JP2008216542A - Method for driving organic semiconductor element, electro-optical device, method for driving electro-optical device and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for driving an organic transistor by which current attenuation due to a charge trap can be prevented, an electro-optical device, a method for driving the electro-optical device and electronic equipment. <P>SOLUTION: Since voltage of polarity for reducing electric resistance in a channel area is applied to a counter electrode during a period (scanning period) for applying the voltage of the polarity for reducing the electric resistance of the channel area to a gate electrode, current attenuation due to the charge trap in the organic transistor can be prevented. Consequently the generation of a display defect and an after-image in an electrophoretic display apparatus using the organic transistor as a switching element can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic semiconductor element driving method, an electro-optical device, an electro-optical device driving method, and an electronic apparatus.

Electro-optical devices such as liquid crystal devices and electrophoretic display devices are used in various fields. The electro-optical device has a configuration in which a plurality of pixels are arranged in a matrix in a plan view on a display surface, and each pixel is provided with a pixel electrode. A switching element is connected to the pixel electrode so as to switch on / off of an electric signal supplied to each pixel electrode. A technique using an organic transistor as a switching element has been proposed. In recent years, as shown in Patent Document 1, a back gate type configuration in which a gate electrode is further arranged on the back surface of the normal top gate type organic transistor (the back surface of the semiconductor layer) has been proposed.
JP 2005-166713 A

  However, if the organic transistor is kept on, a phenomenon called a charge trap occurs, and there is a problem that the current flowing through the organic transistor attenuates with time. When this current is attenuated, the voltage applied to the pixel electrode is attenuated, causing display defects and afterimages.

  In view of the circumstances as described above, an object of the present invention is to provide a driving method of an organic semiconductor element, an electro-optical device, a driving method of an electro-optical device, and an electronic apparatus capable of preventing current attenuation due to a charge trap. It is in.

  In order to achieve the above object, a method for driving an organic semiconductor device according to the present invention includes: an organic semiconductor layer having a channel region, a source region, and a drain region; and a boundary surface between the organic semiconductor layer and another layer. A first electrode provided via a first insulating layer in contact with one boundary surface, and a second insulation in contact with a second boundary surface different from the first boundary surface among the boundary surfaces. An electric resistance of the channel region within a period in which a first voltage for reducing the electric resistance of the channel region is applied to the first electrode. A second voltage for reducing the voltage is applied to the second electrode.

  In the organic semiconductor layer constituting the organic semiconductor element, the inventors have applied other polar voltages that reduce the electrical resistance of the channel region within a period in which a voltage having a polarity that reduces the electrical resistance of the channel region is applied to the electrodes. The present inventors have found that it is possible to prevent the current from being attenuated by the charge trap by applying to the electrode. Therefore, according to the present invention, an organic semiconductor layer having a channel region, a source region, and a drain region, and a first insulating layer in contact with a first boundary surface of the boundary surfaces between the organic semiconductor layer and another layer And a second electrode provided via a second insulating layer in contact with a second boundary surface different from the first boundary surface of the boundary surfaces. When driving the organic semiconductor element, the second voltage for reducing the electrical resistance of the channel region is applied within the period in which the first voltage for reducing the electrical resistance of the channel region is applied to the first electrode. Since the voltage is applied to the second electrode, it is possible to prevent the current from being attenuated by the charge trap.

In the organic semiconductor element, the first boundary surface is a boundary surface with the channel region.
According to the present invention, since the first boundary surface is a boundary surface with the channel region, the first voltage can be efficiently applied to the channel region.

The organic semiconductor element is characterized in that the second boundary surface is a boundary surface with the channel region.
According to the present invention, since the second boundary surface is a boundary surface with the channel region, the second voltage can be efficiently applied to the channel region.

The organic semiconductor element is characterized in that the application period of the second voltage is shorter than the application period of the first voltage.
According to the present invention, since the application period of the second voltage is shorter than the application period of the first voltage, the second voltage can be reliably applied within the application period of the first voltage. . Thus, current attenuation due to the charge trap can be reliably prevented.

The organic semiconductor element is characterized in that, in the organic semiconductor layer, the first boundary surface exists on a side opposite to a side where the second boundary surface exists.
According to the present invention, in the organic semiconductor layer, since the first boundary surface exists on the opposite side of the side where the second boundary surface exists, the first voltage and the second voltage are directly Can be avoided. Thereby, the malfunction of a semiconductor element can be avoided.

The organic semiconductor element is characterized in that the second voltage is a pulse voltage.
According to the present invention, since the second voltage is a pulse voltage, it is possible to avoid a state in which the second voltage is continuously applied to the second electrode. Thereby, it is possible to prevent a charge trap from occurring on the second electrode side. As a result, stable driving can be realized, and display defects and afterimages can be prevented more reliably.

An electro-optical device according to an aspect of the invention opposes one surface of the organic semiconductor layer having a channel region, a source region, and a drain region, and overlaps the channel region of the organic semiconductor layer in plan view. The gate electrode provided between the organic semiconductor layer via an insulating layer and the surface opposite to the one surface of the organic semiconductor layer are opposed to the channel region of the organic semiconductor layer. An active matrix type electro-optical device using an organic transistor as a switching element, which includes an opposing electrode provided through an insulating layer between the organic semiconductor layer so as to overlap in a plan view, A voltage having a polarity that decreases the electric resistance of the channel region is applied to the counter electrode within a period in which a voltage having a polarity that decreases the electric resistance of the region is applied to the gate electrode. As applied, characterized by comprising a control unit for controlling the voltage applied to the counter electrode.
According to the present invention, the counter electrode is applied to the counter electrode so that the voltage having the polarity that decreases the electric resistance of the channel region is applied to the counter electrode during the period in which the voltage of the channel region is decreased. Since the control unit for controlling the voltage to be applied is provided, it is possible to prevent the current from being attenuated by the charge trap by the control of the control unit. Thereby, it is possible to prevent display defects and afterimages.

In the electro-optical device, the control unit performs control so that a period in which no voltage is applied to the counter electrode is longer than a period in which a voltage is applied to the counter electrode.
According to the present invention, the control unit controls the period in which the voltage is not applied to the counter electrode to be longer than the period in which the voltage is applied to the counter electrode, so that a sufficient discharge time is ensured on the counter electrode side. can do. As a result, stable driving can be realized, and display defects and afterimages can be prevented more reliably.

In the electro-optical device, the voltage applied to the counter electrode is a pulse voltage.
According to the present invention, since the voltage applied to the counter electrode is a pulse voltage, it is possible to avoid the state in which the voltage is continuously applied to the counter electrode. Thereby, it is possible to prevent a charge trap from occurring on the counter electrode side. As a result, stable driving can be realized, and display defects and afterimages can be prevented more reliably.

An electro-optical device driving method according to the present invention includes an organic semiconductor layer having a channel region, a source region, and a drain region, and one surface of the organic semiconductor layer facing the channel region of the organic semiconductor layer. The gate electrode provided between the organic semiconductor layer so as to overlap with the organic semiconductor layer via an insulating layer, and the surface opposite to the one surface of the organic semiconductor layer, the surface of the organic semiconductor layer A driving method of an active matrix type electro-optical device using, as a switching element, an organic transistor provided with a counter electrode provided through an insulating layer between the organic semiconductor layer so as to overlap the channel region in plan view And the polarity for decreasing the electrical resistance of the channel region within a period of applying a voltage having a polarity for decreasing the electrical resistance of the channel region to the gate electrode. And applying a voltage to the counter electrode.
According to the present invention, a voltage having a polarity that decreases the electrical resistance of the channel region is applied to the counter electrode within a period in which a voltage having a polarity that decreases the electrical resistance of the channel region is applied to the gate electrode. It is possible to prevent the current from being attenuated by the charge trap by the control of the control unit. Thereby, it is possible to prevent display defects and afterimages.

An electronic apparatus according to the present invention includes the above-described electro-optical device.
According to the aspect of the invention, since the electro-optical device that can prevent the display disturbance and the afterimage is provided, an electronic apparatus having high display characteristics of the display unit can be obtained.

[First Embodiment]
A first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a cross-sectional configuration of an electrophoretic display device 1 according to the present embodiment.
As shown in the figure, the electrophoretic display device 1 includes a display unit 2 in which pixels 7 are arranged in a matrix in a display region, and a region between the pixels 7 extending in the short direction of the display unit 2 in the figure. The data line 5 to be performed, the scanning line 6 extending in the longitudinal direction of the display unit 2 between the pixels 7, the data line driving circuit 3 for supplying a signal to the data line 5, and the signal to the scanning line 6 And a scanning line driving circuit 4 that performs the above operation. Each pixel 7 is provided with an organic transistor 41 as a switching element. The organic transistor 41 is connected to the voltage control circuit 8. The data line driving circuit 3, the scanning line driving circuit 4, and the voltage control circuit 8 are connected to the controller 50, respectively.

FIG. 2 is a cross-sectional view illustrating a configuration of the display unit 2 of the electrophoretic display device 1.
As shown in the figure, the display unit 2 is mainly composed of an element substrate 10, a protective sheet 20, and a microcapsule 30.

The element substrate 10 is a rectangular substrate made of a material such as glass or plastic.
A pixel electrode 11 is formed for each pixel 7 on the inner surface of the element substrate 10 (the surface facing the protective sheet 20). Below the region between the pixel electrodes 11 or below the pixel electrodes, the above-described wirings such as the data lines 5 and the scanning lines 6 (see FIG. 1) and switching elements (see FIG. 4) are provided.

The protective sheet 20 is a rectangular substrate made of a light transmissive material such as glass.
A common electrode 21 is formed on the entire inner surface of the protective sheet 20 (the surface facing the element substrate 10). The common electrode 21 is made of a conductive material such as ITO (Indium Tin Oxide).

FIG. 3A is a diagram illustrating a configuration of the microcapsule 30.
The microcapsule 30 is a capsule having a particle size of, for example, about 50 μm and formed of a light-transmissive polymer resin such as acrylic resin such as polymethyl methacrylate and polyethyl methacrylate, urea resin, and gum arabic. The microcapsule 30 is sandwiched between the common electrode 21 and the pixel electrode 11 described above, and a plurality of microcapsules 30 are arranged vertically and horizontally in one pixel. A binder (not shown) for fixing the microcapsule 30 is provided so as to fill the periphery of the microcapsule 30.

Inside the microcapsule 30, a dispersant 31 and charged particles (white particles 32 and black particles 33) as a dispersoid are enclosed.
Dispersant 31 is, for example, alcohol solvents such as water, methanol, ethanol, isopropanol, butanol, octanol and methyl cellosolve, various esters such as ethyl acetate and butyl acetate, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, Aliphatic hydrocarbons such as pentane, hexane and octane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, benzene, toluene, xylene, hexylbenzene, hebutylbenzene, octylbenzene, nonylbenzene, decylbenzene, Aromatic hydrocarbons such as benzenes having a long chain alkyl group such as undecylbenzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene, etc., halogens such as methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane Hydrocarbons, made from those obtained by blending a surfactant or the like alone or a mixture thereof such as carboxylic acid salts, or other various oils, a liquid that disperses the white particles 32 and black particles 33.

The white particles 32 and the black particles 33 have a property of moving by electrophoresis due to a potential difference in the dispersant 31.
The white particles 32 are particles (polymer or colloid) made of a white pigment such as titanium dioxide, zinc white, and antimony trioxide, and are negatively charged, for example.
The black particles 33 are particles (polymer or colloid) made of a black pigment such as aniline black or carbon black, and are positively charged, for example.

  These pigments include electrolytes, surfactants, metal soaps, resins, rubbers, oils, varnishes, charge control agents composed of particles such as compounds, titanium-based coupling agents, aluminum-based coupling agents, silanes as necessary. A dispersant such as a system coupling agent, a lubricant, a stabilizer, and the like can be added.

  The operation of the microcapsule 30 configured as described above will be described. When a voltage is applied between the pixel electrode 11 and the common electrode 21 so that the voltage of the common electrode 21 is relatively high, the positively charged black particles 33 are subjected to Coulomb force as shown in FIG. Thus, the microcapsule 30 is drawn toward the pixel electrode side. On the other hand, the negatively charged white particles 32 are attracted to the common electrode 21 in the microcapsule 30 by Coulomb force. As a result, the white particles 32 gather on the display surface side in the microcapsule 30, and the color (white) of the white particles 32 is displayed on the display surface 20a.

  On the contrary, when a voltage is applied between the pixel electrode 11 and the common electrode 21 so that the potential of the pixel electrode 11 becomes relatively high, as shown in FIG. Is attracted to the pixel electrode 11 side by the Coulomb force. On the contrary, the positively charged black particles 33 are attracted to the common electrode 21 side by the Coulomb force. As a result, the black particles 33 are collected on the display surface side in the microcapsule 30, and the color of the black particles 33 is displayed on the display surface 20a.

FIG. 4 is a diagram illustrating a circuit configuration of one pixel in the display unit 2.
As shown in the figure, the pixel electrode 11 is connected to the data line 5 via the switching element 41, and the common electrode 21 is connected to a power source or the like that can set a predetermined potential. In the present embodiment, the switching element 41 is a so-called back gate type organic transistor.

  The switching element 41 includes an organic semiconductor layer having a channel region 41C, a source region 41S, and a drain region 41D, and a gate electrode (first electrode) 41G provided to face one surface of the organic semiconductor layer, A counter electrode (second electrode) 41B is mainly formed on the opposite side of the gate electrode 41G across the organic semiconductor layer. The gate electrode 41G is provided so as to overlap the channel region 41C in plan view. A gate insulating layer is provided between the gate electrode 41G and the organic semiconductor layer. The counter electrode 41B is provided in a region overlapping the channel region 41C in plan view. An insulating layer is provided between the counter electrode 41B and the organic semiconductor layer.

  Of the switching element 41, the gate electrode 41 </ b> G is connected to the scanning line 6, the source region 41 </ b> S is connected to the data line 5, and the drain region 41 </ b> D is connected to the pixel electrode 11. The counter electrode 41B is connected to the voltage control circuit 8 described above. The voltage control circuit 8 controls the voltage applied to the counter electrode 41B. A storage capacitor 9 is also connected to the drain electrode 41D.

  The scanning line 6 is connected to the scanning line driving circuit 4 described above. When the scanning line driving circuit 4 supplies a predetermined gate signal to the gate electrode 41G, the electric resistance of the channel region 41C is reduced. Similarly, the voltage control circuit 8 supplies a predetermined signal to the counter electrode 41B, so that the electrical resistance of the channel region 41C is reduced. A data signal supplied to the data line 5 flows into the pixel electrode 11 through the channel region 41C where the electrical resistance is reduced.

  Next, of the operations of the electrophoretic display device 1 configured as described above, the operation for updating the display contents will be described. Here, the description will focus on the writing operation when a new image is displayed in the display area of the display unit 2.

  When a new image is displayed in the display area of the display unit 2, a write voltage is applied between the common electrode 21 and the pixel electrode 11 of the display unit 2 that displays a new image. As shown in FIG. 5, an off voltage (0 V) is applied to the common electrode (COMepd) 21, and an on voltage is applied to the data line 5 in the pixel of the portion displaying a new image. In this state, the scanning lines 6 are scanned one by one so as to be in the scanning period t1. The time t2 is opened during the scanning period t1 of each scanning line 6. During this scanning period t1, an off-voltage is applied to the scanning line 6 (gate electrode 41G) in the pixel of the part displaying a new image (first voltage).

  In addition to this, in the present embodiment, the pulse voltage of the predetermined period t3 is applied to the counter electrode 41B of the switching element 41 (second voltage) within the period t1 of scanning each scanning line 6. This pulse voltage is an off voltage, and is a voltage having a polarity that decreases the electric resistance of the channel region 41C, that is, a voltage having the same polarity as the voltage applied to the gate electrode 41G (off voltage). This pulse voltage is applied at an interval of time t4. It is preferable to apply so that t3 <t4.

  In the example shown in FIG. 5, the voltage of the common electrode 21 is constant. However, the present invention is not limited to this. For example, as shown in FIG. 6, a pulse voltage is applied to the common electrode 21 within the scanning period t1. You may control to do. In this case, an on-voltage is applied as the pulse voltage.

  As described above, according to the present embodiment, the polarity of the channel region 41C is decreased during the period (scanning period t1) in which the voltage having the polarity that decreases the electrical resistance of the channel region 41C is applied to the gate electrode 41G. Since the voltage is applied to the counter electrode 41B, it is possible to prevent the current from being attenuated by the charge trap in the organic transistor. Thereby, it is possible to prevent display defects and afterimages of the electrophoretic display device 1 using the organic transistor as the switching element 41.

  In the present embodiment, the period (t4) in which the voltage is not applied to the counter electrode 41B is longer (t3 <t4) in the voltage control circuit 8 than the period (t3) in which the voltage is applied to the counter electrode 41B. Thus, a sufficient discharge time can be secured on the counter electrode 41B side. As a result, stable driving can be realized, and display defects and afterimages can be prevented more reliably.

  Further, according to the present embodiment, since the voltage applied to the counter electrode 41B is a pulse voltage, it is possible to avoid a state in which a voltage is continuously applied to the counter electrode 41B. Thereby, it is possible to prevent a charge trap from being generated on the counter electrode 41B side. As a result, stable driving can be realized, and display defects and afterimages can be prevented more reliably.

[Second Embodiment]
Next, an electronic apparatus according to a second embodiment of the present invention will be described using an electronic book as an example.
FIG. 7 is a perspective view showing the configuration of the electronic book.
As shown in the figure, the electronic book 131 includes a book-shaped frame 132 and a cover 133 that can be opened and closed on the frame 132. The frame 132 is provided with a display unit 134 with the display surface exposed on the surface thereof, and is further provided with an operation unit 135.
A controller, a counter, and a memory are also built in the frame 132. The electrophoretic display device 1 is mounted as the display unit 134.
As described above, since the electrophoretic display device 1 capable of preventing display disturbance and afterimage generation is mounted, the electronic book 131 having high display characteristics can be obtained.

The technical scope of the present invention is not limited to the above-described embodiment, and appropriate modifications can be made without departing from the spirit of the present invention.
In the above embodiment, the case where the counter electrode 41B in all the pixels is simultaneously driven has been described as an example. However, the present invention is not limited to this. For example, the counter electrode 41B is provided in the pixel 7 in which the off voltage is applied to the gate electrode 41G. The voltage control circuit 8 may control so that the off voltage is applied only to the counter electrode 41B. Thus, the counter electrode 41B can be discharged until the next scanning period after the scanning period t1 ends in one scanning line 6.

  In the above-described embodiment, an electrophoretic display device has been described as an example of an electro-optical device. However, the electro-optical device is not limited thereto, and an electro-optical device driven by an active matrix method such as a liquid crystal device or an organic EL device can be used. The application of the present invention is possible.

1 is a schematic diagram showing a configuration of an electrophoretic display device according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view showing the configuration of the electrophoretic display device according to the embodiment. Sectional drawing which shows the structure of the microcapsule of the electrophoretic display device which concerns on this embodiment. FIG. 3 is a circuit diagram illustrating a configuration of a pixel of the electrophoretic display device according to the embodiment. 4 is a timing chart showing a driving method of the electrophoretic display device according to the embodiment. Same as above, timing chart. The perspective view which shows the structure of the electronic book which concerns on 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrophoretic display device 2 ... Display part 3 ... Data line drive circuit 4 ... Scan line drive circuit 5 ... Data line 6 ... Scan line 7 ... Pixel 8 ... Voltage control circuit 10 ... Element substrate 11 ... Pixel electrode 20a ... Display surface DESCRIPTION OF SYMBOLS 21 ... Common electrode 30 ... Microcapsule 41 ... Switching element 41G ... Gate electrode 41S ... Source electrode 41D ... Drain electrode 41B ... Counter electrode 131 ... Electronic book

Claims (11)

An organic semiconductor layer having a channel region, a source region and a drain region;
A first electrode provided through a first insulating layer in contact with a first interface of the interfaces between the organic semiconductor layer and another layer;
A second electrode provided via a second insulating layer in contact with a second boundary surface different from the first boundary surface of the boundary surfaces;
Comprising
A second voltage for reducing the electrical resistance of the channel region is applied to the second electrode within a period in which a first voltage for reducing the electrical resistance of the channel region is applied to the first electrode. A method for driving an organic semiconductor element, comprising applying the organic semiconductor element.   2. The method of driving an organic semiconductor element according to claim 1, wherein the first boundary surface is a boundary surface with the channel region.   The method of driving an organic semiconductor element according to claim 1, wherein the second boundary surface is a boundary surface with the channel region.   4. The method of driving an organic semiconductor element according to claim 1, wherein the application period of the second voltage is shorter than the application period of the first voltage.   5. The method of driving an organic semiconductor element according to claim 1, wherein in the organic semiconductor layer, the first boundary surface is present on a side opposite to a side on which the second boundary surface is present. . 6. The method of driving an organic semiconductor element according to claim 1, wherein the second voltage is a pulse voltage. An organic semiconductor layer having a channel region, a source region, and a drain region, and the organic semiconductor layer so as to face one surface of the organic semiconductor layer and overlap the channel region of the organic semiconductor layer in plan view The organic semiconductor layer so as to face a surface opposite to the one surface of the organic semiconductor layer and to overlap the channel region of the organic semiconductor layer in plan view. An active matrix type electro-optical device using an organic transistor provided with a counter electrode provided through an insulating layer between a semiconductor layer as a switching element,
A voltage having a polarity that decreases the electrical resistance of the channel region is applied to the counter electrode within a period in which a voltage having a polarity that decreases the electrical resistance of the channel region is applied to the gate electrode. An electro-optical device comprising a control unit that controls a voltage to be generated. The electro-optical device according to claim 7, wherein the control unit performs control so that a period in which no voltage is applied to the counter electrode is longer than a period in which a voltage is applied to the counter electrode. The electro-optical device according to claim 7, wherein the voltage applied to the counter electrode is a pulse voltage. An organic semiconductor layer having a channel region, a source region, and a drain region, and the organic semiconductor layer so as to face one surface of the organic semiconductor layer and overlap the channel region of the organic semiconductor layer in plan view The organic semiconductor layer so as to face a surface opposite to the one surface of the organic semiconductor layer and to overlap the channel region of the organic semiconductor layer in plan view. A driving method of an active matrix type electro-optical device using an organic transistor provided with a counter electrode provided via an insulating layer between a semiconductor layer as a switching element,
An electro-optical device, wherein a voltage having a polarity for decreasing the electrical resistance of the channel region is applied to the counter electrode within a period in which a voltage having a polarity for decreasing the electrical resistance of the channel region is applied to the gate electrode. Driving method.   An electronic apparatus comprising the electro-optical device according to any one of claims 7 to 9.

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