JP2003315781A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display wherein it is not necessary to highly accurately align an array substrate and a counter substrate even when an MVA mode is adopted. <P>SOLUTION: In the liquid crystal display 1, when voltage is applied between electrodes 10 and 16, first and second regions having electric fields having intensities different from each other are formed in a pixel region to be a region of a liquid crystal layer 4 interposed between the electrodes 10 and 16. The first and the second regions have shapes respectively extended in one direction in a plane including the liquid crystal layer 4 and are alternately and repetitively arranged in the direction crossing the direction in the plane. An angle θ formed by the direction in which the first and the second regions are extended and a transmission susceptible axis of a first polarizing plate 5a satisfies any one of inequalities 0°<θ<45° and 45°<θ<90°. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art Liquid crystal display devices have various characteristics such as thinness, light weight and low power consumption, and are applied to various uses such as office automation equipment, information terminals, watches, and televisions. . In particular, a liquid crystal display device having a thin film transistor (hereinafter referred to as a TFT) is used as a monitor for displaying a large amount of information such as a portable television or a computer because of its high responsiveness.

In recent years, as the amount of information has increased, there has been an increasing demand for higher definition of images and higher display speed. Among these requirements, the high definition of the image is described in the above-mentioned T
This is realized by miniaturizing the array structure formed by the FT.

On the other hand, regarding the speeding up of the display speed, an OC using a nematic liquid crystal is used instead of the conventional display mode.
B mode, VAN (Vertical Align Nematic) mode,
HAN mode, π-aligned mode, and surface stabilized ferroelectric liquid crystal (Surface Stabilized) using smectic liquid crystal
The adoption of Ferroelectric Liquid Crystal) mode and antiferroelectric liquid crystal mode is under consideration.

Among these display modes, the VAN mode can obtain a faster response speed than the conventional TN (Twisted Nematic) mode, and further, the rubbing process which causes defects such as electrostatic breakdown due to the vertical alignment is unnecessary. Is. Among them, the multi-domain type VAN mode (hereinafter, referred to as MVA mode) has attracted particular attention because it is relatively easy to design the view angle compensation.

However, in the conventional liquid crystal display device adopting the MVA mode, it is necessary to form a ridge-shaped projection structure not only on the array substrate but also on the counter substrate or to provide a slit or the like in the common electrode on the counter substrate. There is. Therefore, the alignment between the array substrate and the counter substrate must be performed with extremely high accuracy, resulting in an increase in cost and a decrease in reliability.

In recent years, in the manufacture of a TN mode liquid crystal display device, a technique of forming a color filter layer on an array substrate has begun to be put into practical use. According to this technique, when the array substrate and the counter substrate are bonded to each other to form a cell, it is not necessary to align each color region forming the color filter layer with the pixel electrode. Therefore, it is desired to apply such a technique to the manufacture of the MVA mode liquid crystal display device. However, in the conventional MVA mode liquid crystal display device, when an array substrate and a counter substrate are bonded together to form a cell. First, it is necessary to align the ridge structure and the slit between them. Therefore, the conventional M
In the VA mode liquid crystal display device, even if the color filter layer is formed on the array substrate, the benefit obtained in the TN mode liquid crystal display device cannot be enjoyed.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is possible to accurately align the array substrate and the counter substrate even when the MVA mode is adopted. It is an object of the present invention to provide a liquid crystal display device that can be manufactured without any need.

[0009]

In order to solve the above-mentioned problems, the present invention is directed to an array substrate having a pixel electrode on one main surface and a surface of the array substrate facing the pixel electrode. And a liquid crystal layer sandwiched between the array substrate and the counter substrate, and the pixel electrode of the array substrate. A first polarizing plate provided on the back surface side of the surface, and provided on the back surface side of the surface of the counter substrate on which the common electrode is provided and with an easy transmission axis orthogonal to the easy transmission axis of the first polarizing plate. And a second polarizing plate, which is a region sandwiched between the pixel electrode and the common electrode of the liquid crystal layer when a voltage is applied between the pixel electrode and the common electrode. The first and second regions having different electric field strengths The first and second regions each have a shape extending in one direction in a plane including the liquid crystal layer, and are alternately and repeatedly arranged in a direction intersecting the direction in the plane. The angle θ formed by the direction in which the first and second regions extend and the easy transmission axis of the first polarizing plate has an inequality: 0 ° <θ <45 ° and 45 ° <θ <90 °. Provided is a liquid crystal display device which is satisfied.

Further, according to the present invention, an array substrate having a pixel electrode on one main surface and a surface of the array substrate facing the surface on which the pixel electrode is provided and facing the array substrate. A counter substrate provided with a common electrode, a liquid crystal layer sandwiched between the array substrate and the counter substrate, and a first polarizing plate provided on the back surface side of the array substrate on which the pixel electrodes are provided. And a second polarizing plate provided on the back surface side of the surface of the counter substrate on which the common electrode is provided and so that the easy transmission axis is orthogonal to the easy transmission axis of the first polarizing plate. When a voltage is applied between the pixel electrode and the common electrode, the first and second electric fields have different electric field strengths in a pixel region that is a region sandwiched between the pixel electrode and the common electrode of the liquid crystal layer. And a second region, wherein the first and second regions are Has a shape extending in one direction in the plane including the liquid crystal layer and is alternately and repeatedly arranged in a direction intersecting the direction in the plane, and at least one of the first and second regions is the first region. Provided is a liquid crystal display device having an edge perpendicular to the extending direction of the first and second regions.

In the present invention, the first region and the second region, when a voltage is applied between the pixel electrode and the common electrode,
It can be observed as regions having different transmittances or reflectances. That is, the first and second regions can be confirmed by actually measuring the strength of the electric field and / or examining the transmittance or the reflectance.

In the present invention, the first region and the second region do not necessarily have to have a clear boundary. That is, the strength of the electric field and the magnitude of the transmittance or the reflectance may continuously change in the arrangement direction of the first region and the second region.

When the first area and the second area do not have a clear boundary, the sum of the width of the first area and the width of the second area hardly depends on their boundary values. The individual widths of the first and second areas vary depending on where their boundary values are set. Therefore, when it is necessary to find the boundary between the first region and the second region, appropriate values such as the strength of the electric field and the average value of the transmittance or the reflectance are used as the boundary values. You can use it.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or similar components are designated by the same reference numerals, and duplicated description will be omitted.

First, a first embodiment of the present invention will be described.

FIG. 1 is a sectional view schematically showing a liquid crystal display device according to a first embodiment of the present invention. A liquid crystal display device 1 shown in FIG. 1 is an MVA type liquid crystal display device and has a structure in which a liquid crystal layer 4 is sandwiched between an active matrix substrate (or an array substrate) 2 and a counter substrate 3. There is. The distance between the active matrix substrate 2 and the counter substrate 3 is kept constant by spacers (not shown). Polarizing films 5a and 5b are attached to both surfaces of the liquid crystal display device 1.

The active matrix substrate 2 has a transparent substrate 7 such as a glass substrate. Wirings and switching elements 8 are formed on one main surface of the transparent substrate 7. Further, a color filter layer 9, a pixel electrode 10 and an alignment film 11 are sequentially formed on them.

Wirings formed on the transparent substrate 7 are scanning lines and signal lines made of aluminum, molybdenum, copper or the like. The switching element 8 is, for example,
Amorphous silicon or polysilicon as the semiconductor layer,
The TFT is a TFT having a metal layer of aluminum, molybdenum, chromium, copper, tantalum, or the like, and is connected to wirings such as scanning lines and signal lines and the pixel electrode 10. With the active matrix substrate 2 having such a configuration,
It is possible to selectively apply a voltage to a desired pixel electrode 10.

The color filter layer 9 interposed between the transparent substrate 7 and the pixel electrode 10 includes blue, green and red colored layers 9a-9.
It is composed of c. A contact hole is provided in the color filter layer 9, and the pixel electrode 10 is connected to the switching element through this contact hole.

The pixel electrode 10 may be made of a transparent conductive material such as ITO. The pixel electrode 10 can be formed by forming a thin film by, for example, a sputtering method, and then patterning the thin film using a photolithography technique and an etching technique.

The orientation film 11 is composed of a thin film made of a transparent resin such as polyimide. In the present embodiment, the alignment film 11 is given a vertical alignment property without being subjected to rubbing treatment.

The counter substrate 3 has a structure in which a common electrode 16 and an alignment film 17 are sequentially formed on a transparent substrate 15 such as a glass substrate. These common electrode 16 and alignment film 1
7 can be formed of the same material as the pixel electrode 10 and the alignment film 11. In this embodiment, the common electrode 16 is formed as a flat continuous film.

FIG. 2 is a plan view schematically showing an example of a structure that can be used as the pixel electrode 10 of the liquid crystal display device shown in FIG. In the structure shown in FIG. 2, one pixel electrode 10 is composed of four parts 10a to 10d. Pixel electrode 10
A plurality of slit portions 10-1 are provided in each of the portions 10a to 10d constituting the above in a substantially constant cycle and substantially parallel to each other, and the portion 10-2 located between the slit portions 10-1 of the pixel electrode 10 is It has a comb-like shape. That is, each of the portions 10a to 10d forming the pixel electrode 10 is a comb-shaped portion including a plurality of comb tooth portions 10-2. Further, the longitudinal direction of the slit portion 10-1 and the comb-teeth portion 10-2 are the respective portions 10a.
-10d are different from each other. In the liquid crystal display device 1 shown in FIG. 1, by adopting such a configuration, the pixel region is formed into the comb-shaped portions 10a to 1a constituting the pixel electrode 10.
Corresponding to 0d, the liquid crystal molecules can be divided into four domains having different tilt directions. This will be described with reference to FIGS.

FIGS. 3A to 3D are diagrams schematically showing the alignment change of liquid crystal molecules which occurs when the structure shown in FIG. 2 is adopted in the liquid crystal display device shown in FIG. Note that FIG.
3A and 3C are plan views, and FIGS. 3B and 3D are side views of the structure shown in FIGS. 3A and 3C as viewed from the lower side in the drawing. Further, in FIGS. 3A to 3D, some components are omitted for simplification.

When no voltage is applied between the pixel electrode 10 and the common electrode 16, the alignment films 11 and 17 are formed of the liquid crystal layer 4.
The liquid crystal molecules 25 constituting the above, specifically the liquid crystal molecules having a negative dielectric anisotropy, act to vertically align them. Therefore, in the liquid crystal molecules 2, their long axes are oriented to the alignment film 1.
The film is oriented so as to be substantially perpendicular to the film surface of No. 1.

When a relatively low first voltage is applied between the pixel electrode 10 and the common electrode 16, a leak electric field is generated above the slit portion 10-1 provided in the pixel electrode 10. Therefore, there, the lines of electric force are inclined as shown in FIG.

The electric field generated by applying a voltage between the pixel electrode 10 and the common electrode 16 acts to align the liquid crystal molecules 25 in a direction perpendicular to the lines of electric force.
Therefore, the liquid crystal molecules 25 tend to be aligned as shown in FIG. 3A by the action of the alignment films 11 and 17 and the electric field.

However, in the state shown in FIG. 3A, the alignment state of the liquid crystal molecules 25 on the right side and the liquid crystal molecules 2 on the left side.
5 and the alignment state of 5 interfere with each other. Therefore, the liquid crystal molecules 25
In the figure, the tilt direction is changed upward or downward in order to attain a more stable alignment state.

Here, as shown in FIG. 3A, the comb-teeth portion 10-2 of the pixel electrode 10 and its vicinity have a symmetrical (or isotropic) shape in the vertical direction in the figure. Suppose you have it. In this case, the probability that the liquid crystal molecule 25 changes the tilt direction upward as shown by the arrow 31, and the arrow 3
As indicated by 2, the probability of changing the tilt direction downward is equal.

On the other hand, as shown in FIG. 3C, the comb-teeth portion 10-2 of the pixel electrode 10 and its vicinity have an asymmetrical (or anisotropic) shape in the vertical direction in the figure. When it has, the electric force lines are asymmetric between both ends of the pixel electrode 10, and similarly, the electric force lines are also asymmetric between both ends of the slit portion 10-1. Therefore, the alignment state in which the liquid crystal molecules 25 are aligned in the direction indicated by the arrow 32 is more stable than the alignment state in which the liquid crystal molecules 25 are aligned in the direction indicated by the arrow 31. As a result, the average tilt direction (director) of the liquid crystal molecules 25 is downward as shown by the arrow 32 in FIG.

When the voltage applied between the pixel electrode 10 and the common electrode 16 is increased to the second voltage higher than the first voltage, the alignment films 11 and 17 have an action of vertically aligning the liquid crystal molecules 25. On the contrary, the action of the electric field for orienting the liquid crystal molecules 25 in the direction perpendicular to the lines of electric force becomes greater. Therefore, the liquid crystal molecules 25 change the tilt angle in a direction approaching horizontal alignment.

Here, even when the voltage applied between the electrodes 10 and 16 is the second voltage, the liquid crystal molecules 25 have arrows 32 as in the case where the voltage applied between the electrodes 10 and 16 is the first voltage. The liquid crystal molecules 2 are aligned in the direction shown by
5 is more stable as compared with the orientation state in which the orientation is indicated by the arrow 31. Therefore, when the voltage applied between the electrodes 10 and 16 is changed between the first voltage and the second voltage, the director of the liquid crystal molecules 25 changes in a plane perpendicular to the arrangement direction of the slit portions 10-1. . That is, the electrodes 10, 1
When the voltage applied between 6 is changed between the first voltage and the second voltage, the liquid crystal molecules 25 are tilted while maintaining the average tilt direction in a plane perpendicular to the arrangement direction of the slit portions 10-1. Change the corner.

Therefore, the slit portion 10-1 and the comb tooth portion 1 are provided between the four portions 10a to 10d constituting the pixel electrode 10.
By changing the longitudinal direction of 0-2, liquid crystal molecules 2
The tilt angle can be changed while maintaining the tilt direction of No. 5 as shown in FIG. That is, with only the structure provided on the active matrix substrate 2, four domains in which the tilt directions of the liquid crystal molecules 25 are different from each other can be formed in one pixel region. Further, in the present embodiment, the tilt angle can be changed while maintaining the average tilt direction of the liquid crystal molecules 25 in the plane perpendicular to the arrangement direction of the slit portions 10-1 and the comb tooth portions 10-2. In addition to being able to realize a faster response speed, poor orientation is unlikely to occur, and good orientation division is possible.

In the first embodiment, as described above, the intensity distribution of the plane wave electric field is formed in the pixel region, and the intensity is changed to control the optical characteristics of the liquid crystal layer 4 for display. I do. By the way, in the case of performing the control as described above, a stronger electric field is formed in the portion on the comb-teeth portion 10-2 in the liquid crystal layer 4 than in the portion on the slit portion 10-1. Therefore, the liquid crystal molecules 25 in the portion on the comb-teeth portion 10-2 incline more largely than in the portion on the slit portion 10-1. That is, the average tilt angle of the liquid crystal molecules 25 is different between the portion on the comb tooth portion 10-2 and the portion on the slit portion 10-1 of the liquid crystal layer 4. Such a difference in tilt angle can be observed as an optical difference.

FIG. 4 is a diagram showing an example of the transmittance distribution observed when the structure shown in FIG. 2 is adopted in the liquid crystal display device shown in FIG. Note that FIG. 4 shows a planar wave-shaped transmittance distribution observed when a third voltage within the range of the first voltage to the second voltage is applied between the electrodes 10 and 16. Thus, according to the first and second embodiments, the features described with reference to FIGS. 1 to 3 can also be observed as optical features.

By the way, in the first embodiment of the present invention, the change in the transmittance due to the relaxation of the alignment of the liquid crystal molecules 25 is suppressed, and thereby a high response speed is realized.

FIG. 5 is a diagram schematically showing an alignment change occurring in a part of the liquid crystal layer 4 when the voltage applied between the electrodes 10 and 16 is increased from the first voltage to the second voltage. In addition, FIG.
(A) thru | or (c) are figures which show roughly the influence which the angle which the vibration direction of the linearly polarized light which injects into the liquid-crystal layer 4 and the director of a liquid-crystal material give to transmittance. In addition, in FIG.
Due to the arrangement 35a, 35b of liquid crystal molecules 25, the electrodes 10,
FIG. 3C shows the orientation relaxation occurring on both sides of the comb-teeth portion of the pixel electrode 10 when the voltage applied between 16 is increased from the first voltage to the second voltage with time from the upper side to the lower side. ing. Further, in FIG. 5, the arrow 36 indicates the director, and the double-headed arrow 37 indicates the easy transmission axis of the polarizing film 5a. Further, in FIG. 6, reference numeral 30 indicates a light source such as a backlight.

As described with reference to FIGS. 3A to 3D, when the voltage applied between the electrodes 10 and 16 is increased from the first voltage to the second voltage, the liquid crystal molecules 25 are averaged. The tilt angle is changed while maintaining a proper tilt direction within a plane perpendicular to the arrangement direction of the slit portions 10-1. At this time,
In the vicinity of both side ends of the comb-teeth portion 10-2 of the pixel electrode 10 shown in (c), in addition to the tilt angle of the liquid crystal molecules 25 changing, the tilt direction also changes. That is, near the both ends of the comb tooth portion 10-2, as shown in FIG. 5, a change in the tilt direction indicated by reference numeral 35a and a change in the tilt direction indicated by reference numeral 35b occur. These changes in the tilt direction are accompanied by a change in the metastable alignment state obtained by changing the tilt angle to a more stable alignment state.

By the way, the transmittance when the second voltage is applied between the electrodes 10 and 16 is the angle between the vibration direction of the linearly polarized light incident on the liquid crystal layer 4 and the director of the liquid crystal, in other words, the polarizing film. It changes depending on the angle formed by the easy transmission axis of 5a and the slow axis of the liquid crystal layer 4. For example, in FIG.
As shown in (a), the transmittance becomes maximum when the easy axis of transmission of the polarizing film 5a and the slow axis of the liquid crystal layer 4 form an angle of 45 °. As shown in FIG. 6C, the easy axis of transmission of the polarizing film 5a and the slow axis of the liquid crystal layer 4 are 0 °.
Alternatively, the transmittance becomes minimum when the angle is 90 °. Further, as shown in FIG.
When the axis of easy transmission of a and the slow axis of the liquid crystal layer 4 form an angle of greater than 0 ° and less than 45 °, or an angle of greater than 45 ° and less than 90 °,
An intermediate transmittance between the case of (a) and the case of FIG. 6 (c) is obtained.

As described above, the transmittance when the second voltage is applied between the electrodes 10 and 16 changes according to the angle formed by the easy axis of transmission of the polarizing film 5a and the director of the liquid crystal. Therefore, when a change in the tilt direction as indicated by reference numeral 35a in FIG. 5 occurs, the transmittance also changes accordingly. Similarly, when a change in the tilt direction occurs as indicated by reference numeral 35b in FIG. 5, the transmittance also changes accordingly. Therefore, during the change (or orientation relaxation) from such a metastable orientation state to a more stable orientation state,
The average transmittance may continue to change.

In the first embodiment, the easy transmission axis of the polarizing film 5a and the easy transmission axis of the polarizing film 5b are orthogonal to each other, and the angle θ formed by the easy transmission axis of the polarizing film 5a and the director 37 is an inequality: 0 °. <Θ <45 ° or 45 °
The liquid crystal display device 1 is designed so as to satisfy <θ <90 °. With this design, for example, the angle θ is 22.5 °
In the case of, the transmittance decreases as the tilt direction changes from the upper side to the lower side in the array 35a in FIG. 5, and the transmittance increases as the tilt direction changes from the upper side to the lower side in the array 35b. . That is, the reference numeral 35a indicates a change in the transmittance with the change in the tilt direction, and the reference numeral 35b indicates
It is possible to cancel the change in transmittance associated with the change in tilt direction indicated by. Therefore, the average transmittance can be maintained substantially constant during orientation relaxation as shown in FIG.
Therefore, the apparent response speed can be increased.

In this embodiment, the angle θ is an inequality:
12.5 ° <θ <32.5 ° or 57.5 ° <θ <7
It is preferably 7.5 °, more preferably 22.5 ° or 67.5 °. Angle θ is 2
The closer to 2.5 ° or 67.5 °, the greater the effect of increasing the apparent response speed.

In the present embodiment, the angle θ is an inequality: 22.5 ° ≦ θ <45 ° or 45 ° <θ ≦ 6.
It is preferable that the relationship shown in 7.5 ° is satisfied. This is because it is more advantageous that the angle θ is closer to 45 ° from the viewpoint of transmittance.

In the structure described above, the slit portion 10-1
The width of the comb-teeth portion 10-2 is constant, but the slit portion 10-1
Alternatively, the width of the comb tooth portion 10-2 may be changed along the longitudinal direction thereof.

FIG. 7 is a plan view schematically showing another example of the structure which can be used in the liquid crystal display device shown in FIG. Also,
FIG. 8 is a diagram schematically showing an alignment change of liquid crystal molecules which occurs when the structure shown in FIG. 7 is adopted in the liquid crystal display device shown in FIG. In addition, in FIG.
Of the two parts 10a to 10d, only the part 10a is drawn, and in FIG. 8, only part of the part 10a shown in FIG. 7 is drawn.

In the structure shown in FIGS. 7 and 8, the width of the slit portion 10-1 continuously increases from the central portion of the pixel electrode 10 toward the peripheral portion. According to such a structure, as shown in FIG.
As shown in, in addition to the liquid crystal orientation at the lower end of the slit portion 10-1 and the liquid crystal orientation at the upper end of the comb tooth portion 10-2, the liquid crystal orientation at both end portions of the slit portion 10-1 and the comb tooth portion 10-2 is It acts so that the direction of the director becomes the direction indicated by the arrow 32. Therefore, according to the structures shown in FIGS. 7 and 8, the transmittance and the response speed can be further improved.

Next, a second embodiment of the present invention will be described. As described above, in the first embodiment, the apparent response speed can be increased. However, the transmittance θ is sacrificed because the angle θ formed by the director 37 and the easy transmission axis of the polarizing film 5a is deviated from 45 °. In the second embodiment, a high response speed can be realized without sacrificing the transmittance. In the second embodiment, the structure of the pixel electrode 10 is different and the polarization film 5a is different.
The third embodiment is the same as the first embodiment except that the angle θ formed by the easy transmission axis and the director 37 can be arbitrarily set.

FIG. 9A is a plan view showing a part of the pixel electrode 10 usable in the liquid crystal display device 1 according to the second embodiment of the present invention. 9B is a plan view showing a part of the pixel electrode 10 shown in FIG.

As described with reference to FIGS. 3C and 3D, the liquid crystal molecules 25 located in the vicinity of the edges of the slit portion 10-1 and the comb tooth portion 10-2 are the other liquid crystal molecules 25. Plays a role in regulating the tilt direction of the. However, when the edges of the slit portion 10-1 and the comb tooth portion 10-2 form an acute angle with the director 32 of the liquid crystal, as shown in FIG. 9B, the slit portion 10- The tilt direction is changed not only by the liquid crystal molecules 25 located near the side edge of 1 or the comb tooth portion 10-2 but also by the liquid crystal molecules 25 located near those edges. Therefore, if the structure shown in FIG. 9B is adopted,
It takes a relatively long time to relax the orientation.

On the other hand, the slit portion 10-1 and the comb tooth portion 1
When the edge of 0-2 is orthogonal to the director 32 of the liquid crystal, as shown in FIG.
The liquid crystal molecules 25 located in the vicinity of at least one edge of 0-1 and the comb tooth portion 10-2 do not change the tilt direction. Therefore, these liquid crystal molecules 25 quickly regulate the tilt direction of the other liquid crystal molecules 25 to one direction. Moreover, when the liquid crystal molecules 25 do not change the tilt direction when the orientation is relaxed in the vicinity of at least one edge of the slit portion 10-1 and the comb-teeth portion 10-2, the orientation state obtained after the orientation relaxation is completed is further improved. Stabilized. Therefore, the time required for orientation relaxation is shortened, and a high response speed can be realized.

Further, unlike the first embodiment, the second embodiment actually shortens the time required for orientation relaxation. Therefore, according to the present embodiment, the polarizing film 5a
It is possible to set the angle formed by the easy transmission axis and the director 32 to a desired value. Further, when the edges of the slit portion 10-1 and the comb-tooth portion 10-2 are orthogonal to the director 32 of the liquid crystal, the director 2 is set to the alignment direction of more liquid crystal molecules 25.
Can be aligned to 5. Therefore, the polarizing film 5
By appropriately setting the angle formed by the easy transmission axis of a and the director 32, it is possible to realize high transmittance and high response speed at the same time.

In the second embodiment, the polarizing film 5
The angle formed by the easy transmission axis of a and the director 32 is about 45.
It is preferably °. In this case, the transmittance is highest.

As described above, in the first and second embodiments, by providing the slit portion 10-1 and the comb tooth portion 10-2 in the pixel electrode 10, the electric field strength is weak in each domain. An electric field distribution was generated in which the regions and the regions having a strong electric field were arranged alternately and periodically. As described above, when the slit portion 10-1 and the comb tooth portion 10-2 are used, it is possible to design with a relatively high degree of freedom. However, such an electric field distribution can also be generated in other ways. This will be described with reference to FIGS. 10 (a) and 10 (b).

FIGS. 10A and 10B respectively show the first
9A and 9B are cross-sectional views schematically showing another example of a structure that can be used in the liquid crystal display device according to the second embodiment. Figure 10 (a)
In the structure shown in FIG. 3, instead of providing the slit portion 10-1 and the comb-teeth portion 10-2 on the pixel electrode 10, the dielectric layer 21 is provided on the pixel electrode 10 in the same pattern as the slit portion 10-1. There is. In this case, if the dielectric constant of the dielectric layer 21 is lower than that of the liquid crystal material such as acrylic resin, epoxy resin, or novolac resin, the electric field strength above the dielectric layer 21 is weaker. Regions can be formed. Therefore, it is possible to obtain the same effect as when the slit portion 10-1 and the comb tooth portion 10-2 are provided.

In the structure shown in FIG. 10B, the pixel electrode 1
Instead of providing the slit portion 10-1 and the comb tooth portion 10-2 at 0, the wiring 2 is formed on the pixel electrode 10 via the transparent insulator layer 22.
3 is provided. The wiring 23 is, for example, a signal line, a gate line, an auxiliary capacitance wiring, or the like, and is arranged in the same pattern as the comb tooth portion 10-2. According to this structure,
A region in which the strength of the electric field is higher can be formed above the wiring 23. Therefore, also in this case, the slit portion 1
The same effect as when 0-1 and the comb tooth portion 10-2 are provided can be obtained.

When the liquid crystal display device 1 is a transmissive type, it is preferable that the material of the dielectric layer 21 and the wiring 23 is a transparent material from the viewpoint of transmittance. When the liquid crystal display device 1 is a reflection type, the dielectric layer 21 and the wiring 2
As the material of 3, an opaque material such as a metal material may be used in addition to the transparent material.

In the first and second embodiments, the liquid crystal layer
Width W of the region in which the electric field strength in 4 is stronger₁And the strength of the electric field
Width W of weaker area₂Sum W₁₂Is less than 20 μm
Preferably. Usually W₁₂Is less than 20 μm
For example, it is possible to control the orientation of liquid crystal molecules as described above.
Therefore, sufficient transmittance can be realized. Also, the sum W
₁₂Is preferably 6 μm or more. In general, sum W₁₂
Is 6 μm or more, the strength of the electric field in the liquid crystal layer 4 is higher.
There are enough structures to create strong and weaker areas.
In addition to being able to form with high accuracy,
The liquid crystal alignment can be stably generated.

The sum W ₁₂ is the sum of the width of the portion sandwiched by the slit portions 10-1 of the pixel electrode 10 and the width of the slit portion 10-1, and is sandwiched by the dielectric layers 21 on the pixel electrodes 10. The width of the region and the width of the dielectric layer 21, the width of the wiring 23 provided on the pixel electrode 10 and the width of the region sandwiched by the wiring 23, and the tilt angle is larger when the third voltage is applied. It is approximately equal to the sum of the width of the region and the width of the smaller region, the sum of the width of the region having higher transmittance and the width of the lower region when the third voltage is applied. Therefore, these widths are also preferably 20 μm or less and 6 μm or more.

In the first and second embodiments, the width W ₁
And the width W ₂ is preferably 8 μm or less. The width W ₁ and the width W ₂ are preferably 4 μm or more. In this range, practically sufficient performance can be expected in terms of response speed and transmittance.

The width W ₁ and the width W ₂ are the width of the portion sandwiched between the slit portions 10-1 of the pixel electrode 10 and the slit portion 10.
-1 width, the width of the region sandwiched by the dielectric layer 21 on the pixel electrode 10 and the width of the dielectric layer 21, the width of the wiring 23 provided on the pixel electrode 10 and the width of the region sandwiched by the wiring 23. The width of a region having a larger tilt angle and the width of a region having a smaller tilt angle when the third voltage is applied, and the width of a region having a higher transmittance and a region having a lower transmittance when the third voltage is applied. Therefore, these widths are also preferably 8 μm or less and 4 μm or more.

In the first and second embodiments, the length of the region where the electric field strength is stronger and the length of the region where the electric field strength is weaker in the liquid crystal layer 4 are the width W ₁ and the width, respectively. It may be longer than W ₂ , but it is preferably twice or more the width W ₁₂ which is the sum thereof. In this case, more liquid crystal molecules can be aligned in the length direction of those regions.

In the first and second embodiments, both the region where the electric field strength in the liquid crystal layer 4 is stronger and the region where the electric field strength is weaker are asymmetrical with respect to the vertical direction as shown in FIG. 3C. In the first embodiment, as shown in FIG. 3A, the vertical direction may be symmetrical. However, the former case is advantageous in terms of response speed and the like.

In the first and second embodiments, the VAN mode in which a nematic liquid crystal having a negative dielectric anisotropy is vertically aligned is adopted, but a nematic liquid crystal having a positive dielectric anisotropy can also be used. Is. In particular, when high contrast is desired, by adopting the VAN mode and providing normally black, a high contrast of 400: 1 or more and a bright screen design by a high transmittance design are possible.

In the first and second embodiments, the shape of each of the portions 10a to 10d forming the pixel electrode 10 is not particularly limited, and may be rectangular or fan-shaped, for example. Further, in the present embodiment, since the liquid crystal display device 1 is the MVA type, the pixel electrode is composed of the plurality of portions 10a to 10d. However, in the case where one pixel region is not divided into a plurality of domains having different tilt directions. Can configure the pixel electrode with only one portion.

In the first and second embodiments, only the active matrix substrate 2 is provided with a structure that causes a region having a stronger electric field and a region having a weaker electric field in the liquid crystal layer when the third voltage is applied. It may be provided on both the active matrix substrate 2 and the counter substrate 3. However, in the former case, it is not necessary to perform highly accurate positioning using an alignment mark or the like when the active matrix substrate 2 and the counter substrate 3 are bonded to each other to form a cell.

In the first and second embodiments, the color filter layer 9 is provided on the active matrix substrate 2, but the color filter layer 9 may be provided on the counter substrate 3. However, in the former case, it is not necessary to perform highly accurate positioning using an alignment mark or the like when the active matrix substrate 2 and the counter substrate 3 are bonded to each other to form a cell.

[0067]

EXAMPLES Examples of the present invention will be described below.

Example 1 FIG. 11 shows Example 1 of the present invention.
3 is a plan view schematically showing a pixel electrode formed in the liquid crystal display device according to FIG. In this example, the liquid crystal display device 1 shown in FIG. 1 was manufactured by the method described below.

First, film formation and patterning were repeated in the same manner as a normal TFT forming process to form wirings such as scanning lines and signal lines and the TFT 8 on the glass substrate 7. Next, the color filter layer 9 was formed on the surface of the glass substrate 7 on which the TFTs 8 and the like were formed by a conventional method.

Next, with respect to the surface of the glass substrate 7 on which the transparent insulating film 9 is formed, IT is applied through a mask having a predetermined pattern.
O was sputtered. Then, a resist pattern was formed on this ITO film, and the exposed portion of the ITO film was etched using this resist pattern as a mask. As described above, the pixel electrode 10 having the shape shown in FIG. 11 was formed. Here, both the width of the slit portion 10-1 and the width of the comb tooth portion 10-2 were set to 5 μm.

Then, a thermosetting resin is applied to the entire surface of the glass substrate 7 on which the pixel electrodes 10 are formed, and the coating film is baked to form an alignment film 11 having a thickness of 70 nm and exhibiting vertical alignment. did. The active matrix substrate 2 was produced as described above.

Next, an ITO film was formed as the common electrode 16 on the one main surface of the glass substrate 15 prepared separately by using the sputtering method. Then, this common electrode 16
An alignment film 17 was formed on the entire surface of the substrate by the same method as described for the active matrix substrate 2. The counter substrate 3 was produced as described above.

Next, the active matrix substrate 2 and the peripheral edge portion of the opposing surface of the opposing substrate 3 are aligned with the alignment films 11 and 1 thereof.
A liquid crystal cell was formed by bonding with an adhesive so that the surfaces on which 7 were formed faced each other and the injection port for injecting the liquid crystal material was left. The cell gap of this liquid crystal cell is equal to that of the active matrix substrate 2
A spacer having a height of 4 μm is interposed between the counter substrate 3 and the counter substrate 3 to keep the spacer constant. Also, those substrates 2, 3
At the time of bonding, the substrates 2 and 3 were aligned by aligning their end face positions, and highly accurate alignment using an alignment mark or the like was not performed.

After that, a liquid crystal material having a negative dielectric anisotropy is injected into this liquid crystal cell by a usual method to fill the liquid crystal layer 4.
And the liquid crystal injection port was sealed with an ultraviolet curable resin. Furthermore, the liquid crystal display device 1 shown in FIG. 1 was obtained by pasting polarizing films 5a and 5b on both sides of this liquid crystal cell. Here, the polarizing films 5a and 5b are arranged so that their transmission easy axes are orthogonal to each other and form an angle of 22.5 ° or 67.5 ° with respect to the comb tooth portion 10-2 of the pixel electrode 10. Pasted As described above, the liquid crystal display device 1 shown in FIG. 1 was manufactured. In addition, this liquid crystal display device 1
Can be driven, for example, by changing the voltage applied between the pixel electrode 10 and the common electrode 16 between about 1V and about 5V.

Next, the liquid crystal display device 1 manufactured as described above was observed with a voltage of 4 V applied between the pixel electrode 10 and the common electrode 16. As a result, the pixel electrode 1
A transmittance distribution corresponding to the shape of 0 was observed.

Further, the response speed of the liquid crystal display device 1 was examined. That is, the change in transmissivity caused by changing the voltage applied between the pixel electrode 10 and the common electrode 16 from 1 V to 5 V was measured.

FIG. 12 shows a liquid crystal display device 1 according to the first embodiment.
5 is a graph showing the response speed of In the figure, the horizontal axis is electrode 1.
The time elapsed from the time when the voltage applied between 0 and 16 was changed from 1V to 5V is shown, and the vertical axis shows the transmittance. As shown in FIG. 12, in the liquid crystal display device 1 according to the present example, the time from the change in the transmittance to the stabilization was short, and the apparent response time was 10 ms.

Example 2 FIG. 13 shows Example 2 of the present invention.
FIG. 3 is a plan view schematically showing a pixel electrode 10 formed in the liquid crystal display device according to the above. In this example, except that the structure shown in FIG. 13 is adopted and the polarizing films 5a and 5b are attached so that their easy transmission axes form an angle of 45 ° with the longitudinal direction of the comb tooth portion 10-2. In the same manner as described in Example 1, the liquid crystal display device 1 shown in FIG. 1 was manufactured.

Next, the liquid crystal display device 1 manufactured as described above was observed with a voltage of 4 V applied between the pixel electrode 10 and the common electrode 16. As a result, the pixel electrode 1
A transmittance distribution corresponding to the shape of 0 was observed. Further, under the same conditions as described in Example 1, this liquid crystal display device 1
I investigated the response speed of.

FIG. 14 shows a liquid crystal display device 1 according to the second embodiment.
5 is a graph showing the response speed of In the figure, the horizontal axis is electrode 1.
The time elapsed from the time when the voltage applied between 0 and 16 was changed from 1V to 5V is shown, and the vertical axis shows the transmittance. As shown in FIG. 14, in the liquid crystal display device 1 according to this example, the time from the change in the transmittance to the stabilization was short, and the response time could be 20 ms.

(Comparative Example) FIG. 15 is a plan view schematically showing a pixel electrode 10 formed in a liquid crystal display device according to a comparative example. In this example, the structure shown in FIG. 15 is adopted, and the transmission axes of the polarizing films 5a and 5b are arranged in the comb tooth portion 10-2.
A liquid crystal display device 1 shown in FIG. 1 was manufactured by the same method as described in Example 1 except that the liquid crystal display device 1 was attached so as to form an angle of 45 ° with respect to the longitudinal direction.

Next, the response speed of the liquid crystal display device 1 was examined under the same conditions as described in the first embodiment. FIG. 16 is a graph showing the response speed of the liquid crystal display device 1 according to the comparative example. In the figure, the horizontal axis represents the elapsed time from the time when the voltage applied between the electrodes 10 and 16 was changed from 1V to 5V, and the vertical axis represents the transmittance. As shown in FIG. 16, in the liquid crystal display device 1 according to the present example, the time from the change in the transmittance to the stabilization is relatively long, and the response time is 5
It was 0 ms.

[0083]

As described above, according to the present invention, by adopting the predetermined structure, when the predetermined voltage is applied between the pixel electrode and the common electrode, the pixel region in the liquid crystal layer is not affected. , Forming first and second regions, each of which has a shape extending in one direction and which is alternately and repeatedly arranged in the pixel region in a direction intersecting the direction, and the first and second regions form liquid crystal molecules. Control the orientation. The structure for forming these first and second regions can be selectively provided on the array substrate with respect to the counter substrate. Therefore, in this case, highly accurate alignment can be performed when the array substrate and the counter substrate are bonded together. No need to do. That is, according to the present invention,
Provided is a liquid crystal display device that can be manufactured without highly accurately aligning an array substrate and a counter substrate even when the MVA mode is adopted.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a plan view schematically showing an example of a structure that can be used in the liquid crystal display device shown in FIG.

3A to 3D are diagrams schematically showing alignment changes of liquid crystal molecules which occur when the structure shown in FIG. 2 is adopted in the liquid crystal display device shown in FIG.

FIG. 4 is a diagram showing an example of a transmittance distribution observed when the structure shown in FIG. 2 is adopted in the liquid crystal display device shown in FIG.

FIG. 5 is a diagram schematically showing an alignment change that occurs in a part of the liquid crystal layer when the voltage applied between the pixel electrode and the common electrode is increased from the first voltage to the second voltage.

6A to 6C are diagrams schematically showing the influence of the angle formed by the director of the liquid crystal material and the vibration direction of the linearly polarized light incident on the liquid crystal layer on the transmittance.

7 is a plan view schematically showing another example of a structure that can be used in the liquid crystal display device shown in FIG.

8 is a diagram schematically showing an alignment change of liquid crystal molecules which occurs when the structure shown in FIG. 7 is adopted in the liquid crystal display device shown in FIG.

FIG. 9A is a plan view showing a part of a pixel electrode usable in a liquid crystal display device according to a second embodiment of the present invention,
FIG. 3B is a plan view showing a part of the pixel electrode shown in FIG. 2.

10A and 10B are cross-sectional views schematically showing still another example of the structure that can be used in the liquid crystal display device shown in FIG. 1.

FIG. 11 is a plan view schematically showing a pixel electrode formed in the liquid crystal display device according to the first embodiment of the present invention.

FIG. 12 is a graph showing the response speed of the liquid crystal display device according to the first embodiment.

FIG. 13 is a plan view schematically showing a pixel electrode formed in the liquid crystal display device according to the second embodiment of the present invention.

FIG. 14 is a graph showing the response speed of the liquid crystal display device according to the second embodiment.

FIG. 15 is a plan view schematically showing a pixel electrode formed in a liquid crystal display device according to a comparative example.

FIG. 16 is a graph showing the response speed of the liquid crystal display device according to the comparative example.

[Explanation of symbols]

1 ... Liquid crystal display device 2 ... Active matrix substrate 3 ... Counter substrate 4 ... Liquid crystal layer 5a, 5b ... Polarizing film 7 ... Transparent substrate 8 ... Switching element 9 ... Color filter layer 9a to 9c ... Colored layer 10 ... Pixel electrode 10a to 10d ... comb-shaped portion 10-1 ... Slit part 10-2 ... comb teeth 11 ... Alignment film 15 ... Transparent substrate 16 ... Common electrode 17 ... Alignment film 21 ... Dielectric layer 22 ... Transparent insulator layer 23 ... Wiring 25 ... Liquid crystal molecule 30 ... Light source 31, 32, 36, 37 ... Arrows

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/1343 G02F 1/1343 (72) Inventor Kazuyuki Sunohara 1-9-2 Harara-cho, Fukaya-shi, Saitama Toshiba Corporation Fukaya Factory (72) Inventor Yuzo Kutake 1-9-2, Harara-cho, Fukaya-shi, Saitama Toshiba Fukaya Factory (72) Inventor Takeshi Yamaguchi 1-9-2, Harara-cho, Fukaya-shi, Saitama Toshiba Fukaya Corporation In-factory (72) Inventor Kisako Ninomiya 1-9-2 Harara-cho, Fukaya-shi, Saitama, Ltd. Toshiba Fukaya Factory (72) Inventor Natsuko Fujiyama 1-9 2 Harara-cho, Fukaya-shi, Saitama Toshiba-Fukaya, Toshiba Factory F-term (reference) 2H048 BA02 BB02 BB10 BB42 2H049 BA02 BB03 BC14 BC22 2H090 KA04 LA01 LA09 LA15 MA01 MA02 MA06 MA10 MB01 2H091 FA02Y FA08X FA08Z GA01 GA13 HA07 HA12 LA30 2H092 GA14 JA24 NA25 PA13 PA08 PA11

Claims (8)

[Claims] 1. An array substrate having a pixel electrode on one main surface, and a common electrode disposed on the surface of the array substrate facing the pixel electrode and facing the array substrate. A counter substrate, a liquid crystal layer sandwiched between the array substrate and the counter substrate, a first polarizing plate provided on the back surface side of the array substrate on which the pixel electrodes are provided, and the counter substrate. A second polarizing plate provided on the back surface side of the surface of the substrate on which the common electrode is provided and in which the easy transmission axis is orthogonal to the easy transmission axis of the first polarizing plate; When a voltage is applied between the common electrode and the common electrode, the first and second regions having different electric field strengths are formed in the pixel region, which is a region sandwiched between the pixel electrode and the common electrode of the liquid crystal layer. And the first and second regions are respectively formed in the liquid crystal layer. Of the first polarizing plate having a shape extending in one direction in a plane including the first and second regions, and alternately and repeatedly arranged in a direction intersecting the direction in the plane. The angle θ formed by the easy transmission axis satisfies an inequality: 0 ° <θ <45 ° or 45 ° <θ <90 °, which is a liquid crystal display device. 2. The pixel electrode includes a comb-shaped portion, and an angle formed by a longitudinal direction of a comb tooth portion forming the comb-shaped portion and an easy transmission axis of the first polarizing plate is equal to the angle θ. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. 3. The liquid crystal display device according to claim 1, wherein the angle θ is 22.5 °. 4. An array substrate having a pixel electrode on one main surface, and a common electrode disposed on the surface of the array substrate facing the pixel electrode and facing the array substrate. A counter substrate, a liquid crystal layer sandwiched between the array substrate and the counter substrate, a first polarizing plate provided on the back surface side of the array substrate on which the pixel electrodes are provided, and the counter substrate. A second polarizing plate provided on the back surface side of the surface of the substrate on which the common electrode is provided and in which the easy transmission axis is orthogonal to the easy transmission axis of the first polarizing plate; When a voltage is applied between the pixel electrode and the common electrode, first and second regions having different electric field strengths are formed in the pixel region, which is a region sandwiched between the pixel electrode and the common electrode of the liquid crystal layer. And the first and second regions are respectively formed in the liquid crystal layer. Including a shape extending in one direction in a plane including and alternately and repeatedly arranged in a direction intersecting the direction in the plane, and at least one of the first and second regions is the first and second regions. A liquid crystal display device having an edge perpendicular to the extending direction. 5. The pixel electrode includes a comb-shaped portion, and a comb tooth portion forming the comb-shaped portion has an edge perpendicular to a direction in which the first and second regions extend. The liquid crystal display device according to claim 4, wherein 6. A structure that causes a difference in the strength of the electric field between the first and second regions when the voltage is applied between the pixel electrode and the common electrode is the same as that of the counter substrate. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is selectively provided on the array substrate. 7. The liquid crystal layer contains a liquid crystal material having a negative dielectric anisotropy, and when a voltage is applied between the pixel electrode and the common electrode, the liquid crystal layer and the pixel electrode 5. The liquid crystal display device according to claim 1, wherein a plurality of domains having different tilt directions of the liquid crystal molecules are formed in a pixel region which is a region sandwiched by a common electrode. 8. The liquid crystal display device according to claim 1, wherein the array substrate further includes a color filter layer.