WO2017154089A1 - Drive device - Google Patents

Abstract

This drive device is provided with a scan drive circuit (3) for controlling the voltage applied to a scan electrode of a screen, and a common drive circuit (2) for periodically changing the voltage applied to a common electrode of the screen and also gradually changing the applied voltage. The scan drive circuit (3) is provided with a push-pull circuit in which drains of two FETs (31, 32) are connected, and a gate driver (37) for driving the push-pull circuit, and is further provided with a time constant circuit comprising capacitors (35, 36) and resistors (33, 34), the time constant circuit being connected between the push-pull circuit and the gate driver (37). The time constant circuit and the common electrode are also connected by wiring.

Description

Drive device

The present invention relates to a driving device for driving a display unit.

For example, Patent Document 1 discloses a display device that displays an image projected from a projector or the like when a transparent body such as glass is used as a screen and the screen is in a scattering state.

When a liquid crystal display device is used as a screen as in Patent Document 1, since the life of a liquid crystal element is shortened when DC driving is performed, it is common to perform AC driving in which positive and negative AC voltages are applied at regular intervals. . Among them, for example, AC driving for every video cycle such as every frame is called a frame inversion method, and a method for inverting the bias voltage of the common electrode is called a common inversion method. The common inversion method has the advantage of simplifying the circuit configuration because it is not necessary to prepare two positive and negative power supplies.

However, in the case of common inversion driving, a charging / discharging current having a large peak is generated in the potential supply path to the common electrode at the moment of inversion of the common electrode potential, and this current causes radiation noise. .

To solve the above problem, for example, in Patent Document 2, the output stage of the common electrode drive circuit includes a plurality of sub output stages each capable of outputting a voltage to the common electrode, and the common electrode potential of each polarity. It is described that each supply period is divided into a plurality of partial periods and a voltage is supplied to the common electrode.

Japanese Patent No. 5774675 Japanese Patent No. 5323924

When a liquid crystal display device is used as a screen as in Patent Document 1, by changing the potential of an electrode (also referred to as a scan electrode) facing the common electrode in an arbitrary period, the transmission state and the scattering state are changed, Display video in the scattered state. In the case of the common inversion method, since it is necessary to invert the potential of the scan electrode together with the inversion of the potential of the common electrode, by applying the method described in Patent Document 2 to the scan electrode as well, It is possible to reduce the radiation noise generated at the time of common inversion due to a change.

However, if the method of Patent Document 2 is applied also to the scan electrode, the waveform changes gradually at the timing of changing to the transmission state and the scattering state, and the change to the scattering state is delayed to display an image or the like. It will have an effect.

Also, when the screen is divided into a plurality of parts or a plurality of screens are laminated, the common electrode is shared, but a plurality of scan electrodes may be provided. In that case, the method of Patent Document 2 has a problem that the circuit on the scan electrode side becomes complicated and the circuit scale increases.

Therefore, in view of the above-described problems, an object of the present invention is to provide a drive device that can reduce, for example, radiated noise and can prevent an image display from being affected.

In order to solve the above-mentioned problem, a first control circuit is connected between the second control circuit in which the output impedance is larger than before and after the change, and the first drive circuit that drives the first control circuit and the first control circuit. And a constant circuit, wherein the first time constant circuit and the second electrode are connected by wiring.

It is a schematic block diagram of the display apparatus provided with the drive device concerning the 1st Example of the present invention. It is typical sectional drawing of the screen shown by FIG. FIG. 2 is a circuit diagram of the driving device shown in FIG. 1. FIG. 4 is a timing chart of driving waveforms by the circuit shown in FIG. 3. FIG. 5 is a timing chart showing the internal operation of part A and part B in FIG. 4. FIG. 5 is an explanatory diagram showing a current flowing through a scan drive circuit during a portion A in FIG. 4. 4 is a comparison of simulation results between the circuit shown in FIG. 3 and a conventional circuit. It is a schematic block diagram of the display apparatus provided with the drive device concerning the 2nd Example of this invention. It is typical sectional drawing of the screen shown by FIG. FIG. 9 is a circuit diagram of the driving device shown in FIG. 8. It is a timing chart of the drive waveform by the circuit shown in FIG. It is the schematic block diagram which showed the structural example of the other screen which can utilize the circuit shown by FIG. FIG. 13 is a schematic cross-sectional view of the screen shown in FIG. 12. It is a circuit diagram of the drive device in the case of a screen in a normal mode. It is a timing chart of the drive waveform by the circuit shown in FIG. It is typical sectional drawing which showed the structural example of the screen provided with the touch panel.

Hereinafter, a drive device according to an embodiment of the present invention will be described. A driving apparatus according to an embodiment of the present invention periodically changes a voltage applied to a second electrode of the display unit, a first control circuit that controls a voltage applied to the first electrode of the display unit, A second control circuit in which the output impedance at the time of change is greater than before and after the change, and a first time constant electrically connected between the first drive circuit and the first control circuit for driving the first control circuit And a circuit. The first time constant circuit and the second electrode are connected by wiring. Thus, if the first electrode is a scan electrode and the second electrode is a common electrode, the common electrode (second electrode) is driven by the second control circuit by the common inversion driving (common inversion driving). Therefore, the scan electrode (first electrode) also changes gradually by the first time constant circuit under the influence of the change of the common electrode. In addition, since the common electrode does not change at the timing of changing to the scattering state, the first time constant circuit does not act and the scan electrode can be changed sharply. Therefore, it is possible to reduce the radiation noise during the common inversion driving and not to affect the video display.

Also, since the first time constant circuit and the second electrode are connected by wiring, the voltage change time on the common side and the voltage change time on the scan side can be made equal when the common is inverted. Therefore, it is possible to prevent the liquid crystal from being erroneously scattered due to a potential difference between the two electrodes during common inversion.

The first control circuit is a push-pull circuit composed of two transistors, and the first time constant circuit includes a capacitor connected between the gate of the transistor and the second electrode, the capacitor and the first You may be comprised by the resistor connected between drive circuits. In this way, during common inversion driving, the common electrode (second electrode) changes, so that the input capacitance of the gate of the transistor constituting the push-pull circuit is apparently increased, and the switching of the transistor is delayed. Can do. Further, when the common electrode does not change, the input capacitance of the gate of the transistor does not increase apparently, so that a steep change can be made.

Further, a second drive circuit for driving the second control circuit and a second time constant circuit connected between the second control circuit may be provided. By doing so, the common electrode can be gradually changed by the second time constant circuit.

The second control circuit includes a push-pull circuit composed of two transistors. The second time constant circuit has one side connected to the second electrode and the drain or source of the transistor, and the other side connected to the gate of the transistor. And a resistor connected between the gate and the second drive circuit. By doing so, the apparent capacitance of the gate can also be increased on the second electrode (common electrode) side, and the switching of the transistors can be delayed. Further, the circuit configuration can be made substantially the same as that of the first electrode (scan electrode) side, and the circuit design can be facilitated.

Further, a plurality of first control circuits may be provided, and a plurality of first time constant circuits may be provided corresponding to the first control circuit. By doing this, one screen is divided into a plurality of parts, and the scattering state and the transmission state are individually changed, or a plurality of screens are laminated, and the scattering state and the transmission state are individually changed. It is possible to make it. Also in such a case, radiation noise can be reduced.

The plurality of first time constant circuits may be connected to the second electrode by a common wiring. By doing in this way, the circuit connected to the second electrode can be reduced and the circuit can be simplified.

A display device 100 including a driving device according to a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the display device 100 includes a screen 1, a common drive circuit 2, a scan drive circuit 3, a drive control circuit 4, and a projector 5.

The screen 1 may be any screen that can change the optical state by voltage application and can be driven by common inversion driving. As for the optical state of the screen 1, the scattering state is an image state, and the transparent transmission state in which the scattering of incident light is smaller and the parallel light transmittance is higher than that is the non-image state. That is, it is possible to switch between a transmission state and a scattering state with respect to light.

The screen 1 may be, for example, a light control screen that uses a liquid crystal material and changes a scattering state and a transparent transmission state in which scattering of incident light is small. Examples of the light control screen include a screen using a liquid crystal element such as a polymer dispersed liquid crystal.

FIG. 2 shows a schematic cross-sectional view of the screen 1 capable of controlling the optical state. The screen 1 shown in FIG. 2 has an optical layer 15 in which a composite material containing liquid crystal is sandwiched between a pair of transparent glass plates 11 and 12. A common electrode 13 is formed on the entire surface of one glass plate 11 on the optical layer 15 side. A scan electrode 14 is formed on the entire surface of the other glass plate 12 on the optical layer 15 side. An intermediate layer made of an insulator may be formed between the electrodes 13 and 14 and the optical layer 15.

Further, the common electrode 13 and the scan electrode 14 are formed as transparent electrodes by using, for example, ITO (indium tin oxide). The optical layer 15 is disposed between the common electrode 13 and the scan electrode 14.

A voltage is applied to the screen 1 so that a potential difference is generated between the scan electrode 14 as the first electrode and the common electrode 13 as the second electrode. The optical state in the optical layer 15 changes depending on the voltage applied to the common electrode 13 and the scan electrode 14.

The screen 1 is classified into a reverse mode and a normal mode according to a state when a voltage is applied so as to generate a potential difference. The screen 1 operating in the reverse mode is in a transparent transmissive state in a normal state where no voltage is applied. When a voltage is applied, it becomes a scattering state with a scattering rate of parallel rays according to the applied voltage. In the screen operating in the normal mode, the screen 1 is in a scattering state in a normal state where no voltage is applied. When a voltage is applied, a transparent transmission state with parallel light transmittance corresponding to the applied voltage is obtained. As for the optical state of the screen 1, a predetermined scattering state corresponds to an image state, and a transparent transmission state having a higher parallel light transmittance corresponds to a non-image state. In the following description, the reverse mode will be described.

The common drive circuit 2 applies a predetermined voltage to the common electrode 13 based on the control of the drive control circuit 4. Details will be described later.

The scan drive circuit 3 applies a predetermined voltage to the scan electrode 14 based on the control of the drive control circuit 4. Details will be described later.

The drive control circuit 4 controls the common drive circuit 2 and the scan drive circuit 3 so that the screen 1 is switched to the scattering state in accordance with the projection timing of the projector 5. The drive control circuit 4 acquires an image periodic signal such as a vertical synchronization signal from the projector 5 by, for example, a wireless signal, and performs synchronization control between the screen 1 and the projector 5.

Projector 5 projects image light when screen 1 is in a scattering state. The projector 5 can use a transmissive or reflective liquid crystal light valve that sequentially shifts the black state (state in which no projection light is emitted) on the screen 1 during the scanning period, but other elements may be used. . Further, the projector 5 may perform raster scanning in a video scanning cycle and project video light (image light) on the display surface of the screen 1 in a dot sequential manner. That is, video light is projected intermittently at a predetermined cycle. Alternatively, for example, a laser projector that reflects and shakes the irradiation direction of the intensity-modulated light beam with a movable mirror can be used.

The projector 5 only needs to be able to project video light modulated by video information (image information) onto the screen 1. Note that the video information is obtained from a video signal input to the projector 5. Video signals include, for example, NTSC (National Television Standards Committee), analog video signals such as PAL (Phase Alternation by Line), MPEG-TS (Moving Picture Experts Group-Transport Stream) format, HDV (High -There are video signals in digital format such as Definition (Video) format. The projector 5 may receive not only a moving image video signal but also a still image video signal such as JPEG (Joint Photographic Experts Group). In this case, the projector 5 may scan the screen 1 repeatedly with the same video light for displaying a still image.

FIG. 3 shows a circuit example of the common drive circuit 2 and the scan drive circuit 3 according to this embodiment. The common drive circuit 2 and the scan drive circuit 3 constitute a drive device 10 according to this embodiment. The common drive circuit 2 includes FETs 21 and 22, resistors 23 and 24, capacitors 25 and 26, and a gate driver 27.

The FET 21 is a P-channel FET (Field-Effect-Transistor), the source is connected to the power supply Vb, the drain is the drain of the FET 22, one side of the capacitor 26, the other side of the capacitor 25, and the common electrode 13 of the liquid crystal element (screen 1). The scan drive circuit 3 is connected to one side of the capacitor 36 and the other side of the capacitor 35, and the gate is connected to one side of the resistor 23 and one side of the capacitor 25.

The FET 22 is an N-channel FET, the source is grounded, and the drain is the drain of the FET 21, one side of the capacitor 26, the other side of the capacitor 25, the common electrode 13 of the liquid crystal element, and one side of the capacitor 36 of the scan drive circuit 3. The other side of the capacitor 35 is connected, and the gate is connected to one side of the resistor 24 and the other side of the capacitor 26.

The resistor 23 has one side connected to the gate of the FET 21 and one side of the capacitor 25, and the other side connected to the gate driver 27.

The resistor 24 has one side connected to the gate of the FET 22 and the other side of the capacitor 26, and the other side connected to the gate driver 27.

The capacitor 25 has one side connected to the gate of the FET 21 and one side of the resistor 23, and the other side connected to one side of the capacitor 26, the drain of the FET 21, the drain of the FET 22, one side of the capacitor 36 of the scan drive circuit 3, and the other side of the capacitor 35. Connected to the side.

The capacitor 26 has one side connected to the other side of the capacitor 25, the drain of the FET 21, the drain of the FET 22, one side of the capacitor 36 of the scan drive circuit 3, and the other side of the capacitor 35, and the other side to one of the gate of the FET 22 and one of the resistors 23. Connected to the side.

The gate driver 27 is a driver circuit that outputs a drive signal for the common electrode 13 under the control of the drive control circuit 4.

As apparent from the above description, the FET 21 and the FET 22 are push-pull circuits composed of two transistors and function as a second control circuit. The gate driver 27 functions as a second drive circuit that drives the second control circuit, and includes a time constant circuit including a resistor 23 and a capacitor 25, a time constant circuit including a resistor 24 and a capacitor 26, Functions as a second time constant circuit.

The scan drive circuit 3 includes FETs 31 and 32, resistors 33 and 34, capacitors 35 and 36, and a gate driver 37.

The FET 31 is a P-channel FET, the source is connected to the power supply Vb, the drain is connected to the drain of the FET 32 and the scan electrode 14 of the liquid crystal element, and the gate is connected to one side of the resistor 33 and one side of the capacitor 35. Yes.

The FET 32 is an N-channel FET, the source is grounded, the drain is connected to the drain of the FET 31 and the scan electrode 14 of the liquid crystal element, and the gate is connected to one side of the resistor 34 and the other side of the capacitor 36.

The resistor 33 has one side connected to the gate of the FET 31 and one side of the capacitor 35, and the other side connected to the gate driver 37.

The resistor 34 has one side connected to the gate of the FET 32 and the other side of the capacitor 36, and the other side connected to the gate driver 37.

The capacitor 35 has one side connected to the gate of the FET 31 and one side of the resistor 33, and the other side connected to one side of the capacitor 36 and the common electrode 13. That is, the capacitor 35 is also connected to the drain of the FET 21 of the common drive circuit 2, the drain of the FET 22, the other side of the capacitor 25, and one side of the capacitor 26.

The capacitor 36 has one side connected to the other side of the capacitor 35 and the common electrode 13, and the other side connected to the gate of the FET 32 and one side of the resistor 34. That is, the capacitor 36 is also connected to the drain of the FET 21, the drain of the FET 22, the other side of the capacitor 25, and one side of the capacitor 26 of the common drive circuit 2.

The gate driver 37 is a driver circuit that outputs a drive signal for the scan electrode 14 under the control of the drive control circuit 4.

As is clear from the above description, the FET 31 and the FET 32 are push-pull circuits composed of two transistors and function as a first control circuit. The gate driver 37 functions as a first drive circuit that drives the first control circuit, and includes a time constant circuit including a resistor 33 and a capacitor 35, a time constant circuit including a resistor 34 and a capacitor 36, Functions as a first time constant circuit. Further, the first time constant circuit and the common electrode 13 are directly connected by wiring.

The operation of the common drive circuit 2 and the scan drive circuit 3 shown in FIG. 3 will be described with reference to FIGS. FIG. 4 is a timing chart showing drive waveforms of the common electrode 13 and the scan electrode 14 shown in FIG.

As shown in FIG. 4, the common electrode 13 is changed to, for example, Vb volt and 0 volt at a constant period, for example, every frame by the common inversion driving. The scan electrode 14 applies a pulsed voltage so that a potential difference from the common electrode 13 is generated at the timing of the scattering state.

Here, the operations of the common drive circuit 2 and the scan drive circuit 3 will be described with respect to the portions A and B in FIG. FIG. 5A shows a timing chart of the internal operations of the common drive circuit 2 and the scan drive circuit 3 in the portion A of FIG. 4, and the timings of the internal operations of the common drive circuit 2 and the scan drive circuit 3 in the portion B of FIG. The chart is shown in FIG.

First, the operation of part A in FIG. 4 will be described with reference to FIG. First, the common drive circuit 2 side will be described. In the common drive circuit 2, the common Lo gate signal (the gate control signal of the FET 22) output from the gate driver 27 is set to the Hi level in order to turn on the FET 22. Then, a current flows in the direction of the resistor 24 that charges the gate capacitance of the FET 22 and the gate and source of the FET 22. However, when the gate voltage of the FET 22 exceeds the threshold voltage, the drain voltage of the FET 22 = the potential of the common electrode 13 starts to gradually decrease, and the current for charging the capacitor 26 increases. That is, the apparent capacity of the capacitor 26 increases, the charge current of the gate capacity decreases, and the FET 22 is turned on later (FETs 22VGS and VGS are gate-source voltages). Therefore, the voltage change of the common electrode 13 becomes slow (dV / dt becomes low). That is, in the common drive circuit 2, the output impedance when the common voltage changes is larger than before and after the change.

Next, the scan drive circuit 3 side will be described. In the scan drive circuit 3, the common Lo gate signal output from the gate driver 27 becomes Hi level, and at the same time, the scan Lo gate signal output from the gate driver 37 also becomes Hi level. At this time, a current (see FIG. 6A) flowing through the gate capacitance of the FET 32 flows and tries to turn on the FET 32. However, since the common electrode 13 falls at the same time as the scan Lo gate signal becomes Hi level, the current passes through the capacitor 36. The current flowing through the common electrode 13 (see FIG. 6 (2)) increases. In other words, the apparent capacitance of the capacitor 36 is increased, thereby reducing the current flowing through the gate capacitance of the FET 32 and turning on the FET 32 (FET 32VGS). Therefore, the voltage change of the scan electrode 14 is also delayed. Therefore, as shown in FIG. 4 and FIG. 5, the voltage change becomes gentle (dV / dt becomes low) in both the common electrode 13 and the scan electrode 14.

Next, the operation of portion B in FIG. 4 will be described with reference to FIG. In part B of FIG. 4, the voltage of the common electrode 13 is constant. Therefore, since there is no increase in the current flowing through the capacitor 36 to the common electrode 13, the gate capacitance of the FET 32 is charged at a high speed, and the voltage change of the scan electrode 14 is fast. That is, the change in the voltage of the scan electrode 14 becomes steep.

4 to 6, the falling change has been described. Even at the rising change, the FET 21, capacitor 25, and resistor 23 operate on the common drive circuit 2 side, and the FET 31, capacitor 35, and the scan drive circuit 3 side operate. The resistor 33 operates, and the basic action is the same as described above. That is, when the voltage of the common electrode 13 changes, both the common electrode 13 and the scan electrode 14 change gently, and when only the scan electrode 14 changes, it changes sharply.

Fig. 7 shows the simulation results of the circuit shown in Fig. 3 and the conventional circuit. 7 is a simulation result of a circuit without a time constant circuit using a conventional capacitor or resistor, and a countermeasure is a simulation result of the circuit shown in FIG. Further, the capacitive coupling noise in FIG. 7 is a waveform of noise corresponding to a change in the common voltage and the scan voltage, and the capacitive coupling noise (FFT) is a waveform of capacitive coupling noise in the period of one cycle of the waveform of the common electrode 13 (Fast Fourier Transform). ) And frequency analysis results.

According to FIG. 7, when no countermeasure is taken, a large level of capacitive coupling noise is generated at the timing when the common electrode 13 and the scan electrode 14 change simultaneously, but when the countermeasure is taken, the common electrode 13 and the scan are scanned. It became clear that capacitive coupling noise was suppressed at the timing when the electrode 14 changed simultaneously.

According to the present embodiment, the scan drive circuit 3 that controls the voltage applied to the scan electrode 14 of the screen 1 and the voltage applied to the common electrode 13 of the screen 1 are periodically changed, and the output impedance at the time of change is And a common drive circuit 2 that is larger than before and after the change. The scan drive circuit 3 includes a push-pull circuit in which the drains of two FETs are connected to each other, and further includes a gate driver 37 that drives the push-pull circuit, and a capacitor that is connected between the push-pull circuit and the gate driver 37. And a time constant circuit composed of a capacitor 36 and a resistor 34. The time constant circuit composed of the capacitor 35 and the resistor 33 and the time constant circuit composed of the capacitor 36 and the resistor 34 are directly connected to the common electrode 13 by wiring. In this way, when the common electrode 13 is gradually changed by the common drive circuit 2 due to the common inversion drive, the scan electrode 14 is gradually changed by the time constant circuit under the influence of the change of the common electrode 13. To do. In addition, since the common electrode 13 does not change at the timing of changing to the scattering state, the time constant circuit does not act and the scan electrode 14 can be changed sharply. Therefore, it is possible to reduce the radiation noise during the common inversion driving and not to affect the video display.

Since the time constant circuit composed of the capacitor 35 and the resistor 33 and the time constant circuit composed of the capacitor 36 and the resistor 34 are directly connected to the common electrode 13, the voltage change time (dV / dt) and the voltage change time (dV / dt) on the scan side can be made equal. Therefore, it is possible to prevent the liquid crystal from being erroneously scattered due to a potential difference between the two electrodes during common inversion.

The time constant circuit includes capacitors 35 and 36 connected between the gate of the FET and the common electrode, and a resistor 33 connected between the capacitor 35 and the gate driver 37, and between the capacitor 36 and the gate driver 37. And a resistor 34 connected to the. By doing so, when the common inversion drive is performed, the common electrode 13 is changed, so that the input capacitance of the gate of the FET constituting the push-pull circuit is apparently increased, and switching of the FET can be delayed. Further, when the common electrode 13 does not change, the input capacitance of the gate of the FET does not increase apparently, so that a steep change can be made.

The common drive circuit 2 includes a push-pull circuit in which the drains of two FETs are connected to each other, and includes a gate driver 27, a capacitor 25 connected between the push-pull circuit and the gate driver 27, and a resistor 23. And a time constant circuit including a capacitor 26 and a resistor 24. The time constant circuit is connected between the capacitors 25 and 26 connected between the gate and drain of the FET, the resistor 23 connected between the capacitor 25 and the gate driver 27, and the capacitor 26 and the gate driver 27. And a resistor 24. In this way, the common electrode 13 can be gradually changed by the second time constant circuit, and the common electrode 13 side can have substantially the same circuit configuration as the scan electrode 14 side. Can be easily.

A display device according to a second embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

This embodiment is different in that the screen is a screen 1A divided into a plurality of areas as shown in FIGS. Accordingly, the scan drive circuit 3A has n of the first scan drive circuit 301 to the nth scan drive circuit 30n (n is the number of divisions), and the common drive circuit 2 and the scan drive circuit 3A are used in this embodiment. 10A of drive devices concerning this are comprised.

As shown in FIG. 9, in the screen 1A, the common electrode 13 is formed on the entire surface as in the first embodiment. However, the scan electrode 14 is divided into a plurality of parts, and each of the divided scan electrodes is provided on the screen 1A. The first scan drive circuit 301 to the nth scan drive circuit 30n are connected.

FIG. 10 shows a circuit diagram of the common drive circuit 2 and the scan drive circuit 3A according to the present embodiment. FIG. 10 shows an example in which the screen 1A is divided into four parts.

The first scan drive circuit 301 includes FETs 31a and 32a, resistors 33a and 34a, capacitors 35a and 36a, and a gate driver 37a. The second scan drive circuit 302 includes FETs 31b and 32b, resistors 33b and 34b, capacitors 35b and 36b, and a gate driver 37b. The third scan drive circuit 303 includes FETs 31c and 32c, resistors 33c and 34c, capacitors 35c and 36c, and a gate driver 37c. The fourth scan drive circuit 304 includes FETs 31d and 32d, resistors 33d and 34d, capacitors 35d and 36d, and a gate driver 37d. The circuit configuration of these scan drive circuits is the same as that of the first embodiment. That is, a plurality of first control circuits are provided, and a plurality of first time constant circuits are provided corresponding to the first control circuits.

As shown in FIG. 10, the drain of the FET of each scan drive circuit is connected to the scan electrode in the corresponding region. Further, the other end side of the capacitor 35 a and one end side of the capacitor 36 a are connected to the common electrode 13. The other end side of the capacitor 35b and one end side of the capacitor 36b, the other end side of the capacitor 35b and one end side of the capacitor 36b, the other end side of the capacitor 35b, and one end side of the capacitor 36b are also connected to the common electrode 13 in the same manner. The wiring that connects the common electrode 13 and each scan drive circuit is a common wiring.

FIG. 11 shows a timing chart of operations of the common drive circuit 2 and the scan drive circuit 3A according to the present embodiment. By configuring the screen 1A as in the present embodiment, it is possible to switch between the scattering state and the transmission state for each divided region. Further, as shown in FIG. 11, by shifting the voltage waveform applied to each of the first scan electrode, the second scan electrode, and the third scan electrode, the portion irradiated with the image light about the screen 1A is The video state is maintained. Thereby, the image light that scans the screen 1A is scattered by the screen 1A in the scattering state. On the other hand, the portion of the screen 1A that is not irradiated with the image light is controlled to a non-image state. Each divided region is controlled to a transparent transmission state in a non-video state during most periods when scanning with video light is not performed. Therefore, the see-through characteristic of the screen 1A can be obtained while maintaining the visibility of the image during the projection period of the image light.

In addition, although FIG. 8 etc. demonstrated the example in which one screen is divided | segmented into a some area | region, as shown in FIG.12 and FIG.13, what laminated | stacked the some screen may be sufficient. The screen 1B shown in FIG. 12 has three screens stacked as shown in FIG.

The screen 1B includes a first screen having an optical layer 15a between the common electrode 13a and the scan electrode 14a, a second screen having an optical layer 15b between the common electrode 13b and the scan electrode 14b, and a common electrode 13c. A third screen having an optical layer 15c is formed between the scan electrode 14c. The first screen is sandwiched between the transparent glass plate 12 and the transparent glass plate 16, the second screen is sandwiched between the glass plate 16 and the transparent glass plate 17, and the third screen is the glass plate 17 and the transparent glass plate. 11. That is, in the screen 1B, three screens are formed between the glass plates 11 and 12, and the screens are arranged with the glass plates 16 and 17 spaced apart.

In the scan drive circuit 3A in FIG. 12, the first scan drive circuit 301 to the third scan drive circuit 303 (in the case of FIG. 12, the screen 1B has three layers so that there are three) are the scan electrodes of each screen. It is connected to the. The circuit configuration is the same as in FIG. 10 (however, there are three scan drive circuits).

12 and 13 can also be switched between a scattering state and a transmission state for each screen. Then, by operating with the driving waveform as shown in FIG. 11, only one screen irradiated with the image light is maintained in the image state, and the other screens are controlled to non-image information that transmits the image light. Therefore, a three-dimensional display with depth can be achieved by repeatedly switching the screens in the scattering state sequentially.

According to this embodiment, a plurality of scan drive circuits are provided, and each scan drive circuit is provided with a time constant circuit corresponding to a push-pull circuit. By doing this, one screen is divided into a plurality of parts, and the scattering state and the transmission state are individually changed, or a plurality of screens are laminated, and the scattering state and the transmission state are individually changed. It is possible to make it. Also in such a case, radiation noise can be reduced.

In the above-described embodiment, the reverse mode liquid crystal screen has been described. However, the normal mode may be used. A circuit diagram in the normal mode is shown in FIG. In FIG. 14, the channel of the FET of the scan drive circuit 3 is changed. That is, the FET 31 that is a P-channel FET becomes an N-channel FET 31N, and the FET 32 that is an N-channel FET becomes a P-channel FET 32N. The FET 31N has a drain connected to the power supply Vb and a source connected to the source of the FET 32N. The FET 32N has a drain grounded and a source connected to the source of the FET 31N.

FIG. 15 shows an example of drive waveforms in the circuit of FIG. In the normal mode, since there is a scattering state when there is no potential difference between the common electrode 13 and the scan electrode 14, a pulsed waveform as shown in FIG. To do.

Further, when a touch panel is provided on the screen described in the above-described embodiment, it is preferably provided on the common electrode 13 side. FIG. 16 shows an example in which a touch panel 18 is provided on the common electrode 13 side. As described above, since the drive waveform of the common electrode always changes gently, there is little radiation noise, and the touch panel 18 is not easily affected by the noise. Although the drive waveform at the time of the common inversion of the scan electrode 14 changes gently, the scan electrode 14 changes abruptly when the screen is changed to the scattering state, so that radiation noise may occur. Therefore, it is preferably provided on the common electrode 13 side.

In the above-described embodiments, the capacitor is described as an independent element, but the parasitic capacitance of the transistor may be used. Furthermore, the common drive circuit 2 may be configured as described in Patent Document 2 instead of the time constant circuit including a capacitor and a resistor as illustrated. In short, any configuration may be used as long as the common electrode 13 is gradually changed.

Further, the present invention is not limited to the above embodiment. That is, those skilled in the art can implement various modifications in accordance with conventionally known knowledge without departing from the scope of the present invention. Of course, such modifications are included in the scope of the present invention as long as the configuration of the drive device of the present invention is provided.

1, 1A, 1B Screen 2 Common drive circuit 3, 3A Scan drive circuit 10, 10A Drive device 13 Common electrode 13a, 13b, 13c Common electrode 14 Scan electrode 14a, 14b, 14c Scan electrode 21, 22 FET
23, 24 Resistor 25, 26 Capacitor 27 Gate driver 31, 32 FET
31N, 32N FET
33, 34 Resistor 35, 36 Capacitor 37 Gate driver

Claims (6)

A first control circuit for controlling a voltage applied to the first electrode of the display unit;
A second control circuit that periodically changes a voltage applied to the second electrode of the display unit, and in which an output impedance at the time of the change is larger than before and after the change;
A first time constant circuit connected between the first drive circuit for driving the first control circuit and the first control circuit;
The drive device, wherein the first time constant circuit and the second electrode are connected by wiring. The first control circuit is a push-pull circuit composed of two transistors,
The first time constant circuit includes a capacitor connected between the gate of the transistor and the second electrode, and a resistor connected between the capacitor and the first drive circuit.
The drive device according to claim 1. 2. A second drive circuit for driving the second control circuit, and a second time constant circuit connected between the second control circuit and the second drive circuit. 2. The drive device according to 2. The second control circuit includes a push-pull circuit composed of two transistors,
The second time constant circuit includes a capacitor having one side connected to the second electrode and the drain or source of the transistor and the other side connected to the gate of the transistor, and between the gate and the second drive circuit. Consisting of connected resistors,
The drive device according to claim 3. 5. The drive according to claim 1, further comprising a plurality of the first control circuits and a plurality of the first time constant circuits corresponding to the first control circuits. 6. apparatus. 6. The driving apparatus according to claim 5, wherein the plurality of first time constant circuits are connected to the second electrode by a common wiring.

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