JP2955161B2 - 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 a liquid crystal display in which wiring is provided on at least one of a pair of substrates sandwiching a liquid crystal layer.

[0002]

2. Description of the Related Art A liquid crystal display (LCD) has a liquid crystal layer provided between a pair of substrates disposed opposite to each other, and changes the orientation of liquid crystal molecules in the liquid crystal layer to change the optical refractive index. Is displayed. In order to control the alignment of such liquid crystal molecules, a so-called TN (twisted nematic) liquid crystal display device is mainly used. In this liquid crystal display device, liquid crystal molecules are preliminarily oriented so as to be twisted about 90 ° in a direction substantially parallel to the substrates and in the vicinity of both substrates, and a voltage is applied to electrodes formed on the two opposing substrates, An electric field is generated in a direction perpendicular to the substrate, and the liquid crystal molecules are displaced in the direction of the electric field by utilizing the dielectric anisotropy of the liquid crystal, thereby changing the orientation and causing a change in the optical refractive index.

FIG. 6 is a plan view showing a conventional TN type active matrix type liquid crystal display device, and FIG.
It is arrow sectional drawing. As shown in FIG. 7, this liquid crystal display device has a pair of wiring boards 131 and 132 which are disposed to face each other with a liquid crystal layer 133 interposed therebetween. As shown in FIG. 6, one wiring board 131 (lower side in FIG. 7) is wired on an insulating substrate 131a made of glass so that the scanning lines 112 and the signal lines 113 intersect each other. Line 112
A pixel electrode 114 is arranged in a region surrounded by the signal line 113, and a thin film transistor (hereinafter, referred to as a TFT) 120 as a non-linear switching element is provided near an intersection between the scanning line 112 and the signal line 113. I have. TFT
The gate electrode 115 of 120 is connected to the scanning line 112,
The source electrode 116 is connected to the signal line 113 and the drain electrode 11
7 is connected to the picture element electrode 114.

The other (upper side in FIG. 7) wiring board 132 is
A light-shielding film 132d having a window structure having an opening inside a broken line in FIG. 6 is formed on an insulating substrate 132a made of glass, and an opposing electrode 132b is formed almost entirely on the light-shielding film 132d. Note that, in FIG.
Liquid crystal molecules 1 in the liquid crystal layer 133 sandwiched between
The inclination of 33a indicates the orientation direction of the liquid crystal. The interface between the pixel electrode 131b and the liquid crystal layer 133 and the counter electrode 1
At the interface between 32b and the liquid crystal layer 133, an alignment film (not shown) is formed.

Further, seal members made of a resin or the like (not shown) are provided at the ends of the wiring boards 131 and 132.
The liquid crystal layer 133 is sealed with this sealing member. Further, peripheral circuits for driving the liquid crystal are provided on the wiring boards 131 and 13.
2 is implemented in at least one of them.

The tilt of the liquid crystal molecules 133a with respect to the substrate surface is provided in order to prevent the generation of disclination lines due to multi-domains. A method of rubbing an organic alignment film with a polishing cloth, or a method of tilting an inorganic thin film. It is obtained by a method of vapor deposition. Further, the direction in which the liquid crystal molecules rise is determined in advance by the inclination.
In the liquid crystal display device having such a configuration, the inclination of the liquid crystal molecules 133a with respect to the substrate surface, which is provided to prevent the generation of discrimination lines due to multi-domains, causes an angle at which the liquid crystal display device is viewed in a state where an electric field is applied. This causes a phenomenon that the contrast changes. Here, when viewed from the left direction in FIG. 7 (when the liquid crystal molecules are viewed from a direction in which the ends of the elongated liquid crystal molecules that are away from the substrate 131 are present (hereinafter, referred to as tilt directions)), the normal viewing angle is used. The direction when viewed from the opposite direction is referred to as a reverse viewing angle direction. Further, the upper side when the liquid crystal display device of FIG. 6 is viewed from the direction perpendicular to the paper is defined as 12:00, and the 12:00 viewing angle (upward viewing angle direction) and the 6 o'clock viewing angle (upward viewing angle direction is lower) depending on the direction of the forward viewing angle direction. Side). That is, the tilt direction and the viewing angle direction of the liquid crystal molecules are the same. The viewing angle direction can be arbitrarily determined in a process such as rubbing for defining the orientation of the liquid crystal, and is not limited to 12:00 and 6:00.

[0007]

By the way, in the conventional liquid crystal display device, in the liquid crystal layer portion corresponding to the inner portion of the picture element electrode 114, an electric field is applied to the original substrate only in the vertical direction, and the liquid crystal is generated. The torque is in a direction directed by the pretilt angle. However, as shown in FIG.
In the vicinity of the periphery of the pixel electrode 114 formed on the wiring substrate 131, the electric field generated by the signal line 113 or the scanning line 112 is applied to the liquid crystal layer 133, so that the direction is opposite to the direction directed by the pretilt angle. As a result, the liquid crystal alignment disorder called reverse tilt occurs in a part of the outer peripheral portion of the picture element, and the display quality is remarkably deteriorated.

Conventionally, the above-described light-shielding film 132d has been provided in order to hide the deterioration in display quality due to the reverse tilt. ,
It was necessary to narrow the opening of the light shielding film 132d. For this reason, the area ratio, that is, the aperture ratio to the whole of the openings actually contributing to the display is significantly reduced.
In addition, the decrease in the aperture ratio not only decreases the display quality, but also
Since a problem such as an increase in power consumption of a backlight or the like is caused, a higher aperture ratio is better.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems of the prior art, and a liquid crystal display device having improved display quality, which has improved display quality due to reverse tilt, has a high aperture ratio, and has been improved. The purpose is to provide.

[0010]

A liquid crystal display device according to the present invention comprises a first substrate, a second substrate, the first substrate and the second substrate.
And a liquid crystal layer sandwiched between the first substrate and the first substrate.
A scanning line, a signal line intersecting the scanning line, and the scanning line and the signal line.
Is located near the intersection with the highway and covered with a light-shielding film.
Via the switching element and the switching element
And the second substrate is connected to the pixel electrode.
Having a counter electrode opposed to the pole, it is pixel which is a unit of the display A liquid crystal display device are arranged in a matrix, the alignment direction of the average of the liquid crystal molecules in the vicinity of the thickness-direction center of the liquid crystal layer Two or more liquid crystal layer regions having different pretilt directions are formed for each picture element in the average alignment direction projected on the substrate, and in each liquid crystal layer area of each picture element, liquid crystal molecules inside the liquid crystal layer area are formed. and direction changing the direction by the electric field in the thickness direction of the liquid crystal layer, the liquid crystal molecules point in the average orientation direction of the peripheral portion near the liquid crystal layer region is walking the signal line
The pretilt direction is defined so that the direction in which the direction is changed by the electric field from the scanning line is the same as the direction in which the direction is changed.
The two or more liquid crystal layer regions having different tilt directions have a substantially rectangular shape.
Divided by the diagonal of the picture element, and the diagonal is
Intersects or overlaps with each of the switching elements
Since that, the objects can be achieved.

In this liquid crystal display device, in each liquid crystal layer region of each picture element, the liquid crystal molecules inside the liquid crystal layer region change their directions due to an electric field in the thickness direction of the liquid crystal layer in directions other than the average alignment direction. and direction, so that the liquid crystal molecules point in the appropriate direction other than the average orientation direction of the peripheral portion near the liquid crystal layer region and the direction of changing the orientation by an electric field from the signal lines or the scanning lines, the same direction The pretilt direction may be defined as follows. The configuration is achieved by forming at least two liquid crystal layer regions having different pretilt directions by dividing the liquid crystal layer regions by lines extending in a direction intersecting the average alignment direction. As the line, a diagonal line of the picture element having a substantially rectangular shape can be used.

[0012]

According to the present invention, in each liquid crystal layer region of each picture element, the direction in which the liquid crystal molecules inside the liquid crystal layer region change its direction due to the electric field in the thickness direction of the liquid crystal layer and the portion near the periphery of the liquid crystal layer region. The pretilt direction is defined so that the direction in which the liquid crystal molecules at a position in the average alignment direction change direction by the electric field from the wiring is the same direction. Therefore, the inclination of the liquid crystal molecules in the vicinity of the peripheral edge in the average alignment direction in which the average orientation direction of the liquid crystal molecules in contact with the substrate having the wiring is projected on the substrate surface is such that the end closer to the wiring of the liquid crystal molecule is from the wiring. It becomes the direction to go away. As a result, the lines of electric force of the electric field applied from the wiring line and the inclination of the liquid crystal molecules in the vicinity of the periphery match, and the occurrence of reverse tilt is suppressed.

In the same manner in directions other than the average alignment direction, not only the liquid crystal molecules in the vicinity of the peripheral edge in the average alignment direction but also the liquid crystal molecules in the peripheral portion in the direction other than the average alignment direction are included in the peripheral portion. The lines of electric force of the electric field applied from the near wiring and the inclination of the liquid crystal molecules match, and the occurrence of reverse tilt is suppressed in almost the entire area around the picture element.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below.

(Embodiment 1) FIG. 1 is a plan view showing an active matrix type liquid crystal display device to which the present invention is applied, and FIG. 2 is a sectional view taken along the line AA 'of FIG. This liquid crystal display device has an active matrix substrate 31 and a counter substrate 32 with a liquid crystal layer 33 interposed therebetween. The active matrix substrate 31 is wired on an insulating substrate 31a made of glass so that the scanning lines 12 and the signal lines 13 intersect each other, and a pixel electrode is provided in a region surrounded by the scanning lines 12 and the signal lines 13. 14 are provided. The scanning line 12
A TFT 20 as a switching element is formed in the vicinity of the intersection of the signal line 13 and the signal line 13. This TFT 20
Are formed on one side of the two scanning lines 12, 12 sandwiching the pixel electrode 14 and are branched from the signal line 13 to the pixel electrode 14, and from the pixel electrode 14 to the source electrode 16. And a drain electrode 17 branched toward the drain electrode 17. Further, it has a gate electrode 15 located below the source electrode 16 and the drain electrode 17 and branched from the scanning line 12. In this embodiment, an amorphous silicon TFT is used as the TFT 20.

The scanning line 12, the signal line 13, or the TFT
An insulating film (not shown) is formed on the substrate 20 and the like in order to prevent a short circuit between the substrates 31 and 32 and a short circuit between wirings. The insulating film may have a window structure in a picture element portion. Further, an additional capacitance electrode (not shown) may be provided opposite to the picture element electrode 14 to form an additional capacitance for supplementarily storing the voltage applied to the liquid crystal.

The opposing substrate 32 disposed opposite to the active matrix substrate 31 has a light-shielding film 32d having a window structure having an opening inside a broken line in FIG. 1 formed on an insulating substrate 32a made of glass. Further, a counter electrode 32b is formed on substantially the entire surface thereon. In the liquid crystal layer 33 sandwiched between the substrates 31 and 32, two liquid crystal layer regions 18 and 19 having different pretilt directions are formed in one picture element. Note that, in FIG. 2, the tilt direction of the liquid crystal molecules 33a indicates the alignment direction of the liquid crystal. The picture element electrode 14
Between liquid crystal layer 33 and counter electrode 32b and liquid crystal layer 3
An alignment film (not shown) is formed at the interface with each other.

Further, a sealing member made of a resin or the like (not shown) is provided at an end of both substrates 31, 32, and the liquid crystal layer 33 is sealed with this sealing member. Further, a peripheral circuit for driving the liquid crystal is mounted on at least one of the substrates 31 and 32. Note that in the case of performing color display, a structure in which a color filter is provided can be employed.

The manufacturing of the liquid crystal display device having such a configuration can be performed, for example, by the following steps. A step of forming an active matrix substrate 31 having a scanning line 12, a signal line 13, a TFT 20, an alignment film, and the like;
d, a step of forming a counter substrate 32 having a counter electrode 32b and an alignment film, a step of performing a rubbing process on the alignment film formed on both substrates 31, 32, a step of bonding both substrates 31, 32, and a step of bonding both substrates A step of forming a liquid crystal layer 33 by injecting liquid crystal between 31 and 32 is performed, and finally, a peripheral circuit and the like are mounted to complete a liquid crystal display device.

In some of these steps, two liquid crystal layer regions 18 having different pretilt directions are provided in each picture element.
19 is formed. Two liquid crystal layer regions 18, 1 in one pixel
Numeral 9 is provided along the average alignment direction where the average alignment direction of the liquid crystal molecules 33a near the center in the thickness direction of the liquid crystal layer 33 is projected on the substrate 31 (or 32). Such 2
In this embodiment, the two liquid crystal layer regions 18 and 19 were formed by forming an alignment film made of polyimide and then irradiating one of the two portions of the alignment film with ultraviolet rays in an arbitrary step. Specifically, an alignment film portion corresponding to the liquid crystal layer region 19 of the active matrix substrate 31 and a counter substrate 32
Of the alignment film corresponding to the liquid crystal layer region 18 was irradiated with ultraviolet rays.

The pretilt angle of the liquid crystal molecules in contact with the portion of the alignment film to which the ultraviolet irradiation has been performed is reduced. For this reason,
The pretilt angle of the liquid crystal molecules in the liquid crystal layer region 19 of the active matrix substrate 31 is low, and the pretilt angle of the liquid crystal molecules in the liquid crystal layer region 18 is high. Further, the pretilt angle of the liquid crystal molecules in the liquid crystal layer region 18 of the counter substrate 32 is low, and the pretilt angle of the liquid crystal molecules in the liquid crystal layer region 19 is high. At this time, the opposing substrates 31, 32
The pretilt angle of the liquid crystal molecules in contact with the alignment film is determined according to the higher alignment control force.

In FIG. 2, the oblique lines in contact with the substrates 31 and 32 schematically show the inclination and direction of the liquid crystal molecules in contact with each substrate, and the ellipses schematically show the average inclination of the liquid crystal molecules. When an electric field is applied, the liquid crystal molecules rise in the vertical direction. The broken line shows the lines of electric force applied to the edge of the picture element from the scanning line 12.

As described above, since the pretilt angle of the liquid crystal molecules is determined according to the higher alignment regulating force, in the liquid crystal layer region 18, the liquid crystal molecules near the center in the thickness direction of the liquid crystal layer 33 are tilted to the 6 o'clock viewing angle state. In the liquid crystal layer region 19, the liquid crystal layer tilts in the opposite direction at a 12:00 viewing angle. Therefore, in the liquid crystal layer regions 18 and 19, the liquid crystal molecules in the peripheral portions C and D (see FIG. 1) near the peripheral edge of the liquid crystal layer region, which are in the average alignment direction obtained by projecting the average alignment direction of the liquid crystal molecules onto the substrate surface. As shown in FIG. 2, is formed such that the end closer to the scanning line 12 is inclined in a direction away from the scanning line 12. In addition, in the portion e near the periphery on the right side of the liquid crystal layer region 18 and the portion f near the periphery on the left side of the liquid crystal layer region 19, the substrate 3
Since the liquid crystal molecules near 1 are inclined at an angle of about 45 ° with respect to the direction of the liquid crystal molecules near the center in the thickness direction of the liquid crystal layer in the peripheral portions C and D, substantially the same as above with respect to the signal line 13. State. As a result, the peripheral portion C,
The inclination of the liquid crystal molecules at D coincides with the lines of electric force of the electric field applied from the scanning line 12, and the inclination of the liquid crystal molecules at the peripheral portions e and f and the lines of electric force of the electric field applied from the signal line 13 match. They almost match, and the occurrence of reverse tilt can be suppressed. In this embodiment, one o'clock and one o'clock
Since the viewing angle characteristics in both directions at 2 o'clock are formed, it is possible to suppress a decrease in display quality due to the viewing angle of the display characteristics. The rising direction of the liquid crystal can be arbitrarily controlled by controlling the alignment regulating force.

The liquid crystal layer regions 18 and 19 do not need to have the same area, but are shown in FIGS. 3 and 4 (AA 'in FIG. 3).
As shown in an arrow sectional view), the liquid crystal layer region 19 may be formed only at the end portion of the picture element electrode 14, and the liquid crystal layer region 18 may be formed in the remaining wide portion. Further, a region having another different orientation may be formed in a portion other than the end of the pixel electrode 14.

Embodiment 2 Another embodiment of the present invention will be described below. The second embodiment is a case where the occurrence of reverse tilt is more completely prevented.

FIG. 5 is a plan view showing a liquid crystal display device according to the second embodiment. In this liquid crystal display device, the liquid crystal molecules scan the end near the scanning line 12 for the portions C and D near the periphery of the liquid crystal layer regions 18 and 19 in the average alignment direction of the picture element electrodes 14 formed on the active matrix substrate 31. It is formed so as to be inclined in a direction away from the line 12.
In addition, the liquid crystal layer regions 18 and 19 in other directions
In the portions E and F in the vicinity of the peripheral edge of
3 is formed so as to be inclined in a direction away from the signal line 13.

[0027] That is, the liquid crystal layer regions 18 and 19, one of the two diagonal lines connecting the corners of the picture element electrode 14 in which the substantially rectangular shape, formed so as to be divided by a diagonal line towards Ru through the vicinity of the TFT20 I do.

In the case of the present embodiment, the peripheral edge portions E and F where the occurrence of reverse tilt can be suppressed are longer than the peripheral edge portions e and f in the first embodiment, and the occurrence of reverse tilt is suppressed. The part which cannot be done will be lost. Therefore, in the entire outer peripheral portion of the pixel electrode 14,
The occurrence of reverse tilt can be more completely suppressed. However, in FIG. 5 according to this embodiment, since the boundary between the liquid crystal layer regions 18 and 19 intersects the TFT 20, the diagonal line is not completely formed. Because it is covered with the film 32d,
Even if a reverse tilt occurs in this portion, it is hidden.

In the second embodiment, the liquid crystal layer regions 18 and 19 are divided by a diagonal line. However, the present invention is not limited to this, and the liquid crystal layer regions 18 and 19 may be divided into lines inclined clockwise or counterclockwise with respect to the diagonal line. Alternatively, the liquid crystal layer regions 18 and 19 may be divided.

In the above description, an alignment film made of polyimide is used as the alignment film material. However, any material can be used as long as the pretilt angle changes by light irradiation, and an optimum irradiation wavelength or the like may be selected depending on the material. Further, if a laser is used, it can be controlled more efficiently. Further, as the orientation control method, other known methods may be used. For example, a method in which oblique deposition is performed on an inorganic film to perform a rubbing process, or a method in which an inorganic film is partially masked to form a photo. It is also possible to achieve this structure by a method of performing a rubbing process by using lithography.

In the above description, the present invention is applied to an active matrix type liquid crystal display device. However, the present invention is not limited to this and can be applied to a simple matrix type liquid crystal display device. In this case, a portion where the stripe-shaped electrodes formed so as to intersect each other on each of a pair of opposing substrates becomes a picture element, and a reverse tilt generated in a portion near a peripheral edge of the picture element is formed. Occurrence can be prevented.

Further, the present invention can be applied not only to the TN type liquid crystal display device but also to a liquid crystal display device of an arbitrary mode as a measure for preventing the occurrence of reverse tilt.

[0033]

According to the present invention, the lines of electric force of the electric field applied by the wiring and the inclination of the liquid crystal molecules close to the wiring coincide, and the occurrence of reverse tilt can be suppressed. In addition, since one picture element has a plurality of liquid crystal layer regions having different viewing angle directions,
The viewing angle characteristics can be improved. Further, since the area of the light-shielding portion in the light-shielding film for concealing display defects due to reverse tilt can be reduced, the aperture ratio of the liquid crystal display device can be increased, and power consumption of a backlight or the like can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing an active matrix liquid crystal display device to which the present invention is applied.

FIG. 2 is a sectional view taken along the line A-A ′ in FIG. 1;

FIG. 3 is a plan view showing another embodiment of the active matrix type liquid crystal display device to which the present invention is applied.

FIG. 4 is a sectional view taken along the line A-A ′ in FIG. 3;

FIG. 5 is a plan view showing still another embodiment of the active matrix type liquid crystal display device to which the present invention is applied.

FIG. 6 is a plan view showing an example of a conventional active matrix type liquid crystal display device.

FIG. 7 is a sectional view taken along the line A-A ′ of FIG. 6;

[Explanation of symbols]

 Reference Signs List 12 scanning line 13 signal line 14 picture element electrode 15 gate electrode 16 source electrode 17 drain electrode 18 liquid crystal layer region 19 liquid crystal layer region 20 TFT 31 active matrix substrate 31a insulating substrate 32 counter substrate 32a insulating substrate 32b counter electrode 32d light shielding film 33 Liquid crystal layer 33a Liquid crystal molecules C Peripheral edge portion D Peripheral edge portion E Peripheral edge portion F Peripheral edge portion e Peripheral edge portion f Peripheral edge portion

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/1337 505 G02F 1/136 500

Claims (4)

(57) [Claims] A first substrate, a second substrate, and the first substrate;
A liquid crystal layer sandwiched between the second substrate and the first substrate , wherein the first substrate includes a scan line and a signal line intersecting the scan line.
And near the intersection of the scanning line and the signal line,
A switching element covered with an optical film, and the switching element
The second substrate has a counter electrode facing the pixel electrode, and a pixel serving as a display unit is arranged in a matrix. a display device, forming an alignment direction of the average of the liquid crystal molecules in the thickness direction near the center of the liquid crystal layer to the average orientation direction projected onto the substrate, two or more liquid crystal layer regions having different pretilt directions for each pixel In each liquid crystal layer region of each picture element, the direction in which liquid crystal molecules inside the liquid crystal layer region change its direction due to the electric field in the thickness direction of the liquid crystal layer and the average orientation in the portion near the periphery of the liquid crystal layer region walking liquid crystal molecules point in the direction the scanning lines
Has a direction of changing the orientation by an electric field from the signal lines is prescribed the pretilt directions so that the same direction, two or more liquid crystal layer regions having different said pretilt direction is substantially
Is divided by a diagonal line of the rectangular picture element, the diagonal line intersects with each of the switching elements,
Or overlapping liquid crystal display devices. 2. In each liquid crystal layer region of each picture element, a direction in which liquid crystal molecules inside a liquid crystal layer region change direction by an electric field in a thickness direction of the liquid crystal layer also in a direction other than the average alignment direction. The liquid crystal molecules in a portion near the periphery of the layer region in a corresponding direction other than the average orientation direction are the liquid crystal molecules.
2. The liquid crystal display device according to claim 1, wherein the pretilt direction is defined such that a direction of the pretilt direction is changed by the electric field from the signal line or the scanning line . 3. The liquid crystal display device according to claim 2, wherein the two or more liquid crystal layer regions having different pretilt directions are formed by being divided by lines extending in a direction intersecting the average alignment direction. 4. The liquid crystal display device according to claim 3, wherein the line is a diagonal line of the picture element having a substantially rectangular shape.