JPH0743720A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To decrease the free energy possessed by boundary lines and to prevent the absorption of a certain orientation state to the other by forming the liquid crystal display device in such a manner that the boundaries of liquid crystal layer parts having plural different orientation directions continue in at least >=2 picture elements. CONSTITUTION:This liquid crystal display device is constituted by sealing a liquid crystal layer 33 between a pair of an active matrix substrate 31 and counter substrate 32 arranged to face each other and is formed with the parts 19 varying in the orientation directions across >=2 picture elements in the state that the two orientation directions exist within the one picture element. The boundaries X of the parts 19 where the orientation directions vary exist across >=2 picture elements. As a result, the free energy possessed by the boundary is decreased and the absorption of the one orientation state in the other orientation state is prevented. The anisotropy of the refractive index of the liquid crystal molecules is not lost and the optical rotary polarization of light is assured and the dependency on visual field angles is eliminated.

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 device having a novel structure capable of eliminating the viewing angle dependency.

[0002]

2. Description of the Related Art A liquid crystal display (LCD) is a mechanism for changing the orientation of liquid crystal molecules in a liquid crystal layer between a pair of wiring boards and utilizing the resulting change in optical refractive index in the liquid crystal layer for display. Has become. As a liquid crystal display device having this display mechanism, liquid crystal molecules are preliminarily aligned substantially parallel to the wiring boards and twisted by about 90 ° between the wiring boards, and electrode wiring provided on both wiring boards is used. A vertical electric field is generated between the substrates by utilizing the dielectric anisotropy of the liquid crystal to change the orientation of the liquid crystal molecules in the direction of the electric field to change the orientation and change the optical refractive index, so-called TN (twisted nematic). Type liquid crystal display device is mainly used.

FIG. 11 shows a plan view of a typical TN type liquid crystal display device, and FIG. 12 shows a sectional view of a picture element portion. This liquid crystal display device is an active matrix TFT liquid crystal display device, and has wiring boards 131 and 132 arranged to face each other.
And a liquid crystal layer 133 is sandwiched between and. The wiring board 131 has the scanning line 1 on the glass substrate 131a.
The thin film transistor (TFT) 120 as a non-linear element having a switching function is formed in the vicinity of a portion where the scanning line 112 and the signal line 113 intersect each other, and the scanning line 112 is formed. And signal line 11
A pixel electrode 110 is formed through the periphery of the pixel electrode 110.
The TFT 120 has a gate electrode 115 branched from the scanning line 112 and a scanning electrode 116 branched from the signal line 113.
And the drain electrode 117 for connection with the pixel electrode 110
With. Further, an insulating protective film 131d and an alignment film 131e are formed in this order on the insulating protective film 131d. On the other wiring substrate 132, a color filter 132b, a transparent electrode 132c, an insulating protective film 132d, and an alignment film 132e are formed in this order on a glass substrate 132a.

The liquid crystal molecules 133a of the liquid crystal layer 133 sandwiched between the wiring boards 131 and 132 are inclined as described above, and the inclination indicates the alignment direction of the liquid crystal. The ends of the wiring boards 131 and 132 are sealed with a resin or the like (not shown), and peripheral circuits for driving liquid crystal are mounted on the outside thereof. It should be noted that the same structure is adopted in other than the active matrix type liquid crystal display device.

In such a twisted nematic liquid crystal display device, in order to prevent the occurrence of discretization due to multi-domain, the rising direction of the liquid crystal is set in advance as shown in FIG. It is the average vector of directions. However, since the rising direction of the liquid crystal is determined, there occurs a phenomenon that the contrast changes depending on the angle at which the human (observer) views the liquid crystal display device while the electric field is applied. The reason why the contrast changes will be described below.

FIG. 13 shows an example of applied voltage-transmittance characteristics in a normally white mode liquid crystal display device in which light is transmitted to display white when no voltage is applied. Here, in FIG. 12, liquid crystal molecules 133a in a certain alignment state
With respect to the inclination of, the θ1 side is the normal viewing angle and the θ2 side is the reverse viewing angle direction.

A solid line L1 in FIG. 13 is a case where the liquid crystal display device is viewed from directly above (in a direction perpendicular to the substrate surface), in which case the light transmittance decreases as the applied voltage value increases. When the value becomes saturated, the transmittance becomes almost zero, and the transmittance remains almost zero even if the voltage is further increased. On the other hand, when the viewing angle is tilted in the normal viewing angle direction,
As indicated by the solid line L2 in FIG. 13, the transmittance decreases to some extent as the applied voltage increases, and when the applied voltage is further increased and exceeds a specific voltage value, the transmittance increases again, and then gradually again. Fall to. Therefore, when the viewing angle is tilted in the normal viewing angle direction, a phenomenon occurs in which black and white of an image are inverted at a specific angle (this is called an inversion phenomenon). In this phenomenon, the liquid crystal molecules have the same inclination with respect to the incident angle of light (that is, the viewing angle) at a specific angle, and the anisotropy of the refractive index of the liquid crystal molecules is lost, thereby losing the optical rotatory power of the light. It happens because.

When the viewing angle is tilted in the reverse viewing angle direction,
This is because the change in the light transmittance is less likely to occur as shown by the solid line L3 in FIG. 13, and as a result, the contrast is significantly reduced.

As described above, in the twisted nematic mode liquid crystal display device, the reversal phenomenon seen in the normal viewing angle direction and the decrease in contrast seen in the reverse viewing angle direction are very obstacles for the viewer, and the display characteristics of the liquid crystal display device. The result is doubtful.

In order to solve these problems, a rectangular region 119 in which the alignment direction of the liquid crystal is different from the other is formed in a part of the picture element indicated by the broken line in FIG. Part 1
One technique is to form both normal and reverse viewing angle regions within one pixel to compensate for the decrease in contrast at the reverse viewing angle and to suppress the reversal phenomenon at the normal viewing angle. I have to. As another technique, different electric fields are applied to the liquid crystal layers in one picture element to suppress the inversion phenomenon at the normal viewing angle.

[0011]

However, in the shape in which a part of the picture element is divided into rectangles, a phenomenon has been observed in which one alignment state is absorbed by another alignment state over time. Further, at the boundary portion of the portions having different alignment directions, a disclination line is generated in the boundary portion (area indicated by arrow C in FIG. 12) which is influenced by both alignments and as a result cannot drive the liquid crystal. However, this caused a decrease in contrast.

The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a liquid crystal display device which is reliable and has improved display quality.

[0013]

A liquid crystal display device according to the present invention is a liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of wiring substrates arranged to face each other, and picture elements are arranged in a matrix. Since the liquid crystal layer in the picture element has two or more strip-shaped portions having different alignment directions, and the boundary between each strip-shaped portion and an adjacent strip-shaped portion is continuously present over two or more picture elements, Thereby, the above object is achieved.

The liquid crystal display device of the present invention is a liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of wiring substrates which are arranged opposite to each other, and the picture elements are arranged in a matrix. The liquid crystal layer has two or more portions having different alignment directions, and the boundary between adjacent portions is provided in parallel to the alignment direction of the liquid crystal in contact with one of the pair of wiring boards. The purpose is achieved. In this liquid crystal display device, a signal line is routed through the vicinity of each of the picture elements, the picture element and the signal line are connected via a non-linear element, and the boundary is the most distance from the non-linear element. It is preferable to define the alignment direction at the position of the non-linear element or at a portion where the alignment direction is different so as to be farther away.

Further, the liquid crystal display device of the present invention is a liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of wiring substrates arranged to face each other, and the picture elements are provided in a matrix form. The liquid crystal layer has two or more portions with different alignment directions,
Since the boundary between adjacent parts is covered with the light-shielding film, the above-mentioned object is achieved thereby. In this liquid crystal display device, it is preferable that a non-linear element is connected to each of the picture elements and the light-shielding film is formed of the same material as an opaque layer forming the non-linear element.

The light-shielding film can be provided at various boundary portions where the disclination line may occur.

[0017]

According to the present invention, the boundaries of the liquid crystal layer portions having a plurality of different alignment directions are formed so as to be continuous with at least two picture elements or more, so that the free energy of the boundaries is reduced and a certain alignment is achieved. Absorption of the other state is prevented.

Since the boundaries of the liquid crystal layer portions having a plurality of different alignment directions in one picture element are parallel to the alignment direction of the liquid crystal in contact with one substrate, the disturbance of the alignment of the liquid crystal is suppressed,
As a result, the generation of discretization lines is suppressed.

If the boundary is covered with a light-shielding film, that portion will not be displayed regardless of the occurrence of the discriminating line.

If the light-shielding film is made of the material used for the non-linear element, a new process can be omitted.

[0021]

EXAMPLES Examples of the present invention will be described below.

(Embodiment 1) FIG. 1 is a plan view showing an embodiment in which the present invention is applied to a TN mode active matrix liquid crystal display device, and FIG. 2 is a sectional view thereof. In this liquid crystal display device, as shown in FIG. 6, a liquid crystal layer 33 is enclosed between an active matrix substrate 31 and a counter substrate 32 which are arranged to face each other. The active matrix substrate 31 is wired on the insulating substrate 31a made of glass in a state where the plurality of scanning lines 12 and the plurality of signal lines 13 intersect with each other, and is arranged in an area surrounded by the scanning lines 12 and the signal lines 13. A pixel electrode 14 is arranged, and a non-switch element electrically connected to the scanning line 12, the signal line 13 and the pixel electrode 14 is provided in the vicinity of the intersection of the scanning line 12 and the signal line 13. Thin film transistor as a linear element (hereinafter TF
20) is formed. This TFT 20 is
The pixel electrode 14 is formed on the gate electrode 15 branched from the scanning line 12 on one scanning line side, and the gate electrode 15 faces the source electrode 16 branched from the signal line 13 toward the pixel electrode 14. Together with the pixel electrode 14 to the source electrode 1
It is configured so as to face the drain electrode 17 that is branched toward 6. As the TFT 20, an amorphous silicon TFT is used in this embodiment. Note that TFT2
It is also possible to form 0 on the scanning line 12.

The picture element electrode 14 includes the picture element electrode 14
The scanning line 12 adjacent to the scanning line 12 having the TFT 20 connected to is superposed, and the superposed portion causes the additional capacitance 1
8 is formed. The additional capacitance section 18 may be formed on the additional capacitance line by forming an additional capacitance line (not shown) separately from the scanning line 12.

An insulating film (not shown) is formed on the electrode wirings, that is, on the scanning lines 12 and the signal lines 13 and on the TFTs 20, in order to prevent short circuit between the substrate 31a and the electrode wirings. It This insulating film is the pixel electrode 1
It is also possible to form the four portions into a window opening structure.

Active matrix substrate 3 having such a configuration
The counter substrate 32 facing 1 is a color filter 32b and a counter electrode 32 on an insulating substrate 31a made of glass.
c and the alignment film 32e are formed in this order.

By adding the following steps to the liquid crystal display device of the present embodiment having the above-described structure, a device that can be actually driven and displayed is manufactured. That is, in a liquid crystal display device that can be actually driven and displayed, a step of forming the alignment films 31e and 32e on the active matrix substrate 31 and the counter substrate 32, a step of rubbing the alignment film 31e, and a step of facing the active matrix substrate 31. After the step of attaching the substrate 32, the step of injecting liquid crystal between the both substrates 31 and 32 to provide the liquid crystal layer 33, and the like, the peripheral circuit such as a drive circuit is mounted.

In this manufacturing process, a process for forming a plurality of liquid crystal alignment directions in one picture element is performed in several steps. In this embodiment, the alignment film 31e of the active matrix substrate 31 is subjected to the alignment treatment so that two pixels are formed in one pixel.
In the state where one orientation direction exists, the portion 19 having different orientation directions is formed over two or more picture elements. That is, part 1
9 and the other portions were made to have opposite orientation directions. In such an alignment state, an alignment treatment is performed in a state where a protective film is formed on one of two parts having different alignment directions, the protective film is then removed, and another protective film is formed on the other part this time. It can be formed by performing alignment treatment later and removing the other protective film. Alternatively, a part of the surface of the picture element electrode 14 is chemically changed with a liquid such as an acid or alkaline aqueous solution to form an uneven shape, and the tilt angle or the tilt direction is different between the uneven portion and the uneven portion. A method of controlling the orientation direction by utilizing is adopted. As a method of forming the uneven shape, by causing a chemical change by using an electromagnetic wave containing gas, plasma or light,
Alternatively, it may be adopted to cause a physical change by a solid, a gas, plasma, an electromagnetic wave including light, or the like.

When forming an insulating film for preventing a short circuit between the electrode wiring and the substrate above the TFT and between the wirings, the surface of the insulating film contains a liquid of acid or alkali aqueous solution, gas, plasma, or light. The patterning is performed by performing a chemical change due to an electromagnetic wave or the like or a physical change due to an electromagnetic wave including a solid, gas, plasma, light, and patterning, thereby controlling the tilt angle or the tilt direction to control the alignment direction. You may do it.

Therefore, in this embodiment, since there are two orientation directions in one picture element, a portion having a different orientation direction is formed over two or more picture elements. The boundary X of different portions is located over two or more picture elements. This reduces the free energy of the boundary, prevents one alignment state from being absorbed by the other alignment state, does not lose the anisotropy of the refractive index of the liquid crystal molecules, and secures the optical rotatory power of the light. Is possible,
As a result, the viewing angle dependency can be eliminated.

In the above-described embodiment, the alignment treatment is performed on the alignment film 31e of the active matrix substrate 31, but only on the alignment film 32e of the counter substrate 32, or on the alignment films of both substrates 31, 32. You may perform to 31e, 32e. In these cases as well, the viewing angle dependency can be similarly eliminated.

In this embodiment, the boundary X of the portion having a different orientation is formed so as to be parallel to the signal line 13.
The present invention is not limited to this, and as shown in FIG. 3, the boundary X of a portion having a different alignment direction may be formed to be parallel to the scanning line 12. Even in that case, the viewing angle dependency can be eliminated for the same reason as in the above embodiment.

Further, in this embodiment, a portion having different orientation directions is formed over two or more picture elements in the state where two orientation directions exist in one picture element, but the present invention is not limited to this, and one picture element is formed. In a state where there are two or three or more orientation directions in the element, portions having different orientation directions may be formed over two or more picture elements.

Further, the boundary between the parts having different orientations is 2
It only needs to exist over the above picture elements, and it does not need to be continuous over all of the one row of picture elements arranged in a matrix, and may be divided into some.

(Embodiment 2) Another embodiment of the present invention will be described.

FIG. 4 is a plan view showing a liquid crystal display device according to the second embodiment, and FIG. 5 is a sectional view taken along the direction A in FIG. The same parts as those in FIGS. 1 and 2 are designated by the same reference numerals. In this liquid crystal display device, two portions having different alignment directions (one of which is indicated by 19) are formed so as to exist for each picture element. That is, one of the two portions having different alignment directions is a hatched portion, and the other portion is a non-hatched portion. In this embodiment, this alignment state is the alignment film 31e on the active matrix substrate 31 side.
Is formed against. Further, the two portions having different alignment directions are positioned such that the boundary X thereof is parallel to the alignment direction (B direction) of the liquid crystal in contact with the alignment film 31e on the active matrix substrate 31 side. In addition, the same treatment as that in the previous embodiment can be adopted for the alignment treatment to bring such an alignment state.

Therefore, in this liquid crystal display device, the boundary X between the two portions having different alignment directions is located in parallel with the alignment direction (B direction) of the liquid crystal which is in contact with the alignment film 31e on the active matrix substrate 31 side. The disorder of the orientation can be suppressed, and as a result, the generation of the disclination line described above can be suppressed. In the present embodiment, the above-mentioned alignment state is formed for the alignment film 31e on the active matrix substrate 31 side, but it may be formed for the alignment film 32e on the counter substrate side 32 side or both substrates. 31,
It may be formed on the alignment films 31e and 32e of 32. However, in the former case, the boundary X is parallel to the alignment direction of the liquid crystal in contact with the alignment film 32e on the counter substrate side 32 side.
Need to be defined. In the latter case, the boundary X may be set parallel to the alignment direction of the liquid crystal in contact with either the alignment film 31e on the active matrix substrate 31 side or the alignment film 32e on the counter substrate side 32 side.

Further, when the alignment direction (B direction) of the liquid crystal is different from the above as shown in FIG. 6, if two portions having different alignment directions are formed so that the boundary X is parallel to the alignment direction. Good.

In the above case, as shown in FIGS. 4 and 6, the boundary X reaches from one side in the horizontal direction to the other side of the display panel of the liquid crystal display device or from one side in the vertical direction to the other side. Although the pattern is formed in the present invention, the present invention is not limited to this, and the boundary X does not have to reach from one side to the other side. It may be divided.

Furthermore, in the present embodiment, two parts having different orientations are formed in a state of being divided for each picture element, but the present invention is not limited to this, and a continuous picture element is formed as shown in FIG. Two portions having different alignment directions may be formed in the extended state.
In this case, it suffices that the boundary X between the two parts having different alignment directions is parallel to the alignment direction (B direction) of the liquid crystal on the part which becomes the picture element. That is, in the portion other than the picture elements, the orientation direction of the liquid crystal is not so much affected in displaying, so that the direction of the boundary X between the two portions having different orientation directions is the orientation direction of the liquid crystal (B direction). Does not have to be parallel to. In addition, the same treatment as that in the previous embodiment can be adopted for the alignment treatment to bring such an alignment state.

Further, as shown in FIG. 6, in the case of an active matrix type liquid crystal display element having a TFT 20 which is a non-linear element between the picture element and the signal line, the boundary X between two parts having different alignment directions is non-existent. If the distance is farthest from the linear element, it is possible to prevent the deterioration of the nonlinear element in the unevenness forming process.

Also in the second embodiment, it is possible to form three or more portions having different alignment directions so that each boundary is parallel to the alignment direction of the liquid crystal.

(Embodiment 3) Still another embodiment of the present invention will be described.

In this embodiment, two or more portions having different alignment directions are formed, a light shielding film is formed on each boundary, and light leaking from the boundary portion is shielded by the light shielding film. In this case, it is not necessary to make the boundary direction parallel to the alignment direction of the liquid crystal.

FIG. 8 is a plan view showing a liquid crystal display device according to this embodiment, and FIG. 9 is a sectional view thereof. In this liquid crystal display device, a portion having a different alignment direction (one is 19
Boundary) is covered with the light shielding film 21 extending from the drain electrode 17.

Therefore, in the case of the present embodiment, the light leaking from the portion where the disclination line is generated by the above-mentioned boundary can be blocked by the light shielding film 21, and the contrast can be improved. The reason why the light-shielding film 21 is formed of the same material as the drain electrode 17 forming the TFT 20 is as follows. Since the bonding accuracy of the two wiring boards is low, if the light-shielding film 21 is formed independently, after the bonding, the light-shielding film 21 and the TFT 2 which both have a light-shielding function.
This is to prevent the position from 0 from being displaced, resulting in a decrease in the aperture ratio. Further, when they are formed of the same material, the film formation and the etching of the drain electrode 17 can be utilized for the formation of the light-shielding film 21 when the film formation and the etching of the drain electrode 17 are performed, and there is an advantage that the process can be performed as usual. .

As shown in FIG. 9, the width D of the light shielding film 21 may be set to a value capable of shielding the light leaked from the portion where the discriminating line is generated.

Although the light-shielding film 21 is made of the same material as the drain electrode 17 in the above embodiment, it may be made of the same material as the other light-shielding electrodes that constitute the TFT 20. In that case, the same effect can be obtained.

Further, the light shielding film 21 of this embodiment may be formed so as to cover the whole area of the picture element as shown in FIG.
Further, it may be formed in a portion that covers the boundary X in the above-described first and second embodiments.

The techniques of Embodiments 1, 2 and 3 described above are applicable not only to the liquid crystal display device having the above mode and structure, but also to the liquid crystal display device having any mode and structure.

[0050]

According to the present invention, the viewing angle dependence of the liquid crystal display device can be eliminated, and the phenomenon that one alignment state is absorbed by another alignment state due to the passage of time can be suppressed. In addition, it is possible to suppress the generation of disclination lines at the boundaries between the portions having different orientation directions. Further, when the light-shielding film is formed, light leakage from the disclination line can be prevented even if it occurs. Therefore, according to the present invention, it is possible to provide a reliable liquid crystal display device with improved display quality.

[Brief description of drawings]

FIG. 1 is a plan view showing a liquid crystal display device according to a first embodiment.

2 is a cross-sectional view of the liquid crystal display device of FIG.

FIG. 3 is a plan view showing another liquid crystal display device according to the first embodiment.

FIG. 4 is a plan view showing a liquid crystal display device according to a second embodiment.

5 is a cross-sectional view of the liquid crystal display device of FIG.

FIG. 6 is a plan view showing another liquid crystal display device according to the second embodiment.

FIG. 7 is a plan view showing still another liquid crystal display device according to the second embodiment.

FIG. 8 is a plan view showing a liquid crystal display device according to a third embodiment.

9 is a sectional view of the liquid crystal display device of FIG.

FIG. 10 is a plan view showing another liquid crystal display device according to the third embodiment.

FIG. 11 is a plan view showing a conventional liquid crystal display device.

12 is a cross-sectional view of the liquid crystal display device of FIG.

FIG. 13 is a diagram showing applied voltage-transmittance characteristics in a conventional normally white mode liquid crystal display device.

[Explanation of symbols]

 12 scanning line 13 signal line 14 picture element electrode 15 gate electrode 16 source electrode 17 drain electrode 18 additional capacitance 19 different orientation direction 20 TFT (non-linear element) 21 light-shielding film 31 wiring substrate 31a glass substrate 31d insulating protective film 31e Alignment film 32 Wiring substrate 32a Glass substrate 32b Color filter 32c Transparent electrode 32e Alignment film 33 Liquid crystal layer X boundary

Claims (6)

[Claims] 1. A liquid crystal display device, in which a liquid crystal layer is sandwiched between a pair of wiring substrates arranged to face each other, and picture elements are provided in a matrix form. There are two or more parts, and the boundary between each strip and adjacent strips is 2
A liquid crystal display device configured to continuously exist over the above picture elements. 2. In a liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of wiring substrates which are arranged to face each other and the picture elements are provided in a matrix, the liquid crystal layers in each picture element have different alignment directions. A liquid crystal display device having two or more of the above, and a boundary between adjacent parts is provided in parallel to the alignment direction of the liquid crystal in contact with one of the pair of wiring boards. 3. A signal line is routed through the vicinity of each of the picture elements, the picture element and the signal line are connected via a non-linear element, and the boundary is farthest from the non-linear element. 3. The liquid crystal display device according to claim 2, wherein the position of the non-linear element or the alignment direction in a portion where the alignment direction is different is defined so that 4. In a liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of wiring boards arranged to face each other, and the picture elements are provided in a matrix, the liquid crystal layers in each picture element have different alignment directions. A liquid crystal display device having two or more of the above, and a boundary between adjacent parts is covered with a light shielding film. 5. The liquid crystal display device according to claim 1, 2 or 3, wherein the boundary is covered with a light shielding film. 6. The liquid crystal display device according to claim 4, wherein a non-linear element is connected to each of the picture elements, and the light-shielding film is formed of the same material as an opaque layer forming the non-linear element.