduced. FIG. 13 shows a driving waveform, and its timing chart is shown in FIG.
4 and 15.

[0067] As shown in S ₂₅₁ ~S258 in FIG. 15, the dummy signal is live-line sequential scanning is simultaneously applied to the two scanning lines. That is, S ₂₅₁ and S ₂₅₂ are + V
₃ are applied simultaneously. The pulse width and voltage value of the driving waveform shown in FIG. 13 are as follows.

[0068] The _{dt 1 = 70μs dt 2 = 50μs} dt 3 = 31μs dt 4 = 19μs V 0 = 25volt V 1 = 18volt V 2 = 18volt V 3 = 4.5volt information signal voltage _{V i} is x% of the gradation display In this case, a voltage determined by the following equation is applied. When selecting white

[0069]

(Equation 4) When selecting black

[0070]

(Equation 5) And

As described above, by making the fluctuation of the liquid crystal molecules due to the dummy signal small in one scanning line, a more stable ferroelectric display device can be realized. The liquid crystal panel used in the third embodiment is the same as that of the first embodiment, and the other configuration is the same as that of the first embodiment except for the driving conditions described above.

[0072]

As described above, according to the present invention, even if the scanning speed per scanning line is low by applying a dummy signal to another scanning line in synchronization with the selection signal, flicker is unlikely to occur. Good binary display and gradation display can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a display device according to the present invention.

FIG. 2 is a timing chart illustrating an example of a method for driving a display device according to the present invention.

FIG. 3 is a timing chart for explaining another example of the driving method of the display device according to the present invention.

FIG. 4 is a schematic diagram for explaining a relationship between a frame frequency of a selection signal and flicker.

FIG. 5 is a schematic sectional view of a liquid crystal element of the display device according to the first embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a configuration of an electrode of the display device according to the first embodiment.

FIG. 7 is a graph showing a relationship between an applied voltage and a light transmittance of the display device according to the first embodiment.

FIG. 8 is a schematic diagram illustrating a scanning line selection signal (a), an information signal (b), and a dummy signal (c) of the display device according to the first embodiment.

FIG. 9 is a drive timing chart of the display device according to the first embodiment.

FIG. 10 is a drive timing chart of the display device according to the first embodiment.

FIG. 11 is a drive system block diagram of the display device according to the first embodiment.

FIG. 12 is a schematic diagram for explaining a driving method according to a second embodiment of the present invention.

FIG. 13 is a schematic diagram showing a scanning line selection signal (a), an information signal (b), and a dummy signal (c) of a display device according to a third embodiment of the present invention.

FIG. 14 is a driving timing chart of the display device according to the third embodiment.

FIG. 15 is a driving timing chart of the display device according to the third embodiment.

FIG. 16 is a schematic diagram illustrating an example of a display device;
(A) shows the cross-sectional configuration of the device, and (b) shows the planar configuration of the substrate.

FIG. 17 is a circuit configuration diagram of a conventional display device.

FIG. 18 is a timing chart for explaining a conventional display device driving method.

[Explanation of symbols]

21a: lower substrate, 21b: upper substrate, 22a: scanning line, 2
2b: information signal line, 26: ferroelectric liquid crystal (FLC), S ₁
~S _1024, SS ₁ ~SS _6: scanning signal, I ₁ ~I _1000:
Information signal, SD ₁ ~SD _6: dummy signal.

Continuation of the front page (72) Inventor: Yutaka Inaba 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-63-271432 (JP, A) JP-A-63-309927 ( JP, A) JP-A-64-88523 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/133 G09G 3/36

Claims (11)

(57) [Claims] A plurality of scanning lines, a plurality of signal lines intersecting the scanning lines, and a plurality of signal lines arranged at the intersections of the scanning lines and the signal lines in accordance with signals applied to the scanning lines and the signal lines. A display element having a memory state pixel made of a ferroelectric liquid crystal which produces a display state of: and information for applying a selection signal to the scanning line and causing a predetermined display state in the pixel in cooperation with the selection signal Writing means for applying a signal to the plurality of signal lines; and signal application for applying a dummy signal to at least one of the non-selected scanning lines for temporarily changing a display state of a pixel corresponding to the scanning line. Means for applying the selection signal to the scanning line by line-sequential scanning, and applying the dummy signal to the scanning line in a line-sequential manner after a lapse of a predetermined time capable of suppressing flicker after the selection signal is applied. The selection signal Is less than twice the amount of change in the amount of transmitted light of the liquid crystal layer forming the pixel on the scanning line to which the dummy signal is applied. A display device characterized by the above-mentioned. 2. The display device according to claim 1, wherein the predetermined time is 33 ms or less. 3. The display device according to claim 1, wherein the scanning line to which the dummy signal is applied is constituted by a plurality of scanning lines. Wherein said dummy signal is claim 1, wherein the ferroelectric liquid crystal is a signal capable of varying the light transmittance without transition from one stable state to the other stable state The display device according to the above. 5. The display device according to claim 1, wherein the information signal includes gradation information. 6. The display device according to claim 1, wherein the display state includes three states in which the light transmittance of the memory pixel is different. 7. The method according to claim 1, wherein the selection signal includes at least two adjacent signals.
The display device according to claim 1, wherein the voltage is applied to one scanning line. 8. A display element comprising: a plurality of scanning lines; a plurality of signal lines intersecting the scanning lines; and a memory pixel provided at an intersection of the scanning lines and the signal lines. A selection signal application circuit that applies a selection signal to at least two adjacent scanning lines, an information signal application circuit that applies an information signal containing gradation information to the plurality of signal lines, and the selection signal is applied. And a dummy signal applying circuit for applying a dummy signal to at least one of the remaining scanning lines, wherein the selection signal is such that a signal applied to one of the at least two adjacent scanning lines is applied to the other. The selection signal is applied to the scanning line by line-sequential scanning, and after a predetermined time after the selection signal is applied, flicker suppression can be performed, the selection signal is applied to the scanning line. Over signal line are sequentially applied to the scanning lines, the variation amount of the amount of light transmitted through the liquid crystal layer selection signal is composed of ferroelectric liquid crystal to constitute a memory property pixel of the applied scanning line said dummy signal is applied A fluctuation amount of a transmitted light amount of a liquid crystal layer forming a pixel on the scanning line is twice or less. 9. The display device according to claim 8 , wherein the memory pixel includes a liquid crystal layer. 10. The memory pixel according to claim 1, wherein a plurality of domains in the memory pixel are inverted according to the gradation information to display a predetermined gradation state.
9. The display device according to 8 . Wherein said dummy signal application circuit, the claims information driving circuit for applying an information signal to the scanning line driving circuit and the signal line for applying a selection signal to the scanning line, characterized in that provided separately 8-10 The display device according to any one of the above.