JP2698503B2 - Active matrix liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix liquid crystal display device using a TFT (thin film transistor) as a switching element.

[0002]

2. Description of the Related Art FIG. 21 shows an example of an equivalent circuit of an active matrix liquid crystal display device using thin film transistors as switching elements. In FIG.
A large number of scanning electrode lines G1, G2, ..., Gn and a large number of signal electrode lines S1, S2, ..., Sm are wired in a matrix. S is connected to the signal supply circuit 2, a transistor 3 is provided near the intersection of each line, and a capacitor 4 serving as a capacitor and a liquid crystal element 5 are connected to the drain of the transistor 3 to form a circuit. .

In the circuit having the conventional configuration shown in FIG.
The scanning electrode lines G1, G2,..., Gn are sequentially scanned to turn on all the transistors 3 on one scanning electrode line G at once, and in synchronization with this scanning, the signal supply circuit 2 sends the signal electrode lines S1,. The signal charges are stored in the liquid crystal element 5 and the capacitance section 4 corresponding to the liquid crystal element 5 to be displayed, of the capacitance sections 4 connected to the transistor 3 in the ON state via S2,..., Sm. This accumulated signal charge remains unchanged until the next scan even when the transistor 3 is turned off.
Since the corresponding liquid crystal element 5 is continuously excited, the liquid crystal element 5 is controlled by the control signal, and the display is completed. That is, by performing such driving, each liquid crystal element 5 is statically driven even when time-division driving is performed from the external driving circuits 1 and 2.

FIGS. 22 and 23 show a structure of an active matrix substrate provided with scanning electrode lines G and signal electrode lines S in the conventional active matrix liquid crystal display device shown in an equivalent circuit in FIG. It shows a part. In the active matrix substrate shown in FIGS. 22 and 23, the scanning electrode lines G are formed on a transparent substrate 6 such as glass.
And the signal electrode lines S are arranged in a matrix at the intersections of each other with an insulating layer 7 interposed therebetween. Also, the scanning electrode line G
The thin film transistor 3 is provided in the vicinity of the intersection of the signal electrode line S with the thin film transistor S.

[0005] The thin film transistor 3 shown in FIGS.
Has the most general configuration, a gate insulating film 9 shown in FIG. 23 is provided on a gate electrode 8 provided from the scanning electrode line G, and amorphous silicon (a-Si ), And a drain electrode 11 and a source electrode 12 made of a conductor such as aluminum are provided on the semiconductor layer 10. Further, the drain electrode 11 is formed on the semiconductor layer 1.
0 and contact hole 13 opened in gate insulating layer 9
Is connected to the pixel electrode 15 via the. Then, a liquid crystal sealed by a pair of upper and lower transparent substrates provided with an alignment film is provided above the active matrix substrate having the above-described configuration to form an active matrix liquid crystal display device, and the pixel electrode 15 is formed of the liquid crystal. When an electric field is applied to the molecules, the alignment of the liquid crystal molecules can be controlled.

However, if the same polarity of electric charge is continuously applied to the liquid crystal, the remaining ionic substance is lumped to one side by the direct current component, and an electric field is generated by the adsorbed electric charge, causing a problem that the display is burned. Utilizing that the liquid crystal has the same light transmission characteristics even when the polarity of the voltage applied to the pixel electrode 15 is reversed, AC driving of the liquid crystal is performed to solve the problem of the image sticking.

However, when the liquid crystal is AC driven, the gate voltage jumps into the pixel electrode due to the parasitic capacitance of the thin film transistor 3, and a dynamic voltage shift of the potential of the pixel electrode 15 occurs. The parasitic capacitance that causes the voltage shift is because the insulating layer formed in a part of the active matrix liquid crystal display device becomes capacitive. This is because, in the actual structure of the active matrix liquid crystal display device, the scan electrode lines G are formed after the scan electrode lines G are formed on the substrate.
The insulating layer between these parts and the scanning electrode lines G forms a capacitor because of the formation of the thin film transistor 3 and the like by forming various insulating films on the insulating layer. However, this is caused by parasitic capacitance, which is structurally unavoidable in current active matrix liquid crystal display devices.

Further, when the liquid crystal itself is regarded as a capacitive element, anisotropy of the dielectric constant occurs due to the difference in the alignment state of the liquid crystal molecules and the difference in gradation. The amount of voltage shift differs for each drive voltage of the liquid crystal display element, and there is a problem that the voltage shift cannot be completely corrected by simply setting the offset value.

In the above-described voltage shift, the parasitic capacitance is changed to C
Assuming that gd, the capacitance of the capacitor portion is CLc, the capacitance of the liquid crystal is Cs, and the scanning (gate) voltage is VG, the voltage shift amount ΔV can be expressed by the following relational expression. ΔV = Cgd · VG / (CLc + Cgd + Cs)

FIG. 25 shows a reference potential Vcom at the time of AC driving of the liquid crystal and a signal voltage Vs (the maximum value of the signal voltage is VV).
SH, and the minimum value is VSL. ) And the scanning voltage VG (the maximum value of the scanning voltage is VGH and the minimum value is VGL). FIG. 26 shows the pixel electrode voltage Vd when ΔV ≒ ΔVp, and FIG. 21 shows ΔV ≠ ΔVp. Pixel electrode voltage Vd in the case of
Is shown.

Here, in order to perform ideal AC driving of the liquid crystal, if it is assumed that the liquid crystal is driven by an effective value of AC, the pixel electrode voltage Vd is set to the positive voltage side around the reference potential Vcom. It must be symmetric with the negative voltage side. However, since the capacitance of the liquid crystal has anisotropy as described above, the relationship actually becomes ΔV ≠ ΔVp. As shown by the hatched portion in FIG. 27, the hatched portion indicating the effective value of the pixel electrode voltage Vd Is asymmetric between the positive voltage side and the negative voltage side, so that the pixel electrode voltage Vd fluctuates as shown in FIG. 28, and the liquid crystal molecules are distorted.
In other words, a DC component is generated in the liquid crystal driving voltage, which causes problems such as transmittance fluctuation (flicker) and generation of an afterimage due to image sticking.

Therefore, in a conventional liquid crystal display device,
In the above relational expression, if the capacitance (Cs) of the capacitance element is sufficiently large even if the capacitance value (CLC value) slightly changes due to the anisotropy of the liquid crystal, the change in ΔV is reduced. 29, the capacitive element 4 is connected to the scanning electrode line G, or as shown in FIG. 29, a single independent electrode line 1 made of Al or the like is arranged in parallel with the scanning electrode line G.
8 and the capacitive element 4 is connected to the independent electrode line 18 to adopt a structure for canceling the influence of the dielectric anisotropy of the liquid crystal.

[0013]

However, with the structure in which the capacitive element 4 is connected to the scanning electrode line G as shown in FIG. 24, the load capacitance of the scanning electrode line G increases, so that a delay occurs in the scanning signal. This may hinder the driving of the liquid crystal. In the case where the independent electrode lines 18 are provided as shown in FIG. 29, the independent electrode lines 18 are made of a conductive material such as Al.
Is provided separately in addition to the conventional process, so that the number of manufacturing processes such as insulation at the intersections between the independent electrode lines 18 and the signal electrode lines S increases, and the number of manufacturing processes increases. There is a problem of accompanying defect increase. Furthermore,
In order to connect the capacitive element 4 and the independent electrode line 18, it is necessary to form contact holes in various thin films formed between the capacitive element 4 and the independent electrode line 18. And the yield is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and can always provide a stable effective applied voltage even when a change in liquid crystal capacitance or the occurrence of parasitic capacitance occurs. It is an object of the present invention to provide an active matrix liquid crystal display device which eliminates the problem and extends the life.

[0015]

According to a first aspect of the present invention, a scanning electrode line and a signal electrode line are arranged in a matrix, and the scanning electrode line and the signal electrode line are connected to each other. A switching element formed of a thin film transistor and a pixel electrode are provided in the divided portion, and in an active matrix liquid crystal display device in which the pixel electrode is AC-driven, an insulating layer is formed around at least one of the scanning electrode line and the pixel electrode, Around the scanning electrode line and the pixel electrode, connected to at least one of the scanning electrode line and the pixel electrode,
An altered layer adjacent to the other one is formed with an insulating layer interposed therebetween, and the altered layer is formed of a semiconductor layer that becomes conductive by light irradiation.

According to a second aspect of the present invention, in order to solve the above problem, a scanning electrode line and a signal electrode line are wired in a matrix, and a thin film transistor is formed in a portion separated by the scanning electrode line and the signal electrode line. In an active matrix liquid crystal display device in which a switch element and a pixel electrode are provided, and the pixel electrode is AC-driven, an insulating layer is formed on the pixel electrode formed on the substrate, and a deteriorated layer is formed on the insulating layer. The altered layer is composed of a semiconductor layer that becomes conductive by light irradiation, and the altered layer is connected to an independent electrode line formed near the pixel electrode.

According to a third aspect of the present invention, in order to solve the above problem, a scanning electrode line and a signal electrode line are wired in a matrix, and a thin film transistor is formed in a portion separated by the scanning electrode line and the signal electrode line. In an active matrix liquid crystal display device in which a switch element and a pixel electrode are provided, and the pixel electrode is AC-driven, a pixel electrode is formed on a substrate, an independent electrode line is formed near the pixel electrode, and the pixel electrode and An insulating layer is formed between the pixel electrode and the independent electrode line, and is connected to one of the pixel electrode and the independent electrode line near the pixel electrode and the independent electrode line, and is adjacent to the other via the insulating layer. An altered layer is formed, and the altered layer is composed of a semiconductor layer that becomes conductive by light irradiation.

According to a fourth aspect of the present invention, in order to solve the above-mentioned problem, a scanning electrode line and a signal electrode line are wired in a matrix, and a thin film transistor is formed in a portion separated by the scanning electrode line and the signal electrode line. In an active matrix liquid crystal display device in which a switch element and a pixel electrode are provided, and the pixel electrode is AC-driven, a pixel electrode is formed on a substrate, an independent electrode line is formed near the pixel electrode, and the pixel electrode and An insulating layer is formed between the pixel electrode and the independent electrode line, and a deteriorated layer adjacent to the pixel electrode and the independent electrode line via the insulating layer is formed near the pixel electrode and the independent electrode line; Is composed of a semiconductor layer that is made conductive by light irradiation.

According to a fifth aspect of the present invention, in order to solve the above problems, the altered layer according to the first, second, third or fourth aspect is formed of an amorphous Si semiconductor layer constituting a thin film transistor. .

According to a sixth aspect of the present invention, in order to solve the above-mentioned problem, the altered layer according to the first, second, third, fourth or fifth aspect is provided such that the deteriorated layer is formed on a pixel electrode or an independent electrode via a contact hole formed in an insulating layer. These are connected to the electrode wires.

[0021]

[0022]

An altered layer which is made conductive by light irradiation is provided on an insulating layer formed around the pixel electrode and the signal electrode, and the altered layer is connected to at least one of the scanning electrode line and the pixel electrode line. When the light emitted from the backlight is applied to the matrix liquid crystal display element, the deteriorated layer becomes conductive, and an insulating layer is interposed between the pixel electrode and the scanning electrode line to form a capacitor. By this capacitance formation, the influence of the capacitance change accompanying the gradation change of the liquid crystal can be reduced, and the voltage shift amount during the liquid crystal AC driving is reduced.

In a device in which an independent electrode line is provided on a substrate, and a deteriorated layer provided on a pixel electrode via an insulating layer is connected to the independent electrode line, an active matrix liquid crystal display element emits light from a backlight. When the irradiated light is irradiated, the deteriorated layer becomes conductive, and an insulating layer is interposed between the pixel electrode and the independent electrode line to form a capacitor. By this capacitance formation, the influence of the capacitance change accompanying the gradation change of the liquid crystal can be reduced, and the voltage shift amount during the liquid crystal AC driving is reduced.

An independent electrode line is provided on the substrate, and a deteriorated layer is provided via an insulating layer provided between the pixel electrode and the independent electrode line.
When the active matrix liquid crystal display element is irradiated with light emitted from the backlight, the deteriorated layer is turned into a conductor, and the electrode is connected between the pixel electrode and the independent electrode line. The capacitance is formed with the insulating layer interposed. By this capacitance formation, the influence of the capacitance change accompanying the gradation change of the liquid crystal can be reduced, and the voltage shift amount during the liquid crystal AC driving is reduced.

If the semiconductor layer constituting the thin film transistor and the altered layer are formed from the same semiconductor layer,
When a necessary portion is removed by etching after the entire surface of the semiconductor layer is formed on the substrate, a special process is added by etching while leaving a necessary portion for the thin film transistor and a necessary portion for the deteriorated layer. Instead, the deteriorated layer can be formed by the same process as the conventional manufacturing process.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 3 show an embodiment in which the structure according to the present invention is applied to an active matrix liquid crystal display device provided with a semiconductor transistor called a channel-etch type. As shown in FIG. 1, the scanning electrode lines 21 and the signal electrode lines 22 are wired in a matrix, and the scanning electrode lines 21 and the signal electrode lines 22 are arranged.
And a thin film transistor 2 near the intersection of the scanning electrode line 21 and the signal electrode line 22.
3 are provided, and the pixel electrodes 24 are provided so as to occupy most of the portions separated by the scanning electrode lines 21 and the signal electrode lines 22.

In FIG. 1, an independent electrode line 26 is provided in parallel between the pixel electrode 24 and the scanning electrode line 21 below the pixel electrode 24. This independent electrode wire 2
Reference numeral 6 denotes a transparent conductive material such as ITO (Indium Phosphorus Tin Oxide), which is insulated through an insulating layer described later so as not to be electrically connected to the signal electrode lines 22.

The detailed structure of the connection portion between the transistor 23 and the pixel electrode 24 is as shown in FIG. 1 or FIG. 2 showing a cross section along the line aa in FIG. First, in the scanning electrode line 21 in FIG. 1, a scanning electrode 27 is formed so as to protrude from the vicinity of the intersection with the signal electrode 22, and various thin films are stacked above the gate electrode 27 as shown in FIG. A transistor 23 is formed. That is, an insulating layer 28 is formed to cover the signal electrode line 22, the gate electrode 27, and the pixel electrode 24 formed on the substrate 20, and the non-doped amorphous Si (a−) is formed on the insulating layer 28 on the gate electrode 27. A semiconductor layer 29 made of Si) and a contact layer 30 made of n ⁺ amorphous Si for making ohmic contact are formed.

The contact layer 30 on the pixel electrode 24 side
A drain electrode 31 made of a conductive material covering the upper surface of the contact layer 30 and a part of the insulating layer 28 on the pixel electrode 24. The drain electrode 31 is formed on the contact layer formed on the insulating layer 28. It is connected to the pixel electrode 24 via the hole 32. On the contact layer 30 on the side of the scanning electrode line 22, a source electrode 34 made of a conductive material is formed to cover the upper surface of the contact layer 30 and a part of the insulating layer 28 on the scanning electrode line 22. Is connected to the signal electrode line 22 via a contact hole 35 formed in the insulating layer 28 on the signal electrode line 22.

On the other hand, below the portion where the transistor 23 and the pixel electrode 24 are connected in FIG. 1, as shown in FIG. 1 or FIG. 3 showing a cross section along the line bb in FIG. A first layer made of non-doped amorphous Si (a-Si) covering a part of the insulating layer 28 above the electrode 24 and a part of the insulating layer 28 above the independent electrode line 26.
An altered layer 36 and a second altered layer 37 made of n ⁺ amorphous Si are formed. Then, the first altered layer 36
Are connected to the independent electrode lines 26 via contact holes 28a formed in the insulating layer 28. On the second altered layer 37, a conductive layer 38 made of a conductive material equivalent to the conductive material constituting the drain electrode 31 and the source electrode 34 is formed. The conductive layer 38, the first altered layer 36, and the second altered layer 37 have a planar convex shape as shown in FIG. 1, and a large area of each layer is located above the independent electrode line 26. And the small area is located above the pixel electrode 24. In each of the above layers, the second altered layer 37 and the conductive layer 38 may be omitted.

In FIG. 2, a protective film 40 is formed over the insulating layer 28, the drain electrode 31, the semiconductor layer 29, and the source electrode 34. The protective film 40 covers these layers. Are provided, and a transparent electrode layer 43, a black mask 44, and a glass substrate 45 are provided on the upper protective film 41 to constitute an active matrix liquid crystal display device.

In the above structure, since the scanning electrode lines 21 and the signal electrode lines 22 are provided on the substrate 20,
An insulating layer 28 for insulating them is formed at the intersection of these lines, but this insulating layer 28 is omitted in FIG. Further, only the scanning electrode lines 21 and the pixel electrodes 24 are formed on the substrate 20 without forming the signal electrode lines 22,
Next, an insulating layer 28, a semiconductor layer 29, a contact layer 30 and the like are formed, and then a drain electrode 31 and a source electrode 3 are formed.
Of course, the signal electrode line 22 may be formed at the same time as the formation of the fourth.

Next, the operation of the active matrix liquid crystal display device configured as described above will be described. In the liquid crystal display device, as in the conventional liquid crystal display device, a scanning signal is applied to the scanning electrode line 21 from the scanning circuit, and a driving signal is applied to the signal electrode line 22 from the signal supply circuit to drive the pixel electrode 24. Thus, the orientation of the molecules of the liquid crystal 42 is controlled, and the light transmittance is controlled and used. A backlight is provided on the bottom surface (back surface side) of the lower substrate 20 shown in FIG. 2 so that light emitted from the backlight passes through the liquid crystal 42 and reaches the user's eyes. Has been.

The light from the back light from the back side of the substrate 20 is transmitted through the transparent substrate 20 and the independent electrode line 2 made of ITO.
6 and the pixel electrode 24, the first deteriorated layer 36
Is irradiated. Here, since the first altered layer 36 and the second altered layer 37 are layers made of a semiconductor, when light from a luminous body such as a backlight is received, a photocurrent is generated to reduce the resistance. Convert to conductor. Then, as is apparent from FIG. 3, the insulating layer 28 is sandwiched between the independent electrode line 26 made of a conductor and the pixel electrode 24 made of the conductor, and the transformed layer 36 that has become a conductor with the independent electrode line 26 is formed. Since the connection is made with the 37, a capacitor having a structure in which the insulating layer 28 is sandwiched between conductors is formed. Therefore, a capacitor can be formed in this portion. As a result, as described earlier in the equivalent circuit of the active matrix liquid crystal display device using the following equation, the capacitance of Cs shown in the equation can be increased. ΔV = Cgs · VG / (CLC + Cgs + Cs)

Accordingly, even if the CLC constituting the denominator of the above equation slightly changes due to the gradation on display, the influence can be reduced. Therefore, even if a change in the liquid crystal capacitance or some parasitic capacitance occurs due to gradation, an effective applied voltage having a stable value can always be given, eliminating the problem of afterimage and flicker, and extending the life of the active matrix liquid crystal display device. Can be done. Further, in the present embodiment, the first altered layer 36 provided on the independent electrode line 26 has a planar convex shape as shown in FIG. 1, but this is due to the light passing through the transparent independent electrode line 26. This is to increase the deposition of the part to be made conductive by using more and secure a large capacitance, and at the same time, reduce the area where the pixel electrode 24 is hidden by the first altered layer 36 to prevent the aperture ratio from decreasing. .
Therefore, the planar shape of the first deteriorated layer 36 is not particularly limited to a planar convex shape as long as such a capacity can be secured and a decrease in the aperture ratio can be prevented.

Further, a non-doped amorphous S
When a semiconductor layer 29 made of i (a-Si) and a contact layer 30 made of n ⁺ amorphous Si for making ohmic contact are formed, a non-doped type is once formed on the entire upper surface of each thin film laminated on the substrate 20. An amorphous Si (a-Si) layer, ion implantation is performed on this layer to form an n ⁺ amorphous Si layer, and thereafter, patterning for removing unnecessary portions by etching is performed to form a semiconductor layer 29 and a contact layer 30. If a part of these layers is left on the pixel electrode 24 and the independent electrode line 26 by adjusting the shape of the etching mask during this etching, the first alteration is performed by the etching process. The layer 36 and the second altered layer 37 can be formed. Therefore, the above structure can be adopted, but the first altered layer 36 and the second altered layer 37 can be formed in the same steps as the conventional manufacturing steps.

Further, when forming the drain electrode 31 and the source electrode 34, a conductive layer is once formed on the entire upper surface of each thin film on the substrate 20, and thereafter, patterning for removing unnecessary portions by etching is performed. Row and drain electrode 3
1 and a source electrode 34 are formed. At the time of this etching, the shape of the etching mask is changed so that the second altered layer 3 is formed.
If the conductive layer on 7 is left, the conductive layer 38 can be formed by this process. Therefore, when the above structure is adopted, the conductive layer 38 can be formed in the same process as the conventional manufacturing process.

As described above, the semiconductor layer 29, the contact layer 30, the drain electrode 31, and the source electrode 34, which are always performed when manufacturing an active matrix liquid crystal display device.
The first altered layer 36 and the second altered layer 36
If the conductive layer 38 is formed, the first and second altered layers 36 and 37 and the conductive layer 38 can be formed without adding a special film forming step for forming the first and second altered layers. Therefore, the structure of the present embodiment can be realized by simply changing a part of the manufacturing process of the conventional active matrix liquid crystal display device without adding a new process. It can be realized at low cost.

4 and 5 show another example in which the present invention is applied to an active matrix liquid crystal display device having a channel-etch type thin film transistor. In this embodiment, the same components as those in the embodiment described above with reference to FIGS. 1 to 3 are denoted by the same reference numerals, and the description of those portions will be omitted. In this embodiment, the independent electrode wire 2
6 'is formed in parallel with the signal electrode line 22 and the independent electrode line 2
6 'is formed so as to pass over the insulating layer 28 on the pixel electrode 24, and the independent electrode line 26' is provided in a state insulated from the scanning electrode line 21. An altered layer 36 'made of a semiconductor connected to the independent electrode line 26' is formed above the pixel electrode 24.

According to the structure of this example, since the insulating layer 28 is provided between the deteriorated layer 36 'and the pixel electrode 24,
When the deteriorated layer 36 'becomes conductive by light irradiated on the deteriorated layer 36' from the back side of the substrate 20, the insulating layer 28 sandwiched between the deteriorated layer 36 'and the pixel electrode 24 forms a capacitance.
From the above, the same effect as in the above embodiment can be obtained.

FIG. 6 shows an example of the structure shown in FIGS. 1 to 3 in which the independent electrode line 26 '' is not formed of ITO but is formed of a light-shielding metal conductive material such as Al. It is shown. In the case of this structure, the first deteriorated layer 36, the second deteriorated layer 37, and the conductive layer 38 are formed in a plane inverted convex shape as shown in FIG. 6, and the area of these layers on the pixel electrode 24 side is increased. The area on the side of the electrode line 26 ″ is formed small, and the light of the backlight passing through the pixel electrode 24 is mainly used, and the first altered layer 36 is used as a conductor. The other structure in this embodiment is the same as that of the previous embodiment.

The structure shown in FIG. 6 can obtain the same effect as that of the embodiment described above.

FIG. 7 shows the embodiment shown in FIGS.
The contact hole 28a formed in the insulating layer 28 on the independent electrode line 26 is omitted, most of the insulating layer 28 on the upper surface of the pixel electrode 24 is removed, and the first deteriorated layer 36 '' is directly connected to the pixel electrode 24. And the first altered layer 3
This is an embodiment in which the connection between 6 ″ and the independent electrode wire 26 is eliminated. Note that the second altered layer 3 is provided on the first altered layer 36 ''.
7 '' and a conductive layer 38 '' are formed, but these may be omitted.

In the embodiment shown in FIGS. 7 and 8, since the first altered layer 36 "is directly connected to the pixel electrode 24, the light of the backlight causes the first altered layer 36" to become conductive. In this structure, however, the insulating layer 28 interposed between the first deteriorated layer 36 '' and the independent electrode line 26 forms a capacitor. Therefore, in order to increase the capacitance of this portion, as shown in FIG. 7, the first altered layer 36 ″, the second altered layer 37 ″, and the conductive layer 38 ″ on the independent electrode line 26 are formed in a planar convex shape. It is formed in a shape. Even if the structure shown in FIGS. 7 and 8 is adopted, the same effect as that of the embodiment described above can be obtained.

FIGS. 9 to 11 show an embodiment in which the structure according to the present invention is applied to an active matrix liquid crystal display device having a semiconductor transistor called an etch stopper type. The scanning electrode lines 51 and the signal electrode lines 52 are arranged in a matrix in the same manner as in the example described above, and are separated by the scanning electrode lines 51 and the signal electrode lines 52 shown in FIG. A transistor 53 having a thin film structure is provided in the vicinity of the intersection of the scanning electrode line 51 and the signal electrode line 52, and the pixel electrode 54 occupies most of the portion separated by the scanning electrode line 51 and the signal electrode line 52. Is provided.

FIG. 10 shows a cross-sectional structure of an intersection between the scanning electrode line 51 and the signal electrode line 52 and a cross-sectional structure of the transistor 53. The structure of the intersection between the scanning electrode line 51 and the signal electrode line 52 is such that the scanning electrode line 51 made of Ta or the like is formed on a transparent substrate 50 as shown in the left part of FIG. Anodized layer 5 made of Ta ₂ O ₅ or the like
6, an insulating layer 57 made of SiN _x or the like, a semiconductor layer 58 made of non-doped amorphous Si or the like,
This is a structure in which an insulating layer 59 made of SiN _x or the like, a contact layer 60 made of an n ⁺ amorphous layer or the like, and a signal electrode line 52 are stacked.

The structure of the transistor 53 is as follows.
As shown in the right part of FIGS. 9 and 10, a gate electrode 61 made of Ta or the like branched from the scan electrode line 51 is formed on the substrate 50, and an anodic oxide layer 56 is formed thereon. The insulating layer 57 and the semiconductor layer 58 are stacked, and a stopper layer 59 'made of a material equivalent to that of the insulating layer 57 is formed at the center of the upper surface of the semiconductor layer 58 so as to cover both ends of the stopper layer 59'. n ⁺ amorphous Si
Are formed, and a source electrode 65 is formed so as to cover one of the semiconductor layers 58 ′.
A drain electrode 66 is formed so as to cover the other semiconductor layer 58, and the drain electrode 66 is formed of a connection layer 67 made of ITO.
Are connected to the pixel electrode 54 as shown in FIG.

On the other hand, the portion between the pixel electrode 54 shown in FIG.
Independent electrode lines 68 are provided in parallel with the above. The independent electrode wires 68 are made of a transparent conductive material such as ITO (indium phosphide tin oxide), and are insulated through an insulating layer 57 so as not to be electrically connected to the signal electrode wires 52. In FIG. 9, the transistor 53 and the pixel electrode 5
As shown in FIG. 11, which shows a cross section taken along line ee in FIG.
A first altered layer 69 made of non-doped amorphous Si (a-Si) is formed to cover a part of the insulating layer 57 above the insulating layer 4 and a part of the insulating layer 57 above the independent electrode line 68. . The first altered layer 69 is formed of the independent electrode wire 6.
8 Contact hole 57 formed in upper insulating layer 57
is connected to the independent electrode line 68 via a. As shown in FIG. 9, the first altered layer 69 has a planar convex shape, and a large area portion is located above the independent electrode line 68.
The small-area portions are located above the pixel electrodes 54, respectively.

Next, the operation of the active matrix liquid crystal display device configured as described above will be described. FIG.
1 is provided with a backlight on the bottom side (back side) of the substrate 50. Light from the back side from the back side of the substrate 50 is transmitted through the transparent substrate 50, the independent electrode lines 68 made of ITO, and the pixels. Since it passes through the electrode 54, it is irradiated on the first altered layer 69. Here, the first altered layer 69 is
Since the layer is made of a semiconductor, it receives light from a light-emitting body such as a backlight, generates a photocurrent and has a low resistance, and becomes a conductor. Then, as is clear from FIG. 11, the insulating layer 57 is sandwiched between the independent electrode line 68 made of a conductor and the pixel electrode 54 made of the conductor, and the first deteriorated layer made conductive with the independent electrode line 68 is formed. The connection of 69 results in a capacitor having a structure in which the insulating layer 57 is sandwiched between conductors. Therefore, a capacitor can be formed in this portion. With the above structure, the same effects as those of the embodiment described above can be obtained.

Also, a non-doped amorphous S
When the semiconductor layer 69 made of i (a-Si) is formed,
A semiconductor layer 58 is formed by forming a non-doped amorphous Si (a-Si) layer once on the entire upper surface of each thin film laminated on the substrate 50 and then performing patterning for removing unnecessary portions by etching. If a part of these layers is left on the pixel electrode 24 and the independent electrode line 26 at the time of this etching, the first altered layer 69 can be formed by the etching process. Therefore, when the above structure is adopted, the first altered layer 69 can be formed in the same process as the conventional manufacturing process.

Next, a method of manufacturing the substrate for an active matrix liquid crystal display device configured as described above will be described. First, an example of a method for manufacturing an active matrix liquid crystal substrate will be described with reference to FIGS. A transparent substrate made of glass or the like is prepared as a starting material, and patterning is performed on this substrate using a film forming means such as sputtering and a thin film removing means such as etching. As shown in FIG. Is formed.

Next, by the same means as described above, a scanning electrode line 72 and a gate electrode 73 made of a metal conductive material such as Al or Ta are formed on the substrate as shown in FIG. Subsequently, an insulating layer 74 made of SiO _2, SiN _x, or the like is formed on the upper surface of the substrate except for almost the entire upper surface of the pixel electrode 70 as shown in FIG. Further, the contact hole 74 is formed in the insulating layer 74 on the independent electrode line 71.
a is formed.

Next, on the pixel electrode 70 and the insulating layer 74,
A semiconductor layer made of amorphous Si or the like is formed, and ion implantation or the like is performed on the upper surface thereof to form a semiconductor layer made of n ⁺ -Si. Subsequently, patterning is performed, and an altered layer 75 made of a semiconductor such as a planar convex amorphous Si is formed on the insulating layer 74 on the independent electrode line 71 as shown in FIG.
And a semiconductor layer 76 is formed on the insulating layer over the gate electrode 73.

Next, a metal conductive layer is coated and patterned to form a signal electrode line 77 and a source electrode 7 shown in FIG.
8 and a gate electrode 79 are formed. When a protective layer and an alignment film are formed after the above-described processing, a substrate equivalent to the substrate for an active matrix liquid crystal display device shown in FIGS. 1 to 3 is completed. In the active matrix liquid crystal substrate obtained by the above manufacturing method, the signal electrode line 77 is formed simultaneously with the source electrode 78 and the gate electrode 79, and the signal electrode line 77 is formed on the substrate as shown in FIG. Of course, it may be formed directly.

In the above process, after forming the insulating film 74, the insulating layer 74 is left on the entire surface as shown in FIG. 17 (that is, the insulating layer on the pixel electrode 70 is left), and the upper part of the independent electrode line 71 is left. A contact hole 74a is formed in the insulating layer 74, and a contact hole 74b is formed in the insulating layer 74 above the pixel electrode 70. Thereafter, as shown in FIG. 77, a source electrode 78, and a gate electrode 79 may be formed. By implementing the method described above, a circuit of an active matrix liquid crystal display device can be obtained.

Further, in order to form a circuit of the active matrix liquid crystal display device having the structure shown in FIG. 6, it is necessary to change the state shown in FIG. 15 from the state shown in FIG.
May be formed. Further, in this case, when a structure in which an insulating layer is formed also on the upper surface of the pixel electrode 70 is employed, FIG.
In the case of processing to the state shown in FIG. 20, the next step may be sequentially performed without performing the etching removal of the insulating layer, and may be completed as shown in FIG.

As described above, if the deteriorated layer 75 is formed by diverting the manufacturing steps of the semiconductor layer 76, the source electrode 78, and the gate electrode 79, which are always performed when manufacturing the active matrix liquid crystal display device, the deteriorated layer is formed. By modifying the shape of the mask material for etching the semiconductor layer 76 without adding a special film forming process for
5 can be formed. Therefore, the structure of the present embodiment can be realized only by changing a part of the manufacturing process of the conventional active matrix liquid crystal display device without adding a new process, and according to the method described above,
An active matrix liquid crystal display device can be manufactured easily and at low cost.

[0058]

As described above, according to the present invention, an altered layer which is made conductive by light irradiation is provided on an insulating layer formed around at least one of a pixel electrode and a signal electrode, and this altered layer is used as a scanning electrode. Since the active matrix liquid crystal display element is irradiated with light emitted from the backlight because it is connected to at least one of the line and the pixel electrode line, the deteriorated layer becomes conductive and becomes insulated between the pixel electrode and the scanning electrode line. The layer is interposed, and a capacitance is formed in this portion. By this capacitance formation, the influence of the capacitance change accompanying the gradation change of the liquid crystal can be reduced, and the voltage shift amount during the liquid crystal AC driving can be reduced. Therefore, when the liquid crystal is driven by AC, a DC voltage is not applied to the liquid crystal.
It is possible to provide an active matrix liquid crystal display device which has no problem of afterimages and flicker and has a long life.

In the case where an independent electrode line is provided on a substrate, and a deteriorated layer provided on a pixel electrode via an insulating layer is connected to the independent electrode line, an active matrix liquid crystal display element is connected to a backlight. When the emitted light is irradiated,
The deteriorated layer becomes a conductor, and an insulating layer is interposed between the pixel electrode and the independent electrode line to form a capacitor. By this capacitance formation, the influence of the capacitance change accompanying the gradation change of the liquid crystal can be reduced, and the voltage shift amount during the liquid crystal AC driving is reduced. Therefore, it is possible to provide an active matrix liquid crystal display device that does not apply a DC voltage to the liquid crystal when the liquid crystal is driven by an AC drive, eliminates the problem of afterimages and flicker, and has a long life.

Further, in the case where an independent electrode line is provided on a substrate, a deteriorated layer is provided via an insulating layer provided between the pixel electrode and the independent electrode line, and this is connected to the independent electrode line. ,
When the light emitted from the backlight is applied to the active matrix liquid crystal display element, the deteriorated layer becomes conductive, and an insulating layer is interposed between the pixel electrode and the independent electrode line to form a capacitor. By this capacitance formation, the influence of the capacitance change accompanying the gradation change of the liquid crystal can be reduced, and the voltage shift amount during the liquid crystal AC drive is reduced. Therefore, it is possible to provide an active matrix liquid crystal display device that does not apply a DC voltage to the liquid crystal when the liquid crystal is driven by an AC drive, eliminates the problem of afterimages and flicker, and has a long life.

If the semiconductor layer constituting the thin film transistor and the altered layer are formed of the same amorphous Si semiconductor layer, when the semiconductor layer is formed on the entire surface of the substrate and the necessary portions are removed by etching, By etching while leaving a portion necessary for a thin film transistor and a portion necessary for a deteriorated layer, a deteriorated layer can be formed by a process equivalent to the conventional manufacturing process without adding a special process to the conventional manufacturing method. . Thus, the structure of the present invention is easy to implement and can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a circuit of one embodiment in which the present invention is applied to an active matrix liquid crystal display device having a channel-etch type thin film transistor.

FIG. 2 is a sectional view taken along the line aa of FIG. 1;

FIG. 3 is a sectional view taken along the line bb in FIG. 1;

FIG. 4 is a configuration diagram showing a circuit of still another embodiment in which the present invention is applied to an active matrix liquid crystal display device having a channel-etch type thin film transistor.

FIG. 5 is a sectional view taken along the line hh of FIG. 4;

FIG. 6 is a configuration diagram showing a substrate of another example of the active matrix liquid crystal display device according to the present invention.

FIG. 7 is a configuration diagram showing a substrate of another embodiment of the active matrix liquid crystal display device according to the present invention.

FIG. 8 is a sectional view taken along the line cc in FIG. 7;

FIG. 9 is a configuration diagram showing a circuit of one embodiment in which the present invention is applied to an active matrix liquid crystal display device having an etching stopper type thin film transistor.

FIG. 10 is a sectional view taken along the line dd in FIG. 7;

FIG. 11 is a sectional view taken along the line ee in FIG. 7;

FIG. 12 is a plan view illustrating a state in which a pixel electrode and an independent electrode line are formed on a substrate, for explaining an example of the method of the present invention.

FIG. 13 is a plan view showing a state where scanning electrode lines are formed on a substrate.

FIG. 14 is a plan view showing a state where an insulating layer is formed on a substrate.

FIG. 15 is a plan view showing a state where a deteriorated layer is formed on an insulating layer.

FIG. 16 is a plan view showing a state where signal electrode lines are formed.

FIG. 17 is a plan view showing an example in which an insulating layer is formed on the entire surface.

FIG. 18 is a plan view showing a state in which a deteriorated layer is formed on the insulating layer shown in FIG.

FIG. 19 is a plan view showing an example in which an altered layer is formed in an inverted convex shape.

FIG. 20 is a plan view showing another example in which the altered layer is formed in an inverted convex shape.

FIG. 21 is a configuration diagram showing an equivalent circuit of a conventional general active matrix liquid crystal display device.

FIG. 22 is a plan view showing a detailed structure of an intersection between a signal electrode line and a scanning electrode line in the active matrix liquid crystal display device shown in FIG.

FIG. 23 is a cross-sectional view of a main part of the portion shown in FIG. 22;

FIG. 24 is a diagram showing an equivalent circuit in a state in which a capacitance section is connected to a scanning electrode line in a conventional liquid crystal display device.

FIG. 25 is a diagram showing drive voltages applied to an active matrix liquid crystal display device.

FIG. 26 is a diagram showing a change state of the drive voltage shown in FIG. 25 depending on the capacitance.

FIG. 27 is a diagram showing driving voltages actually applied to pixel electrodes of an active matrix liquid crystal display device.

FIG. 28 is a diagram showing a change in transmittance with respect to a drive voltage actually applied to a pixel electrode of an active matrix liquid crystal display device.

FIG. 29 is a diagram showing a state where a capacitor is connected to an independent electrode line provided in a conventional active matrix liquid crystal display device.

[Explanation of symbols]

 20, 50 substrate, 21, 51 scanning electrode line, 22, 52 signal electrode line, 23, 53 transistor, 24, 54 pixel electrode, 26, 26 ', 68 independent electrode line, 27, 61 gate electrode, 28, 57 insulation Layer, 28a, 57a contact hole, 29, 58 semiconductor layer, 30 contact layer, 31, 66 drain electrode, 34, 65 source electrode, 36, 36 ', 69 first altered layer, 37 second altered layer,

Claims (6)

(57) [Claims] A scanning electrode line and a signal electrode line are wired in a matrix, and a switch element formed of a thin film transistor and a pixel electrode are provided in a portion separated by the scanning electrode line and the signal electrode line. In an active matrix liquid crystal display device in which electrodes are AC driven, an insulating layer is formed around at least one of the scan electrode line and the pixel electrode, and at least one of the scan electrode line and the pixel electrode is formed around the scan electrode line and the pixel electrode. Active matrix liquid crystal, wherein an altered layer adjacent to the other is formed via an insulating layer, and the altered layer is formed of a semiconductor layer which becomes conductive by light irradiation. Display device. 2. A scanning element line and a signal electrode line are wired in a matrix, and a switch element and a pixel electrode formed of a thin film transistor are provided in a portion separated by the scanning electrode line and the signal electrode line. In an active matrix liquid crystal display device in which electrodes are AC-driven, an insulating layer is formed on a pixel electrode formed on a substrate, an altered layer is formed on the insulating layer, and the altered layer becomes conductive by light irradiation. An active matrix liquid crystal display device comprising a semiconductor layer, wherein the altered layer is connected to an independent electrode line formed near a pixel electrode. 3. A scanning electrode line and a signal electrode line are wired in a matrix, and a switch element formed of a thin film transistor and a pixel electrode are provided in a portion separated by the scanning electrode line and the signal electrode line. In an active matrix liquid crystal display device in which electrodes are AC-driven, a pixel electrode is formed on a substrate, an independent electrode line is formed near the pixel electrode, and an insulating layer is formed between the pixel electrode and the independent electrode line. Along with the pixel electrode and the independent electrode line, an altered layer connected to one of the pixel electrode and the independent electrode line and adjacent to the other via an insulating layer is formed,
An active matrix liquid crystal display device, wherein the altered layer is constituted by a semiconductor layer which is made conductive by light irradiation. 4. A scanning electrode line and a signal electrode line are wired in a matrix, and a switch element formed of a thin film transistor and a pixel electrode are provided in a portion separated by the scanning electrode line and the signal electrode line. In an active matrix liquid crystal display device in which electrodes are AC-driven, a pixel electrode is formed on a substrate, an independent electrode line is formed near the pixel electrode, and an insulating layer is formed between the pixel electrode and the independent electrode line. In addition, in the vicinity of the pixel electrode and the independent electrode line, an altered layer adjacent to the pixel electrode and the independent electrode line via an insulating layer is formed, and the altered layer is formed of a semiconductor layer which becomes conductive by light irradiation. An active matrix liquid crystal display device comprising: 5. An active matrix liquid crystal display device, wherein the altered layer according to claim 1, 2, 3, or 4 is formed from an amorphous Si semiconductor layer constituting a thin film transistor. 6. The active layer according to claim 1, wherein the altered layer is connected to an independent electrode line or a pixel electrode via a contact hole formed in the insulating layer. Matrix liquid crystal display.