JP2008033073A - Display device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of preventing boundaries of respective columns of pixels arrayed in stripes from being viewed as stripes or in a colored state, and to provide its manufacturing method. <P>SOLUTION: Pixels of R, G, and B are arrayed in the same direction as the scanning direction of an excimer laser without reference to an L-length direction of TFTs 210 forming the pixels. The excimer laser has variance in output in a scan travel direction, so TFTs 210 arrayed in the scan travel direction, i.e. in a column of the same color of, for example, R1, R2, and R3 pixels etc., in Fig. 12 and Fig. 13 have differences in characteristic. However, those are equivalently variance among driving transistors in the column of the same color and therefore hardly viewed. Consequently, stripes viewed at boundaries of respective columns of R, G, and B can be improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display device in which pixel circuits having electro-optic elements such as an organic EL (Electroluminescence) display are arranged in a matrix and a manufacturing method thereof.

In an image display device, such as a liquid crystal display, an image is displayed by arranging a large number of pixels in a matrix and controlling the light intensity for each pixel in accordance with image information to be displayed.
This is the same for an organic EL display or the like, but the organic EL display is a so-called self-luminous display having a light emitting element in each pixel circuit, and has a higher image visibility than a liquid crystal display. There are advantages such as unnecessary and high response speed.
The luminance of each light emitting element is greatly different from a liquid crystal display or the like in that a color gradation is obtained by controlling the luminance of the light emitting element according to the current value flowing therethrough, that is, the light emitting element is a current control type.

  In the organic EL display, as with the liquid crystal display, a simple matrix method and an active matrix method can be used. However, although the former has a simple structure, it is difficult to realize a large and high-definition display. Due to the problems, active matrix systems have been actively developed to control the current flowing through the light-emitting elements inside each pixel circuit by means of active elements provided inside the pixel circuit, generally TFTs (Thin Film Transistors). ing.

FIG. 1 is a block diagram showing a configuration of a general organic EL display device.
As shown in FIG. 1, the display device 1 includes a pixel array unit 2 in which pixel circuits (PXLC) 2 a are arranged in an m × n matrix, a horizontal selector (HSEL) 3, a light scanner (WSCN) 4, a horizontal Data lines DTL1 to DTLn selected by the selector 3 and supplied with data signals corresponding to luminance information, and scanning lines WSL1 to WSLm selectively driven by the write scanner 4 are provided.
The horizontal selector 3 and the light scanner 4 may be formed on the polycrystalline silicon or may be formed around the pixel by MOSIC or the like.

FIG. 2 is a circuit diagram showing a configuration example of the pixel circuit 2a of FIG. 1 (see, for example, Patent Documents 1 and 2).
The pixel circuit in FIG. 2 has the simplest circuit configuration among many proposed circuits, and is a so-called two-transistor driving circuit.

2 includes a p-channel thin film field effect transistor (hereinafter referred to as TFT) 11 and TFT 12, a capacitor C11, and an organic EL element (OLED) 13 which is a light emitting element. In FIG. 2, DTL indicates a data line, and WSL indicates a scanning line.
Since organic EL elements often have rectifying properties, they are sometimes referred to as OLEDs (Organic Light Emitting Diodes). In FIG. 2 and others, the symbol of a diode is used as a light-emitting element. It does not require rectification.
In FIG. 2, the source of the TFT 11 is connected to the power supply potential VCC, and the cathode (cathode) of the light emitting element 13 is connected to the ground potential GND. The operation of the pixel circuit 2a in FIG. 2 is as follows.

Step ST1 :
When the scanning line WSL is in a selected state (here, at a low level) and the write potential Vdata is applied to the data line DTL, the TFT 12 becomes conductive and the capacitor C11 is charged or discharged, and the gate potential of the TFT 11 becomes Vdata.

Step ST2 :
When the scanning line WSL is in a non-selected state (here, high level), the data line DTL and the TFT 11 are electrically disconnected, but the gate potential of the TFT 11 is stably held by the capacitor C11.

Step ST3 :
The current flowing through the TFT 11 and the light emitting element 13 has a value corresponding to the gate-source voltage Vgs of the TFT 11, and the light emitting element 13 continues to emit light with a luminance corresponding to the current value.
The operation of selecting the scanning line WSL and transmitting the luminance information given to the data line to the inside of the pixel as in step ST1 is hereinafter referred to as “writing”.
As described above, in the pixel circuit 2a of FIG. 2, once Vdata is written, the light emitting element 13 continues to emit light with a constant luminance until it is rewritten next time.

As described above, in the pixel circuit 2a, the value of the current flowing through the EL light emitting element 13 is controlled by changing the gate application voltage of the TFT 11 serving as the drive transistor.
At this time, the source of the p-channel drive transistor is connected to the power supply potential VCC, and the TFT 11 always operates in the saturation region. Therefore, the constant current source has a value represented by the following formula 1.

(Equation 1)
Ids = 1/2 · μ (W / L) Cox (Vgs− | Vth |) ² (1)

  Here, μ is the carrier mobility, Cox is the gate capacity per unit area, W is the gate width, L is the gate length, and Vgs is the gate source of the TFT 11. The inter-voltage and Vth indicate the threshold value of the TFT 11, respectively.

  In the simple matrix type image display device, each light emitting element emits light only at the selected moment, whereas in the active matrix, as described above, the light emitting element continues to emit light even after the writing is completed. In comparison, the peak luminance and peak current of the light emitting element can be lowered, and this is particularly advantageous in a large-sized and high-definition display.

  FIG. 3 is a diagram showing a change with time of current-voltage (IV) characteristics of the organic EL element. In FIG. 33, the curve indicated by the solid line indicates the characteristic in the initial state, and the curve indicated by the broken line indicates the characteristic after change with time.

In general, the IV characteristics of an organic EL element deteriorate as time passes, as shown in FIG.
However, since the two-transistor drive in FIG. 2 is driven at a constant current, a constant current continues to flow through the organic EL element as described above, and even if the IV characteristic of the organic EL element deteriorates, the emission luminance deteriorates with time. There is nothing.

  The pixel circuit 2a shown in FIG. 2 is composed of a p-channel TFT. However, if it can be composed of an n-channel TFT, a conventional amorphous silicon (a-Si) process can be used in TFT fabrication. It becomes like this. Thereby, the cost of the TFT substrate can be reduced.

  Next, a basic pixel circuit in which transistors are replaced with n-channel TFTs will be described.

  FIG. 4 is a circuit diagram showing a pixel circuit in which the p-channel TFT in the circuit of FIG. 2 is replaced with an n-channel TFT.

  The pixel circuit 2b in FIG. 4 includes n-channel TFTs 21 and 22, a capacitor C21, and an organic EL element (OLED) 23 that is a light emitting element. In FIG. 4, DTL indicates a data line, and WSL indicates a scanning line.

  In the pixel circuit 2b, the drain side of the TFT 21 as a drive transistor is connected to the power supply potential VCC, and the source is connected to the anode of the EL element 23, thereby forming a source follower circuit.

  FIG. 5 is a diagram showing operating points of the TFT 21 and the EL element 23 as drive transistors in the initial state. In FIG. 5, the horizontal axis represents the drain-source voltage Vds of the TFT 21, and the vertical axis represents the drain-source current Ids.

As shown in FIG. 5, the source voltage is determined by the operating point of the TFT 21 as the drive transistor and the EL element 23, and the voltage has a different value depending on the gate voltage.
Since the TFT 21 is driven in a saturation region, a current Ids having a current value of the equation shown in the above equation 1 is supplied with respect to Vgs with respect to the source voltage at the operating point.

USP 5,684,365 JP-A-8-234683

The pixel circuit described above is the simplest circuit, but actually, a drive transistor connected in series with the OLED, a TFT for mobility and threshold cancellation, and the like are provided.
These TFTs generate a gate pulse by a vertical scanner arranged on both sides or one side of an active matrix organic EL display panel, and this pulse signal is applied to a desired TFT gate of a pixel circuit arranged in a matrix through a wiring. Is done.

FIG. 6 is a diagram illustrating an arrangement example of the pixel array unit.
6 is formed by arranging red (RED), green (GREEN), and blue (BLUE) sub-pixels 2R, 2G, and 2B in a stripe shape.

  In each pixel circuit, when there are two or more TFTs to which the pulse signal of the vertical scanner is applied, the timing of applying each pulse signal is important.

In an active matrix organic EL panel, p-Si • TFT is used and a low temperature process is used to integrate a drive circuit on a glass substrate.
The low-temperature poly-Si · TFT has the advantages of a-Si · TFT, high-temperature poly-Si · TFT, and single crystal Si · FET. In addition, a narrow frame, high definition, thinness, and light weight can be realized.
p-Si is formed by irradiating a high-power pulse of an excimer laser (wavelength 308 nm) to melt, cool, and solidify the a-Si film. This method is called excimer laser annealing (ELA), and high-quality p-Si is obtained at a low temperature over a large area.

In the ELA process, an excimer laser is scanned in one direction on the panel as shown in FIG.
However, since the output of the excimer laser varies in the scanning direction, there is a difference in the characteristics of the TFTs arranged in the scanning direction.

  Here, as an example, as shown in FIG. 8, the RGB pixels are arranged in stripes, and the channel length (L length) direction (current flow direction) of the drive transistor is arranged in the vertical direction in the drawing within each pixel. When the excimer laser is scanned from left to right in the figure, the output of the excimer laser varies in the scanning direction. Therefore, the drive transistor sandwiches the boundary between the R pixel and the G pixel and between the G pixel and the B pixel. The characteristics of will be different.

This is because the generated crystal grain size varies due to variations in the output of the excimer laser.
Since the output of the excimer laser varies in the scanning direction, for example, a difference occurs in the crystal grain size in the L length direction of the transistor, that is, in the current flow path, between the G2 pixel and the B2 pixel. Differences in characteristics such as mobility occur.
Furthermore, the difference in color from pixel to pixel originally overlapped, and there was a disadvantage that the boundary was visually recognized as a streak, and the boundary was colored and visually recognized.

  It is an object of the present invention to provide a display device and a method for manufacturing the display device that can prevent the boundary of each column of pixels arranged in stripes from being visually recognized as a streak and preventing the boundary from being colored and visually recognized.

  A display device according to a first aspect of the present invention includes a pixel array unit in which a plurality of pixel circuits including at least one transistor whose conduction state is controlled in response to a drive signal to a control terminal are arranged. These transistors are formed by irradiation with laser light having a predetermined wavelength scanned in a predetermined direction. In the pixel circuit of the pixel array section, the pixel arrangement direction in which stripes are arranged is the same as the scanning direction of the laser light. It is formed as follows.

  A display device according to a second aspect of the present invention includes a pixel array unit in which a plurality of pixel circuits including at least one transistor whose conduction state is controlled in response to a drive signal to a control terminal are arranged in a matrix, The transistor of the pixel circuit and the transistor of the buffer are formed by irradiation with laser light having a predetermined wavelength scanned in a predetermined direction, and the pixel array section has a channel length direction of the transistor that is the same as the scanning direction of the laser light. The pixel circuit formed so as to be in the direction and the pixel circuit formed so that the channel length direction is perpendicular to the scanning direction of the laser light are mixed.

  A third aspect of the present invention is a method for manufacturing a display device having a pixel array section in which a plurality of pixel circuits including at least one transistor whose conduction state is controlled by receiving a drive signal to a control terminal. The pixel circuit of the pixel array unit is formed so that the pixel arrangement direction in which stripes are arranged is the same direction as the scanning direction of laser light having a predetermined wavelength scanned in a predetermined direction, It is formed by solidifying by laser light irradiation of a predetermined wavelength scanned in the direction.

  A fourth aspect of the present invention is a method for manufacturing a display device having a pixel array section in which a plurality of pixel circuits including at least one transistor whose conduction state is controlled by receiving a drive signal to a control terminal. A pixel circuit formed so that a channel length direction of the transistor is in the same direction as a laser light scanning direction of a predetermined wavelength scanned in a predetermined direction, and the channel length direction is a scanning direction of the laser light. The pixel circuits formed so as to be orthogonal to each other are mixed, and the transistors of the pixel circuits are solidified by irradiation with laser light having a predetermined wavelength scanned in a predetermined direction.

According to the present invention, for example, in a crystallization process using a laser having a predetermined wavelength in a display device, the scanning direction of the laser beam and the pixel arrangement direction in which stripes are arranged are in the same direction.
The laser beam varies in the scanning direction, and there is a difference in the characteristics of the transistors of the same color column. In this case, for example, the transistors vary within the same color, so it is difficult to visually recognize the streak at the boundary of each column.

  According to the present invention, it is possible to prevent the boundary of each column of pixels arranged in a stripe from being visually recognized as a streak, and preventing the boundary from being colored and visually recognized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 9 is a diagram showing a configuration of an organic EL display device employing the pixel circuit according to the embodiment of the present invention.
FIG. 10 is a diagram schematically showing an organic EL display device panel according to an embodiment of the present invention.
FIG. 11 is a circuit diagram showing a specific configuration of the pixel circuit according to the present embodiment.

  As shown in FIGS. 9 and 10, the display device 100 includes a pixel array unit 102 in which pixel circuits 101 are arranged in an m × n matrix, a horizontal selector (HSEL) 103, a write scanner (WSCN) 104, a drive A scanner (DSCN) 105, a first auto-zero circuit (AZRD1) 106, a second auto-zero circuit (AZRD2) 107, a data line DTL selected by the horizontal selector 103 and supplied with a data signal corresponding to luminance information, a write scanner 104 The scanning line WSL as the second drive wiring selectively driven by the drive, the drive line DSL as the first drive wiring selectively driven by the drive scanner 105, and the fourth drive selectively driven by the first auto-zero circuit 106 First auto zero line AZL1 as wiring and second auto zero times The 107 has a second auto-zero line AZL2 as the third driving wiring to be selectively driven.

  These components are formed in an active matrix organic EL display panel 100A as shown in FIG.

  As shown in FIG. 10, the pixel circuit 101 according to the present embodiment is formed by arranging red (RED), green (GREEN), and blue (BLUE) subpixels 101R, 101G, and 101B in a stripe shape. Has been.

9 and 11, the pixel circuit 101 according to the present embodiment includes a p-channel TFT 111, n-channel TFTs 112 to 115, a capacitor C111, and a light-emitting element 116 including an organic EL element (OLED: electro-optical element). , A first node (point A) ND111, and a second node (point B) ND112.
A first switch transistor is formed by the TFT 111, a second switch transistor is formed by the TFT 113, a third switch transistor is formed by the TFT 115, and a fourth switch transistor is formed by the TFT 114.
The supply line (power supply potential) of the power supply voltage VCC corresponds to the first reference potential, and the ground potential GND corresponds to the second reference potential. VSS1 corresponds to the fourth reference potential, and VSS2 corresponds to the third reference potential.

In the pixel circuit 101, between the first reference potential (power supply potential VCC in this embodiment) and the second reference potential (ground potential GND in this embodiment), the TFT 111, the TFT 112 as a drive transistor, the first A node ND111 and a light emitting element (OLED) 116 are connected in series. Specifically, the cathode of the light emitting element 116 is connected to the ground potential GND, the anode is connected to the first node ND111, the source of the TFT 112 is connected to the first node ND111, and the drain of the TFT 111 is connected to the drain of the TFT 111. The source of the TFT 111 is connected to the power supply potential VCC.
The gate of the TFT 112 is connected to the second node ND112, and the gate of the TFT 111 is connected to the drive line DSL.
The drain of the TFT 113 is connected to the first node 111 and the first electrode of the capacitor C111, the source is connected to the fixed potential VSS2, and the gate of the TFT 113 is connected to the second auto zero line AZL2. The second electrode of the capacitor C111 is connected to the second node ND112.
The source / drain of the TFT 114 is connected between the data line DTL and the second node ND112. The gate of the TFT 114 is connected to the scanning line WSL.
Further, the source and drain of the TFT 115 are connected between the second node ND112 and the predetermined potential Vss1, respectively. The gate of the TFT 115 is connected to the first auto zero line AZL1.

As described above, in the pixel circuit 101 according to the present embodiment, the capacitor C111 as the pixel capacitance is connected between the gate and the source of the TFT 112 as the drive transistor, and the source potential of the TFT 112 is connected to the TFT 113 as the switch transistor during the non-light emission period. The threshold voltage Vth is corrected by connecting to a fixed potential through the TFT 112 and connecting between the gate and drain of the TFT 112.
For example, the threshold value Vth is corrected while the TFT 115 is on and the TFT 113 is off.
In addition, mobility correction is performed in a period in which the TFT 111 is turned on and the TFT 114 is turned on.
The drive is controlled by the phase difference between the two kinds of pulses such as mobility correction and threshold value Vth cancellation. Therefore, the timing of each pulse is important.

In the active matrix type organic EL display device panel 100A, a drive circuit is integrated on a glass substrate by using p-Si · TFT and using a low temperature process.
The low-temperature poly-Si · TFT has the advantages of a-Si · TFT, high-temperature poly-Si · TFT, and single crystal Si · FET. In addition, a narrow frame, high definition, thinness, and light weight can be realized.
The p-Si is formed by adopting an ELA (Excimer Laser Annealing) method and irradiating a high output pulse of an excimer laser (wavelength 308 nm) to melt, cool and solidify the a-Si film. Thus, by adopting the ELA method, good quality p-Si can be obtained over a large area at a low temperature.

By the way, the output of the excimer laser varies in the scanning direction.
For this reason, in the present embodiment, in order to prevent the boundary of each column of pixels arranged in stripes from being visually recognized as a streak and to visually recognize the boundary in a colored manner, basically, the following first or first The panel 2 is manufactured by the ELA method using the method 2.

First method: In the ELA crystallization process of the active matrix organic EL display device, the scanning direction of the laser beam and the RGB pixel arrangement direction in the stripe arrangement are made the same direction.
Second method: The L length direction of the transistor (TFT) of the active matrix organic EL display device is mixed in the ELA crystallization step with the laser beam scanning direction and the direction orthogonal to the same direction.

First, the first method will be described.
FIG. 12 is a diagram for explaining a first example of the first method applied to the ELA crystallization process of the active matrix organic EL display device.

  In the first example of the first method, as shown in FIG. 12, in the ELA crystallization process of the active matrix organic EL display device 100, the excimer laser scanning direction 200 and the transistors (that form buffers in the vertical scanner 200) This is a method in which the L length direction (the direction in which current flows) of the TFT 210 is the same direction.

  FIG. 13 is a diagram for explaining a second example of the first method applied to the ELA crystallization process of the active matrix organic EL display device.

  In the second example of the first method, as shown in FIG. 13, in the ELA crystallization process of the active matrix organic EL display device 100, the scan direction 200 of the excimer laser and the transistors (that form buffers in the vertical scanner 200) This is a method in which the L length direction (direction in which current flows) of the TFT 210A is orthogonal.

That is, according to the first method, the scan direction of the excimer laser and the RGB pixel arrangement direction are the same regardless of the L length direction of the TFT 210 forming the pixel.
Since the output of the excimer laser varies in the scanning direction, the characteristics of the TFTs 210 arranged in the scanning direction, that is, the TFTs 210 in the same color row such as R1, R2, and R3 pixels in FIGS.
However, these have a feature that it becomes difficult to visually recognize because the driving transistors vary within the same color.
Therefore, the first method can improve the stripes visually recognized at the boundaries between the RGB columns.

Next, the second method will be described.
For example, when a method is adopted in which the excimer laser scanning direction 200 and the L length direction of the pixel TFT 210 are in the same direction as shown in FIG. 12, for example, in FIG. 12, the columns R2, G2, B2 and R3, G3 , B3 column has a difference in transistor characteristics, and stripes and unevenness may be visually recognized at the boundary of each column.
In the second method, in order to solve this problem, the L length direction of the transistor (TFT) of the active matrix type organic EL display device has a direction orthogonal to the scanning direction of the laser beam in the ELA crystallization process. To be mixed.

  FIG. 14 is a diagram for explaining a first example of the second method applied to the ELA crystallization process of the active matrix organic EL display device.

In the first example of the second method, as shown in FIG. 14, the L-length direction of the in-pixel TFT 210 is arranged differently between adjacent sub-pixels.
In FIG. 14, for example, the TFT 210 of the G2 subpixel is arranged in the horizontal direction, but the adjacent R2, G1, G3, and B2 subpixels are arranged in the vertical direction.
In other words, the TFT 210 forming each pixel circuit 101 is arranged such that the L length direction is the wiring direction of the data line DTL wired to the pixel array unit 102 (scanning line WSL, driving line DSL, auto zero lines AZL1, AZL2). For example, the sub-pixels formed so as to be orthogonal to each other, and the L length direction is orthogonal to the wiring direction of the data lines DTL wired to the pixel array unit 102 (scanning lines WSL, The sub-pixels formed so as to be in the same direction as the wiring direction of the drive line DSL and auto-zero lines AZL1, AZL2 are formed so as to be mixed regularly and periodically.
The excimer laser scan is performed, for example, from the upper side to the lower side in the drawing.
By arranging in this way, the characteristics of adjacent transistors vary. However, since the variations are not concentrated in the column or row direction but are diffused, streaks and unevenness are not noticeable.

  FIG. 15 is a diagram for explaining a second example of the second method applied to the ELA crystallization process of the active matrix organic EL display device.

In the second example of the second method, the arrangement direction of the in-pixel TFT (transistor) 210B is arranged so that the L length direction of the in-pixel TFT 210B is different between adjacent RGB sub-pixels as shown in FIG. This is an example.
Also in this case, since the variation is not concentrated in the column or row direction but is diffused, streaks and unevenness are not noticeable.

  FIG. 16 is a diagram for explaining a third example of the second method applied to the ELA crystallization process of the active matrix organic EL display device.

In the third example of the second method, as shown in FIG. 16, the L-length direction of the in-pixel TFT 210C is arranged differently between adjacent pixels.
Also in this case, since the variation is not concentrated in the column or row direction but is diffused, streaks and unevenness are not noticeable.

Further, in the above example, the arrangement direction (arrangement in the L length direction) of the in-pixel TFT (transistor) 210 is changed between the horizontal direction and the vertical direction, but it may be rotated at an arbitrary angle.
In the ELA crystallization process, it is desirable that the scan direction of the excimer laser be a direction perpendicular to the direction in which the subpixels RGB are arranged. This is to reduce coloring, streaks, and unevenness due to different colors at each RGB boundary.
Therefore, the second method can improve streaking or coloring caused by the difference in characteristics of the TFTs (transistors) in the pixel.

Note that the first method and the second method are applicable to arrangements other than those described above.
For example, as shown in FIGS. 17 and 18, the present invention can be applied to a so-called delta arrangement, and the same effect can be obtained.
The first example of the second method shown in FIG. 14 is applied to the pixel array unit 101D having the delta arrangement in FIG.
Further, the third example of the second method shown in FIG. 16 is applied to the pixel array section 101D having the delta arrangement in FIG.
In these cases as well, the unevenness is not concentrated in the column or row direction but is diffused, and therefore streaks and unevenness are not noticeable.
Accordingly, it is possible to improve streaking or coloring due to the difference in characteristics of the TFTs (transistors) in the pixel.

  By adopting the first and second methods, it is caused by the excimer laser scan in the ELA crystallization process in the active matrix organic EL display device, and the difference in the characteristics of the in-pixel transistors depending on the arrangement direction of the in-pixel transistors. You can improve streaking and coloring.

Next, the operation of the above configuration will be described with reference to FIGS. 19A to 19F, focusing on the operation of the pixel circuit.
19A shows a drive signal applied to the driving DSL, FIG. 19B applied a drive signal WS applied to the scanning line WSL, and FIG. 19C applied to the first auto-zero line AZL1. 19D shows the driving signal AZ1, FIG. 19D shows the driving signal auto-zero signal AZ2 applied to the second auto-zero line AZL2, FIG. 19E shows the potential of the second node ND112, and FIG. The potential of the first node ND111 is shown.

The drive signal DS of the drive line DSL by the drive scanner 105 is held at a high level, the drive signal WS to the scanning line WSL by the write scanner 104 is held at a low level, and the drive signal AZ1 to the auto zero line AZL1 by the auto zero circuit 106 is held at a low level. The driving signal AZ2 to the auto zero line AZL2 by the auto zero circuit 107 is held at a high level.
As a result, the TFT 113 is turned on. At this time, a current flows through the TFT 113, and the source potential Vs of the TFT 112 (the potential of the node ND111) drops to VSS2. Therefore, the voltage applied to the EL light emitting element 116 is also 0 V, and the EL light emitting element 116 does not emit light.
In this case, even if the TFT 114 is turned on, the voltage held in the capacitor C111, that is, the gate voltage of the TFT 112 does not change.

Next, in the non-emission period of the EL light emitting element 116, as shown in FIGS. 19C and 19D, the driving signal AZ2 to the auto zero line AZL2 is held at the high level, and the auto cell line AZL1 is applied. The drive signal AZ1 is set to a high level. As a result, the potential of the second node ND112 becomes VSS1.
Then, after the drive signal AZ2 to the auto zero line AZL2 is switched to the low level, the drive signal DS of the drive line DSL by the drive scanner 105 is switched to the low level only for a predetermined period.
Accordingly, the TFT 113 is turned off and the TFT 115 and the TFT 112 are turned on, whereby a current flows through the path of the TFT 112 and the TFT 111, and the potential of the first node rises.
Then, the drive signal DS of the drive line DSL by the drive scanner 105 is switched to the high level, and the drive signal AZ1 is switched to the low level.
As a result, the threshold Vth correction of the drive transistor TFT112 is performed, and the potential difference between the second node ND112 and the first node ND111 becomes Vth.
In this state, after the elapse of a predetermined period, the drive signal WS to the scanning line WSL by the write scanner 104 is held at a high level for a predetermined period, data is written from the data line to the node ND112, and the drive scanner 105 The drive signal DS of the drive line DSL is switched to the high level, and the drive signal WS is eventually switched to the low level.
At this time, the TFT 112 is turned on, the TFT 114 is turned off, and the mobility is corrected.
In this case, since the TFT 114 is off and the gate-source voltage of the TFT 112 is constant, the TFT 112 passes a constant current Ids to the EL light emitting element 116. Accordingly, the potential of the first node ND111 rises to a voltage Vx through which a current Ids flows through the EL light emitting element 116, and the EL light emitting element 116 emits light.
Here, in this circuit as well, the EL element changes its current-voltage (IV) characteristic when the light emission time becomes long. Therefore, the potential of the first node ND111 also changes. However, since the gate-source voltage Vgs of the TFT 112 is maintained at a constant value, the current flowing through the EL light emitting element 117 does not change. Therefore, even if the IV characteristics of the EL light emitting element 116 deteriorate, the constant current Ids always flows and the luminance of the EL light emitting element 116 does not change.

  In the display device driven in this manner, an excimer laser scan in the ELA crystallization process in the active matrix organic EL display device, and a streak caused by a difference in characteristics of the in-pixel transistor depending on the arrangement direction of the in-pixel transistor, Coloring can be improved and an image with good image quality can be obtained.

It is a block diagram which shows the structure of a common organic electroluminescent display apparatus. FIG. 2 is a circuit diagram illustrating a configuration example of a pixel circuit in FIG. 1. It is a figure which shows the time-dependent change of the electric current-voltage (IV) characteristic of an organic EL element. FIG. 3 is a circuit diagram illustrating a pixel circuit in which a p-channel TFT in the circuit of FIG. 2 is replaced with an n-channel TFT. It is a figure which shows the operating point of TFT and EL element as a drive transistor in an initial state. It is a figure which shows the example of an arrangement | sequence of a pixel array part. It is a figure for demonstrating the scanning direction of the excimer laser in an ELA process. It is a figure for demonstrating the factor which a characteristic dispersion | variation produces in a transistor. It is a figure which shows the structure of the organic electroluminescence display which employ | adopted the pixel circuit which concerns on embodiment of this invention. It is a figure which shows typically the organic electroluminescence display panel which concerns on embodiment of this invention. FIG. 6 is a circuit diagram illustrating a specific configuration of a pixel circuit according to the present embodiment. It is a figure for demonstrating the 1st example of the 1st method applied to the ELA crystallization process of an active matrix type organic electroluminescence display. It is a figure for demonstrating the 1st example of the 1st method applied to the ELA crystallization process of an active matrix type organic electroluminescence display. It is a figure for demonstrating the 1st example of the 2nd method applied to the ELA crystallization process of an active matrix type organic electroluminescence display. It is a figure for demonstrating the 2nd example of the 2nd method applied to the ELA crystallization process of an active-matrix organic electroluminescent display apparatus. It is a figure for demonstrating the 3rd example of the 2nd method applied to the ELA crystallization process of an active matrix type organic electroluminescence display. It is a figure which shows the case where the 1st example of the 2nd method is applied to the delta arrangement | sequence of an active matrix type organic electroluminescent display apparatus. It is a figure which shows the case where the 3rd example of the 2nd method is applied to the delta arrangement | sequence of an active matrix organic electroluminescent display apparatus. It is a timing chart for demonstrating operation | movement of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Display apparatus, 101 ... Pixel circuit, 102 ... Pixel array part, 103 ... Horizontal selector (HSEL), 104 ... Write scanner (WSCN), 105 ... Drive scanner (DSCN), 106 ... 1st auto drive circuit (AZRD1) 107, second auto-zero circuit (AZRD2), DTL, data line, WSL, scanning line, DSL, drive line, AZL1, AZL2, auto-zero line, 111, p-channel TFT as a switch, 112, drive (drive) N-channel TFT as a transistor, 113 to 1152... N-channel TFT N as a switch, D111... First node, ND112... Second node, 200.

Claims (14)

A pixel array unit in which a plurality of pixel circuits including at least one transistor whose conduction state is controlled in response to a drive signal to a control terminal are arranged;
The transistor of the pixel circuit is formed by irradiation with laser light having a predetermined wavelength scanned in a predetermined direction.
The pixel circuit of the pixel array unit is formed such that a pixel arrangement direction in which stripes are arranged is the same as a scanning direction of the laser light. The display device according to claim 1, wherein the transistor in the pixel circuit is formed so that a channel length direction thereof is the same as a scanning direction of the laser light. The display device according to claim 1, wherein the transistor in the pixel circuit is formed so that a channel length direction thereof is a direction orthogonal to a scanning direction of the laser light. A pixel array unit in which a plurality of pixel circuits including at least one transistor whose conduction state is controlled in response to a drive signal to a control terminal are arranged in a matrix;
The transistor of the pixel circuit and the transistor of the buffer are formed by laser light irradiation of a predetermined wavelength scanned in a predetermined direction,
The pixel array section includes a pixel circuit formed so that a channel length direction of a transistor is the same as a scanning direction of the laser light, and a channel length direction orthogonal to the scanning direction of the laser light. A display device formed so that the formed pixel circuits are mixed. The display device according to claim 4, wherein the pixel circuit includes a plurality of subpixels, and the channel length direction of the transistor is different between adjacent subpixels. The display device according to claim 4, wherein the pixel circuit includes a plurality of subpixels, and the channel length direction of the transistor is different between adjacent RGB subpixels. The display device according to claim 4, wherein the pixel circuit includes a plurality of subpixels, and the channel length direction of the transistor is different between adjacent pixels. The pixel circuit includes a plurality of subpixels,
The display device according to claim 4, wherein the scan direction is a direction orthogonal to an arrangement direction of sub-pixels of the pixel circuit. A method of manufacturing a display device having a pixel array portion in which a plurality of pixel circuits including at least one transistor whose conduction state is controlled by receiving a drive signal to a control terminal is arranged,
The pixel circuit of the pixel array unit is formed so that the pixel arrangement direction in which stripes are arranged is the same direction as the scanning direction of laser light having a predetermined wavelength scanned in a predetermined direction,
A method for manufacturing a display device, wherein the transistor of the pixel circuit is solidified by irradiation with laser light having a predetermined wavelength scanned in a predetermined direction. A method of manufacturing a display device having a pixel array portion in which a plurality of pixel circuits including at least one transistor whose conduction state is controlled by receiving a drive signal to a control terminal is arranged,
The pixel array section includes a pixel circuit formed so that a channel length direction of a transistor is in the same direction as a laser beam scan direction of a predetermined wavelength scanned in a predetermined direction, and the channel length direction is a scan direction of the laser beam. It is formed so that pixel circuits formed so as to be in the orthogonal direction are mixed,
A method for manufacturing a display device, wherein the transistor of the pixel circuit is solidified by irradiation with laser light having a predetermined wavelength scanned in a predetermined direction. The method for manufacturing a display device according to claim 10, wherein the pixel circuit includes a plurality of subpixels, and the channel length direction of the transistor is different between adjacent subpixels. The method for manufacturing a display device according to claim 10, wherein the pixel circuit includes a plurality of subpixels, and the channel length direction of the transistor is different between adjacent RGB subpixels. The method for manufacturing a display device according to claim 10, wherein the pixel circuit includes a plurality of subpixels, and the channel length direction of the transistor is different between adjacent pixels. The pixel circuit includes a plurality of subpixels,
The method for manufacturing a display device according to claim 10, wherein the scanning direction is a direction orthogonal to an arrangement direction of sub-pixels of the pixel circuit.

Images