JP5252815B2 - Liquid crystal display - Google Patents

Description

The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device in which one pixel is composed of a plurality of subpixels.

Conventionally, in addition to three sub-pixels corresponding to red (R), green (G), and blue (B), one sub-pixel is configured by four sub-pixels including a sub-pixel corresponding to white (W). A known liquid crystal display device is known (for example, see Patent Document 1).

FIG. 8 is a plan view schematically showing an example of the configuration of one pixel of the above-described conventional liquid crystal display device. Referring to FIG. 8, in the conventional liquid crystal display device, red (R), green (G), blue (B)
One pixel 121 is composed of four sub-pixels 121a, 121b, 121c and 121d corresponding to white and white (W), respectively.

Note that each of the red (R), green (G), blue (B), and white (W) sub-pixels 121a to 121a.
Each thin film transistor 124 connected to the gate line 122 and the data line 123 is provided in 121d. That is, in the conventional liquid crystal display device, red (R
), Green (G), blue (B), and white (W) sub-pixels 121a to 121d, the driving of the pixel 121 is controlled by the thin film transistor 124 provided one by one.

In the conventional liquid crystal display device shown in FIG. 8, the white (W) sub-pixel 121d is further added in addition to the red (R), green (G), and blue (B) sub-pixels 121a to 121c. Thus, the brightness of the displayed image can be improved.

JP 11-295717 A

However, in the conventional liquid crystal display device illustrated in FIG. 8, the thin film transistor 124 is provided in each of the red (R), green (G), blue (B), and white (W) sub-pixels 121a to 121d. Since the drive of the pixel 121 is controlled, the white (W) sub-pixel 1
There is an inconvenience that it is difficult to enlarge a region contributing to the display of 21d (a region where no thin film transistor 124, wiring, or the like exists). As a result, the conventional liquid crystal display device has a problem that it is difficult to further improve the luminance of the displayed image.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a liquid crystal display device capable of further improving the luminance of a displayed image. .

In order to achieve the above object, in a liquid crystal display device according to one aspect of the present invention, one pixel is a plurality of sub-pixels in which a region corresponding to each pixel is surrounded by a black matrix, and a first sub-pixel corresponding to white A pixel and a second sub-pixel corresponding to each of a plurality of colors other than white, and is determined for each second sub-pixel formed in the opening of the black matrix in a region corresponding to the second sub-pixel The color filter of the selected color and the pixel electrode of the first sub-pixel that applies a voltage to the liquid crystal layer are provided in the first sub-pixel region, and one is provided in each region of the second sub-pixel. A pixel electrode of a second subpixel that applies a voltage to the liquid crystal layer, and a switching element that is connected to the pixel electrode of the second subpixel and drives the pixel electrode of the second subpixel. , First sub-pixel The pixel electrode is electrically connected to the pixel electrode of the second subpixel corresponding to the predetermined color, and is driven by a switching element connected to the pixel electrode of the second subpixel corresponding to the predetermined color. Light from a backlight provided on the opposite back side is emitted from the display surface through regions corresponding to the first subpixel and the second subpixel, and a desired image is displayed on the display surface.

In the liquid crystal display device according to this aspect, as described above, one pixel is constituted by a plurality of sub-pixels including at least the first sub-pixel corresponding to white, so that the first sub-pixel corresponding to white is not included. The brightness of the displayed image can be improved as compared with the case where one pixel is constituted by a plurality of sub-pixels. In this case, the pixel electrode of the first sub pixel and the second sub pixel are driven in conjunction with the pixel electrode of the second sub pixel corresponding to a predetermined color other than white. If the switching element is connected to the pixel electrode of the second subpixel by electrically connecting the pixel electrode of the pixel, both the pixel electrode of the first subpixel and the pixel electrode of the second subpixel are interlocked. Can be driven. As a result, the first
Since it is not necessary to install a switching element in the sub-pixel, an area that does not contribute to the display of the first sub-pixel can be reduced. Therefore, since the ratio (aperture ratio) of the region contributing to the display of the first sub-pixel can be improved, the luminance of the displayed image can be further improved. Note that a region that does not contribute to display is a region where switching elements or wirings exist, and a region that contributes to display is a region where switching elements or wirings do not exist.

In the above case, since it is not necessary to install a switching element in the first sub-pixel, the number of switching elements can be reduced as compared with the case where one switching element is installed in each of the plurality of sub-pixels. it can. Thereby, the structure of the liquid crystal display device can be simplified. Since four sub-pixels are driven by three elements, a driver can be used for a liquid crystal display device in which one pixel is constituted by three general sub-pixels. Since the number can be reduced, a framed frame can also be achieved.

Further, 1 a plurality of sub-pixels constituting the pixels, lever lessons distribution as the first sub-pixel and the second sub-pixel are adjacent to each other, without performing routing of complicated wiring, the first sub-pixel The pixel electrode and the pixel electrode of the second sub-pixel can be electrically connected to each other.

The second sub-pixel corresponding to a predetermined color, if is corresponds to green, synchronized from the second sub-pixel corresponding to green to light is emitted from the first sub-pixel corresponding to the white Will also emit light. Here, the normal human visibility is higher in the order of blue, red, and green. For this reason, for example, when the sub-pixels corresponding to red and white are driven in conjunction with each other, the red color with the increased brightness is most easily recognized, and the balance of visibility may be lost. When the display is performed, the displayed image is uncomfortable. Therefore, by making the second sub-pixel correspond to green, it is possible to improve the luminance of green having a higher relative visibility than red or blue, so that when a color image is displayed, the displayed image is It can be visually recognized as a color image without a sense of incongruity.

As described above, according to the present invention, a liquid crystal display device capable of further improving the luminance of a displayed image can be easily obtained.

FIG. 1 is a perspective view of a liquid crystal display panel and a backlight unit constituting a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining a configuration of one pixel of a liquid crystal display panel included in the liquid crystal display device according to the embodiment shown in FIG. 3 is a cross-sectional view of a liquid crystal display panel included in the liquid crystal display device according to the embodiment shown in FIG. 1 (a view corresponding to a cross section taken along line 100-100 in FIG. 2). First, the structure of the liquid crystal display device according to the present embodiment will be described with reference to FIGS.

The liquid crystal display device of this embodiment is used for portable devices, such as a mobile phone which can be carried outdoors, for example. Moreover, the liquid crystal display device of this embodiment is provided with the liquid crystal display panel 20 and the backlight unit 30, as shown in FIG. The liquid crystal display panel 20 includes a plurality of pixels (area surrounded by a broken line) 21 arranged in a matrix, and displays a desired image on the front surface (hereinafter referred to as a display surface 20a). It is configured. Also,
The backlight unit 30 has a back surface 20b opposite to the display surface 20a of the liquid crystal display panel 20.
On the side. The backlight unit 30 includes a back surface 20 of the liquid crystal display panel 20.
The liquid crystal display panel 20 is configured to irradiate backlight light (light generated by the backlight unit 30) L1 from the b side.

As shown in FIGS. 1 and 2, the liquid crystal display panel 20 is configured such that each of the plurality of pixels 21 includes four sub-pixels 21a, 21b, 21c, and 21d. That is, in the present embodiment, one pixel 21 is composed of four sub-pixels 21a to 21d. The four sub-pixels 21a to 21d constituting this one pixel 21 are respectively
It corresponds to red (R), green (G), blue (B) and white (W). White (W
) Is an example of the “first subpixel” in the present invention, and the subpixel 21b corresponding to green (G) is an example of the “second subpixel” in the present invention.

In the present embodiment, the four sub-pixels 21a to 21d constituting one pixel 21 are arranged so that the white (W) sub-pixel 21d and the green (G) sub-pixel 21b are adjacent to each other. . Specifically, the four sub-pixels 21a to 21d are arranged from one side (left side) to the other side (right side) opposite to the one side, red (R) sub-pixel 21a and green (G) sub-pixel. The pixel 21b, the white (W) sub-pixel 21d, and the blue (B) sub-pixel 21c are arranged in this order.

The liquid crystal display panel 20 includes red (R), green (G), blue (B), and white (W).
An image display operation by each of the sub-pixels 21a to 21d is performed in the transmissive display mode. The transmissive display mode refers to the modulated backlight light by transmitting the backlight light L1 incident on the liquid crystal display panel 20 from the back surface 20b of the liquid crystal display panel 20 toward the display surface 20a of the liquid crystal display panel 20. (Display light) In this mode, L1 is emitted from the display surface 20a of the liquid crystal display panel 20.

  Below, the structure of the liquid crystal display panel 20 of this embodiment is demonstrated concretely.

As shown in FIG. 3, the liquid crystal display panel 20 of the present embodiment includes at least a liquid crystal layer 1 and glass substrates 2 and 3 provided on the back side and the front side of the liquid crystal layer 1, respectively.

In a predetermined region on the front surface of the glass substrate 2, a thin film transistor 5 for driving a pixel electrode 14 to be described later is formed via the buffer layer 4. The thin film transistor 5 is an example of the “switching element” in the present invention.

The thin film transistor 5 includes an active layer 6 having source / drain regions, a gate insulating film 7 formed on the front surface of the active layer 6, and a gate electrode formed on the front surface of the gate insulating film 7. 8. The active layer 6 is made of, for example, polysilicon. The gate insulating film 7 is made of, for example, SiO ₂ . The gate electrode 8
Is made of, for example, molybdenum. In addition, as a constituent material of the active layer 6, the gate insulating film 7, and the gate electrode 8, materials other than the above may be used.

In the present embodiment, the thin film transistor 5 includes red (R), green (G), and blue (
B), one is installed in a region corresponding to each of the sub-pixels 21a to 21c, while white (
W is not installed in the area corresponding to the sub-pixel 21d. Specifically, in the present embodiment, the thin film transistor 5 is installed as shown in FIG. Therefore, in this embodiment, the aperture ratio of the white (W) sub-pixel 21d is higher than the aperture ratios of the red (R), green (G), and blue (B) sub-pixels 21a to 21c. Yes.

The thin film transistor 5 is covered with an interlayer insulating film 10 as shown in FIG. A source electrode 11 and a drain electrode 12 are formed in a region corresponding to the thin film transistor 5 on the front surface of the interlayer insulating film 10. The source electrode 11 and the drain electrode 12 are connected to the source region and the drain region of the thin film transistor 5 (active layer 6) through contact holes formed in the interlayer insulating film 10, respectively. The source electrode 11 and the drain electrode 12 are covered with an interlayer insulating film 15.

Although not shown in FIG. 3, the gate electrode 8 of the thin film transistor 5 is connected to the gate line 9 (see FIG. 2). The source electrode 11 is connected to the data line 13 (see FIG. 2).

A pixel electrode (transparent conductive film) 14 for applying a voltage to the liquid crystal layer 1 is formed in a predetermined region on the front surface of the interlayer insulating film 15. This pixel electrode 14 is made of ITO.
(Indium Tin Oxide) etc., red (R), green (G)
, Blue (B) and white (W) subpixels 21a to 21d. The red (R), green (G), and blue (B) sub-pixels 21a to 21b.
The pixel electrode 14 of 1 c is connected to the corresponding drain electrode 12 through a contact hole formed in the interlayer insulating film 15. That is, the pixel electrode 14 of each of the red (R), green (G), and blue (B) subpixels 21 a to 21 c is connected to the corresponding thin film transistor 5 via the drain electrode 12. Accordingly, the pixel electrodes 14 of the red (R), green (G), and blue (B) sub-pixels 21 a to 21 c are driven by the corresponding thin film transistors 5.

Here, in the present embodiment, the pixel electrode 14 of the white (W) sub-pixel 21d is green (G).
The green (G) sub-pixel 21 is driven in conjunction with the pixel electrode 14 of the sub-pixel 21b.
It is electrically connected to the pixel electrode 14 of b. Specifically, the white (W) sub-pixel 21d
The pixel electrodes 14 of the green (G) sub-pixel 21b are electrically connected to each other via a connection layer 14a made of the same layer as the pixel electrode 14. Accordingly, in the present embodiment, the thin film transistor 5 installed in the region corresponding to the green (G) sub-pixel 21b.
Accordingly, the pixel electrodes 14 of the white (W) sub-pixel 21d and the green (G) sub-pixel 21b are driven in conjunction with each other.

A black matrix 16 made of chromium is formed on the back surface of the glass substrate 3. This black matrix 16 has red (R), green (G), and blue (B)
And white (W) sub-pixels 21a to 21d. That is, the openings 16a are formed in regions corresponding to the red (R), green (G), blue (B), and white (W) sub-pixels 21a to 21d of the black matrix 16. The red (R), green (G), blue (B) and white (W) sub-pixels 2
1 a to 21 d are partitioned by a black matrix 16.

Further, a color filter 17a colored in red is formed in a region corresponding to the red (R) sub-pixel 21a so as to fill the opening 16a of the black matrix 16. Further, a color filter 17b colored in green is formed in a region corresponding to the green (G) sub-pixel 21b so as to fill the opening 16a of the black matrix 16. In addition, in a region corresponding to the blue (B) sub-pixel 21c, a color filter 17c colored in blue is formed so as to fill the opening 16a of the black matrix 16. In addition, although the color filter is not formed in the region corresponding to the white (W) sub-pixel 21d, a dent is formed by forming a transparent layer having the same thickness as the color filters 17a to 17c. It may be eliminated.

Thus, in the region corresponding to the red (R) sub-pixel 21a, when the backlight light L1 is incident from the back surface 20b of the liquid crystal display panel 20, the backlight light L1 is liquid crystal via the red color filter 17a. The light is emitted from the display surface 20a of the display panel 20. Also,
In the region corresponding to the green (G) sub-pixel 21b, when the backlight light L1 is incident from the back surface 20b of the liquid crystal display panel 20, the backlight light L1 is converted into the green color filter 1.
The light is emitted from the display surface 20a of the liquid crystal display panel 20 through 7b. In the region corresponding to the blue (B) sub-pixel 21c, when the backlight light L1 is incident from the back surface 20b of the liquid crystal display panel 20, the backlight light L1 is displayed on the liquid crystal display via the blue color filter 17c. The light is emitted from the display surface 20 a of the panel 20. On the other hand, the white (W) sub-pixel 21
In the region corresponding to d, when the backlight light L1 is incident from the back surface 20b of the liquid crystal display panel 20, the backlight light L1 is emitted from the display surface 20a of the liquid crystal display panel 20 without passing through the color filter. become.

In addition, red (R), green (G), blue (B), and white (W) sub-pixels 21a to 21b.
In a region corresponding to 1d, a common electrode (transparent conductive film) 18 made of ITO or the like is formed. Specifically, red (R), green (G), and blue (B) sub-pixels 21a to 21 are provided.
In the region corresponding to c, the common electrode 18 is formed on the back surface of the color filters 17a to 17c. In the region corresponding to the white (W) sub-pixel 21d,
The common electrode 18 is formed so as to fill the opening 16 a of the black matrix 16. The red (R), green (G), blue (B), and white (W) sub-pixels 21a to 21a-
The common electrodes 18 of 21d are electrically connected to each other.

Although not shown, alignment films made of polyimide resin are formed on the front surface of the pixel electrode 14 and the back surface of the common electrode 18, respectively. That is, the liquid crystal layer 1 is sandwiched between a pair of alignment films (not shown).

In the present embodiment, as described above, the pixel electrode 14 of the white (W) sub-pixel 21d is green (
The pixel electrode 14 of the white (W) subpixel 21d and the pixel electrode 14 of the green (G) subpixel 21b are electrically connected so as to be driven in conjunction with the pixel electrode 14 of the G) subpixel 21b. As a result, the thin film transistor 5 provided in the region corresponding to the green (G) sub-pixel 21b causes the pixel electrode 14 of the white (W) sub-pixel 21d and the pixel electrode 14 of the green (G) sub-pixel 21b to Both can be driven in conjunction. As a result, white (W)
Since it is not necessary to install the thin film transistor 5 in a region corresponding to the sub pixel 21d, a region that does not contribute to the display of the white (W) sub pixel 21d can be reduced. Therefore, since the ratio (aperture ratio) of the region contributing to the display of the white (W) sub-pixel 21d can be improved, the luminance of the displayed image can be further improved.

In addition, since it is not necessary to install the thin film transistor 5 in a region corresponding to the white (W) sub-pixel 21d, each of the red (R), green (G), blue (B), and white (W) sub-pixels 21 is provided.
The number of thin film transistors 5 can be reduced as compared with the case where one thin film transistor 5 is provided in a region corresponding to a to 21d. Thereby, the structure of the liquid crystal display device can be simplified.

In the present embodiment, as described above, the white (W) sub-pixel 21d and the green (G)
The thin film transistor 5 for driving each pixel electrode 14 of the sub-pixel 21b is not provided in a region corresponding to the white (W) sub-pixel 21d, and the green (G) sub-pixel 21 is provided.
By providing in the region corresponding to b, the aperture ratio of the white (W) sub-pixel 21d can be easily improved.

In the above case, the following effects can be obtained. That is, as shown in FIG. 4, even if the backlight light L1 incident on the liquid crystal display panel 20 is reflected by the black matrix 16, the reflected backlight light L1 can be absorbed by the color filter 17b. Thereby, since the backlight light L1 reflected by the black matrix 16 can be weakened, even if the backlight light L1 reflected by the black matrix 16 is incident on the thin film transistor 5, there occurs a problem that the thin film transistor 5 malfunctions. Can be suppressed.

In the case where the thin film transistor 5 is provided in a region corresponding to the white (W) sub-pixel 21d, when the backlight light L1 is reflected by the black matrix 16, the reflected backlight light L1 passes through the color filter. Since the light enters the thin film transistor 5 without being interposed, it is difficult to obtain the above-described effect.

In the present embodiment, as described above, the white (W) sub-pixel 21d and the green (G)
The pixel electrode 14 of each of the sub-pixels 21b is electrically connected to each other via a connection layer 14a made of the same layer as the pixel electrode 14, whereby the white (W) sub-pixel 21d and the green (G) When forming each pixel electrode 14 of each of the sub-pixels 21b, the coupling layer 1 is simultaneously formed.
4a can be formed. Thereby, it is not necessary to separately provide a process for forming the coupling layer 14a. Therefore, even if the pixel electrodes 14 of the white (W) sub-pixel 21d and the green (G) sub-pixel 21b are configured to be electrically connected to each other, an increase in the number of manufacturing steps is suppressed. Can do. In the case where the connecting portion 14a made of the same layer as the pixel electrode 14 is not provided, for example, the drain region of the thin film transistor 5 is white (W
) Until the region corresponding to the sub-pixel 21d is reached, and the thin film transistor 5
May be connected to the pixel electrode 14 of the white (W) sub-pixel 21.

In the present embodiment, as described above, the white (W) sub-pixel 21d and the green (G)
By configuring the pixel electrodes 14 of the sub-pixels 21b to operate in conjunction with each other, white (W) sub-pixels are synchronized with the light emitted from the green (G) sub-pixels 21b. Light is also emitted from 21d. For this reason, it is possible to improve the luminance without breaking the balance of normal human visibility that increases in the order of blue, red and green,
When a color image is displayed, the displayed image can be viewed as a color image without a sense of incongruity.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

For example, in the above embodiment, the pixel electrode of the white (W) sub-pixel and the pixel electrode of the green (G) sub-pixel are driven in conjunction with each other. However, the present invention is not limited to this, and the white electrode (W
) Sub-pixel pixel electrode and red (R) sub-pixel pixel electrode may be driven in conjunction with each other, or white (W) sub-pixel pixel electrode and blue (B) You may comprise so that it may drive in conjunction with the pixel electrode of a sub pixel.

In the above embodiment, the four sub-pixels 21a to 21d constituting one pixel 21 are arranged so that the white (W) sub-pixel 21d and the green (G) sub-pixel 21b are adjacent to each other. The present invention is not limited to this, and as in the first modification shown in FIG. 5, the four sub-pixels 21 a to 21 d constituting one pixel 21 are arranged from one side (left side) to the other side opposite to the one side ( Right)
The red (R) sub-pixel 21a, the green (G) sub-pixel 21b, the blue (B) sub-pixel 21c, and the white (W) sub-pixel 21d may be arranged in this order. If comprised in this way, the sub pixel (21b and 21d) of a color with high relative visibility and the sub pixel (21a and 21c) of a color with low relative visibility will be arranged by turns. For this reason, it is possible to suppress the occurrence of inconvenience that streaky luminance unevenness occurs due to solidification of subpixels with high specific visibility (subpixels with low specific visibility). . However, when another sub-pixel is arranged between the green (G) sub-pixel and the white (W) sub-pixel, wiring may be complicated.

Further, the four sub-pixels 21a to 21d constituting one pixel 21 may be arranged as in the second modification shown in FIG. 6 or the third modification shown in FIG.

1 is a perspective view of a liquid crystal display panel and a backlight unit constituting a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining a configuration of one pixel of a liquid crystal display panel included in the liquid crystal display device according to the embodiment shown in FIG. 1. FIG. 2 is a cross-sectional view of a liquid crystal display panel included in the liquid crystal display device according to the embodiment shown in FIG. It is a figure for demonstrating the effect of this invention. It is the schematic for demonstrating the structure for 1 pixel of the liquid crystal display panel contained in the liquid crystal display device by the 1st modification of this invention. It is the schematic for demonstrating the structure for 1 pixel of the liquid crystal display panel contained in the liquid crystal display device by the 2nd modification of this invention. It is the schematic for demonstrating the structure for 1 pixel of the liquid crystal display panel contained in the liquid crystal display device by the 3rd modification of this invention. It is the top view which showed simply an example of the structure of 1 pixel of the conventional liquid crystal display device.

Explanation of symbols

1 Liquid crystal layer 5 Thin film transistor (switching element)
14 pixel electrode 14a connection layer 21 pixel 21a, 21c sub pixel 21b sub pixel (second sub pixel)
21d sub-pixel (first sub-pixel)

Claims (3)

One pixel is a plurality of sub-pixels each having a corresponding area surrounded by a black matrix, a first sub-pixel corresponding to white, and a second sub-pixel corresponding to each of a plurality of colors other than white Consists of
A color filter of a color determined for each of the second sub-pixels formed in an opening of the black matrix in a region corresponding to the second sub-pixel;
A pixel electrode of the first subpixel provided in the region of the first subpixel and applying a voltage to the liquid crystal layer;
Provided one for each region of the second sub-pixel, and the pixel electrode of the second sub-pixel for applying a voltage to the liquid crystal layer,
A switching element connected to the pixel electrode of each of the second sub-pixels and driving the pixel electrode of the second sub-pixel,
The pixel electrode of the first subpixel is electrically connected to the pixel electrode of the second subpixel corresponding to the predetermined color, and is driven by a switching element connected to the pixel electrode of the second subpixel corresponding to the predetermined color. ,
Light from a backlight provided on the back side opposite to the display surface is emitted from the display surface through a region corresponding to each of the first subpixel and the second subpixel, and desired light is applied to the display surface. Display images ,
Liquid crystal display device.   The liquid crystal display device according to claim 1, wherein the first subpixel and the second subpixel corresponding to the predetermined color are arranged adjacent to each other.   The liquid crystal display device according to claim 1, wherein the second sub-pixel corresponding to the predetermined color corresponds to green.

Images