JP2003222869A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device resistant to visual recognition of a residual image and capable of realizing a high transmittance even when a VAN (vertical aligned nematic) mode is adopted. <P>SOLUTION: The liquid crystal display device 1 is characterized by being provided with first and second substrates 7, 15 faced to each other, pixel electrodes 10 arranged on the surface of the first substrate 7 faced to the second substrate 15, an insulating projecting part 11 arranged on the pixel electrode 10 and alienated from the outline of the pixel electrode 10, a common electrode 16 arranged on the counter surface of the second substrate 15 to the first substrate 7, and a liquid crystal layer 4 lying between the pixel electrodes 10 and the common electrode 16. <P>COPYRIGHT: (C)2003,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 a thin shape and low power consumption.
It is widely used as a display for notebook computers, mobile phones, and car navigation systems. In such a liquid crystal display device, at present, an active element such as a thin film transistor (hereinafter referred to as a TFT) is used as a switching element and a TFT-TN mode using a nematic liquid crystal is mainly used. A liquid crystal display device using this display mode has realized a screen size of about 10 inches and full color display, and such a liquid crystal display device is used as a display for an information terminal.

However, when a structure capable of full-color display is adopted in a TN mode liquid crystal display device, there arises a problem that the viewing angle becomes extremely narrow. Further, there is a problem that a trailing phenomenon occurs when a moving image is displayed, and the moving image display quality is low. For these reasons, the applications of liquid crystal display devices using nematic liquid crystals are limited.

In recent years, liquid crystal display devices have been required to be applied to televisions in addition to monitors such as desktop computers and workstations. TN mentioned above
In the mode, the viewing angle characteristics and the response speed required for such applications cannot be realized. Therefore, the OCB mode using the nematic liquid crystal, the VAN (Vertical Ali)
gned Nematic) mode, IPS mode, and interface-stabilized ferroelectric liquid crystal (Surface St
The adoption of abilized Ferroelectric Liquid Crystal) mode and antiferroelectric liquid crystal mode is being considered.

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 VAN mode) in which each pixel region is divided into a plurality of domains in which the tilt directions of liquid crystal molecules are different from each other is particularly noted because it is relatively easy to design the view angle compensation. Are gathering.

However, the VAN mode liquid crystal display device tends to have a lower transmittance than the TN mode liquid crystal display device due to disclination induced by domain division. Further, an afterimage may be visually recognized in a VAN mode liquid crystal display device.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a liquid crystal capable of achieving a high transmittance even when a VAN mode is adopted, in which an afterimage is hardly visible. An object is to provide a display device.

[0008]

In order to solve the above-mentioned problems, the present invention provides a pixel electrode provided on the facing surfaces of the first and second substrates facing each other and the second substrate of the first substrate. An insulating protrusion provided on the pixel electrode and spaced from the contour of the pixel electrode; a common electrode provided on a surface of the second substrate facing the first substrate; the pixel electrode; A liquid crystal display device comprising a liquid crystal layer interposed between the common electrode and the common electrode.

[0009]

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.

FIG. 1 is a sectional view schematically showing a liquid crystal display device according to an embodiment of the present invention. A liquid crystal display device 1 shown in FIG. 1 is a VAN type liquid crystal display device having 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). A polarizing film (not shown) is 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, an insulating protrusion 11, and an alignment film (not shown) 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 is composed of blue, green and red colored layers 9a to 9c. Color filter layer 9
Is provided with a contact hole, and the pixel electrode 1
0 is connected to the switching element 8 through this contact hole. The colored layers 9a to 9c can be formed using a photosensitive resin containing a coloring dye or a coloring pigment.

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 insulating protrusion 11 is separated from the contour of the pixel electrode 10 and the counter substrate 3. Insulating protrusion 11
Can be formed using, for example, a photosensitive resin.

The alignment film formed on the pixel electrode 10 is composed of a thin film made of a transparent resin such as polyimide.
In the present embodiment, the alignment film 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 (not shown) are sequentially formed on a transparent substrate 15 such as a glass substrate. The common electrode 16 and the alignment film can be formed of the same material as the pixel electrode 10 and the alignment film provided on the active matrix substrate 2. In this embodiment, the common electrode 16 is formed as a flat continuous film.

In such a liquid crystal display device 1, lines of electric force generated by applying a voltage between the pixel electrode 10 and the common electrode 16 are curved near the edge of the pixel electrode 10.
When a liquid crystal material having a negative dielectric anisotropy is used, the liquid crystal molecules 25 tend to be aligned in a direction perpendicular to the lines of electric force.
The liquid crystal molecules 25 tilt in different directions between the left and right edges of the pixel electrode 10. That is, the electrode 1 of the liquid crystal layer 4
Domains 4a and 4b in which the tilt directions of the liquid crystal molecules 25 are different from each other are formed in a region located between 0 and 16.

Further, in the liquid crystal display device 1 shown in FIG. 1, since the insulating protrusion 11 is provided on the pixel electrode 10, when a voltage is applied between the pixel electrode 10 and the common electrode 16,
A portion of the liquid crystal layer 4 located between the insulating protrusion 11 and the common electrode 16 has a weaker electric field strength than the surrounding portion. That is, the lines of electric force are also curved in the portion of the liquid crystal layer 4 located near the insulating protrusion 11. Moreover, in the vicinity of the side surface of the insulating protrusion 11, the liquid crystal molecules 25 tend to be aligned along the side surface of the insulating protrusion 11 due to the excluded volume effect. Due to the effect of the bending of the lines of electric force provided by the insulating protrusion 11 and the excluded volume effect, the interference of orientation generated between the domains 4a and 4b is mitigated in the vicinity of the insulating protrusion 11, and The position is limited on the insulating protrusion 11.

FIG. 2 is a plan view schematically showing an example of a structure that can be used in the liquid crystal display device 1 shown in FIG. As shown in FIG. 2, in the present embodiment, the insulating protrusion 11 is arranged, for example, at substantially the center of the pixel electrode 10. With such a structure, when a voltage is applied between the pixel electrode 10 and the common electrode 16, the liquid crystal molecules 25 are oriented from the edge of the pixel electrode 10 toward the insulating protrusion 11. As a result, the liquid crystal layer 4
The region located between the electrodes 10 and 16 of the
It is divided into a plurality of domains that are radially arranged with 1 as the center.

As described above, according to the present embodiment, the edge of the pixel electrode 10 and the insulating protrusion 11 provided on the pixel electrode define the region located between the electrodes 10 and 16 of the liquid crystal layer 4. It is possible to divide the pixel region into a plurality of radially arranged domains and to limit the center of the arrangement to a predetermined position. That is, in this embodiment, it is not necessary to provide the counter substrate 3 with a structure used for orientation control. Therefore, according to the present embodiment, it becomes possible to manufacture a VAN type liquid crystal display device without highly accurately aligning the active matrix substrate 2 and the counter substrate 3.

Further, in this embodiment, the insulating protrusion 11 is formed.
Although the orientation interference occurs at the position of, the region where such orientation interference occurs is sufficiently narrow. Moreover, the position of such alignment interference is limited to above the insulating protrusion 11, so that the alignment interference does not occur at another position and the generated alignment interference does not move to another position. Therefore, according to this embodiment,
A high transmittance and a fast response speed can be realized.
That is, according to the present embodiment, it is possible to realize a liquid crystal display device having a high transmittance in which an afterimage is hardly visible.

In the present embodiment, the shape of the insulating projection 11 is not particularly limited, but the contour of the projection on the substrate 7 preferably has at least one recess. This will be described with reference to FIG.

FIG. 3 is a plan view schematically showing another example of the structure which can be used in the liquid crystal display device 1 shown in FIG. In the vicinity of the side surface of the insulating protrusion 11, the liquid crystal molecules 25 tend to be aligned along the side surface of the insulating protrusion 11 due to the excluded volume effect. In FIG. 3, the insulating protrusion 11 has a star-like shape composed of four taper portions, so that the liquid crystal molecules 25 tend to be oriented in different directions on both sides of each taper portion. As a result, the boundary between adjacent domains extends from each taper portion toward the edge of the pixel electrode 10. That is, when the structure shown in FIG. 3 is adopted, it is possible to limit the boundary position between adjacent domains to a desired position, and thus it is possible to realize a faster response speed.

In the present embodiment, the pattern formed by the contour of the pixel electrode 10 and the contour of the insulating protrusion 11 and the mirror image thereof may be different from each other when observed from the direction perpendicular to the substrate 7. preferable. This will be described with reference to FIGS. 4 and 5.

4A to 4C are plan views schematically showing the alignment state of liquid crystal molecules in the vicinity of the insulating protrusion. Further, FIG. 5 is a plan view schematically showing still another example of the structure that can be used in the liquid crystal display device 1 shown in FIG. 4A to 4C, the broken line 26 indicates the alignment direction of the liquid crystal molecules 25 near the insulating protrusion 11.

As described above, in the vicinity of the side surface of the insulating protrusion 11, the liquid crystal molecules 25 tend to be aligned along the side surface of the insulating protrusion 11 due to the excluded volume effect. Therefore, FIG.
The orientation states shown in (b) and (c) are more stable than the orientation states shown in FIG. That is, the electrode 10,
When a voltage is applied across 16, first, the orientation state shown in FIG. 4A is taken, and then the orientation state shown in FIG.
The orientation changes to that shown in (c).

As shown in FIG. 2, when the shape of the insulating protrusion 11 is cylindrical or conical and the insulating protrusion 11 is arranged at the center of the pixel electrode 10, the orientation shown in FIG. The state and the orientation state shown in FIG. 4C are at the same energy level. Therefore, the probability of taking the orientation state shown in FIG. 4B is equal to the probability of taking the orientation state shown in FIG. 4C, and the orientation state shown in FIG.
A change from the alignment state shown in (c) is also likely to occur. Since such a change in the alignment state is accompanied by a change in the position of the disclination, it should be suppressed from the viewpoint of improving the response speed.

On the other hand, when the structure shown in FIG. 5 is adopted, the alignment state shown in FIG. 4C is more stable than the alignment state shown in FIG. 4B. As a result, the electrode 1
Immediately after the voltage is applied between 0 and 16, the orientation state shown in FIG. 4C is taken, and the orientation state shown in FIG. 4B is not changed. Therefore, by adopting the structure as shown in FIG. 5, a faster response speed can be realized.

Such an effect can be obtained not only when the structure shown in FIG. 5 is adopted, but also when another structure is adopted. For example, in the structure shown in FIG. 3, the above-described effect can be obtained even when the insulating protrusion 11 is slightly rotated clockwise or counterclockwise. In addition, the above-described effect can be obtained even when the insulating protrusion 11 is formed in a prismatic shape and the insulating protrusion 11 is arranged so that its contour is slightly oblique to the contour of the pixel electrode 10. You can Furthermore, the above-described effects can be obtained even when the insulating protrusion 11 is arranged at a position displaced from the vertical and horizontal centerlines of the pixel electrode 10. That is, the above effect can be obtained by appropriately setting the azimuth and / or the position of the insulating protrusion 11 with respect to the pixel electrode 10. However,
As shown in FIG. 5, when the insulating protrusion 11 is in the shape of an impeller, the orientation state can be controlled without depending on the azimuth and position of the insulating protrusion 11.

Further, the control of the alignment state described with reference to FIGS. 4 and 5 can be performed by other methods. For example, when chirality is imparted to the liquid crystal material forming the liquid crystal layer 4 by adding a chiral agent, the above-described control can be performed without adopting the structure shown in FIG. In particular, when the structure described with reference to FIG. 5 and the like and a liquid crystal material having chirality are combined, a faster response speed can be realized.

As described above, in the present embodiment, the position of the alignment interference is controlled by utilizing the effect of the curve of electric force lines provided by the insulating protrusion 11 and the excluded volume effect. For such control, it is important to balance the effect due to the bending of the lines of electric force with the excluded volume effect, and normally, when the excluded volume effect is made larger than the effect due to the bending of the lines of electric force, good control is achieved. It can be carried out.

For example, the use of a material having a relative permittivity ε of 8 or more for an AC voltage having a frequency of 1 kHz for the insulating protrusion 11 can suppress the bending of the lines of electric force. Therefore, the position of orientation interference and the like can be controlled well.

Further, even when a material having a relative dielectric constant ε of less than 8 with respect to an alternating voltage of 1 kHz is used for the insulating protrusion 11, the position of orientation interference can be well controlled. For example, the thickness d of the portion of the liquid crystal layer 4 located between the pixel electrode 10 and the common electrode 16 and the insulating protrusion 1
By setting the height h such that the height h of 1 satisfies the inequality: h ≦ 0.3d, the bending of the lines of electric force can be further suppressed. Therefore, it is possible to better control the position of orientation interference and the like. In addition,
In this case, as a matter of course, h is a value larger than 0.
Moreover, d is usually about 2 to 6 μm.

When a material having a relative permittivity ε of less than 8 with respect to an AC voltage having a frequency of 1 kHz is used for the insulating protrusion 11, the thickness d and the height h have an inequality: h ≧ 0.5d. By setting the height h to satisfy,
It is possible to suppress the bending of the lines of electric force and to reduce the amount of the liquid crystal material which is affected by the alignment state due to the bending of the lines of electric force. Therefore, the position of orientation interference and the like can be controlled well. In this case, h is a value equal to or less than d.

As described above, by suppressing the bending of the lines of electric force induced by the insulating protrusion 11, the effect of the bending of the lines of electric force is balanced with the excluded volume effect. They may be balanced by increasing. This will be described with reference to FIG.

FIGS. 6 (a) and 6 (b) show the liquid crystal display shown in FIG.
Schematic examples of structures that can be used for the insulating protrusion of the display device
It is sectional drawing shown. The size of the excluded volume effect is an insulating protrusion
It depends on the inclination angle of the side surface of the portion 11 and is shown in FIG.
If the structure shown in Fig. 6 (a) is adopted,
A larger excluded volume effect can be obtained as compared with the case of
Usually, the diameter W of the end of the insulating protrusion 11 on the substrate 15 side₁And base
Diameter W of plate 7 end₂And are inequalities: W₁-W₂Shown at ≤5 μm
The insulating protrusion 11 should be formed so as to satisfy the following relationship.
With, the excluded volume effect can be increased,
Therefore, the position of orientation interference can be controlled well.
It Note that the difference W₁-W₂Is too small, the manufacturing process
There is a possibility that the insulating protrusion 11 may fall off during the cleaning. did
Therefore, the difference W ₁-W₂Is greater than -5 μm
And are preferred.

In the present embodiment, the size of the insulating projection 11 as viewed from the direction perpendicular to the substrate surface is not particularly limited, but usually the maximum diameter is about 4 to 10 μm. Further, when the distance from the edge of the pixel electrode 10 to the insulating protrusion 11 is excessively long, the alignment state induced by the bending of the lines of electric force in the vicinity of the edge of the pixel electrode 10 is the insulating protrusion 11. It may not reach into the vicinity. Usually, such a problem can be avoided by setting the distance from the edge of the pixel electrode 10 to the insulating protrusion 11 to about 150 μm or less.

[0039]

EXAMPLES Examples of the present invention will be described below. Example 1 A liquid crystal display device 1 shown in FIG. 1 was produced by the method described below. In this example, the liquid crystal display device 1 has the structure shown in FIG.

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. Further, ITO was sputtered on the color filter layer 9 through a mask provided with a predetermined opening pattern to form a pixel electrode 10 having a thickness of 150 nm. In this example, the size of the pixel electrode 10 is about 100 × 30 μm.

Next, in the center of the pixel electrode 10, an insulating protrusion 1 having a height of 0.7 μm is formed by using an acrylic photosensitive resin.
1 was formed. The relative permittivity ε of the insulating protrusion 11 with respect to an AC voltage having a frequency of 1 kHz is 6. In addition, the diameter W ₂ on the bottom side of the insulating protrusion 11 is 5 μm,
The diameter W ₁ on the top side was 8 μm.

Then, a polyimide (made by JSR) exhibiting vertical alignment is printed to a thickness of 70 nm on the surface of the glass substrate 7 on which the pixel electrode 10 is formed, and is baked at 180 ° C. to form a vertical alignment film. Was formed. The active matrix substrate 2 is completed as described above.

While forming the active matrix substrate 2 by the method described above, the common electrode 1 made of ITO is used.
A glass substrate 15 provided with 6 was prepared, and a vertical alignment film was formed on the common electrode 16 by the same method as described for the active matrix substrate 2. The counter substrate 3 was completed as described above.

Next, the active matrix substrate 2 and the peripheral portion of the counter surface of the counter substrate 3 are arranged so that the surfaces on which the alignment films are formed face each other and an injection port for injecting a liquid crystal material is left. Then, a liquid crystal cell was formed by bonding the same to the above via an adhesive. The cell gap of this liquid crystal cell is determined by the active matrix substrate 2 and the counter substrate 3
A resin ball having a diameter of 3.5 μm (manufactured by Sekisui Fine Chemical Co., Ltd .: Micropearl) was interposed as a spacer between the core and the core to keep the spacer constant. Also, those substrates 2,
When the substrates 3 and 3 were bonded together, 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.

Then, a liquid crystal material having a negative dielectric anisotropy (manufactured by MERCK) was injected into this liquid crystal cell by a usual method to form a liquid crystal layer 4. Further, the liquid crystal display device 1 shown in FIG. 1 was obtained by sealing the liquid crystal injection port with an ultraviolet curable resin.

Liquid crystal display device 1 manufactured as described above
As to the above, while the voltage applied between the electrodes 10 and 16 was changed, a state in which the liquid crystal orientation was changed on the pixel electrode 10 was observed by a polarization microscope. As a result, it was confirmed that the liquid crystal molecules 25 were oriented radially around the insulating protrusion 11. When the entire panel was visually inspected, no uneven brightness was observed.

(Comparative Example) FIG. 7 is a sectional view schematically showing a liquid crystal display device according to a comparative example. In addition, FIG.
FIG. 3 is a plan view showing a pixel electrode of the liquid crystal display device shown in FIG. In addition, in FIG. 8, the broken line 30 indicates schlieren.

In this comparative example, as shown in FIGS. 7 and 8, the insulating projection 11 was not formed, but instead the pixel electrode 1 was formed.
A liquid crystal display device 1 was manufactured by the same method as described in Example 1 except that a slit was provided in 0. Also in this liquid crystal display device 1, a state in which the liquid crystal orientation was changed on the pixel electrode 10 was observed with a polarization microscope while changing the voltage applied between the electrodes 10 and 16. As a result, as shown in the upper part of FIG. 8, the stability of the alignment direction of the liquid crystal molecules 25 is low, and the center of the radial alignment formed by the liquid crystal molecules 25 is
After being generated at the position shown in the lower part of FIG. 8, it moved for several seconds. When the entire panel was visually inspected, sesame salt-like uneven brightness was confirmed.

Example 2 A liquid crystal display device 1 shown in FIG. 1 was produced by the same method as described in Example 1, except that the dimensions of the insulating protrusions 11 were set as follows. That is, in this example, the same material as that used in Example 1 was used for the center of the pixel electrode 10 and the height was 2.0 μm.
The insulative protrusions 11 were formed. The insulating protrusion 1
The diameter W ₂ of the bottom side of 1 is 5 μm and the diameter W ₁ of the top side is 8 μm.
m.

Regarding this liquid crystal display device 1, the electrodes 10,
While changing the voltage applied between 16 pixel electrodes 10
The change of the liquid crystal alignment was observed with a polarization microscope. As a result, it was confirmed that the liquid crystal molecules 25 were oriented radially around the insulating protrusion 11. Also,
When the entire panel was visually inspected, no uneven brightness was observed.

Example 3 A liquid crystal display device 1 shown in FIG. 1 was produced by the same method as described in Example 1 except that the dimensions and the like of the insulating protrusion 11 were set as follows. That is, in this example, the insulating protrusion 11 having a height of 0.7 μm was formed in the center of the pixel electrode 10 by using the acrylic photosensitive resin. The relative permittivity ε of the insulating protrusion 11 with respect to an AC voltage having a frequency of 1 kHz is 9. Further, the diameter W ₂ on the bottom side of the insulating protrusion 11 is 5 μm.
The diameter W ₁ on the top side was 8 μm.

Regarding this liquid crystal display device 1, the electrodes 10,
While changing the voltage applied between 16 pixel electrodes 10
The change of the liquid crystal alignment was observed with a polarization microscope. As a result, it was confirmed that the liquid crystal molecules 25 were oriented radially around the insulating protrusion 11. Also,
When the entire panel was visually inspected, no uneven brightness was observed.

(Embodiment 4) A method similar to that described in Embodiment 1 is adopted except that the structure shown in FIG. 3 is adopted.
A liquid crystal display device 1 shown in was produced. In this example, the same material as that used in Example 1 was used for the insulating protrusion 11, and the height of the insulating protrusion 11 was 0.7 μm and the maximum diameter was 8 μm. Moreover, the cross-sectional shape of the insulating protrusion 11 is substantially rectangular.

Regarding the liquid crystal display device 1, the electrodes 10,
While changing the voltage applied between 16 pixel electrodes 10
The change of the liquid crystal alignment was observed with a polarization microscope. As a result, it was confirmed that the liquid crystal molecules 25 were oriented radially around the insulating protrusion 11. Also,
When the entire panel was visually inspected, no uneven brightness was observed.

(Embodiment 5) A method similar to that described in Embodiment 1 is adopted except that the structure shown in FIG. 5 is adopted.
A liquid crystal display device 1 shown in was produced. In this example, the same material as that used in Example 1 was used for the insulating protrusion 11, and the height of the insulating protrusion 11 was 0.7 μm and the maximum diameter was 8 μm. Moreover, the cross-sectional shape of the insulating protrusion 11 is substantially rectangular.

In this liquid crystal display device 1, the electrodes 10,
While changing the voltage applied between 16 pixel electrodes 10
The change of the liquid crystal alignment was observed with a polarization microscope. As a result, it was confirmed that the liquid crystal molecules 25 were oriented radially around the insulating protrusion 11. Also,
When the entire panel was visually inspected, no uneven brightness was observed.

Example 6 The liquid crystal shown in FIG. 1 was prepared in the same manner as in Example 1 except that a chiral agent was added to the liquid crystal material used in Example 1 so that the helical pitch was 15 μm. The display device 1 was manufactured. With respect to this liquid crystal display device 1, a state in which the liquid crystal orientation was changed on the pixel electrode 10 was observed with a polarization microscope while changing the voltage applied between the electrodes 10 and 16. As a result, the liquid crystal molecule 2
It was confirmed that No. 5 was oriented radially with the insulating protrusion 11 as the center. When the entire panel was visually inspected, no uneven brightness was observed.

[0058]

As described above, in the present invention, the insulating projection is provided on the pixel electrode so as to be spaced from the contour thereof, and the effect due to the bending of the lines of electric force and the excluded volume effect are utilized. To limit the position of orientation interference on the insulating protrusion. Therefore, according to the present invention, high transmittance and high response speed can be realized. That is, according to the present invention, even when the VAN mode is adopted, a liquid crystal display device having a high transmittance in which an afterimage is difficult to be visually recognized is realized.

[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.

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

4A to 4C are plan views schematically showing the alignment state of liquid crystal molecules in the vicinity of the insulating protrusion.

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

6A and 6B are cross-sectional views schematically showing an example of a structure that can be used for the insulating protrusion of the liquid crystal display device shown in FIG. 1.

FIG. 7 is a sectional view schematically showing a liquid crystal display device according to a comparative example.

8 is a plan view showing pixel electrodes of the liquid crystal display device shown in FIG.

[Explanation of symbols]

1 ... Liquid crystal display device 2 ... Active matrix substrate 3 ... Counter substrate 4 ... Liquid crystal layer 7 ... Transparent substrate 8 ... Switching element 9 ... Color filter layer 9a to 9c ... Colored layer 10 ... Pixel electrode 11 ... Insulating protrusion 15 ... Transparent substrate 16 ... Common electrode 25 ... Liquid crystal molecule 26 ... dashed line 30 ... Schlieren

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shoichi Kurauchi             2 shares, 1-9-1 Harara-cho, Fukaya City, Saitama Prefecture             Company Toshiba Fukaya Factory (72) Inventor Manabe Atsuko             2 shares, 1-9-1 Harara-cho, Fukaya City, Saitama Prefecture             Company Toshiba Fukaya Factory (72) Inventor Kazuyuki Sunohara             2 shares, 1-9-1 Harara-cho, Fukaya City, Saitama Prefecture             Company Toshiba Fukaya Factory (72) Inventor Natsuko Miya             2 shares, 1-9-1 Harara-cho, Fukaya City, Saitama Prefecture             Company Toshiba Fukaya Factory F term (reference) 2H088 HA02 HA03 HA04 JA10 LA01                       LA09 MA18                 2H090 HA03 HA05 HA14 HB07Y                       HD14 MA01 MB11 MB14

Claims (11)

[Claims] 1. A first and second substrate facing each other, a pixel electrode provided on a surface of the first substrate facing the second substrate, and a contour of the pixel electrode provided on the pixel electrode. An insulating protrusion that is separated from the common electrode, a common electrode that is provided on a surface of the second substrate that faces the first substrate, and a liquid crystal layer that is interposed between the pixel electrode and the common electrode. Liquid crystal display device characterized by. 2. The liquid crystal display device according to claim 1, wherein a part of the liquid crystal layer is interposed between the insulating protrusion and the common electrode. 3. The pattern formed by the contour of the pixel electrode and the contour of the insulating protrusion and the mirror image thereof are different from each other when observed from a direction perpendicular to the first substrate. The liquid crystal display device according to claim 1. 4. The liquid crystal display device according to claim 1, wherein the contour of the projection of the insulating protrusion on the first substrate has at least one recess. 5. The liquid crystal display device according to claim 1, wherein the projection of the insulating protrusion on the first substrate has an impeller shape. 6. The dielectric constant ε of the insulating protrusion with respect to an AC voltage having a frequency of 1 kHz is less than 8, and a thickness d of a portion of the liquid crystal layer located between the pixel electrode and the common electrode. 2. The liquid crystal display device according to claim 1, wherein the relationship between and the height h of the insulating protrusions satisfies one of the following inequalities: h ≦ 0.3d h ≧ 0.5d. 7. The liquid crystal display device according to claim 1, wherein a relative permittivity ε for an AC voltage having a frequency of 1 kHz of the insulating protrusion is 8 or more. 8. The diameter W _{1 of the} end portion on the second substrate side of the insulating protrusion and the diameter W _{2 of the} end portion on the first substrate side have the relationship shown by the following inequality: W ₁ −W ₂ ≦ 5 μm. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is satisfied. 9. The liquid crystal display device according to claim 1, wherein the liquid crystal layer contains molecules having chirality. 10. When a voltage is applied between the pixel electrode and the common electrode, a region of the liquid crystal layer between the pixel electrode and the common electrode has a director of liquid crystal molecules included in the liquid crystal layer. The liquid crystal according to claim 1, wherein a structure that divides the liquid crystal layer into a plurality of different domains and divides the region of the liquid crystal layer into the plurality of domains is selectively provided on the first substrate. Display device. 11. The liquid crystal display device according to claim 1, further comprising a color filter layer between the first substrate and the pixel electrode.