JPH04114025U - Driving device for liquid crystal display device - Google Patents

Abstract

(57) [Summary] [Structure] The switch 36 generates a bipolar square wave by switching between the positive power supply voltage V _pp and the negative power supply voltage V _NN . This bipolar square wave is selectively led out to output lines O1 to ON from N analog switches S11 to S1N corresponding to N scanning electrodes 3. In addition, the output lines O1 to ON are connected to N analog switches S21 to S2N.
can be selectively grounded. The analog switches S11 to S1N, S21 to S2N connect the shift register 41 to the latch circuits R11 to R1N, R21 to R
The level shifter L corresponds to the display data held in 2N.
Opening/closing is controlled by control signals generated by 11 to L1N and L21 to L2N. [Effect] A ground potential and a bipolar square wave can be derived using two analog switches per output line.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

For example, the present invention uses a liquid crystal that is made of a mixture of high molecular weight liquid crystal and low molecular weight liquid crystal. It is suitable for use in liquid crystal display devices that use a liquid crystal layer with low memory, and A driving device for a liquid crystal display device that is applied to a liquid crystal display device that uses a shaped wave as a driving signal. Regarding.

0002

[Conventional technology]

TN (Twisted Nematic) type and STN (Super Twisted In nematic) type liquid crystal display devices, each surface of a pair of substrates that sandwich the liquid crystal. A plurality of scanning electrodes and signal electrodes are formed so as to cross each other, and the scanning electrodes are By applying voltage to the electrodes in a time-division manner, the electrodes are formed at the intersection of the scanning electrode and the signal electrode. A voltage averaging method that selectively applies voltage to the liquid crystal of each pixel is widely applied. has been done.

0003 However, with this driving method, in an attempt to increase the display capacity, the voltage is As the number of applied scan electrodes increases, the time interval at which one scan electrode is selected is longer, so the unselected time becomes longer, and as a result, the number of on and off pixels increases. The difference in one frame average applied voltage between the pixel and the pixel is reduced. This results in low contrast. I will be lowering it.

0004 On the other hand, even if the applied voltage is removed, the state immediately before that (for example, the light transmitting state or The above problem can be solved by using liquid crystals that have so-called memory properties, in which the light scattering state is maintained. The problem can be solved in principle. In other words, using a liquid crystal with the above-mentioned memory property, a simple marker can be used. By configuring a trix-type liquid crystal display device, each pixel can be controlled even when no voltage is applied. The previous state is maintained, so if the number of scan electrodes is increased, the display duty will be reduced. Contrast does not deteriorate even when the optical density decreases, thus allowing for large display capacity. A liquid crystal display device can be realized. In other words, at each pixel, a voltage is applied Its on/off is reliably controlled even when the contrast is not in use. It is possible to increase the display capacity without causing a decrease.

[0005] A simple matrix liquid crystal display device using such a liquid crystal with memory properties is, for example, "Unexamined Japanese Patent Publication No. 61-103124" and "W.A.Crossland, S.Canter, '85 Socie ty for Information Display International Symposium digest of Technical P apers, pp.124-127, (1985), sesson:8.2''. These documents For this purpose, ferroelectric liquid crystals and smectic dynamic scattering liquid crystals are used, and the memory of these liquid crystals is A technique has been disclosed in which display is performed by simple matrix driving by utilizing the characteristics of the display.

[0006] However, in the above liquid crystal display device, when ferroelectric type liquid crystal is used, sub-sub Manufacturing is difficult as it requires micron precision cell gap adjustment, and When using Mektik dynamic scattering liquid crystal, it is necessary to apply a voltage exceeding 100V. However, it has not been put into practical use due to problems such as the necessity of By the way, recently, a mixture of high molecular weight liquid crystal and low molecular weight liquid crystal has been applied to the liquid crystal layer. As a result, liquid crystal display devices that achieve the above-mentioned memory performance have been proposed (for example, "T.Ka jiyama et al., Chemistry Letters, pp817-820, 1989”, “Unexamined Japanese Patent Publication No. 2-1274 No. 94'' and ``Japanese Unexamined Patent Publication No. 2-193115''. ). When a relatively high voltage at a high frequency (for example, 1 kHz) is applied to the above liquid crystal layer, It becomes a light transmission state where the incident light passes through as it is, and it is ) is applied, a light scattering state occurs in which incident light is scattered. moreover , when a relatively low voltage is applied, the previous state (light transmission state or light scattering state) (disturbed state) is maintained.

[0007] In this way, a simple matrix type liquid crystal display device in which the above mixture is applied to the liquid crystal layer When configuring the As mentioned above, the LCD display has a large display capacity and high contrast. It is hoped that the device will be realized. However, by applying the above mixture to the liquid crystal layer, a simple matrix type liquid crystal display device When trying to utilize the memory properties of the liquid crystal layer, the light transmission state and light scattering of each pixel Select the scan electrode that is not selected among multiple scan electrodes. Since it is necessary to put the pixels corresponding to the above memory state into the above memory state, it is necessary to switch between two types of frequencies. At the same time, the pixel corresponding to the selected scan electrode and the unselected scan electrode are It is necessary to apply different voltages to corresponding pixels.

[0008] A simple matrix driving method using signals having two types of frequencies is, for example, " Disclosed in "M.Nagata, H.Nakamura:Mol.Cryst.Liq.Cryst,vol.139(1986),pp143" etc. However, this method is used to control the three states of pixel on, off and memory. Instead of using the above method, pixels corresponding to non-selected scan electrodes are also forced to be turned on or off. Therefore, the memory property of the liquid crystal as described above is used. It wasn't something I could do.

[0009] In this way, in a liquid crystal display device in which the above-mentioned mixture is applied to the liquid crystal layer, the memory There is no known driving method that utilizes the It was difficult to realize a matrix-type liquid crystal display device using this method. Therefore, in Japanese Patent Application No. 2-403913 filed earlier by the applicant, In order to realize a matrix type liquid crystal display device in which the above mixture is applied to the liquid crystal layer, A method for driving a liquid crystal display device that utilizes the memory properties of the above mixture has been proposed.

0010 The drive method in this proposed example initializes the entire display screen to a light transmitting state or a light scattering state. The erasing operation that erases the image and the optical state (light transmission state or This includes a writing operation in which a display is written by selectively reversing the light scattering state (light scattering state). This proposition In the above write operation in the example, for example, multiple scan electrodes are selected line sequentially, and An effective voltage (a-1)E (for example, a=3, E=30V) is applied to the selected scan electrode. A bipolar square wave is applied and no voltage is applied to the unselected scan electrodes. . In addition, multiple signals are arranged across multiple scanning electrodes with the liquid crystal layer in between. The electrodes correspond to the pixels whose optical state is to be changed in the selected scan electrode. A bipolar square wave of an effective voltage E is applied to the signal electrode with an opposite phase to the scanning waveform. The same phase as the scanning waveform is applied to the signal electrode corresponding to the pixel whose optical state should be maintained. A bipolar square wave of effective voltage E is applied. The voltage applied to each pixel is This is the potential difference between the scanning electrode and the signal electrode. Therefore, during the above write operation, At the selected scan electrode, the pixel whose optical state is to be changed has an effective voltage aE ( When a=3 and E=30, a bipolar square wave of 90V) will be applied, The effective voltage (a-2)E (a=3, E=30) is applied to the pixel whose optical state should be maintained. 30V) is applied. In addition, non-selective scanning electrodes change the optical state. The pixel corresponds to the signal electrode to which a signal is applied to maintain the optical state. The pixel to which the signal of A square wave will be applied.

[0011] As a result, a signal with a waveform having an opposite phase to the scanning waveform is printed on the selected scanning electrode. A bipolar square wave of the effective voltage aE is applied only to the pixel corresponding to the applied signal electrode. As a result, the optical state of this pixel changes. On the other hand, other beliefs In the pixel of the combination of numbers, the effective voltage E or (a-2)E (a=3, E=30V) 30V) is applied, and the optical state of such a pixel is the same as that of the previous one. held in state.

0012 For example, the above erase operation is performed with the entire display screen in a light scattering state, and the write operation This is done by selectively inverting the optical state of each pixel to a light-transmitting state. Assume display mode. In this case, for example, an erase operation is applied to all scan electrodes. , the waveform at the time of the above selection, that is, a bipolar square wave of effective voltage (a-1)E, with a frequency Apply a low wave number signal (e.g. DC to 1Hz) and connect all signal electrodes to scanning electrodes. By applying a bipolar square wave of effective voltage E, which is in opposite phase to the waveform applied to It is done. The write operation is performed using a signal with the above waveform and a high frequency. (for example, 1 kHz).

[0013] Erasing operations are performed by initializing the entire display screen to a light-transmitting state, and writing operations are performed by initializing each pixel. The display mode, which selectively inverts the light scattering state, changes the usage cycle between erasing and writing. This is achieved by exchanging wave numbers. Waves applied to scanning electrodes and signal electrodes Shapes may be interchanged. Liquid crystals made of a mixture of high molecular weight liquid crystals and low molecular weight liquid crystals by the above method. A simple matrix-type liquid crystal display device driven by utilizing the memory properties of layers is realized. . As a result, there is no decrease in contrast even when the number of pixels increases, making it ideal for high-resolution display devices. location can be provided. Moreover, the above mixture itself has film-forming ability. It has self-supporting properties, so it can be used as a spacer to adjust the cell gap. It does not require spraying or the like, and is therefore easy to manufacture. Also, smectic dynamic It can be driven at a lower voltage than when using a scattering type liquid crystal, making it suitable for practical use. is also easy.

[0014] By the way, in order to realize the above driving method, scanning electrodes or signal electrodes must be , (a-1)E, 0, -(a-1)E outputs a signal that changes at three voltage levels. A drive device that can do this is required. The general configuration of such a drive is It is shown in FIG. n electrodes (scanning electrodes or n output circuits 50-1, 50-2, ..., 50-n (general term In this case, an "output circuit 50") is provided. These n output circuits 50 respectively have input lines i1, i2, ..., in (when collectively referred to as "input lines") Display data is given from the "force line i"), and the drive corresponding to this display data is given. The dynamic signals are on the output lines o1, o2,..., on (when collectively referred to as "output lines o") ) is applied to the electrodes.

Each output circuit 50 includes a switch circuit 51 for leading out the positive power supply voltage V _PP (for example, equal to (a-1)E) to the output line o, and a switch circuit for grounding the output line o. 52, and a switch circuit 53 for leading out the negative side power supply voltage V _NN (eg, equal to -(a-1)E) to the output line o. These switch circuits 51 to 53 are configured using analog switches such as field effect transistors, for example. Each of the switch circuits 51 to 53 is controlled to be on/off by a switching control circuit 54 which derives a control signal corresponding to display data from the input line i. The switching control circuit 54 makes one of the switch circuits 51 and 53 conductive based on the polarity switching signal from the line 55. The polarity switching signal may be a rectangular wave with a predetermined frequency, and does not need to have any relationship with display data.

[0016] By the switching control circuit 54 making the switch circuits 51 and 53 conductive alternately, , a bipolar square wave of effective voltage (a-1)E is led out to the output line o. Also, By making the switch circuit 52 conductive, a voltage of 0V can be derived from the output line o. Wear. By switching between these two operations, you can, for example, Two types of signals can be generated.

[0017]

[Problem that the idea aims to solve]

As mentioned above, the switch circuits 51 to 53 usually include field effect transistors. Which analog switch is often used. However, when applying the above mixture to the liquid crystal layer, The liquid crystal display device used requires a relatively high voltage of 30 to 100V to drive it. voltage is required. High-voltage analog switches that can withstand such high voltages are expensive. In addition to the high standard, there are few types of integrated circuits, and the degree of integration of integrated circuits is also low. this Therefore, in the above configuration using three switch circuits 51 to 53 in one output circuit, However, there are problems in that the configuration of the output circuit becomes complicated and the cost increases.

[0018] Therefore, the purpose of this invention is to solve the above-mentioned technical problems and to provide a simple and inexpensive configuration. This is a driving device for a liquid crystal display device that can generate bipolar square waves as a driving signal. The goal is to provide a

[0019]

[Means to solve the problem]

Basic configuration of the driving device of the liquid crystal display device of the present invention to achieve the above objectives is shown in FIG. That is, this drive device has N (N is a natural number of 2 or more) A predetermined 0 level (such as ground potential) and both voltages that vary between positive and negative values with respect to this zero level. It has N drive signal output means 20 that output polar square waves as drive signals. The outputs of the N drive signal output means 20 led out to the output line 11 of the liquid crystal layer are The voltage is applied to N electrodes (not shown) to change the chemical state. be. The above-mentioned bipolar square wave has a positive side that is a voltage on the positive side with respect to the above-mentioned predetermined 0 level. Power supply voltage V_PPand a negative power supply voltage V which is a voltage on the negative side with respect to the predetermined 0 level. _NN It is generated by the switching means 12 which switches between and outputs the output signal. The output of this switching means 12 The signal is commonly given to the N drive signal output means 20.

[0020] Each drive signal output means 20 opens and closes between the switching means 12 and the output line 11. between the first switch circuit 21 and the predetermined 0 level and the output line 11. a second switch circuit 22 that opens and closes, the first switch circuit 21 and the second switch circuit 22; a switching control section 23 that controls opening and closing of the switch circuit 22 based on the display data; It is characterized by having the following. The first switch circuit 21 and the switching control section 23 constitutes a first switching means, which is disconnected from the second switch circuit 22. The switching control section 23 constitutes a second switching means.

[0021]

[Effect]

According to the above configuration, the bipolar square wave generated by switching between the positive power supply voltage V _PP and the negative power supply voltage V _NN by the switching means 12 is shared by the N drive signal output means 20 . Given. Therefore, in the drive signal output means 20, the first switch circuit 21 controls opening/closing between the switching means 12 and the output line 11, thereby increasing the voltage between the positive power supply voltage V _PP and the negative power supply voltage V _NN . It is possible to control the output of a bipolar square wave that varies with . Therefore, the drive signal output means 20 is configured by two switch circuits: the first switch circuit 21, which is controlled by the switching control section 23, and the second switch circuit 22, which controls derivation of a predetermined 0-level signal. , the predetermined 0 level and a bipolar square wave can be output. In this way, driving of the liquid crystal display device is achieved by two switching means per one drive signal output means.

[0022]

【Example】

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 2 shows a liquid crystal display driven by a driving device of a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a sectional view showing the basic configuration of the device. A pair of transparent substrates 1 facing each other , 2 have a plurality of scanning electrodes 3 and a plurality of signal electrodes 4 formed of band-shaped transparent electrode films. A liquid crystal layer 5 is formed between these electrodes 3 and 4. scanning The electrode 3 and the signal electrode 4 are arranged on each surface of the transparent substrates 1 and 2 so as to cross each other and face each other. A pattern is formed, and the intersection of each electrode 3, 4 becomes a pixel.

[0023] The liquid crystal layer 5 may include, for example, a polymer with a main chain of siloxane and a side chain of a group exhibiting liquid crystallinity. A mixture of molecular weight liquid crystals and low molecular weight liquid crystals exhibiting nematic properties is applied. child Examples of mixtures such as poly(4-cyanophenyl 4'hexyloxy) benzoate methylsiloxane) and E63 (manufactured by Merck Japan) and so on.

[0024] In such a liquid crystal layer 5, a predetermined frequency (for example, has a frequency (for example, 1 kHz) or higher (for example, 100 Hz) and has a frequency (for example, 1 kHz) higher than a predetermined value (for example, 50 By applying an AC voltage of an effective voltage (for example, 90 V) or more Set to a light transmitting state (transmittance = 80% or more) in which the incident light to the crystal layer 5 is transmitted as is. be able to. In addition, it has a relatively low frequency (1 Hz to DC) and is higher than the above specified value. When a high voltage of 5% or less). Furthermore, a voltage (for example, 30V) lower than the above-mentioned predetermined value was applied. Sometimes, the previous state (light transmission state or light scattering state) of the liquid crystal layer 5 changes. maintained. That is, this liquid crystal layer 5 has memory properties. The above predetermined values are The value varies depending on the mixture that constitutes the crystal layer.

[0025] This liquid crystal layer 5 also has a film-forming ability itself, for example, transparent Formed into a film by applying a liquid crystal material onto the substrate 1 on which the electrodes 3 are formed. can be done. Therefore, since the liquid crystal layer 5 has self-supporting properties, the liquid crystal layer 5 Unlike when using a liquid crystal layer, there is no need to scatter spacers on the substrate. Large area cells can be easily manufactured by strictly controlling the cell gap. Ma In addition, we have achieved the submicron precision cell gap required for cells using ferroelectric liquid crystals. No alignment film is required for adjustment or monodomain formation. Furthermore, liquid nematic Since it contains liquid crystal (low molecular weight liquid crystal), the local viscosity of the liquid crystal layer is low, compared to smectic dynamic scattering cell using smectic liquid crystal with high crystallinity. Can be driven at low voltage.

[0026] The transparent substrates 1 and 2 can be made of, for example, glass or resin film. However, as mentioned above, since the liquid crystal layer 5 itself has film-forming ability, the resin film is It is advantageous to make the device thinner and lighter, and This has the advantage that a flexible display device can be easily constructed. This resin fill Polyethylene terephthalate, polyethylene naphthalate, or polyethylene Riethersulfone and the like are suitable. In addition, the scanning electrode 3 and the signal electrode 4 are configured. Examples of the transparent electrode film include an indium tin oxide (ITO) film and a tin oxide film. etc. can be applied.

[0027] FIG. 3 is a simplified diagram showing the scanning electrodes 3 and signal electrodes 4 in the above liquid crystal display device. FIG. For example, there are about 50 to 200 scanning electrodes 3 and signal electrodes 4. It is provided once. Generally, the limit on the number of electrodes varies depending on the characteristics of the liquid crystal layer. A scanning signal from a drive device shown in FIG. 6 is applied to the scanning electrode 3, and the signal The electrode 4 receives a signal with a predetermined waveform corresponding to the display content from the data side drive device 40 in FIG. is given. As a result, each image formed at the intersection of the scanning electrode 3 and the signal electrode 4 The elementary state is a light-transmitting state or a light-scattering state, and display is achieved in this way. Ru. In this embodiment, such display operation initializes the entire display screen to a light scattering state. The erase operation erases the display and the state of the necessary pixels of the initialized display screen is Invert the state to a transparent state and maintain the state of the remaining pixels in a light scattering state. and a write operation of writing an image to be displayed.

[0028] FIG. 4 shows each voltage applied to the scanning electrode 3 and the signal electrode 4 during the above erasing operation. The waveform of the signal and the signal applied to the pixel P at the intersection of the electrodes 3 and 4 to which the signal of each waveform is applied. FIG. The waveform shown in column X is applied to the scanning electrode 3. When applying a signal and applying a signal with the waveform shown in the Y column to the signal electrode 4, the X column and Y column A voltage having a waveform shown in the figure is applied to the pixel P at the position where the columns intersect. Sunawa From the scanning electrode 3, an effective voltage (a-1)E (for example, a=2, E=30V) is applied. A low frequency (e.g. 1 Hz) bipolar square wave is applied, sometimes 60 V), and the signal The signal applied from the electrode 4 to the scanning electrode 3 is in reverse phase, and the effective voltage E has both polarities. A square wave is applied. A potential difference between the scanning electrode 3 and the signal electrode 4 is applied to the pixel P. Therefore, during the erase operation, the pixel P is supplied with a low frequency voltage at an effective voltage aE (for example, 90V). A number of bipolar square waves will be applied. This high effective voltage and low frequency bipolar The application of the square wave causes turbulent flow due to the movement of ions in the liquid crystal layer 5. Therefore, the light incident on the liquid crystal layer 5 is scattered, resulting in a light scattering state (cloudy state). did Therefore, each signal as described above is applied to all scanning electrodes 3 and signal electrodes 4, respectively. If it is possible to initialize the entire display screen to a light scattering state.

[0029] FIG. 5 shows each voltage applied to the scanning electrode 3 and the signal electrode 4 during the write operation. The waveform of the signal and the signal applied to the pixel P at the intersection of the electrodes 3 and 4 to which the signal of each waveform is applied. FIG. 3 is a waveform diagram showing all the waveforms of voltages to be applied. This figure 4 is the same as figure 3. The waveform signals shown in the X and Y columns are applied to electrodes 3 and 4, respectively. When applied, the voltage of the waveform shown at the position where each column intersects the electrodes 3 and 4. is applied to the pixel at the intersection of

[0030]The plurality of scan electrodes 3 are selected in line order, and a scan signal X _ON is applied to each scan electrode 3 when selected, and a scan signal X _OFF is applied when not selected. In addition, the signal Y ON is applied to the signal electrode 4 during a period in which the scanning electrode 3 corresponding to the pixel to be in the light transmitting state (on state) is selected, and the signal electrode 4 is in the light scattering state ( _on state). The signal Y _OFF is applied during the period when the scanning electrode 3 corresponding to the pixel to be in the _OFF state is selected.

In this embodiment, the scanning signal X _ON applied to the scanning electrodes 3 line-sequentially selected has a sufficiently high frequency (for example, 500 Hz to 1 kHz), and has an effective voltage (a-1) E( For example, when a=3 and E=30V, it is a bipolar square wave of 60V). Furthermore, the scanning signal X _OFF applied to the unselected scanning electrodes (hereinafter referred to as "unselected scanning electrodes") 3 is a DC signal that does not change at 0V. That is, no voltage is applied to the non-selected scan electrodes 3. Focusing on one scanning electrode 3, the _signal A signal X _OFF is applied during a writing period to the pixel corresponding to the scanning electrode 3 .

On the other hand, the signal Y _ON applied during the period when the scanning electrode 3 corresponding to the pixel to be in the light transmitting state (on state) is selected in each signal electrode 4 is an effective voltage E, The signal X _ON is a bipolar square wave with opposite phase. Further, the signal Y _OFF applied during the period when the scanning electrode 3 corresponding to the pixel to maintain the light transmitting state is selected is an effective voltage E, and is a bipolar square wave having the same phase as the scanning signal X _ON . It is.

Since the potential difference between the scanning electrode 3 and the signal electrode 4 is applied to the pixel at the intersection of the scanning electrode 3 and the signal electrode 4, the selected scanning electrode 3 (to which the scanning signal X _ON is applied) Regarding the scan electrode 3), a voltage having a waveform indicated by reference numeral A1 is applied to the pixel corresponding to the signal electrode 4 to which the signal Y _ON is applied. That is, the applied voltage becomes a bipolar square wave of the effective voltage aE. Regarding the selected scanning electrode 3, in the pixel corresponding to the signal electrode 4 to which the signal Y _OFF is applied, the effective voltage (a-2)E (when a=3, ( a-2) A bipolar square wave with E=E) is applied.

Furthermore, regarding the non-selected scan electrode 3 (the scan electrode 3 to which the scan signal X _OFF is applied), in the pixel corresponding to the signal electrode 4 to which the signal Y _ON is applied, the waveform indicated by reference numeral A3, that is, A bipolar square wave of effective voltage E is applied. Further, to the pixel corresponding to the signal electrode 4 to which the signal Y _OFF is applied, a waveform indicated by reference _symbol A4, that is, a bipolar square wave of the effective voltage E is applied.

In this way, when the signal Y _ON is applied from the signal electrode 4 to the selected scanning electrode 3, an AC voltage of the effective voltage aE (for example, 90 V) is applied to the pixel, and in other cases An AC voltage of effective voltage E or (a-2)E (both 30 V when a=3) is applied to. When a high-frequency alternating current voltage of effective voltage aE is applied, the liquid crystal molecules constituting the liquid crystal layer 5 enter a homeotropic alignment state, thereby inverting the state of the pixel from a light scattering state to a light transmitting state. Further, when the effective voltage E or the AC voltage of (a-2)E is applied, the liquid crystal layer 5 maintains the state before the application of the voltage, so only in the pixels to which the signals X _ON and Y _ON are applied, The optical state of the liquid crystal layer 5 changes from a light scattering state (off state) to a light transmitting state (on state).

[0036] FIG. 6 is a block diagram showing the basic configuration of a drive device provided in relation to the scanning electrode 3. This is a diagram. Display data corresponding to the display content is given to the display control unit 31, and this display control The unit 31 sends scan data corresponding to the scan signal to be applied to the scan electrode 3 to a line 32. The data is then given to the data control unit 33. This data control section 33 converts the scanning data into lines. 34 and 35 in series, and this scan data is divided into N scans (N is a natural number of 2 or more). The signal is applied to N-stage shift registers 41 and 42 corresponding to the scan electrodes 3. these The shift registers 41 and 42 shift one scanning electrode based on the clock signal CK. Scan data corresponding to all N scan electrodes 3 in a time approximately equal to the length of the selection period of 3. is taken inside and held in each stage.

[0037] The data held in each stage of the shift register 41 is all data corresponding to N scanning electrodes 3. At the timing when the scanning data of The signal is applied to all circuits R11, R12, ..., R1N all at once. This latch circuit R1 The outputs of 1 to R1N are controlled by the electric field by level shifters L11, L12, ..., L1N. Controls analog switches S11, S12, ..., S1N such as effect transistors These analog switches S11 to S1 are set to the appropriate level for N as a switching control signal. In this embodiment, analog switches S11 to S1N corresponds to the first switch circuit in FIG. 1, respectively.

[0038] The analog switches S11 to S1N are the outputs of a switch 36 that switches between the positive power supply voltage V _PP (=(a-1)E) and the negative power supply voltage V _NN (=-(a-1)E). The signals are selectively led out to the output lines O1 to ON. The signals derived from the output lines O1 to ON are applied to the N scanning electrodes 3 as scanning signals. The switch 36 changes the power supply voltages V PP and V _NN based on a polarity switching signal from an oscillation circuit 38 that can change the oscillation frequency in response to a frequency switching signal from the display control unit 31 via a line ₃₇ . Switch. Based on the frequency switching signal from the line 37, the oscillation circuit 38 generates a high frequency polarity switching signal of, for example, 500 Hz to 1 kHz during a writing operation to write a display, and generates a low frequency polarity switching signal of about 1 Hz during an erasing operation to erase a display. Generates a frequency polarity switching signal. In the switch 36, a switching operation is performed at the frequency of the polarity switching signal.

[0039] On the other hand, regarding the shift register 42, N latch circuits R21 to R2N, N level shifters L21 to L2N, and N analog switches S21 to S2 N is provided. However, the analog switches S21 to S2N are connected to the scanning electrode 3 An open circuit is established between the output line O1~ON connected to the ground potential which is a predetermined 0 level It is for closing. In addition, level shifters L21 to L2N etc. are analog Switches S21 to S2N are analog switches corresponding to the same output lines O1 to ON. Each of the switches S11 to S1N assumes the opposite state (conducting state or cutoff state). It is composed of In this embodiment, the analog switches S21 to S2N are Each corresponds to the second switch circuit in FIG. In addition, the data control unit 33 foot registers 41, 42, latch circuit R1k (however, 1≦k≦N), R2k, Level shifters L1k, L2k, etc. correspond to the switching control section in FIG. moreover, Drive signal output by this switching control unit and analog log switches S1k, S2k, etc. The means are configured.

Regarding the signal electrode 4, a data-side drive device 40 having a similar configuration is provided, and based on the data given from the display control section 31 via the line 39, the signal electrode 4 is driven in the manner shown in FIGS. A signal having a waveform shown in each Y column of 5 is applied. FIG. 7 is a waveform diagram for explaining the operation. Period T1 is an erase period during which oscillation circuit 38 derives a low frequency (eg 1 Hz) polarity switching signal based on the frequency switching signal from line 37. As a result, the switch 36 outputs a bipolar square wave having a low frequency and an effective voltage (a-1)E (=|V _PP |=|V _NN |). On the other hand, erasing data for erasing the display is derived from the display control section 31, and this erasing data is written into the shift registers 41 and 42 from the data control circuit 33 at high speed. After the writing is completed, when the data held in each stage of the shift registers 41 and 42 is latched into the latch circuits R11 to R1N and R21 to R2N all at once, all of the analog switches S11 to S1N become conductive, and the analog switches S11 to S1N become conductive. All of the switches S21 to S2N are in a cutoff state. As a result, the output signal of the switch 36, that is, the bipolar square wave of the effective voltage (a-1)E at low frequency is derived to all lines O1 to ON. Also during this period, a bipolar square wave of the effective voltage E, which is opposite in phase to the waveform shown in the Y column of FIG. is applied to the signal electrode 4 from As a result, a bipolar square wave (frequency: 1 Hz) of the effective voltage aE is applied to all pixels, and the entire display screen becomes in a light scattering state.

[0041] On the other hand, period T2 after erasing period T1 is a writing period, and during this period, display control is performed. The unit 31 selects one of the N scanning electrodes 3 on the line 32 line-by-line. Deriving scan data for the process. Each scan data corresponding to N scan electrodes 3 The scan data is taken into the shift registers 41 and 42 at high speed, and this scan data is transferred to the latch circuit. When the analog switch S Analog switch S corresponding to one scan electrode 3 selected from 11 to S1N Only 1m (1≦m≦N) becomes conductive, and the remaining analog switches S1k (k ≠m) is in a cutoff state. On the other hand, one of the analog switches S21 to S2N Only the analog switch S2m is in the cut-off state, and the remaining analog switches S2m k (k≠m) is in a conductive state.

[0042] On the other hand, during period T2, the display control unit 31 increases the oscillation frequency of the oscillation circuit 38 to a high frequency. A frequency switching signal for setting the wave number (for example, 1 kHz) is led out to line 37. As a result, during period T2, the switch 36 is switched at a high frequency. , a high frequency bipolar square wave is commonly applied to the analog switches S11 to S1N. It will be done.

[0043] Therefore, the output line Om corresponding to one selected scanning electrode 3 has a high frequency A bipolar square wave of wave numbers will be derived. The display control unit 31 controls the scanning electrode 3. Since scanning data for line-sequential selection is output, the output lines O1 to ON are , in turn, a high-frequency bipolar square wave with a time ΔT equal to the length of the selection period of one scanning electrode. will be derived.

[0044] In this way, in this embodiment, the output lines O1 to ON are connected to the 0V signal and the effective voltage ( a-1) To derive the bipolar square wave of E, for one output line Ok Only two analog switches S1k, S2k are needed. That is, fig. 10, one analog switch per output line. It can be reduced. In this way, the overall configuration of the drive unit is significantly simplified. This can also contribute to cost reduction.

[0045] 8 and 9 are waveform diagrams for explaining the operation of another embodiment of the present invention. . In the description of this embodiment, reference will be made to FIG. 6 described above again. In this example, the display screen The display screen is erased by initializing all the pixels that make up the screen to a light transmitting state. It is possible to selectively invert the state of each pixel of this initialized screen to a light scattering state. The display is written by. That is, in this example, the above first example The inverted display in case of is achieved. In addition, in the description of this example, the light transmission state is defined as the off state, and the light scattering state is defined as the on state.

[0046] FIG. 8 shows the voltage applied to the scanning electrode 3 and the signal electrode 4 during the erasing operation. The signal waveforms shown are similar to those shown in FIG. 4 above. Sunawa That is, during the erasing operation, the plurality of scanning electrodes 3 have a sufficiently high height as shown in the X column. A bipolar square wave of effective voltage (a-1)E with a high frequency (e.g. 1kHz) is printed. added. In addition, as shown in the Y column, the plurality of signal electrodes 4 are applied with the voltage applied to the scanning electrode 3. A bipolar square wave of an effective voltage E is applied, which is in opposite phase to the signal applied. As a result , all pixels making up the display screen are shown at the intersection of the X column and the Y column. A bipolar square wave of effective voltage aE with a sufficiently high frequency is applied, as shown in It will be. As a result, all pixels enter a light transmitting state (off state).

[0047] In this display mode, during the erasing operation, the display control unit 31 causes the line 37 to Deriving a frequency switching signal for increasing the oscillation frequency of the oscillation circuit 38 At the same time, erasing data for giving erasing signals to all scanning electrodes 3 is sent to the line. 32. This erasing data is stored in latch circuits R11 to R1N, R21 to R2. When held at N, all analog switches S11 to S1N become conductive, All of the analog switches S21 to S2N are in a cutoff state. This makes the output A bipolar square wave of effective voltage (a-1)E is simultaneously applied to inputs O1 to ON at high frequency. will be derived.

FIG. 9 shows signal waveforms applied to the scanning electrodes 3 and the signal electrodes 4 during the write operation, and is illustrated similarly to FIG. 5. A plurality of scanning electrodes 3 are selected line-sequentially, and a signal X _ON , which is a bipolar square wave of an effective voltage (a-1)E, is applied to the selected scanning electrodes 3 at a low frequency (for example, 1 Hz). Ru. Then, a signal X _OFF that does not change at 0 V is applied to the non-selected scanning electrode 3 .

[0049] On the other hand, signal_ONIf we pay attention to the scanning electrode 3 to which is applied, we can see that this scanning electrode 3 Among the pixels to be formed, a signal Y is applied to the signal electrode 4 corresponding to the pixel to be turned on. _ON is applied, and the signal Y is applied to the signal electrode 4 corresponding to the remaining pixels._OFFis applied. Signal Y_ONis the signal X_ONIt is a bipolar square wave of effective voltage E and has opposite phase to E. Also, Signal Y_OFFis the signal X_ONIt is a bipolar square wave of effective voltage E and is in phase with E.

In the pixel corresponding to the selected scanning electrode 3, to which the signal Y _ON is applied from the signal electrode 4, a bipolar square wave of the effective voltage aE is applied at a low frequency, as indicated by reference numeral B1. As a result, the state of the pixel changes to a light scattering state (on state). In addition, in the pixel to which the signal Y _OFF is applied from the signal electrode 4, as indicated by reference symbol B2, the effective voltage (a-2)E (when a=3, (a-2)E=E) has both polarities. A square wave is applied, thereby maintaining the state of the pixel in its previous state (light transmission state: off state).

[0051] On the other hand, in the pixels corresponding to the non-selected scanning electrode 3, as indicated by reference symbols B3 and B4, Since a bipolar square wave of effective voltage E is applied to It will be kept in its previous state. In such a write operation, the display control unit 31 sends the oscillation frequency of the oscillation circuit 38 to the line 37. A frequency switching signal is derived to set the wave number to a low frequency (1Hz), and the switching signal is switched to the switching device 36. This is achieved by outputting a low frequency bipolar square wave from the source. Other operations are , the write operation is similar to that of the first embodiment. This causes the output line O1 ~ON, a bipolar square wave of effective voltage (a-1)E is derived at low frequency line sequentially. It will be done.

[0052] In this way, the inverted display in the case of the first embodiment described above can be realized. In addition, the book In an embodiment, during a write operation, a low frequency bipolar square wave is applied to the scan electrode. However, instead, the voltage value is determined over the selected period of one scanning electrode. Apply a DC voltage that does not change at (a-1)E or -(a-1)E to the scanning electrode You can do it like this. In this case, switching of the switch 36 is not necessary. However, For example, it is preferable to switch the switch 36 for each screen; AC drive through multiple screens can be achieved by electrolysis of liquid crystal molecules. It can be prevented.

[0053] Note that the present invention is not limited to the above embodiments. For example, the above fruit In the example, the scanning electrode 3 and the signal electrode 4 both have voltage values centered around 0V. Although it is assumed that a square wave of varying polarity is applied, for example, a predetermined DC voltage The voltage is set to 0 level, and the signals shown in Figures 4, 5, 8, and 9 are superimposed on this DC voltage. The obtained waveform signal may be applied to each electrode 3, 4. In this case, the analog The switching switches S21 to S2N switch the predetermined DC voltage. Ru. Even in this case, a bipolar square wave is ultimately applied to the liquid crystal layer.

[0054] Furthermore, in the above embodiment, the first and second switches are controlled by an analog switch. However, any other analog switch may A switching element or the like may also be applied. Furthermore, in the above embodiment, one screen is displayed by an erase operation and a write operation. However, after the write operation, a relatively low effective voltage AC current is applied to all pixels. Apply voltage or relatively low DC voltage to maintain the state of each pixel at its previous state. A holding operation may also be performed.

[0055] Furthermore, as a mixture of high molecular weight liquid crystal and low molecular weight liquid crystal applied to the liquid crystal layer 5, can cause a state change by switching the frequency, and the applied voltage Memorability that allows the previous state to be maintained for at least a certain period of time by adjusting the can be applied. The present invention also applies to a liquid crystal display device in which a liquid crystal material with memory properties is applied to the liquid crystal layer. However, the electrodes for changing the optical state of the liquid crystal layer are set at a predetermined 0 level and this It is driven by applying a bipolar square wave that fluctuates between positive and negative values with respect to the 0 level. The present invention can be widely implemented in liquid crystal display devices that are operated.

[0056] Various other changes can be made without changing the gist of the present invention. Test examples by the inventors are shown below. Poly(4-cyanophenyl 4'-hexyloxybenzoate methylsiloxane) ) 60 parts by weight, 40 parts by weight of E63 (manufactured by Merck Japan), tetraethylammo A mixture consisting of a small amount of nium bromide was used. By etching this mixture Sandwiched between a pair of patterned transparent electrodes, film thickness 10 μm, 16 × 16 dots. A simple matrix type liquid crystal display device was constructed. This liquid crystal display device is shown in Figure 6 above. The display mode according to the first embodiment (table The device was driven in a display mode in which the entire display screen was set in a light scattering state and the display was erased.

[0057] The display is erased by applying a DC 90V voltage to all pixels. is written to the pixel whose optical state is to be inverted to a light transmitting state at an effective voltage of 90V and a frequency A 1kHz bipolar square wave is applied to the pixels that are to maintain their optical state. The experiment was performed by applying a bipolar square wave with an effective voltage of 30V. like this The operation was performed using signals with the waveforms shown in FIGS. 4 and 5 above. (However, when a=3 and E=30V).

[0058] As a result, display writing can be completed in 2 seconds per scanning line, and the entire display screen can be written in 2 seconds. Now, writing was completed in 32 seconds.

[0059]

[Effect of the idea]

As described above, according to the driving device for a liquid crystal display device of the present invention, driving signals are sent to the N electrodes. The N drive signal output means for providing the signals include first and second switching switches, respectively. Only two switching means are required, compared to conventional configurations. The number of switching means per drive signal output means can be reduced by one. . This means that the greater the number of electrodes, the more switching means are eliminated. It will be. As a result, the configuration of the drive unit is significantly simplified, which This can contribute to lower equipment costs.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of a driving device for a liquid crystal display device of the present invention.

FIG. 2 is a sectional view showing the basic configuration of a liquid crystal display device driven by a liquid crystal display device driving device according to an embodiment of the present invention.

FIG. 3 is a plan view showing a simplified arrangement of scanning electrodes 3 and signal electrodes 4. FIG.

FIG. 4 is a waveform diagram showing signal waveforms applied to scanning electrodes and signal electrodes, and waveforms of voltages applied to pixels.

FIG. 5 is a waveform diagram showing signal waveforms applied to scanning electrodes 3 and signal electrodes 4 and waveforms of voltages applied to pixels.

FIG. 6 is a block diagram showing the basic configuration of the drive device of the above embodiment.

FIG. 7 is a waveform diagram showing waveforms of scanning signals derived to output lines O1 to ON.

FIG. 8 is a waveform diagram showing signal waveforms applied to scanning electrodes 3 and signal electrodes 4 and voltage waveforms applied to pixels in a driving device according to another embodiment of the present invention.

FIG. 9 is a waveform diagram showing signal waveforms applied to scanning electrodes 3 and signal electrodes 4 and waveforms of voltages applied to pixels.

FIG. 10 is a block diagram showing the basic configuration of a general drive device for realizing the drive method of the previously proposed example by the applicant of the present invention.

[Explanation of symbols]

3 Scanning electrode 4 Signal electrode 5 Liquid crystal layer 12 Switching means 20 Drive signal output means 21 First switch circuit 22 Second switch circuit 23 Switching control section 31 Display control section 33 Data control section 36 Switch 38 Oscillation circuit 40 Data side drive device 41 Shift register 42 Shift register R11, R12,..., R1N latch circuit R21, R22,..., R2N latch circuit L11, L12,..., L1N Level shifter L21, L22,..., L2N level shifter S11, S12,..., S1N analog switch S21, S22,..., S2N analog switch

Claims (1)

[Scope of utility model registration request] Claim 1: N for changing the optical state of a liquid crystal layer.
It is used to drive a liquid crystal display device having (N is a natural number of 2 or more) electrodes, and a predetermined 0 level and a predetermined 0 level are applied to the N electrodes based on display data corresponding to the display content. A drive device that applies a bipolar square wave varying between positive and negative values as a drive signal, the drive device comprising: a positive power supply voltage that is a voltage on the positive side with respect to the predetermined 0 level; A switching means for switching and outputting a negative power supply voltage which is a voltage on the negative side with respect to the level is provided corresponding to each of the N electrodes, and an output signal of the switching means is commonly given; The output terminal connected to the electrode includes N drive signal output means for deriving a drive signal corresponding to the display data, and each of the drive signal output means connects between the switching means and the output terminal. It is characterized by comprising a first switching means that opens and closes based on the display data, and a second switching means that opens and closes between the predetermined 0 level and the output terminal based on the display data. Driving device for liquid crystal display device.