JP2010223998A - Display device - Google Patents

Abstract

[PROBLEMS] To reduce the thickness and cost.
A display device having a substrate, a plurality of pixels provided in a display region, and a flexible substrate connected to one side of the substrate, wherein at least one provided in a region other than the display region. The at least one protection diode element is connected to a predetermined terminal of the flexible substrate by a pair of diode wirings. Each of the pixels has an active element formed on the substrate, and the at least one protection diode element is formed in the same process as the active element. The at least one protective diode element is a diode-connected thin film transistor.

Description

  The present invention relates to a display device, and more particularly to a technique effective in reducing the thickness and cost of a display device.

A TFT liquid crystal display device using a thin film transistor as an active element can display a high-definition image, and is therefore used as a display device for a television, a personal computer display, or the like. In particular, a small TFT liquid crystal display device is widely used as a display unit of a cellular phone as described in, for example, Patent Document 1 below.
In general, a liquid crystal display panel of a liquid crystal display device has a region surrounded by two adjacent scanning lines (also referred to as gate lines) and two adjacent video lines (also referred to as source lines or drain lines). A so-called pixel is formed by forming a thin film transistor which is turned on by a scanning signal from a scanning line and a pixel electrode to which a video signal from a video line is supplied through the thin film transistor.
A region where the plurality of pixels are formed is a display region, and there is a peripheral region surrounding the display region. In the peripheral area, semiconductor chips constituting the video driving circuit and the scanning line driving circuit, or wirings for connecting the scanning lines of the display area and the video lines are provided.
Further, the liquid crystal display panel has a terminal group formed in the peripheral portion, and a flexible substrate is electrically and mechanically connected to the terminal group.

JP 2007-25484 A

In a conventional liquid crystal display device, a semiconductor chip formed in a peripheral region of a liquid crystal display panel has a power supply circuit. The flexible substrate is mounted with a voltage stabilizing capacitor and a boosting capacitor constituting the power circuit. Furthermore, a protective diode is also mounted on the flexible substrate.
However, in the conventional liquid crystal display device, it is necessary to mount a voltage stabilizing capacitor, a boosting capacitor, and a protection diode on a flexible substrate, which is disadvantageous in terms of downsizing the liquid crystal display device. There was a point. In addition, since the voltage stabilizing capacitor, the boosting capacitor, and the protection diode use general-purpose chip parts, there is a problem that the manufacturing cost of the liquid crystal display device increases correspondingly.
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a technique capable of reducing the thickness and cost of a display device. is there.
The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
(1) A display device having a substrate, a plurality of pixels provided in a display region, and a flexible substrate connected to one side of the substrate, wherein at least one provided in a region other than the display region A protective diode element is included, and the at least one protective diode element is connected to a predetermined terminal of the flexible substrate by a pair of diode wirings.
(2) In (1), each of the pixels has an active element formed on the substrate, and the at least one protective diode element is formed in the same process as the active element.
(3) In (1) or (2), the at least one protective diode element is a diode-connected thin film transistor.
(4) In any one of (1) to (3), the substrate includes a drive circuit that drives the plurality of pixels, and the drive circuit includes a power supply circuit that generates an internal power supply voltage, A plurality of stabilizing capacitors constituting the power supply circuit in the drive circuit are mounted on the flexible substrate, and the at least one diode element is connected to the external power supply voltage of the flexible substrate on the flexible substrate. Is connected to one terminal among the terminals to which the stabilizing capacitor of the flexible substrate is connected.
(5) In (4), a wiring layer for supplying a driving voltage from the driving circuit to the pixel is formed around the display area of the substrate, and the at least one diode element is the driving circuit. The circuit is formed in a region outside the wiring layer outside at least one of two sides orthogonal to one side of the substrate.
(6) In (4) or (5), a plurality of boosting capacitors constituting the power supply circuit in the drive circuit are mounted on the flexible substrate.

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
According to the display device of the present invention, it is possible to reduce the thickness and the cost.

It is a block diagram which shows schematic structure of the liquid crystal display panel of the liquid crystal display device of the Example of this invention. It is a schematic diagram for demonstrating the 1st board | substrate of a present Example. It is a figure which shows an example of the voltage waveform supplied to each of the voltage of the several voltage level which the power supply circuit of a semiconductor chip produces | generates, and each signal line. It is a schematic diagram for demonstrating the 1st board | substrate (SUB1) of the conventional liquid crystal display panel. FIG. 5 is a diagram for explaining a specific configuration of protection diodes (D1, D2) shown in FIGS. 1 and 4; It is a figure for demonstrating the arrangement position of the protection diode (D1, D2) shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In all the drawings for explaining the embodiments, parts having the same functions are given the same reference numerals, and repeated explanation thereof is omitted.
In this embodiment, a liquid crystal display panel will be described as an example of a display panel. The display panel is not limited to the liquid crystal display panel, and an organic light emitting diode element or a surface conduction electron-emitting element can also be used.
[Example]
FIG. 1 is a block diagram showing a schematic configuration of a liquid crystal display panel of a liquid crystal display device according to an embodiment of the present invention. The liquid crystal display device of this embodiment is a small TFT liquid crystal display device used as a display unit of a mobile phone.
As shown in FIG. 1, the liquid crystal display panel of this embodiment includes a first substrate (also referred to as a TFT substrate or an active matrix substrate) (SUB1) provided with pixel electrodes, thin film transistors, and the like, a color filter, and the like. A second substrate (also referred to as a counter substrate) (SUB2) is stacked with a predetermined gap therebetween, and the two substrates are bonded together by a sealing material provided in a frame shape in the vicinity of the peripheral edge between the two substrates. The liquid crystal is sealed and sealed inside the sealing material between the two substrates from a liquid crystal sealing port provided in a part of the sealing material, and a polarizing plate is attached to the outside of both the substrates.
Thus, the liquid crystal display device of this example has a structure in which the liquid crystal is sandwiched between a pair of substrates.

The first substrate (SUB1) has a larger area than the second substrate (SUB2), and a thin film transistor is provided in a region of the first substrate (SUB1) that does not face the second substrate (SUB2). A semiconductor chip (Dr) that constitutes a driver for driving is mounted, and a flexible printed circuit board (FPC) is mounted on the periphery of one side of the region. In this embodiment, an example in which a display device is driven by a semiconductor chip (Dr) is shown. However, a driving circuit is integrally formed on a first substrate (SUB1) using a thin film transistor or the like so as to incorporate the driving circuit. It may be.
The material of the substrate may be an insulating substrate, and is not limited to glass but may be plastic. Further, the color filter may be provided not on the counter substrate side but on the TFT substrate side. The counter electrode is provided on the counter substrate side in the case of a TN liquid crystal display panel or a VA liquid crystal display panel. In the case of the IPS system, it is provided on the TFT substrate side.
In the present invention, when there is no relation to the internal structure of the liquid crystal display panel, detailed description of the internal structure of the liquid crystal display panel is omitted. Furthermore, the present invention can be applied to a liquid crystal display panel having any structure.

FIG. 2 is a schematic diagram for explaining the first substrate (SUB1) of the present embodiment.
In FIG. 2, 1 is a liquid crystal display panel, AR is a display area, and pixels 2 are formed in a matrix in the display area AR. The pixel 2 includes a pixel electrode (PX) and a thin film transistor (TFT) for applying a video voltage to the pixel electrode (PX). Each pixel 2 is connected with a scanning line (G), a video line (D), and a counter electrode line (C).
The gate electrode of the thin film transistor (TFT) in the row direction is connected to the scanning line (G), and the drain electrode of the thin film transistor (TFT) in the column direction is connected to the video line (D). A source electrode of the thin film transistor (TFT) is connected to the pixel electrode (PX). In addition, a liquid crystal capacitor (C _LC ) is equivalently formed between the pixel electrode (PX) and the counter electrode line (C), and between the pixel electrode (PX) and the counter electrode line (C). Is also provided with a storage capacitor (Cadd).
The scanning line (G) is connected to the semiconductor chip (Dr) via the scanning line wiring (GW), and the counter electrode line (C) is connected to the semiconductor chip (Dr) via the counter electrode line wiring (CW). Note that the video line (D) is also connected to the semiconductor chip (Dr) via a video line wiring (not shown).
In this embodiment, a high level scanning voltage for turning on a thin film transistor (TFT) is sequentially applied to the scanning line (G). Thereby, the thin film transistors (TFTs) in one display line are sequentially turned on, and the video voltage on the video line (D) is applied to the pixel electrode (PX) in one display line. Thereby, an image is displayed on the liquid crystal display panel 1.

A voltage stabilizing capacitor 8 and a boosting capacitor 9 are mounted on a flexible wiring board (FPC) mounted on the periphery of the first substrate (SUB1). Further, D1 and D2 protective diodes 10A are formed outside the display area (AR) in the periphery of the liquid crystal display panel 1.
When an external video signal, a first external power supply voltage (VCI) 11 and a second external power supply voltage (VSS) 12 are input to the flexible substrate (FPC), they are input to the semiconductor chip (Dr), respectively. Is done.
The semiconductor chip (Dr) has a power supply circuit, and this power supply circuit includes a voltage stabilizing capacitor 8, a boosting capacitor 9, and a protection diode 10A. The power supply circuit of the semiconductor chip (Dr) uses a first external power supply voltage (VCI) 11 and a second external power supply voltage (VSS) 12, and uses a voltage stabilizing capacitor 8 and a boosting capacitor 9. The internal power supply voltage of a plurality of voltage levels supplied to each wiring is generated by the charge pump circuit.

FIG. 3 shows an example of voltages at a plurality of voltage levels generated by the power supply circuit in the semiconductor chip (Dr) and voltage waveforms supplied to each signal line. FIG. 3 is a schematic diagram and does not accurately represent each voltage level.
The power supply circuit in the semiconductor chip (Dr) generates a reference voltage (VC) from the first external power supply voltage (VCI) 11 and the second external power supply voltage (VSS) 12 by a regulator circuit or the like. Thereafter, a scanning line positive power source (VG1) 20, a scanning line negative power source (VG2) 21, a video line positive power source (VD1) 22, and a video by a charge pump circuit using the voltage stabilizing capacitor 8 and the boosting capacitor 9 or the like. A line negative power source (VD2) 23, a counter electrode line positive power source (VCOM1) 24, and a counter electrode line negative power source (VCOM2) 25 are further generated.
Using the generated internal power supply voltages 20 to 25, for example, the scanning line voltage 26, the video line voltage 27, and the counter electrode line voltage 28 are respectively converted into the gate electrode and drain electrode of the thin film transistor (TFT), and the counter electrode line. Supply to (C).

The protection diode 10A composed of D1 and D2 suppresses the latch-up of the semiconductor chip (Dr) due to the reverse of the voltage order due to the rise time difference at the time of generating a plurality of voltage levels, and the failure in the semiconductor chip (Dr). belongs to.
Here, the protection diode of D1 is generated by the input terminal of the first external power supply voltage (VCI) 11 and the power supply circuit via the diode wiring (DW) formed on the first substrate (SUB1). The protective diode D2 is formed on the first substrate (SUB1) and connected to a terminal to which a stabilization capacitor (C1) for stabilizing the video line positive power supply (VD1) is connected. Stabilization for stabilizing the input terminal of the second external power supply voltage (VSS) 12 of the semiconductor chip (Dr) and the scanning line negative power supply (VG2) generated by the power supply circuit via the diode wiring (DW). And the terminal to which the capacitor (C2) is connected.
The protective diodes 10 </ b> A for D <b> 1 and D <b> 2 are formed in the same process as the thin film transistor (TFT) in the pixel 2. Similarly, the diode wiring is created in the same process as the scanning line (G) or the video line (D), for example.

FIG. 5 is a diagram for explaining a specific configuration of the protection diode 10A of D1 and D2. As shown in FIG. 5A, the protective diodes 10A of D1 and D2 are so-called diode-connected thin film transistors in which the drain electrode and the gate electrode of the thin film transistors are connected in common.
As described above, the protective diodes 10 </ b> A of D <b> 1 and D <b> 2 are formed in the same process as the thin film transistor (TFT) in the pixel 2. Therefore, when the semiconductor layer of the thin film transistor (TFT) in the pixel 2 is made of amorphous silicon, the semiconductor layer of the protection diode 10A of D1 and D2 is also made of amorphous silicon.
Further, in the case where the driver circuit is integrally formed on the first substrate (SUB1) using a thin film transistor or the like and the driver circuit is incorporated, the semiconductor layer of the thin film transistor (TFT) in the pixel 2 is made of polysilicon. The Therefore, in this case, the semiconductor layer of the protective diode 10A of D1 and D2 is also made of polysilicon.
FIGS. 2 and 4 show the case where only one protection diode 10A for D1 and D2 is provided. However, as shown in FIGS. 5B and 5C, the protection diodes for D1 and D2 are shown. May be one in which two or more diodes are connected in series or in parallel.

FIG. 6 is a circuit diagram for explaining the arrangement positions of the protective diodes 10A of D1 and D2. As shown in FIG. 6, the scanning line wiring (GW) is densely formed around the display area (AR) of the first substrate (SUB1).
Therefore, in order to arrange the protective diodes 10A of D1 and D2 or the diode wiring (DW) around the display area (AR) of the first substrate (SUB1), the area of the first substrate (SUB1) is reduced. It is necessary to spread.
Therefore, the semiconductor chip (Dr) in the scanning line wiring (GW) outside one short side of the semiconductor chip (Dr) or outside the two short sides of the semiconductor chip (Dr) as shown in FIG. By disposing the protective diodes 10A for D1 and D2 on the outside of the diagonal wiring connected to, it is possible to dispose the protective diodes 10A for D1 and D2 without increasing the area of the first substrate (SUB1). It becomes.

[Conventional example]
FIG. 4 is a schematic diagram for explaining a first substrate (SUB1) of a conventional liquid crystal display panel. The conventional liquid crystal display panel shown in FIG. 4 is different from the liquid crystal display panel of this embodiment shown in FIG. 2 in that the protective diodes 10 of D1 and D2 are mounted on a flexible wiring board (FPC). Since the other points are the same, the description thereof will be omitted.
In the conventional liquid crystal display panel 1 shown in FIG. 4, it is necessary to mount a voltage stabilizing capacitor 8, a boosting capacitor 9, and protective diodes (D1, D2) 10 on a flexible substrate (FPC). From the viewpoint of miniaturization of the liquid crystal display panel, it is disadvantageous, and since these components use general-purpose chip components, the manufacturing cost of the liquid crystal display device is increased accordingly.

On the other hand, in this embodiment, a flexible wiring board (FPC) is formed by forming diodes (D1, D2) on the first substrate (SUB1) constituting the liquid crystal display panel and using them as protective diodes. ) The protective diodes (D1, D2) above can be deleted.
As a result, in this embodiment, the liquid crystal display panel 1 can be made smaller than before, and the diode is necessary for forming wirings and thin film transistors (TFTs) in the liquid crystal display panel 1. Since the metal layer and the Si layer can be formed at the same time, diodes (D1, D2) can be formed at the same manufacturing cost as the conventional liquid crystal display panel 1, thereby reducing the manufacturing cost for general-purpose diodes. can do.
As mentioned above, the invention made by the present inventor has been specifically described based on the above embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Of course.

SUB1 First substrate (TFT substrate, active matrix substrate)
SUB2 Second substrate (counter substrate)
Dr semiconductor chip FPC flexible wiring board AR display area PX pixel electrode TFT thin film transistor G scanning line GW scanning line wiring D video line C counter electrode line CW counter electrode line wiring DW diode wiring C _LC liquid crystal capacity Cadd holding capacity 1 liquid crystal display panel 2 pixels 8 Voltage stabilizing capacitor 9 Boosting capacitor 10, 10A Protection diode (D1, D2)

Claims (7)

A substrate,
A plurality of pixels provided in the display area;
A display device having a flexible substrate connected to one side of the substrate,
Having at least one protective diode element provided in a region other than the display region;
The display device, wherein the at least one protective diode element is connected to a predetermined terminal of the flexible substrate by a pair of diode wirings. Each of the pixels has an active element formed on the substrate,
The display device according to claim 1, wherein the at least one protection diode element is formed in the same process as the active element.   3. The display device according to claim 1, wherein the at least one protective diode element is a diode-connected thin film transistor. The substrate has a drive circuit for driving the plurality of pixels,
The drive circuit includes a power supply circuit that generates an internal power supply voltage;
A plurality of stabilizing capacitors constituting the power supply circuit in the drive circuit are mounted on the flexible substrate,
The at least one diode element includes, on the flexible substrate, a terminal to which an external power supply voltage of the flexible substrate is input and one terminal among the terminals to which the stabilization capacitor of the flexible substrate is connected. The display device according to claim 1, wherein the display device is connected between the display devices. A wiring layer for supplying a driving voltage from the driving circuit to the pixel is formed around the display area of the substrate.
The at least one diode element is formed in a region outside the wiring layer outside at least one side of two sides orthogonal to one side of the substrate of the drive circuit. 4. The display device according to 4.   The display device according to claim 4, wherein a plurality of boosting capacitors constituting the power supply circuit in the drive circuit are mounted on the flexible substrate. A counter substrate disposed opposite the substrate;
The display device according to claim 1, further comprising a liquid crystal sandwiched between the substrate and the counter substrate.

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