JP3254974B2 - Liquid crystal display device - 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 device, and more particularly to a liquid crystal display device having a small viewing angle dependency.

[0002]

2. Description of the Related Art A liquid crystal display element used for a liquid crystal display (LCD) or the like, a so-called liquid crystal cell, changes a specific molecular arrangement of liquid crystal into another different molecular arrangement by an external action such as an electric field. Changes in the optical characteristics during that time are used for display as visual changes. Generally, an alignment treatment is performed on the surface of a glass substrate holding liquid crystal in order to arrange liquid crystal molecules in a specific alignment state.

In a conventional twisted nematic (TN) type liquid crystal cell or the like, a so-called rubbing method is used in which an alignment film such as polyimide is formed on the entire glass substrate sandwiching the liquid crystal, and the alignment film is rubbed in one direction with a rubbing cloth. Has been adopted.

For example, as shown in FIG. 13, a rubbing roller 60 having a rubbing cloth such as a cotton cloth wound on a surface thereof is brought into contact with an alignment film 61a on a substrate 61 and is rotated in the direction of arrow A while rotating the substrate surface. When it moves, the alignment process can be performed uniformly in the direction of arrow B on the entire surface of the alignment film 61a.

In the TN type liquid crystal cell, as shown in FIG. 14, a rubbing process is performed so that the orientations of the liquid crystal molecules 64 in the substrate plane are perpendicular to each other between the upper and lower substrates 62 and 63 of the liquid crystal cell. The liquid crystal molecules 64 in contact with the substrate are aligned according to the alignment direction of the substrate.

When the liquid crystal cell is a negative display, the polarizing plates 65 and 66 arranged in parallel Nicols sandwiching the cell are arranged so that their polarization axes are parallel to one rubbing direction. A polarizing plate having a crossed Nicols arrangement is arranged such that its polarization axis is parallel to the rubbing direction of the adjacent substrate.

[0007]

SUMMARY OF THE INVENTION A liquid crystal cell adopting an active drive system, which includes a TFT (thin film transistor) and an M
IM (Metal Insulator Metal)
In the case of rubbing a substrate on which a driving element such as a diode) and wiring are formed on the surface, if the entire surface is rubbed simultaneously as shown in FIG. 13, it is inevitable that those elements are also rubbed simultaneously. In such a case, there is a possibility that the element or its wiring is destroyed or its characteristics are deteriorated due to static electricity generated by rubbing. Rubbing tends to generate fine dust. If these dusts adhere to the substrate surface, it is not easy to completely remove them.

In addition, when the conventional rubbing process is performed, since the orientation direction of the liquid crystal molecules is uniform, the angle at which the display is easy to see (viewing direction) when an observer views the screen is limited to a specific angle range. Viewing angle characteristics are produced.

For example, when an isocontrast curve representing a viewing angle characteristic of a conventional twisted nematic liquid crystal display cell (TN-LCD) is measured, a viewing angle region having high contrast is biased toward a specific angle region. Therefore, such a liquid crystal cell has a viewing angle dependency such that it is easy to see from one direction and hard to see from another direction.

When a liquid crystal cell having such a viewing angle dependence is used as a display device, the contrast is extremely reduced at a certain angle with respect to the display screen, and in extreme cases, the contrast of the display is reversed. .

One of the causes of the liquid crystal cell having a viewing angle characteristic is as follows.
This is because rubbing causes pretilt in liquid crystal molecules. The direction in which the liquid crystal molecules have a pretilt coincides with the rubbing vector direction.

In the rubbing method shown in FIG. 13, all the liquid crystal molecules on one substrate are aligned with a pretilt angle in the same direction. When a voltage is applied vertically to the liquid crystal layer, all the liquid crystal molecules 64 rise in the same direction on a plane having the same depth in the liquid crystal layer as shown in FIG. Therefore, the viewing angle dependence is generated because the state of the liquid crystal molecules is different depending on the viewing direction of the observer 67 (the viewing angle indicated by the arrow).

In order to reduce the viewing angle dependency and increase the viewing angle, it has been proposed to perform a split orientation. For example, this is an alignment processing technique that divides one pixel into a plurality of small regions and reverses or changes the alignment direction of the small regions to obtain a substantially isotropic viewing angle characteristic as a whole pixel.

FIGS. 15 and 16 show examples of the two-divided orientation (for example, Japan Display, 591, 1992).
Page). FIG. 15 shows an example in which an alignment film 72 having a large pretilt angle and an alignment film 73 having a small pretilt angle are selectively exposed in one pixel region of the upper and lower substrates 70 and 71. After forming an alignment film 73 on the entire surface of the substrates 70 and 71, an alignment film 72 having a large pretilt angle is selectively formed. The alignment films 72, 7
3 may be reversed or each may be patterned.

FIG. 16 shows a case where rubbing is performed in directions different from each other in one pixel area divided into two. An alignment film 73 is formed on the entire surface of the upper substrate 70, and rubbing is performed in the same direction. An alignment film 72 is formed on the entire surface of the lower substrate 71,
Each pixel is divided into two and rubbing is performed in opposite directions.

In the divisional alignment process as shown in FIGS. 15 and 16, since it is necessary to pattern a small divided region for each substrate by a photolithography process using a photoresist or the like, the number of liquid crystal cell manufacturing steps increases. And increased costs.

Also, in the case of the split orientation, it is more than 4 than in the case of 2 splits.
It is considered that the division is better because more isotropic viewing angle characteristics can be obtained. However, the method of FIG. 15 has a limit of two divisions. Further, in the method shown in FIG. 16, it is difficult to actually realize the method because the number of times of the alignment process is doubled.

Each of the split orientation treatments shown in FIGS. 15 and 16 is intended to obtain an isotropic viewing angle characteristic by adjusting the pretilt. Therefore, the alignment treatment method is limited to a method that causes a pretilt, such as a rubbing alignment treatment.

In general, when there is no pretilt,
Alternatively, when the pretilt angle is very small, a reverse tilt domain occurs in the liquid crystal cell. An object of the present invention is to provide a liquid crystal display device that can obtain isotropic viewing angle characteristics by a simple manufacturing process.

[0020]

According to the present invention, there is provided a liquid crystal display device comprising a pair of substrates arranged opposite to each other, and a plurality of first substrates formed on one of the pair of substrates in a certain direction. An electrode and a plurality of second electrodes formed on the other substrate in a different direction from the first electrode, and an intersection of the first and second electrodes forms a display region. A pair of electrode groups and a liquid crystal layer provided between the pair of substrates, wherein a pretilt angle of liquid crystal molecules is substantially 0 ° and an electric field is not applied between the pair of electrode groups; The liquid crystal molecules at the center are oriented in the direction parallel to the pair of substrates in a direction intermediate to the direction of the pair of electrodes, and when an electric field is applied between the pair of electrodes, the liquid crystal molecules at the intersections. Molecules split into more orientation regions than in the absence of an electric field And a liquid crystal layer.

The liquid crystal layer has at least one alignment region when no electric field is applied. When an electric field is applied, it is divided into many different alignment regions than when no electric field is applied. If different orientation regions are formed when applying an electric field,
The viewing angle dependency can be reduced.

[0022]

FIG. 2 is an overall configuration diagram of a liquid crystal cell 10 according to an embodiment of the present invention. FIG. 2A is a front view of the liquid crystal cell 10. The liquid crystal cell 10 is a two-dimensional matrix type twisted nematic type liquid crystal cell (TN-LC).
D), wherein a plurality of electrodes Vx in the X-axis direction and a plurality of electrodes Vy in the Y-axis direction form a matrix. The intersection of the electrode Vx and the electrode Vy forms a display area (pixel). When the number of the electrodes Vx is N and the number of the electrodes Vy is M, the number of pixels is N × M.

FIG. 2 (B) shows the liquid crystal cell 10 of FIG. 2 (A).
Is a cross-sectional view taken along line AA ′. The manufacturing process of the liquid crystal cell 10 will be described. First, a glass substrate 1 and a glass substrate 2
Prepare An electrode Vy is formed on a glass substrate 1,
An electrode Vx is formed on the glass substrate 2. Electrodes Vx, V
y is composed of, for example, an ITO (indium tin oxide) film.

Further, the light polarization storage film 3 is applied on the electrode Vy, and the light polarization storage film 4 is applied on the electrode Vx. The light polarization storage films 3 and 4 are, for example, a mixture of polyvinyl alcohol (PVA) and methyl orange.

Next, a polarized laser beam is applied to the optical polarization storage films 3 and 4. When the polarized laser beam is irradiated, the light polarization storage films 3 and 4 are oriented in the polarized direction, and the orientation directions are stored. The orientation direction of the light polarization storage film 3 and the orientation direction of the light polarization storage film 4 are shifted by, for example, 90 °. The details of the photo-alignment treatment are described in FIGS. 2 and 4 in JP-A-7-72484.

The glass substrate 1 and the glass substrate 2 face each other, and a liquid crystal material 5 is injected between them. The liquid crystal material 5 is injected by, for example, vacuum injection or capillary injection. Liquid crystal material 5
Constitutes a TN liquid crystal layer. The feature of the present embodiment lies in the alignment direction of the liquid crystal molecules in the center of the liquid crystal layer 5 between the substrates 1 and 2. Details will be described later.

Thereafter, a spacer 6 made of a resin or the like is sandwiched between the substrate 1 and the substrate 2 to seal the liquid crystal material 5. FIG.
2 is an enlarged view of four pixels in FIG. 2A, and shows the orientation direction of liquid crystal molecules at the center between the substrates.

In the matrix type liquid crystal cell, a plurality of electrodes Vx extend in parallel in the horizontal direction of the figure, and a plurality of electrodes Vy extend in parallel in the vertical direction of the figure. The electrode Vy is connected to the upper substrate 1 (FIG.
(B)), and the electrode Vx is provided on the lower substrate 2.

The pixel PX is a region where the electrode Vx and the electrode Vy overlap in the direction perpendicular to the substrate surface. For example, when there are two electrodes Vx and two electrodes Vy, four pixels are configured.

The alignment direction 11 is a direction parallel to the diagonal line of the pixel PX, and is the alignment direction of the liquid crystal molecules at the center between the substrates. The alignment treatment on the light polarization storage films 3 and 4 needs to be performed so that the liquid crystal molecules at the center between the substrates are aligned in the diagonal direction 11 of the pixel PX. The liquid crystal molecules of the TN liquid crystal layer 5 (FIG. 2B) are aligned at the interfaces with the substrates 1 and 2 according to the alignment structure of the light polarization storage films 3 and 4, respectively, and gradually toward the center of the liquid crystal layer. Twist.

The pixel PX is rectangular and has two diagonal lines. The liquid crystal molecules at the center between the substrates are aligned in the direction 11 of one of the two diagonals.
The liquid crystal molecules at the center between the substrates need not have pretilt.

The photo-alignment treatment generally causes almost no pretilt as compared with the rubbing alignment treatment. In the present embodiment, there may or may not be a pretilt. Therefore, either photo alignment treatment or rubbing alignment treatment may be used.

The alignment treatment may be performed on the substrate by transferring the alignment of the liquid crystal molecules from the mother substrate to the child substrate and transferring the alignment structure of the mother substrate to the child substrate. The details of the transfer method are described in the description of FIGS. 2 and 3 in Japanese Patent Application No. 7-19524.

In addition, various alignment treatment methods can be adopted. The alignment structure may be manufactured using a method not so excellent in mass productivity (an oblique deposition film, a Langmuir-Blodgett (LB) film, a photo-alignment film, a stretched polymer film, or the like).

FIG. 3 is a diagram for explaining the behavior of the liquid crystal molecules 5 when an electric field is applied between the electrode Vx and the electrode Vy. FIG. 3A shows the surface view of FIG.
It is a rotated figure, and represents one pixel PX. Pixel P
X is an overlapping portion between the electrode Vy and the electrode Vx. The alignment direction 11 at the center between the substrates is a diagonal direction of the pixel PX.

When no electric field is applied between the electrode Vy and the electrode Vx, the liquid crystal molecules 5 lie on the plane parallel to the substrate (not shown). When an electric field is applied between the electrode Vy and the electrode Vx, the liquid crystal molecules 5 rise in a plane perpendicular to the substrate including the alignment direction 11.

Next, a sectional view taken along lines BB 'and CC' parallel to the orientation direction 11 will be described. BB 'is a line above the diagonal line of the pixel PX, and CC' is a line
This is a line below the diagonal line of X.

FIG. 3B is a sectional view taken along line BB '.
In order to facilitate the explanation of the behavior of the liquid crystal molecules 5, FIG.
The electrodes Vy and Vx and the liquid crystal molecules 5 are extracted from the cross-sectional view of FIG.

The upper electrode Vy has one end P1 and the other end P2. The lower electrode Vx has one end P3 and the other end P4. The upper electrode Vy and the lower electrode Vy are parallel and have the same length. The upper electrode Vy is located at a position translated to the right with respect to the lower electrode Vx.

The liquid crystal molecules 5a and 5b are liquid crystal molecules at the center between the electrodes Vy and Vx. The liquid crystal molecules 5a are molecules on a line connecting one end P1 of the electrode Vy and one end P3 of the electrode Vx, and a line connecting the other end P2 of the electrode Vy and the other end P4 of the electrode Vx. The liquid crystal molecules 5b are connected to one end P1, of the electrodes Vy, Vx.
The molecule exists inside the line connecting P3 and the line connecting the other ends P2 and P4.

When an electric field is applied between the electrode Vy and the electrode Vx, the direction of the electric field at each end of the electrode Vx and the electrode Vy is determined. That is, one end P1 of the electrode Vy and the electrode Vx
Of the electrode Vy and the other end P2 of the electrode Vy.
A fringe electric field is generated in the direction of the line connecting the other end P4 of the electrode Vx. Inside the electrode intersection, the electric field is perpendicular to the electrodes.

When an electric field is applied between the electrodes Vy and Vx, first, the liquid crystal molecules 5a at both ends of the electrodes rise in a diagonally right electric field direction connecting both ends of the electrodes as shown in the figure. When the liquid crystal molecules 5a at both ends rise, the liquid crystal molecules 5b gradually rise in the same direction as the liquid crystal molecules 5a from the both ends of the electrode toward the center portion in a chain.

The liquid crystal molecules 5a, 5b are connected to one end P1,
The alignment direction when applying an electric field is determined according to the line direction connecting P3 and the line direction connecting the other ends P2 and P4. FIG. 3C is a cross-sectional view taken along line CC ′ of FIG. Similarly to FIG. 3B, the electrodes Vy and Vx and the liquid crystal molecules 5 are extracted from the cross-sectional view of FIG.

The upper electrode Vy has one end P5 and the other end P6. The lower electrode Vx has one end P7 and the other end P8. The upper electrode Vy is opposite to the lower electrode Vx, contrary to FIG.
It is in a position that has been translated to the left.

The liquid crystal molecules 5a are connected to one end P of the electrodes Vy and Vx.
5, molecules on the line connecting P7 and the line connecting the other ends P6 and P8. The liquid crystal molecules 5b are molecules that exist inside the liquid crystal molecules 5a at both ends of the electrode.

When an electric field is applied between the electrodes Vy and Vx, first, the liquid crystal molecules 5a at both ends of the electrode are turned to the left diagonal line direction (electric field direction) connecting both ends of the electrode, contrary to FIG. 3B. Stand up. When the liquid crystal molecules 5a at both ends rise, the liquid crystal molecules 5b gradually rise in the same direction as the liquid crystal molecules 5a from the both ends of the electrode toward the center portion in a chain.

As described above, the liquid crystal molecules 5 rise obliquely to the right in the upper half pixel region PXa (FIG. 3B), with the diagonal line of the pixel PX in FIG. In the pixel region PXb, the liquid crystal molecules 5 rise obliquely to the left (FIG. 3C).

In the pixel PX, the manner in which liquid crystal molecules rise differs between the upper half region PXa and the lower half region PXb.
That is, the pixel PX has two divided areas and has isotropic viewing angle characteristics.

In the above, only the electric field component in the major axis direction of the liquid crystal molecules 5 among the electric fields applied between the electrodes Vy and Vx has been described. Next, all components of the electric field applied between the electrodes Vy and Vx will be described.

FIG. 4 is a diagram for explaining an electric field acting between the electrode Vy and the electrode Vx. The pixel PX is an overlapping portion between the electrode Vy and the electric field Vx. The alignment direction 11 is the pixel P
X is a diagonal direction. As described above, on the diagonal line of the pixel PX, the right end of the liquid crystal molecule 11a rises in the upper half of the pixel, and the left end of the liquid crystal molecule 11b rises in the lower half of the pixel.

The upper electrode Vy passes over the lower electrode Vx. The electrodes Vy and Vx are elongated line electrodes. Electrodes Vy, Vx
The electric fields E and E 'acting on the respective ends of the electrodes Vy and Vx when an electric field is applied to the electrodes Vy and Vx will be described.

The oblique electric field E acts from the end of the lower electrode Vx toward the region of the upper electrode Vy in a direction perpendicular to and outward of the end. The oblique electric field E can be divided into an electric field component Eh in the major axis direction of the liquid crystal molecules and an electric field component Ev in the vertical direction.

The oblique electric field E 'works from the region of the lower electrode Vx toward the end of the upper electrode Vy in the direction perpendicular to and outward of the end. The oblique electric field E ′ can be divided into an electric field component Eh ′ in the major axis direction of the liquid crystal molecules and an electric field component Ev ′ in the vertical direction.

The influence of the electric field components Eh and Eh 'in the same direction as the orientation direction 11 of the liquid crystal molecules on the liquid crystal molecules will be described.
In the upper half region of the pixel, as described with reference to FIG. 3B, an electric field Eh ′ acts in a line direction connecting the left end P3 of the lower electrode Vx and the left end P1 of the upper electrode Vy located inside the lower electrode Vx. Then, an electric field Eh acts in a line direction connecting the right end P4 of the lower electrode Vx and the right end P2 of the upper electrode Vy located outside thereof. As a result, the liquid crystal molecules in the upper half region of the pixel rise at the right end.

In the lower half region of the pixel, the left end P7 of the lower electrode Vx and the left end P5 of the upper electrode Vy located outside thereof
An electric field Eh acts in the line direction connecting. Then, the right end P8 of the lower electrode Vx and the right end P8 of the upper electrode Vy located inside the lower end Vx.
An electric field Eh 'acts in the direction of the line connecting 6. As a result, the liquid crystal molecules in the lower half region of the pixel rise at the left end.

FIG. 5 is a diagram showing the orientation of liquid crystal molecules when no electric field is applied between the electrodes. FIG. 5A is a front view of four pixels extracted from the liquid crystal cell. The four pixels are formed in a region where two electrodes Vy and two electrodes Vx intersect. The alignment direction 11 is a diagonal direction of the pixel.

The line BB is a line obtained by translating the diagonal line of the pixel upward, and the lines CC and DD are lines obtained by translating the diagonal line of the pixel downward. Lines BB and CC are located near the diagonal of the pixel, and line DD is located far from the diagonal of the pixel.

FIG. 5B is a cross-sectional view of the liquid crystal cell of FIG. 5A taken along a line BB. The upper electrode Vy is the lower electrode V
It has been translated slightly to the right of x. Electrodes Vy, V
When no electric field is applied between x, the liquid crystal molecules 5 are sleeping.

FIG. 5C is a cross-sectional view of the liquid crystal cell of FIG. 5A taken along line CC. The upper electrode Vy is the lower electrode V
It is slightly translated to the left of x. FIG. 5 (D)
FIG. 6 is a cross-sectional view of the liquid crystal cell of FIG. 5A taken along a line DD. The upper electrode Vy moves parallel to the left more largely than the lower electrode Vx, and overlaps with the adjacent pixel electrode.

FIG. 6 is a diagram showing the orientation direction of liquid crystal molecules when an electric field is applied between the electrodes. FIG. 6A shows FIG.
FIG. 4 is a front view of four pixels extracted from a liquid crystal cell, similarly to FIG.

FIG. 6B is a cross-sectional view of the liquid crystal cell of FIG. 6A taken along line BB. The upper electrode Vy is the lower electrode V
x slightly shifted to the right from x, the electrodes Vy, Vx
When an electric field is applied therebetween, the liquid crystal molecules 5 rise at the right end.

FIG. 6C is a cross-sectional view of the liquid crystal cell of FIG. 6A taken along line CC. The upper electrode Vy is the lower electrode V
x slightly offset to the left, the electrodes Vy, Vx
When an electric field is applied therebetween, the liquid crystal molecules 5 rise at the left end.

FIG. 6D is a sectional view of the liquid crystal cell of FIG. 6A taken along a line DD. The upper electrode Vy is the lower electrode V
Since it is shifted to the left more than x, when an electric field is applied between the electrodes Vy and Vx, the left end of the liquid crystal molecules 5 rises. However, in the portion where the electrodes Vy and Vx overlap with the adjacent pixel electrode, the voltage rises in reverse depending on the liquid crystal molecules. The directions of these liquid crystal molecules are continuously changing from the liquid crystal molecules in FIG.

As described above, when an electric field is applied between the electrodes, the orientation direction of the liquid crystal molecules is different between the upper half and the lower half of the pixel with respect to the diagonal line of the pixel. One pixel has two regions having different alignment directions (two divided regions).

FIG. 7 is a front view of a liquid crystal cell showing pixels divided into regions. The electrodes Vx and Vy extend in the horizontal and vertical directions, respectively, as shown in FIG. The pixel PX is an overlapping portion of the electrode Vy and the electrode Vx.

The alignment direction 11 is a direction of a diagonal right diagonal line of the pixel PX. With the diagonal line as a boundary, the area is divided into an upper left area and a lower right area. In the upper left area, the liquid crystal molecules 11a rise from the upper right end of the figure, and in the lower right area, the liquid crystal molecules 1a.
1b rises from the lower left of the figure. All pixels PX are
It is divided into two areas, an upper left area and a lower right area.

The above is the description of the two glass substrates 1 and 2 facing each other.
(FIG. 1). Next, the case where the orientation treatment in two directions is performed will be described.

FIG. 8 shows a liquid crystal cell in which each of the glass substrates 1 and 2 performs an orientation process in two directions. FIG.
(A) is a surface view of a liquid crystal cell showing an orientation direction of liquid crystal molecules in a central portion between substrates when an electric field is not applied. Four pixels PX1 to PX, which are overlapping portions of electrodes Vy and Vx
X4 is adjacent. The pixels PX1 and PX2 and the pixels PX3 and PX4 are adjacent to each other in the vertical direction. The pixels PX1 and PX3 and the pixels PX2 and PX4 are adjacent to each other in the horizontal direction.

The pixels PX1 and PX4 are subjected to an alignment process so that the liquid crystal molecules at the central portion between the substrates are aligned in the oblique left direction 32. The pixels PX2 and PX3 are subjected to alignment processing so as to be aligned in the oblique right direction 31. Four pixels PX1
PX4 as one set and two orientation directions 31 and 3
The alignment process is performed so as to have 2.

FIG. 8B is a view showing the orientation direction of liquid crystal molecules when an electric field is applied when the orientation treatment shown in FIG. 8A is performed. When an electric field is applied between the substrates Vy and Vx,
The liquid crystal molecules rise. The pixels PX1 to PX4 are divided into two regions having different alignment directions with each diagonal line as a boundary.

The pixels PX1, PX4 and PX2, PX3
Are different in the direction of the boundary line. Pixels PX2 and PX3
Is oriented so as to be oriented in the oblique right direction 31. Therefore, similarly to the case of the above-described unidirectional orientation treatment (FIG. 7),
It is divided into an upper left area and a lower right area. In the upper left area, the liquid crystal molecules 31a rise from the upper right end of the figure, and in the lower right area, the liquid crystal molecules 31b rise from the lower left end of the figure.

Since the pixels PX1 and PX4 are oriented so as to be oriented in the oblique left direction 32, the pixels PX2 and PX4 are
Unlike X3, it is divided into an upper right area and a lower left area. In the upper right region, the liquid crystal molecules 32a rise from the upper left end of the drawing, and in the lower left region, the liquid crystal molecules 32b rise from the lower right end of the drawing.

By performing the alignment processing in the two directions 31 and 32, it is possible to form pixels having different alignment regions (two divided regions). One type is the pixels PX2 and PX3, and the other type is the pixels PX1 and PX4.

The case where two divided areas are formed for one pixel has been described above. Next, perform the same orientation treatment,
A case in which a pixel having four or eight divided regions is formed will be described.

When dividing the pixel into two, as described above,
The dots PX1 to PX4 may be four different pixels. When dividing a pixel into four, the dots PX1 to PX
With X4 as two pixels, the electric field applied to the electrodes Vy and Vx is controlled. That is, two dots are defined as one pixel. For example, the dots PX1 and PX2 are defined as one pixel, and the dots PX
3, PX4 is another pixel. Also, the dots PX1,
PX3 may be one pixel, and dots P2 and PX4 may be another pixel. One pixel has four regions.

When dividing a pixel into eight, the dots PX1 to PX1
The electric field applied to the electrodes Vy and Vx is controlled with PX4 as one pixel. One pixel has eight regions. Similarly, even when the one-way alignment process (FIG. 7) is performed, by dividing two dots into one pixel or four dots into one pixel, it is possible to form four- or eight-divided pixels. .

Although the case where the dot area where the electrode Vy and the electrode Vx overlap each other is a quadrangle, the dot area need not be a quadrangle. The electrodes Vy and Vx may be formed to have other shapes.

FIG. 17 is a diagram showing a configuration example of the electrodes Vy and Vx having dot areas other than the quadrangular shape. For simplicity, the electrodes Vy on the upper substrate are represented by solid lines, and the electrodes Vy on the lower substrate are represented by broken lines. The overlap region between the electrode Vy and the electrode Vx is, for example, hexagonal. Alignment direction of liquid crystal molecules 11
Is the diagonal direction of one of the hexagons.

In the overlapping region, an electric field E is generated from the edge of the lower electrode Vx toward the region outside the upper electrode Vy. Then, an electric field E ′ is generated from the region outside the lower electrode Vx toward the edge of the upper electrode Vy.

The electric fields E and E ′ each have a component in the orientation direction 11. The liquid crystal molecules rise when receiving the electric field of the component in the alignment direction 11. As a result, as described above, two different alignment regions are formed at the diagonal line in the same direction as the alignment direction 11.

As described above, the region where the upper electrode Vy and the lower electrode Vx overlap is not limited to a quadrangle. However, in the overlapping region, the electric fields E and E ′ acting on the edge of the electrode
It is necessary to configure the electrodes Vy and Vx so as to have a component in the alignment direction 11 of the liquid crystal molecules. That is, the alignment process may be performed such that the alignment direction 11 of the liquid crystal molecules is between the direction of the electrode Vy and the direction of the electrode Vx. Preferably, it is the middle direction between the direction of the electrode Vy and the direction of the electrode Vx.

[0082]

FIG. 9 shows a measuring method when the liquid crystal cell described above is actually manufactured and the viewing angle characteristics of the liquid crystal cell are measured.

In order to measure the viewing angle characteristics of the liquid crystal cell 10,
Pictures were taken using a microscope from three viewpoints on the screen of the liquid crystal cell 10. The three viewpoints are the liquid crystal cell 10
, The viewing angle AC from the front and the viewing angle A from the left
L, which corresponds to a viewing angle AR obliquely from the right.

As described above, the liquid crystal cell 10 shown in FIG.
Matrix type TN-LC as shown in (A) and (B)
D structure. For the optical polarization storage film on the substrate,
One-way alignment treatment (FIG. 1) was performed using a photo-alignment method.
The pretilt angle of the liquid crystal molecules is almost 0 °. here,
The pretilt angle is an angle between the glass substrate surface and the major axis of the liquid crystal molecules.

FIGS. 10 and 11 are sketches of micrographs, each showing the same four-pixel area of the liquid crystal cell. One pixel is about 180 μm square. FIG.
(A) is a sketch of the liquid crystal screen when an electric field is not applied between the electrodes. When no electric field is applied, the liquid crystal molecules are in a lying state. The four pixel regions are observed as one alignment region.

FIG. 10B is a sketch of the liquid crystal screen when the liquid crystal cell is turned on by applying an electric field of a threshold value or more between the electrodes, and is observed from the front of the liquid crystal screen. When no electric field is applied, one alignment region is shown as described above (FIG. 10A), but when an electric field is applied, four alignment regions corresponding to four pixels PX are divided. . Further, each pixel PX has an upper left area PXa and a lower right area PX with the disclination line 16 interposed therebetween.
b.

In the upper left area PXa and the lower right area PXb,
The rising direction and the alignment direction of the liquid crystal molecules are different. The disclination line 16 is generated at the boundary between regions where the rising directions of the liquid crystal molecules are different.

When the liquid crystal screen is observed from the front, the pixel P
Each of the two regions PXa and PXb in X has a good visual recognition state. FIG. 11A is a sketch of the liquid crystal screen when an electric field of a threshold value or more is applied between the electrodes and the liquid crystal cell is turned on, and is observed from the oblique right direction AR of the liquid crystal screen. When an electric field is applied, four alignment regions corresponding to the four pixels PX are divided, and each pixel PX is divided into an upper left region PXa and a lower right region PXb with the disclination line 16 interposed therebetween. When viewed from the oblique right direction AR, the visual recognition state of the lower right area PXb is deteriorated, but the visual recognition state of the upper left area PXa is good.
Even when observed from the right oblique direction AR, the visibility state as a pixel is good.

FIG. 11B is a sketch of the liquid crystal screen when an electric field of a threshold value or more is applied between the electrodes and the liquid crystal cell is turned on, and is observed from the left oblique direction AL of the liquid crystal screen. . When an electric field is applied, four alignment regions corresponding to the four pixels PX are divided, and further, each pixel P
X is divided into an upper left area PXa and a lower right area PXb across the disclination line 16. When viewed from the left oblique direction AL, the upper left area PXa has a poor visibility state, but the lower right area PXb has a good visibility state. Even when observed from the left oblique direction AL, the visibility state as a pixel is good.

Next, the disclination line 16 formed at the boundary between the areas PXa and PXb will be described. For example, a disclination line is generated even when the two-division alignment processing is performed by the conventional technique shown in FIG. In this case, the disclination line is generated at the boundary between the areas subjected to the rubbing processing in different directions. This disclination line is a thick line.

On the other hand, the disclination line 16 generated in the liquid crystal cell of this embodiment is a very thin line, and disappears when the electric field is erased (FIG. 10A). In the present embodiment, the adverse effect of the disclination line is greatly improved as compared with the conventional art.

Next, the reason why the present embodiment has a very thin disclination line as compared with the prior art and disappears when the electric field is erased will be considered. First, the elastic constant of liquid crystal molecules will be described.

FIG. 12 shows three basic elastic constants K1, K2 and K3 of the liquid crystal material. The three elastic constants are elastic constants of the liquid crystal material in different distortion modes. The director 21 indicates the major axis direction of the liquid crystal molecules.

FIG. 12A is a diagram for explaining the splay elastic modulus K1. Spread distortion occurs when the liquid crystal material spreads due to external force. The spray elastic constant K1 is
It is an elastic constant in splay strain.

FIG. 12B is a diagram for explaining the twist elasticity coefficient K2. When the liquid crystal material is twisted by an external force, twist distortion occurs. Twist elastic constant K2
Is the elastic constant at the twist strain.

FIG. 12C is a diagram for explaining the bend elasticity coefficient K3. When the liquid crystal material is bent by an external force, bend distortion occurs. The bend elastic constant K3 is an elastic constant at the bend strain.

The three elastic constants differ in magnitude.
Generally, the splay elastic constant K1 and the bend elastic constant K3
Is larger than the twist elastic constant K2. In the liquid crystal cell of the prior art (FIG. 16), although liquid crystal molecules rise in different directions in the two regions, they rise in opposite directions in the same plane, so that there is no twist. The interaction between liquid crystal molecules is
It can be represented by a splay elastic constant K1 and a bend elastic constant K3.

In the liquid crystal cell of this embodiment, the liquid crystal material is twisted at the boundary between the two regions. The interaction between the liquid crystal molecules is affected by the twist elastic constant K2. Since the twist elastic constant K2 is generally smaller than the splay elastic constant K1 and the bend elastic constant K3, the deformation energy of the liquid crystal material is smaller in the present embodiment than in the prior art. In this embodiment, since the deformation energy is small, it is considered that the line width of the disclination line caused by the deformation of the liquid crystal material becomes thin.

In this embodiment, the dot (electrode Vy and electrode V
The alignment process is performed so that the liquid crystal molecules at the center between the substrates are aligned in the diagonal direction of the (overlapping region of x). The direction is 1
It may be a direction or a plurality of directions. Even when the unidirectional alignment processing is performed, the pixel can have a divided area.

The alignment treatment is not limited to the treatment for giving the liquid crystal molecules a pretilt. Various alignment treatment methods can be adopted. However, the average pretilt angle is almost 0 °
It is preferable that

The pretilt angle of the liquid crystal molecules at the center between the substrates can be reduced to 0 ° by the following method. An alignment process is performed so as to give a certain degree of tilt angle to the liquid crystal molecules at the center between the substrates. At that time, if the orientation processing direction of one substrate is set to the opposite direction of the other substrate, the pretilt angle must also change with the thickness of the liquid crystal layer. The pretilt angle of the liquid crystal molecules at the center is 0 °. The liquid crystal molecules have a certain amount of pretilt at the interface with the substrate, but twist between the substrates by 90 ° so that the pretilt disappears toward the center between the substrates.

The twist angle of the liquid crystal layer need not be 90 °, but may be more or less. Super twisted nematic (STN) liquid crystal may be used. The alignment process is performed so that the liquid crystal molecules at the center between the substrates are aligned in the diagonal direction of the dots when no electric field is applied. The alignment treatment on the substrate
It is not necessary to perform the process on both substrates, and it may be performed on only one substrate. If a chiral agent is added to the liquid crystal material, a TN liquid crystal layer can be formed.

As described above, in the present embodiment, a dot including two regions having two different rising directions and two different orientation directions (an overlapping region of the electrode Vy and the electrode Vx) is formed only by performing the one-way alignment process. can do. If one dot is treated as one pixel (if the electrode voltage is controlled), 1
Each pixel has two divided areas.

To form a two-divided area by the conventional technique,
It was necessary to use different types of alignment films (FIG. 15) and to perform two rubbing alignment treatments (FIG. 16). According to this embodiment, a divided liquid crystal cell can be efficiently manufactured by using one type of alignment film and performing one alignment process.

In this embodiment, when an electric field is applied between the electrodes, a disclination line is generated at the boundary between two regions where the rising directions of the liquid crystal molecules are different.
However, the disclination line is extremely thin as compared with the prior art.

Although the disclination line of the conventional liquid crystal cell does not disappear even when the electric field is erased, the disclination line of the liquid crystal cell of this embodiment disappears when the electric field is erased.

The configurations, materials, and the like of the embodiments described above are merely examples, and the present invention is not limited to these, and it is obvious to those skilled in the art that various modifications, improvements, combinations, and the like can be made. Would.

[0108]

According to the present invention, even when the liquid crystal layer has one orientation in the absence of an electric field, it can be given a different orientation by applying an electric field. The process can reduce the viewing angle dependency.

[Brief description of the drawings]

FIG. 1 is a view showing an alignment direction of liquid crystal molecules in a central portion between substrates according to an embodiment of the present invention.
It is the figure which expanded the pixel part.

FIG. 2 is an overall configuration diagram of a liquid crystal cell according to the present embodiment.
FIG. 2A is a front view of the liquid crystal cell, and FIG.
FIG. 2 is a cross-sectional view of the liquid crystal cell of FIG.

FIG. 3 is a diagram for explaining the behavior of liquid crystal molecules when an electric field is applied between an electrode Vx and an electrode Vy. 3A is a diagram obtained by rotating the surface view of FIG. 2 to the right by 45 °, FIG. 3B is a cross-sectional view taken along the line BB ′ of FIG. FIG. 3C is a cross-sectional view taken along the line CC ′ of FIG.

FIG. 4 is a diagram for explaining an electric field acting between an electrode Vy and an electrode Vx.

FIG. 5 is a diagram showing directions of liquid crystal molecules when an electric field is not applied between electrodes. FIG. 5A is a front view of four pixels extracted from the liquid crystal cell, and FIG.
FIG. 3A is a cross-sectional view of the liquid crystal cell taken along line BB. FIG. 5C is a cross-sectional view of the liquid crystal cell of FIG. 5A taken along a line CC. FIG. 5D is a cross-sectional view of the liquid crystal cell of FIG. 5A taken along a line DD.

FIG. 6 is a diagram showing the orientation direction of liquid crystal molecules when an electric field is applied between electrodes. FIG. 6A shows four of the liquid crystal cells.
FIG. 6 (B) is a surface view in which pixels are extracted, and FIG.
6A is a cross-sectional view of the liquid crystal cell taken along line BB, FIG. 6C is a cross-sectional view of the liquid crystal cell of FIG. 6A taken along line CC, and FIG. FIG. 7 is a cross-sectional view of the liquid crystal cell of FIG. 6A taken along a line DD.

FIG. 7 is a front view of a liquid crystal cell showing pixels divided into regions.

FIG. 8 shows a liquid crystal cell in a case where a glass substrate is subjected to a two-direction alignment treatment. FIG. 8A is a surface view of a liquid crystal cell showing an alignment direction of liquid crystal molecules in a central portion between substrates when an electric field is not applied. FIG. 8B is a view showing an alignment process shown in FIG. FIG. 6 is a diagram illustrating the orientation direction of liquid crystal molecules when an electric field is applied when the measurement is performed.

FIG. 9 is a diagram illustrating a measurement method when a liquid crystal cell is actually manufactured and the viewing angle characteristics of the liquid crystal cell are measured.

10A is a sketch of a liquid crystal screen when an electric field is not applied between electrodes, and FIG. 10B is a view in which an electric field of a threshold value or more is applied between the electrodes and viewed from the front. This is a sketch of the LCD screen.

11A is a sketch of a liquid crystal screen observed obliquely from the right by applying an electric field of a threshold value or more between electrodes, and FIG. 11B is a sketch of an electric field of a threshold value or more between electrodes. 5 is a sketch of the liquid crystal screen observed from the left oblique direction with the application of a voltage.

FIG. 12 shows three basic elastic constants of a liquid crystal material.
12A is a diagram for explaining the splay elastic modulus K1, FIG. 12B is a diagram for explaining the twist elastic modulus K2, and FIG. 12C is a diagram for explaining the bend elastic modulus K3.

FIG. 13 is a perspective view showing a rubbing process according to a conventional technique.

FIG. 14 is a cross-sectional view of a liquid crystal display device manufactured by a conventional technique.

FIG. 15 is a cross-sectional view of a two-divided liquid crystal display element manufactured by a conventional technique.

FIG. 16 is a cross-sectional view of a two-divided liquid crystal display element manufactured by a conventional technique.

FIG. 17 is a diagram showing a configuration example of an electrode according to another embodiment of the present invention.

[Explanation of symbols]

 1, 2 glass substrate 3, 4 alignment film 5 liquid crystal material 6 spacer 10 liquid crystal cell Vx, Vy electrode PX pixel

Claims (6)

(57) [Claims] A pair of substrates (1, 2) arranged opposite to each other.
A plurality of first electrodes formed on one of the pair of substrates in one direction and a plurality of second electrodes formed on the other substrate in a direction different from the first electrode; And a liquid crystal layer provided between the pair of substrates, wherein an intersection where the first and second electrodes intersect is a pair of electrode groups (Vy, Vx) forming a display area. When the pretilt angle of the liquid crystal molecules is substantially 0 ° and an electric field is not applied between the pair of electrode groups, the liquid crystal molecules at the center between the substrates are aligned in a plane parallel to the pair of substrates. When the liquid crystal layer is oriented in an intermediate direction of the direction of the electrode group and an electric field is applied between the pair of electrode groups, the liquid crystal molecules are divided into more alignment regions at the intersections than when no electric field is applied. A liquid crystal display device having: 2. The method according to claim 1, wherein the intersection forms a quadrangle.
The liquid crystal display device according to the above. 3. The liquid crystal layer according to claim 2, wherein when no electric field is applied between the pair of electrode groups, the liquid crystal molecules at the intersections are oriented in a direction parallel to one diagonal of the rectangular intersection. The liquid crystal display device according to the above. 4. The liquid crystal display device according to claim 1, wherein the pair of electrode groups form a display region group having a two-dimensional matrix shape. 5. A liquid crystal display device further comprising a pair of alignment films (3, 4) formed on the pair of electrode groups, at least one of the pair of alignment films being subjected to horizontal alignment processing at an interface with the liquid crystal layer. The liquid crystal display device according to claim 1, wherein 6. The liquid crystal display device according to claim 5, wherein the alignment film has been subjected to photo-alignment treatment.