JPH0845662A - Electroluminescent panel driving circuit - Google Patents

Abstract

PURPOSE:To provide an electroluminescent (EL) panel which is capable of arbitrarily controlling a plurality of arbitrary regions to emit light locally and can control the intensity of light emission to any desired level. CONSTITUTION:A transparent electrode 5 is installed on one of the surfaces while a light emission layer 3 is interposed, and back electrodes 1-1, 1-2, 1-3 are furnished on the other surface. A control signal generated by a drive control circuit 9 is given to a driver circuit 7, which gives a potential difference between the transparent electrode 5 and back electrodes 1-1, 1-2, 1-3 according to a predetermined spatial and temporal orders. Thereby the light emission layer 3 emits light with a lightness determined by the potential difference and frequency. It is possible to allow different parts of the EL surface to emit light at the desired timings or to be dimmed into desired lightness by selecting appropriately the temporal and spatial orders of the drive signals generated by the driver circuit 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display panel driving circuit utilizing electroluminescence, and in particular, the present invention is applicable as a display device to a wide range of fields such as advertisement, advertisement, hobbies, and appreciation. The present invention relates to a drive circuit for an electroluminescent panel capable of producing

[0002]

2. Description of the Related Art The phenomenon of electroluminescence (hereinafter abbreviated as EL) in which phosphor powder is sandwiched between opposed electrodes and light is emitted by an electric field generated between both electrodes when a voltage is applied was discovered in the 1930s, With further improvements, it is now in practical use.

For the physical analysis of this light emission phenomenon, see Haruo Haru, Optoelectronic Device (1990).
Yearly, published by Baifukan) PP50-PP56, so the detailed description is omitted here, and only the general description given above is given. FIG. 5 shows a principle diagram of the EL structure. In the figure, 51 is a glass substrate, 52 is a transparent electrode, 53 is a light emitting layer, 54 is an insulating layer, and 55 is a back electrode.

By applying a potential difference between the transparent electrode 52 and the back electrode, an electric field is generated between the two electrodes, and an electron-hole pair or an electron from the luminescence center is excited by the accelerated electrons, and the excitation is caused. It is said that light is emitted when the state returns to the steady state. FIG. 6 shows a mode of light emission of the EL cell, and 61 is a voltage waveform applied between both electrodes,
The vertical axis represents the amplitude including the polarity and the horizontal axis represents the time, and 62 represents the potential of one of the electrodes as a reference.

Reference numerals 63 and 64 denote time timings when the other electrode has positive and negative potentials with respect to the reference voltage, respectively.
5 is the emission intensity of the light emitted from the light emitting layer, the vertical axis is the emission intensity,
The horizontal axis is represented by a time axis corresponding to 61.
From this, it can be seen that when the voltage applied to both electrodes is a positive and negative alternating voltage, the light emission phenomenon occurs twice within one cycle.

FIG. 7 shows the frequency characteristics of the light emission intensity in EL. The horizontal axis shows the frequency of the voltage applied between both electrodes, and the vertical axis shows the light emission intensity. From the figure, it can be seen that the higher the frequency, the brighter the light, and the lower the frequency, the darker the light. This is a property derived from the essence of the EL light emitting mechanism, and it is possible to realize an efficient dimming function with low loss.

[0007]

As described above, E
L has various characteristics and has many industrial applications, but at present, it is only used as a backlight of a so-called liquid crystal display body to which the characteristics of the flat light source are applied. . As can be seen from the structure of the EL, the EL has a very thin thickness, has a characteristic that the light emission has a uniform intensity over the entire plane, and generates very little heat. It is because it is well suited as.

In the case of this application, in order to obtain a large display contrast by drawing characters or the like on the liquid crystal surface as a difference in light transmittance by utilizing the property that the light transmittance of the liquid crystal can be changed by external control. That is, the EL panel is used to illuminate from the back of the liquid crystal. The illumination emphasizes the difference in shade between the character portion and the background portion as if by the principle of "shadow drawing", so that it becomes easier for human eyes to read.

In this case, the size of the EL panel needs to be large enough to cover the entire liquid crystal display surface, but it is sufficient for the EL panel to emit light at the same time when the entire surface emits light. It is not necessary for the surface to emit light locally. As described above, in the past, the EL has been mainly used only as a backlight of a liquid crystal display body, and the application of the EL has not yet been fully utilized.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a uniform flat light source which is a feature of EL, has a small heat generation, and can be made thin. Also, focusing on the fact that a curved light source can be configured because the material is flexible, taking the conventional usage method of uniformly and simultaneously emitting light over the entire EL panel surface, a plurality of arbitrary areas on the EL surface can be formed. It is an object of the present invention to provide an EL panel having a novel light emission mode by locally emitting light and arbitrarily controlling the light emission intensity.

[0011]

In order to solve the above problems, the invention according to claim 1 of the present invention is directed to an electroluminescent panel, a plurality of counter electrode pairs sandwiching the electroluminescent panel, and a plurality of electrode pairs corresponding to the respective electrode pairs. Is provided, and the counter electrode pair is
The drive control circuit is configured to be driven according to a predetermined spatial drive order.

According to a second aspect of the present invention, an electroluminescent panel, one or a plurality of counter electrode pairs sandwiching the electroluminescent panel, and one or a plurality of drive circuits corresponding to the respective electrode pairs are provided. The pairs are configured to be driven according to the temporal order of the drive waveforms generated by the drive control circuit. According to a third aspect of the present invention, the electroluminescent panel, a plurality of counter electrode pairs sandwiching the electroluminescent panel, a plurality of drive circuits corresponding to the respective electrode pairs, and a plurality of drive circuits are connected to the counter electrode pairs. And a drive control circuit for generating a control signal for driving in accordance with a predetermined spatial and temporal order, wherein the drive control circuit is in a high-level state in a predetermined pattern in which each potential of one electrode of each electrode pair is predetermined. And the low-level state, and the potential of the other electrode of each electrode pair is alternately changed to the high-level state and the low-level state at a preset cycle.

[0013]

As shown in FIG. 1, the transparent electrode 5 is provided on one side of the issuing layer 3 and the back electrodes 1-1, 1- are provided on the other side.
2, 1-3 are provided. Then, a control signal generated by the drive control circuit 9 is given to the drive circuit 7, and the drive circuit 7 causes a predetermined spatial and temporal relationship between the transparent electrode 5 and the back electrodes 1-1, 1-2, 1-3. The potential difference is given according to the order. Thereby, the transparent electrode 5 and each back electrode 1-1, 1-2, 1
The light-emitting layer 3 sandwiched by -3 emits light with brightness according to the applied potential difference and frequency.

Therefore, by selecting the spatial and temporal order of the drive signals generated by the drive circuit 7, it is possible to make each part of the EL surface emit light at a desired timing or to adjust the brightness to a desired brightness. . In the invention of claim 1 of the present invention, as described above, since the counter electrode pair is configured to be driven in accordance with the spatial drive order predetermined by the drive control circuit, the respective parts of the EL surface are arranged in a desired spatial order. Can be made to emit light.

According to the second aspect of the present invention, since the counter electrode pair is driven in accordance with the time sequence of the drive waveform generated by the drive control circuit, each part of the EL surface is arranged in a desired time sequence. Can be made to emit light. In the invention of claim 3 of the present invention, the drive control circuit alternately changes the electric potential of one electrode of each electrode pair to a high level state and a low level state in a predetermined pattern, and
Since the configuration is such that the potential of the other electrode of each electrode pair is alternately changed to the high-level state and the low-level state at a preset cycle, the pattern of the potential applied to each of the one electrode of each electrode pair should be selected. Thus, the EL surface can be made to emit light in an arbitrary spatial and temporal order. In addition, by fixing the pattern of the potential applied to one electrode of each electrode pair and changing the cycle of the potential change applied to the other electrode of the electrode pair, the EL surface is made to have a desired brightness. be able to.

[0016]

【Example】

(Embodiment 1) FIG. 1 shows a functional block diagram of a first embodiment of the present invention. In the figure, 1-1, 1-2, and 1-3
Is a back electrode, 3 is a light emitting layer, and 5 is a transparent electrode, which form an EL panel. 1-1 and 5, 1-2 and 5 and 1-3 and 5 respectively form counter electrode pairs. Incidentally, E shown in FIG.
Compared with the structure of L, the glass plate and the insulating protective layer are omitted in this figure.

Reference numeral 7 denotes a drive circuit, the output of which is electrically connected to the back electrode 1-1 by a connection 6-1 and supplies a predetermined drive voltage to the back electrode 1-1. Similarly, the other output of the drive circuit 7 is connected to the back electrodes 1-2 by the connection -6,
Connection 6-3 connects to the back electrode 1-3 and connection 6-4 connects to the transparent electrode 5, and a predetermined drive voltage output from the drive circuit 7 is supplied to each electrode.

Reference numeral 9 is a drive control circuit, and the drive circuit 7 is connected through a connection 8 (four in this drawing) in accordance with a predetermined drive order of the back electrodes 1-1, 1-2 and 1-3 and / or a drive waveform order. To drive. FIG. 2 shows driving waveforms of the back electrodes 1-1, 1-2, 1-3 and the transparent electrode 5 of this embodiment.

In this figure, reference numeral 24 represents a drive voltage waveform applied to the transparent electrode 5. In the present embodiment, the transparent electrode 5 to be paired with each back electrode is not provided for each back electrode but is a common electrode. In the figure, at each timing of the drive waveform, as shown in the figure, -1, -2, -3, ..., -i, ... -13, -1
Number 4 is attached.

As a method of expressing the time timing of a certain drive waveform, for example, when the drive waveform 24 is taken as an example, it is expressed using the notations 24-1, 24-2, ..., 24-14. These are generally 24 by the subscript variable i.
-I (i = 1 to 14). Timing 2
In 4-i (i = 1 to 14), when i is odd, the voltage level is high, and when it is even, low. The horizontal axis represents the passage of time.

Reference numerals 21, 22, and 23 denote counter back electrodes 1 respectively.
The voltage waveforms applied to -1, 1-2 and 1-3 are shown.
Here, 24-i, 21-i, 22-i, and 23-i specify the same time timing on the time axis. The voltage levels are 21, 22, 23 and 24 in the high state.
Constant values that are equal to each other through
It is assumed that other constant values equal to each other are taken through 2, 23 and 24.

Numeral 25 indicates a time interval at which each of the three electrode pairs is driven once in a series of operations, that is, one driving cycle.
Reference numerals 24 'and 24 "denote drive waveforms obtained by halving the 24 periods, respectively. Next, the operation will be described.

First, the transparent electrode 5 which is a common electrode has 24
Drive waveform is continuously applied. Therefore, a high voltage and a low voltage are alternately applied to this common electrode.
Next, 21 drive waveforms generated from the 24 drive waveforms are applied to the counter electrode 1-1. Considering the relationship between the voltage levels applied to the two electrodes, the timing 24
In Nos. 1 and 21-1, since the voltage levels are both high, there is no potential difference between both electrodes, and therefore no electric field is generated, so that the light emitting layer sandwiched between these electrodes does not emit light.

Next, at the timings 24-2 and 21-2, since the common electrode side is low and the back electrode side is high, a potential difference is generated between both electrodes, and accordingly an electric field is generated, which causes the light emitting layer to emit light. . Also, the next timing 24-3,
At 21-3, an electric field in the opposite direction is generated due to the potential difference in the opposite direction, and light is emitted again.

Hereinafter, for convenience of explanation, the timing of light emission is marked with a circle. Between timings 24-4 and 24-7, the voltage waveforms applied to both electrodes are in phase, so no electric field is generated, and the light emitting layer is not activated and thus does not emit light. At timings 24-8 and 24-9, driving voltages of opposite phases are applied to both electrodes in exactly the same manner, so that an electric field is generated and the light emitting operation is repeated again.

The above light emission conditions are the same for the common electrode drive voltage 24 and the back electrode 1-2 drive timing or 24 and the back electrode 1-3 timing. The back electrode 1-2 drive timing 22 is the back electrode 1-2 drive timing 21.
Is delayed, and the back electrode 1-3 drive timing 23 is further delayed. By providing such a delay, the electric field generation timing of each counter electrode pair can be sequentially shifted. Therefore, the light emission from the light emitting layer sandwiched by the pair of electrodes changes accordingly.

From this, the light emitting layers sandwiched by the back electrodes 1-2 and the common electrode 5 are 24-4, 24-5, and 24-10,
The back electrode 1 emits light at the driving timing of 24-11.
-3 and the common electrode 5 sandwich the light emitting layer 24-6, 24-7,
And 24-13 and 24-14 respectively emit light. As described above, by first generating a potential difference between the back electrode 1-1 and the common electrode 5,
The action of the electric field generated thereby activates the light emitting layer sandwiched by the electrode pair to generate light. This light passes through the transparent electrode itself and is transmitted to the outside, so that the back electrode portion looks bright to human eyes.

At the next timing, the back electrodes 1-2 are similarly used.
The light is seen to move sequentially in such a manner that the part is observed brightly, and then the back electrodes 1-3 are observed brightly. The period in which the three back electrodes are related to light emission in a series of operations is a time interval 25. Next, the drive waveforms 24 'and 24 "will be described.

Reference numerals 24 'and 24 "are drive voltage waveforms for deforming the drive voltage 24 of the common electrode 5 to realize other EL emission modes. First, 24' is the common electrode drive waveform 24 as described above. The back electrode 1-1, 1-2 corresponding to this has a half cycle, that is, a double frequency.
Although the driving waveforms corresponding to 1 and 3 are not shown in the figure, the synchronization relationship with the basic common electrode driving waveform is kept the same as in the above timing.

Then, in this case, the frequency of occurrence of an electric field in each electrode pair per unit time is doubled as compared with the case of the above-mentioned timing, which is equivalent to an increase in drive frequency, and as a result, As is clear from 7, the light emission intensity becomes strong, and it is reflected in human vision that the whole is brightened. On the other hand, 24 "is the common electrode drive waveform 24 having a doubled cycle, that is, a frequency of 1/2 as described above.

Corresponding drive waveforms corresponding to the back electrodes 1-1, 1-2, and 1-3 are not shown, but the synchronization relationship with the basic common electrode drive waveform is the same as in the above timing. And keep it. Then, in this case,
The frequency of occurrence of an electric field in each electrode pair per unit time is half that in the case of the above-mentioned timing, which is equivalent to a lower drive frequency, and as a result, FIG.
As is clear, the light emission intensity is weakened, and it is reflected in the human vision as being totally dark.

That is, by controlling the frequency of the common electrode drive voltage, so-called dimming control for brightening or darkening can be performed uniformly for each electrode pair. (Second Embodiment) Next, a second embodiment of the present invention will be described.

The present embodiment relates to so-called dimming control for independently controlling the brightness of light emission for each of a plurality of light emitting areas while keeping the basic driving frequency constant. The functional block diagram in this embodiment is the same as that shown in FIG. 1, and each circuit function is basically the same as that in the first embodiment. The electrode driving waveforms of this embodiment are shown in FIG.

In FIG. 3, 34, 31, 32 and 33
Drive waveforms of the common electrode 5 and the back electrode 1 shown in FIG.
-1, 1-2 and 1-3. These drive waveforms are preset in the drive control circuit 9.
The horizontal axis is time. In the figure, at each timing of the drive waveform, -1, -2, -3 ...
..., -i, ..., -10 are added. When this is used, the drive waveform 34 is 34-1, 34-2, ...
The time timing can be described by the notation 34-10.

These are generally 34 using the subscript variable i.
-I (i = 1 to 10). In FIG. 3, the driving waveform 34 is at a high voltage when i is an odd number, and is at a low voltage when i is an even number. Further, the time timing 34-i is assumed to be at the same time timing as the other drive waveforms 31-i, 32-i and 33-i. Further, the voltage levels are equal to each other through 31, 32, 33 and 34 in the high state and 31, 32, 33 and 34 in the low state.
Other constant values that are equal to each other through.

The conditions under which the light emitting layer sandwiched between the common electrode of the EL panel and each back electrode emits light are exactly the same as in the first embodiment. First, comparing the common electrode waveform 34 with the drive waveform 31 of the back electrode 1-1, the phases are opposite at all timings from i = 1 to i = 10. Therefore, the light emission sandwiched between the electrode pairs during this period. The layer will continue to emit light.

Next, the common electrode waveform 34 and the back electrodes 1-2
Looking at the relationship with the drive waveform 32, since the phases are opposite to each other at the time timings of i = 2, 3, 6, 7, and 10, the light emitting layers sandwiched by the electrodes emit light at these timings. Next, looking at the relationship between the common electrode waveform 34 and the back electrode 1-3 drive waveform 33, since the phases are opposite to each other at the time timings of i = 2, 3, and 10, the electrodes are driven at these timings. The sandwiched light emitting layers emit light.

Considering these relations with respect to each time timing, with the total time of i = 1 to 10 as 100%,
100% time for the part related to the electrodes 1-1, 50% time for the part related to the electrodes 1-2, and 3% for the part related to the electrodes 1-3.
Each of them emits light at a rate of 0% time, and as a result, it is reflected in human vision as bright, normal, or dark depending on the relative idea.

That is, in the pair of opposing electrodes, the frequency of the drive voltage applied to one electrode is kept constant and the drive voltage waveform applied to the other electrode is controlled, so that the light emission sandwiched by the pair of electrodes is controlled. It is possible to change the light emission frequency of the layer per unit time. This is the realization of the dimming function. The circuit configurations for generating the drive waveforms shown in FIGS. 2 and 3 shown in the above-described embodiments can all be realized by known techniques. For example, the drive control circuit shown in FIG. 1 is provided with an oscillator, a frequency divider that counts pulse signals generated by the oscillator, and a logic circuit including a logical product / logical sum circuit and the like. The logical product of each frequency division output of /
By taking the logical sum, a necessary drive control signal can be generated from the drive control circuit.

Further, in these embodiments, the back electrodes are composed of three as shown in FIG. 1, but the number of electrodes is not limited to this. Further, regarding the counter electrode structure, in the embodiment, the transparent electrode that transmits and transmits the light emitted in the light emitting layer is a common electrode that covers the entire surface of the EL panel.
Although the method of determining the light emitting area by appropriately arranging the plurality of back electrodes has been described, conversely, the back electrode does not cover the entire EL panel and the light emitting area is determined by appropriately arranging the plurality of transparent electrodes. A method is also conceivable, and this embodiment can also adopt this method.

Furthermore, in the present embodiment, the dimming function is realized by frequency modulation of the drive voltage, but it can also be realized by modulating the amplitude of the drive voltage. That is, when the potential difference between both electrodes is large, the generated electric field is also large, and thus the energy for activating the light emitting layer sandwiched by the electrode pair is also large,
This is because the emission intensity becomes stronger, and conversely, when the potential difference between the electrodes is small, the activation energy becomes small and the emission intensity also becomes weak. The point is that if the voltage itself between the electrodes is changed, Because it is good.

The method for realizing the present invention by this amplitude modulation is not particularly shown, but a brief description will be given below.
In the second embodiment, it is assumed that the high voltages are equal to each other and the low voltages are equal to each other through the driving voltages 34, 31, 32 and 33.
This can be achieved by changing at least one of the values, instead of uniformly setting each low voltage.

This is shown in FIG. 3 as drive waveforms 34 and 31.
The relationship will be described as an example. Both of these waveforms are drive voltages applied to the counter electrode pair. The time timings 34-1 and 31-1 show the same time, but the voltage between the electrode pair at this time is the difference between the high potential of 34 and the low potential of 31. Therefore, an electric field having a value corresponding to this voltage is generated between the electrodes, and as a result, light emission having a brightness corresponding to this value is generated.

Now, with respect to the driving waveform of 31, an offset is added to the lower potential so as to be shifted to the higher potential side. As a result of this change, as far as the time timing 34-1 is concerned, the voltage between the electrodes becomes smaller than that before the change, and accordingly the electric field value between the electrodes becomes smaller, so that the brightness also relatively decreases. That is, the dimming function can be realized by changing the amplitude of the drive voltage, in other words, by changing the amplitude.

If this amplitude modulation is performed at each time timing, it is possible to perform light control according to the passage of time. Further, by similarly applying it to other drive waveforms, it becomes possible to perform light control by amplitude modulation in each electrode pair. At this time, it is possible to set the target to which the offset is added to the high potential side and to shift the direction, that is, to add the positive offset or the negative offset. (Embodiment 3) Next, a third embodiment of the present invention will be described.

In FIG. 1 for explaining the first embodiment, the electrode shape is represented by a rectangle, but the shape is not limited to this, and FIG. 4 shows another embodiment of the electrode shape. still,
It has been disclosed in the above detailed description that the EL panel having these electrode configurations is driven to emit light. FIG. 4 will be described below.

In (a), the counter electrodes 1a, 2a and 3a are arranged on the back surface of the transparent electrode 4a with the light emitting layer in between. Therefore, the light emission pattern is concentric, but the order of light emission and the light / dark control can be realized as disclosed in the above embodiment. Similarly, (b) is one in which the counter electrodes 5b, 6b, and 7b are arranged on the back surface of the transparent electrode 8b with the light emitting layer in between. The order of light emission and the light / dark control can be realized by the places disclosed in the above-mentioned embodiments.

In (c), the rectangular counter electrodes 9c, 10c and 11c are arranged on the back surface of the transparent electrode 12c with the light emitting layer in between. The EL panel is formed into a cylindrical shape by utilizing the flexible rigidity of the EL panel. The order of light emission and the light / dark control can be realized by the places disclosed in the above-mentioned embodiments. (D) is a transparent electrode 15d in which a cylindrical strip-shaped opposing electrodes 13d and 14d are arranged with a light emitting layer on the back surface. The EL panel is formed into a cylindrical shape by utilizing the flexible rigidity of the EL panel. The order of light emission and the light / dark control can be realized by the places disclosed in the above-mentioned embodiments.

[0049]

As described above in detail, according to the present invention, it is possible to freely control the blinking and dimming of an electrode having one or a plurality of counter electrodes in an EL panel. As a display device with a new taste, it can meet a wide range of needs in the fields of advertising or advertising, hobbies and appreciation.

Since EL is a self-luminous light source, when a paper sheet on which a message or the like is written is placed in close contact with the transparent electrode, it is illuminated from the back with light emitted by EL and the light is emitted. It is possible to significantly improve the visibility of the message by freely flashing and dimming. This application can meet a wide range of needs from message transmission and guidance to evacuation guidance in an emergency.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing drive waveforms according to the first embodiment of the present invention.

FIG. 3 is a diagram showing drive waveforms according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an electrode configuration of a third embodiment of the present invention.

FIG. 5 is a diagram illustrating a structure of an EL.

FIG. 6 is a diagram showing a light emitting mode of an EL.

FIG. 7 is a diagram showing frequency characteristics of light emission intensity in an EL cell.

[Explanation of symbols]

 1-1, 1-2, 1-3 Rear electrode 3 Light emitting layer 5 Transparent electrode 7 Driving circuit 9 Driving control circuit

Claims (3)

[Claims] 1. An electroluminescent panel, a plurality of counter electrode pairs sandwiching the electroluminescent panel, and a plurality of drive circuits corresponding to the respective electrode pairs, wherein the counter electrode pairs are spatially determined in advance by a drive control circuit. A driving circuit for an electroluminescent panel, which is driven according to a driving order. 2. An electroluminescent panel, one or a plurality of counter electrode pairs sandwiching the electroluminescent panel, and one or a plurality of drive circuits corresponding to the respective electrode pairs, wherein the counter electrode pair has a drive control circuit. A driving circuit for an electroluminescent panel, which is driven according to a temporal order of driving waveforms generated. 3. An electroluminescent panel, a plurality of counter electrode pairs sandwiching the electroluminescent panel, a plurality of drive circuits corresponding to the electrode pairs, and a spatial circuit which is connected to the plurality of drive circuits and which defines the counter electrode pairs in advance. A drive control circuit for generating a control signal for driving in time sequence, wherein the drive control circuit sets a potential of each electrode of one of the electrode pairs to a high level state and a low level state in a predetermined pattern. A driving circuit for an electroluminescent panel, which is alternately changed and the potential of the other electrode of each electrode pair is alternately changed to a high-level state and a low-level state at a preset cycle.