JP2003295192A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a liquid crystal display having high luminance and high reliability by easily and reliably enhancing the aperture ratio without generating inconvenience such as a disclination in a screen. <P>SOLUTION: In a liquid crystal display device wherein a liquid crystal layer 13 has a polymer structure for aligning liquid crystal molecules in a prescribe direction in a liquid crystal and a pixel electrode 15 is worked into a fine comb shape provided with a connecting part 15b for connecting each comb 15a, a bank-shaped protrusion 31 is provided at the part of a CF substrate 12 opposed to the connecting part 15b for correcting the alignment of the liquid crystal molecules above the connecting part 15b for the purpose of suppressing disclination. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display of a vertical alignment type in which the alignment regulating force of a polymer formed by photopolymerization is utilized to control the alignment of liquid crystal molecules. Targets the device.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display (LCD) using an active matrix, a liquid crystal material having a positive dielectric anisotropy is twisted horizontally in a dark state at 90 ° between opposed substrates. Widely used are TN-mode liquid crystal display devices that are aligned in such a manner.

This TN mode liquid crystal display device has a problem of poor viewing angle characteristics, and various studies have been made to improve the viewing angle characteristics. Therefore, as an alternative method, a liquid crystal material having a negative dielectric anisotropy is vertically aligned, and the projections or slits provided on the substrate surface are used to remove the liquid crystal molecules at the time of voltage application without rubbing the alignment film. MVA (Multi-domain V) that regulates the tilt direction to multiple directions
ertical Alignment) method has been developed and has succeeded in significantly improving the viewing angle characteristics.

[0004]

Although the MVA type liquid crystal display device has excellent viewing angle characteristics as described above, a large number of structures such as protrusions for alignment regulation and slits are complicatedly provided in the pixel plane. Inevitably lowers the aperture ratio,
There is a problem of poor brightness. Moreover, it cannot be neglected that forming a large number of fine and precise structures itself complicates the manufacturing process and increases the manufacturing cost.

The present invention has been made in view of the above problems, and can easily and surely improve the aperture ratio without causing inconvenience such as disclination on the screen, and has a high-luminance and highly reliable liquid crystal display. An object of the present invention is to provide a liquid crystal display device that realizes the above.

[0006]

As a result of intensive studies, the present inventor has come up with various aspects of the invention described below.

The liquid crystal display device of the present invention is a liquid crystal display device in which a first substrate having a first electrode and a second substrate having a second electrode are bonded together through an alignment film and a liquid crystal layer. The liquid crystal layer has a polymer structure for orienting the liquid crystal molecules in a liquid crystal in a predetermined direction, and the first substrate has a comb-like shape for the first electrode. ,
A connection portion for connecting the comb teeth is formed at least at one end portion, and the second substrate has a protrusion at a portion facing the connection portion.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION-Basic Gist of the Present Invention-First, the basic skeleton of the present invention will be described. The inventors of the present invention improved the MVA type liquid crystal display device, improved the aperture ratio, increased the brightness, and raised the level in terms of cost. , We have developed an alignment control technology to obtain stable alignment by polymerizing.

This liquid crystal display device, as shown in FIG.
A pair of transparent glass substrates 11 facing each other at a predetermined interval,
12 and a liquid crystal layer 13 sandwiched between these transparent glass substrates 11, 12. The transparent glass substrates 11 and 12 are joined and fixed by a sealing material (not shown).

One transparent glass substrate (TFT substrate) 11
A plurality of pixel electrodes 15 made of ITO and an unillustrated thin film transistor (TFT) serving as an active element are formed on the upper side of the insulating layers 14a and 14b of the same quality, and are transparent so as to cover the pixel electrodes 15. Vertical alignment film 1
6a is formed, and on the other transparent glass substrate (CF substrate) 12, a color filter 17, a common electrode (counter electrode) 18, and a vertical alignment film 16b are sequentially laminated. Then, the vertical alignment film 1 is sandwiched so as to sandwich the liquid crystal layer 13.
6a and 16b are butted to each other to form glass substrates 11 and 12
Are fixed by a sealing material, and the polarizers 19 and 20 are provided outside the substrates 11 and 12, respectively. The pixel electrode 15 is formed with an active matrix (TFT matrix),
In the illustrated example, the data bus line 21 to which the drain electrode of the TFT is connected is shown. Although not shown, a gate bus line to which the gate electrode of the TFT is connected is also formed. The electrodes may be provided on only one substrate.

The liquid crystal layer 13 is formed by injecting liquid crystal through the liquid crystal inlet. In the present embodiment, the liquid crystal is one in which a monomer that undergoes photopolymerization or thermal polymerization is mixed. Then, by applying UV irradiation or heat treatment while applying a predetermined AC voltage to the injected liquid crystal, a polymer structure in which the monomer is polymerized and regulated by the alignment pattern of the comb teeth 15a is formed in the liquid crystal layer 13. Then, the liquid crystal molecules are aligned according to the alignment pattern by being regulated by the polymer structure.

In addition to the above configuration, in order to refine the alignment control of liquid crystal molecules and further improve the light transmittance, FIG.
As shown in ((a) is a plan view and (b) is a sectional view), I
The slit formed in the pixel electrode made of TO is simplified,
A structure has been devised in which liquid crystal molecules are tilted in two directions when a voltage is applied. In addition, in the following FIGS.
A and 16b are omitted for convenience of illustration.

In FIG. 2A, the data bus line 2
A pixel is formed by being surrounded by 1 and a gate bus line 22 which is orthogonal thereto. The pixel electrode 15 is processed into a fine comb tooth shape, and is provided with a connecting portion 15b for connecting each comb tooth 15a. Furthermore, the TFT that becomes the active element
32 is provided at one end of the pixel electrode 15. Connection 1
2b is the left end at the upper part of the pixel electrode 15 in FIG.
In the lower part, it is located in the vicinity of the data bus line 21 at the right end so as to be parallel to the data bus line 21, whereby liquid crystal molecules are inclined in two different directions.

However, in this case, as shown in FIG. 2B, due to the electric field at the connection portion 15b of the pixel electrode 15, the liquid crystal molecules located on the connection portion 15b have comb teeth 15 formed thereon.
A regulating force that tilts in the opposite direction to the liquid crystal molecules located at a acts. Therefore, disclination occurs on the connection portion 15b, which is one of the causes for lowering the transmittance.

The inventor of the present invention has shown in FIG. 3 ((a) is a plan view and (b) is a sectional view) in order to prevent the occurrence of the above disclination in the liquid crystal display device having the structure shown in FIG. As described above, in order to correct the alignment of the liquid crystal molecules on the connection portion 15b, it was conceived to provide the bank-shaped protrusion 31 at a portion of the CF substrate 12 facing the connection portion 15b.

When a protrusion 31 is provided on a portion of the CF substrate 12 that faces the region where the connecting portion 15b and the data bus line 21 closest to the connecting portion 15b exist, the protrusion 31 is formed, as shown in FIG.
As shown in FIG. 5, the liquid crystal molecules that are inclined to tilt in the opposite direction to the liquid crystal molecules of the comb teeth 15a are regulated by the protrusions 31 and
The liquid crystal molecules are tilted in the same direction, and the occurrence of disclination can be prevented.

In order to effectively use the protrusion 31, the protrusion 31
Is preferably located closer to the data bus line 21 than the end of the connecting portion 15b of the pixel electrode 15 (see (i) in FIG. 4). When the highest position of the protrusion 31 comes inward from the end of the connecting portion 15b, the liquid crystal molecules on the connecting electrode 15 are tilted in the opposite direction to the liquid crystal molecules of the comb tooth 15a due to the slope on the opposite side of the protrusion 31 (FIG. 5). However, by disposing the protrusions 31 as shown in FIG. 4I, the liquid crystal molecules are regulated by the slopes of the protrusions 31 and surely incline in the same direction (forward direction) as the liquid crystal molecules of the comb teeth 15a. .

Further, in order to effectively use the protrusion 31, the end of the protrusion 31 on the pixel electrode 15 side should be located inside the pixel electrode 15 with respect to the center of the connecting portion 15a ((i in FIG. 4).
i)) is preferable. That is, the slope of the liquid crystal molecule which is tilted in the forward direction becomes less effective when it is not located in a region wider than the region where the liquid crystal molecule is tilted in the reverse direction due to the electric field (see FIG. 6). By arranging the protrusions 31 in this way, a sufficient forward inclination can be obtained even on the connection portion 15a.

However, the transmittance decreases in the region where the protrusion 31 exists. According to the investigation by the present inventors, it is found that the transmittance of the liquid crystal display device is higher when the protrusion 31 that is included in the pixel region is 5 μm or less than when the protrusion 31 is not provided (FIG. 4 (iii)).

Further, the end portion of the protrusion 31 on the data bus line 21 side is provided so as not to adversely affect adjacent pixels.
It has been found that it is desirable to be inside the outer end of the data bus line 21 (see (iv) in FIG. 4).

Further, if the width of the comb teeth 15a is too narrow, there is a risk of cutting, and if it is too wide, the liquid crystal molecules will not tilt in the direction parallel to the comb teeth 15a. Further, if the distance between the comb teeth 15a is too small, there is a risk of short-circuiting between the adjacent comb teeth 15a. Conversely, if it is too wide, the liquid crystal molecules will not tilt in the direction parallel to the slits. Therefore, the comb teeth 15
The distance between a and the width of the comb teeth 15a is 0.5 μm or more and 5 μm or more.
It is preferably set to m or less. Similarly, the TFT 32
It is also preferable to set the disconnection point between the connection part of 1 and the connection part of the fine IT0 to 0.5 μm or more and 5 μm or less.

Specific Embodiment Based on the basic essence of the present invention described above, a specific embodiment will be described.
Here, the liquid crystal display device shown in FIG. 7 was manufactured.

In this embodiment, since the alignment films 16a and 16b are all vertical alignment films, the liquid crystal has a negative dielectric anisotropy, and the polarizing plates are attached to both sides of the liquid crystal panel in crossed Nicols. The display is normally black, the changing axis of the polarizing plate is in the direction of 45 ° with respect to the data bus line 21, the panel size is 15 type, and the resolution is XGA.

In this liquid crystal display device, the width of the protrusion 31 is 1
The height is 0 μm, and the highest portion (vertex portion) of the protrusion 31 is located at the center of the region sandwiched between the end portion of the pixel electrode 15 and the end portion of the data bus line 21. Further, the end portion of the protrusion 31 on the pixel electrode 15 side is closer to the pixel electrode 1 than the center of the connection portion 15b.
Located inside 5. Here, the portion of the protrusion 31 in the pixel region was 4 μm. This liquid crystal display device is referred to as sample A.

For comparison with sample A, sample B,
C was produced. In the sample B, the width of the protrusion 31 is 10 μm
The apex portion of the protrusion 31 is located 2 μm inside the end portion on the pixel electrode 15 side, and the end portion of the protrusion 31 is 7 inside the pixel.
It is a liquid crystal display device having a structure containing μm. On the other hand, Sample C is a liquid crystal display device having a structure in which the apex portion of the protrusion 31 is located outside the end portion on the pixel electrode 15 side, and the end portion of the protrusion 31 is 5 μm inside the pixel.

In addition to the samples B and C, the liquid crystal display device having the structure shown in FIG. 2A was used as a sample D. When the brightness of the sample D was compared with that of the samples A, B and C, The brightness is improved by 5% in comparison with Sample B, and the brightness is decreased by 1% in comparison with Sample D.
Showed the same brightness as Sample D. Thus, the clear superiority of the sample A of this embodiment was demonstrated.

As described above, according to the liquid crystal display device of the present embodiment, the aperture ratio can be easily and surely improved without causing inconvenience such as disclination on the screen, and high brightness and high reliability can be obtained. It becomes possible to realize a liquid crystal display.

The various aspects of the present invention will be collectively described below as supplementary notes.

(Supplementary Note 1) A liquid crystal display device in which a first substrate having a first electrode and a second substrate having a second electrode are bonded together through an alignment film and a liquid crystal layer, The liquid crystal layer has a polymer structure for orienting the liquid crystal molecules in a predetermined direction in the liquid crystal, and the first substrate has a comb-like shape for the first electrode. A liquid crystal display device, wherein a connecting portion for connecting teeth is formed at least at one end portion, and the second substrate has a protrusion at a portion facing the connecting portion.

(Supplementary Note 2) The liquid crystal display device according to Supplementary Note 1, wherein the first substrate has a data bus line in the vicinity of the connection portion.

(Supplementary Note 3) The supplementary note 1 or 2 is characterized in that the protrusion is formed such that a facing portion of the apex thereof on the first substrate is located outside the connecting portion.
The liquid crystal display device according to item 1.

(Supplementary Note 4) The protrusion is formed such that the end portion of the protrusion on the side of the first electrode facing the first substrate is located inside the center of the connection portion on the pixel side. 5. The liquid crystal display device according to appendix 3, characterized in that.

(Supplementary Note 5) The protrusion is formed such that the distance between the facing portion of the end portion on the side of the first electrode on the first substrate and the outer end portion of the connecting portion is 5 μm or less. 5. The liquid crystal display device according to any one of appendices 1 to 4, characterized in that.

(Supplementary Note 6) The protrusion is formed so that the facing portion of the end of the data bus line side on the first substrate is located inside the outer end of the data bus line. 6. The liquid crystal display device according to any one of appendices 1 to 5.

(Supplementary Note 7) The liquid crystal display device according to any one of Supplementary Notes 1 to 6, wherein a distance between the comb teeth in the first electrode is 0.5 μm to 5 μm.

[0036]

According to the liquid crystal display device of the present invention, the aperture ratio can be easily and surely improved without causing inconvenience such as disclination on the screen, and a liquid crystal display with high brightness and high reliability can be realized. It becomes possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main configuration of a liquid crystal display device.

FIG. 2 is a schematic diagram showing a main configuration of a liquid crystal display device.

FIG. 3 is a schematic diagram showing a main configuration of a liquid crystal display device of the present embodiment.

FIG. 4 is a schematic diagram showing a main configuration of a liquid crystal display device of the present embodiment.

FIG. 5 is a schematic view showing a comparison with the liquid crystal display device of the present embodiment.

FIG. 6 is a schematic view showing a comparison with the liquid crystal display device of the present embodiment.

FIG. 7 is a schematic diagram showing a specific configuration of the liquid crystal display device of the present embodiment.

[Explanation of symbols]

11,12 Transparent glass substrate 13 Liquid crystal layer 14a, 14b insulating layer 15 pixel electrodes 15a comb teeth 15b connection 16a, 16b Alignment film 17 color filters 18 common electrode 19,20 Polarizer 21 Data bus line 22 gate bus line 31 Bank-like protrusions 32 TFT

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H090 HB07Y JA03 JA05 LA01                       LA04 MA01 MA07 MA14                 2H092 GA14 JA24 JA42 JB05 JB13                       JB51 NA04 NA25 NA27 NA29                       PA02

Claims (5)

[Claims] 1. A first substrate having a first electrode, and a second substrate.
A liquid crystal display device, wherein the second substrate having the electrodes is bonded via an alignment film and a liquid crystal layer, wherein the liquid crystal layer is a polymer structure for aligning the liquid crystal molecules in a liquid crystal in a predetermined direction. The first substrate has a comb-teeth shape, and a connecting portion for connecting the comb-teeth is formed on at least one end portion of the first substrate. Is a liquid crystal display device having a projection at a portion facing the connection portion. 2. The liquid crystal display device according to claim 1, wherein the protrusion is formed such that an apex portion of the protrusion on the first substrate is located outside the connection portion. 3. The protrusion is formed such that an end portion of the protrusion on the side of the first electrode facing the first substrate is located inside the pixel from the center of the connection portion. The liquid crystal display device according to claim 2. 4. The protrusion is formed such that the distance between the facing portion of the first electrode side end portion of the first substrate and the outer end portion of the connection portion is 5 μm or less. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. 5. The protrusion is formed such that a facing portion of the end portion of the protrusion on the data bus line side on the first substrate is located inside an outer end portion of the data bus line. Any one of claims 1 to 4
The liquid crystal display device according to item.