JP2003234181A - Display equipment and driving method of display equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide display equipment which performs monochromatic luminescence display that can adjust luminescent intensity without reducing display quality. <P>SOLUTION: To a display panel 11 which performs a white luminescence display using organic EL elements 12 as pixels constituted by laminating two emitter layers 16 and 17, a display control section 19 performs attenuated display by performing PWM control without changing driving voltage level impressed to each EL elements 12. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for displaying light of a single color by using an organic EL element as a pixel, and a driving method of the display device.

[0002]

2. Description of the Related Art FIG. 11 shows a driving method of a display panel using a conventional organic EL element. In the display panel 1,
A plurality of EL elements 2 indicated by diode symbols are arranged in a matrix at intersections of a plurality of anode lines 3 (1) to 3 (m, for example 256) and a plurality of cathode lines 4 (1) to 4 (n, for example 64). It is located in.

Then, either the anode line 3 or the cathode line 4 (for example, the cathode line 4) is scanned by the scan switch 5 at a constant cycle.
(1) to 5 (n) are switched to perform scanning so as to be sequentially connected to the ground, and the other (for example, anode line 3) drive switches 6 (1) to 6 (m) are switched in synchronization with the scanning cycle. By sequentially connecting to the current sources 7 (1) to 7 (n), the EL element 2 at an arbitrary intersection position is caused to emit light. The scan switches 5 (1) to 5 (n) are configured as a scan driver IC 9, and the drive switch 6
(1) to 6 (m) and the current sources 7 (1) to 7 (m) are configured as a signal driver IC8.

For example, when the EL element 2 (1,1) and the EL element 2 (1,2) are caused to emit light, the scanning switch 5 (1) is switched to the ground side as shown in FIG. The cathode line 4 (1) is set to the ground potential, and the drive switches 6 (1) and 6 (2) are connected to the current sources 7 (1) and 7 (7).
Drive switch 6 (3) ~ while switching to the (2) side
6 (256) is switched to the ground side. Then EL
The drive current is supplied only to the elements 2 (1,1) and 2 (1,2) to emit light.

Such a scan switch 5 and a drive switch 6
The EL element 2 at an arbitrary position is caused to emit light by repeating the above switching at high speed, and the human eye visually recognizes that the plurality of EL elements 2 are emitting light at the same time, thereby displaying the image data on the display panel 1. I have to. Further, the reverse bias voltage Vcc having the same potential as the power supply voltage is applied to the non-selected cathode lines 4 (2) to 4 (64) to prevent the other EL elements 2 from erroneously emitting light.

[0006]

When adjusting the brightness of the display panel configured as described above, the setting is made by changing the setting of the output current value of the current source 7 in the signal driver IC 8. ing. For example, EL
Element 2 (1,1) (denoted as E (1,1) in FIG. 12)
12B, the voltage level of the control signal A1 to be output to the current source 7 (1) of the signal driver IC 8 is individually set inside the dimming state shown in FIG. 12B as compared with the normal state shown in FIG. 12A. To V2. That is, a voltage below the voltage threshold value at which the current source 7 (1) is in the constant current output state is applied.

Further, for example, as shown in FIG.
Even when the elements 2 (1,1) to 2 (3,1) are displayed in gradation, the voltage levels of the control signal A1 are also sequentially changed to V2, V.
It is done by reducing it to 3.

However, according to the experiments conducted by the inventors of the present invention, it was confirmed that the luminescence chromaticity of the organic EL element changes when the voltage applied to the element (terminal voltage of the element) changes. . The state of the change is shown in FIG. That is, as the applied voltage changes, the coordinate value of the chromaticity coordinate (X, Y) changes.

Here, in a display device using an organic EL element, a plurality of light emitting layers of organic EL elements having different emission colors are stacked to obtain a single emission color which cannot be obtained by emission of only one layer. Some are configured as follows. In the display device configured as described above, the desired emission color cannot be obtained unless the emission color of each layer is accurately controlled.

Therefore, in the display device having the above structure, when the voltage applied to the element is changed in order to adjust the emission brightness, the emission chromaticity in each layer is changed and the balance is lost, and the emission color of the display device is largely changed. Therefore, there arises a problem that the display quality is deteriorated.

Further, in the case where a single color light emitting display is performed by using an organic EL element having a single light emitting layer as a pixel, the light emitting position in the single light emitting layer is changed, for example, by changing the applied voltage. It was confirmed that the light interference position was changed by changing to the anode side and the cathode side, and accordingly the luminescence chromaticity was changed, and the same problem as in the case of stacking light emitting layers having different luminescent colors occurs.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a display device for performing single-color light emission display in which the light emission brightness can be adjusted without degrading the display quality, and the display thereof. It is to provide a driving method of the device.

[0013]

According to the display device of the present invention, in a structure in which an organic EL element is used as a pixel to perform light emission display of a single color, when the brightness setting of the light emission display is changed, the organic EL element is changed. By setting the drive voltage level applied to the element within a predetermined range, the visually recognized luminescent display color does not change. According to this structure, it is possible to change the setting of the light emission brightness while maintaining the light emission display color that is visually recognized without being changed, so that it is possible to prevent the display quality from being degraded.

According to the display device of the second aspect, when at least a part of the plurality of display areas have different sizes, the drive voltage level applied to each element is kept within a predetermined range. Make sure that the emission color recognized by does not change. That is, even when adjusting so that the light emission luminances of a plurality of display areas of different sizes are almost the same, the same problem as in the case of adjusting the light emission luminance occurs when the applied voltage level is changed. To do. Therefore, also in this case, if the drive voltage level applied to the organic EL element is maintained within a predetermined range,
It is possible to perform the brightness adjustment in a state where the visually recognized luminescent display color is maintained without being changed.

According to the display device of claim 3, the organic E
The L element is formed by stacking a plurality of light emitting layers. That is, by stacking a plurality of light emitting layers that emit light with different chromaticities, it may be possible to easily obtain a certain single emission color. Further, in such a configuration, it is necessary to adjust the emission chromaticity of each light emitting layer to fall within a predetermined range in order to obtain a desired emission color. Therefore, if adjustment is performed while maintaining the drive voltage level applied to each organic EL element within a predetermined range, it is possible to maintain the visually recognized luminescent display color without changing, and to reduce the display quality. Can be prevented.

According to the display device of claim 4, the organic E
The L element is composed of a single light emitting layer. That is, as described above, even in a configuration in which a single emission color is obtained with a single emission layer, the problem that the emission chromaticity changes when the applied voltage changes similarly occurs. Therefore, the present invention can be effectively applied to an organic EL device having a single light emitting layer.

According to the display device of the fifth aspect, the emission display color is white. That is, it has been clarified by sensory evaluation and the like that human vision is more likely to perceive a shift in chromaticity with respect to white than colors such as green, red, and blue. Therefore, if the present invention is applied to a display device that emits white light, it is possible to effectively prevent deterioration of display quality.

According to the display device of the sixth aspect, the luminescent display color has a chromaticity coordinate value of (0.25,0.25)-(0.25,0.45)-
The color corresponds to the range (0.40,0,40) − (0,40,0.25). That is, according to the sensory evaluation by the inventors, it was found that the human visual sense is extremely sensitive to the change in chromaticity with respect to white, which corresponds to the range of the chromaticity coordinate values. Sensitivity means that human eyes can easily perceive smaller chromaticity differences. Therefore, if the present invention is applied to a display device that uses white as an emission color within the range of the above coordinate values, it is possible to more effectively prevent the deterioration of display quality.

According to the display device of the seventh aspect, the predetermined range is set to a voltage corresponding to a chromaticity difference of 0.4 between the luminescent display colors. That is, according to the experiments by the inventors, it became clear that the difference in color can be recognized when the luminescence chromaticity changes 0.4 in the chromaticity coordinate value in human vision. Therefore, if the predetermined range of the voltage applied to the organic EL element is set to a voltage corresponding to the chromaticity difference of 0.4, it is possible to prevent the viewer of the display from perceiving the change in the emission chromaticity.

According to the display device of claim 8, the organic E
Since the dimming display is performed by PWM-controlling the drive voltage applied to the L element, the dimming is performed without changing the chromaticity of the light emission by changing the pulse width of the voltage waveform while making the amplitude of the applied voltage substantially the same. It can be adjusted to display.

According to the display device of claim 9, the organic E
Since gradation display is performed by PWM-controlling the drive voltage applied to the L element, it is possible to perform gradation display without changing the emission chromaticity, as in the eighth aspect.

According to the display device of the tenth aspect, since the dimming display is performed by controlling the drive voltage applied to the organic EL element by PFM control, the amplitude of the applied voltage is made substantially the same and the frequency of the voltage pulse is changed. By doing so, it is possible to perform adjustment so as to perform dimming display without changing the emission chromaticity.

According to the display device of the eleventh aspect, since gradation display is performed by controlling the drive voltage applied to the organic EL element by PFM, the emission chromaticity can be changed in the same manner as in the tenth aspect. It is possible to adjust so that gradation display may be performed without using.

According to the display device of the twelfth aspect, the drive voltage applied to each of the organic EL elements forming both the dot matrix type display area and the segment type display area is PWM-controlled to have a PWM duty. Control so that they are almost the same.

That is, generally, the pixels forming the dot matrix type display area and the pixels forming the segment type display area have relatively large light emitting display areas, but the PWM duty is increased in accordance with the difference in the area. If it is changed, the applied voltage is different, and the chromaticity of light emission is affected to some extent. Therefore, in such a configuration,
The display quality can be maintained by controlling the PWM duty of the voltage applied to the both to be substantially equal to each other so that the emission chromaticities of the both are substantially equal.

According to the display device of the thirteenth aspect, in the structure having both the dot matrix type display region and the segment type display region, the dimming display is performed by changing the PWM duty. The dimming display can be controlled while maintaining the same degree.

According to the display device of the fourteenth aspect, the number of constant current sources of the drive circuit connected to the segment type display area is the same as the number of constant current sources connected to the dot matrix type display area. More than. As described above, since the pixel areas of the two are largely different, the set amount of the drive current is also significantly different accordingly. Therefore, in order to supply the drive current by one current source, it is necessary to increase the variable range of the current.

Therefore, for example, a plurality of constant current sources having substantially the same set current value are prepared, one is connected to the dot matrix type pixel, and a plurality of constant current sources is connected to the segment type pixel. By doing so, the amount of drive current can be easily adjusted. Further, as a result, the structure of the drive circuit is simplified, so that the cost can be reduced.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment in which the present invention is applied to a display device used for an instrument panel of a vehicle will be described below with reference to FIGS. 1 to 5. . The same parts as those in FIG. 11 are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described below. As shown in FIG. 1, the display panel 1 according to the present embodiment.
Reference numeral 1 is a dot matrix type similar to the display panel 1, and instead of the EL element 2, two light emitting layers of blue and yellow respectively are stacked so that the total light emitting color becomes white. The organic EL element 12 configured as described above is arranged.

FIG. 2 shows a schematic structure of the EL element 12. The EL element 12 includes a cathode 13 and an anode 14,
The electron injection layer 15, the blue light emitting layer 16, the yellow light emitting layer 17, and the hole injection layer 18 are laminated. The blue light emitting layer 16 and the yellow light emitting layer 17 are EL layers that emit blue light and yellow light, respectively, when a voltage is applied between the cathode 13 and the anode 14. The electron injection layer 15 and the hole injection layer 18 are layers composed of an organic compound similar to EL, and efficiently inject electrons and holes into the light emitting layers 16 and 17 when a voltage is applied. It is arranged for the purpose of doing.

Further, in FIG. 3, the applied voltage [V] to the EL element 12 and the light emission luminance [Cd / of the light emitting layers 16 and 17].
m ² ]. In this figure, the emission brightness of each of the light emitting layers 16 and 17 rises with different curves as the applied voltage rises. When the blue: red ratio is in the range of approximately 1: 4 to 1: 2, the color obtained by combining the two emission colors is recognized as white by human vision.

The EL element 12 is applied to each layer so that, when a voltage is applied between the cathode 13 and the anode 14, the emission color synthesized by the emission luminance ratio of the two becomes an optimum white color. Voltage ratio is adjusted in advance (for example,
By changing the thickness of each layer).

Here, the chromaticity coordinates are shown in FIG.
In the chromaticity coordinate, white, which is the emission color of the element 12,
(0.25,0.25) − (0.25,0.45) − (0.40,0,40) − (0,40,0.
It is white that belongs to the area of 25). According to the sensory evaluation by the inventors, it has been found that human vision is extremely sensitive to chromaticity change with respect to white, which corresponds to the above range of chromaticity coordinate values. Sensitivity means that human eyes can recognize the image as pure white. Therefore, the display panel 11 is adjusted by emitting white light within the range of the coordinate values. Thus, it becomes possible to display a very high quality white color.

The display panel 11 has a signal driver IC on the basis of a display signal and a dimming command signal provided from the outside.
8 and the scan driver IC 9 control signals A1 to A256, B
A display control unit 19 that outputs 1 to B64 is connected.
A PWM control signal is output to the former. A display device 20 is configured by the display panel 11, the driver ICs 8 and 9, and the display control unit 19.

Next, the operation of this embodiment will be described with reference to FIG. In FIG. 5, the display control unit 19 displays the driver I
It is a timing chart which shows a part of control signal output to C8 and C9. Each of the control signals B1 to B64 is 1
The signals are output to the scan driver IC 9 so as to sequentially become low level in the frame, and the cathode lines 4 (1) to 4 (64)
Are sequentially set to the ground level one by one.

On the other hand, the control signals A1 to A256 are 256 on each cathode line (scanning line) 4 according to the image data signal.
By outputting to the drive driver IC 8 one of the EL elements 12 corresponding to the element 12 to emit light, the corresponding anode line (signal line) 3 (1) to 3 (25) is output.
6) is supplied with the drive current of the current source 7.

For example, "first line (cathode line 4 (1))"
In the "selection" period, only the control signal B1 is at a low level, and the EL element 12 (1,1) on the cathode line 4 (1) is caused to emit light. Therefore, the control signal A1 is at a high level. Next "second line" In the "selection" period, only the control signal B2 is at the low level, and the EL element 2 (1,1) is not emitting light, so the control signal A1 is at the low level.

FIG. 5 (a) shows a case where the vehicle travels during a daytime when the surroundings are bright, for example, when the dimming display of the display panel 11 is not performed normally, and FIG. 5 (b) shows the surroundings. Is when the vehicle is driving during a dark night time,
This is a case where the dimming display of the display panel 11 is performed. That is, a dimming command signal is given to the display controller 19 from, for example, a body ECU of the vehicle.

The display control section 19 compares the high level duty of the control signal A1 in FIG.
By reducing the high-level duty in (b), dimming display is performed. In this case, since the amplitude level of the voltage applied to the EL element 12 via the signal driver IC 8 is the same, the instantaneous luminance during the period in which the EL element 12 emits light becomes equal. Therefore, even when the dimming display is performed, the emission color of the display panel 11 does not change from white.

As described above, according to this embodiment, the organic EL element 12 is formed by stacking the two light emitting layers 16 and 17.
Display panel 11 for displaying white light emission by using as a pixel
On the other hand, the display control unit 19 performs the dimming display by performing the PWM control without changing the drive voltage level applied to each EL element 12. Therefore, the dimming display can be performed without changing the light emission display color of the display panel 11 which is visually recognized, and the deterioration of the display quality can be prevented.

Then, the emission display color of the display panel 11 is changed to
The chromaticity coordinate value is (0.25,0.25) − (0.25,0.45) − (0.40,0,4
0)-(0,40,0.25) The white color is used. That is, according to the sensory evaluation of the inventors, the present invention is applied to a white display corresponding to a range of chromaticity coordinate values at which human vision is most sensitive to a shift in chromaticity change. can do.

(Second Embodiment) FIG. 6 shows a second embodiment of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. explain. The configuration of the second embodiment is similar to that of the first embodiment,
A case where the display control unit 19 performs gradation display on the display panel 11 is shown.

For example, the EL element 12 of the display panel 11
Gradation display is performed for (1, 1), 12 (2, 1), 12 (3, 1). As shown in FIG. 6, the display control unit 19 sets the control signal A1 to the high level during the period in which the first, second, and third lines are selected, so that E
L elements 12 (1,1), 12 (2,1), 12 (3,
Make 1) emit light. At this time, by gradually reducing the PWM duty of the control signal A1, the EL element 12 (1,
Gradation display is performed so that the luminance gradually decreases from 1) to the EL element 12 (3, 1).

That is, by the PWM control, the voltage applied via the signal driver IC 8 becomes the same for any of the EL elements 12 (1,1) to 12 (3,1).
The instantaneous brightness during the period of light emission is the same,
The emission chromaticities are kept equal. And PW
By changing the M duty, the light emission luminance of each element 12 (which is visually recognized) is changed to realize gradation display.

As described above, according to the second embodiment, the drive voltage applied to the EL element 12 is PWM-controlled, so that gradation display can be performed without changing the emission chromaticity. .

(Third Embodiment) FIGS. 7 and 8 show a third embodiment of the present invention. The same parts as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Only the part will be described. In the configuration of the third embodiment, the dot matrix type display panel 11 part is used as a dot matrix display part (display region) 21, and the segment display part (display region) is composed of organic EL elements 22 for performing segment type display. Is added as the display panel 23. The display control unit 19 is not shown.

The signal driver IC 8A has an EL
A switch 6 (seg for supplying drive current to the element 22
) And a current source 7 (seg), and the scan driver IC 9 includes a switch 5 (seg). The display control section 19 also outputs a control signal Aseg for driving and controlling the EL element 22. The display device 24 is configured as described above.

Next, the operation of the third embodiment will be described with reference to FIG. In FIG. 8, the display control unit 19 has the EL element 1
3 is a timing chart of control signals when 2 (1,1) and the EL element 22 are caused to emit light at the same time. That is, the display control unit 19 sets the control signal A1 to the high level and also sets the control signal Aseg to the high level during the period in which the first line is selected.
1) and 22 are caused to emit light at the same time. At this time, the PWM duties of the control signals A1 and Aseg are made the same.

That is, although the EL element 12 (1, 1) and the EL element 22 have a relatively large light emitting display area, if the PWM duty is set to be greatly different depending on the area difference, both elements are displayed. Even if the applied voltage (pulse amplitude) is the same, the chromaticity of light emission is affected to some extent. Therefore, the PWM of the voltage applied to both
By controlling the duty to be the same, both emission chromaticities are made equal to maintain the display quality.

As described above, according to the third embodiment, the display control section 19 has the organic EL elements 12 (1, 1) forming the dot matrix display section 21 and the organic EL elements 22 forming the segment display section. On the other hand, the PWM duty of the drive voltage applied via the signal driver IC8 is controlled to be substantially the same. Therefore, even when the light emitting display areas are relatively different from each other, the emission chromaticities of the two can be made substantially equal to each other, and the display quality can be maintained.

(Fourth Embodiment) FIG. 9 shows a fourth embodiment of the present invention. The fourth embodiment is different in the output form of the control signal by the display control unit 19 when the dimming display is performed as in the first embodiment. For example, the EL element 12
When (1, 1) is made to continuously emit light, in the normal state shown in FIG. 9A, the control signal A1 is set to the same PW for each display cycle.
Output with M duty.

On the other hand, when the light is dimmed as shown in FIG.
The control signal A1 having the same M duty is output every three cycles. In this case, the emission brightness is about 1/3 of the normal brightness. That is, the display control unit 19 changes the output frequency of the control signal to perform the PFM control. Also in the case of the fourth embodiment configured as described above, the dimming display is performed with the same voltage level applied to the EL elements 12 (1, 1) through the signal driver IC 8 and maintaining the emission chromaticity. It can be performed.

(Fifth Embodiment) FIG. 10 shows a fifth embodiment of the present invention. The same parts as those in the third embodiment are designated by the same reference numerals and the description thereof will be omitted. Only the different parts will be described below. explain. In the fifth embodiment, the signal driver IC 8A in the configuration of the third embodiment is replaced with a signal driver IC 8B.

The signal driver IC 8B has three current sources 7 (seg1) to 7 (seg1) to 7 in the third embodiment.
It is configured as a replacement for (seg3). That is, in the current source 7 (seg) of the third embodiment, the drive current amount is different from that of the other current sources 7 (1) to 7 (7) depending on the light emitting area of the EL element 22.
It was necessary to set it to be larger than (256).

On the other hand, the drive current amounts of the current sources 7 (seg1) to 7 (seg3) in the fifth embodiment are the same as those of the other current sources 7.
It is possible to set a value closer to (1) to 7 (256). Then, these three current sources 7 (seg1) to 7
(Seg3) is commonly connected to the anode of the EL element 22 via the switches 6 (seg1) to 6 (seg3), respectively.

According to the fifth embodiment configured as described above, the number of current sources 7 of the signal driver IC 8B connected to the EL element 22 constituting the segment display portion constitutes the dot matrix display portion 21. The number of current sources 7 connected to the EL element 12 is increased.

Therefore, it becomes easy to adjust the drive current amount,
It is possible to more easily adjust the emission brightness between the EL element 12 and the EL element 22. Further, as a result, the configuration of the signal driver IC 8B is simplified, so that the cost can be reduced.

The present invention is not limited to the embodiments described above and shown in the drawings, and the following modifications or expansions are possible. The emission color of the organic EL element is not limited to the white color that belongs to the range of the chromaticity coordinate value as in the above-described embodiment, and may be a white color that is outside the range. The organic EL element is not limited to white, and can be applied to any organic EL element that displays a single color by stacking a plurality of light emitting layers that emit different colors. In the third embodiment, the PWM duty ratios for controlling the display of the EL element 12 and the EL element 22 do not necessarily have to be the same, and if the applied voltage levels are almost equal, the emission chromaticity is the same even if the duty ratios are slightly different. It is possible to make them recognize as Also,
According to the results of the sensory evaluation conducted by the inventors, it was found that the difference in color can be recognized when the luminescence chromaticity changes by about 0.4 in the chromaticity coordinate value with human vision. When the applied voltage corresponding to the coordinate value 0.4 is calculated from FIG. 12, it is about 4V.
Is. Therefore, the PWM duty ratio may be changed within the range in which the applied voltage difference corresponds to 4V. Alternatively, the predetermined range may be set to 4V and the applied voltage levels may be different.

The dot matrix display section and the segment display section are not necessarily formed on the same display panel. For example, both display sections are formed separately and are used in close proximity. Can be similarly applied. Further, it may be applied to one having a plurality of dot matrix display parts having different display sizes. For example,
When the 32 × 32 dot matrix display section and the 64 × 64 dot matrix display section are provided, if the duty ratios of the control signals to be output are set to 1/32 and 1/64, one pixel is provided for each pixel. Since the EL elements constituting the same are the same, the luminescent chromaticity of each display portion is different due to the different integral applied voltages. In such a configuration, the duty ratio is the same (for example, 1/64
If the duty ratio is changed, the emission chromaticity becomes the same.

Further, it may be applied to one having a plurality of segment display parts having different display sizes. You may apply to what laminates three or more light emitting layers. The display device is not limited to an instrument panel of a vehicle, and can be applied to any display device that uses an organic EL element that displays a single color by stacking a plurality of light emitting layers. In the above embodiment,
Although the display device using the organic EL element for displaying a single color by laminating a plurality of light emitting layers has been described, the present invention is also applied to a display device using an organic EL element for displaying a single color having a single light emitting layer. Can be applied. For example, when the applied voltage is changed for a single light emitting layer that emits green fermentation, the light emitting position in the light emitting layer changes, the light interference position changes, and the chromaticity of green changes. is there. Even with respect to such a problem, if the above-described display device configuration or display device driving method is applied, the driving voltage level applied to the organic EL element is maintained within a predetermined range, and thus the inside of the light emitting layer is maintained. It is possible to suppress the change in the light emitting position and the change in the emission chromaticity.

[Brief description of drawings]

FIG. 1 is a diagram showing an electrical configuration of a display device, which is a first embodiment when the present invention is applied to a display device used for an instrument panel of a vehicle.

FIG. 2 is a diagram showing a schematic configuration of an organic EL element.

FIG. 3 is a diagram showing the relationship between the applied voltage [V] to the organic EL element and the emission brightness [Cd / m ² ] of the blue and yellow light emitting layers.

FIG. 4 is a diagram showing chromaticity coordinates.

FIG. 5 is a timing chart showing a part of a control signal output to the driver IC by the display control unit, in which (a) shows a normal time and (b) shows a dimmed time.

FIG. 6 is a view corresponding to FIG. 5 showing a second embodiment of the present invention.

FIG. 7 is a view corresponding to FIG. 1 showing a third embodiment of the present invention.

FIG. 8 is a timing chart showing a part of a control signal output from a display control unit to a driver IC.

FIG. 9 is a view corresponding to FIG. 5 showing a fourth embodiment of the present invention.

FIG. 10 is a view corresponding to FIG. 1 showing a fifth embodiment of the present invention.

FIG. 11 is a view corresponding to FIG. 1 showing a conventional technique.

FIG. 12 is a view corresponding to FIG.

FIG. 13 is a view corresponding to FIG.

FIG. 14 is a diagram showing a state in which the emission chromaticity changes according to the voltage applied to the organic EL element (terminal voltage of the element).

[Explanation of symbols]

Reference numeral 7 is a current source (constant current source), 8, 8A and 8B are signal driver ICs (driving circuits), 11 is a display panel, and 12 is an organic E.
L element, 16 is a blue light emitting layer, 17 is a yellow light emitting layer, 19 is a display control unit, 20 is a display device, 21 is a dot matrix display unit (display area), 22 is an organic EL element (display area), and 23 is a display. A panel 24 is a display device.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 19, 2002 (2002.9.1)
9)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

3. A display device according to claim 1 or 2, wherein the light emitting display color is white.

Wherein said light emitting display color, chromaticity coordinates (0.25,
0.25)-(0.25,0.45)-(0.40,0.40)-(0.40,0.
25) The color corresponding to the range of 25)
The display device according to item 3 .

5. The voltage according to claim 1, wherein the predetermined range is a voltage corresponding to a chromaticity difference of 0.4 between luminescent display colors.
5. The display device according to any one of 4 to 4 .

6. The display device according to any one of claims 1 to 5, characterized in that the dimming display by the drive voltage applied to the organic EL element PWM (Pulse Width Modulation) control.

7. The driving voltage applied to the organic EL element by PWM control, the display device according to any one of claims 1 to 6, characterized in that the gradation display.

Wherein said organic EL device PFM (Pulse Frequency Modulation) drive voltage applied to that control, the display device according to any one of claims 1 to 5, characterized in that the dimming display.

9. The driving voltage applied to the organic EL element by the PFM control, the display device according to claim 1 to 5 or 8, characterized in that the gradation display.

10. A dot matrix type display area,
And a segment type display area, the drive voltage applied to the organic EL element constituting both the display area and PWM control, claims 1 to 9, wherein the controller controls so that the PWM duty is substantially identical The display device according to any one of 1.

11. A display device according to claim 10, characterized in that the dimming display by changing the PWM duty.

12. A drive circuit having a plurality of constant current sources and supplying a drive current to an organic EL element, wherein the number of constant current sources connected to the segment type display region is set to the dot matrix type. the claim 10 or <br/> other, characterized by more than the number of the constant current source connected to the display region display device according to 11.

13. A method for driving a display device that performs light-emitting display of single color by using an organic EL element as a pixel, in the case of changing the brightness setting of the light-emitting display, a driving voltage level applied to the organic EL device Within the specified range,
As the light emitting display color does not change to be visually recognized
The organic EL device emits light of different colors.
A method of driving a display device, which is configured by stacking a plurality of light emitting layers .

14. A method for driving a display device having a plurality of display areas by performing light-emission display of a single color by using an organic EL element as a pixel, the area size of at least a part of the plurality of display areas. Is different,
With the drive voltage level applied to the organic EL element being within a predetermined range, the luminescent display color visually recognized is not changed , and the organic EL element is different.
A method for driving a display device, comprising a plurality of light emitting layers that emit light of different colors .

15. A display device according to the luminous display color in claim 13 or 14, characterized in that white.

16. The luminescent display color has a chromaticity coordinate of (0.2
5,0.25)-(0.25,0.45)-(0.40,0.40)-(0.4
The driving method of the display device according to claim 15 , wherein the color is a color corresponding to a range of 0, 0.25).

The method according to claim 17, wherein the predetermined range, characterized by a voltage corresponding to the chromaticity difference 0.4 luminescent display color claim 1
17. The method for driving a display device according to any one of 3 to 16 .

18. The driving method of a display device according to any one of claims 13 to 17, characterized in that the dimming display by PWM controlling the drive voltage applied to the organic EL element.

19. By PWM control the drive voltage to be applied to the organic EL device, a driving method of a display device according to any one of claims 13 to 18, characterized in that the gradation display.

20. The method of claim 19, wherein the drive voltage applied to the organic EL element in this that the PFM control, the driving method of a display device according to any one of claims 13 to 17, characterized in that the dimming display.

21. By PFM control the drive voltage applied to the organic EL device, a driving method of a display device according to claim 13 or 17 or 20, characterized in that the gradation display.

And type of the display area of 22. dot matrix, the drive voltage applied to the organic EL element for both the respective configuration of a segment type display region PWM control, PWM
The driving method of a display device according to any one of claims 13 to 17 and controls so that the duty is approximately the same.

23. The method for driving a display device according to claim 22 , wherein dimming display is performed by changing the PWM duty.

24., characterized in that more than the number of the constant current source that connects the number of the constant current source of the driving circuit connected to the segment type display region, the display region of the dot-matrix The display device according to claim 22 or 23 .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Delete

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

According to the display device of the first or second aspect , the organic EL element is formed by laminating a plurality of light emitting layers.
That is, by stacking a plurality of light emitting layers that emit light with different chromaticities, it may be possible to easily obtain a certain single emission color. Then, in such a configuration, it is necessary to adjust the emission chromaticity of each light emitting layer to fall within a predetermined range in order to obtain an initial emission color. Therefore, if adjustment is performed while maintaining the drive voltage level applied to each organic EL element within a predetermined range, it is possible to maintain the visually recognized luminescent display color without changing, and to reduce the display quality. Can be prevented.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Delete

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

According to the display device of the third aspect , the emission display color is white. That is, it has been clarified by sensory evaluation and the like that human vision is more likely to perceive a shift in chromaticity with respect to white than colors such as green, red, and blue. Therefore, if the present invention is applied to a display device that emits white light, it is possible to effectively prevent deterioration of display quality.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

According to the display device of the fourth aspect , the luminescent display color has a chromaticity coordinate of (0.25, 0.25)-(0.2
(5,0.45)-(0.40,0.40)-(0.40,0.25) That is, according to the sensory evaluation by the inventors, it was found that the human visual sense is extremely sensitive to the change in chromaticity with respect to white, which corresponds to the range of the chromaticity coordinate values. The sensitivity being sensitive means that it is easy for humans to perceive a smaller chromaticity difference. Therefore, if the present invention is applied to a display device that uses white as an emission color within the range of the above coordinate values, it is possible to more effectively prevent the deterioration of display quality.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

According to the display device of the fifth aspect , the predetermined range is set to a voltage corresponding to a chromaticity difference of 0.4 between the emission display colors. That is, according to the experiments conducted by the present inventors, it has been clarified that a human sense can recognize a color difference when the emission chromaticity changes by 0.4 in the chromaticity coordinate value. Therefore, if the predetermined range of the voltage applied to the organic EL element is set to a voltage corresponding to the chromaticity difference of 0.4, it is possible to prevent the viewer of the display from recognizing the change in the emission chromaticity.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

According to the display device of claim 6 , the organic E
Since the dimming display is performed by PWM controlling the drive voltage applied to the L element, the dimming is performed without changing the emission chromaticity by changing the pulse width of the voltage waveform while making the amplitude of the applied voltage substantially the same. It can be adjusted to display.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

According to the display device of claim 7 , the organic E
Since gradation display is performed by PWM controlling the drive voltage applied to the L element, it is possible to perform gradation display without changing the emission chromaticity in the same manner as in claim 6 .

[Procedure Amendment 10]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

According to the display device of claim 8 , the organic E
Since the dimming display is performed by controlling the drive voltage applied to the L element by PFM control, the dimming display is performed without changing the emission chromaticity by changing the frequency of the voltage pulse while making the amplitude of the applied voltage substantially the same. Can be adjusted to do.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

According to the display device of claim 9 , the organic E
Since gradation display is performed by controlling the drive voltage applied to the L element by PFM control, it is possible to perform gradation display without changing the emission chromaticity in the same manner as in claim 8 .

[Procedure Amendment 12]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

According to the display device of the tenth aspect, the drive voltage applied to each of the organic EL elements forming both the dot matrix type display area and the segment type display area is PWM-controlled to have a PWM duty. Control so that they are almost the same.

[Procedure Amendment 13]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

According to the display device of the eleventh aspect , in the structure including both the dot matrix type display region and the segment type display region, the dimming display is performed by changing the PWM duty. The dimming display can be controlled while maintaining the same degree.

[Procedure Amendment 14]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

According to the display device of the twelfth aspect, the number of constant current sources connected to the segment type display region is larger than the number of constant current sources connected to the dot matrix type display region. To do. As described above, since the pixel areas of the two are largely different, the set amount of the drive current is also significantly different accordingly. Therefore, in order to supply the drive current by one current source, it is necessary to increase the variable range of the current.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/30 G09G 3/30 K H05B 33/12 H05B 33/12 C 33/14 33/14 A (72 ) Inventor Tomohiro Kuno 1-1, Showa-cho, Kariya city, Aichi, DENSO Co., Ltd. (72) Inventor Masaaki Ozaki 1-1-Cho, Showa-cho, Kariya city, Aichi F-term (reference) 3K007 AB02 AB04 BA00 BA06 DA06 DB03 GA04 5C080 AA06 BB02 BB05 DD03 EE30 JJ02 JJ04 JJ05 5C094 AA07 AA08 BA11 BA27 CA14 CA19 CA23 DA13 FB01 FB20 GA10 JA11

Claims (28)

[Claims] 1. A display device for performing single-color light emission display by using an organic EL (Electro Luminescence) element as a pixel, wherein a drive voltage level applied to the organic EL element is changed when the brightness setting of the light emission display is changed. Within the specified range,
A display device, characterized in that the color of light emitted and recognized visually is not changed. 2. A display device having a plurality of display areas for performing light emission display of a single color by using an organic EL (Electro Luminescence) element as a pixel, wherein the size of the area is at least part of the plurality of display areas. Different from each other, the display device is configured so that the luminescent display color visually recognized does not change in a state where the drive voltage level applied to the organic EL element is within a predetermined range. 3. The display device according to claim 1, wherein the organic EL element is formed by stacking a plurality of light emitting layers. 4. The organic EL device according to claim 1, wherein the organic EL device has a single light emitting layer.
Display device described. 5. The display device according to claim 1, wherein the emission display color is white. 6. The luminescent display color has a chromaticity coordinate value of (0.25,
The display device according to claim 5, wherein the color is a color corresponding to a range of (0.25)-(0.25,0.45)-(0.40,0,40)-(0,40,0.25). 7. The predetermined range is a voltage corresponding to a chromaticity difference of 0.4 between luminescent display colors.
7. The display device according to any one of 6 to 6. 8. The display device according to claim 1, wherein dimming display is performed by performing PWM (Pulse Width Modulation) control of a drive voltage applied to the organic EL element. 9. The display device according to claim 1, wherein gradation display is performed by PWM-controlling a drive voltage applied to the organic EL element. 10. The display device according to claim 1, wherein dimming display is performed by controlling a drive voltage applied to the organic EL element by PFM (Pulse Frequency Modulation). 11. The display device according to claim 1, wherein gradation display is performed by performing PFM control of a drive voltage applied to the organic EL element. 12. A dot matrix type display area and a segment type display area are provided, and the drive voltage applied to the organic EL elements constituting both display areas is PWM-controlled so that the PWM duty is substantially the same. The display device according to claim 1, wherein the display device is controlled according to claim 1. 13. The display device according to claim 12, wherein the dimming display is performed by changing the PWM duty. 14. The organic EL device having a plurality of constant current sources,
A driving circuit for supplying a driving current to the element, wherein the number of constant current sources connected to the segment type display region is larger than the number of constant current sources connected to the dot matrix type display region. The display device according to claim 12, wherein: 15. A method of driving a display device for performing light emission display of a single color by using an organic EL element as a pixel, wherein a drive voltage level applied to the organic EL element is changed when the brightness setting of the light emission display is changed. Within the specified range,
A driving method of a display device, which is characterized in that the color of light emission which is visually recognized is not changed. 16. A method of driving a display device having a plurality of display areas by performing light emission display of a single color by using an organic EL element as a pixel, wherein the size of the area is at least part of the plurality of display areas. When the driving voltage level applied to the organic EL element is within a predetermined range, the luminescent display color visually recognized is not changed, and the driving method of the display device. 17. The organic EL element is formed by stacking a plurality of light emitting layers.
Or a method of driving the display device according to item 16. 18. The method of driving a display device according to claim 15, wherein the organic EL element has a single light emitting layer. 19. The driving method for a display device according to claim 15, wherein the display color of the display device is white. 20. The luminescent display color has a chromaticity coordinate value of (0.2
20. The method for driving a display device according to claim 19, wherein the color is a color corresponding to a range of (5,0.25)-(0.25,0.45)-(0.40,0,40)-(0,40,0.25). 21. The predetermined range is set to a voltage corresponding to a chromaticity difference of 0.4 between luminescent display colors.
21. The method for driving a display device according to any one of 5 to 20. 22. The method for driving a display device according to claim 15, wherein dimming display is performed by performing PWM control of a drive voltage applied to the organic EL element. 23. The display device driving method according to claim 15, wherein gradation display is performed by PWM-controlling a driving voltage applied to the organic EL element. 24. The method for driving a display device according to claim 15, wherein the dimming display is performed by performing PFM control of a drive voltage applied to the organic EL element. 25. The method for driving a display device according to claim 15, wherein gradation display is performed by performing PFM control of a drive voltage applied to the organic EL element. 26. An organic EL device that constitutes both a dot matrix type display region and a segment type display region, respectively.
22. The method for driving a display device according to claim 15, wherein the drive voltage applied to the element is PWM-controlled so that the PWM duty is substantially the same. 27. The method for driving a display device according to claim 26, wherein dimming display is performed by changing the PWM duty. 28. The number of constant current sources of the drive circuit connected to the segment type display area is larger than the number of constant current sources connected to the dot matrix type display area. 28. The method for driving a display device according to claim 26.