JP3351426B2 - Signal control device and light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device using electroluminescence and a signal control device for driving an active electroluminescence matrix.
About the.

[0002]

2. Description of the Related Art An electroluminescent element is a light emitting element (hereinafter referred to as an EL element) which utilizes light emission when a driving voltage is applied to a semiconductor material such as zinc sulfide to which manganese is added. Can be used as a character display panel, or a one-dimensional array can be used as an exposure system of an electronic printing apparatus. These light-emitting devices can be manufactured to be thin and lightweight, have a high space utilization rate, and can be easily incorporated into portable devices.
In recent years, research has been rapidly promoted because it has many advantages such as easy-to-read display without bleeding. Above all, an EL element provided with a switching element, a power supply, and the like necessary for controlling its light emission is called an active type.
Developed because external control devices do not have to be complicated,
Improvements are being made ("TFEL Edge Emitter Array for
Optical Imaging Bar Applications ", ZK KUM, et
al., Proceedings of the SID, Vol. 28, Jan. 1987, p.
(p. 81-85)

[0003] Conventionally, an active EL matrix, which is an electric matrix composed of a large number of active EL light-emitting circuits, is a 1-bit basic circuit (hereinafter, referred to as 1) including EL elements driven by an AC power supply as shown in FIG. Bit EL
Circuit or 1-bit circuit). These 1-bit circuit thin film transistor (hereinafter, referred to as TFT) is opened and closed by the switching element Q _D such. A switching element Q _D capacitor Cs for the connected data retention to the gate, another TFT switching element Qw
And is controlled by The data signal DATA sent to each 1-bit circuit is written to the data holding capacitor Cs by turning on / off the TFT switching element Qw.
The switching element Qw is turned on / off by a strobe signal STROBE from a signal control device. When the data signal of the drive signal for emitting the EL element is a high-potential, the capacitor Cs is charged to a high level, as a result of the charging voltage becomes the gate voltage of the switching element Q _D, conducts the switching element Q _D As a result, the EL element _CEL and the driving AC power supply (driving voltage Va) form a series closed circuit, and the EL element _{CEL is} driven by the driving power supply to emit light. When the signal is a signal for not driving the EL element is low, since the element Q _D is turned off when the signal is written in the capacitor Cs, EL
The driving of the element is stopped. Accordingly, a desired light emitting state of the EL matrix can be obtained by scanning one data time sequentially for one frame by writing desired data to the data holding capacitor of each 1-bit circuit. In general, a common drive voltage is applied to each light emitting unit to simplify the circuit configuration.

The active E including many 1-bit circuits
L matrix is m blocks (m is an integer) for convenience of driving
And each block can be formed into an electrical n × m matrix including n (n is an integer) 1-bit circuits (FIG. 3). FIG. 5 shows a method of writing data in this case, in which one scanning time Ts (the time required to scan all the one-bit circuits once) is applied to the blocks under the strobe signals STROBE1 to STROBEm. Driving (light emission) / non-driving (non-light emission) signals are written to the n 1-bit circuits, and the light emission state of the entire matrix is controlled. The 1-bit circuit to which the light emission data has been written by the signal STROBE is driven by the driving power supply during the scanning period after the data writing. Therefore, in this case, the driving period Td of each 1-bit circuit must be the same as the scanning period Ts. That is, if the EL element that was in the driving state in one scanning period changes to the non-driving state in the next scanning period, the EL element attenuates the light emission amount after the transition to the non-light emitting period (FIG. 7).

[0005]

The conventional driving method is EL.
The element driving period Td is the same as one scanning period Ts.
Therefore, it follows the light amount Lon in the light emitting section and the light emitting section.
The light amount Loff in the non-light emitting section is as shown in FIG.
And Loff is the light at the time of decay after shifting to the non-light emitting section.
Amount. EL devices usually have a decay time of about 1 ms.
I do. Therefore one scanning period is much longer than this decay time
If there is no problem, there is no problem.
It is required to increase the ratio Lon / Loff.
This hinders the speeding up of scanning. When an EL matrix is used in an exposure system of an electronic printing apparatus, speeding up of printing is extremely important, and such a conventional driving method and apparatus have serious problems.

Accordingly, the present invention solves this problem in the EL matrix, thereby improving the EL matrix.
Light emitting device realizing high speed driving and signal control used for the same
It is an object to provide a control device .

[0007]

Means for Solving the Problems As means for that,
According to the present invention, a period from driving to emission stop of each EL element of the active thin film EL matrix to driving stop is one scanning period (n ×
Write data to 1-bit circuit belonging to m matrix
From the start of writing, writing the next data to the same 1-bit circuit
Time to start
You.

Further, when this means is specified, data writing to each 1-bit circuit, drive start timing or drive stop
With the right choice of time, within less than one scan period
The operation from driving start to driving stop is performed.

[0009]

According to the above means of the present invention, if one scanning period for light emission and the driving time of the EL element are the same as in the prior art,
And the emission decay can be set longer,
The driving speed of the L matrix can be increased.

[0010]

[Embodiment] The invention according to claim 1, 3, or 7
A signal control device according to an embodiment of the present invention will be described. FIG. 2A shows an EL matrix source using the signal control device of the present invention.
1 shows a configuration of a 1-bit basic circuit of an optical device . As shown in this figure, the 1 bit basic circuit series circuit composed of the EL element C _EL and the switching element Q _D generally power under the control of signal control device from the AC drive power source S via a switch Sw is applied Contains. The switching element Q _D is generally a thin film transistor is (hereinafter, referred to as TFT), the gate G is connected to the register. In the example of FIG. 2A, this register includes a capacitor Cs1 for holding a data signal DATA designating light emission / non-light emission of the EL element, a switching element Qw for writing this data to the capacitor Cs1, A second capacitor Cs2 for holding a data signal, and a capacitor Cs
2 to write the data signal, or a latch element Q _L for erasing. Switching element Qw, also the latch element Q _L is a TFT.

The data line is connected to the input terminal of the switching element Qw, and a first data write / hold capacitor Cs1 is connected between the output terminal and the ground. The gate of the switching element Qw is connected to a strobe signal line of the signal control device.

[0012] The output terminal of the switching element Qw is further connected to an input terminal of the latch element Q _L, the output terminal of the latch element Q _L is connected to the gate G of the switching element Q _D.
Second data holding capacitor Cs2 is connected between the output terminal and the ground of the latch device Q _L.

[0013] The switching elements Qw, latch element Q _L, and the drive power source S is controlled by the signal control device to operate at a desired timing as the data signals DATA and strobe signals.

Since the EL matrix includes a large number of EL elements each having a unit of the 1-bit circuit shown in FIG. 2A, the EL matrix is divided into m blocks (m is an integer) including n 1-bit circuits for convenience of driving. As shown in FIG. 4A, n data DATA1-DATAn (n is an integer) can be written in each block, and the block is formed into an n × m electrical matrix. m
When the blocks are driven simultaneously, the latch signals of the latch elements of all the EL elements of all the blocks are made common. A similar block configuration is sufficient when used as an image bar or the like of an electronic printing apparatus.

FIG. 4B shows a second embodiment of the present invention.
FIG. 2B shows the configuration of the 1-bit basic circuit in the L matrix. This embodiment is different from the conventional 1-bit circuit shown in FIG.
The reset element Q _R for discharging the EL driving data held in s which are connected in parallel with the capacitor Cs. Reset switch Q _R can also be configured with TFT, the current passing through the electrodes are connected in parallel to the capacitor Cs for data retention. The gate is connected to a signal control device. This arrangement since unnecessary latch Q _L is compared with the first embodiment, it is easy on correspondingly structure.

The operation of the EL matrix according to the first embodiment of the present invention will be described with reference to FIG. If each block contains only one 1-bit circuit, it becomes a one-dimensional matrix, but it should be noted that the principle is exactly the same in this case.

During an arbitrary scanning period Ts, the switching element Qw for writing data is turned on for each block by the strobe signal STROBE1-m sent from the signal control device, and data is written to each data holding capacitor Cs1. go. When writing is completed, the switching element
The child Qw is turned off, and data is held on the capacitor Cs1. Written data is held in the capacitor Cs1 to each latch element Q _L is turned by the latch signal LATCH from the signal control unit, each of the switching elements Q
It is not output to the _D gate.

[0018] When the data writing is completed for all blocks (at time Tw has elapsed in FIG. 6 (A)), all of the latch device by a common latch signal LATCH to the latch element is transmitted from the signal controller Q _L conduction Then, the EL element drive data (high potential signal) held in the first data holding capacitor Cs1 is output to the second data holding capacitor Cs2, and the EL element drive data is charged in a form in which the capacitor Cs2 is charged. It is held by the capacitor Cs2. The switching element Q _D This charging voltage is turned on, at this time EL element emits light by being driven by an AC voltage Va is applied.

[0019] Thereafter, when the data signal does not drive the EL element (a low potential signal) is applied to the data line,
The conduction of the switching element Qw and the latch element Q _L,
Until electric charge accumulated in the capacitor Cs2 is discharged, the switching element Q _D is turned off, the driving of the EL element is stopped. Latch element Q _L in all 1-bit basic circuit in this embodiment are connected to a common latch signal, all the EL elements are driven simultaneously stopped.

When a time Td elapses after the application of the latch signal, a drive stop signal is applied to all the 1-bit circuits. In this case, the time (Tw + Td) is shorter than the scanning time Ts. Therefore, the EL element that has received the drive signal for emitting light also stops emitting light during the scanning period. After that, the drive is stopped for a time Tr until the next scan is started, and C
Discharge of s1 and Cs2 is performed (FIG. 6A).

[0021] Since the drive stop any of the EL element is also driven simultaneously at the same time by the latch Q _L, the applied voltage V
a may be operated only during this driving period.

In general, data writing can be performed in a very short time. Thus, by appropriately synchronizing the three kinds of operations in this manner, all of the operations until writing of light emission data, light emission drive, and stop of light emission drive can be performed within the same scanning period. Can be performed. In this regard, according to the signal control device of this embodiment,
That EL matrix driving is very different from the conventional driving method shown in FIG.

Next, claim 2, claim 4, claim 5 or
A signal control device according to an embodiment of the invention according to claim 6 will be described.
Will be explained. FIG. 2 (B) shows the signal control device.
1-bit basic circuit of the driven EL matrix
You. Further, EL shown in FIG. 6 (B) FIG. 2 (B) Matori'
The timing of the driving of the motor is shown. At the time of driving data writing, data is written in the same manner as in the conventional example by turning off the reset switch. E
When the L element is emitted is made conductive to reset the switching element Q _R by a reset signal RST after the predetermined time to turn off the switching element Q _D with. Thus, the driving of the EL element is stopped. However, this reset is performed for a time Td shorter than one scanning time after the start of the light emission drive (Td1, Td2, etc. in FIG. 6B). These EL elements do not always need to emit light at the same time, but may emit light sequentially in a certain order. Therefore, the time T
A signal STROBE j for writing data to another EL 1-bit circuit can be used as a drive stop reset signal after d.

This driving method differs from the first embodiment in that the EL driving power S is always applied during the scanning period. However, it is desirable to keep the difference between the phase of the driving power supply and the phase of the strobe signal constant in order to make the light emitting conditions of each EL element uniform. Since the driving period Td is shorter than one scanning time Ts, the driving period of each EL element is performed only for a part of the scanning time, and after the driving is stopped, the next data is stopped.
During the period Tr = Ts−Td until the data is written, attenuated light emission is performed with the driving stopped.

As shown in FIG. 6A, when there is a period Tw in which data writing is performed with the driving power supply turned off before the light emission by the latch signal, light emission starts Tw after the start of each scanning period. However, since the writing time is very short, this is ignored in FIG.

As described above, if the driving of each EL element and the stop of the driving are included within a period shorter than one scanning period , FIG.
As shown in (1), both light emission during driving and light emission after driving stop exist within one scanning time (“light emission section” in FIGS. 7 and 8) for light emission of the EL element. For example, in the case of an EL bar, the light amount Lon to be used in the light emission section is such that the light emission intensity I within one scanning time Ts after the start of light emission is changed from time zero to time T.
This is the integral amount integrated up to s. In this case, the time integration amount Loff of the light emission intensity I in one scanning period (“non- light emission period” in FIG. 8) Ts not intended for light emission is unnecessary in this case. Therefore, since the significant signal ratio as the EL matrix is Lon / Loff, the driving time Td is reduced while keeping Lon within the allowable limit, and the ratio Lon / L
It is required to increase off. Incidentally, in the case of the driving method of the present invention, L in the conventional driving method (FIG. 7) is used.
Note that the main part of off is included in Lon of the present driving method. Therefore, in the present driving method, by shortening the driving time Td, the above ratio Lon / Lof is immediately obtained.
f is automatically greatly improved. So the remaining problem is Lo
It is only to shorten the drive time Td while keeping n within the allowable limit. For that purpose, appropriate values of the parameters Ts and Td may be selected according to the light emission characteristics I of the selected EL element. Driving period Td, scanning period Ts, and ratio Lo
The qualitative relationship between n / Loff is shown in FIG.
The above parameters can be easily obtained by obtaining a characteristic diagram as shown in FIG. 9 for the selected EL material. For example, when an allowable range of Lon / Loff and an allowable range of Ts are specified, a certain area is formed on FIG. Thus, it can be seen that an appropriate curve, that is, an appropriate Td, should be selected from the group of characteristic curves passing through this region.

[0027]

As described above, according to the present invention, in controlling the driving of an active thin-film EL matrix including switching elements which are turned on / off by a register as matrix points, the active EL matrix is scanned and the switching is performed. Since a data signal for selectively turning on the element is supplied to the register, and each of the selected switching elements is turned off,
It is possible to perform all of the light emission driving and the stop of the light emission driving within a time shorter than one scanning period. as a result,
The EL matrix can be driven at a higher speed than the conventional driving method.

In this driving method, the effective light emission signal ratio Lon / Loff can be easily selected by selecting the ratio between the driving time within one scanning period and the subsequent driving stop period.

According to a seventh aspect of the present invention, in the driving of the active thin film EL matrix , the AC power supply is activated or deactivated based on the start of the scanning and the activation of the register. Since each EL element can be driven by the same phase voltage, there is no uneven light emission in the entire matrix.

[Brief description of the drawings]

FIG. 1 is a diagram showing a 1-bit circuit of a conventional EL matrix.

FIG. 2A shows a 1-bit circuit of an EL matrix according to the first embodiment of the present invention. (B) is a book
7 shows a 1-bit circuit of an EL matrix according to a second embodiment of the present invention .

FIG. 3 is a diagram showing a matrix structure of a conventional EL matrix.

FIG. 4 is a matrix configuration diagram of an EL matrix according to the first and second embodiments of the present invention.

FIG. 5 is a signal timing chart of a conventional example.

FIG. 6 is a signal timing chart of the first embodiment and the second embodiment of the present invention.

FIG. 7 is a diagram showing a light emission intensity distribution of a conventional EL matrix.

FIG. 8 is a diagram showing a light emission intensity distribution of an EL matrix according to the present invention.

FIG. 9 is a diagram showing a relationship between an effective light emission signal ratio of an EL matrix and a scanning time according to the present invention.

[Explanation of symbols]

C _EL EL element SE
L element driving power supply Sw EL element driving power supply switch Va E
L element drive power supply voltage Q _D 1 bit circuit switching element Qw Data write switching element Q _L latch element Cs1 First data holding capacitor Cs2 Second data holding capacitor DATA
Data signal STROBE Strobe signal LATCH
Latch signal RST Reset signal Ts
Scan time Td Drive time T
w Data writing time Tr Non-driving time L
on Light emission amount when driving Loff Light emission amount when not driving

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI H05B 33/14 H05B 33/14 Z (56) References JP-A-3-18892 (JP, A) JP-A-60-250392 ( JP, A) JP-A-62-108073 (JP, A) JP-A-62-189497 (JP, A) JP-A-59-123873 (JP, A) JP-B-62-28476 (JP, B2) JP-B 60-56026 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G09G 3/00-3/38 H05B 33/00-33/28 G02F 1/133 505-580

Claims (8)

(57) [Claims] 1. An electric power supplied from a driving power supply.
An EL element to be driven, and the EL element and the driving power supply.
A switching element connected in series to the
1 bit including a register for turning on / off the switching element
Active EL mat with EL circuit as each matrix point
A signal control device for driving and controlling the RIX, wherein the register is provided with a first data holding unit for holding data corresponding to driving / non-driving of the EL element, and a data signal corresponding to the data is supplied. A data writing unit that writes the data into the first data storage unit; and a second data storage unit that is connected to the switching element and that makes the switching element conductive or nonconductive according to the stored data. the data written to the first data holding unit, at the same time for a plurality of 1-bit EL circuit, which has a latch portion to transfer to the second data holding unit, the signal control unit, the sequentially supplies data signals to 1-bit EL circuit, and outputs a signal for controlling the operation of the latch unit and the data writing unit, the rack After writing data to all 1 bit EL circuit for a latch signal to be output to the section in common ends, and outputs the latch signal to transfer the second data holding unit Hedeta from said first data holding unit, Before writing of the next data is started, for all the 1-bit circuits, a signal for deactivating the EL element is simultaneously sent to the second data holding unit via the data writing unit and the latch unit. A signal control device set to be written. 2. An electric power supplied from a driving power supply.
An EL element to be driven, and the EL element and the driving power supply.
A switching element connected in series to the
1 bit including a register for turning on / off the switching element
Active EL mat with EL circuit as each matrix point
A signal control equipment for driving and controlling the helix, data holding said register holds the data corresponding to the drive / non-drive of the EL element, and conductive or non-conductive the switching device by data held A data writing unit that writes the data to the data holding unit when a data signal corresponding to the data is supplied; and a data holding unit that turns off the switching element when a reset signal is received. And a reset unit for resetting the unit . The signal control device supplies a data signal to each of the one-bit EL circuits, and outputs a signal for controlling the data writing unit and the reset signal . is intended, after the writing of data to the 1-bit EL circuit termination,
Before the next data is written to the same 1-bit EL circuit, and when a predetermined time has elapsed after the EL element of the 1-bit EL circuit has emitted light, the reset signal is output to the reset unit of the 1-bit EL circuit. A signal control device characterized by being set. 3. A signal control apparatus according to claim 1, wherein the active EL matrix are those having a switch which is controlled in accordance with the connection between said driving power source the EL element to the control signal, the latch signal According to the output timing,
The drive power supply and the EL are only used during the period for driving the L element.
A signal control device for outputting the control signal for connecting a device to the switch to the switch. 4. The signal control device according to claim 2, wherein the signal for controlling the data writing unit includes a plurality of signals.
A signal control device for outputting to a bit EL circuit at different timings. 5. The signal control device according to claim 4, wherein the reset signal is also used as a signal for controlling the data writing unit for a 1-bit EL circuit different from the 1-bit EL circuit to which the reset signal is input. A signal processing device characterized by the above-mentioned. 6. The signal control device according to claim 2, wherein a phase difference between a signal for controlling the data writing unit and the drive power supply is controlled so as to be constant between the plurality of 1-bit EL circuits. A signal processing device characterized in that: 7. The signal control device according to claim 1, wherein the active EL matrix has a switch for controlling connection between the driving power supply and the EL element according to a control signal , and the one-bit EL matrix. in the period which respect the circuit writes the data signal, a control signal for disconnecting the said EL element said driving power source, a signal control device and outputs to the switch. 8. A light emitting device comprising: the signal control device according to claim 1; and the active EL matrix driven and controlled by the signal control device.