JPS6024478B2 - Driving method of electrochromic display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrochromic display (hereinafter referred to as EC).
(referred to as D).

Regarding the two basic structures of ECD, the characteristics of ECD, segment display by ECD, basic drive circuit of ECD, etc., the patent application filed by the applicant, including some of the inventors of this invention, etc. Group No. 96 JP-A-52-4
(See Publication No. 3393) As otherwise explained. The present invention relates to a method for driving an ECD without causing uneven coloring or bleaching in order to improve the display quality of the ECD, in which constant potential driving is performed during coloring, and constant voltage driving is performed during bleaching.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on an example in which the present invention is implemented in a speed display device for a vehicle.

FIG. 1 shows a cross-sectional configuration diagram of an ECD cell, in which a reference electrode 14
is added.

FIG. 2 is an example of a circuit for constant potential constant voltage driving when an ECD is used in a vehicle speed display device. FIG. 3 is a signal time chart of each part of the circuit of FIG. 2. FIG. 4 is a power supply circuit of the circuit shown in FIG. 2, and FIG. 5 is a time chart of voltages at various parts in FIG. In FIG. 1, 1 and 4 are transparent electrodes, 2 and 5 are glass substrates, 3 is a substrate and sealing resin, and 6 is a transition metal oxide (for example, W
03) is the deposited thin film, and 7 is the electrolyte.

When the electrode 1 and the substrate 2 form a counter electrode to form a reflective display device, the electrode 1 is made of graphite or a thin film of a noble metal such as platinum or palladium. The electrode 4 and the substrate 5 form a display electrode. 14 is a reference electrode and transparent electrode 1
Made of the same transparent electrode material.

Next, the vehicle and its operation during running will be described in detail using FIGS. 2 and 3.

15 is a rotating permanent magnet attached to the rear wheel axle or propeller shaft of the vehicle, 16 is a coil that detects the rotation, and 17 and 18 are amplifiers for the signals detected by the coils and Nando Schmitt triggers for waveform shaping. It is.

Numeral 19 is a so-called counting circuit that converts the output pulses of the Nand Schmitt trigger 18 into an appropriate number of pulses generated during one cycle of pulses CI, CI2, CI3, which will be described later.

That is, the number of pulses generated from the circuit 19 during one cycle of pulses CI, CI2, CI3 is converted into the number of output pulses of the trigger 18 so that it becomes 5, for example, when the vehicle is traveling at a speed of 1/h. This is a circuit that does this. 20 is an AND gate that stops the input signal to the IG Hayabusa counter 21 when pulses CI, CI2, which will be described later, are high.

22 and 23 are also IG Hayabusa counters similar to the IG Hayabusa counter 21, and advance the count by one when the signal to the input CI changes to Hi or High.

Its output signal a. b, c, d, e, f, and g are 7-segment display signals corresponding to the well-known 7-segment display, and the Hi statement generates a voltage that colors or decolors the corresponding segment. means. CO is a carryout, and the time j when the counter contents change from 9 to 0
gh, and that signal becomes an input signal to the next stage counter. RB1 and RBO are terminals for preventing unnecessary 0 from being displayed. As 21, 22, and 23, commercially available ICs such as RCA CD4033A can be used.

Note that 3 counters 21, 22, and 23 are used.
This is to display the speed of the digits, and it goes without saying that more or fewer digits can be displayed. 3
Numerals 5 to 45 are timing pulse generation circuits for displaying speed.

35 is a basic pulse generator, 36 is a multistage ripple counter that receives the basic pulse as input, and its Q, , Q2
The write pulse W is generated by the NOR gate 37 using the two outputs of
I get it.

The pulse width of the signal W is the time necessary for coloring the ECD, and is suitably about several hundred hsec to lsec. A decolorizing pulse E is obtained by inverting the phase of the signal W.
The period of signal E is 0. Sec to several seconds is appropriate. 38 is a circuit for detecting the rise and fall of E, and its outputs are A and CI, and each pulse E
It corresponds to the rise and fall of .

The block 39 outputs a pulse CI2 at the falling edge of the signal CI, and the block 40 outputs a pulse C1 at the falling edge of the signal CI2.
Take out I3. In other words, W, E, CI, , CI2, in Figure 3
Each signal is generated at the timing indicated by CI3. Reference numeral 41 denotes a strobe switch provided externally, which is turned on when regenerating the display contents of the ECD.

Reference numeral 42 denotes a timer circuit for automatically regenerating the display contents of the ECD at certain fixed time intervals, for example, once every half hour to one hour, and generates a strobe signal.

This circuit 42 receives the signal E as an input, and its output C has a cycle of half an hour to one hour, a pulse width of one cycle of the signals 8 and W, and changes from High to LOW or Low at the fall of the signal E.
Transition from w to Hi mosquito. Block 44 generates a pulse whose output is regeneration instruction pulse Re, and 45 is an R-S flip-flop. As shown in FIG.
is ON and its output signal B is high, or when signal C is
If the signal A becomes Hi when is High, the regeneration instruction pulse Re transitions to Hi state, and this transition coincides with the rise of the erase pulse E. The transition of the pulse Re to Low also occurs at the same time as the erase pulse E rises if the switch 41 is OFF or the pulse A becomes High when the pulse C is low. Let's talk about regeneration.

ECD has the feature of maintaining a colored or bleached state if it is kept electrically open, but in practice it is difficult to achieve a completely open state, which is one factor, and the degree of coloring of the colored segment gradually deteriorates. In addition, the bleached segment may also be colored by irradiation with light. Therefore, in order to compensate for the incompleteness of long-term memory, it is necessary to perform regeneration at appropriate intervals, that is, to perform an operation in which colored segments are once bleached and then colored again, and bleached segments are only bleached. In order to control this operation, it is necessary to match the rise of the regeneration instruction pulse Re with the rise of the erase pulse E, and the rise of the pulse Re with the rise of the write pulse W that has finished coloring, that is, the rise of the erase pulse E as well. There is. In Fig. 2, the pulse widths of the signals CI, CI2, and CI3 are drawn quite large, but this is to clarify the time relationship between them, and in the actual case, the write pulse W and the erase pulse The pulse width is negligible compared to the pulse width of E, for example, several Asec.
~ several low seconds is sufficient.

Now, the signal CI3 is a pulse that resets the counters 21 to 23 at regular time intervals.

Therefore, the contents of these counters immediately before they are reset represent the running speed. Pulse C
I, , CI2 are the clock pulses of the D flip-flops shown at 24,25. One segment signal sa of the counter output is applied to these two D-flipflops 24 and 25, and the signal CI, which comes immediately before the signal CI3,
, is read by CI2.

That is, the output ssa of the flip-flop 24 appears at the output of the flip-flop 25, and one output sa of the counter 21 appears at the output of the flip-flop 24.
The outputs of flip-flops 24 and 25 are exclusive OR 26
Therefore, the output C side of the exclusive OR 26 becomes i-track when the running speed changes and the display state changes due to coloring or bleaching of the a segment, and when the display state of the segment does not change. It's a mountain lol. Block 27 is the signal s
When sa is Hi track, write signal W is applied, and when sa is at peak w, bleaching signal E is passed. The output of the block 27 and the signal Cha turn on the analog switch 30 through the AND gate 29.
-Turn off. That is, 24 to 28 are circuits that should be provided for each segment in order to color or bleach the segment only when it is necessary to change the coloring state of each segment when the number displayed on the ECD changes. In FIG. 2, only one segment is depicted and the others are omitted. The write signal W generated as described above turns on the amplifier 34 and turns on the analog switch 31, and at the same time, the signal ca turns on the analog switch 30 and writes to segment a using the constant potential drive method. make the action take place.

Also, when the decolorization signal E is generated, the analog switch 32
, 33 are turned on to prepare for a current to flow in the opposite direction during writing, and decolorization is performed using a constant potential drive method in which a decolorization signal is applied to the segment where the segment switch is turned on. Also, the signal CI , , CI2's NOR outputs are led to gate 20 in order to prevent the contents of counters 21-23 from changing when the contents of flip-flops 24 and 25 are changed.

Signal Sc2a becomes High when performing regeneration, and S
When sa is High, the bleaching signal B and the write signal W are
When the signal Ssa is low, only the signal E appears, and this signal also controls the switch 30 through the gate 29. This driving method of coloring and decoloring only the segments whose colored state changes when the displayed number changes uses a display device such as an ECD, which has a longer response time than a light emitting diode, to display the speed of the vehicle. It is effective when used for

This is because in the speed display of a vehicle, the displayed number changes the most in the lower digits, and 100 matsu/hlo board/
For high-order digits such as h, it is better to use the ECD memory function to erase all digits than to use a drive method that erases all segments once and then displays the same digits again even though there is no change in the displayed digits. This is preferable as a speed indicator. Next, using FIGS. 4 and 5, the on/off of the engine key will be described when the vehicle starts and stops.

In FIG. 4, block 46 is a monostable multipipe layer that is triggered by the fall of the output signal D of inverter 61, and its output changes to YES at the same time as the trigger.
After a certain period of time, it returns to the original High level. 47 is a battery mounted on the vehicle, and its voltage is 10 VB.

48 is a transistor switch that is turned on and off depending on the signal date, and when the signal is ON, the transistor switch 48 is turned on, and its output voltage is +V, which is a positive voltage stabilized by the Zener diode 49, for example, 5V. This voltage is the power supply voltage V of the circuit shown in FIG.

However, in order to reduce the ON resistance of the analog switch by 4.0, it is also good to make it even higher. Further, the output voltage 1V2 is a voltage of, for example, about 2V, which is obtained by dividing the voltage +V, and this voltage is the power source used for constant fin pressure cancellation in FIG. Therefore, in the time chart of FIG. 3, the Hi level is the voltage +V, and the Low level is the ground potential.
In addition, in Fig. 5, the Hi scale level is a voltage of 1V8, and the Lo
The w level is the ground potential. However, only the high level of 1 is clamped to the fin pressure of 1 V by a diode 62. This is because 1 is connected to the ripple planking input RBI of the counter 21 in FIG. 2, so the levels are matched. In FIG. 5, key is High when the engine key is ON, and Low when the engine key is OFF. Now, when the engine key is OFF, the signal day is Hi track, and no power supply voltage is supplied to the circuit shown in FIG.

When the key is turned on, the signal becomes Low, and the circuit shown in Figure 2 is supplied with a power supply voltage of 10 V and enters the operating state. At this time, the output signal 1 changes from Low to Hi, so the vehicle stops If so, the counter 31 outputs seven segment outputs a to g for displaying zero. In other words, the speed display is counter 2
Only the lowest digit 0 corresponding to 1 is displayed. If this initial display is incomplete, regeneration is performed by manually turning on switch 41 in FIG. 2 and setting signal B to High, and a clear display of only one 0 is performed. Of course, at the same time as the engine key is turned ON, it is easy to make the signal B High for a certain period of time longer than one cycle of the write signal W, and then add a circuit that rubs the peak W'. There is no need for manual regeneration immediately after inserting. Since the subsequent operations while the vehicle is running have already been described, next we will describe the case where the engine key is turned off after the vehicle has stopped running. When the engine key is turned OFF when the speed display is only 0 corresponding to 21 after the vehicle has stopped, the instantaneous signal D transitions to the peak w, and the output G of the monostable multipipulator of the block 46 also shifts to the peak w. For this reason, the key is set to O on the output date.
Even after switching to FF, the period during which the block 46 operates and the output G is at the peak w is still w, and therefore the circuit of FIG. 2 remains in the operating state. However, signal 1 turns the key OFF
The output of the counter 21 is a~
All g's are mountains w'konaru. For this reason, if the time that the output G stays at the peak w is made more than twice the period of the bleaching signal E, the ECD used for speed display will be able to display all of the segments shown in Figure 2 after all segments have been bleached. The circuit stops working. Now,
Finally, the ECD <constant potential = constant voltage drive> method according to the present invention will be described.

The constant potential constant voltage drive described here means constant potential driving for coloring and constant voltage driving for decoloring.

In order to perform constant potential driving, a reference electrode 14 is required as shown in FIG. 1, and a high gain linear amplifier is also required.

In the case of coloring, the current flows from the counter electrode to the segment electrode, and the amount of reaction at the counter electrode interface changes depending on the number of segments to be colored. However, what is important for coloring is the potential difference at the segment interface. Therefore, reference electrode 1
By using 4 and a linear amplifier, the aim is to keep the potential difference at the segment interface, which is important for display, constant even if the amount of reaction at the counter electrode interface changes and the potential difference at that interface changes. is constant potential drive. In the case of decolorization, potentiostatic fly drive is used, but this method uses W03 membrane, etc.
Effective for ECD using transition metal oxides. That is, for example, in the case of W03 film and Mc03 film, they exhibit low resistance when colored and high resistance when decolored. Therefore, even if constant voltage driving is used for bleaching, once bleaching is finished, the segment becomes highly resistant and current no longer flows, resulting in differences in the degree of bleaching. That doesn't happen. However, in the case of coloring, even if a constant voltage is applied to the opposing electrodes, the potential difference at the interface between the opposing electrodes varies depending on the number of segments to be colored, as mentioned above.In other words, the difference in potential between the segments at the interface where a coloring reaction occurs depends on the number of colored segments. This may cause a difference in the degree of coloring of the segments, resulting in lower display quality. In addition, the advantages of the constant potential constant voltage drive method of the present invention as compared to the so-called constant potential drive method in which constant potential drive is used for both coloring and decoloring are as follows.

That is to reduce the influence of the linear amplifier's input bias current. As can be seen in FIG. 2, the reference electrode 14 is connected to the negative input of a linear amplifier, shown by way of example at 34 in FIG. Therefore, the input bias current of the linear amplifier 34 flows directly through the reference electrode, and this current changes the reference electrode interface potential, thereby preventing the original purpose of constant potential drive. In other words, if this bias current is large, the degree of coloring will change over time, for example. However, if constant potential drive is used only during coloring, and the linear amplifier is stopped at other times so that the bias current does not flow, the influence of the bias current will be less and coloring will be more stable. This can be done by potential driving. This method is particularly effective for reducing the influence of input bias current when using a linear amplifier in which the input portion of the linear amplifier is constructed of bipolar transistors and the input bias current is on the order of several microamperes. <Constant potential constant voltage drive> used in FIG. 2 will be explained.

A linear amplifier 34 is used for coloring with constant potential drive. A junction type FET is used for the input to reduce the input bias current, and at the same time, a constant power source using a transistor is installed at the source of the FET to take advantage of the fact that the source potential is higher than the gate potential to achieve common mode rejection. The ratio is improved by using a differential amplifier using a single power supply. A single power supply +V is, for example, about 5V.

The output section uses emitter follower output through two diodes to suppress the maximum amplitude to about 3V and obtain a large unidirectional output current. This is this amplifier 3
4 is a linear amplifier suitable for the driving method of the present invention, which is used only for coloring, and the voltage applied to the positive input using a variable resistor is a unidirectional output current that causes a current to flow into the counter electrode. Therefore, in order to color, the constant current source transistor connected to the FET source is operated with the write signal W, and the same signal W is used to turn the analog switch 31 to OFF.
N, and then synchronize the segment switch 30 connected to the segment you want to color with the signal W and turn it on. Then, that segment will be at a positive potential set by the variable resistor for setting the reference electrode potential of the amplifier 34. The color is then colored by constant potential driving. For bleaching, use bleaching pulse E
This turns on the analog switches 32 and 33.
The switch 32 is connected to a constant voltage +V2 (~2V) for erasing, and the counter electrode 9 is grounded. Then, synchronize with the signal E and turn on the segment switch 30 of the segment to be bleached. In the case of a memory, all analog switches 30 to 33 are turned off, and of course the signal W is also set to Low, and the operation of the amplifier 34 is also stopped. As described above, according to the present invention, a stable and good display can be performed, and it can be driven with a circuit that is advantageous in terms of cost and structure.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an ECD used in the present invention, FIG. 2 is a circuit diagram implementing the driving method of the present invention, FIG. 3 is a time chart of the circuit in FIG. 2, and FIG. 4 is a driving method of the present invention. FIG. 5 is a circuit diagram of a power supply section used in a circuit implementing the above, and FIG. 5 shows a time chart of the circuit shown in FIG. 1 and 4 are transparent electrodes, 6 is a transition metal oxide thin film, 7 is an electrolyte, 14 is a reference electrode, 30, 31, 32, and 33 are analog switches, 34 is a linear amplifier, 10V is a writing voltage, V2 is bleached fin pressure. Figure 1 Figure 4 Figure 5 Figure 2 Figure 3

Claims (1)

[Claims] 1. A display device using an electrochromic phenomenon that colors or decolors by applying an electric current, characterized in that the coloring is performed by a constant potential driving method, and the decoloring is performed by a constant potential driving method. A method of driving an electrochromic display device.