JP2004109857A - Liquid crystal display device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device wherein an added value of a light shielding film in a TFT and an added value of a capacitance line in a holding capacitor can be developed, respectively. <P>SOLUTION: The liquid crystal display device is provided with a switching element 30 formed on an element substrate, a pixel electrode 9 driven by the switching element 30 and a liquid crystal interposed between the pixel electrode 9 and a counter electrode. A conductive light shielding layer 81 and a insulating layer 77 insulating the conductive light shielding layer 81 from the switching element 30 are formed between the element substrate and the switching element 30, the holding capacitor 60 connected to the pixel electrode 9 is formed on the element substrate and one capacitance line (a second capacitance line 63) of the holding capacitor 60 is formed by using the same material as the conductive light shielding layer 81 and insulated from the conductive light shielding layer 81. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device and an electronic apparatus, and more particularly to a liquid crystal display device capable of performing pixel display by a switching element.
[0002]
[Prior art]
An active matrix type liquid crystal display device using a thin film transistor (TFT) as a switching element is used, for example, as a display screen of a mobile phone or a light valve of a projector. Here, when the light from the projector is transmitted through the liquid crystal panel of the liquid crystal display device, the light is reflected by a substrate constituting the liquid crystal panel or by an optical system at a subsequent stage, and is incident on the TFT. May be. Since the polysilicon layer constituting the TFT has a transmittance of 20 to 30% with respect to visible light, a photocarrier may be generated in the TFT and a leak current may be generated. In some cases, cross-talk in which a signal potential is supplied to a pixel which has been in a non-selection period when a TFT is turned on occurs, or a signal potential cannot be held, thereby lowering a contrast ratio.
[0003]
In order to prevent this, for example, Patent Document 1 discloses a technique in which a light-shielding film is formed below a TFT, and the light-shielding film below the TFT is also used as a capacitance line of a storage capacitor connected in parallel to the liquid crystal. Is described.
[0004]
[Patent Document 1]
JP-A-10-111520
[Problems to be solved by the invention]
However, in the above-described technology, since the light-shielding film and the capacitance line are integrally formed, it is not possible to control the energization independently of each other. Was not expected to add value.
[0006]
The present invention has been made in view of the above problems, and a liquid crystal display device having a configuration capable of expressing the added value of a light-shielding film in a TFT and the added value of a capacitance line in a storage capacitor, respectively. The purpose of the present invention is to provide an electronic device provided with the electronic device.
[0007]
[Means for Solving the Problems]
In order to solve the above problem, a liquid crystal display device of the present invention includes a switching element formed on an element substrate, a pixel electrode driven by the switching element, and a pixel electrode and a counter electrode. A liquid crystal display device comprising a liquid crystal layer comprising: a conductive light-shielding layer between the element substrate and the switching element; and an insulating layer that insulates the conductive light-shielding layer from the switching element. On the other hand, a storage capacitor connected to the pixel electrode is formed on the element substrate, and one of the capacitance lines of the storage capacitor is formed of the same material as the conductive light-shielding layer, and It is characterized by being insulated from the conductive light-shielding layer.
[0008]
According to such a liquid crystal display device, since the conductive light-shielding layer of the switching element and the capacitance line of the storage capacitor are made of the same material, they can be integrally formed at the time of manufacturing. Since the capacitor lines are insulated from each other, different signal voltages can be supplied to each of them.
Therefore, the conductive light-blocking layer of the switching element prevents light from entering the switching element, and suppresses the degradation of display quality, while setting the conductive light-blocking layer at a potential at which the switching element is turned off. Malfunction of the switching element can be prevented or suppressed. Also, in synchronization with the operation of the switching element, that is, for example, in synchronization with a scanning signal in a TFT (thin film transistor) or the like, when the scanning signal voltage is in a positive state (TFT is in an ON state), a positive voltage is applied to the conductive light shielding layer. By applying the voltage, the TFT characteristics shift to the depletion side, so that the current supply capability of the TFT is relatively improved. On the other hand, when the scanning signal voltage is zero (TFT is in the OFF state), by applying a negative voltage to the conductive light-shielding layer, the TFT characteristics are shifted to the enhancement side. Generation can be suppressed.
On the other hand, also in the storage capacitor, since the capacitor line shows light-shielding properties, generation of photocarriers from the semiconductor layer forming the storage capacitor can be suppressed. Further, by setting the potential waveform different from that of the conductive light-blocking layer formed below the switching element, a potential waveform suitable for driving the pixel can be set regardless of the control of the characteristics of the switching element.
[0009]
In the liquid crystal display device according to the aspect of the invention, the switching element includes a semiconductor layer connected to the pixel electrode, and a gate electrode formed on the semiconductor layer via a gate insulating film. , A first capacitance portion and a second capacitance portion, wherein the first capacitance portion is provided between the semiconductor layer and a first capacitance line made of the same material as the gate electrode. A second capacitor line including a film, wherein the second capacitor portion is made of the same material as the conductive light-blocking layer, and is insulated from the conductive light-blocking layer; A configuration having the insulating layer interposed therebetween.
[0010]
According to such a configuration, a conductive light-shielding film is formed on the substrate by patterning separately into a switching element formation region and a storage capacitor formation region, and the insulating layer and the semiconductor layer are formed so as to extend over each region. And a gate insulating film, and a conductive film (gate electrode) is patterned on the gate insulating film in the switching element formation region, and a conductive film (capacity line) is formed simultaneously with the gate electrode in the storage capacitor formation region. Since the pattern can be formed, a liquid crystal display device having a configuration according to the present invention can be provided extremely easily.
Further, according to the above configuration, the storage capacitor has a first capacitance portion formed between the first capacitance line (a capacitance line made of the same material as the gate electrode) and the semiconductor layer, and a second capacitance line ( Since the second capacitance portion formed between the semiconductor layer and the conductive light shielding film and the second capacitance portion formed between the semiconductor layers are overlapped and included, the semiconductor layer and the first capacitance portion are not formed. Compared with the case where a capacitor is provided only between the capacitor line and the capacitor line, the area of the storage capacitor can be reduced even when the same capacitance is secured, and the opening area of the pixel can be increased.
[0011]
In the liquid crystal display device of the present invention, the first capacitance line and the second capacitance line can be connected to each other. In this case, the upper and lower capacitance lines can be fixed at the same potential, and stable driving of the storage capacitor can be ensured.
[0012]
Further, in the liquid crystal display device of the present invention, the storage capacitor may be formed in a region below a data line for supplying a data signal to the switching element. In this case, since the second capacitance line of the storage capacitor has a light-shielding property, the second capacitance line can function as a light-shielding film of the data line.
[0013]
Next, an electronic apparatus according to the present invention includes the liquid crystal display device as a display unit. According to such an electronic device, stable driving is possible, and a display portion is configured by a liquid crystal display device including pixels with a high aperture ratio, so that high display characteristics can be provided.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
[Liquid crystal display]
FIG. 1 is a plan view showing one embodiment of the liquid crystal display device of the present invention, together with components, as viewed from the counter substrate side, and FIG. 2 is a cross-sectional view taken along line HH ′ in FIG. FIG. 3 is an equivalent circuit diagram of various elements, wiring, and the like in a plurality of pixels formed in a matrix in an image display area of the liquid crystal display device. FIG. 4 is a partially enlarged plan view showing the configuration of each pixel of the liquid crystal display device. FIG. 5 is a sectional view taken along line AA ′ of FIG.
In each of the drawings used in the following description, the scale of each layer and each member is different so that each layer and each member have a size recognizable in the drawings.
[0015]
As shown in FIGS. 1 and 2, in the liquid crystal display device 100 of the present embodiment, the TFT array substrate 10 and the opposing substrate 20 are bonded to each other with a sealing material 52, and a liquid crystal 50 is formed in a region defined by the sealing material 52. Is enclosed and held. A liquid crystal injection port 55 for injecting liquid crystal after bonding the TFT array substrate 10 and the counter substrate 20 at the time of manufacturing is formed in the sealing material 52, and the liquid crystal injection port 55 is sealed after the liquid crystal is injected. It is sealed by the material 54. Note that, on the inner surface side of the counter substrate 20, a counter electrode 23 and an alignment film 21 are formed.
[0016]
A peripheral partition 53 made of a light-shielding material is formed in a region inside the formation region of the sealing material 52. In a region outside the sealing material 52, a data line driving circuit 201 and mounting terminals 202 are formed along one side of the TFT array substrate 10, and a scanning line driving circuit 204 is formed along two sides adjacent to this one side. Is formed. On one remaining side of the TFT array substrate 10, a plurality of wirings 205 for connecting between the scanning line driving circuits 204 provided on both sides of the image display area are provided. In at least one of the corners of the opposing substrate 20, an inter-substrate conducting material 206 for establishing electric conduction between the TFT array substrate 10 and the opposing substrate 20 is provided.
[0017]
Instead of forming the data line driving circuit 201 and the scanning line driving circuit 204 on the TFT array substrate 10, for example, a TAB (Tape Automated Bonding) substrate on which a driving LSI is mounted and a peripheral portion of the TFT array substrate 10 The formed terminal group may be electrically and mechanically connected via an anisotropic conductive film. Further, in the liquid crystal display device 100, the type of the liquid crystal 50 to be used, that is, an operation mode such as a TN (Twisted Nematic) mode, an STN (Super Twisted Nematic) mode, and a normally white mode / normally black mode. Thus, a retardation plate, a polarizing plate and the like are arranged in a predetermined direction, but are not shown here. Further, when the liquid crystal display device 100 is configured for color display, for example, red (R), green (G), A blue (B) color filter is formed together with the protective film.
[0018]
In the image display area of the liquid crystal display device 100 having such a structure, as shown in FIG. 3, a plurality of pixels 100a are arranged in a matrix, and each of the pixels 100a has a pixel switching device. , Here, a TFT (Thin Film Transistor) 30 is formed, and a data line 6 a for supplying pixel signals S 1, S 2,..., Sn is electrically connected to the source of the TFT 30. The pixel signals S1, S2,..., Sn to be written to the data lines 6a may be supplied line-sequentially in this order, or may be supplied to a plurality of adjacent data lines 6a for each group. . The scanning line 3a is electrically connected to the gate of the TFT 30, and the scanning signals G1, G2,..., Gm are applied to the scanning line 3a in a pulsed manner in this order at a predetermined timing. It is configured.
[0019]
The pixel electrode 9 is electrically connected to the drain of the TFT 30. By turning on the TFT 30 as a switching element for a certain period, the pixel signals S1, S2,... Writing is performed on each pixel at a predetermined timing. The pixel signals S1, S2,..., Sn of a predetermined level written to the liquid crystal via the pixel electrodes 9 are held for a certain period between the counter electrodes 21 of the counter substrate 20 shown in FIG. In order to prevent the held pixel signals S1, S2,..., And Sn from leaking, a storage capacitor 60 is added in parallel with the liquid crystal capacitor formed between the pixel electrode 9 and the counter electrode. For example, the voltage of the pixel electrode 9 is held by the holding capacitor 60 for a time that is three orders of magnitude longer than the time during which the source voltage is applied. Thereby, the charge retention characteristics are improved, and the liquid crystal display device 100 having a high contrast ratio can be realized.
[0020]
Next, FIG. 4 is a plan view schematically showing a configuration of a pixel region including the pixel electrode 9 in the liquid crystal display device 100, and FIG. 5 is a cross-sectional view taken along the line AA 'in FIG. The configuration of the pixel region will be described with reference to FIGS. A transparent pixel electrode 9 having a rectangular shape in a plan view is formed in the pixel 100 a, and a storage capacitor 60 is formed below the pixel electrode 9. As shown in FIG. 5, the storage capacitor 60 includes a first capacitance unit 60a and a second capacitance unit 60b that are arranged in two layers.
[0021]
On the other hand, in the pixel 100a, the data line 6a and the scanning line 3a are provided along the vertical and horizontal boundaries of the pixel electrode 9, and the TFT 30 is formed near the intersection of the data line 6a and the scanning line 3a. As shown in FIG. 5, the TFT 30 includes a semiconductor layer 62 and a gate electrode 3a formed on the semiconductor layer 62 via a gate insulating film 76, and is connected to the data line 6a via a contact hole 72. It has a source region 62a and a drain region 62b connected to the pixel electrode 9 via contact holes 73 and 74.
[0022]
A light-shielding film (conductive light-shielding layer) 81 made of a metal film of Ti, Ta, W or the like is formed via an insulating film 77 corresponding to the active layer forming region from the source region 62a to the drain region 92b of the TFT 30. Have been. Thus, light incidence on the TFT 30 from the side opposite to the pixel electrode 9 is prevented or suppressed, and generation of a leak current due to light incidence on the active layer is prevented or suppressed, and deterioration in display quality is suppressed. I have.
[0023]
Next, the above-described storage capacitor 60 includes a first capacitor portion 60a and a second capacitor portion 60b, and the first capacitor portion 60a is made of the same material (for example, Ta, Cr) as the scanning line (gate electrode) 3a of the TFT 30. , MoW, Al, etc.), and a gate insulating film 76 as a dielectric is sandwiched between a first capacitance line 61 formed of a TFT and an active layer of the TFT 30. On the other hand, the second capacitance section 60b has a configuration in which an insulating film 77 as a dielectric is sandwiched between the second capacitance line 63 made of the same material as the light shielding film 81 and the semiconductor layer 62. No. In addition, as shown in FIG. 4, it is connected to the first capacitance line 61 (corresponding to the capacitance line 3b shown in FIG. 3), and is also connected to the second capacitance line 63 through the contact hole 71. , The first capacitance line 61 and the second capacitance line 63 are set to the same potential.
[0024]
On the other hand, a signal synchronized with the scanning signal of the TFT 30 is supplied to the light shielding film 81 formed below the TFT 30, thereby stabilizing the driving of the TFT 30. Specifically, as shown in FIG. 6, a signal (indicated by a thick broken line) supplied to the light shielding film 81 is synchronized with a scanning signal (indicated by a solid line), and furthermore, a voltage value is controlled so as to control the characteristics of the TFT 30. Are slightly shifted to the minus side from the voltage of the scanning signal.
[0025]
That is, when the scanning signal is +9 V, the TFT is turned on. At this time, by applying a positive voltage of +5 V to the light shielding film 81, the TFT characteristic shifts to the depletion side, and the switching characteristic of the pixel transistor relatively. Is improved. On the other hand, when the scanning signal is 0V, the TFT is turned off. At this time, by applying a negative voltage of -5V to the light shielding film 81, the TFT characteristics are shifted to the enhancement side, and the leakage of the pixel transistor is relatively increased. Current generation can be suppressed.
[0026]
As shown in FIG. 6, the signal supplied to the second capacitance line 63 (shown by a bold line) is fixed to a constant voltage, unlike the signal supplied to the light shielding film 81. By not synchronizing the signal supplied to the second capacitance line 63 on the storage capacitor 60 side with the signal supplied to the light shielding film 81 in this way, for example, the function as the storage capacitor can be sufficiently exhibited without being impaired. Can be.
[0027]
As described above, in the present embodiment, a conductive light-shielding film is formed on the substrate 90, and is divided into a formation region for the TFT 30 and a formation region for the storage capacitor 60, and is patterned. In addition, different signal voltages can be supplied to the conductive light-shielding films (63, 81). Therefore, as described above, it is possible to separately supply a signal voltage under preferable conditions corresponding to the design of each region, and it is possible to perform preferable drive control on the TFT 30 and the storage capacitor 60, respectively.
[0028]
In addition, in the present embodiment, since the storage capacitor 60 has a configuration in which the first capacitance unit 60a and the second capacitance unit 60b overlap each other, for example, the second capacitance line 63 is not formed, and the semiconductor layer 62 and the first capacitance Compared to a configuration in which the capacitance is provided only between the line 61 and the case where the same capacitance is secured, the area of the storage capacitor 60 can be reduced, and the opening area of the pixel 100a can be increased. In this embodiment, as shown in FIG. 4, the storage capacitor 60 is provided below the data line 6a, so that the storage capacitor 60 functions as a black matrix of the data line 6a.
[0029]
That is, according to the present embodiment, the formation of the light-shielding film 81 in the lower layer portion of the TFT 30 prevents or suppresses the occurrence of a light leak current in the TFT 30, and as a result, the capacity of the storage capacitor 60 can be reduced. The area of the storage capacitor 60 can be reduced, which can increase the aperture ratio of the pixel 100a. In addition, as described above, since the storage capacitor 60 is configured to overlap, the area of the storage capacitor 60 can be reduced, and the aperture ratio of the pixel 100a can be increased. Further, in the TFT 30, for example, by setting the light-shielding film 81 to a potential at which the TFT 30 is turned off, malfunction of the TFT 30 can be prevented or suppressed, that is, leakage can be reduced. The area can be reduced, thereby increasing the aperture ratio of the pixel 100a. By such a plurality of actions, the aperture ratio of the pixel 100a can be effectively increased.
[0030]
On the other hand, in the present embodiment, a light-shielding film is formed on the substrate 90, and the light-shielding film is divided into a region for forming the TFT 30 and a region for forming the storage capacitor 60, and the light-shielding film 81 and the second capacitance line 63 are respectively formed. The insulating layer 77, the semiconductor layer 62, and the gate insulating film 76 are formed so as to straddle the respective regions. In the region where the TFT 30 is formed, the gate electrode 3a is formed on the gate insulating film 76 by patterning. In the region where the capacitor 60 is formed, the first capacitor line 61 can be patterned at the same time as the gate electrode 3a, so that the configuration of the pixel 100a shown in FIG. 5 can be provided extremely easily.
[0031]
[Electronics]
Next, a specific example of an electronic apparatus including the liquid crystal display device described in the above embodiment will be described. FIG. 7 is a perspective view showing an example of a mobile phone which is an electronic apparatus including the liquid crystal display device 100 of the above-described embodiment in a display unit. The mobile phone 1000 is a small-sized liquid crystal display device of the present invention. The display unit 1001 includes a plurality of operation buttons, an earpiece, and a mouthpiece. Therefore, in the display unit of the mobile phone 1000, it is possible to provide a stable pixel display and a bright display with a high aperture ratio.
[0032]
The liquid crystal display device 100 of the above embodiment includes an electronic book, a personal computer, a digital still camera, a liquid crystal television, a viewfinder type or a monitor direct view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, a word processor, and a workstation. , A video phone, a POS terminal, a device equipped with a touch panel, etc., and can be used suitably, and any electronic device can provide high-quality display.
[Brief description of the drawings]
FIG. 1 is a plan view showing a liquid crystal display device according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along the line HH ′ of FIG. 1;
FIG. 3 is an equivalent circuit diagram of the liquid crystal display device of FIG.
FIG. 4 is an enlarged plan view showing a pixel portion of the liquid crystal display device of FIG. 1;
FIG. 5 is a sectional view taken along line AA ′ of FIG. 4;
FIG. 6 is an explanatory diagram showing signals supplied to a light shielding film, a second capacitance line, and the like.
FIG. 7 is a perspective view illustrating an example of an electronic apparatus of the invention.
[Explanation of symbols]
9 pixel electrode, 30 TFT (switching element), 50 liquid crystal (electro-optical material), 60 storage capacitance, 61 first capacitance line, 62 semiconductor layer, 63 second capacitance line, 77 insulating layer, 81 light shielding film (conductive light shielding) Layer), 100 liquid crystal display

Claims (6)

A liquid crystal display device including a switching element formed on an element substrate, a pixel electrode driven by the switching element, and a liquid crystal layer sandwiched between the pixel electrode and a counter electrode,
A conductive light-blocking layer and an insulating layer that insulates the conductive light-blocking layer and the switching element are formed between the element substrate and the switching element.
On the element substrate, a storage capacitor connected to the pixel electrode is formed, and one of the capacitance lines of the storage capacitor is formed of the same material as the conductive light-blocking layer, and the conductive light-blocking layer and A liquid crystal display device characterized by being insulated. The switching element includes a semiconductor layer connected to the pixel electrode, and a gate electrode formed on the semiconductor layer via a gate insulating film,
On the other hand, the storage capacitor includes a first capacitance unit and a second capacitance unit,
The first capacitance portion has a configuration in which the gate insulating film is interposed between a first capacitance line formed of the same material as the gate electrode and the semiconductor layer,
The second capacitance portion is formed of the same material as the conductive light-shielding layer, and the insulating layer is sandwiched between a second capacitance line insulated from the conductive light-shielding layer and the semiconductor layer. The liquid crystal display device according to claim 1, comprising a configuration. 3. The liquid crystal display device according to claim 1, wherein signals having different potential waveforms are supplied to the conductive light-shielding layer and the second capacitance line. 4. The liquid crystal display device according to claim 2, wherein the first capacitance line and the second capacitance line are connected to each other. 5. 5. The liquid crystal display device according to claim 1, wherein the storage capacitor is formed in a lower region of a data line for supplying a data signal to the switching element. An electronic apparatus comprising the liquid crystal display device according to claim 1.

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