WO2017187826A1

WO2017187826A1 - Display device, drive method, and electronic apparatus

Info

Publication number: WO2017187826A1
Application number: PCT/JP2017/010369
Authority: WO
Inventors: 西池　昭仁; 安倍　浩信
Original assignee: ソニー株式会社
Priority date: 2016-04-28
Filing date: 2017-03-15
Publication date: 2017-11-02
Also published as: JP2017198877A

Abstract

This display device comprises: a pixel section comprising a plurality of pixels with each pixel including an electrophoretic element; and a drive section for applying drive voltage to each pixel in the pixel section. The drive section is configured so as to apply the drive voltage at each period shorter than one frame period during the effective display period in the one frame period.

Description

Display device, driving method, and electronic apparatus

The present disclosure relates to a display device using an electrophoretic element, a driving method thereof, and an electronic apparatus including the display device.

In recent years, with the widespread use of mobile devices such as mobile phones or personal digital assistants (PDAs), there is an increasing demand for display devices with low power consumption and high image quality. Recently, with the birth of an electronic book distribution business, display devices with display quality suitable for reading applications have been desired.

As such a display device, there are various types such as a cholesteric liquid crystal type, an electrophoretic type, an electrooxidation reduction type, a twist ball type, etc. Among them, a reflection type display device is advantageous. This is because a reflective display device performs bright display using reflection (scattering) of external light as in the case of paper, so that a display quality closer to that of paper can be obtained.

Among reflective display devices, an electrophoretic display device using an electrophoretic element is expected to be a promising candidate because of its low power consumption and fast response speed. As a driving method of the electrophoretic display device, an active matrix driving method using TFT (Thin Film Transistor) or the like, a segment system in which a display body is sandwiched between a pair of divided electrodes, and driving is performed for each electrode. Is mentioned. In the case where a large number of fine characters are displayed as in an electronic book, an active matrix driving method is widely used because high resolution is required.

In a display device using such an electrophoretic element, various driving methods have been proposed in order to improve display quality (for example, Patent Documents 1 to 3).

JP 2013-218342 A Special table 2007-519045 gazette JP 2011-59525 A

However, in the methods of Patent Documents 1 to 3, a voltage is applied to each pixel in a vertical period corresponding to the frame frequency (frame rate). By increasing the frame frequency, fine voltage control is possible and display quality can be improved, but power consumption increases.

It is desirable to provide a display device and a driving method capable of improving display quality while suppressing an increase in power consumption.

A display device according to an embodiment of the present disclosure includes a pixel unit having a plurality of pixels each including an electrophoretic element, and a drive unit that drives the voltage of the pixel unit for each pixel. In the effective display period, voltage driving is performed in units shorter than one frame period.

In the driving method according to the embodiment of the present disclosure, when a plurality of pixels each including an electrophoretic element are voltage-driven for each pixel, the effective display period of one frame period is shorter than one frame period. Voltage driving is performed in units of periods.

An electronic apparatus according to an embodiment of the present disclosure includes the display device according to the embodiment of the present disclosure.

In the display device, the driving method, and the electronic device according to the embodiment of the present disclosure, when each pixel including the electrophoretic element is voltage-driven, the effective display period in one frame period is a period shorter than one frame period. Voltage drive is performed in units. A voltage can be applied to each pixel at an arbitrary timing and pulse width without increasing the frame frequency (frame rate). In other words, the frame frequency is apparently increased, and more fine voltage drive can be performed.

According to the display device, the driving method, and the electronic apparatus according to the embodiment of the present disclosure, when each pixel including the electrophoretic element is voltage-driven, the effective display period in one frame period is longer than the one frame period. Voltage driving is performed in units of short periods. As a result, it is possible to perform more detailed voltage driving without increasing the frame frequency (frame rate). Therefore, it is possible to improve display quality while suppressing an increase in power consumption.

The above content is an example of the present disclosure. The effects of the present disclosure are not limited to those described above, and may be other different effects or may include other effects.

It is a block diagram showing the composition of the display of a 1st embodiment of this indication with the composition of a drive. It is sectional drawing showing the principal part structure of the pixel part shown in FIG. It is a schematic diagram showing the structure of the display body shown in FIG. It is a cross-sectional schematic diagram for demonstrating the drive method of the display apparatus shown in FIG. FIG. 2 is a timing chart for explaining a method for driving the display device shown in FIG. 1. It is a timing chart for explaining an example of a gradation display operation. It is a schematic diagram for demonstrating the transition of the display state with respect to an applied voltage waveform. It is a schematic diagram showing an example of an applied voltage waveform. It is a schematic diagram showing an example of an applied voltage waveform. It is a schematic diagram showing an example of an applied voltage waveform. It is a schematic diagram showing an example of an applied voltage waveform. It is a figure showing the optical response characteristic at the time of applying 0V in the last frame of a writing period. It is a figure showing the optical response characteristic when 0V is not applied in the last frame of the writing period. FIG. 2 is a timing chart for explaining a driving operation (line sequential driving operation in all scanning lines) of the display device shown in FIG. 1. FIG. 2 is a timing chart for explaining a driving operation (line sequential driving operation for each scanning line group) of the display device shown in FIG. 1. 11 is a timing chart for explaining a driving operation (line sequential driving operation for each scanning line group) of a display device according to Modification 1. FIG. 10 is a functional block diagram for explaining a configuration of a display device according to modification example 2. FIG. FIG. 12 is a timing diagram for describing a driving operation of a display device according to a second embodiment of the present disclosure. It is a timing diagram for explaining a drive operation according to a comparative example. It is a characteristic view showing an example of the voltage for display concerning an example. It is a characteristic view showing the optical response characteristic (light reflectivity change with time) by the voltage application shown to FIG. 15A. FIG. 15B is a characteristic diagram illustrating a first combination example of the display voltage and the correction voltage illustrated in FIG. 15A. It is a characteristic view showing the optical response characteristic by the voltage application shown to FIG. 16A. FIG. 15B is a characteristic diagram illustrating a second combination example of the display voltage and the correction voltage illustrated in FIG. 15A. It is a characteristic view showing the optical response characteristic by the voltage application shown to FIG. 17A. 12 is a perspective view illustrating a configuration of an electronic book according to application example 1. FIG. 12 is a perspective view illustrating another configuration of the electronic book according to Application Example 1. FIG. 12 is a perspective view illustrating a state of a configuration of an electronic timepiece according to application example 2. FIG. 12 is a perspective view illustrating another state of the configuration of the electronic timepiece according to application example 2. FIG.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The order of explanation is as follows.
1. First embodiment (an example of a display device in which voltage driving is performed in units of periods shorter than one frame period by dividing and driving all scanning lines into two scanning line groups)
2. Modification 1 (example in which all scanning lines are divided into four scanning line groups)
3. Modification 2 (example in which a plurality of scanning line driving circuits are arranged)
4). Second Embodiment (An example of a display device in which voltage driving is performed in units of periods shorter than one frame period by driving by dividing an ON period in a scanning signal pulse)
5). Example (Example of voltage drive)
6). Application examples (examples of electronic devices)

<First Embodiment>
[Constitution]
FIG. 1 illustrates the configuration of the display device (display device 1) according to the first embodiment of the present disclosure together with the configuration of the drive device (drive device 2). FIG. 2 illustrates a main configuration of the pixel unit 1 A of the display device 1. The display device 1 is an electrophoretic display device that displays an image using an electrophoretic phenomenon, and is a so-called electronic paper display.

The display device 1 includes a plurality of pixels 10 (pixel portions 1A) that are driven to display by an active matrix driving method using TFTs, for example. The plurality of pixels 10 include a display body 10A (electrophoretic element), and display characters and images by changing the light reflectance of the display body 10A for each pixel 10. The pixel portion 1A is connected to the scanning line driving circuit 110 and the signal line driving circuit 120. In the pixel portion 1A, the output end of the scanning line driving circuit 110 and each pixel 10 are connected, and a plurality of scanning lines GL extending along the row direction, the output end of the signal line driving circuit 120, and each pixel 10 are connected. And a plurality of signal lines DL extending in the column direction are arranged. A pixel 10 is formed at each intersection of the plurality of scanning lines GL and the plurality of signal lines DL.

The scanning line driving circuit 110 includes, for example, a shift register circuit and a predetermined logic circuit. The scanning line driving circuit 110 applies the scanning signal sequentially (line-sequentially) to the plurality of scanning lines GL in accordance with the control signal supplied from the driving device 2, thereby causing the pixel unit 1 A (the plurality of pixels 10). It has a function to select line by line. The output terminal of the scanning line driving circuit 110 is connected to the gate terminal of the TFT disposed in each pixel 10 through the scanning line GL.

In the present embodiment, the scanning line driving circuit 110 includes a plurality of scanning line groups (scanning line group GLgrp).
) Each time line-sequential driving (line-sequential scanning) is performed. That is, the scanning line driving circuit 110 can apply a scanning start signal (gate start pulse) to the scanning lines GL of two or more specified lines among all the scanning lines GL (IC: Integrated Circuit). ). As a result, the scanning line driving circuit 110 applies a scanning start signal (Gst) to the scanning line GL of each head line (for example, the top line) of the plurality of scanning line groups GLgrp. The scanning lines GL on the lower line (second and subsequent lines from the top) are sequentially scanned.

The scanning line group GLgrp is a group including a plurality of scanning lines GL configured by dividing all scanning lines GL connected to the output terminal of the scanning line driving circuit 110 by n (n is an integer of 2 or more). . This division number “n” is, for example, a number that can divide the total number of scanning lines, and is determined according to a target scanning period (a period required to select all the scanning lines GL) in one frame period. desirable.

For example, as shown in FIG. 1, when the total number of scanning lines (the number of effective scanning lines) is 720 and n is 2, 720/2 = 360, which is divisible. Line-sequential driving is performed in each of two scanning line groups GLgrp1 and GLgrp2 formed by dividing all scanning lines GL into two. Specifically, scanning line group GLgrp1 include, for example, a total of 360 scanning lines GL from the scanning lines GL ₁ of the first line to the scanning line GL ₃₆₀ of the 360 lines. The line sequential driving of the scanning line groups GLgrp1, scanning lines GL ₁ is a first line, the scanning lines GL ₃₆₀ is the last line. Scanning line group GLgrp2 include, for example, a total of 360 scanning lines GL from the scanning line GL ₃₆₁ of the 361 line to the scanning lines GL ₇₂₀ of the 720 lines. In the line-sequential driving of the scanning line group GLgrp2, the scanning line GL ₃₆₁ is the first line, and the last scanning line GL ₇₂₀ is the last line.

In this example, when the frame frequency is 50 Hz, the vertical period (unit period of voltage driving) when all the scanning lines are sequentially scanned from the first line to the last line is 20 ms. Although details will be described later in the present embodiment, the line sequential driving for each scanning line group GLgrp as described above is shorter than a vertical period corresponding to the frame frequency, that is, one frame period (20 ms in the case of 50 Hz). Voltage driving is performed in units of periods. For example, when the frame frequency is 50 Hz and n = 2, 20/2 = 10 (ms) can be set as the unit period of voltage application.

The signal line driving circuit 120 generates an analog signal corresponding to the display signal in accordance with a control signal supplied from the driving device 2 and applies the analog signal to each signal line DL. A display signal (signal voltage) applied to each signal line DL by the signal line driving circuit 120 is applied to the pixel 10 selected by the scanning line driving circuit 110. This signal line driving circuit 120 has a function of generating and holding a voltage waveform pattern used for voltage driving in units of periods (Th1, Th2), which will be described later, separately from a normal voltage waveform pattern for display. Good.

The drive device 2 generates signals necessary for driving the display device 1 and supplies power. The drive device 2 includes, for example, a control unit 210, a storage unit 211, a signal processing unit 212, and a power supply circuit 213. The signal processor 212 includes, for example, a timing controller 212a and a display signal generator 212b. The timing controller 212a and the display signal generator 212b generate various signals output to the scanning lines GL and the signal lines DL, signals for controlling application timings of these signals, and the like. The driving device 2, the scanning line driving circuit 110, and the signal line driving circuit 120 correspond to a specific example of “driving unit” of the present disclosure.

(Detailed configuration example of the display device 1)
FIG. 3 schematically shows the configuration of the display 10A. In the pixel unit 1 A, for example, a plurality of first electrodes (pixel electrodes) 13 are provided on the first substrate 11 via the TFT layer 12. A sealing layer 14 is formed so as to cover the TFT layer 12 and the first electrode 13, and the display body 10 A is provided on the sealing layer (adhesive layer) 14. A second electrode (counter electrode) 19 and a second substrate 20 are arranged in this order on the display body 10A. The display body 10 A is configured such that the light reflectance changes (generates contrast) according to the voltage applied through the first electrode 13 and the second electrode 19. As an example, the display 10 A includes a porous layer 16 and migrating particles 17 in an insulating liquid 15. The display body 10 A is separated for each pixel 10 by the partition wall 18. Here, the display body 10A is configured to be partitioned by the partition wall 18. However, the configuration of the electrophoretic element is not limited to this, and other configurations (for example, capsule-shaped or without partition). It may be.

The first substrate 11 is made of, for example, an inorganic material, a metal material, or a plastic material. Examples of the inorganic material include silicon (Si), silicon oxide (SiO _x ), silicon nitride (SiN _x ), and aluminum oxide (AlO _x ). Silicon oxide includes, for example, glass or spin-on-glass (SOG). Examples of the metal material include aluminum (Al), nickel (Ni), and stainless steel. Examples of the plastic material include polycarbonate (PC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyethyl ether ketone (PEEK).

The TFT layer 12 is a layer in which switching elements (TFT elements) for selecting pixels are formed. The TFT element may be, for example, an inorganic TFT using an inorganic semiconductor such as amorphous silicon, polysilicon, or oxide as a channel layer, or an organic TFT using an organic semiconductor such as pentacene. The type of the TFT element is not particularly limited, and may be, for example, an inverted stagger structure (so-called bottom gate type) or a stagger structure (so-called top gate type). Further, it may be n-type or p-type. The TFT element is disposed for each pixel 10, and each is electrically connected to the first electrode 13. In this specification, it is assumed that the TFT element is n-type. However, when the TFT element is p-type, the waveform of the scanning signal pulse is inverted between positive and negative.

The first electrode 13 includes at least one of conductive materials such as gold (Au), silver (Ag), and copper (Cu). A plurality of the first electrodes 13 are arranged in a matrix in the pixel portion 1A.

The sealing layer 14 is made of an adhesive resin material.

The insulating liquid 15 is a non-aqueous solvent such as an organic solvent, and is specifically paraffin or isoparaffin. It is preferable that the viscosity and refractive index of the insulating liquid 15 be as low as possible. This is because the mobility (response speed) of the migrating particles 17 is improved and the energy (power consumption) required to move the migrating particles 17 is accordingly reduced. Moreover, since the difference between the refractive index of the insulating liquid 15 and the refractive index of the porous layer 16 becomes large, the light reflectance of the porous layer 16 becomes high.

The insulating liquid 15 may contain various materials as necessary. For example, the insulating liquid 15 may include a colorant, a charge control agent, a dispersion stabilizer, a viscosity adjusting agent, a surfactant, or a resin.

The electrophoretic particles 17 are one or more charged particles that can move between the first electrode 13 and the second electrode 19, and are dispersed in the insulating liquid 15. The migrating particles 17 can move between the first electrode 13 and the second electrode 19 in the insulating liquid 15. The migrating particles 17 are, for example, any one kind or two or more kinds of particles (powder) such as an organic pigment, an inorganic pigment, a dye, a carbon material, a metal material, a metal oxide, glass, or a polymer material (resin). . The migrating particles 17 may be pulverized particles or capsule particles of resin solids containing the above-described particles. However, materials corresponding to carbon materials, metal materials, metal oxides, glass, or polymer materials are excluded from materials corresponding to organic pigments, inorganic pigments, or dyes. As the migrating particles 17, one of the above may be used, or a plurality of types may be used.

The content (concentration) of the migrating particles 17 in the insulating liquid 15 is not particularly limited, and is, for example, 0.1 wt% to 10 wt%. This is because shielding (concealment) and mobility of the migrating particles 17 are ensured. In this case, if it is less than 0.1% by weight, there is a possibility that the migrating particles 17 are difficult to shield the porous layer 16. On the other hand, if the amount is more than 10% by weight, the dispersibility of the migrating particles 17 is lowered, so that the migrating particles 17 are difficult to migrate, and in some cases, there is a possibility of aggregation.

The electrophoretic particles 17 also have arbitrary light reflection characteristics (light reflectivity). The light reflectance of the migrating particles 17 is not particularly limited, but is preferably set so that at least the migrating particles 17 can shield the porous layer 16. This is because contrast is generated by utilizing the difference between the light reflectance of the migrating particles 17 and the light reflectance of the porous layer 16.

The specific forming material of the migrating particles 17 is selected according to the role of the migrating particles 17 in order to cause contrast, for example. For example, the material in the case of bright display (white display) by the migrating particles 17 is, for example, a metal oxide such as titanium oxide, zinc oxide, zirconium oxide, barium titanate or potassium titanate. preferable. This is because it is excellent in electrochemical stability and dispersibility and has high reflectance. On the other hand, the material in the case of dark display (black display) by the migrating particles 17 is, for example, a carbon material or a metal oxide. The carbon material is, for example, carbon black, and the metal oxide is, for example, copper-chromium oxide, copper-manganese oxide, copper-iron-manganese oxide, copper-chromium-manganese oxide, or copper-iron. -Chromium oxide and the like. Among these, a carbon material is preferable. This is because excellent chemical stability, mobility and light absorption are obtained.

When the migrating particles 17 are brightly displayed, the color of the migrating particles 17 viewed from the outside is not particularly limited as long as a contrast can be generated, but for example, white or a color close to white is desirable. On the other hand, when the dark display is performed by the migrating particles 17, the color of the migrating particles 17 visually recognized from the outside is not particularly limited as long as a contrast can be generated, but is desirably black or a color close to black. This is because in either case, the contrast becomes high. When the purpose is to display a color other than white or black, the migrating particles 17 may be colored in a target color.

In addition, it is preferable that the migrating particles 17 are easily dispersed and charged in the insulating liquid 15 for a long period of time and are not easily adsorbed to the porous layer 16. For this reason, in order to disperse the electrophoretic particles 17 by electrostatic repulsion, a dispersant (or a charge adjusting agent) may be used, or the electrophoretic particles 17 may be subjected to a surface treatment, or both may be used in combination.

The porous layer 16 is, for example, a three-dimensional structure (irregular network structure such as a nonwoven fabric) formed of a fibrous structure 16A as shown in FIG. The porous layer 16 has a plurality of gaps (pores H) through which the migrating particles 17 pass in places where the fibrous structure 16A does not exist.

The fibrous structure 16A includes one or more non-migrating particles 16B, and the non-migrating particles 16B are held by the fibrous structure 16A. In the porous layer 16 that is a three-dimensional solid structure, one fibrous structure 16A may be randomly entangled, or a plurality of fibrous structures 16A may be gathered and overlap at random. However, both may be mixed. When there are a plurality of fibrous structures 16A, each fibrous structure 16A preferably holds one or more non-migrating particles 16B. FIG. 3 shows a case where the porous layer 16 is formed of a plurality of fibrous structures 16A.

The reason why the porous layer 16 is a three-dimensional structure is that the irregular three-dimensional structure easily causes external light to be irregularly reflected (multiple scattering), so that the light reflectance of the porous layer 16 increases and the high light This is because the porous layer 16 can be thin in order to obtain reflectance. Thereby, the contrast is increased and the energy required for moving the migrating particles 17 is decreased. Moreover, since the average pore diameter of the pores H increases and the number thereof increases, the migrating particles 17 easily pass through the pores H. As a result, the time required to move the migrating particles 17 is shortened, and the energy required to move the migrating particles 17 is also reduced.

The reason why the non-migrating particles 16B are included in the fibrous structure 16A is that the light reflectance of the porous layer 16 becomes higher because external light is more easily diffusely reflected. Thereby, contrast becomes higher.

The fibrous structure 16A is a fibrous substance having a sufficiently large length with respect to the fiber diameter (diameter). The fibrous structure 16A includes, for example, any one type or two or more types such as a polymer material or an inorganic material, and may include other materials. Polymer materials include, for example, nylon, polylactic acid, polyamide, polyimide, polyethylene terephthalate, polyacrylonitrile, polyethylene oxide, polyvinyl carbazole, polyvinyl chloride, polyurethane, polystyrene, polyvinyl alcohol, polysulfone, polyvinyl pyrrolidone, polyvinylidene fluoride, polyhexa Fluoropropylene, cellulose acetate, collagen, gelatin, chitosan or copolymers thereof. The inorganic material is, for example, titanium oxide. Among these, a polymer material is preferable as a forming material of the fibrous structure 16A. This is because the reactivity (photoreactivity, etc.) is low (chemically stable), so that the unintended decomposition reaction of the fibrous structure 16A is suppressed. In addition, when the fibrous structure 16A is formed of a highly reactive material, the surface of the fibrous structure 16A is preferably covered with an arbitrary protective layer.

The shape (external appearance) of the fibrous structure 16A is not particularly limited as long as the fibrous structure 16A has a sufficiently long length with respect to the fiber diameter as described above. Specifically, it may be linear, may be curled, or may be bent in the middle. Moreover, you may branch to 1 or 2 or more directions on the way, not only extending in one direction. The formation method of the fibrous structure 16A is not particularly limited. For example, a phase separation method, a phase inversion method, an electrostatic (electric field) spinning method, a melt spinning method, a wet spinning method, a dry spinning method, a gel spinning method, A sol-gel method or a spray coating method is preferred. This is because a fibrous substance having a sufficiently large length with respect to the fiber diameter can be easily and stably formed.

The average fiber diameter of the fibrous structure 16A is not particularly limited, but is preferably as small as possible. This is because light easily diffuses and the average pore diameter of the pores H increases. However, the average fiber diameter may be determined so that the fibrous structure 16A can hold the non-migrating particles 16B. For this reason, it is preferable that the average fiber diameter of 16 A of fibrous structures is 10 micrometers or less. In addition, although the minimum of an average fiber diameter is not specifically limited, For example, it is 0.1 micrometer and may be less than that. This average fiber diameter is measured, for example, by microscopic observation using a scanning electron microscope (SEM) or the like. The average length of the fibrous structure 16A may be arbitrary.

The average pore diameter of the pores H is not particularly limited, but is preferably as large as possible. This is because the migrating particles 17 easily pass through the pores H. For this reason, the average pore diameter of the pores H is preferably 0.1 μm to 10 μm.

The thickness of the porous layer 16 is not particularly limited, but is, for example, 5 μm to 100 μm. This is because the shielding property of the porous layer 16 becomes high and the migrating particles 17 easily pass through the pores H.

Particularly, the fibrous structure 16A is preferably a nanofiber. Since the three-dimensional structure is complicated and external light is easily diffusely reflected, the light reflectance of the porous layer 16 is further increased, and the volume ratio of the pores H in the unit volume of the porous layer 16 is increased. This is because the migrating particles 17 easily pass through the pores H. Thereby, the contrast becomes higher and the energy required to move the migrating particles 17 becomes lower. A nanofiber is a fibrous material having a fiber diameter of 0.001 μm to 0.1 μm and a length that is 100 times or more of the fiber diameter. The fibrous structure 16A that is a nanofiber is preferably formed by an electrostatic spinning method using a polymer material. This is because the fibrous structure 16A having a small fiber diameter can be easily and stably formed.

It is preferable that the fibrous structure 16A has an optical reflection characteristic different from that of the migrating particles 17. Specifically, the light reflectance of the fibrous structure 16A is not particularly limited, but is preferably set so that at least the porous layer 16 can shield the migrating particles 17 as a whole. As described above, this is because contrast is generated by utilizing the difference between the light reflectance of the migrating particles 17 and the light reflectance of the porous layer 16.

Non-electrophoretic particles 16B are particles that are fixed to the fibrous structure 16A and do not migrate electrically. The material for forming the non-migrating particles 16B is, for example, the same as the material for forming the migrating particles 17, and is selected according to the role played by the non-migrating particles 16B, as will be described later. The non-migrating particles 16 B have optical reflection characteristics different from those of the migrating particles 17. The light reflectance of the non-migrating particles 16B is not particularly limited, but is preferably set so that at least the porous layer 16 can shield the migrating particles 17 as a whole. As described above, this is because contrast is generated by utilizing the difference between the light reflectance of the migrating particles 17 and the light reflectance of the porous layer 16.

Here, the specific forming material of the non-migrating particles 16B is selected according to the role of the non-migrating particles 16B in order to cause contrast, for example. Specifically, the material when brightly displayed by the non-electrophoretic particles 16B is the same as the material of the electrophoretic particles 17 selected when brightly displayed. On the other hand, the material in the case of dark display by the non-electrophoretic particles 16B is the same as the material of the electrophoretic particles 17 selected in the case of dark display. Among these, as a material selected when brightly displayed by the non-migrating particles 16B, a metal oxide is preferable, and titanium oxide is more preferable. This is because it is excellent in electrochemical stability and fixability, and high reflectance can be obtained. If the contrast can be generated, the material for forming the non-migrating particles 16B may be the same as or different from the material for forming the migrating particles 17.

It should be noted that the color visually recognized when the non-electrophoretic particle 16B is displayed brightly or darkly is the same as the case where the color where the electrophoretic particle 17 is viewed is described.

An example of the procedure for forming the porous layer 16 is as follows. First, a material for forming the fibrous structure 16A (for example, a polymer material) is dispersed or dissolved in an organic solvent to prepare a spinning solution. Subsequently, after adding the non-migrating particles 16B to the spinning solution, the non-migrating particles 16B are dispersed in the spinning solution by sufficiently stirring. Finally, spinning is performed by an electrostatic spinning method using a spinning solution. Thereby, the non-migrating particles 16B are held by the fibrous structure 16A, and the porous layer 16 is formed.

The second electrode 19 is made of, for example, a transparent conductive film. Examples of the transparent conductive film include indium oxide-tin oxide (ITO), antimony oxide-tin oxide (ATO), fluorine-doped tin oxide (FTO), and aluminum-doped zinc oxide (AZO). Here, for example, the second electrode 19 is formed on one surface of the second substrate 20 as an electrode common to all the pixels 10. However, the second electrode 19 may be divided in the same manner as the first electrode 13. May be).

The second substrate 20 is made of the same material as the first substrate 11. However, since an image is displayed on the upper surface of the second substrate 20, a material having optical transparency is used for the second substrate 20. A color filter (not shown) may be provided in contact with one surface of the second substrate 20 or in a layer above the second substrate 20.

[Driving method]
In the display device 1 according to the present embodiment, the driving device 2, the scanning line driving circuit 110, and the signal line driving circuit 120 drive the voltage of the pixel unit 1A for each pixel 10, for example, as described above, for example, the migrating particles 17 By utilizing the difference between the light reflectivity of the light and the light reflectivity of the porous layer 16, contrast can be generated, and white display, black display, or gradation display can be performed. Specifically, by applying a voltage between the first electrode 13 and the second electrode 19 for each pixel 10, the migrating particles 17 are changed according to the magnitude, polarity, application time, and the like of the applied voltage. It moves between the first electrode 13 and the second electrode 19. Thereby, for example, one or both of the light reflection characteristics of the migrating particles 17 and the light reflection characteristics of the porous layer 16 can be exhibited, and the light reflectance of each pixel 10 can be changed.

FIG. 4 schematically shows an example of the display operation of the display device 1 (pixel unit 1A). Thus, for example, a fixed potential (for example, 0 V) is applied to the second electrode 19, and a positive potential (for example, +15 V), a negative potential (for example, −15 V) or 0 V is applied to each first electrode 13. Take the case as an example. As a result, a potential difference is generated between the first electrode 13 and the second electrode 19 for each pixel 10 and a voltage of positive polarity, negative polarity, or 0 V is applied to the display body 10A. As a result, the electrophoretic particles 17 charged positively or negatively (eg, negatively in this case) move to the first electrode 13 side or the second electrode 19 side.

In this example, in the pixel 10 to which +15 V is applied to the first electrode 13, the migrating particles 17 are shielded by the porous layer 16 as the migrating particles 17 move to the first electrode 13 side. That is, the light reflectance of the porous layer 16 becomes dominant, and a display state (for example, white display state) corresponding to the light reflectance of the porous layer 16 is obtained. On the other hand, in the pixel 10 to which −15 V is applied to the first electrode 13, the migrating particles 17 are exposed to the porous layer 16 by moving to the second electrode 19 side. That is, the light reflectance of the migrating particles 17 becomes dominant, and a display state (for example, a black display state) corresponding to the light reflectance of the migrating particles 17 is obtained. The reason for applying 0 V will be described later.

However, in the electrophoretic display device 1, the light reflectance changes in time series according to the optical response characteristics of the display body 10A when shifting from white display to black display or from black display to white display. have. It is desirable to perform voltage driving in consideration of a change in light reflectance according to the optical response characteristics of the display body 10A. In general, switching to a desired display state (gradation) is not performed in one frame period but over a plurality of frame periods (for example, a period corresponding to several frames to several tens frames). That is, a plurality of frame periods are unit periods (hereinafter referred to as “writing periods”) for displaying one screen (or rewriting to another screen). At the end of one writing period, a waveform pattern (Waveform) of an applied voltage is set in advance so that a desired display state is obtained. It is also effective to apply 0 V at a predetermined timing during the writing period. Hereinafter, as an example of the driving operation, a driving operation in the case of shifting (switching) from black display to white display will be described.

(Basic display drive: voltage drive in frame periods)
First, basic display driving of the display device 1 will be described with reference to FIGS. 4, 5A, and 5B. In FIG. 5A, Sig (k) is a voltage waveform (video signal pulse) applied to the signal line DL of the k-th line (k is an integer) G (1), G (2),. m) (m is an integer) indicates a voltage waveform (scanning signal pulse) applied from the first line to the m-th scanning line GL. In this example, one frame period (vertical period corresponding to the frame frequency) V includes an effective display period V _AC and a vertical blanking period V _BL . The frame frequency is not particularly limited, but is 40 to 100 Hz, for example, and one frame period V corresponding to this frame frequency is 10 to 25 ms (milliseconds), for example. Here, one frame period V corresponds to an interval of an on period in a scanning signal pulse applied to one scanning line GL, and is also called a frame or a vertical period. The vertical blanking period V _BL is set to, for example, about 0.1 ~ 4 ms. The effective display period V _AC corresponds to a period other than the vertical blanking period V _BL in one frame period V.

Thus, for example, in one frame period V corresponding to one frame (here, No. 9 frame) of the writing period Tw consisting of 12 frames, the potential Vsig is applied to the signal line DL, while each scanning is performed. The on-potential is applied to the line GL in a line-sequential manner. Thereby, in the selected pixel 10, a voltage corresponding to the potential Vsig is applied to the display body 10A via the TFT element. Specifically, for example, when an on potential is applied to the scanning line GL of the m-th line, the TFT element of the pixel 10 of the m-th line is turned on, and the potential Vsig of the signal line DL at that time is selected, and the first Applied to the electrode 13. Thereby, a voltage corresponding to the potential difference between the first electrode 13 and the second electrode 19 is applied to the display body 10A. This applied voltage is held by a capacitive element (not shown) formed in the pixel 10 even after the TFT element is turned off. Such an operation is performed for each pixel 10, and the electrophoretic element is driven for each pixel 10 by a voltage (corresponding to a potential difference between the first electrode 13 and the second electrode 19) held by the capacitor element. . In each pixel 10, the migrating particles 17 move between the electrodes in accordance with the applied voltage, thereby changing the light reflectance. Such voltage driving is continuously performed over a plurality of frames.

FIG. 5B schematically shows voltage waveforms S11 and S12 applied to the display body 10A and optical response waveforms (temporal changes in light reflectance) L11 and L12 corresponding thereto as an example. For example, as shown in the voltage waveform S11, when the positive polarity voltage is continuously applied in the frames 1 to 4, and then the negative polarity voltage is continuously applied in the frames 5 to 12, the display 10A is displayed. For example, the optical response characteristic indicates a waveform L11. That is, from the start time of frame 1 to the end time of frame 4, the light reflectance gradually increases and shifts from the black display state to the white display state. In addition, the light reflectance gradually decreases from the start time of frame 5 to the end time of frame 12, and the white display state shifts to the black display state.

On the other hand, the applied voltage may be changed in small increments as in the voltage waveform S12. For example, after positive voltage is continuously applied in frames (n-6) and (n-5), 0 V is applied in frames (n-4) and (n-3). Thereafter, a negative voltage is continuously applied in frames (n-2) and (n-1), and 0 V is applied again in the last frame (n). When such driving is performed, the optical response characteristic of the display body 10A shows, for example, a waveform L12. That is, the light reflectance gradually increases from the start time of the frame (n-6) to the end time of the frame (n-5), and shifts from the gradation display state to the white display state, for example. Also, the display state (white display state) of the immediately preceding frame is maintained from the start time of frame (n-4) to the end time of frame (n-3). Thereafter, the light reflectance gradually decreases from the start time of the frame (n-2) to the end time of the frame (n-1), and the white display state shifts to the gradation display state. In the frame (n), the display state (gradation display state) of the immediately preceding frame is maintained.

FIG. 6 shows an image of the gradation change of the frame with the voltage application as described above. As described above, as the voltage waveform S13, for example, a positive voltage is continuously applied in the period T100 corresponding to the frames 1 to 9, and then a negative voltage is continuously applied in the period T101 corresponding to the

frames

10 and 11. Next, 0 V is applied in a period T102 corresponding to the frame 12, and a negative voltage is applied in a period T103 corresponding to the frame 13. In this case, gradation changes as schematically shown in the frames 1 to 13 occur. Thus, gradation display is possible by a pulse width modulation (PMW: Pulse ： Width Modulation) method in units of frames.

As described above, at the time of image display or image switching in the pixel portion 1A including the display body 10A (electrophoretic element), a voltage waveform combining a positive voltage, a negative voltage, 0 V, and the like is written for each writing period. And set according to the optical response characteristics of the display body 10A. In the example described here, the display can be switched toward the white display state by applying a positive voltage, and the display can be switched toward the black display state by applying a negative voltage.

In addition to these positive voltage and negative voltage, a further fine gradation display can be realized by combining the application of 0V. 7A to 7D show voltage waveforms at the time of switching from the black display state to the white display state or the low gradation state as an example. In the example of FIG. 7A, the positive voltage is applied in all frames (for example, 500 ms) in one writing period Tw. By such voltage application, it is possible to switch from the extreme black display state (all black display state) to the extreme white display state (all white display state). In the example of FIG. 7B, a positive voltage is applied in the first half period Tw1 of one writing period Tw, and 0 V is applied in the subsequent period Tw2 (for example, Tw1 <Tw2). In the example of FIG. 7C, a positive voltage is applied in intermittent frames in one writing period Tw, and 0 V is applied in other frames (positive voltage and 0 V are alternately applied repeatedly). ). In the example of FIG. 7D, a positive voltage is applied in the first half period Tw3 of one writing period Tw, and a negative voltage is applied in the subsequent period Tw4 (for example, Tw3> Tw4). In any of the examples shown in FIGS. 7B to 7D, the all-black display state can be switched to the low gradation state. Thus, there are a plurality of patterns of applied voltage waveforms for gradation display, and the present invention is not limited to those illustrated.

Further, by applying 0 V to the last frame of the writing period, there are the following merits. Figure 8A, showing the voltage waveform in the case where 0V is applied to the last frame f _EN the write period Tw Sig (k), and G (m), and a waveform L21 of the optical response characteristic of the display 10A for the applied voltage. Further, FIG. 8B, as a comparative example, the voltage waveform Sig when no 0V is applied to the last frame f _EN the write period Tw (k), and G (m), the optical response characteristics of the display body 10A for the applied voltage The waveform L22 is shown. 8A and 8B, the voltage charge held in the capacitor (Cs) of the pixel 10 is indicated by hatching. In the comparative example shown in FIG. 8B, in the final frame _fEN , the voltage applied in the immediately preceding frame remains in the capacitive element Cs. For this reason, a voltage is continuously applied to the display body 10A, and the light reflectance continues to increase. For this reason, it is difficult to obtain a desired light reflectance. In contrast, as shown in Figure 8A, when 0V is applied to the last frame f _EN, the last frame f _EN, is discharged the capacitor Cs, the light reflection factor in the frame end time of the immediately preceding is maintained The For this reason, it is easy to obtain a desired light reflectance. That is, gradation control by applied voltage × time is facilitated. Thus, in voltage driving using a TFT element, it is desirable to apply 0 V in the last frame of the writing period Tw.

Here, in the drive in units of frames as described above, a vertical period corresponding to one frame period V is a voltage application period to each pixel 10. For example, when driving at a frame frequency of 50 Hz, the pulse width (on period width) of the scanning signal pulse is changed in units of 20 ms. Therefore, usable pulse widths are 20 ms, 40 ms, 60 ms,... For this reason, for example, when driving is performed such that the positive voltage and the negative voltage are alternately repeated every frame, the electrophoretic element exhibits a behavior of alternately repeating the light and dark display. Since one frame period corresponds to a time of several tens of ms, it is visually recognized as flicker, and the display quality may be impaired. Alternatively, it is possible to shorten one frame period V by increasing the frame frequency (increasing the frame rate), but the design change to increase the frame frequency includes, for example, the display signal generation unit 212b and the scanning line. In the logic circuit used for the driving circuit 110, the clock frequency is changed. This leads to an increase in power consumption.

Therefore, in the present embodiment, the scanning line driving circuit 110 has a function of performing line sequential driving (line sequential scanning) for each of a plurality of scanning line groups (scanning line group GLGrp). Specifically, the scanning line driving circuit 110 scans a scanning start signal for the scanning line GL of the first line (uppermost line) of each of a plurality of scanning line groups GLgrp formed by dividing all the scanning lines GL into n. Gst is applied to sequentially scan the scanning lines GL below the first line.

(Line-sequential driving of all scanning lines GL)
First, with reference to FIG. 1 and FIG. 9, the line-sequential driving operation in the normal all scanning lines GL will be described. This driving corresponds to the above-described voltage driving in units of frames (line sequential driving in the “first frame period”). In this example, the total number of scanning lines (the number of effective scanning lines) is 720, and the division number n is 2. Line-sequential driving is performed in each of two scanning line groups GLgrp1 and GLgrp2 formed by dividing all scanning lines GL into two. In FIG. 9, Sig (k) is a voltage waveform (video signal pulse) applied to the signal line DL of the kth line (kth column) (k is an integer), G (1), G (2), .., G (720) indicate voltage waveforms (scanning signal pulses) applied to the scanning lines GL from the first line to the 720th line, respectively. In addition, Pix (1), Pix (2),..., Pix (720) are pixels 10 arranged at intersections of the signal line DL of the kth line and the scanning lines GL of the first line to the 720th line. Represents the voltage held in the. For simplicity, only one period corresponding to the above-described effective display period V _AC is shown as one frame period V.

Specifically, the scanning line drive circuit 110 at time t11, to the scanning lines GL ₁ of the first line is the first line of the scanning line groups GLgrp1, applying a scan start signal GST1. Thus, at time t11 the same time, the scanning lines GL ₁ of the first line, the ON potential is applied. After the application of the scanning start signal Gst1, the ON potential is sequentially applied to the scanning lines GL after the second line (from the second line to the 360th line).

Subsequently, the scanning line driving circuit 110 applies the scanning line GL ₃₆₁ of the 361st line, which is the first line in the scanning line group GLgrp2, at time t12 immediately after the ON potential is applied to the scanning line GL ₃₆₀ of the 360th line. On the other hand, the scanning start signal Gst361 is applied. As a result, at the same time t12, the ON potential is applied to the scanning line GL ₃₆₁ of the 361st line. After the application of the scanning start signal Gst361, the ON potential is sequentially applied to the scanning lines GL from the 362rd line onward (from the 362rd line to the 720th line).

On the other hand, the signal line driver circuit 120 has a constant signal potential for a period until the scanning of all the scanning lines GL with respect to the signal line DL of the k-th line ends (period from time t11 to time t13: period Th). Apply. As a result, in the period Th corresponding to one frame period V, the signal potential is applied to each pixel 10 and this applied voltage is held. When the frame frequency is 50 Hz, this period Th is 20 ms. That is, in this example, one frame period V (period Th) is a unit period for voltage driving.

(Line sequential drive for each scanning line group)
Next, the line-sequential driving operation for each scanning line group GLgrp will be described with reference to FIGS. This driving may be performed instead of the voltage driving in units of frames described above, for example, or may be performed in combination with the driving in units of frames described above. FIG. 10 illustrates an example in which line-sequential driving is performed for each scanning line group GLgrp in a part of the frame period V (second frame period). Also in this example, the total number of scanning lines (the number of effective scanning lines) is 720, and the division number n is 2. Sig (k) is a voltage waveform (video signal pulse) applied to the signal line DL of the kth line (kth column), G (1), G (2),..., G (720) The voltage waveforms (scanning signal pulses) applied to the scanning lines GL from the first line to the 720th line are respectively shown. In addition, Pix (1), Pix (2),..., Pix (720) are pixels 10 arranged at intersections of the signal line DL of the kth line and the scanning lines GL of the first line to the 720th line. Represents the voltage held in the. For simplification, only the above-described effective display period V _AC is shown as one frame period V.

Specifically, the scanning line driver circuit 110, at any time t21, to the scanning lines GL ₁ of the first line is the first line of the scanning line groups GLgrp1, applies a scanning start signal GST1. Thus, at time t11 the same time, the scanning lines GL ₁ of the first line, the ON potential is applied. After the application of the scanning start signal Gst1, the ON potential is sequentially applied to the scanning lines GL after the second line (from the second line to the 360th line).

In this case, the scanning line driving circuit 110, in synchronization with the application timing of the scanning start signal Gst1 to the scanning lines GL ₁ of the first line (at time t21), a first line of the scanning line group GLgrp2 # 361 A scanning start signal Gst ₃₆₁ is applied to the scanning line GL _{361 of the} line. Thus, an ON potential is applied to the scanning line GL ₃₆₁ of the 361st line at the same time t21. After the application of the scanning start signal Gst361, the ON potential is sequentially applied to the scanning lines GL from the 362rd line onward (from the 362rd line to the 720th line).

By the above driving, in the scanning line group GLgrp1, scanning lines GL for a total of 360 lines from the first line to the 360th line are sequentially scanned, and the process ends at time t22. In the scanning line group GLgrp2, scanning lines GL for a total of 360 lines from the 361st line to the 720th line are sequentially scanned, and the process ends at time t22. That is, the period required to scan all the scanning lines GL by line-sequential driving for each scanning line group GLgrp is a period (Th1) that is half (the first half part) of one frame period V (period Th).

In this period Th1 (first unit period), the signal line drive circuit 120 applies a display signal voltage Vsig to the signal line DL, for example.

Thereafter (at time t22), the scanning line driving circuit 110, in the same manner as described above, to the scanning lines GL ₁ of the first line of scanning line group GLgrp1, applies a scanning start signal GST1. As a result, the ON potential is sequentially applied from the first line to the 360-th scanning line GL. Also, this time t22, the scanning line drive circuit 110, to the scanning lines GL ₃₆₁ of the 361 lines of the scanning line groups GLgrp2, applies a scanning start signal Gst361. As a result, the ON potential is sequentially applied to the scanning lines GL from the 361st line to the 720th line.

By the above driving, in the scanning line group GLgrp1, scanning lines GL for a total of 360 lines from the first line to the 360th line are sequentially scanned, and the process ends at time t23. In the scanning line group GLgrp2, scanning lines GL for a total of 360 lines from the 361st line to the 720th line are sequentially scanned, and the process ends at time t23. As described above, the line sequential driving for each scanning line group GLgrp makes it possible to apply a voltage even in the second half period (Th2) of one frame period V (period Th).

In this period Th2 (second unit period), the signal line driving circuit 120 can apply a voltage (for example, a correction voltage Vcrt to be described later) different from that for display to the signal line DL.

Thus, it becomes possible to apply a voltage to each pixel 10 in units of periods (periods Th1, Th2) shorter than one frame period V (period Th). When the frame frequency is 50 Hz, the periods Th1 and Th2 are 20/2 = 10 ms. That is, in this example, voltage driving can be performed in units of periods shorter than one frame period V without increasing the frame frequency (increasing the frame rate). In one frame period V, a scanning signal (scanning signal pulse) can be applied to each scanning line GL once or a plurality of times (here, twice).

[effect]
As described above, in the present embodiment, when each pixel 10 including the electrophoretic element is voltage-driven, in the effective display period V _AC in one frame period V, periods Th1 and Th2 shorter than one frame period V. Voltage drive can be performed in units. A voltage can be applied to each pixel at any timing and pulse width (using a desired voltage waveform pattern) without increasing the frame frequency (frame rate). In other words, the frame frequency is apparently increased, and more fine voltage drive can be performed. Therefore, it is possible to improve display quality while suppressing an increase in power consumption.

For example, voltage driving in units of several ms, which is shorter than one frame period V, is possible instead of voltage driving in units of several tens of ms. The time width of this pulse can be varied freely.

In addition, when driving such that a positive voltage and a negative voltage are alternately applied a plurality of times, the occurrence of flicker is suppressed by enabling voltage application in units of less than one frame period V. be able to.

Next, a modification of the first embodiment will be described. In the following, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

<Modification 1>
FIG. 11 is a timing chart for explaining the drive operation (scan line division drive operation) of the display device according to the first modification. In the first embodiment, the example in which the division number n of all the scanning lines GL is set to 2 and line-sequential driving is performed in each of the two scanning line groups GLgrp1 and GLgrp2 is shown. However, the division number n is limited to two. It may be 3 or more. In this modification, an example in the case of n = 4 is shown.

Also in this modification, the total number of scanning lines (the number of effective scanning lines) is 720, as in the first embodiment. Sig (k) is a voltage waveform (video signal pulse) applied to the signal line DL of the kth line (kth column), and G (1),..., G (720) are from the first line. A voltage waveform (scanning signal pulse) applied to the scanning line GL of the 720th line is shown. Pix (1),..., Pix (720) is a voltage held in the pixel 10 arranged at each intersection of the signal line DL of the kth line and the scanning line GL of the first line to the 720th line. Represents. For simplification, only the above-described effective display period V _AC is shown as one frame period V.

However, in this modification, line-sequential driving is performed for each of the four scanning line groups GLgrp1, GLgrp2, GLgrp3, and GLgrp4 by dividing the entire scanning line GL into four. Each of the scanning line groups GLgrp1, GLgrp2, GLgrp3, and GLgrp4 is composed of a total of 180 (720/4 = 180) scanning lines GL. A scanning start signal (Gst1, Gst181, Gst361, Gst541) is applied to the scanning line GL of the first line (first line, 181st line, 361st line, and 541st line) of each scanning line group GLgrp1, GLgrp2, GLgrp3, GLgrp4. Can be applied synchronously.

In the same manner as in the first embodiment, in the scanning line group GLgrp1, a total of 180 scanning lines GL from the first line to the 180th line are sequentially scanned. Similarly, in the scanning line group GLgrp2, a total of 180 scanning lines GL from the 181st line to the 360th line are sequentially scanned. Similarly, in the scanning line group GLgrp3, a total of 180 scanning lines GL from the 361st line to the 540th line are sequentially scanned. Similarly, in the scanning line group GLgrp4, a total of 180 scanning lines GL from the 541st line to the 720th line are sequentially scanned. That is, the period required to scan all the scanning lines GL by line-sequential driving for each scanning line group GLgrp is a period (Th1 to Th4) that is ¼ of one frame period V (period Th). Therefore, in the case of driving at a frame frequency of 50 Hz, voltage driving can be performed in units of 5 ms (20/4 = 5) periods (periods Th1 to Th4).

The signal line driver circuit 120 applies a display signal voltage (Vsig) in at least one period (for example, the period Th1) of the periods Th1 to Th4, and in other arbitrary periods, for example, a correction voltage (described later) Vcrt) can be applied.

As described above, also in this modification, it is possible to apply a voltage to each pixel 10 in units of periods (periods Th1 to Th4) shorter than one frame period V. Therefore, an effect equivalent to that of the first embodiment can be obtained. Further, by increasing the number of divisions n (increasing the number of scanning line groups GLGrp), voltage control can be performed at finer timing, and driving for improving display quality can be easily realized.

<Modification 2>
FIG. 12 illustrates a main configuration of a display device according to the second modification. In the first embodiment, a circuit in which one scanning line driving circuit 110 can apply a scanning start signal (gate start pulse) to the scanning lines GL of two or more designated lines among all the scanning lines GL. The case where the line sequential driving for each scanning line group GLgrp is performed by including the function (IC) has been described. However, the present invention is not limited to such a configuration. For example, as in the present modification, a plurality of (here, two) scanning

line driving circuits

110A and 110B are provided, and these scanning

line driving circuits

110A and 110B are respectively provided. It may be connected to the scanning line group GLgrp.

Specifically, the scanning line driving circuit 110A is connected to the scanning line group GLgrp1, and the scanning line driving circuit 110B is connected to the scanning line group GLgrp2. The area A1 in the pixel portion 1A is driven using the scanning line group GLgrp1, and the area A2 is driven using the scanning line group GLgrp2.

Even in such a configuration, a line-sequential driving operation for each scanning line group GLgrp is possible, and an effect equivalent to that of the first embodiment can be obtained.

<Second Embodiment>
FIG. 13 is a timing chart for explaining the driving operation of the display device according to the second embodiment of the present disclosure. Similar to the display device 1 of the first embodiment, the display device of the present embodiment is an electrophoretic display device that displays an image using an electrophoretic phenomenon, and is a so-called electronic paper display. In addition, for example, the pixel 10 (pixel unit 1A) is driven and displayed by an active matrix driving method using TFTs. The plurality of pixels 10 include a display body 10A (electrophoretic element), and display characters and images by changing the light reflectance of the display body 10A for each pixel 10. The pixel portion 1A is connected to the scanning line driving circuit 110 and the signal line driving circuit 120. In the pixel portion 1A, the output end of the scanning line driving circuit 110 and each pixel 10 are connected, and a plurality of scanning lines GL extending along the row direction, the output end of the signal line driving circuit 120, and each pixel 10 are connected. And a plurality of signal lines DL extending in the column direction are arranged. A pixel 10 is formed at each intersection of the plurality of scanning lines GL and the plurality of signal lines DL.

FIG. 13 shows an example in which, in some frame periods V, another voltage (for example, a correction voltage) is applied in addition to the display voltage. Also in this example, Sig (k) is a voltage waveform (video signal pulse) applied to the signal line DL of the kth line (kth column), and G (1) and G (2) are the first line. The voltage waveform (scanning signal pulse) applied to the scanning line GL of the second line is shown. Pix1 (k) represents a voltage waveform applied to the pixel 10 arranged at the intersection of the signal line DL of the kth line and the scanning line GL of the first line. For simplification, only the above-described effective display period V _AC is shown as one frame period V.

In the present embodiment, the scanning line driving circuit 110 allocates a first on period b11 corresponding to a part of the on period b1 in the scanning signal pulse, for example, for display, and drives each pixel 10. It has become. The scanning line driving circuit 110 also drives each pixel 10 by assigning, for example, a second on period b12 different from the first on period b11 in the on period b1 for correction. The first on period b11 corresponds to the first half of the on period b1, and the second on period b12 corresponds to the second half of the on period b1. In other words, the first on-period b11 uses the first half phase of the on-period b1, and the second on-period b12 uses the second half phase of the on-period b1. . However, the ON period b1 may be divided into three or more periods, and the lengths (division ratios) of the divided periods may be different.

The signal line driving circuit 120 applies, for example, a display signal voltage (Vsig) to each pixel 10 in the first on period b11, and in the second on period b12, for example, a correction voltage. (Vcrt) is applied. As described above, the signal line driver circuit 120 has the voltage waveform S31 to which a voltage corresponding to each of the first on period b11 and the second on period b12 can be applied. The correction voltage Vcrt can be an arbitrary voltage, for example, a voltage having a polarity opposite to that of the display voltage Vsig.

(Driving method)
First, a general driving operation will be described with reference to FIG. FIG. 14 is a timing diagram illustrating a driving operation according to a comparative example of the present embodiment. In this comparative example, the scanning signal pulse G (1) applied to the scanning line GL of the first line becomes high level (on potential) only once in one frame period V, and the rest is low level. (Off-potential). The TFT in the pixel 10 is turned on during the on potential period (on period b1), and the signal voltage applied to the signal line DL at that time is transmitted to each pixel 10 (Pix1 (k)). In this example, a signal voltage for black display (corresponding to the black portion in FIG. 14) is applied to each pixel 10. The electrophoretic element undergoes an optical change by this applied voltage, and exhibits an optical response as shown in the bottom of FIG. Here, a state in which the optical response level is lowered due to the black display signal being input is shown. On the other hand, in the on period b1 in the scanning signal pulse applied to the scanning lines GL of the second, third, and fourth lines, a signal for shifting from black display to white display (corresponding to a portion close to white in FIG. 14). Is applied to each pixel 10, and the optical response level of the electrophoretic element is increased.

In the optical response of the electrophoretic display element, compared to applying a constant voltage for a long time, applying a reversed voltage several times in the middle improves the response speed or makes a transition to a more extreme optical state. There are advantages such as being easy. However, in voltage driving using TFTs, as described above, one frame period V defined by the frame frequency is a unit period for voltage application. As described above, it is possible to shorten one frame period V by increasing the frame frequency (increasing the frame rate). However, a design change that increases the frame frequency can be applied to, for example, the scanning line driving circuit 110. This involves changing the clock frequency in the logic circuit used. This leads to an increase in power consumption.

Therefore, in the present embodiment, as shown in FIG. 13, the scanning line driving circuit 110 applies the signal voltage Vsig to each pixel 10 in the first on-period b11 that is about half (first half) of the normal on-period b1. Apply. Although the pulse width is shortened in this way, the signal voltage Vsig for black display is applied to the pixel 10 as in the case of the comparative example if the transistor can be sufficiently operated within that time. In FIG. 13, as in the comparative example, the optical response level is lowered by writing the black display signal. In the first on period b11 in the scanning signal pulse applied to the scanning lines GL of the second, third and fourth lines, a signal for shifting from black display to white display is applied to each pixel 10, The optical response level of the electrophoretic element is increasing.

Thus, it is possible to improve the optical characteristics without complicating the scanning line GL connected to the pixel portion 1A.

On the other hand, in a certain selective frame period V, in the scanning signal pulse G (1), after the on potential is applied in the period from the time t31 to the time t32 (first on period b11), at an arbitrary timing ( During the period from time t33 to time t34, a pulse (pulse S32a) is added (an ON potential is applied). The pulse S32a is applied using the second on period b12 of the on period b1. In this way, writing to the pixel 10 is added in the middle of one frame period V (at an arbitrary timing) by applying the pulse S32a whose phase is half shifted from the first on-period b11 for display. Can be done. In this example, since the voltage Vcrt equivalent to the black display signal is applied to the signal line DL, the optical response level L31 decreases from time t33 (L31a). Note that after the time t35 when the next frame period starts, the white display signal is applied to the pixel 10 in the first on-period b11, and the optical level rises again (the display becomes white).

Thus, in the present embodiment, the pulse S32a can be added at an arbitrary timing within one frame period V by dividing and using the ON period b1 in the scanning signal pulse. Driving such as applying a voltage Vcrt having a polarity opposite to that of the display voltage Vsig can be performed by the pulse S32a, and optical characteristics can be improved.

The scanning period (unit period) of the pulse S32a is a period Th5 (t35-t33) from the start time (time t33) of the second on-period b12 to the start time (t35) of the next first on-period b11. It corresponds to. That is, the voltage (voltage Vcrt) can be applied in units of periods shorter than one frame period V. The scanning period (period Th5) of the pulse S32a can be freely adjusted by a signal applied to the scanning line driving circuit 110. Since the pulse S32a can be inserted in one ON period b1 in the scanning signal pulse, for example, when the total number of scanning lines is 720, about 27 μs (20 ms / 720) is required for the scanning period (period) of the pulse S32a. The minimum range of Th5).

Therefore, in the present embodiment, it is possible to apply a correction pulse that was difficult to apply only in units of one frame period V (for example, 20 ms) at an arbitrary timing and pulse width (for example, 5 ms). . In FIG. 13, the pulse S32a is applied once, but may be applied a plurality of times in order to improve optical characteristics.

In a general scanning line driving circuit, scanning signal pulses are automatically and sequentially output to the scanning lines GL for the second and subsequent lines based on the scanning start signal (Gst) input to the scanning line GL of the first line. be able to. For this reason, if the scanning start signal prepared for outputting the scanning signal pulse G (1) of FIG. 13 is input to the IC, the pulse S32a can be similarly applied to the scanning lines GL on and after the second line. it can. That is, it is possible to insert the pulse S32a at an arbitrary timing and pulse width only by changing the signal waveform input to the scanning line driving circuit 110 without changing the wiring state connected to the pixel portion 1A. Become. On the other hand, the signal line driving circuit 120 is required to have high-speed operation performance because the output signal is switched at twice the normal speed. This employs a general semiconductor manufacturing technique used for a normal display. This can be easily realized.

As described above, also in the present embodiment, when each pixel 10 including an electrophoretic element is voltage-driven, a period (period) shorter than one frame period V in the effective display period V _AC in one frame period V. Voltage drive can be performed in units of Th5). A voltage can be applied to each pixel at any timing and pulse width (using a desired voltage waveform pattern) without increasing the frame frequency (frame rate). In other words, the frame frequency is apparently increased, and more fine voltage drive can be performed. Therefore, an effect equivalent to that of the first embodiment can be obtained.

(Example: Correction drive for improving optical response characteristics)
In the display device and the driving method thereof described in the above embodiments and modifications, a voltage different from the display voltage (for example, correction (for example, correction) is realized by realizing voltage driving in a unit shorter than one frame period V. Voltage Vcrt) for adjustment) can be applied. Hereinafter, an example of correction driving using the voltage Vcrt will be described.

As described above, in the electrophoretic display device, the light reflectance is changed for each pixel 10 in accordance with the applied voltage, and white display, black display, or gradation display is performed using this. In such a display device, in order to improve visibility, it is desired that the light reflectance is particularly high during white display.

Here, FIG. 15A shows an example of an applied voltage waveform when switching from black display to white display. FIG. 15B shows optical response characteristics of the display 10A when the voltage waveform shown in FIG. 15A is applied. As described above, in the optical response characteristics of the display 10A, the light reflectance gradually changes over a plurality of frames (in time series). For example, as shown in FIGS. 15A and 15B, a desired reflectance (here, 1) is reached by applying a positive voltage continuously for a certain time (for example, 400 ms).

In the middle of such a writing period, by applying a voltage having a polarity opposite to the voltage for shifting to the white display state (here, positive voltage) or 0 V (here, negative voltage), white display is obtained as a result. The light reflectance at the time can be increased. An example is shown in FIGS. 16A and 16B. FIG. 16A is an example of an applied voltage waveform when switching from black display to white display. In this example, the correction voltage Vcrt is applied as the reverse polarity voltage in one frame period V after about 100 ms has elapsed since the start of application of the positive voltage. After the voltage Vcrt is applied, the positive voltage is continuously applied again. FIG. 16B shows the optical response characteristics of the display body 10A corresponding to the voltage waveform shown in FIG. 16A. As described above, when the reverse polarity voltage is applied in the middle, the light reflectance is instantaneously reduced, but thereafter, the light reflectance is increased again. The increase rate of the light reflectance at this time is larger than that when only the positive voltage is continuously applied (FIG. 15B). As a result, the desired reflectance (1) is likely to be reached at an earlier timing (in this example, after about 200 ms has elapsed) than when only the positive voltage is applied. As described above, it is possible to increase the light reflectance by applying the reverse polarity voltage Vcrt when switching to white display or white display.

However, when a reverse polarity voltage is applied in the middle of white display, the light reflectivity increases as a result, but since the reverse polarity voltage is applied over one frame period V (for example, 20 ms), it is temporarily in the middle of white display. Transition to black display (light reflectance decreases instantaneously), and then returns to white display again. Such a phenomenon is visually recognized as flickering of the image (flickering occurs in the image). This leads to a decrease in display quality.

It is desirable that the period during which the correction voltage Vcrt as described above is applied is shorter than one frame period V. The voltage is applied in units of one frame period V or less by line-sequential driving for each scanning line group GLgrp described in the first embodiment or driving using the additional pulse S32a described in the second embodiment. It can be driven. For this reason, for example, as shown in FIG. 17A, the correction can be performed by applying the voltage Vcrt at an extremely fine timing. As a result, as shown in FIG. 17B, it is possible to make the flickering of the image less visible while increasing the light reflectance at an early timing.

Note that the application timing of the correction voltage Vcrt is not particularly limited within one frame period V (effective display period V _AC ). Further, the voltage Vcrt may be applied only once in one frame period V or may be applied multiple times. Further, in the voltage driving of less than one frame period V, the voltage Vcrt may be applied for the purpose of gradation control and color mixing adjustment without being limited to the positive voltage and negative voltage repetitive driving.

<Application example>
Next, application examples of the display device described in the above embodiments and modifications will be described. However, the configuration of the electronic device described below is merely an example, and the configuration can be changed as appropriate.

18A and 18B show the external configuration of an electronic book (electronic book 3) according to an application example. The electronic book 3 includes, for example, a display unit 810, a non-display unit (housing) 820, and an operation unit 830. Note that the operation unit 830 may be provided on the front surface of the non-display unit 820 as shown in FIG. 18A, or may be provided on the upper surface as shown in FIG. 18B.

The display device 1 described above can be applied to a part of clothing such as a watch (watch), a bag, clothes, a hat, glasses and shoes as a so-called wearable terminal. Below, an example of such an electronic device integrated with clothing is shown.

FIG. 19A and FIG. 19B show the appearance of an electronic timepiece (a wristwatch integrated electronic device). The electronic timepiece has, for example, a dial (character information display portion) 410 and a band portion (color pattern display portion) 420, and the dial 410 and the band portion 420 include the display device 1. It is configured. For example, various characters and designs are displayed on the dial plate 410 as shown in FIGS. 19A and 19B by display driving using the above-described electrophoretic element. The band unit 420 is a part that can be attached to an arm or the like, for example. Various color patterns can be displayed by using the display device 1 for the band unit 420, and the design of the band unit 420 can be changed from the example of FIG. 19A to the example of FIG. 19B. Electronic devices that are also useful in fashion applications can be realized.

As described above, the embodiments and modifications have been described. However, the present disclosure is not limited to the aspects described in the above embodiments and the like, and various modifications are possible. For example, in the above-described embodiment and the like, a case where a voltage having a polarity opposite to the first voltage or 0 V is applied as the second voltage of the present disclosure has been described as an example. However, the second voltage is not necessarily reversed. The voltage may not be a polarity voltage, and may be a voltage different from the first voltage. For example, the second voltage may be 0V. Alternatively, when the first voltage is a positive voltage for shifting from black display to white display, the second voltage may be a voltage lower than the first voltage. However, the reflectance can be effectively improved by applying a voltage having a polarity opposite to that of the first voltage as the second voltage as in the above embodiment. In addition, the effect demonstrated in the said embodiment etc. is an example, The effect of this indication may be other effects and may also include other effects.

Note that the present disclosure may be configured as follows.
(1)
A pixel portion having a plurality of pixels each including an electrophoretic element;
A driving unit for driving the pixel unit for each pixel, and
The display device configured to perform the voltage driving in a unit of period shorter than one frame period in an effective display period of one frame period.
(2)
The drive unit is
A scanning line driving circuit and a signal line driving circuit connected to each pixel;
Line-sequential driving is performed in each of a plurality of scanning line groups obtained by dividing a plurality of scanning lines connecting the output terminal of the scanning line driving circuit and each pixel by n (n is an integer of 2 or more). The display device described in 1.
(3)
The display device according to (2), wherein the scanning line driving circuit supplies a scanning start signal to the scanning line of the first line of each of the plurality of scanning line groups.
(4)
The display device according to (3), wherein the scanning line driving circuit includes a circuit that supplies the scanning start signal for each scanning line group.
(5)
A plurality of the scanning line driving circuits;
The display device according to (3), wherein each of the plurality of scanning line driving circuits is connected to the scanning line group.
(6)
The drive unit is
When applying a signal voltage to each pixel over a plurality of frame periods,
In the first frame period of the plurality of frame periods, the first line scanning line to the last scanning line among all the scanning lines are sequentially driven,
The display device according to any one of (2) to (5), wherein line-sequential driving is performed for each of the scanning line groups in a second frame period of the plurality of frame periods.
(7)
The driving unit applies a display signal voltage in a first unit period of one frame period and applies a correction voltage in a second unit period different from the first unit period. The display device according to any one of (1) to (6), wherein the pixel is driven.
(8)
The drive unit is
A scanning line driving circuit and a signal line driving circuit for performing line sequential driving of each pixel;
The scanning line driving circuit allocates a first on period corresponding to a part of the on period in the scanning signal pulse for display and drives the pixel. Any one of the above (1) to (7) The display device described in 1.
(9)
The scanning line driving circuit further drives the pixel by allocating a second on period different from the first on period among the on periods for correction, and the signal line driving circuit includes: The display device according to (8), wherein a display signal voltage is applied to the pixel during the first on-period and a correction voltage is applied during the second on-period.
(10)
The first on-period corresponds to the first half of the on-period,
The display device according to (9), wherein the second on period corresponds to a second half of the on period.
(11)
The drive unit is
Driving each of the plurality of pixels in a line-sequential manner using a plurality of scanning lines;
The display device according to any one of (1) to (10), wherein a scanning signal is supplied to each pixel one or more times within one frame period.
(12)
When driving a plurality of pixels each including an electrophoretic element for each pixel,
A driving method in which the voltage driving is performed in a unit of period shorter than one frame period in an effective display period of one frame period.
(13)
Driving each of the plurality of pixels in a line-sequential manner using a plurality of scanning lines;
The driving method according to (12), wherein line-sequential driving is performed in each of a plurality of scanning line groups obtained by dividing the plurality of scanning lines by n (n is an integer of 2 or more).
(14)
The driving method according to (13), wherein a scanning start signal is supplied to the first scanning line of each of the plurality of scanning line groups.
(15)
When applying a signal voltage to each pixel over a plurality of frame periods,
In the first frame period of the plurality of frame periods, the first line scanning line to the last scanning line among all the scanning lines are sequentially driven,
The driving method according to any one of (12) to (14), wherein line-sequential driving is performed for each scanning line group in a second frame period of the plurality of frame periods.
(16)
A display signal voltage is applied in a first unit period of one frame period, and a correction voltage is applied in a second unit period different from the first unit period to drive the pixel. The driving method according to any one of (12) to (15).
(17)
Driving each of the plurality of pixels in a line-sequential manner using a plurality of scanning lines;
The driving method according to (12), wherein the pixel is driven by allocating a first on period corresponding to a part of the on period in the scanning signal pulse for display.
(18)
Further, a second on-period different from the first on-period among the on-periods is allocated for correction to drive the pixels, and for each pixel, the display is used for display in the first on-period. And the correction voltage is applied during the second ON period. The driving method according to (17) above.
(19)
The first on-period corresponds to the first half of the on-period,
The driving method according to (18), wherein the second on period corresponds to a second half of the on period.
(20)
A pixel portion having a plurality of pixels each including an electrophoretic element;
A driving unit for driving the pixel unit for each pixel, and
An electronic apparatus comprising: a display device configured to perform the voltage driving in a unit of period shorter than one frame period in an effective display period of one frame period.

This application claims priority on the basis of Japanese Patent Application No. 2016-90212 filed on April 28, 2016 at the Japan Patent Office. The entire contents of this application are incorporated herein by reference. This is incorporated into the application.

Those skilled in the art will envision various modifications, combinations, subcombinations, and changes, depending on design requirements and other factors, which are within the scope of the appended claims and their equivalents. It is understood that

Claims

A pixel portion having a plurality of pixels each including an electrophoretic element;
A driving unit for driving the pixel unit for each pixel, and
The display device configured to perform the voltage driving in a unit of period shorter than one frame period in an effective display period of one frame period.
The drive unit is
A scanning line driving circuit and a signal line driving circuit connected to each pixel;
The line-sequential driving is performed in each of a plurality of scanning line groups obtained by dividing a plurality of scanning lines connecting the output terminal of the scanning line driving circuit and each pixel by n (n is an integer of 2 or more). The display device described.
The display device according to claim 2, wherein the scanning line driving circuit supplies a scanning start signal to the scanning line of the first line of each of the plurality of scanning line groups.
The display device according to claim 3, wherein the scanning line driving circuit includes a circuit that supplies the scanning start signal for each scanning line group.
A plurality of the scanning line driving circuits;
The display device according to claim 3, wherein each of the plurality of scanning line driving circuits is connected to the scanning line group.
The drive unit is
When applying a signal voltage to each pixel over a plurality of frame periods,
In the first frame period of the plurality of frame periods, the first line scanning line to the last scanning line among all the scanning lines are sequentially driven,
The display device according to claim 2, wherein line-sequential driving is performed for each scanning line group in a second frame period of the plurality of frame periods.
The driving unit applies a display signal voltage in a first unit period of one frame period and applies a correction voltage in a second unit period different from the first unit period. The display device according to claim 1, wherein the pixel is driven.
The drive unit is
A scanning line driving circuit and a signal line driving circuit for performing line sequential driving of each pixel;
The display device according to claim 1, wherein the scanning line driving circuit allocates a first on period corresponding to a part of an on period in a scanning signal pulse for display and drives the pixel.
The scanning line driving circuit further drives the pixel by allocating a second on period different from the first on period among the on periods for correction, and the signal line driving circuit includes: The display device according to claim 8, wherein a display signal voltage is applied to the pixel during the first on-period, and a correction voltage is applied during the second on-period.
The first on-period corresponds to the first half of the on-period,
The display device according to claim 9, wherein the second on-period corresponds to a second half of the on-period.
The drive unit is
Driving each of the plurality of pixels in a line-sequential manner using a plurality of scanning lines;
The display device according to claim 1, wherein a scanning signal is supplied to each pixel one or more times within one frame period.
When driving a plurality of pixels each including an electrophoretic element for each pixel,
A driving method in which the voltage driving is performed in a unit of period shorter than one frame period in an effective display period of one frame period.
Driving each of the plurality of pixels in a line-sequential manner using a plurality of scanning lines;
The driving method according to claim 12, wherein line-sequential driving is performed in each of a plurality of scanning line groups obtained by dividing the plurality of scanning lines by n (n is an integer of 2 or more).
The driving method according to claim 13, wherein a scanning start signal is supplied to the first scanning line of each of the plurality of scanning line groups.
When applying a signal voltage to each pixel over a plurality of frame periods,
In the first frame period of the plurality of frame periods, the first line scanning line to the last scanning line among all the scanning lines are sequentially driven,
The driving method according to claim 12, wherein line-sequential driving for each scanning line group is performed in a second frame period of the plurality of frame periods.
A display signal voltage is applied in a first unit period of one frame period, and a correction voltage is applied in a second unit period different from the first unit period to drive the pixel. The driving method according to claim 12.
Driving each of the plurality of pixels in a line-sequential manner using a plurality of scanning lines;
The driving method according to claim 12, wherein the pixel is driven by assigning a first on-period corresponding to a part of the on-period in the scanning signal pulse for display.
Further, a second on-period different from the first on-period among the on-periods is allocated for correction to drive the pixels, and for each pixel, the display is used for display in the first on-period. The driving method according to claim 17, wherein a correction voltage is applied during the second ON period.
The first on-period corresponds to the first half of the on-period,
The driving method according to claim 18, wherein the second on-period corresponds to a second half of the on-period.
A pixel portion having a plurality of pixels each including an electrophoretic element;
A driving unit for driving the pixel unit for each pixel, and
An electronic apparatus comprising: a display device configured to perform the voltage driving in a unit of period shorter than one frame period in an effective display period of one frame period.