JP3139801B2 - 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 type liquid crystal display having a light shielding layer.

[0002]

In recent years, an active matrix type liquid crystal display device using thin film transistors has been developed with the aim of realizing a high definition and high performance liquid crystal display device. In particular , a projection type that achieves a large screen of about 100 inches
The liquid crystal display device has been attracting attention.

In this projection type liquid crystal display device, light from a light source is separated into three colors, and the light is incident on the liquid crystal display device for each color, and the light transmitted through three liquid crystal display devices corresponding to each color is converted into light.
Recombining and projecting. At this time, a black matrix similar to a color direct-view type liquid crystal display device is provided on a counter substrate of each liquid crystal display device in order to protect a thin film transistor in a pixel portion from high-luminance light source light and to perform pixel separation. Is formed.

In the case of a projection type liquid crystal display device, unlike a direct view type liquid crystal device, it is necessary to reduce the substrate size and to achieve high definition. For this reason, the pixel size must be reduced, and a pixel size smaller than 70 μm is required.

Further, in order to secure the brightness of the image,
Since it is necessary to improve the aperture ratio of the pixel portion, it is necessary to improve the alignment accuracy of the black matrix serving as the light-shielding layer of the opposing substrate and to reduce the tilt reverse region of the liquid crystal generated between the signal lines and the pixel electrodes. Has become.

The tilt reverse region is defined as a horizontal electric field caused by a potential difference between a signal line or a scanning line and a pixel electrode, and a vertical electric field between a signal line or a scanning line and a counter electrode. In addition to the interaction, due to poor alignment or poor pretilt of the alignment film material at the pattern step, the signal line or scanning line and the vicinity between the pixel electrodes are
A region different from the normal liquid crystal alignment direction, in which light leakage, contrast reduction, and the like occur.

Another problem in securing the aperture ratio of the pixel portion is that the distance between the signal line and the pixel electrode cannot be reduced. That is, in order to improve the aperture ratio, it is better that the distance between the signal line and the pixel electrode is short. On the contrary, if the distance is too short, capacitive coupling occurs between the signal line and the pixel electrode, and the pixel potential greatly varies. It is necessary to keep a certain distance.

[0008]

As described above, the high-definition projection type liquid crystal device has a problem that a tilt reverse region is generated,
There is a problem that it is difficult to improve the aperture ratio.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has as its object to provide a liquid crystal display device which prevents generation of a tilt reverse region and has a high aperture ratio.

[0010]

According to the present invention, there is provided a liquid crystal display device comprising: a plurality of signal lines and scanning lines arranged in a matrix; and a pixel electrode connected to an intersection of the signal lines and the scanning lines via a thin film transistor. An electrode substrate, a second electrode substrate having a counter electrode facing the pixel electrode, and a liquid crystal portion having a liquid crystal composition sandwiched between the first electrode substrate and the second electrode substrate. In a liquid crystal display device,
And said signal lines or said scanning lines, the thickness of the liquid crystal portion between the second electrode substrate in the region where the signal lines or said scanning lines are opposite, a region where the pixel electrode is displayed
Below 1/5 or 2/3 of the thickness of the liquid crystal portion between facing the second electrode substrate, said signal lines or said scanning
To reduce the horizontal electric field at the
This is to prevent occurrence .

Further, the signal lines or the scanning lines, the thickness of the liquid crystal portion between the second electrode substrate in the region where the signal line or the scanning line is opposite, a region where the pixel electrode is displayed before
Of the liquid crystal unit thickness between opposite to the serial second electrode substrate 1
/ 5 or 2/3 or less is regions are those that are shielded from light by the light shielding region of the first electrode substrate or said second electrode substrate.

[0012]

According to the present invention, light is shielded by a light-shielding region of a first electrode substrate or a second electrode substrate between a signal line or a scanning line and a second electrode substrate in a region opposed to the signal line or the scanning line. the is to have the liquid crystal unit thickness is, first region of the thickness of the liquid crystal portion between which faces the second electrode substrate for displaying the pixel electrode
/ 5 or 2/3 in the following signal lines or the scanning line and the second
By shortening the distance between the substrate of, these signals
Tilt by reducing the horizontal electric field on lines or scan lines
Since the occurrence of the reverse region is prevented, the horizontal electric field generated between the scanning line and the pixel electrode is reduced, and the occurrence of the tilt reverse is suppressed . For this reason, the tilt reverse region of the liquid crystal portion is reduced , so that the width of the light shielding layer portion is reduced and the aperture ratio is increased.

[0013] Incidentally, the signal lines or the scanning lines, the liquid crystal unit thickness between the second electrode substrate in the region where the signal line or the scanning line is opposite, area for displaying the pixel electrode of the second shielding effect as increasing more than 2/3 of the liquid in the thickness of the crystal portion between which faces the electrode substrate is a counter electrode hardly arrive with small, liquid crystal is less likely to be injected and a 1/5 or less.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the liquid crystal display device of the present invention will be described below with reference to FIGS.

The liquid crystal display device 1 shown in FIGS.
As shown in FIG. 1, between a first electrode substrate 2 and a second electrode substrate 3 formed opposite to the first electrode substrate 2.
A liquid crystal layer section 4 as a liquid crystal section is sandwiched.

The first electrode substrate 2 of the liquid crystal display device 1
As shown in FIG. 2, a plurality of signal lines 5 and a plurality of scanning lines 6 are arranged in a matrix, and a switching element is provided at each intersection of the signal lines 5 and the scanning lines 6. The pixel electrode 8 is arranged via the connected thin film transistor 7. The distances between the signal lines 5 and the scanning lines 6 and the pixel electrodes 8 are arranged at intervals of 5 μm in order to sufficiently improve the aperture ratio of the liquid crystal display device 1.

FIG. 1 is a sectional view taken along the line II-II in FIG.

On a first substrate 10, an island-shaped first polycrystalline silicon (Si) layer 11 is provided, and a part of
The drain region 11a and the source region 11b of the thin film transistor 7 are formed by doping (P) ions, and the first polysilicon layer 11 between the drain region 11a and the source region 11b functions as an active layer 11c. .

On the first polycrystalline silicon layer 11, a gate insulating film formed by oxidizing the first polycrystalline silicon layer 11 except for a part of the drain region 11a and the source region 11c.
12 are arranged. On the active layer 11c via the gate insulating film 12, a gate electrode 13 formed integrally with the scanning line 6 in which polycrystalline silicon is doped with phosphorus ions is provided.

In the same step as the gate electrode 13, an auxiliary capacitance line 14 extending in parallel with the scanning line 6 is formed. The auxiliary capacitance line 14 is connected to the first polycrystalline silicon layer 11.
Is formed so as to extend in parallel with the scanning line 6 with the gate insulating film 12 interposed therebetween in a portion extended from the portion of the thin film transistor 7, and an auxiliary capacitance is formed between the thin film transistor 7 and the auxiliary capacitance line 14.

Further, an interlayer insulating film 15 is disposed except for a part of the drain region 11a and the source region 11b of the first polycrystalline silicon layer 11, and the drain region 11a is made of aluminum (A).
l), the source region 11b is also provided with a pixel electrode 8 on the auxiliary capacitance line 14 via the interlayer insulating film 15, and this pixel electrode 8 is made of ITO (Indium Tin Oxide), Al).

A first electrode substrate 2 is formed by sequentially disposing a protective film 17 and an alignment film 18 of 500 Å in thickness made of an organic polymer film on the pixel electrode 8. The thickness of the alignment film 18 is 500 to 100.
Angstrom film thickness is good.

The second electrode substrate 3 provided facing the first electrode substrate 2 is a second substrate made of glass.
2.5 μm consisting of chromium (Cr) in matrix on 21
Thick light-shielding layer portion 22, composed of ITO placed on top
3,000 Å thick counter electrode 23, this counter electrode
The second electrode substrate 3 is formed by disposing an alignment film 24 made of an organic polymer film provided on 23.

The light-shielding layer portion 22 is formed in a matrix, and the pixel electrode 8 of the first electrode substrate 2 is formed.
Are formed so that only the opening region 25 shown in FIG. 1 is exposed. The light-shielding layer 22 may be made of a light-impermeable material. In addition to chromium, a metal material such as aluminum (Al), titanium (Ti), molybdenum (Mo), or a carbon-added material may be used. Alternatively, a carbon-free organic material or the like can be used. However, when an organic material is used as a material for forming the light-shielding layer 22, exposure and development may not be easy if the film thickness is 2 μm or more. In such a case, for example, the adjustment may be made by increasing the thickness of the region of the first electrode substrate 2 that faces the light-shielding layer portion 22.

The pixel electrode 8 of the first electrode substrate 2 and the opposing electrode 23 of the second electrode substrate 3 are arranged so as to oppose each other, and the liquid crystal composition is interposed between the pixel electrode 8 and the opposing electrode 23. The liquid crystal layer unit 4 made of a material is sandwiched therebetween to constitute the liquid crystal display device 1.

Further, according to the liquid crystal display device 1 of the above embodiment, the signal line 5 or the scanning line 6 and the second electrode substrate 3 in a region where the signal line 5 or the scanning line 6 is opposed. The thickness d1 of the liquid crystal layer portion 4 in the light-shielding region 26 which is shielded by a certain light-shielding layer portion 22 is 2.5 μm, and an opening region in which the region displayed by the pixel electrode 8 is opposed to the second electrode substrate 3 The thickness d2 of the 25 liquid crystal layer portions 4 is 5 μm.

That is, the thickness d1 of the liquid crystal layer 4 which is shielded by the light shielding layer 22 is suppressed to の of the thickness d2 of the liquid crystal layer 4 in the opening region 25 which is not shielded by the light shielding layer 22. It is configured.

The thickness d1 is determined by the pixel electrode 8 and the counter electrode 23.
The thickness d2 is based on the average distance between the signal line 5 and the counter electrode 23.

Next, the operation of the liquid crystal display device 1 according to the present embodiment will be described with reference to FIGS.

FIG. 3 is a schematic sectional view of the liquid crystal display device 1 of the present embodiment, taken along the line III-III in FIG.
1 shows a schematic cross-sectional view of a conventional liquid crystal display device 1, and the same portions will be described with the same reference numerals.

Conventionally, the distance between the signal line 5 and the scanning line (not shown) and the pixel electrode 8 is substantially the same as the distance between the signal line 5 and the scanning line and the counter electrode 23. A vertical electric field and a horizontal electric field act on the liquid crystal layer section 5 and the liquid crystal layer portion 4 near the scanning line, and the electric field E as shown in FIG.
Since 1 was applied, a tilt reverse region occurred.

However, in the above-described embodiment, the thickness d1 of the liquid crystal layer 4 which is shielded by the light shielding layer 22 is different from the thickness d1 of the light shielding layer 22.
Thickness d of the liquid crystal layer portion 4 in the opening region 26 which is not shielded by light
2 1/2. Therefore, the distance between the signal line 5 and the scanning line 6 and the pixel electrode 8 is sufficiently larger than the distance between the signal line 5 and the scanning line and the counter electrode 23. Therefore, a vertical electric field mainly acts on the liquid crystal layer portion 4 near the signal line 5 and the scanning line 6, and an electric field E2 as shown in FIG. 3 is applied.

As described above, according to the liquid crystal display device 1 of the above embodiment, the signal line 5 or the scanning line 6 is connected to the second substrate.
By reducing the distance between the signal lines 5 and 21,
Alternatively, reduce the horizontal electric field in the scanning line 6 to tilt
Prevent the occurrence of a reverse area. Therefore, Ki out to reduce the mainly horizontal electric field in the vicinity of the signal lines 5 and the scanning lines 6, the occurrence of tilt reverse region is suppressed
You. As a result, the tilt reverse region of the liquid crystal layer 4 decreases.
Accordingly, the width of the light shielding layer portion 22 is reduced, and a good display image can be obtained.

Further, by reducing such a horizontal electric field, the distance between the signal line 5 and the scanning line 6 and the pixel electrode 8 is reduced so that the crosstalk caused by the coupling capacitance generated between the pixel electrode 8 and the pixel electrode 8 is reduced. No effect, eg 5
To about 7 μm, the pixel electrode 8
Occupied area can be increased. Thereby, in the liquid crystal display device 1 of the embodiment, the aperture ratio can be increased.

Further, according to the above embodiment, the light shielding layer portion 22 is formed.
Is formed with a sufficient thickness, so that undesired obliquely incident light from the outside can be blocked, and the contrast of the displayed image can be improved.

Further, according to the above embodiment, the light shielding layer portion
The thickness of the liquid crystal layer portion 4 that is shielded by the light
The thickness of the liquid crystal layer portion 4 in the opening region 25 which is not shielded from light by the light source.
/ 3 or less. That is, the ratio of this thickness is 1 /
If it is smaller than 5, the light-shielding effect is weakened and the occurrence of the tilt reverse region cannot be sufficiently suppressed. If the thickness ratio exceeds 2/3, it becomes difficult to inject the liquid crystal composition.

It is particularly preferable that the ratio of the thickness be 2/5 or more and 3/5 or less. By setting this range, disconnection of the opposing electrode 23 due to the step portion of the light shielding layer portion 22 can be prevented, which is more preferable in manufacturing. As a method for preventing disconnection due to a step portion of the counter electrode 23, for example, the second method
A counter electrode 23 is provided on a substrate 21 of this type, and a light-shielding layer portion 22 made of a metal having good conductivity is provided on the counter electrode 23.
The same voltage may be supplied to the light-shielding layer 22 and the light-shielding layer 22. In this way, disconnection or the like due to the step portion of the counter electrode 23 can be prevented.

[0038]

According to the liquid crystal display device of the present invention, a signal line or the scanning line, the thickness of the liquid crystal portion between the second electrode substrate in the region where the signal line or the scanning line is opposite, Liquid while the area displayed by the pixel electrode faces the second electrode substrate
By making the thickness of the crystal part 1/5 or more and 2/3 or less and shortening the distance between the signal line or the gate line and the second substrate , the horizontal electric field in the signal line or the scanning line can be reduced.
To prevent the tilt reverse area from occurring,
The horizontal electric field generated between the scanning line and the pixel electrode is reduced,
To suppress the occurrence of the tilt reverse domain of the liquid crystal unit, it is possible to reduce the width of the light shielding layer portion can enlarge the aperture ratio.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a plan view showing the same liquid crystal display device.

FIG. 3 is a diagram illustrating an operation of the liquid crystal display device according to the first embodiment;
FIG. 3 is a sectional view taken along line III-III shown in FIG.

FIG. 4 is a cross-sectional view illustrating an operation of a conventional liquid crystal display device.

[Explanation of symbols]

1 liquid crystal display device 2 first electrode substrate 3 and the second electrode substrate 4 a liquid crystal layer 5 signal lines 6 scan lines 7 TFT 8 pixel electrode 22 light shielding layer 23 facing electrodes 26 light shielding region of a liquid crystal portion

Claims (2)

(57) [Claims] A first signal line including a plurality of signal lines and scanning lines arranged in a matrix, and a pixel electrode connected to an intersection of the signal lines and the scanning lines via a thin film transistor;
An electrode substrate, a second electrode substrate having a counter electrode facing the pixel electrode, and a liquid crystal portion having a liquid crystal composition sandwiched between the first electrode substrate and the second electrode substrate. in the liquid crystal display device, said signal lines or said scanning lines, the thickness of the liquid crystal portion between the second electrode substrate in the region where the signal lines or said scanning lines are opposite, the pixel electrode appears Area
Reducing the horizontal electric field in said liquid at 1/5 or more than 2/3 of the thickness of the crystal unit, the signal lines or said scanning lines while facing the second electrode substrate
A liquid crystal display device wherein a tilt reverse region is prevented from being generated . 2. A signal line or the scanning line, the thickness of the liquid crystal portion between the second electrode substrate in the region where the signal line or the scanning line is opposite, the region where the pixel electrode displays a of the liquid crystal unit thickness while facing the second electrode substrate 1/5
The region which is not less than 2/3 is the first electrode substrate or
2. The liquid crystal display device according to claim 1, wherein light is shielded by a light shielding region of the second electrode substrate.