JP2001203078A - Driving device of light emitting and light receiving element, light emitting and receiving device, communication system and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out light emitting and light receiving with a single unit and to prevent deterioration of the element. SOLUTION: A light emitting and receiving device comprises an organic electroluminescent (EL) element 1 having light emitting and receiving function, a driving device 2 which drives the organic EL element 1 so as to switch over alternately from light emitting to receiving, and a light receiving detection device 3 which detects the light received by the organic EL element 1 and outputs a light signal. The driving device 2 impresses the organic EL element with a prescribed first voltage higher than the threshold voltage of light emitting when light emitting is required, and impresses with a second voltage of reverse direction from the first voltage of ligher than zero in its absolute value and lower than the breakdown voltage of the EL element when the light receiving is required. The light receiving detection circuit 3 detects the light received by the organic EL element by detecting the change in internal impedance of the EL element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a light emitting and receiving element which can be used for optical communication and display devices, and a light emitting and receiving apparatus using the light emitting and receiving element, a communication system and a display device.

[0002]

2. Description of the Related Art In conventional optical communication, an optical signal obtained by controlling on / off of a light emitting element such as a laser diode or a light emitting diode is transmitted through an optical transmission medium such as an optical fiber, and is transmitted by a light receiving element. Communication was performed by receiving light.

On the other hand, in a conventional display device, input of a signal is generally performed through a signal line, and as a special example, there is also a device that performs wireless input. Some display devices include a light receiving device that receives light such as infrared light. In such a display device, an optical signal such as infrared light emitted from a remote control device is received by a light receiving device, converted into an electric signal, and the electric signal is processed to perform various controls. ing.

[0004]

When bidirectional optical communication is performed in the field of optical communication, a transmitting / receiving device for transmitting / receiving optical signals is required. In addition to the light emitting element and the light receiving element, the transmitting and receiving device includes a prism and a beam for causing the light emitted from the light emitting element to enter the optical transmission medium and the light transmitted by the optical transmission medium to enter the light receiving element. Optical components such as a splitter are required. Therefore, there is a problem that the size of the structure of the transmitting and receiving device is increased.

[0005] In the case of multiplex communication in the field of optical communication, a plurality of lights having different wavelengths are generally transmitted by the same optical transmission medium. In this case, the transmitting side requires a plurality of light emitting elements that emit light of different wavelengths, and the receiving side requires a plurality of light receiving elements that receive light of different wavelengths.
Therefore, there is a problem that the size and the circuit scale of the structure of the transmitting and receiving device are increased.

On the other hand, in a display device, generally, a signal relating to display contents is externally input via a signal line. In some display devices that display display contents of a predetermined pattern, data indicating the display contents is held in the display device, and an instruction on which display content is to be displayed is given from the outside to the display device. In this case, the number of signal lines is relatively small. However, a display device having an indefinite display content, for example, a display device displaying a document, a still image, a moving image, or the like, has a problem that the number of signal lines for inputting data indicating the display content increases.

Further, in a display device for wirelessly inputting data indicating display contents, a circuit for receiving, detecting, demodulating, etc., a radio signal and extracting data is required in the display device. There is a problem that it becomes large.

In a television device or a video tape recorder device, a light signal such as infrared light emitted from a remote control device is received and converted into an electric signal, and the electric signal is processed to perform various controls. What is done is widely done. When such a method is used in a display device, a light receiving device is required separately from the display unit, and there has been a problem that the size and circuit size of the structure of the display device are increased.

Conventionally, when signals are exchanged between a plurality of devices having a display unit, they have been performed wirelessly or via signal lines. However, when using wireless,
Each device needs to have at least one of the transmitting device and the receiving device, and there is a problem that the circuit scale becomes large.
In addition, when a signal line is used, each device must be connected by a signal line, which causes a problem that wiring becomes complicated.

By the way, recently, an organic electroluminescent (Electrolumines) which is a light emitting element in which light is emitted on a surface.
cent; hereinafter, referred to as EL. ) Devices are receiving attention. This organic EL device uses an organic material for the light emitting layer,
In addition to red light and green light, blue light, which is difficult to emit with an inorganic EL element or light-emitting diode using an inorganic material for the light-emitting layer, can also emit light, and white can be formed by combining these three primary colors. . Therefore, the organic EL element is
It is particularly noted for use in display devices.

Japanese Patent Application Laid-Open Nos. Hei 7-175420 and Hei 9-22778 disclose an organic EL device having a light emitting function and a light receiving function. If an organic EL element having such a light-emitting function and a light-receiving function is used for optical communication, the size of the transmitting and receiving device can be reduced, and if it is used for a display device, an optical signal can be received using a display unit. become.

However, the organic EL device has the following problems with respect to each of the light emitting function and the light receiving function.

First, the problem of the organic EL device relating to the light emitting function will be described. When the organic EL element is kept in the light emitting state for a long time, polarization occurs in the organic light emitting layer and the calorific value increases. When polarization occurs, the organic E
The electric field required to secure a predetermined luminance in the L element increases. Therefore, when the electric field applied to the organic EL element is kept constant, the light emission luminance of the organic EL element decreases. Further, when the emission luminance of the organic EL element is controlled to be constant, the drive voltage of the organic EL element increases to increase the current density of the organic EL element, and the life of the organic EL element is shortened. In addition, the life of the element is shortened by an increase in the amount of heat generated.

On the other hand, with respect to the light receiving function, when the organic EL element is kept in the light receiving state for a long time, polarization occurs in the organic light emitting layer in a direction opposite to the direction of light emission.
The light receiving sensitivity of the L element decreases.

As described above, in the organic EL device, there is a problem that the characteristics of the device are deteriorated by long-time use in both the light emitting function and the light receiving function.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to drive a light emitting and light receiving element which emits and receives light by using the same element and prevents deterioration of the element. , A light emitting and receiving device, a communication system, and a display device.

[0017]

According to the present invention, there is provided a driving apparatus for driving a light emitting and receiving element having a light emitting function and a light receiving function, wherein the light emitting state and the light receiving state are alternately switched. The light-emitting and light-receiving elements are driven so that the light-emitting and light-receiving elements are driven. In the present invention, the light receiving state refers to a state in which the light receiving function can be exhibited, and it does not matter whether the light emitting and receiving element actually receives light.

A light emitting and receiving device according to the present invention includes a light emitting and receiving element having a light emitting function and a light receiving function, and a driving device for driving the light emitting and receiving element so that the light emitting state and the light receiving state can be alternately switched. It is.

In the light emitting and receiving device driving device or the light emitting and receiving device according to the present invention, the light emitting and receiving device having the light emitting function and the light receiving function is driven so that the light emitting state and the light receiving state are alternately switched.

In the light emitting and receiving device driving device or the light emitting and receiving device according to the present invention, the ratio of the light emitting state period in one cycle of switching between the light emitting state and the light receiving state of the light emitting and receiving element is 50.
%.

Further, in the light emitting and receiving device driving device or the light emitting and receiving device according to the present invention, the frequency of switching between the light emitting state and the light receiving state of the light emitting and receiving element may be lower than 500 kHz.

In the light emitting and receiving device driving device or the light emitting and receiving device according to the present invention, when the light emitting and receiving device is set in the light emitting state, the predetermined first light emitting voltage equal to or higher than the light emitting threshold voltage.
When the light-receiving state is applied by applying the second voltage, a second voltage having an absolute value larger than zero and equal to or lower than the dielectric strength of the light-emitting and light-receiving element is applied in a direction opposite to the first voltage. Good.

Further, in the light emitting / receiving element driving device or the light emitting / receiving apparatus of the present invention, the light emitting / receiving element may be set to the light receiving state immediately before the light emitting state.

Further, in the driving device or the light emitting / receiving device of the light emitting / receiving device of the present invention, the light emitting / receiving device may be an organic electroluminescent element.

A communication system according to the present invention includes a plurality of transmitting and receiving devices for transmitting and receiving optical signals, each transmitting and receiving device having a light emitting and receiving element having a light emitting function and a light receiving function,
A driving device for driving the light-emitting and light-receiving elements so that the light-emitting state and the light-receiving state can be alternately switched.

In the communication system of the present invention, the light emitting state and the light receiving state of the light emitting / receiving element are alternately switched in each transmitting / receiving device, and the transmission / reception of the optical signal is performed between the plurality of transmitting / receiving devices.

A display device according to the present invention includes a display including a plurality of light-emitting and light-receiving elements having a light-emitting function and a light-receiving function, and a drive for driving each light-emitting and light-receiving element so that the light-emitting state and the light-receiving state can be alternately switched. And a device.

[0028] In the display device of the present invention, in the display device,
The light emitting state and the light receiving state of the light emitting / receiving element are alternately switched, and information display and input of an optical signal are performed.

In the display device of the present invention, the driving device is
In the light emitting state of the light emitting and receiving element, the light emitting and receiving element may be driven such that information transmitted by an optical signal is superimposed on the display information. In this case, the driving device may drive the light-emitting and light-receiving element such that the average luminance of the light-emitting and light-receiving element in the light-emitting state is constant regardless of the content of the information to be transmitted.

[0030]

Embodiments of the present invention will be described below in detail with reference to the drawings. [First Embodiment] FIG. 1 is a block diagram showing a configuration of a light emitting and receiving device according to a first embodiment of the present invention.
The driving device 2 according to the present embodiment is a driving device of the light emitting and receiving element according to the present embodiment.

The driving device 2 is provided for the organic EL element 1
When the light emitting state is set, a predetermined first voltage equal to or higher than the light emitting threshold voltage is applied, and when the light receiving state is set, the first voltage is applied.
The second voltage is applied in a direction opposite to the voltage of the second voltage, the absolute value of which is larger than zero and equal to or lower than the withstand voltage of the organic EL element 1.

The light reception detection circuit 3 detects, for example, a change in the internal impedance of the organic EL element 1 to detect the presence or absence of light reception in the organic EL element 1.

FIG. 2 is a cross-sectional view showing an example of the configuration of the organic EL element 1 in the present embodiment. In the organic EL element 1 in this example, a hole injection electrode 12 is formed on a substrate 11, and a hole injection layer 13, a hole transport layer 14, and a light emitting layer 15 which are organic layers are formed on the hole injection electrode 12. , And the electron injection / transport layer 16 are sequentially stacked, and the electron injection electrode 17 is formed on the electron injection / transport layer 16. In this example, the substrate 11 is a glass substrate, and the hole injection electrode 12 is a transparent electrode. Therefore, organic EL
The surface of the element 1 on the side of the hole injection electrode 12 is a light emitting / receiving surface.

The organic EL element 1 emits light when a voltage higher than the light emission threshold voltage is applied in the forward direction. The light emission threshold voltage is a minimum voltage at which an electric field is applied to the light emitting layer 15 and electrons and holes can move in the light emitting layer 15. The light emission threshold voltage varies depending on the material used for the organic EL element 1 and the combination thereof, but is generally 2 to 3 V. The emission intensity of the organic EL element 1 is determined by the number of holes entering the light emitting layer 15 and the probability that the holes will emit light, and is substantially proportional to the value of the current flowing through the organic EL element 1. When a voltage is applied to the organic EL element 1 in the reverse direction, movement of electrons and holes in the organic EL element 1 is hindered, and almost no current flows through the organic EL element 1.

Next, with reference to FIG. 3 to FIG. 8, first to sixth examples relating to the specific configuration of the driving device 2 and the connection position of the light receiving detection circuit 3 will be described.

The driving device 2 in the first example shown in FIG.
Has a changeover switch 21, an open / close switch 22, and a control circuit 23 for controlling the switches 21 and 22. The voltage Vdd is applied to one fixed contact of the switch 21, and the voltage Vss2 is applied to the other fixed contact. The movable contact of the switch 21 is connected to the hole injection electrode 12 of the organic EL element 1. Switch 22
Is connected to the electron injection electrode 17 of the organic EL element 1, and the other contact is applied with the voltage Vss1. Here, the relationship between the voltages Vdd, Vss1, and Vss2 is Vdd>Vss1> Vss2. Vdd-Vss1
Is a first voltage equal to or higher than the light emission threshold voltage of the organic EL element 1. Vss2−Vss1 is in the opposite direction to the first voltage,
The second voltage has an absolute value larger than zero and is equal to or lower than the withstand voltage of the organic EL element 1. The input end of the light receiving detection circuit 3 is connected to the hole injection electrode 12 of the organic EL element 1.

In the driving device 2 in the first example, the organic E
To make the L element 1 emit light, the movable contact of the switch 21 is connected to the fixed contact on the voltage Vdd side, and the switch 22 is turned on.
Close. As a result, the first voltage is applied to the organic EL element 1, and the organic EL element 1 emits light. On the other hand, organic EL
When the element 1 is in the light receiving state, the movable contact of the switch 21 is connected to the fixed contact on the voltage Vss2 side,
Close. Thereby, the second voltage is applied to the organic EL element 1, and the organic EL element 1 enters a light receiving state. When the switch 22 is opened, the organic EL element 1 enters a state in which neither light emission nor light reception is performed.

The driving device 2 in the second example shown in FIG.
In the first embodiment, the switch 22 in the first example is not provided, and the voltage Vss1 is applied to the electron injection electrode 17 of the organic EL element 1. Other configurations in the second example are the same as those in the first example.

In the driving device 2 in the second example, the organic E
To make the L element 1 emit light, the movable contact of the switch 21 is connected to the fixed contact on the voltage Vdd side. As a result, the first voltage is applied to the organic EL element 1 and the organic EL element 1
Element 1 emits light. On the other hand, when the organic EL element 1 is in the light receiving state, the movable contact of the switch 21 is connected to the fixed contact on the voltage Vss2 side. Thereby, the second voltage is applied to the organic EL element 1, and the organic EL element 1 enters a light receiving state.

The driving device 2 in the third example shown in FIG.
In the example, a changeover switch 24 is provided instead of the switch 22 in the first example. A voltage Vdd is applied to one fixed contact of the switch 24, and a voltage Vss1 is applied to the other fixed contact. The movable contact of the switch 24 is the electron injection electrode 1 of the organic EL element 1.
7 is connected. The control circuit 23 includes a switch 21,
24 is controlled. Other configurations in the third example are the same as those in the first example.

In the driving device 2 in the third example, the organic E
To make the L element 1 emit light, the movable contact of the switch 21 is connected to the fixed contact on the voltage Vdd side, and the switch 24 is turned on.
Is connected to the fixed contact on the voltage Vss1 side. As a result, the first voltage is applied to the organic EL element 1, and the organic EL element 1 emits light. On the other hand, when the organic EL element 1 is in the light receiving state, the movable contact of the switch 21 is connected to the voltage Vss.
The movable contact of the switch 24 is connected to the fixed contact on the voltage Vss1 side. Thereby, the organic E
The second voltage is applied to the L element 1, and the organic EL element 1 enters a light receiving state. The movable contact of the switch 21 is set to a voltage V
When the organic EL element 1 is connected to the fixed contact on the dd side and the movable contact of the switch 24 is also connected to the fixed contact on the voltage Vdd side, the organic EL element 1 does not emit or receive light.

In the fourth example shown in FIG. 6, the voltage Vdd is applied to one fixed contact of the changeover switch 21 and the voltage Vss1 is applied to the other contact. Other configurations in the fourth example are the same as those in the third example.

In the driving device 2 in the fourth example, the organic E
To make the L element 1 emit light, the movable contact of the switch 21 is connected to the fixed contact on the voltage Vdd side, and the switch 24 is turned on.
Is connected to the fixed contact on the voltage Vss1 side. As a result, the first voltage is applied to the organic EL element 1, and the organic EL element 1 emits light. On the other hand, when the organic EL element 1 is in the light receiving state, the movable contact of the switch 21 is connected to the voltage Vss.
The movable contact of the switch 24 is connected to the fixed contact on the voltage Vdd side. With this, organic EL
The voltage Vss1-Vdd is applied to the element 1, and the organic EL element 1
Is in a light receiving state. The voltage Vss1-Vdd is in the opposite direction to the first voltage, the absolute value is larger than zero, and
The breakdown voltage is set to be equal to or lower than the dielectric strength of the L element 1. Also, the movable contact of the switch 21 and the movable contact of the switch 24 are both
Connect to the fixed contact on the voltage Vdd side, or connect to the voltage Vss
When the organic EL element 1 is connected to the fixed contact on the first side, the organic EL element 1 does not emit or receive light. According to the fourth example, if the voltage is 2
Since only one type is required, the configuration of the driving device 2 is simplified.

In the fifth example shown in FIG. 7, the input terminal of the light receiving detection circuit 3 is connected to the fixed contact of the switch 21 on the side of the voltage Vss2. Other configurations in the fifth example are the same as those in the third example.

In the sixth example shown in FIG. 8, the input terminal of the light receiving detection circuit 3 is connected to the fixed contact of the switch 24 on the voltage Vss1 side. Other configurations in the sixth example are the same as those in the third example.

Next, two examples of the configuration of the light receiving detection circuit 3 will be described with reference to FIGS.

The light receiving detection circuit 3 in the example shown in FIG.
Has an input terminal 31, an operational amplifier 32, and an output terminal 33. The input terminal 31 has one end of the resistor 34 and the resistor 3
5 is connected to one end. The voltage Vss is applied to the other end of the resistor 34. The other end of the resistor 35 is connected to a non-inverting input terminal of the operational amplifier 32.
One end of a resistor 36 and one end of a resistor 37 are connected to the inverting input terminal of the operational amplifier 32. The reference voltage Vref is applied to the other end of the resistor 36. Resistance 3
The other end of 7 is connected to the output terminal of the operational amplifier 32.
The output terminal of the operational amplifier 32 is connected to the output terminal 33.

In the light receiving detection circuit 3 in the example shown in FIG. 9, the voltage applied to the non-inverting input terminal of the operational amplifier 32 changes according to the internal impedance of the organic EL element 1, whereby the output of the operational amplifier 32 is changed. Change. That is, the output of the operational amplifier 32 changes depending on the presence or absence of light reception in the organic EL element 1, and this is a received signal.

The light receiving detection circuit 3 in the example shown in FIG.
Is the light receiving detection circuit 3 in the example shown in FIG.
An open / close switch 3 is provided between the resistors 34 and 35 and the input terminal 31.
8 is provided. The open / close switch 38 is closed when the organic EL element 1 is in a light receiving state, and is opened when the organic EL element 1 is in another state. As a result, application of an excessive voltage or reverse voltage to the operational amplifier 32 can be prevented, and output of an erroneous signal from the light receiving detection circuit 3 can be prevented.

The configuration of the light receiving detection circuit 3 is not limited to those shown in FIGS. For example, a bipolar transistor or a field-effect transistor is provided in place of the operational amplifier 32, and a resistor 35 is connected to the base of the bipolar transistor or the gate of the field-effect transistor. Turn on the transistor,
The light receiving detection circuit 3 may be configured to be turned off.

In the present embodiment, the driving device 2 drives the organic EL element 1 so that the light emitting state and the light receiving state are alternately switched. Hereinafter, two examples of the driving method of the organic EL element 1 will be described with reference to FIGS. FIGS. 11 and 12 show the voltages applied to the organic EL element 1. FIG. In FIGS. 11 and 12, a positive voltage indicates a forward voltage, and a negative voltage indicates a reverse voltage.

In the driving method in the example shown in FIG. 11, the organic EL element 1 is switched so that the light emitting state and the light receiving state are alternately switched so as not to include the state in which neither light emission nor light reception is performed.
This is a method of driving. In this method, the organic EL element 1 always enters the light receiving state immediately before the light emitting state, and the organic EL element 1 always enters the light emitting state immediately before the light receiving state. FIG.
, The symbol T is 1 for switching between a light emitting state and a light receiving state.
Represents a cycle, te represents a period of a light emitting state, and tr represents a period of a light receiving state. The ratio of the light emitting state period te in one cycle T of switching between the light emitting state and the light receiving state is 50.
% Is preferred.

In the driving method in the example shown in FIG. 12, a period td in a state in which neither light emission nor light reception (hereinafter referred to as a non-operation state) is provided between a light emitting state period te and a light receiving state period tr. In this method, the organic EL element 1 is driven so that the light emitting state and the light receiving state are alternately switched.
Also in this case, one cycle T of switching between the light emitting state and the light receiving state is performed.
Is preferably smaller than 50%.

Next, the relationship between the magnitude of the voltage applied to the organic EL element 1 in the light receiving state and the response speed of the organic EL element 1 for light reception will be described with reference to FIGS. 13 and 14,
(A) shows the voltage applied to the organic EL element 1,
(B) shows a light receiving signal when the organic EL element 1 receives light. In (b), the symbol t1 indicates a period from when the organic EL element 1 enters the light receiving state until the light receiving signal is actually output, and t2 indicates a period during which the light receiving signal is output.

In FIG. 13, the absolute value of the voltage applied to the organic EL element 1 in the light receiving state is smaller than the absolute value of the voltage applied to the organic EL element 1 in the light emitting state. On the other hand, in FIG. 14, the absolute value of the voltage applied to the organic EL element 1 in the light receiving state is larger than the absolute value of the voltage applied to the organic EL element 1 in the light emitting state. As can be seen by comparing FIGS. 13 and 14, when the absolute value of the voltage applied to the organic EL element 1 in the light receiving state is increased, the response of the organic EL element 1 with respect to the light reception is increased.

Next, the operation of the light emitting and receiving device driving device and the light emitting and receiving device according to the present embodiment will be described.

The organic EL element 1 is driven by the driving device 2 to alternately switch between a light emitting state and a light receiving state. In the light emitting state, a first voltage equal to or higher than the light emitting threshold voltage is applied to the organic EL element 1. In the light emitting state,
The peak value of the light emission intensity is determined by the current density of the organic EL element 1, and the light emission intensity per unit time is determined by the time integrated value of the current density.

In the light receiving state, the organic EL element 1
A second voltage is applied in a direction opposite to the first voltage, the absolute value of which is greater than zero and equal to or lower than the dielectric strength of the organic EL element 1. In the light receiving state, the internal impedance of the organic EL element 1 changes by receiving external light. This is because extraneous light, that is, photons enter the organic layer inside the organic EL element 1, and the photons excite electrons and charges inside the organic layer. The light reception detection circuit 3 detects the presence or absence of light reception in the organic EL element 1 by detecting a change in the internal impedance of the organic EL element 1.

In the light receiving state, the light receiving sensitivity changes depending on the magnitude of the second voltage applied to the organic EL element 1. Second
When the absolute value of the voltage is increased, the light receiving sensitivity increases, and even weak light can be detected. However, when the absolute value of the second voltage exceeds the withstand voltage of the organic EL element 1, the organic EL element 1 is destroyed. Therefore, the absolute value of the second voltage needs to be equal to or less than the withstand voltage.

The second voltage is applied to the organic EL in the light emitting state.
It is preferable that the internal electric field in the direction opposite to the internal electric field generated in the element 1 has a voltage that is close to the absolute value and is generated in the organic EL element 1. For example, when a first voltage of 10 V is applied between both ends of the organic EL element 1 in a light emitting state, a second voltage near 10 V in a direction opposite to the first voltage is applied in a light receiving state. I just need. If the light receiving sensitivity is insufficient, the light receiving sensitivity can be increased by increasing the absolute value of the second voltage within a range not exceeding the withstand voltage.

As described above, when the organic EL element 1 is kept in the light emitting state for a long time, polarization occurs in the organic light emitting layer, and the light emission luminance is reduced. Similarly, when the organic EL element 1 is in the light receiving state for a long time, polarization occurs in the organic light emitting layer in a direction opposite to that in the light emitting state, and the light receiving sensitivity is reduced.

In the present embodiment, the organic EL element 1 is driven so that the light emitting state and the light receiving state are alternately switched. In this case, before the light-emitting state, no polarization that lowers the light emission luminance occurs, and similarly, before the light-receiving state, no polarization that lowers the light receiving sensitivity occurs. . Therefore, according to the present embodiment, the organic EL
It is possible to prevent a decrease in light emission luminance and a decrease in light receiving sensitivity of the element 1.

In the present embodiment, in particular, when the organic EL element 1 is driven so as to alternately switch between the light emitting state and the light receiving state so as not to include the state in which neither light emission nor light reception is performed, the following will be described. Effect. That is, in this case, the organic EL element 1 is always in the light receiving state immediately before the light emitting state, and the polarization causing the internal electric field in the same direction as the internal electric field generated in the organic EL element 1 in the light emitting state is generated. It has occurred. Therefore, at the beginning of the light emission state, an internal electric field is generated which is about twice as large as that when no voltage is applied to the organic EL element 1 immediately before the light emission state, and the light emission luminance increases. Further, when the organic EL element 1 is driven so that the light emitting state and the light receiving state are alternately switched so as not to include the state in which neither the light emitting nor the light receiving is performed, the organic EL element 1 must be driven immediately before the light receiving state. It is in a light emitting state,
In the light receiving state, polarization occurs that causes an internal electric field in the same direction as the internal electric field generated in the organic EL element 1. Therefore, at the beginning of the light receiving state, the organic EL
An internal electric field that is about twice that of the case where no voltage is applied to the element 1 is generated, and the light receiving sensitivity is increased.

As described above, according to the present embodiment, the organic E
As compared with the case where the L element 1 is used only as a light emitting element or a light receiving element, deterioration of the organic EL element 1, that is, a decrease in emission luminance and a decrease in light receiving sensitivity can be reduced.

Next, the heat generated by the organic EL element 1 will be considered. Conditions in the light emitting state of the organic EL element 1,
That is, the ratio of the current density or the first voltage of the organic EL element 1 to the period of the light emitting state in one cycle of switching between the light emitting state and the light receiving state (hereinafter, referred to as a light emitting state selection duty) is required. It can be determined based on the average luminance of the EL element 1. Here, when the current density is increased, the light emission luminance increases substantially in proportion to the current density, but the amount of heat generated by the organic EL element 1 also increases. The increase in heat generation shortens the life of the organic EL element 1.

In order to alleviate the increase in the amount of heat generated by the organic EL element 1, light emission may be periodically stopped. In order to stop the light emission, no voltage, a forward voltage lower than the light emission threshold voltage, or a reverse voltage may be applied to the organic EL element 1. Of these, when a voltage is not applied, a small amount of current flows through the organic EL element 1. Therefore, it is preferable not to apply a voltage from the viewpoint of reducing power consumption. However, as described below, in the light receiving state, the higher the temperature of the organic EL element 1 is to some extent, the higher the light receiving sensitivity is. Therefore, when light emission is stopped, a voltage in the opposite direction is applied to the organic EL element 1 to receive light. It is good to be in a state. Thereby, it is possible to improve the light receiving sensitivity while alleviating the increase in the amount of heat generated by the organic EL element 1.

In this embodiment, by detecting a change in the internal impedance of the organic EL element 1, the organic EL element 1
The presence or absence of light reception in the element 1 is detected. Here, as a method of increasing the change of the internal impedance, there are a method of increasing the reverse voltage applied to the organic EL element 1 and a method of increasing the temperature of the organic EL element 1 to increase the sensitivity.
Both methods increase the dark current flowing through the organic EL element 1 when a reverse voltage is applied to the organic EL element 1,
This is a method of increasing the amount of change in dark current due to light reception. In addition, the rise of the light receiving signal becomes faster when the reverse voltage applied to the organic EL element 1 is increased or the temperature of the organic EL element 1 is increased.

Therefore, the current density during light emission is increased to increase the luminance per one light emission, and the temperature of the organic EL element 1 is increased so that the light emitting state is set to the light receiving state. It is possible to improve both the light emission luminance and the light reception sensitivity while alleviating the increase in the calorific value.

However, if the luminance per one light emission is too high, the temperature of the organic EL
Reaches a temperature at which a portion having a small temperature resistance, such as the organic layer, is destroyed, and the organic EL element 1 itself is destroyed. Further, it has been found that even if the temperature does not reach the temperature at which the organic EL element 1 is broken, the life of the organic EL element 1 is shortened if the organic EL element 1 is used at a temperature close to the temperature. Therefore, there is an upper limit on the luminance per light emission.

The upper limit of the temperature of the organic EL element 1 is 70 ° C.
It is preferable to set the degree. It is generally organic EL
This is because, among the materials used for the element 1, the material having the weakest heat has a heat-resistant temperature near 85 ° C.

The relationship between the temperature and the life of the organic EL element 1 is as follows.
It can be inferred from Arrhenius' law and the like expressed by the following equation.

AL = exp ｛(ΔE / k) · ((1 / T
n1)-(1 / Tn2))｝

In the above equation, AL is the acceleration coefficient, ΔE is the activation energy of Arrhenius (here, 0.7 eV), Tn1 and Tn2 are the actual operating temperatures (K) of the organic EL element 1, respectively, and k is Boltzmann. Constant (0.86166 × 1
0 ^-4 ).

From the above formula, for example, the organic E at 75 ° C.
When the life of the L element 1 is 1000 hours, the life of the organic EL element 1 at 55 ° C. is about 2.9 times, 2900 times.
Time. As described above, by lowering the operating temperature of the organic EL element 1, a practical life of the organic EL element 1 can be obtained.

Here, the temperature during operation of the organic EL element 1 is simply set to 70 ° C. By the way, the organic EL element 1
Assuming that the peak value of the current density in one light emission pulse is Ip, the pulse width of one light emission pulse is tw, and the internal resistance of the organic EL element 1 is Ri, the internal loss of the organic EL element 1 per light emission pulse, that is, the amount of generated heat Pp is Ip ² · R
i · tw. By multiplying this value by the frequency of light emission, the amount of heat generated per unit time of the organic EL element 1 is obtained. Then, the temperature of the organic EL element 1 can be obtained from the heat quantity and the thermal resistance value due to the internal structure of the organic EL element 1.

As described above, the amount of heat and the temperature generated by the organic EL element 1 are calculated by multiplying the square of the peak value Ip of the current density in one light emission pulse, the pulse width tw of one light emission pulse, and the light emission frequency. In order to increase the light receiving sensitivity in the light receiving state after light emission of the organic EL element 1 in consideration of the life and emission luminance of the organic EL element 1,
The peak value Ip of the current density in one light emission pulse may be set as high as possible.

In the experiment, better results were obtained for the light emitting state and the light receiving state when the light emitting state selection duty was smaller than 0.5. In particular, when the light emission state selection duty was 0.2 or less, the balance between the average luminance during light emission and the light reception sensitivity during light reception was good. The reason why the emission state selection duty should be reduced as described above is presumed to be as follows. That is, when reducing the light emission state selection duty, it is necessary to increase the current density during light emission. When the current density is increased, the amount of heat generated at the time of light emission is also increased. However, by reducing the light emission state selection duty, the period of the light reception state becomes longer.
Sufficient time is provided for the heat generated during light emission to diffuse into the material around the source. Therefore, the temperature rise of the organic EL element 1 can be suppressed. In addition, an increase in the amount of heat generated at the time of light emission increases the light receiving sensitivity at least at the initial stage of the light receiving state. To obtain a certain level of light sensitivity over the entire period of the light receiving state,
It is preferable that the temperature inside the organic EL element 1 is as uniform as possible. For this purpose, it is advantageous that the period of the light receiving state is long to some extent and that there is sufficient time for the heat generated during light emission to diffuse into the material around the generation source. Further, by using a common power supply and inverting the polarity of the voltage by a switch, the first voltage applied to the organic EL element 1 in the light emitting state and the first voltage applied to the organic EL element 1 in the light receiving state are obtained. In the case of generating the second voltage, if the emission state selection duty is reduced and the absolute value of the first voltage is increased, the absolute value of the second voltage is increased, and the light receiving sensitivity is increased.

As described above, it is preferable to reduce the light emission state selection duty.
Depending on the reaction speed of the L element 1, there is a lower limit to the light emitting state time per light emitting pulse (hereinafter referred to as light emitting state selection time). In the organic EL element 1 used in the experiment, it took about 1 μs each from the start of the light emitting state until a sufficient light emitting intensity was obtained and from the start of the light receiving state to a sufficient light receiving sensitivity. . Therefore, in this case, if the light emitting state selection duty is smaller than 0.5, one cycle of switching between the light emitting state and the light receiving state needs to be longer than 2 μs. For this reason, in the present embodiment, it is preferable that the frequency of switching between the light emitting state and the light receiving state be smaller than 500 kHz. In addition,
If the organic EL element 1 having a higher reaction speed can be used, the frequency of switching between the light emitting state and the light receiving state is set to 50.
It is also possible to set the frequency to 0 kHz or more.

FIG. 15 is a characteristic diagram showing the relationship between the above-described light emission state selection time and the current density during light emission (hereinafter referred to as light emission current density). As shown in this figure, it is necessary to increase the emission current density as the emission state selection time is shortened. However, the light emission state selection time has a lower limit (for example, 1 μs) according to the reaction speed of the organic EL element 1.
Note that the temperature and the brightness of the organic EL element 1 at the time of light emission increase and decrease according to the light emission current density.

FIG. 16 is a characteristic diagram showing the relationship between the light emitting state selection duty and the light emitting current density. As shown in this figure, it is necessary to increase the emission current density as the emission state selection duty is shortened. It is preferable that the light emission state selection duty be smaller than 0.5. However, the emission current density has an upper limit according to the withstand voltage in the forward direction of the organic EL element 1 and the heat-resistant temperature. In addition, organic E at the time of light emission
The temperature and the brightness of the L element 1 increase and decrease according to the emission current density.

As described above, according to the driving device of the light emitting and receiving element and the light emitting and receiving device according to the present embodiment,
Since the organic EL element 1 having the light emitting function and the light receiving function is driven so that the light emitting state and the light receiving state can be alternately switched, light emission and light reception are performed using the same organic EL element 1. And prevent the organic EL element 1 from deteriorating,
Life can be extended.

[Second Embodiment] Next, a communication system according to a second embodiment of the present invention will be described with reference to FIGS. The communication system according to the present embodiment includes a plurality of transmission / reception devices for transmitting / receiving optical signals. Each transmission / reception device is an organic EL as a light emitting and receiving element having a light emitting function and a light receiving function, similarly to the light emitting and receiving device according to the first embodiment shown in FIG.
An element 1, a driving device 2 for driving the organic EL element 1 so that the light emitting state and the light receiving state are alternately switched, and a light receiving detection circuit 3 for detecting the presence or absence of light reception in the organic EL element 1 and outputting a light receiving signal. And

FIG. 17 shows an example of the configuration of the communication system according to the present embodiment. The communication system in this example includes two units as a transmission / reception device, that is, a unit A and a unit B. The unit A and the unit B perform a transmission operation, that is, a light-emitting operation, and a reception operation, that is, a light-receiving operation, and communicate with each other. The transmission of light between the units may be performed through a space or may be performed via an optical transmission unit such as an optical fiber.

Next, an example of the operation of the communication system shown in FIG. 17 will be described with reference to FIG. In FIG. 18, (a) represents a transmission signal of the unit A, and (b)
Represents a light receiving operation period of the unit A (a high level indicates a light receiving operation period), (c) represents a reception signal of the unit A, (d) represents a transmission signal of the unit B, and (e) represents a unit B. (A high level indicates a light receiving operation period), and (f) indicates a received signal of the unit B.

In FIG. 18, the symbol T _AS indicates the transmission period of the unit A, T _AR indicates the reception period of the unit A, T _BS indicates the transmission period of the unit B, and T _BR indicates the reception period of the unit B. Represents a period, and T _S represents a period of a standby state.

In the example shown in FIG.
And the unit B are both in a standby state. This standby state is actually a light receiving state. When either the unit A or the unit B starts transmission from this standby state, the unit A and the unit B thereafter perform the transmission operation and the reception operation alternately to perform communication. The transmission periods T _AS and T _BS are set to a fixed time by a timer of each unit. When the communication is completed, both the unit A and the unit B return to the standby state. In this example, the transmission period T of unit A
It is provided a certain waiting time between the transmission period T _BS of _AS and the unit B. Therefore, the light receiving operation periods of the units A and B are longer than the transmission periods T _AS and T _BS . The waiting time is used as a processing time of the received signal or a time for diffusing the heat of the organic EL element 1 generated at the time of transmission. Further, by providing the waiting time, the light emitting state selection duty is smaller than 0.5 in each unit.

As shown in FIG. 18, when the unit A and the unit B alternately perform the transmission operation and the reception operation for a certain period of time, the unit that has received the data transmits the received data to the transmission source unit. By returning the data as it is, or by transmitting a predetermined calculation result or checksum based on the received data to the source unit, the source unit determines whether the transmitted data has correctly arrived at the destination. It becomes possible to confirm. This enables highly reliable communication.

FIG. 19 is an explanatory diagram showing another example of the configuration and operation of the communication system according to the present embodiment. The communication system in this example includes three units, that is, a unit A, a unit B, and a unit C as transmission / reception devices that communicate with each other. The transmission of light between these units may be performed through a space or may be performed via an optical transmission unit such as an optical fiber.

In the example of the operation shown in FIG. 19, at first, all the units A to C are in the standby state, that is, in the light receiving state. When any of the units A to C starts transmission to the other units from the standby state, the unit that has started transmission and the destination unit alternately perform transmission and reception operations. In the example shown in FIG. 19, the unit A performs a light emitting operation and transmits a signal to the unit B. At this time, both the unit B and the unit C are in the light receiving state, and receive the signal from the unit A. Unit B and Unit C are respectively
Identify whether the received signal is a signal for itself. Unit B determines that the received signal is a signal for itself, performs a light receiving operation, and receives and processes the signal from unit A. Then, unit A and unit B
Communication is performed by performing a light emitting operation and a light receiving operation, respectively.
When the communication, that is, the light emitting operation and the light receiving operation are completed, the unit A and the unit B return to the standby state (light receiving state).

When receiving the signal from unit A, unit C determines that the received signal is not a signal for itself, continues the light receiving operation, and waits until it is called. The unit C remains in a standby state in which the light receiving operation is continued while the unit A and the unit B are communicating and after the communication is completed. If the unit C needs to communicate with another unit while the units A and B are communicating, the unit C monitors the communication status between the units A and B, Unit A
If there is no transmission / reception of a signal for a certain time between the unit and the unit B, the signal may be transmitted to another unit.

As described above, according to the present embodiment, in each unit which is a transmitting / receiving device, light emission (transmission) and light reception (reception) can be performed using the same organic EL element 1. Thus, the size of each unit can be reduced.

The other configurations, operations and effects of the present embodiment are the same as those of the first embodiment.

[Third Embodiment] Next, a display device according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 20 is a block diagram illustrating a configuration of a display device according to the third embodiment of the present invention. The display device according to the present embodiment includes an organic EL display 41, a scan electrode driving unit 42 and a data electrode driving unit 43 for driving the organic EL display 41.
And a control unit 44 for processing and processing display data, controlling the driving units 42 and 43, and the like. The organic EL display 41 corresponds to the display device of the present invention, and includes a scan electrode driver 42, a data electrode driver 43, and a controller 44.
Corresponds to the driving device in the present invention.

The organic EL display 41 has scanning electrodes and data electrodes arranged in a matrix, and a plurality of organic EL elements 1 formed at the intersections of these scanning electrodes and data electrodes and connected to both electrodes. are doing. The organic EL element 1 has a light emitting function and a light receiving function as in the first embodiment.

Scan electrode driving section 42 includes a bidirectional shift register circuit 51 for inputting and shifting data, and a latch 52 for reading and holding input data.
And an output control unit 53 for controlling whether to output the data held in the latch 52, and a level for shifting the level of the output data of the output control unit 53 to generate a signal for driving the scan electrode. It has a shift circuit 54 and an output unit 55 that outputs a signal generated by the level shift circuit 54 to the scan electrode.

The data electrode driving section 43 has a bidirectional shift register circuit 61 for inputting and shifting display data.
And a latch 62 for reading and holding the input data, an output control unit 63 for controlling whether to output the data held in the latch 62, and shifting the level of the output data of the output control unit 63. A level shift circuit 64 for generating a signal for driving the data electrode; and an output unit 65 for outputting a signal generated by the level shift circuit 64 to the data electrode.

The control unit 44 sends data to the scan electrode driving unit 42 via the data line 101,
2, the control data is transmitted to the data electrode driving section 43 via the data line 103, and the control data is transmitted via the control line 104.

The display device according to the present embodiment has a light receiving signal processing circuit 70 connected to data electrode driving section 43.
It has. This light receiving signal processing circuit 70 is an organic EL
The presence or absence of light reception in the element 1 is detected and a light reception signal is output.

FIG. 21 shows a main part of the display device shown in FIG. As shown in this figure, in the present embodiment, the plurality of scanning electrodes of the organic EL display 41 are numbered C-1 to Cm, and the plurality of data electrodes are D-1 to Dn. Numbered.

Next, the operation of the display device according to the present embodiment will be described with reference to FIG. The scan electrode drive unit 42 sequentially selects scan electrodes for a certain period of time based on data from the control unit 44. Scan electrode driver 42
Applies a low-level voltage to a selected scanning electrode and applies a high-level voltage to a non-selected scanning electrode. FIG. 22 shows scan electrodes C-1, C-2 and C-
The change of the voltage applied to m is shown.

The repetition frequency of the selection of the scanning electrode is set to 30.
When the frequency is set to Hz or more, it is possible to perform display so that a continuous image is seen by human eyes. If the image flicker is noticeable, as long as the response of the organic EL element 1 is possible,
It is preferable to increase the repetition frequency of the selection of the scanning electrode. Generally, the frequency is 70 Hz or more, preferably 1 Hz.
When the frequency is 00 Hz or more, a good image without flicker can be obtained.

On the other hand, the data electrode driving section 43 supplies a plurality of organic EL elements 1 connected to the selected scanning electrode based on the data from the control section 44 for each scanning electrode selection period (scanning period). Among them, the data electrode connected to the element to emit light is set to the selected state. The data electrode driving unit 43
A high-level voltage is applied to the selected data electrode,
A low-level voltage is applied to the unselected data electrodes. FIG. 22 shows data electrodes D-1, D-2 and D-
3 shows a change in voltage applied to n.

In this way, a voltage higher than the forward light emission threshold is applied to the organic EL element 1 connected to the selected scanning electrode and the selected data electrode, and
The element 1 is in a light emitting state. FIG. 22 shows the data electrode D-
1 and the organic EL element 1 (shown as D-1-C-1 in the figure) connected to the scanning electrode C-1, and the organic EL element connected to the data electrode D-1 and the scanning electrode C-2. Element 1 (denoted as D-1-C-2 in the figure), and organic EL element 1 (D-D in the figure) connected to data electrode D-2 and scan electrode C-2.
It is described as 2-C-2. ) Shows the change in the voltage applied.

Further, a voltage in a direction opposite to the light emitting state is applied to the organic EL element 1 connected to the non-selected scanning electrodes and the non-selected data electrodes, and the organic EL element 1 enters a light receiving state. .

In the organic EL element 1 connected to the selected scanning electrode and the non-selected data electrode, and the organic EL element 1 connected to the non-selected scanning electrode and the selected data electrode, The applied voltage becomes zero, and neither light emission nor light reception is performed.

In the present embodiment, a period (hereinafter, referred to as a forced non-selection period) Tc in which both the scanning electrode and the data electrode are in the non-selection state is set between the selection periods of each scanning electrode. In the forced non-selection period Tc, all the organic EL elements 1 in the organic EL display 41 are in the light receiving state. Also, by setting the forced non-selection period Tc,
The organic EL element 1 always enters the light receiving state immediately before the light emitting state.

In the present embodiment, the organic EL element 1
Is in the light emitting state only when the scanning electrode connected thereto is in the selected state, so that the light emitting state selection duty is smaller than 0.5. In FIG. 22,
Symbol T represents one cycle of switching between the light emitting state and the light receiving state.

FIG. 23 is a circuit diagram showing an example of the configuration of light receiving signal processing circuit 70 in the present embodiment. In this example, the output section 65 of the data electrode driving section 43 has an output terminal 66 corresponding to each data electrode. Further, the organic EL display 41 has an input terminal 46 corresponding to each data electrode. And the corresponding output terminal 66
And the input terminal 46 are connected. Inside the data electrode driving section 43, the output terminal 66 is connected to the constant current circuit 6
7 and one end of an open / close switch 68 are connected. The other end of the switch 68 is grounded. The constant current circuit 67 is connected to an input terminal 69 of a control signal for controlling on / off of the output of the constant current circuit 67.

The light receiving signal processing circuit 70 shown in FIG.
Each of the data electrodes has a plurality of open / close switches 71 each having one end connected to a connection point between each output terminal 66 and each input terminal 46. All switches 7
The other end of 1 is grounded via a resistor 72,
It is connected to a non-inverting input terminal of an operational amplifier 74 via a resistor 73. A resistor 75 is connected to the inverting input terminal of the operational amplifier 74.
Are connected at one end. The other end of the resistor 75 has a resistor 7
6 is connected to the cathode of the Zener diode 77. A predetermined voltage is applied to the other end of the resistor 76. The anode of the Zener diode 77 is grounded. Further, the other end of the resistor 75 and the output terminal of the operational amplifier 74 are connected via a resistor 78. The output terminal of the operational amplifier 74 is connected to a power supply voltage Vdd via a resistor 79 and connected to an output terminal 80. The switch 68 and the switch 71 are linked to open when the data electrode is in the selected state and close when the data electrode is in the non-selected state.

In the light receiving signal processing circuit 70 shown in FIG. 23, when any of the organic EL elements 1 in the light receiving state receives light, the voltage applied to the non-inverting input terminal of the operational amplifier 74 changes. Output changes. The output of the operational amplifier 74 is extracted from the output terminal 80 as a reception signal.

FIG. 24 is a circuit diagram showing another example of the configuration of light receiving signal processing circuit 70 in the present embodiment. The light receiving signal processing circuit 70 in this example is provided corresponding to each data electrode, and has a plurality of open / close switches 81 each having one end connected to a connection point between each output terminal 66 and the input terminal 46. . The other end of each switch 81 is connected to the base of a transistor 82 provided corresponding to each data electrode, and is grounded via a resistor 83. The emitter of the transistor 82 is grounded. The cathode of a diode 84 is connected to the collector of the transistor 82. A power supply voltage Vdd is applied to the anodes of all the diodes 84 via a resistor 85, and an output terminal 86 is connected to the anodes. Switch 68
And the switch 81 are linked to open when the data electrode is in the selected state and close when the data electrode is in the non-selected state.

In the light receiving signal processing circuit 70 shown in FIG. 24, when any of the organic EL elements 1 in the light receiving state receives light, the transistor 82 corresponding to the data electrode connected to the organic EL element 1 is turned on. The reception signal output from the output terminal 86 becomes low level. At other times, the received signal is at a high level.

In FIG. 24, if the resistor 85 and the output terminal 86 are not provided in common for all data electrodes but the resistor 85 and the output terminal 86 are provided separately, a light receiving signal can be obtained for each data electrode. This enables detection of the light receiving position in the horizontal direction.

FIG. 25 is a block diagram showing another example of the configuration of the display device according to the present embodiment. This example is shown in FIG.
This is an example in which the light receiving signal processing circuit 170 is provided on the scanning electrode drive unit 42 side without providing the light receiving signal processing circuit 70 at 0. The specific configuration of the light receiving signal processing circuit 170 is the same as, for example, FIG. 23 or FIG. 24, and the circuit shown in FIG. 23 or FIG. 24 may be connected to the scanning electrode instead of the data electrode. In this example, the light receiving signal processing circuit 170
May output a light receiving signal when any of the organic EL elements 1 in a light receiving state receives light, or may output a light receiving signal for each scanning electrode. When the light receiving signal processing circuit 170 is configured to output a light receiving signal for each scanning electrode, the light receiving position in the vertical direction can be detected.

FIG. 26 is a block diagram showing still another example of the configuration of the display device according to the present embodiment. This example
This is an example in which a light receiving signal processing circuit 170 is provided on the scanning electrode drive unit 42 side in addition to the light receiving signal processing circuit 70 in FIG. In this example, the light receiving signal processing circuit 70 outputs a light receiving signal for each data electrode, and the light receiving signal processing circuit 170
If it is assumed that a light receiving signal is output for each scanning electrode, the light receiving position can be detected two-dimensionally in the horizontal and vertical directions.

As described above, according to the present embodiment, light emission and light reception can be performed using the same organic EL element 1 in the organic EL display 41. Therefore,
According to the present embodiment, it becomes possible to receive an optical signal using the organic EL display 41. Therefore, according to the present embodiment, information for control in the display device and information representing the display content are sent to the organic EL display 41 as optical signals, and based on the light receiving signal output from the light receiving signal processing circuit, It is possible to control the display device and display information on the organic EL display 41. In addition, if an optical signal for control in the display device is transmitted from the remote control device, an operation similar to the conventional remote control operation using infrared rays or the like can be performed without providing a special reception device in the display device. It becomes possible.

Further, according to the present embodiment, information can be input to the display device by using an optical signal, so that noise such as radio waves does not occur, and components such as an antenna can be used. Since it is not necessary, restrictions on the installation of the display device are reduced.

Further, according to the present embodiment, when the number of signal lines for inputting information to the display device is reduced, or when the amount of information representing the display content is small, all the information representing the display content is converted into an optical signal. Or input to a display device.

Further, according to the present embodiment, the entire display surface of the organic EL display 41 can be used as a light receiving surface, so that the positioning accuracy of the light receiving surface with respect to an optical signal transmitted from a long distance can be reduced. Therefore, according to the present embodiment, it is possible to eliminate the necessity of fine adjustment and positioning mechanism with respect to the installation of the organic EL display 41 serving as the light receiving surface of the optical signal.

In this embodiment, when the light receiving signal processing circuit is configured to output a light receiving signal for each data electrode and each scanning electrode, the light receiving position on the organic EL display 41 is two-dimensionally determined. Can be detected. This makes it possible to use signals such as distinguishing signals for each region of the light receiving surface of the organic EL display 41 and using the organic EL display 41 as a display device, and as a position detecting device as necessary. Become.

Other configurations, operations, and effects of the present embodiment are the same as those of the first embodiment.

[Fourth Embodiment] Next, a display device according to a fourth embodiment of the present invention will be described with reference to FIGS. The display device according to the present embodiment enables optical communication between a plurality of display devices using an organic EL display. The configuration of the display device according to the present embodiment is similar to that of the third embodiment. The transmission of light between the plurality of organic EL displays may be performed through a space or may be performed through an optical transmission unit such as an optical fiber. When a plurality of organic EL displays are arranged side by side, light may be transmitted between the plurality of organic EL displays using reflection by a mirror, glass, a wall, or the like.

In the display device according to the present embodiment, the organic E
By modulating the light emission luminance during the light emission period of each organic EL element 1 of the L display 41, the display information is
Information to be transmitted by an optical signal is superimposed. The modulation of the light emission luminance is performed by, for example, the data electrode driving unit 43.
Is performed by modulating a drive signal for driving the data electrode. Hereinafter, three examples of a method of modulating a drive signal for driving a data electrode will be described with reference to FIGS.

In the method of the first example shown in FIG. 27, the drive signal is modulated into two values of zero and a predetermined peak value based on the information to be transmitted. Further, in this method, in order to keep the average luminance within one scan electrode selection period constant irrespective of the content of the information to be transmitted, the time of the current density of the organic EL element 1 during one scan electrode selection period is reduced. The peak value of the drive signal is controlled so that the integral value becomes constant.

In the method of the second example shown in FIG. 28, a signal modulated based on information to be transmitted is superimposed on a basic signal of a fixed level. Further, in this method, the amplitude of the signal modulated based on the information to be transmitted is controlled in order to keep the average luminance within one scanning electrode selection period constant regardless of the content of the information to be transmitted.

In the method of the third example shown in FIG.
Similarly to the above method, a signal modulated based on information to be transmitted is superimposed on the basic signal. Further, in this method, the level of the basic signal and the amplitude of the signal modulated based on the information to be transmitted are set in order to keep the average luminance within one scan electrode selection period constant regardless of the content of the information to be transmitted. Control both.

Next, referring to FIG. 30, each organic EL display 4 in a case where communication is performed between a plurality of display devices.
An example of the timing of light emission and light reception of No. 1 will be described.
In this example, a forced non-selection period is provided between the selection periods of each scanning electrode as shown in FIG. FIG. 30 shows the state of each organic EL display 41 when communication is performed between three display devices. Panels A, B, and C in FIG. 30 are organic ELs of three display devices.
The display 41 is shown. The high level period of the waveform shown in FIG. 30 indicates a period during which one of the organic EL elements 1 is in a light emitting state, and the low level period of the waveform shown in FIG. Organic E
This represents a period during which the L element 1 is in a light receiving state. In FIG. 30, a symbol T represents one cycle of switching between the light emitting state and the light receiving state. In the example shown in FIG.
At the end of the cycle, apart from the forced non-selection period, a period during which all the organic EL elements 1 are in the light receiving state is provided for a fixed time, but this period does not have to be provided.

In the example shown in FIG. 30, when each display device is not communicating, each display device drives the organic EL display 41 at its own timing. When communication is performed between a plurality of display devices, for example, as illustrated in FIG. 30, the display device that performs communication uses the organic EL display 41 so that the forced non-selection periods do not overlap.
Are shifted from each other. In this case, another display device may change the drive timing based on the drive timing of the display device that has started transmission first, or the drive timing of each display device may have a predetermined relationship. Each display device may change the drive timing.

Since the drive timings of the respective display devices are not synchronized before the start of the communication, the display devices other than the display device which has started the transmission first have the forced non-selection period or 1 drive.
In the light receiving state period provided at the end of the cycle, it is possible to receive a signal from the display device that has started transmitting first. The display device that has received the signal returns a response signal to the display device that has started transmission first. The drive timing of the display device which has started transmission first coincides with the display device of the transmission destination by chance, the signal cannot be received by the display device of the transmission destination, and a response signal is transmitted to the display device which has started transmission first. If not returned, the display device of the transmission destination performs transmission again with the drive timing shifted.

As described above, according to the present embodiment, communication between a plurality of display devices can be performed using the organic EL display 41 without providing a separate communication device. Thereby, for example, it becomes possible to form an image using a plurality of organic EL displays 41 by linking a plurality of display devices. Further, for example, it is possible to arrange a plurality of display devices, sequentially transmit information to an adjacent display device, and perform a display in which display contents such as characters move over a plurality of organic EL displays 41.

In the present embodiment, light emission and light reception of the organic EL element 1 of the organic EL display 41 may be performed in a wide wavelength range from a visible light range to an invisible light range.

The other structures, operations and effects of the present embodiment are the same as those of the third embodiment.

The present invention is not limited to the above embodiments, and various changes can be made. For example, a system for performing communication between a plurality of display devices may include a transmission-only display device or a reception-only display device.

In the display device, only a part of the area of the organic EL display 41 may be made capable of receiving light.
Further, for example, in a multi-color organic EL display, a light receiving signal processing circuit may be provided for each color, and the light receiving signal may be processed for each color component. This enables communication of a signal of a plurality of bits and multiplex communication. Further, as shown in FIG. 26, when light receiving signal processing circuits are provided on both the data electrode driving unit side and the scanning electrode driving unit side, the two light receiving signal processing circuits are selectively used depending on the wavelength, the timing of receiving a signal, and the like. For example, the roles of the two light receiving signal processing circuits may be different.

The light emitting and receiving element in the present invention is not limited to an organic EL element, but may be any element having a light emitting function and a light receiving function. For example, an inorganic EL element may be used.

[0136]

As described above, according to the light emitting / receiving element driving device, the light emitting / receiving apparatus, the communication system, or the display device of the present invention, the light emitting / receiving element having the light emitting function and the light receiving function is changed to the light emitting state. Since the driving is performed so that the light receiving state can be alternately switched, there is an effect that light emission and light reception are performed using the same element, and deterioration of the element can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a light emitting and receiving device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a configuration of the organic EL element according to the first embodiment of the invention.

FIG. 3 is a circuit diagram showing a first example of a specific configuration of the driving device in FIG. 1 and a connection position of a light receiving detection circuit.

FIG. 4 is a circuit diagram showing a second example of a specific configuration of the driving device in FIG. 1 and a connection position of a light receiving detection circuit.

FIG. 5 is a circuit diagram showing a third example of a specific configuration of the driving device in FIG. 1 and a connection position of a light receiving detection circuit.

FIG. 6 is a circuit diagram showing a fourth example of a specific configuration of the driving device in FIG. 1 and a connection position of a light receiving detection circuit.

FIG. 7 is a circuit diagram showing a fifth example of a specific configuration of the driving device in FIG. 1 and a connection position of a light receiving detection circuit.

8 is a circuit diagram showing a sixth example of the specific configuration of the driving device in FIG. 1 and the connection position of the light receiving detection circuit.

FIG. 9 is a circuit diagram illustrating an example of a configuration of a light reception detection circuit in FIG. 1;

FIG. 10 is a circuit diagram showing another example of the configuration of the light receiving detection circuit in FIG. 1;

FIG. 11 shows an organic EL according to the first embodiment of the present invention.
FIG. 4 is a waveform chart showing an example of a method for driving an element.

FIG. 12 shows an organic EL according to the first embodiment of the present invention.
FIG. 9 is a waveform chart showing another example of a method for driving an element.

FIG. 13 is a waveform chart for explaining a relationship between a magnitude of a voltage applied to the organic EL element and a response speed of the organic EL element in a light receiving state in the first embodiment of the present invention.

FIG. 14 is a waveform chart for explaining a relationship between a magnitude of a voltage applied to the organic EL element and a response speed of the organic EL element in a light receiving state in the first embodiment of the present invention.

FIG. 15 is a characteristic diagram showing a relationship between a light emitting state selection time and a light emitting current density according to the first embodiment of the present invention.

FIG. 16 is a characteristic diagram illustrating a relationship between a light emitting state selection duty and a light emitting current density according to the first embodiment of the present invention.

FIG. 17 is a block diagram illustrating an example of a configuration of a communication system according to a second embodiment of the present invention.

FIG. 18 is a waveform chart showing an example of the operation of the communication system shown in FIG.

FIG. 19 is an explanatory diagram showing another example of the configuration and operation of the communication system according to the second embodiment of the present invention.

FIG. 20 is a block diagram illustrating a configuration of a display device according to a third embodiment of the present invention.

FIG. 21 is an explanatory diagram illustrating a main part of the display device illustrated in FIG. 20;

FIG. 22 is a waveform chart showing an operation of the display device according to the third embodiment of the present invention.

FIG. 23 is a circuit diagram illustrating an example of a configuration of a light receiving signal processing circuit according to a third embodiment of the present invention.

FIG. 24 is a circuit diagram showing another example of the configuration of the light receiving signal processing circuit according to the third embodiment of the present invention.

FIG. 25 is a block diagram showing another example of the configuration of the display device according to the third embodiment of the present invention.

FIG. 26 is a block diagram showing still another example of the configuration of the display device according to the third embodiment of the present invention.

FIG. 27 is a waveform chart showing an example of a method of modulating a drive signal for driving a data electrode in the display device according to the fourth embodiment of the present invention.

FIG. 28 is a waveform chart showing another example of a method of modulating a drive signal for driving a data electrode in the display device according to the fourth embodiment of the present invention.

FIG. 29 is a waveform chart showing still another example of a method of modulating a drive signal for driving a data electrode in the display device according to the fourth embodiment of the present invention.

FIG. 30 is a waveform diagram showing an example of timing of light emission and light reception of each organic EL display when communication is performed between a plurality of display devices according to the fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Organic EL element, 2 ... Drive device, 3 ... Light reception detection circuit,
23 ... control circuit, 41 ... organic EL display, 42 ...
Scan electrode driving unit, 43: data electrode driving unit, 44: control unit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 33/14 H04B 9/00 W 5K002 // H01L 31/10 H01L 31/10 G 33/00 F term ( (Reference) 2G065 AB04 BA34 BA40 BC02 BC07 BC22 BD03 CA30 DA15 3K007 AB00 BA05 CA01 CB01 GA00 5C080 AA06 BB05 BB09 DD29 JJ02 JJ03 JJ04 JJ05 JJ06 5F041 AA44 BB13 BB33 CA12 CA45 CA46 CA88 FF01 FF20 MB10 NA10 NB20 A1011 DA21

Claims (16)

[Claims] 1. A driving device for driving a light-emitting and light-receiving element having a light-emitting function and a light-receiving function, wherein the light-emitting and light-receiving element is driven so that a light-emitting state and a light-receiving state are alternately switched. Driving device for light emitting and receiving elements. 2. The method according to claim 1, wherein the ratio of the light emitting state period in one cycle of switching between the light emitting state and the light receiving state of the light emitting and receiving element is 5%.
2. The driving device for a light emitting and receiving element according to claim 1, wherein the driving voltage is set to be smaller than 0%. 3. The driving device for a light emitting and light receiving element according to claim 1, wherein a frequency of switching between a light emitting state and a light receiving state of the light emitting and light receiving element is smaller than 500 kHz. 4. A predetermined first voltage equal to or higher than a light emission threshold voltage is applied to the light emitting / receiving element in a light emitting state, and the first voltage is opposite to the first voltage in a light receiving state. 4. The driving device for a light emitting and receiving element according to claim 1, wherein a second voltage having an absolute value greater than zero and equal to or less than a withstand voltage of the light emitting and receiving element in the direction is applied. 5. The driving device for a light emitting and light receiving element according to claim 1, wherein the light emitting and light receiving element is always set to a light receiving state immediately before the light emitting state. 6. The light-emitting and light-receiving element is an organic electroluminescent element.
A driving device for a light emitting and receiving element according to any one of the above. 7. A light emitting device comprising: a light emitting / receiving element having a light emitting function and a light receiving function; and a driving device for driving the light emitting / receiving element so that the light emitting state and the light receiving state are alternately switched. Light receiving device. 8. The light emitting device according to claim 7, wherein the driving device sets a ratio of a period of a light emitting state in one cycle of switching between a light emitting state and a light receiving state of the light emitting and receiving element to be smaller than 50%. Light receiving device. 9. The light emitting and receiving device according to claim 7, wherein the driving device sets a frequency of switching between a light emitting state and a light receiving state of the light emitting and receiving element to be lower than 500 kHz. 10. The driving device applies a predetermined first voltage equal to or higher than a light emission threshold voltage to the light emitting and receiving element when the light emitting and light receiving element is in a light emitting state. 10. A light emitting and receiving device according to claim 7, wherein a second voltage having an absolute value larger than zero and equal to or lower than the dielectric strength of the light emitting and receiving device is applied in a direction opposite to the voltage of the light emitting and receiving device. apparatus. 11. The light-emitting and light-receiving device according to claim 7, wherein the driving device always sets the light-emitting and light-receiving element to a light-receiving state immediately before a light-emitting state. 12. The light emitting and receiving device according to claim 7, wherein said light emitting and receiving element is an organic electroluminescent element. 13. A transmission / reception device for transmitting / receiving an optical signal, wherein each transmission / reception device has a light emitting / receiving element having a light emitting function and a light receiving function, and a light emitting state and a light receiving state are alternately switched. And a driving device for driving the light emitting and receiving element. 14. A display device comprising a plurality of light-emitting and light-receiving elements having a light-emitting function and a light-receiving function, and a driving device for driving each light-emitting and light-receiving element so that the light-emitting state and the light-receiving state can be alternately switched. A display device characterized by the above-mentioned. 15. The light-emitting and light-receiving element according to claim 14, wherein the driving device drives the light-emitting and light-receiving element such that information transmitted by an optical signal is superimposed on display information in a light-emitting state of the light-emitting and light-receiving element. Display device. 16. The display according to claim 15, wherein the driving device drives the light-emitting and light-receiving element so that the average luminance of the light-emitting and light-receiving element in the light-emitting state is constant regardless of the content of the information to be transmitted. apparatus.