JPS5858675B2 - Hiyojisouchi Nokudosouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Overview The present invention provides an electrolytic device that reversibly changes light absorption characteristics depending on an electric current applied between two support plates, at least one of which is transparent, in contact with at least two electrodes. The present invention relates to a method for driving a display device using a chromic substance.

According to the present invention, an electrochromic display device with reduced wasteful power consumption and excellent display quality has been obtained.

Origin of the invention Display devices using electrochromic substances (hereinafter referred to as EC)
D) is known to be roughly divided into two types.

(For example, L, A, Goodman, '¥)
assive Liquidl) ispiays//,
(See RCA Report 613258) One type uses an inorganic solid membrane, and its typical structure is as shown in FIG.

In FIG. 1, 1 is a layer of carbon powder added with a binder (trade name: Aquadarag), 2 is a stainless steel plate, and these two constitute a counter electrode.

3 is a spacer, 4 is a transparent electrode 5 is a glass substrate, 6 is an inorganic solid film exhibiting an electrochromic phenomenon, and γ is an electrolytic solution.

The most commonly used inorganic material 6 is tungsten oxide (WO3), and its film thickness is about 1μ.

The electrolytic solution 7 is a mixture of sulfuric acid, alcohol such as glycerin, and fine white powder such as titanium oxide.

The alcohol is to dilute the acid and the powder is to provide a white background for coloring phenomena.

The thickness of the electrolyte layer is usually about 1 mm.

A material suitable for functioning as a display device is selected for the counter electrode.

Amorphous tungsten oxide is colored blue when the transparent electrode is brought to a negative potential with respect to the counter electrode.

The applied voltage at that time is about 1.0 to 1.5 volts.

If the polarity of the applied voltage is reversed, the tungsten oxide film returns to its original colorless and transparent state (hereinafter referred to as decolorization).

) This coloration depends on the injection of electrons and protons into the tungsten oxide film.

Further, decolorization occurs because electrons and protons return to their original state due to the reversal of the applied Calo voltage.

Unless a decolorizing voltage is applied, the colored state persists for several days even after the coloring voltage is removed.

Another type of BCD is to reduce a colorless liquid by an electrochemical reaction to form a colored, insoluble film on the cathode.

If there is no oxygen, this colored film will not be decolored unless an electric current is applied.

However, if oxygen remains, the color will gradually discolor (hereinafter referred to as fading).

If the voltage polarity is reversed, the colored film will dissolve and the color will disappear at the same time.

This type of ECD material includes potassium bromide as the supporting electrolyte, heptyl as the substance that produces the colored film,
There is an aqueous solution using viologen and bromide.

The operating voltage is about 1 volt. The basic cell structure is shown in FIG.

The thickness of the liquid is usually one degree thick.

ECD using viologen can be used as a transmission type by using transparent electrodes for both electrodes, or as a reflection type by mixing a reflective pigment into the liquid.

What has been described above is the simple operating principle of the BCD, but next we will list the characteristics of the ECD.

(1) The viewing angle is extremely wide.

(2) Several colors can be selected.

(3) Energy consumption is several times per cycle of coloring and bleaching
It is several tens of mJA and increases in proportion to the number of cycles.

(4) Even after the coloring voltage is removed, if it is kept electrically open, it has a memory effect in that the colored state persists for several hours to several days.

Of course, in this memory state, there is no need to apply external power.

Now, a simple explanatory diagram of a drive circuit when an ECD having the principles and characteristics described above is used as a numeric display device consisting of seven display elements (segments) shown in FIG. 3, for example, is shown in FIG.
It is a diagram.

Segment 81. for simplicity. S2. This is the third digit of S3.

Briefly explain the operation.

Turn on the colored state of the segment and turn off the bleached state.

To turn on only segment S1, turn on switch SWo
to the +V side and turn on switch SW1.

At this time, switch SW2 is kept off.

Segment S! When the segment S1 is sufficiently colored, if the switch SW1 is turned off, the segment S1 maintains its colored state.

Next, when turning off the segment S1, turn the switch SWo to the 1 side and turn on the switch SW.

When segment S1 is sufficiently bleached, switch SW1 is turned on.
Turn off.

When coloring and bleaching multiple segments, you can do the same thing by turning the switch SWo +
Turn the switch SWo to the 1 side and turn the switch of the desired segment to S.
, ~S3 and turn on to bleach the color.

It goes without saying that these switches can be electronically controlled using MOS analog switches.

The present invention relates to a driving method for changing from one display state to another display state.

To explain the main point, as an example, it is assumed that the number 'X2' is currently being displayed and that the number '3' is to be displayed next.

In Figure 3, the number 'X2' is indicated by segment a,
b.

Turn on g, e, and d, and turn on segments a + b t 9 + C and d to display the number 3.

In other words, there are two segments c and e whose display state changes.

As mentioned earlier, ECD has a memory effect that does not require power consumption and lasts for several hours to several days.

Power consumption is required not only when coloring but also when bleaching.

For this reason, in the present invention, in order to reduce power consumption, current is passed only to segments that require a state change.

In the above example, only e is bleached and then only C is colored.

Assuming that the energy required for coloring and bleaching is the same, 'X2
When changing from 〃 to XX3〃, if the display of ``X2'' is completely bleached once and then ゝ3〃 is displayed again, it will consume five times as much energy as compared to the original proposal.

The effectiveness of this proposal can be recognized by looking at this example.

Of course, when applying the present invention, it is necessary to take into account one hour of ECD memory, and the present invention must be used within a time period in which the gradual fading of color in the memory state can be ignored.

In other words, if there is a difference in the coloring state between the previously colored segment and the newly colored segment that is noticeable to the naked eye, this is inconvenient for the display element.

However, if the memory time is sufficiently long, that is, the time during which fading can be confirmed with the naked eye is sufficiently long compared to the time required for the display state to change to the next display state, the present invention is extremely effective.

Figure 5 shows the change in color over time when ECI) was colored until its transmittance reached 30%.

According to this, no change in the coloring state is observed within one day.

From this, it is clear that the present invention can be used, for example, in a digital clock with a 12-hour display.

Furthermore, if one hour of memory is short, the present invention may be used only for the one-minute display portion where the display state changes quickly, for example.

The present invention will be explained more clearly using preferred examples below.

Preferred Embodiment Embodiment 1 This embodiment is a case where the order of change in display state is not determined.

In this case, the following method may be considered as one of the ways to implement this proposal.

For each segment, 1) an element that determines whether the previous display state and the next display state are different; and 2)
If they are different, an element is required to determine whether the next display state is bleached or colored.

An example thereof is shown in FIG.

Although only one segment is shown in FIG. 6 for simplicity, it goes without saying that the circuit shown in FIG. 6 can be easily applied to a case where there are a plurality of segments.

FIG. 7 shows the voltage waveforms of each part in FIG. 6 and their mutual relationships.

6 and 7 will be briefly explained.

A change in the segment signal S is detected by a D-flip-flop and an exclusive OR, and if there is a change, an analog signal connected between the segment and the ground is sent to the coloring side or the bleaching side depending on the change. The switch is turned on and off, and it is synchronized with the applied voltage polarity selection switches SWo+ and 5Wo-.

In this example, the driving circuit is used when it is not known how the display will change next, so the judgment circuit described above is required, but the order in which the numbers change is fixed like a clock. Instead of each display, the segment to be bleached (in the case of changing from SS 2 tt to 3, the segment in Figure 3) e) and the segment to be newly colored (segment C) are shown in advance. Since this is known, if the decoder is configured to bleach the former and color the latter, the judgment circuit described above becomes unnecessary.

In such a display device, if a certain segment remains colored and is left unbleached for a long time, a situation arises in which the colored state deteriorates.

In order to prevent this, in this embodiment, the strobe signal S
It is configured such that the display is once bleached by the mark t and then colored again.

If the change in the display state signal S and the strobe signal St occur simultaneously, the display state change signal takes priority and the switch 5WIT is turned on.

The strobe signal St may be applied at fixed time intervals, may be applied each time a certain state is reached, or may be configured to be applied manually as appropriate.

For example, as shown in FIG. 8, the decolorization signal E is counted by a counter 19 (or other appropriate signals are counted at regular intervals),
If a strobe signal S1 is generated from the output C of this counter 19, the display can be rewritten at fixed time intervals.

FIG. 9 shows waveforms of various parts in this figure.

Also, when used in a totalizer or force calculator, when the display of a certain upper digit (for example, the -10,000 digit) changes, a strobe signal is sent to all digits above the -10,000 digit. Alternatively, a strobe signal may be generated by detecting a display change in the -10,000 digit.

In this way, the display will be rewritten periodically, although not at regular intervals.

Example 2 Figure 10 shows BCI using the present invention and another method in combination.
) This is an example of a drive circuit.

Another method is to first bleach the previous display pattern when changing the display pattern and then recolor the next display pattern (hereinafter, this method is referred to as TED (total e
It is called rasure mountain ving).

First, let's talk about the constant potential drive of ECD.

As generally stated, ECD generally involves passing an electric current through an electrolytic solution and utilizing a reaction at an electrode interface.

This means that it is necessary to maintain the potential difference between the electrolyte and the electrode at an optimal value during the reaction.

This is because if the potential difference is not appropriate, a reduction in reaction rate or other undesirable reactions may occur.

Consider Figure 4. In Figure 4, SWo is V
Suppose that the switch is turned on and SWl is turned on.

Then, the power supply voltage V will be distributed to three parts: the counter electrode interface, the electrolytic solution, and the segment electrode interface.

However, when current flows, the ion concentration in the electrolyte changes locally and momentarily, and the potential applied to the interface also changes over time.

This means that even if a constant voltage is applied externally, that is, between the counter electrode and the segment electrodes, the segment interface potential, which is directly related to the reactions necessary for an actual display device, may change as the reactions progress. means.

In other words, the circuit shown in FIG. 4 may cause side reactions that are inappropriate for use as a display device, or may be accompanied by a reduction in reaction speed.

Therefore, in order to eliminate such drawbacks, a constant potential driving method is used as a voltage application method.

In this driving method, it is necessary to provide a reference electrode for detecting the potential of the electrolyte in addition to the counter electrode and segment electrode.

The purpose of this electrode is to keep the segment interface potential necessary for the reaction constant.

Of course, the reference electrode may detect the voltage applied to the electrolyte in accordance with the segment interface potential, so careful attention must be paid to its placement.

In FIG. 10, a voltage suitable for reaction is applied to the inputs of the differential amplifier, and the electrolyte potential detected by the reference electrode 22 is measured by one of the amplifiers.

When the gain of the amplifier is sufficiently large, the amplifier adjusts the output voltage, that is, the counter electrode voltage, so that the reference electrode potential and the input potential become equal, and performs constant potential driving.

Now, FIG. 10 will be explained again.

is a control signal according to the present invention, and is a control signal according to TED.

However, TED uses a counter 20 (in this example, it is assumed to be a quinary counter to simplify the explanation),
The explanation will be given by taking as an example a case where there are few changes in the display pattern.

Note that FIG. 11 is a waveform diagram of each part in FIG. 10.

S, , S2 are segment signals, but now the signal S1
Signal S2 has a large change speed and the display changes relatively quickly, and changes in synchronization with the rising edge of erase signal E, whereas signal S2 has a small change in display pattern, the output of counter 20 is at H level, and it is colored. The phases are adjusted so that the signal W changes when the signal W rises.

Although the number of segments shown in FIG. 10 is one, it goes without saying that the number of segments can be expanded to multiple segments.

Voltage relationship E of each part in FIG. W, S2. As can be seen from H, when S2 is Low+High, W, Low-), Low when S2 is Low, and High→
In the case of Low, E comes out as an output, and in the case of High→High, the partner of E and W comes out as an output, realizing TED.

Note that the timing of change between Sl and 82 is different in the first
As can be seen from the cell structure schematically shown in Figure 0, even in the case of each digit display (two digits in the figure), there is one counter electrode and one reference electrode each, and E and W are two. This is because it must be used in common for both methods, ie, the main proposal and TED.

Setting the appropriate voltage for the reaction is carried out using variable resistors for bleaching and coloring, which are led to the + (plus) input of the differential amplifier through analog switches controlled by the E and W signals.

Non-memory signal M is the sum of E and W, and is sent to switch T.
is under control.

That is, when M is High, T conducts and operates the amplifier, but when M is Low, T is turned off and the bias current of all transistors is cut off, and the operation of the amplifier is stopped and the amplifier is disconnected from the counter electrode and reference electrode. The seen impedance becomes very large and keeps the ECD in memory.

Of course, you can keep the ECD in memory by turning off the segment selection analog switch, but the M
and T are also intended to eliminate power consumption due to idle current required for linear amplifiers, at least during unnecessary periods of operation as an amplifier.

As described above, the combination of the present invention and TED can be realized extremely easily.

In addition, as an example of an application in which this is used in combination, for example, TED can be applied to the upper number of a frequency counter, and the present invention can be applied to the lower number.Also, as I mentioned a little earlier, in the case of a character display on a clock, the time display can be used. This proposal can also be applied to TED and minute display.

In other words, by taking advantage of the characteristics of ECD, the present invention is used for display areas where the display pattern changes quickly, and TED is used for areas where the display pattern changes slowly.
By applying this, it is possible to prevent deterioration in display quality due to memory deterioration, and at the same time, it is possible to reduce power consumption.

Furthermore, the two methods are applied to each of a plurality of segments in the same cell, that is, in the electrolyte that is electrically connected.
Another feature is that it can be applied using constant potential drive.

As described above, according to the present invention, an electrochromic display device can be driven with low power consumption.

Further, according to the present invention, two MO8FET switching elements are provided on opposing electrodes, and one MO8FET switching element is provided on each segment electrode.
It is useful because it has the advantage of simplifying the configuration of the drive circuit, such as using 8FET switching elements.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the basic configuration of a solid-state ECD. FIG. 2 is a sectional view showing the basic configuration of a liquid ECD. FIG. 3 is a segment layout diagram of the Japanese character type numeric display pattern. FIG. 4 is a basic drive circuit diagram of the BCD. FIG. 5 is a diagram showing the change in light transmittance over time after the coloring voltage is removed. FIG. 6 is a circuit diagram of one embodiment of the present invention, and FIG. 1 is a time chart showing the voltage relationship of each part in FIG. 1... Aquaduck (product name: carbon powder + binder), 2... Stainless steel plate, 3... Spacer, 4... Transparent electrode,
5... Glass substrate, 7... Electrolyte, 8
...Glass substrate, 9...Counter electrode, 1
0... Display electrode, 11... Viologen mixture, 12... Spacer, 13...
- Sealing material, a-g...Each segment of the 7-segment display device, 14...Counter electrode, So...
...Applied voltage polarity switch, S, ~S3...
...Segment, 5I-82...Segment selection switch, Bl, B2...Power supply, 5WIT
...Segment selection analog switch, SWo
+. 5Wo-... Applied voltage polarity selection analog switch, S... Segment signal, CI...
D-Flip-flop clock signal, E...Bleached signal, W...Colored signal, St...Strobe signal. FIG. 8 is a circuit diagram of main parts of another embodiment, and FIG. 9 is a time chart of voltage waveforms at each part. FIG. 10 is a circuit diagram of still another embodiment, and FIG. 11 is a time chart of voltage waveforms at each part. E...Bleaching signal, W...Coloring signal, C
... Counter output, St ... Strobe signal, 19 ... Counter, 20 ...
... Counter 21 ... ECD outer container, 22.
...Reference electrode, 23 ...Counter electrode, 24
...Segment driven by this proposal, 25.
...Segments that are driven by a method in which, when changing the display pattern, all segments are bleached and then the next display pattern is colored anew. E...Bleaching signal, W...Coloring signal, M
...Non-memory signal, CI...Clock, Sl, B2...Segment signal, St...
...Strobe signal, ±■ ...DC power supply,
T...Transistor for amplifier control.

Claims (1)

[Claims] 1 Separate the pattern to be displayed into multiple display elements,
In the method for driving a display device using an electrochromic phenomenon in which a current is applied to the display element to color or decolorize the display element, a counter electrode common to the plurality of display elements,
Positive and negative voltages are applied in accordance with the coloring timing signal and the decoloring timing signal having different phases, and the plurality of display elements are turned on and off. When transitioning from one display pattern in which a 5'% constant is colored to another display pattern in which other display elements are colored, only the segment electrodes of display elements that are not common to the above two display patterns are colored at the above-mentioned timing. A method for driving a display device, characterized in that a display pattern is changed by selecting in synchronization with a signal or a bleaching timing signal and applying a current to only display elements that are not common to cause bleaching or coloring.