JP5422991B2 - Display device and manufacturing method of display device - Google Patents

Description

  The present invention relates to a display device and a manufacturing method of the display device, and more particularly to an active matrix driving color display device including an organic electroluminescent element and a manufacturing method thereof.

  In an active matrix driving display device in which an organic electroluminescent element and a pixel circuit connected thereto are arranged on a substrate, an organic electric field is generated depending on a current amount of a thin film transistor (TFT) constituting the pixel circuit. The luminance of the light emitting element is determined. The pixel circuit that determines the amount of current to be supplied to the organic electroluminescent element includes at least a TFT that samples the video signal, a capacitor that holds the video signal, and a driving TFT that drives the organic electroluminescent element based on the held video signal. Three elements are required, and the layout density of the pixel circuit is higher than that of the liquid crystal element.

  Therefore, by adopting a so-called mirror inversion structure in which the layout of the pixel circuits arranged adjacent to each other in the scanning line direction on the substrate is inverted, one power supply line is shared by the two pixel circuits and the layout density is lowered. A configuration has been proposed (see Patent Documents 1 to 5 below).

  FIG. 20 shows a layout diagram of a thin film transistor substrate for a display device having such a mirror inversion structure. As shown in this figure, scanning lines 11 and power supply lines 12 are wired in parallel within the display area on the substrate 10, and signal lines 13 are wired perpendicularly thereto. Then, corresponding to each intersection of the scanning line 11 and the power supply line 12 and the signal line 13, each sub-pixel a (R) corresponding to three colors of red (R), green (G), and blue (B). ), A (G), and a (B) are arranged in this order. These sub-pixels a (R), a (G), and a (B) constitute a substantially square display pixel A ′ having a set of three colors.

  In each color sub-pixel a, a pixel circuit including thin-film transistors Tr1 'and Tr2' and a capacitive element Cs is arranged. Each thin film transistor Tr <b> 1 ′, Tr <b> 2 ′ includes a gate electrode 14 extending in parallel with the signal line 13. The thin film transistor Tr2 'has a configuration in which one power supply line 12 portion is shared on the drain side between adjacent sub-pixels a. Each of the sub-pixels a has a configuration in which an organic electroluminescence element (not shown) is connected to the thin film transistor Tr2 '.

  Further, as described above, in a display device in which the luminance of the organic electroluminescent element is determined by the amount of current of the thin film transistor that constitutes the pixel circuit, in order to perform good display with reduced luminance unevenness, the variation in characteristics of the thin film transistor is suppressed. This is very important.

  However, when the channel region of the thin film transistor is formed of polycrystalline silicon, transistor characteristics are likely to vary because the size of crystal grains present in the channel region is not uniform. Therefore, as a method of microcrystallizing the semiconductor thin film constituting the channel region to such an extent that the crystal grain size is not nonuniform, crystallization annealing is performed in which the amorphous thin film is microcrystallized using a solid-state laser. Yes.

  Here, when the thin film transistor substrate having the mirror inversion structure described with reference to FIG. 20 is manufactured, such a crystallization annealing step is performed, for example, as follows. First, a gate electrode 14 made of a first metal pattern (21) and other electrodes are formed on the substrate 10, and then a gate insulating film and an amorphous material are formed so as to cover the first metal pattern (21). A semiconductor thin film is formed. Next, after a buffer layer and a photothermal conversion layer are formed on the semiconductor thin film as necessary, the semiconductor thin film is irradiated with laser light generated from the solid laser through these layers. Thereby, the semiconductor thin film portion corresponding to the irradiated portion of the laser light is formed into a microcrystalline semiconductor thin film. At this time, the scanning direction (v) of the laser light is the direction along the scanning line 11, that is, the channel length direction of the thin film transistors Tr1 'and Tr2' and the line width direction of the gate electrode 14.

Patent No. 4036235 JP 2005-266830 A JP 2006-11429 A JP 2006-343768 A JP 2008-33091 A

  However, the crystallization annealing of the semiconductor thin film using the solid-state laser described above has a longer thermal diffusion length when the amount of heat necessary for crystallization of the semiconductor thin film is supplied than the crystallization annealing using the excimer laser. . For this reason, the influence of the heat conduction by the gate electrode provided in the lower layer of the semiconductor thin film is remarkable, and the arrangement state of the gate electrode affects the crystallinity of the semiconductor thin film portion constituting the thin film transistor.

  That is, as described above, when the direction along the scanning line 11 shown in FIG. 20, that is, the line width direction (channel length direction) of the gate electrode 14 is the scanning direction (v) of the laser beam, on the upstream side in the scanning direction. The gate electrode 14 is hardly thermally saturated, and the gate electrode 14 is likely to be thermally saturated on the downstream side in the scanning direction (v) of the laser beam.

  For this reason, since the semiconductor thin film is crystallized before the gate electrode 14 is sufficiently heated by laser light irradiation on the upstream side in the scanning direction (v) of the laser light with the gate electrode 14 interposed therebetween, the crystallinity is improved. Become sparse. On the other hand, the semiconductor thin film is crystallized on the downstream side in the scanning direction (v) of the laser beam with the gate electrode 14 interposed therebetween, while the gate electrode is sufficiently heated by the laser beam irradiation. Becomes dense. That is, in the driving transistors Tr2 ′ of a (R) and a (B) in the left pixel A ′ and the a (G) in the right pixel A ′ in FIG. Is sparse. On the other hand, in the a (G) in the left pixel A ′ and the drive transistors Tr2 ′ in the a (R) and a (B) in the right pixel A in FIG. It becomes dense. Such a crystalline density in the channel length direction in the channel region greatly affects the on-current of the thin film transistor.

  Therefore, if the layout of the adjacent subpixels a is mirror-inverted, the thin film transistor of the subpixel a [for example, the subpixel a (G)] of the same color between the display pixels A ′ adjacent in the scanning line 11 direction. The layout of Tr1 ′ and Tr2 ′ is inverted. For this reason, in the thin film transistors Tr1 'and Tr2' between the sub-pixels a of the same color, a difference occurs in transistor characteristics, for example, on-current, due to the above-described crystalline density at the end in the channel length direction. Thereby, in the sub-pixel a of the same color between the adjacent display pixels A ′, a luminance difference is generated between the light emitting elements connected to the thin film transistors Tr1 ′ and Tr2 ′, and as a result, between the display pixels A ′ adjacent in the scanning line 11 direction. Is visually recognized as luminance unevenness in the scanning line 11 direction.

  Accordingly, an object of the present invention is to provide a display device with a good display characteristic in which luminance unevenness between light emitting elements of the same color is prevented, and a method for manufacturing the same, although having a mirror inversion structure.

In order to achieve such an object, a display device of the present invention includes a plurality of pixel circuits having thin film transistors arranged in a mirror inversion structure. In the mirror inversion structure, each pixel circuit is provided along the arrangement direction in a state where the arrangement directions of the source and drain of the thin film transistors constituting the pixel circuit are alternately inverted. A set of four pixel circuits arranged adjacent to each other in the arrangement direction and a plurality of display pixels in which a light emitting element is connected are configured. A light emitting element that emits the first light is connected to two adjacent pixel circuits among the four pixel circuits constituting the display pixel. Also remaining picture element circuit, a light-emitting element emits a light emitting element and the third color emit a second color are connected. In the plurality of display pixels, the source / drain arrangement directions of the thin film transistors of the pixel circuits connected to the light emitting elements emitting the second color are the same.

  In the display device having such a configuration, in the display device having a mirror inversion structure in which the arrangement of the source / drains of the thin film transistors constituting the pixel circuit is inverted, the even number of pixel circuits adjacent to each other in the inversion direction are grouped into a display pixel Is configured. For this reason, the thin film transistor of the pixel circuit for performing the same color display arranged between the display pixels can have the same source / drain arrangement direction. Therefore, uneven luminance of the same color due to the arrangement direction of the source / drain is prevented. In addition, two pixel circuits among the pixel circuits constituting each display pixel are for performing the same color display. Therefore, display unevenness between different display colors can be prevented by connecting these two pixel circuits to a light emitting element having poor characteristics such as luminance and light emission efficiency.

The manufacturing method of the display device of the present invention performs the following steps. First, a plurality of gate electrodes are formed in the line width direction. Next, a gate insulating film and an amorphous semiconductor thin film are formed in this order so as to cover the gate electrode. Next, the semiconductor thin film is crystallized by irradiating while scanning energy lines in the line width direction of the gate electrode, and a thin film transistor is formed using the crystallized semiconductor thin film. Thereafter, pixel circuits having thin film transistors are formed along the line width direction of the gate electrodes in a state where the arrangement directions of the sources and drains of the thin film transistors are alternately reversed. Thereafter, among the four pixel circuits arranged adjacent to the array direction, it is connected to the light emitting element emitting a first light was connected to two pixel circuits adjacent to the remaining image Motokai paths respectively A plurality of display pixels are formed using the light emitting element emitting the second color and the light emitting element emitting the third color as a set of display pixels. The plurality of display pixels are arranged so that the source / drain arrangement directions of the thin film transistors of the pixel circuits connected to the light emitting elements emitting the second color are the same.

  By the manufacturing method as described above, the display device having the above-described mirror inversion structure of the present invention can be obtained. Particularly in this manufacturing method, the semiconductor thin film constituting the thin film transistor is crystallized by scanning the energy line along the line width direction of the gate electrode. For this reason, in the thin film transistors constituting the pixel circuit provided along the arrangement direction, the thin film transistors that are irradiated with the energy rays with the source side as the upstream and the thin film transistors that are irradiated with the energy rays with the drain side as the upstream are alternately arranged. Will be placed. However, the above-described display device of the present invention obtained by this method forms a set of display pixels by connecting light emitting elements of each color to four or more even pixel circuits. Therefore, as described above, the thin film transistor of the pixel circuit for performing the same color display arranged between the display pixels can have the same source / drain arrangement direction. Therefore, uneven luminance of the same color due to the arrangement direction of the source / drain is prevented. In addition, two pixel circuits among the pixel circuits constituting each display pixel are for performing the same color display. Therefore, display unevenness between different display colors can be prevented by connecting these two pixel circuits to a light emitting element having poor characteristics such as luminance and light emission efficiency.

  As described above, according to the present invention, in the configuration in which the source / drain arrangement of the thin film transistors constituting the pixel circuit is alternately inverted, the same color between the display pixels caused by the different source / drain arrangement directions is obtained. Brightness unevenness can be prevented, and display unevenness between different display colors can also be prevented. As a result, it is possible to obtain a display device capable of displaying with good display characteristics while having a mirror inversion structure.

Hereinafter, embodiments of the present invention will be described in the following order.
1. First embodiment (example in which a green sub-pixel is configured by two pixel circuits and a signal line is shared)
2. Second Embodiment (a modification of the first embodiment, in which one light emitting element is connected to two pixel circuits)
3. Third Embodiment (Example in which a green subpixel is configured by two pixel circuits and signal lines are individually provided)
4). Fourth Embodiment (Example in which a green subpixel is configured by two pixel circuits and a power supply line is shared)

  In each embodiment, the configuration of an active matrix display device in which an organic electroluminescence element is connected to a thin film transistor and the manufacturing method thereof will be described in this order. Further, the same components as those of the conventional configuration described with reference to FIG.

<< 1. First Embodiment >>
<Overall configuration of display device>
FIG. 1 is a plan view showing the overall configuration of the display device 1a of the first embodiment.

  As shown in this figure, the display device 1a includes a display panel 2 and flexible printed boards 3, 4, and 5 connected to the peripheral edge. The flexible printed boards 3, 4, and 5 are, for example, a video signal supply board 3, a power supply board 4, and a scanning signal and power control signal supply board 5.

  The display panel 2 has a planar rectangular shape, and a display area 2a that is substantially similar to the display panel 2 is set at the center thereof. In the display area 2a, scanning lines 11 and power supply lines 12 are wired along the long side direction x of the display area 2a, and signal lines 13 are wired perpendicularly thereto. Sub-pixels a are arranged corresponding to the intersections of the scanning lines 11 and the power supply lines 12 and the signal lines 13. Signals are input to the scanning lines 11 and the power supply lines 12 from the substrate 5 for supplying scanning signals and power supply control signals. A signal is input to the signal line 13 from the video signal supply substrate 3. In addition, a signal is input from the power supply substrate 4 to an electrode common to all the pixels at the cathode (or anode) of the organic electroluminescence element described later.

  Each of the sub-pixels a has a rectangular shape and is arranged with its long side parallel to the signal line 13. Further, these sub-pixels a constitute a substantially square display pixel A in which a set of four sub-pixels a arranged in the direction of the scanning line 11. Two of the four sub-pixels a constituting each display pixel A are provided with light emitting elements of the same color (organic electroluminescence elements described below), and the other two of the four sub-pixels a are The first feature is that light emitting elements of different colors (organic electroluminescent elements described below) are provided.

  Here, in particular, the four subpixels constituting each display pixel A are four subpixels a (R) and a (G) of red (R), green (G), green (G), and blue (B). , A (G), a (B), and two green sub-pixels a (G) that have high visibility and require high luminance light emission are provided.

The four sub-pixels constituting each display pixel A has a signal line 13 direction is a symmetrical line, and that are arranged in a mirror-inverted structure with alternately reversing the layout to the scanning line 11 direction. At this time, two green subpixels a (G) are arranged by arranging two green subpixels a (G) and a (G) of the four subpixels constituting each display pixel A adjacent to each other. ), A (G) share one signal line 13.

  In the display area 2a, the four subpixels a (R), a (G), a (G), and a (B) (represented as a representative) are arranged in the direction of the scanning line 11 as described above. The display pixels A are arranged in a matrix along the scanning lines 11, the power supply lines 12, and the signal lines 13.

<Circuit Configuration of Display Pixel in Display Device>
FIG. 2 is a circuit configuration diagram of the display pixel A including four subpixels a.

  As shown in this figure, a switching thin film transistor Tr1, a driving thin film transistor Tr2, and a capacitive element Cs are arranged in each sub-pixel a, and a pixel circuit is constituted by these. The thin film transistors Tr1 and Tr2 are n-channel MOS transistors here.

  Each pixel circuit is connected to a light emitting element EL (R), EL (G), EL (G), EL (B) of each light emission color in the source S of the driving thin film transistor Tr2. In such a pixel circuit, the video signal written from the signal line 13 through the switching thin film transistor Tr1 selected by the scanning line 11 is held in the holding capacitor Cs. Then, a current corresponding to the held signal amount is supplied from the source S of the driving thin film transistor Tr2 to each light emitting element EL (R), EL (G), EL (G), EL (B). Thereby, each light emitting element EL (R), EL (G), EL (G), EL (B) is configured to emit light with a luminance corresponding to the supplied current value.

<Layout of Pixel Circuit in Display Device>
FIG. 3 shows a layout diagram of the pixel circuit provided in each sub-pixel a. Here, a layout diagram of two display pixels A adjacent in the direction of the scanning line 11 is shown.

  As shown in this figure, a pixel circuit including thin film transistors Tr1 and Tr2 and a capacitor element Cs is disposed in each subpixel a on the glass substrate 10 constituting the display panel. Among these, the thin film transistors Tr1 and Tr2 have a bottom gate structure in which the gate electrodes 14a and 14b are configured using the first metal pattern (21) provided immediately above the glass substrate 10, and the source S and the drain D are disposed thereon. It is. The source S / drain D is composed of a semiconductor thin film not shown here, and the source electrode and the drain electrode composed of the second metal pattern (22) are connected to each other. Further, the capacitive element Cs is formed integrally with the source S side of the driving thin film transistor Tr2 connected to the light emitting element, and between the first metal pattern (21) and the second metal pattern (22), A gate insulating film not shown here is sandwiched.

  The thin film transistors Tr1 and Tr2 are arranged with their channel length directions parallel to the scanning lines 11. As a result, the thin film transistors Tr1 and Tr2 are in a state in which the source S and the drain D are sequentially arranged in the direction of the scanning line 11.

  In such a state, each subpixel a is arranged in a mirror inversion structure in which the layout is alternately inverted in the scanning line 11 direction with the signal line 13 direction as the target line as described above. Accordingly, in the pixel circuit constituting each sub-pixel a, the sources S and drains D of the thin film transistors Tr1 and Tr2 are sequentially laid out along the arrangement direction in a state where the arrangement directions are alternately inverted. Become.

  In each pixel circuit constituting two green subpixels a (G) and a (G) arranged adjacent to each other in each display pixel A, each switching thin film transistor Tr1 has one signal. The line 13 is shared. Thereby, the layout density of the pixel circuit can be suppressed.

  Further, in the driving thin film transistor Tr2 in the pixel circuits arranged adjacent to each other, one power supply line 12 extending from the power supply line 12 is shared as a common drain D. Thereby, the layout density of the pixel circuit can be suppressed.

  Further, in the pixel circuit provided in each sub-pixel a, the channel width of the thin film transistors Tr1 and Tr2 and the layout area of the capacitive element Cs are adjusted for each emission color of the light emitting element connected to the pixel circuit. I will do it.

  In general, an organic electroluminescent element (light emitting element) has a different luminous efficiency for each emission color. For this reason, it is assumed that the channel width of the thin film transistors Tr1 and Tr2 and the layout area of the capacitor Cs in the pixel circuit are set larger for the sub-pixel a provided with a light emitting element having a relatively low emission efficiency. As an example, here, the channel width of the thin film transistors Tr1 and Tr2 and the layout area of the capacitive element Cs increase in the order of red subpixel a (R) <green subpixel a (G) <blue subpixel a (B). It is assumed that the pixel circuit is designed so that

  Here, the thin film transistors Tr1 and Tr2 have a bottom gate structure as described above, and a semiconductor thin film (not shown) formed on the gate electrodes 14a and 14b is crystallized by irradiation with energy rays. It is a microcrystalline thin film transistor. As will be described in detail in the subsequent manufacturing method, the scanning direction v of the laser beam irradiated as the energy beam is the arrangement direction of the source S and the drain D in the thin film transistors Tr1 and Tr2, that is, the direction along the scanning line 11. This is the second feature.

<Cross sectional configuration of the display device>
FIG. 4 is a cross-sectional view of two sub-pixels a (G) and a (G) as a main-part cross-sectional view of the display device. Note that this cross-sectional portion corresponds to the AA ′ cross-section crossing the thin film transistors Tr1 and Tr2 of the two sub-pixels a (G) and a (G) in FIG.

  As shown in this figure, a pixel circuit including thin film transistors Tr1 and Tr2 and a capacitor element not shown here is provided on a glass substrate 10 constituting a display panel. The thin film transistors Tr1 and Tr2 are of the bottom gate type as described above, and the gate electrodes 14a and 14b configured using the first metal pattern (21) are provided immediately above the glass substrate 10. On the gate insulating film 31 covering these, a semiconductor thin film 32A crystallized by laser light irradiation, which will be described later, is provided as a layer constituting the channel region. Further, a source S and a drain D made of a semiconductor thin film, and a source electrode 22s and a drain electrode 22d made of a second metal pattern (22) are provided on the upper portion.

  The pixel circuit including the thin film transistors Tr1 and Tr2 as described above is covered with a passivation film 51, and a planarization insulating film 52 is provided thereon. A light emitting element EL is provided on the planarization insulating film 52 at a position corresponding to each subpixel a.

  Each light emitting element EL includes a lower electrode 53 patterned for each sub-pixel a, a light emitting functional layer 54 made of an organic material provided on the upper electrode 55, and an upper electrode 55 provided on the light emitting functional layer 54. ing.

  Of these, the lower electrode 53 is used as an anode (or a cathode). The light-emitting functional layer 54 includes at least an organic light-emitting layer. For example, a hole injection layer, a hole transport layer, an organic light-emitting layer, an electron transport layer, and the like are stacked as necessary from the anode side. Yes. The light emitting functional layer 54 has a different configuration for each light emitting color of each light emitting element EL. The upper electrode 55 is used as a cathode (or an anode) of the organic electroluminescence element EL, and is provided as an electrode common to all pixels.

  The light emitting element EL having the above configuration is separated by an insulating pattern 56 covering the periphery of the lower electrode 53. Each light emitting element EL is configured to be connected to the source S of the driving thin film transistor Tr2 in the lower electrode 53 through a connection hole (not shown). An auxiliary electrode 53a composed of the same layer as the lower electrode 53 is provided on the planarization insulating film 52. By connecting the auxiliary electrode 53a to the upper electrode 55, a voltage drop in the upper electrode 55 is prevented. It is preferable that it is the structure to perform.

  Although illustration is omitted here, it is preferable that the light-emitting element EL having the above-described configuration is sealed by a counter substrate bonded with an adhesive sealant.

  In the display device 1a of the first embodiment having such a configuration, an even number of pixels adjacent in the inversion direction in the mirror inversion structure in which the arrangement of the sources S / drains D of the thin film transistors Tr1 and Tr2 constituting the pixel circuit is inverted. The display pixel A is configured by a set of circuits. For this reason, the thin film transistors Tr1 and Tr2 of the pixel circuit for performing the same color display arranged between the display pixels A can have the same arrangement direction of the source S / drain D.

  That is, as shown in FIG. 3, in the red light emitting sub-pixel a (R) in all the display pixels A, the thin film transistors Tr1 are arranged in order from the left side to the drain D → the source S, and the thin film transistors Tr2 are arranged on the left side. To source S → drain D in this order.

  Therefore, uneven brightness of the same color due to the arrangement direction of the source S / drain D, which becomes a problem when using the semiconductor thin film 32A crystallized by laser annealing, which will be described in detail in the following manufacturing method, is prevented. The

  In addition, two of the pixel circuits constituting each display pixel A constitute a green sub-pixel a (G) that is highly visible and requires high luminance light emission. Therefore, display unevenness based on visibility can be prevented between different display colors.

<Manufacturing method of display device>
Next, a method for manufacturing the display device having the above-described configuration will be described.

  First, as shown in FIG. 5, a planar rectangular glass substrate 10 is prepared. And the formation area of the two display panels 2 is set with respect to this glass substrate 10, for example. At this time, the short side of the display panel 2 is arranged in parallel to the long side of the glass substrate 10 so that the two display panels 2 can be efficiently arranged on the single glass substrate 10. In each display panel 2, a display area 2a having a substantially rectangular shape and a plane rectangular shape is set.

  Further, a sub-pixel a having a planar rectangular shape is set in the display area 2a. These subpixels a are arranged with the long sides of the subpixels a parallel to the short side direction y of the display region 2a. Furthermore, these sub-pixels a have a substantially square shape with four sub-pixels a of red (R), green (G), green (G), and blue (B) arranged in the short side direction as a set. The display pixel A is configured as described above.

  Next, as shown in the plan view of FIG. 6 and the sectional view of FIG. 7A (corresponding to the AA ′ sectional view of the plan view of FIG. 6), Gate electrodes 14a and 14b made of the first metal pattern (21) are formed. In the same process, another wiring portion made of the first metal pattern (21), for example, a part of the signal line 13, and a lower electrode portion of the capacitive element (Cs) integrated with the gate electrode 14b are formed.

  At this time, the gate electrode 14a of the switching thin film transistor (Tr1) and the gate electrode 14b of the driving thin film transistor (Tr2) are patterned so as to extend in parallel with the short side direction y of the display region 2a. The gate electrodes 14a and 14b are arranged in the line width direction with the long side direction x of the display region 2a being arranged in the line width direction, and a plurality of rows are arranged in the short side direction y. A part of the signal line 13 is patterned so as to be parallel to the short side direction y of the display region 2a.

  The first metal pattern (21) including the gate electrodes 14a and 14b is formed by pattern etching a molybdenum (Mo) film formed by, for example, a sputtering method using a resist pattern as a mask. The first metal pattern (21) is not necessarily made of molybdenum (Mo), and may be a metal having a high melting point that hardly changes in the subsequent heat process.

  Next, in a state of covering these first metal patterns (21), a gate insulating film 31 made of, for example, silicon oxide or silicon nitride is formed, and then a semiconductor thin film 32 made of amorphous silicon is formed. To do.

  Thereafter, as shown in FIG. 7B, a buffer layer 41 using silicon oxide or silicon nitride is formed in a state of covering the semiconductor thin film 32, and then a photothermal conversion layer using molybdenum (Mo). 42 is deposited. The photothermal conversion layer 42 is for absorbing energy rays such as laser light, which will be described later, and converting the light energy into heat energy. Therefore, the photothermal conversion layer 42 has a high absorption rate of laser light (energy rays) used in the subsequent crystallization annealing, a low thermal diffusion rate to the buffer layer 41 and the semiconductor thin film 32, Any material may be used as long as it satisfies the conditions such as a material having a high melting point that is not easily altered by heat generated during subsequent crystallization. For example, carbon (C) is used. May be.

  After the above, as shown in the plan view of FIG. 6 and FIG. 7 (3), the semiconductor thin film 32 is indirectly irradiated with the laser light Lh via the photothermal conversion layer 42 and the buffer layer 41. Heat treatment is performed. At this time, the laser beam Lh using a solid laser as a transmission source is irradiated. As a result, a semiconductor thin film (microcrystalline silicon thin film) 32A is obtained by crystallizing the irradiated portion of the laser light Lh in the semiconductor thin film 32 into nanometer order crystal grains.

  In this case, the laser beam Lh is irradiated while scanning the laser beam Lh in the line width direction of the gate electrodes 14a and 14b. Thereby, the scanning direction v of the laser beam is parallel to the long side direction x of the display region 2a, that is, parallel to the short side of the glass substrate 10 as shown in FIG. Thereby, the energy variation of the laser beam Lh due to the long scanning distance of the laser beam is prevented, and a more uniform crystal can be obtained.

  It is important to perform a so-called raster scan in which the laser light Lh is scanned only in the same scanning direction v along the line width direction for the gate electrodes 14a and 14b arranged in the line width direction. is there. That is, as shown in FIG. 5, the scanning direction v of the laser light is made only from one direction along the long side direction x of the display area 2a. Note that such irradiation with the laser beam Lh may be performed by a multi-head method in which the laser beam Lh can be irradiated to a plurality of row portions at a time.

  In the crystallization as described above, a difference occurs in the crystallinity of the semiconductor thin film due to the influence of the first metal pattern (21) constituting the gate electrodes 14a and 14b provided in the lower layer of the semiconductor thin film 32A. In other words, on the upstream side in the scanning direction (v) of the laser beam across the first metal pattern (21), the semiconductor thin film is crystallized before the first metal pattern (21) is sufficiently heated by the laser beam irradiation. Since this is done, the crystallinity becomes sparse. On the other hand, on the downstream side in the laser beam scanning direction (v) across the first metal pattern (21), the semiconductor thin film is sufficiently heated by the laser beam irradiation. Crystallization takes place. For this reason, crystallinity becomes denser than the upstream side.

  The irradiation width of the laser beam Lh in the direction perpendicular to the scanning direction v only needs to cover the formation part of the transistors (Tr1) and (Tr2). The irradiation with the laser beam Lh here is performed only on the portions corresponding to the formation positions of the thin film transistors (Tr1) and (Tr2) arranged and formed as described with reference to FIG. 3, that is, on the gate electrodes 14a and 14b. What is necessary is just to selectively irradiate the area including the upper part.

  After the laser beam Lh irradiation as described above, as shown in FIG. 7 (4), the photothermal conversion layer 42 and the buffer layer 41 on the semiconductor thin film 32A are removed by etching.

  Next, as shown in FIG. 8A, an insulating stopper layer 33 is patterned on the semiconductor thin film 32A at a position overlapping the gate electrodes 14a and 14b on the semiconductor thin film 32A serving as a channel region. .

  Next, as shown in FIG. 8B, an n-type semiconductor layer 34 made of, for example, silicon containing an n-type impurity is formed in a state of covering the stopper layer 33.

  Thereafter, as shown in FIG. 8C, the n-type semiconductor layer 34 and the semiconductor thin film 32A are patterned in an island shape above the gate electrodes 14a and 14b.

  Thereafter, as shown in FIG. 8 (4), a metal film covering the n-type semiconductor layer 34 is formed and patterned to form a source electrode 22s and a drain electrode 22d made of the second metal pattern (22). Form. The source electrode 22s / drain electrode 22d is in a state of being divided on the stopper layer 33. Further, the n-type semiconductor layer 34 is also patterned so as to be separated on the stopper layer 33, and the source S / drain D composed of the n-type semiconductor layer 34 is formed.

  Thereby, a channel region is formed by the microcrystalline semiconductor thin film 32A, and thin film transistors Tr1 and Tr2 in which the source electrode 22s / drain electrode 22d are connected to the source S / drain D in contact with the channel region are obtained. Further, in the same process as the formation of the source electrode 22s / drain electrode 22d, other wiring portions made of the second metal pattern (22), for example, the scanning line 11, the power supply line 12, and the upper electrode of the capacitive element Cs shown in FIG. A part of the signal line 13 is formed.

  As described above, as shown in FIG. 3, the scanning lines 11, the power supply lines 12, and the signal lines 13 are formed in the display areas set on the glass substrate 10, and the thin film transistors Tr1, A pixel circuit in which Tr2 and the capacitor element Cs are formed is formed. In the formation of the pixel circuit, the wiring is formed so that the sources S and drains D of the thin film transistors Tr1 and Tr2 are alternately inverted in the line width direction of the gate electrodes 14a and 14b.

  Next, a light emitting element is formed over the thin film transistor substrate manufactured as described above. This process will be described with reference to FIG.

  First, a passivation film 51 is formed so as to cover the glass substrate 10 on which the above pixel circuits (only the thin film transistors Tr1 and Tr2 are shown), and a planarization insulating film 52 is formed thereon. Next, a connection hole (not shown) that reaches one of the source electrode 22s / drain electrode 22d (for example, the source electrode 22s) of the thin film transistor Tr2 is formed in the planarization insulating film 52 and the passivation film 51. Next, the lower electrode 53 connected to the source electrode 22 s and the source S through the connection hole is patterned on the planarization insulating film 52. In the same process, the auxiliary wiring 53a is formed.

  Next, an insulating pattern 56 having a shape in which the central portion of the lower electrode 53 is widely exposed to cover the periphery and a part of the auxiliary wiring 53a is exposed is formed. In the insulating pattern 56, an opening portion where the lower electrode 53 is exposed becomes a pixel opening.

  Thereafter, the light emitting functional layer 54 formed using an organic material is formed in a state of covering the lower electrode 53 exposed from the insulating pattern 56. The light emitting functional layer 54 is individually formed in a different process for each light emission color of the light emitting element formed here. Next, the upper electrode 55 common to all the pixels is formed in a state of covering the light emitting functional layer 54 and being connected to the auxiliary wiring 53a.

  As described above, the light emitting element EL in which the light emitting functional layer 54 including the organic light emitting layer is sandwiched between the lower electrode 53 and the upper electrode 55 is formed on the planarization insulating film 52. The light emitting element EL has a configuration in which the lower electrode 53 is connected to the thin film transistor Tr2.

  In particular, here, among the four pixel circuits arranged adjacent to each other in the line width direction of the gate electrodes 14a and 14b, the green light emitting element EL (G) is formed by being connected to two pixel circuits, and the remaining pixels. It is important to form a red light emitting element EL (R) and a blue light emitting element EL (B) in connection with the circuit.

  After the above, a counter substrate is arrange | positioned at the light emitting element EL formation surface side of the glass substrate 10, and the glass substrate 10 and a counter substrate are bonded together through an adhesive sealing agent. And if it is a case where the formation area of the some display panel 2 is set to one glass substrate 10 as shown in FIG. 5, the glass substrate 10 and a counter substrate will be divided | segmented for every display panel 2, The display device 1 is completed by connecting the flexible printed circuit board to each of the divided parts according to the procedure as necessary.

  The mirror inversion structure described with reference to FIGS. 1 to 4 by the manufacturing method of the first embodiment described above, and subpixels using four pixel circuits arranged adjacent to each other along the scanning line 11 are 1 A display device 1a having a display pixel A in a set can be obtained.

  Particularly in this manufacturing method, as shown in FIGS. 3 and 6, during the crystallization annealing of the semiconductor thin film 32 constituting the channel regions of the thin film transistors Tr1 and Tr2, the line width direction (scanning line) of the gate electrodes 14a and 14b is obtained. The laser beam is scanned in the scanning direction v along (11 directions). For this reason, the thin film transistors Tr1 and Tr2 constituting the pixel circuit provided along the arrangement direction are irradiated with energy rays with the source side as an upstream, and irradiated with energy rays with the drain side as an upstream. Are arranged alternately.

Here, FIG. 9 is a graph showing the current characteristics of the thin film transistor for each scanning direction of the laser beam during the crystallization annealing. As shown in this graph, the thin film transistor obtained the source side as an upstream, in the thin film transistor obtained the drain side as upstream, it can be seen that a large difference in the resulting drain current Ids generated.

  However, the display device 1a having the above-described configuration of the first embodiment obtained by the above-described manufacturing method forms a set of display pixels A by connecting light emitting elements of each color to four pixel circuits. Therefore, as described above, the thin film transistors Tr1 and Tr2 of the pixel circuit for performing the same color display arranged between the display pixels A can have the same arrangement direction of the source S / drain D. .

  That is, as shown in FIG. 3, in the red light emitting sub-pixel a (R) in all the display pixels A, the thin film transistors Tr1 are arranged in order from the left side to the drain D → the source S, and the thin film transistors Tr2 are arranged on the left side. To source S → drain D in this order.

  Accordingly, the sub-pixels a (R), a (G), a (G), and a (B) for light emission of each color are configured using thin film transistors Tr1 and Tr2 having uniform current characteristics between the display pixels A, respectively. The pixel circuit is driven. Therefore, it is possible to prevent luminance unevenness of the same color while using an organic electroluminescent element driven by current. In particular, it is important to prevent the luminance unevenness of the same color that the current characteristics of the driving transistor Tr2 are uniform in each emission color.

  In addition, two of the pixel circuits constituting each display pixel A constitute a green sub-pixel a (G) that is highly visible and requires high luminance light emission. Therefore, display unevenness based on visibility can be prevented between different display colors.

≪2. Second Embodiment >>
FIG. 10 is a cross-sectional view of the main part showing the characteristic part of the display device of the second embodiment. The display device 1b of the second embodiment shown in this figure is different from the display device of the first embodiment in that the display The green subpixels a (G) and a (G) provided in the pixel A are connected to only one light emitting element EL (G) in two pixel circuits, and the other configurations are the same. is there. 10 shows a cross-sectional view of two subpixels a (G) and a (G), and in FIG. 3 crosses the thin film transistors Tr1 and Tr2 of the two subpixels a (G) and a (G). It corresponds to the AA ′ cross section.

  In the display device 1b of the second embodiment shown in FIG. 10 as described above, the opening area of the green light emitting element EL (G) in the green subpixel a (G) is compared with the first embodiment shown in FIG. Can be widened. For this reason, the green visibility can be further enhanced. It is also possible to improve the entire opening area of the display pixel A.

≪3. Third Embodiment >>
<Overall configuration of display device>
FIG. 11 to FIG. 13 are drawings showing the characteristic part of the display device of the third embodiment. Among these, FIG. 11 is a top view which shows the whole structure of the display apparatus 1c of 3rd Embodiment. FIG. 12 is a circuit configuration diagram of a display pixel A including four sub-pixels a in the display device 1c according to the third embodiment. Further, FIG. 13 shows a layout diagram of a pixel circuit provided in each sub-pixel a in the display device 1c of the third embodiment.

  The display device 1c of the third embodiment shown in these drawings differs from the display device of the first embodiment in that the green subpixels a (G) and a (G) provided in the display pixel A are respectively It is in the place connected to the separate signal line 13, and the other structure is the same.

  In the display device 1c of the third embodiment having such a configuration, each light emitting element EL (G (G) provided in the green subpixels a (G) and a (G) is compared with the display device of the first embodiment. ) Can be emitted with individual video signals.

  Note that the display device 1c according to the third embodiment can be combined with the second embodiment. In this case, each display device 1c is individually connected to one light emitting element EL (G). A current corresponding to the video signal from the signal line can be supplied.

<< 4. Fourth Embodiment >>
FIG. 14 is a diagram showing a characteristic part of the display device of the fourth embodiment, and shows a layout diagram of a pixel circuit provided in each sub-pixel a in the display device 1d of the fourth embodiment. The display device 1d of the fourth embodiment shown in the figure is different from the display device of the first embodiment in that the green subpixels a (G) and a (G) provided in the display pixel A are individually provided. It is connected to the signal line 13 and shares a portion on the drain D side extended from the common electrode 12, and the other configurations are the same.

In such a configuration, the two pixel circuits of the green subpixels a (G) and a (G) provided in the display pixel A share the single power supply line 12 with respect to the power supply line 12. It is laid out in the symmetric.

  Even if it is such a structure, the effect similar to 1st Embodiment can be acquired.

  In the first to fourth embodiments described above, the configuration in which the green light emitting element EL (G) is connected to the two pixel circuits provided in one display pixel A has been described. However, the light emitting element EL connected to the two pixel circuits provided in one display pixel A is not limited to the green light emitting element EL (G). For example, a blue light emitting element EL (B) or a red light emitting element EL (R) may be used.

  In general, an organic electroluminescent element (light emitting element) has a different luminous efficiency for each emission color. For this reason, as the light emitting element EL connected to the two pixel circuits provided in one display pixel A, the blue light emitting element EL (B) having the relatively lowest luminous efficiency may be used. In this case, the blue light emitting element EL (B) having a relatively low luminous efficiency is connected to each of the two pixel circuits, or one blue light emitting element EL (B) having a large opening area with respect to the two pixel circuits. Connect. Thereby, the brightness | luminance difference of each luminescent color can be made small.

<Application example>
Display devices obtained by the manufacturing method according to the present invention described above include various electronic devices shown in FIGS. 15 to 19, such as digital cameras, notebook personal computers, mobile terminal devices such as mobile phones, video cameras, etc. The present invention can be applied to display devices of electronic devices in various fields that display video signals input to electronic devices or video signals generated in electronic devices as images or videos. An example of an electronic device to which the present invention is applied will be described below.

  FIG. 15 is a perspective view showing a television to which the present invention is applied. The television according to this application example includes a video display screen unit 101 including a front panel 102, a filter glass 103, and the like, and is created by using the display device according to the present invention as the video display screen unit 101.

  16A and 16B are diagrams showing a digital camera to which the present invention is applied. FIG. 16A is a perspective view seen from the front side, and FIG. 16B is a perspective view seen from the back side. The digital camera according to this application example includes a light emitting unit 111 for flash, a display unit 112, a menu switch 113, a shutter button 114, and the like, and is manufactured by using the display device according to the present invention as the display unit 112.

  FIG. 17 is a perspective view showing a notebook personal computer to which the present invention is applied. A notebook personal computer according to this application example includes a main body 121 including a keyboard 122 that is operated when characters and the like are input, a display unit 123 that displays an image, and the like. It is produced by using.

  FIG. 18 is a perspective view showing a video camera to which the present invention is applied. The video camera according to this application example includes a main body 131, a lens 132 for shooting an object on a side facing forward, a start / stop switch 133 at the time of shooting, a display unit 134, and the like. It is manufactured by using such a display device.

  FIG. 19 is a diagram showing a mobile terminal device to which the present invention is applied, for example, a mobile phone, in which (A) is a front view in an open state, (B) is a side view thereof, and (C) is in a closed state. (D) is a left side view, (E) is a right side view, (F) is a top view, and (G) is a bottom view. The mobile phone according to this application example includes an upper housing 141, a lower housing 142, a connecting portion (here, a hinge portion) 143, a display 144, a sub display 145, a picture light 146, a camera 147, and the like. And the sub display 145 is manufactured by using the display device according to the present invention.

It is a top view which shows the whole structure of the display apparatus of 1st Embodiment. It is a circuit block diagram of the display apparatus of 1st Embodiment. FIG. 3 is a layout diagram of a pixel circuit of the display device according to the first embodiment. It is principal part sectional drawing of the display apparatus of 1st Embodiment. It is a board | substrate block diagram for demonstrating the manufacturing process of the display apparatus of this invention. It is a principal part plane process drawing for demonstrating a part of manufacturing process of 1st Embodiment. FIG. 6 is a cross-sectional process diagram (No. 1) for explaining a manufacturing process of the display device of the present invention; FIG. 6 is a cross-sectional process diagram (No. 2) for explaining a manufacturing process of the display device of the present invention; It is a graph which shows the electric current characteristic of a thin-film transistor for every scanning direction of the laser beam in the case of crystallization annealing. It is principal part sectional drawing for demonstrating the characteristic part of the display apparatus of 2nd Embodiment. It is a top view which shows the whole structure of the display apparatus of 3rd Embodiment. It is a circuit block diagram of the display apparatus of 3rd Embodiment. It is a layout diagram of the pixel circuit of the display device of the third embodiment. It is a layout diagram of a pixel circuit for explaining a characteristic part of a fourth embodiment. It is a perspective view which shows the television to which this invention is applied. It is a figure which shows the digital camera to which this invention is applied, (A) is the perspective view seen from the front side, (B) is the perspective view seen from the back side. 1 is a perspective view showing a notebook personal computer to which the present invention is applied. It is a perspective view which shows the video camera to which this invention is applied. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the portable terminal device to which this invention is applied, for example, a mobile telephone, (A) is the front view in the open state, (B) is the side view, (C) is the front view in the closed state , (D) is a left side view, (E) is a right side view, (F) is a top view, and (G) is a bottom view. It is a layout diagram of a thin film transistor substrate for a display device having a conventional mirror inversion structure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1a, 1b, 1c, 1d ... Display apparatus, 12 ... Power supply line, 13 ... Signal line, 14a, 14b ... Gate electrode, 31 ... Gate insulating film, 32 ... Amorphous semiconductor thin film, 32A ... Crystallized semiconductor Thin film, A ... display pixel, D ... drain, EL ... light emitting element, EL (R) ... red light emitting element, EL (G) ... green light emitting element, EL (B) ... blue light emitting element, Lh ... laser light (energy beam) ), S ... source, Tr1 ... thin film transistor, Tr2 ... thin film transistor, v ... scanning direction

Claims (11)

A plurality of pixel circuits provided along the alignment direction in a state in which the alignment direction of the source and drain of the thin film transistor is alternately inverted,
Among the four pixel circuits adjacent to each other in the arrangement direction, a light emitting element that emits a first color connected to two adjacent pixel circuits, and the remaining pixel circuits of the four pixel circuits, respectively. A plurality of display pixels each including a connected light emitting element emitting a second color and a light emitting element emitting a third color as a set of display pixels ,
The display device in which the plurality of display pixels have the same arrangement direction of the source / drain of the thin film transistor of the pixel circuit connected to the light emitting element emitting the second color . The thin film transistor has a bottom gate structure,
The display device according to claim 1, wherein a channel region of the thin film transistor is configured using a semiconductor thin film that is crystallized by irradiating an energy beam while scanning along the arrangement direction. The display device according to claim 1, wherein the first color is green . The display device according to claim 1, wherein the light emitting element that emits the first color is a light emitting element that has lower light emission efficiency than a light emitting element that emits the second color and a light emitting element that emits the third color . The display device according to claim 1, wherein the thin film transistor included in the pixel circuit has a different channel width for each light emission color of the light emitting element connected to the pixel circuit. Display device according to any one of claims 1 to 5 wherein the two pixel circuits adjacent connected to the signal line of the common. Wherein the two pixel circuits adjacent display device according to any one of claims 1 to 6, one light emitting element emitting the first color is connected. The pixel circuit arranged adjacent to the arrangement direction is laid out symmetrically with respect to the power supply line in a state of sharing one power supply line. Display device. The display device according to claim 1, wherein the two adjacent pixel circuits are laid out symmetrically with respect to the power supply line while sharing one power supply line. A step of arranging a plurality of gate electrodes in the line width direction;
Forming a gate insulating film and an amorphous semiconductor thin film in this order so as to cover the gate electrode;
Crystallization of the semiconductor thin film by irradiating while scanning energy lines in the line width direction of the gate electrode, and forming a thin film transistor using the crystallized semiconductor thin film;
Forming a pixel circuit having the thin film transistor along the line width direction of the gate electrode in a state where the arrangement direction of the source and drain of the thin film transistor is alternately reversed;
Of the four pixel circuits adjacent to each other in the arrangement direction, the light emitting element emitting the first light connected to the two adjacent pixel circuits is connected to the remaining pixel circuits of the four pixel circuits. A step of forming a plurality of display pixels using a light emitting element emitting a second color and a light emitting element emitting a third color as a set of display pixels,
A method for manufacturing a display device, wherein the plurality of display pixels are arranged so that the source / drain arrangement directions of the thin film transistors of the pixel circuit connected to the light emitting elements emitting the second color are the same . The method for manufacturing a display device according to claim 10, wherein the energy lines are scanned only in the same scanning direction along the line width direction with respect to the plurality of rows of gate electrodes arranged in the line width direction.

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