JP5604270B2 - Semiconductor device - Google Patents

Description

The present invention relates to a technology of a semiconductor integrated circuit and a driving method thereof. Further, the present invention relates to a light emitting device including a driving circuit portion including a semiconductor integrated circuit of the present invention and a pixel portion. In particular, the present invention relates to an active matrix light-emitting device in which a plurality of pixels are arranged in a matrix and a switching element and a light-emitting element are arranged in each pixel, in which the semiconductor integrated circuit of the present invention is adapted to a signal line driver circuit of a driver circuit portion. .

In recent years, research and development of a light-emitting device using a light-emitting element which is a self-light-emitting element has been advanced as a light-emitting device. These light-emitting devices are widely used as light-emitting devices when using a display screen of a mobile phone or a personal computer, taking advantage of high image quality, thinness, and light weight. In particular, light-emitting devices using light-emitting elements have features such as fast response speed, low voltage, and low power consumption that are suitable for moving image display, so new generation mobile phones and personal digital assistants (PDAs) A wide range of applications is expected, and it is attracting much attention as a next-generation display.

Organic light emitting diode (OLED) as one of the light emitting elements
And an organic compound layer is sandwiched between the anode, the cathode, and the anode and the cathode. This organic compound layer usually has a laminated structure, and a typical example is a laminated structure of “hole transport layer / light emitting layer / electron transport layer” proposed by Tang et al. Of Kodak Eastman Company.

When the light emitting element emits light, the semiconductor element that drives the light emitting element is formed of polysilicon (polycrystalline silicon) having a large on-state current. A polysilicon transistor formed of polysilicon is used as a semiconductor element for driving the light emitting element. The amount of current flowing through the light-emitting element and the luminance of the light-emitting element are in a directly proportional relationship, and the light-emitting element emits light with luminance according to the amount of current flowing through the organic compound layer.

By the way, as a driving method for displaying a multi-gradation image on a light emitting device using a light emitting element, an analog gradation method (analog driving method) and a digital gradation method (digital driving method) can be given. The difference between the two systems is in the method of controlling the light emitting element in each of the light emitting and non-light emitting states of the light emitting element. The former analog gradation method is a method of obtaining gradation by controlling the current flowing through the light emitting element in an analog manner. The latter digital gradation method is a method in which the light emitting element is driven only in two states: an on state (a state where the luminance is approximately 100%) and an off state (a state where the luminance is approximately 0%). .

Moreover, it can classify | categorize according to the kind of signal input into the light-emitting device using a light emitting element, The electric current input system is proposed as one of them. This current input method is said to be able to control the magnitude of the current flowing through the light emitting element regardless of the characteristics of the TFT driving the light emitting element.

As the current input method, both the analog gradation method and the digital gradation method described above are applied.
The current input method is a method in which the video signal input to the pixel is a current, and the luminance of the light emitting element is controlled by flowing a current corresponding to the input video signal (current) to the light emitting element.

Here, an example of a circuit configuration of a pixel to which a current input method is applied in a light-emitting device and a driving method thereof will be briefly described with reference to FIGS. The pixel shown in FIG. 14 includes a signal line 1401,
First to third scanning lines 1402 to 1404, a power supply line 1405, and transistors 1406 to 14
09, a capacitor 1410, and a light-emitting element 1411. The current source circuit 1412 is provided on the signal line.

The gate electrode of the TFT 1406 is connected to the first scan line 1402, the first electrode is connected to the signal line 1401, and the second electrode is the first electrode of the TFT 1407, the first electrode of the TFT 1408, and the TFT 1409. Connected to the first electrode. The gate electrode of the TFT 1407 is connected to the second scanning line 1403, and the second electrode is connected to the gate electrode of the TFT 1408. A second electrode of the TFT 1408 is connected to the current line 1405. A gate electrode of the TFT 1409 is connected to the third scanning line 1404, and a second electrode is connected to one electrode of the light emitting element 1411. The capacitor element 1410 is connected between the gate electrode and the second electrode of the TFT 1408 and holds the gate-source voltage of the TFT 1408. A predetermined potential is input to each of the current line 1405 and the cathode of the light emitting element 1411, and has a potential difference from each other.

Next, operations from video signal writing to light emission will be described. First, a pulse is input to the first scan line 1402 and the second scan line 1403, so that the transistors 1406 and 14.
07 turns on. At this time, the signal current flowing through the signal line 1401 is I _data, and I _data is supplied from the current source circuit 1412.

At the moment when the transistor 1406 is turned on, since the charge is not held in the capacitor 1410, the transistor 1408 is turned off. That is, during this period, the capacitive element 14
Only current due to charge accumulation at 10 is flowing.

After that, electric charges are gradually accumulated in the capacitor element 1410, and a potential difference starts to occur between both electrodes.
When the potential difference between the two electrodes becomes the threshold voltage Vth of the TFT 1408, the transistor 1408
Is turned on and a current is generated. At this time, the current flowing through the capacitor 1410 gradually decreases, but the current still flows, and charge is accumulated in the capacitor 1410.

In the capacitor element 1410, the potential difference between the two electrodes, that is, the voltage between the gate and the source of the transistor 1408 becomes a desired voltage, that is, a voltage (V _GS ) that allows the transistor 1408 to flow the current I _data . Accumulation continues. When the accumulation of electric charge is finished, the current I _data continues to flow through the transistor 1408. Thus, the signal writing operation is completed. Finally, selection of the first scan line 1402 and the second scan line 1403 is completed, and the transistors 1406 and 1407 are turned off.

Subsequently, the light emission operation is started. A pulse is input to the third scan line 1404 and the transistor 1
409 turns on. Since V _GS written earlier is held in the capacitor 1410, the transistor 1408 is on and current flows from the power supply line 1405. Accordingly, the light emitting element 1411 emits light. At this time, if the transistor 1408 operates in the saturation region, even if the voltage between the source and drain of the transistor 1408 changes, the light emission current I _EL flowing through the light emitting element 1411 can flow without changing from I _data. .

As described above, in the current input method, a drain current having a current value that is the same as or proportional to the signal current set by the current source circuit 1412 flows between the source and drain of the transistor 1408, and the luminance corresponding to the drain current is determined. The light-emitting element 1411 emits light. By using the pixel as described above, it is possible to supply a desired current to the light emitting element while suppressing the influence of variation in characteristics of TFTs constituting the pixel. In addition, the current input type pixel circuit
US 6,229,506B1 and JP-A-2001-147659.

In a light emitting device to which a current input method is applied, it is necessary to accurately input a signal current corresponding to a video signal to a pixel. However, a drive circuit responsible for inputting a signal current to the pixel (FIG. 1).
4 corresponds to the current source circuit 1412. ) Is formed of a polysilicon transistor, resulting in variations in characteristics due to defects in the crystal growth direction and grain boundaries, non-uniformity of the laminated film thickness and patterning accuracy of the film. As a result, the displayed image becomes uneven.

That is, in a light-emitting device to which a current input method is applied, it is necessary to suppress the influence of variation in characteristics of transistors included in a driver circuit that inputs a signal current to a pixel. That is, it is necessary to suppress the influence of the characteristic variation of the transistors constituting both the pixel and the drive circuit. That is, since the polysilicon transistor has a large variation, it is difficult to generate an accurate signal current, and the display becomes full of vertical stripes.

The present invention has been made in view of the above problems. Therefore, the present invention provides a semiconductor integrated circuit and a method for driving the semiconductor integrated circuit that suppresses the influence of variation in transistor characteristics in each current source of the current source circuit and is not affected by the characteristics of the transistor. In addition, a light-emitting device including a driving circuit portion including a semiconductor integrated circuit of the present invention and a pixel portion is provided. In particular, an active matrix light-emitting device in which a plurality of pixels are arranged in a matrix and a switching element and a light-emitting element are arranged in each pixel, in which the semiconductor integrated circuit of the present invention is adapted to a signal line driver circuit of a driver circuit portion. provide. In addition, the present invention provides a light-emitting device in which elements of a pixel portion and a drive circuit portion are formed of polysilicon thin film transistors, and the pixel portion and the drive circuit portion are integrally formed on the same substrate.

Note that the current source circuit includes one or more current sources, and the current source includes one or more transistors. In addition, a current source that supplies a constant current may be called a constant current source.

The semiconductor integrated circuit according to the present invention includes a signal line, a current source circuit that outputs a current input to the signal line, and a means for switching the current source circuit connected to the signal line at regular intervals (hereinafter simply switched). The switching means includes a plurality of circuits having a switching function, and is also referred to as a switching circuit).

According to the present invention, it is possible to provide a semiconductor integrated circuit and a method for driving the semiconductor integrated circuit, in which the influence of variation in transistor characteristics in the current source circuit is suppressed and the characteristics of the transistors are not affected. In addition, a light-emitting device including a driver circuit portion including a semiconductor integrated circuit of the present invention and a pixel portion can be provided. In particular, an active matrix light-emitting device in which a plurality of pixels are arranged in a matrix and a switching element and a light-emitting element are arranged in each pixel, in which the semiconductor integrated circuit of the present invention is adapted to a signal line driver circuit of a driver circuit portion. Can be provided. In addition, the present invention can provide a light emitting device in which elements of a pixel portion and a drive circuit portion are formed of polysilicon thin film transistors, and the pixel portion and the drive circuit portion are integrally formed on the same substrate.

1 is a diagram showing a configuration of a semiconductor integrated circuit of the present invention. 1 is a diagram showing a configuration of a semiconductor integrated circuit of the present invention. 1 is a diagram showing a configuration of a semiconductor integrated circuit of the present invention. FIG. 9 is a timing chart of the signal line driving method of the present invention. 1 is a diagram showing a configuration of a semiconductor integrated circuit of the present invention. 1 is a diagram showing a configuration of a semiconductor integrated circuit of the present invention. The figure which shows the structure of the switching means of the semiconductor integrated circuit of this invention. 1 is a diagram showing a configuration of a semiconductor integrated circuit of the present invention. 1 is a diagram showing a configuration of a semiconductor integrated circuit of the present invention. 1 is a diagram showing a configuration of a semiconductor integrated circuit of the present invention. FIG. 9 is a timing chart of the signal line driving method of the present invention. FIG. 6 illustrates a structure of a light-emitting device of the present invention. The figure which shows the structure of the semiconductor integrated circuit of this invention FIG. 6 is a circuit diagram of a pixel of a light-emitting device. FIG. 11 illustrates an electronic device to which a light-emitting device of the present invention is applied.

The switching means of the present invention switches the current source circuit connected to the signal line even if the current output from the current source circuit varies, and accordingly, the current input to the signal line switches at regular intervals. Therefore, the current flowing through the light-emitting element, that is, the luminance appears to be uniform in time, display unevenness can be eliminated, and a light-emitting device that is not affected by variations in transistor characteristics can be provided.

(Embodiment 1)
An outline of a signal line driver circuit which is a semiconductor integrated circuit of the present invention will be described with reference to FIG.
For the sake of clarity in FIG. 6, three current sources C (i) and C (i + 1) in the current source circuit are shown.
, C (i + 2) and the signal line S (m) for supplying current to the pixel will be described. Current source C (
i), C (i + 1), C (i + 2) and signal line S (m)
Are connected via switching means. By this switching means, three current sources C (i) to
It is characterized in that currents I (i) to I (i + 2) supplied from C (i + 2) are switched at regular intervals and input to the signal line S (m).

Next, the switching means will be described. FIG. 7 shows the configuration of the switching means.
Current sources C (i), C (i + 1), and C (i + 2) are current I (i)
, I (i + 1), I (i + 2) flows. And current sources C (i), C (
i + 1) and C (i + 2) are provided so as to be connected to the signal line S (m) through a switch. A signal is input to the switch, and in response to this signal, the switch uses the signal line S (m).
Has a function of switching to be connected to any one of the current sources C (i), C (i + 1), and C (i + 2).

When this switch is connected to the current source C (i), a current I (i) flows to the signal line S (m). When the switch is connected to the current source C (i + 1), the current I (i +) is supplied to the signal line S (m).
1) flows. When the switch is connected to the current source C (i + 2), the current I (i + 2) flows to the signal line S (m). That is, the current flowing through the signal line S (m) is I (i), I (
i + 1) and I (i + 2) switch and flow.

The example described with reference to FIGS. 6 and 7 focuses on one signal line for the sake of clarity, but a plurality of actual signal lines are provided as shown in the following embodiments. Although the switch of the switching means in FIG. 7 is described as having a terminal, actually, as shown in the following embodiment, a switching function is provided by a circuit such as an analog switch.

In the present invention, since the switching period within this fixed period is very short, even if the characteristics of the current source are different, that is, the current supplied from the current source varies, the display appears uniform to the human eye.

Therefore, according to the present invention, a semiconductor integrated circuit including a current source circuit that is not affected by the characteristics of the transistor can be obtained by the switching means as described above. In addition, a light-emitting device that can supply a desired signal current to the light-emitting element and has no display variation is provided.

Further, when generalizing the present invention using a function, m signal lines S ₁ of the present, S _2, · · ·, and S _m, i current sources C _1, C _2, · · ·, and C _i , And a switching means including _n switching units U ₁ , U ₂ ,..., U _n , each of the n switching units including the i switching units. It is connected to j current sources among the current sources, and M
Th of the signal lines S _M is connected to the N-th of the switching unit U _N, the switching unit U _N is F ₁ satisfying the function _{F k (x) (k =} 1~j, x = 1~n) ( N) th current source,
The F ₂ (N) th current source, the F ₃ (N) th current source,..., And the F _j (N) th current source are characterized.

The present invention also includes m signal lines S ₁ , S ₂ ,..., S _m and i current sources C ₁ , C ₂ ,.
A semiconductor integrated circuit having a current source circuit having C _i and switching means including _n switching units U ₁ , U ₂ ,..., U _n , wherein the n switching units are Each of the i current sources is connected to j current sources, the Mth signal line S _M is connected to the _Nth switching unit _UN, and the switching unit _UN has a function F _k (x ) (K =
1 to j, x = ₁ to n) satisfying F ₁ (N) th current source, F ₂ (N) th current source, F ₃ (
N) th current source,..., F _j (N) th current source, and the (M−1) th signal line S _M-1 is connected to the (N−1) th switching unit U. _The switching unit U _N-1 is connected to _N-1 and the F ₁ (N-1) th current source, F ₂ (N-1) th current source, F ₃ (N-1) satisfying the function ,..., F _j (N−1) th current source.

The present invention can also share a current source between adjacent switching units. Expressing this using the above function, for example, when i = 3, the current source is F3 (N) = F2 (N + 1) =
F1 (N + 2). That is, Nth, N + 1th, N + of adjacent switching units
Secondly, the current source can be shared. As another example, when i = 5 is satisfied, the current source is F5 (N) = F4 (N + 1) = F3 (N + 2) = F4 (N + 3) = F5 (N + 4), and the Nth, N + 1 of the adjacent switching units Th, N + 2nd, N + 3rd, N +
The current source can be shared at the fourth place.

Thus, since the present invention can share a current source in each switching unit, there is no boundary between a certain signal line and an adjacent signal line, and all signal lines are averaged in the same way. As a result, a boundary is not generated in any part of the display screen, and a light-emitting device free from display streaks and uneven brightness can be provided.

Note that the present invention solves variations in characteristics of elements used in a semiconductor integrated circuit, and even an element other than a polysilicon transistor, for example, a single crystal that is desired to control variation in element characteristics. The same effect can be obtained even with a silicon transistor.

In this embodiment, a structure and a driving method of a current source circuit included in a signal line driver circuit will be specifically described by applying the semiconductor integrated circuit of the present invention to a signal line driver circuit of a driver circuit portion.

A specific example of the present invention is shown in FIG. In this embodiment, an example in which the current source is composed of an N-channel transistor will be described. The polarity of the transistor may be either n-channel or p-channel, and is generally determined by the polarity of the pixel. That is, the polarity when the current flows from the pixel to the current source circuit is preferably N-type, and the polarity when the current flows from the current source circuit toward the pixel is preferably P-type. This is because it is more convenient that the source potential of the transistor is fixed.

Referring to FIG. 1, transistors Tr (i) to T constituting current sources C (i) to C (i + 5).
r (i + 5), switching means, and signal lines S (m) to S (m + 5). The gate electrodes of the transistors Tr (i) to Tr (i + 5) are connected to the current control line, and since they are N-channel type, the source electrode is connected to Vss. The current value is controlled by the voltage applied to the current control line.

Here, for the sake of simplicity, the same current control line is connected to the gate electrodes of Tr (i) to Tr (i + 5). However, a current control line is provided for each transistor, and the voltage of the current control line is changed. The current value may be changed. However, in this case, since the output destination of the current of each transistor is switched, it is necessary to switch the voltage applied to each current control line accordingly.

At this time, if the characteristics of the transistors Tr (i) to Tr (i + 5) are uniform, the current I (i)
The values of ~ I (i + 5) are equal. However, in reality, the transistor Tr (i)
The variation in characteristics of .about.Tr (i + 5) is large, and the values of currents I (i) to I (i + 5) also vary. However, the currents I (i) to I input to the signal line by the switching means of the present invention.
(I + 5) can be selected and switched at regular intervals.
Therefore, the current flowing through the light emitting element is also switched at regular intervals. As a result, the human eye sees light emission that is uniformed over time, and uneven brightness is reduced.

Next, FIG. 2 shows a configuration of switching means provided with an analog switch (also referred to as a transfer gate). 2, the same parts as those in FIG. 1 are denoted by the same reference numerals. The drain electrodes of the transistor lines Tr (i) to Tr (i + 5) are signal lines S (m) to S (m + 5).
). However, one signal line can be connected to three current sources. That is, any of the three current sources can be selected by the switching function.

For example, when a signal for selecting the terminal 1 is input to the switching function, the signal line S (m + 1)
) Is connected to the current source C (i), the signal line S (m + 2) is connected to the current source C (i + 1),
Similarly, the signal line and the current source are connected. Next, when a signal for selecting the terminal 2 is input to the switching function, the signal line S (m + 1) is connected to the current source C (i + 1), and the signal line S (m
+2) is connected to the current source C (i + 2), and the signal line and the current source are connected in the same manner. Next, when a signal for selecting the terminal 3 is input to the switching function, the signal line S (m + 1)
Is connected to the current source C (i + 2), the signal line S (m + 2) is connected to the current source C (i + 3), and the signal line and the current source are connected in the same manner.

Expressing this connection using a function to generalize the connection of the present invention, when i = 3, the current source is F1 (N) = N + a, F2 (N) = N + b, F3 (N)
= N + c, where a, b and c are integers and a ≠ b ≠ c, and a
= -1, b = 0, c = 1.

As described above, variations in display can be suppressed by switching the currents from the three current sources to one signal line.

FIG. 3 illustrates a specific example in which an analog switch is used as switching means having a switching function. In FIG. 3, the same parts as those in FIG. 2 are denoted by the same reference numerals.
The current sources C (i) to C (i + 5) have transistors Tr (i) to Tr (i + 5).

A (l) to A (l + 2) and A (l) b to A (l + 2) b shown in FIG. 3 are wirings and are connected to a plurality of analog switches. These analog switches form a group connected to one signal line (this is called a switching unit). Referring to FIG. 3, the switching units U (n) to U (n + 5) having three analog switches are connected to the signal line S (
m) to S (m + 5). A plurality of these switching units constitute a switching means.

Looking at the current source C (i + 1), the drain electrode of the transistor Tr (i + 1) is one analog switch of the switching unit U (n + 1), one analog switch of the switching unit U (n), and the switching unit U. And (n + 2) one analog switch. That is, the drain electrode of the transistor is connected to one analog switch of the three switching unit. Similarly, current sources C (i), C (i + 2), C (i
+3), C (i + 4), and C (i + 5) are also connected to the respective analog switches.

When a signal is input to the wirings A (l) and A (l) b, the connected analog switch is selected and becomes conductive. Then, a current flows from the current source C (i + 1) connected to the selected analog switch to the signal line S (m + 2). Similarly, each current source C (i + 1), C
(I + 3), C (i + 4), C (i + 5), C (i + 6) to signal line S (m),
S (m + 2), S (m + 3), S (m + 4)
, S (m + 5) current flows. This is referred to as selection (1).

Next, when signals are input to the wirings A (l + 1) and A (l + 1) b, the analog switch to be connected is selected and becomes conductive. Then, a current flows from the current source C (i + 1) connected to the selected analog switch to the signal line S (m + 1).
Similarly, each current source C (i + 1), C (i + 3), C (i + 4), C (i + 5), C (i + 6)
) To signal lines S (m + 1), S (m + 3), S (m + 4), S (m + 5), S (
Current flows to m + 6). Further, although the current source C (i + 6) is not described, the current source C (i +
This is the current source on the right side of 5). This is referred to as selection (2).

Next, when a signal is input to the wirings A (l + 2) and A (l + 2) b, the connected analog switch is selected and becomes conductive. Then, a current flows from the current source C (i + 1) connected to the selected analog switch to the signal line S (m). Similarly, each current source C (i + 1),
Signal lines S (m−) from C (i + 3), C (i + 4), C (i + 5), and C (i + 6), respectively.
1) Current flows through S (m + 1), S (m + 2), S (m + 3), and S (m + 4). Further, the signal line S (m−1) is not described, but is a signal line adjacent to the left of the signal line S (m). This is referred to as selection (3).

By repeating this selection (1) to selection (3) at regular intervals, the currents input from the current sources (i) to (i + 5) to the signal lines S (m) to S (m + 5) vary. Even so, the display appears uniform.

Here, the switching period of the signal line driver circuit of the present invention will be described with reference to the timing chart of FIG. F1 to F3 in FIG. 4 are frame periods, which indicate periods during which the light emitting device displays one image. Note that one frame period is normally set to about 1/60 seconds so that human eyes do not feel flicker. A (l) to A (l + 2) and A (l) b to
A (l + 2) b indicates the potential of signals input to the wirings A (l) to A (l + 2) and the wirings A (l) b to A (l + 2) b.

The potential of the signal input to A (l) provided in the first frame period F1 is High (H
) And the potential of the signal input to A (l) b is Low (L),
The analog switches connected to the wirings A (l) and A (l) b are turned on, and a current from a transistor connected to the conducted analog switch is input to the signal line. Therefore, there is only one analog switch that is in a conductive state for each switching unit.

The potential of the signal input to A (l + 1) provided in the second frame period F2 is High.
(H) and the potential of the signal input to A (l + 1) b is Low (L)
In the switching period, the analog switches connected to the wirings A (l + 1) and A (l + 1) b are turned on, and a current from a transistor connected to the conducted analog switch is input to the signal line.

The potential of the signal input to A (l + 2) provided in the third frame period F3 is High.
(H) and the potential of the signal input to A (l + 2) b is Low (L)
In the switching period, the analog switches connected to the wirings A (l + 2) and A (l + 2) b are turned on, and a current from a transistor connected to the conducted analog switch is input to the signal line.

By repeating the frame periods F1 to F3, the switching means is connected to the signal lines S (m) to
The current flowing through S (m + 5) can be sequentially switched.

In this embodiment, the power supply line connected to the current source having the N-type transistor is Vss,
Although the configuration in which current flows from the pixel to Vss has been described, the polarity of the transistor may be set according to the polarity of the pixel as described above. Therefore, in the case of a structure in which a current flows to the pixel, the power supply line may be Vdd and the current source transistor may be a P-type conductivity type.

Next, the case where the current source has a DA conversion function will be described. For example, a case where a current having an analog value of 8 gradations is output for a 3-bit digital video signal will be described.

FIG. 5 shows a specific circuit configuration of the current source circuit as described above. As shown in FIG. 5, each current source has three transistors Tr1 (i), Tr2 (i), and Tr3 (i). Then, W (3) of the three transistors Tr1 (i), Tr2 (i), Tr3 (i)
If the gate width) / L (gate length) is set to 1: 2: 4, when the same gate voltage is applied, the current flowing through the transistors Tr1 (i), Tr2 (i), and Tr3 (i) is 1: 2
: 4. That is, the current supplied from the current source is 1: 2: 4, and the magnitude of the current can be controlled in 2 ³ = 8 steps. Then, the current source circuit can output a current having an analog value of 8 gradations for a 3-bit digital video signal.

Note that which of the transistors Tr1 (i), Tr2 (i), and Tr3 (i) is turned on and which is turned off may be controlled by controlling the voltage applied to each gate. Thereby, the current value output from the current sources C (i) to C (i + 5) can be controlled. However,
By the switching means, current sources C (i) to C (i + 5)
Which of the currents S (m) to S (m + 5) is input varies. Accordingly, the transistors Tr1 (i) and Tr2 of the current sources C (i) to C (i + 5) are accordingly adjusted.
It is also necessary to switch the voltage applied to (i) and Tr3 (i).

In this way, by providing the current source with the DA conversion function, it is possible to perform highly accurate gradation display. The number of bits may be set as appropriate by the practitioner, and the transistor may be designed according to the number of bits.

In the light-emitting device using the signal line driver circuit of the present invention described above, a light-emitting device that provides a uniform and display-free display in which display unevenness of pixels is visually reduced can be obtained. Even in the case of inputting to a signal line using an external circuit, by applying the present invention to the external circuit, a uniform pixel with no display unevenness can be provided.

Further, in the case where the semiconductor element of the signal line driver circuit is formed using a polysilicon transistor, a polysilicon transistor can be used for the semiconductor element of the pixel portion. Therefore, the periphery including the pixel portion and the signal line driver circuit on the same substrate. The circuit portion can be integrally formed, and a reduction in size and weight can be achieved. Further, it is not necessary to attach an external circuit by integrally forming the pixel portion and the peripheral circuit portion on the same substrate. Therefore, complicated processes and defects when connecting the signal line and the external circuit are omitted, and the reliability is improved.

Note that the connection between the signal line and the current source of the present invention is such that if there are two or more current sources for one signal line, the number of current sources (current source columns) may be asymmetrical. The source (column number of the current source) may be in an asymmetric position, and the display appears to be uniformed by switching the current flowing to the signal line. In the present embodiment, a connection configuration of the switching unit of the switching means, the signal line, and the current source is illustrated.

In FIG. 8, current sources C (i) to C (i + 5) and signal lines S (m) to S (m + 5) are connected via switching means. The switching means only needs to have a function of switching the current from the current source. In order to avoid the complexity of the drawing, the switching means is described with a configuration having three terminals schematically showing the switching function and a switching function.

For example, when looking at the signal line S (m + 2), current sources C (i + 2), C (i + 3), C (i + 4)
) Can be connected with either. That is, the signal line can be connected to the nearest current source and the two current sources on the right side. The signal lines S (m), S (m + 1), S (
m + 3), S (m + 4), S (m + 5) and the signal line are connected.

Expressing this connection using a function to generalize the connection of the present invention, when i = 3, the current source is F1 (N) = N + a, F2 (N) = N + b, F3 (N)
= N + c, where a, b, and c are integers and a ≠ b ≠ c, a = −2, b = −
1 and c = 0 can be expressed.

In addition, the connection relationship between the current source and the signal line of the present invention is not required to connect the current source and the signal line in the nearest position, that is, in the column, and is connected to the current source and the signal line in a distant position. It doesn't matter. As an example, the connection configuration shown in FIG. 9 will be described.

In FIG. 9, current sources C (i) to C (i + 6) and signal lines S (m) to S (m + 6) are connected via switching means. This switching means is also described with a configuration having three terminals and a switch.

For example, the signal line S (m + 2) can be connected to any one of the current sources C (i), C (i + 2), and C (i + 4). That is, the signal line can be connected to the nearest current source and two adjacent current sources with one between them. The signal lines S (m), S (m
+1), S (m + 3), S (m + 4), S (m + 5)
, S (m + 6) and a current source are connected.

Expressing this connection using a function to generalize the connection of the present invention, when i = 3, the current source is F1 (N) = N + a, F2 (N) = N + b, F3 (N)
= N + c, where a, b, and c are integers and a ≠ b ≠ c, and a = −2, b = 0
, C = −2 can be expressed.

The connection relationship between the current source and the signal line of the present invention is not limited to three current sources connected to the signal line. FIG. 10 shows an example in which five current sources are connected in one switching unit.

FIG. 10 shows current sources C (i) to C (i + 6) and signal lines S (m) to S (m + 6).
Are connected via the switching means. Similarly, the switching unit in this switching means is described as having a configuration having five terminals and a switch.

For example, when looking at the signal line S (m + 2), current sources C (i), C (i + 1), C (i + 2),
It can be connected to either C (i + 3) or C (i + 4). That is, the signal line can be connected to the nearest current source and two adjacent current sources. In the same rule, the signal line S
(M), S (m + 1), S (m + 3), S (m + 4)
, S (m + 5) and a current source are connected.

Expressing this connection using a function to generalize the connection of the present invention, when i = 5, the current source is F1 (N) = N + a, F2 (N) = N + b, F3 (N)
= N + c, F4 (N) = N + d, F5 (N) = N + e, where a, b, c, d and e are integers and a ≠ b ≠ c ≠ d ≠ e, and a = −2 , B = −1, c = 0, d = 1, e =
2 can be expressed.

As the number of current sources that can be connected to one signal line increases as shown in FIG. 10, the display appears to be uniform, and variation can be suppressed.

In this embodiment, the current flowing to the signal line can be switched by the method of switching the current source using the analog switch described in the first embodiment. Also, the first embodiment may be referred to when the current source has a DA conversion function.

As described above, in the connection between the signal line and the current source of the present invention, two current sources are used for one signal line.
As long as there are two or more, the number may be asymmetric, the position may be asymmetric, and the current flowing to the signal line may be switched.

  This embodiment can be used in combination with the switching means described in the first embodiment.

In this embodiment, when one frame period (within a unit frame period corresponding to the synchronization timing of the input video signal) is divided for each subframe period to display gradation (referred to as time gradation drive display), An example to which the present invention is applied is shown.

First, time gradation drive display will be described. In the case of a time grayscale driving method (digital driving method) using a digital video signal, a writing period Ta and a display period (also referred to as a lighting period) Ts repeatedly appear in one frame period, so that one image is displayed. Can be displayed.

For example, when an image is displayed by an n-bit video signal, at least n writing periods and n display periods are provided in one frame period. n writing periods and n
Each display period corresponds to each bit of the video signal.

As shown in FIG. 11A, a display period corresponding to the same number of bits, in this case Tsm, appears after the writing period Tam (m is an arbitrary number from 1 to n). The writing period Ta and the display period Ts are collectively referred to as a subframe period SF. The subframe period having the writing period Tam and the display period Tsm corresponding to the m-th bit is SFm. Display period Ts1
The length of Tsn satisfies Ts1: Ts2: ...: Tsn = 2 ⁰ : 2 ¹ : ...: 2 ^(n-1) .

Whether or not the light emitting element emits light in each subframe period is selected by each bit of the digital video signal. Then, the number of gradations can be controlled by controlling the sum of the lengths of the display periods during which light is emitted during one frame period.

Note that a subframe period having a long display period may be divided into several parts in order to improve image quality on display. A specific method of division is disclosed in Japanese Patent Application No. 2000-267164, and can be referred to.

In this embodiment, it is desirable to switch the current flowing from the current source to the signal line in the display period of the subframe period. This is because if the switching is performed during the writing period, the input current, that is, whether or not the light emitting element is caused to emit light may not be transmitted successfully. By switching at such a short period, variation in luminance of the light emitting elements is further suppressed, and display uniformity is improved.

Specifically, the case of 3 bits is shown in FIG. Referring to FIG. 11B, one frame period has subframe periods SF1, SF2, and SF3, and each subframe SF1, SF2,
SF3 has writing periods Ta1, Ta2, and Ta3 and display periods Ts1, Ts2, and Ts3. Then, periods (hereinafter simply referred to as switching periods) 1 to 3 for switching the current source are provided in the display periods Ts1 to Ts3.
By switching the current input to the signal line during the switching periods 1 to 3, the switching can be performed every short period, and the display appears to be more uniform.

In FIG. 11B, the switching periods 1 to 3 are all shown to be immediately before the writing period, but any switching period may be provided as long as it is during the display period.

FIG. 11C shows a timing chart of signals input to the analog switch. In the first frame, SF1, A1 is on, in SF2, A2 is on, in SF3, A3 is on, in SF1, A2 is on, in SF2, A3 is on, and in SF3, A1 is on. Yes. Although not shown in FIG. 11C, similarly, in the third frame, A3 is turned on in SF1, A1 is turned on in SF2, and A2 is turned on in SF3.

In the subframe periods SF1 to SF3, the ON states of A1 to A3 are fixed (from the first frame to the third frame, all A1 is on in SF1, all A2 is on in SF2, S
If all of A3 are turned on in F3, the variation is not sufficiently uniform. Therefore, as in the present embodiment, it is desirable to switch every subframe period and also every frame period.

This embodiment is an example, and what signal is input in which subframe period may be appropriately set. A specific signal input method may be referred to FIG.

In order to increase the gradation display, it is preferably used in combination with the current source having the DA conversion function described in the first embodiment, and this embodiment can be used in combination with the inventions described in the first and second embodiments.

  In this example, the structure of the light-emitting device of the present invention will be described with reference to FIG.

A light-emitting device of the present invention includes a pixel portion 402 in which a plurality of pixels are arranged in a matrix on a substrate 401, and the signal line driver circuit 1203 of the present invention and a first scan are arranged around the pixel portion 402. A line driver circuit 404 and a second scan line driver circuit 405 are provided.
In FIG. 12A, a signal line driver circuit 1203 and two sets of scanning line driver circuits 404, 4
However, the present invention is not limited to this, and can be arbitrarily designed according to the configuration of the pixel. A signal is supplied to the signal line driver circuit 1203, the first scan line driver circuit 404, and the second scan line driver circuit 405 from the outside through the FPC 406.

The structure of the first scan line driver circuit 404 and the second scan line driver circuit 405 is shown in FIG.
A description will be given using B). The first scan line driver circuit 404 and the second scan line driver circuit 405 include a shift register 407 and a buffer 408. In brief, the shift register 407 sequentially outputs sampling pulses in accordance with a clock signal (G-CLK), a start pulse (S-SP), and a clock inversion signal (G-CLKb). After that, the sampling pulse amplified by the buffer 408 is input to the scanning line and selected one row at a time. Then, the signal current Idata is sequentially written from the signal line to the pixels controlled by the selected scanning line.

Note that a level shifter circuit may be provided between the shift register 407 and the buffer 408. By arranging the level shifter circuit, the voltage amplitude can be increased.

The configuration of the signal line driver circuit 1203 will be described later. In addition, the present embodiment is the same as the first embodiment.
2 and 3 can be arbitrarily combined.

In addition, the arrangement of the current sources provided in the signal line driver circuit of the present invention may not be a straight line, and may be shifted in the signal line driver circuit. Further, two signal line driver circuits may be provided symmetrically with the pixel portion. That is, the present invention is not limited to the arrangement of the current source, as long as it is connected to the current source and the signal line via the switching means.

In this embodiment, a structure and operation of the signal line driver circuit 1203 illustrated in FIG. 13A will be described. In this embodiment, a signal line driver circuit 1203 used in the case of performing 1-bit digital gradation display will be described with reference to FIG.

FIG. 13A shows a signal line driver circuit 1 in the case of performing 1-bit digital gradation display.
A schematic diagram of 203 is shown. The signal line driver circuit 1203 includes a shift register 1211, a first latch circuit 1212, a second latch circuit 1213, and a constant current circuit 1214. The shift register 1211, the first latch circuit 1212, and the second latch circuit 1213 function as the video signal switch shown in FIG.

The operation will be briefly described. The shift register 1211 includes a plurality of columns of flip-flop circuits (FF) and the like, and includes a clock signal (S-CLK), a start pulse (S-SP), and a clock inversion signal (S-CLKb). Is entered. Sampling pulses are sequentially output according to the timing of these signals.

The sampling pulse output from the shift register 1211 is supplied to the first latch circuit 12.
12 is input. A digital video signal is input to the first latch circuit 1212, and the video signal is held in each column in accordance with the timing at which the sampling pulse is input.

When the first latch circuit 1212 completes holding the video signal up to the last column, a latch pulse is input to the second latch circuit 1213 and held in the first latch circuit 1212 during the horizontal blanking period. The video signals are transferred all at once to the second latch circuit 1213. Then, the video signal held in the second latch circuit 1213 is input to the video switch for one row at the same time. By turning this video switch on and off, it is controlled whether or not a signal is input to the pixel, and gradation is expressed.

While the video signal held in the second latch circuit 1213 is being input to the constant current circuit 1214, the sampling pulse is output again in the shift register 1211. Thereafter, this operation is repeated to process a video signal for one frame.

The constant current circuit 1214 is configured using a plurality of current source circuits. FIG. 13B illustrates specific circuits of the shift register 1211, the first latch circuit 1212, and the second latch circuit 1213.

In addition, this embodiment can be arbitrarily combined with the inventions described in Embodiments 1, 2, and 3.

As an electronic device using the light emitting device of the present invention, a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a sound reproduction device (car audio, audio component, etc.), a notebook type personal computer, a game device, Play back a recording medium such as a portable information terminal (mobile computer, mobile phone, portable game machine, electronic book, etc.) or recording medium (specifically, Digital Versatile Disc (DVD)) A device having a display capable of displaying). In particular, it is desirable to use a light-emitting device for a portable information terminal that often has an opportunity to see a screen from an oblique direction because the wide viewing angle is important. Specific examples of these electronic devices are shown in FIGS.

FIG. 15A illustrates a light-emitting device, which includes a housing 2001, a support base 2002, a display portion 2003, a speaker portion 2004, a video input terminal 2005, and the like. The light emitting device of the present invention has a display unit
03. Further, according to the present invention, FIG.
The light emitting device shown in FIG. Since the light-emitting device is self-luminous, no backlight is required.
The display portion can be thinner than the liquid crystal display. The light emitting device includes all information display light emitting devices such as a personal computer, a TV broadcast receiver, and an advertisement display.

FIG. 15B illustrates a digital still camera, which includes a main body 2101, a display portion 2102, an image receiving portion 2103, operation keys 2104, an external connection port 2105, a shutter 2106, and the like.
The light emitting device of the present invention can be used for the display portion 2102. Further, according to the present invention, FIG.
The digital still camera shown in B) is completed.

FIG. 15C illustrates a laptop personal computer, which includes a main body 2201, a housing 2202,
A display portion 2203, a keyboard 2204, an external connection port 2205, a pointing mouse 2206, and the like are included. The light-emitting device of the present invention can be used for the display portion 2203. Further, according to the present invention, the light emitting device shown in FIG. 15C is completed.

FIG. 15D illustrates a mobile computer, which includes a main body 2301, a display portion 2302, a switch 2303, operation keys 2304, an infrared port 2305, and the like. The light emitting device of the present invention can be used for the display portion 2302. Further, according to the present invention, the mobile computer shown in FIG. 15D is completed.

FIG. 15E illustrates a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 2401, a housing 2402, a display portion A2403, a display portion B2404, a recording medium (
DVD, etc.) includes a reading unit 2405, operation keys 2406, a speaker unit 2407, and the like. Although the display portion A 2403 mainly displays image information and the display portion B 2404 mainly displays character information, the light-emitting device of the present invention can be used for the display portions A, B 2403, and 2404. Note that an image reproducing device provided with a recording medium includes a home game machine and the like. Further, according to the present invention, the DVD reproducing apparatus shown in FIG.

FIG. 15F illustrates a goggle type display (head mounted display), which includes a main body 2501, a display portion 2502, and an arm portion 2503. The light emitting device of the present invention includes the display unit 250.
2 can be used. Further, according to the present invention, the goggle type display shown in FIG. 15F is completed.

FIG. 15G illustrates a video camera, which includes a main body 2601, a display portion 2602, a housing 2603,
External connection port 2604, remote control receiving unit 2605, image receiving unit 2606, battery 260
7, voice input unit 2608, operation key 2609, and the like. The light emitting device of the present invention includes the display unit 260.
2 can be used. Further, according to the present invention, the video camera shown in FIG. 15G is completed.

Here, FIG. 15H illustrates a mobile phone, which includes a main body 2701, a housing 2702, and a display portion 2703.
, Audio input unit 2704, audio output unit 2705, operation keys 2706, external connection port 270
7, antenna 2708 and the like. The light emitting device of the present invention can be used for the display portion 2703. Note that the display portion 2703 can suppress current consumption of the mobile phone by displaying white characters on a black background. Further, according to the present invention, the mobile phone shown in FIG. 15H is completed.

If the emission luminance of the luminescent material is increased in the future, the light including the output image information can be enlarged and projected by a lens or the like to be used for a front type or rear type projector.

In addition, the electronic devices often display information distributed through electronic communication lines such as the Internet and CATV (cable television), and in particular, opportunities to display moving image information are increasing. Since the response speed of the light emitting material is very high, the light emitting device is preferable for displaying moving images.

In addition, since the light emitting device consumes power in the light emitting portion, it is desirable to display information so that the light emitting portion is minimized. Therefore, when a light emitting device is used for a display unit mainly including character information, such as a portable information terminal, particularly a mobile phone or a sound reproduction device, it is driven so that character information is formed by the light emitting part with the non-light emitting part as the background It is desirable to do.

As described above, the applicable range of the present invention is so wide that it can be used for electronic devices in various fields. Further, the electronic device of this embodiment can use any of the signal line driver circuits shown in Embodiments 1 to 5.

Claims (6)

A first signal line;
A second signal line;
A third signal line;
A first circuit having a first transistor;
A second circuit having a second transistor;
A third circuit having a third transistor;
A fourth circuit having a fourth transistor;
A fifth circuit having a fifth transistor;
A first light emitting element to which a signal is input from the first signal line;
A second light emitting element to which a signal is input from the second signal line;
A third light emitting element to which a signal is input from the third signal line,
The first signal line is electrically connected to the first to third circuits through a switching circuit, and is electrically connected to the fourth circuit and the fifth circuit. Without
The second signal line is electrically connected to the second to fourth circuits through the switching circuit, and is electrically connected to the first circuit and the fifth circuit. not,
The third signal line is electrically connected to the third circuit to the fifth circuit through the switching circuit, and is electrically connected to the first circuit and the second circuit. not,
The first signal line to the third signal line are not electrically connected to two or more of the first circuit to the fifth circuit at the same time,
The switching circuit causes conduction between said first signal line of the first circuit in the first frame, so conduction between said first signal line and the second circuit in the second frame, the A semiconductor device having a function of electrically connecting the first signal line and the third circuit in a third frame. A first signal line;
A second signal line;
A third signal line;
A first circuit having a first transistor;
A second circuit having a second transistor;
A third circuit having a third transistor;
A fourth circuit having a fourth transistor;
A fifth circuit having a fifth transistor;
A sixth circuit having a sixth transistor;
A seventh circuit having a seventh transistor;
A first light emitting element to which a signal is input from the first signal line;
A second light emitting element to which a signal is input from the second signal line;
A third light emitting element to which a signal is input from the third signal line,
The first signal line is electrically connected to the first circuit, the third circuit, and the fifth circuit through a switching circuit, and the second circuit and the fourth circuit. , Not electrically connected to the sixth circuit and the seventh circuit,
The second signal line is electrically connected to the second circuit, the fourth circuit, and the sixth circuit through the switching circuit, and the first circuit, the third circuit, Not electrically connected to the circuit, the fifth circuit, and the seventh circuit;
The third signal line is electrically connected to the third circuit, the fifth circuit, and the seventh circuit through the switching circuit, and the first circuit and the second circuit Not electrically connected to the circuit, the fourth circuit, and the sixth circuit;
The first signal line to the third signal line are not electrically connected to two or more circuits among the first circuit to the seventh circuit at the same time,
The switching circuit causes conduction between said first signal line of the first circuit in the first frame, so conduction between said first signal line and the second circuit in the second frame, the A semiconductor device having a function of electrically connecting the first signal line and the third circuit in a third frame. A first signal line;
A second signal line;
A first circuit having a first transistor;
A second circuit having a second transistor;
A third circuit having a third transistor;
A fourth circuit having a fourth transistor;
A first light emitting element to which a signal is input from the first signal line;
A second light emitting element to which a signal is input from the second signal line,
The first signal line is electrically connected to the first to third circuits through a switching circuit, and is not electrically connected to the fourth circuit.
The second signal line is electrically connected to the second circuit to the fourth circuit through the switching circuit, and is not electrically connected to the first circuit,
Each of the first signal line and the second signal line is not electrically connected to two or more of the first circuit to the fourth circuit at the same time,
The switching circuit causes conduction between said first signal line of the first circuit in the first frame, so conduction between said first signal line and the second circuit in the second frame, the A semiconductor device having a function of electrically connecting the first signal line and the third circuit in a third frame. A first signal line;
A second signal line;
A third signal line;
A fourth signal line;
A first circuit having a first transistor;
A second circuit having a second transistor;
A third circuit having a third transistor;
A fourth circuit having a fourth transistor;
A fifth circuit having a fifth transistor;
A sixth circuit having a sixth transistor;
A first light emitting element to which a signal is input from the first signal line;
A second light emitting element to which a signal is input from the second signal line;
A third light emitting element to which a signal is input from the third signal line;
A fourth light emitting element to which a signal is input from the third signal line,
The first signal line is electrically connected to the first circuit to the third circuit through a switching circuit, and is electrically connected to the fourth circuit to the sixth circuit. Without
The second signal line is electrically connected to the second circuit to the fourth circuit through the switching circuit, and the first circuit, the fifth circuit, and the sixth circuit Not electrically connected to the circuit,
The third signal line is electrically connected to the third to fifth circuits via the switching circuit, and the first circuit, the second circuit, and the sixth circuit Not electrically connected to the circuit,
The fourth signal line is electrically connected to the fourth circuit to the sixth circuit through the switching circuit and electrically connected to the first circuit to the third circuit. not,
The first signal line to the fourth signal line are not electrically connected to two or more circuits among the first circuit to the sixth circuit at the same time,
The switching circuit causes conduction between said first signal line of the first circuit in the first frame, so conduction between said first signal line and the second circuit in the second frame, the A semiconductor device having a function of electrically connecting the first signal line and the third circuit in a third frame. In any one of Claims 1 thru | or 4,
The semiconductor device, wherein the switching circuit includes an analog switch. In any one of Claims 1 thru | or 5,
The semiconductor device, wherein the transistor includes polysilicon.

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